Abteilung Siedlungswasserwirtschaft

Publikationen von SWW

Peer Reviewed Publikationen

Beutler, P., Larsen, T. A., Maurer, M., Staufer, P., & Lienert, J. (2024). A participatory multi-criteria decision analysis framework reveals transition potential towards non-grid wastewater management. Journal of Environmental Management, 367, 121962 (15 pp.). doi:10.1016/j.jenvman.2024.121962, Institutional Repository

Many public environmental decisions are wicked problems due to high complexity and uncertainty. We test a participatory value-based framework based on multi-criteria decision analysis (MCDA) to tackle such problems. Our framework addresses two important gaps identified in reviews of MCDA applications to environmental problems: including stakeholders and treating uncertainty. We applied our framework in two complex real-world cases concerning a paradigm shift in the wastewater sector; the transition from centralized wastewater systems to decentralized non-grid systems. Non-grid systems may solve some problems of centralized systems by reducing costs, increasing flexibility, and addressing growing demands on environmental issues, especially in rural areas. But non-grid systems have rarely been implemented in OECD countries, because it is unclear whether a transition is recommendable, and whether stakeholders would accept this shift. This problem allows addressing several fundamental research questions. As theoretical contribution, we found that stakeholder participation in MCDA is necessary, because different preferences of stakeholders can lead to different best-performing options in the assessments. Compared to the typical integrated assessment (IA) approach that excludes stakeholders' preferences, the MCDA process led to clearer outcomes. Results indicate that including the uncertainty of predicted consequences of options with Monte Carlo simulation helped discriminate between options and identify best-performing options. Challenging the uncertainty of elicited stakeholder preferences with sensitivity analyses, we found that best-performing options were especially sensitive to the MCDA aggregation model. Despite the high uncertainty, it was possible to suggest robust consensus options that would perform reasonably well for all stakeholders. As practical contribution, results indicated that a transition from the centralized to decentralized non-grid systems seems feasible. Most stakeholders assigned highest weights to environmental protection objectives in decision-making workshops. These stakeholder preferences implemented in MCDA led to a generally better assessment of innovative non-grid systems, especially when including urine source separation. Stakeholders perceived the MCDA process as beneficial and found results plausible. We conclude that the proposed participatory value-based framework is rigorous, but still feasible in practice. The framework is certainly transferable to any context and is open to testing and refinement in various applications to wicked decision problems.
Blackman, R., Couton, M., Keck, F., Kirschner, D., Carraro, L., Cereghetti, E., … Altermatt, F. (2024). Environmental DNA: the next chapter. Molecular Ecology, 33(11), e17355 (17 pp.). doi:10.1111/mec.17355, Institutional Repository

Molecular tools are an indispensable part of ecology and biodiversity sciences and implemented across all biomes. About a decade ago, the use and implementation of environmental DNA (eDNA) to detect biodiversity signals extracted from environmental samples opened new avenues of research. Initial eDNA research focused on understanding population dynamics of target species. Its scope thereafter broadened, uncovering previously unrecorded biodiversity via metabarcoding in both well-studied and understudied ecosystems across all taxonomic groups. The application of eDNA rapidly became an established part of biodiversity research, and a research field by its own. Here, we revisit key expectations made in a land-mark special issue on eDNA in Molecular Ecology in 2012 to frame the development in six key areas: (1) sample collection, (2) primer development, (3) biomonitoring, (4) quantification, (5) behaviour of DNA in the environment and (6) reference database development. We pinpoint the success of eDNA, yet also discuss shortfalls and expectations not met, highlighting areas of research priority and identify the unexpected developments. In parallel, our retrospective couples a screening of the peer-reviewed literature with a survey of eDNA users including academics, end-users and commercial providers, in which we address the priority areas to focus research efforts to advance the field of eDNA. With the rapid and ever-increasing pace of new technical advances, the future of eDNA looks bright, yet successful applications and best practices must become more interdisciplinary to reach its full potential. Our retrospect gives the tools and expectations towards concretely moving the field forward.
Cavadini, G. B., Rodriguez, M., Nguyen, T., & Cook, L. M. (2024). Can blue-green infrastructure counteract the effects of climate change on combined sewer overflows? Study of a swiss catchment. Environmental Research Letters, 19(9), 094025 (12 pp.). doi:10.1088/1748-9326/ad6462, Institutional Repository

Combined sewer overflows (CSOs), the discharge of untreated sewage mixed with stormwater into surface waters, are expected to increase under climate change as a result of more extreme rainfall. Blue-green infrastructure (BGI), such as bioretention cells and porous pavements, can help to reduce the amount of stormwater entering combined sewer systems, thus reducing CSO discharge. However, our understanding of the potential for BGI to mitigate CSOs in a future climate is still lacking, as performance is typically evaluated for individual BGI elements with fixed implementation areas under historical climate conditions or limited future scenarios. In response, this study investigates the performance of 30 combinations of BGI elements and implementation rates to prevent increases in CSOs under a range of future climate scenarios in an urban catchment near Zurich, Switzerland. Median total annual rainfall, projected to increase by as much as 46%, could double the median annual CSO volume and increase median annual CSO frequency by up to 52%. Four BGI combinations that include bioretention cells show the most promise to prevent increases in CSO volume and frequency in a future climate; and given the diverse responses of BGI elements to distinct rainfall patterns, their combinations can enhance CSO discharge reduction across varying climate patterns. BGI is also likely to become more cost-effective under future climatic conditions as projected increases in total rainfall led to larger CSO volume reductions obtained through BGI. However, there is a trade-off between robustness to climate change and cost-effectiveness, since CSO volume reduction capacity scales with BGI implementation rate but cost-effectiveness declines. Our study illustrates the effectiveness of various BGI combinations to prevent increases in CSOs in a future climate, calling for a range of BGI elements and implementation areas to be considered for urban drainage adaptation.
Cavadini, G. B., Rodriguez, M., & Cook, L. M. (2024). Connecting blue-green infrastructure elements to reduce combined sewer overflows. Journal of Environmental Management, 365, 121465 (15 pp.). doi:10.1016/j.jenvman.2024.121465, Institutional Repository

By infiltrating and retaining stormwater, Blue-Green Infrastructure (BGI) can help to reduce Combined Sewer Overflows (CSOs), one of the main causes of urban water pollution. Several studies have evaluated the ability of individual BGI types to reduce CSOs; however, the effect of combining these elements, likely to occur in reality, has not yet been thoroughly evaluated. Moreover, the CSO volume reduction potential of relevant components of the urban drainage system, such as detention ponds, has not been quantified using hydrological models. This study presents a systematic way to assess the potential of BGI combinations to mitigate CSO discharge in a catchment near Zurich (Switzerland). Sixty BGI combinations, including four BGI elements (bioretention cells, permeable pavement, green roofs, and detention ponds) and four different implementation rates (25%, 50%, 75%, and 100% of the available sewer catchment area) are evaluated for four runoff routing schemes. Results reveal that BGI combinations can provide substantial CSO volume reductions; however, combinations including detention ponds can potentially increase CSO frequency, due to runoff prolongation. When runoff from upstream areas is routed to the BGI, the CSO discharge reductions from combinations of BGI elements differ from the cumulative CSO discharge reductions achieved by individual BGI types, indicating that the sum of effects from individual BGI types cannot accurately predict CSO discharge in combined BGI scenarios. Moreover, larger BGI implementation areas are not consistently more cost-effective than small implementation areas, since the additional CSO volume reduction does not outweigh the additional costs. The best-performing BGI combination depends on the desired objective, being CSO volume reduction, CSO frequency reduction or cost-effectiveness. This study emphasizes the importance of BGI combinations and detention ponds in CSO mitigation plans, highlighting their critical factors—BGI types, implementation area, and runoff routing— and offering a novel and systematic approach to develop tailored BGI strategies for urban catchments facing CSO challenges.
Chaudhary, P., Leitão, J. P., Schindler, K., & Wegner, J. D. (2024). Flood water depth prediction with convolutional temporal attention networks. Water, 16(9), 1286 (19 pp.). doi:10.3390/w16091286, Institutional Repository

Robust and accurate flood hazard maps are essential for early warning systems and flood risk management. Although physically based models are effective in estimating pluvial flooding, the computational burden makes them difficult to use for real-time flood prediction. In contrast, data-driven models can provide faster flood predictions if trained offline. While most studies have focused on predicting maximum water depth, in this study, we predict pixel-wise water depth maps for entire catchments at a lead time of 2 h. To that end, we propose a deep learning approach that uses a sequence encoding network with temporal self-attention. We also adapt the popular hydrological performance metric Nash–Sutcliffe efficiency (NSE) as our loss function. We test the effectiveness and generalizability of our method using a new dataset called SwissFlood, which consists of 100 catchments and 1500 rainfall events extracted from real observations in Switzerland. Our method produces 2 m spatial resolution flood maps with absolute error as low as 27 cm for water depth exceeding 1 m.
 
Chen, J., Bach, P. M., Nice, K. A., & Leitão, J. P. (2024). Investigating the efficacy of a fast urban climate model for spatial planning of green and blue spaces for heat mitigation. Science of the Total Environment, 955, 176925 (13 pp.). doi:10.1016/j.scitotenv.2024.176925, Institutional Repository

Problems caused by urban heat have prompted the exploration of urban greenery and blue spaces for heat mitigation. Various numerical models can simulate heat-related processes, but their use as support-tools to urban planners remains underexplored, particularly at the city-scale, due to high computational demand and complexity of such models. This study investigates the spatial relationships between urban heat, urban form and urban green and blue spaces with the fast climate model TARGET (The Air-temperature Response to Green/blue-infrastructure Evaluation Tool), which only requires minimal inputs of standard meteorological data, land cover and building geometry data. Using the City of Zurich as our case study, we: (i) validated the TARGET model against air temperature measurements from private sensor networks, (ii) performed a sensitivity analysis to identify key variables affecting urban heat, and (iii) investigated urban heat relationships with blue-green cover at locations frequented by pedestrians. Presence of urban green and blue spaces across the region shows potential for reducing local air temperatures by up to 5.2 °C (with urban forest). Investigating this relationship at different locations in the city revealed key districts that should potentially be targeted for reduction of pedestrian heat-impacts, due to their high pedestrian traffic, fewer green and blue spaces and high daytime air temperatures. Our results not only provide insights into the cooling effect of different amounts of green and blue features in the urban environment, but also demonstrates the application and integration potential of simplified models like TARGET to support the planning of more liveable future cities.
Cook, L. M., Good, K. D., Moretti, M., Kremer, P., Wadzuk, B., Traver, R., & Smith, V. (2024). Towards the intentional multifunctionality of urban green infrastructure: a paradox of choice?. npj Urban Sustainability, 4(1), 12 (13 pp.). doi:10.1038/s42949-024-00145-0, Institutional Repository

Decades of research on multifunctional Green Infrastructure (GI) has yet to translate into holistic implementation in the built environment. This oversight stems from assumptions that many ecosystem services occur passively and thus potential synergies are overlooked during planning and design. This study offers specific guidance for coordinating GI planning, design, and construction by examining the current state of academic literature on these aspects. It identifies 15 GI elements (e.g., green roofs) and 15 objectives (e.g., biodiversity) to collectively consider before implementation. The literature tends to isolate discussions of “engineered” GI elements with water-related objectives, while more “natural” GI are linked to biodiversity and human well-being. Coordinating across GI objectives and elements remains imperative, but evaluating too many options risks a paradox of choice. This study recommends short-term adherence to principles of adaptive design and, in the long-term, reemphasizes multifunctionality assessments, inter and transdisciplinary collaboration, and political will.
Dietzel, A., Moretti, M., & Cook, L. M. (2024). Shrinkage-based Bayesian variable selection for species distribution modelling in complex environments: an application to urban biodiversity. Ecological Informatics, 81, 102561 (9 pp.). doi:10.1016/j.ecoinf.2024.102561, Institutional Repository

Robust, quantitative understanding of the diverse ecological needs of species is needed to inform effective biodiversity conservation, now and in the future, but is lacking for most species. The advent of "big data" in ecology presents unprecedented opportunities to fill this gap and to disentangle the diverse drivers of biodiversity. Variable and model selection in sparse (small sample sizes for most species), high-dimensional (large pool of candidate predictors) problems is, however, non-trivial. Here, we employ cross-validated Bayesian projection predictive variable selection and shrinkage priors to identify, from a list of 70 ecological and biophysical candidate predictor variables, the minimal subset that best predicts the habitat preferences and distributions of 103 species of amphibians, birds, butterflies, dragonflies, and grasshoppers using the city of Zurich, Switzerland, as a case study. We contrast the predictive performance and ecological inference of models fit with the full set of predictors using shrinkage priors (exhaustive models) to models fit with a limited number of predictors obtained by compiling predictors from the full list of predictors using weakly informative priors (selective models). We show that exhaustive models excel in predictive performance, albeit at the cost of greater model complexity compared to selective models. Results from the selective models reveal the importance of access to aquatic habitat for a wide range of taxa, relative to other drivers such as urbanisation, vegetation and environmental hazards. These results are complemented by more nuanced insights from the exhaustive models into the importance of specific types of aquatic habitat (ponds, lakes, streams) and vegetation (herb, shrub, canopy cover) for the distribution of urban biodiversity, as well as the different spatial scales at which drivers are of predictive relevance. Our findings demonstrate the potential of shrinkage-based Bayesian variable selection to leverage big ecological data for species distribution modelling, and contribute to the development of concrete guidelines for urban planning and infrastructure design that account for biodiversity conservation.
Duque, N., Scholten, L., & Maurer, M. (2024). Exploring transitions of sewer wastewater infrastructure towards decentralisation using the modular model TURN-Sewers. Water Research, 257, 121640 (14 pp.). doi:10.1016/j.watres.2024.121640, Institutional Repository

We present a new modular model called TURN-Sewers for exploring different adaptations of centralised wastewater infrastructure towards more decentralised wastewater systems under different urban development scenarios. The modular model is flexible and computationally efficient in exploring transitions at the city scale, allowing for the comparison of different policies and management strategies for sanitary wastewater infrastructure. TURN-Sewers includes independent modules that simulate the generation, dimensioning, deterioration, management, and calculation of performance indicators for different wastewater systems. This model can use readily available spatial information to support infrastructure planners and other stakeholders in exploring different transition pathways from centralised to decentralised wastewater infrastructure. An illustrative example demonstrates how TURN-Sewers can generate multiple future alternatives, define different infrastructure management strategies regarding system expansion, rehabilitation and transition, and assess the economic, hydraulic and structural impacts.
Duque, N., Scholten, L., & Maurer, M. (2024). When does infrastructure hybridisation outperform centralised infrastructure paradigms? – Exploring economic and hydraulic impacts of decentralised urban wastewater system expansion. Water Research, 254, 121327 (13 pp.). doi:10.1016/j.watres.2024.121327, Institutional Repository

We explore the dynamics of centralised and decentralised wastewater infrastructure across various scenarios and introduce novel insights into their performance regarding structural vulnerability, hydraulic capacity, and costs. This study determines circumstances under which infrastructure hybridisation outperforms traditional centralised infrastructure paradigms. We combined system analysis to map out the modelling problem with the model-based exploration of the transition space using the novel TURN-Sewers model. System diagramming was used to identify the parameters or combinations of parameters that significantly influence the performance indicators being assessed. This allowed the creation of relevant simulation scenarios to identify circumstances where a decentralised sewer system could outperform a centralised one. TURN-Sewers was applied to model the infrastructure maintenance and generation of new infrastructure over 20 years for a municipality on the Swiss Plateau, considering a population growth rate of 0.03 a−1. Results show that decentralisation in expansion areas with higher densification can outperform the hydraulic performance and structural vulnerability of expanding centralised sanitary wastewater infrastructure. Decentralised systems can also offer economic advantages when capital expenditure costs for small-scale wastewater treatment plants are significantly reduced compared to current costs, particularly at higher discount rates, e.g. reaping effects of economies of scale. The findings of this study emphasise the potential of transition pathways towards decentralisation in urban water infrastructures and the value of models that allow the exploration of this transition space.
Fappiano, F., Maurer, M., & Leitão, J. P. (2024). Coupling sewers to the surface: systematic approaches to correcting data discrepancies for 1D-2D drainage modelling. Journal of Hydrology, 645, 132239 (14 pp.). doi:10.1016/j.jhydrol.2024.132239, Institutional Repository

One-dimensional (1D) drainage models coupled with two-dimensional (2D) surface models have been recognised as most suitable for simulating pluvial floods in urban areas. However, discrepancies between the 1D drainage network and the 2D Digital Terrain Model (DTM) surface elevation datasets are often observed. These incompatibilities are commonly adjusted manually, impacting the transparency and reproducibility of flood modelling results. No automated and reproducible methods are currently available to ensure compatibility and consistency between a 1D drainage network and the 2D DTM elevation dataset. We present two methods for automatically correcting these discrepancies: Method 1, which corrects the discrepancies by editing the 1D drainage network, and Method 2, which corrects the discrepancies by editing the elevation of the 2D surface. Both methods ensure 1D–2D data compatibility. The two methods were evaluated through hydraulic and hydrological simulations using a synthetic case study, demonstrating strong performance for both approaches. Additionally, we propose a procedure to guide practitioners and modellers in discerning between 1D data and 2D data errors and choosing which method to use. This procedure is demonstrated for a real case study. The two presented methodologies can improve the process of creating 1D-2D urban drainage models and their reproducibility.
Hassoun, L., & Cook, L. M. (2024). Global analysis of combined photovoltaic green and cool roofs under climate change. Advanced Sustainable Systems. doi:10.1002/adsu.202400097, Institutional Repository

Sustainable roofing configurations, including green and white roofs, can reduce rooftop surface temperatures compared to conventional surfaces and can therefore enhance photovoltaic (PV) system performance due to the temperature dependence of PV cells. Previous research, primarily experimental, recognized the synergy of combining PV with green or cool roofs. However, the influence of geographic and climatic factors on the performance of these combined systems, particularly in future climates affected by climate change, remains unclear. This work integrates three roof configurations (gravel, green, and white) into rooftop solar energy modeling across thirteen cities with different climate types, under current and future climate scenarios. Results indicate limited efficiency gains (< 2%) across all cities and climates, challenging previous findings. Yield is expected to increase in some cities receiving more solar irradiation in the future but decrease in others due to rising temperatures. Green and cool roofs can partially offset the effects of climate change on yield. PV-white roofs consistently outperform PV-green roofs, with the performance gap expected to widen in future climates. PV-green roofs excel in tropical climates with high irradiation and precipitation levels. Overall, the outcomes of this study inform the design and planning of sustainable buildings in response to climate change challenges.
Ho, H. C., & Altermatt, F. (2024). Predicted community consequences of spatially explicit global change-induced processes on plant–insect networks. Ecology and Evolution, 14(9), e70272 (13 pp.). doi:10.1002/ece3.70272, Institutional Repository

Plant–insect trophic systems should be particularly sensitive to processes altering species spatial co-occurrences, as impacts on one level can cascade effectively through the strong trophic reliance to the other level. Here, we predicted the biogeography of Lepidoptera–plant communities under global-change scenarios, exploiting spatially resolved data on 423 Lepidoptera species and their 848 food plants across the German state of Baden-Württemberg (ca. 36,000 km2). We performed simulations of plant extinction and Lepidoptera expansion, and respectively assessed their cascading consequences—namely secondary extinction of Lepidoptera and change in functional distance of plants—on the interaction networks. Importantly, the simulations were spatially explicit, as we accounted for realistic landscape contexts of both processes: Plant extinctions were simulated as "regional" (a species goes extinct in the whole region at once) vs. "isolation-driven" (a species gradually goes extinct from the peripheral or isolated localities according to its real regional distribution); Lepidoptera expansions were simulated with random, northward, and upward directions according to real topography. The consequences were assessed based on empirical community composition and trophic relationships. When evaluated by regional richness, the robustness of Lepidoptera assemblages against secondary extinctions was higher under isolation-driven plant extinctions than regional plant extinction; however, this relationship was reversed when evaluated by averaged local richness. Also, with isolation-driven plant extinctions, Lepidoptera at the central sub-region of Baden-Württemberg appeared to be especially vulnerable. With Lepidoptera expansions, plants' functional distances in local communities dropped, indicating a possible increase of competition among plants, yet to a lesser extent particularly with upward movements. Together, our results suggested that the communities' composition context at the landscape scale (i.e., how communities, with respective species composition, are arranged within the landscape) matters when assessing global-change influences on interaction systems; spatially explicit consideration of such context can reveal localised consequences that are not necessarily captured via a spatially implicit, regional perspective.
Jensen, D. M. R., Mutzner, L., Wei, Y., Mikkelsen, P. S., & Vezzaro, L. (2024). Temporal variations in micropollutant inlet concentrations matter when planning the design and compliance assessment of stormwater control measures. Journal of Environmental Management, 356, 120583 (10 pp.). doi:10.1016/j.jenvman.2024.120583, Institutional Repository

Stormwater Control Measures (SCMs) contribute to reducing micropollutant emissions from separate sewer systems. SCM planning and design are often performed by looking at the hydrological performance. Assessment of pollutant removal and the ability to comply with discharge concentration limits is often simplified due to a lack of data and limited monitoring resources. This study analyses the impact of using different time resolutions of input stormwater concentrations when assessing the compliance of SCMs against water quality standards. The behaviour of three indicator micropollutants (MP - Copper, Diuron, Benzo[a]pyrene) was assessed in four SCM archetypes, which were defined to represent typical SCM removal processes. High resolution MP data were extrapolated by using high resolution (2 min) measurements of TSS over a long period (343 events). The compliance assessment showed that high resolution input concentrations can result in a different level of compliance with water quality standards, especially when discharged concentrations are close to the limit values. This study underlines the importance of considering the high temporal variability of stormwater micropollutants when planning and designing SCMs to identify the most effective solutions for stormwater pollution management and to ensure a thorough consideration of all the environmental implications.
Julian, T. R., Devaux, A. J., Brülisauer, L., Conforti, S., Rusch, J. C., Gan, C., … Ort, C. (2024). Monitoring an emergent pathogen at low incidence in wastewater using qPCR: Mpox in Switzerland. Food and Environmental Virology, 16, 269-279. doi:10.1007/s12560-024-09603-5, Institutional Repository

Wastewater-based epidemiology offers a complementary approach to clinical case-based surveillance of emergent diseases and can help identify regions with infected people to prioritize clinical surveillance strategies. However, tracking emergent diseases in wastewater requires reliance on novel testing assays with uncertain sensitivity and specificity. Limited pathogen shedding may cause detection to be below the limit of quantification or bordering the limit of detection. Here, we investigated how the definition of limit of detection for quantitative polymerase chain reaction (qPCR) impacts epidemiological insights during an mpox outbreak in Switzerland. 365 wastewater samples from three wastewater treatment plants in Switzerland from 9 March through 31 October 2022 were analyzed for mpox DNA using qPCR. We detected mpox DNA in 22% (79 of 365) wastewater samples based on a liberal definition of qPCR detection as any exponentially increasing fluorescence above the threshold. Based on a more restrictive definition as the lowest concentration at which there is 95% likelihood of detection, detection was 1% (5 of 365). The liberal definition shows high specificity (90%) and accuracy (78%), but moderate sensitivity (64%) when benchmarked against available clinical case reporting, which contrasts with higher specificity (98%) but lower sensitivity (10%) and accuracy (56%) of the 95% likelihood definition. Wastewater-based epidemiology applied to an emergent pathogen will require optimizing public health trade-offs between reporting data with high degrees of uncertainty and delaying communication and associated action. Information sharing with relevant public health stakeholders could couple early results with clear descriptions of uncertainty. Impact Statement: When a novel pathogen threatens to enter a community, wastewater-based epidemiology offers an opportunity to track its emergence and spread. However, rapid deployment of methods for to detect a novel pathogen may rely on assays with uncertain sensitivity and specificity. Benchmarking the detection of mpox DNA in Swiss wastewaters with reported clinical cases in 2022, we demonstrate how definitions of detection of a qPCR assay influence epidemiological insights from wastewater. The results highlight the need for information sharing between public health stakeholders that couple early insights from wastewater with descriptions of methodological uncertainty to optimize public health actions.
Lechevallier, P., Villez, K., Felsheim, C., & Rieckermann, J. (2024). Towards non-contact pollution monitoring in sewers with hyperspectral imaging. Environmental Science: Water Research and Technology, 10(5), 1160-1170. doi:10.1039/D3EW00541K, Institutional Repository

Monitoring water quality in sewers is challenging, particularly because state-of-the-art technologies require contact with the raw wastewater. The presence of fat, oil, grease, and solids makes automated grab sampling difficult and causes sensor fouling. To overcome these limitations, non-contact methods based on light reflectance, such as hyperspectral imaging (HSI), are gaining attention. However, HSI has never been tested for raw wastewater. To assess its accuracy for measuring pollution, we developed a laboratory setup and performed targeted experiments with a combination of raw and diluted wastewater, as well as synthetic turbidity stock solutions. We measured seven pollution variables: chemical oxygen demand, turbidity, dissolved organic compounds, ammonium, total nitrogen, phosphate, and sulphates. We used automated pixel selection and partial least squares regression to retrieve pollution information from the hyperspectral images. Our results, based on 144 samples, suggest that HSI can estimate pollution levels with a precision in the range of state-of-the-art absorbance spectrophotometric methods. Additionally, we found that the combination of pixel and wavelength selection, enabled by the hyperspectral data structure, significantly influences the performance of partial least square modelling. Overall, our findings indicate that HSI is a promising technology for non-contact monitoring of water quality in raw wastewater.
Li, S., Leitão, J. P., Wang, Z., & Bach, P. M. (2024). A drainage network-based impact matrix to support targeted blue-green-grey stormwater management solutions. Science of the Total Environment, 912, 168623 (10 pp.). doi:10.1016/j.scitotenv.2023.168623, Institutional Repository

Urban floods will continue to be an alarming issue worldwide due to climate change and urban expansion. The costly and less environmentally friendly grey infrastructure is not always the most adequate solution to resolve urban pluvial flooding issues. The combination of grey and blue-green infrastructures, also called hybrid infrastructure, has been considered a promising solution for urban stormwater management. Existing approaches for identifying suitable hybrid solutions frequently rely on global multi-objective optimization algorithms. We developed a pre-screening method that decomposes a drainage network into clusters of pipes connected to sub-catchments, based on pipe hydraulic characteristic that allows for the impact of infrastructure combinations (blue-green and grey) to be mapped. Four impact matrices are proposed to map the total, local, upstream, and downstream flood reduction of all possible blue-green, grey, and hybrid solutions. Using an urban catchment in Guangzhou (China) as a case study, results showed that such an exercise could identify prime candidate locations for blue-green and grey infrastructure while filtering out ineffective locations for flood reduction. Furthermore, the impact matrices enabled the identification of flood zones where blue-green infrastructure could handle flood mitigation without the need of local grey infrastructure upgrades. As such, they are not only useful for quick screening of suitable interventions for each flooded zone, but can also potentially serve as a priori knowledge before diving into the data and computationally expensive process of finding the most effective flood mitigation solutions.
Liu, H., Kong, F., Yin, H., Cook, L. M., Huang, J., Lensky, I. M., & Tan, T. (2024). Substrate microorganisms can be an ideal tool for improving green roof sustainability. Urban Forestry and Urban Greening, 91, 128179 (11 pp.). doi:10.1016/j.ufug.2023.128179, Institutional Repository

Green roof (GR) ecosystems function as a result of a series of complex interactions between plants and substrates, which are poorly understood. This ambiguity hinders the scientific application of GRs to tackle urban eco-environmental problems. The goal of this study was to clarify the response of plants to various abiotic and biotic characteristics of GR substrates, including physical properties, nutrients, and microbes. We systematically analyzed the statistical association between 43 indicators of plant and substrate characteristics using four GR substrates and one common plant type (Sedum lineare Thunb) in a subtropical monsoon climate. Height, coverage, root-shoot ratio, total carbon, total nitrogen, total phosphorus, total potassium, root vitality, and malondialdehyde levels were considered sensitive indicators of the plant's response to the substrate. Substrate nutrients and microbial biomass were most closely associated with the plant response, whereas the material properties of the substrate could indirectly affect plant growth by influencing substrate microbes and plant nutrients. Our results suggest that when optimizing GR substrates for plant responses, it is necessary to respect the plants and account for the abiotic and biotic relationships. It may be possible to manage GR performance in a more scientific and effective manner through the control of substrate microorganisms.
Martínez-Núñez, C., Casanelles Abella, J., Frey, D., Zanetta, A., & Moretti, M. (2024). Local and landscape factors shape alpha and beta trophic interaction diversity in urban gardens. Proceedings of the Royal Society B: Biological Sciences, 291(2023), 20232501 (12 pp.). doi:10.1098/rspb.2023.2501, Institutional Repository

Promoting urban green spaces is an effective strategy to increase biodiversity in cities. However, our understanding of how local and landscape factors influence trophic interactions in these urban contexts remains limited. Here, we sampled cavity-nesting bees and wasps and their natural enemies within 85 urban gardens in Zurich (Switzerland) to identify factors associated with the diversity and dissimilarity of antagonistic interactions in these communities. The proportions of built-up area and urban green area at small landscape scales (50 m radius), as well as the management intensity, sun exposure, plant richness and proportion of agricultural land at the landscape scale (250 m radius), were key drivers of interaction diversity. This increased interaction diversity resulted not only from the higher richness of host and natural enemy species, but also from species participating in more interactions. Furthermore, dissimilarity in community structure and interactions across gardens (beta-diversity) were primarily influenced by differences in built-up areas and urban green areas at the landscape scale, as well as by management intensity. Our study offers crucial insights for urban planning and conservation strategies, supporting sustainability goals by helping to understand the factors that shape insect communities and their trophic interactions in urban gardens.
Micev, K., Steiner, J., Aydin, A., Rieckermann, J., & Delbruck, T. (2024). Measuring diameters and velocities of artificial raindrops with a neuromorphic event camera. Atmospheric Measurement Techniques, 17(1), 335-357. doi:10.5194/amt-17-335-2024, Institutional Repository

Hydrometers that measure size and velocity distributions of precipitation are needed for research and corrections of rainfall estimates from weather radars and microwave links. Existing optical disdrometers measure droplet size distributions, but underestimate small raindrops and are impractical for widespread always-on IoT deployment. We study the feasibility of measuring droplet size and velocity using a neuromorphic event camera. These dynamic vision sensors asynchronously output a sparse stream of pixel brightness changes. Droplets falling through the plane of focus of a steeply down-looking camera create events generated by the motion of the droplet across the field of view. Droplet size and speed are inferred from the hourglass-shaped stream of events. Using an improved hard disk arm actuator to reliably generate artificial raindrops with a range of small sizes, our experiments show maximum errors of 7% (mean absolute percentage error) for droplet sizes from 0.3 to 2.5mm and speeds from 1.3 to 8.0ms-1. Measurements with the same setup from a commercial PARSIVEL disdrometer show similar results. Both devices slightly overestimate the small droplet volume with a volume overestimation of 25% from the event camera measurements and 50% from the PARSIVEL instrument. Each droplet requires processing of 5000 to 50000 brightness change events, potentially enabling low-power always-on disdrometers that consume power proportional to the rainfall rate. Data and code are available at the paper website https://sites.google.com/view/dvs-disdrometer/home .
Nadeau, S., Devaux, A. J., Bagutti, C., Alt, M., Hampe, E. I., Kraus, M., … Stadler, T. (2024). Influenza transmission dynamics quantified from RNA in wastewater in Switzerland. Swiss Medical Weekly, 154(1), 3503 (20 pp.). doi:10.57187/s.3503, Institutional Repository

INTRODUCTION: Influenza infections are challenging to monitor at the population level due to many mild and asymptomatic cases and similar symptoms to other common circulating respiratory diseases, including COVID-19. Methods for tracking cases outside of typical reporting infrastructure could improve monitoring of influenza transmission dynamics. Influenza shedding into wastewater represents a promising source of information where quantification is unbiased by testing or treatment-seeking behaviours. METHODS: We quantified influenza A and B virus loads from influent at Switzerland's three largest wastewater treatment plants, serving about 14% of the Swiss population (1.2 million individuals). We estimated trends in infection incidence and the effective reproductive number (Re) in these catchments during a 2021/22 epidemic and compared our estimates to typical influenza surveillance data. RESULTS: Wastewater data captured the same overall trends in infection incidence as laboratory-confirmed case data at the catchment level. However, the wastewater data were more sensitive in capturing a transient peak in incidence in December 2021 than the case data. The Reestimated from the wastewater data was roughly at or below the epidemic threshold of 1 during work-from-home measures in December 2021 but increased to at or above the epidemic threshold in two of the three catchments after the relaxation of these measures. The third catchment yielded qualitatively the same results but with wider confidence intervals. The confirmed case data at the catchment level yielded comparatively less precise R_e estimates before and during the work-from-home period, with confidence intervals that included one before and during the work-fromhome period. DISCUSSION: Overall, we show that influenza RNA in wastewater can help monitor nationwide influenza transmission dynamics. Based on this research, we developed an online dashboard for ongoing wastewater-based influenza surveillance in Switzerland.
Peleg, N., Wright, D. B., Fowler, H. J., Leitão, J. P., Sharma, A., & Marra, F. (2024). A simple and robust approach for adapting design storms to assess climate-induced changes in flash flood hazard. Advances in Water Resources, 193, 104823 (9 pp.). doi:10.1016/j.advwatres.2024.104823, Institutional Repository

Hydrologists and civil engineers often use design storms to assess flash flood hazards in urban, rural, and mountainous catchments. These synthetic storms are not representations of real extreme rainfall events, but rather simplified versions parameterized to mimic extreme precipitation statistics often obtained from intensity–duration–frequency (IDF) curves. To construct design storms for the future climate, it is thus necessary first to recalculate IDF curves to represent rainfall under warmer conditions. We propose a framework for adjusting IDF curves and design storms to future climate conditions using the TENAX model, a novel statistical approach that can provide future short-duration precipitation return levels based on projected temperature changes. For most applications, information from climate models at the daily scale can be used to construct design storms at the sub-hourly scale without any downscaling or bias adjustment. Our approach is illustrated through a re-parameterization of the Chicago Design Storm (CDS) in the context of climate change. As a case study demonstration, we apply the TENAX model to data from the city of Zurich to calculate changes in the historical IDF curve for durations ranging from 10 min to 3 h. We then construct synthetic 100-year return period design storms based on the CDS for present and future climates and use the CAFlood model to produce flood inundation maps to assess changes in flood hazard. The codes for adapting design storms to climate change are simple to implement, easily applicable by practitioners, and made freely available.
Perrelet, K., Moretti, M., Dietzel, A., Altermatt, F., & Cook, L. M. (2024). Engineering blue-green infrastructure for and with biodiversity in cities. npj Urban Sustainability, 4(1), 27 (11 pp.). doi:10.1038/s42949-024-00163-y, Institutional Repository

Blue-green infrastructure (BGI), combining semi-natural and engineered elements, offers multifaceted benefits like stormwater management, water purification, heat mitigation, and habitat provision. However, current BGI designs prioritize engineering goals, overlooking its ecological potential. Here we advocate for integrating engineering and ecological objectives into BGI design to enhance performance and biodiversity. Through an interdisciplinary literature review, we emphasize the importance of species diversity, abundance, and ecological processes, to improve engineering performance and resilience, and lower management costs. We emphasize the importance of interdisciplinary collaboration to navigate trade-offs between engineering and ecological objectives, ultimately enabling us to engineer both for and with biodiversity.
Poggioli, M., Cavadini, G. B., Zheng, Z., Rodriguez, M., & Mutzner, L. (2024). The impact of blue-green infrastructure on trace contaminants: a catchment-wide assessment. Water Research X, 25, 100261 (11 pp.). doi:10.1016/j.wroa.2024.100261, Institutional Repository

Blue-green infrastructure (BGI) reduce urban combined sewer overflows (CSOs) and stormwater outlets (SWOs). However, most conventional BGI are not designed to remove trace organic contaminants. Little is known about the potential of conventional BGI to improve surface water quality by reducing the discharge of trace organic contaminants. We derived wash-off loads for street runoff (6PPD-q, DPG, and HMMM), construction materials (diuron), and wastewater-derived contaminants (diclofenac) based on measurements in the combined sewer system. Subsequently, the performance of four BGI types (bioretention cells, green roofs, porous pavements, and urban wetlands) to reduce the discharge of trace organic contaminants via SWOs and CSOs was quantified with a hydrodynamic SWMM model. Moreover, the catchment-wide impact of SWOs and CSOs on surface water was assessed using risk quotients. We found that the annually discharged load can be considerably reduced by implementing BGI. Among the studied BGI types, bioretention cells are the most effective, with a load reduction of up to 80% to surface waters, mainly due to a larger suitable implementation area and a substantial stormwater infiltration. BGI implemented in the separate sewer system are more effective in reducing stormwater contaminant loads than BGI in the combined system. The assessment of the risk quotient in the surface water showed that the concentrations during SWO and CSO discharges exceed the acute environmental threshold in the surface water for 6PPD-q, DPG, diuron, and diclofenac during several events. The implementation of BGI reduced the hours of exceeded risk quotient in the surface water by 93% for bioretention cells. These findings underscore the need for a catchment-wide assessment of future BGI implementations to quantify, manage, and mitigate the impacts of urban pollution.
Regueiro-Picallo, M., Langeveld, J., Wei, H., Bertrand-Krajewski, J. L., & Rieckermann, J. (2024). Combining a daily temperature pattern analysis and a heat-pulse system to estimate sediment depths in sewer systems. Environmental Science: Water Research and Technology, 10(4), 922-935. doi:10.1039/d3ew00825h, Institutional Repository

Sediments in urban drainage systems (UDS) significantly impact their operation, so effective strategies are required to reduce their negative effects. Monitoring sediment accumulation provides valuable insights into sediment characteristics, sediment transport dynamics, and system performance. However, the effectiveness of monitoring systems is limited due to cost constraints and installation challenges. This study describes the development and application of a new system based on temperature dynamics to measure sediment depths in sewer systems. The methodology involves the analysis of temperature time series under dry weather flow conditions to identify harmonic patterns between wastewater and sediment-bed temperatures. These patterns are increasingly attenuated by increasing sediment depth. This study combines a system called MONitoring Temperatures in SEdiments (MONTSE), which integrates a dual-probe heat-pulse (DPHP) method to characterize sediment thermal properties, and a surrogate model, which includes temperature pattern analysis, to estimate sediment depths. Likewise, laboratory-scale experiments were performed to validate the temperature monitoring system and the surrogate model performance. The maximum absolute errors in measured sediment depths were less than 22 mm, and the uncertainty of the system was estimated at ±7.3 mm. Groundbreaking measurements of thermal properties of UDS sediments were also reported. Reliable information on sediment depths and properties was provided, so the system could significantly optimize sewer system operation and cleaning strategies.
Rodriguez, M., Cavadini, G. B., & Cook, L. M. (2024). Do baseline assumptions alter the efficacy of green stormwater infrastructure to reduce combined sewer overflows?. Water Research, 253, 121284 (12 pp.). doi:10.1016/j.watres.2024.121284, Institutional Repository

Green stormwater infrastructure (GSI) is growing in popularity to reduce combined sewer overflows (CSOs) and hydrologic simulation models are a tool to assess their reduction potential. Given the numerous and interacting water flows that contribute to CSOs, such as evapotranspiration (ET) and groundwater (GW), these models should ideally account for them. However, due to the complexity, simplified models are often used, and it is currently unknown how these assumptions affect estimates of CSOs, GSI effectiveness, and ultimately planning guidance. This study evaluates the effect on estimates of CSOs and GSI effectiveness when different flows and hydrologic processes are neglected. We modified an existing EPA SWMM model of a combined sewer system in Switzerland to include ET, GW, and upstream inflows. Historical rainfall data over 30 years are used to assess volume and duration of CSOs with and without three types of GSI (bioretention basins, permeable pavements and green roofs). Results demonstrate that neglect of certain flows in modelling can alter CSO volumes from -15 % to 40 %. GSI effectiveness also varies considerably, resulting in differences in simulated percent of CSO volume reduced from 8 % to 35 %, depending on the GSI type and modeled flow or process. Representation of GW within models is particularly crucial when infiltrating GSI are present, as CSOs could increase in certain subcatchments due to higher GW levels from increased infiltration. When basing GSI planning decisions on modeled estimates of CSOs, all relevant hydrologic processes should be included to the extent possible, and uncertainty and assumptions should always be considered.
Rodriguez, M., Fu, G., Butler, D., Yuan, Z., & Cook, L. (2024). The effect of green infrastructure on resilience performance in combined sewer systems under climate change. Journal of Environmental Management, 353, 120229 (12 pp.). doi:10.1016/j.jenvman.2024.120229, Institutional Repository

Climate change is currently reshaping precipitation patterns, intensifying extremes, and altering runoff dynamics. Particularly susceptible to these impacts are combined sewer systems (CSS), which convey both stormwater and wastewater and can lead to combined sewer overflow (CSO) discharges during heavy rainfall. Green infrastructure (GI) can help mitigate these discharges and enhance system resilience under historical conditions; however, the quantification of its effect on resilience in a future climate remains unknown in the literature. This study employs a modified Global Resilience Analysis (GRA) framework for continuous simulation to quantify the impact of climate change on CSS resilience, particularly CSOs. The study assesses the efficacy of GI interventions (green roofs, permeable pavements, and bioretention cells) under diverse future rainfall scenarios based on EURO-CORDEX regional climate models (2085–2099) and three Representative Concentration Pathways (2.6, 4.5, 8.5 W/m2). The findings underscore a general decline in resilience indices across the future rainfall scenarios considered. Notably, the total yearly CSO discharge volume increases by a range of 145 % to 256 % in response to different rainfall scenarios. While GI proves effective in increasing resilience, it falls short of offsetting the impacts of climate change. Among the GI options assessed, green roofs routed to pervious areas exhibit the highest adaptive capacity, ranging from 9 % to 22 % at a system level, followed by permeable pavements with an adaptation capacity between 7 and 13 %. By linking the effects of future rainfall scenarios on CSO performance, this study contributes to understanding GI's potential as a strategic tool for enhancing urban resilience.
Salgueiro-Gonzalez, N., Béen, F., Bijlsma, L., Boogaerts, T., Covaci, A., Baz-Lomba, J. A., … Castiglioni, S. (2024). Influent wastewater analysis to investigate emerging trends of new psychoactive substances use in Europe. Water Research, 254, 121390 (11 pp.). doi:10.1016/j.watres.2024.121390, Institutional Repository

Wastewater-based epidemiology (WBE) can provide objective and timely information on the use of new psychoactive substances (NPS), originally designed as legal alternatives of internationally controlled drugs. NPS have rapidly emerged on the global drug market, posing a challenge to drug policy and constituting a risk to public health. In this study, a WBE approach was applied to monitor the use of more than 300 NPS, together with fentanyl and its main metabolite norfentanyl, in influent wastewater collected from 12 European cities during March-June 2021. Quantitative and qualitative analysis of NPS in composite 24 h influent wastewater samples were based on solid phase extraction and liquid chromatography-mass spectrometry. In-sample stability tests demonstrated the suitability of most investigated biomarkers, except for a few synthetic opioids, synthetic cannabinoids and phenetylamines. Fentanyl, norfentanyl and eight NPS were quantified in influent wastewater and at least three substances were found in each city, demonstrating their use in Europe. N,N-dimethyltryptamine and 3-methylmethcathinone (3-MMC) were the most common NPS found, with the latter having the highest mass loads (up to 24.8 mg/day/1000 inhabitants). Seven additional substances, belonging to five categories of NPS, were identified in different cities. Spatial trends of NPS use were observed between cities and countries, and a changing weekly profile of use was observed for 3-MMC. WBE is a useful tool to rapidly evaluate emerging trends of NPS use, complementing common indicators (i.e. population surveys, seizures) and helping to establish measures for public health protection.
Van Wichelen, N., Burgard, D., Campos-Mañas, M. C., Simarro-Gimeno, C., Hernández, F., Ort, C., … Bijlsma, L. (2024). A key factor in monitoring cannabis consumption trends through wastewater analysis: partitioning of THC[sbnd]COOH between the liquid and solid phase of influent wastewater. Water Research, 267, 122462 (9 pp.). doi:10.1016/j.watres.2024.122462, Institutional Repository

Current wastewater-based epidemiology (WBE) studies are predominantly focused on the analysis of urinary biomarkers present in the liquid phase of influent wastewater (IWW). This approach systematically underestimates less polar metabolites, such as cannabis biomarkers. These biomarkers can potentially sorb to and desorb from suspended particulate matter (SPM) present in IWW. This study investigates the bidirectional partitioning of THC[sbnd]COOH between the liquid phase and SPM of IWW by performing multiple sorption experiments using THC[sbnd]COOH-D9 as a surrogate due to the unavailability of blank SPM and blank IWW. In addition, this study involves the analysis of IWW collected from eight wastewater treatment plants (WWTP) (n = 56) across four European countries, where raw IWW, the liquid phase and SPM were separately analysed to identify potential trends in the fraction of THC[sbnd]COOH in the SPM between and withing the examined locations. Based on the performed sorption experiments, bidirectional partitioning of THC[sbnd]COOH between the liquid phase and SPM was noted, showing partition between both phases when only one of the two phases was spiked. It was illustrated that the concentration of SPM had a notable influence on the THC[sbnd]COOH partitioning between both phases. In addition to the inter location variability (average THC[sbnd]COOH present in the SPM ranged 31–59 %), a substantial intra location variation was also observed, e.g., in one location ranged 17–58 %. While the determination of a correction factor for the amount of THC[sbnd]COOH present in SPM would be ideal, this is challenging, since the amount of SPM is not fixed in all IWW samples. Although SPM has influence on the THC[sbnd]COOH partition, no correlation (p value Spearman correlation = 0.3160) was observed between the SPM concentration and the fraction of THC[sbnd]COOH in the solid phase. Moreover, the collection of homogenized samples is difficult, and the time required to reach an equilibration in partitioning of THC[sbnd]COOH between both IWW phases remains unclear. Due to i) the large inter-and intra-location variation of THC[sbnd]COOH present in the SPM, ii) the variability in SPM concentration in IWW samples, and iii) the time required to reach a partitioning equilibration, an analytical procedure based on liquid-liquid extraction (LLE) that considers both the liquid phase and SPM of IWW is recommended to reduce the overall uncertainty for THC[sbnd]COOH measurement in IWW. It was illustrated that this extraction method is capable to recover the total concentration of THC[sbnd]COOH in both phases.
Wang, W., Wang, Z., Guan, M., Wani, O., Bai, Y., Wang, K., & Leitao, J. P. (2024). Evaluation of stormwater mitigation performance with LID infrastructures, in-sewer space, and real-time control strategies. Journal of Hydrologic Engineering, 29(5), 05024016 (14 pp.). doi:10.1061/JHYEFF.HEENG-6185, Institutional Repository

Because low-impact development (LID) infrastructures are effective in capturing and utilizing urban stormwater runoff, real-time control (RTC) strategies can be viewed as soft infrastructures, offering an additional suite of opportunities to improve the stormwater drainage system performance. However, there is a paucity of analyses that disentangle the contributing sources of performance enhancement in these joint hard-soft stormwater infrastructures. This study evaluated the stormwater system performance with integrated LID infrastructures, in-sewer storage capacity, and RTC strategies. Our results showed that LID infrastructures play a major role in mitigating the flow peaks and high volumes, whereas adding RTC to the storage unit and in-sewer flow control mostly improves the performance under relatively small rainfall events, e.g., those with a 3-year return period. The critical contribution of RTC is realized by utilizing storage units as much as possible during the rainfall event. A downstream storage unit that is too close to the outfall may not be suitable for RTC application together with in-sewer capacity utilization. In the present case, the combination of a midstream storage unit and upstream control site at branch pipes worked better than those at other locations. The results suggest that the integration of LID and RTC on a simulation-system level can enhance the reduction of the peak runoff and total discharged volume only if the storage site and control locations are selected carefully.
Yin, Y., Zhang, D., Zhu, M., Zhang, H., Liu, D., Sun, Y., … Wang, P. (2024). Improving land-use efficiency of solar power in China and policy implications. Solar Energy, 280, 112867 (11 pp.). doi:10.1016/j.solener.2024.112867, Institutional Repository

Improving the power output of solar photovoltaic (PV) farms is critical to maximize the potential of PV power and reduce extensive land use in the context of large-scale deployment of renewable energy. In this paper we developed an integrated solar power potential assessment framework to quantify the gap between technical potential and actual generation of solar PV farms on national, provincial, and plant scales, and identify the key factors that cause the underperformance of PV farms. Specifically, to assess technical potential, hourly meteorological reanalysis data is adopted and the power generation-related parameters are calculated (i.e. optimal panel tilt, array spacing, packing factor etc.) with consideration of their spatial variability. For actual power generation, a detailed plant-level dataset is first established by this study which integrates technical, operational, and geospatial information from 145 solar farms across seven provinces in China. Our results show that the actual PV power generation per square meter is only 1/3 of the estimated technical potential. Technological factor is the primary factor, accounting for 48.43% of the underperformance, followed by engineering and management factors, accounting for 38.55% and 13.02%, respectively. The novelty of our study is revealing the underperformance level of solar farms in reality, identifying the causing factors, and highlighting the importance of integrating land-use efficiency indicators into solar power planning and development.
Zhang, K., Zheng, Z., Mutzner, L., Shi, B., McCarthy, D., Le-Clech, P., … Deletic, A. (2024). Review of trace organic chemicals in urban stormwater: concentrations, distributions, risks, and drivers. Water Research, 258, 121782 (11 pp.). doi:10.1016/j.watres.2024.121782, Institutional Repository

Urban stormwater, increasingly seen as a potential water resource for cities and towns, contains various trace organic chemicals (TrOCs). This study, conducted through a comprehensive literature review of 116 publications, provides a detailed report on the occurrence, concentration distribution, health, and ecological risks of TrOCs, as well as the impact of land use and rainfall characteristics on their concentrations. The review uncovers a total of 629 TrOCs detected at least once in urban stormwater, including 228 pesticides, 132 pharmaceutical and personal care products (PPCPs), 29 polycyclic aromatic hydrocarbons (PAHs), 30 per- and polyfluorinated substances (PFAS), 28 flame retardants, 24 plasticizers, 22 polychlorinated biphenyls (PCBs), nine corrosion inhibitors, and 127 other industrial chemicals/intermediates/solvents. Concentration distributions were explored, with the best fit being log-normal distribution. Risk assessment highlighted 82 TrOCs with high ecological risk quotients (ERQ > 1.0) and three with potential health risk quotients (HQ > 1.0). Notably, 14 TrOCs (including six PAHs, five pesticides, three flame-retardants, and one plasticizer) out of 68 analyzed were significantly influenced by land-use type. Relatively weak relationships were observed between rainfall characteristics and pollutant concentrations, warranting further investigation. This study provides essential information about the occurrence and risks of TrOCs in urban stormwater, offering valuable insights for managing these emerging chemicals of concern.
Back, Y., Kumar, P., Bach, P. M., Rauch, W., & Kleidorfer, M. (2023). Integrating CFD-GIS modelling to refine urban heat and thermal comfort assessment. Science of the Total Environment, 858(1), 159729 (14 pp.). doi:10.1016/j.scitotenv.2022.159729, Institutional Repository

Constant urban growth exacerbates the demand for residential, commercial and traffic areas, leading to progressive surface sealing and urban densification. With climate change altering precipitation and temperature patterns worldwide, cities are exposed to multiple risks, demanding holistic and anticipatory urban planning strategies and adaptive measures that are multi-beneficial. Sustainable urban planning requires comprehensive tools that account for different aspects and boundary conditions and are capable of mapping and assessing crucial processes of land-atmosphere interactions and the impacts of adaptation measures on the urban climate system. Here, we combine Computational Fluid Dynamics (CFD) and Geographic Information System (GIS) capabilities to refine an existing 2D urban micro- and bioclimatic modelling approach. In particular, we account for the vertical and horizontal variability in wind speed and air temperature patterns in the urban canopy layer. Our results highlight the importance of variability of these patterns in analysing urban heat development, intensity and thermal comfort at multiple heights from the ground surface. Neglecting vertical and horizontal variability, non-integrated CFD modelling underestimates mean land surface temperature by 7.8 °C and the Universal Thermal Climate Index by 6.9 °C compared to CFD-integrated modelling. Due to the strong implications of wind and air temperature patterns on the relationship between surface temperature and human thermal comfort, we urge caution when relying on studies solely based on surface temperatures for urban heat assessment and hot spot analysis as this could lead to misinterpretations of hot and cool spots in cities and, thus, mask the anticipated effects of adaptation measures. The integrated CFD-GIS modelling approach, which we demonstrate, improves urban climate studies and supports more comprehensive assessments of urban heat and human thermal comfort to sustainably develop resilient cities.
Blach, T., Lechevallier, P., & Engelhart, M. (2023). Effect of temperature during the hydrothermal carbonization of sewage sludge on the aerobic treatment of the produced process waters. Journal of Water Process Engineering, 51, 103368 (9 pp.). doi:10.1016/j.jwpe.2022.103368, Institutional Repository

The treatment of the highly contaminated process water produced during the hydrothermal carbonization (HTC) of waste activated sludge is of major concern for the full-scale implementation of the HTC process. So far, no satisfying treatment strategies have been elaborated and the biodegradability under aerobic conditions has hardly been studied. To fill these gaps, aerobic tests were first carried out in batches with HTC process waters produced at 190 °C, 218 °C and 249 °C, and two parallel sequencing batch reactors (SBR) were operated to treat process waters produced at 190 °C and 217 °C. Both experiments show that the HTC temperature has only a little effect on the elimination of dissolved organic carbon (DOC). In the aerobic batch tests, DOC removal were 80.5–81.9 %. In the SBR, 28 % of the initial DOC was found to be recalcitrant, and 25–28 % of the initial nitrogen. In the SBR experiments, the nitrification was also monitored, and nitrification inhibition test were conducted on both process waters obtained at 190 °C and 217 °C. Nitrification the initial SBR reactors was only possible after dilution of the process waters, which indicates the presence of inhibiting substances. The inhibition tests validated those observations, and showed that process waters derived at 217 °C had a higher inhibition potential. This study demonstrates that aerobically treated HTC process waters are still too polluted to be discharged in a wastewater treatment plant: model calculations showed an increase in effluent DOC of 8.3 mg C/L.
Boebel, M., Frei, F., Blumensaat, F., Ebi, C., Meli, M. L., & Rüst, A. (2023). Batteryless sensor devices for underground infrastructure - a long-term experiment on urban water pipes. Journal of Low Power Electronics and Applications, 13(2), 31 (23 pp.). doi:10.3390/jlpea13020031, Institutional Repository

Drinking water is becoming increasingly scarce as the world’s population grows and climate change continues. However, there is great potential to improve drinking water pipelines, as 30% of fresh water is lost between the supplier and consumer. While systematic process monitoring could play a crucial role in the early detection and repair of leaks, current practice requires manual inspection, which is both time-consuming and costly. This project envisages maintenance-free measurements at numerous locations within the underground infrastructure, a goal that is to be achieved through the use of a harvesting device mounted on the water pipe. This device extracts energy from the temperature difference between the water pipe and the soil using a TEG (thermoelectric generator), takes sensor measurements, processes the data and transmits it wirelessly via LoRaWAN. We built 16 harvesting devices, installed them in four locations and continuously evaluated their performance throughout the project. In this paper, we focus on two devices of a particular type. The data for a full year show that enough energy was available on 94% of the days, on average, to take measurements and transmit data. This study demonstrates that it is possible to power highly constrained sensing devices with energy harvesting in underground environments.
Devanand, V. B., Mubeen, A., Vojinovic, Z., Sanchez Torres, A., Paliaga, G., Abdullah, A. F., … Fröhle, P. (2023). Innovative methods for mapping the suitability of nature-based solutions for landslide risk reduction. Land, 12(7), 1357 (15 pp.). doi:10.3390/land12071357, Institutional Repository

The impacts of climate change are becoming more widespread across the world, with hydro-meteorological extreme events on the rise, causing severe threats to nature and communities. Increasing trends in the frequency and intensity of floods and landslides have been projected by climate models. This necessitates the development of more effective measures such as nature-based solutions (NBS) which can complement grey infrastructures. Recent studies have identified knowledge gaps and limitations in existing research and tools that aid in spatial planning for the implementation of large-scale NBS and proposed new methodologies for the spatial allocation of large-scale NBS for flood risk reduction. This work presents a novel method for mapping the suitability of NBS addressing geo-hydrological hazards such as shallow landslides, debris flow, and rockfall, which are typically caused due to slope instability. This methodology incorporates landslide susceptibility mapping, and was used to create a toolbox ESRI ArcGIS environment to aid decision-makers in the planning and implementation of large-scale NBS. The spatial allocation toolbox was applied to the case study Portofino promontory, Liguria region, Italy, and 70% of the area was found to be highly susceptible to landslides. The produced suitability maps show that 41%, 33%, and 65% of the study area is suitable for the restoration of terraces, bio-engineering, and vegetative measures such as NBS for landslide risk reduction.
Figueroa, A., Hadengue, B., Leitão, J. P., & Blumensaat, F. (2023). A framework for modelling in-sewer thermal-hydraulic dynamic anomalies driven by stormwater runoff and seasonal effects. Water Research, 229, 119492 (10 pp.). doi:10.1016/j.watres.2022.119492, Institutional Repository

RRain-induced surface runoff and seasons lead to short- to medium-term anomalies in combined storm- and wastewater flows and temperatures, and influence treatment processes in wastewater resource recovery facilities (WRRF). Additionally, the implementation of decentralized heat recovery (HR) technologies for energy reuse in buildings affect energy-related processes across the urban water cycle and WRRFs heat inflows. However, quantitative insights on thermal-hydraulic dynamics in sewers at network scale and across different scales are very rare.
To enhance the understanding of thermal-hydraulic dynamics and the water-energy nexus across the urban water cycle we present a modular framework that couples thermal-hydraulic processes: i) on the surface, ii) in the public sewer network, iii) in households (including in-building HR systems), and iv) in lateral connections. We validate the proposed framework using field measurements at full network scale, present modelling results of extended time periods to illustrate the effect of seasons and precipitation events simultaneously, and quantify the impact of decentralized HR devices on thermal-hydraulics.
Simulation results suggest that the presented framework can predict temperature dynamics consistently all year long including short- to long-term variability of in-sewer temperature. The study provides quantitative evidence that the impact of household HR technologies on WRRF inflow heat budgets is reduced by approximately 20% during wet-weather periods in comparison to dry-weather conditions. The presented framework has potential to support multiple research initiatives that will improve the understanding of the water-energy nexus, pollutant dispersion and degradation, and support maintenance campaigns at network scale.
Furrer, V., Mutzner, L., Ort, C., & Singer, H. (2023). Micropollutant concentration fluctuations in combined sewer overflows require short sampling intervals. Water Research X, 21, 100202 (8 pp.). doi:10.1016/j.wroa.2023.100202, Institutional Repository

Combined sewer overflows (CSOs) are an important pathway of organic micropollutants from urban areas to open water bodies. Understanding the temporal dynamics of these micropollutants during overflow events is crucial for applying appropriate sampling methods and implementing effective management strategies. Yet, little is known about the dynamics of micropollutants in CSOs, because most studies report concentrations from single grab samples or event mean concentrations (EMCs). With unique high temporal resolution measurements (3 min), we show the real dynamics of polar organic micropollutants in CSOs of one small (2,700 people: P) and one large (159,000 P) urban catchment, for two micropollutant categories: (i) 33 micropollutants in municipal wastewater and (ii) 13 micropollutants from urban surface runoff. The concentration dynamics depend on the substance source and the catchment size. Indoor substances such as pharmaceuticals show high temporal dynamics with changes of 1 to 2 orders of magnitude within 9 min in the CSO of the small catchment. In contrast, outdoor substances at the small catchment and all substances at the large catchment display considerably lower variation. We tested various time-proportional sampling strategies to assess the range of error when estimating EMCs. We recommend an interval of 3 min to capture the dynamics of indoor substances in CSOs from small catchments. The results highlight that both future monitoring campaigns and the planning and management of urban wet-weather treatment systems will benefit from high temporal sampling resolutions, not only to understand dynamics but also to minimize errors of estimated EMCs.
Gobatti, L., & Leite, B. C. C. (2023). Unmanaged vegetated roofs hydrological performance in subtropical areas: an investigation in São Paulo, Brazil. Science of the Total Environment, 874, 162417 (11 pp.). doi:10.1016/j.scitotenv.2023.162417, Institutional Repository

Extensive vegetated roofs are Nature-based Solution with the ability to manage rainwater runoff in densely built spaces. Despite the large amount of research demonstrating its water management abilities, its performance is poorly quantified under subtropical climates and when using unmanaged vegetation. The present work aims at characterizing the runoff retention and detention of vegetated roofs under the climate of São Paulo, Brazil, accepting the growth of spontaneous species. By using real scale prototypes under natural rain, a vegetated roof hydrological performance was compared with a ceramic tiled roof. By using models with different substrate depths under artificial rain, changes in the hydrological performance were monitored for different antecedent soil moisture contents. Results from the prototypes showed that the (i) extensive roof attenuated from 30 % up to 100 % the peak rainfall runoff; (ii) delayed the peak runoff from 14 up to 37 min and (iii) retained from 34 % up to 100 % the total rainfall. Furthermore, results from the testbeds indicated that (iv) when comparing two rainfalls with same depths, the one with longer duration can saturate more the vegetated roof and thus undermine more its ability to retain water; and (v) when not managing the vegetation, the vegetated roof's soil moisture content loses correlation with the substrate depth, as plants will also develop more and will more effectively restore the substrate retention capacity. Conclusions point to extensive vegetated roofs as a relevant sustainable drainage system in subtropical areas, but demonstrate that its performance is highly dependent on structural factors, weather factors and level of maintenance. Such findings are expected to be useful for practitioners dimensioning these roofs as well as for policy makers towards a more accurate standardization of vegetated roofs in subtropical regions and Latin American developing countries.
Gobatti, L., Bach, P. M., Scheidegger, A., & Leitão, J. P. (2023). Using satellite imagery to investigate Blue-Green Infrastructure establishment time for urban cooling. Sustainable Cities and Society, 97, 104768 (11 pp.). doi:10.1016/j.scs.2023.104768, Institutional Repository

The process of urbanization can alter the local climate to the point that it threatens citizens’ well-being by creating heat-related hazards. The construction of Blue-Green Infrastructure (BGI) can improve the regulation of surface energy exchange processes and address this problem. However, the time needed for a BGI to deliver a stable cooling performance, referred to here as the Cooling Establishment Time (CET), is poorly understood and quantified in the literature and dependent on environmental, design and maintenance factors. Here, we analyze the feasibility of using satellite data to derive the CET for different BGIs across the city of Zurich, Switzerland. Results showed that remote sensing can quantify the land surface temperature impact of BGIs and assist in estimating their CET. BGI with trees or climbing plants required a longer CET (seven to ten years) before any notable shift in surface temperatures were visible, while grasses or artificial irrigated systems led to shorter CETs (one to three years). These results allow us to better account for BGI cooling establishment when planning for areas that need urgent action under warming climates. This work supports evidence-based urban greenery planning and design towards cooling our increasingly warming cities in a timely manner.
Keshaviah, A., Diamond, M. B., Wade, M. J., Scarpino, S. V., Ahmed, W., Amman, F., … Ort, C. (2023). Wastewater monitoring can anchor global disease surveillance systems. Lancet Global Health, 11(6), e976-e981. doi:10.1016/S2214-109X(23)00170-5, Institutional Repository

To inform the development of global wastewater monitoring systems, we surveyed programmes in 43 countries. Most programmes monitored predominantly urban populations. In high-income countries (HICs), composite sampling at centralised treatment plants was most common, whereas grab sampling from surface waters, open drains, and pit latrines was more typical in low-income and middle-income countries (LMICs). Almost all programmes analysed samples in-country, with an average processing time of 2·3 days in HICs and 4·5 days in LMICs. Whereas 59% of HICs regularly monitored wastewater for SARS-CoV-2 variants, only 13% of LMICs did so. Most programmes share their wastewater data internally, with partnering organisations, but not publicly. Our findings show the richness of the existing wastewater monitoring ecosystem. With additional leadership, funding, and implementation frameworks, thousands of individual wastewater initiatives can coalesce into an integrated, sustainable network for disease surveillance—one that minimises the risk of overlooking future global health threats.
Manny, L. (2023). Socio-technical challenges towards data-driven and integrated urban water management: a socio-technical network approach. Sustainable Cities and Society, 90, 104360 (28 pp.). doi:10.1016/j.scs.2022.104360, Institutional Repository

Data-driven and integrated urban water management have been proposed to reduce surface water pollution in light of climate change and urbanization impacts. Besides technological innovation, data-driven and integrated management require information exchange among many actors, e.g., operators, engineers, or authorities. With the aim of achieving a more profound understanding of socio-technical infrastructures, such as urban water systems, I draw on the approach of socio-technical networks to study actors and infrastructure elements as well as multiple relations in-between. In this article, I investigate whether underlying socio-technical dependencies influence social interactions such as information exchange. More specifically related to data-driven and integrated management, I analyze potential challenges, such as organizational fragmentation, data access, and diverging perceptions. Based on empirical data from three case studies in Switzerland, I provide inferential results obtained from fitting exponential random graph models. Findings showed that actors' relatedness to infrastructure elements affects their information exchange. Among the cases, the presence of the three challenges varied and is potentially contingent upon system size, organizational form, or progress in terms of data-driven and integrated management. Thus, incorporating a socio-technical perspective on social actors and infrastructure elements could help to improve policy design and implementation aiming to achieve more sustainable cities.
Maurer, B., Lienert, J., & Cook, L. M. (2023). Comparing PV-green and PV-cool roofs to diverse rooftop options using decision analysis. Building and Environment, 245, 110922 (15 pp.). doi:10.1016/j.buildenv.2023.110922, Institutional Repository

Flat roofs can employ a range of technologies to improve sustainability, such as photovoltaic (PV) panels, green roofs, cool roofs, or a combination of these options. Yet, weighing the benefits, costs, and performance of different roofing technologies is complex, especially when different stakeholders are involved. Decision analysis techniques, such as multi-criteria decision analysis (MCDA), can be used to systematically evaluate a diverse range of rooftop options to assess trade-offs in a quantitative way and avoid decision biases. This study offers a holistic comparison of different roof types, considering stakeholder preferences and uncertainty using MCDA. Ten flat roof options are compared, including black, gravel, cool, extensive green and semi-intensive green roofs, each with or without a rooftop PV installation, for nine objectives and three hypothetical stakeholder profiles. Performance is evaluated using building energy simulation, hydrologic modeling, and literature research. Uncertainty analyses are used to evaluate the effects of model assumptions on the MCDA results. For assumed preferences of an urban planner and environmentalist, semi-intensive green roofs with integrated PV installation are the best performing option; however, for a hypothetical building owner more concerned with costs, a gravel roof with PV ranks best. Uncertainty plays a role in the results, in particular, the uncertainty of the predicted outcome of options for the building owner, which can change the top-ranking options considerably. The uncertainty analyses are useful to identify consensus options over all three stakeholder types. Despite considerable uncertainty, extensive and semi-intensive green roofs with PV are recommended as relatively robust best-performing options.
McFadden, I. R., Sendek, A., Brosse, M., Bach, P. M., Baity‐Jesi, M., Bolliger, J., … Narwani, A. (2023). Linking human impacts to community processes in terrestrial and freshwater ecosystems. Ecology Letters, 26(2), 203-218. doi:10.1111/ele.14153, Institutional Repository

Human impacts such as habitat loss, climate change and biological invasions are radically altering biodiversity, with greater effects projected into the future. Evidence suggests human impacts may differ substantially between terrestrial and freshwater ecosystems, but the reasons for these differences are poorly understood. We propose an integrative approach to explain these differences by linking impacts to four fundamental processes that structure communities: dispersal, speciation, species-level selection and ecological drift. Our goal is to provide process-based insights into why human impacts, and responses to impacts, may differ across ecosystem types using a mechanistic, eco-evolutionary comparative framework. To enable these insights, we review and synthesise (i) how the four processes influence diversity and dynamics in terrestrial versus freshwater communities, specifically whether the relative importance of each process differs among ecosystems, and (ii) the pathways by which human impacts can produce divergent responses across ecosystems, due to differences in the strength of processes among ecosystems we identify. Finally, we highlight research gaps and next steps, and discuss how this approach can provide new insights for conservation. By focusing on the processes that shape diversity in communities, we aim to mechanistically link human impacts to ongoing and future changes in ecosystems.
Molné, F., Donati, G. F. A., Bolliger, J., Fischer, M., Maurer, M., & Bach, P. M. (2023). Supporting the planning of urban blue-green infrastructure for biodiversity: a multi-scale prioritisation framework. Journal of Environmental Management, 342, 118069 (12 pp.). doi:10.1016/j.jenvman.2023.118069, Institutional Repository

Primary considerations for urban blue-green infrastructure (BGI) encompass sustainable stormwater/urban heat management while biodiversity conservation is often considered an inherent benefit rather than a core planning requirement. However, ecological function of BGI as 'stepping stones' or linear corridors for otherwise fragmented habitats is undisputed. While quantitative approaches for modelling ecological connectivity in conservation planning are well established, mismatches in scope and scale with models that support the planning of BGI makes their adoption and integration difficult across disciplines. Technical complexities have led to ambiguity around circuit and network-based approaches, focal node placement, spatial extents, and resolution. Furthermore, these approaches are often computationally intensive, and considerable gaps remain in their use for identifying local-scale critical "pinch-points" that urban planners may respond to with the integration of BGI interventions that address biodiversity enhancement among other ecosystem services. Here, we present a framework that simplifies and integrates the merits of regional connectivity assessments with a focus on urban areas to prioritise BGI planning interventions while reducing computational demands. Our framework facilitates: (1) modelling potential ecological corridors at a coarse regional scale, (2) prioritising local-scale BGI interventions based on the relative contribution of individual nodes in this regional network, and (3) inferring connectivity hot- and cold-spots for local-scale BGI interventions. We illustrate this in the Swiss lowlands, demonstrating how, compared to previous work, we are able to identify and rank different priority locations across the region for BGI interventions in support of biodiversity enhancement and how their local-scale functional design may be benefited by addressing specific environmental variables.
Mutzner, L., Zhang, K., Luthy, R. G., Arp, H. P. H., & Spahr, S. (2023). Urban stormwater capture for water supply: look out for persistent, mobile and toxic substances. Environmental Science: Water Research and Technology, 9, 3094-3102. doi:10.1039/D3EW00160A, Institutional Repository

Urban stormwater was traditionally managed for flood control and property protection. But this view is changing as urban stormwater is increasingly recognized as an underused water resource. As cities implement stormwater capture, treatment, and use practices, there is a growing need to address water quality criteria beyond traditional pollutants such as nutrients, total suspended solids, pathogens, and metals. Current use practice and regulations are lacking on the occurrence of persistent, mobile and toxic (PMT) and very persistent, very mobile (vPvM) organic substances. These substances are poorly removed in conventional stormwater treatment systems, e.g., urban blue-green infrastructure, and, thus, may pose a risk when urban runoff is used to augment drinking water sources or discharged to surface waters. We reviewed 97 stormwater monitoring studies and identified 49 PMT/vPvM substances detected in urban stormwater. Although detection does not equate with risk, this highlights the potential importance of urban stormwater as a source of PMT/vPvM substances released to water resources. There is a lack of surveillance data on PMT/vPvM substances in urban stormwater and their fate in stormwater control measures, which hinders reliable risk assessments of stormwater capture. Unified guidelines are needed to (i) monitor PMT/vPvM substances in urban stormwater runoff, (ii) assess the human and environmental risks PMT/vPvM substances may pose for urban stormwater capture and use, and (iii) establish improved stormwater management and use criteria to ensure safe stormwater capture for water supply.
Pakizer, K., Lieberherr, E., Farrelly, M., Bach, P. M., Saurí, D., March, H., … Binz, C. (2023). Policy sequencing for early-stage transition dynamics - a process model and comparative case study in the water sector. Environmental Innovation and Societal Transitions, 48, 100730 (20 pp.). doi:10.1016/j.eist.2023.100730, Institutional Repository

Sustainability scholars increasingly recognize that policy mixes can positively impact socio-technical transitions. However, the temporal dimension of policy interventions remains under-researched, especially in the context of early transition dynamics that typically emerge in niche contexts. In this article, we explore how policy sequencing can play a key role in supporting the scaling-up of early-stage transition dynamics to drive wider system change. We contribute to transition research by proposing a process model for analyzing policy sequences by focusing on the interplay between policy instruments and institutional barriers. We conceptualize two ideal-type policy sequencing patterns - strategic and reactive - which we illustrate with empirical examples from early transition dynamics in the urban water sector of San Francisco (United States) and Sant Cugat del Vallès (Spain). Applying the process model to these case studies reveals how different sequences of policy (instrument) mixes can assist in overcoming institutional barriers, thus supporting transition trajectories.
Peleg, N., Torelló-Sentelles, H., Mariéthoz, G., Benoit, L., Leitão, J. P., & Marra, F. (2023). Brief communication: the potential use of low-cost acoustic sensors to detect rainfall for short-term urban flood warnings. Natural Hazards and Earth System Sciences, 23(3), 1233-1240. doi:10.5194/nhess-23-1233-2023, Institutional Repository

Floods in urban areas are one of the most common natural hazards. Due to climate change enhancing extreme rainfall and cities becoming larger and denser, the frequency, magnitude, and impact of these events are expected to increase. Pluvial floods can occur in urban areas within minutes. A fast and reliable rainfall detection system should thus be implemented in flood-prone cities to warn the public of upcoming floods and save lives and reduce damage. The purpose of this brief communication is to discuss the potential implementation of low-cost acoustic rainfall sensors in short-term flood warning systems.
Regueiro-Picallo, M., Anta, J., Naves, A., Figueroa, A., & Rieckermann, J. (2023). Towards urban drainage sediment accumulation monitoring using temperature sensors. Environmental Science: Water Research and Technology, 9, 3200-3212. doi:10.1039/d2ew00820c, Institutional Repository

Sewer sediments are among the main concerns related to urban drainage system management as they represent the largest contribution of suspended solid loads during rainfall events due to their resuspension. This study presents a novel methodology to detect and assess bed deposits in urban drainage systems based on temperature monitoring by using well-known thermodynamics and sediment properties. To illustrate the heat transfer processes in a liquid–sediment system and their relation to accumulation, a lab-scale experimental campaign was performed using sewer sediments and simulating water temperature gradients in sewers. Wastewater temperatures showed a marked daily pattern, while the presence of sediment dampened dynamics. Sediment thickness could therefore be estimated from the time evolution of the temperature differences measured between the bottom of the sediment bed and the water phase. Likewise, experimental data were used to calibrate a 1D heat transfer model, from which several sediment accumulation scenarios were simulated by using real wastewater temperature series. Thus, the influence of sediment properties on accumulation processes was assessed, and the range of potentially measurable sediments within an optimal range of [5–20] cm was identified. As a conclusion, temperature measurements and heat transfer model analysis can be used to approximate and monitor the sediments deposited in urban drainage systems. Future studies will extend the method to spatially-resolved sediment monitoring and active temperature sensing to improve sediment accumulation monitoring capabilities.
Reynaert, E., Steiner, P., Yu, Q., D'Olif, L., Joller, N., Schneider, M. Y., & Morgenroth, E. (2023). Predicting microbial water quality in on-site water reuse systems with online sensors. Water Research, 240, 120075 (13 pp.). doi:10.1016/j.watres.2023.120075, Institutional Repository

Widespread implementation of on-site water reuse is hindered by the limited availability of monitoring approaches that ensure microbial quality during operation. In this study, we developed a methodology for monitoring microbial water quality in on-site water reuse systems using inexpensive and commercially available online sensors. An extensive dataset containing sensor and microbial water quality data for six of the most critical types of disruptions in membrane bioreactors with chlorination was collected. We then tested the ability of three typological machine learning algorithms - logistic regression, support-vector machine, and random forest - to predict the microbial water quality as "safe" or "unsafe" for reuse. The main criteria for model optimization was to ensure a low false positive rate (FPR) - the percentage of safe predictions when the actual condition is unsafe - which is essential to protect users health. This resulted in enforcing a fixed FPR ≤ 2%. Maximizing the true positive rate (TPR) - the percentage of safe predictions when the actual condition is safe - was given second priority. Our results show that logistic-regression-based models using only two out of the six sensors (free chlorine and oxidation-reduction potential) achieved the highest TPR. Including sensor slopes as engineered features allowed to reach similar TPRs using only one sensor instead of two. Analysis of the occurrence of false predictions showed that these were mostly early alarms, a characteristic that could be regarded as an asset in alarm management. In conclusion, the simplest algorithm in combination with only one or two sensors performed best at predicting the microbial water quality. This result provides useful insights for water quality modeling or for applications where small datasets are a common challenge and a general advantage might be gained by using simpler models that reduce the risk of overfitting, allow better interpretability, and require less computational power.
Rodriguez, M., Fu, G., Butler, D., Yuan, Z., & Cook, L. (2023). Global resilience analysis of combined sewer systems under continuous hydrologic simulation. Journal of Environmental Management, 344, 118607 (11 pp.). doi:10.1016/j.jenvman.2023.118607, Institutional Repository

Managing and reducing combined sewer overflow (CSO) discharges is crucial for enhancing the resilience of combined sewer systems (CSS). However, the absence of a standardised resilience analysis approach poses challenges in developing effective discharge reduction strategies. To address this, our study presents a top-down method that expands the existing Global Resilience Analysis to quantify resilience performance in CSS. This approach establishes a link between threats (e.g., rainfall) and impacts (e.g., CSOs) through continuous and long-term simulation, accommodating various rainfall patterns, including extreme events. We assess CSO discharge impacts from a resilience perspective by introducing eight new metrics. We conducted a case study in Fehraltorf, Switzerland, analysing the performance of three green infrastructure (GI) types (bioretention cells, green roofs, and permeable pavements) over 38 years. The results demonstrated that GI enhanced all resilience indices, with variations observed in individual CSO performance metrics and their system locations. Notably, in Fehraltorf, green roofs emerged as the most effective GI type for improving resilience, while the downstream outfall displayed the highest resilience enhancement. Overall, our proposed method enables a shift from event-based to continuous simulation analysis, providing a standardised approach for resilience assessment. This approach informs the development of strategies for CSO discharge reduction and the enhancement of CSS resilience.
Roldán-Valcarce, A., Jato-Espino, D., Manchado, C., Bach, P. M., & Kuller, M. (2023). Vulnerability to urban flooding assessed based on spatial demographic, socio-economic and infrastructure inequalities. International Journal of Disaster Risk Reduction, 95, 103894 (14 pp.). doi:10.1016/j.ijdrr.2023.103894, Institutional Repository

Urban flooding is a priority in natural risk management and mitigation because it is the most frequent natural disaster in densely urbanised environments. This research explores flood vulnerability in cities by developing an index that can be easily implemented across the world. Our methodology is based on the arrangement of a series variables into three different classes (demography, socioeconomics and infrastructure) and the determination of their spatial variability through a Principal Component Analysis (PCA). We tested the proposed approach in the city of Santander (Spain) where a vulnerability index map was generated based on the combination of the proposed classes. The analysis show that we can reduce complexity from an initially identified 159 relevant variables to 16 representative and impactful variables in terms of spatial variance. Classification of the variables into three different classes made it possible to quantify the main causes of vulnerability to flooding across space. We produce a flood risk map by integrating our findings with a flood hazard map for the same area. This flood risk map gives urban planners detailed information about the most affected areas and allows them to design measures that mitigate the severity and effects of floods optimising available resources.
Schneider, M. Y., Harada, H., Villez, K., & Maurer, M. (2023). Several small or single large? Quantifying the catchment-wide performance of on-site wastewater treatment plants with inaccurate sensors. Environmental Science and Technology, 57(2), 1114-1122. doi:10.1021/acs.est.2c05945, Institutional Repository

On-site wastewater treatment plants (OSTs) often lack monitoring, resulting in unreliable treatment performance. They thus appear to be a stopgap solution despite their potential contribution to circular water management. Low-maintenance but inaccurate soft sensors are emerging that address this concern. However, how their inaccuracy impacts the catchment-wide treatment performance of a system of many OSTs has not been quantified. We develop a stochastic model to estimate catchment-wide OST performances with a Monte Carlo simulation. In our study, soft sensors with a 70% accuracy improved the treatment performance from 66% of the time functional to 98%. Soft sensors optimized for specificity, indicating the true negative rate, improve the system performance, while sensors optimized for sensitivity, indicating the true positive rate, quantify the treatment performance more accurately. This new insight leads us to suggest programming two soft sensors in practical settings with the same hardware sensor data as input: one soft sensor geared to high specificity for maintenance scheduling and one geared to high sensitivity for performance quantification. Our findings suggest that a maintenance strategy combining inaccurate sensors with appropriate alarm management can vastly improve the mean catchment-wide treatment performance of a system of OSTs.
Tan, T., Kong, F., Yin, H., Cook, L. M., Middel, A., & Yang, S. (2023). Carbon dioxide reduction from green roofs: a comprehensive review of processes, factors, and quantitative methods. Renewable and Sustainable Energy Reviews, 182, 113412 (12 pp.). doi:10.1016/j.rser.2023.113412, Institutional Repository

Green roofs can mitigate climate change through various mechanisms, including carbon sequestration, thermal process regulation, and building energy savings. While those mechanisms have been well studied, it remains unclear how to quantify carbon dioxide reduction and design green roofs properly for optimal performance. This review summarizes the processes, factors, and quantitative methods for carbon dioxide reduction from peer-reviewed literature. Firstly, the processes that account for how green roofs reduce carbon dioxide directly (by absorbing ambient CO2 and storing it in biomass and substrate) and indirectly (thermal process regulation reduces energy consumption) are focused. The factors affecting CO2 reduction (i.e., vegetation, substrate, building environment, and maintenance) are then discussed to investigate how these factors impact the performance of green roofs. Lastly, quantitative methods, including field experiments and simulation models to evaluate direct and indirect CO2 reductions from green roofs, are discussed considering different spatial scales. The review found that a better understanding of green roofs' carbon reduction mechanisms is needed. Recommendations also should be developed on customized green roof system designs for various climate conditions. Lastly, there is a lack of green roof decarbonization evaluation at multiple spatial and temporal scales to effectively implement green roofs in urban areas. Overall, this comprehensive review facilitates an understanding of how green roofs reduce CO2, the driving factors, and quantitative methods, which will advance research on designing and building green roofs as effective climate mitigation solutions in urban areas.
Tondera, K., Brelot, E., Fontanel, F., Cherqui, F., Ellerbæk Nielsen, J., Brüggemann, T., … Anta, J. (2023). European stakeholders' visions and needs for stormwater in future urban drainage systems. Urban Water Journal, 20(7), 831-843. doi:10.1080/1573062X.2023.2211559, Institutional Repository

Transitioning urban drainage systems to serve water-smart societies requires the involvement of different disciplines and stakeholders. However, stakeholders have different visions and needs from the transitioning process (e.g in terms of financing, policy adaptation and system management) these also vary between regions and countries. Identifying such different needs for stakeholders is necessary to propose practical adaptation strategies. Therefore, evidence of needs as reflected in policy papers and legislation in seven European countries was collected. Knowledgeable individuals in the urban drainage community were asked about their visions. Results show that whilst there is consensus on the challenges, visions on how to transition are diverse, indicating that more interaction between the different stakeholder groups is required to develop consensus. Additionally, organisational and legislative structures often slow down the necessary change processes.
Caduff, L., Dreifuss, D., Schindler, T., Devaux, A. J., Ganesanandamoorthy, P., Kull, A., … Julian, T. R. (2022). Inferring transmission fitness advantage of SARS-CoV-2 variants of concern from wastewater samples using digital PCR, Switzerland, December 2020 through March 2021. Eurosurveillance: bulletin européen sur les maladies transmissibles, 27(10), 2100806 (20 pp.). doi:10.2807/1560-7917.ES.2022.27.10.2100806, Institutional Repository

BackgroundThroughout the COVID-19 pandemic, SARS-CoV-2 genetic variants of concern (VOCs) have repeatedly and independently arisen. VOCs are characterised by increased transmissibility, increased virulence or reduced neutralisation by antibodies obtained from prior infection or vaccination. Tracking the introduction and transmission of VOCs relies on sequencing, typically whole genome sequencing of clinical samples. Wastewater surveillance is increasingly used to track the introduction and spread of SARS-CoV-2 variants through sequencing approaches.AimHere, we adapt and apply a rapid, high-throughput method for detection and quantification of the relative frequency of two deletions characteristic of the Alpha, Beta, and Gamma VOCs in wastewater.MethodsWe developed drop-off RT-dPCR assays and an associated statistical approach implemented in the R package WWdPCR to analyse temporal dynamics of SARS-CoV-2 signature mutations (spike Δ69-70 and ORF1a Δ3675-3677) in wastewater and quantify transmission fitness advantage of the Alpha VOC.ResultsBased on analysis of Zurich wastewater samples, the estimated transmission fitness advantage of SARS-CoV-2 Alpha based on the spike Δ69-70 was 0.34 (95% confidence interval (CI): 0.30-0.39) and based on ORF1a Δ3675-3677 was 0.53 (95% CI: 0.49-0.57), aligning with the transmission fitness advantage of Alpha estimated by clinical sample sequencing in the surrounding canton of 0.49 (95% CI: 0.38-0.61).ConclusionDigital PCR assays targeting signature mutations in wastewater offer near real-time monitoring of SARS-CoV-2 VOCs and potentially earlier detection and inference on transmission fitness advantage than clinical sequencing.
Campos-Mañas, M. C., Van Wichelen, N., Covaci, A., van Nuijs, A. L. N., Ort, C., Béen, F., … Bijlsma, L. (2022). Analytical investigation of cannabis biomarkers in raw urban wastewater to refine consumption estimates. Water Research, 223, 119020 (8 pp.). doi:10.1016/j.watres.2022.119020, Institutional Repository

Wastewater analysis of Δ9-tetrahydrocannabinol (THC) biomarkers can provide essential information on trends in cannabis consumption. Although analysis is mostly focused on the aqueous phase, previous studies have illustrated the need of improving the measurements of raw influent wastewater (IWW) considering also suspended solids. This is important for cannabis biomarkers, because a substantial part of them is expected to be found in the suspended solids due to their more lipophilic character compared with other metabolites/drugs included in these types of studies. However, it remains open to which extent trend estimates might be affected by solely analysing the liquid phase. To investigate this aspect, robust analytical methodologies are required to measure both the liquid and solid phases of IWW. In this work, we firstly tested liquid-liquid extraction (LLE) for THC and its major metabolites (THC-OH, and THC-COOH). Using LLE, no filtration or centrifugation step was required for raw IWW analysis, and the three analytes were extracted from both the liquid and the solid phase simultaneously. In parallel, the raw IWW was centrifuged and the obtained solid and liquid phases were analyzed separately: the liquid phase by both LLE and solid phase extraction (SPE) for comparison of data, and the suspended solids by solid-liquid extraction (SLE). The separate analysis of both phases in a number of samples revealed that a significant amount of cannabis biomarkers (ranging from 42 to 90%) was found in the suspended solids. In addition, the total amount of cannabis biomarkers obtained by analysing raw IWW on the one hand, and by separate analysis of the liquid and the solid phases, on the other hand, was in good agreement. Data from this study show that the sole analysis of the liquid phase would lead to a notable underestimation of cannabis biomarkers concentrations in IWW.
Cariti, F., Tuñas Corzon, A., Fernandez-Cassi, X., Ganesanandamoorthy, P., Ort, C., Julian, T. R., & Kohn, T. (2022). Wastewater reveals the spatiotemporal spread of SARS-CoV-2 in the Canton of Ticino (Switzerland) during the onset of the COVID-19 pandemic. ACS ES&T Water, 2(11), 2194-2200. doi:10.1021/acsestwater.2c00082, Institutional Repository

Wastewater-based epidemiology (WBE) has emerged as an effective tool for monitoring SARS-CoV-2 dynamics during the COVID-19 pandemic. Here, we add a spatial component to WBE and use it to investigate SARS-CoV-2 spread in the canton of Ticino during the onset of the pandemic in Switzerland (end of February 2020 to beginning of March 2020). Ticino is located at the border to Northern Italy, where a large COVID-19 outbreak occurred in February 2020. Not surprisingly, Ticino was the site of the first clinically confirmed COVID-19 case in Switzerland. We retrospectively analyzed daily influent samples from nine wastewater treatment plants in Ticino that jointly cover an area of 20 km × 60 km and 351,000 people (>99% of the population). Our result is a fine-grained view of the spatiotemporal evolution of the COVID-19 pandemic in this canton. The wastewater analysis revealed that by February 29, 2020, SARS-CoV-2 had already spread to all catchments. At the same time, only four individual cases had been clinically confirmed across the region served by the treatment plants investigated. Our results demonstrate that WBE could serve as a versatile tool to monitor the introduction and spread of an infectious agent on a regional scale. To fully exploit its utility, WBE should be implemented in real time and become an integral part of future disease surveillance efforts.
Chaudhary, P., Leitão, J. P., Donauer, T., D’Aronco, S., Perraudin, N., Obozinski, G., … Russo, S. (2022). Flood uncertainty estimation using deep ensembles. Water, 14(19), 2980 (24 pp.). doi:10.3390/w14192980, Institutional Repository

We propose a probabilistic deep learning approach for the prediction of maximum water depth hazard maps at high spatial resolutions, which assigns well-calibrated uncertainty estimates to every predicted water depth. Efficient, accurate, and trustworthy methods for urban flood management have become increasingly important due to higher rainfall intensity caused by climate change, the expansion of cities, and changes in land use. While physically based flood models can provide reliable forecasts for water depth at every location of a catchment, their high computational burden is hindering their application to large urban areas at high spatial resolution. While deep learning models have been used to address this issue, a disadvantage is that they are often perceived as "black-box" models and are overconfident about their predictions, therefore decreasing their reliability. Our deep learning model learns the underlying phenomena a priori from simulated hydrodynamic data, obviating the need for manual parameter setting for every new rainfall event at test time. The only inputs needed at the test time are a rainfall forecast and parameters of the terrain such as a digital elevation model to predict the maximum water depth with uncertainty estimates for complete rainfall events. We validate the accuracy and generalisation capabilities of our approach through experiments on a dataset consisting of catchments within Switzerland and Portugal and 18 rainfall patterns. Our method produces flood hazard maps at 1 m resolution and achieves mean absolute errors as low as 21 cm for extreme flood cases with water above 1 m. Most importantly, we demonstrate that our approach is able to provide an uncertainty estimate for every water depth within the predicted hazard map, thus increasing the model's trustworthiness during flooding events.
Donati, G. F. A., Bolliger, J., Psomas, A., Maurer, M., & Bach, P. M. (2022). Reconciling cities with nature: Identifying local Blue-Green Infrastructure interventions for regional biodiversity enhancement. Journal of Environmental Management, 316, 115254 (14 pp.). doi:10.1016/j.jenvman.2022.115254, Institutional Repository

Increasing urbanization degrades quantity, quality, and the functionality of spatial cohesion of natural areas essential to biodiversity and ecosystem functioning worldwide. The uncontrolled pace of building activity and the erosion of blue (i.e., aquatic) and green (i.e., terrestrial) landscape elements threaten existing habitat ranges and movability of wildlife. Local scale measures, such as nature-inspired engineered Blue-Green Infrastructure (BGI) are emerging mitigation solutions. Originally planned to promote sustainable stormwater management, adaptation to climate change and improved human livability in cities, such instruments offer interesting synergies for biodiversity in support of existing ecological infrastructure. BGI are especially appealing for globally declining amphibians, a rich and diverse vertebrate assemblage sensitive to urbanization. We integrated biological and highly resolved urban-rural land-cover data, ensemble models of habitat suitability, and connectivity models based on circuit theory to improve multi-scale and multi-species protection of core habitats and ecological corridors in the Swiss lowlands. Considering a broad spectrum of amphibian biodiversity, we identified distributions of amphibian biodiversity hotspots and four landscape elements essential to amphibian movability at the regional scale, namely i) forest edges, ii) wet-forest habitats, iii) soils with variable moisture and iv) riparian zones. Our work shows that cities can make a substantial contribution (e.g., up to 15% of urban space in the study area) to wider landscape habitat connectivity. We highlight the importance of planning BGI locally in strategic locations across urban and peri-urban areas to promote the permeability and availability of ‘stepping stone’ habitats in densely populated landscapes, essential to the maintenance of regional habitat connectivity and thereby enhancing biodiversity and ecosystem functioning.
Duque, N., Bach, P. M., Scholten, L., Fappiano, F., & Maurer, M. (2022). A simplified sanitary sewer system generator for exploratory modelling at city-scale. Water Research, 209, 117903 (12 pp.). doi:10.1016/j.watres.2021.117903, Institutional Repository

Future climatic, demographic, technological, urban and socio-economic challenges call for more flexible and sustainable wastewater infrastructure systems. Exploratory modelling can help to investigate the consequences of these developments on the infrastructure. In order to explore large numbers of adaptation strategies, we need to re-balance the degree of realism of sewer network and ability to reflect key performance characteristics against the model's parsimony and computational efficiency. We present a spatially explicit algorithm for creating sanitary sewer networks that realistically represent key characteristics of a real system. Basic topographic, demographic and urban characteristics are abstracted into a squared grid of 'Blocks' which are the foundation for the sewer network's topology delineation. We compare three different pipe dimensioning approaches and found a good balance between detail and computational efficiency. With a basic hydraulic performance assessment, we demonstrate that we attain a computationally efficient and high-fidelity wastewater sewer network with adequate hydraulic performance. A spatial resolution of 250 m Block size in combination with a sequential Pipe-by-Pipe (PBP) design algorithm provides a sound trade-off between computational time and fidelity of relevant structural and hydraulic properties for exploratory modelling. We can generate a simplified sewer network (both topology and hydraulic design) in 18 s using PBP, versus 36 min using a highly detailed model or 1 s using a highly abstract model. Moreover, this simplification can cut up to 1/10th to 1/50th the computational time for the hydraulic simulations depending on the routing method implemented. We anticipate our model to be a starting point for sophisticated exploratory modelling into possible infrastructure adaptation measures of topological and loading changes of sewer systems for long-term planning.
Guo, Z., Moosavi, V., & Leitão, J. P. (2022). Data-driven rapid flood prediction mapping with catchment generalizability. Journal of Hydrology, 609, 127726 (12 pp.). doi:10.1016/j.jhydrol.2022.127726, Institutional Repository

Data-driven and machine learning models have recently received increasing interest to resolve the computational speed challenge faced by various physically-based simulations. A few studies have explored the application of these models to develop new, and fast, applications for fluvial and pluvial flood prediction, extent mapping, and flood susceptibility assessment. However, most studies have focused on model development for specific catchment areas, drainage networks or gauge stations. Hence, their results cannot be directly reused to other contexts unless extra data are available and the models are further trained. This study explores the generalizability potential of convolutional neural networks (CNNs) as flood prediction models. The study proposes a CNN-based model that can be reused in different catchment areas with different topography once the model is trained. The study investigates two options, patch- and resizing-based options, to process catchment areas of different sizes and different shapes. The results showed that the CNN-based model predicts accurately on "unseen" catchment areas with significantly less computational time when compared to physically-based models. The obtained results also suggest that the patch-based option is more effective than the resizing-based option in terms of prediction accuracy. In addition, all experiments have shown that the prediction of flow velocity is more accurate than water depth, suggesting that the water accumulation is more sensitive to global elevation information than flow velocity.
Hadengue, B., Morgenroth, E., & Larsen, T. A. (2022). How to get your feet wet: Integrating urban water and building engineering for low-energy domestic hot water systems. Energy and Buildings, 271, 112318 (6 pp.). doi:10.1016/j.enbuild.2022.112318, Institutional Repository

Thanks to intense research efforts, modern low-energy buildings consume only a fraction of the space heating loads of their older counterparts. However, reducing their energy footprint further requires optimization of domestic hot water systems. This is a difficult task, because the relationship between water and energy in domestic systems is intricate and complex. In general, the intrinsic uncertainty and variability of water demand makes the planning and assessment of new technologies challenging, but also risks related for instance to water pathogens like Legionella pneumophila impose trade-offs that diminish the performance of energy-saving measures. In this short communication, we argue that truly sustainable solutions will only be found if a multi-scale, multi-disciplinary mindset is adopted by the community. We show how the collaboration and knowledge integration between experts of various fields, notably urban water specialists and building engineers, is a prerequisite to resolve some of the most pressing issues on the way to optimizing domestic hot water systems. Through concrete examples, we describe how a new, common modeling framework has already triggered the required knowledge integration, and how it could be expanded further to integrate additional disciplines.
Hadengue, B., Morgenroth, E., Larsen, T. A., & Baldini, L. (2022). Performance and dynamics of active greywater heat recovery in buildings. Applied Energy, 305, 117677 (13 pp.). doi:10.1016/j.apenergy.2021.117677, Institutional Repository

In the effort to de-carbonize the building stock, heat pumps are increasingly utilized in Switzerland, with 70% of the fast-growing heat pump market using ambient air as heat source. Inexpensive and easy to implement, these heat pumps are, however, less efficient than their ground- or water-source counterparts. In this modeling study, we aim at increasing the efficiency of air-source heat pumps using domestic greywater-contained heat. We assess the performance improvement relative to standard heat pump configurations across various climates, seasons, building envelopes, and domestic hot water consumption patterns. The results show that the annually-averaged coefficient of performance improves by 4.1% on average - ranging from 0.6% to 7.5%. This efficiency gain translates on average to 1.8 kWh/week of compressor electricity savings. Although attractive due to its simplicity, the proposed open-loop configuration - preheating of an external heat source - only leads to moderate performance improvement of air-source heat pumps. Based on these results, we extensively discuss and compare alternative system configurations and identify several fundamental differences in the heat recovery dynamics of each configuration. We show that closed-loop systems - using greywater as direct heat source - show the largest performance improvement potential, although being more expensive and complex to implement.
Hadengue, B., Morgenroth, E., & Larsen, T. A. (2022). Screening innovative technologies for energy-efficient domestic hot water systems. Journal of Environmental Management, 320, 115713 (9 pp.). doi:10.1016/j.jenvman.2022.115713, Institutional Repository

Domestic hot water systems are large energy consumers. With the aim of reducing the energy footprint of these systems, we selected and simulated five technologies across a wide range of technology readiness levels: established technologies - pipe insulation and low-flow faucets -, relatively new technologies - shower drain heat exchangers and an innovative pipe system - and a novel experimental technology - a heat exchanger connected to membrane bioreactor for on-site greywater treatment. Using the WaterHub modeling framework, we simulated the technologies alone and in combination and compared the energetic performance of fifteen scenarios with a validated reference domestic hot water system. Low-flow appliances as standalone technologies performed best with 30% less energy required for the boiler tank, but combining low-flow appliances with a membrane bioreactor heat exchanger performed best overall (50% reduction). Deep insights into the temperature dynamics at all locations in the system led to the identification of technological competition patterns to prevent and synergies to exploit. Through our results, we are able to discuss and recommend further investigations regarding critical aspects like hygiene and economic performance.
Harpaz, C., Russo, S., Leitão, J. P., & Penn, R. (2022). Potential of supervised machine learning algorithms for estimating the impact of water efficient scenarios on solids accumulation in sewers. Water Research, 216, 118247 (16 pp.). doi:10.1016/j.watres.2022.118247, Institutional Repository

Understanding the negative effects of widespread implementation of optimal water efficient solutions may have on existing centralised sewer systems is still limited – one of these effects is the accumulation of solids in sewer pipes. Predicting these effects requires setting up and simulating complex detailed hydraulic sewer network models. Often, precise details of the sewer network layout and diurnal patterns of the wastewater flows are not available, limiting the applicability of using model predictions for such phenomena. In this study, the applicability of supervised machine learning (ML) algorithms for the development of a simplified surrogate model to predict solid accumulation in sewer pipes was investigated. A large number of highly variable sewer networks were synthetically generated and used to produce results that can be generalizable within the limitations of the current study. A hydrodynamic sewer model was set up and simulated for each synthetic sewer network and various scenarios in which different water-efficient solutions were considered. Simulation results indicated that the most impacts are expected to occur in the upstream part of the sewer networks, and that with 50% reduction in (waste-)water flows, 3–20% more pipes are expected to accumulate solids. It was further found that ML algorithms can be used to successfully predict locations of solids accumulation in sewer pipes without using hydrodynamic models. A simple tool based on the findings of this study, sparing the need to conduct complex hydraulic simulations, was developed. It allows the user to enter a set of pipe characteristics and the proportion of flow that is reduced due to the implementation of water efficient solutions, and it predicts whether the pipe will accumulate solids or not. The study results and the proposed ML algorithms can support the implementation of optimal water-efficient solutions that will promote designing and managing the water sensitive cities of the future.
Huisman, J. S., Scire, J., Caduff, L., Fernandez-Cassi, X., Ganesanandamoorthy, P., Kull, A., … Julian, T. R. (2022). Wastewater-based estimation of the effective reproductive number of SARS-CoV-2. Environmental Health Perspectives, 130(5), 057011 (12 pp.). doi:10.1289/EHP10050, Institutional Repository

BACKGROUND: The effective reproductive number, Re, is a critical indicator to monitor disease dynamics, inform regional and national policies, and estimate the effectiveness of interventions. It describes the average number of new infections caused by a single infectious person through time. To date, Re estimates are based on clinical data such as observed cases, hospitalizations, and/or deaths. These estimates are temporarily biased when clinical testing or reporting strategies change.
OBJECTIVES: We show that the dynamics of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA in wastewater can be used to estimate Re in near real time, independent of clinical data and without the associated biases.
METHODS: We collected longitudinal measurements of SARS-CoV-2 RNA in wastewater in Zurich, Switzerland, and San Jose, California, USA. We combined this data with information on the temporal dynamics of shedding (the shedding load distribution) to estimate a time series proportional to the daily COVID-19 infection incidence. We estimated a wastewater-based Re from this incidence.
RESULTS: The method to estimate Re from wastewater worked robustly on data from two different countries and two wastewater matrices. The resulting estimates were as similar to the Re estimates from case report data as Re estimates based on observed cases, hospitalizations, and deaths are among each other. We further provide details on the effect of sampling frequency and the shedding load distribution on the ability to infer Re.
DISCUSSION: To our knowledge, this is the first time Re has been estimated from wastewater. This method provides a low-cost, rapid, and independent way to inform SARS-CoV-2 monitoring during the ongoing pandemic and is applicable to future wastewater-based epidemiology targeting other pathogens.
Jahn, K., Dreifuss, D., Topolsky, I., Kull, A., Ganesanandamoorthy, P., Fernandez-Cassi, X., … Beerenwinkel, N. (2022). Early detection and surveillance of SARS-CoV-2 genomic variants in wastewater using COJAC. Nature Microbiology, 7, 1151-1160. doi:10.1038/s41564-022-01185-x, Institutional Repository

The continuing emergence of SARS-CoV-2 variants of concern and variants of interest emphasizes the need for early detection and epidemiological surveillance of novel variants. We used genomic sequencing of 122 wastewater samples from three locations in Switzerland to monitor the local spread of B.1.1.7 (Alpha), B.1.351 (Beta) and P.1 (Gamma) variants of SARS-CoV-2 at a population level. We devised a bioinformatics method named COJAC (Co-Occurrence adJusted Analysis and Calling) that uses read pairs carrying multiple variant-specific signature mutations as a robust indicator of low-frequency variants. Application of COJAC revealed that a local outbreak of the Alpha variant in two Swiss cities was observable in wastewater up to 13 d before being first reported in clinical samples. We further confirmed the ability of COJAC to detect emerging variants early for the Delta variant by analysing an additional 1,339 wastewater samples. While sequencing data of single wastewater samples provide limited precision for the quantification of relative prevalence of a variant, we show that replicate and close-meshed longitudinal sequencing allow for robust estimation not only of the local prevalence but also of the transmission fitness advantage of any variant. We conclude that genomic sequencing and our computational analysis can provide population-level estimates of prevalence and fitness of emerging variants from wastewater samples earlier and on the basis of substantially fewer samples than from clinical samples. Our framework is being routinely used in large national projects in Switzerland and the UK.
Kuller, M., Farrelly, M., Marthanty, D. R., Deletic, A., & Bach, P. M. (2022). Planning support systems for strategic implementation of nature-based solutions in the global south: current role and future potential in Indonesia. Cities, 126, 103693 (11 pp.). doi:10.1016/j.cities.2022.103693, Institutional Repository

Nature Based Solutions (NBS) are increasingly used for improving water quality, reducing urban flooding and providing ecological and amenity benefits. Although predominantly developed and implemented in industrialised countries, NBS are gaining traction in the Global South. Strategic planning is required to deliver the anticipated benefits and ensure successful integration into urban landscapes. Spatial software and planning support systems (PSS), can inform such decision-making. We seek to understand the efficacy of utilising PSS for advancing NBS practices within Indonesian urban settings. Through workshops and in-depth interviews with urban planning practitioners, we examined (i) the current NBS planning context, (ii) tacit experiences with contemporary PSS, and (iii) potential utility of PSS to address identified challenges with NBS planning. While strategic planning processes were perceived as improving over past decades, significant challenges remain including inadequate collaboration between actors, insufficient capacity and resources of local governments and limited access to high-quality spatial data. Although strategic planners employ contemporary PSS, further embedding those into decision-making processes requires rethinking the socio-institutional and political context within which they operate. Results revealed keen interest to adopt innovative PSS. However, without access to high-quality spatial information, strategic planning will continue to be compromised, potentially leading to ill-sited NBS interventions.
Langeveld, J. G., Cherqui, F., Tscheikner-Gratl, F., Muthanna, T. M., Fernandez-Delgado Juarez, M., Leitão, J. P., … Rulleau, B. (2022). Asset management for blue-green infrastructures: a scoping review. Blue-Green Systems, 4(2), 272-290. doi:10.2166/bgs.2022.019, Institutional Repository

Urban drainage systems have developed way beyond the traditional piped combined or separate sewer systems. Many 'new' systems are being introduced, ranging from stormwater infiltration facilities to green roofs. However, the widely advocated blue-green infrastructures are typically overlooked by asset managers, which will very likely have detrimental effects on their performance, service life, and wider adoption. In this paper, the working group on Urban Drainage Asset Management (UDAM - https://udam.home.blog/) of the IWA and IAHR Joint Committee on Urban Drainage discusses whether the state-of-the-art knowledge based on conventional sewer asset management is sufficient to develop asset management for blue-green infrastructures (BGIs). The discussion is structured around the five preconditions for effective control and asset management. Results show that asset management for BGIs is still underdeveloped due to a lack of monitoring techniques covering the broad range of BGI benefits and performance indicators, inspection techniques covering relevant failure mechanisms and models describing these mechanisms, maintenance and rehabilitation options, and sufficient support tools to aid inhabitants in the operation and maintenance of their individual BGIs such as green roofs or vegetated swales.
Manny, L., Angst, M., Rieckermann, J., & Fischer, M. (2022). Socio-technical networks of infrastructure management: network concepts and motifs for studying digitalization, decentralization, and integrated management. Journal of Environmental Management, 318, 115596 (14 pp.). doi:10.1016/j.jenvman.2022.115596, Institutional Repository

Networked infrastructure systems - including energy, transportation, water, and wastewater systems — provide essential services to society. Globally, these services are undergoing major transformative processes such as digitalization, decentralization, or integrated management. Such processes not only depend on technical changes in infrastructure systems but also include important social and socio-technical dimensions. In this article, we propose a socio-technical network perspective to study the ensemble of social actors and technical elements involved in an infrastructure system, and their complex relations. We conceptualize structurally explicit socio-technical networks of networked infrastructure systems based on methodological considerations from network analysis and draw on concepts from socio-technical system theories and social-ecological network studies. Based on these considerations, we suggest analytical methods to study basic network concepts such as density, reciprocity, and centrality in a socio-technical network. We illustrate socio-technical motifs, i.e., meaningful sub-structures in socio-technical networks of infrastructure management. Drawing on these, we describe how infrastructure systems can be analyzed in terms of digitalization, decentralization, and integrated management from a socio-technical network perspective. Using the example of urban wastewater systems, we illustrate an empirical application of our approach. The results of an empirical case study in Switzerland demonstrate the potential of socio-technical networks to promote a deeper understanding of complex socio-technical relations in networked infrastructure systems. We contend that such a deeper understanding could improve management practices of infrastructure systems and is becoming even more important for enabling future data-driven, decentralized, and more integrated infrastructure management.
Mutzner, L., Furrer, V., Castebrunet, H., Dittmer, U., Fuchs, S., Gernjak, W., … Vezzaro, L. (2022). A decade of monitoring micropollutants in urban wet-weather flows: what did we learn?. Water Research, 223, 118968 (14 pp.). doi:10.1016/j.watres.2022.118968, Institutional Repository

Urban wet-weather discharges from combined sewer overflows (CSO) and stormwater outlets (SWO) are a potential pathway for micropollutants (trace contaminants) to surface waters, posing a threat to the environment and possible water reuse applications. Despite large efforts to monitor micropollutants in the last decade, the gained information is still limited and scattered. In a metastudy we performed a data-driven analysis of measurements collected at 77 sites (683 events, 297 detected micropollutants) over the last decade to investigate which micropollutants are most relevant in terms of 1) occurrence and 2) potential risk for the aquatic environment, 3) estimate the minimum number of data to be collected in monitoring studies to reliably obtain concentration estimates, and 4) provide recommendations for future monitoring campaigns. We highlight micropollutants to be prioritized due to their high occurrence and critical concentration levels compared to environmental quality standards. These top-listed micropollutants include contaminants from all chemical classes (pesticides, heavy metals, polycyclic aromatic hydrocarbons, personal care products, pharmaceuticals, and industrial and household chemicals). Analysis of over 30,000 event mean concentrations shows a large fraction of measurements (> 50%) were below the limit of quantification, stressing the need for reliable, standard monitoring procedures. High variability was observed among events and sites, with differences between micropollutant classes. The number of events required for a reliable estimate of site mean concentrations (error bandwidth of 1 around the "true" value) depends on the individual micropollutant. The median minimum number of events is 7 for CSO (2 to 31, 80%-interquantile) and 6 for SWO (1 to 25 events, 80%-interquantile). Our analysis indicates the minimum number of sites needed to assess global pollution levels and our data collection and analysis can be used to estimate the required number of sites for an urban catchment. Our data-driven analysis demonstrates how future wet-weather monitoring programs will be more effective if the consequences of high variability inherent in urban wet-weather discharges are considered.
Nguyen, T. T., Bach, P. M., & Pahlow, M. (2022). Multi-scale stormwater harvesting to enhance urban resilience to climate change impacts and natural disasters. Blue-Green Systems, 4(1), 58-74. doi:10.2166/bgs.2022.008, Institutional Repository

Stormwater harvesting systems are a viable option to adapt cities to cope with climate change and reduce pressure on water supply services. This is particularly crucial in the event of natural disasters (e.g., earthquakes, floods), where large parts of cities may become disconnected from a secure water supply for prolonged time periods. We demonstrate how optimum location, density and storage size can be determined using UrbanBEATS, a spatial planning-support system for planning and design of sustainable Blue-Green Infrastructure strategies. We investigate the Otakaro/Avon River catchment, Christchurch, New Zealand for the time periods 2011-2020, 2041-2050 and 2091-2100 (for the RCP 8.5 climate change scenario). For targets of 30% of potable water substitution and 70% storage volumetric reliability, we found that stormwater harvesting systems in all climate scenarios required a larger capacity compared to the baseline. Most storages achieved their set targets and were larger than the municipality's recommended 9 m3 for flood inundation, indicating that the identified storages would also reduce minor flooding while ensuring water savings. A shift in the spatial layout of modelled systems from highly distributed to more centralised, however, raises a potential conflict with disaster resilience where more local solutions would be preferable.
Pastorek, J., Fencl, M., Rieckermann, J., & Bares, V. (2022). Precipitation estimates from commercial microwave links: practical approaches to wet-antenna correction. IEEE Transactions on Geoscience and Remote Sensing, 60, 4104409 (9 pp.). doi:10.1109/TGRS.2021.3110004, Institutional Repository

An inadequate correction for wet-antenna attenuation (WAA) often causes a notable bias in quantitative precipitation estimates (QPEs) from commercial microwave links (CMLs) limiting the usability of these rainfall data in hydrological applications. This article analyzes how WAA can be corrected without dedicated rainfall monitoring for a set of 16 CMLs. Using data collected over 53 rainfall events, the performance of six empirical WAA models was studied, both when calibrated to rainfall observations from a permanent municipal rain gauge network and when using model parameters from the literature. The transferability of WAA model parameters among CMLs of various characteristics has also been addressed. The results show that high-quality QPEs with a bias below 5% and root-mean-square error (RMSE) of 1 mm/h in the median could be retrieved, even from subkilometer CMLs where WAA is relatively large compared to raindrop attenuation. Models in which WAA is proportional to rainfall intensity provide better WAA estimates than constant and time-dependent models. It is also shown that the parameters of models deriving WAA explicitly from rainfall intensity are independent of CML frequency and path length and, thus, transferable to other locations with CMLs of similar antenna properties.
Peleg, N., Ban, N., Gibson, M. J., Chen, A. S., Paschalis, A., Burlando, P., & Leitão, J. P. (2022). Mapping storm spatial profiles for flood impact assessments. Advances in Water Resources, 166, 104258 (11 pp.). doi:10.1016/j.advwatres.2022.104258, Institutional Repository

Synthetic design storms are often used to plan new drainage systems or assess flood impacts on infrastructure. To simulate extreme rainfall events under climate change, design storms can be modified to match a different return frequency of extreme rainfall events as well as a modified temporal distribution of rainfall intensities. However, the same magnitude of change to the rainfall intensities is often applied in space. Several hydrological applications are limited by this. Climate change impacts on urban pluvial floods, for example, require the use of 2D design storms (rainfall fields) at sub-kilometer and sub-hourly scales. Recent kilometer scale climate models, also known as convection-permitting climate models (CPM), provide rainfall outputs at a high spatial resolution, although rainfall simulations are still restricted to a limited number of climate scenarios and time periods. We nevertheless explored the potential use of rainfall data obtained from these models for hydrological flood impact studies by introducing a method of spatial quantile mapping (SQM). To demonstrate the new methodology, we extracted high-resolution rainfall simulations from a CPM for four domains representing different urban areas in Switzerland. Extreme storms that are plausible under the present climate conditions were simulated with a 2D stochastic rainfall model. Based on the CPM-informed stochastically generated rainfall fields, we modified the design storms to fit the future climate scenario using three different methods: the SQM, a uniform quantile mapping, and a uniform adjustment based on a rainfall–temperature relationship. Throughout all storms, the temporal distribution of rainfall was the same. Using a flood model, we assessed the impact of different rainfall adjustment methods on urban flooding. Significant differences were found in the flood water depths and areas between the three methods. In general, the SQM method results in a higher flood impact than the storms that were modified otherwise. The results suggest that spatial storm profiles may need to be re-adjusted when assessing flood impacts.
Probst, N., Bach, P. M., Cook, L. M., Maurer, M., & Leitão, J. P. (2022). Blue Green Systems for urban heat mitigation: mechanisms, effectiveness and research directions. Blue-Green Systems, 4(2), 348-376. doi:10.2166/bgs.2022.028, Institutional Repository

Reflected in the growing body of literature, urban heat mitigation is increasingly relevant as cities experience extreme heat, exacerbated by climate change and rapid urbanisation. Most studies focus on urban–rural temperature differences, known as the Urban Heat Island, which does not provide insight into urban heat dynamics. Here, we synthesise current knowledge on spatio-temporal variations of heat sources and sinks, showing that a targeted and absolute understanding of urban heat dynamics rather than an urban–rural comparison should be encouraged. We discuss mechanisms of heat sinks for microclimate control, provide a clear classification of Blue Green Systems and evaluate current knowledge of their effectiveness in urban heat mitigation. We consider planning and optimisation aspects of Blue Green Infrastructure (greenery and water bodies/features), interactions with hard surfaces and practices that ensure space and water availability. Blue Green Systems can positively affect urban microclimates, especially when strategically planned to achieve synergies. Effectiveness is governed by their dominant cooling mechanisms that show diurnal and seasonal variability and depend upon background climatic conditions and characteristics of surrounding urban areas. Situationally appropriate combination of various types of Blue Green Systems and their connectivity increases heat mitigation potential while providing multiple ecosystem services but requires further research.
Prodanovic, V., Jamali, B., Kuller, M., Wang, Y., Bach, P. M., Coleman, R. A., … Deletic, A. (2022). Calibration and sensitivity analysis of a novel water flow and pollution model for future city planning: Future Urban Stormwater Simulation (FUSS). Water Science and Technology, 85(4), 961-969. doi:10.2166/wst.2022.046, Institutional Repository

Planning for future urban development and water infrastructure is uncertain due to changing human activities and climate. To quantify these changes, we need adaptable and fast models that can reliably explore scenarios without requiring extensive data and inputs. While such models have been recently considered for urban development, they are lacking for stormwater pollution assessment. This work proposes a novel Future Urban Stormwater Simulation (FUSS) model, utilizing previously developed urban planning algorithm (UrbanBEATS) to dynamically assess pollution changes in urban catchments. By using minimal input data and adding stochastic point-source pollution to the build-up/wash-off approach, this study highlights calibration and sensitivity analysis of flow and pollution modules, across the range of common stormwater pollutants. The results highlight excellent fit to measured values in a continuous rainfall simulation for the flow model, with one significant calibration parameter. The pollution model was more variable, with TSS, TP and Pb showing high model efficiency, while TN was predicted well only across event-based assessment. The work further explores the framework for the model application in future pollution assessment, and points to the future work aiming to developing land-use dependent model parameter sets, to achieve flexibility for model application across varied urban catchments.
Robinson, C. T., Jolidon, C., Consoli, G., Bloem, S., & Ebi, C. (2022). Temporal dynamics in the physico-chemistry of a high-alpine stream network in the Swiss National Park. eco.mont, 14(2), 11-23. doi:10.1553/eco.mont-14-2s11, Institutional Repository

The Macun lakes form a high-alpine (> 2,600 m asl) cirque landscape (3.6 km2) in the Swiss National Park, comprising 26 small lakes together with a number of temporary ponds. Streams interconnect the four largest lakes, forming the drainage network that flows into the Inn River at the town of Lavin. The drainage network of Macun consists of a north and a south basin that overlie an ortho-gneiss, meta-granitoid bedrock. The south basin is influenced by various rock glaciers. The physico-chemistry of surface waters at 10 sites has been monitored annually in midsummer since 2001. Further, an YSI EXO2 Multiparameter Sonde (Exosonde) with various water quality sensors has been employed since 2016 at the last lake in the network to examine seasonal and diel patterns in physico-chemistry. Results showed clear physico-chemical differences between the two basins, which mostly reflect rockglacier inputs in the south basin. Nitrogen values were two-fold higher and particulate phosphorus values two-fold lower in the south basin than in the north basin. Over time, the physico-chemistry in the two basins became more homogeneous, with a reduction in rock-glacial inputs in the south basin and an overall decrease in nitrogen in the catchment. Data from 30 springs and tributaries sampled in 2002 and 2017 reflected the basin differences and temporal changes observed at the primary study sites. Continuous temperature records showed north basin streams to be ca. 3°C warmer than south-basin streams, but with high inter-annual variation that reflected annual differences in weather and no evidence of a general change over time (increase or decrease). Exosonde data revealed strong seasonality in measured parameters as well as seasonality in diel patterns (e. g., dissolved oxygen, temperature, chlorophyll-a); diel fluctuations were most pronounced in summer and least in winter. The results highlight the importance of long-term monitoring for understanding ecosystem state changes in alpine freshwaters, especially during periods of rapid environmental change.
Shi, B., Catsamas, S., Deletic, B., Wang, M., Bach, P. M., Lintern, A., … McCarthy, D. T. (2022). Illicit discharge detection in stormwater drains using an Arduino-based low-cost sensor network. Water Science and Technology, 85(5), 1372-1383. doi:10.2166/wst.2022.034, Institutional Repository

Illicit discharges in urban stormwater drains are a major environmental concern that deteriorate downstream waterway health. Conventional detection methods such as stormwater drain visual inspection and dye testing have fundamental drawbacks and limitations which can prevent easy location and elimination of illegal discharges in a catchment. We deployed 22 novel low-cost level, temperature and conductivity sensors across an urban catchment in Melbourne for a year to monitor the distributed drainage network, thereby detecting likely illicit discharges ranging from a transitory flow with less than 10 minutes to persistent flows lasting longer than 20 hours. We discuss rapid deployment methods, real-time data collection and online processing. The ensemble analysis of all dry weather flow data across all sites indicates that: (i) large uncertainties are associated with discharge frequency, duration, and variation in water quality within industrial and residential land uses; (ii) most dry weather discharges are intermittent and transient flows which are difficult to detect and not simply due to cross-connections with the sewerage network; (iii) detectable diurnal discharge patterns can support mitigation efforts, including policies and regulatory measures (e.g., enforcement or education) to protect receiving waterways; and, (iv) that it is possible to cost effectively isolate sources of dry weather pollution using a distributed sensor network.
Back, Y., Bach, P. M., Jasper-Tönnies, A., Rauch, W., & Kleidorfer, M. (2021). A rapid fine-scale approach to modelling urban bioclimatic conditions. Science of the Total Environment, 756, 143732 (17 pp.). doi:10.1016/j.scitotenv.2020.143732, Institutional Repository

Surface characteristics play a vital role in simulations for urban bioclimatic conditions. Changing relationships and distribution patterns of sealed and vegetated surfaces as well as building geometry across different scales in urban environments influence surface temperatures. Cities comprise different urban forms, which, depending on their surface characteristics, enhance the heating process, increasing the emergence of urban heat islands (UHIs). Detecting priority areas to introduce multi-beneficial climate change adaptation measures is set to be a key task for the cities long-term strategies to improve climatic conditions across different urban structures and scales. We introduce a simple and fast spatial modelling approach to carry out fine-scale simulations for land surface temperature (LST), mean radiant temperature (MRT) and Universal Thermal Climate Index (UTCI) in a 2D environment. Capabilities of our modelling approach are demonstrated in evaluating urban thermal comfort in the alpine city of Innsbruck, the capital of Tyrol in western Austria. Results show a major contrast between sealed and vegetated surfaces reflected in the distributional patterns and values of LST, MRT and UTCI, correlating with the appearance and frequency of specific surface classes. We found the Sky View Factor to have a substantial impact on calculations for bioclimatic conditions and see high-albedo surfaces decrease LST but increase the apparent temperature (MRT and UTCI values) effecting human thermal comfort. Furthermore, MRT and UTCI are more sensitive to changes in emissivity values, whereas LST is more sensitive to changes in Bowen Ratio values. Application of our modelling approach can be used to identify priority areas and maximise multi-functionality of climate change adaptation measures, to support urban planning processes for heat mitigation and the implementation of policy suggestions to achieve sustainable development goals and other political objectives.
Browne, S., Lintern, A., Jamali, B., Leitão, J. P., & Bach, P. M. (2021). Stormwater management impacts of small urbanising towns: The necessity of investigating the 'devil in the detail'. Science of the Total Environment, 757, 143835 (13 pp.). doi:10.1016/j.scitotenv.2020.143835, Institutional Repository

In many parts of the world, small towns are experiencing high levels of population growth and development. However, there is little understanding of how urban growth in these regional towns will impact urban runoff. We used the case study of Wangaratta, located in South-East Australia, between 2006 and 2016, to investigate land cover changes and their impacts on urban runoff discharge. Detailed spatio-temporal analysis (including neighbourhood composition analysis and supervised classification of aerial imagery) identified that population, land use and land cover changes in Wangaratta, although subtle, were mostly driven by residential growth in the outskirts of the town, where there were large increases in impervious surface area. Overall, the urban growth was minimal. However, in spite of these small changes, a sub-catchment only SWMM model showed that the increase in impervious surface area nevertheless resulted in a statistically significant increase in total runoff across the town. Particularly, this increase was most pronounced for frequent and shorter storms. The analysis of urban development pattern changes coupled with urban hydrological modelling indicated that land cover changes in regional towns, especially when analysed in detail, may result in hydrological changes in the urban region (likely to be exacerbated in coming years by changing climate) and that adaptation efforts will need to adopt a variety of approaches in both existing and growth zones. Our findings highlight the necessity of detailed fine-scale analyses in small towns as even subtle changes will have substantial future implications and robust planning and adaptation decisions are even more important when compared to larger cities due to the greater economic constraints that small towns face and their important relationship with the surrounding hinterlands.
Cavadini, G. B., & Cook, L. M. (2021). Green and cool roof choices integrated into rooftop solar energy modelling. Applied Energy, 296, 117082 (13 pp.). doi:10.1016/j.apenergy.2021.117082, Institutional Repository

Due to their cooling ability, sustainable roofing configurations, such as green and cool roofs, have the potential to increase solar panel yield, which is temperature dependent. However, the influence of sustainable roofing configurations on panel yield is not yet considered in rooftop photovoltaic (PV) planning models; thus, the significance of these integrated systems cannot be evaluated. In order to quantify the potential benefits of sustainable rooftops on solar energy, the first goal of this study is to develop a method that systematically accounts for roof surface characteristics in the simulation of PV panel energy yield. To do so, a rooftop energy balance model is linked with a physically-based solar energy model (the System Advisor Model, SAM) to quantify the energy yield of PV installations on sustainable roofing configurations. Roof surface temperatures are first estimated using non-linear energy balance equations, then integrated into a revised version of SAM to simulate energy yield. This new method improves the accuracy of PV yield simulations, compared to prior assumptions of roof surface temperature equal to ambient temperature. This updated model is used for the second goal of the study, to understand how four roofing configurations (black membrane, rock ballasted, white membrane, and vegetated) influence PV panel yield, which is currently not well understood in cooler climates. For a flat rooftop PV installation near Zurich, Switzerland (temperate climate), results show that, compared to a conventional roof, green roofs can increase annual PV energy yield, on average, by 1.8%, whereas cool roofs can increase it by 3.4%. For the case-study installation, an inverse correlation between the 95th-quantile roof surface temperature and the PV energy yield was identified; an increase of 1 °C leads to a 71 kWh reduction in energy yield per year. Overall, cool roofs outperform green roofs in terms of increases in PV energy yield; however, potential improvements of both systems are non-negligible, even in relatively cooler climate regions like Switzerland. By providing a systematic method to evaluate the influence of the roofing configuration on PV energy yield, solar energy planners are able to differentiate between the benefits of traditional and sustainable rooftop configurations - the first step towards the coupling of distributed energy and sustainable building systems. In the future, this integrated method could be used as part of a holistic evaluation of the environmental, economic, and social objectives of green and cool roofs, as well as, other infrastructure systems.
Cook, L. M., & Larsen, T. A. (2021). Towards a performance-based approach for multifunctional green roofs: an interdisciplinary review. Building and Environment, 188, 107489 (14 pp.). doi:10.1016/j.buildenv.2020.107489, Institutional Repository

Green roofs have the potential to offer numerous ecosystem services; however, they are rarely designed to achieve them. Instead, design is restricted by perceived structural and maintenance constraints, which consequently diminish the achievable benefits. For green roofs to improve sustainability and resilience of cities, their design should match their promised multi-functional application using performance-based design. The first step towards a comprehensive performance model is to synthesize design recommendations across disciplines to identify synergies and trade-offs in design objectives for multiple benefits. This study discusses design strategies that could alter the energy and water balance in the green roof in order to attenuate urban stormwater, increase building energy performance, mitigate urban heat, and improve the output of solar panels placed on top of green roofs. These benefits are mathematically linked to quantifiable processes (discharge rate, water content, evapotranspiration, sensible heat, net radiation, insulation, and thermal mass), forming the foundation for a performance-based design model. Design recommendations are then summarized for each process, followed by a discussion of synergies, trade-offs, and research needs that arise when green roofs are designed to achieve multiple functions. Selecting vegetation with high leaf area and albedo improves multiple benefits without affecting structural constraints, whereas choosing plants with low stomatal resistance leads to trade-offs between higher evapotranspiration and higher irrigation requirements. Trade-offs in substrate depth and properties including organic matter and moisture are also apparent. Interdisciplinary collaborations are needed to simulate and optimize design parameters based on stakeholder preferences related to co-benefits and constraints.
Cook, L. M., VanBriesen, J. M., & Samaras, C. (2021). Using rainfall measures to evaluate hydrologic performance of green infrastructure systems under climate change. Sustainable and Resilient Infrastructure, 6(3-4), 156-180. doi:10.1080/23789689.2019.1681819, Institutional Repository

As climate change alters precipitation patterns, stakeholders will need to understand how performance of green stormwater infrastructure (GSI) could change in response. As an alternative to using on-site monitoring, which may not always feasible, we propose that changes in performance could be tracked using annual rainfall measures (e.g., maximum daily rainfall per year). We estimated performance of GSI in 17 U.S. cities using rainfall measures by establishing linear relationships with specific performance metrics (e.g., frequency of discharge). Prediction accuracy was evaluated in 2 cities for the period 2020 to 2060 by comparing performance predicted from rainfall trends from regional climate models (RCMs) with simulated performance in SWMM using the same RCMs as input. Findings suggest that tracking rainfall measures can provide insight into the hydrologic performance of green infrastructure by predicting the direction of change, as well as, the magnitude within 25% to 50% percent change.
Fernandez-Cassi, X., Scheidegger, A., Bänziger, C., Cariti, F., Tuñas Corzon, A., Ganesanandamoorthy, P., … Kohn, T. (2021). Wastewater monitoring outperforms case numbers as a tool to track COVID-19 incidence dynamics when test positivity rates are high. Water Research, 200, 117252 (9 pp.). doi:10.1016/j.watres.2021.117252, Institutional Repository

Wastewater-based epidemiology (WBE) has been shown to coincide with, or anticipate, confirmed COVID-19 case numbers. During periods with high test positivity rates, however, case numbers may be underreported, whereas wastewater does not suffer from this limitation. Here we investigated how the dynamics of new COVID-19 infections estimated based on wastewater monitoring or confirmed cases compare to true COVID-19 incidence dynamics. We focused on the first pandemic wave in Switzerland (February to April, 2020), when test positivity ranged up to 26%. SARS-CoV-2 RNA loads were determined 2–4 times per week in three Swiss wastewater treatment plants (Lugano, Lausanne and Zurich). Wastewater and case data were combined with a shedding load distribution and an infection-to-case confirmation delay distribution, respectively, to estimate infection incidence dynamics. Finally, the estimates were compared to reference incidence dynamics determined by a validated compartmental model. Incidence dynamics estimated based on wastewater data were found to better track the timing and shape of the reference infection peak compared to estimates based on confirmed cases. In contrast, case confirmations provided a better estimate of the subsequent decline in infections. Under a regime of high-test positivity rates, WBE thus provides critical information that is complementary to clinical data to monitor the pandemic trajectory.
Figueroa, A., Hadengue, B., Leitão, J. P., Rieckermann, J., & Blumensaat, F. (2021). A distributed heat transfer model for thermal-hydraulic analyses in sewer networks. Water Research, 204, 117649 (11 pp.). doi:10.1016/j.watres.2021.117649, Institutional Repository

Thermal-hydraulic considerations in urban drainage networks are essential to utilise available heat capacities from waste- and stormwater. However, available models are either too detailed or too coarse; fully coupled thermal-hydrodynamic modelling tools are lacking. To predict efficiently water-energy dynamics across an entire urban drainage network, we suggest the SWMM-HEAT model, which extends the EPA-StormWater Management Model with a heat-balance component. This enables conducting more advanced thermal-hydrodynamic simulation at full network scale than currently possible. We demonstrate the usefulness of the approach by predicting temperature dynamics in two independent real-world cases under dry weather conditions. We furthermore screen the sensitivity of the model parameters to guide the choice of suitable parameters in future studies. Comparison with measurements suggest that the model predicts temperature dynamics adequately, with RSR values ranging between 0.71 and 1.1. The results of our study show that modelled in-sewer wastewater temperatures are particularly sensitive to soil and headspace temperature, and headspace humidity. Simulation runs are generally fast; a five-day period simulation at high temporal resolution of a network with 415 nodes during dry weather was completed in a few minutes. Future work should assess the performance of the model for different applications and perform a more comprehensive sensitivity analysis under more scenarios. To facilitate the efficient estimation of available heat budgets in sewer networks and the integration into urban planning, the SWMM-HEAT code is made publicly available.
Figueroa, A., Jackiewicz, Z., & Löhner, R. (2021). Efficient two-step Runge-Kutta methods for fluid dynamics simulations. Applied Numerical Mathematics, 159, 1-20. doi:10.1016/j.apnum.2020.08.013, Institutional Repository

Explicit two-step Runge-Kutta (TSRK) methods offer an efficient alternative to traditional explicit Low-Storage Runge-Kutta (LSRK) schemes for solving the Navier-Stokes equations. A special class of TSRK methods that reduce requirement compared to previous TSRK schemes are derived. Schemes of fourth, fifth and sixth order are implemented and tested. The new schemes are evaluated with two common test cases, a 2D cylinder and a 3D Taylor-Green vortex. The results are compared with classical time discretization strategies. Timings obtained in three different hardware configurations show that the new TSRK methods of order four are 25% faster than LSRK schemes of the same order. Fifth and sixth order TSRK methods are tested with the same 3D test case and the results are compared to LSRK algorithms. Results show TSRK schemes of fifth and sixth order are competitive compared to LSRK methods of the same orders, as LSRK methods are of second order for non linear differential systems.
Gundlach, J., Bryla, M., Larsen, T. A., Kristoferitsch, L., Gründl, H., & Holzner, M. (2021). Novel NoMix toilet concept for efficient separation of urine and feces and its design optimization using computational fluid mechanics. Journal of Building Engineering, 33, 101500 (6 pp.). doi:10.1016/j.jobe.2020.101500, Institutional Repository

Separation of urine from feces in NoMix toilets bears a large potential for mitigating problems associated with the efficient reuse of excreta. A challenge lies in the design of these toilets that should maximize the amount of collected urine while at the same time minimizing its mixing with flush water that partly spills into the urine collector. We present a novel design idea that takes advantage of the so-called tea pot effect, which describes the attachment of liquids to a curved wall due to surface tension. This effect is used to efficiently guide the urine along a curved entrance into the collector. Computational Fluid Dynamics (CFD) simulations of the two phase (water/urine - air) system are carried out on different toilet geometries where we vary the inflow to the urine collector. In particular, we investigate two different radial curvatures and two V-profile grooves whose combinations result in four toilet geometries that are tested. We demonstrate that the urine collection can be dramatically improved by tailoring curvature radius and V-profile grooves, while keeping the amount of flush water in the urine collector at a minimum. A reduction to less the 2.5% of flush water entering the urine collector could be achieved by implementing a curvature radius of 15 mm and a V-profile groove width of 60 mm. The improved geometry's performance makes it an appealing candidate for broad application both in western and developing counties and we anticipate that this technology might replace traditional toilet designs in the future.
Guo, Z., Leitão, J. P., Simões, N. E., & Moosavi, V. (2021). Data-driven flood emulation: speeding up urban flood predictions by deep convolutional neural networks. Journal of Flood Risk Management, 14(1), e12684 (14 pp.). doi:10.1111/jfr3.12684, Institutional Repository

Computational complexity has been the bottleneck for applying physically based simulations in large urban areas with high spatial resolution for efficient and systematic flooding analyses and risk assessment. To overcome the issue of long computational time and accelerate the prediction process, this paper proposes that the prediction of maximum water depth can be considered an image-to-image translation problem in which water depth rasters are generated using the information learned from data instead of by conducting simulations. The proposed data-driven urban pluvial flood approach is based on a deep convolutional neural network trained using flood simulation data obtained from three catchments and 18 hyetographs. Multiple tests to assess the accuracy and validity of the proposed approach were conducted with both design and real hyetographs. The results show that flood prediction based on neural networks use only 0.5% of the time compared with that of physically based models, with promising accuracy and generalizability. The proposed neural network can also potentially be applied to different but relevant problems, including flood analysis for flood-safe urban layout planning.
Hadengue, B., Joshi, P., Figueroa, A., Larsen, T. A., & Blumensaat, F. (2021). In-building heat recovery mitigates adverse temperature effects on biological wastewater treatment: a network-scale analysis of thermal-hydraulics in sewers. Water Research, 204, 117552 (11 pp.). doi:10.1016/j.watres.2021.117552, Institutional Repository

Heat recovery from wastewater is a robust and straightforward strategy to reduce water-related energy consumption. Its implementation, though, requires a careful assessment of its impacts across the entire wastewater system as adverse effects on the water and resource recovery facility and competition among heat recovery strategies may arise. A model-based assessment of heat recovery from wastewater therefore implies extending the modeling spatial scope, with the aim of enabling thermal-hydraulic simulations from the household tap along its entire flow path down to the wastewater resource recovery facility. With this aim in mind, we propose a new modeling framework interfacing thermal-hydraulic simulations of (i) households, (ii) private lateral connections, and (iii) the main public sewer network. Applying this framework to analyze the fate of wastewater heat budgets in a Swiss catchment, we find that heat losses in lateral connections are large and cannot be overlooked in any thermal-hydraulic analysis, due to the high-temperature, low-flow wastewater characteristics maximizing heat losses to the environment. Further, we find that implementing shower drain heat recovery devices in 50% of the catchment's households lower the wastewater temperature at the recovery facility significantly less – only 0.3 K – than centralized in-sewer heat recovery, due to a significant thermal damping effect induced by lateral connections and secondary sewer lines. In-building technologies are thus less likely to adversely affect biological wastewater treatment processes. The proposed open-source modeling framework can be applied to any other catchment. We thereby hope to enable more efficient heat recovery strategies, maximizing energy harvesting while minimising impacts on biological wastewater treatment.
Hess, A., Baum, C., Schiessl, K., Besmer, M. D., Hammes, F., & Morgenroth, E. (2021). Stagnation leads to short-term fluctuations in the effluent water quality of biofilters: a problem for greywater reuse?. Water Research X, 13, 100120 (9 pp.). doi:10.1016/j.wroa.2021.100120, Institutional Repository

A key characteristic of decentralized greywater treatment and reuse is high variability in both nutrient concentrations and flow. This variability in flow leads to stagnant water in the system and causes short-term fluctuations in the effluent water quality. Automated monitoring tools provide data to understand the mechanisms underlying the dynamics and to adapt control strategies accordingly. We investigated the fluctuations in a building-scale greywater treatment system comprising a membrane bioreactor followed by a biological activated carbon filter. Short-term dynamics in the effluent of the biological activated carbon filter were monitored with automated flow cytometry and turbidity, and the impact of these fluctuations on various hygiene-relevant parameters in the reuse water was evaluated. Continuous biofilm detachment into the stagnant water in the biological activated carbon filter led to temporarily increased turbidity and cell concentrations in the effluent after periods of stagnation. The fluctuations in cell concentrations were consistent with a model assuming higher detachment rates during flow than during times with stagnant water. For this system, total cell concentration and turbidity were strongly correlated. We also showed that the observed increase in cell concentration was not related to either an increase of organic carbon concentration or the concentration of two opportunistic pathogens, P. aeruginosa and L. pneumophila. Our findings demonstrate that turbidity measurements are sensitive to changes in the effluent water quality and can be used to monitor the fluctuations caused by intermittent flow. Intermittent flow did not lead to an increase in opportunistic pathogens, and this study provides no indications that stagnant water in biological activated carbon filters need be prevented.
Jamali, B., Haghighat, E., Ignjatovic, A., Leitão, J. P., & Deletic, A. (2021). Machine learning for accelerating 2D flood models: potential and challenges. Hydrological Processes, 35(4), e14064 (14 pp.). doi:10.1002/hyp.14064, Institutional Repository

Two-dimensional hydrodynamic models numerically solve full Shallow Water Equations (SWEs). Despite their high accuracy, these models have long simulation run times and therefore are of limited use for exploratory or real-time flood predictions. We investigated the possibility of improving flood modelling speed using Machine Learning (ML). We propose a new method that replaces the computationally expensive parts of the hydrodynamic models with simple and efficient data-driven approximations. Our hypothesis is that by integrating ML with physics-based numerical methods, we can achieve improved generalization performance: that is, the trained model for one case study can be used in other studies without the need for new training. We tested two ML approaches: for the first, we integrated curve fitting, and, for the second, artificial neural networks (ANN) with a finite volume scheme to solve the local inertial approximation of the SWEs. The data-driven models approximated the Momentum Equation, which explicitly solved the time derivative of flow rates. Water depths were then updated by applying a water balance equation. We also tested two different training datasets: the simulated dataset, generated from the results of hydrodynamic model, and the random dataset, generated by directly solving the momentum equation on randomly sampled input data. Various combinations of input features, for example, water slope and depth, were explored. The proposed models were trained in a small hypothetical case and tested in a different hypothetical and in two real case studies. Results showed that the curve-fitting method can be implemented successfully, given sufficient training and input data. The ANN model trained with a random dataset was substantially more accurate than that of the model trained with the simulated dataset. However, it was not successful in the real case studies. The curve-fitting method resulted in better generalization performance and increased the simulation speed of the local inertial model by 23%. Future research should test the performance of ML in terms of an increase in stable time step size and approximation of the full SWEs.
Joshi, P., Leitão, J. P., Maurer, M., & Bach, P. M. (2021). Not all SuDS are created equal: impact of different approaches on combined sewer overflows. Water Research, 191, 116780 (13 pp.). doi:10.1016/j.watres.2020.116780, Institutional Repository

Sustainable urban drainage systems (SuDS) help in stormwater management by reducing runoff volume, increasing runoff concentration time and thereby improving the drainage system capacity. This study investigated the potential and cost-effectiveness of SuDS in reducing combined sewer overflows (CSOs). We simulated the performance of four SuDS techniques (bioretention cell, permeable pavement, rain barrel and green roof) at incremental levels of spatial coverage for a small urban catchment with a combined sewer system. We also used an Analytic Hierarchy Process (AHP) considering end-point CSO, land use, imperviousness, slope and elevation criteria to identify priority areas for SuDS deployment. Results show that CSO volume attenuation ranged a maximum of 50-99% for the catchment, depending on the deployment strategy and underlying mechanisms of each technology. We also found that deployment of SuDS in AHP-selected sub-catchments improved CSO reduction only for rain barrels and green roofs, but not for bioretention cells and permeable pavements. SuDS were also a cost-effective retrofit option: for a 40% volume reduction, the SuDS cost, at most, 25% of the equivalent cost required for a large CSO tank. Outcomes of this study demonstrate the efficacy of SuDS in controlling CSOs, adding yet another tangible benefit to their increasingly recognised multi-functionality.
Larsen, T. A., Riechmann, M. E., & Udert, K. M. (2021). State of the art of urine treatment technologies: a critical review. Water Research X, 13, 100114 (20 pp.). doi:10.1016/j.wroa.2021.100114, Institutional Repository

Over the last 15 years, urine treatment technologies have developed from lab studies of a few pioneers to an interesting innovation, attracting attention from a growing number of process engineers. In this broad review, we present literature from more than a decade on biological, physical-chemical and electrochemical urine treatment processes. Like in the first review on urine treatment from 2006, we categorize the technologies according to the following objectives: stabilization, volume reduction, targeted N-recovery, targeted P-recovery, nutrient removal, sanitization, and handling of organic micropollutants. We add energy recovery as a new objective, because extensive work has been done on electrochemical energy harvesting, especially with bio-electrochemical systems. Our review reveals that biological processes are a good choice for urine stabilization. They have the advantage of little demand for chemicals and energy. Due to instabilities, however, they are not suited for bathroom applications and they cannot provide the desired volume reduction on their own. A number of physical-chemical treatment technologies are applicable at bathroom scale and can provide the necessary volume reduction, but only with a steady supply of chemicals and often with high demand for energy and maintenance. Electrochemical processes is a recent, but rapidly growing field, which could give rise to exciting technologies at bathroom scale, although energy production might only be interesting for niche applications. The review includes a qualitative assessment of all unit processes. A quantitative comparison of treatment performance was not the goal of the study and could anyway only be done for complete treatment trains. An important next step in urine technology research and development will be the combination of unit processes to set up and test robust treatment trains. We hope that the present review will help guide these efforts to accelerate the development towards a mature technology with pilot scale and eventually full-scale implementations.
Larsen, T. A., Gruendl, H., & Binz, C. (2021). The potential contribution of urine source separation to the SDG agenda - a review of the progress so far and future development options. Environmental Science: Water Research and Technology, 7(7), 1161-1176. doi:10.1039/D0EW01064B, Institutional Repository

Sanitation and wastewater management are highly relevant for reaching a number of interconnected sustainable development goals (SDGs), especially SDG 6, the provision of safe drinking water and adequate sanitation for all as well as protection of water resources against pollution, and SDG 14.1, reducing nutrient emissions to the marine environment. Recent evidence increasingly shows that conventional sewer-based wastewater management will not be able to reach these targets. Rather than further optimizing and diffusing this ageing infrastructure paradigm, radical innovations like urine source separation technologies could help to leapfrog towards faster achievement of the SDGs. The technology would simplify on-site sanitation and develop a closed-loop nutrient cycle, thereby allowing for exceptionally high nutrient removal from wastewater and direct reuse in agriculture from the first day of implementation. Radical innovations, however, need decades to materialize. Based on a review of relevant academic and grey literature, we show how the past three decades of development of urine source separation have brought breakthroughs in toilet design and treatment processes, enabling the technology's value chain to reach the brink of maturity. In a short outlook, we discuss how the technology may reach global diffusion over the next decade, with the main remaining challenges relating to the creation of mass-markets for urine-diverting toilets, automation and mass-production of treatment systems, and the legitimation of fertilizer produced from urine in the agricultural sector.
Leite, A., & Leitão, J. (2021). The new town of Angra (Terceira, the Azores): confirming a contested urban planning history using reverse historical analysis and flood modelling tools. Urban History, 48(1), 20-36. doi:10.1017/S0963926819001093, Institutional Repository

The Portuguese discovered the uninhabited Azores archipelago in 1427 and started to settle it during the fifteenth century. Angra, located on Terceira Island, soon became the most important Azorean city, leading to rapid urban development. This article investigates the overlooked role of streams in the rise of Angra as a pivotal Atlantic urban centre. Through the intersection of historical and flood modelling methods, it makes a unique contribution to our understanding of Angra's urban morphologic development, highlighting the potential of applying urban flood modelling to analysis of the rise of coastal urban settlement.
Manny, L., Duygan, M., Fischer, M., & Rieckermann, J. (2021). Barriers to the digital transformation of infrastructure sectors. Policy Sciences, 54, 943-983. doi:10.1007/s11077-021-09438-y, Institutional Repository

Digital technologies can be important to policy-makers and public servants, as these technologies can increase infrastructure performance and reduce environmental impacts. For example, utilizing data from sensors in sewer systems can improve their management, which in turn may result in better surface water quality. Whether such big data from sensors is utilized is, however, not only a technical issue, but also depends on different types of social and institutional conditions. Our article identifies individual, organizational, and institutional barriers at the level of sub-states that hinder the evaluation of data from sewer systems. We employ fuzzy-set Qualitative Comparative Analysis (fsQCA) to compare 23 Swiss sub-states and find that two barriers at different levels can each hinder data evaluation on their own. More specifically, either a lack of vision at the individual level or a lack of resources at the organizational level hinder the evaluation of data. Findings suggest that taking into account different levels is crucial for understanding digital transformation in public organizations.
Merz, E., Kozakiewicz, T., Reyes, M., Ebi, C., Isles, P., Baity-Jesi, M., … Pomati, F. (2021). Underwater dual-magnification imaging for automated lake plankton monitoring. Water Research, 203, 117524 (12 pp.). doi:10.1016/j.watres.2021.117524, Institutional Repository

The Dual Scripps Plankton Camera (DSPC) is a new approach for automated in-situ monitoring of phyto- and zooplankton communities based on a dual magnification dark-field imaging microscope. Here, we present the DSPC and its associated image processing while evaluating its capabilities in i) detecting and characterizing plankton species of different size and taxonomic categories and ii) measuring their abundance in both laboratory and field applications. In the laboratory, body size and abundance estimates by the DSPC significantly and robustly scaled with measurements derived by microscopy. In the field, a DSPC installed permanently at 3 m depth in Lake Greifensee (Switzerland) delivered images of plankton individuals, colonies, and heterospecific aggregates at hourly timescales without disrupting natural arrangements of interacting organisms, their microenvironment or their behavior. The DSPC was able to track the dynamics of taxa, mostly at the genus level, in the size range between ∼10 μm to ∼ 1 cm, covering many components of the planktonic food web (including parasites and potentially toxic cyanobacteria). Comparing data from the field-deployed DSPC to traditional sampling and microscopy revealed a general overall agreement in estimates of plankton diversity and abundances. The most significant disagreements between traditional methods and the DSPC resided in the measurements of zooplankton community properties. Our data suggest that the DSPC is better equipped to study the dynamics and demography of heterogeneously distributed organisms such as zooplankton, because high temporal resolution and continuous sampling offer more information and less variability in taxa detection and quantification than traditional sampling. Time series collected by the DSPC depicted ecological succession patterns, algal bloom dynamics and diel fluctuations with a temporal frequency and morphological resolution that was never observed by traditional methods. Access to high frequency, reproducible and real-time data of a large spectrum of the planktonic ecosystem expands our understanding of both applied and fundamental plankton ecology. We conclude the DSPC is robust for both research and water quality monitoring and suitable for stable long-term deployments.
Narayan, A. S., Maurer, M., & Lüthi, C. (2021). The clean plan: analysing sanitation planning in India using the CWIS planning framework. Journal of Water Sanitation and Hygiene for Development, 11(6), 1036-1047. doi:10.2166/washdev.2021.130, Institutional Repository

Sanitation in India has received national attention for over a decade, especially with the Swachh Bharat Mission (SBM) making it a political priority. However, due to the lack of appropriate sanitation planning practices, there have been little long-term gains made in urban sanitation beyond the ending of open defaecation. In this paper, we analyse the key barriers to sanitation planning, in India, in the context of the emerging paradigm of Citywide Inclusive Sanitation (CWIS). A mixed method approach of shit flow diagrams, social network analysis, policy analysis, interviews and workshops at the national, state (2) and city (4) levels was conducted. Eight factors were identified as important barriers for planning including inadequate planning capacities, lack of ownership of city sanitation plans among city governments, poor community involvement, absence of a uniform planning framework, unreliable political and financial support, overlapping jurisdictions, and scheme-based funding. The paper also proposes the CWIS Planning Framework which offers a perspective at overcoming these barriers with the recommendation of bridging top-down and bottom-up planning approaches. While there is increasingly more clarity on what CWIS means, there is little understanding on how to plan for it. Therefore, this framework provides the theoretical basis for planning with the CWIS approach.
Penn, R., & Maurer, M. (2021). Effects of transition to water‐efficient solutions on existing centralized sewer systems - an integrated biophysical modelling approach. Water Resources Research, 57(9), e2020WR027616 (19 pp.). doi:10.1029/2020WR027616, Institutional Repository

Technical alternatives offering high water efficiency are being developed to complement existing centralized water and wastewater conveyance and treatment systems. Understanding of the negative effects wide-spread implementation of such alternative systems may have on existing systems is still limited, despite the importance of this inevitable transition. In this paper we present a novel approach to systematically identify these negative impacts. A comprehensive model integrating transport and transformation processes in sewer pipes was set up and simulated for various transition scenarios. A significant finding of this research is that reduced flows and increased chemical oxygen demand (COD) concentrations result in the accumulation of sediments and sulphides in sewer pipes. For the examined sewer system, when reducing the total daily flow by 50%, 30% of the pipes were found to accumulate sediments and 30% of the pipes experienced effects due to the presence of sulphides in different states depending on the wastewater temperature. It was found that an optimal spatial distribution of these water-efficient solutions will most likely require compromises between sediment and sulphide accumulation. The product of two design parameters, diameter and bed slope, was found to be a suitable predictor of the potential of a pipe to accumulate sediments. This research provides novel approaches to assessing the feasibility of transition to solutions offering higher water efficiency. The results indicate where the most affected points in the systems are expected to occur and might help in preparing an experimental approach to assess such negative effects, increasing urban water management efficiency.
Penn, R., Ward, B. J., Strande, L., & Maurer, M. (2021). Faecal sludge simulants: review of synthetic human faeces and faecal sludge for sanitation and wastewater research. In K. Velkushanova, L. Strande, M. Ronteltap, T. Koottatep, D. Brdjanovic, & C. Buckley (Eds.), Methods for faecal sludge analysis (pp. 195-234). London: IWA Publishing. , Institutional Repository
Ramgraber, M., Weatherl, R., Blumensaat, F., & Schirmer, M. (2021). Non‐Gaussian parameter inference for hydrogeological models using Stein Variational Gradient Descent. Water Resources Research, 57(4), e2020WR029339 (21 pp.). doi:10.1029/2020WR029339, Institutional Repository

The sustainable management of groundwater demands a faithful characterization of the subsurface. This, in turn, requires information which is generally not readily available. To bridge the gap between data need and availability, numerical models are often used to synthesize plausible scenarios not only from direct information but also additional, indirect data. Unfortunately, the resulting system characterizations will rarely be unique. This poses a challenge for practical parameter inference: Computational limitations often force modelers to resort to methods based on questionable assumptions of Gaussianity, which do not reproduce important facets of ambiguity such as Pareto fronts or multi‐modality. In search of a remedy, an alternative could be found in Stein Variational Gradient Descent (SVDG), a recent development in the field of statistics. This ensemble‐based method iteratively transforms a set of arbitrary particles into samples of a potentially non‐Gaussian posterior, provided the latter is sufficiently smooth. A prerequisite for this method is knowledge of the Jacobian, which is usually exceptionally expensive to evaluate. To address this issue, we propose an ensemble‐based, localized approximation of the Jacobian. We demonstrate the performance of the resulting algorithm in two cases: a simple, bimodal synthetic scenario, and a complex numerical model based on a real‐world, pre‐alpine catchment. Promising results in both cases - even when the ensemble size is smaller than the number of parameters - suggest that Stein Variational Gradient Descent can be a valuable addition to hydrogeological parameter inference.
Russo, S., Besmer, M. D., Blumensaat, F., Bouffard, D., Disch, A., Hammes, F., … Villez, K. (2021). The value of human data annotation for machine learning based anomaly detection in environmental systems. Water Research, 206, 117695 (10 pp.). doi:10.1016/j.watres.2021.117695, Institutional Repository

Anomaly detection is the process of identifying unexpected data samples in datasets. Automated anomaly detection is either performed using supervised machine learning models, which require a labelled dataset for their calibration, or unsupervised models, which do not require labels. While academic research has produced a vast array of tools and machine learning models for automated anomaly detection, the research community focused on environmental systems still lacks a comparative analysis that is simultaneously comprehensive, objective, and systematic. This knowledge gap is addressed for the first time in this study, where 15 different supervised and unsupervised anomaly detection models are evaluated on 5 different environmental datasets from engineered and natural aquatic systems. To this end, anomaly detection performance, labelling efforts, as well as the impact of model and algorithm tuning are taken into account. As a result, our analysis reveals the relative strengths and weaknesses of the different approaches in an objective manner without bias for any particular paradigm in machine learning. Most importantly, our results show that expert-based data annotation is extremely valuable for anomaly detection based on machine learning.
Shi, B., Catsamas, S., Kolotelo, P., Wang, M., Lintern, A., Jovanovic, D., … McCarthy, D. T. (2021). A low‐cost water depth and electrical conductivity sensor for detecting inputs into urban stormwater networks. Sensors, 21(9), 3056 (22 pp.). doi:10.3390/s21093056, Institutional Repository

High‐resolution data collection of the urban stormwater network is crucial for future asset management and illicit discharge detection, but often too expensive as sensors and ongoing frequent maintenance works are not affordable. We developed an integrated water depth, electrical conductivity (EC), and temperature sensor that is inexpensive (USD 25), low power, and easily implemented in urban drainage networks. Our low‐cost sensor reliably measures the rate‐of‐change of water level without any re‐calibration by comparing with industry‐standard instruments such as HACH and HORIBA’s probes. To overcome the observed drift of level sensors, we developed an automated re‐calibration approach, which significantly improved its accuracy. For applications like monitoring stormwater drains, such an approach will make higher‐resolution sensing feasible from the budget control considerations, since the regular sensor re‐calibration will no longer be required. For other applications like monitoring wetlands or wastewater networks, a manual re‐calibration every two weeks is required to limit the sensor’s inaccuracies to ±10 mm. Apart from only being used as a calibrator for the level sensor, the conductivity sensor in this study adequately monitored EC between 0 and 10 mS/cm with a 17% relative uncertainty, which is sufficient for stormwater monitoring, especially for real‐time detection of poor stormwater quality inputs. Overall, our proposed sensor can be rapidly and densely deployed in the urban drainage network for revolutionised high‐density monitoring that cannot be achieved before with high‐end loggers and sensors.
Spuhler, D., Scheidegger, A., & Maurer, M. (2021). Ex-ante quantification of nutrient, total solids, and water flows in sanitation systems. Journal of Environmental Management, 280, 111785 (17 pp.). doi:10.1016/j.jenvman.2020.111785, Institutional Repository

To prioritise sustainable sanitation systems in strategic sanitation planning, indicators such as local appropriateness or resource recovery have to be known at the pre-planning phase. The quantification of resource recovery remains a challenge because existing substance flow models require large amounts of input data and can therefore only be applied for a few options at a time for which implementation examples exist. This paper aims to answer two questions: How can we predict resource recovery and losses of sanitation systems ex-ante at the pre-planning phase? And how can we do this efficiently to consider the entire sanitation system option space? The approach builds on an existing model to create all valid sanitation systems from a set of conventional and emerging technologies and to evaluate their appropriateness for a given application case. It complements the previous model with a Substance Flow Model (SFM) and with transfer coefficients from a technology library to quantify nutrients (phosphorus and nitrogen), total solids (as an indicator for energy and organics), and water flows in sanitation systems ex ante. The transfer coefficients are based on literature data and expert judgement. Uncertainties resulting from the variability of literature data or ignorance of experts are explicitly considered, allowing to assess the robustness of the model output. Any (future) technologies or additional products can easily be added to the library. The model is illustrated with a small didactic example showing how 12 valid system configurations are generated from a few technologies, and how substance flows, recovery ratios, and losses to soil, air, and water are quantified considering uncertainties. The recovery ratios vary between 0 and 28% for phosphorus, 0–10% for nitrogen, 0–26% for total solids, and 0–12% for water. The uncertainties reflect the high variability of the literature data but are comparable to those obtained in studies using a conventional post-ante material flow analysis (generally about 30% variability at the scale of a an urban area). Because the model is fully automated and based on literature data, it can be applied ex-ante to a large and diverse set of possible sanitation systems as shown with a real application case. From the 41 technologies available in the library, 101,548 systems are generated and substance flows are modelled. The resulting recovery ratios range from nothing to almost 100%. The two examples also show that recovery depend on technology interactions and has therefore to be assessed for all possible system configurations and not at the single technology level only. The examples also show that there exist trade-offs among different types of reuse (e.g. energy versus nutrients) or different sustainability indicators (e.g. local appropriateness versus resource recovery). These results show that there is a need for such an automated and generic approach that provides recovery data for all system configurations already at the pre-planning phase. The approach presented enables to integrate transparently the best available knowledge for a growing number of sanitation technologies into a planning process. The resulting resource recovery and loss ratios can be used to prioritise resource efficient systems in sanitation planning, either for the pre-selection or the detailed evaluation of options using e.g. MCDA. The results can also be used to guide future development of technology and system innovations. As resource recovery becomes more relevant and novel sanitation technologies and system options emerge, the approach presents itself as a useful tool for strategic sanitation planning in line with the Sustainable Development Goals (SDGs).
Strande, L., Englund, M., Andriessen, N., Carbajal, J. P., & Scheidegger, A. (2021). Estimating quantities and qualities (Q&Q) of faecal sludge at community to city‐wide scales. In K. Velkushanova, L. Strande, M. Ronteltap, T. Koottatep, D. Brdjanovic, & C. Buckley (Eds.), Methods for faecal sludge analysis (pp. 115-144). London: IWA Publishing. , Institutional Repository
Stravs, M. A., Stamm, C., Ort, C., & Singer, H. (2021). Transportable automated HRMS platform "mS2field" enables insights into water-quality dynamics in real time. Environmental Science and Technology Letters, 8(5), 373-380. doi:10.1021/acs.estlett.1c00066, Institutional Repository

Tracking the occurrence of a broad variety of chemicals in the aquatic environment at a high temporal resolution over extended time periods is challenging. Here, we present a transportable platform integrating sample preparation, liquid chromatography-high-resolution mass spectrometry measurement, automated data processing, and remote control and surveillance. The system is capable of quantifying pollutants at 20 min intervals with high sensitivity (limit of quantification down to 10 ng/L) and operated stably on-site over prolonged periods (<3 ppm mass drift over two weeks, <0.3 min retention time drift over six weeks). Field campaigns under different conditions demonstrated unprecedented insights into pollutant dynamics. Time-resolved measurements in a small creek revealed concentration peaks with up to 10-fold exceedances of environmental quality standards. The quantification of illicit drugs and their metabolites in raw wastewater distinguished fractions of consumed and discarded cocaine. Frequency analyses and data mining showed clusters of diurnal, episodic, and possibly industry-related pollutants, including newly identified substances. With this enabling technology the potential for researching and managing chemicals in natural and technical environments can be significantly expanded beyond our current capabilities, for example, real-time control in process engineering and sewer operation (water management and environmental toxicology), industrial surveillance, and wastewater-based epidemiology.
Wang, W., Leitão, J. P., & Wani, O. (2021). Is flow control in a space-constrained drainage network effective? A performance assessment for combined sewer overflow reduction. Environmental Research, 202, 111688 (11 pp.). doi:10.1016/j.envres.2021.111688, Institutional Repository

Recurring combined sewer overflows (CSOs) can have a significant impact on the ecological condition of receiving water bodies. There are several structural measures, like adding retention basins and switching to low impact development solutions, that have been proposed to reduce the number of sewage overflows. Besides, several flow control strategies have been discussed in scientific literature that take advantage of the space within urban drainage networks, which is assumed to be adequate, for temporary storage. The adequacy of such storage space, however, is not a universally valid assumption as a large fraction of drainage networks frequently operate close to their design discharge. In this paper, we investigate the efficacy of flow control for a space-constrained drainage network. We employ a low-cost, heuristic real time control strategy with the use of flow control devices (FCDs) and available in-sewer space to reduce the magnitude of CSOs. We consider the performance of the proposed control strategy and discuss the effect of FCD location on CSO reduction. Our results, based on over 300 rainfall-event simulations, show that the flow control strategy using limited sewer capacity is more efficient during relatively small rainfall events, where the CSO is large enough to enable reduction using the chosen control rules. The CSO is reduced, to varying degrees, for around 80% of rainfall events with peak intensity between 10 and 20 mm h−1. For larger rainfall events, the flow control is more unstable in response to abrupt water release during control operation, which seems to be unavoidable because of the water accumulation effect and the transition to pressurized pipe flow in space-constrained networks. We also found that the flow control performance is highly sensitive to the FCD location – as it depends on the interplay of the peak rainfall intensity and the water level condition immediately upstream of the FCD. The efficacy of a location for flow control is determined by the unfilled capacity (i.e., effective in-sewer storage potential) in the pipe upstream of the FCD during the rainfall peak; furthermore, the location also has to be resistant to the water accumulation effect. Using our analysis, we substantiate two anticipated caveats to flow control strategies when the storage space is limited in a drainage network: diminished performance in CSO reduction and the appearance of additional control-related challenges, which are otherwise mitigated in more spacious networks.
Špačková, A., Bareš, V., Fencl, M., Schleiss, M., Jaffrain, J., Berne, A., & Rieckermann, J. (2021). A year of attenuation data from a commercial dual-polarized duplex microwave link with concurrent disdrometer, rain gauge, and weather observations. Earth System Science Data, 13(8), 4219-4240. doi:10.5194/essd-13-4219-2021, Institutional Repository

Commercial microwave links (CMLs) in telecommunication networks can provide relevant information for remote sensing of precipitation and other environmental variables, such as path-averaged drop size distribution, evaporation, or humidity. The CoMMon field experiment (COmmercial Microwave links for urban rainfall MONitoring) mainly focused on the rainfall observations by monitoring a 38 GHz dual-polarized CML of 1.85 km path length at a high temporal resolution (4 s), as well as a co-located array of five disdrometers and three rain gauges over 1 year. The dataset is complemented with observations from five nearby weather stations. Raw and pre-processed data, which can be explored with a custom static HTML viewer, are available at https://doi.org/10.5281/zenodo.4923125 (Špačková et al., 2021). The data quality is generally satisfactory for further analysis, and potentially problematic measurements are flagged to help the analyst identify relevant periods for specific study purposes. Finally, we encourage potential applications and discuss open issues regarding future remote sensing with CMLs.
Bach, P. M., Kuller, M., McCarthy, D. T., & Deletic, A. (2020). A spatial planning-support system for generating decentralised urban stormwater management schemes. Science of the Total Environment, 726, 138282 (16 pp.). doi:10.1016/j.scitotenv.2020.138282, Institutional Repository

Current Water Sensitive Urban Design (WSUD) models are either purely technical or overly simplified, lacking consideration of urban planning and stakeholder preferences to adequately support stakeholders. We developed the Urban Biophysical Environments and Technologies Simulator (UrbanBEATS), which integrates stormwater management with urban planning to support the design and implementation of WSUD. This study specifically describes and tests UrbanBEATS' WSUD Planning Module, which combines spatial analysis, infrastructure design, preference elicitation and Monte Carlo methods to generate feasible stormwater management and harvesting infrastructure options in greenfield and existing urban environments. By applying UrbanBEATS to a real-world greenfield development case study in Melbourne, Australia (with data sourced from the project's water management plans and design consultants), we explore the variety of options generated by the model and analyse them collectively to demonstrate that UrbanBEATS can design similar WSUD systems (e.g. select suitable technology types, their sizes and locations) to actual infrastructure choices.
Chaudhary, P., D'Aronco, S., Leitão, J. P., Schindler, K., & Wegner, J. D. (2020). Water level prediction from social media images with a multi-task ranking approach. ISPRS Journal of Photogrammetry and Remote Sensing, 167, 252-262. doi:10.1016/j.isprsjprs.2020.07.003, Institutional Repository

Floods are among the most frequent and catastrophic natural disasters and affect millions of people worldwide. It is important to create accurate flood maps to plan (offline) and conduct (real-time) flood mitigation and flood rescue operations. Arguably, images collected from social media can provide useful information for that task, which would otherwise be unavailable. We introduce a computer vision system that estimates water depth from social media images taken during flooding events, in order to build flood maps in (near) real-time. We propose a multi-task (deep) learning approach, where a model is trained using both a regression and a pairwise ranking loss. Our approach is motivated by the observation that a main bottleneck for image-based flood level estimation is training data: it is difficult and requires a lot of effort to annotate uncontrolled images with the correct water depth. We demonstrate how to efficiently learn a predictor from a small set of annotated water levels and a larger set of weaker annotations that only indicate in which of two images the water level is higher, and are much easier to obtain. Moreover, we provide a new dataset, named DEEPFLOOD, with 8145 annotated ground-level images, and show that the proposed multi-task approach can predict the water level from a single, crowd-sourced image with ≈11 cm root mean square error.
Cheng, T., Xu, Z., Yang, H., Hong, S., & Leitao, J. P. (2020). Analysis of effect of rainfall patterns on urban flood process by coupled hydrological and hydrodynamic modeling. Journal of Hydrologic Engineering, 25(1), 04019061 (14 pp.). doi:10.1061/(ASCE)HE.1943-5584.0001867, Institutional Repository

Urban flooding poses an increasing threat to citizens and property and has become a global challenge. The primary cause of urban flooding is rapid urbanization, which is outpacing infrastructure development and drainage system improvements. This paper utilizes a verified flood model that couples hydrological and hydrodynamic processes to investigate the flood response under rainfall events with different patterns. A sponge city pilot area in China is taken as a case study. Drainage system performance, surface inundation patterns, and relation between them are investigated by carrying out statistical analysis and Pearson correlation analysis, respectively. Results show that with increases in the rainfall recurrence interval (RRI) and peak position ratio (PPR), drainage system performance indicators (DSPIs) generally become worse, and the total inundation area (TIA) and surface inundation areas of larger depths become larger. The response time exhibits varied patterns but generally decreases with increasing recurrence intervals and peak ratios. For surface inundation, the recurrence interval presents an increasingly significant role compared with the peak ratio as rainfall becomes heavier. Compared with other DSPIs, the volume of overflowed manholes (VOMs) shows a delayed response to rainfall and has a stronger relationship with the inundation areas with greater water depths, which indicates a possible solution of utilizing manhole storage for water management and flood control. Analyzing the response of drainage systems and flood patterns to different rainfall events using a model coupling hydrological and hydrodynamic processes comprehensively reveals the specific problems of the study area and possible innovative solutions. The analytical method and knowledge gained can help support urban flood management in China and around the world.
Cook, L. M., McGinnis, S., & Samaras, C. (2020). The effect of modeling choices on updating intensity-duration-frequency curves and stormwater infrastructure designs for climate change. Climatic Change, 159, 289-308. doi:10.1007/s10584-019-02649-6, Institutional Repository

Intensity-duration-frequency (IDF) curves, commonly used in stormwater infrastructure design to represent characteristics of extreme rainfall, are gradually being updated to reflect expected changes in rainfall under climate change. The modeling choices used for updating lead to large uncertainties; however, it is unclear how much these uncertainties affect the design and cost of stormwater systems. This study investigates how the choice of spatial resolution of the regional climate model (RCM) ensemble and the spatial adjustment technique affect climate-corrected IDF curves and resulting stormwater infrastructure designs in 34 US cities for the period 2020 to 2099. In most cities, IDF values are significantly different between three spatial adjustment techniques and two RCM spatial resolutions. These differences have the potential to alter the size of stormwater systems designed using these choices and affect the results of climate impact modeling more broadly. The largest change in the engineering decision results when the design storm is selected from the upper bounds of the uncertainty distribution of the IDF curve, which changes the stormwater pipe design size by five increments in some cases, nearly doubling the cost. State and local agencies can help reduce some of this variability by setting guidelines, such as avoiding the use of the upper bound of the future uncertainty range as a design storm and instead accounting for uncertainty by tracking infrastructure performance over time and preparing for adaptation using a resilience plan.
Duque, N., Duque, D., Aguilar, A., & Saldarriaga, J. (2020). Sewer network layout selection and hydraulic design using a mathematical optimization framework. Water, 12(12), 3337 (22 pp.). doi:10.3390/w12123337, Institutional Repository

This paper proposes an iterative mathematical optimization framework to solve the layout and hydraulic design problems of sewer networks. The layout selection model determines the flow rate and direction per pipe using mixed-integer programming, which results in a tree-like structured network. This network layout parametrizes a second model that determines hydraulic features including the diameter and the upstream and downstream invert elevations of pipes using a shortest path algorithm. These models are embedded in an iterative scheme that refines a cost function approximation for the first model upon learning the actual design cost from the second model. The framework was successfully tested on two sewer network benchmarks from the literature and a real sewer network located in Bogotá, Colombia, that is proposed as a new instance. For both benchmarks, the proposed methodology found a better solution with up to 42% cost reduction compared to the best methodologies reported in the literature. These are near-optimal solutions with respect to construction cost that satisfy all hydraulic and pipe connectivity constraints of a sewer system.
González‐Mariño, I., Baz‐Lomba, J. A., Alygizakis, N. A., Andrés‐Costa, M. J., Bade, R., Barron, L. P., … Ort, C. (2020). Spatio‐temporal assessment of illicit drug use at large scale: evidence from 7 years of international wastewater monitoring. Addiction, 115(1), 109-120. doi:10.1111/add.14767, Institutional Repository

Background and aims Wastewater‐based epidemiology is an additional indicator of drug use that is gaining reliability to complement the current established panel of indicators. The aims of this study were to: (i) assess spatial and temporal trends of population‐normalized mass loads of benzoylecgonine, amphetamine, methamphetamine and 3,4‐methylenedioxymethamphetamine (MDMA) in raw wastewater over 7 years (2011-17); (ii) address overall drug use by estimating the average number of combined doses consumed per day in each city; and (iii) compare these with existing prevalence and seizure data. Design Analysis of daily raw wastewater composite samples collected over 1 week per year from 2011 to 2017. Setting and Participants Catchment areas of 143 wastewater treatment plants in 120 cities in 37 countries. Measurements Parent substances (amphetamine, methamphetamine and MDMA) and the metabolites of cocaine (benzoylecgonine) and of Δ9‐tetrahydrocannabinol (11‐nor‐9‐carboxy‐Δ9‐tetrahydrocannabinol) were measured in wastewater using liquid chromatography-tandem mass spectrometry. Daily mass loads (mg/day) were normalized to catchment population (mg/1000 people/day) and converted to the number of combined doses consumed per day. Spatial differences were assessed world‐wide, and temporal trends were discerned at European level by comparing 2011-13 drug loads versus 2014-17 loads. Findings Benzoylecgonine was the stimulant metabolite detected at higher loads in southern and western Europe, and amphetamine, MDMA and methamphetamine in East and North-Central Europe. In other continents, methamphetamine showed the highest levels in the United States and Australia and benzoylecgonine in South America. During the reporting period, benzoylecgonine loads increased in general across Europe, amphetamine and methamphetamine levels fluctuated and MDMA underwent an intermittent upsurge. Conclusions The analysis of wastewater to quantify drug loads provides near real‐time drug use estimates that globally correspond to prevalence and seizure data.
Guozden, T., Carbajal, J. P., Bianchi, E., & Solarte, A. (2020). Optimized balance between electricity load and wind-solar energy production. Frontiers in Energy Research, 8, 16 (10 pp.). doi:10.3389/fenrg.2020.00016, Institutional Repository

One of the greatest obstacles in the exploitation of wind and solar resources is the uncertainty in their availability, usually known as intermittence. These effects can be greatly diminished by combining wind and solar resources from different locations. In this article we propose a numerical optimization of future renewable capacity additions aimed to minimize the dispersion of the residual power, which is the remaining electricity load after subtracting the contribution of renewables. Results show that penetration of wind and solar power may increase in another 10% of energy share while keeping the dispersion of the residual power constant, by adding capacity at sites most positively correlated with electricity load. For further increments, an optimized distribution of wind and solar facilities compensates variations between renewables. In this situation, wind sites that anticorrelate with solar cycle play an important role.
Hadengue, B., Scheidegger, A., Morgenroth, E., & Larsen, T. A. (2020). Modeling the water-energy nexus in households. Energy and Buildings, 225, 110262 (10 pp.). doi:10.1016/j.enbuild.2020.110262, Institutional Repository

One third of the global carbon emissions are emitted by the building sector. Over the last decades, space heating loads have decreased in modern buildings, and domestic hot water (DHW) is now oftentimes the largest energy consumer in the household. We developed the WaterHub modeling framework to assess the potential of technologies or measures targeting DHW energy demand. The framework combines process-based technological models and stochastic water demand modeling in a modular way to allow for holistic simulations of complex DHW systems. In two rigorous tests of the modeling framework, we demonstrated the importance of water consumption dynamics in the modeling of DHW systems, showing that static modeling leads to underestimated heat losses and wrong energy consumption predictions. In an exemplary case study, we identified and quantified the synergistic interactions between water boiler temperatures and a drain water heat recovery device, demonstrating the strength of this methodology for optimizing strategies targeting DHW systems. With its modular structure, this open-source modeling framework can be extended to include any DHW-related technology, providing a useful common platform for collaboration between technology developers and water experts.
Hoffmann, S., Feldmann, U., Bach, P. M., Binz, C., Farrelly, M., Frantzeskaki, N., … Udert, K. M. (2020). A research agenda for the future of urban water management: exploring the potential of non-grid, small-grid, and hybrid solutions. Environmental Science and Technology, 54(9), 5312-5322. doi:10.1021/acs.est.9b05222, Institutional Repository

Recent developments in high- and middle-income countries have exhibited a shift from conventional urban water systems to alternative solutions that are more diverse in source separation, decentralization, and modularization. These solutions include non-grid, small-grid, and hybrid systems to address such pressing global challenges as climate change, eutrophication, and rapid urbanization. They close loops, recover valuable resources, and adapt quickly to changing boundary conditions such as population size. Moving to such alternative solutions requires both technical and social innovations to co-evolve over time into integrated socio-technical urban water systems. Current implementations of alternative systems in high- and middle-income countries are promising, but they also underline the need for research questions to be addressed from technical, social, and transformative perspectives. Future research should apply a transdisciplinary research approach through socio-technical "lighthouse" projects that apply alternative urban water systems at scale. Such research should leverage experience from lighthouse projects in a range of socio-economic contexts, identify their potentials and limitations from an integrated perspective, and share their successes and failures across the urban water sector.
Jamali, B., Bach, P. M., & Deletic, A. (2020). Rainwater harvesting for urban flood management - an integrated modelling framework. Water Research, 171, 115372 (11 pp.). doi:10.1016/j.watres.2019.115372, Institutional Repository

It is well known that rainwater harvesting (RWH) can augment water supply and reduce stormwater pollutant discharges. Due to the lack of continuous 2D modelling of urban flood coverage and its associated damage, the ability of RWH to reduce urban flood risks has not been fully evaluated. Literature suggests that small distributed storage spaces using RWH tanks will reduce flood damage only during small to medium flooding events and therefore cumulative assessment of their benefits is needed. In this study we developed a new integrated modelling framework that implements a semi-continuous simulation approach to investigate flood prevention and water supply benefits of RWH tanks. The framework includes a continuous mass balance simulation model that considers antecedent rainfall conditions and water demand/usage of tanks and predicts the available storage prior to each storm event. To do so, this model couples a rainfall-runoff tank storage model with a detailed stochastic end-use water demand model. The available storage capacity of tanks is then used as a boundary condition for the novel rapid flood simulation model. This flood model was developed by coupling the U.S. EPA Storm Water Management Model (SWMM) to the Cellular-Automata Fast Flood Evaluation (CA-ffé) model to predict the inundation depth caused by surcharges over the capacity of the drainage network. The stage-depth damage curves method was used to calculate time series of flood damage, which are then directly used for flood risk and cost-benefit analysis. The model was tested through a case study in Melbourne, using a recorded rainfall time series of 85 years (after validating the flood model against 1D-2D MIKE-FLOOD). Results showed that extensive implementation of RWH tanks in the study area is economically feasible and can reduce expected annual damage in the catchment by up to approximately 30 percent. Availability of storage space and temporal distribution of rainfall within an event were important factors affecting tank performance for flood reduction.
Moy de Vitry, M., & Leitão, J. P. (2020). The potential of proxy water level measurements for calibrating urban pluvial flood models. Water Research, 175, 115669 (14 pp.). doi:10.1016/j.watres.2020.115669, Institutional Repository

Urban pluvial flood models need to be calibrated with data from actual flood events in order to validate and improve model performance. Due to the lack of conventional sensor solutions, alternative sources of data such as citizen science, social media, and surveillance cameras have been proposed in literature. Some of the methods proposed boast high scalability but without an on-site survey, they can only provide proxy measurements for physical flooding variables (such as water level). In this study, the potential value of such proxy measurements was evaluated by calibrating an urban pluvial flood model with data from experimental flood events conducted in a 25 × 25 m facility, monitored with surveillance cameras and conventional sensors in parallel. Both ideal proxy data and actual image-based proxy measurements with noise were tested, and the effects of measurement location and measurement noise were investigated separately. The results with error-free proxy data confirm the theoretic potential of such measurements, as in half of the calibration configurations tested, ideal proxy data increases model performance by at least 70% compared to sensor data. However, image-based proxy data can contain complex correlated errors, which have a complex and predominantly negative effect on performance.
Mutzner, L., Bohren, C., Mangold, S., Bloem, S., & Ort, C. (2020). Spatial differences among micropollutants in sewer overflows: a multisite analysis using passive samplers. Environmental Science and Technology, 54(11), 6584-6593. doi:10.1021/acs.est.9b05148, Institutional Repository

Untreated sewer overflows can contaminate receiving waters with micropollutants. Although concentrations of discharged micropollutants can be ecotoxicologically relevant, only limited data is available to assess occurrence and spatial differences among sewer overflow catchments. Therefore, we present an innovative type of data obtained with passive samplers at 20 combined sewer overflow sites (2-7 events per site; 95 events in total). The data sheds light on concentration ranges for 13 representative polar organic micropollutants and shows that micropollutants in both municipal wastewater and stormwater can be relevant sources of contaminants. We identify indicator micropollutants for further studies: benzotriazole (80% interquantile of time-weighted average concentration: 250–4800 ng/L), carbamazepine (33-910 ng/L), diclofenac (78-1000 ng/L), carbendazim (21-900 ng/L), diazinon (2.1-53 ng/L), diuron (22-1100 ng/L), mecoprop (98–5300 ng/L), metolachlor (6-230 ng/L), and terbutryn (29-810 ng/L). These concentration estimates are assumed to be on the safe side for comparison with environmental quality standards (EQS). A majority of sewer overflow sites (13 of 20) show discharge concentrations above acute EQS for at least one micropollutant and thus would have to rely on dilution by receiving waters to not exceed any EQS. The intersite variability among sewer overflows exceed the within-site variability. Hence, future monitoring studies should cover more sewer overflow sites. No correlation could be found with event durations, specific storage volume or land use data, thus showing the complexity of micropollutant occurrence and indicating that other factors led to the observed high spatial variability. In conclusion, our results clearly show the potential relevance of micropollutants in sewer overflows and the need to assess site-specific measures.
Nagel, J. B., Rieckermann, J., & Sudret, B. (2020). Principal component analysis and sparse polynomial chaos expansions for global sensitivity analysis and model calibration: application to urban drainage simulation. Reliability Engineering and System Safety, 195, 106737 (16 pp.). doi:10.1016/j.ress.2019.106737, Institutional Repository

This paper presents an efficient surrogate modeling strategy for the uncertainty quantification and Bayesian calibration of a hydrological model. In particular, a process-based dynamical urban drainage simulator that predicts the discharge from a catchment area during a precipitation event is considered. The goal of the case study is to perform a global sensitivity analysis and to identify the unknown model parameters as well as the measurement and prediction errors. These objectives can only be achieved by cheapening the incurred computational costs, that is, lowering the number of necessary model runs. With this in mind, a regularity-exploiting metamodeling technique is proposed that enables fast uncertainty quantification. Principal component analysis is used for output dimensionality reduction and sparse polynomial chaos expansions are used for the emulation of the reduced outputs. Sobol’ sensitivity indices are obtained directly from the expansion coefficients by a mere post-processing. Bayesian inference via Markov chain Monte Carlo posterior sampling is drastically accelerated.
Naves, J., Rieckermann, J., Cea, L., Puertas, J., & Anta, J. (2020). Global and local sensitivity analysis to improve the understanding of physically-based urban wash-off models from high-resolution laboratory experiments. Science of the Total Environment, 709, 136152 (15 pp.). doi:10.1016/j.scitotenv.2019.136152, Institutional Repository

Physically-based urban wash-off models are a promising means of studying the transport of finer suspended solids and their associated pollutants during rain events, considering spatial and temporal heterogeneities. This study contributes to the understanding of these models through an in-depth sensitivity analysis to provide the necessary information to simplify the model and deal with parameter identifiability. First, based on twelve tailored high-resolution experiments, the accurate measurement of input variables was used to study the parameters of the Hairsine-Rose sediment transport model through a global sensitivity analysis. Using Standardized Regression Coefficients (SRC) and Extended Fourier Amplitude Sensitivity Test (EFAST) methods, the analysis showed that both the total washed-off mass and the TSS peaks concentration are highly sensitive to the critical mass, which considers the reduction in the detachment of particles when the sediment available decreases and is scattered over the surface. In addition, the rain- and flow-driven detachment parameters were presented as key for smaller and larger sediment particles, respectively. Then, those uncertainties that are associated in field studies with the determination of the model input variables were also considered by conducting a local sensitivity analysis. The initial load of sediment and the mean grain size were seen to be the most important variables, thus underlining the need for very accurate measurements here. Moreover, a precise definition of Harsine-Rose parameters is also necessary to achieve reliable results in order to work on treatment and management techniques to minimize the impact of urban surface contaminants on urban environments.
Paillex, A., Siebers, A. R., Ebi, C., Mesman, J., & Robinson, C. T. (2020). High stream intermittency in an alpine fluvial network: Val Roseg, Switzerland. Limnology and Oceanography, 65, 557-568. doi:10.1002/lno.11324, Institutional Repository

More than one‐third of the world's rivers cease to flow and go dry on a periodic basis—so‐called intermittent rivers. The frequency and duration of flow intermittency in running waters are increasing due to climate change and water demands for human use. Intermittency effects on stream biodiversity and ecosystem functioning are dramatic and are expected to become increasingly prevalent in alpine landscapes in the near future. This project used modified field sensors to measure flow intermittency, temperature, and water origin (groundwater, precipitation, glacier) at high spatio‐temporal resolution throughout an alpine fluvial network (Val Roseg, Switzerland). We continuously recorded water presence in 30 tributary streams and validated sensor performance with field‐collected measures. Three different flow regimes were observed in the network, including periodically intermittent, seasonally intermittent, and permanently flowing streams. Twenty‐four streams (80% of recorded streams) dried at least once during the sampling period. Principal components analysis along with generalized additive models showed alpine streams with low average temperature and high conductivity (groundwater‐fed) were prone to permanent flow, whereas streams with higher average temperature and low conductivity (glacier‐fed) typically had intermittent flow. The field sensors proved precise for simultaneously measuring flow intermittency, temperature, and water origin at high resolution throughout the river network. Overall, this approach provides an effective way to develop eco‐hydrological models that examine the effects of flow intermittency on biodiversity and ecosystem functioning in riverine networks.
Schneider, M. Y., Furrer, V., Sprenger, E., Carbajal, J. P., Villez, K., & Maurer, M. (2020). Benchmarking soft sensors for remote monitoring of on-site wastewater treatment plants. Environmental Science and Technology, 54(17), 10840-10849. doi:10.1021/acs.est.9b07760, Institutional Repository

On-site wastewater treatment plants (OSTs) are usually unattended, so failures often remain undetected and lead to prolonged periods of reduced performance. To stabilize the performance of unattended plants, soft sensors could expose faults and failures to the operator. In a previous study, we developed soft sensors and showed that soft sensors with data from unmaintained physical sensors can be as accurate as soft sensors with data from maintained ones. The monitored variables were pH and dissolved oxygen (DO), and soft sensors were used to predict nitrification performance. In the present study, we use synthetic data and monitor three plants to test these soft sensors. We find that a long solids retention time and a moderate aeration rate improve the pH soft-sensor accuracy and that the aeration regime is the main operational parameter affecting the accuracy of the DO soft sensor. We demonstrate that integrated design of monitoring and control is necessary to achieve robustness when extrapolating from one OST to another in the absence of plant-specific fine-tuning. Additionally, we provide a unique labeled dataset for further feature and data-driven soft-sensor development. Our benchmarking results indicate that it is feasible to monitor OSTs with unmaintained sensors and without plant-specific tuning of the developed soft sensors. This is expected to drastically reduce monitoring costs for OST-based sanitation systems.
Sitzenfrei, R., Kleidorfer, M., Bach, P. M., & Bacchin, T. K. (2020). Green infrastructures for urban water system: balance between cities and nature. Water, 12(5), 1456 (4 pp.). doi:10.3390/w12051456, Institutional Repository

Urban water systems face severe challenges such as urbanisation, population growth and climate change. Traditional technical solutions, i.e., pipe-based, grey infrastructure, have a single purpose and are proven to be unsustainable compared to multi-purpose nature-based solutions. Green Infrastructure encompasses on-site stormwater management practices, which, in contrast to the centralised grey infrastructure, are often decentralised. Technologies such as green roofs, walls, trees, infiltration trenches, wetlands, rainwater harvesting and permeable pavements exhibit multi-functionality. They are capable of reducing stormwater runoff, retaining stormwater in the landscape, preserving the natural water balance, enhancing local climate resilience and also delivering ecological, social and community services. Creating multi-functional, multiple-benefit systems, however, also warrants multidisciplinary approaches involving landscape architects, urban planners, engineers and more to successfully create a balance between cities and nature. This Special Issue aims to bridge this multidisciplinary research gap by collecting recent challenges and opportunities from on-site systems up to the watershed scale.
Spuhler, D., Scheidegger, A., & Maurer, M. (2020). Comparative analysis of sanitation systems for resource recovery: influence of configurations and single technology components. Water Research, 186, 116281 (18 pp.). doi:10.1016/j.watres.2020.116281, Institutional Repository

Resource recovery and emissions from sanitation systems are critical sustainability indicators for strategic urban sanitation planning. In this context, sanitation systems are the most often structured using technology-driven templates rather than performance-based sustainability indicators. In this work, we answer two questions: Firstly, can we estimate generic resource recovery and loss potentials and their uncertainties for a diverse and large set of sanitation systems? And secondly, can we identify technological aspects of sanitation systems that indicate a better overall resource recovery performance? The aim is to obtain information that can be used as an input into any strategic planning process and to help shape technology development and system design for resource recovery in the future.
Starting from 41 technologies, which include novel and conventional options, we build 101,548 valid sanitation systems. For each system we quantify phosphorus, nitrogen, total solids, and water flows and use that to calculate recovery potentials and losses to the environment, i.e. the soil, air, or surface water. The four substances cover different properties and serve as a proxy for nutrient, organics, energy, and water resources. For modelling the flows ex-ante, we use a novel approach to consider a large range of international literature and expert data considering uncertainties. Thus all results are generic and can therefore be used as input into any strategic planning process or to help guide future technology development.
A detailed analysis of the results allows us to identify factors that influence recovery and losses. These factors include the type of source, the length of systems, and the level of containment in storage and treatment. The factors influencing recovery are related to interactions of different technologies in a system which shows the relevance of an modelling approach that allows to look at all possible system configurations systematically. Based on our analysis, we developed five recommendations for the optimization of resource recovery: (i) prioritize short systems that close the loop at the lowest possible level; (ii) separate waste streams as much as possible, because this allows for higher recovery potentials; (iii) use storage and treatment technologies that contain the products as much as possible, avoid leaching technologies (e.g. single pits) and technologies with high risk of volatilization (e.g. drying beds); (iv) design sinks to optimise recovery and avoid disposal sinks; and (v) combine various reuse options for different side streams (e.g. urine diversion systems that combine reuse of urine and production of biofuel from faeces).
Spuhler, D., Germann, V., Kassa, K., Abebe Ketema, A., Manandhar Sherpa, A., Gyalzen Sherpa, M., … Langergraber, G. (2020). Developing sanitation planning options: a tool for systematic consideration of novel technologies and systems. Journal of Environmental Management, 271, 111004 (21 pp.). doi:10.1016/j.jenvman.2020.111004, Institutional Repository

To provide access to sustainable sanitation for the entire world population, novel technologies and systems have been developed. These options are often independent of sewers, water, and energy and therefore promise to be more appropriate for fast-growing urban areas. They also allow for resource recovery and and are adaptable to changing environmental and demographic conditions what makes them more sustainable. More options, however, also enhance planning complexity. Structured decision making (SDM) can help balance opposing interests. Yet, most of the current research focuses on the selection of a preferred option, assuming that a set of appropriate options is available. There is a lack of reproducible methods for the identification of sanitation system planning options that can consider the growing number of available technology and the many possible system configurations. Additionally, there is a lack of data, particularly for novel options, to evaluate the various sustainability criteria for sanitation.To overcome this limitation, we present a novel software supported approach: the SANitation sysTem Alternative GeneratOr (Santiago). To be optimally effective, Santiago is required to be integrated into an SDM approach. In this paper, we present all the elements that such an integration requires and illustrate these methods at the case of Arba Minch, a fast growing town in Ethiopia. Based on this example and experiences from other cases, we discuss the lessons learnt and present the advantages potentially brought by Santiago for sanitation planning The integration requires four elements: a set of technologies to be looked at, decision objectives for sustainable sanitation, screening criteria to evalute technology appropriateness, and about the technologies and the casea. The main output is a set of sanitation system options that is locally appropriate, diverse in order to reveal trade-offs, and of a manageable size. To support the definition of decision objectives, we developed a generic objective hierarchy for sustainable sanitation. Because one of the main challenges lies in the quantification of screening criteria, we established the data for 27 criteria and 41 technologies in a library.The case studies showed, that if the integration is successful, then Santiago can provide substantial benefits: (i) it is systematic and reproducible; (ii) it opens up the decision space with novel and potentially more appropriate solutions; (iii) it makes international data accessible for more empirical decision making; (iv) it enables decisions based on strategic objectives in line with the sustainable development goals; (v) it allows to prioritise appropriate and resource efficient systems right from the beginning (vi) and it contributes to a more citywide inclusive approach by birding strategic objectives with an area-based appropriateness assessment. The here presented approach enables the prioritisation of appropriate and resource efficient sanitation technologies and systems in strategic planning. Thereby this approach contributes to SDG 6.2, 6.3, and 11, sustainable sanitation for all.
Spuhler, D., & Lüthi, C. (2020). Review of frameworks and tools for urban strategic sanitation planning: considering technology innovations and sustainability. Journal of Water Sanitation and Hygiene for Development, 10(4), 768-785. doi:10.2166/washdev.2020.062, Institutional Repository

To achieve citywide inclusive sanitation in developing countries, a strategic sanitation planning approach (SSA) needs to provide a variety of technical solutions that respond to different urban realities. Despite the development of various SSA frameworks, sanitation planning still often follows a 'one-size-fits-all' approach. Structured decision making (SDM) can help by balancing trade-offs among different solutions. But SDM requires a set of appropriate sanitation options to choose from. Because conventional sewer-based sanitation is often inappropriate, many novel technologies and systems have been developed (e.g. container-based sanitation). While these innovations enhance sustainability, they also increase planning complexity. In this review, we look at available frameworks and tools for SSA and discover a lack of systematic tools for the identification of planning options that are able to consider the growing portfolio of available solutions and multiple sustainability criteria. Therefore, we critically compare 15 tools from which we compile eight qualities that could help any future tool address the current sanitation challenge: it should be comprehensive, automated to deal with a large number of options, systematic, flexible towards future innovation and should consider all sustainability dimensions, make a contextualized evaluation, allow for participation, and consider uncertainties to be applicable ex-ante also for novel technologies.
Villez, K., Del Giudice, D., Neumann, M. B., & Rieckermann, J. (2020). Accounting for erroneous model structures in biokinetic process models. Reliability Engineering and System Safety, 203, 107075 (8 pp.). doi:10.1016/j.ress.2020.107075, Institutional Repository

In engineering practice, model-based design requires not only a good process-based model, but also a good description of stochastic disturbances and measurement errors to learn credible parameter values from observations. However, typical methods use Gaussian error models, which often cannot describe the complex temporal patterns of residuals. Consequently, this results in overconfidence in the identified parameters and, in turn, optimistic reactor designs. In this work, we assess the strengths and weaknesses of a method to statistically describe these patterns with autocorrelated error models. This method produces increased widths of the credible prediction intervals following the inclusion of the bias term, in turn leading to more conservative design choices. However, we also show that the augmented error model is not a universal tool, as its application cannot guarantee the desired reliability of the resulting wastewater reactor design.
Werner, T. T., Bach, P. M., Yellishetty, M., Amirpoorsaeed, F., Walsh, S., Miller, A., … Wu, X. (2020). A geospatial database for effective mine rehabilitation in Australia. Minerals, 10(9), 745 (21 pp.). doi:10.3390/min10090745, Institutional Repository

The Australian landscape is affected by abandoned mines that pose environmental, public health and safety risks. To promote the beneficial reuse, rehabilitation and/or remediation of these sites and understand their spatial arrangement, we compiled, classified and analysed a country-wide geospatial database of all known inactive hard rock mine sites. Following extensive review and classification of disparate records of such sites that have been terminated, neglected or classified as heritage, plus those under care and maintenance in Australia, we assessed state-by-state reporting and cross-border rehabilitation requirements. This was enabled by the development of the Mining Incidence Documentation & Assessment Scheme (MIDAS) that can be used to catalogue and compare active or inactive mine data regardless of reporting conventions. At a national level, and with four case studies, we performed GIS-based spatial analyses and environmental risk assessments to demonstrate potential uses of our database. Analyses considered the proximity of sites to factors such as infrastructure and sensitive environmental receptors. As Australia struggles to manage the ongoing technical, socioeconomic and environmental challenges of effective mine rehabilitation, the insights enabled by this national-level spatial database may be key to developing coordinated responses that extend beyond state boundaries. Our classification and methodology are easily transferable, thereby encouraging more formalized, systematic and widespread documentation of abandoned mines worldwide.
Zhang, K., Deletic, A., Dotto, C. B. S., Allen, R., & Bach, P. M. (2020). Modelling a 'business case' for blue-green infrastructure: lessons from the water sensitive cities toolkit. Blue-Green Systems, 2(1), 383-403. doi:10.2166/bgs.2020.018, Institutional Repository

Stormwater management through Blue-Green Infrastructure (BGI) delivers multiple benefits across urban environments. However, current integrated modelling tools fail to provide a simplified way of assessing these benefits. In this study, we reflected upon the development of an interdisciplinary BGI planning-support tool, known as the Water Sensitive Cities Toolkit (the WSC Toolkit) and offer guidance for effective tool development going forward. Based on interdisciplinary research, the WSC Toolkit incorporates a suite of independent sub-modules but can be connected together to provide integrated assessment, allowing evidence-based quantification of multiple benefits associated with BGI, e.g., stormwater treatment and harvesting, stream hydrology, erosion, minor flooding, urban microclimate, etc. Distinguished from other larger complex models, the WSC Toolkit was characterised by its simplicity, modularity and extensibility, providing scenario-based integrated assessment of these benefits. Through case studies, we demonstrated how the WSC Toolkit can be used to support improved decision-making towards maximising the benefits of BGI. We also showed how it can act as a platform for practical application of latest research outcomes and meanwhile encouraging interdisciplinary collaboration. We reflect upon five key lessons that could guide future researchers in developing effective integrated assessment tools, particularly within highly interdisciplinary fields such as BGI.
Zhang, K., Bach, P. M., Mathios, J., Dotto, C. B. S., & Deletic, A. (2020). Quantifying the benefits of stormwater harvesting for pollution mitigation. Water Research, 171, 115395 (12 pp.). doi:10.1016/j.watres.2019.115395, Institutional Repository

Stormwater harvesting (SWH) provides multiple benefits to urban water management. Other than providing water for human use, it also reduces the volume of polluted stormwater discharge to the environment. There are currently no methods available to quantify the additional environmental benefits, which could encourage greater uptake of the practice. This paper investigates a number of factors (climate and catchment characteristics, pollutant reduction targets, etc.) that could impact upon the benefits of SWH for pollution reduction through sensitivity analyses. A method was developed and tested for quantification of the pollution mitigation benefits by SWH under different scenarios. A novel indicator, Impervious Area Offset (IAO), was proposed to reflect the additional impervious area that can be left untreated to achieve the equivalent pollution load reduction targets due to the introduction of SWH. Results indicate significant correlations (p < 0.01) between IAO values and extraction rate (proportion of total annual runoff removed due to the harvesting system and water use substitution), system type, and pollutant reduction targets. The proposed linear empirical relationships between IAO values and extraction rate for different types of system configurations and pollution reduction targets were well represented by observed linear regression (average R2 = 0.98 for all tested scenarios). Empirical relationships were validated successfully against different scenarios, with differences between predicted IAO and baseline IAO values being only ±4.5% for the majority of the validation scenarios. Using this simple and reliable method to rapidly quantify SWH benefits can further add to the growing business case of adopting SWH practices.
Blumensaat, F., Leitão, J. P., Ort, C., Rieckermann, J., Scheidegger, A., Vanrolleghem, P. A., & Villez, K. (2019). How urban storm- and wastewater management prepares for emerging opportunities and threats: digital transformation, ubiquitous sensing, new data sources, and beyond – a horizon scan. Environmental Science and Technology, 53(15), 8488-8498. doi:10.1021/acs.est.8b06481, Institutional Repository

Ubiquitous sensing will create many opportunities and threats for urban water management, which are only poorly understood today. To identify the most relevant trends, we conducted a horizon scan regarding how ubiquitous sensing will shape the future of urban drainage and wastewater management. Our survey of the international urban water community received an active response from both the academics and the professionals from the water industry. The analysis of the responses demonstrates that emerging topics for urban water will often involve experts from different communities, including aquatic ecologists, urban water system engineers and managers, as well as information and communications technology professionals and computer scientists. Activities in topics that are identified as novel will either require (i) cross-disciplinary training, such as importing new developments from the IT sector, or (ii) research in new areas for urban water specialists, for example, to help solve open questions in aquatic ecology. These results are, therefore, a call for interdisciplinary research beyond our own discipline. They also demonstrate that the water management community is not yet prepared for the digital transformation, where we will experience a data demand, i.e. a “pull” of urban water data into external services. The results suggest that a lot remains to be done to harvest the upcoming opportunities. Horizon scanning should be repeated on a routine basis, under the umbrella of an experienced polling organization.
Boller, D., Moy de Vitry, M., Wegner, J. D., & Leitão, J. P. (2019). Automated localization of urban drainage infrastructure from public-access street-level images. Urban Water Journal, 16(7), 480-493. doi:10.1080/1573062X.2019.1687743, Institutional Repository

Comprehensive management of urban drainage network infrastructure is essential for sustaining the operation of these systems despite stresses from component deterioration, urban densification, and a predicted intensification of rainfall events. In this context, up-to-date and accurate urban drainage network data is key. However, such data is often absent, outdated, or incomplete. In this study, a new approach to localize manhole covers and storm drains, using deep learning to mine publicly available street-level images, is presented, tested, and assessed. Thus, the time-consuming and costly acquisition of the location of these system components can be avoided. The approach is evaluated using 5,000 high-resolution panoramas covering 500 km of public roads in Switzerland. The object detection approach proposed shows good performance and an improvement over state of the art image-based urban drainage infrastructure component detection. While the geographical localization of the detected objects still contains errors, the accuracy achieved is nevertheless sufficient for some applications, e.g. flood risk assessment.
Chaudhary, P., D'Aronco, S., Moy de Vitry, M., Leitão, J. P., & Wegner, J. D. (2019). Flood-water level estimation from social media images. In G. Vosselman, S. J. Oude Elberink, & M. Y. Yang (Eds.), ISPRS annals of the photogrammetry, remote sensing and spatial information sciences: Vol. IV-2/W5. ISPRS geospatial week (pp. 5-12). doi:10.5194/isprs-annals-IV-2-W5-5-2019, Institutional Repository

In the event of a flood, being able to build accurate flood level maps is essential for supporting emergency plan operations. In order to build such maps, it is important to collect observations from the disaster area. Social media platforms can be useful sources of information in this case, as people located in the flood area tend to share text and pictures depicting the current situation. Developing an effective and fully automatized method able to retrieve data from social media and extract useful information in real-time is crucial for a quick and proper response to these catastrophic events. In this paper, we propose a method to quantify flood-water from images gathered from social media. If no prior information about the zone where the picture was taken is available, one possible way to estimate the flood level consists of assessing how much the objects appearing in the image are submerged in water. There are various factors that make this task difficult: i) the precise size of the objects appearing in the image might not be known; ii) flood-water appearing in different zones of the image scene might have different height; iii) objects may be only partially visible as they can be submerged in water. In order to solve these problems, we propose a method that first locates selected classes of objects whose sizes are approximately known, then, it leverages this property to estimate the water level. To prove the validity of this approach, we first build a flood-water image dataset, then we use it to train a deep learning model. We finally show the ability of our trained model to recognize objects and at the same time predict correctly flood-water level.
Ebi, C., Schaltegger, F., Rust, A., & Blumensaat, F. (2019). Synchronous LoRa mesh network to monitor processes in underground infrastructure. IEEE Access, 7, 57663-57677. doi:10.1109/ACCESS.2019.2913985, Institutional Repository

Collecting precise real-time information on urban drainage system performance is essential to identify, predict and manage critical loading situations, such as urban flash floods and sewer overflows. Although emerging low-power wireless communication techniques allow efficient data transfers with great above-ground performance, for underground or indoor applications a large coverage range is difficult to achieve due to physical and topological limitations, particularly in dense urban areas. In this paper, we first discuss range limitations of the LoRaWAN standard based on a systematic evaluation of a long-term operation of a sensor network monitoring in-sewer process dynamics. Analyses reveal an –. on average – five-fold higher data packet loss for sub-surface nodes, which steadily grows with increasing distance to the gateway. Secondly, we present a novel LPWAN concept based on the LoRa. technology that i) enhances transmission reliability, efficiency and flexibility in range-critical situations through meshed multi-hop routing, and ii) ensures a precise time-synchronization through optional GPS or DCF77 long-wave time signaling. We thirdly illustrate the usefulness of the newly developed concept by evaluating the radio transmission performance for two independent full-scale field tests. Test results show that the synchronous LoRa mesh network approach clearly outperforms the standard LoRaWAN technique with regard to the reliability of packet delivery when transmitting from range-critical locations. Hence, the approach is expected to generally ease data collection from difficult-to-access locations, such as underground areas.
Ehlers, L. B., Wani, O., Koch, J., Sonnenborg, T. O., & Refsgaard, J. C. (2019). Using a simple post-processor to predict residual uncertainty for multiple hydrological model outputs. Advances in Water Resources, 129, 16-30. doi:10.1016/j.advwatres.2019.05.003, Institutional Repository

Regardless of the complexity of the hydrological model employed, uncertainty assessment (UA) is predominantly performed for the aggregated catchment response discharge. For coupled integrated models that simulate various hydrological states and fluxes on a grid cell basis, this represents a severe shortcoming. We test a simple data-driven technique (k-NN resampling) to evaluate its ability to provide reliable residual uncertainty estimates for the multi-variable (discharge, hydraulic head, soil moisture and actual evapotranspiration), deterministic output of two coupled groundwater-surface water models with different complexities. Being a nonparametric method, no explicit prior assumptions about the error distribution of different hydrological variables are required. When conditioning the algorithm, we propose to limit the number of error lags to be included based on inspection of the partial autocorrelation function (PACF). Our results confirm previous findings regarding reliability and robustness of the k-NN technique for discharge simulations and conclude that k-NN resampling also provides reliable and robust results for other variables like hydraulic head, soil moisture and actual evapotranspiration, even for underlying hydrological models with varying levels of performance. The 90% prediction intervals (PI) capture the observations in the testing period satisfactorily for all hydrological variables (92.6–97.3%), while Alpha indices (0.84–0.95) indicate very reliable PIs for all error quantiles. Differences in error structure between hydrological variables are successfully inferred from historical data and reflected in the results. We conclude that k-NN resampling represents a potent, cost-efficient UA technique for applications in operational hydrology, facilitating a near-simultaneous, easy uncertainty assessment for various outputs of computationally heavy hydrological models.
Gao, J., Li, J., Jiang, G., Shypanski, A. H., Nieradzik, L. M., Yuan, Z., … Thai, P. K. (2019). Systematic evaluation of biomarker stability in pilot scale sewer pipes. Water Research, 151, 447-455. doi:10.1016/j.watres.2018.12.032, Institutional Repository

Transformation of biomarkers (or their stability) during sewer transport is an important issue for wastewater-based epidemiology (WBE). Most studies so far have been conducted in the laboratory, which usually employed unrealistic conditions. In the present study, we utilized a pilot sewer system including a gravity pipe and a rising main pipe to investigate the fate of 24 pharmaceutical biomarkers. A programmable logic controller was used to control and monitor the system including sewer operational conditions and wastewater properties. Sequential samples were collected that can represent hydraulic retention time (HRT) of up to 8 h in a rising main and 4 h in a gravity sewer. Wastewater parameters and biomarker concentrations were analysed to evaluate the stability and transformation kinetics. The wastewater parameters of the pilot system were close to the conditions of real sewers. The findings of biomarker transformation were also close to real sewer data with seventeen biomarkers reported as stable while buprenorphine, caffeine, ethyl-sulfate, methadone, paracetamol, paraxanthine and salicylic acid degraded to variable extents. Both zero-order and first-order kinetics were used to model the degradation of unstable biomarkers and interestingly the goodness of fit R2 for the zero-order model was higher than the first-order model for all unstable biomarkers in the rising main. The pilot sewer system simulates more realistic conditions than benchtop laboratory setups and may provide a more accurate approach for assessing the in-sewer transformation kinetics and stability of biomarkers.
Haag, F., Reichert, P., Maurer, M., & Lienert, J. (2019). Integrating uncertainty of preferences and predictions in decision models: an application to regional wastewater planning. Journal of Environmental Management, 252, 109652 (16 pp.). doi:10.1016/j.jenvman.2019.109652, Institutional Repository

Decision-making in environmental management requires eliciting preferences of stakeholders and predicting outcomes of decision alternatives. Usually, preferences and predictions are both uncertain. Uncertainty of predictions can be tackled by multi-attribute utility theory, but the uncertainty of preferences remains a challenge. We demonstrate an approach for including both uncertainties in a multi-criteria decision analysis (MCDA), using utility theory and the concept of expected expected utility. For a decision regarding a regional merger of wastewater infrastructure in Switzerland, we constructed preference models for four stakeholders. These models also allowed for non-additive interactions between objectives. We evaluated the performance of eleven decision alternatives for which we predicted potential outcomes. Even though uncertainties were high, we could draw conclusions based on the expected expected utility of alternatives. Building a pipeline to discharge treated wastewater to a larger river emerged as a potential consensus alternative to mitigate the problem of micropollutants in a small stream. We investigated the robustness of the findings with sensitivity analysis regarding the preference parameters and the included objectives. In their actual decision, the stakeholders partly preferred other alternatives than those proposed by the model. Their choices could be explained by reduced decision models in which only few objectives were included. This may indicate the use of simplified choice heuristics by the stakeholders. The presented approach is feasible for supporting other difficult environmental or engineering decisions in practice, for which we give a number of recommendations.
Harder, R., Wielemaker, R., Larsen, T. A., Zeeman, G., & Öberg, G. (2019). Recycling nutrients contained in human excreta to agriculture: pathways, processes, and products. Critical Reviews in Environmental Science and Technology, 49(8), 696-743. doi:10.1080/10643389.2018.1558889, Institutional Repository

The need for better nutrient management has spurred efforts towards more comprehensive recycling of nutrients contained in human excreta to agriculture. Research in this direction has intensified throughout the past years, continuously unfolding new knowledge and technologies. The present review aspires to provide a systematic synthesis of the field by providing an accessible overview of terminology, recovery pathways and treatment options, and products rendered by treatment. Our synthesis suggests that, rather than focusing on a specific recovery pathway or product and on a limited set of nutrients, there is scope for exploring how to maximize nutrient recovery by combining individual pathways and products and including a broader range of nutrients. To this end, finding ways to more effectively share and consolidate knowledge and information on recovery pathways and products would be beneficial. The present review aims to provide a template that aims to facilitate designing human excreta management for maximum nutrient recovery, and that can serve as foundation for organizing and categorizing information for more effective sharing and consolidation.
Jamali, B., Bach, P. M., Cunningham, L., & Deletic, A. (2019). A cellular automata fast flood evaluation (CA‐ffé) model. Water Resources Research, 55(6), 4936-4953. doi:10.1029/2018WR023679, Institutional Repository

The simulation speed of two‐dimensional hydrodynamic flood models is a limiting factor when catchments are large, a considerable number of simulations is required (e.g., exploratory modeling, Monte‐Carlo flood simulations, or predicting probabilistic flood maps), or when there is a need for real‐time flood emergency management. Rapid Flood Models (RFMs) that rely only on topographic depressions and the water balance equation have been successfully implemented to predict maximum urban flood inundation depths within seconds to a few minutes. However, the preprocessing step (identification of depressions and their attributes) and the postprocessing step (marking up possible flow paths of flood water in between flooded depressions) of RFMs is time consuming. In this study, we developed a new fast flood inundation model based on the cellular automata (CA) approach. The new model does not require the preprocessing and postprocessing steps of RFMs and therefore can provide more simulation speed. The performance of our new model, referred to as Cellular Automata fast flood evaluation (CA‐ffé), was compared to two well‐known hydrodynamic flood models (HEC‐RAS and TUFLOW) in 20 simulation experiments conducted in five different urban subcatchments. CA‐ffé predicted maximum inundation depth with reasonable accuracy in a matter of seconds to a few minutes for a single rainfall event simulation. The CA‐ffé model performed exceptionally well in areas with low‐lying depressions. However, in areas where floodwaters had higher momentum and velocity, the model usually was not able to estimate inundation depths calculated by HEC‐RAS or TUFLOW. CA‐ffé's key drawback is also its inability to represent the temporal evolution of flooding and flow velocities. Nevertheless, its ability to provide spatial flood extents and depths in a fraction of the time compared to its hydrodynamic counterparts is a significant advancement toward exploratory approaches for water systems planning, model‐based predictive control, and real‐time flood management.
Kuller, M., Bach, P. M., Roberts, S., Browne, D., & Deletic, A. (2019). A planning-support tool for spatial suitability assessment of green urban stormwater infrastructure. Science of the Total Environment, 686, 856-868. doi:10.1016/j.scitotenv.2019.06.051, Institutional Repository

Distributed green stormwater management infrastructure is increasingly applied worldwide to counter the negative impacts of urbanisation and climate change, while providing a range of benefits related to ecosystem services. They are known as Water Sensitive Urban Design (WSUD) in Australia, Nature Based Solutions (NBS) in Europe, Low Impact Development (LID) in the USA, and Sponge City systems in China. Urban planning for WSUD has been ad-hoc, lacking strategy and resulting in sub-optimal outcomes. The purpose of this study is to help improve strategic WSUD planning and placement through the development of a Planning Support System. This paper presents the development of Spatial Suitability ANalysis TOol (SSANTO), a rapid GIS-based Multi-Criteria Decision Analysis tool using a flexible mix of techniques to map suitability for WSUD assets across urban areas. SSANTO applies a novel WSUD suitability framework, which conceptualises spatial suitability for WSUD implementation from two perspectives: 'Needs' and 'Opportunities' for WSUD. It combines biophysical as well as socio-economic, planning and governance criteria ('Opportunities') with criteria relating to ecosystem services ('Needs'). Testing SSANTO through comparing its results to work done by a WSUD consultancy successfully verified its algorithms and demonstrated its capability to reflect and potentially enhance the outcomes of planning processes. Manual GIS based suitability analysis is time and resource intensive. Through its rapid suitability analysis, SSANTO facilitates iterative spatial analysis for exploration of scenarios and stakeholder preferences. It thus facilitates collaborative planning and deeper understanding of the relationship between diverse and complex urban contexts and urban planning outcomes for WSUD.
McGrath, G., Kaeseberg, T., Reyes Silva, J. D., Jawitz, J. W., Blumensaat, F., Borchardt, D., … Rao, P. S. C. (2019). Network topology and rainfall controls on the variability of combined sewer overflows and loads. Water Resources Research, 55(11), 9578-9591. doi:10.1029/2019WR025336, Institutional Repository

Water and pollutant fluxes from combined sewer overflows (CSO) have a significant impact on receiving waters. The random nature of rainfall forcing dominates the variability of sewer discharges, pollutant loads, and concentrations. An analytical model developed here shows how sewer network topology and rainfall properties variously impact the stochasticity of CSO functioning. Probability distributions of sewer discharge and concentration compare well with the results from a calibrated Storm Water Management Model in an application to a sewershed located in Dresden, Germany. The model is determined by only four parameters, three of which can be predicted a priori, two from the rainfall record and one from the network topology using geomorphological flow recession theory, while the fourth can be estimated from a short discharge time series. The sensitivity of CSO and wastewater treatment loads to network structure suggests simple topologies may be more vulnerable to poor performance. The analytical model is useful for evaluating various CSO management strategies to reduce adverse impacts on receiving waters in a probabilistic setting.
Moy de Vitry, M., Kramer, S., Wegner, J. D., & Leitão, J. P. (2019). Scalable flood level trend monitoring with surveillance cameras using a deep convolutional neural network. Hydrology and Earth System Sciences, 23(11), 4621-4634. doi:10.5194/hess-23-4621-2019, Institutional Repository

In many countries, urban flooding due to local, intense rainfall is expected to become more frequent because of climate change and urbanization. Cities trying to adapt to this growing risk are challenged by a chronic lack of surface flooding data that are needed for flood risk assessment and planning. In this work, we propose a new approach that exploits existing surveillance camera systems to provide qualitative flood level trend information at scale. The approach uses a deep convolutional neural network (DCNN) to detect floodwater in surveillance footage and a novel qualitative flood index (namely, the static observer flooding index – SOFI) as a proxy for water level fluctuations visible from a surveillance camera's viewpoint. To demonstrate the approach, we trained the DCNN on 1218 flooding images collected from the Internet and applied it to six surveillance videos representing different flooding and lighting conditions. The SOFI signal obtained from the videos had a 75 % correlation to the actual water level fluctuation on average. By retraining the DCNN with a few frames from a given video, the correlation is increased to 85 % on average. The results confirm that the approach is versatile, with the potential to be applied to a variety of surveillance camera models and flooding situations without the need for on-site camera calibration. Thanks to this flexibility, this approach could be a cheap and highly scalable alternative to conventional sensing methods.
Moy de Vitry, M., Schneider, M. Y., Wani, O., Manny, L., Leitão, J. P., & Eggimann, S. (2019). Smart urban water systems: what could possibly go wrong?. Environmental Research Letters, 14(8), 081001 (4 pp.). doi:10.1088/1748-9326/ab3761, Institutional Repository

Urban water systems are being redefined for a digital age, promising substantial advantages for service users and providers, and for society as a whole. However, beside the much-discussed benefits of smart urban water systems in future smart cities, the transition will also bring unique challenges, particularly with respect to privacy and cybersecurity. A preemptive delineation of these risks and providing appropriate recommendations will help to guide digital transformations of urban water towards sustainable solutions. Faced with emerging risks of digitalization, urban water management needs to look beyond technology while recognizing the central and multifaceted role of research.
In smart city initiatives, urban water systems remain largely out of the digitalization spotlight compared to other types of infrastructure. Oftentimes, the management and planning of urban water systems still follow traditional, steel and concrete-based approaches that treat used water as waste and not as a resource [1]. The need for innovation, however, is significant: the infrastructure, operation, and maintenance cost of urban water systems around the world already ranges in the hundred billion dollars annually and water-related stresses are expected to continue rising. Digitalization could not only increase the flexibility and effectiveness of existing urban water systems, but could also allow for the provisions of new services to society. The envisioned transformation, as outlined for example in the literature [2–4], entails novel data collection and transmission techniques, analytical methods, models, and automation. For example, smart water meter data can be combined with noise loggers to detect and roughly locate leaks in water mains. Together with automated control infrastructure, pressure can be regulated to reduce water losses [4]. By this and numerous other smart solutions, not only water distribution but also sewers and wastewater treatment will be transformed. In particular, digitalization facilitates large-scale implementation of disruptive technologies like decentralized wastewater treatment [5] and direct potable reuse, which will help cities to cope with climate change and urbanization.
However, we argue that as the benefits of smart urban water systems are increasingly explored and showcased in literature, it is time to also give attention to potential risks that might emerge. Recurring data breaches and the growing use of cyber-attacks for geopolitical ends are a reminder that the digitalization of society indeed carries risks. Given the critical role of water services in society and within the water-energy-food nexus, these risks must be identified and managed pro-actively. In the following, we raise awareness and suggest ways forward in approaching the unique privacy and security issues that accompany the digitalization of urban water systems. Finally, we highlight the central role of researchers in assessing and mitigating the potential risks of the smart urban water solutions they propose.
Mutzner, L., Vermeirssen, E. L. M., & Ort, C. (2019). Passive samplers in sewers and rivers with highly fluctuating micropollutant concentrations – Better than we thought. Journal of Hazardous Materials, 361, 312-320. doi:10.1016/j.jhazmat.2018.07.040, Institutional Repository

Considerable pollutant loads can enter surface waters during rain events. Three factors challenge quantification of these pollutant fluxes using traditional sampling methods: (i) concentration fluctuations; (ii) unknown event duration; and (iii) placement, operation, and maintenance of equipment. Passive samplers offer the advantage of sampling in a continuous mode without power supply. However, variable uptake rates due to environmental factors and desorption in the case of fluctuating concentrations can affect the accuracy of time-weighted average (TWA) concentration estimates. While uncertainties related to environmental factors could be accounted for with additional effort, we can neither control nor quantify the concentration variability. We present measured and modelled concentration profiles at high temporal resolution and provide a systematic approach to assessing deviations from true TWA concentration due to fluctuating concentration profiles. We evaluate sampling of sewer overflows (0.3–14 h) with Chemcatcher and 1-week sampling in rivers. The uncertainty due to fluctuating concentrations is small, and other factors such as chemical analyses and sampler calibration have a similar or higher impact. The uncertainty due to fluctuations clearly increases with the sampling duration, particularly when exceeding the half-life of equilibrium. We conclude that passive sampling can also be used in wastewater systems with potentially high concentration variations.
Mutzner, L., Vermeirssen, E. L. M., Mangold, S., Maurer, M., Scheidegger, A., Singer, H., … Ort, C. (2019). Passive samplers to quantify micropollutants in sewer overflows: accumulation behaviour and field validation for short pollution events. Water Research, 160, 350-360. doi:10.1016/j.watres.2019.04.012, Institutional Repository

Contaminants in sewer overflows can contribute to exceedances of environmental quality standards, thus the quantification of contaminants during rainfall events is of relevance. However, monitoring is challenged by i) high spatiotemporal variability of contaminants in events of hard-to-predict durations, and ii) a large number of remote sites, which would imply enormous efforts with traditional sampling equipment. Therefore, we evaluate the applicability of passive samplers (Empore styrene-divinylbenzene reverse phase sulfonated (SDB-RPS)) to monitor a set of 13 polar organic contaminants. We present calibration experiments at high temporal resolution to assess the rate limiting accumulation mechanisms for short events (<36 h), report parameters for typical sewer conditions and compare passive samplers with composite water samples in a field study (three locations, total 10 events). With sampling rates of 0.35–3.5 L/d for 1 h reference time, our calibration results indicate a high sensitivity of passive samplers to sample short, highly variable sewer overflows. The contaminant uptake kinetic shows a fast initial accumulation, which is not well represented with the typical first-order model. Our results indicate that mass transfer to passive samplers is either controlled by the water boundary layer and the sorbent, or by the sorbent alone. Overall, passive sampler concentration estimates are within a factor 0.4 to 3.1 in comparison to composite water samples in the field study. We conclude that passive samplers are a promising approach to monitor a large number of discharge sites although it cannot replace traditional stormwater quality sampling in some cases (e.g. exact load estimates, high temporal resolution). Passive samplers facilitate identifying and prioritizing locations that may require more detailed investigations.
Muñoz, D. F., Simões, N. E., de Sousa, L. M., Maluf, L., Sá Marques, A., & Leitão, J. P. (2019). Generalizing multi-reward functions aimed at identifying the best locations to install flow control devices in sewer systems. Urban Water Journal, 16(8), 564-574. doi:10.1080/1573062X.2019.1700284, Institutional Repository

Multi-criteria decision models have been recently implemented in many urban flood risk management schemes due to the increasing demand of low-cost and reliable solutions to prevent and control overflow from sewer systems. Based on specific targets, these decision models encompass multiple reward (or objective) functions according to socio-economic requirements, vulnerability assessments and physical constraints on existing sewer systems. In this study, we present a simple algorithm to generalize reward functions aimed at locating the best sites to install in-sewer flow control devices, and thus controlling sewer overflow. The algorithm uses the mathematical structure of reward functions previously established, and adjust them based on hydraulic simulation results of two real sewer networks. Our results indicate that a single generalized reward function can efficiently identify strategic locations to guarantee (i) maximum in-sewer storage, (ii) minimum impact of possible flow control device failures and (iii) maximum flow discharge reduction upstream flood-prone urban areas.
O'Brien, J. W., Grant, S., Banks, A. P. W., Bruno, R., Carter, S., Choi, P. M., … Mueller, J. F. (2019). A national wastewater monitoring program for a better understanding of public health: a case study using the Australian census. Environment International, 122, 400-411. doi:10.1016/j.envint.2018.12.003, Institutional Repository

Wastewater contains a large range of biological and chemical markers of human activity and exposures. Through systematic collection and analysis of these markers within wastewater samples it is possible to measure the public health of whole populations. The analysis of effluent and biosolids can also be used to understand the release of chemicals from wastewater treatment plants into the environment. Wastewater analysis and comparison with catchment specific data (e.g. demographics) however remains largely unexplored. This manuscript describes a national wastewater monitoring study that combines influent, effluent and biosolids sampling with the Australian Census. An archiving program allows estimation of per capita exposure to and consumption of chemicals, public health information, as well as per capita release of chemicals into the environment. The paper discusses the study concept, critical steps in setting up a coordinated national approach and key logistical and other considerations with a focus on lessons learnt and future applications. The unique combination of archived samples, analytical data and associated census-derived population data will provide a baseline dataset that has wide and potentially increasing applications across many disciplines that include public health, epidemiology, criminology, toxicology and sociology.
Ohmura, K., Thürlimann, C. M., Kipf, M., Carbajal, J. P., & Villez, K. (2019). Characterizing long-term wear and tear of ion-selective pH sensors. Water Science and Technology, 80(3), 541-550. doi:10.2166/wst.2019.301, Institutional Repository

Today, the development and testing of methods for fault detection and identification in wastewater treatment research relies on two important assumptions: (i) that sensor faults appear at distinct times in different sensors and (ii) that any given sensor will function near-perfectly for a significant amount of time following installation. In this work, we show that such assumptions are unrealistic, at least for sensors built around an ion-selective measurement principle. Indeed, long-term exposure of sensors to treated wastewater shows that sensors exhibit fault symptoms that appear simultaneously and with similar intensity. Consequently, this suggests that future research should be reoriented towards methods that do not rely on the assumptions mentioned above. This study also provides the first empirically validated sensor fault model for wastewater treatment simulation, which is useful for effective benchmarking of both fault detection and identification methods and advanced control strategies. Finally, we evaluate the value of redundancy for remote sensor validation in decentralized wastewater treatment systems.
Pastorek, J., Fencl, M., Rieckermann, J., & Bareš, V. (2019). Commercial microwave links for urban drainage modelling: the effect of link characteristics and their position on runoff simulations. Journal of Environmental Management, 251, 109522 (11 pp.). doi:10.1016/j.jenvman.2019.109522, Institutional Repository

Commercial microwave links (CMLs), radio connections widely used in telecommunication networks, can provide path-integrated quantitative precipitation estimates (QPEs) which could complement traditional precipitation observations. This paper assesses the ability of individual CMLs to provide relevant QPEs for urban rainfall-runoff simulations and specifically investigates the influence of CML characteristics and position on the predicted runoff. The analysis is based on a 3-year-long experimental data set from a small (1.3 km2) urban catchment located in Prague, Czech Republic. QPEs from real world CMLs are used as inputs for urban rainfall-runoff predictions and subsequent modelling performance is assessed by comparing simulated runoffs with measured stormwater discharges. The results show that model performance is related to both the sensitivity of CML to rainfall and CML position. The bias propagated into the runoff predictions is inversely proportional to CML path length. The effect of CML position is especially pronounced during heavy rainfalls, when QPEs from shorter CMLs, located within or close to catchment boundaries, better reproduce runoff dynamics than QPEs from longer CMLs extending far beyond the catchment boundaries. Interestingly, QPEs averaged from all available CMLs best reproduce the runoff temporal dynamics. Adjusting CML QPEs to three rain gauges located 2–3 km outside of the catchment substantially reduces the bias in CML QPEs. Unfortunately, this compromises the ability of the CML QPEs to reproduce runoff dynamics during heavy rainfalls. More experimental case studies are necessary to provide specific recommendations on CML preprocessing methods tailored to different water management tasks, catchments and CML networks.
Penn, R., Maurer, M., Michalec, F. G., Scheidegger, A., Zhou, J., & Holzner, M. (2019). Quantifying physical disintegration of faeces in sewers: stochastic model and flow reactor experiments. Water Research, 152, 159-170. doi:10.1016/j.watres.2018.12.037, Institutional Repository

We present a novel stochastic model for quantifying gross solids (GS) physical disintegration under varying turbulent flow conditions and used a unique experimental setup for model calibration and validation. The stochastic deterioration model predicts faeces size evolution over time. It conceptually entails the two main processes of solid fragmentation, namely breakage and erosion. Model parameters were calibrated on synthetic faeces and validated with real human ones. A cylindrical reactor was used, where turbulent flow was forced by an array of water jets and the physical disintegration of the faeces was monitored using a high speed camera. Image analysis of breakage experiments obtained under backlight illumination allowed determination of the evolution of the solids’ size over time. The flow field in the reactor was characterised by particle image velocimetry (PIV) using tracer particles seeded into the water. We found different disintegration behaviours depending on turbulence intensity and water content of the solid. In conditions of low shear stress, dense solids hardly disintegrated. Generally, the model predictions mirrored the broad range in the solids disintegration rate imparted by the high variability in flow conditions and in solids characteristics. It is expected that, similar to our experiments, also in real sewer systems both flow conditions and solid characteristics are highly variable and the stochastic model can be tailored to capture this variability. We thus anticipate that the model can be integrated into existing sewer models predicting sewer flows and solids’ movement. From these, shear stress, flow velocities and transport of individual solids can be inferred. The integration of the present solids disintegration model may provide better predictions of hot-spots for solids accumulation and blockages in sewers.
Schertenleib, A., Sigrist, J., Friedrich, M. N. D., Ebi, C., Hammes, F., & Marks, S. J. (2019). Construction of a low-cost mobile incubator for field and laboratory use. Journal of Visualized Experiments (145), e58443 (17 pp.). doi:10.3791/58443, Institutional Repository

Incubators are essential for a range of culture-based microbial methods, such as membrane filtration followed by cultivation for assessing drinking water quality. However, commercially available incubators are often costly, difficult to transport, not flexible in terms of volume, and/or poorly adapted to local field conditions where access to electricity is unreliable. The purpose of this study was to develop an adaptable, low-cost and transportable incubator that can be constructed using readily available components. The electronic core of the incubator was first developed. These components were then tested under a range of ambient temperature conditions (3.5 °C - 39 °C) using three types of incubator shells (polystyrene foam box, hard cooler box, and cardboard box covered with a survival blanket). The electronic core showed comparable performance to a standard laboratory incubator in terms of the time required to reach the set temperature, inner temperature stability and spatial dispersion, power consumption, and microbial growth. The incubator set-ups were also effective at moderate and low ambient temperatures (between 3.5 °C and 27 °C), and at high temperatures (39 °C) when the incubator set temperature was higher. This incubator prototype is low-cost (< 300 USD) and adaptable to a variety of materials and volumes. Its demountable structure makes it easy to transport. It can be used in both established laboratories with grid power or in remote settings powered by solar energy or a car battery. It is particularly useful as an equipment option for field laboratories in areas with limited access to resources for water quality monitoring.
Schneider, M. Y., Carbajal, J. P., Furrer, V., Sterkele, B., Maurer, M., & Villez, K. (2019). Beyond signal quality: the value of unmaintained pH, dissolved oxygen, and oxidation-reduction potential sensors for remote performance monitoring of on-site sequencing batch reactors. Water Research, 161, 639-651. doi:10.1016/j.watres.2019.06.007, Institutional Repository

Sensor maintenance is time-consuming and is a bottleneck for monitoring on-site wastewater treatment systems. Hence, we compare maintained and unmaintained sensors to monitor the biological performance of a small-scale sequencing batch reactor (SBR). The sensor types are ion-selective pH, optical dissolved oxygen (DO), and oxidation-reduction potential (ORP) with platinum electrode. We created soft sensors using engineered features: ammonium valley for pH, oxidation ramp for DO, and nitrite ramp for the ORP. Four soft sensors based on unmaintained pH sensors correctly identified the completion of the ammonium oxidation (89–91 out of 107 cycles), about as many times as soft sensors based on a maintained pH sensor (91 out of 107 cycles). In contrast, the DO soft sensor using data from a maintained sensor showed slightly better (89 out of 96 cycles) detection performance than that using data from two unmaintained sensors (77, respectively 82 out of 96 correct). Furthermore, the DO soft sensor using maintained data is much less sensitive to the optimisation of cut-off frequency and slope tolerance than the soft sensor using unmaintained data. The nitrite ramp provided no useful information on the state of nitrite oxidation, so no comparison of maintained and unmaintained ORP sensors was possible in this case. We identified two hurdles when designing soft sensors for unmaintained sensors: i) Sensors’ type- and design-specific deterioration affects performance. ii) Feature engineering for soft sensors is sensor type specific, and the outcome is strongly influenced by operational parameters such as the aeration rate. In summary, the results with the provided soft sensors show that frequent sensor maintenance is not necessarily needed to monitor the performance of SBRs. Without sensor maintenance monitoring smalls-scale SBRs becomes practicable, which could improve the reliability of unstaffed on-site treatment systems substantially.
Shi, B., Bach, P. M., Lintern, A., Zhang, K., Coleman, R. A., Metzeling, L., … Deletic, A. (2019). Understanding spatiotemporal variability of in-stream water quality in urban environments – a case study of Melbourne, Australia. Journal of Environmental Management, 246, 203-213. doi:10.1016/j.jenvman.2019.06.006, Institutional Repository

To support sustainable urban planning and the design of water pollution mitigation strategies, the spatial and temporal trends of water quality in urban streams needs to be further understood. This study analyses over ten years of surface water quality data from 53 upstream catchments (20 of them predominated by a single type of land use) and two lowland sites across Greater Melbourne, Australia. We evaluated the impact of various catchment characteristics, especially urban land uses, on spatial and temporal urban water quality trends. Here, we focused on common urban pollutants: total suspended solids (TSS), total phosphorous (TP), total nitrogen (TN), zinc (Zn), copper (Cu) and nickel (Ni). Site median nutrient and heavy metal concentrations were negatively correlated with the catchment's elevation and its average annual rainfall. Further analysis shows that such trends were driven by the geographical pattern of Melbourne – i.e. low-laying sites tend to have less rainfall and be more urbanised. Only median concentrations of heavy metals (Zn and Cu) were correlated to catchment imperviousness. Further characterising of the urban environment was done into specific land uses (residential, industrial and commercial), yet median concentrations of all pollutants were not significantly correlated with land uses. This is because simple metrics, such as land use proportions, do not adequately reflect the significant variability in pollution sources that can exist even within the same land use type. Indeed, our temporal analysis found that the water quality difference between catchments with similar land uses is likely caused by their site-specific pollutant sources (construction and illegal discharge) and environmental management actions (wastewater management actions) regardless of similarities in land use. A 3-stage urbanisation cycle (development, operation and renewal) is suggested to further explain the urban water quality variance, but more data from small areas of an urban catchment is required to directly understand the unique impact of each urbanisation stage on water quality.
Tscharke, B. J., O’Brien, J. W., Ort, C., Grant, S., Gerber, C., Bade, R., … Mueller, J. F. (2019). Harnessing the power of the census: characterizing wastewater treatment plant  catchment populations for wastewater-based epidemiology. Environmental Science and Technology, 53(17), 10303-10311. doi:10.1021/acs.est.9b03447, Institutional Repository

Wastewater studies that provide per capita estimates of consumption (influent) or release (effluent) via wastewater systems rely heavily on accurate population data. This study evaluated the accuracy of Wastewater Treatment Plant (WWTP) reported populations, as well as hydrochemical parameters, against accurate populations from a population census. 104 catchment maps were received from WWTPs, geolocated in geospatial software and overlaid with the smallest area unit of the Australian census, equating to 14.9 million Australians or 64% of the national population. We characterized each catchment for population counts, as well as by age profile, income profile, and education level. For a subset of sites, population estimates using hydrochemical parameters BOD, COD, and dissolved ammonia were evaluated for accuracy against census populations. Population estimates provided by WWTP personnel were on average 18% higher than census-based populations. Furthermore, hydrochemical-based population estimates had high RSD (>44%) for BOD, COD, and ammonium between sites, suggesting that their applicability for use in population estimation may not be appropriate for every WWTP. Catchment age distributions were evaluated and 46% of catchments had skewed age distributions: 6% were skewed older, and 40% were skewed younger. Through this process WWTP catchment populations can be characterized in a way that will enhance the interpretations of per capita estimates.
Tscheikner-Gratl, F., Caradot, N., Cherqui, F., Leitão, J. P., Ahmadi, M., Langeveld, J. G., … Clemens, F. (2019). Sewer asset management - state of the art and research needs. Urban Water Journal, 16(9), 662-675. doi:10.1080/1573062X.2020.1713382, Institutional Repository

Sewer asset management gained momentum and importance in recent years due to economic considerations, since infrastructure maintenance and rehabilitation directly represent major investments. Because physical urban water infrastructure has life expectancies of up to 100 years or more, contemporary urban drainage systems are strongly influenced by historical decisions and implementations. The current decisions taken in sewer asset management will, therefore, have a long-lasting impact on the functionality and quality of future services provided by these networks. These decisions can be supported by different approaches ranging from various inspection techniques, deterioration models to assess the probability of failure or the technical service life, to sophisticated decision support systems crossing boundaries to other urban infrastructure. This paper presents the state of the art in sewer asset management in its manifold facets spanning a wide field of research and highlights existing research gaps while giving an outlook on future developments and research areas.
Wani, O., Scheidegger, A., Cecinati, F., Espadas, G., & Rieckermann, J. (2019). Exploring a copula-based alternative to additive error models—for non-negative and autocorrelated time series in hydrology. Journal of Hydrology, 575, 1031-1040. doi:10.1016/j.jhydrol.2019.06.006, Institutional Repository

Inaccurate description of uncertainty in the error models can cause biases in parameter estimation. When the parameters of the deterministic model and the error model are inferred jointly from the observations, the posterior converges to regions that reflect the processes in both high and low flows. If the nature of errors in low and high flows is different to the extent that the same error description cannot be used for both, biases in inference are introduced. In such cases, the parameter posterior will adjust to the region of the hydrograph with longer proportionate presence in the calibration time series. In this paper we demonstrate that the autoregressive order 1 (AR1) description of errors can lead to sub-optimally performing predictive models if the calibration period has substantial sections of inadequately modelled flows. Inference is performed within the Bayesian framework. We show this for a synthetic example as well as a case study. We also see that the predictive uncertainty bands that we get using the AR1 description can be overconfident and also admit negative values. To mitigate this, we analyze an alternative to additive error models. We use a distribution with a non-negative support, gamma in this study, reflecting the uncertainty in the system response at every time step. The gamma distribution is conditioned on the deterministic model output, which determines its mode and standard deviation. We capture autocorrelation in time using copulas. Given that copulas can capture dependence between different marginals, we use different specifications of the marginal distribution for high and low flows. The results show that 1) biases in parameter estimation can be reduced if a representative error description is attained using the flexibility of a copula-based likelihood. 2) The non-negative support allows to make more realistic uncertainty intervals for low flows. 3) However, the autocorrelation parameter in copulas severely interacts with the model and heteroscedasticity parameters. 4) While the formulation, in principle, should be of added value for parameter inference, in case of less informative priors, the flexibility of this description can produce non-robust inference.
Zhang, K., Manuelpillai, D., Raut, B., Deletic, A., & Bach, P. M. (2019). Evaluating the reliability of stormwater treatment systems under various future climate conditions. Journal of Hydrology, 568, 57-66. doi:10.1016/j.jhydrol.2018.10.056, Institutional Repository

Water Sensitive Urban Design (WSUD) stormwater systems, also known as Low Impact Development (LID) systems or Nature Based Solutions (NBS), are currently implemented based on the underlying assumption of statistical stationarity of rainfall, which threatens to become outdated under climatic uncertainty. This paper applies a new downscaling method to examine the implications of climate change on future rainfall and evaluate the reliability of WSUD stormwater infrastructure in pollution reduction, flow frequency mitigation and reliability as an alternative water supply. A variety of future atmospheric scenarios are considered as part of this comprehensive assessment by analysing an ensemble of eight different downscaled General Circulation Models (GCMs). High resolution catchment-scale rainfall projections for Melbourne, Australia were generated using a scheme called High-resolution Downscaling of Rainfall Using STEPS (HiDRUS) at a fine 1 km and 6-min scale for more precise analysis with uncertainty estimates. Statistical analyses show that, in general, the climate models predict a drier future with fewer rainfall events and longer dry periods when comparing the simulated near future (2040–2049) periods against the base-line period (1995–2004). The difference simulated between historical and future rainfall projections show minimum difference of WSUD performance in pollution removal and flow frequency reduction, with slightly lower harvesting reliability ( < 3%) observed under future climate; high variabilities, however, were observed across GCM simulations, indicating big uncertainties of system reliability under various conditions, e.g. design wetland sizes may vary from 2.5% to 4.0% of the impervious catchment area according to different future projects across GCMs. Larger WSUD systems are recommended to ensure reliable performance of pollution removal, as well as harvesting reliability under simulated future conditions. The significance of considering an ensemble of different GCMs as opposed to many scenarios generated by a single 'best' climate model was also demonstrated for the robust estimation of uncertainty in future WSUD reliability. This work highlights important considerations for the future design, management and quantitative evaluation of WSUD reliability.
Zhang, K., Deletic, A., Bach, P. M., Shi, B., Hathaway, J. M., & McCarthy, D. T. (2019). Testing of new stormwater pollution build-up algorithms informed by a genetic programming approach. Journal of Environmental Management, 241, 12-21. doi:10.1016/j.jenvman.2019.04.009, Institutional Repository

Pollution build-up and wash-off processes are often included in urban stormwater quality models. However, these models are often unreliable and have poor performance at large scales and in complicated catchments. This study tried to improve stormwater quality models by adopting the genetic programming (GP) approach to generate new build-up algorithms for three different pollutants (total suspend solids – TSS, total phosphorus – TP and total nitrogen – TN). This was followed by testing of the new models (also traditional build-up and wash-off models as benchmark) using data collected from different catchments in Australia and the USA. The GP approach informed new sets of build-up algorithms with the inclusion of not just the typical antecedent dry weather period (ADWP), but also other less 'traditional' variables - previous rainfall depth for TSS and maximum air temperatures for TP and TN simulation. The traditional models had relatively poor performance (Nash-Sutcliffe coefficient, E < 0.0), except for TP at Gilby Road (GR) (E = 0.21 in calibration and 0.43 in validation). Improved performance was observed using the models with new build-up algorithms informed by GP. Taking TP at GR for example, the best performing model had E of 0.46 in calibration and 0.54 in validation. The best performing models for TSS, TP, and TN are often different, suggesting that specific models shall be used for different pollutants. Insights into further improvements possible for stormwater quality models were given. It is recommended that in addition to the typical build-up and wash-off process, new generations of stormwater quality models should be able to account for the non-conventional pollutant sources (e.g. cross-connections, septic tank leakage, illegal discharges) through stochastic approaches. Emission inventories with information like intensity-frequency-duration (IFD) of pollutant loads from each type of non-conventional source are suggested to be built for stochastic modelling.
Zheng, Y., Mutzner, L., Ort, C., Kaegi, R., & Gottschalk, F. (2019). Modelling engineered nanomaterials in wet-weather discharges. NanoImpact, 16, 100188 (8 pp.). doi:10.1016/j.impact.2019.100188, Institutional Repository

The impacts of the unintended release of engineered nanomaterials (ENMs) and the resulting exposure to the ecosystems are still poorly understood and intensively debated. In current mass flow models, a global transfer coefficient is used to account for ENMs discharged from sewer systems to surface waters during rain events.
However, different types of sewer systems and specific ENM applications likely require a more elaborate approach to quantify ENM loads entering surface waters during rain events. Therefore, we evaluated the impact of distinguishing between different application areas of ENMs (indoor/outdoor) and different types of sewer systems (combined/separate) on the loads of selected ENMs passing through wastewater systems and reaching the surface water. We applied a dynamic mass flow analysis to eight substances (TiO2, ZnO, Ag, SiO2, FeOx, CuO, CeO2 and carbon black) for six different sewer system configurations. To estimate the runoff from streets and facades, we used a hydrological model developed for dissolved substances. For areas with separate sewer systems only and ENMs predominantly used in and released from outdoor applications (e.g. CuO, carbon black), up to ~80% of the annual loads entering the sewer systems never reach a sewage treatment plant. Those ENMs are directly discharged to surface waters via stormwater outlets. For combined sewer systems and ENMs mainly applied indoors (e.g. Ag, ZnO), the percentage of ENM bypassing sewage treatment plants remains below 2%. Although the model is setup for Switzerland and other geographical areas will show for example different rain characteristics, the relative importance of the different release pathways will broadly remain the same and the results should, therefore, be transferrable to other countries.
Amado, C., Carvalho, G., Brito, R. S., Coelho, S. T., & Leitão, J. P. (2018). Analysing the importance of variables for sewer failure prediction. Urban Water Journal, 15(4), 338-345. doi:10.1080/1573062X.2018.1459748, Institutional Repository

When defining the variables to predict sewer failure and therefore optimise sewer systems maintenance, it is important to identify the ones that most significantly influence the quality of the predictions or to define the smallest number of variables that is sufficient to obtain accurate predictions. In this study, three different statistical variable selection algorithms are applied for the first time to identify the most important variables for sewer failure prediction: the mutual information indicator, the out-of-bag samples concept, based on the random forest algorithm, and the stepwise search approach. The methods were applied to a real data-set that consists of the categorisation of sewer condition and associated physical characteristics. The mutual information and the stepwise search methods provided good predictions while those obtained using out-of-bag samples based on random forest were somewhat different, justified by the lack of robustness to imbalanced class distributions.
Bach, P. M., Deletic, A., Urich, C., & McCarthy, D. T. (2018). Modelling characteristics of the urban form to support water systems planning. Environmental Modelling and Software, 104, 249-269. doi:10.1016/j.envsoft.2018.02.012, Institutional Repository

A spatial model is presented, based on urban planning concepts for abstracting urban form characteristics in new and existing areas. Requiring input maps of land use, elevation, population and parameters from planning regulations, the model conceptualises (on a spatial grid) attributes including impervious fraction, allotment geometry and roof areas among other relevant characteristics for integrated urban water management. The model is calibrated to three different Melbourne districts, varying in size (10–60 km2) and land use. Performance was evaluated by comparing modelled outputs with observations of total dwelling count, employment and spatial distribution of impervious fraction and residential roof areas. Results not only highlight reasonably good prediction, particularly with spatially variable indicators such as imperviousness across all case studies, but also logical contrasts and consistency in the chosen planning parameters across the different case study districts. Discrepancies highlight aspects needing improvement and potential for exploring auto-calibration and model sensitivity.
Blumensaat, F., Scheidegger, A., Ebi, C., Dicht, S., Schaltegger, F., Rüst, A., … Maurer, M. (2018). Digitalization meets reality - concept and experiences from long-term wireless data collection with 50+ sewer monitors. In G. Mannina (Ed.), Proceedings of 11th international conference on urban drainage modelling (pp. 360-363). sine loco: IWA. , Institutional Repository

Blossoming visions foresee an ubiquitous availability of data enabled through emerging sensors, novel transmission technologies and revisited data analysis techniques. It is often expected that this likewise applies to urban water management (Kerkez et al., 2016; Eggimann et al., 2017). Contrary to the envisioned easiness to collect data, an in-creasing number of studies report about a declining effort to conduct experimental field re-search in catchment and urban hydrology, implying the risk of scientific advancement to be misdirected (Blume et al., 2017; van Emmerik et al., 2018). In this paper, we present re-sults from a unique sensor network that collects, transmits, and organizes very high resolu-tion status information from an urban drainage catchment. Our findings are based on a two-year operation at full-scale with more than 50 sensor nodes connected to a low-power wireless sensor network (LPWSN). In essence we i) illustrate the scalability of LPWSNs, ii) reveal telemetry limitations of the LoRaWAN standard (LoRa®Alliance 2015), iii) suggest a novel technique (LoRaMesh) to master this constraint, and iv) discuss challenges associ-ated with managing the amount of data collected from diverse sources. We find: 1. the proposed transmission technique considerably improves telemetry performance of the en-tire network without introducing additional gateway stations (total packet loss 2.2 %). 2. Dynamic and flexible data management solutions come at a price. 3. It is not the pure amount of data that is most challenging but the diversity of different signals. 4. Full metada-ta integration in the data warehouse is laborious but clearly consolidates data interpretation in the long-term run.
Caravelli, F., & Carbajal, J. P. (2018). Memristors for the curious outsiders. Technologies, 6(4), 118 (42 pp.). doi:10.3390/technologies6040118, Institutional Repository

We present both an overview and a perspective of recent experimental advances and proposed new approaches to performing computation using memristors. A memristor is a 2-terminal passive component with a dynamic resistance depending on an internal parameter. We provide an brief historical introduction, as well as an overview over the physical mechanism that lead to memristive behavior. This review is meant to guide nonpractitioners in the field of memristive circuits and their connection to machine learning and neural computation.
Castonguay, A. C., Iftekhar, M. S., Urich, C., Bach, P. M., & Deletic, A. (2018). Integrated modelling of stormwater treatment systems uptake. Water Research, 142, 301-312. doi:10.1016/j.watres.2018.05.037, Institutional Repository

Nature-based solutions provide a variety of benefits in growing cities, ranging from stormwater treatment to amenity provision such as aesthetics. However, the decision-making process involved in the installation of such green infrastructure is not straightforward, as much uncertainty around the location, size, costs and benefits impedes systematic decision-making. We developed a model to simulate decision rules used by local municipalities to install nature-based stormwater treatment systems, namely constructed wetlands, ponds/basins and raingardens. The model was used to test twenty-four scenarios of policy-making, by combining four asset selection, two location selection and three budget constraint decision rules. Based on the case study of a local municipality in Metropolitan Melbourne, Australia, the modelled uptake of stormwater treatment systems was compared with attributes of real-world systems for the simulation period. Results show that the actual budgeted funding is not reliable to predict systems’ uptake and that policy-makers are more likely to plan expenditures based on installation costs. The model was able to replicate the cumulative treatment capacity and the location of systems. As such, it offers a novel approach to investigate the impact of using different decision rules to provide environmental services considering biophysical and economic factors.
Castrignanò, E., Yang, Z., Bade, R., Baz-Lomba, J. A., Castiglioni, S., Causanilles, A., … Kasprzyk-Hordern, B. (2018). Enantiomeric profiling of chiral illicit drugs in a pan-European study. Water Research, 130, 151-160. doi:10.1016/j.watres.2017.11.051, Institutional Repository

The aim of this paper is to present the first study on spatial and temporal variation in the enantiomeric profile of chiral drugs in eight European cities. Wastewater-based epidemiology (WBE) and enantioselective analysis were combined to evaluate trends in illicit drug use in the context of their consumption vs direct disposal as well as their synthetic production routes. Spatial variations in amphetamine loads were observed with higher use in Northern European cities. Enantioselective analysis showed a general enrichment of amphetamine with the R-(−)-enantiomer in wastewater indicating its abuse. High loads of racemic methamphetamine were detected in Oslo (EF = 0.49 ± 0.02). This is in contrast to other European cities where S-(+)-methamphetamine was the predominant enantiomer. This indicates different methods of methamphetamine synthesis and/or trafficking routes in Oslo, compared with the other cities tested. An enrichment of MDMA with the R-(−)-enantiomer was observed in European wastewaters indicating MDMA consumption rather than disposal of unused drug. MDA's chiral signature indicated its enrichment with the S-(+)-enantiomer, which confirms its origin from MDMA metabolism in humans. HMMA was also detected at quantifiable concentrations in wastewater and was found to be a suitable biomarker for MDMA consumption. Mephedrone was only detected in wastewater from the United Kingdom with population-normalised loads up to 47.7 mg 1000 people−1 day−1. The enrichment of mephedrone in the R-(+)-enantiomer in wastewater suggests stereoselective metabolism in humans, hence consumption, rather than direct disposal of the drug. The investigation of drug precursors, such as ephedrine, showed that their presence was reasonably ascribed to their medical use.
Causanilles, A., Rojas Cantillano, D., Emke, E., Bade, R., Baz-Lomba, J. A., Castiglioni, S., … de Voogt, P. (2018). Comparison of phosphodiesterase type V inhibitors use in eight European cities through analysis of urban wastewater. Environment International, 115, 279-284. doi:10.1016/j.envint.2018.03.039, Institutional Repository

In this work a step forward in investigating the use of prescription drugs, namely erectile dysfunction products, at European level was taken by applying the wastewater-based epidemiology approach. 24-h composite samples of untreated wastewater were collected at the entrance of eight wastewater treatment plants serving the catchment within the cities of Bristol, Brussels, Castellón, Copenhagen, Milan, Oslo, Utrecht and Zurich. A validated analytical procedure with direct injection of filtered aliquots by liquid chromatography-tandem mass spectrometry was applied. The target list included the three active pharmaceutical ingredients (sildenafil, tadalafil and vardenafil) together with (bio)transformation products and other analogues. Only sildenafil and its two human urinary metabolites desmethyl- and desethylsildenafil were detected in the samples with concentrations reaching 60 ng L−1. The concentrations were transformed into normalized measured loads and the estimated actual consumption of sildenafil was back-calculated from these loads. In addition, national prescription data from five countries was gathered in the form of the number of prescribed daily doses and transformed into predicted loads for comparison. This comparison resulted in the evidence of a different spatial trend across Europe. In Utrecht and Brussels, prescription data could only partly explain the total amount found in wastewater; whereas in Bristol, the comparison was in agreement; and in Milan and Oslo a lower amount was found in wastewater than expected from the prescription data. This study illustrates the potential of wastewater-based epidemiology to investigate the use of counterfeit medication and rogue online pharmacy sales.
Eggimann, S., Truffer, B., Feldmann, U., & Maurer, M. (2018). Screening European market potentials for small modular wastewater treatment systems – an inroad to sustainability transitions in urban water management?. Land Use Policy, 78, 711-725. doi:10.1016/j.landusepol.2018.07.031, Institutional Repository

Urban water management represents a core economic sector exposed to global water-related challenges. Recently, small modular system configurations have been identified to enable a potential sustainability transition in this lasting and rather conservative sector. The identification of current market potentials of decentralised wastewater treatment is a first step to assess whether decentralised treatment technologies could potentially be deployed on a larger scale in Europe, which would allow current decentralised wastewater treatment technologies to develop and mature. The paper elaborates a method to assess the market potential for decentralised wastewater treatment systems by starting from a raster-based geospatial modelling framework, to determine the optimal degrees of centralisation for the case of Switzerland. The resulting market potential is shown to be twenty times higher than the current market share of decentralised systems. In order to extrapolate these findings to other countries, the calculated optimal degrees of centralisation were correlated with different spatial density measures to determine a reliable and widely available proxy: population density. Based on this indicator, the European market potentials for decentralised treatment systems are estimated to be about 100,000 units per annum serving around 35 million population equivalents. The paper concludes by discussing implications for future sustainability transitions in urban water management by large-scale installation of small modular wastewater treatment systems.
Hernández, F., Castiglioni, S., Covaci, A., de Voogt, P., Emke, E., Kasprzyk-Hordern, B., … Bijlsma, L. (2018). Mass spectrometric strategies for the investigation of biomarkers of illicit drug use in wastewater. Mass Spectrometry Reviews, 37(3), 258-280. doi:10.1002/mas.21525, Institutional Repository

The analysis of illicit drugs in urban wastewater is the basis of wastewater-based epidemiology (WBE), and has received much scientific attention because the concentrations measured can be used as a new non-intrusive tool to provide evidence-based and real-time estimates of community-wide drug consumption. Moreover, WBE allows monitoring patterns and spatial and temporal trends of drug use. Although information and expertise from other disciplines is required to refine and effectively apply WBE, analytical chemistry is the fundamental driver in this field. The use of advanced analytical techniques, commonly based on combined chromatography—mass spectrometry, is mandatory because the very low analyte concentration and the complexity of samples (raw wastewater) make quantification and identification/confirmation of illicit drug biomarkers (IDBs) troublesome. We review the most-recent literature available (mostly from the last 5 years) on the determination of IDBs in wastewater with particular emphasis on the different analytical strategies applied. The predominance of liquid chromatography coupled to tandem mass spectrometry to quantify target IDBs and the essence to produce reliable and comparable results is illustrated. Accordingly, the importance to perform inter-laboratory exercises and the need to analyze appropriate quality controls in each sample sequence is highlighted. Other crucial steps in WBE, such as sample collection and sample pre-treatment, are briefly and carefully discussed. The article further focuses on the potential of high-resolution mass spectrometry. Different approaches for target and non-target analysis are discussed, and the interest to perform experiments under laboratory-controlled conditions, as a complementary tool to investigate related compounds (e.g., minor metabolites and/or transformation products in wastewater) is treated. The article ends up with the trends and future perspectives in this field from the authors’ point of view.
Jamali, B., Löwe, R., Bach, P. M., Urich, C., Arnbjerg-Nielsen, K., & Deletic, A. (2018). A rapid urban flood inundation and damage assessment model. Journal of Hydrology, 564, 1085-1098. doi:10.1016/j.jhydrol.2018.07.064, Institutional Repository

Urban pluvial flooding is a global challenge that is frequently caused by the lack of available infiltration, retention and drainage capacity in cities. This paper presents RUFIDAM, an urban pluvial flood model, developed using GIS technology with the intention of rapidly estimating flood extent, depth and its associated damage. RUFIDAM integrates a 1D hydraulic drainage network model (SWMM or MOUSE) with an adapted version of rapid flood inundation models. One-metre resolution topographic data was used to identify depressions in an urban catchment. Volume-elevation relationships and minimum elevation between adjacent depressions were determined. Mass balance considerations were then used to simulate movement of water between depressions. Surcharge volumes from the 1D drainage network model were fed statically into the rapid inundation model. The model was tested on three urban catchments located in southeast Melbourne. Results of flood depth, extent and damage costs were compared to those produced using MIKE FLOOD; a well-known 1D-2D hydrodynamic model. Results showed that RUFIDAM can predict flood extent and accumulated damage cost with acceptable accuracy. Although some variations in the simulated location of flooding were observed, simulation time was reduced by two orders of magnitude compared to MIKE FLOOD. As such, RUFIDAM is suitable for large-scale flood studies and risk-based approaches that rely on a large number of simulations.
Kinyua, J., Negreira, N., McCall, A. K., Boogaerts, T., Ort, C., Covaci, A., & van Nuijs, A. L. N. (2018). Investigating in-sewer transformation products formed from synthetic cathinones and phenethylamines using liquid chromatography coupled to quadrupole time-of-flight mass spectrometry. Science of the Total Environment, 634, 331-340. doi:10.1016/j.scitotenv.2018.03.253, Institutional Repository

Recent studies have demonstrated the role of biofilms on the stability of drug residues in wastewater. These factors are pertinent in wastewater-based epidemiology (WBE) when estimating community-level drug use. However, there is scarce information on the biotransformation of drug residues in the presence of biofilms and the potential use of transformation products (TPs) as biomarkers in WBE.
The purpose of this work was to investigate the formation of TPs in sewage reactors in the presence of biofilm mimicking conditions during in-sewer transport. Synthetic cathinones (methylenedioxypyrovalerone, methylone, mephedrone) and phenethylamines (4-methoxy-methamphetamine and 4-methoxyamphetamine) were incubated in individual reactors over a 24 h period. Analysis of parent species and TPs was carried out using liquid chromatography coupled to quadrupole time-of-flight mass spectrometry (LC-QToFMS). Identification of TPs was done using suspect and non-target workflows.
In total, 18 TPs were detected and identified with reduction of β-keto group, demethylenation, demethylation, and hydroxylation reactions observed for the synthetic cathinones. For the phenethylamines, N- and O-demethylation reactions were identified. Overall, the experiments showed varying stability for the parent species in wastewater in the presence of biofilms. The newly identified isomeric forms of TPs particularly for methylone and mephedrone can be used as potential target biomarkers for WBE studies due to their specificity and detectability within a 24 h residence time.
Kuller, M., Farrelly, M., Deletic, A., & Bach, P. M. (2018). Building effective planning support systems for green urban water infrastructure – practitioners' perceptions. Environmental Science and Policy, 89, 153-162. doi:10.1016/j.envsci.2018.06.011, Institutional Repository

The multiple benefits of adopting distributed, green stormwater technologies in the local environment are increasingly recognised, particularly in relation to water quality, flood mitigation, amenity and aesthetics. To advance the integration of these systems into everyday decision-making practices, Planning Support Systems (PSS) are considered vital. Despite several PSS available to support planners and key decision-makers, their uptake remains constrained; a phenomenon known as the 'implementation gap'. While scholars have hypothesised why the adoption of PSS is limited, there remains little empirical investigation regarding the reasons why. This paper tests the hypotheses underlying the implementation gap in relation to water sensitive urban design (WSUD) planning. Drawing on the tacit experience of 24 key urban water planning professionals in the front-runner city of Melbourne, Australia, in-depth semi-structured interviews were undertaken to unpack the contemporary planning processes used and reveal characteristics leading to success and failure of PSS application. Data analysis revealed WSUD planning professionals regard the adoption of PSS as a significant step towards improving contemporary decision-making practices, which are regarded as opportunistic rather than strategic. PSS use was widespread, though the type, intensity and sophistication of use varied among interview participants. Confirming the hypotheses from planning literature, practitioners suggested PSS need to be user-friendly and align closely to planning practice. Additionally, however, it was found that it is crucial for PSS to meet industry conventions. Suggested improvements to current PSS included incorporating socio-economic factors alongside biophysical and planning factors, hence the role for GIS-based suitability analysis tools. Overall, this study provides current and future PSS-developers with critical insights regarding the type, function and characteristics of an 'ideal' PSS aimed at enhancing the usefulness and uptake of PSS, and thus improve planning that supports expediting green infrastructure implementation.
Kuller, M., Bach, P. M., Ramirez-Lovering, D., & Deletic, A. (2018). What drives the location choice for water sensitive infrastructure in Melbourne, Australia?. Landscape and Urban Planning, 175, 92-101. doi:10.1016/j.landurbplan.2018.03.018, Institutional Repository

Distributed and green urban drainage infrastructure known as Water Sensitive Urban Design (WSUD) is increasingly being implemented in cities globally to combat climate change and urbanisation effects. Rigorous consideration of the urban context in terms of biophysical, socio-economic and urban form related factors is crucial for optimal design outcomes. The extent to which the urban context is considered in current planning and decision-making processes remains unclear. This study investigates this relationship between current WSUD infrastructure in Melbourne (Australia) and each of the aforementioned factors for the first time. We obtained and pre-processed one of the most extensive and complete geo-located WSUD asset databases in the world (containing over 2000 WSUD assets), and undertook an evidence-based analysis of WSUD planning outcomes. Relationships were investigated using spatial analysis techniques (e.g. overlaying), as well as a number of statistical methods (e.g. exploratory regression). It was found that biophysical and urban form factors strongly explained variability in WSUD location choice, while socio-economic factors appeared to be overlooked. Our findings imply that the current WSUD planning practices are primarily governed by standard engineering design. Opportunistic WSUD planning leads to unintentional outcomes that fail to capitalise on the full potential of WSUD benefits. Increased investment in asset inventory development and analysis is critical to inform WSUD planning moving forward. Knowledge gained from this and additional studies can further planning through application in planning-support systems, to deal with the complexity and diversity of the broad set of decision criteria.
Leitão, J. P., Carbajal, J. P., Rieckermann, J., Simões, N. E., Sá Marques, A., & de Sousa, L. M. (2018). Identifying the best locations to install flow control devices in sewer networks to enable in-sewer storage. Journal of Hydrology, 556, 371-383. doi:10.1016/j.jhydrol.2017.11.020, Institutional Repository

The activation of available in-sewer storage volume has been suggested as a low-cost flood and combined sewer overflow mitigation measure. However, it is currently unknown what the attributes for suitable objective functions to identify the best location for flow control devices are and the impact of those attributes on the results. In this study, we present a novel location model and efficient algorithm to identify the best location(s) to install flow limiters. The model is a screening tool that does not require hydraulic simulations but rather considers steady state instead of simplistic static flow conditions. It also maximises in-sewer storage according to different reward functions that also considers the potential impact of flow control device failure. We demonstrate its usefulness on two real sewer networks, for which an in-sewer storage potential of approximately 2,000 m3 and 500 m3 was estimated with five flow control devices installed.
Leitão, J. P., & de Sousa, L. M. (2018). Towards the optimal fusion of high-resolution Digital Elevation Models for detailed urban flood assessment. Journal of Hydrology, 561, 651-661. doi:10.1016/j.jhydrol.2018.04.043, Institutional Repository

Newly available, more detailed and accurate elevation data sets, such as Digital Elevation Models (DEMs) generated on the basis of imagery from terrestrial LiDAR (Light Detection and Ranging) systems or Unmanned Aerial Vehicles (UAVs), can be used to improve flood-model input data and consequently increase the accuracy of the flood modelling results. This paper presents the first application of the MBlend merging method and assesses the impact of combining different DEMs on flood modelling results. It was demonstrated that different raster merging methods can have different and substantial impacts on these results. In addition to the influence associated with the method used to merge the original DEMs, the magnitude of the impact also depends on (i) the systematic horizontal and vertical differences of the DEMs, and (ii) the orientation between the DEM boundary and the terrain slope. The greater water depth and flow velocity differences between the flood modelling results obtained using the reference DEM and the merged DEMs ranged from −9.845 to 0.002 m, and from 0.003 to 0.024 m s−1 respectively; these differences can have a significant impact on flood hazard estimates. In most of the cases investigated in this study, the differences from the reference DEM results were smaller for the MBlend method than for the results of the two conventional methods. This study highlighted the importance of DEM merging when conducting flood modelling and provided hints on the best DEM merging methods to use.
Leitão, J. P., Peña-Haro, S., Lüthi, B., Scheidegger, A., & Moy de Vitry, M. (2018). Urban overland runoff velocity measurement with consumer-grade surveillance cameras and surface structure image velocimetry. Journal of Hydrology, 565, 791-804. doi:10.1016/j.jhydrol.2018.09.001, Institutional Repository

Physically-based models are important tools for evaluating the hydraulic behaviour of urban drainage systems and, more specifically, assessing flood risk. While it is well known that such models should be calibrated and validated with monitoring data, overland runoff information is seldom available for this purpose. This study investigates the potential of using surveillance camera footage to measure surface flow velocity thanks to an LSPIV-based method called Surface Structure Image Velocimetry (SSIV). Seven real-scale experiments conducted in a specialized flood training facility were used to test the SSIV method under varied and challenging conditions. SSIV performance was evaluated by benchmarking bulk (mean) velocity against that measured by a conventional sensor array. In the best conditions tested, SSIV and conventional flow sensors differed by only 1.7% (0.1% standard deviation). While the method proved sensitive to light conditions, our results suggest that infrared lighting could be used to increase measurement consistency. Our study concludes that for measuring overland flow velocity in urban areas, surveillance and traffic cameras can be considered as a low-maintenance and easy-to-install alternative to conventional sensor systems.
Mahmoodian, M., Carbajal, J. P., Bellos, V., Leopold, U., Schutz, G., & Clemens, F. (2018). A hybrid surrogate modelling strategy for simplification of detailed urban drainage simulators. Water Resources Management, 32(15), 5241-5256. doi:10.1007/s11269-018-2157-4, Institutional Repository

Urban drainage modelling typically requires development of highly detailed simulators due to the nature of various underlying surface and drainage processes, which makes them computationally too expensive. Application of such simulators is still challenging in activities such as real-time control (RTC), uncertainty quantification analysis or model calibration in which numerous simulations are required. The focus of this paper is to present a rather simple hybrid surrogate modelling (or emulation) strategy to simplify and accelerate a detailed urban drainage simulator (UDS). The proposed surrogate modelling strategy includes: a) identification of the variables to be emulated; b) development of a simplified conceptual model in which every component contributing to the variables identified in step (a) is replaced by a function; c) definition of these functions, either based on knowledge about the mechanisms of the simulator, or based on the data produced by the simulator; and finally, d) validation of the results produced by the surrogate model in comparison with the original detailed simulator. Herein, a detailed InfoWorks ICM simulator was selected for surrogate modelling. The case study area was a small urban drainage network in Luxembourg. An emulator was developed to map the rainfall time series, as input, to a storage tank volume and combined sewer overflow (CSO) in the case study network. The results showed that the introduced strategy provides a reliable method to simplify the simulator and reduce its run time significantly. For the specific case study, the emulator was approximately 1300 times faster than the original detailed simulator. For quantification of the emulation error, an ensemble of 500 rainfall scenarios with 1 month duration was generated by application of a multivariate autoregressive model for conditional simulation of rainfall time series. The results produced by the emulator were compared to the ones produced by the simulator. Finally, as an indicator of the emulation error, distributions of Nash-Sutcliffe efficiency (NSE) between the emulator and simulator results for prediction of storage tank volume and CSO flow time series were presented.
Moreira de Sousa, L., & Leitão, J. P. (2018). HexASCII: a file format for cartographical hexagonal rasters. Transactions in GIS, 22(1), 217-232. doi:10.1111/tgis.12304, Institutional Repository

Hexagonal segmentations of space have long been known for their advantages vis à vis squared partitions in discretizing spatial variables, be it natural phenomena or human-related features. However, readily available and easy-to-use tools to manipulate and interact with hexagonal rasters remain widely unavailable today. This article presents a first step to enable the use of hexagonal rasters in the GIS field. A format to encode cartographical hexagonal meshes as simple ASCII files is specified through a context-free grammar. Named HexASCII, this file format provides a simple means of storing and sharing such rasters. A set of simple tools based on the HexASCII format is presented, allowing their creation and basic interaction with traditional GIS software.
Moy de Vitry, M., Schindler, K., Rieckermann, J., & Leitão, J. P. (2018). Sewer inlet localization in UAV image clouds: improving performance with multiview detection. Remote Sensing, 10(5), 706 (18 pp.). doi:10.3390/rs10050706, Institutional Repository

Sewer and drainage infrastructure are often not as well catalogued as they should be, considering the immense investment they represent. In this work, we present a fully automatic framework for localizing sewer inlets from image clouds captured from an unmanned aerial vehicle (UAV). The framework exploits the high image overlap of UAV imaging surveys with a multiview approach to improve detection performance. The framework uses a Viola–Jones classifier trained to detect sewer inlets in aerial images with a ground sampling distance of 3–3.5 cm/pixel. The detections are then projected into three-dimensional space where they are clustered and reclassified to discard false positives. The method is evaluated by cross-validating results from an image cloud of 252 UAV images captured over a 0.57-km2 study area with 228 sewer inlets. Compared to an equivalent single-view detector, the multiview approach improves both recall and precision, increasing average precision from 0.65 to 0.73. The source code and case study data are publicly available for reuse.
Muthusamy, M., Wani, O., Schellart, A., & Tait, S. (2018). Accounting for variation in rainfall intensity and surface slope in wash-off model calibration and prediction within the Bayesian framework. Water Research, 143, 561-569. doi:10.1016/j.watres.2018.06.022, Institutional Repository

Exponential wash-off models are the most widely used method to predict sediment wash-off from urban surfaces. In spite of many studies, there is still a lack of knowledge on the effect of external drivers such as rainfall intensity and surface slope on wash-off predictions. In this study, a more physically realistic "structure" is added to the original exponential wash-off model (OEM) by replacing the invariant parameters with functions of rainfall intensity and catchment surface slope, so that the model can better represent catchment and rainfall conditions without the need for lookup tables and interpolation/extrapolation. In the proposed new exponential model (NEM), two such functions are introduced. One function describes the maximum fraction of the initial load that can be washed off by a rainfall event for a given slope and the other function describes the wash-off rate during a rainfall event for a given slope. The parameters of these functions are estimated using data collected from a series of laboratory experiments carried out using an artificial rainfall generator, a 1 m2 bituminous road surface and a continuous wash-off measuring system. These experimental data contain high temporal resolution measurements of wash-off fractions for combinations of five rainfall intensities ranging from 33 to 155 mm/h and three catchment slopes ranging from 2 to 8%. Bayesian inference, which allows the incorporation of prior knowledge, is implemented to estimate parameter values. Explicitly accounting for model bias and measurement errors, a likelihood function representative of the wash-off process is formulated, and the uncertainty in the prediction of the NEM is quantified. The results of this study show: 1) even when the OEM is calibrated for every experimental condition, the NEM's performance, with parameter values defined by functions, is comparable to the OEM. 2) Verification indices for estimates of uncertainty associated with the NEM suggest that the error model used in this study is able to capture the uncertainty well.
Novic, A. J., Ort, C., O'Brien, D. S., Lewis, S. E., Davis, A. M., & Mueller, J. F. (2018). Understanding the uncertainty of estimating herbicide and nutrient mass loads in a flood event with guidance on estimator selection. Water Research, 132, 99-110. doi:10.1016/j.watres.2017.12.055, Institutional Repository

The aim of this study was to understand the uncertainty of estimating loads for observed herbicides and nutrients during a flood event and provide guidance on estimator selection. A high-resolution grab sampling campaign (258 samples over 100 h) was conducted during a flood event in a tropical waterway in Queensland, Australia. Ten herbicides and three nutrient compounds were detected at elevated concentrations. Each had a unique chemograph with differences in transport processes (e.g. dependence on flow, dilution processes and timing of concentration pulses). Resampling from the data set was used to assess uncertainty. Bias existed at lower sampling efforts but depended on estimator properties as sampling effort increased: the interpolation, ratio and regression estimators became unbiased. Large differences were observed in precision and the importance of sampling effort and estimator selection depended on the relationship between the chemograph and hydrograph. The variety of transport processes observed and the resultant variability in uncertainty suggest that useful load estimates can only be obtained with sufficient samples and appropriate estimator selection. We provide a rationale to show the latter can be guided across sampling periods by selecting an estimator where the sampling regime or the relationship between the chemograph and hydrograph meet its assumptions: interpolation becomes more correct as sampling effort increases and the ratio becomes more correct as the r2 correlation between flux and flow increases (e.g. > 0.9); a stratified composite sampling approach, even with random samples, is a promising alternative.
Patsch, D., van Vliet, S., Garbani Marcantini, L., & Johnson, D. R. (2018). Generality of associations between biological richness and the rates of metabolic processes across microbial communities. Environmental Microbiology, 20(12), 4356-4368. doi:10.1111/1462-2920.14352, Institutional Repository

Biological richness is positively associated with the rates of some metabolic processes performed by microbial communities. It remains unclear, however, whether these positive associations are a general feature of the metabolic processes performed by microbial communities or whether they are specific to certain types of metabolic processes. For example, it was hypothesized that the strength of any particular positive association depends on how many different genotypes within a microbial community perform the metabolic process of interest (i.e. the 'rarity hypothesis'). We tested the generality of these positive associations by measuring the taxonomic richness, functional gene richness and rate constants for 71 different metabolic processes across 30 independent microbial communities. We found that both taxonomic and functional gene richness do indeed tend to positively associate with the rates of metabolic processes. In addition, we found that positive associations occur across a wide range of different environmental conditions. Counter to the 'rarity hypothesis', however, we did not detect a relationship between the strengths of the positive associations and the rarity of each metabolic process. Together, our data provide empirical evidence that positive associations with biological richness may indeed be a general feature of the metabolic processes performed by microbial communities.
Penn, R., Ward, B. J., Strande, L., & Maurer, M. (2018). Review of synthetic human faeces and faecal sludge for sanitation and wastewater research. Water Research, 132, 222-240. doi:10.1016/j.watres.2017.12.063, Institutional Repository

Investigations involving human faeces and faecal sludge are of great importance for urban sanitation, such as operation and maintenance of sewer systems, or implementation of faecal sludge management. However, working with real faecal matter is difficult as it not only involves working with a pathogenic, malodorous material but also individual faeces and faecal sludge samples are highly variable, making it difficult to execute repeatable experiments. Synthetic faeces and faecal sludge can provide consistently reproducible substrate and alleviate these challenges. A critical literature review of simulants developed for various wastewater and faecal sludge related research is provided. Most individual studies sought to develop a simulant representative of specific physical, chemical, or thermal properties depending on their research objectives. Based on the review, a suitable simulant can be chosen and used or further developed according to the research needs. As an example, the authors present such a modification for the development of a simulant that can be used for investigating the motion (movement, settling and sedimentation) of faeces and their physical and biological disintegration in sewers and in on-site sanitation systems.
Penn, R., Schuetze, M., Jens, A., & Friedler, E. (2018). Tracking and simulation of gross solids transport in sewers. Urban Water Journal, 15(6), 584-591. doi:10.1080/1573062X.2018.1529190, Institutional Repository

Investigation of various phenomena occurring in sewer systems is critical for increasing the sustainability of such systems. Such investigations also includes gross solids (GS) transport. GS transport may be affected by reduction of flows resulting from population decrease and/or reduced domestic water consumption. The present paper reports on the development of a model for describing GS velocity as a function of wastewater flow characteristics. The model was calibrated and validated with field experiments, in which two methods for GS tracking in sewers were developed, using small light sticks tracked by computerized light detector, and RFID based tracking. The model is integrated in a simulator which allows a description of the movement of individual GS through sewer systems. The developed model may assist in analysing existing sewer systems that are subject to changes in their input flows and prevent undesired failures (e.g. sedimentations, blockages, toxic gases) or in designing new systems.
Spuhler, D., Scheidegger, A., & Maurer, M. (2018). Generation of sanitation system options for urban planning considering novel technologies. Water Research, 145, 259-278. doi:10.1016/j.watres.2018.08.021, Institutional Repository

The identification of appropriate sanitation systems is particularly challenging in developing urban areas where local needs are not met by conventional solutions. While structured decision-making frameworks such as Community-Led Urban Environmental Sanitation (CLUES) can help facilitate this process, they require a set of sanitation system options as input. Given the large number of possible combinations of sanitation technologies, the generation of a good set of sanitation system options is far from trivial.
This paper presents a procedure for generating a set of locally appropriate sanitation system options, which can then be used in a structured decision-making process. The systematic and partly automated procedure was designed (i) to enhance the reproducibility of option generation; (ii) to consider all types of conventional and novel technologies; (iii) to provide a set of sanitation systems that is technologically diverse; and (iv) to formally account for uncertainties linked to technology specifications and local conditions.
We applied the procedure to an emerging small town in Nepal. We assessed the appropriateness of 40 technologies and generated 17,955 appropriate system options. These were classified into 16 system templates including on-site, urine-diverting, biogas, and blackwater templates. From these, a subset of 36 most appropriate sanitation system options were selected, which included both conventional and novel options.
We performed a sensitivity analysis to evaluate the impact of different elements on the diversity and appropriateness of the set of selected sanitation system options. We found that the use of system templates is most important, followed by the use of a weighted multiplicative aggregation function to quantify local appropriateness. We also show that the optimal size of the set of selected sanitation system options is equal to or slightly greater than the number of system templates.
As novel technologies are developed and added to the already large portfolio technology options, the procedure presented in this work may become an essential tool for generating and exploring appropriate sanitation system options.
Zeisl, P., Mair, M., Kastlunger, U., Bach, P. M., Rauch, W., Sitzenfrei, R., & Kleidorfer, M. (2018). Conceptual urban water balance model for water policy testing: an approach for large scale investigation. Sustainability, 10(3), 716 (24 pp.). doi:10.3390/su10030716, Institutional Repository

Urban water management will face various challenges in the future. Growing population in cities, changing climatic conditions and uncertain availability of water resources necessitate forward-looking water policy strategies. In this paper, we introduce a new water balance model to evaluate urban water strategies at a city scale. The aim is to evaluate decentralised water management measures within a large-scale investigation and to reduce external potable water demand. The upscaling process of local information (water demand, areal data) to a conceptual model approach is described. The modelling approach requires simplification of detailed processes to enable the execution with limited computing capacity. The model was applied to Greater Metropolitan Melbourne, Australia, a highly sprawled city with nearly four million inhabitants. Scenario analysis demonstrated the impact of using different water resources of different quality classes, the extensive implementation of water saving appliances and decentralised water storage strategies on the city’s water balance. Results indicate a potential reduction of potable water demand of up to 25% with a conservative rainwater reuse and, even 60% with widespread implementation of rain- and greywater recycling. Furthermore, we demonstrate that even small systems implemented at a local level can have noticeable effects when operated as clustered schemes.
Zheng, F., Tao, R., Maier, H. R., See, L., Savic, D., Zhang, T., … Popescu, I. (2018). Crowdsourcing methods for data collection in geophysics: state of the art, issues, and future directions. Reviews of Geophysics, 56(4), 698-740. doi:10.1029/2018RG000616, Institutional Repository

Data are essential in all areas of geophysics. They are used to better understand and manage systems, either directly or via models. Given the complexity and spatiotemporal variability of geophysical systems (e.g., precipitation), a lack of sufficient data is a perennial problem, which is exacerbated by various drivers, such as climate change and urbanization. In recent years, crowdsourcing has become increasingly prominent as a means of supplementing data obtained from more traditional sources, particularly due to its relatively low implementation cost and ability to increase the spatial and/or temporal resolution of data significantly. Given the proliferation of different crowdsourcing methods in geophysics and the promise they have shown, it is timely to assess the state of the art in this field, to identify potential issues and map out a way forward. In this paper, crowdsourcing-based data acquisition methods that have been used in seven domains of geophysics, including weather, precipitation, air pollution, geography, ecology, surface water, and natural hazard management, are discussed based on a review of 162 papers. In addition, a novel framework for categorizing these methods is introduced and applied to the methods used in the seven domains of geophysics considered in this review. This paper also features a review of 93 papers dealing with issues that are common to data acquisition methods in different domains of geophysics, including the management of crowdsourcing projects, data quality, data processing, and data privacy. In each of these areas, the current status is discussed and challenges and future directions are outlined.
van Nuijs, A. L. N., Lai, F. Y., Been, F., Andres-Costa, M. J., Barron, L., Baz-Lomba, J. A., … Ort, C. (2018). Multi-year inter-laboratory exercises for the analysis of illicit drugs and metabolites in wastewater: development of a quality control system. Trends in Analytical Chemistry, 103, 34-43. doi:10.1016/j.trac.2018.03.009, Institutional Repository

Thirty-seven laboratories from 25 countries present the development of an inter-laboratory testing scheme for the analysis of seven illicit drug residues in standard solutions, tap- and wastewater. Almost 10 000 concentration values were evaluated: triplicates of up to five samples and 26 laboratories per year. The setup was substantially improved with experiences gained across the six repetitions (e.g. matrix type, sample conditions, spiking levels). From this, (pre-)analytical issues (e.g. pH adjustment, filtration) were revealed for specific analytes which resulted in formulation of best-practice protocols for inter-laboratory setup and analytical procedures. The results illustrate the effectiveness of the inter-laboratory setup to assess laboratory performance in the framework of wastewater-based epidemiology. The exercise proved that measurements of laboratories were of high quality (>80% satisfactory results for six out of seven analytes) and that analytical follow-up is important to assist laboratories in improving robustness of wastewater-based epidemiology results.
Aymerich, I., Acuña, V., Ort, C., Rodríguez-Roda, I., & Corominas, L. (2017). Fate of organic microcontaminants in wastewater treatment and river systems: an uncertainty assessment in view of sampling strategy, and compound consumption rate and degradability. Water Research, 125, 152-161. doi:10.1016/j.watres.2017.08.011, Institutional Repository

The growing awareness of the relevance of organic microcontaminants on the environment has led to a growing number of studies on attenuation of these compounds in wastewater treatment plants (WWTP) and rivers. However, the effects of the sampling strategies (frequency and duration of composite samples) on the attenuation estimates are largely unknown. Our goal was to assess how frequency and duration of composite samples influence uncertainty of the attenuation estimates in WWTPs and rivers. Furthermore, we also assessed how compound consumption rate and degradability influence uncertainty. The assessment was conducted through simulating the integrated wastewater system of Puigcerdà (NE Iberian Peninsula) using a sewer pattern generator and a coupled model of WWTP and river. Results showed that the sampling strategy is especially critical at the influent of WWTP, particularly when the number of toilet flushes containing the compound of interest is small (≤100 toilet flushes with compound day-1), and less critical at the effluent of the WWTP and in the river due to the mixing effects of the WWTP. For example, at the WWTP, when evaluating a compound that is present in 50 pulses.d-1 using a sampling frequency of 15-min to collect a 24-h composite sample, the attenuation uncertainty can range from 94% (0% degradability) to 9% (90% degradability). The estimation of attenuation in rivers is less critical than in WWTPs, as the attenuation uncertainty was lower than 10% for all evaluated scenarios. Interestingly, the errors in the estimates of attenuation are usually lower than those of loads for most sampling strategies and compound characteristics (e.g. consumption and degradability), although the opposite occurs for compounds with low consumption and inappropriate sampling strategies at the WWTP. Hence, when designing a sampling campaign, one should consider the influence of compounds' consumption and degradability as well as the desired level of accuracy in attenuation estimations.
Bade, R., Bijlsma, L., Sancho, J. V., Baz-Lomba, J. A., Castiglioni, S., Castrignanò, E., … Hernández, F. (2017). Liquid chromatography-tandem mass spectrometry determination of synthetic cathinones and phenethylamines in influent wastewater of eight European cities. Chemosphere, 168, 1032-1041. doi:10.1016/j.chemosphere.2016.10.107, Institutional Repository

The popularity of new psychoactive substances (NPS) has grown in recent years, with certain NPS commonly and preferentially consumed even following the introduction of preventative legislation. With the objective to improve the knowledge on the use of NPS, a rapid and very sensitive method was developed for the determination of ten priority NPS (N-ethylcathinone, methylenedioxypyrovalerone (MDPV), methylone, butylone, methedrone, mephedrone, naphyrone, 25-C-NBOMe, 25-I-NBOMe and 25-B-NBOMe) in influent wastewater. Sample clean-up and pre-concentration was made by off-line solid phase extraction (SPE) with Oasis MCX cartridges. Isotopically labelled internal standards were used to correct for matrix effects and potential SPE losses. Following chromatographic separation on a C18 column within 6 min, the compounds were measured by tandem mass spectrometry in positive ionization mode. The method was optimised and validated for all compounds. Limits of quantification were evaluated by spiking influent wastewater samples at 1 or 5 ng/L. An investigation into the stability of these compounds in influent wastewater was also performed, showing that, following acidification at pH 2, all compounds were relatively stable for up to 7 days. The method was then applied to influent wastewater samples from eight European countries, in which mephedrone, methylone and MDPV were detected. This work reveals that although NPS use is not as extensive as for classic illicit drugs, the application of a highly sensitive analytical procedure makes their detection in wastewater possible. The developed analytical methodology forms the basis of a subsequent model-based back-calculation of abuse rate in urban areas (i.e. wastewater-based epidemiology).
Besmer, M. D., Hammes, F., Sigrist, J. A., & Ort, C. (2017). Evaluating monitoring strategies to detect precipitation-induced microbial contamination events in karstic springs used for drinking water. Frontiers in Microbiology, 8, 2229 (12 pp.). doi:10.3389/fmicb.2017.02229, Institutional Repository

Monitoring of microbial drinking water quality is a key component for ensuring safety and understanding risk, but conventional monitoring strategies are typically based on low sampling frequencies (e.g., quarterly or monthly). This is of concern because many drinking water sources, such as karstic springs are often subject to changes in bacterial concentrations on much shorter time scales (e.g., hours to days), for example after precipitation events. Microbial contamination events are crucial from a risk assessment perspective and should therefore be targeted by monitoring strategies to establish both the frequency of their occurrence and the magnitude of bacterial peak concentrations. In this study we used monitoring data from two specific karstic springs. We assessed the performance of conventional monitoring based on historical records and tested a number of alternative strategies based on a high-resolution data set of bacterial concentrations in spring water collected with online flow cytometry (FCM). We quantified the effect of increasing sampling frequency and found that for the specific case studied, at least bi-weekly sampling would be needed to detect precipitation events with a probability of >90%. We then proposed an optimized monitoring strategy with three targeted samples per event, triggered by precipitation measurements. This approach is more effective and efficient than simply increasing overall sampling frequency. It would enable the water utility to (1) analyze any relevant event and (2) limit median underestimation of peak concentrations to approximately 10%. We conclude with a generalized perspective on sampling optimization and argue that the assessment of short-term dynamics causing microbial peak loads initially requires increased sampling/analysis efforts, but can be optimized subsequently to account for limited resources. This offers water utilities and public health authorities systematic ways to evaluate and optimize their current monitoring strategies.
Blumensaat, F., Ebi, C., Dicht, S., Rieckermann, J., & Maurer, M. (2017). IoT driven low-power radio technology for highly distributed in-sewer monitoring - a data collection technique that shifts paradigms?. In 14th IWA/IAHR international conference on urban drainage. Conference proceedings (pp. 1542-1547). Prague: c-in. , Institutional Repository

Urban drainage systems traditionally lack adequate monitoring and evaluation technologies. Although weather radar and high-resolution remote sensing technologies promise vast advances for rainfall and land-use data collection, it is still challenging to deploy dense hydrological monitoring networks for sewers. Low-power data transmission technology, which is the communication backbone in the Internet-Of-Things (IoT), has the potential to contribute to a game change towards an evidence-based management of urban drainage systems. In this paper, we share our experiences with establishing and operating a wireless sensor network (WSN) at full-scale with approximately a 1 sensor per hectare connected catchment area and a monitoring frequency of 5 minutes or less. Specifically, we discuss i) the monitoring and deployment approach and ii) the adequacy of sensorand LoRaWANTM wireless data transmission technology for monitoring applications in sewer networks. A thorough evaluation of the telemetry performance provides evidence that the proposed technique allows a highly distributed monitoring of drainage capacity, sewer infiltration, performance of retention basins and overflows, with a far less effort compared to conventional methods. Remaining challenges concern the radio network architecture to allow better access to deep underground structures and efficient methods for automated data quality control to handle this type of data in the future.
Carbajal, J. P., Leitão, J. P., Albert, C., & Rieckermann, J. (2017). Appraisal of data-driven and mechanistic emulators of nonlinear simulators: the case of hydrodynamic urban drainage models. Environmental Modelling and Software, 92, 17-27. doi:10.1016/j.envsoft.2017.02.006, Institutional Repository

System identification, sensitivity analysis, optimization and control, require a large number of model evaluations. Accurate simulators are too slow for these applications. Fast emulators provide a solution to this efficiency demand, sacrificing unneeded accuracy for speed. There are many strategies for developing emulators but selecting one remains subjective. Herein we compare the performance of two kinds of emulators: mechanistic emulators that use knowledge of the simulator's equations, and purely data-driven emulators using matrix factorization. We borrow simulators from urban water management, because more stringent performance criteria on water utilities have made emulation a crucial tool within this field. Results suggest that naive data-driven emulation outperforms mechanistic emulation. We discuss scenarios in which mechanistic emulation seems favorable for extrapolation in time and dealing with sparse and unevenly sampled data. We also point to advances in Machine Learning that have not permeated yet into the environmental science community.
Causanilles, A., Baz-Lomba, J. A., Burgard, D. A., Emke, E., González-Mariño, I., Krizman-Matasic, I., … Bijlsma, L. (2017). Improving wastewater-based epidemiology to estimate cannabis use: focus on the initial aspects of the analytical procedure. Analytica Chimica Acta, 988, 27-33. doi:10.1016/j.aca.2017.08.011, Institutional Repository

Wastewater-based epidemiology is a promising and complementary tool for estimating drug use by the general population, based on the quantitative analysis of specific human metabolites of illicit drugs in urban wastewater. Cannabis is the most commonly used illicit drug and of high interest for epidemiologists. However, the inclusion of its main human urinary metabolite 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (THC-COOH) in wastewater-based epidemiology has presented several challenges and concentrations seem to depend heavily on environmental factors, sample preparation and analyses, commonly resulting in an underestimation. The aim of the present study is to investigate, identify and diminish the source of bias when analysing THC-COOH in wastewater. Several experiments were performed to individually assess different aspects of THC-COOH determination in wastewater, such as the number of freeze-thaw cycles, filtration, sorption to different container materials and in-sample stability, and the most suitable order of preparatory steps. Results highlighted the filtration step and adjustment of the sample pH as the most critical parameters to take into account when analysing THC-COOH in wastewater. Furthermore, the order of these initial steps of the analytical procedure is crucial. Findings were translated into a recommended best-practice protocol and an inter-laboratory study was organized with eight laboratories that tested the performance of the proposed procedure. Results were found satisfactory with z-scores ≤ 2.
Cecinati, F., Wani, O., & Rico-Ramirez, M. A. (2017). Comparing approaches to deal with non-Gaussianity of rainfall data in kriging-based radar-gauge rainfall merging. Water Resources Research, 53(11), 8999-9018. doi:10.1002/2016WR020330, Institutional Repository

Merging radar and rain gauge rainfall data is a technique used to improve the quality of spatial rainfall estimates and in particular the use of Kriging with External Drift (KED) is a very effective radar-rain gauge rainfall merging technique. However, kriging interpolations assume Gaussianity of the process. Rainfall has a strongly skewed, positive, probability distribution, characterized by a discontinuity due to intermittency. In KED rainfall residuals are used, implicitly calculated as the difference between rain gauge data and a linear function of the radar estimates. Rainfall residuals are non-Gaussian as well. The aim of this work is to evaluate the impact of applying KED to non-Gaussian rainfall residuals, and to assess the best techniques to improve Gaussianity. We compare Box-Cox transformations with λ parameters equal to 0.5, 0.25, and 0.1, Box-Cox with time-variant optimization of λ, normal score transformation, and a singularity analysis technique. The results suggest that Box-Cox with λ=0.1 and the singularity analysis is not suitable for KED. Normal score transformation and Box-Cox with optimized λ, or λ=0.25 produce satisfactory results in terms of Gaussianity of the residuals, probability distribution of the merged rainfall products, and rainfall estimate quality, when validated through cross-validation. However, it is observed that Box-Cox transformations are strongly dependent on the temporal and spatial variability of rainfall and on the units used for the rainfall intensity. Overall, applying transformations results in a quantitative improvement of the rainfall estimates only if the correct transformations for the specific data set are used.
Chong, N., Bach, P. M., Moilleron, R., Bonhomme, C., & Deroubaix, J. F. (2017). Use and utility: exploring the diversity and design of water models at the science-policy interface. Water, 9(12), 983 (28 pp.). doi:10.3390/w9120983, Institutional Repository

Effort to narrow the gap between the production and use of scientific knowledge for environmental decision-making is gaining traction, yet in practice, supply and demand remains largely unbalanced. A qualitative study based on empirical analysis offers a novel approach to exploring key factors, focussing on seven water models in the context of two organisations at the science-policy interface: the PIREN-Seine in France and the CRC for Water Sensitive Cities in Australia. Tentative linkages drawn from these examples identify: (1) objective and expertise; (2) knowledge and tools; and (3) support structures as main drivers influencing the production of scientific knowledge which, in turn, affect the use and utility of modelling tools. Further insight is gained by highlighting the wide spectrum of uses and utilities existing in practice, suggesting that such 'boundary organisations' facilitate interactions and exchanges that give added value to scientific knowledge. Coordinated strategies that integrate inter-, extra-, and intra-boundary activities, framed through collaborative scenario building and the use of interactive modelling platforms, may offer ways to enhance the use and utility of scientific knowledge (and its tools) to better support water resources management, policy and planning decisions, thus promoting a more cohesive relationship between science and policy.
Eggimann, S., Mutzner, L., Wani, O., Schneider, M. Y., Spuhler, D., Moy de Vitry, M., … Maurer, M. (2017). The potential of knowing more: a review of data-driven urban water management. Environmental Science and Technology, 51(5), 2538-2553. doi:10.1021/acs.est.6b04267, Institutional Repository

The promise of collecting and utilising large amounts of data has never been greater in the history of urban water management (UWM). This paper reviews several data-driven approaches which play a key role in bringing forward a sea change. It critically investigates whether data-driven UWM offers a promising foundation for addressing current challenges and supporting fundamental changes in UWM. We discuss the examples of better rain-data management, urban pluvial flood-risk management and forecasting, drinking water and sewer network operation and management, integrated design and management, increasing water productivity, wastewater-based epidemiology and on-site water and wastewater treatment. The accumulated evidence assembled from research documented in the literature points towards a future UWM that offers significant potential benefits thanks to increased collection and utilisation of data. The findings show that data-driven UWM allows us to develop and apply novel methods, to optimize the efficiency of the current network-based approach, and an extended functionality of today’s systems. However, generic challenges related to data-driven approaches (e.g. data processing, data availability, data quality, data costs) and the specific challenges of data-driven UWM need to be addressed, namely data access and ownership, current engineering practices and the difficulty of assessing the cost benefits of data-driven UWM.
Fencl, M., Dohnal, M., Rieckermann, J., & Bareš, V. (2017). Gauge-adjusted rainfall estimates from commercial microwave links. Hydrology and Earth System Sciences, 21(1), 617-634. doi:10.5194/hess-21-617-2017, Institutional Repository

Increasing urbanization makes it more and more important to have accurate stormwater runoff predictions, especially with potentially severe weather and climatic changes on the horizon. Such stormwater predictions in turn require reliable rainfall information. Especially for urban centres, the problem is that the spatial and temporal resolution of rainfall observations should be substantially higher than commonly provided by weather services with their standard rainfall monitoring networks. Commercial microwave links (CMLs) are non-traditional sensors, which have been proposed about a decade ago as a promising solution. CMLs are line-of-sight radio connections widely used by operators of mobile telecommunication networks. They are typically very dense in urban areas and can provide path-integrated rainfall observations at sub-minute resolution. Unfortunately, quantitative precipitation estimates (QPEs) from CMLs are often highly biased due to several epistemic uncertainties, which significantly limit their usability. In this manuscript we therefore suggest a novel method to reduce this bias by adjusting QPEs to existing rain gauges. The method has been specifically designed to produce reliable results even with comparably distant rain gauges or cumulative observations. This eliminates the need to install reference gauges and makes it possible to work with existing information. First, the method is tested on data from a dedicated experiment, where a CML has been specifically set up for rainfall monitoring experiments, as well as operational CMLs from an existing cellular network. Second, we assess the performance for several experimental layouts of "ground truth" from rain gauges (RGs) with different spatial and temporal resolutions. The results suggest that CMLs adjusted by RGs with a temporal aggregation of up to 1 h (i) provide precise high-resolution QPEs (relative error <7%, Nash–Sutcliffe efficiency coefficient >0.75) and (ii) that the combination of both sensor types clearly outperforms each individual monitoring system. Unfortunately, adjusting CML observations to RGs with longer aggregation intervals of up to 24 h has drawbacks. Although it substantially reduces bias, it unfavourably smoothes out rainfall peaks of high intensities, which is undesirable for stormwater management. A similar, but less severe, effect occurs due to spatial averaging when CMLs are adjusted to remote RGs. Nevertheless, even here, adjusted CMLs perform better than RGs alone. Furthermore, we provide first evidence that the joint use of multiple CMLs together with RGs also reduces bias in their QPEs. In summary, we believe that our adjustment method has great potential to improve the space–time resolution of current urban rainfall monitoring networks. Nevertheless, future work should aim to better understand the reason for the observed systematic error in QPEs from CMLs.
Gracia-Lor, E., Rousis, N. I., Zuccato, E., Bade, R., Baz-Lomba, J. A., Castrignanò, E., … Castiglioni, S. (2017). Estimation of caffeine intake from analysis of caffeine metabolites in wastewater. Science of the Total Environment, 609, 1582-1588. doi:10.1016/j.scitotenv.2017.07.258, Institutional Repository

Caffeine metabolites in wastewater were investigated as potential biomarkers for assessing caffeine intake in a population. The main human urinary metabolites of caffeine were measured in the urban wastewater of ten European cities and the metabolic profiles in wastewater were compared with the human urinary excretion profile. A good match was found for 1,7-dimethyluric acid, an exclusive caffeine metabolite, suggesting that might be a suitable biomarker in wastewater for assessing population-level caffeine consumption. A correction factor was developed considering the percentage of excretion of this metabolite in humans, according to published pharmacokinetic studies. Daily caffeine intake estimated from wastewater analysis was compared with the average daily intake calculated from the average amount of coffee consumed by country per capita. Good agreement was found in some cities but further information is needed to standardize this approach. Wastewater analysis proved useful to providing additional local information on caffeine use.
Honti, M., Schuwirth, N., Rieckermann, J., & Stamm, C. (2017). Can integrative catchment management mitigate future water quality issues caused by climate change and socio-economic development?. Hydrology and Earth System Sciences, 21(3), 1593-1609. doi:10.5194/hess-21-1593-2017, Institutional Repository

The design and evaluation of solutions for integrated surface water quality management requires an integrated modelling approach. Integrated models have to be comprehensive enough to cover the aspects relevant for management decisions, allowing for mapping of larger-scale processes such as climate change to the regional and local contexts. Besides this, models have to be sufficiently simple and fast to apply proper methods of uncertainty analysis, covering model structure deficits and error propagation through the chain of sub-models. Here, we present a new integrated catchment model satisfying both conditions. The conceptual "iWaQa" model was developed to support the integrated management of small streams. It can be used to predict traditional water quality parameters, such as nutrients and a wide set of organic micropollutants (plant and material protection products), by considering all major pollutant pathways in urban and agricultural environments. Due to its simplicity, the model allows for a full, propagative analysis of predictive uncertainty, including certain structural and input errors. The usefulness of the model is demonstrated by predicting future surface water quality in a small catchment with mixed land use in the Swiss Plateau. We consider climate change, population growth or decline, socio-economic development, and the implementation of management strategies to tackle urban and agricultural point and non-point sources of pollution. Our results indicate that input and model structure uncertainties are the most influential factors for certain water quality parameters. In these cases model uncertainty is already high for present conditions. Nevertheless, accounting for today's uncertainty makes management fairly robust to the foreseen range of potential changes in the next decades. The assessment of total predictive uncertainty allows for selecting management strategies that show small sensitivity to poorly known boundary conditions. The identification of important sources of uncertainty helps to guide future monitoring efforts and pinpoints key indicators, whose evolution should be closely followed to adapt management. The possible impact of climate change is clearly demonstrated by water quality substantially changing depending on single climate model chains. However, when all climate trajectories are combined, the human land use and management decisions have a larger influence on water quality against a time horizon of 2050 in the study.
Leitão, J. P., Simões, N. E., Pina, R. D., Ochoa-Rodriguez, S., Onof, C., & Sá Marques, A. (2017). Stochastic evaluation of the impact of sewer inlets’ hydraulic capacity on urban pluvial flooding. Stochastic Environmental Research and Risk Assessment, 31(8), 1907-1922. doi:10.1007/s00477-016-1283-x, Institutional Repository

Sewer inlet structures are vital components of urban drainage systems and their operational conditions can largely affect the overall performance of the system. However, their hydraulic behaviour and the way in which it is affected by clogging is often overlooked in urban drainage models, thus leading to misrepresentation of system performance and, in particular, of flooding occurrence. In the present paper, a novel methodology is proposed to stochastically model stormwater urban drainage systems, taking the impact of sewer inlet operational conditions (e.g. clogging due to debris accumulation) on urban pluvial flooding into account. The proposed methodology comprises three main steps: (i) identification of sewer inlets most prone to clogging based upon a spatial analysis of their proximity to trees and evaluation of sewer inlet locations; (ii) Monte Carlo simulation of the capacity of inlets prone to clogging and subsequent simulation of flooding for each sewer inlet capacity scenario, and (iii) delineation of stochastic flood hazard maps. The proposed methodology was demonstrated using as case study design storms as well as two real storm events observed in the city of Coimbra (Portugal), which reportedly led to flooding in different areas of the catchment. The results show that sewer inlet capacity can indeed have a large impact on the occurrence of urban pluvial flooding and that it is essential to account for variations in sewer inlet capacity in urban drainage models. Overall, the stochastic methodology proposed in this study constitutes a useful tool for dealing with uncertainties in sewer inlet operational conditions and, as compared to more traditional deterministic approaches, it allows a more comprehensive assessment of urban pluvial flood hazard, which in turn enables better-informed flood risk assessment and management decisions.
McCall, A. K., Palmitessa, R., Blumensaat, F., Morgenroth, E., & Ort, C. (2017). Modeling in-sewer transformations at catchment scale – implications on drug consumption estimates in wastewater-based epidemiology. Water Research, 122, 655-668. doi:10.1016/j.watres.2017.05.034, Institutional Repository

To which extent illicit drugs are transformed during in-sewer transport, depends on a number of factors: i) substance-specific transformation rates, ii) environmental conditions, iii) point of discharge (location of drug user) and iv) sewer network properties, primarily hydraulic residence time (HRT) and the ratio of biofilm contact area to wastewater volume (A/Veq).
Assessing associated uncertainties typically requires numerous simulations. Therefore, we propose a new two-step modeling framework: 1) Quantify hydrodynamic conditions. This computationally demanding step was performed once in SWMM to derive HRT and A/Veq for each potential point of discharge (node) in three catchments of different size. 2) Estimate biomarker loss. In this step, Monte Carlo simulations were performed for defined scenarios. Depending on assumptions about drug user distribution and prevalence, a number of nodes was sampled. For each node an empirical first-order transformation model was applied with flow-path-corresponding HRT and A/Veq from step 1. Biotic and abiotic transformation rates were sampled from distributions combining variability of different biofilms.
In our modeling study, median losses were >30% for amphetamine, 6-monoacetylmorphine and 6-acetylcodeine in all three catchments with high uncertainty (5%–100% loss), which would imply a systematic underestimation of consumption when neglecting in-sewer processes. Median losses for 21 other investigated biomarkers were <10% with different uncertainty ranges – “no substantial transformation” was confirmed for nine substances in a real sewer segment with a 2-h residence time. Transferability of these results must be tested for other catchments. To further reduce uncertainty, mainly additional knowledge on transformation rates, particularly in biofilm, and their distribution across a sewer network is needed to update model input objectively. Our approach allows efficient testing and, furthermore, can be expanded for many other human biomarkers. Accounting for biomarker stability during in-sewer transport will avoid biased estimates and further improve wastewater-based epidemiology.
Moy de Vitry, M., Dicht, S., & Leitão, J. P. (2017). floodX: urban flash flood experiments monitored with conventional and alternative sensors. Earth System Science Data, 9(2), 657-666. doi:10.5194/essd-9-657-2017, Institutional Repository

The data sets described in this paper provide a basis for developing and testing new methods for monitoring and modelling urban pluvial flash floods. Pluvial flash floods are a growing hazard to property and inhabitants’ well-being in urban areas. However, the lack of appropriate data collection methods is often cited as an impediment for reliable flood modelling, thereby hindering the improvement of flood risk mapping and early warning systems. The potential of surveillance infrastructure and social media is starting to draw attention for this purpose. In the floodX project, 22 controlled urban flash floods were generated in a flood response training facility and monitored with state-of-the-art sensors as well as standard surveillance cameras. With these data, it is possible to explore the use of video data and computer vision for urban flood monitoring and modelling. The floodX project stands out as the largest documented flood experiment of its kind, providing both conventional measurements and video data in parallel and at high temporal resolution. The data set used in this paper is available at https://doi.org/10.5281/zenodo.830513.
O’Brien, J. W., Banks, A. P. W., Novic, A. J., Mueller, J. F., Jiang, G., Ort, C., … Thai, P. K. (2017). Impact of in-sewer degradation of pharmaceutical and personal care products (PPCPs) population markers on a population model. Environmental Science and Technology, 51(7), 3816-3823. doi:10.1021/acs.est.6b02755, Institutional Repository

A key uncertainty of wastewater-based epidemiology is the size of the population which contributed to a given wastewater sample. We previously developed and validated a Bayesian inference model to estimate population size based on 14 population markers which: (1) are easily measured and (2) have mass loads which correlate with population size. However, the potential uncertainty of the model prediction due to in-sewer degradation of these markers was not evaluated. In this study, we addressed this gap by testing their stability under sewer conditions and assessed whether degradation impacts the model estimates. Five markers, which formed the core of our model, were stable in the sewers while the others were not. Our evaluation showed that the presence of unstable population markers in the model did not decrease the precision of the population estimates providing that stable markers such as acesulfame remained in the model. However, to achieve the minimum uncertainty in population estimates, we propose that the core markers to be included in population models for other sites should meet two additional criteria: (3) negligible degradation in wastewater to ensure the stability of chemicals during collection; and (4) < 10% in-sewer degradation could occur during the mean residence time of the sewer network.
Peleg, N., Blumensaat, F., Molnar, P., Fatichi, S., & Burlando, P. (2017). Partitioning the impacts of spatial and climatological rainfall variability in urban drainage modeling. Hydrology and Earth System Sciences, 21(3), 1559-1572. doi:10.5194/hess-21-1559-2017, Institutional Repository

The performance of urban drainage systems is typically examined using hydrological and hydrodynamic models where rainfall input is uniformly distributed, i.e., derived from a single or very few rain gauges. When models are fed with a single uniformly distributed rainfall realization, the response of the urban drainage system to the rainfall variability remains unexplored. The goal of this study was to understand how climate variability and spatial rainfall variability, jointly or individually considered, affect the response of a calibrated hydrodynamic urban drainage model. A stochastic spatially distributed rainfall generator (STREAP – Space-Time Realizations of Areal Precipitation) was used to simulate many realizations of rainfall for a 30-year period, accounting for both climate variability and spatial rainfall variability. The generated rainfall ensemble was used as input into a calibrated hydrodynamic model (EPA SWMM – the US EPA's Storm Water Management Model) to simulate surface runoff and channel flow in a small urban catchment in the city of Lucerne, Switzerland. The variability of peak flows in response to rainfall of different return periods was evaluated at three different locations in the urban drainage network and partitioned among its sources. The main contribution to the total flow variability was found to originate from the natural climate variability (on average over 74 %). In addition, the relative contribution of the spatial rainfall variability to the total flow variability was found to increase with longer return periods. This suggests that while the use of spatially distributed rainfall data can supply valuable information for sewer network design (typically based on rainfall with return periods from 5 to 15 years), there is a more pronounced relevance when conducting flood risk assessments for larger return periods. The results show the importance of using multiple distributed rainfall realizations in urban hydrology studies to capture the total flow variability in the response of the urban drainage systems to heavy rainfall events.
Penn, R., Schütze, M., Alex, J., & Friedler, E. (2017). Impacts of onsite greywater reuse on wastewater systems. Water Science and Technology, 75(8), 1862-1872. doi:10.2166/wst.2017.057, Institutional Repository

Together with significant water savings that onsite greywater reuse (GWR) may provide, it may also affect the performance of urban sewer systems and wastewater treatment plants (WWTPs). In order to examine these effects, an integrated stochastic simulation system for GWR in urban areas was developed. The model includes stochastic generators of domestic wastewater streams and gross solids (GSs), a sewer network model which includes hydrodynamic simulation and a GS transport module, and a dynamic process model of the WWTP. The developed model was applied to a case study site in Israel. For the validation of the sewer simulator, field experiments in a real sewer segment were conducted. The paper presents the integration and implementation of these modules and depicts the results of the effects of various GWR scenarios on GS movement in sewers and on the performance of the WWTP.
Rousis, N. I., Gracia-Lor, E., Zuccato, E., Bade, R., Baz-Lomba, J. A., Castrignanò, E., … Castiglioni, S. (2017). Wastewater-based epidemiology to assess pan-European pesticide exposure. Water Research, 121, 270-279. doi:10.1016/j.watres.2017.05.044, Institutional Repository

Human biomonitoring, i.e. the determination of chemicals and/or their metabolites in human specimens, is the most common and potent tool for assessing human exposure to pesticides, but it suffers from limitations such as high costs and biases in sampling. Wastewater-based epidemiology (WBE) is an innovative approach based on the chemical analysis of specific human metabolic excretion products (biomarkers) in wastewater, and provides objective and real-time information on xenobiotics directly or indirectly ingested by a population. This study applied the WBE approach for the first time to evaluate human exposure to pesticides in eight cities across Europe. 24 h-composite wastewater samples were collected from the main wastewater treatment plants and analyzed for urinary metabolites of three classes of pesticides, namely triazines, organophosphates and pyrethroids, by liquid chromatography-tandem mass spectrometry. The mass loads (mg/day/1000 inhabitants) were highest for organophosphates and lowest for triazines. Different patterns were observed among the cities and for the various classes of pesticides. Population weighted loads of specific biomarkers indicated higher exposure in Castellon, Milan, Copenhagen and Bristol for pyrethroids, and in Castellon, Bristol and Zurich for organophosphates. The lowest mass loads (mg/day/1000 inhabitants) were found in Utrecht and Oslo. These results were in agreement with several national statistics related to pesticides exposure such as pesticides sales. The daily intake of pyrethroids was estimated in each city and it was found to exceed the acceptable daily intake (ADI) only in one city (Castellon, Spain). This was the first large-scale application of WBE to monitor population exposure to pesticides. The results indicated that WBE can give new information about the “average exposure” of the population to pesticides, and is a useful complementary biomonitoring tool to study population-wide exposure to pesticides.
Santos, P., Amado, C., Coelho, S. T., & Leitão, J. P. (2017). Stochastic data mining tools for pipe blockage failure prediction. Urban Water Journal, 14(4), 343-353. doi:10.1080/1573062X.2016.1148178, Institutional Repository

Failure prediction plays an important role in the management of urban water systems infrastructures. An accurate description of the deterioration of urban drainage systems is essential for optimal investment and rehabilitation planning. In the study presented in this paper, a new method to predict sewer pipe failure based on robust decision trees is proposed. Five other different stochastic failure prediction models – the non-homogeneous Poisson process, the zero-inflated non-homogeneous Poisson process, classical decision tress (CART and Random Forest algorithms), the Weibull accelerated lifetime model and the linear extended Yule process – are also implemented and explored in order to identify models that combine good failure prediction results with robustness. The six models were tested on the asset register and pipe failure register of a large US wastewater utility; only pipe blockage failures were considered in this study. The linear extended Yule process and the zero-inflated non-homogeneous Poisson process presented the overall best results throughout the models’ comparison, showing a good ability to detect pipes with high likelihood of blockage failure. Decision trees based on robust random forests only detected pipes with high likelihood of failure when considering a short-term prediction window; the accuracy of the predictions was one of the best when using the robust decision tree model. The Weibull accelerated lifetime model provided some of the best medium-term predictions but performed less well for shorter prediction windows.
Schmitt, R. J. P., Morgenroth, E., & Larsen, T. A. (2017). Robust planning of sanitation services in urban informal settlements: an analytical framework. Water Research, 110, 297-312. doi:10.1016/j.watres.2016.12.007, Institutional Repository

New types of sanitation services are emerging to tackle the sanitation crisis in informal settlements. These services link toilet facilities to semi-decentralized treatment plants via frequent, road-based transport of excreta. However, information for the planning of such sanitation services is scarce, and their future operating conditions are highly uncertain. The key questions of this paper are therefore: a) what are the drivers behind success or failure of a service-based sanitation system in informal settlements and b) on what scales and under which conditions can such a system operate successfully? To answer these questions, already at an early stage of the planning process, we introduce a stochastic model to analyze a wide range of system designs under varying technical designs, socio-economic factors, and spatial condition. Based on these initial results, we design a sanitation service and use the numeric model to study its reliability and costs over a wide range of scales, i.e., system capacities, from very few to many hundred users per semi-decentralized treatment unit. Key findings are that such a system can only operate within a narrow, but realistic range of conditions. Key requirements are toilet facilities, which can be serviced rapidly, and a flexible workforce. A high density of facilities will also lower the costs. Under these premises, we develop a road-based sanitation service and model its functionality in different settings and under many scenarios. Results show that the developed sanitation system using a single vehicle is scalable (100–700 users), can provide reliable service, and can be cheap (<1.5 c/p/day). Hence, this paper demonstrates opportunities for road-based sanitation in informal settlements and presents a quantitative framework for designing such systems.
Scholten, L., Maurer, M., & Lienert, J. (2017). Comparing multi-criteria decision analysis and integrated assessment to support long-term water supply planning. PLoS One, 12(5), e0176663 (30 pp.). doi:10.1371/journal.pone.0176663, Institutional Repository

We compare the use of multi-criteria decision analysis (MCDA)–or more precisely, models used in multi-attribute value theory (MAVT)–to integrated assessment (IA) models for supporting long-term water supply planning in a small town case study in Switzerland. They are used to evaluate thirteen system scale water supply alternatives in four future scenarios regarding forty-four objectives, covering technical, social, environmental, and economic aspects. The alternatives encompass both conventional and unconventional solutions and differ regarding technical, spatial and organizational characteristics. This paper focuses on the impact assessment and final evaluation step of the structured MCDA decision support process. We analyze the performance of the alternatives for ten stakeholders. We demonstrate the implications of model assumptions by comparing two IA and three MAVT evaluation model layouts of different complexity. For this comparison, we focus on the validity (ranking stability), desirability (value), and distinguishability (value range) of the alternatives given the five model layouts. These layouts exclude or include stakeholder preferences and uncertainties. Even though all five led us to identify the same best alternatives, they did not produce identical rankings. We found that the MAVT-type models provide higher distinguishability and a more robust basis for discussion than the IA-type models. The needed complexity of the model, however, should be determined based on the intended use of the model within the decision support process. The best-performing alternatives had consistently strong performance for all stakeholders and future scenarios, whereas the current water supply system was outperformed in all evaluation layouts. The best-performing alternatives comprise proactive pipe rehabilitation, adapted firefighting provisions, and decentralized water storage and/or treatment. We present recommendations for possible ways of improving water supply planning in the case study and beyond.
Tobias, R., O'Keefe, M., Künzle, R., Gebauer, H., Gründl, H., Morgenroth, E., … Larsen, T. A. (2017). Early testing of new sanitation technology for urban slums: the case of the Blue Diversion Toilet. Science of the Total Environment, 576, 264-272. doi:10.1016/j.scitotenv.2016.10.057, Institutional Repository

The toilets used most in informal urban settlements have detrimental consequences for the environment and human health due to the lack of proper collection and treatment of toilet waste. Concepts for safe, sustainable and affordable sanitation systems exist, but their feasibility and acceptance have to be investigated at an early stage of development, which is difficult due to the high costs of building working models. In this paper, we present an approach to estimate acceptance in a valid and representative form with only one working model, and apply it to test an innovative zero-emission toilet with recycling of wash water. Four basic principles were specified for investigation and nine hypotheses formulated to test the feasibility and acceptance of these principles: source separation of urine and feces with subsequent collection for resource recovery; provision of wash water in a separate cycle with on-site recovery through a membrane bioreactor; a convenient and attractive overall design; and a financially sustainable business plan. In Kampala (Uganda), in 2013, data was collected from 22 regular users, 308 one-time users and a representative sample of 1538 participants. Qualitative data was collected from the users, who evaluated their likes, perceived benefits, social norms and expected ease of use based on verbal and visual information. Most of the hypotheses were confirmed, indicating the feasibility and acceptance of the basic principles. Source separation and on-site water recovery were found to be feasible and accepted, provided users can be convinced that the emptying service and water recovery process work reliably. In the survey, the toilet was evaluated favorably and 51% of the participants agreed to be placed on a bogus waiting list. However, some design challenges were revealed, such as the size of the toilet, hiding feces from view and improving the separation of urine and water
Torres, M. N., Rodríguez, J. P., & Leitão, J. P. (2017). Geostatistical analysis to identify characteristics involved in sewer pipes and urban tree interactions. Urban Forestry and Urban Greening, 25, 36-42. doi:10.1016/j.ufug.2017.04.013, Institutional Repository

Tree roots cause significant and costly damage to sewer systems. However, the contributions made by tree and sewer characteristics to sewer system damage are not yet well understood. Previous research has proved inconclusive and there is a lack of agreement on the importance of the variables involved, which means that the results cannot be extrapolated globally. This study presents a methodology to improve the understanding of tree root-sewer conflicts through a geostatistical analysis of a tree inventory and CCTV video fault reports. The methodology is applied to a 11 km2 case study in Bogotá, Colombia. The analysis used tree and sewer pipe georeferenced data, principal component analysis, and linear, Logit, and Poisson regression models. The proposed methodology identifies the pipe characteristics and the tree species most responsible for the root intrusion events into sewers. As expected, larger trees are prone to cause more pipe damage; therefore tree-pipe distance is a relevant parameter control for reducing potential deterioration. Cumulative precipitation and pipe length showed no effect on observed root intrusion events, and pipes made from brick had higher odds to present root intrusion in contrast with concrete pipes. The presented methodology uses readily available information and software, and can be modified depending on the requirements of each particular case study. This approach will therefore allow for more efficient use of costly, site-specific pipe investigations, and is especially useful for cases where there is a general lack of knowledge regarding the characteristics that favour the negative interactions between pipes and tree roots.
Wani, O., Scheidegger, A., Carbajal, J. P., Rieckermann, J., & Blumensaat, F. (2017). Parameter estimation of hydrologic models using a likelihood function for censored and binary observations. Water Research, 121, 290-301. doi:10.1016/j.watres.2017.05.038, Institutional Repository

Observations of a hydrologic system response are needed to accurately model system behaviour. Nevertheless, often very few monitoring stations are operated because collecting such reference data adequately and accurately is laborious and costly. It has been recently suggested to use observations not only from dedicated flow meters but also from simpler sensors, such as level or event detectors, which are available more frequently but only provide censored information. Binary observations can be considered as extreme censoring. It is still unclear, however, how to use censored observations most effectively to learn about model parameters. To this end, we suggest a formal likelihood function that incorporates censored observations, while accounting for model structure deficits and uncertainty in input data. Using this likelihood function, the parameter inference is performed within the Bayesian framework. We demonstrate the implementation of our methodology on a case study of an urban catchment, where we estimate the parameters of a hydrodynamic rainfall-runoff model from binary observations of combined sewer overflows. Our results show, first, that censored observations make it possible to learn about model parameters, with an average decrease of 45% in parameter standard deviation from prior to posterior. Second, the inference substantially improves model predictions, providing higher Nash-Sutcliffe efficiency. Third, the gain in information largely depends on the experimental design, i.e. sensor placement. Given the advent of Internet of Things, we foresee that the plethora of censored data promised to be available can be used for parameter estimation within a formal Bayesian framework.
Wani, O., Beckers, J. V. L., Weerts, A. H., & Solomatine, D. P. (2017). Residual uncertainty estimation using instance-based learning with applications to hydrologic forecasting. Hydrology and Earth System Sciences, 21(8), 4021-4036. doi:10.5194/hess-21-4021-2017, Institutional Repository

A non-parametric method is applied to quantify residual uncertainty in hydrologic streamflow forecasting. This method acts as a post-processor on deterministic model forecasts and generates a residual uncertainty distribution. Based on instance-based learning, it uses a k nearest-neighbour search for similar historical hydrometeorological conditions to determine uncertainty intervals from a set of historical errors, i.e. discrepancies between past forecast and observation. The performance of this method is assessed using test cases of hydrologic forecasting in two UK rivers: the Severn and Brue. Forecasts in retrospect were made and their uncertainties were estimated using kNN resampling and two alternative uncertainty estimators: quantile regression (QR) and uncertainty estimation based on local errors and clustering (UNEEC). Results show that kNN uncertainty estimation produces accurate and narrow uncertainty intervals with good probability coverage. Analysis also shows that the performance of this technique depends on the choice of search space. Nevertheless, the accuracy and reliability of uncertainty intervals generated using kNN resampling are at least comparable to those produced by QR and UNEEC. It is concluded that kNN uncertainty estimation is an interesting alternative to other post-processors, like QR and UNEEC, for estimating forecast uncertainty. Apart from its concept being simple and well understood, an advantage of this method is that it is relatively easy to implement.
de Oliveira Girão, L. F., da Cruz Simões, N. E., Almeida de Sá Marques, J. A., Correia Leitão, J. P., & Pina, R. D. (2017). Modelação hidráulica e de qualidade da água dos sistemas de drenagem em meios urbanos. Hydraulic and water quality modelling of urban drainage systems. Engenharia Sanitária e Ambiental, 22(2), 351-360. doi:10.1590/s1413-41522016161318, Institutional Repository

Urban floods are becoming more frequent. Thus, the European Union published the Directive 2007/60/CE to mitigate costs related with this phenomenon and to impose limits on the concentration of pollutants in pluvial water. The purpose of this study was to present the modelling of drainage systems in flood situations, based on the software of the United States Environmental Protection Agency (EPA), the Storm Water Management Model (SWMM), in which the study case is to analyze a unitary urban drainage system of Zona Central catchment in Coimbra, Portugal. By using the Automatic Overland Flow Delineation (AOFD) methodology for the generation of a superficial drainage network and implementing it in the SWMM, it was obtained a dual drainage model that allows the flow analysis in flood conditions, including flow control between the surface and collectors network and also modeling of water quality at the surface. This model allows quantifying the pollution load at the surface, relatively to the parameter of total suspended solids, for any extreme rainfall event.
Banta-Green, C. J., Brewer, A. J., Ort, C., Helsel, D. R., Williams, J. R., & Field, J. A. (2016). Using wastewater-based epidemiology to estimate drug consumption—statistical analyses and data presentation. Science of the Total Environment, 568, 856-863. doi:10.1016/j.scitotenv.2016.06.052, Institutional Repository

Aim: Analysis of wastewater samples can be used to assess population drug use, but reporting and statistical issues have limited the utility of the approach for epidemiology due to analytical results that are below the limit of quantification or detection. Unobserved or non-quantifiable—censored—data are common and likely to persist as the methodology is applied to more municipalities and a broader array of substances. We demonstrate the use of censored data techniques and account for measurement errors to explore distributions and annual estimates of the daily mean level of drugs excreted per capita.
Measurements: Daily 24-hour composite wastewater samples for 56 days in 2009 were obtained using a random sample stratified by day of week and season for 19 municipalities in the Northwest region of the U.S.
Methods: Methamphetamine, benzoylecgonine (cocaine metabolite), 3,4 methylenedioxymethamphetamine (MDMA), methadone, oxycodone and hydrocodone were identified and quantified in wastewater samples. Four statistical approaches (reporting censoring, Maximum Likelihood Estimation, Kaplan-Meier estimates, or complete data calculations) were used to estimate an annual average, including confidence bounds where appropriate, dependent upon the amount of censoring in the data.
Findings: The proportion of days within a year with censored data varied greatly by drug across the 19 municipalities, with MDMA varying the most (4% to 94% of observations censored). The different statistical approaches each needed to be used given the levels of censoring of measured drug concentrations. Figures incorporating confidence bounds allow visualization of the data that facilitates appropriate comparisons across municipalities.
Conclusions: Results from wastewater sampling that are below detection or quantification limits contain important information and can be incorporated to create a more complete and valid estimate of drug excretion.
Baz-Lomba, J. A., Salvatore, S., Gracia-Lor, E., Bade, R., Castiglioni, S., Castrignanò, E., … Thomas, K. (2016). Comparison of pharmaceutical, illicit drug, alcohol, nicotine and caffeine levels in wastewater with sale, seizure and consumption data for 8 European cities. BMC Public Health, 16, 1035 (11 pp.). doi:10.1186/s12889-016-3686-5, Institutional Repository

Background: Monitoring the scale of pharmaceuticals, illicit and licit drugs consumption is important to assess the needs of law enforcement and public health, and provides more information about the different trends within different countries. Community drug use patterns are usually described by national surveys, sales and seizure data. Wastewater-based epidemiology (WBE) has been shown to be a reliable approach complementing such surveys.
Method: This study aims to compare and correlate the consumption estimates of pharmaceuticals, illicit drugs, alcohol, nicotine and caffeine from wastewater analysis and other sources of information. Wastewater samples were collected in 2015 from 8 different European cities over a one week period, representing a population of approximately 5 million people. Published pharmaceutical sale, illicit drug seizure and alcohol, tobacco and caffeine use data were used for the comparison.
Results: High agreement was found between wastewater and other data sources for pharmaceuticals and cocaine, whereas amphetamines, alcohol and caffeine showed a moderate correlation. methamphetamine and 3,4-methylenedioxymethamphetamine (MDMA) and nicotine did not correlate with other sources of data. Most of the poor correlations were explained as part of the uncertainties related with the use estimates and were improved with other complementary sources of data.
Conclusions: This work confirms the promising future of WBE as a complementary approach to obtain a more accurate picture of substance use situation within different communities. Our findings suggest further improvements to reduce the uncertainties associated with both sources of information in order to make the data more comparable.
Been, F., Bijlsma, L., Benaglia, L., Berset, J. D., Botero-Coy, A. M., Castiglioni, S., … Ort, C. (2016). Assessing geographical differences in illicit drug consumption—a comparison of results from epidemiological and wastewater data in Germany and Switzerland. Drug and Alcohol Dependence, 161, 189-199. doi:10.1016/j.drugalcdep.2016.02.002, Institutional Repository

Background: Wastewater analysis is an innovative approach that allows monitoring illicit drug use at the community level. This study focused on investigating geographical differences in drug consumption by comparing epidemiological, crime and wastewater data.
Methods: Wastewater samples were collected in 19 cities across Germany and Switzerland during one week, covering a population of approximately 8.1 million people. Self-report data and consumption offences for the investigated areas were used for comparison and to investigate differences between the indicators.
Results: Good agreement between data sources was observed for cannabis and amphetamine-type stimulants, whereas substantial discrepancies were observed for cocaine. In Germany, an important distinction could be made between Berlin, Dortmund and Munich, where cocaine and particularly amphetamine were more prevalent, and Dresden, where methamphetamine consumption was clearly predominant. Cocaine consumption was relatively homogenous in the larger urban areas of Switzerland, although prevalence and offences data suggested a more heterogeneous picture. Conversely, marked regional differences in amphetamine and methamphetamine consumption could be highlighted.
Conclusions: Combining the available data allowed for a better understanding of the geographical differences regarding prevalence, typology and amounts of substances consumed. For cannabis and amphetamine-type stimulants, the complementarity of survey, police and wastewater data could be highlighted, although notable differences could be identified when considering more stigmatised drugs (i.e. cocaine and heroin). Understanding illicit drug consumption at the national scale remains a difficult task, yet this research illustrates the added value of combining complementary data sources to obtain a more comprehensive and accurate picture of the situation.
Brewer, A. J., Banta-Green, C. J., Ort, C., Robel, A. E., & Field, J. (2016). Wastewater testing compared with random urinalyses for the surveillance of illicit drug use in prisons. Drug and Alcohol Review, 35(2), 133-137. doi:10.1111/dar.12185, Institutional Repository

Introduction and Aims. Illicit drug use is known to occur among inmate populations of correctional (prison) facilities. Conventional approaches to monitor illicit drug use in prisons include random urinalyses (RUA). Conventional approaches are expected to be prone to bias because prisoners may be aware of which days of the week RUAs are conducted. Therefore, we wanted to compare wastewater loads for methamphetamine and cocaine during days with RUA testing and without. Design and Methods. We collected daily 24-h composite samples of wastewater by continuous sampling, computed daily loads for 1 month and compared the frequency of illicit drug detection to the number of positive RUAs. Diurnal data also were collected for 3 days to determine within-day patterns of illicit drugs excretion.Results. Methamphetamine was observed in each sample of prison wastewater with no significant difference in daily mass loads between RUA testing and non-testing days. Cocaine and its major metabolite, benzoylecgonine, were observed only at levels below quantification in prison wastewater. Six RUAs were positive for methamphetamine during the month while none were positive for cocaine out of the 243 RUAs conducted.Discussion and Conclusions. Wastewater analyses offer data regarding the frequency of illicit drug excretion inside the prison that RUAs alone could not detect.
Burdon, F. J., Reyes, M., Alder, A. C., Joss, A., Ort, C., Räsänen, K., … Stamm, C. (2016). Environmental context and magnitude of disturbance influence trait-mediated community responses to wastewater in streams. Ecology and Evolution, 6(12), 3923-3939. doi:10.1002/ece3.2165, Institutional Repository

Human land uses and population growth represent major global threats to biodiversity and ecosystem services. Understanding how biological communities respond to multiple drivers of human-induced environmental change is fundamental for conserving ecosystems and remediating degraded habitats. Here, we used a replicated ‘real-world experiment’ to study the responses of invertebrate communities to wastewater perturbations across a land-use intensity gradient in 12 Swiss streams. We used different taxonomy and trait-based community descriptors to establish the most sensitive indicators detecting impacts and to help elucidate potential causal mechanisms of change. First, we predicted that streams in catchments adversely impacted by human land-uses would be less impaired by wastewater inputs because their invertebrate communities should be dominated by pollution-tolerant taxa (‘environmental context’). Second, we predicted that the negative effects of wastewater on stream invertebrate communities should be larger in streams that receive proportionally more wastewater (‘magnitude of disturbance’). In support of the ‘environmental context’ hypothesis, we found that change in the Saprobic Index (a trait-based indicator of tolerance to organic pollution) was associated with upstream community composition; communities in catchments with intensive agricultural land uses (e.g., arable cropping and pasture) were generally more resistant to eutrophication associated with wastewater inputs. We also found support for the ‘magnitude of disturbance’ hypothesis. The SPEAR Index (a trait-based indicator of sensitivity to pesticides) was more sensitive to the relative input of effluent, suggesting that toxic influences of wastewater scale with dilution. Whilst freshwater pollution continues to be a major environmental problem, our findings highlight that the same anthropogenic pressure (i.e., inputs of wastewater) may induce different ecological responses depending on the environmental context and community metrics used. Thus, remediation strategies aiming to improve stream ecological status (e.g., rehabilitating degraded reaches) need to consider upstream anthropogenic influences and the most appropriate indicators of restoration success.
Del Giudice, D., Albert, C., Rieckermann, J., & Reichert, P. (2016). Describing the catchment-averaged precipitation as a stochastic process improves parameter and input estimation. Water Resources Research, 52(4), 3162-3186. doi:10.1002/2015WR017871, Institutional Repository

Rainfall input uncertainty is one of the major concerns in hydrological modeling. Unfortunately, during inference, input errors are usually neglected, which can lead to biased parameters and implausible predictions. Rainfall multipliers can reduce this problem but still fail when the observed input (precipitation) has a different temporal pattern from the true one or if the true nonzero input is not detected. In this study, we propose an improved input error model which is able to overcome these challenges and to assess and reduce input uncertainty. We formulate the average precipitation over the watershed as a stochastic input process (SIP) and, together with a model of the hydrosystem, include it in the likelihood function. During statistical inference, we use “noisy” input (rainfall) and output (runoff) data to learn about the “true” rainfall, model parameters, and runoff. We test the methodology with the rainfall-discharge dynamics of a small urban catchment. To assess its advantages, we compare SIP with simpler methods of describing uncertainty within statistical inference: (i) standard least squares (LS), (ii) bias description (BD), and (iii) rainfall multipliers (RM). We also compare two scenarios: accurate versus inaccurate forcing data. Results show that when inferring the input with SIP and using inaccurate forcing data, the whole-catchment precipitation can still be realistically estimated and thus physical parameters can be “protected” from the corrupting impact of input errors. While correcting the output rather than the input, BD inferred similarly unbiased parameters. This is not the case with LS and RM. During validation, SIP also delivers realistic uncertainty intervals for both rainfall and runoff. Thus, the technique presented is a significant step toward better quantifying input uncertainty in hydrological inference. As a next step, SIP will have to be combined with a technique addressing model structure uncertainty.
Eggimann, S., Truffer, B., & Maurer, M. (2016). Economies of density for on-site waste water treatment. Water Research, 101, 476-489. doi:10.1016/j.watres.2016.06.011, Institutional Repository

Decentralised wastewater treatment is increasingly gaining interest as a means of responding to sustainability challenges. Cost comparisons are a crucial element of any sustainability assessment. While the cost characteristics of centralised waste water management systems (WMS) have been studied extensively, the economics of decentralised WMS are less understood. A key motivation for studying the costs of decentralised WMS is to compare the cost of centralised and decentralised WMS in order to decide on cost-efficient sanitation solutions. This paper outlines a model designed to assess those costs which depend on the spatial density of decentralised wastewater treatment plants in a region. Density-related costs are mostly linked to operation and maintenance activities which depend on transportation, like sludge removal or the visits of professionals to the plants for control, servicing or repairs. We first specify a modelled cost-density relationship for a region in a geometric two-dimensional space by means of heuristic routing algorithms that consider time and load-capacity restrictions. The generic model is then applied to a Swiss case study for which we specify a broad range of modelling parameters. As a result, we identify a ‘hockey-stick’-shaped cost curve that is characterised by strong cost reductions at high density values which level out at around 1 to 1.5 plants per km2. Variations in the cost curves are mostly due to differences in management approaches (scheduled or unscheduled emptying). In addition to the well-known diseconomies of scale in the case of centralised sanitation, we find a similar generic cost behaviour for decentralised sanitation due to economies of density. Low densities in sparsely populated regions thus result in higher costs for both centralised and decentralised system. Policy implications are that efforts to introduce decentralised options in a region should consider the low-density/high-cost problem when comparing centralised and decentralised options.
Eggimann, S., Truffer, B., & Maurer, M. (2016). The cost of hybrid waste water systems: a systematic framework for specifying minimum cost-connection rates. Water Research, 103, 472-484. doi:10.1016/j.watres.2016.07.062, Institutional Repository

To determine the optimal connection rate (CR) for regional waste water treatment is a challenge that has recently gained the attention of academia and professional circles throughout the world. We contribute to this debate by proposing a framework for a total cost assessment of sanitation infrastructures in a given region for the whole range of possible CRs. The total costs comprise the treatment and transportation costs of centralised and on-site waste water management systems relative to specific CRs. We can then identify optimal CRs that either deliver waste water services at the lowest overall regional cost, or alternatively, CRs that result from households freely choosing whether they want to connect or not. We apply the framework to a Swiss region, derive a typology for regional cost curves and discuss whether and by how much the empirically observed CRs differ from the two optimal ones. Both optimal CRs may be reached by introducing specific regulatory incentive structures.
Gao, J., O'Brien, J., Du, P., Li, X., Ort, C., Mueller, J. F., & Thai, P. K. (2016). Measuring selected PPCPs in wastewater to estimate the population in different cities in China. Science of the Total Environment, 568, 164-170. doi:10.1016/j.scitotenv.2016.05.216, Institutional Repository

Sampling and analysis of wastewater from municipal wastewater treatment plants (WWTPs) has become a useful tool for understanding exposure to chemicals. Both wastewater based studies and management and planning of the catchment require information on catchment population in the time of monitoring. Recently, a model has been developed and calibrated using selected pharmaceutical and personal care products (PPCPs) measured in influent wastewater for estimating population in different catchments in Australia. The present study aimed at evaluating the feasibility of utilizing this population estimation approach in China. Twenty-four hour composite influent samples were collected from 31 WWTPs in 17 cities with catchment sizes from 200,000–3,450,000 people representing all seven regions of China. The samples were analyzed for 19 PPCPs using liquid chromatography coupled to tandem mass spectrometry in direct injection mode. Eight chemicals were detected in more than 50% of the samples. Significant positive correlations were found between individual PPCP mass loads and population estimates provided by WWTP operators. Using the PPCP mass load modeling approach calibrated with WWTP operator data, we estimated the population size of each catchment with good agreement with WWTP operator values (between 50–200% for all sites and 75–125% for 23 of the 31 sites). Overall, despite much lower detection and relatively high heterogeneity in PPCP consumption across China the model provided a good estimate of the population contributing to a given wastewater sample. Wastewater analysis could also provide objective PPCP consumption status in China.
Humphries, M. A., Bruno, R., Lai, F. Y., Thai, P. K., Holland, B. R., O’Brien, J. W., … Mueller, J. F. (2016). Evaluation of monitoring schemes for wastewater-based epidemiology to identify drug use trends using cocaine, methamphetamine, MDMA and methadone. Environmental Science and Technology, 50(9), 4760-4768. doi:10.1021/acs.est.5b06126, Institutional Repository

Wastewater-based epidemiology is increasingly being used as a tool to monitor drug use trends. To minimize costs, studies have typically monitored a small number of days. However, cycles of drug use may display weekly and seasonal trends that affect the accuracy of monthly or annual drug use estimates based on a limited number of samples. This study aimed to rationalize sampling methods for minimizing the number of samples required while maximizing information about temporal trends. A range of sampling strategies were examined: (i) targeted days (e.g., weekends), (ii) completely random or stratified random sampling, and (iii) a number of sampling strategies informed by known weekly cycles in drug use data. Using a time-series approach, analysis was performed for four drugs (MDMA, methamphetamine, cocaine, methadone) collected through a continuous sampling program over 14 months. Results showed, for drugs with weekly cycles (MDMA, methamphetamine and cocaine in this sample), sampling strategies which made use of those weekly cycles required fewer samples to obtain similar information as sampling 5 days per week and had better accuracy than stratified random sampling techniques.
Kuroda, K., Itten, R., Kovalova, L., Ort, C., Weissbrodt, D. G., & McArdell, C. S. (2016). Hospital-use pharmaceuticals in Swiss waters modeled at high spatial resolution. Environmental Science and Technology, 50(9), 4742-4751. doi:10.1021/acs.est.6b00653, Institutional Repository

A model to predict the mass flows and concentrations of pharmaceuticals predominantly used in hospitals across a large number of sewage treatment plant (STP) effluents and river waters was developed at high spatial resolution. It comprised 427 geo-referenced hospitals and 742 STPs serving 98% of the general population in Switzerland. In the modeled base scenario, domestic, pharmaceutical use was geographically distributed according to the population size served by the respective STPs. Distinct hospital scenarios were set up to evaluate how the predicted results were modified when pharmaceutical use in hospitals was allocated differently; for example, in proportion to number of beds or number of treatments in hospitals. The hospital scenarios predicted the mass flows and concentrations up to 3.9 times greater than in the domestic scenario for iodinated X-ray contrast media (ICM) used in computed tomography (CT), and up to 6.7 times greater for gadolinium, a contrast medium used in magnetic resonance imaging (MRI). Field measurements showed that ICM and gadolinium were predicted best by the scenarios using number of beds or treatments in hospitals with the specific facilities (i.e., CT and/or MRI). Pharmaceuticals used both in hospitals and by the general population (e.g., cyclophosphamide, sulfamethoxazole, carbamazepine, diclofenac) were predicted best by the scenario using the number of beds in all hospitals, but the deviation from the domestic scenario values was only small. Our study demonstrated that the bed number-based hospital scenarios were effective in predicting the geographical distribution of a diverse range of pharmaceuticals in STP effluents and rivers, while the domestic scenario was similarly effective on the scale of large river-catchments.
Lai, F. Y., O'Brien, J. W., Thai, P. K., Hall, W., Chan, G., Bruno, R., … Mueller, J. F. (2016). Cocaine, MDMA and methamphetamine residues in wastewater: consumption trends (2009–2015) in South East Queensland, Australia. Science of the Total Environment, 568, 803-809. doi:10.1016/j.scitotenv.2016.05.181, Institutional Repository

Wastewater analysis, or wastewater-based epidemiology, has become a common tool to monitor trends of illicit drug consumption around the world. In this study, we examined trends in cocaine, 3,4-methylenedioxymethamphetamine (MDMA) and methamphetamine consumption by measuring their residues in wastewater from two wastewater treatment plants in Australia (specifically, an urban and a rural catchment, both in South East Queensland) between 2009 and 2015. With direct injection of the samples, target analytes were identified and quantified using liquid chromatography-mass spectrometry. Cocaine and MDMA residues and metabolites were mainly quantifiable in the urban catchment while methamphetamine residues were consistently detected in both urban and rural catchments. There was no consistent trend in the population normalised mass loads observed for cocaine and MDMA at the urban site between 2009 and 2015. In contrast, there was a five-fold increase in methamphetamine consumption over this period in this catchment. For methamphetamine consumption, the rural area showed a very similar trend as the urban catchment starting at a lower baseline. The observed increase in per capita loads of methamphetamine via wastewater analysis over the past six years in South East Queensland provides objective evidence for increased methamphetamine consumption in the Australian population while the use of other illicit stimulants remained relatively stable.
Larsen, T. A., Hoffmann, S., Lüthi, C., Truffer, B., & Maurer, M. (2016). Emerging solutions to the water challenges of an urbanizing world. Science, 352(6288), 928-933. doi:10.1126/science.aad8641, Institutional Repository

The top priorities for urban water sustainability include the provision of safe drinking water, wastewater handling for public health, and protection against flooding. However, rapidly aging infrastructure, population growth, and increasing urbanization call into question current urban water management strategies, especially in the fast-growing urban areas in Asia and Africa. We review innovative approaches in urban water management with the potential to provide locally adapted, resource-efficient alternative solutions. Promising examples include new concepts for stormwater drainage, increased water productivity, distributed or on-site treatment of wastewater, source separation of human waste, and institutional and organizational reforms. We conclude that there is an urgent need for major transdisciplinary efforts in research, policy, and practice to develop alternatives with implications for cities and aquatic ecosystems alike.
Leitão, J. P., Moy de Vitry, M., Scheidegger, A., & Rieckermann, J. (2016). Assessing the quality of digital elevation models obtained from mini unmanned aerial vehicles for overland flow modelling in urban areas. Hydrology and Earth System Sciences, 20(4), 1637-1653. doi:10.5194/hess-20-1637-2016, Institutional Repository

Precise and detailed digital elevation models (DEMs) are essential to accurately predict overland flow in urban areas. Unfortunately, traditional sources of DEM, such as airplane light detection and ranging (lidar) DEMs and point and contour maps, remain a bottleneck for detailed and reliable overland flow models, because the resulting DEMs are too coarse to provide DEMs of sufficient detail to inform urban overland flows. Interestingly, technological developments of unmanned aerial vehicles (UAVs) suggest that they have matured enough to be a competitive alternative to satellites or airplanes. However, this has not been tested so far. In this study we therefore evaluated whether DEMs generated from UAV imagery are suitable for urban drainage overland flow modelling. Specifically, 14 UAV flights were conducted to assess the influence of four different flight parameters on the quality of generated DEMs: (i) flight altitude, (ii) image overlapping, (iii) camera pitch, and (iv) weather conditions. In addition, we compared the best-quality UAV DEM to a conventional lidar-based DEM. To evaluate both the quality of the UAV DEMs and the comparison to lidar-based DEMs, we performed regression analysis on several qualitative and quantitative metrics, such as elevation accuracy, quality of object representation (e.g. buildings, walls and trees) in the DEM, which were specifically tailored to assess overland flow modelling performance, using the flight parameters as explanatory variables. Our results suggested that, first, as expected, flight altitude influenced the DEM quality most, where lower flights produce better DEMs; in a similar fashion, overcast weather conditions are preferable, but weather conditions and other factors influence DEM quality much less. Second, we found that for urban overland flow modelling, the UAV DEMs performed competitively in comparison to a traditional lidar-based DEM. An important advantage of using UAVs to generate DEMs in urban areas is their flexibility that enables more frequent, local, and affordable elevation data updates, allowing, for example, to capture different tree foliage conditions.
Leitão, J. P., Prodanović, D., & Maksimović, Č. (2016). Improving merge methods for grid-based digital elevation models. Computers and Geosciences, 88, 115-131. doi:10.1016/j.cageo.2016.01.001, Institutional Repository

Digital Elevation Models (DEMs) are used to represent the terrain in applications such as, for example, overland flow modelling or viewshed analysis. DEMs generated from digitising contour lines or obtained by LiDAR or satellite data are now widely available. However, in some cases, the area of study is covered by more than one of the available elevation data sets. In these cases the relevant DEMs may need to be merged. The merged DEM must retain the most accurate elevation information available while generating consistent slopes and aspects. In this paper we present a thorough analysis of three conventional grid-based DEM merging methods that are available in commercial GIS software. These methods are evaluated for their applicability in merging DEMs and, based on evaluation results, a method for improving the merging of grid-based DEMs is proposed. DEMs generated by the proposed method, called MBlend, showed significant improvements when compared to DEMs produced by the three conventional methods in terms of elevation, slope and aspect accuracy, ensuring also smooth elevation transitions between the original DEMs. The results produced by the improved method are highly relevant different applications in terrain analysis, e.g., visibility, or spotting irregularities in landforms and for modelling terrain phenomena, such as overland flow.
Leitão, J. P., Coelho, S. T., Alegre, H., Cardoso, M. A., Silva, M. S., Ramalho, P., … Carriço, N. (2016). Moving urban water infrastructure asset management from science into practice. Urban Water Journal, 13(2), 133-141. doi:10.1080/1573062X.2014.939092, Institutional Repository

iGPI, the National Initiative for Infrastructure Asset Management is a Portuguese collaborative project led by LNEC (National Civil Engineering Laboratory, Portugal) through which 19 water utilities develop their own infrastructure asset management (IAM) systems and plans in a joint training and capacitation programme. Technical assistance to the participating utilities is ensured by LNEC, IST (Technical University of Lisbon) and Addition, a software development company. The water utilities get collective as well as one-on-one support and specific training. They benefit from networking with the other utilities in a common and simultaneous process, with similar difficulties and challenges, leading to an effective sharing of solutions. The developed products, including training materials, templates and guidelines for developing strategic and tactical IAM plans, are available to the general public. This project has greatly contributed to the establishment of reference methodologies and standards for IAM planning, in a range of utilities of widely diverse size and context, effectively defining an accepted best practice. This paper discusses the project's format and its advantages, and goes on to describe the main outcomes, including selected cases and final products.
McCall, A. K., Bade, R., Kinyua, J., Lai, F. Y., Thai, P. K., Covaci, A., … Ort, C. (2016). Critical review on the stability of illicit drugs in sewers and wastewater samples. Water Research, 88, 933-947. doi:10.1016/j.watres.2015.10.040, Institutional Repository

Wastewater-based epidemiology (WBE) applies advanced analytical methods to quantify drug residues in wastewater with the aim to estimate illicit drug use at the population level. Transformation processes during transport in sewers (chemical and biological reactors) and storage of wastewater samples before analysis are expected to change concentrations of different drugs to varying degrees. Ignoring transformation for drugs with low to medium stability will lead to an unknown degree of systematic under- or overestimation of drug use, which should be avoided. This review aims to summarize the current knowledge related to the stability of commonly investigated drugs and, furthermore, suggest a more effective approach to future experiments. From over 100 WBE studies, around 50 mentioned the importance of stability and 24 included tests in wastewater. Most focused on in-sample stability (i.e., sample preparation, preservation and storage) and some extrapolated to in-sewer stability (i.e., during transport in real sewers). While consistent results were reported for rather stable compounds (e.g., MDMA and methamphetamine), a varying range of stability under different or similar conditions was observed for other compounds (e.g., cocaine, amphetamine and morphine). Wastewater composition can vary considerably over time, and different conditions prevail in different sewer systems. In summary, this indicates that more systematic studies are needed to: i) cover the range of possible conditions in sewers and ii) compare results more objectively. To facilitate the latter, we propose a set of parameters that should be reported for in-sewer stability experiments. Finally, a best practice of sample collection, preservation, and preparation before analysis is suggested in order to minimize transformation during these steps.
McCall, A. K., Scheidegger, A., Madry, M. M., Steuer, A. E., Weissbrodt, D. G., Vanrolleghem, P. A., … Ort, C. (2016). Influence of different sewer biofilms on transformation rates of drugs. Environmental Science and Technology, 50(24), 13351-13360. doi:10.1021/acs.est.6b04200, Institutional Repository

To estimate drug consumption more reliably, wastewater-based epidemiology would benefit from a better understanding of drug residue stability during in-sewer transport. We conducted batch experiments with real, fresh wastewater and sewer biofilms. Experimental conditions mimic small to medium-sized gravity sewers with a relevant ratio of biofilm surface area to wastewater volume (33 m2 m–3). The influences of biological, chemical, and physical processes on the transformation of 30 illicit drug and pharmaceutical residues were quantified. Rates varied among locations and over time. Three substances were not stable—that is, >20% transformation, mainly due to biological processes—at least for one type of tested biofilm for a residence time ≤2 h: amphetamine, 6-acetylcodeine, and 6-monoacetylmorphine. Cocaine, ecgonine methyl ester, norcocaine, cocaethylene, and mephedrone were mainly transformed by chemical hydrolysis and, hence, also unstable in sewers. In contrast, ketamine, norketamine, O-desmethyltramadol, diclofenac, carbamazepine, and methoxetamine were not substantially affected by in-sewer processes under all tested conditions and residence times up to 12 h. Our transformation rates include careful quantification of uncertainty and can be used to identify situations in which specific compounds are not stable. This will improve accuracy and uncertainty estimates of drug consumption when applied to the back-calculation.
Mutzner, L., Staufer, P., & Ort, C. (2016). Model-based screening for critical wet-weather discharges related to micropollutants from urban areas. Water Research, 104, 547-557. doi:10.1016/j.watres.2016.08.003, Institutional Repository

Wet-weather discharges contribute to anthropogenic micropollutant loads entering the aquatic environment. Thousands of wet-weather discharges exist in Swiss sewer systems, and we do not have the capacity to monitor them all. We consequently propose a model-based approach designed to identify critical discharge points in order to support effective monitoring.
We applied a dynamic substance flow model to four substances representing different entry routes: indoor (Triclosan, Mecoprop, Copper) as well as rainfall-mobilized (Glyphosate, Mecoprop, Copper) inputs. The accumulation on different urban land-use surfaces in dry weather and subsequent substance-specific wash-off is taken into account. For evaluation, we use a conservative screening approach to detect critical discharge points. This approach considers only local dilution generated onsite from natural, unpolluted areas, i.e. excluding upstream dilution.
Despite our conservative assumptions, we find that the environmental quality standards for Glyphosate and Mecoprop are not exceeded during any 10-min time interval over a representative one-year simulation period for all 2500 Swiss municipalities. In contrast, the environmental quality standard is exceeded during at least 20% of the discharge time at 83% of all modelled discharge points for Copper and at 71% for Triclosan. For Copper, this corresponds to a total median duration of approximately 19 days per year. For Triclosan, discharged only via combined sewer overflows, this means a median duration of approximately 10 days per year. In general, stormwater outlets contribute more to the calculated effect than combined sewer overflows for rainfall-mobilized substances. We further evaluate the Urban Index (Aurban,impervious/Anatural) as a proxy for critical discharge points: catchments where Triclosan and Copper exceed the corresponding environmental quality standard often have an Urban Index >0.03.
A dynamic substance flow analysis allows us to identify the most critical discharge points to be prioritized for more detailed analyses and monitoring. This forms a basis for the efficient mitigation of pollution.
Randall, D. G., Krähenbühl, M., Köpping, I., Larsen, T. A., & Udert, K. M. (2016). A novel approach for stabilizing fresh urine by calcium hydroxide addition. Water Research, 95, 361-369. doi:10.1016/j.watres.2016.03.007, Institutional Repository

In this study, we investigated the prevention of enzymatic urea hydrolysis in fresh urine by increasing the pH with calcium hydroxide (Ca(OH)2) powder. The amount of Ca(OH)2 dissolving in fresh urine depends significantly on the composition of the urine. The different urine compositions used in our simulations showed that between 4.3 and 5.8 g Ca(OH)2 dissolved in 1 liter of urine at 25 °C. At this temperature, the pH at saturation is 12.5 and is far above the pH of 11, which we identified as the upper limit for enzymatic urea hydrolysis. However, temperature has a strong effect on the saturation pH, with higher values being achieved at lower temperatures. Based on our results, we recommend a dosage of 10 g Ca(OH)2·L−1 of fresh urine to ensure solid Ca(OH)2 always remains in the urine reactor which ensures sufficiently high pH values. Besides providing sufficient Ca(OH)2, the temperature has to be kept in a certain range to prevent chemical urea hydrolysis. At temperatures below 14 °C, the saturation pH is higher than 13, which favors chemical urea hydrolysis. We chose a precautionary upper temperature of 40 °C because the rate of chemical urea hydrolysis increases at higher temperatures but this should be confirmed with kinetic studies. By considering the boundaries for pH and temperature developed in this study, urine can be stabilized effectively with Ca(OH)2 thereby simplifying later treatment processes or making direct use easier.
Ryu, Y., Barceló, D., Barron, L. P., Bijlsma, L., Castiglioni, S., de Voogt, P., … Thomas, K. V. (2016). Comparative measurement and quantitative risk assessment of alcohol consumption through wastewater-based epidemiology: an international study in 20 cities. Science of the Total Environment, 565, 977-983. doi:10.1016/j.scitotenv.2016.04.138, Institutional Repository

Quantitative measurement of drug consumption biomarkers in wastewater can provide objective information on community drug use patterns and trends. This study presents the measurement of alcohol consumption in 20 cities across 11 countries through the use of wastewater-based epidemiology (WBE), and reports the application of these data for the risk assessment of alcohol on a population scale using the margin of exposure (MOE) approach. Raw 24-h composite wastewater samples were collected over a one-week period from 20 cities following a common protocol. For each sample a specific and stable alcohol consumption biomarker, ethyl sulfate (EtS) was determined by liquid chromatography coupled to tandem mass spectrometry. The EtS concentrations were used for estimation of per capita alcohol consumption in each city, which was further compared with international reports and applied for risk assessment by MOE. The average per capita consumption in 20 cities ranged between 6.4 and 44.3 L/day/1000 inhabitants. An increase in alcohol consumption during the weekend occurred in all cities, however the level of this increase was found to differ. In contrast to conventional data (sales statistics and interviews), WBE revealed geographical differences in the level and pattern of actual alcohol consumption at an inter-city level. All the sampled cities were in the "high risk" category (MOE < 10) and the average MOE for the whole population studied was 2.5. These results allowed direct comparisons of alcohol consumption levels, patterns and risks among the cities. This study shows that WBE can provide timely and complementary information on alcohol use and alcohol associated risks in terms of exposure at the community level.
Ryu, Y., Gracia-Lor, E., Bade, R., Baz-Lomba, J. A., Bramness, J. G., Castiglioni, S., … Thomas, K. V. (2016). Increased levels of the oxidative stress biomarker 8-iso-prostaglandin F2α in wastewater associated with tobacco use. Scientific Reports, 6, 1-7. doi:10.1038/srep39055, Institutional Repository

Wastewater analysis has been demonstrated to be a complementary approach for assessing the overall patterns of drug use by a population while the full potential of wastewater-based epidemiology has yet to be explored. F2-isoprostanes are a prototype wastewater biomarker to study the cumulative oxidative stress at a community level. In this work, 8-iso-prostaglandin F2α (8-iso-PGF2α) was analysed in raw 24 h-composite wastewater samples collected from 4 Norwegian and 7 other European cities in 2014 and 2015. Using the same samples, biomarkers of alcohol (ethyl sulfate) and tobacco (trans-3′-hydroxycotinine) use were also analysed to investigate any possible correlation between 8-iso-PGF2α and the consumption of the two drugs. The estimated per capita daily loads of 8-iso-PGF2α in the 11 cities ranged between 2.5 and 9.9 mg/day/1000 inhabitants with a population-weighted mean of 4.8 mg/day/1000 inhabitants. There were no temporal trends observed in the levels of 8-iso-PGF2α, however, spatial differences were found at the inter-city level correlating to the degree of urbanisation. The 8-iso-PGF2α mass load was found to be strongly associated with that of trans-3′-hydroxycotinine while it showed no correlation with ethyl sulfate. The present study shows the potential for 8-iso-PGF2α as a wastewater biomarker for the assessment of community public health.
Thomaidis, N. S., Gago-Ferrero, P., Ort, C., Maragou, N. C., Alygizakis, N. A., Borova, V. L., & Dasenaki, M. E. (2016). Reflection of socioeconomic changes in wastewater: licit and illicit drug use patterns. Environmental Science and Technology, 50(18), 10065-10072. doi:10.1021/acs.est.6b02417, Institutional Repository

The economic crisis plaguing Greece was expected to impact consumption of pharmaceuticals and illicit drugs – a priori to an unknown extent. We quantified the change of use for various classes of licit and illicit drugs by monitoring Athens’ wastewater from 2010 to 2014. A high increase in the use of psychoactive drugs was detected between 2010 and 2014, especially for antipsychotics (35-fold), benzodiazepines (19-fold), and antidepressants (11-fold). This directly reflects the perceived increase of incidences associated with mental illnesses in the population, as a consequence of severe socioeconomic changes. Other therapeutic classes, like antiepileptics, hypertensives, and gastric and ulcer drugs also showed an increase in use (from 2-fold increase for antiepileptics to 13-fold for hypertensives). In contrast, the overall use of antibiotics and NSAIDs decreased. For mefenamic acid, an almost 28-fold decrease was observed. This finding is likely related to the reduction in drug expenditure applied in public health. A 2-fold increase of methamphetamine use was detected, associated with a cheap street drug called ″sisa″ (related to marginal conducts), which is a health concern. MDMA (5-fold) and methadone (7-fold) use showed also an increase, while cocaine and cannabis estimates did not show a clear trend.
Van Dyken, E., Lai, F. Y., Thai, P. K., Ort, C., Bruno, R., Hall, W., … Prichard, J. (2016). Challenges and opportunities in using wastewater analysis to measure drug use in a small prison facility. Drug and Alcohol Review, 35(2), 138-147. doi:10.1111/dar.12156, Institutional Repository

Introduction and Aims. Wastewater analysis (WWA) is intended to be a direct and objective method of measuring substance use in large urban populations. It has also been used to measure prison substance use in two previous studies. The application of WWA in this context has raised questions as to how best it might be used to measure illicit drug use in prisons, and whether it can also be used to measure prescription misuse. We applied WWA to a small regional prison to measure the use of 12 licit and illicit substances. We attempted to measure the non-medical use of methadone and buprenorphine and to compare our findings with the results of the prison's mandatory drug testing (MDT). Design and Methods. Representative daily composite samples were collected for two periods of 12 consecutive days in May to July 2013 and analysed for 18 drug metabolites. Prescription data and MDT results were obtained from the prison and compared with the substance use estimates calculated from WWA data. Results. Daily use of methamphetamine, methadone, buprenorphine and codeine was detected, while sporadic detection of ketamine and methylone was also observed. Overall buprenorphine misuse appeared to be greater than methadone misuse. Discussion and Conclusions. Compared with MDT, WWA provides a more comprehensive picture of prison substance use. WWA also has the potential to measure the misuse of medically prescribed substances. However, a great deal of care must be exercised in quantifying the usage of any substance in small populations, such as in prisons.
Zheng, J., Egger, C., & Lienert, J. (2016). A scenario-based MCDA framework for wastewater infrastructure planning under uncertainty. Journal of Environmental Management, 183(3), 895-908. doi:10.1016/j.jenvman.2016.09.027, Institutional Repository

Wastewater infrastructure management is increasingly important because of urbanization, environmental pollutants, aging infrastructures, and climate change. We propose a scenario-based multi-criteria decision analysis (MCDA) framework to compare different infrastructure alternatives in terms of their sustainability. These range from the current centralized system to semi- and fully decentralized options. Various sources of uncertainty are considered, including external socio-economic uncertainty captured by future scenarios, uncertainty in predicting outcomes of alternatives, and incomplete preferences of stakeholders. Stochastic Multi-criteria Acceptability Analysis (SMAA) with Monte Carlo simulation is performed, and rank acceptability indices help identify robust alternatives. We propose step-wise local sensitivity analysis, which is useful for practitioners to effectively elicit preferences and identify major sources of uncertainty. The approach is demonstrated in a Swiss case study where ten stakeholders are involved throughout. Their preferences are quantitatively elicited by combining an online questionnaire with face-to-face interviews. The trade-off questions reveal a high concern about environmental and an unexpectedly low importance of economic criteria. This results in a surprisingly good ranking of high-tech decentralized wastewater alternatives using urine source separation for most stakeholders in all scenarios. Combining scenario planning and MCDA proves useful, as the performance of wastewater infrastructure systems is indeed sensitive to socio-economic boundary conditions and the other sources of uncertainty. The proposed sensitivity analysis suggests that a simplified elicitation procedure is sufficient in many cases. Elicitation of more information such as detailed marginal value functions should only follow if the sensitivity analysis finds this necessary. Moreover, the uncertainty of rankings can be considerably reduced by better predictions of the outcomes of alternatives. Although the results are case based, the proposed decision framework is generalizable to other decision contexts.
Čepický, J., & Moreira de Sousa, L. (2016). New implementation of OGC web processing service in Python programming language. PyWPS-4 and issues we are facing with processing of large raster data using OGC WPS. In L. Halounova, F. Sunar, M. Potůčková, L. Patková, M. Yoshimura, U. Soergel, … B. Zagajewski (Eds.), The international archives of the photogrammetry, remote sensing and spatial information sciences: Vol. XLI-B7. XXIII ISPRS congress, commission VII (pp. 927-930). doi:10.5194/isprs-archives-XLI-B7-927-2016, Institutional Repository

The OGC® Web Processing Service (WPS) Interface Standard provides rules for standardizing inputs and outputs (requests and responses) for geospatial processing services, such as polygon overlay. The standard also defines how a client can request the execution of a process, and how the output from the process is handled. It defines an interface that facilitates publishing of geospatial processes and client discovery of processes and and binding to those processes into workflows. Data required by a WPS can be delivered across a network or they can be available at a server.
PyWPS was one of the first implementations of OGC WPS on the server side. It is written in the Python programming language and it tries to connect to all existing tools for geospatial data analysis, available on the Python platform. During the last two years, the PyWPS development team has written a new version (called PyWPS-4) completely from scratch.
The analysis of large raster datasets poses several technical issues in implementing the WPS standard. The data format has to be defined and validated on the server side and binary data have to be encoded using some numeric representation. Pulling raster data from remote servers introduces security risks, in addition, running several processes in parallel has to be possible, so that system resources are used efficiently while preserving security. Here we discuss these topics and illustrate some of the solutions adopted within the PyWPS implementation.
Albert, C., Künsch, H. R., & Scheidegger, A. (2015). A simulated annealing approach to approximate Bayes computations. Statistics and Computing, 25(6), 1217-1232. doi:10.1007/s11222-014-9507-8, Institutional Repository

Approximate Bayes computations (ABC) are used for parameter inference when the likelihood function of the model is expensive to evaluate but relatively cheap to sample from. In particle ABC, an ensemble of particles in the product space of model outputs and parameters is propagated in such a way that its output marginal approaches a delta function at the data and its parameter marginal approaches the posterior distribution. Inspired by Simulated Annealing, we present a new class of particle algorithms for ABC, based on a sequence of Metropolis kernels, associated with a decreasing sequence of tolerances w.r.t. the data. Unlike other algorithms, our class of algorithms is not based on importance sampling. Hence, it does not suffer from a loss of effective sample size due to re-sampling. We prove convergence under a condition on the speed at which the tolerance is decreased. Furthermore, we present a scheme that adapts the tolerance and the jump distribution in parameter space according to some mean-fields of the ensemble, which preserves the statistical independence of the particles, in the limit of infinite sample size. This adaptive scheme aims at converging as close as possible to the correct result with as few system updates as possible via minimizing the entropy production of the process. The performance of this new class of algorithms is compared against two other recent algorithms on two toy examples as well as on a real-world example from genetics.
Del Giudice, D., Löwe, R., Madsen, H., Mikkelsen, P. S., & Rieckermann, J. (2015). Comparison of two stochastic techniques for reliable urban runoff prediction by modeling systematic errors. Water Resources Research, 51(7), 5004-5022. doi:10.1002/2014WR016678, Institutional Repository

In urban rainfall-runoff, commonly applied statistical techniques for uncertainty quantification mostly ignore systematic output errors originating from simplified models and erroneous inputs. Consequently, the resulting predictive uncertainty is often unreliable. Our objective is to present two approaches which use stochastic processes to describe systematic deviations and to discuss their advantages and drawbacks for urban drainage modeling. The two methodologies are an external bias description (EBD) and an internal noise description (IND, also known as stochastic gray-box modeling). They emerge from different fields and have not yet been compared in environmental modeling. To compare the two approaches, we develop a unifying terminology, evaluate them theoretically, and apply them to conceptual rainfall-runoff modeling in the same drainage system. Our results show that both approaches can provide probabilistic predictions of wastewater discharge in a similarly reliable way, both for periods ranging from a few hours up to more than 1 week ahead of time. The EBD produces more accurate predictions on long horizons but relies on computationally heavy MCMC routines for parameter inferences. These properties make it more suitable for off-line applications. The IND can help in diagnosing the causes of output errors and is computationally inexpensive. It produces best results on short forecast horizons that are typical for online applications.
Del Giudice, D., Reichert, P., Bareš, V., Albert, C., & Rieckermann, J. (2015). Model bias and complexity - understanding the effects of structural deficits and input errors on runoff predictions. Environmental Modelling and Software, 64, 205-214. doi:10.1016/j.envsoft.2014.11.006, Institutional Repository

Oversimplified models and erroneous inputs play a significant role in impairing environmental predictions. To assess the contribution of these errors to model uncertainties is still challenging. Our objective is to understand the effect of model complexity on systematic modeling errors. Our method consists of formulating alternative models with increasing detail and flexibility and describing their systematic deviations by an autoregressive bias process. We test the approach in an urban catchment with five drainage models. Our results show that a single bias description produces reliable predictions for all models. The bias decreases with increasing model complexity and then stabilizes. The bias decline can be associated with reduced structural deficits, while the remaining bias is probably dominated by input errors. Combining a bias description with a multimodel comparison is an effective way to assess the influence of structural and rainfall errors on flow forecasts.
Egger, C., & Maurer, M. (2015). Importance of anthropogenic climate impact, sampling error and urban development in sewer system design. Water Research, 73, 78-97. doi:10.1016/j.watres.2014.12.050, Institutional Repository

Urban drainage design relying on observed precipitation series neglects the uncertainties associated with current and indeed future climate variability. Urban drainage design is further affected by the large stochastic variability of precipitation extremes and sampling errors arising from the short observation periods of extreme precipitation. Stochastic downscaling addresses anthropogenic climate impact by allowing relevant precipitation characteristics to be derived from local observations and an ensemble of climate models. This multi-climate model approach seeks to reflect the uncertainties in the data due to structural errors of the climate models. An ensemble of outcomes from stochastic downscaling allows for addressing the sampling uncertainty. These uncertainties are clearly reflected in the precipitation-runoff predictions of three urban drainage systems. They were mostly due to the sampling uncertainty. The contribution of climate model uncertainty was found to be of minor importance. Under the applied greenhouse gas emission scenario (A1B) and within the period 2036–2065, the potential for urban flooding in our Swiss case study is slightly reduced on average compared to the reference period 1981–2010. Scenario planning was applied to consider urban development associated with future socio-economic factors affecting urban drainage. The impact of scenario uncertainty was to a large extent found to be case-specific, thus emphasizing the need for scenario planning in every individual case. The results represent a valuable basis for discussions of new drainage design standards aiming specifically to include considerations of uncertainty.
Eggimann, S., Truffer, B., & Maurer, M. (2015). To connect or not to connect? Modelling the optimal degree of centralisation for wastewater infrastructures. Water Research, 84, 218-231. doi:10.1016/j.watres.2015.07.004, Institutional Repository

The strong reliance of most utility services on centralised network infrastructures is becoming increasingly challenged by new technological advances in decentralised alternatives. However, not enough effort has been made to develop planning tools designed to address the implications of these new opportunities and to determine the optimal degree of centralisation of these infrastructures. We introduce a planning tool for sustainable network infrastructure planning (SNIP), a two-step techno-economic heuristic modelling approach based on shortest path-finding and hierarchical-agglomerative clustering algorithms to determine the optimal degree of centralisation in the field of wastewater management. This SNIP model optimises the distribution of wastewater treatment plants and the sewer network outlay relative to several cost and sewer-design parameters. Moreover, it allows us to construct alternative optimal wastewater system designs taking into account topography, economies of scale as well as the full size range of wastewater treatment plants. We quantify and confirm that the optimal degree of centralisation decreases with increasing terrain complexity and settlement dispersion while showing that the effect of the latter exceeds that of topography. Case study results for a Swiss community indicate that the calculated optimal degree of centralisation is substantially lower than the current level.
Fencl, M., Rieckermann, J., Sýkora, P., Stránský, D., & Bareš, V. (2015). Commercial microwave links instead of rain gauges: fiction or reality?. Water Science and Technology, 71(1), 31-37. doi:10.2166/wst.2014.466, Institutional Repository

Commercial microwave links (MWLs) were suggested about a decade ago as a new source for quantitative precipitation estimates (QPEs). Meanwhile, the theory is well understood and rainfall monitoring with MWLs is on its way to being a mature technology, with several well-documented case studies, which investigate QPEs from multiple MWLs on the mesoscale. However, the potential of MWLs to observe microscale rainfall variability, which is important for urban hydrology, has not been investigated yet. In this paper, we assess the potential of MWLs to capture the spatio-temporal rainfall dynamics over small catchments of a few square kilometres. Specifically, we investigate the influence of different MWL topologies on areal rainfall estimation, which is important for experimental design or to a priori check the feasibility of using MWLs. In a dedicated case study in Prague, Czech Republic, we collected a unique dataset of 14 MWL signals with a temporal resolution of a few seconds and compared the QPEs from the MWLs to reference rainfall from multiple rain gauges. Our results show that, although QPEs from most MWLs are probably positively biased, they capture spatio-temporal rainfall variability on the microscale very well. Thus, they have great potential to improve runoff predictions. This is especially beneficial for heavy rainfall, which is usually decisive for urban drainage design.
Helbling, D. E., Johnson, D. R., Lee, T. K., Scheidegger, A., & Fenner, K. (2015). A framework for establishing predictive relationships between specific bacterial 16S rRNA sequence abundances and biotransformation rates. Water Research, 70, 471-484. doi:10.1016/j.watres.2014.12.013, Institutional Repository

The rates at which wastewater treatment plant (WWTP) microbial communities biotransform specific substrates can differ by orders of magnitude among WWTP communities. Differences in taxonomic compositions among WWTP communities may predict differences in the rates of some types of biotransformations. In this work, we present a novel framework for establishing predictive relationships between specific bacterial 16S rRNA sequence abundances and biotransformation rates. We selected ten WWTPs with substantial variation in their environmental and operational metrics and measured the in situ ammonia biotransformation rate constants in nine of them. We isolated total RNA from samples from each WWTP and analyzed 16S rRNA sequence reads. We then developed multivariate models between the measured abundances of specific bacterial 16S rRNA sequence reads and the ammonia biotransformation rate constants. We constructed model scenarios that systematically explored the effects of model regularization, model linearity and non-linearity, and aggregation of 16S rRNA sequences into operational taxonomic units (OTUs) as a function of sequence dissimilarity threshold (SDT). A large percentage (greater than 80%) of model scenarios resulted in well-performing and significant models at intermediate SDTs of 0.13–0.14 and 0.26. The 16S rRNA sequences consistently selected into the well-performing and significant models at those SDTs were classified as Nitrosomonas and Nitrospira groups. We then extend the framework by applying it to the biotransformation rate constants of ten micropollutants measured in batch reactors seeded with the ten WWTP communities. We identified phylogenetic groups that were robustly selected into all well-performing and significant models constructed with biotransformation rates of isoproturon, propachlor, ranitidine, and venlafaxine. These phylogenetic groups can be used as predictive biomarkers of WWTP microbial community activity towards these specific micropollutants. This work is an important step towards developing tools to predict biotransformation rates in WWTPs based on taxonomic composition.
Kaeseberg, T., Blumensaat, F., Zhang, J., & Krebs, P. (2015). Assessing antibiotic resistance of microorganisms in sanitary sewage. Water Science and Technology, 71(2), 168-173. doi:10.2166/wst.2014.467, Institutional Repository

The release of antimicrobial substances into surface waters is of growing concern due to direct toxic effects on all trophic levels and the promotion of antibiotic resistance through sub-inhibitory concentration levels. This study showcases (1) the variation of antibiotics in sanitary sewage depending on different timescales and (2) a method to assess the antibiotic resistance based on an inhibition test. The test is based on the measurement of the oxygen uptake rate (OUR) in wastewater samples with increasing concentrations of the selected antibiotic agents. The following antibiotics were analysed in the present study: clarithromycin (CLA) was selected due to its high toxicity to many microorganisms (low EC50), ciprofloxacin (CIP) which is used to generally fight all bacteria concerning interstitial infections and doxycyclin (DOX) having a broad spectrum efficacy. Results show that CLA inhibited the OUR by approximately 50% at a concentration of about 10 mg L−1, because Gram-negative bacteria such as Escherichia coli are resistant, whereas CIP inhibited about 90% of the OUR at a concentration equal to or greater than 10 mg L−1. In the case of DOX, a moderate inhibition of about 38% at a concentration of 10 mg L−1 was identified, indicating a significant antibiotic resistance. The results are consistent with the corresponding findings from the Clinical and Laboratory Standards Institute. Thus, the presented inhibition test provides a simple but robust alternative method to assess antibiotic resistance in biofilms instead of more complex clinical tests.
Kinyua, J., Covaci, A., Maho, W., McCall, A. K., Neels, H., & van Nuijs, A. L. N. (2015). Sewage-based epidemiology in monitoring the use of new psychoactive substances: validation and application of an analytical method using LC-MS/MS. Drug Testing and Analysis, 7(9), 812-818. doi:10.1002/dta.1777, Institutional Repository

Sewage-based epidemiology (SBE) employs the analysis of sewage to detect and quantify drug use within a community. While SBE has been applied repeatedly for the estimation of classical illicit drugs, only few studies investigated new psychoactive substances (NPS). These compounds mimic effects of illicit drugs by introducing slight modifications to chemical structures of controlled illicit drugs. We describe the optimization, validation, and application of an analytical method using liquid chromatography coupled to positive electrospray tandem mass spectrometry (LC-ESI-MS/MS) for the determination of seven NPS in sewage: methoxetamine (MXE), butylone, ethylone, methylone, methiopropamine (MPA), 4-methoxymethamphetamine (PMMA), and 4-methoxyamphetamine (PMA). Sample preparation was performed using solid-phase extraction (SPE) with Oasis MCX cartridges. The LC separation was done with a HILIC (150 x 3 mm, 5 µm) column which ensured good resolution of the analytes with a total run time of 19 min. The lower limit of quantification (LLOQ) was between 0.5 and 5 ng/L for all compounds. The method was validated by evaluating the following parameters: sensitivity, selectivity, linearity, accuracy, precision, recoveries and matrix effects. The method was applied on sewage samples collected from sewage treatment plants in Belgium and Switzerland in which all investigated compounds were detected, except MPA and PMA. Furthermore, a consistent presence of MXE has been observed in most of the sewage samples at levels higher than LLOQ.
Künzle, R., Pronk, W., Morgenroth, E., & Larsen, T. A. (2015). An energy-efficient membrane bioreactor for on-site treatment and recovery of wastewater. Journal of Water Sanitation and Hygiene for Development, 5(3), 448-455. doi:10.2166/washdev.2015.116, Institutional Repository

The present study describes the development of a new type of aerated membrane bioreactor referred to as a biologically activated membrane bioreactor (BAMBi) for on-site treatment of high-strength wastewater. The treated wastewater is reused for flushing and personal hygiene. BAMBi is an adaptation of a gravity-driven membrane reactor, originally developed for the purpose of treating river water to drinking water quality. Initially, a series of reactor configurations were tested and it was found that the simplest possible configuration could treat the wastewater to an acceptable standard, provided that a polishing step for color removal and disinfection was introduced. A commercial electrolysis unit was utilized for polishing. The energy consumption of BAMBi is 0.8 kWh/m3 of water treated, which can be considered low for an on-site membrane bio reactor application.
Lai, F. Y., Anuj, S., Bruno, R., Carter, S., Gartner, C., Hall, W., … Ort, C. (2015). Systematic and day-to-day effects of chemical-derived population estimates on wastewater-based drug epidemiology. Environmental Science and Technology, 49(2), 999-1008. doi:10.1021/es503474d, Institutional Repository

Population size is crucial when estimating population-normalized drug consumption (PNDC) from wastewater-based drug epidemiology (WBDE). Three conceptually different population estimates can be used: de jure (common census, residence), de facto (all persons within a sewer catchment), and chemical loads (contributors to the sampled wastewater). De facto and chemical loads will be the same where all households contribute to a central sewer system without wastewater loss. This study explored the feasibility of determining a de facto population and its effect on estimating PNDC in an urban community over an extended period. Drugs and other chemicals were analyzed in 311 daily composite wastewater samples. The daily estimated de facto population (using chemical loads) was on average 32% higher than the de jure population. Consequently, using the latter would systemically overestimate PNDC by 22%. However, the relative day-to-day pattern of drug consumption was similar regardless of the type of normalization as daily illicit drug loads appeared to vary substantially more than the population. Using chemical loads population, we objectively quantified the total methodological uncertainty of PNDC and reduced it by a factor of 2. Our study illustrated the potential benefits of using chemical loads population for obtaining more robust PNDC data in WBDE.
Larsen, T. A., Gebauer, H., Gründl, H., Künzle, R., Lüthi, C., Messmer, U., … Ranner, B. (2015). Blue Diversion: a new approach to sanitation in informal settlements. Journal of Water Sanitation and Hygiene for Development, 5(1), 64-71. doi:10.2166/washdev.2014.115, Institutional Repository

The sanitation concept ‘Blue Diversion’ (www.bluediversiontoilet.com) was developed as a possible answer to the sanitation crisis in urban slums. It is based on two main elements: (1) diversion of urine, feces, and water at the source as the basis for efficient resource recovery, and (2) linking different scales (family toilets and semi-centralized resource recovery). Our objective was to develop an attractive ‘grid-free’ (i.e. functioning without piped water, sewer, and electrical grid) dry urine-diverting toilet, which provides water (through recycling on-site) for flushing, personal hygiene (anal cleansing and menstrual hygiene), and hand washing. This service, including the entire sanitation value chain, should eventually be made available as a profitable business with total user fees of 5 ¢/p/d. The results presented in this paper are (1) a toilet design model, (2) the development of a new type of membrane bioreactor for treating flush and wash water, (3) main results of a geographic information system-based stochastic service model to link the family-scale toilet to a community-scale Resource Recovery Plant, and (4) a business model that yields maximum profit for the local community. We conclude that the approach is feasible, but challenging from a technical as well as an organizational point of view.
Larsen, T. A. (2015). CO2-neutral wastewater treatment plants or robust, climate-friendly wastewater management? A systems perspective. Water Research, 87, 513-521. doi:10.1016/j.watres.2015.06.006, Institutional Repository

CO2-neutral wastewater treatment plants can be obtained by improving the recovery of internal wastewater energy resources (COD, nutrients, energy) and reducing energy demand as well as direct emissions of the greenhouse gases N2O and CH4. Climate-friendly wastewater management also includes the management of the heat resource, which is most efficiently recovered at the household level, and robust wastewater management must be able to cope with a possible resulting temperature decrease. At the treatment plant there is a substantial energy optimization potential, both from improving electromechanical devices and sludge treatment as well as through the implementation of more energy-efficient processes like the mainstream anammox process or nutrient recovery from urine. Whether CO2 neutrality can be achieved depends not only on the actual net electricity production, but also on the type of electricity replaced: the cleaner the marginal electricity the more difficult to compensate for the direct emissions, which can be substantial, depending on the stability of the biological processes. It is possible to combine heat recovery at the household scale and nutrient recovery from urine, which both have a large potential to improve the climate friendliness of wastewater management.
Lienert, J., Scholten, L., Egger, C., & Maurer, M. (2015). Structured decision-making for sustainable water infrastructure planning and four future scenarios. EURO Journal on Decision Processes, 3, 107-140. doi:10.1007/s40070-014-0030-0, Institutional Repository

Water supply and wastewater infrastructures are vital for human well-being and environmental protection; they adhere to the highest standards, are expensive and long-lived. Because they are also aging, substantial planning is required. Climate and socio-economic change create large planning uncertainties and simple projections of past developments are no longer adequate. This paper presents the initial phases of a structured decision-making (SDM) procedure which is designed to increase the sustainability of water infrastructure planning and includes various stakeholders in an exemplary Swiss case study. We evaluate the SDM approach critically based on stakeholder feedback, give general recommendations and provide ample material to make it applicable to other settings. We carried out 27 interviews and two stakeholder workshops. We identified important objectives for water infrastructure planning, including all three sustainability pillars and their respective attributes (indicators, benchmarks) to measure how well the objectives are achieved. We then created strategic decision alternatives, including "business-as-usual" upgrades of the central water supply and wastewater system as well as semi- to fully decentralized alternatives. To tackle future uncertainty, we developed four socio-demographic scenarios. We used these to test the robustness of decision alternatives in a later Multi-Attribute Utility Theory analysis. Additionally, we contribute to the topical discussion of combining scenario planning with multi-criteria decision analysis and demonstrate how various scenarios can stimulate creativity when generating decision alternatives. Their internal consistency is ensured by rigorously specifying them using a strategy generation table. Our SDM procedure can be adapted to inform decisions about sustainable water infrastructures in other contexts.
Neumann, M. B., Rieckermann, J., Hug, T., & Gujer, W. (2015). Adaptation in hindsight: dynamics and drivers shaping urban wastewater systems. Journal of Environmental Management, 151, 404-415. doi:10.1016/j.jenvman.2014.12.047, Institutional Repository

Well-planned urban infrastructure should meet critical loads during its design lifetime. In order to proceed with design, engineers are forced to make numerous assumptions with very little supporting information about the development of various drivers. For the wastewater sector, these drivers include the future amount and composition of the generated wastewater, effluent requirements, technologies, prices of inputs such as energy or chemicals, and the value of outputs produced such as nutrients for fertilizer use. When planning wastewater systems, there is a lack of methods to address discrepancies between the timescales at which fundamental changes in these drivers can occur, and the long physical life expectancy of infrastructure (on the order of 25–80 years). To explore these discrepancies, we take a hindsight perspective of the long-term development of wastewater infrastructure and assess the stability of assumptions made during previous designs. Repeatedly we find that the drivers influencing wastewater loads, environmental requirements or technological innovation can change at smaller timescales than the infrastructure design lifetime, often in less than a decade. Our analysis shows that i) built infrastructure is continuously confronted with challenges it was not conceived for, ii) significant adaptation occurs during a structure's lifetime, and iii) "muddling-through" is the pre-dominant strategy for adaptive management. As a consequence, we argue, there is a need to explore robust design strategies which require the systematic use of scenario planning methods and instruments to increase operational, structural, managerial, institutional and financial flexibility. Hindsight studies, such as this one, may inform the development of robust design strategies and assist in the transition to more explicit forms of adaptive management for urban infrastructures.
O'Brien, J. W., Thai, P. K., Brandsma, S. H., Leonards, P. E. G., Ort, C., & Mueller, J. F. (2015). Wastewater analysis of Census day samples to investigate per capita input of organophosphorus flame retardants and plasticizers into wastewater. Chemosphere, 138, 328-334. doi:10.1016/j.chemosphere.2015.06.014, Institutional Repository

The use of organophosphate esters (PFRs) as flame retardants and plasticizers has increased due to the ban of some brominated flame retardants. There is however some concern regarding the toxicity, particularly carcinogenicity and neurotoxicity, of some of the PFRs. In this study we applied wastewater analysis to assess use of PFRs by the Australian population. Influent samples were collected from eleven wastewater treatment plants (STPs) in Australia on Census day and analysed for PFRs using gas chromatography coupled with mass spectrometry (GC-MS). Per capita mass loads of PFRs were calculated using the accurate Census head counts. The results indicate that tris(2-butoxyethyl) phosphate (TBOEP) has the highest per capita input into wastewater followed by tris(2-chloroisopropyl) phosphate (TCIPP), tris(isobutyl) phosphate (TIBP), tris(2-chloroethyl) phosphate (TCEP) and tris(1,3-dichloroisopropyl) phosphate (TDCIPP). Similar PFR profiles were observed across the Australian STPs and a comparison with European and U.S. STPs indicated similar PFR concentrations. We estimate that approximately 2.1 mg person−1 day−1 of PFRs are input into Australian wastewater which equates to 16 tonnes per annum.
Scheidegger, A., Leitão, J. P., & Scholten, L. (2015). Statistical failure models for water distribution pipes – a review from a unified perspective. Water Research, 83, 237-247. doi:10.1016/j.watres.2015.06.027, Institutional Repository

This review describes and compares statistical failure models for water distribution pipes in a systematic way and from a unified perspective. The way the comparison is structured provides the information needed by scientists and practitioners to choose a suitable failure model for their specific needs.
The models are presented in a novel framework consisting of: 1) Clarification of model assumptions. The models originally formulated in different mathematical forms are all presented as failure rate. This enables to see differences and similarities across the models. Furthermore, we present a new conceptual failure rate that an optimal model would represent and to which the failure rate of each model can be compared. 2) Specification of the detailed data assumptions required for unbiased model calibration covering the structure and completeness of the data. 3) Presentation of the different types of probabilistic predictions available for each model.
Nine different models and their variations or further developments are presented in this review. For every model an overview of its applications published in scientific journals and the available software implementations is provided.
The unified view provides guidance to model selection. Furthermore, the model comparison presented herein enables to identify areas where further research is needed.
Scholten, L., Schuwirth, N., Reichert, P., & Lienert, J. (2015). Tackling uncertainty in multi-criteria decision analysis – an application to water supply infrastructure planning. European Journal of Operational Research, 242(1), 243-260. doi:10.1016/j.ejor.2014.09.044, Institutional Repository

We present a novel approach for practically tackling uncertainty in preference elicitation and predictive modeling to support complex multi-criteria decisions based on multi-attribute utility theory (MAUT). A simplified two-step elicitation procedure consisting of an online survey and face-to-face interviews is followed by an extensive uncertainty analysis. This covers uncertainty of the preference components (marginal value and utility functions, hierarchical aggregation functions, aggregation parameters) and the attribute predictions. Context uncertainties about future socio-economic developments are captured by combining MAUT with scenario planning. We perform a global sensitivity analysis (GSA) to assess the contribution of single uncertain preference parameters to the uncertainty of the ranking of alternatives. This is exemplified for sustainable water infrastructure planning in a case study in Switzerland. We compare 11 water supply alternatives ranging from conventional water supply systems to novel technologies and management schemes regarding 44 objectives. Their performance is assessed for four future scenarios and 10 stakeholders from different backgrounds and decision-making levels. Despite uncertainty in the ranking of alternatives, potential best and worst solutions could be identified. We demonstrate that a priori assumptions such as linear value functions or additive aggregation can result in misleading recommendations, unless thoroughly checked during preference elicitation and modeling. We suggest GSA to focus elicitation on most sensitive preference parameters. Our GSA results indicate that output uncertainty can be considerably reduced by additional elicitation of few parameters, e.g. the overall risk attitude and aggregation functions at higher-level nodes. Here, rough value function elicitation was sufficient, thereby substantially reducing elicitation time.
Sikorska, A. E., Del Giudice, D., Banasik, K., & Rieckermann, J. (2015). The value of streamflow data in improving TSS predictions - Bayesian multi-objective calibration. Journal of Hydrology, 530, 241-254. doi:10.1016/j.jhydrol.2015.09.051, Institutional Repository

The concentration of total suspended solids (TSS) in surface waters is a commonly used indicator of water quality impairments. Its accurate prediction remains, however, problematic because: i) TSS build-up, erosion, and wash-off are not easily identifiable; ii) calibrating a TSS model requires observations of sediment loads, which are rare, and streamflow observations to calculate concentrations; iii) predicted TSS usually deviate systematically from observations, an effect which is commonly neglected. Ignoring systematic errors during calibration can lead to overconfident (i.e. unreliable) uncertainty estimates during predictions. In this paper, we therefore investigate whether a statistical description of systematic model errors makes it possible to generate reliable predictions for TSS. In addition, we explore how the reliability of TSS predictions increases when streamflow data are additionally used in model calibration. A key aspect of our study is that we use a Bayesian multi-output calibration and a novel autoregressive error model, which describes the model predictive error as a sum of independent random noise and autocorrelated bias. Our results show that using a statistical description of model bias provides more reliable uncertainty estimates of TSS than before and including streamflow data into calibration makes TSS predictions more precise. For a case study of a small ungauged catchment, this improvement was as much as 15%. Our approach can be easily implemented for other water quality variables which are dependent on streamflow.
Simões, N. E., Ochoa-Rodríguez, S., Wang, L. P., Pina, R. D., Marques, A. S., Onof, C., & Leitão, J. P. (2015). Stochastic urban pluvial flood hazard maps based upon a spatial-temporal rainfall generator. Water, 7(7), 3396-3406. doi:10.3390/w7073396, Institutional Repository

It is a common practice to assign the return period of a given storm event to the urban pluvial flood event that such storm generates. However, this approach may be inappropriate as rainfall events with the same return period can produce different urban pluvial flooding events, i.e., with different associated flood extent, water levels and return periods. This depends on the characteristics of the rainfall events, such as spatial variability, and on other characteristics of the sewer system and the catchment. To address this, the paper presents an innovative contribution to produce stochastic urban pluvial flood hazard maps. A stochastic rainfall generator for urban-scale applications was employed to generate an ensemble of spatially—and temporally—variable design storms with similar return period. These were used as input to the urban drainage model of a pilot urban catchment (~9 km2) located in London, UK. Stochastic flood hazard maps were generated through a frequency analysis of the flooding generated by the various storm events. The stochastic flood hazard maps obtained show that rainfall spatial-temporal variability is an important factor in the estimation of flood likelihood in urban areas. Moreover, as compared to the flood hazard maps obtained by using a single spatially-uniform storm event, the stochastic maps generated in this study provide a more comprehensive assessment of flood hazard which enables better informed flood risk management decisions.
Tokarczyk, P., Leitao, J. P., Rieckermann, J., Schindler, K., & Blumensaat, F. (2015). High-quality observation of surface imperviousness for urban runoff modelling using UAV imagery. Hydrology and Earth System Sciences, 19(10), 4215-4228. doi:10.5194/hess-19-4215-2015, Institutional Repository

Modelling rainfall–runoff in urban areas is increasingly applied to support flood risk assessment, particularly against the background of a changing climate and an increasing urbanization. These models typically rely on high-quality data for rainfall and surface characteristics of the catchment area as model input.
While recent research in urban drainage has been focusing on providing spatially detailed rainfall data, the technological advances in remote sensing that ease the acquisition of detailed land-use information are less prominently discussed within the community. The relevance of such methods increases as in many parts of the globe, accurate land-use information is generally lacking, because detailed image data are often unavailable. Modern unmanned aerial vehicles (UAVs) allow one to acquire high-resolution images on a local level at comparably lower cost, performing on-demand repetitive measurements and obtaining a degree of detail tailored for the purpose of the study.
In this study, we investigate for the first time the possibility of deriving high-resolution imperviousness maps for urban areas from UAV imagery and of using this information as input for urban drainage models. To do so, an automatic processing pipeline with a modern classification method is proposed and evaluated in a state-of-the-art urban drainage modelling exercise. In a real-life case study (Lucerne, Switzerland), we compare imperviousness maps generated using a fixed-wing consumer micro-UAV and standard large-format aerial images acquired by the Swiss national mapping agency (swisstopo). After assessing their overall accuracy, we perform an end-to-end comparison, in which they are used as an input for an urban drainage model. Then, we evaluate the influence which different image data sources and their processing methods have on hydrological and hydraulic model performance. We analyse the surface runoff of the 307 individual subcatchments regarding relevant attributes, such as peak runoff and runoff volume. Finally, we evaluate the model's channel flow prediction performance through a cross-comparison with reference flow measured at the catchment outlet.
We show that imperviousness maps generated from UAV images processed with modern classification methods achieve an accuracy comparable to standard, off-the-shelf aerial imagery. In the examined case study, we find that the different imperviousness maps only have a limited influence on predicted surface runoff and pipe flows, when traditional workflows are used. We expect that they will have a substantial influence when more detailed modelling approaches are employed to characterize land use and to predict surface runoff. We conclude that UAV imagery represents a valuable alternative data source for urban drainage model applications due to the possibility of flexibly acquiring up-to-date aerial images at a quality compared with off-the-shelf image products and a competitive price at the same time. We believe that in the future, urban drainage models representing a higher degree of spatial detail will fully benefit from the strengths of UAV imagery.
Been, F., Rossi, L., Ort, C., Rudaz, S., Delémont, O., & Esseiva, P. (2014). Population normalization with ammonium in wastewater-based epidemiology: application to illicit drug monitoring. Environmental Science and Technology, 48(14), 8162-8169. doi:10.1021/es5008388, Institutional Repository

Fluctuations in ammonium (NH4 +), measured as NH 4-N loads using an ion-selective electrode installed at the inlet of a sewage treatment plant, showed a distinctive pattern which was associated to weekly (i.e., commuters) and seasonal (i.e., holidays) fluctuations of the population. Moreover, population size estimates based on NH4-N loads were lower compared to census data. Diurnal profiles of benzoylecgonine (BE) and 11-nor-9-carboxy-δ9-tetrahydrocannabinol (THC-COOH) were shown to be strongly correlated to NH4-N. Characteristic patterns, which reflect the prolonged nocturnal activity of people during the weekend, could be observed for BE, cocaine, and a major metabolite of MDMA (i.e., 4-hydroxy-3- methoxymethamphetamine). Additional 24 h composite samples were collected between February and September 2013. Per-capita loads (i.e., grams per day per 1000 inhabitants) were computed using census data and NH4-N measurements. Normalization with NH4-N did not modify the overall pattern, suggesting that the magnitude of fluctuations in the size of the population is negligible compared to those of illicit drug loads. Results show that fluctuations in the size of the population over longer periods of time or during major events can be monitored using NH4-N loads: either using raw NH4-N loads or population size estimates based on NH 4-N loads, if information about site-specific NH4-N population equivalents is available.
Blumensaat, F., Seydel, J., Krebs, P., & Vanrolleghem, P. A. (2014). Model structure sensitivity of river water quality models for urban drainage impact assessment. In D. P. Ames, N. W. T. Quinn, & A. E. Rizzoli (Eds.), Vol. 2. Proceedings of the 7th international congress on environmental modelling and software (pp. 609-618). San Diego, California, USA: International Environmental Modelling and Software Society. , Institutional Repository

Numerical modeling of physicochemical conditions in rivers influenced by urban drainage and other pressures is increasingly used as supportive method for an integrative environmental impact assessment. In various European countries, protocols for water quality based impact assessment (WQA protocols) are in use, of which many propose the use of water quality models. Despite the increased effort to study uncertainty issues in river water quality modeling in recent years, identifying and differentiating model structure uncertainty remains a challenging task. This study elaborates upon a key conflict in model development: the need to simplify and to still ensure structural adequacy to obtain reliable modeling results. The paper evaluates the adequacy of diverse river water quality modeling approaches when subjected to a changing model structure. This evaluation is achieved by applying a set of calibrated candidate models to two different river case studies under varying pollution conditions. The term 'model structure sensitivity' is introduced to quantify the output variation as a result of a changing model structure. Sensitivity is here, in contrast to previous works, positively interpreted as model flexibility. The study illustrates that the interdependence bet ween model sensitivity and model error is conditional upon complexity, but model adequacy differs depending on the pollution dynamics in the modeled system. Results show that model structure uncertainty has a composite nature: effects related to transport and conversion model contribute with varying shares. Two actions should be considered to improve model structure characterization: i) use of a variety of model structures combined with an analysis of structure and parameter sensitivity, and ii) acquisition of high-resolution reference data to capture varying pollution load dynamics.
Dürrenmatt, D. J., & Wanner, O. (2014). A mathematical model to predict the effect of heat recovery on the wastewater temperature in sewers. Water Research, 48(1), 548-558. doi:10.1016/j.watres.2013.10.017, Institutional Repository

Raw wastewater contains considerable amounts of energy that can be recovered by means of a heat pump and a heat exchanger installed in the sewer. The technique is well established, and there are approximately 50 facilities in Switzerland, many of which have been successfully using this technique for years. The planning of new facilities requires predictions of the effect of heat recovery on the wastewater temperature in the sewer because altered wastewater temperatures may cause problems for the biological processes used in wastewater treatment plants and receiving waters. A mathematical model is presented that calculates the discharge in a sewer conduit and the spatial profiles and dynamics of the temperature in the wastewater, sewer headspace, pipe, and surrounding soil. The model was implemented in the simulation program TEMPEST and was used to evaluate measured time series of discharge and temperatures. It was found that the model adequately reproduces the measured data and that the temperature and thermal conductivity of the soil and the distance between the sewer pipe and undisturbed soil are the most sensitive model parameters. The temporary storage of heat in the pipe wall and the exchange of heat between wastewater and the pipe wall are the most important processes for heat transfer. The model can be used as a tool to determine the optimal site for heat recovery and the maximal amount of extractable heat.
Gulde, R., Helbling, D. E., Scheidegger, A., & Fenner, K. (2014). pH-dependent biotransformation of ionizable organic micropollutants in activated sludge. Environmental Science and Technology, 48(23), 13760-13768. doi:10.1021/es5037139, Institutional Repository

Removal of micropollutants (MPs) during activated sludge treatment can mainly be attributed to biotransformation and sorption to sludge flocs, whereby the latter process is known to be of minor importance for polar organic micropollutants. In this work, we investigated the influence of pH on the biotransformation of MPs with cationic-neutral speciation in an activated sludge microbial community. We performed batch biotransformation, sorption control, and abiotic control experiments for 15 MPs with cationic-neutral speciation, one control MP with neutral-anionic speciation, and two neutral MPs at pHs 6, 7, and 8. Biotransformation rate constants corrected for sorption and abiotic processes were estimated from measured concentration time series with Bayesian inference. We found that biotransformation is pH-dependent and correlates qualitatively with the neutral fraction of the ionizable MPs. However, a simple speciation model based on the assumption that only the neutral species is efficiently taken up and biotransformed by the cells tends to overpredict the effect of speciation. Therefore, additional mechanisms such as uptake of the ionic species and other more complex attenutation mechanisms are discussed. Finally, we observed that the sorption coefficients derived from our control experiments were small and showed no notable pH-dependence. From this we conclude that pH-dependent removal of polar, ionizable organic MPs in activated sludge systems is less likely an effect of pH-dependent sorption but rather of pH-dependent biotransformation. The latter has the potential to cause marked differences in the removal of polar, ionizable MPs at different operational pHs during activated sludge treatment.
Honti, M., Scheidegger, A., & Stamm, C. (2014). The importance of hydrological uncertainty assessment methods in climate change impact studies. Hydrology and Earth System Sciences, 18(8), 3301-3317. doi:10.5194/hess-18-3301-2014, Institutional Repository

Climate change impact assessments have become more and more popular in hydrology since the middle 1980s with a recent boost after the publication of the IPCC AR4 report. From hundreds of impact studies a quasi-standard methodology has emerged, to a large extent shaped by the growing public demand for predicting how water resources management or flood protection should change in the coming decades. The "standard" workflow relies on a model cascade from global circulation model (GCM) predictions for selected IPCC scenarios to future catchment hydrology. Uncertainty is present at each level and propagates through the model cascade. There is an emerging consensus between many studies on the relative importance of the different uncertainty sources. The prevailing perception is that GCM uncertainty dominates hydrological impact studies. Our hypothesis was that the relative importance of climatic and hydrologic uncertainty is (among other factors) heavily influenced by the uncertainty assessment method. To test this we carried out a climate change impact assessment and estimated the relative importance of the uncertainty sources. The study was performed on two small catchments in the Swiss Plateau with a lumped conceptual rainfall runoff model. In the climatic part we applied the standard ensemble approach to quantify uncertainty but in hydrology we used formal Bayesian uncertainty assessment with two different likelihood functions. One was a time series error model that was able to deal with the complicated statistical properties of hydrological model residuals. The second was an approximate likelihood function for the flow quantiles. The results showed that the expected climatic impact on flow quantiles was small compared to prediction uncertainty. The choice of uncertainty assessment method actually determined what sources of uncertainty could be identified at all. This demonstrated that one could arrive at rather different conclusions about the causes behind predictive uncertainty for the same hydrological model and calibration data when considering different objective functions for calibration.
Leidel, M., Hagemann, N., Seegert, J., Weigelt, C., Zakorchevna, N., & Blumensaat, F. (2014). Supporting decisions in water management by exploring information and capacity gaps: Experiences from an IWRM study in the Western Bug River Basin, Ukraine. Environmental Earth Sciences, 72(12), 4771-4786. doi:10.1007/s12665-014-3863-8, Institutional Repository

Key problems of Integrated Water Resources Management refer to interactions between various levels, scales and existing coordination gaps, such as inadequate governance structures and insufficient knowledge and capacities. In this study we describe a management framework that aligns model-based systems analysis with capacity assessments suggesting a concept for improving cross-scale interactions and thus for overcoming both, water-related pressures and coordination gaps. In the study we (i) identify the missing link between technical development approaches and capacity development, (ii) outline interrelations between environmental pressures on aquatic systems and capacity and information gaps in a transparent way, and (iii) introduce a practice-relevant method to combine model-based system planning with capacity assessments for deriving management options that support water management actors in reducing pressures and gaps. The results of the integrated analysis are made explicit by introducing a matrix approach that is inspired by an existing framework to systematically differentiate water quality-related pressures (cf. Blumensaat et al. 2013). The approach confronts pressures and gaps and so jointly addresses technical issues, institutional challenges, organizational development, information needs, and human resources development. The concept supports a transparent decision making process by identifying knowledge and capacities required for the implementation of corresponding technical intervention options and vice versa. The application of the method in the International Water Research Alliance Saxony model region 'Ukraine' is illustrated to demonstrate the added value as a boundary object between scales that is supporting actors in streamlining model-based planning and capacity development.
Logar, I., Brouwer, R., Maurer, M., & Ort, C. (2014). Cost-benefit analysis of the Swiss national policy on reducing micropollutants in treated wastewater. Environmental Science and Technology, 48(21), 12500-12508. doi:10.1021/es502338j, Institutional Repository

Contamination of freshwater with micropollutants (MPs) is a growing concern worldwide. Even at very low concentrations, MPs can have adverse effects on aquatic ecosystems and possibly also on human health. Switzerland is one of the first countries to start implementing a national policy to reduce MPs in the effluents of municipal sewage treatment plants (STPs). This paper estimates the benefits of upgrading STPs based on public’s stated preferences. To assess public demand for the reduction of the environmental and health risks of MPs, we conducted a choice experiment in a national online survey. The results indicate that the average willingness to pay per household is CHF 100 (US$ 73) annually for reducing the potential environmental risk of MPs to a low level. These benefits, aggregated over households in the catchment of the STPs to be upgraded, generate a total annual economic value of CHF 155 million (US$ 113 million). This compares with estimated annual costs for upgrading 123 STPs of CHF 133 million (US$ 97 million) or CHF 86 (US$ 63) per household connected to these STPs. Hence, a cost-benefit analysis justifies the investment decision from an economic point of view and supports the implementation of the national policy in the ongoing political discussion.
McConville, J. R., Künzle, R., Messmer, U., Udert, K. M., & Larsen, T. A. (2014). Decision support for redesigning wastewater treatment technologies. Environmental Science and Technology, 48(20), 12238-12246. doi:10.1021/es501854x, Institutional Repository

This paper offers a methodology for structuring the design space for innovative process engineering technology development. The methodology is exemplified in the evaluation of a wide variety of treatment technologies for source-separated domestic wastewater within the scope of the Reinvent the Toilet Challenge. It offers a methodology for narrowing down the decision-making field based on a strict interpretation of treatment objectives for undiluted urine and dry feces and macroenvironmental factors (STEEPLED analysis) which influence decision criteria. Such an evaluation identifies promising paths for technology development such as focusing on space-saving processes or the need for more innovation in low-cost, energy-efficient urine treatment methods. Critical macroenvironmental factors, such as housing density, transportation infrastructure, and climate conditions were found to affect technology decisions regarding reactor volume, weight of outputs, energy consumption, atmospheric emissions, investment cost, and net revenue. The analysis also identified a number of qualitative factors that should be carefully weighed when pursuing technology development; such as availability of O&M resources, health and safety goals, and other ethical issues. Use of this methodology allows for coevolution of innovative technology within context constraints; however, for full-scale technology choices in the field, only very mature technologies can be evaluated.
O'Brien, J. W., Thai, P. K., Eaglesham, G., Ort, C., Scheidegger, A., Carter, S., … Mueller, J. F. (2014). A model to estimate the population contributing to the wastewater using samples collected on census day. Environmental Science and Technology, 48(1), 517-525. doi:10.1021/es403251g, Institutional Repository

An important uncertainty when estimating per capita consumption of, for example, illicit drugs by means of wastewater analysis (sometimes referred to as "sewage epidemiology") relates to the size and variability of the de facto population in the catchment of interest. In the absence of a day-specific direct population count any indirect surrogate model to estimate population size lacks a standard to assess associated uncertainties. Therefore, the objective of this study was to collect wastewater samples at a unique opportunity, that is, on a census day, as a basis for a model to estimate the number of people contributing to a given wastewater sample. Mass loads for a wide range of pharmaceuticals and personal care products were quantified in influents of ten sewage treatment plants (STP) serving populations ranging from approximately 3500 to 500 000 people. Separate linear models for population size were estimated with the mass loads of the different chemical as the explanatory variable: 14 chemicals showed good, linear relationships, with highest correlations for acesulfame and gabapentin. De facto population was then estimated through Bayesian inference, by updating the population size provided by STP staff (prior knowledge) with measured chemical mass loads. Cross validation showed that large populations can be estimated fairly accurately with a few chemical mass loads quantified from 24-h composite samples. In contrast, the prior knowledge for small population sizes cannot be improved substantially despite the information of multiple chemical mass loads. In the future, observations other than chemical mass loads may improve this deficit, since Bayesian inference allows including any kind of information relating to population size.
Ort, C., Eppler, J. M., Scheidegger, A., Rieckermann, J., Kinzig, M., & Sörgel, F. (2014). Challenges of surveying wastewater drug loads of small populations and generalizable aspects on optimizing monitoring design. Addiction, 109(3), 472-481. doi:10.1111/add.12405, Institutional Repository

Aims. Quantifying illicit drug loads through wastewater analysis (WWA) is an alternative approach to estimating population drug use. This study investigated the variability of daily drug loads in wastewater and their relationships to environmental factors over an extended period to: (i) explore the suitability of WWA in small populations and (ii) optimize the monitoring design for future studies.
Design, Setting, Participants. Daily wastewater samples (n = 1369 consecutive days) from a German village with approximately 7160 inhabitants.
Measurements. Samples were analysed for cocaine and benzoylecgonine with liquid chromatography-tandem mass spectrometry. Time-series analysis was used to explore the effects of weather and other factors on daily cocaine loads. Subsampling was used to assess monitoring design.
Findings. Cocaine loads [mean = 652 mgCOC/day, standard deviation (SD) = 498 mgCOC/day] increased over the study period, with higher values during winter and spring. Despite high day-to-day variation, loads were significantly higher during weekends [+161 mgCOC/day, 95% confidence interval (CI) = 115–207 mgCOC/day, P < 10−4] and days with frost (+114 mgCOC/day, 95% CI = 6–223 mgCOC/day, P = 0.039) or snow (+150 mgCOC/day, 95% CI = 46–253 mgCOC/day, P = 0.005). Annual means estimated from 1-week periods were subject to approximately 60% relative error. Increasing sample size and changing sampling from consecutive days to stratified random decreased this uncertainty.
Conclusions. Day-to-day variation and seasonality of drug loads from the few long-term wastewater studies available to date suggest that up to 56 stratified random samples are required to obtain reliable (expected uncertainty around 10%) annual estimates of drug loads. Successfully assessing changes in consumption patterns or relationships to external factors requires larger sample sizes than estimating annual means, which holds true for high-prevalence drugs in small communities and low-prevalence drugs in big cities.
Ort, C., Banta-Green, C. J., Bijlsma, L., Castiglioni, S., Emke, E., Gartner, C., … van Nuijs, A. L. N. (2014). Sewage-based epidemiology requires a truly transdisciplinary approach. GAIA: Ecological Perspectives for Science and Society, 23(3), 266-268. doi:10.14512/gaia.23.3.12, Institutional Repository

If asked whether you had consumed illicit drugs recently, would you admit it? If yes, could you precisely recall types of drug, times and amounts used? If you were the person commissioned with the task of quantifying drug use, what approach would you use given the social stigma attached with such behavior? We measure drug residues in sewage, which represents urine of entire populations, to provide an objective estimate of total drug use in a region. In transdisciplinary projects, sewage-based results provide valuable information at unrivaled spatiotemporal resolution complementing traditional data.
Ort, C., van Nuijs, A. L. N., Berset, J. D., Bijlsma, L., Castiglioni, S., Covaci, A., … Thomas, K. V. (2014). Spatial differences and temporal changes in illicit drug use in Europe quantified by wastewater analysis. Addiction, 109(8), 1338-1352. doi:10.1111/add.12570, Institutional Repository

Aims. To perform wastewater analyses to assess spatial differences and temporal changes of illicit drug use in a large European population.
Design. Analyses of raw wastewater over a 1-week period in 2012 and 2013.
Setting and Participants. Catchment areas of wastewater treatment plants (WWTPs) across Europe, as follows: 2012: 25 WWTPs in 11 countries (23 cities, total population 11.50 million); 2013: 47 WWTPs in 21 countries (42 cities, total population 24.74 million).
Measurements. Excretion products of five illicit drugs (cocaine, amphetamine, ecstasy, methamphetamine, cannabis) were quantified in wastewater samples using methods based on liquid chromatography coupled to mass spectrometry.
Findings. Spatial differences were assessed and confirmed to vary greatly across European metropolitan areas. In general, results were in agreement with traditional surveillance data, where available. While temporal changes were substantial in individual cities and years (P ranging from insignificant to <10−3), overall means were relatively stable. The overall mean of methamphetamine was an exception (apparent decline in 2012), as it was influenced mainly by four cities.
Conclusions. Wastewater analysis performed across Europe provides complementary evidence on illicit drug consumption and generally concurs with traditional surveillance data. Wastewater analysis can measure total illicit drug use more quickly and regularly than is the current norm for national surveys, and creates estimates where such data does not exist.
Scholten, L., Scheidegger, A., Reichert, P., Mauer, M., & Lienert, J. (2014). Strategic rehabilitation planning of piped water networks using multi-criteria decision analysis. Water Research, 49(1), 124-143. doi:10.1016/j.watres.2013.11.017, Institutional Repository

To overcome the difficulties of strategic asset management of water distribution networks, a pipe failure and a rehabilitation model are combined to predict the long term performance of rehabilitation strategies. Bayesian parameter estimation is performed to calibrate the failure and replacement model based on a prior distribution inferred from three large water utilities in Switzerland. Multi criteria decision analysis (MCDA) and scenario planning build the framework for evaluating 18 strategic rehabilitation alternatives under future uncertainty. Outcomes for three fundamental objectives (low costs, high reliability, and high intergenerational equity) are assessed. Exploitation of stochastic dominance concepts helps to identify twelve non dominated alternatives and local sensitivity analysis of stakeholder preferences is used to rank them under four scenarios. Strategies with annual replacement of 1.5 2% of the network perform reasonably well under all scenarios. In contrast, the commonly used reactive replacement is not recommendable unless cost is the only relevant objective. Exemplified for a small Swiss water utility, this approach can readily be adapted to support strategic asset management for any utility size and based on objectives and preferences that matter to the respective decision makers.
Seegert, J., Berendonk, T. U., Bernhofer, C., Blumensaat, F., Dombrowsky, I., Fuehner, C., … Krebs, P. (2014). Integrated water resources management under different hydrological, climatic and socio-economic conditions: results and lessons learned from a transdisciplinary IWRM project IWAS. Environmental Earth Sciences, 72(12), 4677-4687. doi:10.1007/s12665-014-3877-2, Institutional Repository

The International Water Research Alliance Saxony (IWAS) is addressing the global challenges concerning water quality in the areas of drinking water and sanitation, agricultural irrigation and the quality of surface and ground waters, as well as developing specific ecosystem-relevant services to be implemented on an exemplary basis in selected model regions. Locations (model regions) have been selected in Eastern Europe (R1), Central and Southeast Asia (R2 and R3), the Middle East (R4) and Latin America (R5) that are representative international regions with respect to climate, land use and demographic change (Ibisch et al., Helmholtz Centre for Environmental Research—UFZ, Department of Aquatic Ecosystem analysis and management, 2013). The causes of water problems and the relevant boundary conditions vary from region to region (Borchardt and Ibisch, Integrated water resources management in a changing world : lessons learnt and innovative perspectives, pp 225, 2013). Mongolia and Vietnam were selected model regions in the first IWAS phase; the research was transferred and continued in one of the cross-cutting projects in IWAS II (Vietnam → capacity development) or in the frame of related project activities in Central Asia (R2 Mongolia, Karthe et al., Environ Earth Sci, doi:10.1007/s12665-014-3789-1, 2014). The IWAS consortium exists on scientific institutions like the Technische Universität Dresden and the Helmholtz Centre for Environmental Research—UFZ, Leipzig, as well as partners from industry like the Stadtentwässerung Dresden GmbH (SE-DD), DREBERIS—Dresden consulting for international strategies, and itwh—institute for technical-scientific Hydrology, Hanover. This thematic issue compiles the most important scientific results of the second phase of the IWAS project. The project itself and findings of the first phase were already introduced in a previous special issue by Kalbus et al. (Environ Earth Sci 65:1363–1366, 2012). Main results: The IWAS project is structured by the model regions (R) as well as by cross-cutting activities scenario analysis (Q1), technology development (Q2), governance (Q3) and capacity development (Q4).
Veronesi, M., Chawla, F., Maurer, M., & Lienert, J. (2014). Climate change and the willingness to pay to reduce ecological and health risks from wastewater flooding in urban centers and the environment. Ecological Economics, 98, 1-10. doi:10.1016/j.ecolecon.2013.12.005, Institutional Repository

Climate change scenarios predict an increase of extreme rain events, which will increase the risk of wastewater flooding and of missing legal water quality targets. This study elicits the willingness to pay to reduce ecological and health risks from combined sewer overflows (CSOs) in rivers and lakes, and wastewater flooding of residential and commercial zones under the uncertainty of climate change. We implement a discrete choice experiment on a large representative sample of the Swiss population. We find that about 71% of the respondents are willing to pay a higher annual local tax to reduce the risk of CSOs in rivers and lakes. Swiss households strongly value the protection of water bodies, and mostly, the avoidance of high ecological risks and health risks for children related to CSOs in rivers and lakes. Our findings also show that climate change perception has a significant effect on the willingness to pay to reduce these risks. These results are important to support policy makers' decisions on how to deal with emerging risks of climate change in the water sector and where to set priorities.
van Dyken, E., Thai, P., Lai, F. Y., Ort, C., Prichard, J., Bruno, R., … Mueller, J. F. (2014). Monitoring substance use in prisons: assessing the potential value of wastewater analysis. Science and Justice, 54(5), 338-345. doi:10.1016/j.scijus.2014.06.006, Institutional Repository

Prison substance use is a major concern for prison authorities and the wider community. Australia has responded to this problem by implementing the National Corrections Drug Strategy. Across Australia, the true extent of prison substance use cannot be determined. As a result, the effectiveness of the interventions employed as part of this strategy cannot be properly assessed. This has important implications for the allocation of corrective services resources and future policy development. This article explores the benefits and limitations, as well as the ethical and practical issues in using wastewater analysis (WWA) to measure levels of substance use in prisons. It reports results from the first application of WWA to an Australian prison, which supports the use of WWA in this context. Given the increasing concern for prescription misuse in prisons, we also highlight the novel use of WWA to measure the extent of prescription misuse by prisoners. The article concludes that as a result of its objectivity, sensitivity and cost-effectiveness, the use of WWA in prisons warrants further consideration in Australia.
Bianchi, B., Rieckermann, J., & Berne, A. (2013). Quality control of rain gauge measurements using telecommunication microwave links. Journal of Hydrology, 492, 15-23. doi:10.1016/j.jhydrol.2013.03.042, Institutional Repository

Accurate rain rate measurements are essential for many hydrological applications. Although rain gauge remains the reference instrument for the measurement of rain rate, the strong spatial and temporal variability of rainfall makes it difficult to spot faulty rain gauges. Due to the poor spatial representativeness of the point rainfall measurements, this is particularly difficult where their density is low. Taking advantage of the high density of telecommunication microwave links in urban areas, a consistency check is proposed to identify faulty rain gauges using nearby microwave links. The methodology is tested on a data set from operational rain gauges and microwave links, in Zürich (Switzerland). The malfunctioning of rain gauges leading to errors in the occurrence of dry/rainy periods are well identified. In addition, the gross errors affecting quantitative rain gauge measurements during rainy periods, such as blocking at a constant value, random noise and systematic bias, can be detected. The proposed approach can be implemented in real time.
Castiglioni, S., Bijlsma, L., Covaci, A., Emke, E., Hernández, F., Reid, M., … Zuccato, E. (2013). Evaluation of uncertainties associated with the determination of community drug use through the measurement of sewage drug biomarkers. Environmental Science and Technology, 47(3), 1452-1460. doi:10.1021/es302722f, Institutional Repository

The aim of this study was to integrally address the uncertainty associated with all the steps used to estimate community drug consumption through the chemical analysis of sewage biomarkers of illicit drugs. Uncertainty has been evaluated for sampling, chemical analysis, stability of drug biomarkers in sewage, back-calculation of drug use (specific case of cocaine), and estimation of population size in a catchment using data collected from a recent Europe-wide investigation and from the available literature. The quality of sampling protocols and analytical measurements has been evaluated by analyzing standardized questionnaires collected from 19 sewage treatments plants (STPs) and the results of an interlaboratory study (ILS), respectively. Extensive reviews of the available literature have been used to evaluate stability of drug biomarkers in sewage and the uncertainty related to back-calculation of cocaine use. Different methods for estimating population size in a catchment have been compared and the variability among the collected data was very high (7–55%). A reasonable strategy to reduce uncertainty was therefore to choose the most reliable estimation case by case. In the other cases, the highest uncertainties are related to the analysis of sewage drug biomarkers (uncertainty as relative standard deviation; RSD: 6–26% from ILS) and to the back-calculation of cocaine use (uncertainty; RSD: 26%). Uncertainty can be kept below 10% in the remaining steps, if specific requirements outlined in this work are considered. For each step, a best practice protocol has been suggested and discussed to reduce and keep to a minimum the uncertainty of the entire procedure and to improve the reliability of the estimates of drug use.
Clouzot, L., Choubert, J. M., Cloutier, F., Goel, R., Love, N. G., Melcer, H., … Vanrolleghem, P. A. (2013). Perspectives on modelling micropollutants in wastewater treatment plants. Water Science and Technology, 68(2), 448-461. doi:10.2166/wst.2013.272, Institutional Repository

Models for predicting the fate of micropollutants (MPs) in wastewater treatment plants (WWTPs) have been developed to provide engineers and decision-makers with tools that they can use to improve their understanding of, and evaluate how to optimize, the removal of MPs and determine their impact on the receiving waters. This paper provides an overview of such models, and discusses the impact of regulation, engineering practice and research on model development. A review of the current status of MP models reveals that a single model cannot represent the wide range of MPs that are present in wastewaters today, and that it is important to start considering classes of MPs based on their chemical structure or ecotoxicological effect, rather than the individual molecules. This paper identifies potential future research areas that comprise (i) considering transformation products in MP removal analysis, (ii) addressing advancements in WWTP treatment technologies, (iii) making use of common approaches to data acquisition for model calibration and (iv) integrating ecotoxicological effects of MPs in receiving waters.
Del Giudice, D., Honti, M., Scheidegger, A., Albert, C., Reichert, P., & Rieckermann, J. (2013). Improving uncertainty estimation in urban hydrological modeling by statistically describing bias. Hydrology and Earth System Sciences, 17(10), 4209-4225. doi:10.5194/hess-17-4209-2013, Institutional Repository

Hydrodynamic models are useful tools for urban water management. Unfortunately, it is still challenging to obtain accurate results and plausible uncertainty estimates when using these models. In particular, with the currently applied statistical techniques, flow predictions are usually overconfident and biased. In this study, we present a flexible and relatively efficient methodology (i) to obtain more reliable hydrological simulations in terms of coverage of validation data by the uncertainty bands and (ii) to separate prediction uncertainty into its components. Our approach acknowledges that urban drainage predictions are biased. This is mostly due to input errors and structural deficits of the model. We address this issue by describing model bias in a Bayesian framework. The bias becomes an autoregressive term additional to white measurement noise, the only error type accounted for in traditional uncertainty analysis. To allow for bigger discrepancies during wet weather, we make the variance of bias dependent on the input (rainfall) or/and output (runoff) of the system. Specifically, we present a structured approach to select, among five variants, the optimal bias description for a given urban or natural case study. We tested the methodology in a small monitored stormwater system described with a parsimonious model. Our results clearly show that flow simulations are much more reliable when bias is accounted for than when it is neglected. Furthermore, our probabilistic predictions can discriminate between three uncertainty contributions: parametric uncertainty, bias, and measurement errors. In our case study, the best performing bias description is the output-dependent bias using a log-sinh transformation of data and model results. The limitations of the framework presented are some ambiguity due to the subjective choice of priors for bias parameters and its inability to address the causes of model discrepancies. Further research should focus on quantifying and reducing the causes of bias by improving the model structure and propagating input uncertainty.
Dürrenmatt, D. J., Del Giudice, D., & Rieckermann, J. (2013). Dynamic time warping improves sewer flow monitoring. Water Research, 47(11), 3803-3816. doi:10.1016/j.watres.2013.03.051, Institutional Repository

Successful management and control of wastewater and storm water systems requires accurate sewer flow measurements. Unfortunately, the harsh sewer environment and insufficient flow meter calibration often lead to inaccurate and biased data. In this paper, we improve sewer flow monitoring by creating redundant information on sewer velocity from natural wastewater tracers. Continuous water quality measurements upstream and downstream of a sewer section are used to estimate the travel time based on i) cross-correlation (XCORR) and ii) dynamic time warping (DTW). DTW is a modern data mining technique that warps two measured time series non-linearly in the time domain so that the dissimilarity between the two is minimized. It has not been applied in this context before. From numerical experiments we can show that DTW outperforms XCORR, because it provides more accurate velocity estimates, with an error of about 7% under typical conditions, at a higher temporal resolution. In addition, we can show that pre-processing of the data is important and that tracer reaction in the sewer reach is critical. As dispersion is generally small, the distance between the sensors is less influential if it is known precisely. Considering these findings, we tested the methods on a real-world sewer to check the performance of two different sewer flow meters based on temperature measurements. Here, we were able to detect that one of two flow meters was not performing satisfactorily under a variety of flow conditions. Although theoretical analyses show that XCORR and DTW velocity estimates contain systematic errors due to dispersion and reaction processes, these are usually small and do not limit the applicability of the approach.
Egger, C., Scheidegger, A., Reichert, P., & Maurer, M. (2013). Sewer deterioration modeling with condition data lacking historical records. Water Research, 47(17), 6762-6779. doi:10.1016/j.watres.2013.09.010, Institutional Repository

Accurate predictions of future conditions of sewer systems are needed for efficient rehabilitation planning. For this purpose, a range of sewer deterioration models has been proposed which can be improved by calibration with observed sewer condition data. However, if datasets lack historical records, calibration requires a combination of deterioration and sewer rehabilitation models, as the current state of the sewer network reflects the combined effect of both processes. Otherwise, physical sewer lifespans are overestimated as pipes in poor condition that were rehabilitated are no longer represented in the dataset. We therefore propose the combination of a sewer deterioration model with a simple rehabilitation model which can be calibrated with datasets lacking historical information. We use Bayesian inference for parameter estimation due to the limited information content of the data and limited identifiability of the model parameters. A sensitivity analysis gives an insight into the model's robustness against the uncertainty of the prior. The analysis reveals that the model results are principally sensitive to the means of the priors of specific model parameters, which should therefore be elicited with care. The importance sampling technique applied for the sensitivity analysis permitted efficient implementation for regional sensitivity analysis with reasonable computational outlay. Application of the combined model with both simulated and real data shows that it effectively compensates for the bias induced by a lack of historical data. Thus, the novel approach makes it possible to calibrate sewer pipe deterioration models even when historical condition records are lacking. Since at least some prior knowledge of the model parameters is available, the strength of Bayesian inference is particularly evident in the case of small datasets.
Fencl, M., Rieckermann, J., Schleiss, M., Stránský, D., & Bareš, V. (2013). Assessing the potential of using telecommunication microwave links in urban drainage modelling. Water Science and Technology, 68(8), 1810-1818. doi:10.2166/wst.2013.429, Institutional Repository

The ability to predict the runoff response of an urban catchment to rainfall is crucial for managing drainage systems effectively and controlling discharges from urban areas. In this paper we assess the potential of commercial microwave links (MWL) to capture the spatio-temporal rainfall dynamics and thus improve urban rainfall-runoff modelling. Specifically, we perform numerical experiments with virtual rainfall fields and compare the results of MWL rainfall reconstructions to those of rain gauge (RG) observations. In a case study, we are able to show that MWL networks in urban areas are sufficiently dense to provide good information on spatio-temporal rainfall variability and can thus considerably improve pipe flow prediction, even in small subcatchments. In addition, the better spatial coverage also improves the control of discharges from urban areas. This is especially beneficial for heavy rainfall, which usually has a high spatial variability that cannot be accurately captured by RG point measurements.
Kaegi, R., Voegelin, A., Ort, C., Sinnet, B., Thalmann, B., Krismer, J., … Mueller, E. (2013). Fate and transformation of silver nanoparticles in urban wastewater systems. Water Research, 47(12), 3866-3877. doi:10.1016/j.watres.2012.11.060, Institutional Repository

Discharge of silver nanoparticles (Ag-NP) from textiles and cosmetics, todays major application areas for metallic Ag-NP, into wastewater is inevitable. Transformation and removal processes in sewers and wastewater treatment plants (WWTP) will determine the impact of Ag-NP on aquatic and terrestrial environments, via the effluents of the WWTP and via the use of digested sludge as fertilizer. We thus conducted experiments addressing the behavior of Ag-NP in sewers and in WWTP.
We spiked Ag-NP to a 5 km long main trunk sewer and collected 40 wastewater samples after 500 m, 2400 m and 5000 m each according to the expected travel times of the Ag-NP. Excellent mass closure of the Ag derived by multiplying the measured Ag concentrations times the volumetric flow rates indicate an efficient transport of the Ag-NP without substantial losses to the sewer biofilm. Ag-NP reacted with raw wastewater in batch experiments were sulfidized to roughly 15% after 5 h reaction time as revealed by X-ray absorption spectroscopy (XAS). However, acid volatile sulfide (AVS) concentrations were substantially higher in the sewer channel (100 μM) compared to the batch experiments (3 μM; still sufficient to sulfidize spiked 2 μM Ag) possibly resulting in a higher degree of sulfidation in the sewer channel. We further investigated the removal efficiency of 10 nm and 100 nm Ag- and gold (Au)-NP coated with citrate or polyvinylpyrrolidone in activated sludge batch experiments. We obtained very high removal efficiencies (∼99%) irrespective of size and coating for Ag- and Au-NP, the latter confirming that the particle type was of minor importance with respect to the degree of NP removal. We observed a strong size dependence of the sulfidation kinetics. We conclude that Ag-NP discharged to the wastewater stream will become sulfidized to various degrees in the sewer system and are efficiently transported to the WWTP. The sulfidation of the Ag-NP will continue in the WWTP, but primarily depending on the size the Ag-NP, may not be complete. Very high removal efficiencies in the WWTP will divert most of the Ag-NP mass flow to the digester and only a small fraction of the Ag will be released to surface waters.
Kenway, S. J., Scheidegger, R., Larsen, T. A., Lant, P., & Bader, H. P. (2013). Water-related energy in households: a model designed to understand the current state and simulate possible measures. Energy and Buildings, 58, 378-389. doi:10.1016/j.enbuild.2012.08.035, Institutional Repository

Energy use in households, including private transport, accounts for about 30% of primary energy use in industrialised countries. Therefore, households are important key drivers of energy use and related greenhouse gas emissions. In order to understand energy use related to water in households a detailed mathematical flow analysis of materials, energy, CO2 emissions and costs (MMFA) for household water use was set up and tested for a specific family household in Brisbane, Australia. The simulation results for the current state of this household were well within 20% of the monitored data. After calibration, a detailed scenario investigation determined the impact of (i) potential and (ii) realistic reduction values for all relevant (a) behavioural and (b) technical parameters, including a shift from gas to a solar hot-water system. The reduction potentials for water use, greenhouse gas emissions, water-related energy consumption, water costs and water-related energy costs were 4–77%, 14–85%, 15–93%, 1–31% and 13–90% respectively. The study showed that for this household, technical improvements alone, without changing to a solar hot-water system, result in less than a 15% change in terms of energy and greenhouse gas emissions. In contrast, combined behavioural and technical changes have a much higher reduction potential.
Lai, F. Y., Bruno, R., Leung, H. W., Thai, P. K., Ort, C., Carter, S., … Mueller, J. F. (2013). Estimating daily and diurnal variations of illicit drug use in Hong Kong: a pilot study of using wastewater analysis in an Asian metropolitan city. Forensic Science International, 233(1-3), 126-132. doi:10.1016/j.forsciint.2013.09.003, Institutional Repository

The measurement of illicit drug metabolites in raw wastewater is increasingly being adopted as an approach to objectively monitor population-level drug use, and is an effective complement to traditional epidemiological methods. As such, it has been widely applied in western countries. In this study, we utilised this approach to assess drug use patterns over nine days during April 2011 in Hong Kong. Raw wastewater samples were collected from the largest wastewater treatment plant serving a community of approximately 3.5 million people and analysed for excreted drug residues including cocaine, ketamine, methamphetamine, 3,4-methylenedioxymethamphetamine (MDMA) and key metabolites using liquid chromatography coupled with tandem mass spectrometry. The overall drug use pattern determined by wastewater analysis was consistent with that have seen amongst people coming into contact with services in relation to substance use; among our target drugs, ketamine (estimated consumption: 1400–1600 mg/day/1000 people) was the predominant drug followed by methamphetamine (180–200 mg/day/1000 people), cocaine (160–180 mg/day/1000 people) and MDMA (not detected). The levels of these drugs were relatively steady throughout the monitoring period. Analysing samples at higher temporal resolution provided data on diurnal variations of drug residue loads. Elevated ratios of cocaine to benzoylecgonine were identified unexpectedly in three samples during the evening and night, providing evidence for potential dumping events of cocaine. This study provides the first application of wastewater analysis to quantitatively evaluate daily drug use in an Asian metropolitan community. Our data reinforces the benefit of wastewater monitoring to health and law enforcement authorities for strategic planning and evaluation of drug intervention strategies.
Lai, F. Y., Bruno, R., Hall, W., Gartner, C., Ort, C., Kirkbride, P., … Mueller, J. F. (2013). Profiles of illicit drug use during annual key holiday and control periods in Australia: wastewater analysis in an urban, a semi-rural and a vacation area. Addiction, 108(3), 556-565. doi:10.1111/add.12006, Institutional Repository

Aims: To examine changes in illicit drug consumption between peak holiday season (23 December-3 January) in Australia and a control period two months later in a coastal urban area, an inland semi-rural area and an island populated predominantly by vacationers during holidays. Design: Analysis of representative daily composite wastewater samples collected from the inlet of the major wastewater treatment plant in each area. Setting: Three wastewater treatment plants. Participants: Wastewater treatment plants serviced approximately 350 000 persons in the urban area, 120 000 in the semi-rural area and 1100-2400 on the island. Measurements: Drug residues were analysed using liquid chromatography coupled to a tandem mass spectrometer. Per capita drug consumption was estimated. Changes in drug use were quantified using Hedges' g. Findings: During the holidays, cannabis consumption in the semi-rural area declined (g=-2.8) as did methamphetamine (-0.8), whereas cocaine (+1.5) and ecstasy (+1.6) use increased. In the urban area, consumption of all drugs increased during holidays (cannabis +1.6, cocaine +1.2, ecstasy +0.8 and methamphetamine +0.3). In the vacation area, methamphetamine (+0.7), ecstasy (+0.7) and cocaine (+1.1) use increased, but cannabis (-0.5) use decreased during holiday periods. Conclusions: While the peak holiday season in Australia is perceived as a period of increased drug use, this is not uniform across all drugs and areas. Substantial declines in drug use in the semi-rural area contrasted with substantial increases in urban and vacation areas. Per capita drug consumption in the vacation area was equivalent to that in the urban area, implying that these locations merit particular attention for drug use monitoring and harm minimisation measures.
Lai, F. Y., Thai, P. K., O'Brian, J., Gartner, C., Bruno, R., Kele, B., … Mueller, J. F. (2013). Using quantitative wastewater analysis to measure daily usage of conventional and emerging illicit drugs at an annual music festival. Drug and Alcohol Review, 32(6), 594-602. doi:10.1111/dar.12061, Institutional Repository

Introduction and Aims. Wastewater analysis provides a non-intrusive way of measuring drug use within a population. We used this approach to determine daily use of conventional illicit drugs [cannabis, cocaine, methamphetamine and 3,4-methylenedioxymethamphetamine (MDMA)] and emerging illicit psychostimulants (benzylpiperazine, mephedrone and methylone) in two consecutive years (2010 and 2011) at an annual music festival. Design and Methods. Daily composite wastewater samples, representative of the festival, were collected from the on-site wastewater treatment plant and analysed for drug metabolites. Data over 2 years were compared using Wilcoxon matched-pair test. Data from 2010 festival were compared with data collected at the same time from a nearby urban community using equivalent methods. Results. Conventional illicit drugs were detected in all samples whereas emerging illicit psychostimulants were found only on specific days. The estimated per capita consumption of MDMA, cocaine and cannabis was similar between the two festival years. Statistically significant (P < 0.05; Z = −2.0–2.2) decreases were observed in use of methamphetamine and one emerging illicit psychostimulant (benzyl piperazine). Only consumption of MDMA was elevated at the festival compared with the nearby urban community. Discussion and Conclusions. Rates of substance use at this festival remained relatively consistent over two monitoring years. Compared with the urban community, drug use among festival goers was only elevated for MDMA, confirming its popularity in music settings. Our study demonstrated that wastewater analysis can objectively capture changes in substance use at a music setting without raising major ethical issues. It would potentially allow effective assessments of drug prevention strategies in such settings in the future.
Maurer, M., Scheidegger, A., & Herlyn, A. (2013). Quantifying costs and lengths of urban drainage systems with a simple static sewer infrastructure model. Urban Water Journal, 10(4), 268-280. doi:10.1080/1573062X.2012.731072, Institutional Repository

A generic model is introduced that is capable of quantitatively representing the combined sewer infrastructure of a settlement. It consists of a catchment area module, which calculates the length and size distribution of the needed sewer pipes on the basis of rain, housing densities and area size. These results are fed into the sewer construction costs module in order to estimate the combined sewer costs of the entire catchment area.
The model could be successfully fitted to existing Swiss sewer systems, indicating that it can emulate their principal characteristics. It could also identify fundamental differences in sewer designs in cities with historic roots. The results confirm that there are economies of scale for combined sewer systems in Switzerland. The modelling approach proved to be an effective tool for understanding the factors underlying the cost structure for water network infrastructures.
Plósz, B. G., Benedetti, L., Daigger, G. T., Langford, K. H., Larsen, H. F., Monteith, H., … Vanrolleghem, P. A. (2013). Modelling micro-pollutant fate in wastewater collection and treatment systems: status and challenges. Water Science and Technology, 67(1), 1-15. doi:10.2166/wst.2012.562, Institutional Repository

This paper provides a comprehensive summary on modelling of micro-pollutants' (MPs) fate and transport in wastewater. It indicates the motivations of MP modelling and summarises and illustrates the current status. Finally, some recommendations are provided to improve and diffuse the use of such models. In brief, we conclude that, in order to predict the contaminant removal in centralised treatment works, considering the dramatic improvement in monitoring and detecting MPs in wastewater, more mechanistic approaches should be used to complement conventional, heuristic and other fate models. This is crucial, as regional risk assessments and model-based evaluations of pollution discharge from urban areas can potentially be used by decision makers to evaluate effluent quality regulation, and assess upgrading requirements, in the future.
Scheidegger, A., Scholten, L., Maurer, M., & Reichert, P. (2013). Extension of pipe failure models to consider the absence of data from replaced pipes. Water Research, 47(11), 3696-3705. doi:10.1016/j.watres.2013.04.017, Institutional Repository

Predictions of the expected number of failures of water distribution network pipes are important to develop an optimal management strategy. A number of probabilistic pipe failure models have been proposed in the literature for this purpose. They have to be calibrated on failure records. However, common data management practices mean that replaced pipes are often absent from available data sets. This leads to a 'survival selection bias', as pipes with frequent failures are more likely to be absent from the data.
To address this problem, we propose a formal statistical approach to extend the likelihood function of a pipe failure model by a replacement model. Frequentist maximum likelihood estimation or Bayesian inference can then be applied for parameter estimation. This approach is general and is not limited to a particular failure or replacement model.
We implemented this approach with a Weibull-exponential failure model and a simple constant probability replacement model. Based on this distribution assumptions, we illustrated our concept with two examples. First, we used simulated data to show how replacement causes a 'survival selection bias' and how to successfully correct for it. A second example with real data illustrates how a model can be extended to consider covariables.
Schleiss, M., Rieckermann, J., & Berne, A. (2013). Quantification and modeling of wet-antenna attenuation for commercial microwave links. IEEE Geoscience and Remote Sensing Letters, 10(5), 1195-1199. doi:10.1109/LGRS.2012.2236074, Institutional Repository

Data from a new experimental setup deployed in Dübendorf (Switzerland) are used to quantify and model the magnitude and dynamics of the wet-antenna attenuation (WAA) affecting a 1.85-km commercial microwave link at 38 GHz. The results show that the WAA exhibits the following properties: 1) It is bounded by a maximum value of about 2.3 dB; 2) it increases exponentially toward 2.3 dB during the first 5-20 min of rainfall; and 3) it decreases exponentially as soon as the rain stops. A new dynamic WAA model that reproduces these three features and can be calibrated using solely link measurements is proposed. Its performance is evaluated at different temporal resolutions and compared with other wet-antenna models from the literature. The results show that the dynamic model outperforms all other models and significantly reduces the uncertainty of the retrieved path-averaged rain rates.
Scholten, L., Scheidegger, A., Reichert, P., & Maurer, M. (2013). Combining expert knowledge and local data for improved service life modeling of water supply networks. Environmental Modelling and Software, 42, 1-16. doi:10.1016/j.envsoft.2012.11.013, Institutional Repository

The presented approach aims to overcome the scarce data problem in service life modeling of water networks by combining subjective expert knowledge and local replacement data. A procedure to elicit imprecise quantile estimates of survival functions from experts, considering common cognitive biases, was developed and applied. The individual expert priors of the parameters of the service life distribution are obtained by regression over the stated distribution quantiles and aggregated into a single prior distribution. Furthermore, a likelihood function for the commonly encountered censored and truncated pipe replacement data is formulated. The suitability of the suggested Bayesian approach based on elicitation data from eight experts and real network data is demonstrated. Robust parameter estimates could be derived in data situations where frequentist maximum likelihood estimation is unsatisfactory, and to show how the consideration of imprecision and in-between-variance of experts improves posterior inference.
Sikorska, A. E., Scheidegger, A., Banasik, K., & Rieckermann, J. (2013). Considering rating curve uncertainty in water level predictions. Hydrology and Earth System Sciences, 17(11), 4415-4427. doi:10.5194/hess-17-4415-2013, Institutional Repository

Streamflow cannot be measured directly and is typically derived with a rating curve model. Unfortunately, this causes uncertainties in the streamflow data and also influences the calibration of rainfall-runoff models if they are conditioned on such data. However, it is currently unknown to what extent these uncertainties propagate to rainfall-runoff predictions. This study therefore presents a quantitative approach to rigorously consider the impact of the rating curve on the prediction uncertainty of water levels. The uncertainty analysis is performed within a formal Bayesian framework and the contributions of rating curve versus rainfall-runoff model parameters to the total predictive uncertainty are addressed. A major benefit of the approach is its independence from the applied rainfall-runoff model and rating curve. In addition, it only requires already existing hydrometric data. The approach was successfully demonstrated on a small catchment in Poland, where a dedicated monitoring campaign was performed in 2011. The results of our case study indicate that the uncertainty in calibration data derived by the rating curve method may be of the same relevance as rainfall-runoff model parameters themselves. A conceptual limitation of the approach presented is that it is limited to water level predictions. Nevertheless, regarding flood level predictions, the Bayesian framework seems very promising because it (i) enables the modeler to incorporate informal knowledge from easily accessible information and (ii) better assesses the individual error contributions. Especially the latter is important to improve the predictive capability of hydrological models.
Blumensaat, F., Staufer, P., Heusch, S., Reußner, F., Schütze, M., Seiffert, S., … Rieckermann, J. (2012). Water quality-based assessment of urban drainage impacts in Europe - where do we stand today?. Water Science and Technology, 66(2), 304-313. doi:10.2166/wst.2012.178, Institutional Repository

Traditionally, design and optimisation of urban drainage systems was mainly driven by cost efficiency, surface flood prevention, and later by emission reduction. More recent procedures explicitly include ecological conditions of the receiving water in the definition of acceptable pollutant discharges via sewer system and treatment plant outlets. An ambient Water Quality based impact Assessment (WQA) principle therefore requires an integrative system optimisation. However, a broad range of mostly national WQA protocols exist across Europe varying in structure and complexity, assessment concept, spatial and temporal scope and handling of uncertainty. This variety inherently implies a considerable risk of subjectivity in the impact assessment with highly variable outcomes. The present review identifies differences and similarities of WQA protocols in use and discusses their strengths and weaknesses through: (i) a systematic comparison of WQA protocols by selected attributes, (ii) a review of real-life cases reported in the literature and expert interviews, and (iii) an illustration of our main findings by applying selected WQA in an instructive example. The review discusses differences in structure and concept, which are mainly identified for simplistic WQA protocols. The application of selected protocols to an example case shows a wide variety of numerical results and conclusive decisions. It is found that existing protocols target different questions within the decision making process, which users should be more aware of. Generally, to make assessments more reliable, further fundamental research is required to fully understand the relationship between stressors and stream ecosystem responses which will make assessments more reliable. Technically, tools suggested in WQA protocols show severe deficiencies and an uncertainty assessment should be mandatory.
Brewer, A. J., Ort, C., Banta-Green, C. J., Berset, J. D., & Field, J. A. (2012). Normalized diurnal and between-day trends in illicit and legal drug loads that account for changes in population. Environmental Science and Technology, 46(15), 8305-8314. doi:10.1021/es202447r, Institutional Repository

Drug concentrations in composite municipal wastewater samples and census-based estimates of population are used to derive daily loads of illicit substances that are indexed to population. However, such estimates do not provide information on the diurnal trends of substance excretion nor can they account for changes in population. To address these limitations, a series of 1 h composites created by sampling wastewater influent at 6 min intervals was collected over four consecutive days at a single wastewater treatment plant. Creatinine (a urinary indicator), caffeine, methamphetamine, benzoylecgonine (BZE), and cocaine were analyzed by liquid chromatography/tandem mass spectrometry (LC-MS/MS). Diurnal trends and between-day trends were substance specific and related to the number of estimated doses and excretory half-life. Normalization to creatinine yielded trends in substances that differed significantly from non-normalized trends by accounting for changes in population within the municipality studied. Increases in normalized substance excretion observed during early morning hours originate from individuals among the resident population of the municipality due to the absence of commuters.
Burkhardt, M., Zuleeg, S., Vonbank, R., Bester, K., Carmeliet, J., Boller, M., & Wangler, T. (2012). Leaching of biocides from Façades under natural weather conditions. Environmental Science and Technology, 46(10), 5497-5503. doi:10.1021/es2040009, Institutional Repository

Biocides are included in organic building façade coatings as protection against biological attack by algae and fungi but have the potential to enter the environment via leaching into runoff from wind driven rain. The following field study correlates wind driven rain to runoff and measured the release of several commonly used organic biocides (terbutryn, Irgarol 1051, diuron, isoproturon, OIT, DCOIT) in organic façade coatings from four coating systems. During one year of exposure of a west oriented model house façade in the Zurich, Switzerland area, an average of 62.7 L/m2, or 6.3% of annual precipitation came off the four façade panels installed as runoff. The ISO method for calculating wind driven rain loads is adapted to predict runoff and can be used in the calculation of emissions in the field. Biocide concentrations tend to be higher in the early lifetime of the coatings and then reach fairly consistent levels later, generally ranging on the order of mg/L or hundreds of μg/L. On the basis of the amount remaining in the film after exposure, the occurrence of transformation products, and the calculated amounts in the leachate, degradation plays a significant role in the overall mass balance.
Derlon, N., Peter-Varbanets, M., Scheidegger, A., Pronk, W., & Morgenroth, E. (2012). Predation influences the structure of biofilm developed on ultrafiltration membranes. Water Research, 46(10), 3323-3333. doi:10.1016/j.watres.2012.03.031, Institutional Repository

This study investigates the impact of predation by eukaryotes on the development of specific biofilm structures in gravity-driven dead-end ultrafiltration systems. Filtration systems were operated under ultra-low pressure conditions (65 mbar) without the control of biofilm formation. Three different levels of predation were evaluated: (1) inhibition of eukaryotic organisms, (2) addition of cultured protozoa (Tetrahymena pyriformis), and (3) no modification of microbial community as a control. The system performance was evaluated based on permeate flux and structures of the biofilm. It was found that predation had a significant influence on both the total amount and also the structure of the biofilm. An open and heterogeneous structure developed in systems with predation whereas a flat, compact, and thick structure that homogeneously covered the membrane surface developed in absence of predation. Permeate flux was correlated with the structure of the biofilm with increased fluxes for smaller membrane coverage. Permeate fluxes in the presence or absence of the predators was 10 and 5 L m−2 h−1, respectively. It was concluded that eukaryotic predation is a key factor influencing the performance of gravity-driven ultrafiltration systems.
Hall, W., Prichard, J., Kirkbride, P., Bruno, R., Thai, P. K., Gartner, C., … Mueller, J. F. (2012). An analysis of ethical issues in using wastewater analysis to monitor illicit drug use. Addiction, 107(10), 1767-1773. doi:10.1111/j.1360-0443.2012.03887.x, Institutional Repository

Aims: To discuss ethical issues that may arise in using WWA to monitor illicit drug use in the general population and in entertainment precincts, prisons, schools and work-places. Method: Review current applications of WWA and identify ethical and social issues that may be raised with current and projected future uses of this method. Results: Wastewater analysis (WWA) of drug residues is a promising method of monitoring illicit drug use that may overcome some limitations of other monitoring methods. When used for monitoring purposes in large populations, WWA does not raise major ethical concerns because individuals are not identified and the prospects of harming residents of catchment areas are remote. When WWA is used in smaller catchment areas (entertainment venues, prisons, schools or work-places) their results could, possibly, indirectly affect the occupants adversely. Researchers will need to take care in reporting their results to reduce media misreporting. Fears about possible use of WWA for mass individual surveillance by drug law enforcement officials are unlikely to be realized, but will need to be addressed because they may affect public support adversely for this type of research. Conclusions: Using wastewater analysis to monitor illicit drug use in large populations does not raise major ethical concerns, but researchers need to minimize possible adverse consequences in studying smaller populations, such as workers, prisoners and students.
Hering, J. G., Hoehn, E., Klinke, A., Maurer, M., Peter, A., Reichert, P., … Wehrli, B. (2012). Moving targets, long-lived infrastructure, and increasing needs for integration and adaptation in water management: an illustration from Switzerland. Environmental Science and Technology, 46(1), 112-118. doi:10.1021/es202189s, Institutional Repository
Hug, T., & Maurer, M. (2012). Stochastic modeling to identify requirements for centralized monitoring of distributed wastewater treatment. Water Science and Technology, 65(6), 1067-1075. doi:10.2166/wst.2012.945, Institutional Repository

Distributed wastewater treatment is increasingly considered as an alternative to the predominantly transport based combination of sewer network and centralized wastewater treatment plant. If substantial amount of wastewater of a particular area is processed in small distributed treatment units, the sum of these units must be considered as one system providing an overall service. This paper focuses on the monitoring for centralized operation of such distributed units. We present a simple stochastic model to calculate probability distributions of process performance. We thereby simulated a fleet of simple treatment units with stochastic failure rates, unreliable sensors and regular routine inspections. All calculated performance indicators exhibit a considerable difference between the true performance and the perceived that is based on sensor observations. The results also show that there is a trade-off between investing into more reliable technology or into more frequent human interventions to achieve a certain performance. The simulations can quantify both effects and thereby support the identification of requirements for centralized monitoring of distributed treatment units. The model approach is generic and can be extended and applied to various distributed wastewater treatment technologies and contexts.
Le Corre, K. S., Ort, C., Kateley, D., Allen, B., Escher, B. I., & Keller, J. (2012). Consumption-based approach for assessing the contribution of hospitals towards the load of pharmaceutical residues in municipal wastewater. Environment International, 45(1), 99-111. doi:10.1016/j.envint.2012.03.008, Institutional Repository

Hospitals are considered as major sources of pharmaceutical residues discharged to municipal wastewater, but recent experimental studies showed that the contribution of hospitals to the loads of selected, quantifiable pharmaceuticals in sewage treatment plant (STP) influents was limited. However such conclusions are made based on the experimental analysis of pharmaceuticals in hospital wastewater which is hindered by a number of factors such as access to suitable sampling sites, difficulties in obtaining representative samples and availability of analytical methods. Therefore, this study explores a refined and extended consumption-based approach to predict the contribution of six selected Australian hospitals to the loads of 589 pharmaceuticals in municipal wastewater. In addition, the possibility that hospital-specific substances are present at levels that may pose a risk for human health was evaluated. For 63 to 84% of the pharmaceuticals investigated, the selected hospitals are not a major point source with individual contributions likely to be less than 15% which is in line with previous experimental studies. In contrast, between 10 and 20% of the pharmaceuticals consumed in the selected hospitals are exclusively used in these hospitals. For these hospital-specific substances, 57 distinct pharmaceuticals may cause concerns for human health as concentrations predicted in hospital effluents are less than 100-fold lower than effect thresholds. However, when concentrations were predicted in the influent of the corresponding STP, only 12 compounds (including the antineoplastic vincristine, the antibiotics tazobactam and piperacillin) remain in concentration close to effect thresholds, but further decrease is expected after removal in STP, dilution in the receiving stream and drinking water treatment. The results of this study suggest that risks of human exposure to the pharmaceuticals exclusively administered in the investigated hospitals are limited and decentralised wastewater treatment at these sites would not have a substantial impact on pharmaceutical loads entering STPs, and finally the environment. Overall, our approach demonstrates a unique opportunity to screen for pharmaceuticals used in hospitals and identifying priority pollutants in hospital wastewater explicitly accounting for site-specific conditions. Being based on consumption and loads discharged by hospitals into municipal wastewater, it is not limited by 1) the big effort to obtain representative samples from sewers, 2) the availability of sensitive chemical analysis or 3) a pre-selection of consumption data (e.g. consumption volume).
Maurer, M., Bufardi, A., Tilley, E., Zurbrügg, C., & Truffer, B. (2012). A compatibility-based procedure designed to generate potential sanitation system alternatives. Journal of Environmental Management, 104(Aug), 51-61. doi:10.1016/j.jenvman.2012.03.023, Institutional Repository

Regarding multi-criteria decision analysis (MCDA), the problem of generating alternatives has not received the attention it deserves. Most research is currently devoted to the problem of alternative selection, where it is assumed that a set of appropriate alternatives is already given. This paper addresses the generation of potential alternatives in the domain of sanitation systems planning and decision-making. A compatibility assessment procedure is proposed to determine the set of technically feasible or potential sanitation system alternatives. This is based on a clear definition of such an alternative containing sub-processes that include a user interface, storage, conveyance treatment and reuse/disposal. A newly developed compatibility matrix is applied to identify incompatibilities between the options of the sub-processes.
A potential sanitation system alternative is therefore defined by the absence of two-by-two incompatibility between all its options.
The compatibility assessment acts as a first filter on the set of sanitation system alternatives to eliminate those that are inoperable before the feasibility assessment. The objective of both steps is to obtain a set of alternatives that are of reasonable and manageable size from which the final solution may be selected.
Prichard, J., Lai, F. Y., Kirkbride, P., Bruno, R., Ort, C., Carter, S., … Mueller, J. F. (2012). Measuring drug use patterns in Queensland through wastewater analysis. Trends & Issues in Crime and Criminal Justice, 442, 1-8. Retrieved from https://www.aic.gov.au/publications/tandi/tandi442, Institutional Repository

Illicit drug use results in considerable social and economic costs to Australia (Collins & Lapsley 2008) but the magnitude of use is inherently difficult to measure. Besides being a clandestine behaviour, drug use in the community is not static and can peak at certain events (such as music festivals; Hesse, Tutenges & Schliewe 2010) or celebratory times of the year (such as New Year Eve; van Nuijs et al. 2011). Drug trends are triangulated across monitoring systems that employ different research methods and a mix of strengths with respect to, among other things, timeliness, reliability, drug-specificity and sample size (see Griffith & Mounteney 2010).
Scheidegger, A., & Maurer, M. (2012). Identifying biases in deterioration models using synthetic sewer data. Water Science and Technology, 66(11), 2363-2369. doi:10.2166/wst.2012.471, Institutional Repository

The assessment and validation of sewer deterioration models is difficult because reliable data are missing. This makes it hard to find the most suitable model for a particular application. A network condition simulator (NetCoS) is used to generate synthetic sewer data for defined test scenarios. Thereby, the deterioration and replacement of pipes, the expansion of the sewer network, and classification errors are considered. Based on such synthetic data, deterioration models are calibrated and their results compared with the predefined scenario. While this approach is not capable of proving that a model performs correctly on a real application, it highlights the strengths and weaknesses of a model. The influence of condition classification errors and the age of the sewer system is investigated for two deterioration models. The results show, that classification errors can introduce substantial biases in the parameter estimation of the Markov model while in comparison the applied cohort model is fairly robust. Young sewer systems with fewer pipes in bad condition states on the other hand, have a very strong influence on the parameter uncertainties of the cohort model while the Markov model proved to be less sensitive.
Sikorska, A. E., Scheidegger, A., Banasik, K., & Rieckermann, J. (2012). Bayesian uncertainty assessment of flood predictions in ungauged urban basins for conceptual rainfall-runoff models. Hydrology and Earth System Sciences, 16(4), 1221-1236. doi:10.5194/hess-16-1221-2012, Institutional Repository

Urbanization and the resulting land-use change strongly affect the water cycle and runoff-processes in watersheds. Unfortunately, small urban watersheds, which are most affected by urban sprawl, are mostly ungauged. This makes it intrinsically difficult to assess the consequences of urbanization. Most of all, it is unclear how to reliably assess the predictive uncertainty given the structural deficits of the applied models. In this study, we therefore investigate the uncertainty of flood predictions in ungauged urban basins from structurally uncertain rainfall-runoff models. To this end, we suggest a procedure to explicitly account for input uncertainty and model structure deficits using Bayesian statistics with a continuous-time autoregressive error model. In addition, we propose a concise procedure to derive prior parameter distributions from base data and successfully apply the methodology to an urban catchment in Warsaw, Poland. Based on our results, we are able to demonstrate that the autoregressive error model greatly helps to meet the statistical assumptions and to compute reliable prediction intervals. In our study, we found that predicted peak flows were up to 7 times higher than observations. This was reduced to 5 times with Bayesian updating, using only few discharge measurements. In addition, our analysis suggests that imprecise rainfall information and model structure deficits contribute mostly to the total prediction uncertainty. In the future, flood predictions in ungauged basins will become more important due to ongoing urbanization as well as anthropogenic and climatic changes. Thus, providing reliable measures of uncertainty is crucial to support decision making.
Staufer, P., Scheidegger, A., & Rieckermann, J. (2012). Assessing the performance of sewer rehabilitation on the reduction of infiltration and inflow. Water Research, 46(16), 5185-5196. doi:10.1016/j.watres.2012.07.001, Institutional Repository

Inflow and Infiltration (I/I) into sewer systems is generally unwanted, because, among other things, it decreases the performance of wastewater treatment plants and increases combined sewage overflows. As sewer rehabilitation to reduce I/I is very expensive, water managers not only need methods to accurately measure I/I, but also they need sound approaches to assess the actual performance of implemented rehabilitation measures. However, such performance assessment is rarely performed. On the one hand, it is challenging to adequately take into account the variability of influential factors, such as hydro-meteorological conditions. On the other hand, it is currently not clear how experimental data can indeed support robust evidence for reduced I/I. In this paper, we therefore statistically assess the performance of rehabilitation measures to reduce I/I. This is possible by using observations in a suitable reference catchment as a control group and assessing the significance of the observed effect by regression analysis, which is well established in other disciplines. We successfully demonstrate the usefulness of the approach in a case study, where rehabilitation reduced groundwater infiltration by 23.9%. A reduction of stormwater inflow of 35.7%, however, was not statistically significant. Investigations into the experimental design of monitoring campaigns confirmed that the variability of the data as well as the number of observations collected before the rehabilitation impact the detection limit of the effect. This implies that it is difficult to improve the data quality after the rehabilitation has been implemented. Therefore, future practical applications should consider a careful experimental design. Further developments could employ more sophisticated monitoring methods, such as stable environmental isotopes, to directly observe the individual infiltration components. In addition, water managers should develop strategies to effectively communicate statistically not significant I/I reduction ratios to decision makers.
Staufer, P., Siekmann, M., Loos, S., & Pinnekamp, J. (2012). Numerical modeling of water levels on pavements under extreme rainfall. Journal of Transportation Engineering, 138(6), 732-740. doi:10.1061/(ASCE)TE.1943-5436.0000373, Institutional Repository

This study presents an advanced model for calculating water levels on impervious areas. The approach combines information about rain intensity and flow condition to dynamically determine overland roughness values. When water levels on profiled surfaces of less than 500 m are calculated, the full dynamic wave approximation is necessary because the transition of flow differs compared to kinetic wave theory at the beginning of the runoff event. The application of the model to a civil airport demonstrates how the frequency of critical water levels changes when the cutting of grooves into the runways is considered. The local storm water characteristics are defined by heavy convective precipitation during summer. A critical event was presumed when the water level may cause aquaplaning. The results present a reduction of the number of critical events during a period of 10 years by 68%, even without recognizing the additional friction by the grooves. If increasing friction was included, the remaining frequency would be 0.2 times per year.
Thomas, K. V., Bijlsma, L., Castiglioni, S., Covaci, A., Emke, E., Grabic, R., … de Voogt, P. (2012). Comparing illicit drug use in 19 European cities through sewage analysis. Science of the Total Environment, 432, 432-439. doi:10.1016/j.scitotenv.2012.06.069, Institutional Repository

The analysis of sewage for urinary biomarkers of illicit drugs is a promising and complementary approach for estimating the use of these substances in the general population. For the first time, this approach was simultaneously applied in 19 European cities, making it possible to directly compare illicit drug loads in Europe over a 1-week period. An inter-laboratory comparison study was performed to evaluate the analytical performance of the participating laboratories. Raw 24-hour composite sewage samples were collected from 19 European cities during a single week in March 2011 and analyzed for the urinary biomarkers of cocaine, amphetamine, ecstasy, methamphetamine and cannabis using in-house optimized and validated analytical methods. The load of each substance used in each city was back-calculated from the measured concentrations. The data show distinct temporal and spatial patterns in drug use across Europe. Cocaine use was higher in Western and Central Europe and lower in Northern and Eastern Europe. The extrapolated total daily use of cocaine in Europe during the study period was equivalent to 356. kg/day. High per capita ecstasy loads were observed in Dutch cities, as well as in Antwerp and London. In general, cocaine and ecstasy loads were significantly elevated during the weekend compared to weekdays. Per-capita loads of methamphetamine were highest in Helsinki and Turku, Oslo and Budweis, while the per capita loads of cannabis were similar throughout Europe. This study shows that a standardized analysis for illicit drug urinary biomarkers in sewage can be applied to estimate and compare the use of these substances at local and international scales. This approach has the potential to deliver important information on drug markets (supply indicator).
Wang, Z., Schleiss, M., Jaffrain, J., Berne, A., & Rieckermann, J. (2012). Using Markov switching models to infer dry and rainy periods from telecommunication microwave link signals. Atmospheric Measurement Techniques, 5(7), 1847-1859. doi:10.5194/amt-5-1847-2012, Institutional Repository

A Markov switching algorithm is introduced to classify attenuation measurements from telecommunication microwave links into dry and rainy periods. It is based on a simple state-space model and has the advantage of not relying on empirically estimated threshold parameters. The algorithm is applied to data collected using a new and original experimental set-up in the vicinity of Zürich, Switzerland. The false dry and false rain detection rates of the algorithm are evaluated and compared to 3 other algorithms from the literature. The results show that, on average, the Markov switching model outperforms the other algorithms. It is also shown that the classification performance can be further improved if redundant information from multiple channels is used.
Wangler, T. P., Zuleeg, S., Vonbank, R., Bester, K., Boller, M., Carmeliet, J., & Burkhardt, M. (2012). Laboratory scale studies of biocide leaching from façade coatings. Building and Environment, 54, 168-173. doi:10.1016/j.buildenv.2012.02.021, Institutional Repository

Organic architectural coatings require the use of biocides to prevent microbial defacement of building façades. The biocides are meant to slowly release to the surface, but they can still potentially enter the environment via runoff during rain events. Accurate source emissions estimates are necessary for risk assessments, and knowledge of the release mechanism can aid both regulators and producers alike. In this study, several biocides and several market and reference coating systems were subjected to regular irrigation and drying cycles with varying temperature conditions. The results were compared to other studies and models from the controlled release literature, demonstrating diffusion controlled release with dependence on the experimental conditions. The role of wetting and drying cycles in accelerating release is highlighted.
Burkhardt, M., Zuleeg, S., Vonbank, R., Schmid, P., Hean, S., Lamani, X., … Boller, M. (2011). Leaching of additives from construction materials to urban storm water runoff. Water Science and Technology, 63(9), 1974-1982. doi:10.2166/wst.2011.128, Institutional Repository

Urban water management requires further clarification about pollutants in storm water. Little is known about the release of organic additives used in construction materials and the impact of these compounds to storm water runoff. We investigated sources and pathways of additives used in construction materials, i.e., biocides in facades' render as well as root protection products in bitumen membranes for rooftops. Under wet-weather conditions, the concentrations of diuron, terbutryn, carbendazim, irgarol®1051 (all from facades) and mecoprop in storm water and receiving water exceeded the predicted no-effect concentrations values and the Swiss water quality standard of 0.1 mg/L. Under laboratory conditions maximum concentrations of additives were in the range of a few milligrams and a few hundred micrograms per litre in runoff of facades and bitumen membranes. Runoff from aged materials shows approximately one to two orders of magnitude lower concentrations. Concentrations decreased also during individual runoff events. In storm water and receiving water the occurrence of additives did not follow the typical first flush model. This can be explained by the release lasting over the time of rainfall and the complexity of the drainage network. Beside the amounts used, the impact of construction materials containing hazardous additives on water quality is related clearly to the age of the buildings and the separated sewer network. The development of improved products regarding release of hazardous additives is the most efficient way of reducing the pollutant load from construction materials in storm water runoff.
Escher, B. I., Baumgartner, R., Koller, M., Treyer, K., Lienert, J., & McArdell, C. S. (2011). Environmental toxicology and risk assessment of pharmaceuticals from hospital wastewater. Water Research, 45(1), 75-92. doi:10.1016/j.watres.2010.08.019, Institutional Repository

In this paper, we evaluated the ecotoxicological potential of the 100 pharmaceuticals expected to occur in highest quantities in the wastewater of a general hospital and a psychiatric center in Switzerland. We related the toxicity data to predicted concentrations in different wastewater streams to assess the overall risk potential for different scenarios, including conventional biological pretreatment in the hospital and urine source separation. The concentrations in wastewater were estimated with pharmaceutical usage information provided by the hospitals and literature data on human excretion into feces and urine. Environmental concentrations in the effluents of the exposure scenarios were predicted by estimating dilution in sewers and with literature data on elimination during wastewater treatment. Effect assessment was performed using quantitative structure-activity relationships because experimental ecotoxicity data were only available for less than 20% of the 100 pharmaceuticals with expected highest loads. As many pharmaceuticals are acids or bases, a correction for the speciation was implemented in the toxicity prediction model.
The lists of Top-100 pharmaceuticals were distinctly different between the two hospital types with only 37 pharmaceuticals overlapping in both datasets. 31 Pharmaceuticals in the general hospital and 42 pharmaceuticals in the psychiatric center had a risk quotient above 0.01 and thus contributed to the mixture risk quotient. However, together they constituted only 14% (hospital) and 30% (psychiatry) of the load of pharmaceuticals. Hence, medical consumption data alone are insufficient predictors of environmental risk. The risk quotients were dominated by amiodarone, ritonavir, clotrimazole, and diclofenac. Only diclofenac is well researched in ecotoxicology, while amiodarone, ritonavir, and clotrimazole have no or very limited experimental fate or toxicity data available. The presented computational analysis thus helps setting priorities for further testing.
Separate treatment of hospital wastewater would reduce the pharmaceutical load of wastewater treatment plants, and the risk from the newly identified priority pharmaceuticals. However, because high-risk pharmaceuticals are excreted mainly with feces, urine source separation is not a viable option for reducing the risk potential from hospital wastewater, while a sorption step could be beneficial.
Gottschalk, F., Ort, C., Scholz, R. W., & Nowack, B. (2011). Engineered nanomaterials in rivers - exposure scenarios for Switzerland at high spatial and temporal resolution. Environmental Pollution, 159(12), 3439-3445. doi:10.1016/j.envpol.2011.08.023, Institutional Repository

Probabilistic material flow analysis and graph theory were combined to calculate predicted environmental concentrations (PECs) of engineered nanomaterials (ENMs) in Swiss rivers: 543 river sections were used to assess the geographical variability of nano-TiO2, nano-ZnO and nano-Ag, and flow measurements over a 20-year period at 21 locations served to evaluate temporal variation. A conservative scenario assuming no ENM removal and an optimistic scenario covering complete ENM transformation/deposition were considered. ENM concentrations varied by a factor 5 due to uncertain ENM emissions (15%–85% quantiles of ENM emissions) and up to a factor of 10 due to temporal river flow variations (15%–85% quantiles of flow). The results indicate highly variable local PECs and a location- and time-dependent risk evaluation. Nano-TiO2 median PECs ranged from 11 to 1′623 ng L−1 (conservative scenario) and from 2 to 1′618 ng L−1 (optimistic scenario). The equivalent values for nano-ZnO and nano-Ag were by factors of 14 and 240 smaller.
Kaegi, R., Voegelin, A., Sinnet, B., Zuleeg, S., Hagendorfer, H., Burkhardt, M., & Siegrist, H. (2011). Behavior of metallic silver nanoparticles in a pilot wastewater treatment plant. Environmental Science and Technology, 45(9), 3902-3908. doi:10.1021/es1041892, Institutional Repository

We investigated the behavior of metallic silver nanoparticles (Ag-NP) in a pilot wastewater treatment plant (WWTP) fed with municipal wastewater. The treatment plant consisted of a nonaerated and an aerated tank and a secondary clarifier. The average hydraulic retention time including the secondary clarifier was 1 day and the sludge age was 14 days. Ag-NP were spiked into the nonaerated tank and samples were collected from the aerated tank and from the effluent. Ag concentrations determined by inductively coupled plasma-mass spectrometry (ICP-MS) were in good agreement with predictions based on mass balance considerations. Transmission electron microscopy (TEM) analyses confirmed that nanoscale Ag particles were sorbed to wastewater biosolids, both in the sludge and in the effluent. Freely dispersed nanoscale Ag particles were only observed in the effluent during the initial pulse spike. X-ray absorption spectroscopy (XAS) measurements indicated that most Ag in the sludge and in the effluent was present as Ag2S. Results from batch experiments suggested that Ag-NP transformation to Ag2S occured in the nonaerated tank within less than 2 h. Physical and chemical transformations of Ag-NP in WWTPs control the fate, the transport and also the toxicity and the bioavailability of Ag-NP and therefore must be considered in future risk assessments.
Lai, F. Y., Ort, C., Gartner, C., Carter, S., Prichard, J., Kirkbride, P., … Mueller, J. F. (2011). Refining the estimation of illicit drug consumptions from wastewater analysis: co-analysis of prescription pharmaceuticals and uncertainty assessment. Water Research, 45(15), 4437-4448. doi:10.1016/j.watres.2011.05.042, Institutional Repository

Wastewater analysis is a promising monitoring tool to estimate illicit drug consumption at the community level. The advantage of this technique over traditional surveys and other surveillance methods has been emphasized in recent studies. However, there are methodological challenges that can affect reliability. The objectives of this study were to systematically reduce and assess uncertainties associated with sampling (through a stringent optimization of the sampling method) and the back calculation of per capita drug consumption (through a refined estimation of the number of people actively contributing to the wastewater in a given period). We applied continuous flow-proportional sampling to ensure the collection of representative raw wastewater samples. Residues of illicit drugs, opioids, prescription pharmaceuticals and one artificial sweetener were analyzed by liquid chromatography coupled with tandem mass spectrometry. A parameter estimating the number of people actively contributing to wastewater over a given period was calculated from the measured loads of prescription pharmaceuticals, their annual consumption and relative excretion data. For the calculation of substance loads in sewage, uncertainties were propagated considering five individual components: sampling, chemical analysis, flow measurements, excretion rates and the number of people contributing to the wastewater. The daily consumption per 1000 inhabitants was estimated to be almost 1000 mg for cannabis and several hundred mg for cocaine, methamphetamine and ecstasy. With the best sampling practice and current chemical analysis, we calculated the remaining uncertainty to be in the range of 20–30% (relative standard deviation, RSD) for the estimation of consumed drug masses in the catchment; RSDs for the per capita consumption were lower (14–24%), as one of the biggest uncertainty components (i.e. error in flow measurements) cancels out in the proposed method for the estimation of the number of people contributing to the daily wastewater volume. In this study, we provide methodological improvements that substantially enhance the reliability of the estimation method – a prerequisite for the application of this technique to meaningfully assess changes in drug consumption and the success of drug intervention strategies in future studies.
Mathieu, C., Rieckermann, J., Berset, J. D., Schürch, S., & Brenneisen, R. (2011). Assessment of total uncertainty in cocaine and benzoylecgonine wastewater load measurements. Water Research, 45(20), 6650-6660. doi:10.1016/j.watres.2011.09.049, Institutional Repository

To check the effectiveness of campaigns preventing drug abuse or indicating local effects of efforts against drug trafficking, it is beneficial to know consumed amounts of substances in a high spatial and temporal resolution. The analysis of drugs of abuse in wastewater (WW) has the potential to provide this information. In this study, the reliability of WW drug consumption estimates is assessed and a novel method presented to calculate the total uncertainty in observed WW cocaine (COC) and benzoylecgonine (BE) loads. Specifically, uncertainties resulting from discharge measurements, chemical analysis and the applied sampling scheme were addressed and three approaches presented. These consist of (i) a generic model-based procedure to investigate the influence of the sampling scheme on the uncertainty of observed or expected drug loads, (ii) a comparative analysis of two analytical methods (high performance liquid chromatography–tandem mass spectrometry and gas chromatography–mass spectrometry), including an extended cross-validation by influent profiling over several days, and (iii) monitoring COC and BE concentrations in WW of the largest Swiss sewage treatment plants. In addition, the COC and BE loads observed in the sewage treatment plant of the city of Berne were used to back-calculate the COC consumption. The estimated mean daily consumed amount was 107 ± 21 g of pure COC, corresponding to 321 g of street-grade COC.
Rieckermann, J., Anta, J., Scheidegger, A., & Ort, C. (2011). Assessing wastewater micropollutant loads with Approximate Bayesian Computations. Environmental Science and Technology, 45(10), 4399-4406. doi:10.1021/es1030432, Institutional Repository

Wastewater production, like many other engineered and environmental processes, is inherent stochastic in nature and requires the use of complex stochastic models, for example, to predict realistic patterns of down-the-drain chemicals or pharmaceuticals and personal care products. Up until now, a formal method of statistical inference has been lacking for many of those models, where explicit likelihood functions were intractable. In this Article, we investigate Approximate Bayesian Computation (ABC) methods to infer important parameters of stochastic environmental models. ABC methods have been recently suggested to perform model-based inference in a Bayesian setting when model likelihoods are analytically or computationally intractable and have not been applied to environmental systems analysis or water quality modeling before. In a case study, we investigate the performance of three different algorithms to infer the number of wastewater pulses contained in three high-resolution data series of benzotriazole and total nitrogen loads in sewers. We find that all algorithms perform well and that the uncertainty in the inferred number of corresponding wastewater pulses varies between 6% and 28%. In our case, the results are more sensitive to substance characteristics than to catchment properties. Although the application of ABC methods requires careful tuning and attention to detail, they have a great general potential to update stochastic model parameters with monitoring data and improve their predictive capabilities.
Scheidegger, A., Hug, T., Rieckermann, J., & Maurer, M. (2011). Network condition simulator for benchmarking sewer deterioration models. Water Research, 45(16), 4983-4994. doi:10.1016/j.watres.2011.07.008, Institutional Repository

Anaccurate description of aging and deterioration of urban drainage systemsis necessary for optimal investment and rehabilitation planning. Due to a general lack of suitable datasets, network condition models are rarely validated, and if so with varying levels of success. We therefore propose a novel network condition simulator (NetCoS) that produces a synthetic population of sewer sections with a given condition-class distribution. NetCoS can be used to benchmark deterioration models and guide utilities in the selection of appropriate models and data management strategies. The underlying probabilistic model considers three main processes: a) deterioration, b) replacement policy, and c) expansions of the sewer network. The deterioration model features a semi-Markov chain that uses transition probabilities based on user-defined survival functions. The replacement policy is approximated with a condition-class dependent probability of replacing a sewer pipe. The model then simulates the course of the sewer sections from the installation of the first line to the present, adding new pipes based on the defined replacement and expansion program. We demonstrate the usefulness of NetCoS in two examples where we quantify the influence of incomplete data and inspection frequency on the parameter estimation of a cohort survival model and a Markov deterioration model. Our results show that typical available sewer inventory data with discarded historical data overestimate the average life expectancy by up to 200 years. Although NetCoS cannot prove the validity of a particular deterioration model, it is useful to reveal its possible limitations and shortcomings and quantifies the effects of missing or uncertain data. Future developments should include additional processes, for example to investigate the long-term effect of pipe rehabilitation measures, such as inliners.
Velten, S., Knappe, D. R. U., Traber, J., Kaiser, H. P., von Gunten, U., Boller, M., & Meylan, S. (2011). Characterization of natural organic matter adsorption in granular activated carbon adsorbers. Water Research, 45(13), 3951-3959. doi:10.1016/j.watres.2011.04.047, Institutional Repository

The removal of natural organic matter (NOM) from lake water was studied in two pilot-scale adsorbers containing granular activated carbon (GAC) with different physical properties. To study the adsorption behavior of individual NOM fractions as a function of time and adsorber depth, NOM was fractionated by size exclusion chromatography (SEC) into biopolymers, humics, building blocks, and low molecular weight (LMW) organics, and NOM fractions were quantified by both ultraviolet and organic carbon detectors. High molecular weight biopolymers were not retained in the two adsorbers. In contrast, humic substances, building blocks and LMW organics were initially well and irreversibly removed, and their effluent concentrations increased gradually in the outlet of the adsorbers until a pseudo-steady state concentration was reached. Poor removal of biopolymers was likely a result of their comparatively large size that prevented access to the internal pore structure of the GACs. In both GAC adsorbers, adsorbability of the remaining NOM fractions, compared on the basis of partition coefficients, increased with decreasing molecular size, suggesting that increasingly larger portions of the internal GAC surface area could be accessed as the size of NOM decreased. Overall DOC uptake at pseudo-steady state differed between the two tested GACs (18.9 and 28.6 g-C/kg GAC), and the percent difference in DOC uptake closely matched the percent difference in the volume of pores with widths in the 1–50 nm range that was measured for the two fresh GACs. Despite the differences in NOM uptake capacity, individual NOM fractions were removed in similar proportions by the two GACs.
Velten, S., Boller, M., Köster, O., Helbing, J., Weilenmann, H. U., & Hammes, F. (2011). Development of biomass in a drinking water granular active carbon (GAC) filter. Water Research, 45(19), 6347-6354. doi:10.1016/j.watres.2011.09.017, Institutional Repository

Indigenous bacteria are essential for the performance of drinking water biofilters, yet this biological component remains poorly characterized. In the present study we followed biofilm formation and development in a granular activated carbon (GAC) filter on pilot-scale during the first six months of operation. GAC particles were sampled from four different depths (10, 45, 80 and 115 cm) and attached biomass was measured with adenosine tri-phosphate (ATP) analysis. The attached biomass accumulated rapidly on the GAC particles throughout all levels in the filter during the first 90 days of operation and maintained a steady state afterward. Vertical gradients of biomass density and growth rates were observed during start-up and also in steady state. During steady state, biomass concentrations ranged between 0.8–1.83 x 10−6 g ATP/g GAC in the filter, and 22% of the influent dissolved organic carbon (DOC) was removed. Concomitant biomass production was about 1.8 × 1012 cells/m2h, which represents a yield of 1.26 × 106 cells/μg. The bacteria assimilated only about 3% of the removed carbon as biomass. At one point during the operational period, a natural 5-fold increase in the influent phytoplankton concentration occurred. As a result, influent assimilable organic carbon concentrations increased and suspended bacteria in the filter effluent increased 3-fold as the direct consequence of increased growth in the biofilter. This study shows that the combination of different analytical methods allows detailed quantification of the microbiological activity in drinking water biofilters.
Zimmermann, S. G., Wittenwiler, M., Hollender, J., Krauss, M., Ort, C., Siegrist, H., & von Gunten, U. (2011). Kinetic assessment and modeling of an ozonation step for full-scale municipal wastewater treatment: micropollutant oxidation, by-product formation and disinfection. Water Research, 45(2), 605-617. doi:10.1016/j.watres.2010.07.080, Institutional Repository

The kinetics of oxidation and disinfection processes during ozonation in a full-scale reactor treating secondary wastewater effluent were investigated for seven ozone doses ranging from 0.21 to 1.24 g O3 g−1 dissolved organic carbon (DOC). Substances reacting fast with ozone, such as diclofenac or carbamazepine (kP,O3 > 104 M−1), were eliminated within the gas bubble column, except for the lowest ozone dose of 0.21 g O3 g−1 DOC. For this low dose, this could be attributed to short-circuiting within the reactor. Substances with lower ozone reactivity (kP,O3 < 104 M−1 s−1) were only fully eliminated for higher ozone doses.
The predictions of micropollutant oxidation based on coupling reactor hydraulics with ozone chemistry and reaction kinetics were up to a factor of 2.5 higher than full-scale measurements. Monte Carlo simulations showed that the observed differences were higher than model uncertainties. The overestimation of micropollutant oxidation was attributed to a protection of micropollutants from ozone attack by the interaction with aquatic colloids. Laboratory-scale batch experiments using wastewater from the same full-scale treatment plant could predict the oxidation of slowly-reacting micropollutants on the full-scale level within a factor of 1.5. The Rct value, the experimentally determined ratio of the concentrations of hydroxyl radicals and ozone, was identified as a major contribution to this difference.
An increase in the formation of bromate, a potential human carcinogen, was observed with increasing ozone doses. The final concentration for the highest ozone dose of 1.24 g O3 g−1 DOC was 7.5 μg L−1, which is below the drinking water standard of 10 μg L−1. N-Nitrosodimethylamine (NDMA) formation of up to 15 ng L−1 was observed in the first compartment of the reactor, followed by a slight elimination during sand filtration. Assimilable organic carbon (AOC) increased up to 740 μg AOC L−1, with no clear trend when correlated to the ozone dose, and decreased by up to 50% during post-sand filtration. The disinfection capacity of the ozone reactor was assessed to be 1–4.5 log units in terms of total cell counts (TCC) and 0.5 to 2.5 log units for Escherichia coli (E. coli). Regrowth of up to 2.5 log units during sand filtration was observed for TCC while no regrowth occurred for E. coli. E. coli inactivation could not be accurately predicted by the model approach, most likely due to shielding of E. coli by flocs.
Burkhardt, M., Zuleeg, S., Kägi, R., Sinnet, B., Eugster, J., Boller, M., & Siegrist, H. (2010). Verhalten von Nanosilber in Kläranlagen und dessen Einfluss auf die Nitrifikationsleistung in Belebtschlamm. Fate of nanosilver in wastewater treatment plants and their impact on nitrification activity in sewage sludge. Umweltwissenschaften und Schadstoff-Forschung, 22(5), 529-540. doi:10.1007/s12302-010-0153-2, Institutional Repository

Background, aim and scope The application of nanosilver is increasing. Knowledge on the fate and behavior of nanosilver in wastewater and wastewater treatment plants is scarce. Studies under real world conditions are completely lacking. We studied (1) the impact of nanosilver on the nitrification of sewage sludge, (2) quantified the mass flow of nanosilver in a pilot-plant, and (3) verified the mass balance in a full-scale municipal wastewater treatment plant where nanosilver is introduced to the municipal plant by an indirect discharger.
Materials and Methods The addition of four different nanosilver additives on ammonia oxidation in activated sludge has been studied in batch-reactors at two concentrations (1, 100 mg/L Ag) with two exposure times (2 h, 6 days). The pilot-plant treating 70 population equivalents of domestic wastewater is operated with a 12 day sludge age. Nanosilver was applied to the activated sludge tank within two sludge ages. The silver concentrations were measured in sludge and effluent samples during dosing and the following two sludge ages. The adsorption and speciation of silver particles has been analyzed using scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX). Influent, effluent and sludge were sampled on a full-scale plant (60 000 equivalent inhabitants) and analyzed for silver.
Results Silver nitrate, metallic nanosilver, nano-scaled silver chloride and microcomposite silver did not show any effect on ammonia oxidation after the addition of 1 mg/L Ag to the activated sludge (corresponding to 250 mg Ag per kg solids). In contrast, 100 mg/L Ag inhibited the nitrification process by 100 % after the addition of silver nitrate and 20–30 % after addition of colloidal polymer-coated nanosilver. A complete mass balance of the pilot-plant, a steady-state system with known fluxes, demonstrates significant enrichment of silver in the sewage sludge (96 %) after the addition of silver chloride to the plant and small losses of silver into the secondary effluent (4 %). The mass fluxes are similar to metallic colloidal nanosilver investigated under the same conditions. The mass balance has been consistently confirmed by the full-scale study in a municipal wastewater treatment plant. The silver fluxes correspond to the fluxes of the suspended solids in sludge and effluent. Overall, it is estimated that from public wastewater treatment plants about 4–40 mg/a Ag per inhabitant equivalent are discharged annually to the receiving water. The analysis by SEM-EDX demonstrates adsorption and incorporation of nanosilver on biological flocs. This method yields first insight into complex building and transformation of silver associated with sulfide after adding metallic nanosilver and silver chloride to wastewater.
Discussion Silver ions released from nanosilver react immediately with large amounts of chloride present in wastewater to form silver chloride. Silver ions may react with organic ligands or sulfide groups additionally. Consequently, even silver nitrate added with 1 mg/L Ag (250 mg Ag/kg TS) to activated sludge did not inhibit nitrification activity. Very high amounts of nanosilver, i. e. 100 mg/L Ag, overburdened the system and equilibrium condition between silver ion release and ligands was not reached. The mass balance reflects the excellent attachment of nanosilver to activated sludge and biological flocs. Therefore, the main elimination process of nanosilver is attachment to the activated sludge. The elimination of nanosilver is high compared to organic and inorganic micro pollutants omnipresent in wastewater. Any further reduction of suspended solids in the effluent water will reduce the silver load.
Conclusions Generally, in wastewater nanosilver occurs bonded to activated sludge flocs and therefore the elimination of nanosilver is efficient under operation conditions typical for wastewater treatment plants. The major fraction of nanosilver is removed from the system by the excess sludge withdrawal. Nonetheless, the efficiency may be further improved by a tertiary filtration step. All analyses of influent, effluent and sludge confirmed that silver exists as silver sulfide. Due to a negligible water solubility of this silver species, silver ions are not subsequently released.
Recommendations and perspectives Nanosilver research should be driven to the identification of transformation processes in real environmental matrices and the influence of coatings on the adsorption behavior. There is no need for action to take special measures for nanosilver removal in the area of municipal wastewater treatment plants compared to ubiquitous hazardous organic pollutants may present in wastewater. Nevertheless, source control measures following the precautionary principle should be performed.
Escher, B. I., Bramaz, N., Lienert, J., Neuwoehner, J., & Straub, J. O. (2010). Mixture toxicity of the antiviral drug Tamiflu® (oseltamivir ethylester) and its active metabolite oseltamivir acid. Aquatic Toxicology, 96(3), 194-202. doi:10.1016/j.aquatox.2009.10.020, Institutional Repository

Tamiflu® (oseltamivir ethylester) is an antiviral agent for the treatment of influenza A and B. The pro-drug Tamiflu® is converted in the human body to the pharmacologically active metabolite, oseltamivir acid, with a yield of 75%. Oseltamivir acid is indirectly photodegradable and slowly biodegradable in sewage works and sediment/water systems. A previous environmental risk assessment has concluded that there is no bioaccumulation potential of either of the compounds. However, little was known about the ecotoxicity of the metabolite. Ester hydrolysis typically reduces the hydrophobicity and thus the toxicity of a compound. In this case, a zwitterionic, but overall neutral species is formed from the charged parent compound. If the speciation and predicted partitioning into biological membranes is considered, the metabolite may have a relevant contribution to the overall toxicity. These theoretical considerations triggered a study to investigate the toxicity of oseltamivir acid (OA), alone and in binary mixtures with its parent compound oseltamivir ethylester (OE). OE and OA were found to be baseline toxicants in the bioluminescence inhibition test with Vibrio fischeri. Their mixture effect lay between predictions for concentration addition and independent action for the mixture ratio excreted in urine and nine additional mixture ratios of OE and OA. In contrast, OE was an order of magnitude more toxic than OA towards algae, with a more pronounced effect when the direct inhibition of photosystem II was used as toxicity endpoint opposed to the 24 h growth rate endpoint. The binary mixtures in this assay yielded experimental mixture effects that agreed with predictions for independent action. This is consistent with the finding that OE exhibits slightly enhanced toxicity, while OA acts as baseline toxicant. Therefore, with respect to mixture classification, the two compounds can be considered as acting according to different modes of toxic action, although there are indications that the difference is a toxicokinetic effect, not a true difference of mechanism of toxicity. The general mixture results illustrate the need to consider the role of metabolites in the risk assessment of pharmaceuticals. However, in the concentration ratio of parent to metabolite excreted by humans, the experimental results confirm that the active metabolite does not significantly contribute to the risk quotient of the mixture.
Kaegi, R., Sinnet, B., Zuleeg, S., Hagendorfer, H., Mueller, E., Vonbank, R., … Burkhardt, M. (2010). Release of silver nanoparticles from outdoor facades. Environmental Pollution, 158(9), 2900-2905. doi:10.1016/j.envpol.2010.06.009, Institutional Repository

In this study we investigate the release of metallic silver nanoparticles (Ag-NP) from paints used for outdoor applications. A facade panel mounted on a model house was exposed to ambient weather conditions over a period of one year. The runoff volume of individual rain events was determined and the silver and titanium concentrations of 36 out of 65 runoff events were measured. Selected samples were prepared for electron microscopic analysis. A strong leaching of the Ag-NP was observed during the initial runoff events with a maximum concentration of 145 μ Ag/l. After a period of one year, more than 30% of the Ag-NP were released to the environment. Particles were mostly <15 nm and are released as composite colloids attached to the organic binders of the paint. Microscopic results indicate that the Ag-NP are likely transformed to considerably less toxic forms such as Ag2S.
Larsen, T. A., Maurer, M., Eggen, R. I. L., Pronk, W., & Lienert, J. (2010). Decision support in urban water management based on generic scenarios: the example of NoMix technology. Journal of Environmental Management, 91(12), 2676-2687. doi:10.1016/j.jenvman.2010.07.032, Institutional Repository

Urine source separation (NoMix technology) followed by processing the concentrated nutrient solution has the potential to become a cost-efficient alternative to conventional end-of-pipe nutrient elimination. A choice of processing technologies can only be made for specific scenarios, and there is currently no methodology for analyzing generic situations. In setting up a formalized decision-support methodology (based on STEEPLED analysis), we discuss how to create such generic scenarios, how to couple them with process engineering objectives, how to define the technology requirements, and finally how to produce a realistic subset of technology alternatives. The methodology is tested in five real scenarios. We also touch on the criteria for a final choice of technology taking into account large uncertainties about the performance of real technologies. We conclude that technology development is one of the most important requirements for implementing urine source separation in practice. There is an urgent need to develop cost-efficient processing technologies that satisfy the requirements of stakeholders.
Latkoczy, C., Kägi, R., Fierz, M., Ritzmann, M., Günther, D., & Boller, M. (2010). Development of a mobile fast-screening laser-induced breakdown detection (LIBD) system for field-based measurements of nanometre sized particles in aqueous solutions. Journal of Environmental Monitoring, 12(7), 1422-1429. doi:10.1039/c002020f, Institutional Repository

Laser-induced breakdown detection (LIBD) is a promising method to detect trace amounts of nanoparticles (NP, <100 nm) in aqueous suspensions. Based on available systems, we developed a mobile LIBD, designed for on-site and on-line measurements. We used the energy ratio of every laser pulse before and after passing the laser beam through the aqueous sample as a new method to detect laser-induced plasma events. The particle size and the particle number density are derived from recorded energy curves. Our LIBD is operated with a Nd:YAG laser at 100 Hz significantly reducing the measurement times compared to other LIBD systems operated at 20 Hz and increasing the capabilities for monitoring purposes. Long-term experiments on water samples revealed losses of NP up to 75% in 15 mL and 35% in 5 L sample containers after 3 months. The size of the particles remained constant (5 L) or slightly decreased (15 mL) indicating significant adsorption of NP to the walls of the sampling containers. Furthermore, we monitored the NP content of water after different purification steps at a drinking water plant (Maennedorf, Lake Zurich, Switzerland). Activated carbon filtration resulted in an increase of the particle size from ∼20 nm to ∼75 nm possibly caused by the release of organic fragments derived from the biology within the activated carbon tank. After the final ultrafiltration step the particle size was around 10 nm in agreement with the nominal cutoff of 100 kDa of the membrane. The results underline the strength of a fast-screening LIBD to detect relative changes in NP size and concentration.
Lienert, J., & Larsen, T. A. (2010). High acceptance of urine source separation in seven European countries: a review. Environmental Science and Technology, 44(2), 556-566. doi:10.1021/es9028765, Institutional Repository

Urine source separation (NoMix-technology) is a promising innovation aiming at a resource-oriented, decentralized approach in urban water management. However, NoMix-technology has a sensitive end-point: people’s bathrooms. NoMix-technology is increasingly applied in European pilot projects, but the success from a user point-of-view has rarely been systematically monitored. We aim at closing this gap. We review surveys on acceptance, including reuse of human urine as fertilizer, from 38 NoMix-projects in 7 Northern and Central European countries with 2700 respondents. Additionally, we identify explanatory variables with logistic regression of a representative Swiss library survey. NoMix-technology is well accepted; around 80% of users liked the idea, 75−85% were satisfied with design, hygiene, smell, and seating comfort of NoMix-toilets, 85% regarded urine-fertilizers as good idea (50% of farmers), and 70% would purchase such food. However, 60% of users encountered problems; NoMix-toilets need further development. We found few differences among countries, but systematic differences between public and private settings, where people seem more critical. Information was positively correlated with acceptance, and, e.g., a good mood or environmentally friendly behavior. For future success of NoMix-projects, we recommend authorities follow an integral strategy. Lay people will then find the NoMix-concept appealing and support this promising bathroom innovation.
Maurer, M., Wolfram, M., & Anja, H. (2010). Factors affecting economies of scale in combined sewer systems. Water Science and Technology, 62(1), 36-41. doi:10.2166/wst.2010.241, Institutional Repository

A generic model is introduced that represents the combined sewer infrastructure of a settlement quantitatively. A catchment area module first calculates the length and size distribution of the required sewer pipes on the basis of rain patterns, housing densities and area size. These results are fed into the sewer-cost module in order to estimate the combined sewer costs of the entire catchment area. A detailed analysis of the relevant input parameters for Swiss settlements is used to identify the influence of size on costs. The simulation results confirm that an economy of scale exists for combined sewer systems. This is the result of two main opposing cost factors: (i) increased construction costs for larger sewer systems due to larger pipes and increased rain runoff in larger settlements, and (ii) lower costs due to higher population and building densities in larger towns. In Switzerland, the more or less organically grown settlement structures and limited land availability emphasise the second factor to show an apparent economy of scale. This modelling approach proved to be a powerful tool for understanding the underlying factors affecting the cost structure for water infrastructures.
Ort, C., Lawrence, M. G., Rieckermann, J., & Joss, A. (2010). Sampling for pharmaceuticals and personal care products (PPCPs) and illicit drugs in wastewater systems: are your conclusions valid? A critical review. Environmental Science and Technology, 44(16), 6024-6035. doi:10.1021/es100779n, Institutional Repository

The analysis of 87 peer-reviewed journal articles reveals that sampling for pharmaceuticals and personal care products (PPCPs) and illicit drugs in sewers and sewage treatment plant influents is mostly carried out according to existing tradition or standard laboratory protocols. Less than 5% of all studies explicitly consider internationally acknowledged guidelines or methods for the experimental design of monitoring campaigns. In the absence of a proper analysis of the system under investigation, the importance of short-term pollutant variations was typically not addressed. Therefore, due to relatively long sampling intervals, potentially inadequate sampling modes, or insufficient documentation, it remains unclear for the majority of reviewed studies whether observed variations can be attributed to “real” variations or if they simply reflect sampling artifacts. Based on results from previous and current work, the present paper demonstrates that sampling errors can lead to overinterpretation of measured data and ultimately, wrong conclusions. Depending on catchment size, sewer type, sampling setup, substance of interest, and accuracy of analytical method, avoidable sampling artifacts can range from “not significant” to “100% or more” for different compounds even within the same study. However, in most situations sampling errors can be reduced greatly, and sampling biases can be eliminated completely, by choosing an appropriate sampling mode and frequency. This is crucial, because proper sampling will help to maximize the value of measured data for the experimental assessment of the fate of PPCPs as well as for the formulation and validation of mathematical models. The trend from reporting presence or absence of a compound in “clean” water samples toward the quantification of PPCPs in raw wastewater requires not only sophisticated analytical methods but also adapted sampling methods. With increasing accuracy of chemical analyses, inappropriate sampling increasingly represents the major source of inaccuracy. A condensed step-by-step Sampling Guide is proposed as a starting point for future studies.
Rieckermann, J., Borsuk, M. E., Sydler, D., Gujer, W., & Reichert, P. (2010). Bayesian experimental design of tracer studies to monitor wastewater leakage from sewer networks. Water Resources Research, 46(8), 1-14. doi:10.1029/2009WR008630, Institutional Repository

Despite more than a decade of research, the magnitude of wastewater leakage from defective sewer systems into groundwater supplies is still largely unknown, partly because reliable measurement methods are lacking. Although recently suggested in-sewer tracer studies present a promising solution, it is unclear how to optimally design such studies in network settings. In this study we present a formal experimental design procedure, which uses Bayesian data analysis to improve the diagnosis of sewer leakage by combining tracer test data with prior knowledge on network topology and condition. From a simulation study, we show that (1) if a single sewer section is expected to have high leakage, that section should be distinguished in measurement layouts through isolated tests or appropriate overlapping of multiple tests; (2) if multiple sections are expected to have high leakage, layouts with tests that cover more than one high-leakage section should be avoided; and (3) if a robust experimental design is desired, a balanced layout of tests that overlap multiple sections of high leakage, yet minimizes stretch length, should be chosen. This design will have the additional benefit of inducing covariance in the posterior distribution of exfiltration estimates, which can be used to advantage in subsequent studies. We apply these guidelines to a case study of a catchment in Zurich, Switzerland, and find that optimal layout design can improve the anticipated gain of information substantially relative to designs based on practical considerations alone. Remaining concerns regarding the procedure include (1) the generally poor understanding of the mechanisms governing sewer leakage, which can hamper reliable prior information on exfiltration; (2) the currently low measurement precision of sewer tracer studies, which might only allow for the detection of large leaks; and (3) the need for numerical implementation of the Bayesian inference procedure, which requires careful tuning and long computation times. In general, we were able to demonstrate that the incorporation of prior information through a Bayesian procedure adds significant value to experimental design, especially in situations with few "hard" data but good site-specific knowledge, which is common in water resources research.
Ronteltap, M., Maurer, M., Hausherr, R., & Gujer, W. (2010). Struvite precipitation from urine - influencing factors on particle size. Water Research, 44(6), 2038-2046. doi:10.1016/j.watres.2009.12.015, Institutional Repository

Struvite crystallisation is a fast and reliable phosphorus removal and recovery process for concentrated waste streams – such as hydrolysed human urine. In order to optimise P-elimination efficiency, it is beneficial to obtain larger particle sizes: they are easier to separate and less prone to wash-out than smaller particles. This paper presents the results of a study on the effect of process parameters on particle size in a single step struvite precipitation. Crystals formed in batch experiments with real hydrolysed urine were shown to have an average size of >90 μm at pH 9 and 20 °C. This is reduced to 45 μm when changing stirrer type. Particle size increases with lower supersaturation. The results showed that under otherwise constant conditions, particle size decreases with lower temperature and has a minimum between pH 9 and 10. Deviating trends are observed at pH <8. Struvite formation in a CSTR (continuously stirred tank reactor) process was shown to be a reliable stable process that does not require any pH control. A method based on conductivity measurement is presented to estimate ionic strength, which is needed for equilibrium calculations.
Burkhardt, M., Junghans, M., Zuleeg, S., Schoknecht, U., Lamani, X., Bester, K., … Boller, M. (2009). Biozide in Gebäudefassaden – ökotoxikologische Effekte, Auswaschung und Belastungsabschätzung für Gewässer. Umweltwissenschaften und Schadstoff-Forschung, 21(1), 36-47. doi:10.1007/s12302-008-0033-1, Institutional Repository

Background, aim and scope Sources of organic micropollutants occuring in surface waters are often unknown. Regarding environmental risk assessments for surface waters, construction materials have as till now, not been given much consideration, although biocides used as preservatives are known to reach urban storm water runoff. The study focused on biocides for facades coatings and aimed (1) to determine ecotoxicological effect values, (2) to quantify the leaching behaviour and (3) to assess the environmental risk for surface waters using a dynamic transport model.
Materials and methods Eight biocides used in resin based facade coatings were investigated. Some biocides are substances known as pesticides for agricultural purposes like diuron, carbendazim and terbutryn. Ecotoxicological effect values for aquatic organisms were determined for every biocide. Leaching of four biocides from a render under UV-irradiation has been investigated in the laboratory including the influence of varying temperatures. Using 80 irrigation intervals over 28 days, facade runoff was sampled and followed by biocide chemical analysis. The total losses were calculated based on the concentration patterns. These data were used for modelling the transport of cybutryn from facades to surface waters. Biocide specific effect values and leaching characteristics have been taken into consideration.
Results Acute and chronic effect values as well as predicted no effect concentrations for the investigated biocides indicate their high potential to affect aquatic organisms. The leaching of four biocides (diuron, terbutryn, cybutryn, carbendazim) from the facade render under the experimental conditions delivers high concentrations in the beginning followed by an exponential decrease. Rising temperature increased the concentration of biocides in the runoff. The total losses were between 7 % and 29 % depending on the substances. More than half of the losses occur in the runoff within the first 15 min of runoff from a 60 min irrigation cycle. The modelling result for cybutryn underlines its high environmental risk for small surface waters.
Discussion The leaching of the biocides, their potential ecotoxic effects and persistence show clearly that the environmental risk for surface waters and soils seems to be high for certain biocides; whereas for others the risk seems to be significantly lower. With respect water quality criteria, polluted facades runoff has to be diluted before runoff can enter the discharge. Diuron and carbendazim are however also used as pesticides and preservatives for other materials and cybutryn is also used as an antifouling agent. All pathways have to be evaluated in order to identify relevant sources and to act more efficiently with respect to water and soil protection.
Conclusions Concentrations with high environmental risk are expected at new facades, especially at facades with thermal insulation. With the given low predicted no effect concentrations in a range of a few ng/L and large amounts of biocides applied in paints and renders, the environmental risk for common biocides used in facade coatings has to be investigated in laboratory and field scale. It seems plausible that source control measures as the most efficient and sustainable precautionary principle need to be evaluated.
Recommendations and perspectives Biocides and additives applied in construction materials have to be taken into consideration as relevant sources when evaluating the quality of storm water runoff, discharge into urban areas and the impact to soil and surface waters. A sustainable construction material management and storm water management are required. It is expected that ongoing laboratory and field studies with exterior paints, renders and flat sheets for waterproofing containing biocides and additives will give further insight into their environmental impact.
Jermann, D., Pronk, W., Boller, M., & Schäfer, A. I. (2009). The role of NOM fouling for the retention of estradiol and ibuprofen during ultrafiltration. Journal of Membrane Science, 329(1–2), 75-84. doi:10.1016/j.memsci.2008.12.016, Institutional Repository

The impact of membrane fouling by natural organic matter (NOM) on the behavior of micropollutants during ultrafiltration (UF) was investigated. Batch experiments with radioactively labeled estradiol and ibuprofen in the presence of NOM model compounds (alginate, Nordic aquatic and Aldrich humic acid) were performed using a hydrophilic and a hydrophobic membrane. The results indicate that the impact of the NOM fractions studied on micropollutant retention correlated with the fouling mechanism of the individual NOM fractions. NOM substances of high molecular weight such as alginate and Aldrich HA that foul the membrane by pore blocking and cake/gel formation had a greater impact than the Nordic aquatic humic acid of lower molecular weight. The effect of cake formation was attributed partly to micropollutant-NOM partitioning and subsequent NOM retention and partly to the effect of the fouling layer itself acting as a kind of second membrane. Fouling by NOM cake/gel formation led to a significantly increased retention of estradiol, whereas the impact of fouling on ibuprofen retention was negligible due to significantly lower log Koc values of ibuprofen compared to estradiol. Moreover, NOM adsorption on the membrane can lower the adsorption of hydrophobic micropollutants. Membrane adsorption of estradiol was in the order of mg/m2 and was largely reversible with caustic solutions. The results of this study may prove useful for predicting the mass flow of micropollutants in UF applications.
Maurer, M. (2009). Specific net present value: an improved method for assessing modularisation costs in water services with growing demand. Water Research, 43(8), 2121-2130. doi:10.1016/j.watres.2009.02.008, Institutional Repository

A specific net present value (SNPV) approach is introduced as a criterion in economic engineering decisions. The SNPV expresses average costs, including the growth rate and plant utilisation over the planning horizon, factors that are excluded from a standard net present value approach. The use of SNPV favours alternatives that are cheaper per service unit and are therefore closer to the costs that a user has to cover. It also shows that demand growth has a similar influence on average costs as an economy of scale. In a high growth scenario, solutions providing less idle capacity can have higher present value costs and still be economically favourable.
The SNPV approach is applied in two examples to calculate acceptable additional costs for modularisation and comparable costs for on-site treatment (OST) as an extreme form of modularisation. The calculations show that: (i) the SNPV approach is suitable for quantifying the comparable costs of an OST system in a different scenario; (ii) small systems with projected high demand growth rates and high real interest rates are the most probable entry market for OST water treatment systems; (iii) operating expenses are currently the main economic weakness of membrane-based wastewater OST systems; and (iv) when high growth in demand is expected, up to 100% can be additionally invested in modularisation and staging the expansion of a treatment plant.
Rossi, L., Lienert, J., & Larsen, T. A. (2009). Real-life efficiency of urine source separation. Journal of Environmental Management, 90(5), 1909-1917. doi:10.1016/j.jenvman.2009.01.006, Institutional Repository

Urine source separation (NoMix technology) is a promising innovation in wastewater management. To improve and further develop NoMix technology, it has been implemented in four Swiss households and at our research institute (Eawag). We conducted measurements during one year on frequency of toilet usage (in households 5.2/person/day for weekdays, and 6.3/person/day for weekends), flushing behavior (30-85% small flushes), and recovered urine. We calculate the amount of urine effectively recovered per voiding in NoMix toilets (138 ml/flush in households; 309 ml/flush in women's toilets at Eawag), and waterfree urinals (225 ml/usage). We estimate urine recovery in the households to be maximally 70-75% of the expected quantity, leaving room for technical and behavioral improvements. Based on sampling of N and P concentrations, we suspect nitrogen losses in the extended urine piping system. For households and workplaces, the daily and weekly flushing pattern is recorded. Our results are in accordance with literature data from a shorter period but with more people. These results represent a good dimensioning basis for future urine source separation applications. An example of extrapolation to an entire watershed is presented. The flushing pattern corresponds well with the typical nitrogen loading of a treatment plant.
Schoknecht, U., Gruycheva, J., Mathies, H., Bergmann, H., & Burkhardt, M. (2009). Leaching of biocides used in façade coatings under laboratory test conditions. Environmental Science and Technology, 43(24), 9321-9328. doi:10.1021/es9019832, Institutional Repository

The European Biocidal Products Directive 98/8/EC requires a risk assessment concerning possible effects of active ingredients on the environment. Biocides can be leached from treated materials exposed to outdoor use. These emissions have to be estimated and evaluated during the authorization procedure. Different immersion and irrigation tests were performed to investigate leaching of biocides from façade coatings. Several marketed formulations of textured coatings and paints spiked with a mixture of commonly used active ingredients (OIT, DCOIT, IPBC, carbendazim, isoproturon, diuron, terbutryn, and Irgarol 1051) were investigated. The emission process can be described by time-dependent functions that depend on the test conditions. The results of all test procedures confirm that leachability is related to water solubility and n-octanol−water partition coefficient of the active ingredients and that leaching of biocides from façade coatings is mainly a diffusion controlled process. Other factors like the composition of the product, availability and transport of water, concentration of active ingredients in the coatings, as well as UV-exposure of the coatings influence biocide emissions.
Störmer, E., Truffer, B., Dominguez, D., Gujer, W., Herlyn, A., Hiessl, H., … Ruef, A. (2009). The exploratory analysis of trade-offs in strategic planning: lessons from regional infrastructure foresight. Technological Forecasting and Social Change, 76(9), 1150-1162. doi:10.1016/j.techfore.2009.07.008, Institutional Repository

The sustainable transformation of infrastructure sectors represents a challenge of prime importance worldwide. Due to long life times of infrastructures, strategic decision making has to explicitly consider uncertainties in context conditions, value considerations and available technological alternatives. However currently, strategic infrastructure planning is often carried out in a very narrow perspective. The present paper argues that foresight informed strategic planning, allows addressing trade-offs related to context uncertainties, value conflicts and sustainability deficits in a structured way. The paper introduces a specific procedural proposal, the Regional Infrastructure Foresight method (RIF) and illustrates its potential virtues through an application to urban water management planning in a Swiss region (Kiesental).
Bester, K., Klasmeier, J., & Kupper, T. (2008). Emissions of OTNE (Iso-E-super) – mass flows in sewage treatment plants. Chemosphere, 71(11), 2003-2010. doi:10.1016/j.chemosphere.2008.02.004, Institutional Repository

The fate and mass flows of OTNE ([1,2,3,4,5,6,7,8-octahydro-2,3,8,8-tetramethylnaphthalen-2yl]ethan-1-one) which is commercialized as Iso-E-Super were studied in three large scale sewage treatment plants (STPs) in detail. The results are compared to 14 smaller ones located in Germany and Switzerland. OTNE inflow concentrations ranged from 4000 to 13 000 ng l−1 while the effluent concentrations ranged from 500 to 6900 ng l−1. It is eliminated from the waste water with 56–64% during waste water treatment. High OTNE concentrations in sewage sludge showed that the elimination was mainly driven by sorption to sludge. This complies with major elimination in the first settling basins (primary settling tanks) while it was removed to a lesser extent in the aeration basin of the activated sludge treatment or in successive biofilters.
The mass flows of OTNE in the influent of the German STPs were between 0.9 and 1.9 g per inhabitant and year. In the annual effluents mass flows of OTNE ranged between 0.2 and 0.8 g per inhabitant which complies with data measured in 13 smaller STPs from Switzerland. The similarity of data suggests that the observed mass flow data might be extrapolated to other European regions.
Borsuk, M. E., Maurer, M., Lienert, J., & Larsen, T. A. (2008). Charting a path for innovative toilet technology using multicriteria decision analysis. Environmental Science and Technology, 42(6), 1855-1862. doi:10.1021/es702184p, Institutional Repository

Practical and theoretically sound methods for analyzing innovative environmental technologies are needed to inform public and private decisions regarding research and development, risk management, and stakeholder communication. By integrating scientific assessments with a characterization of values, multicriteria decision analysis (MCDA) supports the ranking of alternative technology pathways on the basis of technical, financial, and social concerns. We applied MCDA to evaluate the use of NoMix urine separating toilets for managing environmental risk and postponing expensive upgrades to a large wastewater treatment plant near Zürich, Switzerland. Results indicate that, given current priorities, no single, fixed course of action (including the status quo) will be desirable to all stakeholders over the considered time horizon. However, a path forward is suggested that is not significantly disadvantageous to any stakeholder now and leaves open future options, allowing society to achieve overall greater benefits if priorities change, new environmental risks are revealed, or technology improves. While our analysis focuses on a particular catchment in Switzerland, many communities worldwide are faced with an aging and inefficient wastewater treatment infrastructure while also experiencing growth and development. Our framework can help these communities balance the conflicting objectives of diverse stakeholders and gain insight into the role that urine separation can play in transitioning to a more comprehensive and sustainable urban water management system.
Burkhardt, M., Rossi, L., & Boller, M. (2008). Diffuse release of environmental hazards by railways. Desalination, 226(1–3), 106-113. doi:10.1016/j.desal.2007.02.102, Institutional Repository

There is increasing concern about environmental pollution by diffuse emissions of various environmental hazards emitted by transportation activities. For the first time substances released by railways to the environment were investigated. We considered the significant sources and the amounts emitted by regular operation within the Swiss Federal Railways (SBB) network (7200 km tracks). The main substances are about 2270 t y−1 metals, 1357 t y−1 hydrocarbons and 3.9 t y−1 herbicides. Most of the released metals are particles emitted by friction processes with iron, followed by copper, zinc, manganese, chromium, nickel, vanadium and lead. Only a small amount of metals is expected to be leached in dissolved phase. The emission of hydrocarbons may be diffusive (e.g. operational losses) or at point-sources (e.g. track-switch). The wooden sleepers seem to be the most important sources of hydrocarbons, followed by lubricants from track-switches and wheel flanges. The emissions reflect a spatial and temporal exposure pattern. The assessment is valuable for regulatory authorities working on soil and water protection as well as for railway companies determining their necessity of water and soil protection measures. Based on the results, selected studies may establish an understanding on relevant processes and environmental risk of railway imissions to soil, drainage water and groundwater.
Burkhardt, M., Kasteel, R., Vanderborght, J., & Vereecken, H. (2008). Field study on colloid transport using fluorescent microspheres. European Journal of Soil Science, 59(1), 82-93. doi:10.1111/j.1365-2389.2007.00989.x, Institutional Repository

Understanding colloid movement through the vadose zone is important, because colloids may facilitate transport of some less mobile contaminants. Experimental evidence of colloid transport in the vadose zone, especially at the field scale, is rare. We developed and tested a method to detect and quantify local concentrations of fluorescent microspheres (MS) with a diameter of 1 μm in unsaturated soil based on fluorescent microscopy. The detection limit was 400 × 106 MS kg−1 field-moist soil for an automated counting method, and 20 × 103 MS kg−1 for manual counting. To test the method in the field, we applied a 40-mm pulse with an input concentration of 14.6 × 109 MS litre−1 on two plots during 6 hours, together with bromide (Br−) and the food dye Brilliant Blue (BB). The concentrations of MS were determined on horizontal cross-sections by a randomly distributed sampling scheme, either directly after application or 90 days after application and a rainfall of 100 mm. Mass recoveries for the MS of 85 and 65% were acceptable in view of the field conditions. Even after infiltration of particle-free water, the largest MS concentrations were measured at the soil’s surface, which pointed at physical retention mechanisms. An additional selective sampling of hydrologically active preferential flow pathways, guided by the dye infiltration patterns, revealed that the MS were transported to similar depths as BB, that is 0.80 m directly after irrigation and 1.7 m after 90 days. This implies that also a small fraction of the particulate tracers was rapidly transported to larger depths, regardless of their physico-chemical properties.
Dodd, M. C., Zuleeg, S., von Gunten, U., & Pronk, W. (2008). Ozonation of source-separated urine for resource recovery and waste minimization: process modeling, reaction chemistry, and operational considerations. Environmental Science and Technology, 42(24), 9329-9337. doi:10.1021/es800560r, Institutional Repository

Bench-scale, semibatch experiments were performed to examine physical−chemical constraints on ozone (O3) absorption and micropollutant oxidation during ozonation of source-separated hydrolyzed urine and the concentrate and diluate streams produced via electrodialysis of hydrolyzed urine. O3 consumption by each matrix was found to occur within a fast pseudo-first-order kinetic regime. Critical constraints on micropollutant oxidation were found through mass transfer modeling to be (i) micropollutant diffusion from the bulk solution into the gas−liquid interfacial film for compounds recalcitrant toward O3 (i.e., kO′′3,app ≤ 103 M−1 s−1), and (ii) aqueous-phase mixing for compounds highly reactive toward O3 (i.e., kO′′3,app > 103 M−1 s−1). Homogeneous chemical reaction modeling indicated that aqueous reaction chemistry is significantly influenced by the degree to which incidentally produced hydroxyl radicals are consumed by NH3 in each matrix, in terms of (a) micropollutant oxidation efficiencies, and (b) potential yields of oxidation byproducts. On the basis of the experimental data reported here, per capita energy requirements were estimated for treatment of source-separated urine via (1) ozonation, (2) ozonation with postelectrodialysis, and (3) electrodialysis with postozonation. These estimates indicate that scenario (1) would likely be less energy efficient than ozonation of municipal wastewater effluent in achieving equivalent reductions in urine-derived micropollutant loads, whereas scenarios (2 and 3) could be more efficient than equivalent centralized wastewater treatment strategies in achieving equivalent levels of urine-derived nutrient and micropollutant attenuation. Furthermore, experimental and model data suggest that urine ozonation efficiency may be substantially improved by optimizing aqueous-phase mixing and specific gas−liquid interfacial area.
Dürrenmatt, D. J., & Wanner, O. (2008). Simulation of the wastewater temperature in sewers with TEMPEST. Water Science and Technology, 57(11), 1809-1815. doi:10.2166/wst.2008.291, Institutional Repository

TEMPEST is a new interactive simulation program for the estimation of the wastewater temperature in sewers. Intuitive graphical user interfaces assist the user in managing data, performing calculations and plotting results. The program calculates the dynamics and longitudinal spatial profiles of the wastewater temperature in sewer lines. Interactions between wastewater, sewer air and surrounding soil are modeled in TEMPEST by mass balance equations, rate expressions found in the literature and a new empirical model of the airflow in the sewer. TEMPEST was developed as a tool which can be applied in practice, i.e., it requires as few input data as possible. These data include the upstream wastewater discharge and temperature, geometric and hydraulic parameters of the sewer, material properties of the sewer pipe and surrounding soil, ambient conditions, and estimates of the capacity of openings for air exchange between sewer and environment. Based on a case study it is shown how TEMPEST can be applied to estimate the decrease of the downstream wastewater temperature caused by heat recovery from the sewer. Because the efficiency of nitrification strongly depends on the wastewater temperature, this application is of practical relevance for situations in which the sewer ends at a nitrifying wastewater treatment plant.
Jermann, D., Pronk, W., Kägi, R., Halbeisen, M., & Boller, M. (2008). Influence of interactions between NOM and particles on UF fouling mechanisms. Water Research, 42(14), 3870-3878. doi:10.1016/j.watres.2008.05.013, Institutional Repository

This study focused on the mechanistic effects of molecular interactions between inorganic particles (kaolinite) and the two main NOM fouling fractions of polysaccharides (alginate) and humics (humic acids) in ultrafiltration. Fouling effects were studied during the dead-end filtration of individual and mixed compounds as well as during the subsequent filtration of individual compounds. SEM analyses were performed to further study the fouling-layer structure. A significant synergistic effect was observed during combined particle–NOM fouling, which was considerably greater than the sum of particle and organic fouling alone. Synergistic fouling could be explained by NOM–particle interactions in the feed solution and during the fouling process. Kaolinite alone formed a fouling layer of particle aggregates, whereas humic acid adsorption onto kaolinite resulted in a fouling layer of stabilized colloids of humic acid and kaolinite. In the case of alginate, simultaneous pore-blocking and cake-layer formation of NOM and kaolinite dominated the fouling. In both cases, incorporation of the organics in the kaolinite fouling layer resulted in a fouling cake of significantly reduced porosity compared to individual particle filtration. Irreversible fouling by NOM could not be prevented by kaolinite. SEM images showed patches of the particle-fouling layer remaining on the membrane surface after backwashing, which can be linked to particle–membrane associations by NOM bridging.
Jermann, D., Pronk, W., & Boller, M. (2008). Mutual influences between natural organic matter and inorganic particles and their combined effect on ultrafiltration membrane fouling. Environmental Science and Technology, 42(24), 9129-9136. doi:10.1021/es800654p, Institutional Repository

Fouling is one of the most critical aspects of membrane technology and is strongly influenced by natural water characteristics. This study focuses on a mechanistic understanding of the impact of interactions between natural organic matter (NOM) and particles on fouling. The model substances used were humic acid, alginate (polysaccharide), and kaolinite. NOM−kaolinite adsorption experiments, particle characterization, and dead-end ultrafiltration (UF) batch experiments were performed. The adsorption experiments indicated particle stabilization at low NOM equilibrium concentrations, whereas calcium induced significant aggregation, especially with alginate. UF experiments implicated a synergistic fouling effect of particle−NOM combinations, which was greatly reduced by calcium. Moreover, irreversible NOM fouling was only prevented by particles in the presence of calcium. On the basis of our results, we present a mechanistic model suggesting that synergistic fouling effects occur due to particle stabilization by NOM adsorption, especially shown for HA, and antagonistic effects due to particle destabilization by calcium. However, synergistic fouling can also be based on sterical interferences between larger NOM in the form of polysaccharides and particles during simultaneous pore blocking and cake formation. A heterogeneous NOM−particle fouling layer is ultimately formed with membrane associations dominated by NOM. The combined fouling is conclusively determined by the type of NOM, its specific fouling mechanisms, and its particle interactions prior to and during the filtration process.
Kaegi, R., Wagner, T., Hetzer, B., Sinnet, B., Tzvetkov, G., & Boller, M. (2008). Size, number and chemical composition of nanosized particles in drinking water determined by analytical microscopy and LIBD. Water Research, 42(10–11), 2778-2786. doi:10.1016/j.watres.2008.02.009, Institutional Repository

In this paper we comprehensively characterized particles in drinking water originating from a lake water source. We focused on particles smaller than a few hundred nm. Several analytical techniques were applied to obtain information on number concentration, size distribution, morphology and chemical composition of the particles. Morphological information was obtained by atomic force microscopy (AFM) analysis. Two types of particles, spherical aggregates up to a few tens of nm and elongated fibers were identified. Similar structures were also observed in transmission electron microscope (TEM) images. A size distribution of the particles was obtained by applying image analysis (IA) tools on the TEM images. IA results showed an exponential increase of the particle number concentration down to 40 nm, which is the lower detection limit of our setup. The total number of particles down to 10 nm and the average particle diameter were determined with the laser-induced breakdown detection (LIBD) method. The results were in good agreement with the TEM-IA data and showed a total number concentration of roughly 108 particles/mL in the purified water. The carbon of the particles was investigated with scanning transmission X-ray microscopy (STXM), which revealed that most particles were organic matter; the C-1s spectra were typical for dissolved organic matter.
The methods were applied to characterize the particles from two different drinking waters treated with different methods (conventional vs. ultrafiltration (cut-off 100 kDa)). The results showed that the particle number density following ultrafiltration was lower by a factor of 5–10, compared to conventional treatment. However, the average particle diameter in the finished water of both treatment trains was roughly the same.
Kaegi, R., Ulrich, A., Sinnet, B., Vonbank, R., Wichser, A., Zuleeg, S., … Boller, M. (2008). Synthetic TiO2 nanoparticle emission from exterior facades into the aquatic environment. Environmental Pollution, 156(2), 233-239. doi:10.1016/j.envpol.2008.08.004, Institutional Repository

We present direct evidence of the release of synthetic nanoparticles from urban applications into the aquatic environment. We investigated TiO2 particles as these particles are used in large quantities in exterior paints as whitening pigments and are to some extent also present in the nano-size range.
TiO2 particles were traced from exterior facade paints to the discharge into surface waters. We used a centrifugation based sample preparation which recovers TiO2 particles between roughly 20 and 300 nm. Analytical electron microscopy revealed that TiO2 particles are detached from new and aged facade paints by natural weather conditions and are then transported by facade runoff and are discharged into natural, receiving waters. Microscopic investigations are confirmed by bulk chemical analysis. By combining results from microscopic investigations with bulk chemical analysis we calculated the number densities of synthetic TiO2 particles in the runoff.
Larsbo, M., Fenner, K., Stoob, K., Burkhardt, M., Abbaspour, K., & Stamm, C. (2008). Simulating sulfadimidine transport in surface runoff and soil at the microplot and field scale. Journal of Environmental Quality, 37(3), 788-797. doi:10.2134/jeq2007.0432, Institutional Repository

To prevent residues of veterinary medicinal products (VMPs) from contaminating surface waters and ground water, an environmental impact assessment is required before a new product is allowed on the market. Physically based simulation models are advocated for the calculation of predicted environmental concentrations at higher tiers of the assessment process. However, the validation status of potentially useful models is poor for VMP transport. The objective of this study was to evaluate the dual-permeability model MACRO for simulation of transport of sulfonamide antibiotics in surface runoff and soil. Special focus was on effects of solute application in liquid manure, which may alter the hydraulic properties at the soil surface. To this end we used data from a microplot runoff experiment and a field experiment, both conducted on the same clay loam soil prone to preferential flow. Results showed that the model could accurately simulate concentrations of sulfadimidine and the nonreactive tracer bromide in runoff and in soil from the microplot experiments. The use of posterior parameter distributions from calibrations using the microplot data resulted in poor simulations for the field data of total sulfadimidine losses. The poor results may be due to surface runoff being instantly transferred off the field in the model, whereas in reality re-infiltration may occur. The effects of the manure application were reflected in smaller total and micropore hydraulic conductivities compared with the application in aqueous solution. These effects could easily be accounted for in regulatory modeling.
Liu, Y., Mahmoud, M., Hartmann, H., Stewart, S., Wagener, T., Semmens, D., … White, D. (2008). Formal scenario development for environmental impact assessment studies. In A. J. Jakeman, A. A. Voinov, A. E. Rizzoli, & S. H. Chen (Eds.), Developments in integrated environmental assessment: Vol. 3. Environmental modelling, software and decision support (pp. 145-162). doi:10.1016/S1574-101X(08)00609-1, Institutional Repository
Rutsch, M., Rieckermann, J., Cullmann, J., Ellis, J. B., Vollertsen, J., & Krebs, P. (2008). Towards a better understanding of sewer exfiltration. Water Research, 42(10–11), 2385-2394. doi:10.1016/j.watres.2008.01.019, Institutional Repository

This paper gives a full review of the importance of sewer leakage, which has received increased attention throughout the last decades. Despite the intensive interdisciplinary research that has been invested, its magnitude is still unclear and a comprehensive solution for the assessment of sewer exfiltration does not seem to be at hand. However, given that mechanisms of exfiltration and the factors influencing its extent are similar all over the world, it seems possible to develop a generic leakage approach. Several methods for modelling sewer leakage are reviewed and the available measuring techniques are critically evaluated. Based on this evaluation, we suggest a unifying framework to facilitate focused model building. Specifically, we identify open research questions and propose to (i) standardise measurement results to enable better understanding, (ii) perform more long-term experiments under realistic field conditions, and (iii) assess the uncertainty of measurement and model results so that findings are not over-interpreted.
Udert, K. M., Kind, E., Teunissen, M., Jenni, S., & Larsen, T. A. (2008). Effect of heterotrophic growth on nitritation/anammox in a single sequencing batch reactor. Water Science and Technology, 58(2), 277-284. doi:10.2166/wst.2008.389, Institutional Repository

The combination of nitritation and autotrophic denitrification (anammox) in a single sequencing batch reactor (SBR) is an energy efficient process for nitrogen removal from high-strength ammonia wastewaters. So far, the process has been successfully applied to digester supernatant. However, the process could also be suitable to treat source-separated urine, which has very high ammonium and organic substrate concentrations (up to 8,200 gN/m3 and 10,000 gCOD/m3). In this study, reactor performance was tested for digester supernatant and diluted source-separated urine. Ammonium concentrations in both solutions were similar (between 611 and 642 gN/m3), thus reactor performance could be directly compared. Differences were mainly due to higher activity of heterotrophic bacteria in urine. Nitrogen removal was slightly higher for source-separated urine, because heterotrophic bacteria denitrified the nitrate that was produced by anammox bacteria. In spite of higher heterotrophic growth with source-separated urine, calculated sludge concentrations at steady state were higher with digester supernatant due to accumulation of inert particulate organic matter from the influent. Although the sludge concentrations are less problematic for source-separated urine, process instabilities are more likely, because lower pH values are reached and heterotrophic denitrification can cause sudden increases of nitrite concentrations and/or nitric oxide. Both compounds inhibit aerobic ammonium oxidizing bacteria, heterotrophic bacteria and, most importantly, anammox bacteria. Nitrite and nitric oxide production by heterotrophic denitrification must be better understood to optimize nitritation/anammox for source-separated urine.
Brändli, R. C., Bucheli, T. D., Kupper, T., Mayer, J., Stadelmann, F. X., & Tarradellas, J. (2007). Fate of PCBs, PAHs and their source characteristic ratios during composting and digestion of source-separated organic waste in full-scale plants. Environmental Pollution, 148(2), 520-528. doi:10.1016/j.envpol.2006.11.021, Institutional Repository

Composting and digestion are important waste management strategies. However, the resulting products can contain significant amounts of organic pollutants such as polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs). In this study we followed the concentration changes of PCBs and PAHs during composting and digestion on field-scale for the first time. Concentrations of low-chlorinated PCBs increased during composting (about 30%), whereas a slight decrease was observed for the higher chlorinated congeners (about 10%). Enantiomeric fractions of atropisomeric PCBs were essentially racemic and stable over time. Levels of low-molecular-weight PAHs declined during composting (50–90% reduction), whereas high-molecular-weight compounds were stable. The PCBs and PAHs concentrations did not seem to vary during digestion. Source apportionment by applying characteristic PAH ratios and molecular markers in input material did not give any clear results. Some of these parameters changed considerably during composting. Hence, their diagnostic potential for finished compost must be questioned.
Brändli, R. C., Bucheli, T. D., Kupper, T., Furrer, R., Stahel, W. A., Stadelmann, F. X., & Tarradellas, J. (2007). Organic pollutants in compost and digestate. Part 1. Polychlorinated biphenyls, polycyclic aromatic hydrocarbons and molecular markers. Journal of Environmental Monitoring, 9(5), 456-464. doi:10.1039/b617101j, Institutional Repository

In Europe, 9.3 x 106 tdry weight (dw) of compost and digestate are produced per year. Most of this is applied to agricultural land, which can lead to considerable inputs of organic pollutants, such as polychlorinated biphenyls (PCB) and polycyclic aromatic hydrocarbons (PAH) to soil. This paper presents an inventory of the pollutant situation in source-separated composts, digestates and presswater in Switzerland by a detailed analysis of over 70 samples. PCB concentrations (ΣPCB 28, 52, 101, 118, 138, 153, 180) were significantly higher in urban (median: 30 μg kgdw–1, n = 52) than in rural samples (median: 14 μg kgdw–1, n = 16). Together with low concentrations in general, this points to aerial deposition on compost input material as the major contamination pathway. Enantiomeric fractions of atropisometric PCB were close to racemic. Median PAH concentration was 3010 μg kgdw–1, (Σ15PAH, n = 69), and one quarter of the samples exhibited concentrations above the relevant Swiss guide value for compost (4000 μg kgdw–1). The levels were influenced by the treatment process (digestate > compost), the season of input material collection (spring–summer > winter > autumn), the particle size (coarse-grained > fine-grained), and maturity (mature > less mature). The main source of PAH in compost was pyrogenic, probably in. uenced mainly by liquid fossil fuel combustion and some asphalt abrasion, as suggested by multiple linear regression. This study, together with a companion paper reporting on other organic contaminates including emerging compound classes, provides a starting point for a better risk-benefit estimation of the application of compost and digestate to agricultural soil in Switzerland.
Brändli, R. C., Kupper, T., Bucheli, T. D., Zennegg, M., Huber, S., Ortelli, D., … Tarradellas, J. (2007). Organic pollutants in compost and digestate. Part 2. Polychlorinated dibenzo-p-dioxins, and -furans, dioxin-like polychlorinated biphenyls, brominated flame retardants, perfluorinated alkyl substances, pesticides, and other compounds. Journal of Environmental Monitoring, 9(5), 465-472. doi:10.1039/b617103f, Institutional Repository

Compost and digestate are important recycling fertilizers and have beneficial effects on soil parameters. However, they can contain significant amounts of organic pollutants. Here, the first comprehensive data set on dibenzo-p-dioxins and -furans (PCDD/F), dioxin-like polychlorinated biphenyls (DL-PCB), brominated flame retardants, perfluorinated alkyl substances (PFAS), pesticides, phthalates, nonylphenol and chlorinated paraffins (CP) in source-separated compost and digestate from Switzerland is presented (n = 3–18). The median ∑17PCDD/F and ∑12DL-PCB concentrations were at 3.2 ng I-TEQ kg−1dry weight (dw) and 3.0 ng WHO-TEQ kg−1dw, respectively. Brominated diphenyl ether 209 (BDE 209) accounted for 72% of the total polyBDE content (10 μg kg−1dw). Hexabromocyclododecane (HBCD) and tetrabromobisphenol A (TBBPA) levels were at 100 and 0.51 μg kg−1dw, respectively. PFAS were identified for the first time in compost and digestate (median concentration 6.3 μg kg−1dw, ∑21compounds). Out of 269 pesticides analysed, 30 fungicides, 14 herbicides, eight insecticides and one acaricide were detected. Di-(2-ethylhexyl)phthalate (DEHP) median concentration accounted for 280 μg kg−1dw and nonylphenol was below the detection limit of 1 mg kg−1dw. The sum of short and medium chain CP was between 90 and 390 μg kg−1dw. The concentrations observed were at or above the levels found in background soils, which are the main recipient of compost and digestate. Where actually applied, compost can contribute considerably to the total input of organic pollutants to the soil. However, on a total Swiss agricultural area base, inputs seem to be limited.
Burkhardt, M., Kupper, T., Hean, S., Haag, R., Schmid, P., Kohler, M., & Boller, M. (2007). Biocides used in building materials and their leaching behavior to sewer systems. Water Science and Technology, 56(12), 63-67. doi:10.2166/wst.2007.807, Institutional Repository

There is increasing concern about diffuse pollution of aquatic systems by biocides used in urban areas. We investigated sources and pathways of biocides significant for the pollution of storm water runoff. Main sources seem to be building envelopes, i.e. facades (paints, plasters) and roof sealing membranes. First results from a defined urban catchment drained by a separated sewer system without any agricultural activities reveal a substantial occurrence. Even after the first flush, concentrations of terbutryn, carbendazim, mecoprop as well as Irgarol 1051® and its metabolite exceeded the Swiss water quality standard of 0.1 μg/L. In laboratory experiments, leaching of mecoprop used as a root protection agent in bitumen sheets for roof waterproofing was determined. The concentrations differed in 16 different sheets two orders of magnitude, depending on the product composition. Using optimized products, it is expected to be the most efficient and sustainable way to reduce the environmental impact. To understand transport dynamics and environmental risk, further storm water events will be analyzed. Based on the ongoing project URBIC, first measures will be proposed to limit the release to surface and ground water.
Burkhardt, M., & Stamm, C. (2007). Depth distribution of sulfonamide antibiotics in pore water of an undisturbed loamy grassland soil. Journal of Environmental Quality, 36(2), 588-596. doi:10.2134/jeq2006.0358, Institutional Repository

Despite the concern raised by the detections of veterinary antibiotics like sulfonamides (SA) in the environment, their fate in soils is still not sufficiently understood. In a previous article, we demonstrated that manure may substantially influence losses of SA via runoff from soils. Here, we report on the effect of manure on SA availability in soil pore water. Three sulfonamides (sulfadimidine, sulfadiazine, sulfathiazole) and two tracers (bromide and Brilliant Blue) were either applied in manure or as aqueous solution on grassland plots. After I and 3 d contact time, the plots were irrigated with deionized water. One day after irrigation, soil cores were taken and profiles of pore water concentrations were determined. The median SA concentrations of the top layer on manured plots varied between 40 and 60 mu g L-1 and between 10 and 30 mu g L-1 on the controls. For the conservative tracer Br the mass recovery was about 60 to 75% and much lower for the SA (2 to 14%). Apparent distribution coefficients Kd,app of the SA in the topsoil ranged between 3 and 15 L kg-1 on the manured plots and between 30 to 35 kg L-1 on the controls. Below the top layer, the concentration distribution showed a pattern typical for preferential flow. Locally, SA concentrations down to 30- to 50-cm depth were as high as in the top 5 cm with little effect of the two application matrices. In the topmost layer, the data indicate that 10 to 25% of sulfadimidine were transformed to its acetyl-metabolite.
Courdouan, A., Christl, I., Meylan, S., Wersin, P., & Kretzschmar, R. (2007). Characterization of dissolved organic matter in anoxic rock extracts and in situ pore water of the Opalinus Clay. Applied Geochemistry, 22(12), 2926-2939. doi:10.1016/j.apgeochem.2007.09.001, Institutional Repository

Dissolved organic matter (DOM) from the Opalinus Clay, a potential host rock for the disposal of radioactive waste, was isolated under strictly anoxic conditions from ground rock material and compared with DOM of in situ pore water samples. For the extractions, deionized water, synthetic pore water (SPW, water containing all major ions at pore water concentrations but no organic matter) and 0.1 M NaOH were used. The influence of the solid-to-liquid ratio, extraction time, acid -pretreatment and O2 exposure of the rock material on the isolated DOM were investigated. Liquid chromatography coupled with a total organic C detector (LC-OCD) and reverse-phase ion chromatography were used to characterize the DOM size distributions and to determine the low molecular weight organic acid (LMWOA) contents in the pore water samples and the rock extracts.
The results revealed that only a small portion of the total organic C of the rock material (<0.38%) was extractable, even after removal of carbonates by acid-pretreatment. The concentrations of dissolved organic C (DOC) were found to range from 3.9 ± 0.4 to 8.0 ± 0.8 mg/L in the anoxic extracts. The pore waters exhibited similar DOC concentrations ranging from 1.2 to 15.8 ± 0.5 mg/L. The analysis by LC-OCD showed that the DOM extracted under anoxic conditions and the pore water DOM mainly consisted of hydrophilic compounds of less than 500 Da. The DOM extracted with SPW was most similar in size to the pore water DOM. Grinding the rock under oxic conditions increased the DOC yields and shifted the size distribution toward higher molecular weight compounds compared to the strictly anoxic treatment. Acetate, lactate and formate were identified in all extracts and in the pore water. In total, LMWOA accounted for 36% of the total DOC in both pore water and SPW extracts. The results imply that controlled anoxic conditions and the use of SPW as an extractant are required to isolate DOM from Opalinus Clay rocks which most resembles the in situ pore water DOM with respect to its size distribution and the LMWOA contents.
Courdouan, A., Christl, I., Meylan, S., Wersin, P., & Kretzschmar, R. (2007). Isolation and characterization of dissolved organic matter from the Callovo–Oxfordian formation. Applied Geochemistry, 22(7), 1537-1548. doi:10.1016/j.apgeochem.2007.04.001, Institutional Repository

Characterizing dissolved organic matter (DOM) in the pore water of the Callovo-Oxfordian formation, a potential host rock for the disposal of radioactive waste, is important to estimate its potential influence on the mobility of radionuclides in the rock. To isolate DOM, crushed rock material was extracted under anoxic conditions with deionized water, 0.1 M NaOH and synthetic pore water (SPW, water containing all major ions at pore water concentrations but no organic matter), respectively. The effects of extraction parameters on the extracted DOM including the solid-to-liquid ratio, extraction time, exposure to O2 and acid pretreatment of the rock material prior to the anoxic extraction were evaluated. In addition, DOM in one of the first pore water samples collected in the underground rock laboratory at Bure (France) was characterized for comparison. The size distribution and the low molecular weight organic acid contents of the extracts and pore water DOM were determined by liquid chromatography coupled with an organic C detector (LC-OCD) and by ion chromatography. The results revealed that only a fraction of less than 1.2% of the total organic C present in the rock was extractable. Maximum dissolved organic C (DOC) concentrations in the anoxic extracts ranged from 5.5 ± 0.3 mg/L for SPW extracts to 14.2 ± 1.1 mg/L for 0.1 M NaOH extracts. The major portion of the DOC in the anoxic extracts consisted of hydrophilic compounds (48–78%) having a molecular weight of less than 500 Da. Up to 21% of DOC in the anoxic extracts was identified as acetate, formate, lactate and malate. The short-term exposure of rock material to O2 during rock crushing strongly increased DOC concentrations and led to a shift towards smaller molecular weight compounds and to a higher low molecular weight organic acid (LMWOA) content as compared to the strictly anoxic extraction. The pore water sampled from a packed-off borehole exhibited a higher DOC concentration (56.7 mg/L) than the rock extracts. The pore water DOM was almost exclusively composed of acetate and propionate (88% of the DOC). The predominance of LMWOA in the pore water compared to the anoxic extracts may arise from the heterogeneity of the rock material, a more effective DOM filtration by the rock formation compared to laboratory extractions, or possibly, bacterial activity in the pore water induced by the borehole disturbance.
Fierz, M., Kaegi, R., & Burtscher, H. (2007). Theoretical and experimental evaluation of a portable electrostatic TEM sampler. Aerosol Science and Technology, 41(5), 520-528. doi:10.1080/02786820701253327, Institutional Repository

In this study, we present the design, calibration, and performance evaluation of a portable TEM sampler to collect ultrafine particles on TEM grids. The sampler is based on electrostatic deposition. We performed calibration experiments with monodisperse model particles of different size, morphology, and chemistry to evaluate the efficiency of the device. Additionally, we modeled the performance of the TEM sampler using finite element calculations to calculate the sampling efficiency as function of particle size. We find a good agreement between the model calculations and calibration experiments, but with a systematic deviation of about 30%. We present further experiments with polydisperse particles and derive particle size distributions and absolute number concentrations from TEM images. The shape of the size distribution is very similar to the corresponding SMPS measurements, while the total number concentration has a larger uncertainty. Thanks to the compact design of the sampler, it can be used to collect ultrafine particles even in remote or hostile environments, where no electric power is available.
Hammes, F., Meylan, S., Salhi, E., Köster, O., Egli, T., & von Gunten, U. (2007). Formation of assimilable organic carbon (AOC) and specific natural organic matter (NOM) fractions during ozonation of phytoplankton. Water Research, 41(7), 1447-1454. doi:10.1016/j.watres.2007.01.001, Institutional Repository

Ozonation of natural surface water increases the concentration of oxygen-containing low molecular weight compounds. Many of these compounds support microbiological growth and as such are termed assimilable organic carbon (AOC). Phytoplankton can contribute substantially to the organic carbon load when surface water is used as source for drinking water treatment. We have investigated dissolved organic carbon (DOC) formation from the ozonation of a pure culture of Scenedesmus vacuolatus under defined laboratory conditions, using a combination of DOC fractionation, analysis of selected organic acids, aldehydes and ketones, and an AOC bioassay. Ozonation of algae caused a substantial increase in the concentration of DOC and AOC, notably nearly instantaneously upon exposure to ozone. As a result of ozone exposure the algal cells shrunk, without disintegrating entirely, suggesting that DOC from the cell cytoplasm leaked through compromised cell membranes. We have further illustrated that the specific composition of newly formed AOC (as concentration of organic acids, aldehydes and ketones) in ozonated lake water differed in the presence and absence of additional algal biomass. It is therefore conceivable that strategies for the removal of phytoplankton before pre-ozonation should be considered during the design of drinking water treatment installations, particularly when surface water is used.
Jermann, D., Pronk, W., Meylan, S., & Boller, M. (2007). Interplay of different NOM fouling mechanisms during ultrafiltration for drinking water production. Water Research, 41(8), 1713-1722. doi:10.1016/j.watres.2006.12.030, Institutional Repository

Ultrafiltration is an emerging technology for drinking water production, but a main challenge remains the lack of understanding about fouling. This paper investigates the impact of molecular interactions between different natural organic matter (NOM) compounds on ultrafiltration fouling mechanisms. We performed dead-end filtration experiments with individual and mixed humic acid and alginate (polysaccharide). Alginate showed detrimental, but mostly reversible, flux decline and high solute retention. Our results indicate that this was caused by pore blocking transformed into cake building and weak molecular foulant-membrane and foulant-foulant interactions. In the presence of calcium, aggravated fouling was observed, related to complexation of alginate and its subsequently induced gel formation. With humic acid, more severe irreversible fouling occurred due to humic acid adsorption. Minor adsorption of alginate onto the membrane was also observed, which probably caused the substantial irreversible flux decline. The fouling characteristics in the mixtures reflected a combination of the individual humic acid and alginate experiments and we conclude, that the individual fouling mechanisms mutually influence each other. A model elucidates this interplay of the individual fouling mechanisms via hydrophobic and electrostatic interactions. In our study such an interplay resulted in an alginate cake, or gel in the presence of calcium, which is relatively irreversibly adsorbed onto the membrane by humic acid associations. This study shows the importance of mutual influences between various foulants for improved understanding of fouling phenomena. Furthermore it shows that substances with a minor individual influence might have a large impact in mixed systems such as natural water.
Larsen, T. A., Maurer, M., Udert, K. M., & Lienert, J. (2007). Nutrient cycles and resource management: implications for the choice of wastewater treatment technology. Water Science and Technology, 56(5), 229-237. doi:10.2166/wst.2007.576, Institutional Repository

We look at the most important issues of the global nitrogen and phosphorus cycle and conclude that the nutrients from human metabolism are of no importance for the global nitrogen cycle and of minor importance for the global phosphorus cycle. However, for water pollution control, N and P from the human metabolism are of extreme importance. Nitrogen is mainly an issue for coastal waters, whereas P is an issue for freshwater and coastal areas alike. It is by now generally recognised that coastal ecosystems are exceedingly important for human well-being and at the same time highly endangered. The recycling issue is of high importance in areas where nutrient application is low due to economic constraints. NoMix technology (urine source separation) holds a large promise to become an efficient mainstream technology. The largest short-term potential is found in densely populated areas in coastal areas without existing infrastructure and in areas with nutrient deficiency, especially in urban areas with a large nutrient potential. We believe, however, that these technologies will, with time, also become competitive in Europe.
Lienert, J., Bürki, T., & Escher, B. I. (2007). Reducing micropollutants with source control: substance flow analysis of 212 pharmaceuticals in faeces and urine. Water Science and Technology, 56(5), 87-96. doi:10.2166/wst.2007.560, Institutional Repository

Pharmaceuticals in the aquatic environment are raising concern. It is expected that many anthropogenic pharmaceuticals are largely excreted via urine; a popular argument for introducing urine source separation. However, to date, this assumption lacks verification. We close this gap with quantitative screening of official pharmaceutical data. We analysed the excretion pathways of 212 pharmaceuticals' active ingredients (Al), equalling 1,409 products. On average, 64% (± 27%) of each Al was excreted via urine, and 35% (± 26%) via faeces. In urine, 42% (± 28%) of each Al was excreted as metabolites. However, these numbers need cautious interpretation. We found an extreme variability (1) between different therapeutic groups, (2) within some groups and (3) sometimes even between products of the same Al. We discuss various therapeutic groups and include Swiss sales' quantities. For instance, urine source separation could very effectively remove the highly sold and non-degradable x-ray contrast media: 94% (± 4%) are excreted via urine. However, for different pharmaceuticals belonging to cytostatics, excretion via urine was 6-98%. Because of such large variability we advise caution to introduce the still imperfect urine separation technology solely because of pharmaceuticals. Nonetheless, together with other good arguments for this innovation, removal of pharmaceuticals is a welcome side effect.
Lienert, J., Güdel, K., & Escher, B. I. (2007). Screening method for ecotoxicological hazard assessment of 42 pharmaceuticals considering human metabolism and excretory routes. Environmental Science and Technology, 41(12), 4471-4478. doi:10.1021/es0627693, Institutional Repository

We assessed the ecotoxicological hazard potential of 42 pharmaceuticals from 22 therapeutic groups, including metabolites formed in humans. We treated each parent drug and its metabolites as a mixture of similarly acting compounds. If physicochemical or effect literature data were missing, we estimated these with quantitative structure-activity relationships (QSAR). Additionally, we estimated micropollutant removal efficiency of urine source separation using pharmaceutical information. On average, 50% of a parent drug was metabolized, and 70% was excreted with urine, albeit with large variations among drugs. Metabolism reduced the toxic potential of all but eight drugs. The subsequently modeled risk quotient was mostly below the threshold of one. However, ibuprofen and its metabolites in a mixture could pose an ecotoxicologal risk; and possibly also acetylsalicylic acid, bezafibrate, carbamazepine, diclofenac, fenofibrate, and paracetamol. Lipophilicity and sale quantities of parent drugs alone were insufficient to estimate their ecotoxicological risk. Urine separation could decrease the ecotoxicological risk of some, but not all drugs. The estimated risk quotients were equal in urine and feces, again with large variations among compounds. Because of scientific limitations of the model and inconsistent literature data the results are somewhat uncertain. However, this new approach allows first tier screening of single drugs, thus supporting decision-making.
Lienert, J., & Larsen, T. A. (2007). Soft paths in wastewater management – the pros and cons of urine source separation. GAIA: Ecological Perspectives for Science and Society, 16(4), 280-288. doi:10.14512/gaia.16.4.10, Institutional Repository

Although our water-borne urban wastewater system is successful, it has drawbacks in industrialized and developing countries alike, particularly in arid regions. It is inflexible and often inefficient. Of late, source control measures are being postulated as a paradigm change. In the Swiss transdisciplinary project Novaquatis, urine source separation, or NoMix technology, was studied. We compare NoMix technology with central wastewater treatment. Separate collection of urine has the potential to eliminate 70 to 80 percent of nitrogen from wastewater, 15 to 50 percent of phosphorus, and at least 50 percent of human pharmaceuticals. Hence, NoMix technology can contribute substantially in the reduction of eutrophication of marine ecosystems near fast-growing cities. We discuss the shortcomings of using sewage sludge or urine as fertilizers in agriculture – concerning pharmaceuticals, we also consider the societal perspective. Furthermore, NoMix technology introduces flexibility to wastewater management, important especially in light of growing uncertainties with respect to population development and climate change.
Lorenzo, R., Kaegi, R., Gehrig, R., Scherrer, L., Grobéty, B., & Burtscher, H. (2007). A thermophoretic precipitator for the representative collection of atmospheric ultrafine particles for microscopic analysis. Aerosol Science and Technology, 41(10), 934-943. doi:10.1080/02786820701581834, Institutional Repository

In this article, the potential of a thermophoretic sampling device to derive quantitative particle size distributions and number concentrations of aerosols based on microscopic single particle analysis is explored. For that purpose a plate-to-plate thermophoretic precipitator to collect ultrafine atmospheric particles for TEM (transmission electron microscopy) analysis has been calibrated and characterized. The representativeness of the samples has been verified in a series of experiments. Results show that, for particles with diameters of 15 nm to 300 nm, the precipitator's collection efficiency is independent of size, shape, and composition of the particles. Hence, its samples accurately represent the original aerosol. A numerical model of thermophoretic deposition within the device has been developed and tailored to the specifications of the precipitator. The model has been used to derive the particle number density and size distribution of several calibration aerosols using the TEM analysis of the samples taken with the thermophoretic precipitator as input parameters. The results agree very well with the on-line measurements of the calibration aerosols. This work demonstrates that our thermophoretic sampling device can be used to derive quantitative particle size distributions and number concentrations of ultrafine particles based on microscopic single particle analysis.
Maurer, M., Escher, B. I., Richle, P., Schaffner, C., & Alder, A. C. (2007). Elimination of β-blockers in sewage treatment plants. Water Research, 41(7), 1614-1622. doi:10.1016/j.watres.2007.01.004, Institutional Repository

β-Blockers are used to treat high blood pressure as well as patients recovering from heart attacks. In several studies, they were detected in surface water, thus indicating incomplete degradability of these substances in sewage treatment plants (STPs). In this study, we determined the sorption coefficients (KD) and degradation rates of the four β-blockers sotalol, atenolol, metoprolol and propranolol in sludge from an STP operating with municipal wastewater.
The sorption coefficients (KD, standard deviations in brackets) were determined as 0.04(+/-0.035), 0.04(+/-0.033), 0.00(+/-0.023) and 0.32(+/-0.058) L g-1COD, and the pseudo-first-order degradation rate constants were estimated to be 0.29(+/-0.02), 0.69(+/-0.05), 0.58(+/-0.05) and 0.39(+/-0.07) L d-1 g-1COD for sotalol, atenolol, metoprolol and propranolol, respectively.
These values translate into a typical elimination in STPs (sludge concentrations of 4 gCOD L-1 and a hydraulic retention time of 6 h) of 25%, 37%, 44% and 50% for sotalol, propranolol, metoprolol and atenolol, respectively. These results are also confirmed by measurements in two municipal STPs for atenolol, sotalol and propranolol. The estimated eliminations are slightly too high for metoprolol.
Medilanski, E., Chuan, L., Mosler, H. J., Schertenleib, R., & Larsen, T. A. (2007). Identifying the institutional decision process to introduce decentralized sanitation in the city of Kunming (China). Environmental Management, 39(5), 648-662. doi:10.1007/s00267-005-0321-0, Institutional Repository

We conducted a study of the institutional barriers to introducing urine source separation in the urban area of Kunming, China. On the basis of a stakeholder analysis, we constructed stakeholder diagrams showing the relative importance of decision-making power and (positive) interest in the topic. A hypothetical decision-making process for the urban case was derived based on a successful pilot project in a periurban area. All our results were evaluated by the stakeholders. We concluded that although a number of primary stakeholders have a large interest in testing urine source separation also in an urban context, most of the key stakeholders would be reluctant to this idea. However, the success in the periurban area showed that even a single, well-received pilot project can trigger the process of broad dissemination of new technologies. Whereas the institutional setting for such a pilot project is favorable in Kunming, a major challenge will be to adapt the technology to the demands of an urban population. Methodologically, we developed an approach to corroborate a stakeholder analysis with the perception of the stakeholders themselves. This is important not only in order to validate the analysis but also to bridge the theoretical gap between stakeholder analysis and stakeholder involvement. We also show that in disagreement with the assumption of most policy theories, local stakeholders consider informal decision pathways to be of great importance in actual policy-making.
Meylan, S., Hammes, F., Traber, J., Salhi, E., von Gunten, U., & Pronk, W. (2007). Permeability of low molecular weight organics through nanofiltration membranes. Water Research, 41(17), 3968-3976. doi:10.1016/j.watres.2007.05.031, Institutional Repository

The removal of natural organic matter (NOM) using nanofiltration (NF) is increasingly becoming an option for drinking water treatment. Low molecular weight (LMW) organic compounds are nevertheless only partially retained by such membranes. Bacterial regrowth and biofilm formation in the drinking water distribution system is favoured by the presence of such compounds, which in this context are considered as the assimilable organic carbon (AOC). In this study, the question of whether NF produces microbiologically stable water was addressed. Two NF membranes (cut-off of about 300 Da) were tested with different natural and synthetic water samples in a cross-flow filtration unit. NOM was characterised by liquid chromatography with organic carbon detection (LC-OCD) using a size-exclusion column in addition to specific organic acid measurements, while AOC was measured in a batch growth bioassay.
Similarly to high molecular weight organic compounds like polysaccharides or humic substances that have a permeability lower than 1%, charged LMW organic compounds were efficiently retained by the NF membranes tested and showed a permeability lower than 3%. However, LMW neutrals and hydrophobic organic compounds permeate to a higher extent through the membranes and have a permeability of up to 6% and 12%, respectively. Furthermore, AOC was poorly retained by NF and the apparent AOC concentration measured in the permeated water was above the proposed limit for microbiologically stable water. This indicates that the drinking water produced by NF might be biologically unstable in the distribution system. Nevertheless, in comparison with the raw water, NF significantly reduced the AOC concentration.
Pronk, W., Zuleeg, S., Lienert, J., Escher, B., Koller, M., Berner, A., … Boller, M. (2007). Pilot experiments with electrodialysis and ozonation for the production of a fertiliser from urine. Water Science and Technology, 56(5), 219-227. doi:10.2166/wst.2007.575, Institutional Repository

Pilot tests were performed with a process combination of electrodialysis and ozonation for the removal of micropollutants and the concentration of nutrients in urine. In continuous and batch experiments, maximum concentration factors up to 3.5 and 4.1 were obtained, respectively. The desalination capacity did not decrease significantly during continuous operation periods of several weeks. Membrane cleaning after 195 days resulted in approximately 35% increase in desalination rate. The Yeast Estrogen Screen (YES), a bioassay that selectively detects oestrogenic compounds, confirmed that about 90% of the oestrogenic activity was removed by electrodialysis. HPLC analysis showed that ibuprofen was removed to a high extent, while other micropollutants were below the detection limit. In view of the fact that ibuprofen is among the most rapidly transported micropollutants in electrodialysis processes, this result indicates that electrodialysis provides an effective barrier for micropollutants. Standardised plant growth tests were performed in the field with the salt solution resulting from the treatment by electrodialysis and subsequent ozonation. The results show that the plant height is comparable to synthetic fertilisers, but the crop yield is slightly lower. The latter is probably caused by volatilisation losses during field application, which can be prevented by improved application technologies.
Ronteltap, M., Maurer, M., & Gujer, W. (2007). Struvite precipitation thermodynamics in source-separated urine. Water Research, 41(5), 977-984. doi:10.1016/j.watres.2006.11.046, Institutional Repository

Struvite (MgNH4PO4·6H2O) precipitation eliminates phosphate efficiently from urine, a small but highly concentrated stream in the total flux of domestic wastewater. Precipitation experiments with hydrolysed urine evaluated the solubility product of struvite. The stored and fully hydrolysed urine had an ionic strength of between 0.33 and 0.56 M and required the estimation of activity coefficients. From our data, we identified the Davies approximation with the two constants A=0.509 and B=0.3 as agreeing best with our laboratory results. The standard solubility product Ks0=f1[NH4+]f2[Mg2+]f3[PO43−] ([ ]=concentration of the species; fx=corresponding activity coefficient) of struvite in urine was found to be 10−13.26±0.057 at 25 °C and the enthalpy of struvite formation ΔH was 22.6(±1.1) kJ mol−1. The equilibrium calculations required the following dissolved complexes: [MgCO3]aq, [MgHCO3]+, [MgPO4]−, [NH4HPO4]−, and [NaHPO4]− and to a lesser extent [MgSO4]aq and [NH4SO4]−. Organic complexes do not seem to influence the solubility product substantially.
For practical purposes, a conditional solubility product Kscond=[Mgaq]·[NH4++NH3]·[Portho]=10−7.57 M3 was derived to calculate struvite solubility in urine at 25 °C, pH=9.0 and ionic strength I=0.4 M directly from measured concentrations.
Ronteltap, M., Maurer, M., & Gujer, W. (2007). The behaviour of pharmaceuticals and heavy metals during struvite precipitation in urine. Water Research, 41(9), 1859-1868. doi:10.1016/j.watres.2007.01.026, Institutional Repository

Separating urine from wastewater at the source reduces the costs of extensive wastewater treatment. Recovering the nutrients from urine and reusing them for agricultural purposes adds resource saving to the benefits. Phosphate can be recovered in the form of struvite (magnesium ammonium phosphate). In this paper, the behaviour of pharmaceuticals and heavy metals during the precipitation of struvite in urine is studied.
When precipitating struvite in urine spiked with hormones and non-ionic, acidic and basic pharmaceuticals, the hormones and pharmaceuticals remain in solution for more than 98%.
For heavy metals, initial experiments were performed to study metal solubility in urine. Solubility is shown to be affected by the chemical conditions of stored and therefore hydrolysed urine. Thermodynamic modelling reveals low or very low equilibrium solute concentrations for cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), nickel (Ni) and lead (Pb). Experiments confirmed Cd, Cu and Pb carbonate and hydroxide precipitation upon metal addition in stored urine with a reaction half-life of ca. 7 days.
For all metals considered, the maximum specific metal concentrations per gram phosphate or nitrogen showed to be typically several orders of magnitudes lower in urine than in commercially available fertilizers and manure. Heavy metals in struvite precipitated from normal stored urine could not be detected.
Phosphate recovery from urine over struvite precipitation is shown to render a product free from most organic micropollutants and containing only a fraction of the already low amounts of heavy metals in urine.
Steiner, M., Boller, M., Schulz, T., & Pronk, W. (2007). Modelling heavy metal fluxes from traffic into the environment. Journal of Environmental Monitoring, 9(8), 847-854. doi:10.1039/b703509h, Institutional Repository

A new method is presented which allows emissions of traffic into the environment to be described as a function of road distance. The method distinguishes different types of emissions (runoff, spray and drift), which are determined by measurements and mass balances of a specified road section. The measurement of two-dimensional pollutant concentrations in the road shoulder is an important part of the method. In a case study performed at Burgdorf, Switzerland, the method was applied to the determination of the spatial distribution of heavy metal emissions. The results show that between 36 and 65% of the heavy metals Cd, Cr, Cu, Pb and Zn are present in runoff and spray and between 35 and 64% are dispersed diffusely in the environment (defined as drift). The runoff infiltrates into the vegetated road shoulder up to a distance of approx. 1 m from the road. The distribution of spray shows a maximum at 1 m and decreases steadily up to a distance of 5 m. This information can serve as a basis for the quantitative evaluation of road-runoff treatment scenarios. Although the results of the Burgdorf study are case-specific, several general guidelines for the reduction of traffic-related emissions can be derived from it.
Velten, S., Hammes, F., Boller, M., & Egli, T. (2007). Rapid and direct estimation of active biomass on granular activated carbon through adenosine tri-phosphate (ATP) determination. Water Research, 41(9), 1973-1983. doi:10.1016/j.watres.2007.01.021, Institutional Repository

Granular activated carbon (GAC) filtration is used during drinking water treatment for the removal of micropollutants such as taste and odour compounds, halogenated hydrocarbons, pesticides and pharmaceuticals. In addition, the active microbial biomass established on GAC is responsible for the removal of biodegradable dissolved organic carbon compounds present in water or formed during oxidation (e.g., ozonation and chlorination) processes. In order to conduct correct kinetic evaluations of DOC removal during drinking water treatment, and to assess the state and performance of full-scale GAC filter installations, an accurate and sensitive method for active biomass determination on GAC is required. We have developed a straight-forward method based on direct measurement of the total adenosine tri-phosphate (ATP) content of a GAC sample and other support media. In this method, we have combined flow-cytometric absolute cell counting and ATP analysis to derive case-specific ATP/cell conversion values. In this study, we present the detailed standardisation of the ATP method. An uncertainty assessment has shown that heterogeneous colonisation of the GAC particles makes the largest contribution to the combined standard uncertainty of the method. The method was applied for the investigation of biofilm formation during the start-up period of a GAC pilot-scale plant treating Lake Zurich water. A rapid increase in the biomass of up to 1.1×1010 cells/g GAC dry weight (DW) within the first 33 days was observed, followed by a slight decrease to an average steady-state concentration of 7.9×109 cells/g GAC DW. It was shown that the method can be used to determine the biomass attached to the GAC for both stable and developing biofilms.
Aryal, R. K., Furumai, H., Nakajima, F., & Boller, M. (2006). Characteristics of particle-associated PAHs in a first flush of a highway runoff. Water Science and Technology, 53(2), 245-251. doi:10.2166/wst.2006.058, Institutional Repository

Runoff monitoring of six rainfall events was carried out in a highway, Winterthur, Switzerland focusing on first flush (runoff volume up to 2.88 mm). Six runoff events were used to investigate the characteristics of particle-associated PAHs in first flush. The fine fraction (<45 μm) had a relatively higher contribution than the coarse fraction. A significant contribution of the coarse fraction was observed at some periods when the runoff flow rapidly increased. Fluctuation of PAH content during a runoff event was significant in the coarse fraction and, in contrast, the PAH content in the fine fraction was less fluctuating. The weighted average PAH content in each event ranged from 17 to 62 μg/g in total SS, from 23 to 54 μg/g in the fine fraction and from 16 to 84 μg/g in the coarse fraction. The loading of particle-associated PAHs from the first flush of highway runoff ranged from 0.06 to 0.22 g/ha in a total of 12 PAH species.
Brändli, R. C., Bucheli, T. D., Kupper, T., Stadelmann, F. X., & Tarradellas, J. (2006). Optimised accelerated solvent extraction of PCBs and PAHs from compost. International Journal of Environmental Analytical Chemistry, 86(7), 505-525. doi:10.1080/03067310500410839, Institutional Repository

This study is the first thorough method optimisation for accelerated solvent extraction (ASE) of polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) from chemically dried compost. For PCBs, optimised solvent composition, temperature, pressure, number of static cycles, duration, and flush volume were as follows: toluene/ acetone 1:3 (v/v), 120 degrees C, 2000 psi, 3 x 5 min, and 50%, respectively. Limits of quantification and method precision were between 0.16 and 2.46 μg kg-1 dw and 6 - 17% respectively for individual PCBs. Absolute recoveries of isotope- labelled extraction standards used for each of the analytes ranged from 65 to 105% and relative recoveries were between 85 and 99%. The method proofed to be robust and was successfully applied to different compost samples.
The optimisation of PAHs extraction was performed and resulted in the following conditions: solvent: hexane/acetone 1/3 (v:v), temperature: 140°C, pressure: 1500 psi, extraction time: 3 x 5 min, and 50% flush volume. Limits of detection and method precision for individual PAHs were between 1.1 and 37.2 μg kg-1 dw and 12 - 34% respectively. Absolute and relative recoveries ranged from 24 to 68% and from 85 to 99%, respectively. Optimal extraction conditions for PAHs were more difficult to determine due to the inhomogeneous distribution of PAHs in samples. However, the method appeared to be feasible and suggestions for further improvements are presented.
Escher, B. I., Bramaz, N., Richter, M., & Lienert, J. (2006). Comparative ecotoxicological hazard assessment of beta-blockers and their human metabolites using a mode-of-action-based test battery and a QSAR approach. Environmental Science and Technology, 40(23), 7402-7408. doi:10.1021/es052572v, Institutional Repository

We analyzed nontarget effects of the β-blockers propranolol, metoprolol, and atenolol with a screening test battery encompassing nonspecific, receptor-mediated, and reactive modes of toxic action. All β-blockers were baseline toxicants and showed no specific effects on energy transduction nor endocrine activity in the yeast estrogen and androgen screen, and no reactive toxicity toward proteins and DNA. However, in a phytotoxicity assay based on the inhibition of the photosynthesis efficiency in green algae, all β-blockers were 10 times more toxic than their modeled baseline toxicity. Baseline- and phytotoxicity effects increased with hydrophobicity. The β-blockers showed concentration addition in mixture experiments, indicating a mutual specific nontarget effect on algae. Using literature data and quantitative structure-activity relationships (QSAR), we modeled the total toxic potential of mixtures of the β-blockers and their associated human metabolites for the phytotoxicity endpoint with two scenarios. The realistic scenario (I) assumes that the metabolites lose their specific activity and act as baseline toxicants. In the worst-case scenario (II) the metabolites exhibit the same specific mode of action as their parent drug. For scenario (II), metabolism hardly affected the overall toxicity of atenolol and metoprolol, whereas propranolol's hazard potential decreased significantly. In scenario (I), metabolism reduced the apparent EC50 of the mixture of parent drug and metabolite even further. The proposed method is a simple approach to initial hazard assessment of pharmaceuticals and can guide higher tier testing. It can be applied to other classes of pollutants, e.g., biocides, as well as to environmental transformation products of pollutants.
Escher, B. I., Pronk, W., Suter, M. J. F., & Maurer, M. (2006). Monitoring the removal efficiency of pharmaceuticals and hormones in different treatment processes of source-separated urine with bioassays. Environmental Science and Technology, 40(16), 5095-5101. doi:10.1021/es060598w, Institutional Repository

Urine can be collected separately from the general wastewater with the aim of recycling the nutrients. Urine source-separation not only prevents wasting nutrients but also prevents potentially hazardous micropollutants from entering the wastewater stream and tainting a final fertilizer product. We assessed various urine treatment technologies for their performance to remove micropollutants such as pharmaceuticals, natural and synthetic steroid hormones, and their human biotransformation products. Removal efficiencies were determined with a combination of bioassays and chemical target analysis. The yeast estrogen screen yielded information on estrogenicity. Specific phytotoxicity and nonspecific baseline toxicity was determined with an algae chlorophyll fluorescence test. Filtration methods, such as nanofiltration and electrodialysis, were highly efficient with respect to toxicity reduction. Micropollutant degradation during biological treatment in a sequencing batch reactor was very compound specific. Ozonation removed the target analytes and the estrogenicity completely, but the baseline toxicity was only reduced by 50-60% depending on the ozone doses. Struvite precipitation produced a very "clean" fertilizer product that is ready to use. The examples show that bioassays and chemical analysis yield complementary information, but are very useful to monitor treatment efficiencies and to assess the ecotoxicological potential of byproducts of urine treatment processes. The results of this study present a method to assess the micropollutant removal efficiency, and therefore, support the choice of an appropriate urine processing technique for real-world applications.
Hug, T., Gujer, W., & Siegrist, H. (2006). Modelling seasonal dynamics of "Microthrix parvicella". Water Science and Technology, 54(1), 189-198. doi:10.2166/wst.2006.387, Institutional Repository

The filamentous bacteria "Microthrix parvicella" can cause serious bulking and scumming in wastewater treatment plants (WWTPs) all over the world. Decades of research have identified Microthrix as a specialized lipid consumer but could not clarify the processes that allow this organism to successfully compete in activated sludge systems. In this study we developed a model, based on ASM3, that describes the pronounced seasonal variations of Microthrix abundance observed in a full-scale WWTP. We hypothesize that low temperatures reduce the solubility of lipids and inhibit their uptake by non-specialized bacteria. The presented model structure and parameters successfully fit the measured data; however they do not necessarily reflect the only and true selection mechanism for Microthrix. This model is not yet to be used for prediction; it is rather a valuable research tool to coordinate the discussion and plan future research activities in order to identify the relevant selection mechanisms favoring Microthrix in activated sludge systems.
Lacqua, A., Wanner, O., Colangelo, T., Martinotti, M. G., & Landini, P. (2006). Emergence of biofilm-forming subpopulations upon exposure of Escherichia coli to environmental bactriophages. Applied and Environmental Microbiology, 72(1), 956-959. doi:10.1128/AEM.72.1.956-959.2006, Institutional Repository

Exposure of Escherichia coli MG1655 to environmental bacteriophages results in rapid selection for phage-tolerant subpopulations displaying increased biofilm formation. Analysis of one phage-tolerant strain revealed large amounts of the DNA-binding Dps protein in the outer membrane protein and production of fimbria-like structures. In dps and fimA mutant derivatives of MG1655, no selection of phage-tolerant bacteria upon exposure to bacteriophages occurred, suggesting a role for Dps and type I pili in bacteriophage tolerance.
Lienert, J., & Larsen, T. A. (2006). Considering user attitude in early development of environmentally friendly technology: a case study of NoMix toilets. Environmental Science and Technology, 40(16), 4838-4844. doi:10.1021/es060075o, Institutional Repository

Urine source separation (NoMix technology) has been proposed as a sustainable alternative to centralized wastewater treatment systems. Radical changes necessitate an early inclusion of sociological expertise, thus offering a real chance for transdisciplinary collaboration. The practical aim of our survey is to find out how users accept and use existing NoMix toilets and how this could be encouraged. We collected 1249 questionnaires from 2002 to 2004 in one Swiss school and one Swiss research institute. The technological immaturity of NoMix toilets was noted by many. Nevertheless, acceptance was high: 72% liked the idea and 86% would move into apartments with NoMix toilets. Moreover, most users found that NoMix toilets equal conventional toilets with respect to design (78%), hygiene (84%), and smell (78%). Like many other innovations, the NoMix technology only functions properly if it is used adequately, which we demonstrate for water saving and sitting to urinate. Many users adopted this behavior, e. g., 72% sat. Because perception and use of NoMix toilets is subjective, it can be influenced with certain measures such as good information and cleaning, or discussions with peers. We discuss the importance of social psychology for understanding the factors that influence the acceptance of environmentally friendly innovations.
Lienert, J., Monstadt, J., & Truffer, B. (2006). Future scenarios for a sustainable water sector: a case study from Switzerland. Environmental Science and Technology, 40(2), 436-442. doi:10.1021/es0514139, Institutional Repository

Uncertainties about the long-term prospects of urban water management systems have increased substantially over the past decade due to an increasing variety of regulations, technologies, and demand structures. In Switzerland, this uncertainty is mirrored by growing difficulties of utility managers and (waste)water scientists to agree on shared strategies: Water professionals demand support for pressing management problems, while researchers fundamentally question the longer-term sustainability of the established water management system. To reestablish shared orientation, we conducted a foresight study for the Swiss (waste)water sector in 2004. Based on interviews with 29 experts from Swiss water management and research to collect 56 drivers of change, a team of 17 experts developed three scenarios: (A) regional mergers of water utilities leading to enhanced professionalism in the sector, (B) consequent material flows management leading to a radically restructured urban water management system, and (C) generalized financial crisis leading to a breakdown of centralized utility services. These scenarios helped identifying shared research priorities. We conclude that scenario analysis is a powerful tool for framing long-term strategies, defining priorities, and integrating different interests in the multidisciplinary contexts of sustainability science, which are marked by high uncertainties and concern a wide range of stakeholder groups.
Lienert, J., Thiemann, K., Kaufmann-Hayoz, R., & Larsen, T. A. (2006). Young users accept NoMix toilets – a questionnaire survey on urine source separating toilets in a college in Switzerland. Water Science and Technology, 54(11-12), 403-412. doi:10.2166/wst.2006.920, Institutional Repository

We studied user behavior and acceptance of NoMix toilets by collecting 271 questionnaires from young adults. We discriminated between short- and long-term users (months of habituation). Most respondents noticed that the NoMix toilet is different. Nevertheless, the existing NoMix technology was well accepted regarding design, hygiene and smell in this institutional setting. Only few respondents changed their sitting or flushing behavior. The necessity to sit when urinating might be slightly problematic (62% sit), but it seems possible that people adopt this new behavior required by the NoMix toilet. General acceptance of the NoMix toilet was high: 70% of respondents found the idea convincing – many for environmental reasons – 87% were willing to move into an apartment with a NoMix toilet, and 20% would pay substantially more for a NoMix toilet. We informed about the NoMix toilet with instructions for use in the toilet cabin, an information poster, and an information leaflet that we distributed after questioning. Our information was noted by most respondents and significantly increased the knowledge about and the acceptance of the NoMix toilet. We recommend that future pilot projects with NoMix toilets consider a well devised information policy to support decision making and acceptance of this new technology.
Maurer, M., Rothenberger, D., & Larsen, T. A. (2006). Decentralised wastewater treatment technologies from a national perspective: At what cost are they competitive?. Water Science and Technology: Water Supply, 5(6), 145-154. doi:10.2166/ws.2005.0059, Institutional Repository

In this paper we estimate at what cost decentralised wastewater treatment can be competitive compared with conventional centralised technologies. For the current wastewater infrastructure in Western Europe and North America, typical replacement costs are 2,600 US$/cap for large countries and 4,800 US$/cap for small ones. In the same literature, average annual operating costs are reported to be 3.8% of replacement costs. However, if a long-term interest rate of 3% is consistently applied, this value increases to 4.7% for small countries and 5.5% for large ones. Assuming that alternative wastewater systems will only be accepted if their costs are similar to existing ones, the possible investments for alternative wastewater treatment technologies are calculated. Between 640 and 2,170 US$/cap can be invested in new technologies for scenarios without a sewer system. The corresponding figures for scenarios with sewer systems are between 260 and 680 US$/cap. Acceptable maintenance requirements are calculated on the basis of unit size. Transition periods are not accounted for.
Maurer, M., Pronk, W., & Larsen, T. A. (2006). Treatment processes for source-separated urine. Water Research, 40(17), 3151-3166. doi:10.1016/j.watres.2006.07.012, Institutional Repository

The separate collection and treatment of urine has attracted considerable attention in the engineering community in the last few years and is seen as a viable option for enhancing the flexibility of wastewater treatment systems. This comprehensive review focuses on the status of current urine treatment processes and summarises the properties of collected urine. We distinguish between seven main purposes of urine-treatment processes: hygienisation (storage), volume reduction (evaporation, freeze-thaw, reverse osmosis), stabilisation (acidification, nitrification), P-recovery (struvite formation), N-recovery (ion treatment exchange, ammonia stripping, isobutylaldehyde-diurea (IBDU) precipitation), nutrient removal (anammox) and handling of micropollutants (electrodialysis, nanofiltration, ozonation). The review shows clearly that a wide range of technical options is available to treat collected urine effectively, but that none of these single options can accomplish all seven purposes. Depending on the overall goal of the treatment process, a specific technical solution or a combination of solutions can be found to meet the requirements. Such combinations are not discussed in this paper unless they are explicitly presented in the literature. Except for 'evaporation' and 'storage', none of the processes described have so far advanced beyond the laboratory stage. Considerable development work remains to be done to optimise urine-processing techniques in order to create marketable products.
Medilanski, E., Chuan, L., Mosler, H. J., Schertenleib, R., & Larsen, T. A. (2006). Wastewater management in Kunming, China: a stakeholder perspective on measures at the source. Environment and Urbanization, 18(2), 353-368. doi:10.1177/0956247806069615, Institutional Repository

Large sewer systems with central wastewater treatment plants were long considered a successful model that could be exported to practically any city of the world. This centralized, highly water-consuming system has, however, shown its limits in some developing and transition countries, especially in fastgrowing cities with limited water resources. This study from around Lake Dianchi in Yunnan, China, investigated the feasibility of introducing measures at the source for the different urban wastewater contributions in the city of Kunming, and the stakeholder perspectives on this approach. In addition, the stakeholders evaluated the potential of two different sanitation alternatives that allowed the separation and re-use of human excreta as fertilizer. Most of those interviewed approved of measures at the source, especially for industrial wastewater and toilet waste. There was a prevailing optimism with respect to the potential of technical developments and the likelihood of increased environmental awareness within a relatively short time span of 20 years. The findings suggest that China will prove to be one of the most interesting and productive "laboratories" for the development of decentralized wastewater treatment alternatives.
Pronk, W., Sinnet, B., Meylan, S., & Boller, M. (2006). Characterization of nano- and microparticles in Swiss waters and their role in potable water production. Water Science and Technology: Water Supply, 6(1), 21-29. doi:10.2166/ws.2006.004, Institutional Repository

Particles in lake water samples originating from the Swiss lakes of Zurich and Constance were analysed, showing an exponential increase of particle number with decreasing particle size down to the detection limit (350 nm). Investigation of nanoparticles in Lake Zurich by microscopic methods showed that relatively large numbers of clay particles are present with different Al/Si composition and sizes. The small-sized clay particles (ca. 80 nm) tend to build aggregates with a size of 500-1,000 nm. In karstic spring water, the particle count and size distribution is strongly dependent on the precipitation rate. At high precipitation rates, channel flow occurs in the subsoil, leading to high particle counts among the whole size range and a larger average particle size. In membrane treatment by microfiltration and ultrafiltration this leads to membrane fouling due to pore blocking and cake formation, the latter being associated with the presence of organic compounds.
Pronk, W., Biebow, M., & Boller, M. (2006). Electrodialysis for recovering salts from a urine solution containing micropollutants. Environmental Science and Technology, 40(7), 2414-2420. doi:10.1021/es051921i, Institutional Repository

Electrodialysis was investigated for the separation of micropollutants from nutrients in anthropogenic urine. In a continuously operated process, the nutrients were concentrated up to a factor of 3.2. The concentration factor was limited by water transport across the membrane. Water transport was caused by osmosis and electroosmosis, and a model was developed to describe these phenomena. The removal of several spiked micropollutants was investigated in continuous electrodialysis experiments, Ethinylestradiol was removed completely during the whole operating period. Diclofenac and carbamazepine were initially retained, but limited permeation (5-10%) occurred after longer operating times (90 days). Retentions of propranolol and ibuprofen were also high initially, but substantial breakthroughs occurred during extended operation. Considerable adsorption on the membranes was observed for all compounds. The permeation mechanism of several compounds appears to depend on the adsorbed amount on the membrane, which indicates that partitioning and diffusion mechanisms play an important role in the permeation transport. Partial desorption occurred in leaching experiments with polarity reversal, and almost quantitative desorption was observed after incubation of the membranes with Filter Count Gel Solution. Because environmental concentrations are much lower than the concentrations spiked here, it can be anticipated that operation without significant permeation is possible in practice during extended periods of time.
Pronk, W., Palmquist, H., Biebow, M., & Boller, M. (2006). Nanofiltration for the separation of pharmaceuticals from nutrients in source-separated urine. Water Research, 40(7), 1405-1412. doi:10.1016/j.watres.2006.01.038, Institutional Repository

The potential of nanofiltration for the separation of pharmaceutical and estrogenic compounds from salts in urine was investigated with the aim of producing a micropollutant-free nutrient solution that can be used as a fertilizer. A fresh urine solution and a synthetic solution of similar inorganic composition were tested at different pH values in order to investigate their separation behavior. These solutions were spiked with the micropollutants propranolol, ethinylestradiol, ibuprofen, diclofenac and carbamazepine. Among the membranes tested, NF270 showed the best performance with respect to the retention of micropollutants. The optimum retention of micropollutants was obtained at values of around pH 5. At this point, the retention of all micropollutants in non-hydrolysed urine was above 92%, while the corresponding value for the synthetic urine solution was above 73%. From the results, it can be concluded that the retention mechanism is determined by steric and electrostatic effects as well as by the partitioning of the micropollutants in the membrane. The nutrients urea and ammonia were well permeated, but phosphate and sulfate were almost completely retained. Nanofiltration can consequently be used to produce a permeate which contains most of the nitrogen and a greatly reduced proportion of micropollutants.
Pronk, W., Biebow, M., & Boller, M. (2006). Treatment of source-separated urine by a combination of bipolar electrodialysis and a gas transfer membrane. Water Science and Technology, 53(3), 139-146. doi:10.2166/wst.2006.086, Institutional Repository

Urine contains nutrients which can be applied usefully as a fertiliser in agriculture, but the relatively high pH can lead to ammonia evaporation. Electrodialysis with bipolar membranes was combined with an additional mass transfer unit in order to render a product containing ammonium and phosphate at a low pH. In one case, the additional mass transfer unit consisted of bubble columns placed in acid and basic concentrate streams, connected with a circulating gas phase. In the other case, the unit consisted of a gas-filled (hydrophobic) membrane placed in between the circulating acid and basic concentrate streams. The results showed that ammonia was transferred through the gas phase, but also carbonate, which is present in stored urine originating from the hydrolysis of urea. Although the pH in the product stream decreases initially, it rises above pH 7 at longer operation times. This pH increase can be attributed to a combination of proton compensating effects. The use of ammonia-selective membranes for the transfer into the acid concentrate could provide a solution to generate an ammonium phosphate product at low pH and high recoveries.
Rieckermann, J., Daebel, H., Ronteltap, M., & Bernauer, T. (2006). Assessing the performance of international water management at Lake Titicaca. Aquatic Sciences, 68(4), 502-516. doi:10.1007/s00027-006-0863-0, Institutional Repository

In this article, we study the performance of international water management at Lake Titicaca in order to assess the empirical applicability of a new concept for measuring policy performance. This performance measurement concept (PER) is a function of three variables: optimum performance (OP), actual performance (AP), and counterfactual performance (CP). In examining the joint management of Lake Titicaca by Bolivia and Peru, we identify practical difficulties in applying PER and suggest extensions of the concept to assess uncertainty. We find that this measurement concept has several advantages: it takes into account counterfactual performance; the analysis can be performed in a structured, standardized, and transparent manner; and the formal framework allows for an assessment of uncertainty. Problems in applying the concept include: choice of attributes, identification of optimum performance, time-scale, and subjectivity of information. We conclude that, on balance, this approach is superior to other policy performance assessment measures developed to date.
Rieckermann, J., Borsuk, M. E., & Gujer, W. (2006). Using decision analysis to determine optimal experimental design for monitoring sewer exfiltration with tracers. Water Science and Technology, 54(6-7), 161-168. doi:10.2166/wst.2006.615, Institutional Repository

The tracer methods developed to assess exfiltration from sewers in the European project APUSS (assessment of the performance of sewer systems) have a high degree of freedom with regard to the choice of tracer and the dosing strategy. These can lead to very different degrees of uncertainty in the measured exfiltration ratio. In this study, we demonstrate how to select an optimal experimental design using decision analysis, which accounts for this uncertainty and its associated costs. Although the results are site-specific, we can conclude generally that, when NaCl is used as the tracer, the accuracy of the exfiltration estimate is most sensitive to the amount of tracer used and the starting time of the experiment.
Steiner, M., & Boller, M. (2006). Copper and zinc removal from roof runoff: from research to full-scale adsorber systems. Water Science and Technology, 53(3), 199-207. doi:10.2166/wst.2006.093, Institutional Repository

Large, uncoated copper and zinc roofs cause environmental problems if their runoff is infiltrated into the underground or discharged into receiving waters. Since source control is not always feasible, barrier systems for efficient copper and zinc removal are recommended in Switzerland. During the last few years, research carried out in order to test the performance of GIH-calcite adsorber filters as a barrier system. Adsorption and mass transport processes were assessed and described in a mathematical model. However, this model is not suitable for practical design, because it does not give explicit access to design parameters such as adsorber diameter and adsorber bed depth. Therefore, for e.g. engineers, an easy to use design guideline for GIH-calcite adsorber systems was developed, mainly based on the mathematical model. The core of this guideline is the design of the depth of the GIH-calcite adsorber layer. The depth is calculated by adding up the GIH depth for sorption equilibrium and the depth for the mass transfer zone (MTZ). Additionally, the arrangement of other adsorber system components such as particle separation and retention volume was considered in the guideline. Investigations of a full-scale adsorber confirm the successful application of this newly developed design guideline for the application of GIH-calcite adsorber systems in practice.
Steiner, M., Pronk, W., & Boller, M. (2006). Modeling of copper sorption onto GFH and design of full-scale GFH adsorbers. Environmental Science and Technology, 40(5), 1629-1635. doi:10.1021/es051324w, Institutional Repository

During rain events, copper wash-off occurring from copper roofs results in environmental hazards. In this study, columns filled with granulated ferric hydroxide (GFH) were used to treat copper-containing roof runoff. It was shown that copper could be removed to a high extent. A model was developed to describe this removal process. The model was based on the Two Region Model (TRM), extended with an additional diffusion zone. The extended model was able to describe the copper removal in long-term experiments (up to 125 days) with variable flow rates reflecting realistic runoff events. The four parameters of the model were estimated based on data gained with specific column experiments according to maximum sensitivity for each parameter. After model validation, the parameter set was used for the design of full-scale adsorbers. These full-scale adsorbers show high removal rates during extended periods of time.
Udert, K. M., Larsen, T. A., & Gujer, W. (2006). Fate of major compounds in source-separated urine. Water Science and Technology, 54(11-12), 413-420. doi:10.2166/wst.2006.921, Institutional Repository

Urine separation is a promising alternative to present-day’s waste water management. It can help to manage our nutrient flows in a sustainable way. Currently, techniques are being developed to recycle and treat source-separated urine. These techniques, however, must consider the spontaneous processes that change the separated urine. The initial cause of changes is the contamination with microorganisms, which can hardly be avoided in urine-collecting systems. The most important transformation processes are microbial urea hydrolysis, mineral precipitation and ammonia volatilisation. Additionally, a variety of microorganisms, including pathogens, may grow in source-separated urine. In this paper we give an overview of the effects that the spontaneous transformation processes may have. We focus on nitrogen, phosphorus, magnesium, calcium, potassium, sulphur, organic substances, pathogens and the buffering capacity. The discussion is based on own research results and literature reviews. This overview will help to develop appropriate technologies for urine recycling.

Andere Publikationen

Cavadini, G. B., Mutzner, L., Cook, L., Rodriguez, M., & Poggioli, M. (2024). BGI reduzieren Gewässerbelastung. Modellstudien zu Entlastungen und Wasserqualität sowie Auswirkungen des Klimawandels. Aqua & Gas, 104(10), 46-52. , Institutional Repository

Indem blau-grüne Infrastrukturen die Mischwasserentlastungen reduzieren, werden auch die Einträge von Mikroverunreinigungen verkleinert. Besonders Versickerungsflächen senken die eingeleiteten Volumina und Frachten in Oberflächengewässer. Klimawandelprognosen lassen eine Zunahme von Entlastungen erwarten. Blau-grüne Infrastrukturen können daher einen wichtigen Beitrag leisten, um unerwünschte Effekte zu vermeiden oder zu reduzieren.
Sitzenfrei, R., Annus, I., Langeveld, J., Rieckermann, J., & Rauch, W. (2024). Editorial: Developments and applications of IoT-based sensors for wastewater and drainage systems. Water Science and Technology, 89(4), iii-v. doi:10.2166/wst.2024.058, Institutional Repository
Carriço, N., do Céu Almeida, M., & Leitão, J. P. (2023). Management of urban drainage infrastructure. In T. Bolognesi, F. Silva Pinto, & M. Farrelly (Eds.), Routledge environment and sustainability handbooks. Routledge handbook of urban water governance (pp. 145-162). doi:10.4324/9781003057574-12, Institutional Repository
Fischer, M., Ingold, K., Duygan, M., Manny, L., & Pakizer, K. (2023). Actor networks in urban water governance. In T. Bolognesi, F. Silva Pinto, & M. Farrelly (Eds.), Routledge environment and sustainability handbooks. Routledge handbook of urban water governance (pp. 243-256). doi:10.4324/9781003057574-21, Institutional Repository

A network perspective to urban water governance provides a useful analytical perspective. Network approaches allow systematic descriptions and analysis of the structure of interactions among actors and technical elements. This chapter presents conceptual approaches, theoretical elements, and methodological tools related to actor networks in urban water governance. The chapter starts by presenting theoretical aspects and related research questions at the intersection of network governance and urban water governance. After an introduction to the main concepts and measures of Social Network Analysis, the chapter focuses on how network approaches can help in analyzing processes of digitalization and decentralization, not least with the concept of sociotechnical network approaches that combine actor networks with technical networks.
Jato-Espino, D., Charlesworth, S., Leitão, J. P., & Rodríguez Sánchez, J. P. (2023). Editorial: Urban drainage in a context of climate and land cover changes. Frontiers in Water, 4, 1118338 (2 pp.). doi:10.3389/frwa.2022.1118338, Institutional Repository
Maurer, M., Tilley, E., & Udert, K. (2023). Andere Wege für das Abwasser. Globe, 23(2), 26-28. , Institutional Repository

Die Wasserwirtschaft mit Kanalisation und zentralen Kläranlagen ist nicht mehr zukunftsfähig und global keine Lösung. Umweltingenieur:innen der ETH Zürich und der Eawag bereiten den Weg zu einer kreislauffähigen und dezentraleren Wasserinfrastruktur.
Maurer, M. (2023). Sanitation systems. Are hybrid systems sustainable or does winner takes all?. In T. Bolognesi, F. Silva Pinto, & M. Farrelly (Eds.), Routledge environment and sustainability handbooks. Routledge handbook of urban water governance (pp. 134-144). doi:10.4324/9781003057574-11, Institutional Repository

Hybrid wastewater systems can be defined as the coexistence of centralized and modular systems in the same catchment. Currently, we have no explicit knowledge if such hybrid systems can be stable over the long term or if modular systems always will be a stopgap solution.
Current evidence indicates that, depending on the settlement structure, centralized systems can have diseconomies of scale, and modelling studies show that there are conditions where hybrid systems are cost-effective. Decisive factors are the costs of modular systems and the heterogeneity of urban areas. Overall, there are good reasons to believe that fortifying centralized systems with modular systems enable overcoming some of the critical weaknesses of the one-size-fits-all centralized systems approach.
However, centralized systems show strong path dependencies. Besides a wide range of institutional and organizational barriers, current engineering economic and planning methodologies also need to be improved and adapted. From a purely engineering perspective, the following research needs can be identified: (i) long-term transition planning tools that are spatially explicit and can consider a wide range of modular technologies; (ii) cross-sectoral integration methodologies; (iii) better methods to integrate multi-criteria decision analysis (MCDA) to consider the broader range of benefits hybrid systems can provide; and (iv) improved engineering economic methodologies considering uncertainties, unused capacity, and the value of adaptability.
Nascimento, N., Armitage, N., Sanches, J. P. R., & Leitao, J. P. (2023). Editorial: UWJ special edition on water management in developing countries. Urban Water Journal, 20(10), 1231-1236. doi:10.1080/1573062X.2023.2266635, Institutional Repository
Perrelet, K., Moretti, M., Dietzel, A., Maurer, M., & Cook, L. (2023). Schwammstädte - Für und mit Biodiversität gestalten. Hotspot, 48, 24-25. , Institutional Repository

Eine blau-grüne Infrastruktur aus Fliessgewässern, Pflanzenkläranlagen oder Gründächern kann den Siedlungsraum und vor allem Städte sowohl biodiverser als auch resilienter gegenüber dem Klimawandel machen. Voraussetzung ist die Zusammenarbeit von Ingenieur- und Naturwissenschaften.
Perrelet, K., Moretti, M., Dietzel, A., Maurer, M., & Cook, L. (2023). Villes éponges: pour et avec la biodiversité. Hotspot, 48, 22-23. , Institutional Repository

Une infrastructure bleue et verte composée de cours d’eau, de stations d’épuration végétales ou de toits verts peut rendre l’espace urbain, et surtout les villes, à la fois biodiverses et résistantes aux aléas climatiques. La condition préalable est la collaboration entre l’ingénierie et les sciences naturelles.
Smith, V., Cook, L. M., & Oppliger, S. (2023). Umsetzung blau-grüner Infrastruktur weltweit. Was kann die Schweiz daraus lernen?. Aqua & Gas, 103(9), 16-24. , Institutional Repository

Die Umsetzung Blau-Grüner Infrastrukturen ist in allen grösseren Schweizer Städten ein äusserst aktuelles Thema. Treibende Faktoren waren meist die Förderung der Biodiversität und die Not-wendigkeit von hitzemindernden Massnahmen im urbanen Raum, und weniger die Siedlungswas-serwirtschaft. Ausserhalb der Schweiz hingegen wurde die Umsetzung in den vergangenen Jahr-zehnten stark auch aus Sicht der Regenwasserbewirtschaftung und Sicherung der Wasserqualität in den oberflächlichen Gewässern vorangetrieben. Dieser Artikel fasst wichtige Erfahrungen und Erkenntnisse aus der weltweiten Umsetzung zusammen.
Julian, T. R., Fernandez, X., Ort, C., & Kahn, T. (2022). How wastewater informs COVID-19 policy in Switzerland. Water Science Policy (3 pp.). doi:10.53014/BHET9151, Institutional Repository
Schnorf, H., Bergamini, A., Cook, L., & Moretti, M. (2022). Revitalisierte Bäche leisten einen Beitrag zur städtischen Pflanzenvielfalt. Les ruisseaux revitalisés favorisent la diversité spécifique de la flore urbaine. Nature et Paysage. Natur und Landschaft: Inside (4), 35-39. , Institutional Repository

Bevor sie grösstenteils in den Untergrund verlegt wurden, prägten Bäche das Bild der Schweiz, auch in der Stadt Zürich. Im Rahmen des naturnahen Wasserbaus werden in Zürich diese Bäche seit 35 Jahren wieder an die Oberfläche gebracht. In dieser Studie untersuchten wir die Vielfalt der Gefässpflanzen an wieder geöffneten Bächen in der Stadt Zürich.

Avant d’être en majeure partie enfouis, les ruisseaux étaient des marqueurs omniprésents du paysage en Suisse, y compris dans l’espace urbain. Depuis 35 ans, les petits cours d’eau de la ville de Zurich sont progressivement remis à ciel ouvert dans le cadre d’un plan de réaménagement tendant vers l’état naturel. Une étude s’est intéressée à la diversité des plantes vasculaires présentes dans le courant et au bord des ruisseaux ainsi revitalisés.
Truffer, B., Maurer, M., & Heiberg, J. (2022). Modulare Wasserinfrastrukturen. Optionen für eine Zukunftsfähige Siedlungswasserwirtschaft. Aqua & Gas, 102(9), 60-65. , Institutional Repository

Modulare Systeme ermöglichen eine dezentralere und damit flexiblere Gestaltung der Siedlungswasserwirtschaft. Im Rahmen des Nationalen Forschungsprogramms 73 «Nachhaltige Wirtschaft» untersuchte das Forschungsteam des Projekts COMIX die zu erwartenden Chancen und Risiken, die sich aus diesen Entwicklungen für einen nachhaltigeren Umgang mit der Ressource Wasser in der Schweiz ergeben könnten.
Aerts, R., & Blumensaat, F. (2021). Bewertung von Entwässerungssystemen. Herausforderungen emissionsbasierter Optimierungsstrategien. Aqua & Gas, 101(10), 52-63. , Institutional Repository

Schmutzfrachtmodelle können helfen, die Einflüsse der Siedlungsentwässerung auf die Gewässerökologie besser einzuschätzen. Doch anhand welcher Leistungsindikatoren soll diese Einschätzung vorgenommen werden? Wie gehen wir mit inhärenten Daten- und Modellunsicherheiten um?
Bach, P. M., Probst, N., & Maurer, M. (2021). Urbane Strategien zur Hitzeminderung. Wie wirksam sind blau-grüne Infrastrukturen?. Aqua & Gas, 101(10), 20-25. , Institutional Repository

Schwammstadt, grüne Infrastruktur, WSUD, LID, SuDS – für das Konzept, den Wasserhaushalt in der Stadt naturnaher zu gestalten, gibt es viele Namen. All diese Ansätze versprechen verschiedenste naturnahe Servicefunktionen, die für die Adaptation unserer Städte an den Klimawandel eine zentrale Rolle spielen. Dieser Artikel geht der Frage nach, was wir über die Wirkung für die Hitzereduktion solcher «blau-grüner Infrastrukturen» wissen, wie wir diese quantifizieren und effektiv planen können.
Barth, L., & Rieckermann, J. (2021). Messdatenbasierte Leistungsanalyse von Abflussregelungen. Aqua & Gas, 101(10), 42-50. , Institutional Repository

Abflussregelungen können oft kostengünstige Massnahmen sein, um den Gewässerschutz bei Regenwetter durch die bessere Auslastung der vorhandenen Infrastruktur zu verbessern. In Zukunft könnte die tatsächliche Leistung von Abflussregelungen mit Betriebsdaten und statistischen Methoden beurteilt werden. Eine verlässliche messdatenbasierte Leistungsanalyse von Regelungssystemen muss Variabilität und Unsicherheiten in den Messdaten berücksichtigen. Der «Potential Outcome»-Ansatz und flexible Regressionsmethoden, wie z. B. Random Forest, scheinen vielversprechende Lösungen zu sein, um den Effekt einer Abflussregelung zu schätzen.
Beutler, P., Larsen, T. A., Maurer, M., Staufer, P., & Lienert, J. (2021). Potenzial dezentraler Abwassersysteme. Aqua & Gas, 101(1), 66-75. , Institutional Repository

Werterhalt und Bewirtschaftung von Kanalisation und ARA können kleine Gemeinden vor Herausforderungen stellen. Es gibt Alternativen, aber lohnen sich diese? Zwei Gemeinden wurden bei der strategischen Planung für ihr neues Abwassersystem unterstützt. Viele Ziele wurden als entscheidungsrelevant identifiziert, insbesondere Umweltschutzziele. Es zeigte sich, dass dezentrale Technologien mit Stoffstromseparierung die Anforderungen häufig besser erfüllen können als konventionelle Abwassersysteme.
Donati, G. F. A., Bolliger, J., Psomas, A., Maurer, M., & Bach, P. M. (2021). Blau-grüne Infrastuktur: eine Möglichkeit zur Förderung der biologischen Vielfalt in vom Menschen geprägten Landschaften? Les infrastructures bleues-vertes: une opportunité pour améliorer la biodiversité dans les paysages dominés par l'homme?. Nature et Paysage. Natur und Landschaft: Inside (4), 41-44. , Institutional Repository

Intensiv genutzte Landschaften und Lebensraumfragmentierung sind mitverantwortlich für den Rückgang der Biodiversität, weil Lebensraumqualität und grundlegende biologische Prozesse wie z.B. die Ausbreitung gestört werden. Stetig wachsende Städte als überregionale Barrieren für die Vernetzung natürlicher Lebensräume stellen eine besondere Herausforderung dar (Abb. 1). Wir zeigen am Beispiel von Amphibien auf, wie eine gezielte Platzierung blaugrüner Infrastrukturen die Durchlässigkeit von Städten verbessern könnte und dadurch Lebensräume und Laichgebiete von regionaler Bedeutung besser vernetzt werden. Die Einrichtung blaugrüner Infrastrukturen ist eine vielversprechende Massnahme, um die Anpassung an den Klimawandel zu fördern und die Lebensqualität zu verbessern. Synergien zur Vernetzung der Biodiversität bieten sich auf lokaler und regionaler Ebene an.

L'utilisation intensive des paysages et la fragmentation des habitats sont en partie co-responsables du déclin de la biodiversité, dans la mesure où la qualité des habitats et des processus biologiques fondamentaux tels que la dispersion sont perturbés. L'urbanisation croissante constitue un défi particulier dans ce contexte, notamment en tant qu'obstacle transrégional à la connectivité des habitats naturels. En prenant l'exemple des amphibiens, nous montrons comment la planification ciblée d'infrastructures bleuesvertes pourrait améliorer la perméabilité des villes en reliant mieux les habitats naturels et les sites de reproduction d'importance régionale. L'installation d'infrastructures bleues-vertes est une mesure prometteuse qui est actuellement planifiée dans de nombreuses villes surtout pour promouvoir l'adaptation au changement climatique ainsi que pour l'amélioration de la qualité de vie. Cependant, des synergies pour la mise en réseau de la biodiversité sont aussi disponibles non seulement à niveaux local mais aussi régional.
Bijlsma, L., Burgard, D. A., Been, F., Ort, C., Matias, J., & Yargeau, V. (2020). The estimation of cannabis consumption through wastewater analysis. In I. Ferrer & E. M. Thurman (Eds.), Comprehensive analytical chemistry. Analysis of Cannabis (pp. 453-482). doi:10.1016/bs.coac.2020.04.005, Institutional Repository
Dax, A., Stravs, M., Stamm, C., Ort, C., la Cecilia, D., & Singer, H. (2020). MS2field: Mikroverunreinigungen mobil messen. Aqua & Gas, 100(12), 14-19. , Institutional Repository

Konzentrationsspitzen von Pestiziden können von grosser biologischer und regulatorischer Bedeutung sein, werden aber selten und nur mit hohem Aufwand erfasst. Die neue MS2field-Plattform ist eine der ersten mobilen Messinfrastrukturen, die kontinuierliche und zeitlich hochaufgelöste Messungen von Mikroverunreinigungen in umweltrelevanten Konzentrationen im Feld erlaubt. Wie vielfältig Konzentrationsdynamiken von Pestiziden sein können und in welchem Ausmass Spitzenkonzentrationen mit konventionellen Probenahme- und Messtechniken bisher unterschätzt wurden, macht eine Messkampagne in einem landwirtschaftlich stark geprägten Bach sichtbar.
Deletic, A., Qu, J., Bach, P. M., Liu, G., Wang, A., & Zhang, K. (2020). The multi-faceted nature of Blue-Green Systems coming to light. Blue-Green Systems, 2(1), 186-187. doi:10.2166/bgs.2020.002, Institutional Repository
Doll, C., Larsen, T. A., Strande, L., Udert, K. M., & Morgenroth, E. (2020). Water Hub im NEST-Gebäude. Eine Plattform zum Testen von innovativen ressourcenorientierten Sanitärsystemen. Aqua & Gas, 100(2), 52-57. , Institutional Repository

Mit innovativen Technologien werden im Water Hub unter realen Bedingungen Ressourcen aus dem Abwasser gewonnen und Kreisläufe geschlossen. Die Forschung in diesem Living Lab erlaubt es, praxisnahe Erfahrungen zu machen, Schwachstellen schnell zu identifizieren und das System zu optimieren. Bei der Implementierung dieser dezentralen Technologien spielen die lokalen Herausforderungen und Begebenheiten stets eine wichtige Rolle.
Larsen, T. A. (2020). Urine source separation for global nutrient management. In D. J. O’Bannon (Ed.), Women in engineering and science. Women in water quality. Investigations by prominent female engineers (pp. 99-111). doi:10.1007/978-3-030-17819-2_6, Institutional Repository

The sewer-based paradigm for wastewater management at the global scale is not successful neither from a humanitarian nor from an environmental perspective. The systems are too expensive for the largest part of the global population. Source separation and resource recovery offer an alternative for sanitation and water pollution control. This chapter illustrates the importance but also the challenges of urine source separation for efficient nutrient removal and recovery.
 
Blumensaat, F., Dicht, S., & Ebi, C. (2019). Niedrigenergiefunk im Untergrund. Möglichkeiten und Grenzen einer neuen Daten-Fernübertragung in der Siedlungsentwässerung. Aqua & Gas, 99(3), 52-60. , Institutional Repository

Hat Niedrigenergiefunk das Potenzial, die Prozessüberwachung in Entwässerungsnetzen und anderen Infrastrukturen im Untergrund zu revolutionieren? Ein Langzeitexperiment im Vollmassstab in der Gemeinde Fehraltorf zeigt die Möglichkeiten, Grenzen und Entwicklungspotenziale der neuartigen Übertragungstechnologie auf. Grundsätzlich unterstreicht das Experiment die Eignung des Niedrigenergiefunks für eine komplementäre Systemüberwachung. Sinnvoll eingesetzt kann diese Neuerung wesentlich zu einer evidenzbasierten Bewirtschaftung von Ver- und Entsorgungssystemen beitragen.
Blumensaat, F., Dicht, S., Ebi, C., & Maurer, M. (2019). Niedrigenergiefunk in der Siedlungsentwässerung. Neuartige Übertragungstechnologien für eine effiziente Prozessüberwachung im Untergrund–Erfahrungen aus dem Urbanhydrologischen Feldlabor der Eawag. gwf Wasser, Abwasser, 160(3), 44-47. , Institutional Repository

Hat Niedrigenergiefunk das Potenzial, die Prozessüberwachung in Entwässerungssystemen und anderen Infrastrukturen im Untergrund zu revolutionieren? Inwieweit verbessern technologische Neuerungen unser Verständnis für Daten und deren Nutzung für Betriebsoptimierung, Investitionsplanung und Erfolgskontrolle?
Disch, A., Scheidegger, A., Wani, O., & Rieckermann, J. (2019). Impact of different sources of precipitation data on urban rainfall-runoff predictions: a comparison of rain gauges, commercial microwave links and radar. In N. Peleg & P. Molnar (Eds.), Rainfall monitoring, modelling and forecasting in urban environments. Conference Proceedings UrbanRain18 (pp. 27-32). Zurich: ETH Zurich. , Institutional Repository

In this study, we investigate whether commercial microwave links (CML) can bridge the gap between rain gauge and radar. We performed a rainfall-runoff monitoring experiment with rain gauges, CMLs and weather radar in a small urbanized catchment during several months. The results of comparing rainfall data and resulting sewer flows suggest that quantitative precipitation estimates from CMLs require adjustment to local rain gauges to produce satisfactory results in a similar fashion as weather radar. In our study, CML with baseline removal and wet-antenna correction, but without adjustment, lead to substantial bias and underestimate rainfall-runoff ratios by more than 48% (Radar: ca. 40%). In contrast, adjusted CML produced results very similar to those from a dense rain gauge network and underestimated rainfall-runoff by about 11%. Further work is needed to better understand influential factors on the data quality of QPEs from CML. In addition, incentives are needed to motivate both telecommunication companies to provide CML data and weather service companies to use them in their products, i.e. commercializing information from opportunistic sensors.
Gründl, H., & Larsen, T. A. (2019). The toilet revolution: improved water pollution control and reuse of wastewater in urban slums and in modern cities. World Architecture (06), 36-39. , Institutional Repository

With two new toilet systems, one for urban slums and the other for modern cities, we can at the same time improve water pollution control and further the economic reuse of wastewater. For urban slums, the Blue Diversion Toilet is an appealing, affordable and safe technical solution. It is designed for industrialised manufacturing and implements a sustainable sanitation value chain with total resource recovery and zero discharge. The important concept of the toilet is urine source separation. This concept that can also revolutionise wastewater management in the modern cities of industrialised and fast industrialising countries. With the new urine-separating toilet Save! this toilet revolution can spread on a global scale, offering a cost-efficient measure to help save surface water from eutrophication, make reuse of wastewater easier and cheaper and – as a side effect - provide fertiliser for urban and rural agriculture.
Manny, L., Fischer, M., Staufer, P., & Rieckermann, J. (2019). Saubere Gewässer dank Messdatenmanagement. Instrumente für einen guten Umgang mit Messdaten in der Schweizer Siedlungsentwässerung. Aqua & Gas, 99(1), 58-65. , Institutional Repository

Mit der fortschreitenden Digitalisierung gilt es heute als Stand der Technik, Messdaten über das Abwassersystem zu erheben, auszuwerten und zu archivieren. Wie der Wert von Messdaten für Betrieb, Planung und Leistungsüberprüfung ausgeschöpft werden kann, ist jedoch unklar. Um einen einheitlichen Einsatz von Messtechnik, z.B. an Regenüberlaufbecken, sowie einen guten Umgang mit erfassten Messdaten in der Schweizer Praxis zu schaffen, sind Anpassungen auf organisatorischer Ebene notwendig.
Maurer, M., & Hoffmann, S. (2019). Eaux usées: des égouts à assainir. Volkswirtschaft, 89(6), 12-15. Retrieved from https://dievolkswirtschaft.ch/fr/2019/05/maurer-hoffmann-06-2019fr/, Institutional Repository

Avec une valeur de remplacement de 230 milliards de francs, les infrastructures d’approvisionnement en eau et d’élimination des eaux usées sont parmi les plus précieuses de Suisse. Les canalisations vieillissantes, l’évolution démographique et l’urbanisation croissante nécessitent d’investir 130 milliards de francs ces 30 prochaines années. Au niveau mondial, l’OCDE estime à 900 milliards de francs les fonds alloués chaque année à la gestion des eaux urbaines. Ce grand besoin d’investissements et la pression internationale accrue pour trouver de nouvelles approches favorisent des solutions innovantes. La recherche de pointe menée en Suisse dans ce domaine et la nécessité de renouveler les infrastructures confèrent un potentiel inexploité de marché pilote à notre pays. Un programme d’impulsion national permettant de coordonner les décisions d’infrastructure fragmentées des communes est néanmoins nécessaire.
Maurer, M., & Hoffmann, S. (2019). Sanierungsfall Abwassersystem. Volkswirtschaft, 89(6), 12-15. Retrieved from https://dievolkswirtschaft.ch/de/2019/05/hoffmann-maurer-06-2019/, Institutional Repository

Mit einem Wiederbeschaffungswert von 230 Milliarden Franken zählt die Wasserversorgung und Abwasserentsorgung in der Schweiz zu den wertvollsten Infrastrukturbauten. Alternde Leitungen, steigende Bevölkerungszahlen und zunehmende Urbanisierung verlangen in den nächsten 30 Jahren Investitionen von insgesamt 130 Milliarden Franken. Auf globaler Ebene schätzt die OECD die Investitionen in die Siedlungswasserwirtschaft auf jährlich 900 Milliarden Franken. Dieser hohe Investitionsbedarf und der global steigende Druck, neue Ansätze zu finden, bieten einen Spielraum für innovative Lösungen. Die Schweiz hat mit ihrer Spitzenforschung in diesem Bereich und dem aktuellen Bedarf an Infrastrukturerneuerung ein ungenutztes «Lead-Market»-Potenzial. Dazu braucht es aber ein gesamtschweizerisches Impulsprogram, das die fragmentierten Infrastrukturentscheide der Gemeinden koordiniert.
Mutzner, L., Mangold, S., Dicht, S., Bohren, C., Vermeirssen, E. L. M., Scheidegger, A., … Ort, C. (2019). Mikroverunreinigungen aus Siedlungen. Messungen in 20 Mischabwasserentlastungen mit Passivsammler. Aqua & Gas, 99(10), 28-35. , Institutional Repository

Niederschlags- und Mischabwasserentlastungen aus Siedlungen tragen zu Mikroverunreinigungen in Gewässern bei. Mit Passivsammlern wurden erstmals Konzentrationsbereiche an 20 Standorten für insgesamt 95 Ereignisse bestimmt, was die Analyse von Unterschieden zwischen Standorten sowie die Identifikation relevanter Eintragspfade unterstützt. An 13 Standorten waren bei mindestens einer Substanz die Konzentrationen im Mischabwasser höher als akute Qualitätskriterien.
Perret, D., Leppard, G. G., & Mavrocordatos, D. (2019). Microscopy | environmental applications. In P. Worsfold, C. Poole, A. Townshend, & M. Miró (Eds.), Vol. 7. Encyclopedia of analytical science. Reference module in chemistry, molecular sciences and chemical engineering (pp. 39-46). doi:10.1016/B978-0-08-101983-2.00390-X, Institutional Repository
Peña-Haro, S., Carrel, M., Lüthi, B., Wang, L., Dicht, S., & Leitão, J. P. (2019). Abflussmessungen mittels Videos. Einsatz von Webcams und Smartphones. Aqua & Gas, 99(10), 42-45. , Institutional Repository

Mit kurzen Videosequenzen von Überwachungskameras und Smartphones können Oberflächengeschwindigkeiten in Abwasserkanälen gemessen werden. Eingesetzt wird dabei die bildbasierte Methode namens Surface Structure Image Velocimetry, kurz SSIV. Die resultierenden Ergebnisse stimmen gut mit Ultraschall-Referenzmessungen überein und unterstreichen das Potenzial der innovativen Methode.
Peña-Haro, S., Lüthi, B., Carrel, M., Scheidegger, A., de Vitry, M. M., & Leitão, J. P. (2019). Es überschwemmt und keiner sieht zu?! Oberflächenabflussmessungen im urbanen Raum mittels Videomaterial von Überwachungskameras. Aqua & Gas, 99(5), 44-50. , Institutional Repository

Messungen von Oberflächenabflüssen werden selten im urbanen Raum durchgeführt, weil traditionelle Messgeräte zu teuer sind oder direkt über oder innerhalb des Fliessgewässers installiert werden müssen. Deswegen sind Daten über Überschwemmungen im urbanen Raum nur selten vorhanden, was die Kalibrierung und Validierung von Überflutungsmodellen erschwert. In dieser Studie wird ein Ansatz vorgestellt, bei dem marktübliche Überwachungskameras zur Durchflussmessung eingesetzt werden.
Purtschert, I., Gutmann, M., Bitterli, C., Joss, A., & Blumensaat, F. (2019). Abwasserentsorgung - Wie viel ist gut genug?. Aqua & Gas, 99(1), 85-86. , Institutional Repository

Das Gesamtsystem «Abwasserentsorgung», bestehend aus Einzugsgebiet, Kanalisation, ARA und Gewässer, ist über mehrere Ebenen vernetzt. Der diesjährige VSA-Fortbildungskurs «Abwasserentsorgung im Spannungsfeld von Ökologie, Ökonomie, Gesellschaft – Wie viel ist gut genug?» in Emmetten hat mit verschiedenen Referaten und Workshops diese Vernetzung aus technischer, gesellschaftlicher und finanzieller Sicht sowie von unterschiedlichen Standpunkten aus beleuchtet.
Beutler, P., Kianfar, B., Blumensaat, F., & Maurer, M. (2018). Klimawandel und Starkregen. Führt der Klimawandel zu veränderten Starkregen in der Schweiz? Ein Statusbericht. Aqua & Gas, 98(10), 14-20. , Institutional Repository

Ist in der Zukunft ein Einfluss des Klimawandels auf die für die Dimensionierung der Siedlungsentwässerung relevanten Starkregen erkennbar? Untersuchungen zeigen kein erkennbares Klimasignal, weder für die nahe (2035–2064) noch für die ferne Zukunft (2070–2099). Dies gilt für die Wiederkehrintervalle 5, 10 und 30 Jahre mit je drei Dauerstufen (10 Min., 60 Min., 24 Std.) und für die vier Niederschlagsregionen in der Schweiz, repräsentiert durch 22 MeteoSchweiz-Wetterstationen.
Englund, M., Carbajal, J. P., & Strande, L. (2018). Method to estimate quantities and qualities of faecal sludge. Sandec News, 19, 8-9. , Institutional Repository

The design of appropriate management and treatment solutions for faecal sludge depends on knowing its quantities and qualities. Previously there has been no method to determine reasonable estimates of quantities and qualities; however, Sandec's research is addressing this need.
Manny, L., Fischer, M., & Rieckermann, J. (2018). Policy analysis for better protection of receiving waters during wet weather. Presented at the 11th international conference on urban drainage modelling (UDM 2018). Palermo, Italy. , Institutional Repository

Although CSOs are expensive infrastructures, which are important to reduce pollution from urban areas during wet weather, they are often not operated effectively. Despite of technical difficulties, major problems in CSO monitoring and performance assessment are caused by non-technical bottlenecks. Through a policy analysis we identified organisational and political problems as the biggest obstacles to the effective operation of CSOs. In addition, we investigated effective measures or incentives to overcome organisational and political obstacles. Our results suggest that a surprisingly high 84% of the CSOs operated by Swiss wastewater associations are monitored. In most cases the information is used to improve operation, but not for better planning or for regulatory performance assessment. The most desirable instrument seem to be legislative performance targets, which is preferred by both wastewater associations and cantonal stakeholders. From a political point of view, the cantonal authorities also consider a transfer of competences from the municipalities to the wastewater associations to be effective, i.e. wastewater associations should operate CSOs instead of municipalities. In contrast, Swiss associations prefer financial incentives, such as a one-off subsidy for the installation of CSO monitoring equipment. Before implementing certain instruments, and in particular regulatory instruments, we highly recommend to assess their impact on overall policy processes and individual stakeholders. In the long term, only the implementation of a carefully balanced, uniform strategy can overcome organizational and political barriers and thus can lead to effective success in water protection.
Mauchle, A., Brögli, M., Balmer, H., & Blumensaat, F. (2018). Integrierte Simulation von Kanalnetz und Ara. Modellbasierte Beurteilung von Bewirtschaftungsstrategien an einem Praxisbeispiel. Aqua & Gas, 98(10), 22-29. , Institutional Repository

Für die Optimierung und effektive Ausnutzung bestehender Abwasserinfrastruktur leistet eine integrierte Modellierung einen wichtigen Beitrag. Durch die zusammenhängende Betrachtung von Kanalnetz und ARA ergeben sich vielversprechende Möglichkeiten für einen ganzheitlichen Gewässerschutz. Die Durchführung der vorliegenden Simulationsstudie für das Abwassersystem der ARA Furthof hat gezeigt, dass je nach Bewirtschaftungsstrategie eine Reduktion der Ammoniumemissionen des Gesamtsystems von bis zu 17% im Vergleich zum Referenzzustand möglich ist.
Maurer, M. (2018). Die Zukunft gestalten. Aqua & Gas, 98(10), 30-33. , Institutional Repository

Die Aufgaben der Siedlungsentwässerung werden immer komplexer und anspruchsvoller. Umso wichtiger ist es, engagierte Talente für die Siedlungswasserwirtschaft zu begeistern. Wie das gelingt, erklären sieben junge Forscherinnen und Forscher aus ihrer ganz persönlichen Sicht.
Ort, C., Bijlsma, L., Castiglioni, S., Covaci, A., de Voogt, P., Emke, E., … Kasprzyk-Hordern, B. (2018). Wastewater analysis for community-wide drugs use assessment. In H. H. Maurer & S. D. Brandt (Eds.), Handbook of experimental pharmacology: Vol. 252. New psychoactive substances. Pharmacology, clinical, forensic and analytical toxicology (pp. 543-566). doi:10.1007/164_2018_111, Institutional Repository

Wastewater-based epidemiology (WBE) complements existing epidemiologybased estimation techniques and provides objective, evidence-based estimates of illicit drug use. After consumption, biomarkers drugs and their metabolites - excreted to toilets and flushed into urban sewer networks can be measured in raw wastewater samples. The quantified loads can serve as an estimate for the collective consumption of all people contributing to the wastewater sample. This transdisciplinary approach, further explained in this chapter, has developed, matured and is now established for monitoring substances such as cocaine and amphetamine-type stimulants. Research currently underway is refining WBE to new applications including new psychoactive substances (NPS).
Blumensaat, F., Ebi, C., Dicht, S., Rieckermann, J., & Maurer, M. (2017). Langzeitüberwachung der Raum-Zeit-Dynamik in Entwässerungssystemen mittels Niedrigenergiefunk. KA: Korrespondenz Abwasser Abfall, 64(7), 594-603. doi:10.3242/kae2017.07.001, Institutional Repository

Obgleich gegenwärtig mittels Regenradar und hochauflösender Fernerkundung immer effizienter Daten zu Niederschlag, Topographie und Landnutzung erhoben werden, ist es nach wie vor schwierig, eine hydrologische Überwachung für Entwässerungssysteme mit hinreichender Informationsdichte und -konsistenz zu realisieren. Ob und inwieweit die Technologie des Niedrigenergiefunks (LPWAN) – als Kommunikations-Backbone des Internet der Dinge (IoT) bekannt – das Potenzial hat, diese Lücke zu schließen, diskutieren wir in diesem Beitrag. Grundlage dafür sind unsere Erfahrungen beim Aufbau und dem bis dato einjährigen Betrieb eines Drahtlossensornetzwerks in einem mittelgroßen Schweizer Siedlungsentwässerungsnetz mit einer Sensordichte von über einem Sensor pro Hektar und einer Überwachungsfrequenz von fünf Minuten. Im Einzelnen erörtern wir i) das zugrundeliegende Monitoringkonzept, ii) die technische Spezifikation der Sensorik und der Datenübertragungstechnologie LoRaWANTM und iii) die bisherigen Erfahrungen zur Systemperformance, illustriert durch ein Anwendungsbeispiel.
Spuhler, D., & Rath, M. (2017). Pre-selecting sanitation technology options in Arba Minch, Ethiopia. Sandec News, 18, 16-17. , Institutional Repository

Identifying appropriate, sustainable sanitation technologies is a complex multi-criteria decision-making problem. This systematic procedure has been developed to determine sets of sanitation technology options as input when structured sanitation planning frameworks are used.
Altermatt, F., & Scheidegger, A. (2016). Schmetterlinge. Neujahrsblatt der Naturforschenden Gesellschaft in Zürich NGZH, 218, 105-116. doi:10.5167/uzh-123628, Institutional Repository

Schmetterlinge gehören zu den bekanntesten Insekten. Es gibt eine grosse Vielfalt an Arten. In der Umgangssprache werden die Schmetterlinge in Tagfalter und Nachtfalter (oder «Motten») eingeteilt. Es gibt in der Schweiz 210 verschiedene Tagfalterarten. Ihnen stehen rund 3460 Arten an «Nachtfaltern» gegenüber. Die meisten dieser Arten sind tatsächlich nachtaktiv, es gibt aber eine kleine Gruppe «Nachtfalter», welche auch am Tag zu finden sind (Widderchen sind ebenfalls tagaktiv). Tagfalter haben kolbenförmig verdickte Fühler und stellen die Flügel in Ruheposition senkrecht über dem Körper auf. Nachtfalter haben meist fadenartige oder kammartige Fühler. Sie falten ihre Flügel in der Ruhestellung typischerweise rückwärts über den Körper und fallen, beispielsweise auf einem Baumstamm sitzend, tagsüber kaum auf. Tagaktive Arten kann man auch mit einem Fernglas beobachten. Nachtaktive Arten entziehen sich mehr der Beobachtung. Weil die meisten Arten vom Licht angelockt werden, können sie an einem Lichtturm beobachtet und bestimmt werden. Einige Arten muss man zwecks Bestimmung einfangen.
Fast alle Schmetterlinge sind auf bestimmte Lebensräume angewiesen, und sie können dadurch als Indikatorarten verwendet werden. Am Pfäikersee leben viele Schmetterlingsarten, darunter auch sehr seltene und bedrohte, welche auf Feuchtgebiete angewiesen sind. Wir fanden bei den Tagfaltern vor allem Arten, welche auf Hochstaudenluren, Streuwiesen und Flachmoore spezialisiert sind. Bei den Nachtfaltern gibt es auch einige auf Hochmoore spezialisierte Arten.
Garbani Marcantini, L., Schegg, S., Gresch, M., Mischler, B., & Rieckermann, J. (2016). Ein hierarchischer Regelungsalgorithmus. Praxistaugliche Abflussregelung von Entwässerungsnetzen. Aqua & Gas, 96(10), 48-53. , Institutional Repository

Für einen effektiven Betrieb eines Abwassersystems bietet sich vielerorts eine Abflussregelung an. Dazu empfiehlt sich ein regelbasierter, selbstadaptiver und hierarchischer Regelungsalgorithmus, der allgemein anwendbar ist. Bei der ARA Wohlen steigerte er die Leistung des Entwässerungsnetzes im Mittel um 10–20% und kann ca. 25% der Entlastungsereignisse verhindern.
Rieckermann, J. (2016). "Wir müssen mit Nichtwissen und Unsicherheiten leben und trotzdem schon entscheiden.". Aqua & Gas, 96(10), 10-13. , Institutional Repository

In der schönen Bergwelt von Rigi Kaltbad fand die von Eawag und VSA organisierte Aqua Urbanica 2016 statt. Jörg Rieckermann (Eawag) und seine Mitorganisatoren Günter Gruber (TU Graz), Ulrich Dittmer (Universität Stuttgart) und Michael Burkhardt (HSR Hochschule für Technik Rapperswil) diskutieren im Interview die Themen und Hintergründe der Tagung. Unter anderem unterhalten sie sich über den Wert von guten Messdaten und Modellen, den Umgang mit Spurenstoffen und Unsicherheiten in der Planung sowie die fortschreitende Digitalisierung der Siedlungsentwässerung.
Egger, C., & Maurer, M. (2015). Kanalnetzbemessung unter Unsicherheit. Die Bedeutung des Klimawandels für die hydraulische Funktion von Kanalnetzen. Aqua & Gas, 95(11), 56-63. , Institutional Repository

Menschlich bedingte Einflüsse auf das Klimasystem und eine einhergehende Erhöhung von extremen Niederschlagsintensitäten (in diesem Zusammenhang sind Ereignisse mit Wiederkehrintervall von etwa mindestens einem Jahr von Bedeutung) haben mancherorts bereits zu Anpassungen der Entwässerungssysteme und den zugrunde liegenden Bemessungsregeln geführt. Im vorliegenden Artikel wird die Bedeutung des Klimawandels an einem Beispiel in der Schweiz analysiert und mit anderen niederschlagsbezogenen Unsicherheiten in Verhältnis gesetzt.
Egger, C., Scheidegger, A., Maurer, M., & Reichert, P. (2015). Schätzung der Kanalalterung. Modellbasierte Schätzung des Alterungsverhaltens von Kanalnetzen ohne Datenhistorie. Aqua & Gas, 95(11), 48-54. , Institutional Repository

Modellbasierte Prognosen über die Alterung von Kanalnetzen helfen (langfristige) Konsequenzen möglicher Sanierungsstrategien zu evaluieren. Die Schätzung von Modellparametern, basierend auf heute verfügbaren und oftmals limitierten Informationen, birgt Herausforderungen. Im vorliegenden Artikel wird das Problem fehlender historischer Leitungsdaten erläutert und ein Lösungsansatz dazu aufgezeigt.
Logar, I., Brouwer, R., Maurer, M., & Ort, C. (2015). Wert der Spurenstoffelimination. Eine ökonomische Analyse zum Ausbau Schweizer Abwasserreinigungsanlagen. Aqua & Gas, 95(2), 42-48. , Institutional Repository

Welchen Wert misst die Bevölkerung der Elimination von Mikroverunreinigungen in den Kläranlagen zu? Aus den Antworten von 1000 Deutschschweizern und Deutschschweizerinnen wurde der wirtschaftliche Nutzen des Ausbaus von Abwasserreinigungsanlagen abgeleitet. Der Vergleich mit den veranschlagten Kosten zeigt, dass der Ausbau in der Schweiz gerechtfertigt ist.
Tokarczyk, P., Leitao, J. P., Rieckermann, J., Schindler, K., & Blumensaat, F. (2015). Nutzung von Drohnen und Luftbildern in der Siedlungswasserwirtschaft. Geomatik Schweiz, Géomatique Suisse, Geomatica Svizzera, 113(9), 346-350. doi:10.5169/seals-513919, Institutional Repository

Vor dem Hintergrund von zunehmender Urbanisierung, Klimawandel und alternder Infrastrukturen gewinnt die Analyse und Bewertung von Überflutungen im urbanen Raum aufgrund von Starkregenereignissen zunehmend an Bedeutung. Dazu sind Modelle erforderlich, die das Niederschlag-Abflussverhalten in einem angemessenen zeitlichen und räumlichen Detail beschreiben. Neben Daten zur Menge und Verteilung des Niederschlags gehen in die Modellierung auch Oberflächeneigenschaften ein, insbesondere der Versiegelungsgrad und die Flächennutzung. In dieser Studie untersuchen wir erstmals die Möglichkeit, hochauflösende Landnutzungskarten städtischer Gebiete aus Drohnen(UAV)-Bildern abzuleiten und die Eignung solcher Karten als Datengrundlage für Modellanwendungen in der Siedlungswasserwirtschaft. Wir zeigen, dass die aus UAV-Bildern (automatisch) abgeleiteten Karten zum Versiegelungsgrad hinsichtlich ihrer Genauigkeit mit Karten auf Basis konventioneller Luftbilder vergleichbar sind. Darüber hinaus zeigt sich in unseren Experimenten, dass sich die Genauigkeit der Versiegelungskarten bedeutend steigern lässt, indem man diskriminative Lernverfahren in Verbindung mit Bildinformation aus einer grösseren Nachbarschaft benutzt.
Larsen, T. A., Udert, K. M., & Lienert, J. (2014). Abwassertrennung und Dezentralisierung. Aqua & Gas, 94(1), 52-54. , Institutional Repository

Ist eine ressourcenschonende Abwasserreinigung durch Abwassertrennung und Dezentralisierung realistisch? Rund 40 international bekannte Wissenschafter und Wissenschafterinnen behandeln auf 520 Seiten in einem 2013 erschienenen Buch nuanciert diese Fragestellung. Die Editoren der Eawag diskutieren das Thema des Buches im Schweizer Kontext.
Maurer, M., & Lienert, J. (2014). La durabilité des infrastructures dans un avenir incertain. Eawag News [éd. fr.] (2), 1-9. Retrieved from http://newsletter.eawag.ch/e/8bbab41cc9ae86ac/nl/webversion/c55eed59e3a945f06c3247b5/fr.html, Institutional Repository

Les infrastructures d’eau potable et d’assainissement sont des biens pérennes appelés à être transmis de génération en génération. Leur gestion et leur planification s’inscrivent donc dans la durée. Mais comment assurer leur efficacité dans un avenir nécessairement incertain? Comment gérer les incertitudes? Comment quantifier la durabilité dans la planification? L’Eawag s’est penché sur ces questions dans le Programme national de recherche 61.
Maurer, M., & Lienert, J. (2014). Sustainable water infrastructure planning for an uncertain future. Eawag News [engl. ed.] (2), 1-8. Retrieved from http://newsletter.eawag.ch/e/8bbab41cc9ae86ac/nl/webversion/c55eed59e3a945f06c3247b5/en.html, Institutional Repository

Water supply and wastewater disposal networks have a long service life and thus require long planning horizons. How can the services they provide be assured for future generations? How are we to deal with the associated uncertainties? How can sustainability be included in our planning procedures using quantitative methods? These questions were addressed by Eawag as part of National Research Programme 61.
Maurer, M., & Lienert, J. (2014). Wasserinfrastrukturen nachhaltig in eine unsichere Zukunft führen. Eawag News [dtsch. Ausg.] (2), 1-8. Retrieved from http://newsletter.eawag.ch/e/8bbab41cc9ae86ac/nl/webversion/c55eed59e3a945f06c3247b5/de.html, Institutional Repository

Die Wasserversorgung und Abwasserentsorgung sind Generationenbauwerke mit langer Lebensdauer und entsprechend langen Planungshorizonten. Wie können wir ihre Leistungen nachhaltig in die Zukunft führen? Wie gehen wir mit den Unsicherheiten um? Wie beziehen wir die Nachhaltigkeit quantitativ in unsere Planungsansätze ein? Im Rahmen des nationalen Forschungsprogramms 61 ging die Eawag diesen Fragen nach.
Ronteltap, M., Dodane, P. H., & Bassan, M. (2014). Overview of treatment technologies. In L. Strande, M. Ronteltap, & D. Brdjanovic (Eds.), Faecal sludge management. Systems approach for implementation and operation (pp. 97-122). London: IWA Publishing. , Institutional Repository

In the preceding chapters the characteristics of faecal sludge (FS) were discussed, an introduction to treatment mechanisms was given, and it was described how FS can be collected from the point of storage and delivered to treatment facilities. [...]
Scholten, L., Egger, C., Zheng, J., & Lienert, J. (2014). Multikriterielle Entscheidungsanalyse. Neue Ansätze für langfristige Infrastrukturplanung in der Wasserver- und -entsorgung. Aqua & Gas, 94(5), 62-69. , Institutional Repository

Im NFP-61-Forschungsprojekt «Langfristige Planung nachhaltiger Wasserinfrastrukturen» der Eawag wurden für die Planung der Wasserver- und Abwasserentsorgung unterschiedliche Alternativen miteinander verglichen. Die multikriterielle Entscheidungsanalyse berücksichtigt dabei die Präferenzen der Akteure und die Szenarienanalyse testet die Robustheit der Alternativen gegenüber unsicheren Zukunftsentwicklungen. Dieser neue Ansatz ergänzt die generelle Wasserversorgungsplanung (GWP) sowie die generelle Entwässerungsplanung (GEP) und bringt die Infrastrukturplanung auf eine nachhaltige Basis.
Scholten, L., Maurer, M., & Scheidegger, A. (2014). Zustandsmodellierung kleiner Versorgungsnetze. Ergebnisse aus dem NFP-61-Projekt "Langfristige Planung nachhaltiger Wasserinfrastrukturen". Aqua & Gas, 94(6), 51-58. , Institutional Repository

Den zukünftigen Sanierungsbedarf abzuschätzen, ist eine der grossen Herausforderungen für viele Wasserversorger. Dabei haben insbesondere kleinere Netze mit viel Erfahrungswissen und wenigen Daten besondere Schwierigkeiten. Der Artikel gibt einen Überblick zur Vorhersage des Netzzustandes und über wichtige Aspekte bei der Wahl der entsprechenden Modelle. Ein Folgeartikel zeigt an einem Beispiel die Anwendung des an der Eawag neu entwickelten Schadensmodells.
Zabaleta, I., Scholten, L., & Zurbrügg, C. (2014). A decision support tool for selecting organic waste treatment technologies. Sandec News, 15, 5. , Institutional Repository

Sandec is instituting the Selecting Organic Waste Treatment Technologies Project in order to develop a decision support tool that will assist municipalities in their organic waste treatment decisions. The first field test takes place in 2014 in San Fernando City, La Union, Philippines.
Boller, M. (2013). Source control and source separation: the Swiss experience. In T. A. Larsen, K. M. Udert, & J. Lienert (Eds.), Source separation and decentralization for wastewater management (pp. 439-446). London: IWA Publishing. , Institutional Repository

In recent years, several buildings have been constructed in Switzerland based on decentralized concepts of fully or partly self-sufficient energy and water management. These first attempts covered rainwater and snowmelt harvesting, reuse of greywater, brownwater and blackwater, urine separation and recovery of nutrients from urine. They demonstrate that in-house technology is now ready to accommodate dramatic changes in urban water cycles to achieve higher levels of environmental sustainability. As a rule, the technologies tested in six key buildings usually performed successfully and could be operated satisfactorily over long periods. Some conditions necessary for constructing such systems and possible reasons for project failures are discussed.
Erisman, J. W., & Larsen, T. A. (2013). Nitrogen economy of the 21st century. In T. A. Larsen, K. M. Udert, & J. Lienert (Eds.), Source separation and decentralization for wastewater management (pp. 45-58). London: IWA Publishing. , Institutional Repository

In the past 50 100 years, the world's nitrogen cycle has been radically altered by global food and energy production systems, which have caused an increase in the total production rate of reactive nitrogen by a factor of 1.5 to 2 compared to its natural production. Reactive nitrogen, Nr, encompasses all forms of nitrogen occurring on earth except for atmospheric N2. Reactive nitrogen both promotes and endangers human welfare. Humanity benefits from energy use and particularly from the food and feed produced through the availability of mineral fertilizer. These activities bring enormous benefits, but losses of nitrogen from agriculture, human waste and combustion processes also have detrimental effects on the environment (see e.g., Galloway et al. 2008). These effects include the exceeding of critical loads resulting in loss of biodiversity, groundwater pollution, eutrophication of inland ecosystems and coastal areas causing algae blooms and fish kills, elevated atmospheric levels of ammonia, nitrogen oxide, nitrous oxide and aerosols resulting in climate change and/or human health impacts (Cowling et al. 2002; Galloway et al. 2003, 2008; Townsend et al. 2003; Reid et al. 2005). [...]
Larsen, T. A., Udert, K. M., & Lienert, J. (2013). Editorial. In T. A. Larsen, K. M. Udert, & J. Lienert (Eds.), Source separation and decentralization for wastewater management (pp. 1-10). London: IWA Publishing. , Institutional Repository

Why are we editing a book about source separation and decentralization? We live in Switzerland, an industrialized country with a highly advanced and well-functioning wastewater management system. But even in Switzerland, the central system is reaching its limits, shortcomings, which become very obvious from a global perspective. We are proud to have been able to assemble contributions from renowned authors worldwide from both research and practice. They share with us their experience and thoughts about the current wastewater system. They analyze its advantages, but also deficiencies and they have the courage to breach the paradigm that central wastewater treatment is the only possible approach in urban areas. Many of the authors of this book are pioneers in the field and have been paving the way to a more sustainable and equitable handling of wastewater. We are greatly indebted to all the authors for their contributions to this book, but even more so for their continuous research on source separation and decentralization. We hope that this book will help develop this new area into a mature field in science as well as in practice. [...]
Larsen, T. A., & Gujer, W. (2013). Implementation of source separation and decentralization in cities. In T. A. Larsen, K. M. Udert, & J. Lienert (Eds.), Source separation and decentralization for wastewater management (pp. 135-150). London: IWA Publishing. , Institutional Repository

In the next decades, global population growth will be dominated by an increasing urban population. As seen from Figure 10.1, this growth will primarily take place in "less developed" regions. Maintaining urban hygiene and healthy water resources in these regions will be a formidable, expensive and time consuming task. In Switzerland, water pollution control had a very high public priority in the period from 1960 to 1990 and the construction of sewers and centralized wastewater treatment plants was highly subsidized by federal and state agencies in order to speed up the construction process. Nevertheless it took about 27 years to increase the connection of the population and industry to first-generation wastewater treatment plants (BOD removal only) from 10% to 90%. Second-generation treatment, which includes nutrient removal, is still in progress. Thus, experience tells us that under ideal conditions, in a rich country, with a well established engineering community and well organized state agencies, the establishment of efficient and stable wastewater treatment infrastructure is subject to a time constant of at least 50 years. [...]
Maurer, M., & Jordi, B. (2013). Besseres Management der Infrastruktur. Organisatorische, betriebliche und technische Anpassungen im Abwasserbereich. Aqua & Gas, 93(2), 24-32. , Institutional Repository

Die Abwasserinfrastruktur in der Schweiz ist weitgehend gebaut. In Zukunft soll die Leistungsfähigkeit der Kanalnetze und Kläranlagen gesichert und die Siedlungsentwässerung durch organisatorische, betriebliche und technische Anpassungen gezielt optimiert werden. Moderne Mess- und Regeltechnik sowie die Fernüberwachung erlauben heute die Anwendung anspruchsvollerer Verfahren. Dies ermöglicht Kanalisation und ARA als Einheit zu bewirtschaften und dadurch zum Beispiel bestehende Kapazitätsreserven besser zu nutzen. Der Eawag-Bericht «Abwasserentsorgung 2025» unterbreitet zahlreiche Vorschläge für ein besseres Management der Infrastruktur.
Maurer, M. (2013). Full costs (dis-)economies of scale and the price of uncertainty. In T. A. Larsen, K. M. Udert, & J. Lienert (Eds.), Source separation and decentralization for wastewater management (pp. 85-100). London: IWA Publishing. , Institutional Repository

The sewage systems of the 19th century were introduced as an emergency solution to a health crisis. In Britain, an average of 26% of children died before the age of five, in the cities this average was around 48% (Brown 2003). The draining of excrements and excess water in European cities improved the quality of life and health standards dramatically. The powerful sewer system also enabled a freshwater supply network which further improved the functions of the sewers. Since then, this successful solution has been continuously improved, but at its core it remains a conveyance system with some very important characteristics: [...]
Scheidegger, A., Beutler, P., & Maurer, M. (2013). Prognosen zum Sanierungsbedarf. Schweizer Kanalisation – der Wert guter Daten für Einsichten in die Zukunft. Aqua & Gas, 93(1), 16-20. , Institutional Repository

Die Schweiz hat hervorragend ausgebaute Infrastrukturnetze. Dies gilt auch für die öffentliche Kanalisation, die einen geschätzten Wiederbeschaffungswert von rund 66,4 Mia. Franken hat (VSA 2011, [1]). In den letzten Jahren wurde vermehrt darauf hingewiesen, dass nicht ausreichend in den Unterhalt investiert wird und somit zukünftig mit einem grossen Anstieg des Sanierungsbedarfs zu rechnen ist. Im vorliegenden Artikel wird eine Prognose für den schweizweiten Sanierungsbedarf der Kanalisation vorgestellt.
Strähl, S., Ort, C., Siegrist, H., Thomann, M., Obrecht, J., & Kurz, E. (2013). Stickstoffelimination in Schweizer ARA. Weitere Entlastung der Oberflächengewässer. Aqua & Gas, 93(5), 74-84. , Institutional Repository

Mit dem Abwasser gelangen pro Jahr rund 41 000 t Stickstoff (N) in die Schweizer Kläranlagen. Davon werden heute etwa 18 000 t in den ARA eliminiert. Mit Hilfe einer Kombination von neu entwickelten Reinigungsverfahren, die zum Teil bereits gut etabliert und auf dem Stand der Technik sind, liessen sich die Oberflächengewässer im Inland um weitere 6600 t Stickstoff entlasten, wie die vorliegende Studie zeigt. Bei Ausschöpfung des Reduktionspotenzials in den 160 grösseren ARA ist mit Gesamtinvestitionen von 344 Mio. Franken und jährlichen Betriebskosten von 27 Mio. Franken zu rechnen.
von Horn, J., & Jordi, B. (2013). Abwasserentsorgung der Zukunft. Entwicklung und Zustand der Wasserqualität als Folge der Siedlungsentwässerung. Aqua & Gas, 93(2), 16-23. , Institutional Repository

Aus Sicht der Wasserqualität zählen die Belastung der Vorfluter durch Mikroverunreinigungen, Mischwasserentlastungen aus dem Kanalnetz sowie die Auswirkungen des Klimawandels zu den grössten Herausforderungen für den Abwassersektor in der Schweiz. Zu diesem Schluss kommt der Bericht «Abwasserentsorgung 2025», den das Wasserforschungsinstitut Eawag im Auftrag des Bundesamtes für Umwelt (BAFU) erarbeitet hat. Ausgehend von einer Situationsanalyse der Siedlungsentwässerung und Abwasserbehandlung deckt die Studie bestehende Schwächen auf und leitet daraus eine Reihe von Handlungsempfehlungen zur Optimierung der Systeme ab.
von Horn, J., Maurer, M., Londong, J., Lautenschläger, S., Steinmetz, H., Hillenbrand, T., & Dockhorn, T. (2013). Welche neuartigen Sanitärsysteme (NASS) sind für Deutschland besonders Erfolg versprechend?. KA: Korrespondenz Abwasser Abfall, 60(8), 673-683. doi:10.3242/kae2013.08.002, Institutional Repository

The paper summarizes the current state of knowledge regarding novel sanitation systems. It is based on the outcomes of a DWA workshop in June 2012, at which the most important drivers for implementing novel sanitation systems in Germany were identified and at which participants determined those novel sanitation systems that were most promising for Germany in the next 15 years. In addition to the outcomes of the workshop itself, the paper also contains additional material from reference literature and thus provides a comprehensive overview of the current situation.
Koch, G., Lienert, J., & Maurer, M. (2012). Judit Lienert: "Wir arbeiten mit einer multikriteriellen Entscheidungsanalyse.". Aqua & Gas, 92(5), 8-9. , Institutional Repository

Das Nationale Forschungsprogramm NFP 61 will wissenschaftlich fundierte Grundlagen zum künftigen Umgang mit Wasser bereitstellen. Es verfügt über einen Finanzrahmen von zwölf Millionen Franken und dauert ab Januar 2010 vier Jahre. Die Praxisrelevanz wird im Programm stark gewichtet. Aqua & Gas stellt an dieser Stelle jeweils ein Projekt vor. In diesem Beitrag geben Judit Lienert und Max Maurer vom NFP-61-Projekt «Langfristige Planung nachhaltiger Wasserinfrastrukturen» (SWIP) Einblick in ihre Projektarbeit.
Staufer, P., & Ort, C. (2012). Diffuse Einträge aus Siedlungen. Ergebnisse einer Situationsanalyse. Aqua & Gas, 92(11), 42-50. , Institutional Repository

Regenwassereinleitungen und Mischwasserentlastungen tragen erheblich zu den Frachten im Gewässer bei. Die Situationsanalyse charakterisiert diese Emissionen für Mikroverunreinigungen aus dem häuslichen Abwasser und dem Regenabfluss. Die Modellergebnisse weisen substanzabhängig auf kritische Stellen in kleinen und mittelgrossen Gewässern in verdichteten Siedlungsräumen hin.
Boller, M. (2011). Forschen und lehren für die Praxis. Eawag News [dtsch. Ausg.], 71, 30-33. , Institutional Repository

Während fast vierzig Jahren an der Eawag hat Willi Gujer die Siedlungswasserwirtschaft in der Schweiz und international massgeblich mitgeprägt. Wichtig waren dem Forscher dabei immer auch der Brückenschlag in die Praxis und die Ausbildung junger Fachleute. Ein Rückblick und eine Würdigung aus Anlass seiner Pensionierung.
Boller, M. (2011). Research and teaching for practitioners. Eawag News [engl. ed.], 71, 30-33. , Institutional Repository

During a career at Eawag which spanned almost 40 years, Willi Gujer helped to shape the urban water management sector both in Switzerland and internationally. As a researcher, he always attached great importance to training young specialists and reaching out to practitioners. Here, to mark his retirement, we look back over his career and celebrate his achievements.
Dockhorn, T., Hillenbrandt, T., Langergraber, G., Londong, J., Maurer, M., Niederste-Hollenberg, J., … Thaler, S. (2011). Bedarf für Forschung und Entwicklung im Bereich Neuartiger Sanitärsysteme (NASS). Arbeitsbericht der DWA-Arbeitsgruppe KA-1.8 „F+E-Bedarf" im Fachausschuss „Neuartige Sanitärsysteme". KA: Korrespondenz Abwasser Abfall, 58(6), 646-655. doi:10.3242/kae2011.07.002, Institutional Repository

Need for Research and Development in the Field of Novel Sanitation Systems
Report by DWA Working Group KA-1.8 “R&D Needs” within the Technical Committee “Novel Sanitation Systems”
Within DWA Technical Committee KA-1 “Novel sanitation systems”, working group KA-1.8 “R&D needs” has elaborated the present report on the need for R&D in the field of novel sanitation systems. The term novel sanitation systems comprises two basic approaches that promise to extent the limits and possibilities of “conventional” urban drainage systems. On the one hand, the goal is to utilize sewage ingredients (nutrients, organic substances, etc.), and on the other hand, the intention is to do without the complex and expensive transport of sewage in large pipes. The basic principle of resource-oriented sanitation systems is the separate collection and treatment of partial flows. Currently, novel sanitation systems are not in conformity with generally accepted engineering standards. The report identifies existing deficits and necessary developments in the affected technical areas (above all capturing of material flow and separation, collection, transport and discharge as well as treatment of material flow) and illustrates relevant, cross-system aspects (e.g. legal framework conditions, drivers and obstacles, acceptance and evaluation). A systematic status analysis has shown a great need for further research and development. Among other things, research, development, and pilot projects are necessary for a successful introduction of novel sanitation systems. Politicians must create effective incentives and control mechanisms.
Larsen, T. A. (2011). Cleantech for wastewater treatment of the future. Eawag News [engl. ed.], 70, 30-33. , Institutional Repository

In wastewater treatment, environmentally sound and resource-efficient technologies should also exploit the resources contained in wastewater itself. Radically new approaches such as urine source separation and the recovery of nutrients for urine based fertilizers point the way to a future which goes beyond conventional sewers and wastewater treatment plants.
Larsen, T. A. (2011). Cleantech für die Abwasserreinigung der Zukunft. Eawag News [dtsch. Ausg.], 70, 30-33. , Institutional Repository

Umwelt- und ressourcenschonende Technologien in der Abwasserreinigung müssen auch eine optimale Nutzung der Ressourcen im Abwasser einschliessen. Völlig neue Konzepte wie die Separierung des Urins direkt an der Quelle und die Aufbereitung von dessen Nährstoffen zu Dünger weisen in eine Zukunft jenseits der konventionellen Kläranlage und Kanalisation.
Larsen, T. A., & Maurer, M. (2011). Source separation and decentralization. In P. Wilderer (Ed.), Vol. 4. Treatise on water science (pp. 203-229). doi:10.1016/B978-0-444-53199-5.00083-X, Institutional Repository

Toward the end of the 1990s, a special issue on sustainable sanitation was published by Water Science and Technology, a journal of the International Water Association (IWA). In this issue, several authors discussed the issue of source-separation technologies in the area of wastewater management (Henze, 1997). All major sources of combined wastewater were covered: industrial wastewater (Visvanathan and Hufemia, 1997), storm water (Boller, 1997), gray water (domestic wastewater without toilet waste; Jeffrey et al., 1997), urine (Hanäus et al., 1997; Larsen and Gujer, 1997), and black water (combined toilet waste; Otterpohl et al., 1997).
Whereas separate discharge of storm water and separate treatment of industrial wastewater were already well-known concepts, source separation for domestic wastewater was at that time primarily recognized as an inexpensive sanitation technology for poor, rural areas. For urban areas, only sewer-based wastewater management was considered suitable. The above-mentioned special issue challenged this conventional wisdom with the idea that source separation could potentially compete with end-of-pipe technologies for all wastewaters, even in urban areas. The main concepts behind this idea were that, on the one hand, it would be more resource efficient to treat very concentrated solutions such as urine (Larsen and Gujer, 1997) and that, on the other hand, local recycling of (gray) water would increase flexibility of the urban water management system (Jeffrey et al., 1997). [...]
Maurer, M. (2011). Die zukünftige Wasserinfrastruktur planen. Eawag News [dtsch. Ausg.], 70, 22-25. , Institutional Repository

Eine nachhaltige Zukunftsplanung der Schweizer Trinkwasserversorgung und Abwasserentsorgung muss auch zukünftige Bedürfnisse und Unsicherheiten berücksichtigen. Gute Lösungen zeichnen sich dabei weniger durch möglichst geringe Kosten aus, sondern berücksichtigen den optimalen Nutzen über die gesamte Lebensdauer und sind lokal angepasst. Eine Standardlösung für die Schweiz gibt es nicht.
Maurer, M. (2011). Strategic planning of urban water infrastructure. Eawag News [engl. ed.], 70, 22-25. , Institutional Repository

Sustainable strategic planning of Switzerland's drinking water supply and wastewater management infrastructure has to take future demand and uncertainties into account. Rather than aiming to reduce costs as far as possible, sound solutions seek to optimize benefits over the entire lifespan and are adapted to local conditions. There is no "one-size-fits-all" solution for the country as a whole.
Vollenweider, S., Bukowiecki, A., Dominguez, D., & Maurer, M. (2011). Management kommunaler Netzinfrastruktur. Standortbestimmung und Handlungsbedarf am Beispiel des Wassersektors. GWA Gas, Wasser, Abwasser, 91(5), 309-314. , Institutional Repository

Management of Municipal Network. Infratructures. Status Assessment and Requirement for Action using the Example of the Water Sector. Municipal authorities manage a substantial infrastructure portfolio, which includes safe supply in line with demand, drainage from residential areas, transport and communications. These municipal authority network infrastructures have a replacement value of CHF 460 billion. Long-term maintenance of the services associated with them is an important public duty. A working group from Wasser-Agenda 21 (Water Agenda 21) analysed the deficits which threaten the fulfilment of this duty using the example of the water sector. The article summarises the group’s findings, highlights areas where action needs to be taken and discusses appropriate countermeasures.
Hug, T., Dominguez, D., & Maurer, M. (2010). The cost of uncertainty and the value of flexibility in water and wastewater infrastructure planning. Proceedings of the Water Environment Federation. (pp. 487-500). Presented at the Cities of the future/urban river restoration 2010. doi:10.2175/193864710798284832, Institutional Repository

Planning of urban water and wastewater infrastructures is based on assumptions about the longterm future of the service area. Important factors, such as demand development, carry large uncertainties and have a substantial impact on plant size and ultimately on costs. In this paper we attempt to quantify the economic consequences of these uncertainties for wastewater treatment plants. As a measure for the specific costs we applied the specific net present value (SNPV) as introduced by Maurer (2009). Based on an exponential growth rate model we simulated random scenarios with different demand development and their economic effect. The results demonstrate that the SNPV rises with increasing rate of demand growth or decline, as well as with increasing uncertainty about the future demand. This indicates that ignoring uncertainty in an engineering economic analysis, may considerably under-estimate specific costs. Over-sizing plants as one strategy to cope with future demand uncertainty increases the specific costs even further. Implementing flexible systems as another strategy, however, reduces such additional costs as they can follow the actual demand more closely than large centralized plants. Consequently, there is an economic value of flexibility. We discuss its role in strategic planning of urban water infrastructure.
Behra, R., Kägi, R., Navarro, E., Burkhardt, M., & Sigg, L. (2009). Effects of engineered nanoparticles. Eawag News [engl. ed.], 67, 22-24. , Institutional Repository

As nanoparticles are already widely used, it was only too likely that they would ultimately find their way into the environment. This has now been demonstrated for the first time by Eawag studies - which also show how engineered nanoparticles can exert toxic effects on aquatic organisms.
Behra, R., Kaegi, R., Navarro, E., Burkhardt, M., & Sigg, L. (2009). Les nanoparticules synthétiques et leurs effets. Eawag News [éd. fr.], 67, 22-24. , Institutional Repository

Les nanoparticules sont déjà employées dans un grand nombre de domaines. Il semble donc hautement probable qu’elles se retrouvent tôt ou tard dans l’environnement. Des études de l’Eawag ont démontré pour la première fois la réalité de ce phénomène et ­montrent d’autre part de quelle manière les nanoparticules synthétiques peuvent perturber les organismes aquatiques.
Behra, R., Kaegi, R., Navarro, E., Burkhardt, M., & Sigg, L. (2009). Synthetische Nanopartikel und ihre Wirkung. Eawag News [dtsch. Ausg.], 67, 22-24. , Institutional Repository

Nanopartikel werden heute bereits breit eingesetzt. Da ist es nur wahrscheinlich, dass sie früher oder später auch in der Umwelt landen. Studien der Eawag wiesen dies nun erstmals nach und zeigen darüber hinaus, auf welche Weise sich synthetische Nanopartikel negativ auf Gewässerorganismen auswirken können.
Burkhardt, M., Zuleeg, S., Marti, T., Boller, M., Vonbank, R., Brunner, S., … Chèvre, N. (2009). Biocides dans les eaux de façades – solutions à trouver. Bulletin de l'ARPEA: Journal Romand de l'Environnement, 45(241), 13-16. , Institutional Repository

Les peintures de façades, de même que les enduits, contiennent des biocides pour les protéger contre le développement d’algues et de champignons. Nos études ont montré que ces substances pouvaient être lessivées par les pluies et ainsi polluer les eaux de ruissellement ainsi que les eaux de surface. Le lessivage des façades est influencé par différents paramètres comme l’architecture, l’exposition, le temps, les substances actives ou les produits utilisés. Pour le législateur se pose ainsi la question de la gestion durable des eaux de ruissellement. Or, c’est seulement en réunissant tous les acteurs touchés par cette problématique que des solutions durables pour le sol et les eaux pourront être trouvées.
Burkhardt, M., Zuleeg, S., Marti, T., Boller, M., Vonbank, R., Brunner, S., … Carmeliet, J. (2009). Schadstoffe aus Fassaden. Tec21, 135(3-4), 28-31. doi:10.5169/seals-108210, Institutional Repository

Zum Schutz vor Algen- und Pilzbefall werden kunststoff gebundene Farben und Putze für Aussenwärmedämmungen mit Bioziden ausgerüstet. Neue Untersuchungen zeigen, dass diese Problemstoffe ausgewaschen werden und über das abfliessende Regenwasser in die Gewässer gelangen können. Damit wird die bisher praktizierte Regenwasserentsorgung infrage gestellt. Bei der Lösung des Problems sind nicht nur die Produkthersteller gefordert, sondern auch Architekten und Bauherren.
Maurer, M. (2009). Approvisionnement en eau 2025. Sécurité de l’approvisionnement. GWA Gas, Wasser, Abwasser, 89(9), 741-747. , Institutional Repository

In Switzerland, the public waterworks do not even use two percent of the annual rainfall for drinking water supply. In view of the available reserves in lakes and ground water deposits, the country will not be threatened in the foreseeable future with supply shortages. Primarily during longer dry periods supply shortfalls can definitely occur on a local or regional level, as was shown in the hot summer of 2003. However, possible shortages are absorbed by highly capable technical and organisational networking among water suppliers.
Maurer, M. (2009). Ganzheitliches Einzugsgebietsmanagement (GEM). Schlussfolgerungen aus dem Expertenworkshop vom 1.– 3. Oktober 2008 in Emmetten. GWA Gas, Wasser, Abwasser, 89(3), 197-202. , Institutional Repository

Integrales oder Ganzheitliches Einzugsgebietsmanagement (GEM) ist eine der aktuellen Forderungen an die moderneWasserwirtschaft. Politische, organisatorische und fachtechnische Grenzen sollen überwunden werden, um die Gewässer, die Wasserressourcen und die Infrastrukturen ganzheitlich und kosteneffizient zu bewirtschaften. Wie aber soll dies konkret in der Schweiz aussehen? Wird die Wasser-Rahmenrichtlinie der EU übernommen oder gilt es, eine schweizerische Version zu erarbeiten? Der VSA Expertenworkshop vom 1.–3. Oktober 2008 in Emmetten nahm sich dieser Frage an, entwickelte gangbare Ideen und lotete den Handlungsbedarf für die Umsetzung von GEM in der Schweiz aus.
Maurer, M. (2009). Ganzheitliches Einzugsgebietsmanagement: Ansätze und Formen. Ingenieurbiologie: Mitteilungsblatt, 19(2), 3-7. , Institutional Repository

Ganzheitliches oder integrales Einzugsgebietsmanagement (IEM) ist eine der aktuellen Forderungen an die moderne Wasserwirtschaft. Wie das IEM in der Schweiz konkret aussehen könnte, wurde im VSA-Expertenworkshop vom 1. bis 3. Oktober 2008 in Emmetten diskutiert. Vielversprechende Ansätze für IEM sind in der Schweiz bereits vorhanden, die aber alle im Moment auch noch substantielle Schwächen zeigen. Deutlich wurde, dass das ganzheitliche Einzugsgebietsmanagement für die schweizerische Siedlungswasserwirtschaft ein zentrales Thema wird. Als Konsequenz dieser Veranstaltung hat der VSA-Vorstand das IEM als Kernthema in seine Arbeiten und Bestrebungen aufgenommen.
Maurer, M. (2009). Wasserversorgung 2025. Aspekte der Versorgungssicherheit. GWA Gas, Wasser, Abwasser, 89(1), 7-12. , Institutional Repository

In Switzerland, the public waterworks do not even use two percent of the annual rainfall for drinking water supply. In view of the available reserves in lakes and ground water deposits, the country will not be threatened in the foreseeable future with supply shortages. Primarily during longer dry periods supply shortfalls can definitely occur on a local or regional level, as was shown in the hot summer of 2003. However, possible shortages are absorbed by highly capable technical and organisational networking among water suppliers.
Rossi, L., Lienert, J., & Larsen, T. (2009). Lutte à la source pour la rétention de microplluants dans les eaux. Le concept NoMix. Techniques, Sciences, Méthodes, 104(4), 53-59. doi:10.1051/tsm/200904053, Institutional Repository

Micropollutants represent one of today’s main concerns for surface water management. One of the major sources of micropollutants to the environment is linked with the discharge of pharmaceutical residues by the population. Although some technologies exist today to deal with these kinds of discharges, source-control strategies constitute a very interesting solution and are illustrated in this paper. We focus here on the NoMix technology, an innovative at-source solution to separate liquid and solid wastes. The NoMix new technology proposes to separate urine directly at the source. Urine (1.5 litre/inhabitant per day)constitutes less than 1% of the volume processed in waste water treatment plants. However, it contains the most important part of nutrients (80% nitrogen, 50% phosphorus) and a major part of the pharmaceuticals released by the human metabolism (64%, ± 27%). A separate collection and treatment of urine offers thus an interesting potential for micropollutants removal. The NoMix concept has been studied for many years by Eawag (Swiss Federal Institute of Aquatic Science and Technology) within the framework of an inter- and trans-disciplinary project entitled “Novaquatis”.The results of this project show that the NoMix technology would be significant to reduce at-source micropollutants. Moreover, it allows the nutrients produced in urban areas to be recycled, once treated, as fertilisers for agriculture. This article briefly presents the concept of at-source control, as wellas the main results of the Novaquatis project.
Wittmer, I., & Burkhardt, M. (2009). Dynamics of biocide and pesticide input. Eawag News [engl. ed.], 67, 8-11. , Institutional Repository

Biocides and pesticides are used to control harmful organisms in agriculture and in urban areas. But how do these substances ultimately find their way into natural waters? And is agriculture in fact the main source of water pollution? These questions are being investigated by Eawag researchers in various projects.
Wittmer, I., & Burkhardt, M. (2009). Dynamik von Biozid- und Pestizideinträgen. Eawag News [dtsch. Ausg.], 67, 8-11. , Institutional Repository

Biozide und Pestizide werden in der Landwirtschaft und im Siedlungsraum eingesetzt, um Schädlinge zu bekämpfen. Doch welche Wege nehmen diese Stoffe vom Einsatzort bis ins Gewässer? Und ist die Landwirtschaft tatsächlich die Hauptverursacherin der Gewässerbelastung? Fragen, die die Eawag in verschiedenen Projekten erforscht.
Wittmer, I., & Burkhardt, M. (2009). Dynamique des rejets de biocides et de pesticides. Eawag News [éd. fr.], 67, 8-11. , Institutional Repository

Les produits biocides et les pesticides sont utilisés dans l’agriculture et en milieu urbain pour lutter contre divers types de nuisibles. Mais quel chemin ces composés parcourent-ils de leur lieu d’utilisation jusqu’au milieu aquatique? Et l’agriculture, est-elle vraiment la principale source de pollution des eaux? Ce sont là des questions que l’Eawag aborde dans le cadre de différents projets.
Zurbrügg, C., Bufardi, A., Tilley, E., Maurer, M., & Truffer, B. (2009). Decision-making for sanitation systems. Sandec News, 10, 20-21. , Institutional Repository

This Eawag project addresses the various decision-making aspects in sanitation system and technology selection as a support tool for choosing the best available options to secure sustainable sanitation systems.
Boller, M. (2008). Maßnahmen im urbanen Bereich. In S. Fuchs, S. Fach, & H. H. Hahn (Eds.), Schriftenreihe SWW: Vol. 128. Stoffströme in Flussgebieten - von der Bilanzierung zur Bewirtschaftung (pp. 184-197). Retrieved from https://isww.iwg.kit.edu/2055.php, Institutional Repository

Die in den letzten Jahren erarbeiteten Übersichten zu grossräumigen Bilanzierungen von Stoffströmen in Flusseinzugsgebieten haben wesentlich dazu beigetragen, die Relevanz einzelner Schadstoffe, insbesondere aber die Herkunft dieser Stoffe zu gewichten. Daraus abgeleitet, konnten Prioritäten gesetzt und mögliche Massnahmen abgeleitet werden. Die Quantifizierung der Stoffeinträge in die Gewässer und andere Umweltkompartimente erlaubte, das Augenmerk von Entscheidungsträgern auf die Problematik bisher wenig oder nicht beachteter Stoffströme zu lenken und auf diese Weise einen gewissen politischen Druck auf Initiativen zu weitergehenden Massnahmen im Gewässerschutz auszuüben. Inzwischen wurde von Behörden und Fachgremien die Problematik von Dach- und Strassenwasserabflüssen erkannt und die Bereitschaft, entsprechende Massnahmen zur Eindämmung und Umlenkung umweltschädigender Stoffströme einzuleiten, ist erheblich gestiegen.
Es ist jedoch offensichtlich, dass grossräumige Massenbilanzen einzelner Schadstoffe nicht ausreichen, eine detaillierte Massnahmenplanung durchzuführen. Vor allem technische Massnahmen bedingen die Kenntnis der lokalen Verhältnisse, um im Sinne von Kosten-Nutzen-Betrachtungen die besten Lösungen zu treffen. Der Nachweis ökologischer Beeinträchtigungen wird oft nur kleinräumig sichtbar, beispielsweise auf gewissen Flussstrecken, in kleinen Fliessgewässern oder in Versickerungsanlagen.
Boller, M., Velten, S., Peter, A., Hammes, F., & Helbing, J. (2008). Trinkwasseraufbereitung mittels Aktivkohle. Neue Erkenntnisse. GWA Gas, Wasser, Abwasser, 88(1), 27-35. , Institutional Repository

Also in new process trains for potable water production including ozonation, activated carbon and membrane filtration, activated carbon contributes substantially to quality improvement and assurance. The treatment fulfills three tasks such as particle separation, adsorption and fixed bed biofiltration. Experiments with lake water reveal that fresh activated carbon exhibits an enormous capacity to adsorb specific micropollutants as well as fractions of the natural organic material (NOM) which may have detrimental effects on subsequent ultrafiltration. Unfortunately, the presence of certain high-molecular NOM fractions leads to a rapid decrease of the adsorption performance. On the other hand, microbiological growth and attachment takes place within a few weeks of filter operation adding to the production of a biologically stable drinking water.
Burkhardt, M., Kägi, R., Sinnet, B., Zuleeg, S., Simmler, H., Vonbank, R., … Boller, M. (2008). Biozide - Suche nach Alternativen. Nanopartikel in Fassadenbeschichtungen. Coviss, 4, 14-17. , Institutional Repository

Gegen Algen und Pilze auf Fassaden werden in der Regel Biozide eingesetzt. Ob Nanosilber und photoaktives Nanotitandioxid unproblematische Alternativen oder Ergänzungen zu Bioziden darstellen, ist unklar. Die Eawag und Empa, zwei Forschungsinstitute des ETH-Bereichs, untersuchen erstmals die Auswaschung aus Fassadenanstrichen im Labor und unter Feldbedingungen. Damit werden wesentliche Grundlagen zur Dauerhaftigkeit und Risikobewertung erarbeitet.
Jermann, D., Pronk, W., & Boller, M. (2008). Membranfouling. Forschungsergebnisse zu den Mechanismen. GWA Gas, Wasser, Abwasser, 88(1), 37-44. , Institutional Repository

Membrane fouling (deposition of water substances on the membrane surface) is a crucial problem during ultrafiltration for drinking water production. Despite many international research efforts the phenomenon of fouling is only partly understood, mainly because of the complexity and variety of influencing factors. These reasons are described in the following article which shows, how mechanistic studies can provide new insight into membrane fouling. Fouling models gained from lab experiments are presented and compared to first results from a pilot plant. The main outcome of the presented study: Interactions between different foulants can impact fouling significantly.
Kleijer, A., Chèvre, N., & Burkhardt, M. (2008). Biocides et protection du bois. Liste de substances chimiques à surveiller. GWA Gas, Wasser, Abwasser, 88(12), 965-973. , Institutional Repository

Wood used in construction is treated with chemical products which increase its durability and protect it against attack by harmful organisms. The substances used are often extremely toxic and may be leached by the action of rainwater and find their way into surface water. They thus pose a risk to aquatic organisms and should be monitored. In the study summarised in this article, 51 wood protection substances were evaluated and a priority list of 18 substances to be monitored was drawn up. This should be updated on a regular basis as new products come onto the market and new research findings emerge.
Störmer, E., Klinke, A., Maurer, M., Ruef, A., & Truffer, B. (2008). Regional Infrastructure Foresight. Partizipative Strategieentwicklung für eine nachhaltige regionale Abwasserwirtschaft. GWA Gas, Wasser, Abwasser, 88(11), 843-850. , Institutional Repository

The Swiss sanitation sector has to face high reinvestment needs after over thirty years of operation time. Solutions have to be detected which work properly under changing framework conditions during the entire constructions' Iifetime of at least 25 years. Solutions have to be integrated in an efficient and effective sanitation system from the source of the waste water producer to the receiving water. The regional urban water management system needs an integrative strategy to tackle this requirements. The strategy frames the design of the whole system and its elements. Strategy development has to handle complexities and uncertainties of long living infrastructures. This paper presents the participative planning approach «Regional Infrastructure Foresight - RIF›› with the help of one case study.
Walser, A., Burkhardt, M., Zuleeg, S., & Boller, M. (2008). Gewässerbelastung durch Biozide aus Gebäudefassaden. GWA Gas, Wasser, Abwasser, 88(8), 639-647. , Institutional Repository

A whole series of hazardous substances may be emitted from urban surfaces during rainfall and washed out into the receiving waters. Among these are various biocides which are used in large amounts in renders and wall paints against algae and fungi growth. A rainfall-discharge model combined with an experimentally based leaching model has been developed and used in a real urban catchment to simulate concentration and load dynamics of the biocides Terbutryne and Cybutryne in facade runoff and in the receiving water. It also allowed predicting statistical information on ecotoxicological risks in the receiving water. The results reveal that for both biocides the concentrations in the receiving water exceed acute and chronic quality standards fairly often, especially in small rivers. The most severe case was identified to be an area with new or newly renovated buildings discharging the surface runoff through separate sewers directly into the receiving water.
Baccini, P., Baumgartner, F., Lichtensteiger, T., Michaeli, M., & Thalmann, E. (2007). Urbane Schweiz. In OcCC & ProClim- (Eds.), Klimaänderung und die Schweiz 2050. Erwartete Auswirkungen auf Umwelt, Gesellschaft und Wirtschaft (pp. 123-136). Retrieved from http://www.occc.ch/products/ch2050/CH2050-bericht_d.html, Institutional Repository

Die Schweiz ist urban geprägt, das heisst Stadt und Land sind durch starke Personen- und Güterflüsse eng vernetzt: Dieses Netzwerk aus Knoten und Flüssen bildet das urbane System. Die Entwicklung dieses Systems hängt von zahlreichen Faktoren ab. Von den verschiedenen kulturellen, politischen, wirtschaftlichen, räumlichen und ökologischen Einflüssen stellt das Klima nur eine Grösse dar. Wie stark und auf welche Weise sich die erwartete Klimaänderung auf die Siedlungsentwicklung auswirken wird, ist abhängig von der zukünftigen Form des urbanen Systems Schweiz. Für die vorliegende Beurteilung wurden drei mögliche Szenarien gewählt, für welche anhand von sechs Schlüsselgrössen der Einfluss der Klimaänderung beschrieben wird:
1. Als Referenzzustand das heute existierende System: CHheute.
2. Ein Szenario CH2050plus, das von einer Fortsetzung bereits eingeleiteter Anpassungen ausgeht.
3. Ein Szenario CH2050eco, das auf einem Kurswechsel nach den Kriterien einer nachhaltigen Entwicklung basiert.
Als Schlüsselgrössen dienen
1) Bevölkerung
2) Siedlungsmuster
3) Bauwerk (Bestand an Hoch- und Tiefbauten)
4) Transport und Kommunikation
5) Ressourcen sowie
6) Beziehungen innerhalb der Schweiz und zum Ausland.
Boller, M. (2007). Fertilizer from the library. Eawag News [engl. ed.], 63, 17-19. , Institutional Repository

Producing a hazard-free fertilizer from urine is a new concept. Initial experience is being gained at the Basel-Landschaft Cantonal Library in Liestal, which is fitted exclusively with NoMix toilets. The urine collected at this institution is processed to yield a liquid fertilizer. But before the product can be applied, a number of obstacles need to be overcome. Similar challenges also face pilot projects in other countries.
Burkhardt, M., Rossi, L., & Boller, M. (2007). Auch Eisenbahnverkehr setzt Stoffe frei. Eawag Jahresbericht, 2006, 14-15. , Institutional Repository

Was entlang von Strassen an Luft-, Boden- und Gewässerbelastung auftritt, ist gut untersucht. Nicht so bei der Eisenbahn. Die Eawag hat erstmals eine Bilanz der Stoffemissionen der SBB erstellt: Jährlich werden allein durch Abrieb von Fahrleitungen, Rädern, Schienen und Bremsen rund 2500 Tonnen Metalle freigesetzt. Dazu kommen unter anderem 1300 Tonnen Kohlenwasserstoffe aus Schmiermitteln und den Holzschwellen.
Burkhardt, M., Kupper, T., Eugster, J., Rossi, L., & Boller, M. (2007). Biozide und Additive in Gebäudehüllen: ein Risiko für die Gewässer?. Eawag Jahresbericht, 2006, 49. , Institutional Repository

Mit dem Niederschlag können problematische Stoffe aus Fassaden- und Dachmaterialien ausgewaschen werden und in die Gewässer gelangen. Im Rahmen des Projekts URBIC werden die Freisetzung von Bioziden und Additiven sowie deren Transportverhalten in der Siedlungsentwässerung erstmals systematisch untersucht.
Burkhardt, M., Kägi, R., Simmler, H., Ulrich, A., & Boller, M. (2007). Nanopartikel auf Fassaden erforschen. Thema Umwelt, 2, 12-13. , Institutional Repository

Nanosilber und Nanotitandioxid haben das Potenzial, problematische Biozide zur Bekämpfung von Algen und Pilzen auf Fassaden zu ergänzen oder zu ersetzen. Allerdings ist bis heute völlig unklar, ob und in welchem Umfang diese Nanopartikel die Umwelt und die menschliche Gesundheit beeinträchtigen können. Um die Chancen und Risiken dieser Technologie abwägen und mit den heute üblichen Bioziden vergleichen zu können, haben Eawag und Empa, zwei Forschungsinstitute des ETH-Bereichs, ein Forschungsprojekt lanciert.
Burkhardt, M. (2007). Release of biocides from urban areas into aquatic systems in Switzerland (URBIC). IWA Newsletter (26), 15-17. , Institutional Repository

Biocidal products are widely used in urban areas for material protection. Their mode of action is specific against algae and fungi. Carbendazim, diuron and Irgarol 1051 are representatives for biocides in paints and plaster of facades. Similar applications of biocides are known or expected for plastic membranes on flat roofs and bitumen sheets for roof waterproofing. Pesticides used in urban and rural areas may have the same active ingredients.
Escher, B., & Lienert, J. (2007). Can NoMix help to prevent environmental problems caused by medicines?. Eawag News [engl. ed.], 63, 23-25. , Institutional Repository

One of the aims of the NoMix system is to produce fertilizers from source-separated urine. But urine also contains traces of pharmaceuticals and hormones, which need to be completely removed during treatment. To assess the efficiency of treatment processes, we developed a procedure combining chemical and ecotoxicological analytical methods.
Herlyn, A., & Maurer, M. (2007). Status quo der Schweizer Abwasserentsorgung. Kosten, Zustand und Investitionsbedarf. GWA Gas, Wasser, Abwasser, 87(3), 171-176. , Institutional Repository

The Swiss waste water is treated in 759 central treatment plants with more than 500 population equivalents. The replacement value is CHF 10.1 billion. In total, the annual costs of waste water treatment are CHF 875 million. 47,400 km public sewers remove waste- and stormwater with an estimated value of CHF 55.2 billion. CHF 875 million are spent for operation costs and capital expenditures every year. Two thirds of the sewage system was built within the last 50 years, whereas cities have significantly older facilities than rural communities. About 23 % of the investigated sewers show sewere damages. In addition, more than 3,400 individual sewage treatment plants, about 42,000 km private sewers and estimated 1,700,000 house connections contribute to the high level of sanitation service.
Larsen, T. A., Bader, H. P., Mosler, H. J., Gujer, W., Medilanski, E., Scheidegger, R., … Schertenleib, R. (2007). Applying traditional Chinese knowledge. Eawag News [engl. ed.], 63, 26-28. , Institutional Repository

Kunming, Zurich's sister city in China, is determined to tackle its wastewater problem. In the development of measures based on nutrient recycling - a long-established principle in China - it is receiving support from Eawag in technical as well as social issues.
Larsen, T., & Lienert, J. (2007). NoMix-Technologie. Chance für Siedlungswasserwirtschaft. GWA Gas, Wasser, Abwasser, 87(4), 255-262. , Institutional Repository

Could urine source separation replace the conventional nutrient elimination on wastewater treatment plants? Divided in nine work packages, the Eawag cross-cutting project Novaquatis pursued this question and highlighted the potential advantages and difficulties of such an enterprise. In many rapidly growing cities, the NoMix technology offers a rapid defense against nutrients in coastal waters, without waiting for the long and tiresome construction of sewers and treatment plants. In order to avoid the urine transport, an important next step will be the rapid development of decentralized process engineering opportunities. Also in Switzerland, the NoMix technology has a future, especially in the case of growing requirements for water pollution control.
Larsen, T. A., & Lienert, J. (2007). Spotlight on NoMix. Eawag News [engl. ed.], 63, 4-7. , Institutional Repository

Novaquatis, an inter- and transdisciplinary Eawag project, investigated urine source separation and treatment as an option for modern wastewater management. The results indicate that the so-called NoMix technology is a highly versatile innovation, offering advantages in a variety of scenarios. In particular, it could help to resolve global nutrient-related issues.
Lienert, J. (2007). A good idea, but surely no takers!. Eawag News [engl. ed.], 63, 8-10. , Institutional Repository

Right? No, wrong! According to our studies of user attitudes in pilot projects involving public buildings and private households, and among farmers, many people approve of NoMix toilets and urine-based fertilizers. However, NoMix toilets have a number of weak points which would need to be remedied by the sanitary industry before large-scale implementation can be recommended.
Burkhardt, M., Kupper, T., Rossi, L., Boller, M., & Seehafer, P. (2006). Einsatz von Bioziden in Fassaden. Applica: Zeitschrift für das Maler- und Gipsergewerbe, 113(12), 2-6. , Institutional Repository

Gegen mikrobiellen Bewuchs auf Beschichtungen und Putzen werden Biozide eingesetzt. Ende 2005 wurde im Schweizerischen Maler- und Gipserunternehmer-Verband (SMGV) eine Umfrage zum Biozideinsatz an Fassaden durchgeführt. Die Ergebnisse bestätigen die grosse Verbreitung von biozidhaltigen Fassadenbeschichtungen bei steigender Tendenz – und dies trotz der durch die neue Biozidprodukteverordnung auferlegten Einschränkungen (vgl. Artikel auf Seite 4).
Burkhardt, M., Kupper, T., Rossi, L., Boller, M., Hean, S., Haag, R., … Schmid, P. (2006). Umweltrelevante Stoffe in Flachdachabdichtungen. Tec21, 132(31-32), 27. Retrieved from https://www.e-periodica.ch/digbib/view?pid=sbz-004%3A2006%3A132%3A%3A3066, Institutional Repository

Das Projekt «Urbic-Dächer» untersucht das Auswaschungsverhalten von Bioziden und Additiven aus flexiblen Flachdachabdichtungen und deren Verbleib in der Siedlungsentwässerung.
Burkhardt, M. (2006). Untersuchung zum Auswaschverhalten. Schweizer BauJournal, 6, 44. , Institutional Repository

Das Projekt «Urbic-Dächer» untersucht das Auswaschungsverhalten von Bioziden und Additiven aus flexiblen Flachdachabdichtungen und deren Verbleib in der Siedlungsentwässerung.
Lienert, J., & Larsen, T. A. (2006). Novaquatis - a building block for innovative sanitation technology. In K. Lanz, L. Müller, C. Rentsch, & R. Schwarzenbach (Eds.), Who owns the water? (pp. 380-381). Retrieved from https://www.lars-mueller-publishers.com/who-owns-water, Institutional Repository

This is the paradox of conventional wastewater management-drinking water is used to flush human excreta into the sewer system where it is further diluted by household wastewater from kitchens and baths. As a result, wastewater treatment plants must employ ever more complex process engineering to remove pollutants and recycle valuable nutrients. If we had to redesign wastewater disposal systems based on what we know today, we would certainly not opt for the same package of technologies.
Lienert, J., & Larsen, T. A. (2006). Novaquatis: Baustein für eine Sanitärtechnologie der Zukunft. In K. Lanz, L. Müller, C. Rentsch, & R. Schwarzenbach (Eds.), Wem gehört das Wasser? (pp. 380-381). Retrieved from https://www.lars-mueller-publishers.com/wem-gehort-das-wasser, Institutional Repository

Paradoxon konventioneller Abwasserentsorgung: Die menschlichen Ausscheidungen werden mit Trinkwasser weg gespült und in der Kanalisation mit gering verschmutztem Wasser aus Küche und Bad weiter verdünnt. In der Kläranlage muss dann ein immer grösserer technischer Aufwand betrieben werden, um Schadstoffe aus dem Abwasser heraus zu holen und wertvolle Nährstoffe zurück zu gewinnen. Könnten wir auf Grund aller heutigen Erkenntnisse neu entscheiden, würden wir sicher nicht die gleiche Strategie wählen.

Publikationen nach Autoren

Lauren Cook

Cavadini, G. B., Mutzner, L., Cook, L., Rodriguez, M., & Poggioli, M. (2024). BGI reduzieren Gewässerbelastung. Modellstudien zu Entlastungen und Wasserqualität sowie Auswirkungen des Klimawandels. Aqua & Gas, 104(10), 46-52. , Institutional Repository

Indem blau-grüne Infrastrukturen die Mischwasserentlastungen reduzieren, werden auch die Einträge von Mikroverunreinigungen verkleinert. Besonders Versickerungsflächen senken die eingeleiteten Volumina und Frachten in Oberflächengewässer. Klimawandelprognosen lassen eine Zunahme von Entlastungen erwarten. Blau-grüne Infrastrukturen können daher einen wichtigen Beitrag leisten, um unerwünschte Effekte zu vermeiden oder zu reduzieren.
Cavadini, G. B., Rodriguez, M., Nguyen, T., & Cook, L. M. (2024). Can blue-green infrastructure counteract the effects of climate change on combined sewer overflows? Study of a swiss catchment. Environmental Research Letters, 19(9), 094025 (12 pp.). doi:10.1088/1748-9326/ad6462, Institutional Repository

Combined sewer overflows (CSOs), the discharge of untreated sewage mixed with stormwater into surface waters, are expected to increase under climate change as a result of more extreme rainfall. Blue-green infrastructure (BGI), such as bioretention cells and porous pavements, can help to reduce the amount of stormwater entering combined sewer systems, thus reducing CSO discharge. However, our understanding of the potential for BGI to mitigate CSOs in a future climate is still lacking, as performance is typically evaluated for individual BGI elements with fixed implementation areas under historical climate conditions or limited future scenarios. In response, this study investigates the performance of 30 combinations of BGI elements and implementation rates to prevent increases in CSOs under a range of future climate scenarios in an urban catchment near Zurich, Switzerland. Median total annual rainfall, projected to increase by as much as 46%, could double the median annual CSO volume and increase median annual CSO frequency by up to 52%. Four BGI combinations that include bioretention cells show the most promise to prevent increases in CSO volume and frequency in a future climate; and given the diverse responses of BGI elements to distinct rainfall patterns, their combinations can enhance CSO discharge reduction across varying climate patterns. BGI is also likely to become more cost-effective under future climatic conditions as projected increases in total rainfall led to larger CSO volume reductions obtained through BGI. However, there is a trade-off between robustness to climate change and cost-effectiveness, since CSO volume reduction capacity scales with BGI implementation rate but cost-effectiveness declines. Our study illustrates the effectiveness of various BGI combinations to prevent increases in CSOs in a future climate, calling for a range of BGI elements and implementation areas to be considered for urban drainage adaptation.
Cavadini, G. B., Rodriguez, M., & Cook, L. M. (2024). Connecting blue-green infrastructure elements to reduce combined sewer overflows. Journal of Environmental Management, 365, 121465 (15 pp.). doi:10.1016/j.jenvman.2024.121465, Institutional Repository

By infiltrating and retaining stormwater, Blue-Green Infrastructure (BGI) can help to reduce Combined Sewer Overflows (CSOs), one of the main causes of urban water pollution. Several studies have evaluated the ability of individual BGI types to reduce CSOs; however, the effect of combining these elements, likely to occur in reality, has not yet been thoroughly evaluated. Moreover, the CSO volume reduction potential of relevant components of the urban drainage system, such as detention ponds, has not been quantified using hydrological models. This study presents a systematic way to assess the potential of BGI combinations to mitigate CSO discharge in a catchment near Zurich (Switzerland). Sixty BGI combinations, including four BGI elements (bioretention cells, permeable pavement, green roofs, and detention ponds) and four different implementation rates (25%, 50%, 75%, and 100% of the available sewer catchment area) are evaluated for four runoff routing schemes. Results reveal that BGI combinations can provide substantial CSO volume reductions; however, combinations including detention ponds can potentially increase CSO frequency, due to runoff prolongation. When runoff from upstream areas is routed to the BGI, the CSO discharge reductions from combinations of BGI elements differ from the cumulative CSO discharge reductions achieved by individual BGI types, indicating that the sum of effects from individual BGI types cannot accurately predict CSO discharge in combined BGI scenarios. Moreover, larger BGI implementation areas are not consistently more cost-effective than small implementation areas, since the additional CSO volume reduction does not outweigh the additional costs. The best-performing BGI combination depends on the desired objective, being CSO volume reduction, CSO frequency reduction or cost-effectiveness. This study emphasizes the importance of BGI combinations and detention ponds in CSO mitigation plans, highlighting their critical factors—BGI types, implementation area, and runoff routing— and offering a novel and systematic approach to develop tailored BGI strategies for urban catchments facing CSO challenges.
Cook, L. M., Good, K. D., Moretti, M., Kremer, P., Wadzuk, B., Traver, R., & Smith, V. (2024). Towards the intentional multifunctionality of urban green infrastructure: a paradox of choice?. npj Urban Sustainability, 4(1), 12 (13 pp.). doi:10.1038/s42949-024-00145-0, Institutional Repository

Decades of research on multifunctional Green Infrastructure (GI) has yet to translate into holistic implementation in the built environment. This oversight stems from assumptions that many ecosystem services occur passively and thus potential synergies are overlooked during planning and design. This study offers specific guidance for coordinating GI planning, design, and construction by examining the current state of academic literature on these aspects. It identifies 15 GI elements (e.g., green roofs) and 15 objectives (e.g., biodiversity) to collectively consider before implementation. The literature tends to isolate discussions of “engineered” GI elements with water-related objectives, while more “natural” GI are linked to biodiversity and human well-being. Coordinating across GI objectives and elements remains imperative, but evaluating too many options risks a paradox of choice. This study recommends short-term adherence to principles of adaptive design and, in the long-term, reemphasizes multifunctionality assessments, inter and transdisciplinary collaboration, and political will.
Dietzel, A., Moretti, M., & Cook, L. M. (2024). Shrinkage-based Bayesian variable selection for species distribution modelling in complex environments: an application to urban biodiversity. Ecological Informatics, 81, 102561 (9 pp.). doi:10.1016/j.ecoinf.2024.102561, Institutional Repository

Robust, quantitative understanding of the diverse ecological needs of species is needed to inform effective biodiversity conservation, now and in the future, but is lacking for most species. The advent of "big data" in ecology presents unprecedented opportunities to fill this gap and to disentangle the diverse drivers of biodiversity. Variable and model selection in sparse (small sample sizes for most species), high-dimensional (large pool of candidate predictors) problems is, however, non-trivial. Here, we employ cross-validated Bayesian projection predictive variable selection and shrinkage priors to identify, from a list of 70 ecological and biophysical candidate predictor variables, the minimal subset that best predicts the habitat preferences and distributions of 103 species of amphibians, birds, butterflies, dragonflies, and grasshoppers using the city of Zurich, Switzerland, as a case study. We contrast the predictive performance and ecological inference of models fit with the full set of predictors using shrinkage priors (exhaustive models) to models fit with a limited number of predictors obtained by compiling predictors from the full list of predictors using weakly informative priors (selective models). We show that exhaustive models excel in predictive performance, albeit at the cost of greater model complexity compared to selective models. Results from the selective models reveal the importance of access to aquatic habitat for a wide range of taxa, relative to other drivers such as urbanisation, vegetation and environmental hazards. These results are complemented by more nuanced insights from the exhaustive models into the importance of specific types of aquatic habitat (ponds, lakes, streams) and vegetation (herb, shrub, canopy cover) for the distribution of urban biodiversity, as well as the different spatial scales at which drivers are of predictive relevance. Our findings demonstrate the potential of shrinkage-based Bayesian variable selection to leverage big ecological data for species distribution modelling, and contribute to the development of concrete guidelines for urban planning and infrastructure design that account for biodiversity conservation.
Hassoun, L., & Cook, L. M. (2024). Global analysis of combined photovoltaic green and cool roofs under climate change. Advanced Sustainable Systems. doi:10.1002/adsu.202400097, Institutional Repository

Sustainable roofing configurations, including green and white roofs, can reduce rooftop surface temperatures compared to conventional surfaces and can therefore enhance photovoltaic (PV) system performance due to the temperature dependence of PV cells. Previous research, primarily experimental, recognized the synergy of combining PV with green or cool roofs. However, the influence of geographic and climatic factors on the performance of these combined systems, particularly in future climates affected by climate change, remains unclear. This work integrates three roof configurations (gravel, green, and white) into rooftop solar energy modeling across thirteen cities with different climate types, under current and future climate scenarios. Results indicate limited efficiency gains (< 2%) across all cities and climates, challenging previous findings. Yield is expected to increase in some cities receiving more solar irradiation in the future but decrease in others due to rising temperatures. Green and cool roofs can partially offset the effects of climate change on yield. PV-white roofs consistently outperform PV-green roofs, with the performance gap expected to widen in future climates. PV-green roofs excel in tropical climates with high irradiation and precipitation levels. Overall, the outcomes of this study inform the design and planning of sustainable buildings in response to climate change challenges.
Liu, H., Kong, F., Yin, H., Cook, L. M., Huang, J., Lensky, I. M., & Tan, T. (2024). Substrate microorganisms can be an ideal tool for improving green roof sustainability. Urban Forestry and Urban Greening, 91, 128179 (11 pp.). doi:10.1016/j.ufug.2023.128179, Institutional Repository

Green roof (GR) ecosystems function as a result of a series of complex interactions between plants and substrates, which are poorly understood. This ambiguity hinders the scientific application of GRs to tackle urban eco-environmental problems. The goal of this study was to clarify the response of plants to various abiotic and biotic characteristics of GR substrates, including physical properties, nutrients, and microbes. We systematically analyzed the statistical association between 43 indicators of plant and substrate characteristics using four GR substrates and one common plant type (Sedum lineare Thunb) in a subtropical monsoon climate. Height, coverage, root-shoot ratio, total carbon, total nitrogen, total phosphorus, total potassium, root vitality, and malondialdehyde levels were considered sensitive indicators of the plant's response to the substrate. Substrate nutrients and microbial biomass were most closely associated with the plant response, whereas the material properties of the substrate could indirectly affect plant growth by influencing substrate microbes and plant nutrients. Our results suggest that when optimizing GR substrates for plant responses, it is necessary to respect the plants and account for the abiotic and biotic relationships. It may be possible to manage GR performance in a more scientific and effective manner through the control of substrate microorganisms.
Perrelet, K., Moretti, M., Dietzel, A., Altermatt, F., & Cook, L. M. (2024). Engineering blue-green infrastructure for and with biodiversity in cities. npj Urban Sustainability, 4(1), 27 (11 pp.). doi:10.1038/s42949-024-00163-y, Institutional Repository

Blue-green infrastructure (BGI), combining semi-natural and engineered elements, offers multifaceted benefits like stormwater management, water purification, heat mitigation, and habitat provision. However, current BGI designs prioritize engineering goals, overlooking its ecological potential. Here we advocate for integrating engineering and ecological objectives into BGI design to enhance performance and biodiversity. Through an interdisciplinary literature review, we emphasize the importance of species diversity, abundance, and ecological processes, to improve engineering performance and resilience, and lower management costs. We emphasize the importance of interdisciplinary collaboration to navigate trade-offs between engineering and ecological objectives, ultimately enabling us to engineer both for and with biodiversity.
Rodriguez, M., Cavadini, G. B., & Cook, L. M. (2024). Do baseline assumptions alter the efficacy of green stormwater infrastructure to reduce combined sewer overflows?. Water Research, 253, 121284 (12 pp.). doi:10.1016/j.watres.2024.121284, Institutional Repository

Green stormwater infrastructure (GSI) is growing in popularity to reduce combined sewer overflows (CSOs) and hydrologic simulation models are a tool to assess their reduction potential. Given the numerous and interacting water flows that contribute to CSOs, such as evapotranspiration (ET) and groundwater (GW), these models should ideally account for them. However, due to the complexity, simplified models are often used, and it is currently unknown how these assumptions affect estimates of CSOs, GSI effectiveness, and ultimately planning guidance. This study evaluates the effect on estimates of CSOs and GSI effectiveness when different flows and hydrologic processes are neglected. We modified an existing EPA SWMM model of a combined sewer system in Switzerland to include ET, GW, and upstream inflows. Historical rainfall data over 30 years are used to assess volume and duration of CSOs with and without three types of GSI (bioretention basins, permeable pavements and green roofs). Results demonstrate that neglect of certain flows in modelling can alter CSO volumes from -15 % to 40 %. GSI effectiveness also varies considerably, resulting in differences in simulated percent of CSO volume reduced from 8 % to 35 %, depending on the GSI type and modeled flow or process. Representation of GW within models is particularly crucial when infiltrating GSI are present, as CSOs could increase in certain subcatchments due to higher GW levels from increased infiltration. When basing GSI planning decisions on modeled estimates of CSOs, all relevant hydrologic processes should be included to the extent possible, and uncertainty and assumptions should always be considered.
Rodriguez, M., Fu, G., Butler, D., Yuan, Z., & Cook, L. (2024). The effect of green infrastructure on resilience performance in combined sewer systems under climate change. Journal of Environmental Management, 353, 120229 (12 pp.). doi:10.1016/j.jenvman.2024.120229, Institutional Repository

Climate change is currently reshaping precipitation patterns, intensifying extremes, and altering runoff dynamics. Particularly susceptible to these impacts are combined sewer systems (CSS), which convey both stormwater and wastewater and can lead to combined sewer overflow (CSO) discharges during heavy rainfall. Green infrastructure (GI) can help mitigate these discharges and enhance system resilience under historical conditions; however, the quantification of its effect on resilience in a future climate remains unknown in the literature. This study employs a modified Global Resilience Analysis (GRA) framework for continuous simulation to quantify the impact of climate change on CSS resilience, particularly CSOs. The study assesses the efficacy of GI interventions (green roofs, permeable pavements, and bioretention cells) under diverse future rainfall scenarios based on EURO-CORDEX regional climate models (2085–2099) and three Representative Concentration Pathways (2.6, 4.5, 8.5 W/m2). The findings underscore a general decline in resilience indices across the future rainfall scenarios considered. Notably, the total yearly CSO discharge volume increases by a range of 145 % to 256 % in response to different rainfall scenarios. While GI proves effective in increasing resilience, it falls short of offsetting the impacts of climate change. Among the GI options assessed, green roofs routed to pervious areas exhibit the highest adaptive capacity, ranging from 9 % to 22 % at a system level, followed by permeable pavements with an adaptation capacity between 7 and 13 %. By linking the effects of future rainfall scenarios on CSO performance, this study contributes to understanding GI's potential as a strategic tool for enhancing urban resilience.
Maurer, B., Lienert, J., & Cook, L. M. (2023). Comparing PV-green and PV-cool roofs to diverse rooftop options using decision analysis. Building and Environment, 245, 110922 (15 pp.). doi:10.1016/j.buildenv.2023.110922, Institutional Repository

Flat roofs can employ a range of technologies to improve sustainability, such as photovoltaic (PV) panels, green roofs, cool roofs, or a combination of these options. Yet, weighing the benefits, costs, and performance of different roofing technologies is complex, especially when different stakeholders are involved. Decision analysis techniques, such as multi-criteria decision analysis (MCDA), can be used to systematically evaluate a diverse range of rooftop options to assess trade-offs in a quantitative way and avoid decision biases. This study offers a holistic comparison of different roof types, considering stakeholder preferences and uncertainty using MCDA. Ten flat roof options are compared, including black, gravel, cool, extensive green and semi-intensive green roofs, each with or without a rooftop PV installation, for nine objectives and three hypothetical stakeholder profiles. Performance is evaluated using building energy simulation, hydrologic modeling, and literature research. Uncertainty analyses are used to evaluate the effects of model assumptions on the MCDA results. For assumed preferences of an urban planner and environmentalist, semi-intensive green roofs with integrated PV installation are the best performing option; however, for a hypothetical building owner more concerned with costs, a gravel roof with PV ranks best. Uncertainty plays a role in the results, in particular, the uncertainty of the predicted outcome of options for the building owner, which can change the top-ranking options considerably. The uncertainty analyses are useful to identify consensus options over all three stakeholder types. Despite considerable uncertainty, extensive and semi-intensive green roofs with PV are recommended as relatively robust best-performing options.
Perrelet, K., Moretti, M., Dietzel, A., Maurer, M., & Cook, L. (2023). Schwammstädte - Für und mit Biodiversität gestalten. Hotspot, 48, 24-25. , Institutional Repository

Eine blau-grüne Infrastruktur aus Fliessgewässern, Pflanzenkläranlagen oder Gründächern kann den Siedlungsraum und vor allem Städte sowohl biodiverser als auch resilienter gegenüber dem Klimawandel machen. Voraussetzung ist die Zusammenarbeit von Ingenieur- und Naturwissenschaften.
Perrelet, K., Moretti, M., Dietzel, A., Maurer, M., & Cook, L. (2023). Villes éponges: pour et avec la biodiversité. Hotspot, 48, 22-23. , Institutional Repository

Une infrastructure bleue et verte composée de cours d’eau, de stations d’épuration végétales ou de toits verts peut rendre l’espace urbain, et surtout les villes, à la fois biodiverses et résistantes aux aléas climatiques. La condition préalable est la collaboration entre l’ingénierie et les sciences naturelles.
Rodriguez, M., Fu, G., Butler, D., Yuan, Z., & Cook, L. (2023). Global resilience analysis of combined sewer systems under continuous hydrologic simulation. Journal of Environmental Management, 344, 118607 (11 pp.). doi:10.1016/j.jenvman.2023.118607, Institutional Repository

Managing and reducing combined sewer overflow (CSO) discharges is crucial for enhancing the resilience of combined sewer systems (CSS). However, the absence of a standardised resilience analysis approach poses challenges in developing effective discharge reduction strategies. To address this, our study presents a top-down method that expands the existing Global Resilience Analysis to quantify resilience performance in CSS. This approach establishes a link between threats (e.g., rainfall) and impacts (e.g., CSOs) through continuous and long-term simulation, accommodating various rainfall patterns, including extreme events. We assess CSO discharge impacts from a resilience perspective by introducing eight new metrics. We conducted a case study in Fehraltorf, Switzerland, analysing the performance of three green infrastructure (GI) types (bioretention cells, green roofs, and permeable pavements) over 38 years. The results demonstrated that GI enhanced all resilience indices, with variations observed in individual CSO performance metrics and their system locations. Notably, in Fehraltorf, green roofs emerged as the most effective GI type for improving resilience, while the downstream outfall displayed the highest resilience enhancement. Overall, our proposed method enables a shift from event-based to continuous simulation analysis, providing a standardised approach for resilience assessment. This approach informs the development of strategies for CSO discharge reduction and the enhancement of CSS resilience.
Smith, V., Cook, L. M., & Oppliger, S. (2023). Umsetzung blau-grüner Infrastruktur weltweit. Was kann die Schweiz daraus lernen?. Aqua & Gas, 103(9), 16-24. , Institutional Repository

Die Umsetzung Blau-Grüner Infrastrukturen ist in allen grösseren Schweizer Städten ein äusserst aktuelles Thema. Treibende Faktoren waren meist die Förderung der Biodiversität und die Not-wendigkeit von hitzemindernden Massnahmen im urbanen Raum, und weniger die Siedlungswas-serwirtschaft. Ausserhalb der Schweiz hingegen wurde die Umsetzung in den vergangenen Jahr-zehnten stark auch aus Sicht der Regenwasserbewirtschaftung und Sicherung der Wasserqualität in den oberflächlichen Gewässern vorangetrieben. Dieser Artikel fasst wichtige Erfahrungen und Erkenntnisse aus der weltweiten Umsetzung zusammen.
Tan, T., Kong, F., Yin, H., Cook, L. M., Middel, A., & Yang, S. (2023). Carbon dioxide reduction from green roofs: a comprehensive review of processes, factors, and quantitative methods. Renewable and Sustainable Energy Reviews, 182, 113412 (12 pp.). doi:10.1016/j.rser.2023.113412, Institutional Repository

Green roofs can mitigate climate change through various mechanisms, including carbon sequestration, thermal process regulation, and building energy savings. While those mechanisms have been well studied, it remains unclear how to quantify carbon dioxide reduction and design green roofs properly for optimal performance. This review summarizes the processes, factors, and quantitative methods for carbon dioxide reduction from peer-reviewed literature. Firstly, the processes that account for how green roofs reduce carbon dioxide directly (by absorbing ambient CO2 and storing it in biomass and substrate) and indirectly (thermal process regulation reduces energy consumption) are focused. The factors affecting CO2 reduction (i.e., vegetation, substrate, building environment, and maintenance) are then discussed to investigate how these factors impact the performance of green roofs. Lastly, quantitative methods, including field experiments and simulation models to evaluate direct and indirect CO2 reductions from green roofs, are discussed considering different spatial scales. The review found that a better understanding of green roofs' carbon reduction mechanisms is needed. Recommendations also should be developed on customized green roof system designs for various climate conditions. Lastly, there is a lack of green roof decarbonization evaluation at multiple spatial and temporal scales to effectively implement green roofs in urban areas. Overall, this comprehensive review facilitates an understanding of how green roofs reduce CO2, the driving factors, and quantitative methods, which will advance research on designing and building green roofs as effective climate mitigation solutions in urban areas.
Probst, N., Bach, P. M., Cook, L. M., Maurer, M., & Leitão, J. P. (2022). Blue Green Systems for urban heat mitigation: mechanisms, effectiveness and research directions. Blue-Green Systems, 4(2), 348-376. doi:10.2166/bgs.2022.028, Institutional Repository

Reflected in the growing body of literature, urban heat mitigation is increasingly relevant as cities experience extreme heat, exacerbated by climate change and rapid urbanisation. Most studies focus on urban–rural temperature differences, known as the Urban Heat Island, which does not provide insight into urban heat dynamics. Here, we synthesise current knowledge on spatio-temporal variations of heat sources and sinks, showing that a targeted and absolute understanding of urban heat dynamics rather than an urban–rural comparison should be encouraged. We discuss mechanisms of heat sinks for microclimate control, provide a clear classification of Blue Green Systems and evaluate current knowledge of their effectiveness in urban heat mitigation. We consider planning and optimisation aspects of Blue Green Infrastructure (greenery and water bodies/features), interactions with hard surfaces and practices that ensure space and water availability. Blue Green Systems can positively affect urban microclimates, especially when strategically planned to achieve synergies. Effectiveness is governed by their dominant cooling mechanisms that show diurnal and seasonal variability and depend upon background climatic conditions and characteristics of surrounding urban areas. Situationally appropriate combination of various types of Blue Green Systems and their connectivity increases heat mitigation potential while providing multiple ecosystem services but requires further research.
Schnorf, H., Bergamini, A., Cook, L., & Moretti, M. (2022). Revitalisierte Bäche leisten einen Beitrag zur städtischen Pflanzenvielfalt. Les ruisseaux revitalisés favorisent la diversité spécifique de la flore urbaine. Nature et Paysage. Natur und Landschaft: Inside (4), 35-39. , Institutional Repository

Bevor sie grösstenteils in den Untergrund verlegt wurden, prägten Bäche das Bild der Schweiz, auch in der Stadt Zürich. Im Rahmen des naturnahen Wasserbaus werden in Zürich diese Bäche seit 35 Jahren wieder an die Oberfläche gebracht. In dieser Studie untersuchten wir die Vielfalt der Gefässpflanzen an wieder geöffneten Bächen in der Stadt Zürich.

Avant d’être en majeure partie enfouis, les ruisseaux étaient des marqueurs omniprésents du paysage en Suisse, y compris dans l’espace urbain. Depuis 35 ans, les petits cours d’eau de la ville de Zurich sont progressivement remis à ciel ouvert dans le cadre d’un plan de réaménagement tendant vers l’état naturel. Une étude s’est intéressée à la diversité des plantes vasculaires présentes dans le courant et au bord des ruisseaux ainsi revitalisés.
Cavadini, G. B., & Cook, L. M. (2021). Green and cool roof choices integrated into rooftop solar energy modelling. Applied Energy, 296, 117082 (13 pp.). doi:10.1016/j.apenergy.2021.117082, Institutional Repository

Due to their cooling ability, sustainable roofing configurations, such as green and cool roofs, have the potential to increase solar panel yield, which is temperature dependent. However, the influence of sustainable roofing configurations on panel yield is not yet considered in rooftop photovoltaic (PV) planning models; thus, the significance of these integrated systems cannot be evaluated. In order to quantify the potential benefits of sustainable rooftops on solar energy, the first goal of this study is to develop a method that systematically accounts for roof surface characteristics in the simulation of PV panel energy yield. To do so, a rooftop energy balance model is linked with a physically-based solar energy model (the System Advisor Model, SAM) to quantify the energy yield of PV installations on sustainable roofing configurations. Roof surface temperatures are first estimated using non-linear energy balance equations, then integrated into a revised version of SAM to simulate energy yield. This new method improves the accuracy of PV yield simulations, compared to prior assumptions of roof surface temperature equal to ambient temperature. This updated model is used for the second goal of the study, to understand how four roofing configurations (black membrane, rock ballasted, white membrane, and vegetated) influence PV panel yield, which is currently not well understood in cooler climates. For a flat rooftop PV installation near Zurich, Switzerland (temperate climate), results show that, compared to a conventional roof, green roofs can increase annual PV energy yield, on average, by 1.8%, whereas cool roofs can increase it by 3.4%. For the case-study installation, an inverse correlation between the 95th-quantile roof surface temperature and the PV energy yield was identified; an increase of 1 °C leads to a 71 kWh reduction in energy yield per year. Overall, cool roofs outperform green roofs in terms of increases in PV energy yield; however, potential improvements of both systems are non-negligible, even in relatively cooler climate regions like Switzerland. By providing a systematic method to evaluate the influence of the roofing configuration on PV energy yield, solar energy planners are able to differentiate between the benefits of traditional and sustainable rooftop configurations - the first step towards the coupling of distributed energy and sustainable building systems. In the future, this integrated method could be used as part of a holistic evaluation of the environmental, economic, and social objectives of green and cool roofs, as well as, other infrastructure systems.
Cook, L. M., & Larsen, T. A. (2021). Towards a performance-based approach for multifunctional green roofs: an interdisciplinary review. Building and Environment, 188, 107489 (14 pp.). doi:10.1016/j.buildenv.2020.107489, Institutional Repository

Green roofs have the potential to offer numerous ecosystem services; however, they are rarely designed to achieve them. Instead, design is restricted by perceived structural and maintenance constraints, which consequently diminish the achievable benefits. For green roofs to improve sustainability and resilience of cities, their design should match their promised multi-functional application using performance-based design. The first step towards a comprehensive performance model is to synthesize design recommendations across disciplines to identify synergies and trade-offs in design objectives for multiple benefits. This study discusses design strategies that could alter the energy and water balance in the green roof in order to attenuate urban stormwater, increase building energy performance, mitigate urban heat, and improve the output of solar panels placed on top of green roofs. These benefits are mathematically linked to quantifiable processes (discharge rate, water content, evapotranspiration, sensible heat, net radiation, insulation, and thermal mass), forming the foundation for a performance-based design model. Design recommendations are then summarized for each process, followed by a discussion of synergies, trade-offs, and research needs that arise when green roofs are designed to achieve multiple functions. Selecting vegetation with high leaf area and albedo improves multiple benefits without affecting structural constraints, whereas choosing plants with low stomatal resistance leads to trade-offs between higher evapotranspiration and higher irrigation requirements. Trade-offs in substrate depth and properties including organic matter and moisture are also apparent. Interdisciplinary collaborations are needed to simulate and optimize design parameters based on stakeholder preferences related to co-benefits and constraints.
Cook, L. M., VanBriesen, J. M., & Samaras, C. (2021). Using rainfall measures to evaluate hydrologic performance of green infrastructure systems under climate change. Sustainable and Resilient Infrastructure, 6(3-4), 156-180. doi:10.1080/23789689.2019.1681819, Institutional Repository

As climate change alters precipitation patterns, stakeholders will need to understand how performance of green stormwater infrastructure (GSI) could change in response. As an alternative to using on-site monitoring, which may not always feasible, we propose that changes in performance could be tracked using annual rainfall measures (e.g., maximum daily rainfall per year). We estimated performance of GSI in 17 U.S. cities using rainfall measures by establishing linear relationships with specific performance metrics (e.g., frequency of discharge). Prediction accuracy was evaluated in 2 cities for the period 2020 to 2060 by comparing performance predicted from rainfall trends from regional climate models (RCMs) with simulated performance in SWMM using the same RCMs as input. Findings suggest that tracking rainfall measures can provide insight into the hydrologic performance of green infrastructure by predicting the direction of change, as well as, the magnitude within 25% to 50% percent change.
Cook, L. M., McGinnis, S., & Samaras, C. (2020). The effect of modeling choices on updating intensity-duration-frequency curves and stormwater infrastructure designs for climate change. Climatic Change, 159, 289-308. doi:10.1007/s10584-019-02649-6, Institutional Repository

Intensity-duration-frequency (IDF) curves, commonly used in stormwater infrastructure design to represent characteristics of extreme rainfall, are gradually being updated to reflect expected changes in rainfall under climate change. The modeling choices used for updating lead to large uncertainties; however, it is unclear how much these uncertainties affect the design and cost of stormwater systems. This study investigates how the choice of spatial resolution of the regional climate model (RCM) ensemble and the spatial adjustment technique affect climate-corrected IDF curves and resulting stormwater infrastructure designs in 34 US cities for the period 2020 to 2099. In most cities, IDF values are significantly different between three spatial adjustment techniques and two RCM spatial resolutions. These differences have the potential to alter the size of stormwater systems designed using these choices and affect the results of climate impact modeling more broadly. The largest change in the engineering decision results when the design storm is selected from the upper bounds of the uncertainty distribution of the IDF curve, which changes the stormwater pipe design size by five increments in some cases, nearly doubling the cost. State and local agencies can help reduce some of this variability by setting guidelines, such as avoiding the use of the upper bound of the future uncertainty range as a design storm and instead accounting for uncertainty by tracking infrastructure performance over time and preparing for adaptation using a resilience plan.

Tove Larsen

Beutler, P., Larsen, T. A., Maurer, M., Staufer, P., & Lienert, J. (2024). A participatory multi-criteria decision analysis framework reveals transition potential towards non-grid wastewater management. Journal of Environmental Management, 367, 121962 (15 pp.). doi:10.1016/j.jenvman.2024.121962, Institutional Repository

Many public environmental decisions are wicked problems due to high complexity and uncertainty. We test a participatory value-based framework based on multi-criteria decision analysis (MCDA) to tackle such problems. Our framework addresses two important gaps identified in reviews of MCDA applications to environmental problems: including stakeholders and treating uncertainty. We applied our framework in two complex real-world cases concerning a paradigm shift in the wastewater sector; the transition from centralized wastewater systems to decentralized non-grid systems. Non-grid systems may solve some problems of centralized systems by reducing costs, increasing flexibility, and addressing growing demands on environmental issues, especially in rural areas. But non-grid systems have rarely been implemented in OECD countries, because it is unclear whether a transition is recommendable, and whether stakeholders would accept this shift. This problem allows addressing several fundamental research questions. As theoretical contribution, we found that stakeholder participation in MCDA is necessary, because different preferences of stakeholders can lead to different best-performing options in the assessments. Compared to the typical integrated assessment (IA) approach that excludes stakeholders' preferences, the MCDA process led to clearer outcomes. Results indicate that including the uncertainty of predicted consequences of options with Monte Carlo simulation helped discriminate between options and identify best-performing options. Challenging the uncertainty of elicited stakeholder preferences with sensitivity analyses, we found that best-performing options were especially sensitive to the MCDA aggregation model. Despite the high uncertainty, it was possible to suggest robust consensus options that would perform reasonably well for all stakeholders. As practical contribution, results indicated that a transition from the centralized to decentralized non-grid systems seems feasible. Most stakeholders assigned highest weights to environmental protection objectives in decision-making workshops. These stakeholder preferences implemented in MCDA led to a generally better assessment of innovative non-grid systems, especially when including urine source separation. Stakeholders perceived the MCDA process as beneficial and found results plausible. We conclude that the proposed participatory value-based framework is rigorous, but still feasible in practice. The framework is certainly transferable to any context and is open to testing and refinement in various applications to wicked decision problems.
Hadengue, B., Morgenroth, E., & Larsen, T. A. (2022). How to get your feet wet: Integrating urban water and building engineering for low-energy domestic hot water systems. Energy and Buildings, 271, 112318 (6 pp.). doi:10.1016/j.enbuild.2022.112318, Institutional Repository

Thanks to intense research efforts, modern low-energy buildings consume only a fraction of the space heating loads of their older counterparts. However, reducing their energy footprint further requires optimization of domestic hot water systems. This is a difficult task, because the relationship between water and energy in domestic systems is intricate and complex. In general, the intrinsic uncertainty and variability of water demand makes the planning and assessment of new technologies challenging, but also risks related for instance to water pathogens like Legionella pneumophila impose trade-offs that diminish the performance of energy-saving measures. In this short communication, we argue that truly sustainable solutions will only be found if a multi-scale, multi-disciplinary mindset is adopted by the community. We show how the collaboration and knowledge integration between experts of various fields, notably urban water specialists and building engineers, is a prerequisite to resolve some of the most pressing issues on the way to optimizing domestic hot water systems. Through concrete examples, we describe how a new, common modeling framework has already triggered the required knowledge integration, and how it could be expanded further to integrate additional disciplines.
Hadengue, B., Morgenroth, E., Larsen, T. A., & Baldini, L. (2022). Performance and dynamics of active greywater heat recovery in buildings. Applied Energy, 305, 117677 (13 pp.). doi:10.1016/j.apenergy.2021.117677, Institutional Repository

In the effort to de-carbonize the building stock, heat pumps are increasingly utilized in Switzerland, with 70% of the fast-growing heat pump market using ambient air as heat source. Inexpensive and easy to implement, these heat pumps are, however, less efficient than their ground- or water-source counterparts. In this modeling study, we aim at increasing the efficiency of air-source heat pumps using domestic greywater-contained heat. We assess the performance improvement relative to standard heat pump configurations across various climates, seasons, building envelopes, and domestic hot water consumption patterns. The results show that the annually-averaged coefficient of performance improves by 4.1% on average - ranging from 0.6% to 7.5%. This efficiency gain translates on average to 1.8 kWh/week of compressor electricity savings. Although attractive due to its simplicity, the proposed open-loop configuration - preheating of an external heat source - only leads to moderate performance improvement of air-source heat pumps. Based on these results, we extensively discuss and compare alternative system configurations and identify several fundamental differences in the heat recovery dynamics of each configuration. We show that closed-loop systems - using greywater as direct heat source - show the largest performance improvement potential, although being more expensive and complex to implement.
Hadengue, B., Morgenroth, E., & Larsen, T. A. (2022). Screening innovative technologies for energy-efficient domestic hot water systems. Journal of Environmental Management, 320, 115713 (9 pp.). doi:10.1016/j.jenvman.2022.115713, Institutional Repository

Domestic hot water systems are large energy consumers. With the aim of reducing the energy footprint of these systems, we selected and simulated five technologies across a wide range of technology readiness levels: established technologies - pipe insulation and low-flow faucets -, relatively new technologies - shower drain heat exchangers and an innovative pipe system - and a novel experimental technology - a heat exchanger connected to membrane bioreactor for on-site greywater treatment. Using the WaterHub modeling framework, we simulated the technologies alone and in combination and compared the energetic performance of fifteen scenarios with a validated reference domestic hot water system. Low-flow appliances as standalone technologies performed best with 30% less energy required for the boiler tank, but combining low-flow appliances with a membrane bioreactor heat exchanger performed best overall (50% reduction). Deep insights into the temperature dynamics at all locations in the system led to the identification of technological competition patterns to prevent and synergies to exploit. Through our results, we are able to discuss and recommend further investigations regarding critical aspects like hygiene and economic performance.
Beutler, P., Larsen, T. A., Maurer, M., Staufer, P., & Lienert, J. (2021). Potenzial dezentraler Abwassersysteme. Aqua & Gas, 101(1), 66-75. , Institutional Repository

Werterhalt und Bewirtschaftung von Kanalisation und ARA können kleine Gemeinden vor Herausforderungen stellen. Es gibt Alternativen, aber lohnen sich diese? Zwei Gemeinden wurden bei der strategischen Planung für ihr neues Abwassersystem unterstützt. Viele Ziele wurden als entscheidungsrelevant identifiziert, insbesondere Umweltschutzziele. Es zeigte sich, dass dezentrale Technologien mit Stoffstromseparierung die Anforderungen häufig besser erfüllen können als konventionelle Abwassersysteme.
Cook, L. M., & Larsen, T. A. (2021). Towards a performance-based approach for multifunctional green roofs: an interdisciplinary review. Building and Environment, 188, 107489 (14 pp.). doi:10.1016/j.buildenv.2020.107489, Institutional Repository

Green roofs have the potential to offer numerous ecosystem services; however, they are rarely designed to achieve them. Instead, design is restricted by perceived structural and maintenance constraints, which consequently diminish the achievable benefits. For green roofs to improve sustainability and resilience of cities, their design should match their promised multi-functional application using performance-based design. The first step towards a comprehensive performance model is to synthesize design recommendations across disciplines to identify synergies and trade-offs in design objectives for multiple benefits. This study discusses design strategies that could alter the energy and water balance in the green roof in order to attenuate urban stormwater, increase building energy performance, mitigate urban heat, and improve the output of solar panels placed on top of green roofs. These benefits are mathematically linked to quantifiable processes (discharge rate, water content, evapotranspiration, sensible heat, net radiation, insulation, and thermal mass), forming the foundation for a performance-based design model. Design recommendations are then summarized for each process, followed by a discussion of synergies, trade-offs, and research needs that arise when green roofs are designed to achieve multiple functions. Selecting vegetation with high leaf area and albedo improves multiple benefits without affecting structural constraints, whereas choosing plants with low stomatal resistance leads to trade-offs between higher evapotranspiration and higher irrigation requirements. Trade-offs in substrate depth and properties including organic matter and moisture are also apparent. Interdisciplinary collaborations are needed to simulate and optimize design parameters based on stakeholder preferences related to co-benefits and constraints.
Gundlach, J., Bryla, M., Larsen, T. A., Kristoferitsch, L., Gründl, H., & Holzner, M. (2021). Novel NoMix toilet concept for efficient separation of urine and feces and its design optimization using computational fluid mechanics. Journal of Building Engineering, 33, 101500 (6 pp.). doi:10.1016/j.jobe.2020.101500, Institutional Repository

Separation of urine from feces in NoMix toilets bears a large potential for mitigating problems associated with the efficient reuse of excreta. A challenge lies in the design of these toilets that should maximize the amount of collected urine while at the same time minimizing its mixing with flush water that partly spills into the urine collector. We present a novel design idea that takes advantage of the so-called tea pot effect, which describes the attachment of liquids to a curved wall due to surface tension. This effect is used to efficiently guide the urine along a curved entrance into the collector. Computational Fluid Dynamics (CFD) simulations of the two phase (water/urine - air) system are carried out on different toilet geometries where we vary the inflow to the urine collector. In particular, we investigate two different radial curvatures and two V-profile grooves whose combinations result in four toilet geometries that are tested. We demonstrate that the urine collection can be dramatically improved by tailoring curvature radius and V-profile grooves, while keeping the amount of flush water in the urine collector at a minimum. A reduction to less the 2.5% of flush water entering the urine collector could be achieved by implementing a curvature radius of 15 mm and a V-profile groove width of 60 mm. The improved geometry's performance makes it an appealing candidate for broad application both in western and developing counties and we anticipate that this technology might replace traditional toilet designs in the future.
Hadengue, B., Joshi, P., Figueroa, A., Larsen, T. A., & Blumensaat, F. (2021). In-building heat recovery mitigates adverse temperature effects on biological wastewater treatment: a network-scale analysis of thermal-hydraulics in sewers. Water Research, 204, 117552 (11 pp.). doi:10.1016/j.watres.2021.117552, Institutional Repository

Heat recovery from wastewater is a robust and straightforward strategy to reduce water-related energy consumption. Its implementation, though, requires a careful assessment of its impacts across the entire wastewater system as adverse effects on the water and resource recovery facility and competition among heat recovery strategies may arise. A model-based assessment of heat recovery from wastewater therefore implies extending the modeling spatial scope, with the aim of enabling thermal-hydraulic simulations from the household tap along its entire flow path down to the wastewater resource recovery facility. With this aim in mind, we propose a new modeling framework interfacing thermal-hydraulic simulations of (i) households, (ii) private lateral connections, and (iii) the main public sewer network. Applying this framework to analyze the fate of wastewater heat budgets in a Swiss catchment, we find that heat losses in lateral connections are large and cannot be overlooked in any thermal-hydraulic analysis, due to the high-temperature, low-flow wastewater characteristics maximizing heat losses to the environment. Further, we find that implementing shower drain heat recovery devices in 50% of the catchment's households lower the wastewater temperature at the recovery facility significantly less – only 0.3 K – than centralized in-sewer heat recovery, due to a significant thermal damping effect induced by lateral connections and secondary sewer lines. In-building technologies are thus less likely to adversely affect biological wastewater treatment processes. The proposed open-source modeling framework can be applied to any other catchment. We thereby hope to enable more efficient heat recovery strategies, maximizing energy harvesting while minimising impacts on biological wastewater treatment.
Larsen, T. A., Riechmann, M. E., & Udert, K. M. (2021). State of the art of urine treatment technologies: a critical review. Water Research X, 13, 100114 (20 pp.). doi:10.1016/j.wroa.2021.100114, Institutional Repository

Over the last 15 years, urine treatment technologies have developed from lab studies of a few pioneers to an interesting innovation, attracting attention from a growing number of process engineers. In this broad review, we present literature from more than a decade on biological, physical-chemical and electrochemical urine treatment processes. Like in the first review on urine treatment from 2006, we categorize the technologies according to the following objectives: stabilization, volume reduction, targeted N-recovery, targeted P-recovery, nutrient removal, sanitization, and handling of organic micropollutants. We add energy recovery as a new objective, because extensive work has been done on electrochemical energy harvesting, especially with bio-electrochemical systems. Our review reveals that biological processes are a good choice for urine stabilization. They have the advantage of little demand for chemicals and energy. Due to instabilities, however, they are not suited for bathroom applications and they cannot provide the desired volume reduction on their own. A number of physical-chemical treatment technologies are applicable at bathroom scale and can provide the necessary volume reduction, but only with a steady supply of chemicals and often with high demand for energy and maintenance. Electrochemical processes is a recent, but rapidly growing field, which could give rise to exciting technologies at bathroom scale, although energy production might only be interesting for niche applications. The review includes a qualitative assessment of all unit processes. A quantitative comparison of treatment performance was not the goal of the study and could anyway only be done for complete treatment trains. An important next step in urine technology research and development will be the combination of unit processes to set up and test robust treatment trains. We hope that the present review will help guide these efforts to accelerate the development towards a mature technology with pilot scale and eventually full-scale implementations.
Larsen, T. A., Gruendl, H., & Binz, C. (2021). The potential contribution of urine source separation to the SDG agenda - a review of the progress so far and future development options. Environmental Science: Water Research and Technology, 7(7), 1161-1176. doi:10.1039/D0EW01064B, Institutional Repository

Sanitation and wastewater management are highly relevant for reaching a number of interconnected sustainable development goals (SDGs), especially SDG 6, the provision of safe drinking water and adequate sanitation for all as well as protection of water resources against pollution, and SDG 14.1, reducing nutrient emissions to the marine environment. Recent evidence increasingly shows that conventional sewer-based wastewater management will not be able to reach these targets. Rather than further optimizing and diffusing this ageing infrastructure paradigm, radical innovations like urine source separation technologies could help to leapfrog towards faster achievement of the SDGs. The technology would simplify on-site sanitation and develop a closed-loop nutrient cycle, thereby allowing for exceptionally high nutrient removal from wastewater and direct reuse in agriculture from the first day of implementation. Radical innovations, however, need decades to materialize. Based on a review of relevant academic and grey literature, we show how the past three decades of development of urine source separation have brought breakthroughs in toilet design and treatment processes, enabling the technology's value chain to reach the brink of maturity. In a short outlook, we discuss how the technology may reach global diffusion over the next decade, with the main remaining challenges relating to the creation of mass-markets for urine-diverting toilets, automation and mass-production of treatment systems, and the legitimation of fertilizer produced from urine in the agricultural sector.
Doll, C., Larsen, T. A., Strande, L., Udert, K. M., & Morgenroth, E. (2020). Water Hub im NEST-Gebäude. Eine Plattform zum Testen von innovativen ressourcenorientierten Sanitärsystemen. Aqua & Gas, 100(2), 52-57. , Institutional Repository

Mit innovativen Technologien werden im Water Hub unter realen Bedingungen Ressourcen aus dem Abwasser gewonnen und Kreisläufe geschlossen. Die Forschung in diesem Living Lab erlaubt es, praxisnahe Erfahrungen zu machen, Schwachstellen schnell zu identifizieren und das System zu optimieren. Bei der Implementierung dieser dezentralen Technologien spielen die lokalen Herausforderungen und Begebenheiten stets eine wichtige Rolle.
Hadengue, B., Scheidegger, A., Morgenroth, E., & Larsen, T. A. (2020). Modeling the water-energy nexus in households. Energy and Buildings, 225, 110262 (10 pp.). doi:10.1016/j.enbuild.2020.110262, Institutional Repository

One third of the global carbon emissions are emitted by the building sector. Over the last decades, space heating loads have decreased in modern buildings, and domestic hot water (DHW) is now oftentimes the largest energy consumer in the household. We developed the WaterHub modeling framework to assess the potential of technologies or measures targeting DHW energy demand. The framework combines process-based technological models and stochastic water demand modeling in a modular way to allow for holistic simulations of complex DHW systems. In two rigorous tests of the modeling framework, we demonstrated the importance of water consumption dynamics in the modeling of DHW systems, showing that static modeling leads to underestimated heat losses and wrong energy consumption predictions. In an exemplary case study, we identified and quantified the synergistic interactions between water boiler temperatures and a drain water heat recovery device, demonstrating the strength of this methodology for optimizing strategies targeting DHW systems. With its modular structure, this open-source modeling framework can be extended to include any DHW-related technology, providing a useful common platform for collaboration between technology developers and water experts.
Hoffmann, S., Feldmann, U., Bach, P. M., Binz, C., Farrelly, M., Frantzeskaki, N., … Udert, K. M. (2020). A research agenda for the future of urban water management: exploring the potential of non-grid, small-grid, and hybrid solutions. Environmental Science and Technology, 54(9), 5312-5322. doi:10.1021/acs.est.9b05222, Institutional Repository

Recent developments in high- and middle-income countries have exhibited a shift from conventional urban water systems to alternative solutions that are more diverse in source separation, decentralization, and modularization. These solutions include non-grid, small-grid, and hybrid systems to address such pressing global challenges as climate change, eutrophication, and rapid urbanization. They close loops, recover valuable resources, and adapt quickly to changing boundary conditions such as population size. Moving to such alternative solutions requires both technical and social innovations to co-evolve over time into integrated socio-technical urban water systems. Current implementations of alternative systems in high- and middle-income countries are promising, but they also underline the need for research questions to be addressed from technical, social, and transformative perspectives. Future research should apply a transdisciplinary research approach through socio-technical "lighthouse" projects that apply alternative urban water systems at scale. Such research should leverage experience from lighthouse projects in a range of socio-economic contexts, identify their potentials and limitations from an integrated perspective, and share their successes and failures across the urban water sector.
Larsen, T. A. (2020). Urine source separation for global nutrient management. In D. J. O’Bannon (Ed.), Women in engineering and science. Women in water quality. Investigations by prominent female engineers (pp. 99-111). doi:10.1007/978-3-030-17819-2_6, Institutional Repository

The sewer-based paradigm for wastewater management at the global scale is not successful neither from a humanitarian nor from an environmental perspective. The systems are too expensive for the largest part of the global population. Source separation and resource recovery offer an alternative for sanitation and water pollution control. This chapter illustrates the importance but also the challenges of urine source separation for efficient nutrient removal and recovery.
 
Gründl, H., & Larsen, T. A. (2019). The toilet revolution: improved water pollution control and reuse of wastewater in urban slums and in modern cities. World Architecture (06), 36-39. , Institutional Repository

With two new toilet systems, one for urban slums and the other for modern cities, we can at the same time improve water pollution control and further the economic reuse of wastewater. For urban slums, the Blue Diversion Toilet is an appealing, affordable and safe technical solution. It is designed for industrialised manufacturing and implements a sustainable sanitation value chain with total resource recovery and zero discharge. The important concept of the toilet is urine source separation. This concept that can also revolutionise wastewater management in the modern cities of industrialised and fast industrialising countries. With the new urine-separating toilet Save! this toilet revolution can spread on a global scale, offering a cost-efficient measure to help save surface water from eutrophication, make reuse of wastewater easier and cheaper and – as a side effect - provide fertiliser for urban and rural agriculture.
Hadengue, B., Scheidegger, A., Morgenroth, E., & Larsen, T. A. (2019). The waterhub modules: material and energy flow analysis of domestic hot water systems. In A. Haumer (Ed.), Linköping Electronic Conference Proceedings: Vol. 157. Proceedings of the 13th international modelica conference (pp. 639-646). doi:10.3384/ecp19157639, Institutional Repository

Domestic Hot Water (DHW) systems are large energy consumers in newly-built residential buildings. Mitigation measures involve more efficient hot water appliances and distribution systems, waste heat recovery systems, or changes in consumer habits. However, the implementation of these measures must be investigated carefully, as combinations may lead to unforeseen systemic interactions limiting their potential. In this article, we present tools to identify and optimize these interactions. The WaterHub modules were developed for Material and Energy Flow Analyses (MEFA) of domestic hot water systems. Two modules are available: (i) the WaterHub Modelica library includes models for MEFA system definition, and (ii) The HydroGen Python module provides methods for the stochastic generation of appliance-specific hydrographs, used as input data for the simulation of the system energy and water flows. First, we describe the technical aspects of these modules. Second, we provide an example of how they may be used in a didactic scenario analysis of a heat recovery device.
Harder, R., Wielemaker, R., Larsen, T. A., Zeeman, G., & Öberg, G. (2019). Recycling nutrients contained in human excreta to agriculture: pathways, processes, and products. Critical Reviews in Environmental Science and Technology, 49(8), 696-743. doi:10.1080/10643389.2018.1558889, Institutional Repository

The need for better nutrient management has spurred efforts towards more comprehensive recycling of nutrients contained in human excreta to agriculture. Research in this direction has intensified throughout the past years, continuously unfolding new knowledge and technologies. The present review aspires to provide a systematic synthesis of the field by providing an accessible overview of terminology, recovery pathways and treatment options, and products rendered by treatment. Our synthesis suggests that, rather than focusing on a specific recovery pathway or product and on a limited set of nutrients, there is scope for exploring how to maximize nutrient recovery by combining individual pathways and products and including a broader range of nutrients. To this end, finding ways to more effectively share and consolidate knowledge and information on recovery pathways and products would be beneficial. The present review aims to provide a template that aims to facilitate designing human excreta management for maximum nutrient recovery, and that can serve as foundation for organizing and categorizing information for more effective sharing and consolidation.
Schmitt, R. J. P., Morgenroth, E., & Larsen, T. A. (2017). Robust planning of sanitation services in urban informal settlements: an analytical framework. Water Research, 110, 297-312. doi:10.1016/j.watres.2016.12.007, Institutional Repository

New types of sanitation services are emerging to tackle the sanitation crisis in informal settlements. These services link toilet facilities to semi-decentralized treatment plants via frequent, road-based transport of excreta. However, information for the planning of such sanitation services is scarce, and their future operating conditions are highly uncertain. The key questions of this paper are therefore: a) what are the drivers behind success or failure of a service-based sanitation system in informal settlements and b) on what scales and under which conditions can such a system operate successfully? To answer these questions, already at an early stage of the planning process, we introduce a stochastic model to analyze a wide range of system designs under varying technical designs, socio-economic factors, and spatial condition. Based on these initial results, we design a sanitation service and use the numeric model to study its reliability and costs over a wide range of scales, i.e., system capacities, from very few to many hundred users per semi-decentralized treatment unit. Key findings are that such a system can only operate within a narrow, but realistic range of conditions. Key requirements are toilet facilities, which can be serviced rapidly, and a flexible workforce. A high density of facilities will also lower the costs. Under these premises, we develop a road-based sanitation service and model its functionality in different settings and under many scenarios. Results show that the developed sanitation system using a single vehicle is scalable (100–700 users), can provide reliable service, and can be cheap (<1.5 c/p/day). Hence, this paper demonstrates opportunities for road-based sanitation in informal settlements and presents a quantitative framework for designing such systems.
Tobias, R., O'Keefe, M., Künzle, R., Gebauer, H., Gründl, H., Morgenroth, E., … Larsen, T. A. (2017). Early testing of new sanitation technology for urban slums: the case of the Blue Diversion Toilet. Science of the Total Environment, 576, 264-272. doi:10.1016/j.scitotenv.2016.10.057, Institutional Repository

The toilets used most in informal urban settlements have detrimental consequences for the environment and human health due to the lack of proper collection and treatment of toilet waste. Concepts for safe, sustainable and affordable sanitation systems exist, but their feasibility and acceptance have to be investigated at an early stage of development, which is difficult due to the high costs of building working models. In this paper, we present an approach to estimate acceptance in a valid and representative form with only one working model, and apply it to test an innovative zero-emission toilet with recycling of wash water. Four basic principles were specified for investigation and nine hypotheses formulated to test the feasibility and acceptance of these principles: source separation of urine and feces with subsequent collection for resource recovery; provision of wash water in a separate cycle with on-site recovery through a membrane bioreactor; a convenient and attractive overall design; and a financially sustainable business plan. In Kampala (Uganda), in 2013, data was collected from 22 regular users, 308 one-time users and a representative sample of 1538 participants. Qualitative data was collected from the users, who evaluated their likes, perceived benefits, social norms and expected ease of use based on verbal and visual information. Most of the hypotheses were confirmed, indicating the feasibility and acceptance of the basic principles. Source separation and on-site water recovery were found to be feasible and accepted, provided users can be convinced that the emptying service and water recovery process work reliably. In the survey, the toilet was evaluated favorably and 51% of the participants agreed to be placed on a bogus waiting list. However, some design challenges were revealed, such as the size of the toilet, hiding feces from view and improving the separation of urine and water
Larsen, T. A., Hoffmann, S., Lüthi, C., Truffer, B., & Maurer, M. (2016). Emerging solutions to the water challenges of an urbanizing world. Science, 352(6288), 928-933. doi:10.1126/science.aad8641, Institutional Repository

The top priorities for urban water sustainability include the provision of safe drinking water, wastewater handling for public health, and protection against flooding. However, rapidly aging infrastructure, population growth, and increasing urbanization call into question current urban water management strategies, especially in the fast-growing urban areas in Asia and Africa. We review innovative approaches in urban water management with the potential to provide locally adapted, resource-efficient alternative solutions. Promising examples include new concepts for stormwater drainage, increased water productivity, distributed or on-site treatment of wastewater, source separation of human waste, and institutional and organizational reforms. We conclude that there is an urgent need for major transdisciplinary efforts in research, policy, and practice to develop alternatives with implications for cities and aquatic ecosystems alike.
Randall, D. G., Krähenbühl, M., Köpping, I., Larsen, T. A., & Udert, K. M. (2016). A novel approach for stabilizing fresh urine by calcium hydroxide addition. Water Research, 95, 361-369. doi:10.1016/j.watres.2016.03.007, Institutional Repository

In this study, we investigated the prevention of enzymatic urea hydrolysis in fresh urine by increasing the pH with calcium hydroxide (Ca(OH)2) powder. The amount of Ca(OH)2 dissolving in fresh urine depends significantly on the composition of the urine. The different urine compositions used in our simulations showed that between 4.3 and 5.8 g Ca(OH)2 dissolved in 1 liter of urine at 25 °C. At this temperature, the pH at saturation is 12.5 and is far above the pH of 11, which we identified as the upper limit for enzymatic urea hydrolysis. However, temperature has a strong effect on the saturation pH, with higher values being achieved at lower temperatures. Based on our results, we recommend a dosage of 10 g Ca(OH)2·L−1 of fresh urine to ensure solid Ca(OH)2 always remains in the urine reactor which ensures sufficiently high pH values. Besides providing sufficient Ca(OH)2, the temperature has to be kept in a certain range to prevent chemical urea hydrolysis. At temperatures below 14 °C, the saturation pH is higher than 13, which favors chemical urea hydrolysis. We chose a precautionary upper temperature of 40 °C because the rate of chemical urea hydrolysis increases at higher temperatures but this should be confirmed with kinetic studies. By considering the boundaries for pH and temperature developed in this study, urine can be stabilized effectively with Ca(OH)2 thereby simplifying later treatment processes or making direct use easier.
Künzle, R., Pronk, W., Morgenroth, E., & Larsen, T. A. (2015). An energy-efficient membrane bioreactor for on-site treatment and recovery of wastewater. Journal of Water Sanitation and Hygiene for Development, 5(3), 448-455. doi:10.2166/washdev.2015.116, Institutional Repository

The present study describes the development of a new type of aerated membrane bioreactor referred to as a biologically activated membrane bioreactor (BAMBi) for on-site treatment of high-strength wastewater. The treated wastewater is reused for flushing and personal hygiene. BAMBi is an adaptation of a gravity-driven membrane reactor, originally developed for the purpose of treating river water to drinking water quality. Initially, a series of reactor configurations were tested and it was found that the simplest possible configuration could treat the wastewater to an acceptable standard, provided that a polishing step for color removal and disinfection was introduced. A commercial electrolysis unit was utilized for polishing. The energy consumption of BAMBi is 0.8 kWh/m3 of water treated, which can be considered low for an on-site membrane bio reactor application.
Larsen, T. A., Gebauer, H., Gründl, H., Künzle, R., Lüthi, C., Messmer, U., … Ranner, B. (2015). Blue Diversion: a new approach to sanitation in informal settlements. Journal of Water Sanitation and Hygiene for Development, 5(1), 64-71. doi:10.2166/washdev.2014.115, Institutional Repository

The sanitation concept ‘Blue Diversion’ (www.bluediversiontoilet.com) was developed as a possible answer to the sanitation crisis in urban slums. It is based on two main elements: (1) diversion of urine, feces, and water at the source as the basis for efficient resource recovery, and (2) linking different scales (family toilets and semi-centralized resource recovery). Our objective was to develop an attractive ‘grid-free’ (i.e. functioning without piped water, sewer, and electrical grid) dry urine-diverting toilet, which provides water (through recycling on-site) for flushing, personal hygiene (anal cleansing and menstrual hygiene), and hand washing. This service, including the entire sanitation value chain, should eventually be made available as a profitable business with total user fees of 5 ¢/p/d. The results presented in this paper are (1) a toilet design model, (2) the development of a new type of membrane bioreactor for treating flush and wash water, (3) main results of a geographic information system-based stochastic service model to link the family-scale toilet to a community-scale Resource Recovery Plant, and (4) a business model that yields maximum profit for the local community. We conclude that the approach is feasible, but challenging from a technical as well as an organizational point of view.
Larsen, T. A. (2015). CO2-neutral wastewater treatment plants or robust, climate-friendly wastewater management? A systems perspective. Water Research, 87, 513-521. doi:10.1016/j.watres.2015.06.006, Institutional Repository

CO2-neutral wastewater treatment plants can be obtained by improving the recovery of internal wastewater energy resources (COD, nutrients, energy) and reducing energy demand as well as direct emissions of the greenhouse gases N2O and CH4. Climate-friendly wastewater management also includes the management of the heat resource, which is most efficiently recovered at the household level, and robust wastewater management must be able to cope with a possible resulting temperature decrease. At the treatment plant there is a substantial energy optimization potential, both from improving electromechanical devices and sludge treatment as well as through the implementation of more energy-efficient processes like the mainstream anammox process or nutrient recovery from urine. Whether CO2 neutrality can be achieved depends not only on the actual net electricity production, but also on the type of electricity replaced: the cleaner the marginal electricity the more difficult to compensate for the direct emissions, which can be substantial, depending on the stability of the biological processes. It is possible to combine heat recovery at the household scale and nutrient recovery from urine, which both have a large potential to improve the climate friendliness of wastewater management.
Morgenroth, E., Derlon, N., Pronk, W., & Larsen, T. A. (2015). Von der Grundlagenforschung zur Anwendung: Trinkwasseraufbereitung und Sanitärversorgung (p. (14 pp.). Presented at the 48. Essener Tagung für Wasser- und Abfallwirtschaft "Forschung trifft Praxis". Aachen, Germany. , Institutional Repository
Larsen, T. A., Udert, K. M., & Lienert, J. (2014). Abwassertrennung und Dezentralisierung. Aqua & Gas, 94(1), 52-54. , Institutional Repository

Ist eine ressourcenschonende Abwasserreinigung durch Abwassertrennung und Dezentralisierung realistisch? Rund 40 international bekannte Wissenschafter und Wissenschafterinnen behandeln auf 520 Seiten in einem 2013 erschienenen Buch nuanciert diese Fragestellung. Die Editoren der Eawag diskutieren das Thema des Buches im Schweizer Kontext.
McConville, J. R., Künzle, R., Messmer, U., Udert, K. M., & Larsen, T. A. (2014). Decision support for redesigning wastewater treatment technologies. Environmental Science and Technology, 48(20), 12238-12246. doi:10.1021/es501854x, Institutional Repository

This paper offers a methodology for structuring the design space for innovative process engineering technology development. The methodology is exemplified in the evaluation of a wide variety of treatment technologies for source-separated domestic wastewater within the scope of the Reinvent the Toilet Challenge. It offers a methodology for narrowing down the decision-making field based on a strict interpretation of treatment objectives for undiluted urine and dry feces and macroenvironmental factors (STEEPLED analysis) which influence decision criteria. Such an evaluation identifies promising paths for technology development such as focusing on space-saving processes or the need for more innovation in low-cost, energy-efficient urine treatment methods. Critical macroenvironmental factors, such as housing density, transportation infrastructure, and climate conditions were found to affect technology decisions regarding reactor volume, weight of outputs, energy consumption, atmospheric emissions, investment cost, and net revenue. The analysis also identified a number of qualitative factors that should be carefully weighed when pursuing technology development; such as availability of O&M resources, health and safety goals, and other ethical issues. Use of this methodology allows for coevolution of innovative technology within context constraints; however, for full-scale technology choices in the field, only very mature technologies can be evaluated.
Erisman, J. W., & Larsen, T. A. (2013). Nitrogen economy of the 21st century. In T. A. Larsen, K. M. Udert, & J. Lienert (Eds.), Source separation and decentralization for wastewater management (pp. 45-58). London: IWA Publishing. , Institutional Repository

In the past 50 100 years, the world's nitrogen cycle has been radically altered by global food and energy production systems, which have caused an increase in the total production rate of reactive nitrogen by a factor of 1.5 to 2 compared to its natural production. Reactive nitrogen, Nr, encompasses all forms of nitrogen occurring on earth except for atmospheric N2. Reactive nitrogen both promotes and endangers human welfare. Humanity benefits from energy use and particularly from the food and feed produced through the availability of mineral fertilizer. These activities bring enormous benefits, but losses of nitrogen from agriculture, human waste and combustion processes also have detrimental effects on the environment (see e.g., Galloway et al. 2008). These effects include the exceeding of critical loads resulting in loss of biodiversity, groundwater pollution, eutrophication of inland ecosystems and coastal areas causing algae blooms and fish kills, elevated atmospheric levels of ammonia, nitrogen oxide, nitrous oxide and aerosols resulting in climate change and/or human health impacts (Cowling et al. 2002; Galloway et al. 2003, 2008; Townsend et al. 2003; Reid et al. 2005). [...]
Kenway, S. J., Scheidegger, R., Larsen, T. A., Lant, P., & Bader, H. P. (2013). Water-related energy in households: a model designed to understand the current state and simulate possible measures. Energy and Buildings, 58, 378-389. doi:10.1016/j.enbuild.2012.08.035, Institutional Repository

Energy use in households, including private transport, accounts for about 30% of primary energy use in industrialised countries. Therefore, households are important key drivers of energy use and related greenhouse gas emissions. In order to understand energy use related to water in households a detailed mathematical flow analysis of materials, energy, CO2 emissions and costs (MMFA) for household water use was set up and tested for a specific family household in Brisbane, Australia. The simulation results for the current state of this household were well within 20% of the monitored data. After calibration, a detailed scenario investigation determined the impact of (i) potential and (ii) realistic reduction values for all relevant (a) behavioural and (b) technical parameters, including a shift from gas to a solar hot-water system. The reduction potentials for water use, greenhouse gas emissions, water-related energy consumption, water costs and water-related energy costs were 4–77%, 14–85%, 15–93%, 1–31% and 13–90% respectively. The study showed that for this household, technical improvements alone, without changing to a solar hot-water system, result in less than a 15% change in terms of energy and greenhouse gas emissions. In contrast, combined behavioural and technical changes have a much higher reduction potential.
Larsen, T. A., Udert, K. M., & Lienert, J. (2013). Editorial. In T. A. Larsen, K. M. Udert, & J. Lienert (Eds.), Source separation and decentralization for wastewater management (pp. 1-10). London: IWA Publishing. , Institutional Repository

Why are we editing a book about source separation and decentralization? We live in Switzerland, an industrialized country with a highly advanced and well-functioning wastewater management system. But even in Switzerland, the central system is reaching its limits, shortcomings, which become very obvious from a global perspective. We are proud to have been able to assemble contributions from renowned authors worldwide from both research and practice. They share with us their experience and thoughts about the current wastewater system. They analyze its advantages, but also deficiencies and they have the courage to breach the paradigm that central wastewater treatment is the only possible approach in urban areas. Many of the authors of this book are pioneers in the field and have been paving the way to a more sustainable and equitable handling of wastewater. We are greatly indebted to all the authors for their contributions to this book, but even more so for their continuous research on source separation and decentralization. We hope that this book will help develop this new area into a mature field in science as well as in practice. [...]
Larsen, T. A., & Gujer, W. (2013). Implementation of source separation and decentralization in cities. In T. A. Larsen, K. M. Udert, & J. Lienert (Eds.), Source separation and decentralization for wastewater management (pp. 135-150). London: IWA Publishing. , Institutional Repository

In the next decades, global population growth will be dominated by an increasing urban population. As seen from Figure 10.1, this growth will primarily take place in "less developed" regions. Maintaining urban hygiene and healthy water resources in these regions will be a formidable, expensive and time consuming task. In Switzerland, water pollution control had a very high public priority in the period from 1960 to 1990 and the construction of sewers and centralized wastewater treatment plants was highly subsidized by federal and state agencies in order to speed up the construction process. Nevertheless it took about 27 years to increase the connection of the population and industry to first-generation wastewater treatment plants (BOD removal only) from 10% to 90%. Second-generation treatment, which includes nutrient removal, is still in progress. Thus, experience tells us that under ideal conditions, in a rich country, with a well established engineering community and well organized state agencies, the establishment of efficient and stable wastewater treatment infrastructure is subject to a time constant of at least 50 years. [...]
Larsen, T. A., Udert, K. M., & Lienert, J. (Eds.). (2013). Source separation and decentralization for wastewater management. doi:10.2166/9781780401072, Institutional Repository

Is sewer-based wastewater treatment really the optimal technical solution in urban water management? This paradigm is increasingly being questioned. Growing water scarcity and the insight that water will be an important limiting factor for the quality of urban life are main drivers for new approaches in wastewater management. Source Separation and Decentralization for Wastewater Management sets up a comprehensive view of the resources involved in urban water management. It explores the potential of source separation and decentralization to provide viable alternatives to sewerbased urban water management.
During the 1990s, several research groups started working on sourceseparating technologies for wastewater treatment. Source separation was not new, but had only been propagated as a cheap and environmentally friendly technology for the poor. The novelty was the discussion whether source separation could be a sustainable alternative to existing end-of-pipe systems, even in urban areas and industrialized countries.
Since then, sustainable resource management and many different sourceseparating technologies have been investigated. The theoretical framework and also possible technologies have now developed to a more mature state. At the same time, many interesting technologies to process combined or concentrated wastewaters have evolved, which are equally suited for the treatment of source-separated domestic wastewater.
The book presents a comprehensive view of the state of the art of source separation and decentralization. It discusses the technical possibilities and practical experience with source separation in different countries around the world. The area is in rapid development, but many of the fundamental insights presented in this book will stay valid.
Source Separation and Decentralization for Wastewater Management is intended for all professionals and researchers interested in wastewater mamagement, wheter or not they are familiar with source separation.
Larsen, T., Gebauer, H., Künzle, R., Lüthi, C., McConville, J., Messmer, U., … Tumwebaze, I. K. (2012). Final report. Reinvent the toilet challenge. Round 1. Diversion for safe saniation. Dübendorf: Eawag. , Institutional Repository
Larsen, T. A. (2011). Cleantech for wastewater treatment of the future. Eawag News [engl. ed.], 70, 30-33. , Institutional Repository

In wastewater treatment, environmentally sound and resource-efficient technologies should also exploit the resources contained in wastewater itself. Radically new approaches such as urine source separation and the recovery of nutrients for urine based fertilizers point the way to a future which goes beyond conventional sewers and wastewater treatment plants.
Larsen, T. A. (2011). Cleantech für die Abwasserreinigung der Zukunft. Eawag News [dtsch. Ausg.], 70, 30-33. , Institutional Repository

Umwelt- und ressourcenschonende Technologien in der Abwasserreinigung müssen auch eine optimale Nutzung der Ressourcen im Abwasser einschliessen. Völlig neue Konzepte wie die Separierung des Urins direkt an der Quelle und die Aufbereitung von dessen Nährstoffen zu Dünger weisen in eine Zukunft jenseits der konventionellen Kläranlage und Kanalisation.
Larsen, T. A. (2011). Redesigning wastewater infrastructure to improve resource efficiency. Water Science and Technology, 63(11), 2535-2541. doi:10.2166/wst.2011.502, Institutional Repository

Resource efficiency of wastewater management is a question of optimizing at the same time the management of resources in wastewater (e.g. water), the resources spent on treatment and transport (e.g. energy), the natural resources to protect (e.g. the receiving waters), and the anthropogenic resources (e.g. capital). For instance, wastewater can be treated to any given quality, but only at the expense of energy and investment costs. Today, many up-coming problems are solved incrementally, leading to resource consuming solutions optimized for water pollution control in well off countries, whereas large parts of the world have at the best very simple wastewater treatment. From a global point of view, a system change is necessary in order to solve the immense problems arising from global population growth, urban development and climate change. Source separation is a promising concept for resource efficient wastewater management, but a more concerted effort is necessary from the international community in order to develop competitive technologies and overcome the inflexibility of the present end-of-pipe technology. Much more research and development are necessary, not only in the area of engineering, but also with respect to the socio-economic dimensions, especially in the area of regulation, suitable governance and management models, and concerning the involvement of industrial partners.
Larsen, T. A., & Maurer, M. (2011). Source separation and decentralization. In P. Wilderer (Ed.), Vol. 4. Treatise on water science (pp. 203-229). doi:10.1016/B978-0-444-53199-5.00083-X, Institutional Repository

Toward the end of the 1990s, a special issue on sustainable sanitation was published by Water Science and Technology, a journal of the International Water Association (IWA). In this issue, several authors discussed the issue of source-separation technologies in the area of wastewater management (Henze, 1997). All major sources of combined wastewater were covered: industrial wastewater (Visvanathan and Hufemia, 1997), storm water (Boller, 1997), gray water (domestic wastewater without toilet waste; Jeffrey et al., 1997), urine (Hanäus et al., 1997; Larsen and Gujer, 1997), and black water (combined toilet waste; Otterpohl et al., 1997).
Whereas separate discharge of storm water and separate treatment of industrial wastewater were already well-known concepts, source separation for domestic wastewater was at that time primarily recognized as an inexpensive sanitation technology for poor, rural areas. For urban areas, only sewer-based wastewater management was considered suitable. The above-mentioned special issue challenged this conventional wisdom with the idea that source separation could potentially compete with end-of-pipe technologies for all wastewaters, even in urban areas. The main concepts behind this idea were that, on the one hand, it would be more resource efficient to treat very concentrated solutions such as urine (Larsen and Gujer, 1997) and that, on the other hand, local recycling of (gray) water would increase flexibility of the urban water management system (Jeffrey et al., 1997). [...]
Larsen, T. A., Maurer, M., Eggen, R. I. L., Pronk, W., & Lienert, J. (2010). Decision support in urban water management based on generic scenarios: the example of NoMix technology. Journal of Environmental Management, 91(12), 2676-2687. doi:10.1016/j.jenvman.2010.07.032, Institutional Repository

Urine source separation (NoMix technology) followed by processing the concentrated nutrient solution has the potential to become a cost-efficient alternative to conventional end-of-pipe nutrient elimination. A choice of processing technologies can only be made for specific scenarios, and there is currently no methodology for analyzing generic situations. In setting up a formalized decision-support methodology (based on STEEPLED analysis), we discuss how to create such generic scenarios, how to couple them with process engineering objectives, how to define the technology requirements, and finally how to produce a realistic subset of technology alternatives. The methodology is tested in five real scenarios. We also touch on the criteria for a final choice of technology taking into account large uncertainties about the performance of real technologies. We conclude that technology development is one of the most important requirements for implementing urine source separation in practice. There is an urgent need to develop cost-efficient processing technologies that satisfy the requirements of stakeholders.
Lienert, J., & Larsen, T. A. (2010). High acceptance of urine source separation in seven European countries: a review. Environmental Science and Technology, 44(2), 556-566. doi:10.1021/es9028765, Institutional Repository

Urine source separation (NoMix-technology) is a promising innovation aiming at a resource-oriented, decentralized approach in urban water management. However, NoMix-technology has a sensitive end-point: people’s bathrooms. NoMix-technology is increasingly applied in European pilot projects, but the success from a user point-of-view has rarely been systematically monitored. We aim at closing this gap. We review surveys on acceptance, including reuse of human urine as fertilizer, from 38 NoMix-projects in 7 Northern and Central European countries with 2700 respondents. Additionally, we identify explanatory variables with logistic regression of a representative Swiss library survey. NoMix-technology is well accepted; around 80% of users liked the idea, 75−85% were satisfied with design, hygiene, smell, and seating comfort of NoMix-toilets, 85% regarded urine-fertilizers as good idea (50% of farmers), and 70% would purchase such food. However, 60% of users encountered problems; NoMix-toilets need further development. We found few differences among countries, but systematic differences between public and private settings, where people seem more critical. Information was positively correlated with acceptance, and, e.g., a good mood or environmentally friendly behavior. For future success of NoMix-projects, we recommend authorities follow an integral strategy. Lay people will then find the NoMix-concept appealing and support this promising bathroom innovation.
Larsen, T., & Lienert, J. (2009). Novaquatis - neue Wege in der Siedlungswasserwirtschaft. In H. Horn & W. Günthert (Eds.), Berichte aus der Siedlungswasserwirtschaft: Vol. 195. Perspektiven in der Siedlungswasserwirtschaft (pp. 51-79). München: Technische Universität München. , Institutional Repository
Larsen, T. A., Alder, A. C., Eggen, R. I. L., Maurer, M., & Lienert, J. (2009). Source separation: Will we see a paradigm shift in wastewater handling?. Environmental Science and Technology, 43(16), 6121-6125. doi:10.1021/es803001r, Institutional Repository
Rossi, L., Lienert, J., & Larsen, T. (2009). Lutte à la source pour la rétention de microplluants dans les eaux. Le concept NoMix. Techniques, Sciences, Méthodes, 104(4), 53-59. doi:10.1051/tsm/200904053, Institutional Repository

Micropollutants represent one of today’s main concerns for surface water management. One of the major sources of micropollutants to the environment is linked with the discharge of pharmaceutical residues by the population. Although some technologies exist today to deal with these kinds of discharges, source-control strategies constitute a very interesting solution and are illustrated in this paper. We focus here on the NoMix technology, an innovative at-source solution to separate liquid and solid wastes. The NoMix new technology proposes to separate urine directly at the source. Urine (1.5 litre/inhabitant per day)constitutes less than 1% of the volume processed in waste water treatment plants. However, it contains the most important part of nutrients (80% nitrogen, 50% phosphorus) and a major part of the pharmaceuticals released by the human metabolism (64%, ± 27%). A separate collection and treatment of urine offers thus an interesting potential for micropollutants removal. The NoMix concept has been studied for many years by Eawag (Swiss Federal Institute of Aquatic Science and Technology) within the framework of an inter- and trans-disciplinary project entitled “Novaquatis”.The results of this project show that the NoMix technology would be significant to reduce at-source micropollutants. Moreover, it allows the nutrients produced in urban areas to be recycled, once treated, as fertilisers for agriculture. This article briefly presents the concept of at-source control, as wellas the main results of the Novaquatis project.
Rossi, L., Lienert, J., & Larsen, T. A. (2009). Real-life efficiency of urine source separation. Journal of Environmental Management, 90(5), 1909-1917. doi:10.1016/j.jenvman.2009.01.006, Institutional Repository

Urine source separation (NoMix technology) is a promising innovation in wastewater management. To improve and further develop NoMix technology, it has been implemented in four Swiss households and at our research institute (Eawag). We conducted measurements during one year on frequency of toilet usage (in households 5.2/person/day for weekdays, and 6.3/person/day for weekends), flushing behavior (30-85% small flushes), and recovered urine. We calculate the amount of urine effectively recovered per voiding in NoMix toilets (138 ml/flush in households; 309 ml/flush in women's toilets at Eawag), and waterfree urinals (225 ml/usage). We estimate urine recovery in the households to be maximally 70-75% of the expected quantity, leaving room for technical and behavioral improvements. Based on sampling of N and P concentrations, we suspect nitrogen losses in the extended urine piping system. For households and workplaces, the daily and weekly flushing pattern is recorded. Our results are in accordance with literature data from a shorter period but with more people. These results represent a good dimensioning basis for future urine source separation applications. An example of extrapolation to an entire watershed is presented. The flushing pattern corresponds well with the typical nitrogen loading of a treatment plant.
Borsuk, M. E., Maurer, M., Lienert, J., & Larsen, T. A. (2008). Charting a path for innovative toilet technology using multicriteria decision analysis. Environmental Science and Technology, 42(6), 1855-1862. doi:10.1021/es702184p, Institutional Repository

Practical and theoretically sound methods for analyzing innovative environmental technologies are needed to inform public and private decisions regarding research and development, risk management, and stakeholder communication. By integrating scientific assessments with a characterization of values, multicriteria decision analysis (MCDA) supports the ranking of alternative technology pathways on the basis of technical, financial, and social concerns. We applied MCDA to evaluate the use of NoMix urine separating toilets for managing environmental risk and postponing expensive upgrades to a large wastewater treatment plant near Zürich, Switzerland. Results indicate that, given current priorities, no single, fixed course of action (including the status quo) will be desirable to all stakeholders over the considered time horizon. However, a path forward is suggested that is not significantly disadvantageous to any stakeholder now and leaves open future options, allowing society to achieve overall greater benefits if priorities change, new environmental risks are revealed, or technology improves. While our analysis focuses on a particular catchment in Switzerland, many communities worldwide are faced with an aging and inefficient wastewater treatment infrastructure while also experiencing growth and development. Our framework can help these communities balance the conflicting objectives of diverse stakeholders and gain insight into the role that urine separation can play in transitioning to a more comprehensive and sustainable urban water management system.
Kraj, A. (2008). Importance of heterotrophic bacteria in the single stage nitritation-anammox process of nitrogen removal from source-separated urine (Master thesis). 70 p. , Institutional Repository

Preliminary studies have shown that source-separated urine is a suitable medium for nitrogen removal via aerobic and anoxic ammonia oxidation (Udert et al., 2003). Furthermore, denitrifying bacteria can use the sufficient high concentration of dissolved organic matter, which is build up during the anammox process. Combination of all aerobic and anoxic processes leads to an increased nitrogen removal and savings in the oxygen consumption. On the basis of previous studies, a single aerobic/anoxic sequencing batch reactor was chosen as a most powerful tool for the integration of these microbiological processes.
During this diploma thesis further experiments were made in order to better understand the overall process of nitrogen removal. Thanks to intensive sampling some problems in the course of the reactor were observed. It was noticed that at the beginning of each cycle, only organic matter is consumed, whereas nitrogen concentration stays at the same level. This caused a delay in the nitrogen elimination and was considered as a dysfunction of the process. The evaluation of the toxicity of urine showed that urine contains some toxic substances which are responsible for the inhibition of ammonium oxidizing bacteria. However, it could be observed that during the course of the cycle, the toxicity decreases to a lower level which enables autotrophic bacteria to start ammonium oxidation. Since during this initial time only heterotrophic bacteria show their activity, the decline of toxicity was attributed to these microorganisms. Thanks to this observation it could be showed that heterotrophs play a very important role in the overall process: on the one side through anoxic respiration they reduce nitrite and nitrate which results in better overall nitrogen removal, and on the other side via removal of organic matter they decrease the inhibition effects on ammonium oxidizing bacteria.

Bisherige Studien zeigten, dass ein einstufiges Nitritation-Anammox-Verfahren eine effiziente Lösung zur Stickstoffentfernung ist. Udert et al. (2003) konnten beweißen, dass das Verfahren sich ebenfalls für die Behandlung von menschlichen Urin gut eignet. Urin enthält große Mengen von Ammonium und relativ hohe Konzentrationen organischer Substanz. Diese Zusammensetzung ermöglicht neben einer autotrophen Stickstoffentfernung (Ammonium-Oxidation folgend durch Anammox) auch eine heterotrophe (Denitrifikation) Stickstoffentfernung. Eine Kombination dieser mikrobiologischen Prozesse erhöht die Effizienz und reduziert die Kosten des Verfahrens. Zum optimalen Einsatz des Verfahrens wurde SBR Reaktor gewählt.
Im Rahmen dieser Diplomarbeit wurden weitere Versuche durchgeführt, die dem besseren Verständnis und der Charakterisierung der Ablaufenden mikrobiologischen Prozesse dienten. Anhand von gemessenen Daten, konnte festgestellt werden, dass die Stickstoffentfernung gestört ist. Beobachtungen zeigten, dass am Anfang des SBR-Zyklus nur die organische Substanz assimiliert wird und keine Ammonium-Oxidation stattfindet. Demzufolge wird die Stickstoffentfernung in der Zeit versetzt, was zur Verlängerung des Zyklus führt. Weitergehende Untersuchungen zeigten, dass Urin toxische Stoffe enthält, die für diese Inhibierung der Ammonium-Oxidanten verantwortlich sein könnten. Es wurde beobachtet, dass während eines SBR-Zyklus die gemessene Toxizität sinkt: demzufolge nehmen auch die Inhibierungseffekte auf die autotrophen Mikroorganismen ab und die Ammonium-Oxidation kann beginnen. Diese Abnahme der Toxizität geschieht in der ersten Phase des Zyklus. In dieser Zeit sind die heterotrophen Bakterien am aktivsten. Daher wirkt sich die heterotrophe Aktivität auf den gesamten Prozess positiv aus.
Als Resümee der Versuche, stellte sich heraus, dass die heterotrophen Mikroorganismen eine große Rolle in dem Verfahren spielen. Einerseits werden durch die anoxische Atmung Nitrit und Nitrat entfernt, was zur Effizienz des Prozesses beiträgt. Andererseits werden durch ihre aerobe Aktivität die toxischen Stoffe abgebaut und die Ammonium-Oxidation ermöglicht.
Udert, K. M., Kind, E., Teunissen, M., Jenni, S., & Larsen, T. A. (2008). Effect of heterotrophic growth on nitritation/anammox in a single sequencing batch reactor. Water Science and Technology, 58(2), 277-284. doi:10.2166/wst.2008.389, Institutional Repository

The combination of nitritation and autotrophic denitrification (anammox) in a single sequencing batch reactor (SBR) is an energy efficient process for nitrogen removal from high-strength ammonia wastewaters. So far, the process has been successfully applied to digester supernatant. However, the process could also be suitable to treat source-separated urine, which has very high ammonium and organic substrate concentrations (up to 8,200 gN/m3 and 10,000 gCOD/m3). In this study, reactor performance was tested for digester supernatant and diluted source-separated urine. Ammonium concentrations in both solutions were similar (between 611 and 642 gN/m3), thus reactor performance could be directly compared. Differences were mainly due to higher activity of heterotrophic bacteria in urine. Nitrogen removal was slightly higher for source-separated urine, because heterotrophic bacteria denitrified the nitrate that was produced by anammox bacteria. In spite of higher heterotrophic growth with source-separated urine, calculated sludge concentrations at steady state were higher with digester supernatant due to accumulation of inert particulate organic matter from the influent. Although the sludge concentrations are less problematic for source-separated urine, process instabilities are more likely, because lower pH values are reached and heterotrophic denitrification can cause sudden increases of nitrite concentrations and/or nitric oxide. Both compounds inhibit aerobic ammonium oxidizing bacteria, heterotrophic bacteria and, most importantly, anammox bacteria. Nitrite and nitric oxide production by heterotrophic denitrification must be better understood to optimize nitritation/anammox for source-separated urine.
Larsen, T. A., Bader, H. P., Mosler, H. J., Gujer, W., Medilanski, E., Scheidegger, R., … Schertenleib, R. (2007). Applying traditional Chinese knowledge. Eawag News [engl. ed.], 63, 26-28. , Institutional Repository

Kunming, Zurich's sister city in China, is determined to tackle its wastewater problem. In the development of measures based on nutrient recycling - a long-established principle in China - it is receiving support from Eawag in technical as well as social issues.
Larsen, T., & Lienert, J. (2007). NoMix-Technologie. Chance für Siedlungswasserwirtschaft. GWA Gas, Wasser, Abwasser, 87(4), 255-262. , Institutional Repository

Could urine source separation replace the conventional nutrient elimination on wastewater treatment plants? Divided in nine work packages, the Eawag cross-cutting project Novaquatis pursued this question and highlighted the potential advantages and difficulties of such an enterprise. In many rapidly growing cities, the NoMix technology offers a rapid defense against nutrients in coastal waters, without waiting for the long and tiresome construction of sewers and treatment plants. In order to avoid the urine transport, an important next step will be the rapid development of decentralized process engineering opportunities. Also in Switzerland, the NoMix technology has a future, especially in the case of growing requirements for water pollution control.
Larsen, T. A., & Lienert, J. (2007). NoMix. A new approach to urban water management. Final report Novaquatis. Dübendorf: Eawag. , Institutional Repository

The NoMix technology promotes water pollution control and conserves resources. Public attitudes to this innovation are favourable. Various methods have been developed for treating urine and removing micropollutants. Urine transport remains problematic. The results of the Novaquatis project suggest that it would be worth finding solutions to this problem - or avoiding it altogether by treating urine directly on site. For urine source separation could make a significant contribution to resolving the world's increasingly serious water pollution control issues.
Larsen, T. A., & Lienert, J. (2007). NoMix. Neue Wege in der Siedlungswasserwirtschaft. Abschlussbericht Novaquatis. Dübendorf: Eawag. , Institutional Repository

Die NoMix-Technologie fördert den Gewässerschutz und schont Ressourcen. Die Bevölkerung steht der Neuerung positiv gegenüber. Es wurden verschiedene Verfahren entwickelt, um Urin aufzubereiten und Mikroverunreinigungen zu entfernen. Knackpunkt ist der Transport des Urins. Die Resultate aus Novaquatis deuten darauf hin, dass es sich lohnt, Lösungen für das Problem zu finden - oder es durch eine Urinaufbereitung direkt im Haus zu umgehen. Denn die NoMix-Technologie kann wesentlich dazu beitragen, die weltweit zunehmenden Gewässerschutzprobleme zu lösen.
Larsen, T. A., Maurer, M., Udert, K. M., & Lienert, J. (2007). Nutrient cycles and resource management: implications for the choice of wastewater treatment technology. Water Science and Technology, 56(5), 229-237. doi:10.2166/wst.2007.576, Institutional Repository

We look at the most important issues of the global nitrogen and phosphorus cycle and conclude that the nutrients from human metabolism are of no importance for the global nitrogen cycle and of minor importance for the global phosphorus cycle. However, for water pollution control, N and P from the human metabolism are of extreme importance. Nitrogen is mainly an issue for coastal waters, whereas P is an issue for freshwater and coastal areas alike. It is by now generally recognised that coastal ecosystems are exceedingly important for human well-being and at the same time highly endangered. The recycling issue is of high importance in areas where nutrient application is low due to economic constraints. NoMix technology (urine source separation) holds a large promise to become an efficient mainstream technology. The largest short-term potential is found in densely populated areas in coastal areas without existing infrastructure and in areas with nutrient deficiency, especially in urban areas with a large nutrient potential. We believe, however, that these technologies will, with time, also become competitive in Europe.
Larsen, T. A., & Lienert, J. (2007). Spotlight on NoMix. Eawag News [engl. ed.], 63, 4-7. , Institutional Repository

Novaquatis, an inter- and transdisciplinary Eawag project, investigated urine source separation and treatment as an option for modern wastewater management. The results indicate that the so-called NoMix technology is a highly versatile innovation, offering advantages in a variety of scenarios. In particular, it could help to resolve global nutrient-related issues.
Lienert, J., & Larsen, T. A. (2007). Pilot projects in bathrooms: a new challenge for wastewater professionals. Water Practice and Technology, 2(3), 1-14. doi:10.2166/wpt.2007.057, Institutional Repository

Household-centered technologies such as urine source separation (NoMix technology) could induce a paradigm change in urban wastewater management, hereby improving water pollution control and resource management. Technological innovations need real-world application for further development. The Swiss research project Novaquatis accompanied five pilot projects from 1997 on. We give a systematic overview of our experience, summarizing various important aspects, a fundamental one being a clearly defined goal. Early stakeholder involvement is crucial, because the still imperfect NoMix technology depends on people’s goodwill. We reference data sheets, legal documents, etc. and make suggestions for installation, maintenance, and technology improvement. We identify areas for future research necessitating pilot projects and discuss their requirements to optimize the cost-benefit factor. This paper is intended as support to wastewater professionals to avoid the most serious pitfalls when conducting NoMix pilot projects. It contributes to increased interaction between research and real-world application of urban European household innovations.
Lienert, J., & Larsen, T. A. (2007). Soft paths in wastewater management – the pros and cons of urine source separation. GAIA: Ecological Perspectives for Science and Society, 16(4), 280-288. doi:10.14512/gaia.16.4.10, Institutional Repository

Although our water-borne urban wastewater system is successful, it has drawbacks in industrialized and developing countries alike, particularly in arid regions. It is inflexible and often inefficient. Of late, source control measures are being postulated as a paradigm change. In the Swiss transdisciplinary project Novaquatis, urine source separation, or NoMix technology, was studied. We compare NoMix technology with central wastewater treatment. Separate collection of urine has the potential to eliminate 70 to 80 percent of nitrogen from wastewater, 15 to 50 percent of phosphorus, and at least 50 percent of human pharmaceuticals. Hence, NoMix technology can contribute substantially in the reduction of eutrophication of marine ecosystems near fast-growing cities. We discuss the shortcomings of using sewage sludge or urine as fertilizers in agriculture – concerning pharmaceuticals, we also consider the societal perspective. Furthermore, NoMix technology introduces flexibility to wastewater management, important especially in light of growing uncertainties with respect to population development and climate change.
Lienert, J., & Larsen, T. A. (2007). Urinseparierung - Schlussfolgerungen nach sechs Jahren transdisziplinärer Forschung in Novaquatis. In R. Haberl (Ed.), Wiener Mitteilungen: Vol. 207. 1. Österreichischer Kleinkläranlagentag: ÖWAV-Seminar, Wien, 27. September 2007 (pp. K1-K28). Wien: Universität für Bodenkultur. , Institutional Repository

Unsere Siedlungswasserwirtschaft ist erfolgreich und effizient, hat aber auch Nachteile, vor allem beim Export in Entwicklungs- und Schwellenländer. Die Zukunft bringt neue Herausforderungen: Klimawandel und Wasserknappheit, neue Stoffe wie Pharmazeutika sowie Bevölkerungsexplosion mit fatalen Folgen für Küstengewässer wegen ungenügender Nährstoffelimination. Kann unser heutiges System damit umgehen? Wir postulieren, dass Massnahmen an der Quelle und dezentrale On-Site Technologien erfolgreicher sein könnten. Heute sind sie noch keine echte Alternative in einem modernen, urbanen Umfeld: es braucht noch viel Forschungs- und Entwicklungsarbeit. Im schweizerischen Forschungsprojekt Novaquatis wurde von 2000 bis 2006 eine mögliche Massnahme an der Quelle intensiv studiert: die separate Sammlung und Behandlung des Urins. Diese NoMix- Technologie könnte viele der genannten Anforderungen erfüllen; sie ermöglicht zum Beispiel einen verbesserten Gewässerschutz bezüglich Nährstoffen und Pharmazeutika. Dieser Artikel gibt einen Überblick über unsere Hauptresultate: Die NoMix-WCs werden trotz Nachteilen gut akzeptiert. Es gibt viele mögliche Verfahrenstechniken, um den Urin zu behandeln, was die Flexibilität der Abwasserbehandlung erhöht. Der Urin kann dann zum Beispiel - frei von Pharmazeutika - als Dünger verwendet werden. Noch gibt es offene Fragen und Hürden, bis die NoMix-Technologie konkurrenzfähig ist. Nach sechs Jahren Forschung, sind wir aber davon überzeugt, dass es sich lohnt, daran zu arbeiten.
Medilanski, E., Chuan, L., Mosler, H. J., Schertenleib, R., & Larsen, T. A. (2007). Identifying the institutional decision process to introduce decentralized sanitation in the city of Kunming (China). Environmental Management, 39(5), 648-662. doi:10.1007/s00267-005-0321-0, Institutional Repository

We conducted a study of the institutional barriers to introducing urine source separation in the urban area of Kunming, China. On the basis of a stakeholder analysis, we constructed stakeholder diagrams showing the relative importance of decision-making power and (positive) interest in the topic. A hypothetical decision-making process for the urban case was derived based on a successful pilot project in a periurban area. All our results were evaluated by the stakeholders. We concluded that although a number of primary stakeholders have a large interest in testing urine source separation also in an urban context, most of the key stakeholders would be reluctant to this idea. However, the success in the periurban area showed that even a single, well-received pilot project can trigger the process of broad dissemination of new technologies. Whereas the institutional setting for such a pilot project is favorable in Kunming, a major challenge will be to adapt the technology to the demands of an urban population. Methodologically, we developed an approach to corroborate a stakeholder analysis with the perception of the stakeholders themselves. This is important not only in order to validate the analysis but also to bridge the theoretical gap between stakeholder analysis and stakeholder involvement. We also show that in disagreement with the assumption of most policy theories, local stakeholders consider informal decision pathways to be of great importance in actual policy-making.
Lienert, J., & Larsen, T. A. (2006). Considering user attitude in early development of environmentally friendly technology: a case study of NoMix toilets. Environmental Science and Technology, 40(16), 4838-4844. doi:10.1021/es060075o, Institutional Repository

Urine source separation (NoMix technology) has been proposed as a sustainable alternative to centralized wastewater treatment systems. Radical changes necessitate an early inclusion of sociological expertise, thus offering a real chance for transdisciplinary collaboration. The practical aim of our survey is to find out how users accept and use existing NoMix toilets and how this could be encouraged. We collected 1249 questionnaires from 2002 to 2004 in one Swiss school and one Swiss research institute. The technological immaturity of NoMix toilets was noted by many. Nevertheless, acceptance was high: 72% liked the idea and 86% would move into apartments with NoMix toilets. Moreover, most users found that NoMix toilets equal conventional toilets with respect to design (78%), hygiene (84%), and smell (78%). Like many other innovations, the NoMix technology only functions properly if it is used adequately, which we demonstrate for water saving and sitting to urinate. Many users adopted this behavior, e. g., 72% sat. Because perception and use of NoMix toilets is subjective, it can be influenced with certain measures such as good information and cleaning, or discussions with peers. We discuss the importance of social psychology for understanding the factors that influence the acceptance of environmentally friendly innovations.
Lienert, J., & Larsen, T. A. (2006). Novaquatis - a building block for innovative sanitation technology. In K. Lanz, L. Müller, C. Rentsch, & R. Schwarzenbach (Eds.), Who owns the water? (pp. 380-381). Retrieved from https://www.lars-mueller-publishers.com/who-owns-water, Institutional Repository

This is the paradox of conventional wastewater management-drinking water is used to flush human excreta into the sewer system where it is further diluted by household wastewater from kitchens and baths. As a result, wastewater treatment plants must employ ever more complex process engineering to remove pollutants and recycle valuable nutrients. If we had to redesign wastewater disposal systems based on what we know today, we would certainly not opt for the same package of technologies.
Lienert, J., & Larsen, T. A. (2006). Novaquatis, a cross-cutting research project from Switzerland. Why we consider urine source separation (p. (15 pp.). Presented at the Abschlussseminar des EU-Demonstrationsvorhabens SCST (sanitation concepts for separate treatment). Berlin, Germany. , Institutional Repository

We discuss the current centralized urban water management system, which is well-established and successful in Central Europe. Nonetheless, it might not be the best of solutions. The infrastructure costs are high and there are several drawbacks; a major one being its extreme inflexibility. Moreover, it consumes large amounts of drinking water, nutrients are lost, the system leaks, and the treatment processes always lag behind emerging environmental problems; a new one being micropollutants (pharmaceuticals, hormones). We present the concepts of source control and waste design, which would strongly increase flexibility and allow for innovative and environmental-friendly solutions that could be driven by market forces. We use urine source separation or NoMix technology as illustration, which is being intensively studied in the Swiss research project Novaquatis (www.novaquatis.eawag.ch). The Novaquatis research results will be presented in detail on the projects' closing event on 7th March 2007. Here, we discuss some selected results on acceptance and functioning of the NoMix technology. We introduce technologies to process urine in order to reclaim or remove nutrients and eliminate micropollutants. We then discuss the integration of the NoMix technology into the existing system and shortly present the Swiss pilot projects. We conclude that there are indeed ways out of the current lock-in situation and that alternatives with the potential of increasing the sustainability of the water sector do exist.
Lienert, J., & Larsen, T. A. (2006). Novaquatis: Baustein für eine Sanitärtechnologie der Zukunft. In K. Lanz, L. Müller, C. Rentsch, & R. Schwarzenbach (Eds.), Wem gehört das Wasser? (pp. 380-381). Retrieved from https://www.lars-mueller-publishers.com/wem-gehort-das-wasser, Institutional Repository

Paradoxon konventioneller Abwasserentsorgung: Die menschlichen Ausscheidungen werden mit Trinkwasser weg gespült und in der Kanalisation mit gering verschmutztem Wasser aus Küche und Bad weiter verdünnt. In der Kläranlage muss dann ein immer grösserer technischer Aufwand betrieben werden, um Schadstoffe aus dem Abwasser heraus zu holen und wertvolle Nährstoffe zurück zu gewinnen. Könnten wir auf Grund aller heutigen Erkenntnisse neu entscheiden, würden wir sicher nicht die gleiche Strategie wählen.
Lienert, J., Thiemann, K., Kaufmann-Hayoz, R., & Larsen, T. A. (2006). Young users accept NoMix toilets – a questionnaire survey on urine source separating toilets in a college in Switzerland. Water Science and Technology, 54(11-12), 403-412. doi:10.2166/wst.2006.920, Institutional Repository

We studied user behavior and acceptance of NoMix toilets by collecting 271 questionnaires from young adults. We discriminated between short- and long-term users (months of habituation). Most respondents noticed that the NoMix toilet is different. Nevertheless, the existing NoMix technology was well accepted regarding design, hygiene and smell in this institutional setting. Only few respondents changed their sitting or flushing behavior. The necessity to sit when urinating might be slightly problematic (62% sit), but it seems possible that people adopt this new behavior required by the NoMix toilet. General acceptance of the NoMix toilet was high: 70% of respondents found the idea convincing – many for environmental reasons – 87% were willing to move into an apartment with a NoMix toilet, and 20% would pay substantially more for a NoMix toilet. We informed about the NoMix toilet with instructions for use in the toilet cabin, an information poster, and an information leaflet that we distributed after questioning. Our information was noted by most respondents and significantly increased the knowledge about and the acceptance of the NoMix toilet. We recommend that future pilot projects with NoMix toilets consider a well devised information policy to support decision making and acceptance of this new technology.
Maurer, M., Rothenberger, D., & Larsen, T. A. (2006). Decentralised wastewater treatment technologies from a national perspective: At what cost are they competitive?. Water Science and Technology: Water Supply, 5(6), 145-154. doi:10.2166/ws.2005.0059, Institutional Repository

In this paper we estimate at what cost decentralised wastewater treatment can be competitive compared with conventional centralised technologies. For the current wastewater infrastructure in Western Europe and North America, typical replacement costs are 2,600 US$/cap for large countries and 4,800 US$/cap for small ones. In the same literature, average annual operating costs are reported to be 3.8% of replacement costs. However, if a long-term interest rate of 3% is consistently applied, this value increases to 4.7% for small countries and 5.5% for large ones. Assuming that alternative wastewater systems will only be accepted if their costs are similar to existing ones, the possible investments for alternative wastewater treatment technologies are calculated. Between 640 and 2,170 US$/cap can be invested in new technologies for scenarios without a sewer system. The corresponding figures for scenarios with sewer systems are between 260 and 680 US$/cap. Acceptable maintenance requirements are calculated on the basis of unit size. Transition periods are not accounted for.
Maurer, M., Pronk, W., & Larsen, T. A. (2006). Treatment processes for source-separated urine. Water Research, 40(17), 3151-3166. doi:10.1016/j.watres.2006.07.012, Institutional Repository

The separate collection and treatment of urine has attracted considerable attention in the engineering community in the last few years and is seen as a viable option for enhancing the flexibility of wastewater treatment systems. This comprehensive review focuses on the status of current urine treatment processes and summarises the properties of collected urine. We distinguish between seven main purposes of urine-treatment processes: hygienisation (storage), volume reduction (evaporation, freeze-thaw, reverse osmosis), stabilisation (acidification, nitrification), P-recovery (struvite formation), N-recovery (ion treatment exchange, ammonia stripping, isobutylaldehyde-diurea (IBDU) precipitation), nutrient removal (anammox) and handling of micropollutants (electrodialysis, nanofiltration, ozonation). The review shows clearly that a wide range of technical options is available to treat collected urine effectively, but that none of these single options can accomplish all seven purposes. Depending on the overall goal of the treatment process, a specific technical solution or a combination of solutions can be found to meet the requirements. Such combinations are not discussed in this paper unless they are explicitly presented in the literature. Except for 'evaporation' and 'storage', none of the processes described have so far advanced beyond the laboratory stage. Considerable development work remains to be done to optimise urine-processing techniques in order to create marketable products.
Medilanski, E., Chuan, L., Mosler, H. J., Schertenleib, R., & Larsen, T. A. (2006). Wastewater management in Kunming, China: a stakeholder perspective on measures at the source. Environment and Urbanization, 18(2), 353-368. doi:10.1177/0956247806069615, Institutional Repository

Large sewer systems with central wastewater treatment plants were long considered a successful model that could be exported to practically any city of the world. This centralized, highly water-consuming system has, however, shown its limits in some developing and transition countries, especially in fastgrowing cities with limited water resources. This study from around Lake Dianchi in Yunnan, China, investigated the feasibility of introducing measures at the source for the different urban wastewater contributions in the city of Kunming, and the stakeholder perspectives on this approach. In addition, the stakeholders evaluated the potential of two different sanitation alternatives that allowed the separation and re-use of human excreta as fertilizer. Most of those interviewed approved of measures at the source, especially for industrial wastewater and toilet waste. There was a prevailing optimism with respect to the potential of technical developments and the likelihood of increased environmental awareness within a relatively short time span of 20 years. The findings suggest that China will prove to be one of the most interesting and productive "laboratories" for the development of decentralized wastewater treatment alternatives.
Udert, K. M., Larsen, T. A., & Gujer, W. (2006). Fate of major compounds in source-separated urine. Water Science and Technology, 54(11-12), 413-420. doi:10.2166/wst.2006.921, Institutional Repository

Urine separation is a promising alternative to present-day’s waste water management. It can help to manage our nutrient flows in a sustainable way. Currently, techniques are being developed to recycle and treat source-separated urine. These techniques, however, must consider the spontaneous processes that change the separated urine. The initial cause of changes is the contamination with microorganisms, which can hardly be avoided in urine-collecting systems. The most important transformation processes are microbial urea hydrolysis, mineral precipitation and ammonia volatilisation. Additionally, a variety of microorganisms, including pathogens, may grow in source-separated urine. In this paper we give an overview of the effects that the spontaneous transformation processes may have. We focus on nitrogen, phosphorus, magnesium, calcium, potassium, sulphur, organic substances, pathogens and the buffering capacity. The discussion is based on own research results and literature reviews. This overview will help to develop appropriate technologies for urine recycling.
Udert, K. M., Lienert, J., & Larsen, T. A. (2006). Novaquatis – Neue Wege in der Siedlungswasserwirtschaft. In J. Pinnekamp (Ed.), Gewässerschutz - Wasser & Abwasser - GWA: Vol. 204. 1. Aachener Kongress dezentrale Infrastruktur Wasser - Energie - Abfall (p. (13 pp.). Aachen: Gesellschaft zur Förderung der Siedlungswasserwirtschaft an der RWTH Aachen e.V. , Institutional Repository
Larsen, T. A., Lienert, J., Maurer, M., & Gujer, W. (2005). Ökologische Infrastrukturinnovationen in der Siedlungswasserwirtschaft. Ansätze und Perspektiven. In R. Loske & R. Schaeffer (Eds.), Ökologie und Wirtschaftsforschung: Vol. 57. Die Zukunft der Infrastrukturen. Intelligente Netzwerke für eine nachhaltige Entwicklung (pp. 347-367). Retrieved from https://www.metropolis-verlag.de/Die-Zukunft-der-Infrastrukturen/502/book.do, Institutional Repository

Die Infrastrukturen der Siedlungswasserwirtschaft (Trinkwasserversorgung und Abwasserreinigung) sind teuer, langlebig und weitgehend unsichtbar. Ursprünglich durch nationale Subventionen ermöglicht, müssen sie heute in den meisten Fällen lokal unterhalten und erneuert werden. Ist die heutige Gesellschaft überhaupt dazu bereit, gibt es bessere Organisationsformen als die heute vorherrschende und technische Alternativen, die mit weniger Infrastruktur auskommen? Solche Fragen werden heute intensiv diskutiert, und man stößt, je nach fachlichem Hintergrund und politischem Standpunkt der Diskussionsteilnehmer, auf viele verschiedene Antworten.
Typischerweise rechnet man bei den Infrastrukturen der Abwasserreinigung in Europa mit Wiederbeschaffungswerten von 2.500 - 5.500 Euro pro Person, wobei die Kanalisation allein ca. 80% der Investitionen ausmacht (Maurer et al.). Die Situation in der Wasserversorgung ist ähnlich (Lehmann 1994). Sprechen wir also von den Infrastrukturen der Siedlungswasserwirtschaft, meinen wir vor allem den unsichtbaren Teil, die Rohrleitungen im Untergrund. Sowohl die Wasserversorgung als auch die Kanalisation sind mit den Siedlungen gewachsen, und ihre Komponenten haben eine Lebensdauer von bis zu 100 Jahren. Sie müssen dauernd erneuert und unterhalten werden, damit das System als Ganzes funktioniert.
In diesem Aufsatz werden wir ökologische Infrastrukturinnovationen in der Abwasserreinigung diskutieren. Weil das Kapital vor allem an die Kanalisation gebunden ist, heißt das nichts anderes als eine Diskussion über Sinn und Zweck der Schwemmkanalisation und mögliche Alternativen dazu.
Lienert, J., & Larsen, T. A. (2005). Making the first step towards a more sustainable urban water management system - with the NoMix toilet (p. (15 pp.). Presented at the European water day, 84th ASTEE congress. Nanterre: ASTEE. , Institutional Repository

We discuss the drawbacks of the current urban water management system; a major one being its extreme inflexibility. The infrastructure costs are high and pricing destabilizes the system. Moreover, the sustainability of the wastewater treatment system is questionable: it consumes large amounts of drinking water, nutrients are lost, the system leaks, and the treatment processes always lag behind emerging environmental problems; a new one being micropollutants (pharmaceuticals, hormones). We present the concepts of source control and waste design, which would strongly increase flexibility and allow for innovative and environmental-friendly solutions that could be driven by market forces. We use urine source separation or NoMix technology as illustration, which is being intensively studied in the Swiss research project NOVAQUATIS. We present the most important results on acceptance and functioning of the NoMix technology. We introduce technologies to process urine in order to reclaim nutrients and eliminate micropollutants, as well as results on the fertilizer suitability of urine. We then discuss the integration of the NoMix technology into the existing system and present experience from some European pilot projects. We conclude that there are indeed ways out of the current lock-in situation and that alternatives with the potential of increasing the sustainability of the water sector do exist.
Tillman, D. E., Larsen, T. A., Pahl-Wostl, C., & Gujer, W. (2005). Simulating development strategies for water supply systems. Journal of Hydroinformatics, 7(1), 41-51. doi:10.2166/hydro.2005.0005, Institutional Repository

The objective of this paper is to point out existing risks of current design and management strategies in water supply systems and to identify possible ways of designing and operating schemes which minimize these risks. This paper is motivated by the observation that existing design principles and engineering rules (best practice) seem to cope insufficiently or even conflict with current trends of declining water demand. In order to evaluate this situation, an agent-based model comprising the current rules of best practice was developed in a participatory process. Once the model was multiple-scenario testing was used to explore different validated with data sets from a real utility, thus allowing ideas for developing alternative management and design schemes to design strategies, be generated. The simulations show that the traditional risk of insufficient supply security must be supplemented by considering the opposite risk of excessive security (over-capacity). The introduction of demand-side measures may help to calibrate existing best practice with the trends of the current operating environment. ideas are brought forward on how to shape incentive systems for stakeholders in order to facilitate such a shift.
Udert, K. M., Larsen, T. A., & Gujer, W. (2005). Chemical nitrite oxidation in acid solutions as a consequence of microbial ammonium oxidation. Environmental Science and Technology, 39(11), 4066-4075. doi:10.1021/es048422m, Institutional Repository

In long-term experiments with membrane aerated biofilm reactors we observed complete nitrite oxidation in highly concentrated ammonium nitrite solutions with a contaminant pH decrease to values below 3. The maximum initial concentration for ammonium was 42 mM and for nitrite was 41 mM. We hypothesized that (1) acid-tolerant ammonium oxidizing bacteria were responsible for the pH decrease, and (2) chemical processes caused complete nitrite oxidation at low pH values. To test this hypothesis we set up a mechanistic computer model based on kinetic data from literature and we validated the model with additional experiments. The simulations fitted the measurements very well. Additionally, an experiment with the inhibitor allylthiourea showed that ammonium-oxidizing bacteria were active at pH values far below 5.5. Experiments in a sterile reactor confirmed the chemical nitrite oxidation to nitrate. Nitrogen balances revealed that 8 ± 4% of the initial nitrogen (ammonium, nitrite, and nitrate) were lost during the cycles. On the basis of measurements and simulations we concluded that volatilization was responsible for the significant nitrogen loss. We estimated that about half of the lost nitrogen volatilized as nitrous acid HNO2. The rest mainly volatilized as dinitrogen N2 and nitrous oxide N2O.
Larsen, T. A., & Lienert, J. (2004). Coping with micropollutants in urine-based fertilizer. In Proceedings of the DeSa/R-Symposium (pp. 155-169). Berching: Huber Technology. , Institutional Repository

We conclude that coping with micropollutant in a urine-based fertilizer is not only a question of natural and engineering science, but also involves the participation of stakeholders. Experience with sewage sludge shows that the general public is increasingle able to influence politics. In Switzerland, in the case of sewage sludge, public pressure was exerted via the large retailers wanting to protect their popular label food products. In Sweden, the national farmers organization recommended their members to stop using sewage sludge as a fertilizer, based on the same main arguments as in Switzerland.
Contrary to the case of sewage sludge, however, purification of urine is possible due to the low organic content. Additionally, a phosphorus fertilizer based on urine is practically free of heavy metals, a large advantage in comparison to mineral fertilizers produced from phosphate rock and sewage sludge. We thus conclude that in the case of a urine based fertilizer, the precautionary principle and the sustainability principle of phosphorus recycling can be concomitantly met.
Larsen, T. A., Lienert, J., Joss, A., & Siegrist, H. (2004). How to avoid pharmaceuticals in the aquatic environment. Journal of Biotechnology, 113(1-3), 295-304. doi:10.1016/j.jbiotec.2004.03.033, Institutional Repository

Pharmaceuticals and other micropollutants in wastewater pose a new challenge to wastewater professionals as well as to the pharmaceutical industry. Although there is a great deal of uncertainty concerning the possible detrimental effects on the aquatic ecosystems, the precautionary principle — or possibly new scientific evidence — may give rise to more stringent demands on wastewater treatment in the future. In conventional wastewater treatment plants, a combination of biological treatment with high sludge residence times and ozonation of the effluent seems to be the most promising technology. Ozonation, however, is an energy-intensive technology. Moreover, in conventional end-of-pipe systems a large part of the pollutants will always be lost to the environment due to leaking, primarily during rain. In the long term, source separation offers the more sustainable solution to the entire wastewater problem, including organic micropollutants. Urine source separation is an elegant solution to the problems of nutrients and pharmaceuticals alike and losses of untreated pollutants to the environment can be minimized. Although few technologies for the separate treatment of urine have been developed to date, the 100-500 times higher concentrations of micropollutants promise more efficient conditions for all removal technologies known from conventional wastewater treatment.
Udert, K. M., Larsen, T. A., Gujer, W., & Högger, R. (2004). Fällungsprodukte in Urinalen und NoMix-Toiletten. GWA Gas, Wasser, Abwasser, 84(12), 913-920. , Institutional Repository

Precipitates from urine cause severe blockages in urinals of public restrooms, waterless urinals and NoMix toilets.
This paper presents a study in which the precipitation phenomena were investigated in detail.
The results show:
- the precipitates mainly consist of the phosphate minerals struvite and hydroxylapatite
- the bacterial degradation of urea triggers precipitation
- the use of flushing water reduces the formation of precipitates and is not the promoter
The study helps to develop processes that prevent blockages caused by urine precipitation. Possible approaches are presented in this paper.
Udert, K. M., Högger, R., Larsen, T. A., & Gujer, W. (2004). Urinausfällungen in Urinalen und NoMix-Toiletten. Installateur, 11, 46-48. , Institutional Repository

Die Siphons und Leitungen von öffentlichen, hochfrequentierten Urinalen können sehr rasch verstopfen. Ein gutes Beispiel dafür sind die Urinale im Ankunftsterminal A des Flughafens Zürich. Die Siphons und Leitungen dieser Urinale müssen rund alle drei Monate ausgewechselt bzw. gereinigt werden.
Huang, D., Schertenleib, R., Siegrist, H., Larsen, T. A., & Gujer, W. (2003). Assessment method for evaluating existing and alternative measures of urban water management. In C. Werner, V. Avendaño, S. Demsat, I. Eicher, L. Hernandez, C. Jung, … M. Wafler (Eds.), Ecosan - closing the loop. Proceedings of the 2nd international symposium, 7th - 11th April 2003, Lubeck, Germany (pp. 749-756). Eschborn, Germany: Deutsche Gesellschaft fur Technische Zusammenarbeit (GTZ). , Institutional Repository

Development of appropriate and sustainable sanitation options are required to face the problem of inadequate sewer systems in developing countries. High population densities and eutrophic ation problems of freshwater make source control a necessary alternative. To support decision-makers in assessing sewer system and source control, we developed a method to determine the origins of the wastewater and its property changes if source control measures are applied. The prototype of the method is based on a case study conducted in Zurich, which will later be adapted to a case study in Kunming, China. Analysis of uncertainty has been included in the method, as data quality will affect decision-making. Responses of wastewater amount, NH4 -N, TKN, and TP load, as well as concentration after urine separation, are simulated to study further treatment strategies of the new wastewater. The following methods were used: statistical pattern recognition, sensitivity analysis and system identification.
Larsen, T. A., & Lienert, J. (2003). Societal implications of re-engineering the toilet. In Water intelligence online. Sustainability in the water sector (p. (15 pp.). London: IWA Publishing. , Institutional Repository

Although urine constitutes less than 0.5 % of total domestic wastewater, it plays a major role for water pollution control. We discuss the social implications of introducing different versions of NoMix (urine separating) technology, ranging from straightforward implementation in local settings to transition scenarios based on complex real time control and partially non-existing technology. The major stakeholders in the new technology are households, farmers, sanitary firms, and wastewater professionals. To assess the attitude of stakeholders, surveys, informal contacts, and a literature study were performed. We use diffusion theory to describe the perception of NoMix technology by wastewater professionals. Consumers and farmers proved surprisingly positive towards the concept, under the condition that adequate technology is provided. Sanitary firms are confident that they can solve the problem, but demand strong leadership from wastewater professionals before they invest in the technology. Early diffusion amongst wastewater professionals is the most critical factor for the development of sustainable wastewater treatment technology: only with a strong commitment is it possible to develop innovative technology with the same high standard as we know from conventional sanitary and wastewater technology. Our analysis supports that the transition strategies will have more chances to lead to rapid diffusion of the concept amongst wastewater professionals.
Lienert, J., Haller, M., Berner, A., Stauffacher, M., & Larsen, T. A. (2003). How farmers in Switzerland perceive fertilizers from recycled anthropogenic nutrients (urine). Water Science and Technology, 48(1), 47-56. doi:10.2166/wst.2003.0013, Institutional Repository

We studied acceptance of a urine-based fertilizer product using a mail survey of 467 Swiss farmers. We distinguished among four production types: organic or IP farming, and with or without vegetable production. Considering that the idea of urine-based fertilizers is new, acceptance among the answering farmers was surprisingly high, with 57% explicitly stating that they thought it was a good or very good idea, and 42% willing to purchase such a product. The farmers of different production types did not differ strongly in their attitude towards urine-based fertilizers. Especially IP and vegetable farmers, who purchased additional fertilizers anyway, seem willing to accept urine-based fertilizers, hereby preferring a grainy, odorless ammonium nitrate fertilizer. Absolutely essential is a hazard-free product: 30% of all farmers had concerns regarding micropollutants. Based on fertilizer data, we demonstrate an existing demand for the nutrients N, P, and K in Switzerland, which could be partially substituted by a recycled urine product. Finally, we discuss methodological requirements of social science surveys. To obtain representative data on an entire population in a mail survey, multiple contacts with respondents are necessary. We argue that information and participation of stakeholders at an early stage is essential for successful technology transfer.
Lienert, J., & Larsen, T. A. (2003). Introducing urine separation in Switzerland: NOVAQUATIS, an interdisciplinary research project. In C. Werner, V. Avedaño, S. Demsat, I. Eicher, L. Hernández, C. Jung, … M. Wafler (Eds.), Ecosan - closing the loop. Proceedings of the 2nd international symposium, 7th - 11th April 2003, Lubeck, Germany (pp. 891-899). Eschborn: Deutsche Gesellschaft fur Technische Zusammenarbeit (GTZ). , Institutional Repository

Successful urine source separation (NoMix technology) poses a challenge to scientists, stakeholders, and society. Low-tech approaches are appropriate for rural areas; for large urban areas - in Europe and fast-industrializing countries - other solutions are needed. NOVAQUATIS focuses on NoMix technology in modern households, transport strategies, methodology to eliminate micropollutants (pharmaceuticals, hormones), and technologies to produce a fertilizer. First results are promising: feedback from consumers and farmers was positive, provided that high safety and comfort is maintained at low costs. To overcome the lock-in effect of the present system, technologically advanced transition strategies are needed, which allow to gradually implement NoMix technology into the urban wastewater system. Computer simulations of a strategy with small urine storage tanks integrated into the toilet indicate a positive effect on nitrification capacity (+30%) and emissions from combined sewer overflows (-50%). Results from experiments and modeling of precipitation in urine conducting pipes will help solving maintenance problems of NoMix toilets due to clogging. So far, engineering technologies for urine stabilization, nitrification, denitrification, and P-recovery via forced struvite precipitation have been proposed. Hopefully, the early implementation of NoMix technology in pilot projects and the integration of emerging countries into our scientific research will enhance successful technology transfer.
Lienert, J., & Larsen, T. A. (2003). NoMix technology: how good is the acceptability?. Eawag News [engl. ed.], 57, 14-17. , Institutional Repository

The successful implementation of an innovative technology depends on many factors. Apart from its technical superiority compared to traditional solutions, the needs of the stakeholders play a vital role. We were interested to know whether the market is ready for the NoMix technology, a sanitary concept for urine source separation, which would revolutionize our current system of wastewater management. Surveys showed that consumers and farmers have a positive attitude, given that the NoMix technology is adequate, inexpensive, and safe. Sanitary firms are confident that they can further develop NoMix toilets, but they demand strong commitment from wastewater professionals who will, therefore, play a deciding role in putting the NoMix technology into practice.
Lienert, J., & Larsen, T. A. (2003). NoMix-Technologie: Wie gut ist die Akzeptanz?. Eawag News [dtsch. Ausg.], 57, 14-17. , Institutional Repository

Ob sich eine neue Technologie in der Praxis durchsetzen kann, hängt von vielen Faktoren ab. Neben der technischen Überlegenheit gegenüber gängigen Lösungen spielen auch die Bedürfnisse der Beteiligten eine zentrale Rolle. Wir wollten wissen, ob der Markt bereit ist für die NoMix-Technologie, einem Sanitärkonzept zur Urinseparierung, welches das heutige System der Abwasserentsorgung grundlegend verändern würde. Umfragen bei Konsumenten und Bauern ergaben eine positive Einstellung, vorausgesetzt, die NoMix-Technologie ist adäquat, kostengünstig und sicher. Sanitärfirmen sind fähig und bereit, NoMix WCs weiterzuentwickeln. Sie warten jedoch auf ein starkes Engagement der Abwasserfachleute, denen damit eine entscheidende Rolle zukommt, der NoMix-Technologie den Weg in die Praxis zu ebnen.
Lienert, J., & Larsen, T. A. (2003). Technologie NoMix: quel est son degré d’acceptation?. Eawag News [éd. fr.], 57, 14-17. , Institutional Repository

Le fait qu’une innovation technologique soit adoptée ou non dans la pratique dépend de nombreux facteurs. En plus de présenter des avantages techniques certains par rapport aux technologies en cours, elle doit impérativement répondre aux besoins des groupes de population concernés. Nous avons cherché à savoir si le marché était prêt à accepter l’arrivée de la technologie NoMix, basée sur un concept de collecte et de traitement séparé des urines qui révolutionnerait le système actuel d’assainissement. Les sondages effectués auprès des consommateurs et des agriculteurs ont montré que l’opinion était plutôt favorable. Les fabricants d’articles sanitaires sont en mesure et prêts à développer les toilettes NoMix si les professionnels de l’assainissement font preuve d’un engagement important pour cette technologie. C’est ainsi à ces derniers que revient la tâche importante et décisive de préparer le terrain à la technologie NoMix.
Maurer, M., Schwegler, P., & Larsen, T. A. (2003). Nutrients in urine: energetic aspects of removal and recovery. Water Science and Technology, 48(1), 37-46. doi:10.2166/wst.2003.0011, Institutional Repository

The analysis of different removal and recovery techniques for nutrients in urine shows that in many cases recovery is energetically more efficient than removal and new-production from natural resources. Considering only the running electricity and fossil energy requirements for the traditional way of wastewater treatment and fertiliser production, the following specific energy requirements can be calculated: 45 MJ kg–1 N for denitrification in a WWTP, 49 MJ kg–1 P for P-precipitation in a WWTP, 45 MJ kg–1 N for N-fertiliser and 29 MJ kg–1 P for P-fertiliser production. These numbers are higher than the values derived for thermal volume reduction of urine (35 MJ kg –1 N for eliminating 90% water) or production of struvite (102 MJ kg–1 N, including 2.2 kg P). Considering only the electricity and fossil energy for the traditional way of wastewater treatment and fertiliser production, the energy value of 1 PE urine is 0.87 MJ PE–1d–1 (fertiliser value: 0.44, wastewater treatment: 0.43 MJ PE–1d–1).
A more detailed life cycle assessment (LCA) of the entire urine collection system, including the required materials and the environmental burden, support the energy analysis. The LCA compares conventional denitrification in a wastewater treatment plant with collecting urine in households, reducing the volume by evaporation and using it as a multi-nutrient fertiliser. The primary energy consumption for recovery and reuse of urine, including the nutrients N, P and K, is calculated with 65 MJ kg–1 N, compared with 153 MJ kg–1 N derived for the conventional 'recycling over the atmosphere'.
Pahl-Wostl, C., Schönborn, A., Willi, N., Muncke, J., & Larsen, T. A. (2003). Investigating consumer attitudes towards the new technology uf urine separation. Water Science and Technology, 48(1), 57-64. doi:10.2166/wst.2003.0015, Institutional Repository

The technology of urine separation and the recycling of anthropogenic nutrients as fertilizer in agriculture are considered as major innovations to improve the sustainability of today's urban wastewater management. The acceptance of consumers will be key for the introduction of the new technology. Citizens will have to make important decisions in their role as tenants and owners of houses and as consumers buying products fertilized with urine. Consumer attitudes towards the new technology were explored in a number of citizen focus groups in Switzerland. Focus groups are deliberate, moderated group discussions with informed citizens on a certain topic. The information was provided by a computer based information system specifically designed for this purpose. The acceptance of individual citizens for the new technology proved to be quite high. The majority of the citizens expressed their willingness to move into an apartment with NoMix toilets and to buy food fertilized with urine. However, they were not willing to accept additional financial costs or efforts. Arguments related to long-term sustainability (closing nutrient cycles) were of less importance than arguments that relate directly to the effects of micropollutants on human and ecosystem health. For the introduction of the new technology on a wide scale it will thus be crucial to explore the fate and effects of micropollutants.
Rauch, W., Brockmann, D., Peters, I., Larsen, T. A., & Gujer, W. (2003). Combining urine separation with waste design: an analysis using a stochastic model for urine production. Water Research, 37(3), 681-689. doi:10.1016/S0043-1354(02)00364-0, Institutional Repository

This paper explores the stochastic properties of human urine production in order to assess the potential of combining urine separation with waste design. The aim is to provide specific information about the dynamics of urine production at a microscopic level for the design and the control of the urine waste stream. Based on measured data a stochastic model is developed that is capable of providing stochastic information on the frequency, timing, and volume of urine releases into each single toilet in a catchment. It is then demonstrated in a virtual case study that the design of the human wastewater stream in terms of urine content can (1) reduce the ammonia peak loads at dry weather flow conditions by approx. 30% (which could effectively substitute the expansion of wastewater treatment plants) and (2) reduce the impact of combined sewer overflows on the aquatic environment. With respect to the latter a reduction of more than 50% is demonstrated in terms of annual urine volume released via the overflow.
Udert, K. M., Larsen, T. A., & Gujer, W. (2003). Biologically induced precipitation in urine-collecting systems. Water Science and Technology: Water Supply, 3(3), 71-78. doi:10.2166/ws.2003.0010, Institutional Repository

Precipitation in urine-separating toilets (NoMix toilets), waterless urinals, and conventional urinals causes severe maintenance problems. Additionally, the partial fixation of nutrients in precipitates may affect the later use and treatment of source-separated urine. The goal of this study was to characterise the mineral composition of the precipitates and to identify the main causes for precipitation. X-ray diffraction analysis showed that the main crystalline compounds are struvite, hydroxyapatite, and calcite. We measured concentrations in the solutions of the traps and of the urine collection tank for estimating saturation indices, extent of urea degradation, urine dilution, and elimination of solutes. Our results indicate that bacterial urea degradation triggers precipitation. The composition of the precipitates depends on the urine dilution with flushing water: in low diluted urine, struvite is the main compound, while calcite dominates in systems with high urine dilution. HAP occurs over a wide range of dilution factors. A high fraction of phosphate is incorporated into the precipitates. Dilution with tap water increases this fraction by providing the limiting calcium and magnesium ions. Currently, constructing exchangeable traps seems to be the best solution to deal with problematic precipitation.
Udert, K. M., Larsen, T. A., & Gujer, W. (2003). Estimating the precipitation potential in urine-collecting systems. Water Research, 37(11), 2667-2677. doi:10.1016/S0043-1354(03)00071-X, Institutional Repository

Precipitation in urine-separating toilets (NoMix toilets) and waterless urinals causes severe maintenance problems and can strongly reduce the content of soluble phosphate. In this study, we present a computer model for estimating the precipitation potential (PP) in urine-collecting systems. Calculating the PP enables to predict the composition and mass concentration of precipitates. We used our computer model for investigating how urea hydrolysis and dilution with flushing water affect precipitation. In a previous study, we found that microbial urea hydrolysis (ureolysis) triggers precipitation and that the amount of precipitates is limited by calcium and magnesium. With the present simulations, we could confirm these findings. We determined that only a small fraction of urea has to be hydrolysed for reaching 95% of the maximum PP. Since urease-positive bacteria are abundant in urine-collecting systems, strong precipitation is very likely. In further simulations, we determined that struvite (MgNH4PO4·6H2O) and hydroxyapatite (HAP, Ca10(PO4)6(OH)2) are the main precipitate compounds. If urine is highly diluted with tapwater, calcite (CaCO3) occurs as well. HAP is the only calcium phosphate mineral, although several others were supersaturated. Additionally, the simulations indicated that urine dilution diminishes the risk of blockages, since the mass concentration of precipitates decreases with the volume of flushing water. Rainwater flushing is more effective than flushing with tapwater. Moreover, flushing with tapwater leads to high phosphate fixation, because the total amount of calcium and magnesium ions increases, while the total amount of phosphate keeps constant. Finally, we compared simulation results with field measurements and found good agreement at low and very high urine dilution.
Udert, K. M., Fux, C., Münster, M., Larsen, T. A., Siegrist, H., & Gujer, W. (2003). Nitrification and autotrophic denitrification of source-separated urine. Water Science and Technology, 48(1), 119-130. doi:10.2166/wst.2003.0031, Institutional Repository

In laboratory experiments, source-separated urine was stabilised with nitrification and denitrified via nitritation and anaerobic ammonium oxidation. The highest total ammonia concentration in the influent was 7,300 gN/m3, the maximum pH 9.2. In a moving bed biofilm reactor (MBBR) with Kaldnes® biofilm carriers, we stabilised urine as a 1:1 ammonium nitrate solution. The maximum nitrification rate was 380 gN/m3/d corresponding to 1.7 gN/m2 biofilm/d. Nitrite ammonium solutions were produced in a continuous flow stirred tank reactor (CSTR) with 4.8 days sludge retention time (SRT) at 30°C and in a sequencing batch reactor (SBR) with more than 30 days SRT. Nitrate build-up was negligible in both reactors. Nitritation rates were 780 gN/m3/d in the CSTR and 280 gN/m3/d in the SBR, respectively. However, shortening the cycles would increase nitritation in the SBR. High concentrations of nitrous acid, salts, and presumably hydroxylamine suppressed nitrite oxidation in the nitritation reactors. In all three nitrification reactors, maximally 50% of the influent total ammonia was oxidised without pH control. None of the common inhibition or limitation approaches could explain why ammonia oxidation always stopped at pH values around 6. In a batch experiment, we showed that source-separated urine can be denitrified autotrophically by anammox bacteria.
Udert, K. M., Larsen, T. A., Biebow, M., & Gujer, W. (2003). Urea hydrolysis and precipitation dynamics in a urine-collecting system. Water Research, 37(11), 2571-2582. doi:10.1016/S0043-1354(03)00065-4, Institutional Repository

Blockages caused by inorganic precipitates are a major problem of urine-collecting systems. The trigger of precipitation is the hydrolysis of urea by bacterial urease. While the maximum amount of precipitates, i.e. the precipitation potential, can be estimated with equilibrium calculations, little is known about the dynamics of ureolysis and precipitation. To gain insight in these processes, we performed batch experiments with precipitated solids and stored urine from a urine-collecting system and later simulated the results with a computer model. We found that urease-active bacteria mainly grow in the pipes and are flushed into the collection tank. Both, bacteria and free urease, hydrolyse urea. Only few days are necessary for complete urea depletion in the collection tank. Two experiments with precipitated solids from the pipes showed that precipitation sets in soon after ureolysis has started. At the end of the experiments, 11% and 24% of urea was hydrolysed while the mass concentration of newly formed precipitates already corresponded to 87% and 97% of the precipitation potential, respectively. We could simulate ureolysis and precipitation with a computer model based on the surface dislocation approach. The simulations showed that struvite and octacalcium phosphate (OCP) are the precipitating minerals. While struvite precipitates already at low supersaturation, OCP precipitation starts not until a high level of supersaturation is reached. Since measurements and computer simulations show that hydroxyapatite (HAP) is the final calcium phosphate mineral in urine solutions, OCP is only a precursor phase which slowly transforms into HAP.
Wilsenach, J. A., Maurer, M., Larsen, T. A., & van Loosdrecht, M. C. M. (2003). From waste treatment to integrated resource management. Water Science and Technology, 48(1), 1-9. doi:10.2166/wst.2003.0002, Institutional Repository

Wastewater treatment was primarily implemented to enhance urban hygiene. Treatment methods were improved to ensure environmental protection by nutrient removal processes. In this way, energy is consumed and resources like potentially useful minerals and drinking water are disposed of. An integrated management of assets, including drinking water, surface water, energy and nutrients would be required to make wastewater management more sustainable. Exergy analysis provides a good method to quantify different resources, e.g. utilisable energy and nutrients. Dilution is never a solution for pollution. Waste streams should best be managed to prevent dilution of resources. Wastewater and sanitation are not intrinsically linked. Source separation technology seems to be the most promising concept to realise a major breakthrough in wastewater treatment. Research on unit processes, such as struvite recovery and treatment of ammonium rich streams, also shows promising results. In many cases, nutrient removal and recovery can be combined, with possibilities for a gradual change from one system to another.
Larsen, T. A., & Gujer, W. (2002). Waste Design, Source Control und On-Site-Technologien: Der Weg zu einer nachhaltigen Siedlungswasserwirtschaft. KA: Korrespondenz Abwasser Abfall, 49(10), 1372-1379. , Institutional Repository

A comprehensive analysis of the problems in today's wastewater management identifies deficits in the handling of micropollutants, the management of nutrients as well as management strategies in general. Based on waste design, source control and on-site technologies a possible path out of today's technological lock-in situation is designed. The advantages of waste design are discussed based on urine separation: Wastewater composition is optimized in view of wastewater treatment and the technology offers a variety of possibilities for long term transition scenarios. In addition the integration of on-site technologies into household appliances is identified as a possible future development, which may help to improve the efficiency of wastewater handling and may provide new management strategies.
Lienert, J., & Larsen, T. A. (2002). Urinseparierung - eine Alternative für die schweizerische Siedlungswasserwirtschaft?. GWA Gas, Wasser, Abwasser, 82(11), 819-826. , Institutional Repository

Urine source separation in NoMix toilets with subsequent processing of urine offers the possibility to improve water pollution control and to recycle nutrients. Urine contains most of the nutrients ending up in wastewater and many micropollutants from the human metabolism. In most cases, efficient urine source separation would render nutrient removal at wastewater treatment plants obsolete. To obtain more stringent threshold values for phosphorus, merely a small technical effort would be necessary. The interdisciplinary research project NOVAQUATIS investigates the technical feasibility, social acceptance and possibilities of introducing urine source separation in Switzerland.
Maurer, M., Muncke, J., & Larsen, T. A. (2002). Technologies for nitrogen recovery and reuse. In P. Lens, L. Hulshoff Pol, P. Wilderer, & T. Asano (Eds.), Integrated environmental technology series. Water recycling and resource recovery in industry. Analysis, technologies and implementation (pp. 491-510). Retrieved from https://iwaponline.com/ebooks/book/143/Water-Recycling-and-Resource-Recovery-in-Industry, Institutional Repository

In industrial countries traditional waste management treats nitrogen as a waste. Discharged into our environment they boost nutrient cycles and lead to adverse effects such as over-fertilisation and eutrophication of lakes or ecotoxicological problems in river waters caused by ammonia and nitrite. On the other hand, significant amount of synthetic nitrogen fertiliser is produced and used in agriculture. In order to cut down the environmental burden from N-pollution and fertiliser production it would be beneficial to recover nitrogen from wastes and reuse it.
The following paragraphs give an overview over the currently available techniques to recover nitrogen from waste streams. The examples focus mainly on municipal wastewater. This is one of the biggest point sources of nitrogen and has a major impact on aquatic systems in many areas. For N-containing liquid industrial waste (e.g. pig manure or polyurethane production) treatment options are very similar.
Tillman, D. E., Larsen, T. A., Pahl-Wostl, C., & Gujer, W. (2002). Risikoverminderung. Durch Steuerung des Wasserverbrauchs. GWA Gas, Wasser, Abwasser, 82(10), 743-750. , Institutional Repository

The objective of this paper is to point out existing risks of current design and management strategies in water supply systems, and to identify possible ways of designing and operating schemes which minimize these risks. The paper is motivated by the fact that existing design principals and engineering rules (best practice) insufficiently cope or even conflict with current trends of declining water demand. In order to evaluate this situation, an agent-based model comprising the current rules of best practice was subsequently developed in a participatory process. Once the model was validated with data sets from a real utility, multiple-scenario testing was used to explore strategies, thus allowing ideas for developing flexible management and design schemes to be generated.
Udert, K. M. (2002). The fate of nitrogen and phosphorus in source-separated urine (Doctoral dissertation). doi:10.3929/ethz-a-004541820, Institutional Repository

Introduction
Intensive agriculture and urban sewage burden the environment with high nutrient loads. An improved nutrient management is necessary to remove present damages and to prevent future impacts. Nutrient losses to the environment can be strongly reduced, if nutrients from waste water are recycled to agriculture.
Human urine is the most important nutrient source of household waste water. It contributes about 80% of nitrogen and 60% of phosphorus, but accounts for less than one percent of the waste water volume. Separate collection of human urine would strongly reduce the demands on waste water treatment, because no enhanced nutrient elimination would be necessary to prevent eutrophication. Furthermore the separate collection and application of urine would be an efficient method to recycle nutrients from urban sewerage to agriculture.
Waterless urinals and NoMix toilets are available for urine separation. In urine-collecting systems the separated urine is directed to a collection tank where it is stored for later transport to a treatment facility.
In existing systems biological and chemical processes hamper the technical realisation of urine separation. By hydrolysing urea, bacteria cause a strong increase of ammonia and pH. Under these conditions large amounts of phosphate minerals precipitate, which can lead to pipe blockages. The produced ammonia is volatile. Degassing of ammonia can cause odour problems and significant nitrogen losses. [...]

Einleitung
Intensive Landwirtschaft und Siedlungsabwässer belasten die Umwelt mit hohen Nährstoffeinträgen. Ein besseres Nährstoffmanagement ist notwendig, um entstandene Schäden zu beheben und künftige zu verhindern. Nährstoffverluste in die Umwelt können stark verringert werden, wenn die Nährstoffe aus dem Abwasser in die Landwirtschaft rezykliert werden.
Menschlicher Urin ist die wichtigste Nährstoffquelle des kommunalen Abwassers. Er liefert ca. 80% des Stickstoffs und 60% des Phosphors, macht aber weniger als ein Prozent des Abwasservolumens aus. Die getrennte Sammlung von Urin würde die Abwasserreinigung stark entlasten, weil in Kläranlagen keine erweiterte Nährstoffelimination mehr notwendig wäre, um die Gewässereutrophierung zu bekämpfen. Die separate Sammlung und Ausbringung von Urin wäre zudem eine sehr effiziente Massnahme, um Nährstoffe von der Siedlungswasserwirtschaft in die Landwirtschaft zu rezyklieren.
Für die separate Sammlung von Urin stehen wasserlose Urinale und NoMix-Toiletten zur Verfügung. In Urinsammelanlagen wird der Urin nach der Abtrennung in einen Sammeltank geleitet und dort zwischengelagert, bevor er zur Weiterverarbeitung abtransportiert wird.
In bestehenden Systemen erschweren allerdings biologische und chemische Prozesse die Urinseparierung. Bakterien hydrolisieren den im Urin enthaltenen Harnstoff und erhöhen dadurch die Ammoniakkonzentration und den pH. Unter diesen Bedingungen fallen grosse Mengen an Phosphatmineralien aus, was zu Verstopfungen der Leitungen führen kann. Das produzierte Ammoniak ist flüchtig. Ausgasungen können Geruchsbelästigungen und erheblichen Stickstoffverluste verursachen. [...]
Hügel, K., Larsen, T. A., & Gujer, W. (2001). Ökobilanz als Massstab für die Ressourcen-Effizienz in der Abwasserentsorgung. In B. Weigert & C. Steinberg (Eds.), Schriftenreihe Wasserforschung: Vol. 7. Nachhaltige Entwicklung in der Wasserwirtschaft: Konzepte, Planung und Entscheidungsfindung (pp. 129-141). Berlin: Interdisziplinärer Forschungsverbund Wasserforschung. , Institutional Repository
Larsen, T. A., & Gujer, W. (2001). Elimination von Mikroverunreinigungen. Mit Massnahmen an der Quelle zu mehr Flexibilität in der Abwasserreinigung. GWA Gas, Wasser, Abwasser, 81(3), 159-166. , Institutional Repository

The concepts of waste design and control are introduced as contracts between wastewater handling agencies and consumers and consumers and industry respectively. Waste design serves to produce waste streams that are optimised in composition and time sequence for easy transport and treatment. Source control makes services and installations available, which allow the consumer to adhere to the specifications of waste design. Increased delegation of responsibility to the consumer is expected to result in more flexible wastewater handling systems. The concepts presented in this article are well suited to tackle the micropollutant problem in wastewater handling at the source.
Larsen, T. A., & Boller, M. A. (2001). Perspectives of nutrient recovery in DESAR concepts. In P. Lens, G. Zeeman, & G. Lettinga (Eds.), Integrated environmental technology series. Decentralised sanitation and reuse. Concepts, systems and implementation (pp. 387-410). Retrieved from https://iwaponline.com/ebooks/book/374/Decentralised-Sanitation-and-Reuse-Concepts, Institutional Repository

Domestic sewage carries substantial amounts of valuable nutrients among which nitrogen (N) and phosphorus (P) are dominant in terms of detrimental effects in the receiving waters. In traditional waste management of industrial countries, these nutrients are wasted either to the effluent, to the sludge or into the air. Discharged into receiving waters, the nutrients start to boost nutrient cycles in the aquatic environment leading to adverse effects such as over-fertilization and eutrophication of lakes and reservoirs by phosphorus and nitrogen. This causes ecotoxicological problems in river waters caused by nitrogen compounds such as ammonia and nitrite. Aware of the fact that nutrients should not be discharged into receiving waters, wastewater managers in the 1990s designed treatment plants to enhance nutrient removal by introducing new treatment steps such as biological and/or chemical P and biological N removal. Thus, the N and P loads into receiving water bodies are minimized by converting ammonia (NH4+) into nitrate (NO3-) and subsequently to N2 gas while P is retained in the sludge. However, nutrient removal in wastewater treatment plants caused a wave of tremendous and ongoing capital investment into the enlargement and enhancement of existing treatment facilities. The issue at stake here is to separate the nutrients from the wastewater by technical means in order to protect the aquatic environment. Possible alternatives for nutrient recycling are rarely considered in nutrient removal concepts. Apart from the enrichment of sewage sludge with phosphorus by chemical or biological P removal and consequent disposal in agriculture, additional treatment steps for concentrating and processing nitrogen and phosphorus for reuse were assessed as being noneconomical. [...]
Larsen, T. A., Peters, I., Alder, A., Eggen, R., Maurer, M., & Muncke, J. (2001). Re-engineering the toilet for sustainable wastewater management. Could one answer be a new toilet that separates urine from wastewater streams?. Environmental Science and Technology, 35(9), 192A-197A. doi:10.1021/es012328d, Institutional Repository
Larsen, T., Alder, A., Eggen, R., Maurer, M., Muncke, J., & Peters, I. (2001). Testlauf im KraftWerk1. Unimagazin. Zeitschrift der Universität Zürich / Bulletin. Magazin der ETH Zürich, 281, 47-49. Retrieved from https://www.magazin.uzh.ch/de/issues/unimagazin-01-1.html, Institutional Repository

Bitte nehmen Sie Platz! - Die Koevolution des umweltbewussten Menschen und des intelligenten WCs findet im KraftWerk1 in Zürich statt. Ein neues Sanitärkonzept könnte die traditionelle Abwasserreinigung revolutionieren.
Larsen, T. A., & Gujer, W. (2001). Waste design and source control lead to flexibility in wastewater management. Water Science and Technology, 43(5), 309-317. doi:10.2166/wst.2001.0313, Institutional Repository

The concepts of waste design and source control are introduced as contracts between wastewater handling agencies and consumers and consumers and industry respectively. Waste design serves to produce waste streams that are optimized in composition and time sequence for easy transport and treatment. Source control makes services and installations available, which allow the consumer to adhere to the specifications of waste design. Increased delegation of responsibility to the consumer is expected to result in more flexible wastewater handling systems.
Larsen, T. A., Rauch, W., & Gujer, W. (2001). Waste design paves the way for sustainable urban wastewater management. In J. A. Tejada-Guibert & Č. Maksimović (Eds.), Technical documents in hydrology: Vol. 45. Proceedings. Frontiers in urban water management: deadlock or hope? Actes. Frontières de la gestion de l'eau urbaine: impasse ou espoir? (pp. 219-229). Retrieved from https://unesdoc.unesco.org/ark:/48223/pf0000122949, Institutional Repository

A vision of sustainable urban wastewater management is presented, on the basis of extended on-site technology; which leaves only unpolluted wastewater to be dealt with by the public. The first easily attainable milestone of this vision is urine separation, which is further discussed with respect to some of its advantages and challenges. Finally, in the main part of the paper, we describe how urine separation can be introduced as a measure of waste design, allowing for necessary technological and environmental learning processes. It is further suggested in the discussion that waste design can substitute the enlargement of wastewater treatment plants and combined sewer overflow (CSO) retention tanks in a cost-efficient way. The strategy for achieving this goal involves simple household technology and extended real time control.
Tillman, T., Larsen, T. A., Pahl-Wostl, C., & Gujer, W. (2001). Interaction analysis of stakeholders in water supply systems. Water Science and Technology, 43(5), 319-326. doi:10.2166/wst.2001.0316, Institutional Repository

An analysis of the characteristic goals, strategies and rules of behavior of relevant stakeholders allows the efficacy and potential risks of past and current engineering and management concepts to be estimated. The study is driven by the observable shift from security to cost-centered strategies by water utilities and the difficulties of balancing technical and financial needs in an uncertain future. Its benefits include a methodology with a twofold result. With the aid of domain knowledge from experts involved in a participatory process, the interactions of a subset of stakeholders are quantified and documented in a rule catalog. This leads to an improved understanding of their decision-making rules. An agent-based model comprising these stakeholders' rules of behavior in subsequently development. Once the model is validated with data sets from a real utility, multiple-scenario testing helps to explore different strategies and can be used to generate ideas for developing flexible management and design schemes. Despite the complexity of the system described, simple model rules which are repeated annually can replicate the general development of both capacity and cost-related parameters. Scenario simulations show the effects of different management strategies on key parameters such as capacity, water price and financial debt.
Tillman, D. E. (2001). Stakeholder analysis in water supply systems (Doctoral dissertation). doi:10.3929/ethz-a-004107705, Institutional Repository

A shift of focus is essential if water supply systems are to be optimized and further developed. Emphasis was traditionally placed predominantly on the technical aspects. However, the technical problems have now been largely solved: strongly fluctuating demand for water can be satisfied at any time by a high-quality service. Nevertheless, the water utilities must cope with increasing pressure from a public claiming a lack of efficiency. Why, for example, was capacity expanded in the last 25 years in spite of a decline in consumption? Technical reasons alone cannot explain such phenomena. The interests, characteristic behavior and factual constraints of the stakeholders involved must also be taken into account and the focus broadened to include such aspects.
Furthermore, utilities face an increasing danger of becoming insufficiently flexible to anticipate existing and new challenges. Whereas they developed under stable and predictable conditions in the past, they are now exposed to a more dynamic and uncertain environment (e.g. uncertain consumption development, new technologies such as the local use of rainwater competing with the centralized supply network, strong liberalization pressures etc.). Although flexibility is required to cope with this development, the long life span of the infrastructure, existing regulations and the prevailing "supply-oriented" incentives given to various stakeholders impede adequate system management. The traditional means of ensuring the required flexibility - large infrastructures with built-in redundancy - are no longer suitable in view of the explicit need for overall efficiency. Existing engineering rules must be rethought in the light of these recent changes. [...]

Um Wasserversorgungssysteme optimieren und weiterentwickeln zu konnen, muss zunächst der Blickwinkel verbreitert werden. Denn traditionellerweise wurde fast ausschliesslich auf technischen Aspekten fokussiert. Heute sind die technischen Probleme aber weitgehend behoben: eine stark schwankende Wassernachfrage kann jederzeit befriedigt und dabei Lebensmittelqualität des Wassers garantiert werden. Trotzdem sind die Wasserversorgungen massiv unter Druck geraten, da ihnen mangelnde Effizienz vorgeworfen wird. Warum wurde zum Beispiel mancherorts die Lieferkapazität in den letzten 25 Jahren trotz sinkender Wassernachfrage erhöht? Solche Phänomene lassen sich mit technischen Argumenten allein nicht erklaren. Offensichtlich spielen die nicht technischen Aspekte eine wesentliche Rolle. Der Blickwinkel muss auf die Interessen, Anreize oder Sachzwänge der involvierten Akteure (Ingenieure, Politiker, Konsumenten, Staat etc.) erweitert werden.
Auch müssen die Wasserversorgungen vermehrt flexibel auf sich andernde Umwelteinflüsse reagieren konnen (unsichere Verbrauchsentwicklung, konkurenzierende Regenwassernutzung, Liberalisierungsdruck etc.). Die traditionellen Massnahmen zur Erhöhung der Flexibilität - Redundanz im Leitungssystem und grosse Kapazitätsreserven - sind dazu aufgrund des allgemeinen Effizienzdrucks nicht mehr geeignet. Entsprechend müssen die Sichtweise geandert, die gangigen Ingenieurregeln hinterfragt und neue Versorgungskonzepte entwickelt werden. [...]
Huisman, J. L., Burckhardt, S., Larsen, T. A., Krebs, P., & Gujer, W. (2000). Propagation of waves and dissolved compounds in sewer. Journal of Environmental Engineering, 126(1), 12-20. doi:10.1061/(Asce)0733-9372(2000)126:1(12), Institutional Repository

The phenomenon of the surface wave propagating faster than the fluid. that induced it is studied experimentally and numerically. The study focuses on the importance of the wave phenomenon for the urban hydrology system, where it can determine the impact of combined sewer overflows on the environment and the operation of a novel urine (anthropogenic nutrient solution) separation system. Urine would be stored decentrally and released during the night hours so that a wave would form in the sewer. The full-scale experiments were carried out in a 2-km section of a main sewer. The wave was induced with the aid of fire hydrant water traced by salt. Five measurements and sampling stations were operated downstream through which the transport of both fluid and compounds were analyzed. Numerical simulations of the results are discussed focusing on the reliability of friction approaches and dispersion prediction. Although difficult to model with commercial tools, it was shown that the wave phenomenon has no adverse effects on the practicability of the urine separation system, but can lead to the release of undiluted wastewater during a rain event.
Larsen, T. A., & Gujer, W. (2000). Intervenir à la source, dans les ménages aussi. Eawag News [éd. fr.], 48, 6-7. , Institutional Repository

Intervenir à la source, voilà qui simplifierait le processus d'épuration tout en résolvant des problèmes pratiquement insolubles aujourd'hui. Mais de telles mesures ont aussi leur prix et ne sont guère concurrentielles. Le but est de trouver un système qui ait d'emblée un succès durable, aussi bien sous nos latitudes que dans les pays en voie de développement. La solution? Il faut étudier les mesures possibles à la source.
Larsen, T. A., & Gujer, W. (2000). Tackling problems at the source - even in the household. Eawag News [engl. ed.], 48, 6-7. , Institutional Repository

By pursuing measures at the source, the water treatment process is not only simplified, but allows us to overcome problems which have to date been impossible to solve. Such measures have their cost, however, and are only rarely profitable in a financial sense. In order to design a system which in its conception will be viable at our latitude as well as in developing countries, we have to consider a host of actions at the source.
Tillman, D., Larsen, T. A., Pahl-Wostl, C., & Gujer, W. (2000). Assessing effects of behavior patterns. Early recognition of structural problems. Eawag News [engl. ed.], 48, 8-9. , Institutional Repository

What effects do the different behavior patterns of involved parties have on the technical and financial aspects of water systems supply? Analysis and modeling of these behavior patterns and interactions allow us to assess the efficiency and potential risks of engineering and management measures currently being implemented and to recognize problems early on.
Tillman, D., Larsen, T. A., Pahl-Wostl, C., & Gujer, W. (2000). Eau potable: évaluation des acteurs. Prévention des problèmes structurels. Eawag News [éd. fr.], 48, 8-9. , Institutional Repository

La distribution d'eau potable est un système déterminé, tant financièrement que techniquement, par différents acteurs. Grâce à l'analyse et à la modélisation de leur comportement et de leurs interactions, nous sommes en mesure d'évaluer l'efficacité des stratégies d'ingénierie et de gestion actuellement appliquées, ainsi que de détecter et de prévenir leurs risques potentiels.
Larsen, T. A., & Gujer, W. (1999). Massnahmen an der Quelle - auch im Haushalt. Eawag News [dtsch. Ausg.], 48, 6-7. , Institutional Repository

Mit Massnahmen an der Quelle könnte der Reinigungsvorgang vereinfacht werden, gleichzeitig würden heute fast unlösbare Probleme einer Lösung zugeführt. Solche Massnahmen haben aber auch ihre Kosten und sind heute nur noch in Ausnahmefällen konkurrenzfähig. Um ein System zu entwerfen, das vom Konzept her sowohl in unseren Breitengraden als auch in den Entwicklungsländern Zukunft hat, müssen verschiedenen Massnahmen an der Quelle in Betracht gezogen werden.
Larsen, T. A. (1999). Nährstoffkreisläufe in der Siedlungswasserwirtschaft. Technische Möglichkeiten von Eliminations- und Recyclingverfahren. Schweizer Ingenieur und Architekt, 117(19), 394-396. doi:10.5169/seals-79728, Institutional Repository

Das 19. Jahrhundert erfand die Siedlungshygiene, das 20. Jahrhundert den Gewässerschutz. Welche Anforderungen wird das 21. Jahrhundert an die Siedlungswasserwirtschaft stellen? Die nachhaltige Ressourcenbewirtschaftung, wie sie in Rio 1992 postuliert wurde, ist eine mögliche Antwort. Die Nährstoffe stellen eine dieser Ressourcen dar.
Larsen, T. A., & Udert, K. M. (1999). Urinseparierung - ein Konzept zur Schliessung der Nährstoffkreisläufe. Wasser und Boden, 51(11), 6-9. , Institutional Repository

Nutrient control is generally acknowledged to be an important part of domestic wastewater treatment. However, it is not as widely recognised that nutrient control is only necessary due to the presence of urine in wastewater. With urine separation and a subsequent treatment or recycling, only solids and organic matter need to be removed for the treatment of domestic wastewater. Urine separation combined with recycling of primary and secondary sludge would make it possible to close nutrient cycles. Problems with pharmaceutics and hormones in the receiving waters would be alleviated. From a technical point of view, the separate collection of urine is possible with a so-called 'No-Mix'-Toilet: after separation the urine is stored in the household and in the night, when the sewers are more or less empty, it is led through the sewers are more or less empty, it is led through the sewers to the treatment plant. Just before it reaches the treatment plant, the urine must be collected and separately treated or recycled.
Tillman, D., Larsen, T. A., Pahl-Wostl, C., & Gujer, W. (1999). Handlungsauswirkungen abschätzen. Früherkennung struktureller Probleme. Eawag News [dtsch. Ausg.], 48, 8-9. , Institutional Repository

Wie wirken sich die verschiedenen Handlungsmuster der Beteiligten technisch und finanziell auf das System Trinkwasserversorgung aus? - Mittels Analyse und Modellierung dieser Verhaltensweisen und Interaktionen können wir die Wirksamkeit und die potentiellen Risiken heutiger Ingenieur- und Managementstrategien frühzeitig erkennen.
Tillman, D., Larsen, T. A., Pahl-Wostl, C., & Gujer, W. (1999). Modeling the actors in water supply systems. Water Science and Technology, 39(4), 203-211. doi:10.1016/S0273-1223(99)00055-4, Institutional Repository

A methodology is developed to reveal the dynamics of behavior and interactions among actors (stakeholders) in water supply systems and their effect on the technical network and the ecological and socio-economic environment. An agent-based model is under construction which allows to simulate different scenarios of the actors' behavior and to compare the results with observed phenomena (stylized facts) of Swiss cities. First results further clarify the significance of demand trend analysis. We envision the model in a final stage as being helpful to tackle the task of illuminating the diffusive claims, expectations and interactions of the actors involved. Knowledge about these processes is crucial to uncover bottlenecks hindering the sustainable development of our water supply systems into the future.
Jancarkova, I., Larsen, T. A., & Gujer, W. (1997). Distribution of nitrifying bacteria in a shallow stream. Water Science and Technology, 36(8-9), 161-166. doi:10.1016/S0273-1223(97)00604-5, Institutional Repository

A project investigating the dynamics of self-purification processes in a shallow stream is carried out. Effects of the concentration gradient due to the distance to the pollution source, of hydraulic conditions in the river bed and of storm floods on the distribution of nitrifying bacteria were studied with the help of laboratory and field experiments. Nitrifiers density on the surface of the stream bed increased rapidly up to a distance of 300 m from the WWTP indicating possible competition of the nitrifiers with the heterotrophic bacteria close to the WWTP. Afterwards a slight decrease in the downstream direction was observed. In vertical profiles, higher bacterial densities were found at sites with rapid infiltration of channel water to the stream bed than at sites with no exchange between channel water and stream bed water or where stream bed water exfiltrated. A major flood event scoured the nitrifiers nearly totally from the surface of the river bed. Major floods belong so to the most dominant processes controlling self-purification in shallow streams. Minor floods, however, don't scour bacteria in the depth of the stream bed that could then be important for the self-purification processes.
Krebs, P., & Larsen, T. A. (1997). Guiding the development of urban drainage systems by sustainability criteria. Water Science and Technology, 35(9), 89-98. doi:10.1016/S0273-1223(97)00187-X, Institutional Repository

The development of urban drainage towards sustainability is discussed, primarily on the basis of case studies of mature urban drainage systems. Typical problems and a series of possible measures to enhance the systems performance are evaluated. We consider CSOs, receiving water quality, and decreasing ground water levels as actual problems. We distinguish between improvement strategies which focus on the technical system itself (e.g. storm water retention tanks, real time control) and strategies which may be described either as source control or as improving the resilience of the receiving water. Their efficiency is evaluated on the basis of short term ‘conventional’ criteria and by means of the following sustainability criteria: systems definition (time and space constants), resource efficiency and degrees of freedom. Surprisingly, the rating of the different strategies according to the two sets of criteria are quite close: In both cases, the measures which do not narrowly focus on the technical system obtain the better score.
Larsen, T. A., & Gujer, W. (1997). The concept of sustainable urban water management. Water Science and Technology, 35(9), 3-10. doi:10.1016/S0273-1223(97)00179-0, Institutional Repository

Urban Water Management involves the fields of water supply, urban drainage, wastewater treatment and sludge handling. On the basis of the Agenda 21, principles and guidelines for sustainable urban water management are discussed. Sustainable technology leads to acceptable gradients in state variables. New technologies departing from an analysis of required services rather than stepwise improvement of existing technology is preferred. An efficient use of resources will lead to a minimal increase of entropy and will require an active rather than a reactive approach. The analysis of the transition period from today's to a sustainable situation is important. An example is introduced which deals with global cycling of nutrients and which may be approached on a regional scale.
Rüede, A., Dürrenberger, G., Larsen, T., & Pahl-Wostl, C. (1997). WissenschaftlerInnen und regionale Akteure im Dialog. Teil I. Vorstellungen zur regionalen Nachhaltigkeit im Tösstal. sine loco: Eawag. , Institutional Repository

Die Intensivierung des Kontaktes und des Austausches mit der Praxis bildete eines der Hauptanliegen des Forschungsschwerpunktes 93 - 97 der EAWAG. Eine wesentliche Rolle beim Dialog zwischen Forschung und Praxis spielen implizite und explizite Bewertungsfragen, insbesondere wenn es um die Umsetzung von Forschungsergebnissen geht. In einem zweiteiligen, anderthalbjährigen Forschungsprojekt wurde diese Schnittstelle mit zwei unterschiedlichen methodischen Verfahren, nämlich qualitativen Interviews und Fokusgruppen untersucht. Thematisch ging es beim einen Teilprojekt um Vorstellungen über eine nachhaltige Regionalentwicklung, beim andern um die nachhaltige Verwendung von Kupfer als Baustoff im Aussenbereich. [...]
Rüede, A., Meyer, C., Dürrenberger, G., Larsen, T., & Pahl-Wostl, C. (1997). WissenschaftlerInnen und regionale Akteure im Dialog. Teil II. Zur Verwendung von Kupfer als Baustoff im Aussenbereich. sine loco: Eawag. , Institutional Repository

Die Intensivierung des Kontaktes und des Austausches mit der Praxis bildete eines der Hauptanliegen des Forschungsschwerpunktes 93 - 97 der EAW AG. Eine wesentliche Rolle beim Dialog zwischen Forschung und Praxis spielen implizite und explizite Bewertungsfragen, insbesondere wenn es um die Umsetzung von Forschungsergebnissen geht. In einem zweiteiligen, anderthalbjährigen Forschungsprojekt wurde diese Schnittstelle mit zwei unterschiedlichen methodischen Verfahren, nämlich qualitativen Interviews und Fokusgruppen untersucht. Thematisch ging es beim einen Teilprojekt um Vorstellungen über eine nachhaltige Regionalentwicklung, beim andern um die nachhaltige Verwendung von Kupfer als Baustoff im Aussenbereich. [...]
Larsen, T. A., & Gujer, W. (1996). Separate management of anthropogenic nutrient solutions (human urine). Water Science and Technology, 34(3-4), 87-94. doi:10.1016/0273-1223(96)00560-4, Institutional Repository

Anthropogenic Nutrient Solution (ANS, Urine) adds about 75% of the nitrogen and 50% of the phosphorus to domestic wastewater. It is proposed to collect ANS at the source and release it sequentially, so that it arrives all at the same time at the treatment plant where it could be treated separately. The proposed system would have many advantages relative to the conventional technology. A stepwise transition from the conventional to the proposed technology would slowly improve system performance.
Gujer, W., & Larsen, T. A. (1995). The implementation of biokinetics and conservation principles in ASIM. Water Science and Technology, 31(2), 257-266. doi:10.1016/0273-1223(95)00198-V, Institutional Repository

The Activated Sludge SIMulation program ASIM is introduced as a didactic tool to be used in design courses for the simulation of the dynamic behaviour of modern nutrient removal activated sludge systems. It allows for free definition of the biokinetic model, the flow scheme, process control strategies and load variation. Its user interface is simple enough to be used in the classroom but powerful enough to support even professional work.
The most difficult aspect of ASIM is the preparation of the biokinetic model (transformation processes) to be used. A systematic use of stoichiometric conservation principles simplifies this task and at the same time reduces the number of empirical parameters. The practical application of conservation principles for charge, elements and theoretical COD is presented in detail. Composition equations are introduced as a link to the wastewater treatment plant reality.
Gujer, W., & Larsen, T. A. (1988). Technologische Anforderungen an eine nachhaltige Siedlungswasserwirtschaft. In B. Weigert (Ed.), Schriftenreihe Wasserforschung: Vol. 3. Wasserwirtschaft in urbanen Räumen (pp. 65-82). Berlin: Franke. , Institutional Repository

Es werden Kriterien, Optionen und konkrete Beispiele von nachhaltigen Technologien in der Siedlungswasserwirtschaft vorgestellt und diskutiert. Neben der Hardware werden auch die Rahmenbedingungen wie Finanzierung und Datenmanagement in den Technologiebegriff aufgenommen. Eine umfassende Definition von Ressourcen wird gegeben, die neben unseren materiellen auch die anthropogenen Möglichkeiten umfasst.
Zukünftige technische Systeme in der Siedlungswasserwirtschaft werden vermehrt von den Dienstleistungen ausgehen, die sie erbringen müssen. Sie werden unsere Flexibilität erhöhen und die Übergangsperioden von der heutigen zur zukünftigen Situation berücksichtigen. Aktive Massnahmen an der Quelle werden reaktive 'end of pipe' Massnahmen ablösen.

João Leitão

Chaudhary, P., Leitão, J. P., Schindler, K., & Wegner, J. D. (2024). Flood water depth prediction with convolutional temporal attention networks. Water, 16(9), 1286 (19 pp.). doi:10.3390/w16091286, Institutional Repository

Robust and accurate flood hazard maps are essential for early warning systems and flood risk management. Although physically based models are effective in estimating pluvial flooding, the computational burden makes them difficult to use for real-time flood prediction. In contrast, data-driven models can provide faster flood predictions if trained offline. While most studies have focused on predicting maximum water depth, in this study, we predict pixel-wise water depth maps for entire catchments at a lead time of 2 h. To that end, we propose a deep learning approach that uses a sequence encoding network with temporal self-attention. We also adapt the popular hydrological performance metric Nash–Sutcliffe efficiency (NSE) as our loss function. We test the effectiveness and generalizability of our method using a new dataset called SwissFlood, which consists of 100 catchments and 1500 rainfall events extracted from real observations in Switzerland. Our method produces 2 m spatial resolution flood maps with absolute error as low as 27 cm for water depth exceeding 1 m.
 
Chen, J., Bach, P. M., Nice, K. A., & Leitão, J. P. (2024). Investigating the efficacy of a fast urban climate model for spatial planning of green and blue spaces for heat mitigation. Science of the Total Environment, 955, 176925 (13 pp.). doi:10.1016/j.scitotenv.2024.176925, Institutional Repository

Problems caused by urban heat have prompted the exploration of urban greenery and blue spaces for heat mitigation. Various numerical models can simulate heat-related processes, but their use as support-tools to urban planners remains underexplored, particularly at the city-scale, due to high computational demand and complexity of such models. This study investigates the spatial relationships between urban heat, urban form and urban green and blue spaces with the fast climate model TARGET (The Air-temperature Response to Green/blue-infrastructure Evaluation Tool), which only requires minimal inputs of standard meteorological data, land cover and building geometry data. Using the City of Zurich as our case study, we: (i) validated the TARGET model against air temperature measurements from private sensor networks, (ii) performed a sensitivity analysis to identify key variables affecting urban heat, and (iii) investigated urban heat relationships with blue-green cover at locations frequented by pedestrians. Presence of urban green and blue spaces across the region shows potential for reducing local air temperatures by up to 5.2 °C (with urban forest). Investigating this relationship at different locations in the city revealed key districts that should potentially be targeted for reduction of pedestrian heat-impacts, due to their high pedestrian traffic, fewer green and blue spaces and high daytime air temperatures. Our results not only provide insights into the cooling effect of different amounts of green and blue features in the urban environment, but also demonstrates the application and integration potential of simplified models like TARGET to support the planning of more liveable future cities.
Fappiano, F., Maurer, M., & Leitão, J. P. (2024). Coupling sewers to the surface: systematic approaches to correcting data discrepancies for 1D-2D drainage modelling. Journal of Hydrology, 645, 132239 (14 pp.). doi:10.1016/j.jhydrol.2024.132239, Institutional Repository

One-dimensional (1D) drainage models coupled with two-dimensional (2D) surface models have been recognised as most suitable for simulating pluvial floods in urban areas. However, discrepancies between the 1D drainage network and the 2D Digital Terrain Model (DTM) surface elevation datasets are often observed. These incompatibilities are commonly adjusted manually, impacting the transparency and reproducibility of flood modelling results. No automated and reproducible methods are currently available to ensure compatibility and consistency between a 1D drainage network and the 2D DTM elevation dataset. We present two methods for automatically correcting these discrepancies: Method 1, which corrects the discrepancies by editing the 1D drainage network, and Method 2, which corrects the discrepancies by editing the elevation of the 2D surface. Both methods ensure 1D–2D data compatibility. The two methods were evaluated through hydraulic and hydrological simulations using a synthetic case study, demonstrating strong performance for both approaches. Additionally, we propose a procedure to guide practitioners and modellers in discerning between 1D data and 2D data errors and choosing which method to use. This procedure is demonstrated for a real case study. The two presented methodologies can improve the process of creating 1D-2D urban drainage models and their reproducibility.
Li, S., Leitão, J. P., Wang, Z., & Bach, P. M. (2024). A drainage network-based impact matrix to support targeted blue-green-grey stormwater management solutions. Science of the Total Environment, 912, 168623 (10 pp.). doi:10.1016/j.scitotenv.2023.168623, Institutional Repository

Urban floods will continue to be an alarming issue worldwide due to climate change and urban expansion. The costly and less environmentally friendly grey infrastructure is not always the most adequate solution to resolve urban pluvial flooding issues. The combination of grey and blue-green infrastructures, also called hybrid infrastructure, has been considered a promising solution for urban stormwater management. Existing approaches for identifying suitable hybrid solutions frequently rely on global multi-objective optimization algorithms. We developed a pre-screening method that decomposes a drainage network into clusters of pipes connected to sub-catchments, based on pipe hydraulic characteristic that allows for the impact of infrastructure combinations (blue-green and grey) to be mapped. Four impact matrices are proposed to map the total, local, upstream, and downstream flood reduction of all possible blue-green, grey, and hybrid solutions. Using an urban catchment in Guangzhou (China) as a case study, results showed that such an exercise could identify prime candidate locations for blue-green and grey infrastructure while filtering out ineffective locations for flood reduction. Furthermore, the impact matrices enabled the identification of flood zones where blue-green infrastructure could handle flood mitigation without the need of local grey infrastructure upgrades. As such, they are not only useful for quick screening of suitable interventions for each flooded zone, but can also potentially serve as a priori knowledge before diving into the data and computationally expensive process of finding the most effective flood mitigation solutions.
Peleg, N., Wright, D. B., Fowler, H. J., Leitão, J. P., Sharma, A., & Marra, F. (2024). A simple and robust approach for adapting design storms to assess climate-induced changes in flash flood hazard. Advances in Water Resources, 193, 104823 (9 pp.). doi:10.1016/j.advwatres.2024.104823, Institutional Repository

Hydrologists and civil engineers often use design storms to assess flash flood hazards in urban, rural, and mountainous catchments. These synthetic storms are not representations of real extreme rainfall events, but rather simplified versions parameterized to mimic extreme precipitation statistics often obtained from intensity–duration–frequency (IDF) curves. To construct design storms for the future climate, it is thus necessary first to recalculate IDF curves to represent rainfall under warmer conditions. We propose a framework for adjusting IDF curves and design storms to future climate conditions using the TENAX model, a novel statistical approach that can provide future short-duration precipitation return levels based on projected temperature changes. For most applications, information from climate models at the daily scale can be used to construct design storms at the sub-hourly scale without any downscaling or bias adjustment. Our approach is illustrated through a re-parameterization of the Chicago Design Storm (CDS) in the context of climate change. As a case study demonstration, we apply the TENAX model to data from the city of Zurich to calculate changes in the historical IDF curve for durations ranging from 10 min to 3 h. We then construct synthetic 100-year return period design storms based on the CDS for present and future climates and use the CAFlood model to produce flood inundation maps to assess changes in flood hazard. The codes for adapting design storms to climate change are simple to implement, easily applicable by practitioners, and made freely available.
Wang, W., Wang, Z., Guan, M., Wani, O., Bai, Y., Wang, K., & Leitao, J. P. (2024). Evaluation of stormwater mitigation performance with LID infrastructures, in-sewer space, and real-time control strategies. Journal of Hydrologic Engineering, 29(5), 05024016 (14 pp.). doi:10.1061/JHYEFF.HEENG-6185, Institutional Repository

Because low-impact development (LID) infrastructures are effective in capturing and utilizing urban stormwater runoff, real-time control (RTC) strategies can be viewed as soft infrastructures, offering an additional suite of opportunities to improve the stormwater drainage system performance. However, there is a paucity of analyses that disentangle the contributing sources of performance enhancement in these joint hard-soft stormwater infrastructures. This study evaluated the stormwater system performance with integrated LID infrastructures, in-sewer storage capacity, and RTC strategies. Our results showed that LID infrastructures play a major role in mitigating the flow peaks and high volumes, whereas adding RTC to the storage unit and in-sewer flow control mostly improves the performance under relatively small rainfall events, e.g., those with a 3-year return period. The critical contribution of RTC is realized by utilizing storage units as much as possible during the rainfall event. A downstream storage unit that is too close to the outfall may not be suitable for RTC application together with in-sewer capacity utilization. In the present case, the combination of a midstream storage unit and upstream control site at branch pipes worked better than those at other locations. The results suggest that the integration of LID and RTC on a simulation-system level can enhance the reduction of the peak runoff and total discharged volume only if the storage site and control locations are selected carefully.
Carriço, N., do Céu Almeida, M., & Leitão, J. P. (2023). Management of urban drainage infrastructure. In T. Bolognesi, F. Silva Pinto, & M. Farrelly (Eds.), Routledge environment and sustainability handbooks. Routledge handbook of urban water governance (pp. 145-162). doi:10.4324/9781003057574-12, Institutional Repository
Devanand, V. B., Mubeen, A., Vojinovic, Z., Sanchez Torres, A., Paliaga, G., Abdullah, A. F., … Fröhle, P. (2023). Innovative methods for mapping the suitability of nature-based solutions for landslide risk reduction. Land, 12(7), 1357 (15 pp.). doi:10.3390/land12071357, Institutional Repository

The impacts of climate change are becoming more widespread across the world, with hydro-meteorological extreme events on the rise, causing severe threats to nature and communities. Increasing trends in the frequency and intensity of floods and landslides have been projected by climate models. This necessitates the development of more effective measures such as nature-based solutions (NBS) which can complement grey infrastructures. Recent studies have identified knowledge gaps and limitations in existing research and tools that aid in spatial planning for the implementation of large-scale NBS and proposed new methodologies for the spatial allocation of large-scale NBS for flood risk reduction. This work presents a novel method for mapping the suitability of NBS addressing geo-hydrological hazards such as shallow landslides, debris flow, and rockfall, which are typically caused due to slope instability. This methodology incorporates landslide susceptibility mapping, and was used to create a toolbox ESRI ArcGIS environment to aid decision-makers in the planning and implementation of large-scale NBS. The spatial allocation toolbox was applied to the case study Portofino promontory, Liguria region, Italy, and 70% of the area was found to be highly susceptible to landslides. The produced suitability maps show that 41%, 33%, and 65% of the study area is suitable for the restoration of terraces, bio-engineering, and vegetative measures such as NBS for landslide risk reduction.
Figueroa, A., Hadengue, B., Leitão, J. P., & Blumensaat, F. (2023). A framework for modelling in-sewer thermal-hydraulic dynamic anomalies driven by stormwater runoff and seasonal effects. Water Research, 229, 119492 (10 pp.). doi:10.1016/j.watres.2022.119492, Institutional Repository

RRain-induced surface runoff and seasons lead to short- to medium-term anomalies in combined storm- and wastewater flows and temperatures, and influence treatment processes in wastewater resource recovery facilities (WRRF). Additionally, the implementation of decentralized heat recovery (HR) technologies for energy reuse in buildings affect energy-related processes across the urban water cycle and WRRFs heat inflows. However, quantitative insights on thermal-hydraulic dynamics in sewers at network scale and across different scales are very rare.
To enhance the understanding of thermal-hydraulic dynamics and the water-energy nexus across the urban water cycle we present a modular framework that couples thermal-hydraulic processes: i) on the surface, ii) in the public sewer network, iii) in households (including in-building HR systems), and iv) in lateral connections. We validate the proposed framework using field measurements at full network scale, present modelling results of extended time periods to illustrate the effect of seasons and precipitation events simultaneously, and quantify the impact of decentralized HR devices on thermal-hydraulics.
Simulation results suggest that the presented framework can predict temperature dynamics consistently all year long including short- to long-term variability of in-sewer temperature. The study provides quantitative evidence that the impact of household HR technologies on WRRF inflow heat budgets is reduced by approximately 20% during wet-weather periods in comparison to dry-weather conditions. The presented framework has potential to support multiple research initiatives that will improve the understanding of the water-energy nexus, pollutant dispersion and degradation, and support maintenance campaigns at network scale.
Gobatti, L., Bach, P. M., Scheidegger, A., & Leitão, J. P. (2023). Using satellite imagery to investigate Blue-Green Infrastructure establishment time for urban cooling. Sustainable Cities and Society, 97, 104768 (11 pp.). doi:10.1016/j.scs.2023.104768, Institutional Repository

The process of urbanization can alter the local climate to the point that it threatens citizens’ well-being by creating heat-related hazards. The construction of Blue-Green Infrastructure (BGI) can improve the regulation of surface energy exchange processes and address this problem. However, the time needed for a BGI to deliver a stable cooling performance, referred to here as the Cooling Establishment Time (CET), is poorly understood and quantified in the literature and dependent on environmental, design and maintenance factors. Here, we analyze the feasibility of using satellite data to derive the CET for different BGIs across the city of Zurich, Switzerland. Results showed that remote sensing can quantify the land surface temperature impact of BGIs and assist in estimating their CET. BGI with trees or climbing plants required a longer CET (seven to ten years) before any notable shift in surface temperatures were visible, while grasses or artificial irrigated systems led to shorter CETs (one to three years). These results allow us to better account for BGI cooling establishment when planning for areas that need urgent action under warming climates. This work supports evidence-based urban greenery planning and design towards cooling our increasingly warming cities in a timely manner.
Jato-Espino, D., Charlesworth, S., Leitão, J. P., & Rodríguez Sánchez, J. P. (2023). Editorial: Urban drainage in a context of climate and land cover changes. Frontiers in Water, 4, 1118338 (2 pp.). doi:10.3389/frwa.2022.1118338, Institutional Repository
Nascimento, N., Armitage, N., Sanches, J. P. R., & Leitao, J. P. (2023). Editorial: UWJ special edition on water management in developing countries. Urban Water Journal, 20(10), 1231-1236. doi:10.1080/1573062X.2023.2266635, Institutional Repository
Peleg, N., Torelló-Sentelles, H., Mariéthoz, G., Benoit, L., Leitão, J. P., & Marra, F. (2023). Brief communication: the potential use of low-cost acoustic sensors to detect rainfall for short-term urban flood warnings. Natural Hazards and Earth System Sciences, 23(3), 1233-1240. doi:10.5194/nhess-23-1233-2023, Institutional Repository

Floods in urban areas are one of the most common natural hazards. Due to climate change enhancing extreme rainfall and cities becoming larger and denser, the frequency, magnitude, and impact of these events are expected to increase. Pluvial floods can occur in urban areas within minutes. A fast and reliable rainfall detection system should thus be implemented in flood-prone cities to warn the public of upcoming floods and save lives and reduce damage. The purpose of this brief communication is to discuss the potential implementation of low-cost acoustic rainfall sensors in short-term flood warning systems.
Tondera, K., Brelot, E., Fontanel, F., Cherqui, F., Ellerbæk Nielsen, J., Brüggemann, T., … Anta, J. (2023). European stakeholders' visions and needs for stormwater in future urban drainage systems. Urban Water Journal, 20(7), 831-843. doi:10.1080/1573062X.2023.2211559, Institutional Repository

Transitioning urban drainage systems to serve water-smart societies requires the involvement of different disciplines and stakeholders. However, stakeholders have different visions and needs from the transitioning process (e.g in terms of financing, policy adaptation and system management) these also vary between regions and countries. Identifying such different needs for stakeholders is necessary to propose practical adaptation strategies. Therefore, evidence of needs as reflected in policy papers and legislation in seven European countries was collected. Knowledgeable individuals in the urban drainage community were asked about their visions. Results show that whilst there is consensus on the challenges, visions on how to transition are diverse, indicating that more interaction between the different stakeholder groups is required to develop consensus. Additionally, organisational and legislative structures often slow down the necessary change processes.
Chaudhary, P., Leitão, J. P., Donauer, T., D’Aronco, S., Perraudin, N., Obozinski, G., … Russo, S. (2022). Flood uncertainty estimation using deep ensembles. Water, 14(19), 2980 (24 pp.). doi:10.3390/w14192980, Institutional Repository

We propose a probabilistic deep learning approach for the prediction of maximum water depth hazard maps at high spatial resolutions, which assigns well-calibrated uncertainty estimates to every predicted water depth. Efficient, accurate, and trustworthy methods for urban flood management have become increasingly important due to higher rainfall intensity caused by climate change, the expansion of cities, and changes in land use. While physically based flood models can provide reliable forecasts for water depth at every location of a catchment, their high computational burden is hindering their application to large urban areas at high spatial resolution. While deep learning models have been used to address this issue, a disadvantage is that they are often perceived as "black-box" models and are overconfident about their predictions, therefore decreasing their reliability. Our deep learning model learns the underlying phenomena a priori from simulated hydrodynamic data, obviating the need for manual parameter setting for every new rainfall event at test time. The only inputs needed at the test time are a rainfall forecast and parameters of the terrain such as a digital elevation model to predict the maximum water depth with uncertainty estimates for complete rainfall events. We validate the accuracy and generalisation capabilities of our approach through experiments on a dataset consisting of catchments within Switzerland and Portugal and 18 rainfall patterns. Our method produces flood hazard maps at 1 m resolution and achieves mean absolute errors as low as 21 cm for extreme flood cases with water above 1 m. Most importantly, we demonstrate that our approach is able to provide an uncertainty estimate for every water depth within the predicted hazard map, thus increasing the model's trustworthiness during flooding events.
Guo, Z., Moosavi, V., & Leitão, J. P. (2022). Data-driven rapid flood prediction mapping with catchment generalizability. Journal of Hydrology, 609, 127726 (12 pp.). doi:10.1016/j.jhydrol.2022.127726, Institutional Repository

Data-driven and machine learning models have recently received increasing interest to resolve the computational speed challenge faced by various physically-based simulations. A few studies have explored the application of these models to develop new, and fast, applications for fluvial and pluvial flood prediction, extent mapping, and flood susceptibility assessment. However, most studies have focused on model development for specific catchment areas, drainage networks or gauge stations. Hence, their results cannot be directly reused to other contexts unless extra data are available and the models are further trained. This study explores the generalizability potential of convolutional neural networks (CNNs) as flood prediction models. The study proposes a CNN-based model that can be reused in different catchment areas with different topography once the model is trained. The study investigates two options, patch- and resizing-based options, to process catchment areas of different sizes and different shapes. The results showed that the CNN-based model predicts accurately on "unseen" catchment areas with significantly less computational time when compared to physically-based models. The obtained results also suggest that the patch-based option is more effective than the resizing-based option in terms of prediction accuracy. In addition, all experiments have shown that the prediction of flow velocity is more accurate than water depth, suggesting that the water accumulation is more sensitive to global elevation information than flow velocity.
Harpaz, C., Russo, S., Leitão, J. P., & Penn, R. (2022). Potential of supervised machine learning algorithms for estimating the impact of water efficient scenarios on solids accumulation in sewers. Water Research, 216, 118247 (16 pp.). doi:10.1016/j.watres.2022.118247, Institutional Repository

Understanding the negative effects of widespread implementation of optimal water efficient solutions may have on existing centralised sewer systems is still limited – one of these effects is the accumulation of solids in sewer pipes. Predicting these effects requires setting up and simulating complex detailed hydraulic sewer network models. Often, precise details of the sewer network layout and diurnal patterns of the wastewater flows are not available, limiting the applicability of using model predictions for such phenomena. In this study, the applicability of supervised machine learning (ML) algorithms for the development of a simplified surrogate model to predict solid accumulation in sewer pipes was investigated. A large number of highly variable sewer networks were synthetically generated and used to produce results that can be generalizable within the limitations of the current study. A hydrodynamic sewer model was set up and simulated for each synthetic sewer network and various scenarios in which different water-efficient solutions were considered. Simulation results indicated that the most impacts are expected to occur in the upstream part of the sewer networks, and that with 50% reduction in (waste-)water flows, 3–20% more pipes are expected to accumulate solids. It was further found that ML algorithms can be used to successfully predict locations of solids accumulation in sewer pipes without using hydrodynamic models. A simple tool based on the findings of this study, sparing the need to conduct complex hydraulic simulations, was developed. It allows the user to enter a set of pipe characteristics and the proportion of flow that is reduced due to the implementation of water efficient solutions, and it predicts whether the pipe will accumulate solids or not. The study results and the proposed ML algorithms can support the implementation of optimal water-efficient solutions that will promote designing and managing the water sensitive cities of the future.
Langeveld, J. G., Cherqui, F., Tscheikner-Gratl, F., Muthanna, T. M., Fernandez-Delgado Juarez, M., Leitão, J. P., … Rulleau, B. (2022). Asset management for blue-green infrastructures: a scoping review. Blue-Green Systems, 4(2), 272-290. doi:10.2166/bgs.2022.019, Institutional Repository

Urban drainage systems have developed way beyond the traditional piped combined or separate sewer systems. Many 'new' systems are being introduced, ranging from stormwater infiltration facilities to green roofs. However, the widely advocated blue-green infrastructures are typically overlooked by asset managers, which will very likely have detrimental effects on their performance, service life, and wider adoption. In this paper, the working group on Urban Drainage Asset Management (UDAM - https://udam.home.blog/) of the IWA and IAHR Joint Committee on Urban Drainage discusses whether the state-of-the-art knowledge based on conventional sewer asset management is sufficient to develop asset management for blue-green infrastructures (BGIs). The discussion is structured around the five preconditions for effective control and asset management. Results show that asset management for BGIs is still underdeveloped due to a lack of monitoring techniques covering the broad range of BGI benefits and performance indicators, inspection techniques covering relevant failure mechanisms and models describing these mechanisms, maintenance and rehabilitation options, and sufficient support tools to aid inhabitants in the operation and maintenance of their individual BGIs such as green roofs or vegetated swales.
Peleg, N., Ban, N., Gibson, M. J., Chen, A. S., Paschalis, A., Burlando, P., & Leitão, J. P. (2022). Mapping storm spatial profiles for flood impact assessments. Advances in Water Resources, 166, 104258 (11 pp.). doi:10.1016/j.advwatres.2022.104258, Institutional Repository

Synthetic design storms are often used to plan new drainage systems or assess flood impacts on infrastructure. To simulate extreme rainfall events under climate change, design storms can be modified to match a different return frequency of extreme rainfall events as well as a modified temporal distribution of rainfall intensities. However, the same magnitude of change to the rainfall intensities is often applied in space. Several hydrological applications are limited by this. Climate change impacts on urban pluvial floods, for example, require the use of 2D design storms (rainfall fields) at sub-kilometer and sub-hourly scales. Recent kilometer scale climate models, also known as convection-permitting climate models (CPM), provide rainfall outputs at a high spatial resolution, although rainfall simulations are still restricted to a limited number of climate scenarios and time periods. We nevertheless explored the potential use of rainfall data obtained from these models for hydrological flood impact studies by introducing a method of spatial quantile mapping (SQM). To demonstrate the new methodology, we extracted high-resolution rainfall simulations from a CPM for four domains representing different urban areas in Switzerland. Extreme storms that are plausible under the present climate conditions were simulated with a 2D stochastic rainfall model. Based on the CPM-informed stochastically generated rainfall fields, we modified the design storms to fit the future climate scenario using three different methods: the SQM, a uniform quantile mapping, and a uniform adjustment based on a rainfall–temperature relationship. Throughout all storms, the temporal distribution of rainfall was the same. Using a flood model, we assessed the impact of different rainfall adjustment methods on urban flooding. Significant differences were found in the flood water depths and areas between the three methods. In general, the SQM method results in a higher flood impact than the storms that were modified otherwise. The results suggest that spatial storm profiles may need to be re-adjusted when assessing flood impacts.
Probst, N., Bach, P. M., Cook, L. M., Maurer, M., & Leitão, J. P. (2022). Blue Green Systems for urban heat mitigation: mechanisms, effectiveness and research directions. Blue-Green Systems, 4(2), 348-376. doi:10.2166/bgs.2022.028, Institutional Repository

Reflected in the growing body of literature, urban heat mitigation is increasingly relevant as cities experience extreme heat, exacerbated by climate change and rapid urbanisation. Most studies focus on urban–rural temperature differences, known as the Urban Heat Island, which does not provide insight into urban heat dynamics. Here, we synthesise current knowledge on spatio-temporal variations of heat sources and sinks, showing that a targeted and absolute understanding of urban heat dynamics rather than an urban–rural comparison should be encouraged. We discuss mechanisms of heat sinks for microclimate control, provide a clear classification of Blue Green Systems and evaluate current knowledge of their effectiveness in urban heat mitigation. We consider planning and optimisation aspects of Blue Green Infrastructure (greenery and water bodies/features), interactions with hard surfaces and practices that ensure space and water availability. Blue Green Systems can positively affect urban microclimates, especially when strategically planned to achieve synergies. Effectiveness is governed by their dominant cooling mechanisms that show diurnal and seasonal variability and depend upon background climatic conditions and characteristics of surrounding urban areas. Situationally appropriate combination of various types of Blue Green Systems and their connectivity increases heat mitigation potential while providing multiple ecosystem services but requires further research.
Browne, S., Lintern, A., Jamali, B., Leitão, J. P., & Bach, P. M. (2021). Stormwater management impacts of small urbanising towns: The necessity of investigating the 'devil in the detail'. Science of the Total Environment, 757, 143835 (13 pp.). doi:10.1016/j.scitotenv.2020.143835, Institutional Repository

In many parts of the world, small towns are experiencing high levels of population growth and development. However, there is little understanding of how urban growth in these regional towns will impact urban runoff. We used the case study of Wangaratta, located in South-East Australia, between 2006 and 2016, to investigate land cover changes and their impacts on urban runoff discharge. Detailed spatio-temporal analysis (including neighbourhood composition analysis and supervised classification of aerial imagery) identified that population, land use and land cover changes in Wangaratta, although subtle, were mostly driven by residential growth in the outskirts of the town, where there were large increases in impervious surface area. Overall, the urban growth was minimal. However, in spite of these small changes, a sub-catchment only SWMM model showed that the increase in impervious surface area nevertheless resulted in a statistically significant increase in total runoff across the town. Particularly, this increase was most pronounced for frequent and shorter storms. The analysis of urban development pattern changes coupled with urban hydrological modelling indicated that land cover changes in regional towns, especially when analysed in detail, may result in hydrological changes in the urban region (likely to be exacerbated in coming years by changing climate) and that adaptation efforts will need to adopt a variety of approaches in both existing and growth zones. Our findings highlight the necessity of detailed fine-scale analyses in small towns as even subtle changes will have substantial future implications and robust planning and adaptation decisions are even more important when compared to larger cities due to the greater economic constraints that small towns face and their important relationship with the surrounding hinterlands.
Figueroa, A., Hadengue, B., Leitão, J. P., Rieckermann, J., & Blumensaat, F. (2021). A distributed heat transfer model for thermal-hydraulic analyses in sewer networks. Water Research, 204, 117649 (11 pp.). doi:10.1016/j.watres.2021.117649, Institutional Repository

Thermal-hydraulic considerations in urban drainage networks are essential to utilise available heat capacities from waste- and stormwater. However, available models are either too detailed or too coarse; fully coupled thermal-hydrodynamic modelling tools are lacking. To predict efficiently water-energy dynamics across an entire urban drainage network, we suggest the SWMM-HEAT model, which extends the EPA-StormWater Management Model with a heat-balance component. This enables conducting more advanced thermal-hydrodynamic simulation at full network scale than currently possible. We demonstrate the usefulness of the approach by predicting temperature dynamics in two independent real-world cases under dry weather conditions. We furthermore screen the sensitivity of the model parameters to guide the choice of suitable parameters in future studies. Comparison with measurements suggest that the model predicts temperature dynamics adequately, with RSR values ranging between 0.71 and 1.1. The results of our study show that modelled in-sewer wastewater temperatures are particularly sensitive to soil and headspace temperature, and headspace humidity. Simulation runs are generally fast; a five-day period simulation at high temporal resolution of a network with 415 nodes during dry weather was completed in a few minutes. Future work should assess the performance of the model for different applications and perform a more comprehensive sensitivity analysis under more scenarios. To facilitate the efficient estimation of available heat budgets in sewer networks and the integration into urban planning, the SWMM-HEAT code is made publicly available.
Guo, Z., Leitão, J. P., Simões, N. E., & Moosavi, V. (2021). Data-driven flood emulation: speeding up urban flood predictions by deep convolutional neural networks. Journal of Flood Risk Management, 14(1), e12684 (14 pp.). doi:10.1111/jfr3.12684, Institutional Repository

Computational complexity has been the bottleneck for applying physically based simulations in large urban areas with high spatial resolution for efficient and systematic flooding analyses and risk assessment. To overcome the issue of long computational time and accelerate the prediction process, this paper proposes that the prediction of maximum water depth can be considered an image-to-image translation problem in which water depth rasters are generated using the information learned from data instead of by conducting simulations. The proposed data-driven urban pluvial flood approach is based on a deep convolutional neural network trained using flood simulation data obtained from three catchments and 18 hyetographs. Multiple tests to assess the accuracy and validity of the proposed approach were conducted with both design and real hyetographs. The results show that flood prediction based on neural networks use only 0.5% of the time compared with that of physically based models, with promising accuracy and generalizability. The proposed neural network can also potentially be applied to different but relevant problems, including flood analysis for flood-safe urban layout planning.
Jamali, B., Haghighat, E., Ignjatovic, A., Leitão, J. P., & Deletic, A. (2021). Machine learning for accelerating 2D flood models: potential and challenges. Hydrological Processes, 35(4), e14064 (14 pp.). doi:10.1002/hyp.14064, Institutional Repository

Two-dimensional hydrodynamic models numerically solve full Shallow Water Equations (SWEs). Despite their high accuracy, these models have long simulation run times and therefore are of limited use for exploratory or real-time flood predictions. We investigated the possibility of improving flood modelling speed using Machine Learning (ML). We propose a new method that replaces the computationally expensive parts of the hydrodynamic models with simple and efficient data-driven approximations. Our hypothesis is that by integrating ML with physics-based numerical methods, we can achieve improved generalization performance: that is, the trained model for one case study can be used in other studies without the need for new training. We tested two ML approaches: for the first, we integrated curve fitting, and, for the second, artificial neural networks (ANN) with a finite volume scheme to solve the local inertial approximation of the SWEs. The data-driven models approximated the Momentum Equation, which explicitly solved the time derivative of flow rates. Water depths were then updated by applying a water balance equation. We also tested two different training datasets: the simulated dataset, generated from the results of hydrodynamic model, and the random dataset, generated by directly solving the momentum equation on randomly sampled input data. Various combinations of input features, for example, water slope and depth, were explored. The proposed models were trained in a small hypothetical case and tested in a different hypothetical and in two real case studies. Results showed that the curve-fitting method can be implemented successfully, given sufficient training and input data. The ANN model trained with a random dataset was substantially more accurate than that of the model trained with the simulated dataset. However, it was not successful in the real case studies. The curve-fitting method resulted in better generalization performance and increased the simulation speed of the local inertial model by 23%. Future research should test the performance of ML in terms of an increase in stable time step size and approximation of the full SWEs.
Joshi, P., Leitão, J. P., Maurer, M., & Bach, P. M. (2021). Not all SuDS are created equal: impact of different approaches on combined sewer overflows. Water Research, 191, 116780 (13 pp.). doi:10.1016/j.watres.2020.116780, Institutional Repository

Sustainable urban drainage systems (SuDS) help in stormwater management by reducing runoff volume, increasing runoff concentration time and thereby improving the drainage system capacity. This study investigated the potential and cost-effectiveness of SuDS in reducing combined sewer overflows (CSOs). We simulated the performance of four SuDS techniques (bioretention cell, permeable pavement, rain barrel and green roof) at incremental levels of spatial coverage for a small urban catchment with a combined sewer system. We also used an Analytic Hierarchy Process (AHP) considering end-point CSO, land use, imperviousness, slope and elevation criteria to identify priority areas for SuDS deployment. Results show that CSO volume attenuation ranged a maximum of 50-99% for the catchment, depending on the deployment strategy and underlying mechanisms of each technology. We also found that deployment of SuDS in AHP-selected sub-catchments improved CSO reduction only for rain barrels and green roofs, but not for bioretention cells and permeable pavements. SuDS were also a cost-effective retrofit option: for a 40% volume reduction, the SuDS cost, at most, 25% of the equivalent cost required for a large CSO tank. Outcomes of this study demonstrate the efficacy of SuDS in controlling CSOs, adding yet another tangible benefit to their increasingly recognised multi-functionality.
Leite, A., & Leitão, J. (2021). The new town of Angra (Terceira, the Azores): confirming a contested urban planning history using reverse historical analysis and flood modelling tools. Urban History, 48(1), 20-36. doi:10.1017/S0963926819001093, Institutional Repository

The Portuguese discovered the uninhabited Azores archipelago in 1427 and started to settle it during the fifteenth century. Angra, located on Terceira Island, soon became the most important Azorean city, leading to rapid urban development. This article investigates the overlooked role of streams in the rise of Angra as a pivotal Atlantic urban centre. Through the intersection of historical and flood modelling methods, it makes a unique contribution to our understanding of Angra's urban morphologic development, highlighting the potential of applying urban flood modelling to analysis of the rise of coastal urban settlement.
Wang, W., Leitão, J. P., & Wani, O. (2021). Is flow control in a space-constrained drainage network effective? A performance assessment for combined sewer overflow reduction. Environmental Research, 202, 111688 (11 pp.). doi:10.1016/j.envres.2021.111688, Institutional Repository

Recurring combined sewer overflows (CSOs) can have a significant impact on the ecological condition of receiving water bodies. There are several structural measures, like adding retention basins and switching to low impact development solutions, that have been proposed to reduce the number of sewage overflows. Besides, several flow control strategies have been discussed in scientific literature that take advantage of the space within urban drainage networks, which is assumed to be adequate, for temporary storage. The adequacy of such storage space, however, is not a universally valid assumption as a large fraction of drainage networks frequently operate close to their design discharge. In this paper, we investigate the efficacy of flow control for a space-constrained drainage network. We employ a low-cost, heuristic real time control strategy with the use of flow control devices (FCDs) and available in-sewer space to reduce the magnitude of CSOs. We consider the performance of the proposed control strategy and discuss the effect of FCD location on CSO reduction. Our results, based on over 300 rainfall-event simulations, show that the flow control strategy using limited sewer capacity is more efficient during relatively small rainfall events, where the CSO is large enough to enable reduction using the chosen control rules. The CSO is reduced, to varying degrees, for around 80% of rainfall events with peak intensity between 10 and 20 mm h−1. For larger rainfall events, the flow control is more unstable in response to abrupt water release during control operation, which seems to be unavoidable because of the water accumulation effect and the transition to pressurized pipe flow in space-constrained networks. We also found that the flow control performance is highly sensitive to the FCD location – as it depends on the interplay of the peak rainfall intensity and the water level condition immediately upstream of the FCD. The efficacy of a location for flow control is determined by the unfilled capacity (i.e., effective in-sewer storage potential) in the pipe upstream of the FCD during the rainfall peak; furthermore, the location also has to be resistant to the water accumulation effect. Using our analysis, we substantiate two anticipated caveats to flow control strategies when the storage space is limited in a drainage network: diminished performance in CSO reduction and the appearance of additional control-related challenges, which are otherwise mitigated in more spacious networks.
Chaudhary, P., D'Aronco, S., Leitão, J. P., Schindler, K., & Wegner, J. D. (2020). Water level prediction from social media images with a multi-task ranking approach. ISPRS Journal of Photogrammetry and Remote Sensing, 167, 252-262. doi:10.1016/j.isprsjprs.2020.07.003, Institutional Repository

Floods are among the most frequent and catastrophic natural disasters and affect millions of people worldwide. It is important to create accurate flood maps to plan (offline) and conduct (real-time) flood mitigation and flood rescue operations. Arguably, images collected from social media can provide useful information for that task, which would otherwise be unavailable. We introduce a computer vision system that estimates water depth from social media images taken during flooding events, in order to build flood maps in (near) real-time. We propose a multi-task (deep) learning approach, where a model is trained using both a regression and a pairwise ranking loss. Our approach is motivated by the observation that a main bottleneck for image-based flood level estimation is training data: it is difficult and requires a lot of effort to annotate uncontrolled images with the correct water depth. We demonstrate how to efficiently learn a predictor from a small set of annotated water levels and a larger set of weaker annotations that only indicate in which of two images the water level is higher, and are much easier to obtain. Moreover, we provide a new dataset, named DEEPFLOOD, with 8145 annotated ground-level images, and show that the proposed multi-task approach can predict the water level from a single, crowd-sourced image with ≈11 cm root mean square error.
Cheng, T., Xu, Z., Yang, H., Hong, S., & Leitao, J. P. (2020). Analysis of effect of rainfall patterns on urban flood process by coupled hydrological and hydrodynamic modeling. Journal of Hydrologic Engineering, 25(1), 04019061 (14 pp.). doi:10.1061/(ASCE)HE.1943-5584.0001867, Institutional Repository

Urban flooding poses an increasing threat to citizens and property and has become a global challenge. The primary cause of urban flooding is rapid urbanization, which is outpacing infrastructure development and drainage system improvements. This paper utilizes a verified flood model that couples hydrological and hydrodynamic processes to investigate the flood response under rainfall events with different patterns. A sponge city pilot area in China is taken as a case study. Drainage system performance, surface inundation patterns, and relation between them are investigated by carrying out statistical analysis and Pearson correlation analysis, respectively. Results show that with increases in the rainfall recurrence interval (RRI) and peak position ratio (PPR), drainage system performance indicators (DSPIs) generally become worse, and the total inundation area (TIA) and surface inundation areas of larger depths become larger. The response time exhibits varied patterns but generally decreases with increasing recurrence intervals and peak ratios. For surface inundation, the recurrence interval presents an increasingly significant role compared with the peak ratio as rainfall becomes heavier. Compared with other DSPIs, the volume of overflowed manholes (VOMs) shows a delayed response to rainfall and has a stronger relationship with the inundation areas with greater water depths, which indicates a possible solution of utilizing manhole storage for water management and flood control. Analyzing the response of drainage systems and flood patterns to different rainfall events using a model coupling hydrological and hydrodynamic processes comprehensively reveals the specific problems of the study area and possible innovative solutions. The analytical method and knowledge gained can help support urban flood management in China and around the world.
Moy de Vitry, M., & Leitão, J. P. (2020). The potential of proxy water level measurements for calibrating urban pluvial flood models. Water Research, 175, 115669 (14 pp.). doi:10.1016/j.watres.2020.115669, Institutional Repository

Urban pluvial flood models need to be calibrated with data from actual flood events in order to validate and improve model performance. Due to the lack of conventional sensor solutions, alternative sources of data such as citizen science, social media, and surveillance cameras have been proposed in literature. Some of the methods proposed boast high scalability but without an on-site survey, they can only provide proxy measurements for physical flooding variables (such as water level). In this study, the potential value of such proxy measurements was evaluated by calibrating an urban pluvial flood model with data from experimental flood events conducted in a 25 × 25 m facility, monitored with surveillance cameras and conventional sensors in parallel. Both ideal proxy data and actual image-based proxy measurements with noise were tested, and the effects of measurement location and measurement noise were investigated separately. The results with error-free proxy data confirm the theoretic potential of such measurements, as in half of the calibration configurations tested, ideal proxy data increases model performance by at least 70% compared to sensor data. However, image-based proxy data can contain complex correlated errors, which have a complex and predominantly negative effect on performance.
Blumensaat, F., Leitão, J. P., Ort, C., Rieckermann, J., Scheidegger, A., Vanrolleghem, P. A., & Villez, K. (2019). How urban storm- and wastewater management prepares for emerging opportunities and threats: digital transformation, ubiquitous sensing, new data sources, and beyond – a horizon scan. Environmental Science and Technology, 53(15), 8488-8498. doi:10.1021/acs.est.8b06481, Institutional Repository

Ubiquitous sensing will create many opportunities and threats for urban water management, which are only poorly understood today. To identify the most relevant trends, we conducted a horizon scan regarding how ubiquitous sensing will shape the future of urban drainage and wastewater management. Our survey of the international urban water community received an active response from both the academics and the professionals from the water industry. The analysis of the responses demonstrates that emerging topics for urban water will often involve experts from different communities, including aquatic ecologists, urban water system engineers and managers, as well as information and communications technology professionals and computer scientists. Activities in topics that are identified as novel will either require (i) cross-disciplinary training, such as importing new developments from the IT sector, or (ii) research in new areas for urban water specialists, for example, to help solve open questions in aquatic ecology. These results are, therefore, a call for interdisciplinary research beyond our own discipline. They also demonstrate that the water management community is not yet prepared for the digital transformation, where we will experience a data demand, i.e. a “pull” of urban water data into external services. The results suggest that a lot remains to be done to harvest the upcoming opportunities. Horizon scanning should be repeated on a routine basis, under the umbrella of an experienced polling organization.
Boller, D., Moy de Vitry, M., Wegner, J. D., & Leitão, J. P. (2019). Automated localization of urban drainage infrastructure from public-access street-level images. Urban Water Journal, 16(7), 480-493. doi:10.1080/1573062X.2019.1687743, Institutional Repository

Comprehensive management of urban drainage network infrastructure is essential for sustaining the operation of these systems despite stresses from component deterioration, urban densification, and a predicted intensification of rainfall events. In this context, up-to-date and accurate urban drainage network data is key. However, such data is often absent, outdated, or incomplete. In this study, a new approach to localize manhole covers and storm drains, using deep learning to mine publicly available street-level images, is presented, tested, and assessed. Thus, the time-consuming and costly acquisition of the location of these system components can be avoided. The approach is evaluated using 5,000 high-resolution panoramas covering 500 km of public roads in Switzerland. The object detection approach proposed shows good performance and an improvement over state of the art image-based urban drainage infrastructure component detection. While the geographical localization of the detected objects still contains errors, the accuracy achieved is nevertheless sufficient for some applications, e.g. flood risk assessment.
Chaudhary, P., D'Aronco, S., Moy de Vitry, M., Leitão, J. P., & Wegner, J. D. (2019). Flood-water level estimation from social media images. In G. Vosselman, S. J. Oude Elberink, & M. Y. Yang (Eds.), ISPRS annals of the photogrammetry, remote sensing and spatial information sciences: Vol. IV-2/W5. ISPRS geospatial week (pp. 5-12). doi:10.5194/isprs-annals-IV-2-W5-5-2019, Institutional Repository

In the event of a flood, being able to build accurate flood level maps is essential for supporting emergency plan operations. In order to build such maps, it is important to collect observations from the disaster area. Social media platforms can be useful sources of information in this case, as people located in the flood area tend to share text and pictures depicting the current situation. Developing an effective and fully automatized method able to retrieve data from social media and extract useful information in real-time is crucial for a quick and proper response to these catastrophic events. In this paper, we propose a method to quantify flood-water from images gathered from social media. If no prior information about the zone where the picture was taken is available, one possible way to estimate the flood level consists of assessing how much the objects appearing in the image are submerged in water. There are various factors that make this task difficult: i) the precise size of the objects appearing in the image might not be known; ii) flood-water appearing in different zones of the image scene might have different height; iii) objects may be only partially visible as they can be submerged in water. In order to solve these problems, we propose a method that first locates selected classes of objects whose sizes are approximately known, then, it leverages this property to estimate the water level. To prove the validity of this approach, we first build a flood-water image dataset, then we use it to train a deep learning model. We finally show the ability of our trained model to recognize objects and at the same time predict correctly flood-water level.
Moy de Vitry, M. (2019). Public surveillance and the future of urban pluvial flood modelling (Doctoral dissertation). doi:10.3929/ethz-b-000397587, Institutional Repository

Motivation and objective
Urban pluvial flooding is an issue of increasingly critical importance due to climate change and urbanization. However, the numerical models used for flood forecasting and risk mitigation suffer from a pronounced lack of monitoring data, which affects model accuracy. Monitoring data are necessary so the models, which contain undefined parameters, can be calibrated and validated against real flood events. In particular, it is important that the models are able to reproduce flood behavior in and around buildings, where the most damage is caused. However, conventional flow and water level sensors reach their limits in public spaces like streets due to irregular topography, moving obstacles, and the risk of vandalism. It has been suggested that surveillance cameras and social media could provide the necessary surface flooding data at a fraction of the cost of conventional sensors. The objective of this thesis is to explore how trend-like data can be extracted from surveillance footage and assimilated to boost the reliability of urban pluvial flood models. [...]

Motivation und Zielsetzung
Urbane regenbedingte Überschwemmungen sind aufgrund des Klimawandels und der Urbanisierung von immer größerer Bedeutung, aber den numerischen Modellen zur Hochwasservorhersage und Risikominderung mangelt es an Überwachungsdaten, was die Modellgenauigkeit einschränkt. Überwachungsdaten sind notwendig, damit die Modelle, welche unsichere Parameter enthalten, gegen echte Hochwasserereignisse kalibriert und validiert werden können. Insbesondere ist es wichtig, dass die Modelle das Überschwemmungsverhalten in und um Gebäude herum nachbilden können, wo die meisten Schäden verursacht werden. Herkömmliche Strömungs- und Wasserstandsensoren stoßen jedoch im öffentlichen Raum, wie Straßen, aufgrund unregelmäßiger Topographie, beweglicher Hindernisse und der Gefahr von Vandalismus an ihre Grenzen. Deswegen gibt es Interesse für alternative Datenquellen wie Überwachungskameras und soziale Medien, aus denen Oberflächenabflussdaten zu einem Bruchteil der Kosten herkömmlicher Sensoren gewonnen werden könnte. Das Ziel dieser Arbeit ist es, zu untersuchen, wie trendartige Daten aus Überwachungsbildern extrahiert und assimiliert werden können, um die Zuverlässigkeit von Überschwemmungsmodellen zu erhöhen. [...]
Moy de Vitry, M., Kramer, S., Wegner, J. D., & Leitão, J. P. (2019). Scalable flood level trend monitoring with surveillance cameras using a deep convolutional neural network. Hydrology and Earth System Sciences, 23(11), 4621-4634. doi:10.5194/hess-23-4621-2019, Institutional Repository

In many countries, urban flooding due to local, intense rainfall is expected to become more frequent because of climate change and urbanization. Cities trying to adapt to this growing risk are challenged by a chronic lack of surface flooding data that are needed for flood risk assessment and planning. In this work, we propose a new approach that exploits existing surveillance camera systems to provide qualitative flood level trend information at scale. The approach uses a deep convolutional neural network (DCNN) to detect floodwater in surveillance footage and a novel qualitative flood index (namely, the static observer flooding index – SOFI) as a proxy for water level fluctuations visible from a surveillance camera's viewpoint. To demonstrate the approach, we trained the DCNN on 1218 flooding images collected from the Internet and applied it to six surveillance videos representing different flooding and lighting conditions. The SOFI signal obtained from the videos had a 75 % correlation to the actual water level fluctuation on average. By retraining the DCNN with a few frames from a given video, the correlation is increased to 85 % on average. The results confirm that the approach is versatile, with the potential to be applied to a variety of surveillance camera models and flooding situations without the need for on-site camera calibration. Thanks to this flexibility, this approach could be a cheap and highly scalable alternative to conventional sensing methods.
Moy de Vitry, M., Schneider, M. Y., Wani, O., Manny, L., Leitão, J. P., & Eggimann, S. (2019). Smart urban water systems: what could possibly go wrong?. Environmental Research Letters, 14(8), 081001 (4 pp.). doi:10.1088/1748-9326/ab3761, Institutional Repository

Urban water systems are being redefined for a digital age, promising substantial advantages for service users and providers, and for society as a whole. However, beside the much-discussed benefits of smart urban water systems in future smart cities, the transition will also bring unique challenges, particularly with respect to privacy and cybersecurity. A preemptive delineation of these risks and providing appropriate recommendations will help to guide digital transformations of urban water towards sustainable solutions. Faced with emerging risks of digitalization, urban water management needs to look beyond technology while recognizing the central and multifaceted role of research.
In smart city initiatives, urban water systems remain largely out of the digitalization spotlight compared to other types of infrastructure. Oftentimes, the management and planning of urban water systems still follow traditional, steel and concrete-based approaches that treat used water as waste and not as a resource [1]. The need for innovation, however, is significant: the infrastructure, operation, and maintenance cost of urban water systems around the world already ranges in the hundred billion dollars annually and water-related stresses are expected to continue rising. Digitalization could not only increase the flexibility and effectiveness of existing urban water systems, but could also allow for the provisions of new services to society. The envisioned transformation, as outlined for example in the literature [2–4], entails novel data collection and transmission techniques, analytical methods, models, and automation. For example, smart water meter data can be combined with noise loggers to detect and roughly locate leaks in water mains. Together with automated control infrastructure, pressure can be regulated to reduce water losses [4]. By this and numerous other smart solutions, not only water distribution but also sewers and wastewater treatment will be transformed. In particular, digitalization facilitates large-scale implementation of disruptive technologies like decentralized wastewater treatment [5] and direct potable reuse, which will help cities to cope with climate change and urbanization.
However, we argue that as the benefits of smart urban water systems are increasingly explored and showcased in literature, it is time to also give attention to potential risks that might emerge. Recurring data breaches and the growing use of cyber-attacks for geopolitical ends are a reminder that the digitalization of society indeed carries risks. Given the critical role of water services in society and within the water-energy-food nexus, these risks must be identified and managed pro-actively. In the following, we raise awareness and suggest ways forward in approaching the unique privacy and security issues that accompany the digitalization of urban water systems. Finally, we highlight the central role of researchers in assessing and mitigating the potential risks of the smart urban water solutions they propose.
Muñoz, D. F., Simões, N. E., de Sousa, L. M., Maluf, L., Sá Marques, A., & Leitão, J. P. (2019). Generalizing multi-reward functions aimed at identifying the best locations to install flow control devices in sewer systems. Urban Water Journal, 16(8), 564-574. doi:10.1080/1573062X.2019.1700284, Institutional Repository

Multi-criteria decision models have been recently implemented in many urban flood risk management schemes due to the increasing demand of low-cost and reliable solutions to prevent and control overflow from sewer systems. Based on specific targets, these decision models encompass multiple reward (or objective) functions according to socio-economic requirements, vulnerability assessments and physical constraints on existing sewer systems. In this study, we present a simple algorithm to generalize reward functions aimed at locating the best sites to install in-sewer flow control devices, and thus controlling sewer overflow. The algorithm uses the mathematical structure of reward functions previously established, and adjust them based on hydraulic simulation results of two real sewer networks. Our results indicate that a single generalized reward function can efficiently identify strategic locations to guarantee (i) maximum in-sewer storage, (ii) minimum impact of possible flow control device failures and (iii) maximum flow discharge reduction upstream flood-prone urban areas.
Peña-Haro, S., Carrel, M., Lüthi, B., Wang, L., Dicht, S., & Leitão, J. P. (2019). Abflussmessungen mittels Videos. Einsatz von Webcams und Smartphones. Aqua & Gas, 99(10), 42-45. , Institutional Repository

Mit kurzen Videosequenzen von Überwachungskameras und Smartphones können Oberflächengeschwindigkeiten in Abwasserkanälen gemessen werden. Eingesetzt wird dabei die bildbasierte Methode namens Surface Structure Image Velocimetry, kurz SSIV. Die resultierenden Ergebnisse stimmen gut mit Ultraschall-Referenzmessungen überein und unterstreichen das Potenzial der innovativen Methode.
Peña-Haro, S., Lüthi, B., Carrel, M., Scheidegger, A., de Vitry, M. M., & Leitão, J. P. (2019). Es überschwemmt und keiner sieht zu?! Oberflächenabflussmessungen im urbanen Raum mittels Videomaterial von Überwachungskameras. Aqua & Gas, 99(5), 44-50. , Institutional Repository

Messungen von Oberflächenabflüssen werden selten im urbanen Raum durchgeführt, weil traditionelle Messgeräte zu teuer sind oder direkt über oder innerhalb des Fliessgewässers installiert werden müssen. Deswegen sind Daten über Überschwemmungen im urbanen Raum nur selten vorhanden, was die Kalibrierung und Validierung von Überflutungsmodellen erschwert. In dieser Studie wird ein Ansatz vorgestellt, bei dem marktübliche Überwachungskameras zur Durchflussmessung eingesetzt werden.
Tscheikner-Gratl, F., Caradot, N., Cherqui, F., Leitão, J. P., Ahmadi, M., Langeveld, J. G., … Clemens, F. (2019). Sewer asset management - state of the art and research needs. Urban Water Journal, 16(9), 662-675. doi:10.1080/1573062X.2020.1713382, Institutional Repository

Sewer asset management gained momentum and importance in recent years due to economic considerations, since infrastructure maintenance and rehabilitation directly represent major investments. Because physical urban water infrastructure has life expectancies of up to 100 years or more, contemporary urban drainage systems are strongly influenced by historical decisions and implementations. The current decisions taken in sewer asset management will, therefore, have a long-lasting impact on the functionality and quality of future services provided by these networks. These decisions can be supported by different approaches ranging from various inspection techniques, deterioration models to assess the probability of failure or the technical service life, to sophisticated decision support systems crossing boundaries to other urban infrastructure. This paper presents the state of the art in sewer asset management in its manifold facets spanning a wide field of research and highlights existing research gaps while giving an outlook on future developments and research areas.
Amado, C., Carvalho, G., Brito, R. S., Coelho, S. T., & Leitão, J. P. (2018). Analysing the importance of variables for sewer failure prediction. Urban Water Journal, 15(4), 338-345. doi:10.1080/1573062X.2018.1459748, Institutional Repository

When defining the variables to predict sewer failure and therefore optimise sewer systems maintenance, it is important to identify the ones that most significantly influence the quality of the predictions or to define the smallest number of variables that is sufficient to obtain accurate predictions. In this study, three different statistical variable selection algorithms are applied for the first time to identify the most important variables for sewer failure prediction: the mutual information indicator, the out-of-bag samples concept, based on the random forest algorithm, and the stepwise search approach. The methods were applied to a real data-set that consists of the categorisation of sewer condition and associated physical characteristics. The mutual information and the stepwise search methods provided good predictions while those obtained using out-of-bag samples based on random forest were somewhat different, justified by the lack of robustness to imbalanced class distributions.
Boller, D., Moy de Vitry, M., Wegner, J. D., & Leitão, J. P. (2018). Automatisierte Erfassung von Siedlungsentwässerungsinfrastruktur mittels Strassenbildern und eines künstlichen neuronalen Netzwerks. In T. G. Schmitt (Ed.), Schriftenreihe Wasser Infrastruktur Ressourcen: Vol. 1. Regenwasser in urbanen Räumen. aqua urbanica trifft RegenwasserTage 2018. Tagungsband (pp. 251-254). Kaiserslautern: Institut Wasser Infrastruktur Ressourcen. , Institutional Repository

Ein künstliches neuronales Netzwerk wurde darauf trainiert, Schachtdeckel und Einlaufschächte in sehr hochauflösenden Google Street View-Panoramen zu detektieren. Die Standorte der detektierten Objekte werden anschliessend anhand der Panorama-Metadaten und Annahmen über die Datenerhebung sowie das umgebende Gelände approximiert. Durch die Nutzung bereits gesammelter Daten ist der Ansatz kostengünstig und in Regionen, in denen Google Street View verfügbar ist, leicht umsetzbar.
Leitão, J. P., Peña, S., Lüthi, B., & Moy de Vitry, M. (2018). Automatisierte Erfassung von Siedlungsentwässerungsinfrastruktur mittels Strassenbildern und eines künstlichen neuronalen Netzwerks. In T. G. Schmitt (Ed.), Schriftenreihe Wasser Infrastruktur Ressourcen: Vol. 1. Regenwasser in urbanen Räumen. aqua urbanica trifft RegenwasserTage 2018. Tagungsband (pp. 269-272). Kaiserslautern: Institut Wasser Infrastruktur Ressourcen. , Institutional Repository

Oberflächenabflüsse im urbanen Raum werden selten gemessen und fast nie für die Validierung von Siedlungsentwässerungmodellen verwendet. In dieser Studie wird vorgeführt, wie die Fliessgeschwindigkeit von Oberflächenabflüssen ausschließlich mit Videomaterial von Überwachungskameras und ohne Zusatz von Tracking-Partikeln ermittelt werden kann.
Leitão, J. P., Carbajal, J. P., Rieckermann, J., Simões, N. E., Sá Marques, A., & de Sousa, L. M. (2018). Identifying the best locations to install flow control devices in sewer networks to enable in-sewer storage. Journal of Hydrology, 556, 371-383. doi:10.1016/j.jhydrol.2017.11.020, Institutional Repository

The activation of available in-sewer storage volume has been suggested as a low-cost flood and combined sewer overflow mitigation measure. However, it is currently unknown what the attributes for suitable objective functions to identify the best location for flow control devices are and the impact of those attributes on the results. In this study, we present a novel location model and efficient algorithm to identify the best location(s) to install flow limiters. The model is a screening tool that does not require hydraulic simulations but rather considers steady state instead of simplistic static flow conditions. It also maximises in-sewer storage according to different reward functions that also considers the potential impact of flow control device failure. We demonstrate its usefulness on two real sewer networks, for which an in-sewer storage potential of approximately 2,000 m3 and 500 m3 was estimated with five flow control devices installed.
Leitão, J. P., & de Sousa, L. M. (2018). Towards the optimal fusion of high-resolution Digital Elevation Models for detailed urban flood assessment. Journal of Hydrology, 561, 651-661. doi:10.1016/j.jhydrol.2018.04.043, Institutional Repository

Newly available, more detailed and accurate elevation data sets, such as Digital Elevation Models (DEMs) generated on the basis of imagery from terrestrial LiDAR (Light Detection and Ranging) systems or Unmanned Aerial Vehicles (UAVs), can be used to improve flood-model input data and consequently increase the accuracy of the flood modelling results. This paper presents the first application of the MBlend merging method and assesses the impact of combining different DEMs on flood modelling results. It was demonstrated that different raster merging methods can have different and substantial impacts on these results. In addition to the influence associated with the method used to merge the original DEMs, the magnitude of the impact also depends on (i) the systematic horizontal and vertical differences of the DEMs, and (ii) the orientation between the DEM boundary and the terrain slope. The greater water depth and flow velocity differences between the flood modelling results obtained using the reference DEM and the merged DEMs ranged from −9.845 to 0.002 m, and from 0.003 to 0.024 m s−1 respectively; these differences can have a significant impact on flood hazard estimates. In most of the cases investigated in this study, the differences from the reference DEM results were smaller for the MBlend method than for the results of the two conventional methods. This study highlighted the importance of DEM merging when conducting flood modelling and provided hints on the best DEM merging methods to use.
Leitão, J. P., Peña-Haro, S., Lüthi, B., Scheidegger, A., & Moy de Vitry, M. (2018). Urban overland runoff velocity measurement with consumer-grade surveillance cameras and surface structure image velocimetry. Journal of Hydrology, 565, 791-804. doi:10.1016/j.jhydrol.2018.09.001, Institutional Repository

Physically-based models are important tools for evaluating the hydraulic behaviour of urban drainage systems and, more specifically, assessing flood risk. While it is well known that such models should be calibrated and validated with monitoring data, overland runoff information is seldom available for this purpose. This study investigates the potential of using surveillance camera footage to measure surface flow velocity thanks to an LSPIV-based method called Surface Structure Image Velocimetry (SSIV). Seven real-scale experiments conducted in a specialized flood training facility were used to test the SSIV method under varied and challenging conditions. SSIV performance was evaluated by benchmarking bulk (mean) velocity against that measured by a conventional sensor array. In the best conditions tested, SSIV and conventional flow sensors differed by only 1.7% (0.1% standard deviation). While the method proved sensitive to light conditions, our results suggest that infrared lighting could be used to increase measurement consistency. Our study concludes that for measuring overland flow velocity in urban areas, surveillance and traffic cameras can be considered as a low-maintenance and easy-to-install alternative to conventional sensor systems.
Moreira de Sousa, L., & Leitão, J. P. (2018). HexASCII: a file format for cartographical hexagonal rasters. Transactions in GIS, 22(1), 217-232. doi:10.1111/tgis.12304, Institutional Repository

Hexagonal segmentations of space have long been known for their advantages vis à vis squared partitions in discretizing spatial variables, be it natural phenomena or human-related features. However, readily available and easy-to-use tools to manipulate and interact with hexagonal rasters remain widely unavailable today. This article presents a first step to enable the use of hexagonal rasters in the GIS field. A format to encode cartographical hexagonal meshes as simple ASCII files is specified through a context-free grammar. Named HexASCII, this file format provides a simple means of storing and sharing such rasters. A set of simple tools based on the HexASCII format is presented, allowing their creation and basic interaction with traditional GIS software.
Moreira de Sousa, L., & Leitão, J. P. (2018). Improvements to DEM merging with r.mblend. In C. Grueau, R. Laurini, & L. Ragia (Eds.), Proceedings of the 4th international conference on geographical information systems theory, applications and management (pp. 42-49). doi:10.5220/0006672500420049, Institutional Repository

r.mblend is an implementation of the MBlend method for merging Digital Elevation Models (DEMs). This method produces smooth transitions between contiguous DEMs of different spatial resolution, for instance, when acquired by different sensors. r.mblend is coded on the Python API provided by the Geographic Resources Analysis Support System (GRASS), being fully integrated in that GIS software. It introduces improvements to the original method and provides the user with various parameters to fine tune the merging procedure. This article showcases the main differences between r.mblend and two conventional DEM merge methods: Cover and Average.
Moy de Vitry, M., Schindler, K., Rieckermann, J., & Leitão, J. P. (2018). Sewer inlet localization in UAV image clouds: improving performance with multiview detection. Remote Sensing, 10(5), 706 (18 pp.). doi:10.3390/rs10050706, Institutional Repository

Sewer and drainage infrastructure are often not as well catalogued as they should be, considering the immense investment they represent. In this work, we present a fully automatic framework for localizing sewer inlets from image clouds captured from an unmanned aerial vehicle (UAV). The framework exploits the high image overlap of UAV imaging surveys with a multiview approach to improve detection performance. The framework uses a Viola–Jones classifier trained to detect sewer inlets in aerial images with a ground sampling distance of 3–3.5 cm/pixel. The detections are then projected into three-dimensional space where they are clustered and reclassified to discard false positives. The method is evaluated by cross-validating results from an image cloud of 252 UAV images captured over a 0.57-km2 study area with 228 sewer inlets. Compared to an equivalent single-view detector, the multiview approach improves both recall and precision, increasing average precision from 0.65 to 0.73. The source code and case study data are publicly available for reuse.
Carbajal, J. P., Leitão, J. P., Albert, C., & Rieckermann, J. (2017). Appraisal of data-driven and mechanistic emulators of nonlinear simulators: the case of hydrodynamic urban drainage models. Environmental Modelling and Software, 92, 17-27. doi:10.1016/j.envsoft.2017.02.006, Institutional Repository

System identification, sensitivity analysis, optimization and control, require a large number of model evaluations. Accurate simulators are too slow for these applications. Fast emulators provide a solution to this efficiency demand, sacrificing unneeded accuracy for speed. There are many strategies for developing emulators but selecting one remains subjective. Herein we compare the performance of two kinds of emulators: mechanistic emulators that use knowledge of the simulator's equations, and purely data-driven emulators using matrix factorization. We borrow simulators from urban water management, because more stringent performance criteria on water utilities have made emulation a crucial tool within this field. Results suggest that naive data-driven emulation outperforms mechanistic emulation. We discuss scenarios in which mechanistic emulation seems favorable for extrapolation in time and dealing with sparse and unevenly sampled data. We also point to advances in Machine Learning that have not permeated yet into the environmental science community.
Leitão, J. P., Simões, N. E., Pina, R. D., Ochoa-Rodriguez, S., Onof, C., & Sá Marques, A. (2017). Stochastic evaluation of the impact of sewer inlets’ hydraulic capacity on urban pluvial flooding. Stochastic Environmental Research and Risk Assessment, 31(8), 1907-1922. doi:10.1007/s00477-016-1283-x, Institutional Repository

Sewer inlet structures are vital components of urban drainage systems and their operational conditions can largely affect the overall performance of the system. However, their hydraulic behaviour and the way in which it is affected by clogging is often overlooked in urban drainage models, thus leading to misrepresentation of system performance and, in particular, of flooding occurrence. In the present paper, a novel methodology is proposed to stochastically model stormwater urban drainage systems, taking the impact of sewer inlet operational conditions (e.g. clogging due to debris accumulation) on urban pluvial flooding into account. The proposed methodology comprises three main steps: (i) identification of sewer inlets most prone to clogging based upon a spatial analysis of their proximity to trees and evaluation of sewer inlet locations; (ii) Monte Carlo simulation of the capacity of inlets prone to clogging and subsequent simulation of flooding for each sewer inlet capacity scenario, and (iii) delineation of stochastic flood hazard maps. The proposed methodology was demonstrated using as case study design storms as well as two real storm events observed in the city of Coimbra (Portugal), which reportedly led to flooding in different areas of the catchment. The results show that sewer inlet capacity can indeed have a large impact on the occurrence of urban pluvial flooding and that it is essential to account for variations in sewer inlet capacity in urban drainage models. Overall, the stochastic methodology proposed in this study constitutes a useful tool for dealing with uncertainties in sewer inlet operational conditions and, as compared to more traditional deterministic approaches, it allows a more comprehensive assessment of urban pluvial flood hazard, which in turn enables better-informed flood risk assessment and management decisions.
Moreira de Sousa, L., & Leitão, J. P. (2017). Hex-utils: a tool set supporting HexASCII hexagonal rasters. In L. Ragia, J. G. Rocha, & R. Laurini (Eds.), Proceedings of the 3rd international conference on geographical information systems theory, applications and management (pp. 177-183). doi:10.5220/0006275801770183, Institutional Repository

The advantages of hexagonal meshes over squared grids in discretising spatial variables have been known for long. Notwithstanding, the raster data formats used in geo-spatial disciplines to this purpose are still today almost exclusively reliant on squared grids. The HexASCII file format is a core element in an attempt to introduce hexagonal rasters to mainstream GIS, defining a simple vehicle to store and share such data structures. This article describes the hex-utils tool-kit, an Application Programming Interface (API) and a set of command line tools enabling the use of HexASCII rasters. Basic operations are supported: creation of new hexagonal rasters from different inputs and transformation into file formats readable by desktop GIS programmes. The API sets a framework for the development of urther functionality.
Moy de Vitry, M., Dicht, S., & Leitão, J. P. (2017). floodX: urban flash flood experiments monitored with conventional and alternative sensors. Earth System Science Data, 9(2), 657-666. doi:10.5194/essd-9-657-2017, Institutional Repository

The data sets described in this paper provide a basis for developing and testing new methods for monitoring and modelling urban pluvial flash floods. Pluvial flash floods are a growing hazard to property and inhabitants’ well-being in urban areas. However, the lack of appropriate data collection methods is often cited as an impediment for reliable flood modelling, thereby hindering the improvement of flood risk mapping and early warning systems. The potential of surveillance infrastructure and social media is starting to draw attention for this purpose. In the floodX project, 22 controlled urban flash floods were generated in a flood response training facility and monitored with state-of-the-art sensors as well as standard surveillance cameras. With these data, it is possible to explore the use of video data and computer vision for urban flood monitoring and modelling. The floodX project stands out as the largest documented flood experiment of its kind, providing both conventional measurements and video data in parallel and at high temporal resolution. The data set used in this paper is available at https://doi.org/10.5281/zenodo.830513.
Santos, P., Amado, C., Coelho, S. T., & Leitão, J. P. (2017). Stochastic data mining tools for pipe blockage failure prediction. Urban Water Journal, 14(4), 343-353. doi:10.1080/1573062X.2016.1148178, Institutional Repository

Failure prediction plays an important role in the management of urban water systems infrastructures. An accurate description of the deterioration of urban drainage systems is essential for optimal investment and rehabilitation planning. In the study presented in this paper, a new method to predict sewer pipe failure based on robust decision trees is proposed. Five other different stochastic failure prediction models – the non-homogeneous Poisson process, the zero-inflated non-homogeneous Poisson process, classical decision tress (CART and Random Forest algorithms), the Weibull accelerated lifetime model and the linear extended Yule process – are also implemented and explored in order to identify models that combine good failure prediction results with robustness. The six models were tested on the asset register and pipe failure register of a large US wastewater utility; only pipe blockage failures were considered in this study. The linear extended Yule process and the zero-inflated non-homogeneous Poisson process presented the overall best results throughout the models’ comparison, showing a good ability to detect pipes with high likelihood of blockage failure. Decision trees based on robust random forests only detected pipes with high likelihood of failure when considering a short-term prediction window; the accuracy of the predictions was one of the best when using the robust decision tree model. The Weibull accelerated lifetime model provided some of the best medium-term predictions but performed less well for shorter prediction windows.
Torres, M. N., Rodríguez, J. P., & Leitão, J. P. (2017). Geostatistical analysis to identify characteristics involved in sewer pipes and urban tree interactions. Urban Forestry and Urban Greening, 25, 36-42. doi:10.1016/j.ufug.2017.04.013, Institutional Repository

Tree roots cause significant and costly damage to sewer systems. However, the contributions made by tree and sewer characteristics to sewer system damage are not yet well understood. Previous research has proved inconclusive and there is a lack of agreement on the importance of the variables involved, which means that the results cannot be extrapolated globally. This study presents a methodology to improve the understanding of tree root-sewer conflicts through a geostatistical analysis of a tree inventory and CCTV video fault reports. The methodology is applied to a 11 km2 case study in Bogotá, Colombia. The analysis used tree and sewer pipe georeferenced data, principal component analysis, and linear, Logit, and Poisson regression models. The proposed methodology identifies the pipe characteristics and the tree species most responsible for the root intrusion events into sewers. As expected, larger trees are prone to cause more pipe damage; therefore tree-pipe distance is a relevant parameter control for reducing potential deterioration. Cumulative precipitation and pipe length showed no effect on observed root intrusion events, and pipes made from brick had higher odds to present root intrusion in contrast with concrete pipes. The presented methodology uses readily available information and software, and can be modified depending on the requirements of each particular case study. This approach will therefore allow for more efficient use of costly, site-specific pipe investigations, and is especially useful for cases where there is a general lack of knowledge regarding the characteristics that favour the negative interactions between pipes and tree roots.
de Oliveira Girão, L. F., da Cruz Simões, N. E., Almeida de Sá Marques, J. A., Correia Leitão, J. P., & Pina, R. D. (2017). Modelação hidráulica e de qualidade da água dos sistemas de drenagem em meios urbanos. Hydraulic and water quality modelling of urban drainage systems. Engenharia Sanitária e Ambiental, 22(2), 351-360. doi:10.1590/s1413-41522016161318, Institutional Repository

Urban floods are becoming more frequent. Thus, the European Union published the Directive 2007/60/CE to mitigate costs related with this phenomenon and to impose limits on the concentration of pollutants in pluvial water. The purpose of this study was to present the modelling of drainage systems in flood situations, based on the software of the United States Environmental Protection Agency (EPA), the Storm Water Management Model (SWMM), in which the study case is to analyze a unitary urban drainage system of Zona Central catchment in Coimbra, Portugal. By using the Automatic Overland Flow Delineation (AOFD) methodology for the generation of a superficial drainage network and implementing it in the SWMM, it was obtained a dual drainage model that allows the flow analysis in flood conditions, including flow control between the surface and collectors network and also modeling of water quality at the surface. This model allows quantifying the pollution load at the surface, relatively to the parameter of total suspended solids, for any extreme rainfall event.
FitzGerald, D. V. (2016). Taking into account future uncertainty when designing urban water supply systems: a flexible approach (Master thesis). 59 p. , Institutional Repository

Water supply networks have to be designed while taking into account the long-term future water demand. Given the difficulties in estimating the future water demand, a flexible approach for planning water supply systems was implemented. The flexibility in engineering design approach (de Neufville and Scholtes, 2011) is a procedure for designing systems in the face of an uncertain future. This approach was applied to a fictitious town, which is expected to expand in the near future and will need to extend its water supply network to the new areas.
To model the uncertain future water demand, 1000 scenarios were generated by randomly projecting the population of the town. A decision rule, which governs when the network must be modified, was defined based on the pressure that is required at the nodes of the network. Four different design alternatives were tested: the deterministic design, which is completely built in advance based on one single scenario, and three flexible designs, which consist in expanding the network as the water demand changes.
The design alternatives were simulated using the hydraulic solver EPANET and were evaluated in terms of costs, using the specific net present value, and in terms of performance based on the pressure and residence time of water in the network. The results showed that the flexible design alternatives provide a significant decrease in the specific costs compared to the deterministic design, thus demonstrating the value of flexible designs. By evaluating the designs over a range of water demand scenarios, different results were obtained compared to the case where only one scenario was used. This showed that the flexibility in engineering design approach is a helpful tool for designing water supply networks in the context of an uncertain future.
Keller, C. (2016). Understanding the urban drainage system of Fehraltorf. Enhancing the reliability of Fehraltorf’s SWMM model through calibration (Master thesis). 30 p. , Institutional Repository

The hydraulic behavior and the capacity of sewer systems are assessed through hydrodynamic modeling. They are widely used in drainage planning, although their parameters are mostly estimated and the models are only checked for general plausibility. The Master‘s Thesis assessed the effect of calibration on the model reliability on the basis of a case study, namely Fehraltorf.
Fehraltorf is located in the agglomeration of Zurich and Winterthur and is inhabited by 6’292 people. Most of the village of Russikon and Fehraltorf are connected to the WWTP of Fehraltorf. The DWF amounts up to 66 l/s, whereas the residual flow Q347 of the main receiving water (Luppmen) is 72 l/s. The infiltration of the groundwater is 30.1 l/s, as a significant share of the drainage system was built below the average groundwater table.
During the thesis the conversion of the Mike Urban model to SWMM was revised and further adjustments were implemented. The data for input and calibration was chosen depending on its reliability and further processed if necessary. Rain events were selected and split for calibration and validation. Parameters known to be changed in the calibrations were selected and in the sensitivity analysis the most sensitive, and thus, important parameters were determined. Then, the calibration was conducted manually as well as automatically with simulated annealing. The effect of calibration was assessed for the calibration and validation events visually and with various objective functions, viz. Nash-Sutcliffe Efficiency, total volume, peak flow and time to peak. The hydraulic performance of the sewer system was tested by simulating a 10-year design rainfall event in the uncalibrated and the calibrated model.
For the simulations, the data of the rain gauge on the WWTP had to be discarded because it showed high deviations to the ones installed by EAWAG. The rainfall data and flow data (of the FloDars) collected by EAWAG were assessed to be reliable, but as the measurements were installed recently, only four rain events were available for calibration and validation. The objective functions could be raised to a satisfying level in the manual calibration and were further improved in the automatic calibration. The validation confirmed that the reliability of the model could be increased with calibration. Furthermore, the assessment of the sewer system revealed that there are less capacity limits in the calibrated model then in the uncalibrated one, but further adjustments are needed due to numerical instabilities.
Even though the validation suggests that manual as well as automatic calibration enhance the reliability of the model because of improved goodness of fit assessed by different objective functions, further input data and reliable calibration data is needed to perform the calibration once more.
After all, calibration is strongly recommended by the author of this thesis to not only improve parameter values which were only estimated in the uncalibrated models but also to detect systematic errors in the data and the model structure.
Leitão, J. P., Moy de Vitry, M., Scheidegger, A., & Rieckermann, J. (2016). Assessing the quality of digital elevation models obtained from mini unmanned aerial vehicles for overland flow modelling in urban areas. Hydrology and Earth System Sciences, 20(4), 1637-1653. doi:10.5194/hess-20-1637-2016, Institutional Repository

Precise and detailed digital elevation models (DEMs) are essential to accurately predict overland flow in urban areas. Unfortunately, traditional sources of DEM, such as airplane light detection and ranging (lidar) DEMs and point and contour maps, remain a bottleneck for detailed and reliable overland flow models, because the resulting DEMs are too coarse to provide DEMs of sufficient detail to inform urban overland flows. Interestingly, technological developments of unmanned aerial vehicles (UAVs) suggest that they have matured enough to be a competitive alternative to satellites or airplanes. However, this has not been tested so far. In this study we therefore evaluated whether DEMs generated from UAV imagery are suitable for urban drainage overland flow modelling. Specifically, 14 UAV flights were conducted to assess the influence of four different flight parameters on the quality of generated DEMs: (i) flight altitude, (ii) image overlapping, (iii) camera pitch, and (iv) weather conditions. In addition, we compared the best-quality UAV DEM to a conventional lidar-based DEM. To evaluate both the quality of the UAV DEMs and the comparison to lidar-based DEMs, we performed regression analysis on several qualitative and quantitative metrics, such as elevation accuracy, quality of object representation (e.g. buildings, walls and trees) in the DEM, which were specifically tailored to assess overland flow modelling performance, using the flight parameters as explanatory variables. Our results suggested that, first, as expected, flight altitude influenced the DEM quality most, where lower flights produce better DEMs; in a similar fashion, overcast weather conditions are preferable, but weather conditions and other factors influence DEM quality much less. Second, we found that for urban overland flow modelling, the UAV DEMs performed competitively in comparison to a traditional lidar-based DEM. An important advantage of using UAVs to generate DEMs in urban areas is their flexibility that enables more frequent, local, and affordable elevation data updates, allowing, for example, to capture different tree foliage conditions.
Leitão, J. P., Prodanović, D., & Maksimović, Č. (2016). Improving merge methods for grid-based digital elevation models. Computers and Geosciences, 88, 115-131. doi:10.1016/j.cageo.2016.01.001, Institutional Repository

Digital Elevation Models (DEMs) are used to represent the terrain in applications such as, for example, overland flow modelling or viewshed analysis. DEMs generated from digitising contour lines or obtained by LiDAR or satellite data are now widely available. However, in some cases, the area of study is covered by more than one of the available elevation data sets. In these cases the relevant DEMs may need to be merged. The merged DEM must retain the most accurate elevation information available while generating consistent slopes and aspects. In this paper we present a thorough analysis of three conventional grid-based DEM merging methods that are available in commercial GIS software. These methods are evaluated for their applicability in merging DEMs and, based on evaluation results, a method for improving the merging of grid-based DEMs is proposed. DEMs generated by the proposed method, called MBlend, showed significant improvements when compared to DEMs produced by the three conventional methods in terms of elevation, slope and aspect accuracy, ensuring also smooth elevation transitions between the original DEMs. The results produced by the improved method are highly relevant different applications in terrain analysis, e.g., visibility, or spotting irregularities in landforms and for modelling terrain phenomena, such as overland flow.
Leitão, J. P., Coelho, S. T., Alegre, H., Cardoso, M. A., Silva, M. S., Ramalho, P., … Carriço, N. (2016). Moving urban water infrastructure asset management from science into practice. Urban Water Journal, 13(2), 133-141. doi:10.1080/1573062X.2014.939092, Institutional Repository

iGPI, the National Initiative for Infrastructure Asset Management is a Portuguese collaborative project led by LNEC (National Civil Engineering Laboratory, Portugal) through which 19 water utilities develop their own infrastructure asset management (IAM) systems and plans in a joint training and capacitation programme. Technical assistance to the participating utilities is ensured by LNEC, IST (Technical University of Lisbon) and Addition, a software development company. The water utilities get collective as well as one-on-one support and specific training. They benefit from networking with the other utilities in a common and simultaneous process, with similar difficulties and challenges, leading to an effective sharing of solutions. The developed products, including training materials, templates and guidelines for developing strategic and tactical IAM plans, are available to the general public. This project has greatly contributed to the establishment of reference methodologies and standards for IAM planning, in a range of utilities of widely diverse size and context, effectively defining an accepted best practice. This paper discusses the project's format and its advantages, and goes on to describe the main outcomes, including selected cases and final products.
Scheidegger, A., Leitão, J. P., & Scholten, L. (2015). Statistical failure models for water distribution pipes – a review from a unified perspective. Water Research, 83, 237-247. doi:10.1016/j.watres.2015.06.027, Institutional Repository

This review describes and compares statistical failure models for water distribution pipes in a systematic way and from a unified perspective. The way the comparison is structured provides the information needed by scientists and practitioners to choose a suitable failure model for their specific needs.
The models are presented in a novel framework consisting of: 1) Clarification of model assumptions. The models originally formulated in different mathematical forms are all presented as failure rate. This enables to see differences and similarities across the models. Furthermore, we present a new conceptual failure rate that an optimal model would represent and to which the failure rate of each model can be compared. 2) Specification of the detailed data assumptions required for unbiased model calibration covering the structure and completeness of the data. 3) Presentation of the different types of probabilistic predictions available for each model.
Nine different models and their variations or further developments are presented in this review. For every model an overview of its applications published in scientific journals and the available software implementations is provided.
The unified view provides guidance to model selection. Furthermore, the model comparison presented herein enables to identify areas where further research is needed.
Simões, N. E., Ochoa-Rodríguez, S., Wang, L. P., Pina, R. D., Marques, A. S., Onof, C., & Leitão, J. P. (2015). Stochastic urban pluvial flood hazard maps based upon a spatial-temporal rainfall generator. Water, 7(7), 3396-3406. doi:10.3390/w7073396, Institutional Repository

It is a common practice to assign the return period of a given storm event to the urban pluvial flood event that such storm generates. However, this approach may be inappropriate as rainfall events with the same return period can produce different urban pluvial flooding events, i.e., with different associated flood extent, water levels and return periods. This depends on the characteristics of the rainfall events, such as spatial variability, and on other characteristics of the sewer system and the catchment. To address this, the paper presents an innovative contribution to produce stochastic urban pluvial flood hazard maps. A stochastic rainfall generator for urban-scale applications was employed to generate an ensemble of spatially—and temporally—variable design storms with similar return period. These were used as input to the urban drainage model of a pilot urban catchment (~9 km2) located in London, UK. Stochastic flood hazard maps were generated through a frequency analysis of the flooding generated by the various storm events. The stochastic flood hazard maps obtained show that rainfall spatial-temporal variability is an important factor in the estimation of flood likelihood in urban areas. Moreover, as compared to the flood hazard maps obtained by using a single spatially-uniform storm event, the stochastic maps generated in this study provide a more comprehensive assessment of flood hazard which enables better informed flood risk management decisions.
Tokarczyk, P., Leitao, J. P., Rieckermann, J., Schindler, K., & Blumensaat, F. (2015). High-quality observation of surface imperviousness for urban runoff modelling using UAV imagery. Hydrology and Earth System Sciences, 19(10), 4215-4228. doi:10.5194/hess-19-4215-2015, Institutional Repository

Modelling rainfall–runoff in urban areas is increasingly applied to support flood risk assessment, particularly against the background of a changing climate and an increasing urbanization. These models typically rely on high-quality data for rainfall and surface characteristics of the catchment area as model input.
While recent research in urban drainage has been focusing on providing spatially detailed rainfall data, the technological advances in remote sensing that ease the acquisition of detailed land-use information are less prominently discussed within the community. The relevance of such methods increases as in many parts of the globe, accurate land-use information is generally lacking, because detailed image data are often unavailable. Modern unmanned aerial vehicles (UAVs) allow one to acquire high-resolution images on a local level at comparably lower cost, performing on-demand repetitive measurements and obtaining a degree of detail tailored for the purpose of the study.
In this study, we investigate for the first time the possibility of deriving high-resolution imperviousness maps for urban areas from UAV imagery and of using this information as input for urban drainage models. To do so, an automatic processing pipeline with a modern classification method is proposed and evaluated in a state-of-the-art urban drainage modelling exercise. In a real-life case study (Lucerne, Switzerland), we compare imperviousness maps generated using a fixed-wing consumer micro-UAV and standard large-format aerial images acquired by the Swiss national mapping agency (swisstopo). After assessing their overall accuracy, we perform an end-to-end comparison, in which they are used as an input for an urban drainage model. Then, we evaluate the influence which different image data sources and their processing methods have on hydrological and hydraulic model performance. We analyse the surface runoff of the 307 individual subcatchments regarding relevant attributes, such as peak runoff and runoff volume. Finally, we evaluate the model's channel flow prediction performance through a cross-comparison with reference flow measured at the catchment outlet.
We show that imperviousness maps generated from UAV images processed with modern classification methods achieve an accuracy comparable to standard, off-the-shelf aerial imagery. In the examined case study, we find that the different imperviousness maps only have a limited influence on predicted surface runoff and pipe flows, when traditional workflows are used. We expect that they will have a substantial influence when more detailed modelling approaches are employed to characterize land use and to predict surface runoff. We conclude that UAV imagery represents a valuable alternative data source for urban drainage model applications due to the possibility of flexibly acquiring up-to-date aerial images at a quality compared with off-the-shelf image products and a competitive price at the same time. We believe that in the future, urban drainage models representing a higher degree of spatial detail will fully benefit from the strengths of UAV imagery.
Tokarczyk, P., Leitao, J. P., Rieckermann, J., Schindler, K., & Blumensaat, F. (2015). Nutzung von Drohnen und Luftbildern in der Siedlungswasserwirtschaft. Geomatik Schweiz, Géomatique Suisse, Geomatica Svizzera, 113(9), 346-350. doi:10.5169/seals-513919, Institutional Repository

Vor dem Hintergrund von zunehmender Urbanisierung, Klimawandel und alternder Infrastrukturen gewinnt die Analyse und Bewertung von Überflutungen im urbanen Raum aufgrund von Starkregenereignissen zunehmend an Bedeutung. Dazu sind Modelle erforderlich, die das Niederschlag-Abflussverhalten in einem angemessenen zeitlichen und räumlichen Detail beschreiben. Neben Daten zur Menge und Verteilung des Niederschlags gehen in die Modellierung auch Oberflächeneigenschaften ein, insbesondere der Versiegelungsgrad und die Flächennutzung. In dieser Studie untersuchen wir erstmals die Möglichkeit, hochauflösende Landnutzungskarten städtischer Gebiete aus Drohnen(UAV)-Bildern abzuleiten und die Eignung solcher Karten als Datengrundlage für Modellanwendungen in der Siedlungswasserwirtschaft. Wir zeigen, dass die aus UAV-Bildern (automatisch) abgeleiteten Karten zum Versiegelungsgrad hinsichtlich ihrer Genauigkeit mit Karten auf Basis konventioneller Luftbilder vergleichbar sind. Darüber hinaus zeigt sich in unseren Experimenten, dass sich die Genauigkeit der Versiegelungskarten bedeutend steigern lässt, indem man diskriminative Lernverfahren in Verbindung mit Bildinformation aus einer grösseren Nachbarschaft benutzt.

Max Maurer

Beutler, P., Larsen, T. A., Maurer, M., Staufer, P., & Lienert, J. (2024). A participatory multi-criteria decision analysis framework reveals transition potential towards non-grid wastewater management. Journal of Environmental Management, 367, 121962 (15 pp.). doi:10.1016/j.jenvman.2024.121962, Institutional Repository

Many public environmental decisions are wicked problems due to high complexity and uncertainty. We test a participatory value-based framework based on multi-criteria decision analysis (MCDA) to tackle such problems. Our framework addresses two important gaps identified in reviews of MCDA applications to environmental problems: including stakeholders and treating uncertainty. We applied our framework in two complex real-world cases concerning a paradigm shift in the wastewater sector; the transition from centralized wastewater systems to decentralized non-grid systems. Non-grid systems may solve some problems of centralized systems by reducing costs, increasing flexibility, and addressing growing demands on environmental issues, especially in rural areas. But non-grid systems have rarely been implemented in OECD countries, because it is unclear whether a transition is recommendable, and whether stakeholders would accept this shift. This problem allows addressing several fundamental research questions. As theoretical contribution, we found that stakeholder participation in MCDA is necessary, because different preferences of stakeholders can lead to different best-performing options in the assessments. Compared to the typical integrated assessment (IA) approach that excludes stakeholders' preferences, the MCDA process led to clearer outcomes. Results indicate that including the uncertainty of predicted consequences of options with Monte Carlo simulation helped discriminate between options and identify best-performing options. Challenging the uncertainty of elicited stakeholder preferences with sensitivity analyses, we found that best-performing options were especially sensitive to the MCDA aggregation model. Despite the high uncertainty, it was possible to suggest robust consensus options that would perform reasonably well for all stakeholders. As practical contribution, results indicated that a transition from the centralized to decentralized non-grid systems seems feasible. Most stakeholders assigned highest weights to environmental protection objectives in decision-making workshops. These stakeholder preferences implemented in MCDA led to a generally better assessment of innovative non-grid systems, especially when including urine source separation. Stakeholders perceived the MCDA process as beneficial and found results plausible. We conclude that the proposed participatory value-based framework is rigorous, but still feasible in practice. The framework is certainly transferable to any context and is open to testing and refinement in various applications to wicked decision problems.
Binz, C., Sedlak, D., O’Callaghan, P., Truffer, B., Nesi, M., Morgenroth, E., … Wellauer, S. (2024). Mainstreaming decentralized urban water management solutions for sustainable cities. doi:10.55408/eawag:33039, Institutional Repository

Climate change, rapid urbanization and other grand challenges increasingly force cities to rethink their urban (water) infrastructure. In particular, decentralized urban water management solutions, which can recover valuable resources close to the source are increasingly applied to remediate water scarcity, sanitation or environmental pollution challenges. Yet, although interesting demonstration projects with decentralized solutions (from here on labeled ‘decentralized UWM solutions’) are underway in several world regions, actors developing and implementing this transformative innovation are not effectively coordinating their efforts and sharing the latest knowledge. While effective technologies, business models, or regulative frameworks increasingly exist that could inform, inspire and improve similar activities elsewhere, details of local successes and failures are still (too) rarely shared or transferred across space. Drawing from experience on the mainstreaming of other transformative infrastructure solutions (like renewable energies, electric mobility or circular waste management), we posit that the global diffusion of decentralized UWM solutions has been significantly slowed down by this lack of interaction among key stakeholders, and the resulting lack of an effective innovation ecosystem.
Duque, N., Scholten, L., & Maurer, M. (2024). Exploring transitions of sewer wastewater infrastructure towards decentralisation using the modular model TURN-Sewers. Water Research, 257, 121640 (14 pp.). doi:10.1016/j.watres.2024.121640, Institutional Repository

We present a new modular model called TURN-Sewers for exploring different adaptations of centralised wastewater infrastructure towards more decentralised wastewater systems under different urban development scenarios. The modular model is flexible and computationally efficient in exploring transitions at the city scale, allowing for the comparison of different policies and management strategies for sanitary wastewater infrastructure. TURN-Sewers includes independent modules that simulate the generation, dimensioning, deterioration, management, and calculation of performance indicators for different wastewater systems. This model can use readily available spatial information to support infrastructure planners and other stakeholders in exploring different transition pathways from centralised to decentralised wastewater infrastructure. An illustrative example demonstrates how TURN-Sewers can generate multiple future alternatives, define different infrastructure management strategies regarding system expansion, rehabilitation and transition, and assess the economic, hydraulic and structural impacts.
Duque, N., Scholten, L., & Maurer, M. (2024). When does infrastructure hybridisation outperform centralised infrastructure paradigms? – Exploring economic and hydraulic impacts of decentralised urban wastewater system expansion. Water Research, 254, 121327 (13 pp.). doi:10.1016/j.watres.2024.121327, Institutional Repository

We explore the dynamics of centralised and decentralised wastewater infrastructure across various scenarios and introduce novel insights into their performance regarding structural vulnerability, hydraulic capacity, and costs. This study determines circumstances under which infrastructure hybridisation outperforms traditional centralised infrastructure paradigms. We combined system analysis to map out the modelling problem with the model-based exploration of the transition space using the novel TURN-Sewers model. System diagramming was used to identify the parameters or combinations of parameters that significantly influence the performance indicators being assessed. This allowed the creation of relevant simulation scenarios to identify circumstances where a decentralised sewer system could outperform a centralised one. TURN-Sewers was applied to model the infrastructure maintenance and generation of new infrastructure over 20 years for a municipality on the Swiss Plateau, considering a population growth rate of 0.03 a−1. Results show that decentralisation in expansion areas with higher densification can outperform the hydraulic performance and structural vulnerability of expanding centralised sanitary wastewater infrastructure. Decentralised systems can also offer economic advantages when capital expenditure costs for small-scale wastewater treatment plants are significantly reduced compared to current costs, particularly at higher discount rates, e.g. reaping effects of economies of scale. The findings of this study emphasise the potential of transition pathways towards decentralisation in urban water infrastructures and the value of models that allow the exploration of this transition space.
Fappiano, F., Maurer, M., & Leitão, J. P. (2024). Coupling sewers to the surface: systematic approaches to correcting data discrepancies for 1D-2D drainage modelling. Journal of Hydrology, 645, 132239 (14 pp.). doi:10.1016/j.jhydrol.2024.132239, Institutional Repository

One-dimensional (1D) drainage models coupled with two-dimensional (2D) surface models have been recognised as most suitable for simulating pluvial floods in urban areas. However, discrepancies between the 1D drainage network and the 2D Digital Terrain Model (DTM) surface elevation datasets are often observed. These incompatibilities are commonly adjusted manually, impacting the transparency and reproducibility of flood modelling results. No automated and reproducible methods are currently available to ensure compatibility and consistency between a 1D drainage network and the 2D DTM elevation dataset. We present two methods for automatically correcting these discrepancies: Method 1, which corrects the discrepancies by editing the 1D drainage network, and Method 2, which corrects the discrepancies by editing the elevation of the 2D surface. Both methods ensure 1D–2D data compatibility. The two methods were evaluated through hydraulic and hydrological simulations using a synthetic case study, demonstrating strong performance for both approaches. Additionally, we propose a procedure to guide practitioners and modellers in discerning between 1D data and 2D data errors and choosing which method to use. This procedure is demonstrated for a real case study. The two presented methodologies can improve the process of creating 1D-2D urban drainage models and their reproducibility.
Duque Villarreal, N. (2023). Transitions in urban networks: towards decentralised wastewater infrastructure (Doctoral dissertation). doi:10.3929/ethz-b-000648618, Institutional Repository

Centralised urban water systems currently dominate water supply and urban drainage in OECD countries. However, with rapidly ageing infrastructure and predicted climatic, demographic, technological, urban and socio-economic developments, current infrastructure must adapt to meet future requirements and address challenges related to service provision. This adaptation process should consider technical considerations, resource efficiency, resilience, and sustainability. Recent research suggests that future urban drainage systems should incorporate decentralised wastewater treatment to improve water resource management, for example by locally reusing treated wastewater.

The transition towards decentralised wastewater treatment needs the implementation of progressive spatial adaptation measures to integrate innovative treatment technologies. This complex problem involves several external and internal factors, and its solution extends beyond the field of optimization alone. Unlike optimization modelling, which seeks to identify an optimal solution, exploratory modelling acknowledges the existence of multiple alternatives, uncertainties, stakeholders, and diverse outcomes of interest. Exploratory modelling can effectively examine the potential impact of implementing decentralised wastewater treatment in the existing urban drainage infrastructure.

This PhD thesis aims to study mid- to long-term adaptation measures for the transformation of existing urban drainage networks towards decentralised or hybrid systems in cities, particularly foul/sanitary sewers. To address the limitations of existing integrated models, the thesis raises the research question: "How to develop a simple yet sufficiently accurate model for the generation and exploration of possible transition pathways from centralised towards hybrid or decentralised foul urban drainage systems?"

In response to this question, a modular model called 'Transitions in URban Networks towards decentralisation in Sewer systems' (TURN-Sewers) was developed. The model systematically generates and explores multiple transition pathways and reduces conceptual shortcomings in representing the transformation strategies of urban drainage systems. The model utilizes a GIS-based spatial representation. This thesis consists of three main chapters (chapters two to four), presented as individual journal publications. [...]
Maurer, M., Tilley, E., & Udert, K. (2023). Andere Wege für das Abwasser. Globe, 23(2), 26-28. , Institutional Repository

Die Wasserwirtschaft mit Kanalisation und zentralen Kläranlagen ist nicht mehr zukunftsfähig und global keine Lösung. Umweltingenieur:innen der ETH Zürich und der Eawag bereiten den Weg zu einer kreislauffähigen und dezentraleren Wasserinfrastruktur.
Maurer, M. (2023). Sanitation systems. Are hybrid systems sustainable or does winner takes all?. In T. Bolognesi, F. Silva Pinto, & M. Farrelly (Eds.), Routledge environment and sustainability handbooks. Routledge handbook of urban water governance (pp. 134-144). doi:10.4324/9781003057574-11, Institutional Repository

Hybrid wastewater systems can be defined as the coexistence of centralized and modular systems in the same catchment. Currently, we have no explicit knowledge if such hybrid systems can be stable over the long term or if modular systems always will be a stopgap solution.
Current evidence indicates that, depending on the settlement structure, centralized systems can have diseconomies of scale, and modelling studies show that there are conditions where hybrid systems are cost-effective. Decisive factors are the costs of modular systems and the heterogeneity of urban areas. Overall, there are good reasons to believe that fortifying centralized systems with modular systems enable overcoming some of the critical weaknesses of the one-size-fits-all centralized systems approach.
However, centralized systems show strong path dependencies. Besides a wide range of institutional and organizational barriers, current engineering economic and planning methodologies also need to be improved and adapted. From a purely engineering perspective, the following research needs can be identified: (i) long-term transition planning tools that are spatially explicit and can consider a wide range of modular technologies; (ii) cross-sectoral integration methodologies; (iii) better methods to integrate multi-criteria decision analysis (MCDA) to consider the broader range of benefits hybrid systems can provide; and (iv) improved engineering economic methodologies considering uncertainties, unused capacity, and the value of adaptability.
Molné, F., Donati, G. F. A., Bolliger, J., Fischer, M., Maurer, M., & Bach, P. M. (2023). Supporting the planning of urban blue-green infrastructure for biodiversity: a multi-scale prioritisation framework. Journal of Environmental Management, 342, 118069 (12 pp.). doi:10.1016/j.jenvman.2023.118069, Institutional Repository

Primary considerations for urban blue-green infrastructure (BGI) encompass sustainable stormwater/urban heat management while biodiversity conservation is often considered an inherent benefit rather than a core planning requirement. However, ecological function of BGI as 'stepping stones' or linear corridors for otherwise fragmented habitats is undisputed. While quantitative approaches for modelling ecological connectivity in conservation planning are well established, mismatches in scope and scale with models that support the planning of BGI makes their adoption and integration difficult across disciplines. Technical complexities have led to ambiguity around circuit and network-based approaches, focal node placement, spatial extents, and resolution. Furthermore, these approaches are often computationally intensive, and considerable gaps remain in their use for identifying local-scale critical "pinch-points" that urban planners may respond to with the integration of BGI interventions that address biodiversity enhancement among other ecosystem services. Here, we present a framework that simplifies and integrates the merits of regional connectivity assessments with a focus on urban areas to prioritise BGI planning interventions while reducing computational demands. Our framework facilitates: (1) modelling potential ecological corridors at a coarse regional scale, (2) prioritising local-scale BGI interventions based on the relative contribution of individual nodes in this regional network, and (3) inferring connectivity hot- and cold-spots for local-scale BGI interventions. We illustrate this in the Swiss lowlands, demonstrating how, compared to previous work, we are able to identify and rank different priority locations across the region for BGI interventions in support of biodiversity enhancement and how their local-scale functional design may be benefited by addressing specific environmental variables.
Perrelet, K., Moretti, M., Dietzel, A., Maurer, M., & Cook, L. (2023). Schwammstädte - Für und mit Biodiversität gestalten. Hotspot, 48, 24-25. , Institutional Repository

Eine blau-grüne Infrastruktur aus Fliessgewässern, Pflanzenkläranlagen oder Gründächern kann den Siedlungsraum und vor allem Städte sowohl biodiverser als auch resilienter gegenüber dem Klimawandel machen. Voraussetzung ist die Zusammenarbeit von Ingenieur- und Naturwissenschaften.
Perrelet, K., Moretti, M., Dietzel, A., Maurer, M., & Cook, L. (2023). Villes éponges: pour et avec la biodiversité. Hotspot, 48, 22-23. , Institutional Repository

Une infrastructure bleue et verte composée de cours d’eau, de stations d’épuration végétales ou de toits verts peut rendre l’espace urbain, et surtout les villes, à la fois biodiverses et résistantes aux aléas climatiques. La condition préalable est la collaboration entre l’ingénierie et les sciences naturelles.
Schneider, M. Y., Harada, H., Villez, K., & Maurer, M. (2023). Several small or single large? Quantifying the catchment-wide performance of on-site wastewater treatment plants with inaccurate sensors. Environmental Science and Technology, 57(2), 1114-1122. doi:10.1021/acs.est.2c05945, Institutional Repository

On-site wastewater treatment plants (OSTs) often lack monitoring, resulting in unreliable treatment performance. They thus appear to be a stopgap solution despite their potential contribution to circular water management. Low-maintenance but inaccurate soft sensors are emerging that address this concern. However, how their inaccuracy impacts the catchment-wide treatment performance of a system of many OSTs has not been quantified. We develop a stochastic model to estimate catchment-wide OST performances with a Monte Carlo simulation. In our study, soft sensors with a 70% accuracy improved the treatment performance from 66% of the time functional to 98%. Soft sensors optimized for specificity, indicating the true negative rate, improve the system performance, while sensors optimized for sensitivity, indicating the true positive rate, quantify the treatment performance more accurately. This new insight leads us to suggest programming two soft sensors in practical settings with the same hardware sensor data as input: one soft sensor geared to high specificity for maintenance scheduling and one geared to high sensitivity for performance quantification. Our findings suggest that a maintenance strategy combining inaccurate sensors with appropriate alarm management can vastly improve the mean catchment-wide treatment performance of a system of OSTs.
Donati, G. F. A., Bolliger, J., Psomas, A., Maurer, M., & Bach, P. M. (2022). Reconciling cities with nature: Identifying local Blue-Green Infrastructure interventions for regional biodiversity enhancement. Journal of Environmental Management, 316, 115254 (14 pp.). doi:10.1016/j.jenvman.2022.115254, Institutional Repository

Increasing urbanization degrades quantity, quality, and the functionality of spatial cohesion of natural areas essential to biodiversity and ecosystem functioning worldwide. The uncontrolled pace of building activity and the erosion of blue (i.e., aquatic) and green (i.e., terrestrial) landscape elements threaten existing habitat ranges and movability of wildlife. Local scale measures, such as nature-inspired engineered Blue-Green Infrastructure (BGI) are emerging mitigation solutions. Originally planned to promote sustainable stormwater management, adaptation to climate change and improved human livability in cities, such instruments offer interesting synergies for biodiversity in support of existing ecological infrastructure. BGI are especially appealing for globally declining amphibians, a rich and diverse vertebrate assemblage sensitive to urbanization. We integrated biological and highly resolved urban-rural land-cover data, ensemble models of habitat suitability, and connectivity models based on circuit theory to improve multi-scale and multi-species protection of core habitats and ecological corridors in the Swiss lowlands. Considering a broad spectrum of amphibian biodiversity, we identified distributions of amphibian biodiversity hotspots and four landscape elements essential to amphibian movability at the regional scale, namely i) forest edges, ii) wet-forest habitats, iii) soils with variable moisture and iv) riparian zones. Our work shows that cities can make a substantial contribution (e.g., up to 15% of urban space in the study area) to wider landscape habitat connectivity. We highlight the importance of planning BGI locally in strategic locations across urban and peri-urban areas to promote the permeability and availability of ‘stepping stone’ habitats in densely populated landscapes, essential to the maintenance of regional habitat connectivity and thereby enhancing biodiversity and ecosystem functioning.
Duque, N., Bach, P. M., Scholten, L., Fappiano, F., & Maurer, M. (2022). A simplified sanitary sewer system generator for exploratory modelling at city-scale. Water Research, 209, 117903 (12 pp.). doi:10.1016/j.watres.2021.117903, Institutional Repository

Future climatic, demographic, technological, urban and socio-economic challenges call for more flexible and sustainable wastewater infrastructure systems. Exploratory modelling can help to investigate the consequences of these developments on the infrastructure. In order to explore large numbers of adaptation strategies, we need to re-balance the degree of realism of sewer network and ability to reflect key performance characteristics against the model's parsimony and computational efficiency. We present a spatially explicit algorithm for creating sanitary sewer networks that realistically represent key characteristics of a real system. Basic topographic, demographic and urban characteristics are abstracted into a squared grid of 'Blocks' which are the foundation for the sewer network's topology delineation. We compare three different pipe dimensioning approaches and found a good balance between detail and computational efficiency. With a basic hydraulic performance assessment, we demonstrate that we attain a computationally efficient and high-fidelity wastewater sewer network with adequate hydraulic performance. A spatial resolution of 250 m Block size in combination with a sequential Pipe-by-Pipe (PBP) design algorithm provides a sound trade-off between computational time and fidelity of relevant structural and hydraulic properties for exploratory modelling. We can generate a simplified sewer network (both topology and hydraulic design) in 18 s using PBP, versus 36 min using a highly detailed model or 1 s using a highly abstract model. Moreover, this simplification can cut up to 1/10th to 1/50th the computational time for the hydraulic simulations depending on the routing method implemented. We anticipate our model to be a starting point for sophisticated exploratory modelling into possible infrastructure adaptation measures of topological and loading changes of sewer systems for long-term planning.
Manny, L. (2022). Socio-technical challenges towards smart urban water systems (Doctoral dissertation). doi:10.3929/ethz-b-000578852, Institutional Repository

Globally, urbanization, climate change, and ageing assets affect urban water management. One potential solution is recognized in smart urban water systems, which rely on monitoring data from infrastructure elements, e.g., combined sewer overflows (CSOs). Such monitoring data provides evidence on system functioning and performance and allows a dynamic control to exploit all existing infrastructure capacities, for example during heavy rainfalls. As a result, smart urban water systems hold the potential to improve performance outcomes, to reduce environmental impacts on surface waters, and to manage infrastructures more efficiently.
However, despite the availability of digital technologies for monitoring, data transfer, and control, only few examples of smart urban water systems exist. Where monitoring data is already obtained, it is often not optimally handled. Potential reasons cannot be found at the technical level only, but require an understanding of smart urban water systems in their social and socio-technical dimensions. To achieve smart urban water systems, not only technical innovation, but also adaptations of the surrounding social system are needed. [...]
Pakizer, K. M. (2022). Flexibility through hybridity: governance arrangements for sustainable urban water systems (Doctoral dissertation). doi:10.3929/ethz-b-000554583, Institutional Repository

Conventional large-scale water infrastructures in urban areas are increasingly under pressure to transition toward more flexible and sustainable modes to cope with the major challenges of the 21st century. Climate change and population growth coupled with increased urbanization will likely expand the demand for water services, which are already confronted with water scarcity due to hydro-climatic variability. On top of these challenges, ageing water supply and sanitation infrastructures are facing underinvestment and shrinking subsidies. Integrating decentralized water technologies that are multifunctional and fit-for-purpose could enable a more efficient treatment of resources and diversify water assets, creating mixed-scale or hybrid water systems. Although such technological solutions already exist, the implementation rate remains low, as the transition of infrastructures also necessitates institutional change, altering, e.g., user practices, regulations, organizational structures and markets. As institutions provide stability and regularity to urban water infrastructures and their management, however, they are not easily changed. [...]

Konventionelle gross angelegte Wasserinfrastrukturen im urbanen Raum stehen unter steigendem Druck flexibler und nachhaltiger zu werden, um die Herausforderungen des 21. Jahrhunderts zu bewältigen. Klimawandel und Bevölkerungswachstum zusammen mit zunehmender Urbanisierung werden die Nachfrage nach Wasserdienstleistungen wahrscheinlich steigern. Diese sind bereits heute mit Wasserknappheit auf Grund von hydroklimatischen Schwankungen konfrontiert. Dazu kommt noch, dass alternde Wasserversorgungs- und Abwasserreinigungsinfrastrukturen geringen Investitionen und sinkenden Subventionen ausgesetzt sind. Die Integration von zweckmässigen ('fit-for-purpose') und multifunktionalen dezentralen Wassertechnologien in konventionelle Wasserinfrastrukturen könnte einen effizienteren Umgang mit Ressourcen ermöglichen und Wasserressourcen diversifizieren. So entstünden gemischte ('mixed-scale') oder hybride Wassersysteme. Obwohl diese technischen Lösungen bereits bestehen, werden sie nur selten implementiert. Dies liegt daran, dass die Transformation von Infrastrukturen auch institutionellen Wandel voraussetzt: das Verändern von Nutzerverhalten, Gesetzen, organisatorischen Strukturen und Märkten. Da Institutionen urbane Wasserinfrastrukturen und deren Management stabilisieren, sind diese jedoch nicht leicht zu verändern. [...]
Probst, N., Bach, P. M., Cook, L. M., Maurer, M., & Leitão, J. P. (2022). Blue Green Systems for urban heat mitigation: mechanisms, effectiveness and research directions. Blue-Green Systems, 4(2), 348-376. doi:10.2166/bgs.2022.028, Institutional Repository

Reflected in the growing body of literature, urban heat mitigation is increasingly relevant as cities experience extreme heat, exacerbated by climate change and rapid urbanisation. Most studies focus on urban–rural temperature differences, known as the Urban Heat Island, which does not provide insight into urban heat dynamics. Here, we synthesise current knowledge on spatio-temporal variations of heat sources and sinks, showing that a targeted and absolute understanding of urban heat dynamics rather than an urban–rural comparison should be encouraged. We discuss mechanisms of heat sinks for microclimate control, provide a clear classification of Blue Green Systems and evaluate current knowledge of their effectiveness in urban heat mitigation. We consider planning and optimisation aspects of Blue Green Infrastructure (greenery and water bodies/features), interactions with hard surfaces and practices that ensure space and water availability. Blue Green Systems can positively affect urban microclimates, especially when strategically planned to achieve synergies. Effectiveness is governed by their dominant cooling mechanisms that show diurnal and seasonal variability and depend upon background climatic conditions and characteristics of surrounding urban areas. Situationally appropriate combination of various types of Blue Green Systems and their connectivity increases heat mitigation potential while providing multiple ecosystem services but requires further research.
Sankara Narayan, A. (2022). Planning citywide inclusive sanitation. Mapping the paradigm shift in the Global and Indian context (Doctoral dissertation). doi:10.3929/ethz-b-000561822, Institutional Repository

Sanitation is fundamental to a city’s health, liveability, and social and economic development. Yet, as the world continues to urbanise, progress in urban sanitation is outpaced by rapid urbanisation and population growth. Today, about 40% of the world’s urban residents do not have safely managed sanitation, with a vast majority of them are living in low- and middle-income countries (LMICs). In the last five decades, numerous international development agendas on urban sanitation have been set and failed to reach the expected sanitation outcomes in LMICs. Reasons for this failure include poor planning, narrow infrastructure focussed approach, inadequate consideration of contextual factors, lack of attention to policy and institutions, and absence of community involvement. [...]

Die Abwasserentsorgung ist von grundlegender Bedeutung für die Gesundheit, die Lebensqualität sowie die soziale und wirtschaftliche Entwicklung einer Stadt. Doch während die Welt immer weiter verstädtert, werden die Fortschritte bei der städtischen Abwasserentsorgung durch die rasche Urbanisierung und das Bevölkerungswachstum überholt. Heute verfügen etwa 40 % der Stadtbewohner weltweit nicht über eine sichere Abwasserentsorgung, wobei die überwiegende Mehrheit von ihnen in Ländern mit niedrigem und mittlerem Einkommen (LMICs) lebt. In den letzten fünf Jahrzehnten wurden zahlreiche internationale Entwicklungspläne für die städtische Abwasserentsorgung aufgestellt, ohne dass die erwarteten Ergebnisse in den LMICs erreicht wurden. Zu den Gründen für dieses Scheitern gehören schlechte Planung, ein eng auf die Infrastruktur ausgerichteter Ansatz, eine unzureichende Berücksichtigung kontextbezogener Faktoren, mangelnde Aufmerksamkeit für Politik und Institutionen sowie eine fehlende Einbeziehung der Bevölkerung. [...]
Schönenberger, U. T. (2022). The overlooked pathway: hydraulic shortcuts and their influence on pesticide transport in agricultural areas (Doctoral dissertation). doi:10.3929/ethz-b-000539927, Institutional Repository

Introduction. Pesticides used in agriculture are transported to surface waters through various pathways and pose a major threat to aquatic ecosystems. Farmers and authorities take various measures to reduce pesticide transport to surface waters and to protect them from harmful effects. However, such actions can only be effective if the underlying processes driving the pesticide risk are understood well enough. Previous research suggests that so-called hydraulic shortcuts may be an important pesticide transport pathway that has been overlooked in the past. The term hydraulic shortcuts refers to inlet or maintenance shafts of agricultural storm drainage systems, but also to roads, farm tracks, channel drains, and ditches. Even though the relevance of hydraulic shortcuts for pesticide transport has been shown in single cases, it is unclear how often these structures occur and how relevant they are in general for pesticide transport compared to other pathways.
Objectives. This thesis aimed on quantifying the relevance of pesticide losses via hydraulic shortcuts to Swiss surface waters. For this, the following four research questions were investigated: 1) How often do hydraulic shortcuts occur in Swiss agricultural areas? 2) What is their relevance for surface runoffrelated pesticide transport? 3) What is their relevance for spray drift-related pesticide transport? 4) What pesticide concentrations and loads are found in hydraulic shortcuts? [...]
Truffer, B., Maurer, M., & Heiberg, J. (2022). Modulare Wasserinfrastrukturen. Optionen für eine Zukunftsfähige Siedlungswasserwirtschaft. Aqua & Gas, 102(9), 60-65. , Institutional Repository

Modulare Systeme ermöglichen eine dezentralere und damit flexiblere Gestaltung der Siedlungswasserwirtschaft. Im Rahmen des Nationalen Forschungsprogramms 73 «Nachhaltige Wirtschaft» untersuchte das Forschungsteam des Projekts COMIX die zu erwartenden Chancen und Risiken, die sich aus diesen Entwicklungen für einen nachhaltigeren Umgang mit der Ressource Wasser in der Schweiz ergeben könnten.
Wani, O., Maurer, M., Rieckermann, J., & Blumensaat, F. (2022). Does distributed monitoring improve the calibration of urban drainage models? (p. (3 pp.). Presented at the 12th urban drainage modeling conference. Retrieved from https://udm2022.org/2021/11/09/does-distributed-monitoring-improve-the-calibration-of-urban-drainage-models/, Institutional Repository

We conclude that while distributed sensing of discharge and water level helps understanding the dynamics of the stormwater runoff, it is not always straightforward to make better predictive models of complex urban drainage networks using this data. This analysis - by delineating the bottlenecks towards informative inference - provides via-negativa recommendations for the placement of distributed sensors, when improved model performance is also one of the motivating factors for such data collection campaigns.
Beutler, P., Larsen, T. A., Maurer, M., Staufer, P., & Lienert, J. (2021). Potenzial dezentraler Abwassersysteme. Aqua & Gas, 101(1), 66-75. , Institutional Repository

Werterhalt und Bewirtschaftung von Kanalisation und ARA können kleine Gemeinden vor Herausforderungen stellen. Es gibt Alternativen, aber lohnen sich diese? Zwei Gemeinden wurden bei der strategischen Planung für ihr neues Abwassersystem unterstützt. Viele Ziele wurden als entscheidungsrelevant identifiziert, insbesondere Umweltschutzziele. Es zeigte sich, dass dezentrale Technologien mit Stoffstromseparierung die Anforderungen häufig besser erfüllen können als konventionelle Abwassersysteme.
Donati, G. F. A., Bolliger, J., Psomas, A., Maurer, M., & Bach, P. M. (2021). Blau-grüne Infrastuktur: eine Möglichkeit zur Förderung der biologischen Vielfalt in vom Menschen geprägten Landschaften? Les infrastructures bleues-vertes: une opportunité pour améliorer la biodiversité dans les paysages dominés par l'homme?. Nature et Paysage. Natur und Landschaft: Inside (4), 41-44. , Institutional Repository

Intensiv genutzte Landschaften und Lebensraumfragmentierung sind mitverantwortlich für den Rückgang der Biodiversität, weil Lebensraumqualität und grundlegende biologische Prozesse wie z.B. die Ausbreitung gestört werden. Stetig wachsende Städte als überregionale Barrieren für die Vernetzung natürlicher Lebensräume stellen eine besondere Herausforderung dar (Abb. 1). Wir zeigen am Beispiel von Amphibien auf, wie eine gezielte Platzierung blaugrüner Infrastrukturen die Durchlässigkeit von Städten verbessern könnte und dadurch Lebensräume und Laichgebiete von regionaler Bedeutung besser vernetzt werden. Die Einrichtung blaugrüner Infrastrukturen ist eine vielversprechende Massnahme, um die Anpassung an den Klimawandel zu fördern und die Lebensqualität zu verbessern. Synergien zur Vernetzung der Biodiversität bieten sich auf lokaler und regionaler Ebene an.

L'utilisation intensive des paysages et la fragmentation des habitats sont en partie co-responsables du déclin de la biodiversité, dans la mesure où la qualité des habitats et des processus biologiques fondamentaux tels que la dispersion sont perturbés. L'urbanisation croissante constitue un défi particulier dans ce contexte, notamment en tant qu'obstacle transrégional à la connectivité des habitats naturels. En prenant l'exemple des amphibiens, nous montrons comment la planification ciblée d'infrastructures bleuesvertes pourrait améliorer la perméabilité des villes en reliant mieux les habitats naturels et les sites de reproduction d'importance régionale. L'installation d'infrastructures bleues-vertes est une mesure prometteuse qui est actuellement planifiée dans de nombreuses villes surtout pour promouvoir l'adaptation au changement climatique ainsi que pour l'amélioration de la qualité de vie. Cependant, des synergies pour la mise en réseau de la biodiversité sont aussi disponibles non seulement à niveaux local mais aussi régional.
Joshi, P., Leitão, J. P., Maurer, M., & Bach, P. M. (2021). Not all SuDS are created equal: impact of different approaches on combined sewer overflows. Water Research, 191, 116780 (13 pp.). doi:10.1016/j.watres.2020.116780, Institutional Repository

Sustainable urban drainage systems (SuDS) help in stormwater management by reducing runoff volume, increasing runoff concentration time and thereby improving the drainage system capacity. This study investigated the potential and cost-effectiveness of SuDS in reducing combined sewer overflows (CSOs). We simulated the performance of four SuDS techniques (bioretention cell, permeable pavement, rain barrel and green roof) at incremental levels of spatial coverage for a small urban catchment with a combined sewer system. We also used an Analytic Hierarchy Process (AHP) considering end-point CSO, land use, imperviousness, slope and elevation criteria to identify priority areas for SuDS deployment. Results show that CSO volume attenuation ranged a maximum of 50-99% for the catchment, depending on the deployment strategy and underlying mechanisms of each technology. We also found that deployment of SuDS in AHP-selected sub-catchments improved CSO reduction only for rain barrels and green roofs, but not for bioretention cells and permeable pavements. SuDS were also a cost-effective retrofit option: for a 40% volume reduction, the SuDS cost, at most, 25% of the equivalent cost required for a large CSO tank. Outcomes of this study demonstrate the efficacy of SuDS in controlling CSOs, adding yet another tangible benefit to their increasingly recognised multi-functionality.
Narayan, A. S., Maurer, M., & Lüthi, C. (2021). The clean plan: analysing sanitation planning in India using the CWIS planning framework. Journal of Water Sanitation and Hygiene for Development, 11(6), 1036-1047. doi:10.2166/washdev.2021.130, Institutional Repository

Sanitation in India has received national attention for over a decade, especially with the Swachh Bharat Mission (SBM) making it a political priority. However, due to the lack of appropriate sanitation planning practices, there have been little long-term gains made in urban sanitation beyond the ending of open defaecation. In this paper, we analyse the key barriers to sanitation planning, in India, in the context of the emerging paradigm of Citywide Inclusive Sanitation (CWIS). A mixed method approach of shit flow diagrams, social network analysis, policy analysis, interviews and workshops at the national, state (2) and city (4) levels was conducted. Eight factors were identified as important barriers for planning including inadequate planning capacities, lack of ownership of city sanitation plans among city governments, poor community involvement, absence of a uniform planning framework, unreliable political and financial support, overlapping jurisdictions, and scheme-based funding. The paper also proposes the CWIS Planning Framework which offers a perspective at overcoming these barriers with the recommendation of bridging top-down and bottom-up planning approaches. While there is increasingly more clarity on what CWIS means, there is little understanding on how to plan for it. Therefore, this framework provides the theoretical basis for planning with the CWIS approach.
Penn, R., & Maurer, M. (2021). Effects of transition to water‐efficient solutions on existing centralized sewer systems - an integrated biophysical modelling approach. Water Resources Research, 57(9), e2020WR027616 (19 pp.). doi:10.1029/2020WR027616, Institutional Repository

Technical alternatives offering high water efficiency are being developed to complement existing centralized water and wastewater conveyance and treatment systems. Understanding of the negative effects wide-spread implementation of such alternative systems may have on existing systems is still limited, despite the importance of this inevitable transition. In this paper we present a novel approach to systematically identify these negative impacts. A comprehensive model integrating transport and transformation processes in sewer pipes was set up and simulated for various transition scenarios. A significant finding of this research is that reduced flows and increased chemical oxygen demand (COD) concentrations result in the accumulation of sediments and sulphides in sewer pipes. For the examined sewer system, when reducing the total daily flow by 50%, 30% of the pipes were found to accumulate sediments and 30% of the pipes experienced effects due to the presence of sulphides in different states depending on the wastewater temperature. It was found that an optimal spatial distribution of these water-efficient solutions will most likely require compromises between sediment and sulphide accumulation. The product of two design parameters, diameter and bed slope, was found to be a suitable predictor of the potential of a pipe to accumulate sediments. This research provides novel approaches to assessing the feasibility of transition to solutions offering higher water efficiency. The results indicate where the most affected points in the systems are expected to occur and might help in preparing an experimental approach to assess such negative effects, increasing urban water management efficiency.
Penn, R., Ward, B. J., Strande, L., & Maurer, M. (2021). Faecal sludge simulants: review of synthetic human faeces and faecal sludge for sanitation and wastewater research. In K. Velkushanova, L. Strande, M. Ronteltap, T. Koottatep, D. Brdjanovic, & C. Buckley (Eds.), Methods for faecal sludge analysis (pp. 195-234). London: IWA Publishing. , Institutional Repository
Spuhler, D., Scheidegger, A., & Maurer, M. (2021). Ex-ante quantification of nutrient, total solids, and water flows in sanitation systems. Journal of Environmental Management, 280, 111785 (17 pp.). doi:10.1016/j.jenvman.2020.111785, Institutional Repository

To prioritise sustainable sanitation systems in strategic sanitation planning, indicators such as local appropriateness or resource recovery have to be known at the pre-planning phase. The quantification of resource recovery remains a challenge because existing substance flow models require large amounts of input data and can therefore only be applied for a few options at a time for which implementation examples exist. This paper aims to answer two questions: How can we predict resource recovery and losses of sanitation systems ex-ante at the pre-planning phase? And how can we do this efficiently to consider the entire sanitation system option space? The approach builds on an existing model to create all valid sanitation systems from a set of conventional and emerging technologies and to evaluate their appropriateness for a given application case. It complements the previous model with a Substance Flow Model (SFM) and with transfer coefficients from a technology library to quantify nutrients (phosphorus and nitrogen), total solids (as an indicator for energy and organics), and water flows in sanitation systems ex ante. The transfer coefficients are based on literature data and expert judgement. Uncertainties resulting from the variability of literature data or ignorance of experts are explicitly considered, allowing to assess the robustness of the model output. Any (future) technologies or additional products can easily be added to the library. The model is illustrated with a small didactic example showing how 12 valid system configurations are generated from a few technologies, and how substance flows, recovery ratios, and losses to soil, air, and water are quantified considering uncertainties. The recovery ratios vary between 0 and 28% for phosphorus, 0–10% for nitrogen, 0–26% for total solids, and 0–12% for water. The uncertainties reflect the high variability of the literature data but are comparable to those obtained in studies using a conventional post-ante material flow analysis (generally about 30% variability at the scale of a an urban area). Because the model is fully automated and based on literature data, it can be applied ex-ante to a large and diverse set of possible sanitation systems as shown with a real application case. From the 41 technologies available in the library, 101,548 systems are generated and substance flows are modelled. The resulting recovery ratios range from nothing to almost 100%. The two examples also show that recovery depend on technology interactions and has therefore to be assessed for all possible system configurations and not at the single technology level only. The examples also show that there exist trade-offs among different types of reuse (e.g. energy versus nutrients) or different sustainability indicators (e.g. local appropriateness versus resource recovery). These results show that there is a need for such an automated and generic approach that provides recovery data for all system configurations already at the pre-planning phase. The approach presented enables to integrate transparently the best available knowledge for a growing number of sanitation technologies into a planning process. The resulting resource recovery and loss ratios can be used to prioritise resource efficient systems in sanitation planning, either for the pre-selection or the detailed evaluation of options using e.g. MCDA. The results can also be used to guide future development of technology and system innovations. As resource recovery becomes more relevant and novel sanitation technologies and system options emerge, the approach presents itself as a useful tool for strategic sanitation planning in line with the Sustainable Development Goals (SDGs).
Hoffmann, S., Feldmann, U., Bach, P. M., Binz, C., Farrelly, M., Frantzeskaki, N., … Udert, K. M. (2020). A research agenda for the future of urban water management: exploring the potential of non-grid, small-grid, and hybrid solutions. Environmental Science and Technology, 54(9), 5312-5322. doi:10.1021/acs.est.9b05222, Institutional Repository

Recent developments in high- and middle-income countries have exhibited a shift from conventional urban water systems to alternative solutions that are more diverse in source separation, decentralization, and modularization. These solutions include non-grid, small-grid, and hybrid systems to address such pressing global challenges as climate change, eutrophication, and rapid urbanization. They close loops, recover valuable resources, and adapt quickly to changing boundary conditions such as population size. Moving to such alternative solutions requires both technical and social innovations to co-evolve over time into integrated socio-technical urban water systems. Current implementations of alternative systems in high- and middle-income countries are promising, but they also underline the need for research questions to be addressed from technical, social, and transformative perspectives. Future research should apply a transdisciplinary research approach through socio-technical "lighthouse" projects that apply alternative urban water systems at scale. Such research should leverage experience from lighthouse projects in a range of socio-economic contexts, identify their potentials and limitations from an integrated perspective, and share their successes and failures across the urban water sector.
Schneider, M. Y., Furrer, V., Sprenger, E., Carbajal, J. P., Villez, K., & Maurer, M. (2020). Benchmarking soft sensors for remote monitoring of on-site wastewater treatment plants. Environmental Science and Technology, 54(17), 10840-10849. doi:10.1021/acs.est.9b07760, Institutional Repository

On-site wastewater treatment plants (OSTs) are usually unattended, so failures often remain undetected and lead to prolonged periods of reduced performance. To stabilize the performance of unattended plants, soft sensors could expose faults and failures to the operator. In a previous study, we developed soft sensors and showed that soft sensors with data from unmaintained physical sensors can be as accurate as soft sensors with data from maintained ones. The monitored variables were pH and dissolved oxygen (DO), and soft sensors were used to predict nitrification performance. In the present study, we use synthetic data and monitor three plants to test these soft sensors. We find that a long solids retention time and a moderate aeration rate improve the pH soft-sensor accuracy and that the aeration regime is the main operational parameter affecting the accuracy of the DO soft sensor. We demonstrate that integrated design of monitoring and control is necessary to achieve robustness when extrapolating from one OST to another in the absence of plant-specific fine-tuning. Additionally, we provide a unique labeled dataset for further feature and data-driven soft-sensor development. Our benchmarking results indicate that it is feasible to monitor OSTs with unmaintained sensors and without plant-specific tuning of the developed soft sensors. This is expected to drastically reduce monitoring costs for OST-based sanitation systems.
Schneider, M. Y. (2020). Monitoring and quantifying the treatment performance of on-site wastewater treatment plants (Doctoral dissertation). doi:10.3929/ethz-b-000445338, Institutional Repository

Motivation. On-site wastewater treatment plants (OSTs) treat wastewater from a single household or dwelling directly on site. Because of the low initial investment costs, high flexibility, and resource recovery potential, they are used worldwide. Their core problem is that they are mostly operated without constant supervision. To keep costs low, common practice is to have one to four annual inspections. But with no online monitoring in place, treatment performance of such plants is low. Furthermore, failures are not noticed promptly after their occurrence, but only during the next inspection, if at all. This leads to reduced overall treatment performance and reinforces the widespread prejudice that OSTs are a makeshift solution.
Aim. The overall goal of this work is to see if OST systems can achieve treatment performances that are comparable to conventional centralised systems. The vision is that treatment performance should no longer be a criterion to rule out OSTs in the future any more. To get closer to this overall objective, two main objectives were defined:
• To identify a performance sensor that only requires maintenance annually or less frequent. This could greatly reduce maintenance costs, therefore enabling large-scale monitoring of OSTs.
• To investigate how such a nominally inaccurate sensor influences the treatment performance of a single OST unit as well as a system of OSTs and its quantification.
A specific hurdle when monitoring individual OSTs is sensor accuracy. In a nutrient-rich wet environment such as wastewater, biofilm grows everywhere within a few days. Therefore, manufacturers usually recommend monthly or even weekly sensor maintenance routines. Our idea was to use established, but unmaintained sensors for monitoring. [...]
Spuhler, D., Scheidegger, A., & Maurer, M. (2020). Comparative analysis of sanitation systems for resource recovery: influence of configurations and single technology components. Water Research, 186, 116281 (18 pp.). doi:10.1016/j.watres.2020.116281, Institutional Repository

Resource recovery and emissions from sanitation systems are critical sustainability indicators for strategic urban sanitation planning. In this context, sanitation systems are the most often structured using technology-driven templates rather than performance-based sustainability indicators. In this work, we answer two questions: Firstly, can we estimate generic resource recovery and loss potentials and their uncertainties for a diverse and large set of sanitation systems? And secondly, can we identify technological aspects of sanitation systems that indicate a better overall resource recovery performance? The aim is to obtain information that can be used as an input into any strategic planning process and to help shape technology development and system design for resource recovery in the future.
Starting from 41 technologies, which include novel and conventional options, we build 101,548 valid sanitation systems. For each system we quantify phosphorus, nitrogen, total solids, and water flows and use that to calculate recovery potentials and losses to the environment, i.e. the soil, air, or surface water. The four substances cover different properties and serve as a proxy for nutrient, organics, energy, and water resources. For modelling the flows ex-ante, we use a novel approach to consider a large range of international literature and expert data considering uncertainties. Thus all results are generic and can therefore be used as input into any strategic planning process or to help guide future technology development.
A detailed analysis of the results allows us to identify factors that influence recovery and losses. These factors include the type of source, the length of systems, and the level of containment in storage and treatment. The factors influencing recovery are related to interactions of different technologies in a system which shows the relevance of an modelling approach that allows to look at all possible system configurations systematically. Based on our analysis, we developed five recommendations for the optimization of resource recovery: (i) prioritize short systems that close the loop at the lowest possible level; (ii) separate waste streams as much as possible, because this allows for higher recovery potentials; (iii) use storage and treatment technologies that contain the products as much as possible, avoid leaching technologies (e.g. single pits) and technologies with high risk of volatilization (e.g. drying beds); (iv) design sinks to optimise recovery and avoid disposal sinks; and (v) combine various reuse options for different side streams (e.g. urine diversion systems that combine reuse of urine and production of biofuel from faeces).
Spuhler, D., Germann, V., Kassa, K., Abebe Ketema, A., Manandhar Sherpa, A., Gyalzen Sherpa, M., … Langergraber, G. (2020). Developing sanitation planning options: a tool for systematic consideration of novel technologies and systems. Journal of Environmental Management, 271, 111004 (21 pp.). doi:10.1016/j.jenvman.2020.111004, Institutional Repository

To provide access to sustainable sanitation for the entire world population, novel technologies and systems have been developed. These options are often independent of sewers, water, and energy and therefore promise to be more appropriate for fast-growing urban areas. They also allow for resource recovery and and are adaptable to changing environmental and demographic conditions what makes them more sustainable. More options, however, also enhance planning complexity. Structured decision making (SDM) can help balance opposing interests. Yet, most of the current research focuses on the selection of a preferred option, assuming that a set of appropriate options is available. There is a lack of reproducible methods for the identification of sanitation system planning options that can consider the growing number of available technology and the many possible system configurations. Additionally, there is a lack of data, particularly for novel options, to evaluate the various sustainability criteria for sanitation.To overcome this limitation, we present a novel software supported approach: the SANitation sysTem Alternative GeneratOr (Santiago). To be optimally effective, Santiago is required to be integrated into an SDM approach. In this paper, we present all the elements that such an integration requires and illustrate these methods at the case of Arba Minch, a fast growing town in Ethiopia. Based on this example and experiences from other cases, we discuss the lessons learnt and present the advantages potentially brought by Santiago for sanitation planning The integration requires four elements: a set of technologies to be looked at, decision objectives for sustainable sanitation, screening criteria to evalute technology appropriateness, and about the technologies and the casea. The main output is a set of sanitation system options that is locally appropriate, diverse in order to reveal trade-offs, and of a manageable size. To support the definition of decision objectives, we developed a generic objective hierarchy for sustainable sanitation. Because one of the main challenges lies in the quantification of screening criteria, we established the data for 27 criteria and 41 technologies in a library.The case studies showed, that if the integration is successful, then Santiago can provide substantial benefits: (i) it is systematic and reproducible; (ii) it opens up the decision space with novel and potentially more appropriate solutions; (iii) it makes international data accessible for more empirical decision making; (iv) it enables decisions based on strategic objectives in line with the sustainable development goals; (v) it allows to prioritise appropriate and resource efficient systems right from the beginning (vi) and it contributes to a more citywide inclusive approach by birding strategic objectives with an area-based appropriateness assessment. The here presented approach enables the prioritisation of appropriate and resource efficient sanitation technologies and systems in strategic planning. Thereby this approach contributes to SDG 6.2, 6.3, and 11, sustainable sanitation for all.
Spuhler, D. (2020). Generation and evaluation of sanitation options for urban planning. Systematic consideration of technology innovations and sustainability criteria (Doctoral dissertation). doi:10.3929/ethz-b-000444234, Institutional Repository

Motivation. It is particularly challenging to reach SDG 6.2, access to sanitation for all, in urban areas of developing countries, where most of the current global population growth is taking place. Traditionally, urban sanitation planning is based on top-down, one-size-fits-all approaches. This has often led to inappropriate technology choices and failing projects worldwide, particularly in urban areas of developing countries. Conventional centralized sanitation is often inappropriate in these areas because it depends on capital-intensive sewer networks, large quantities of water, stable institutions with adequate capacities, and long planning horizons. Increasing investments in the development of novel technologies (e.g. urine separation) and system configurations (e.g. container-based sanitation) have been the result. These innovations can be more appropriate (independent from sewers, water and energy) and sustainable (adaptable to changing environmental and socio-demographic conditions, and saving/recovering water, nutrients, and energy).

Research need. While novel technologies and system configurations potentially enhance sustainability, they also increase planning complexity. Structured decision-making (SDM) has been found to assist the planning process, by combining decision analysis with engineering, and balancing opposing interests in a facilitated framework that embraces all relevant steps. To support the application of SDM, several frameworks were developed over the past decades (e.g. Community-led Urban Environmental Sanitation, CLUES, or Sanitation21). Yet, they are rarely used in practice. Recent research focuses on developing tools that operationalize the different planning steps, but these tend to prioritize methods for understanding the problems (e.g. Shit Flow Diagrams, SFDs), or for the selection of preferred options (e.g. multi-criteria decision analysis), assuming that the options to choose from are given. However, the currently available technologies result in an unmanageable number of possible system configurations (>100’000). The present technological development requires methods that generate a manageable number of locally appropriate sanitation decision options and that are systematic and can deal with the growing portfolio of technologies and sustainability criteria. Moreover, there is a lack of generic methods to quantify the performance of novel sanitation system configurations at the scale of an entire city. The identification of options and their comparison is further hampered by the lack of knowledge or data, particularly for novel options.

Research objectives. The objective of this thesis is to develop systematic and generic methods to identify locally appropriate sanitation system options and to evaluate their performance in terms of resource efficiency. The aim is to use these results as an input into the decision-making process. The methods shall: (i) consider entire sanitation systems from the toilet to reuse or disposal; (ii) be applicable to a large and diverse range of technologies and system configurations; and (iii) integrate criteria from all sustainability dimensions. Given the context of expanding urban areas and the focus on novel technologies, the methods should also be able to deal with uncertainties. The thesis covers three specific objectives: (I) methods for sanitation system options generation; (II) methods to quantify resource recovery potentials of entire systems as a performance indicator for the evaluation of their sustainability; and (III) a procedure for the integration of the methods in SDM and their practical application. The third objective also includes the analysis of the implementation of practical applications in Nepal, Ethiopia, South Africa, and Peru. [...]
Blumensaat, F., Dicht, S., Ebi, C., & Maurer, M. (2019). Niedrigenergiefunk in der Siedlungsentwässerung. Neuartige Übertragungstechnologien für eine effiziente Prozessüberwachung im Untergrund–Erfahrungen aus dem Urbanhydrologischen Feldlabor der Eawag. gwf Wasser, Abwasser, 160(3), 44-47. , Institutional Repository

Hat Niedrigenergiefunk das Potenzial, die Prozessüberwachung in Entwässerungssystemen und anderen Infrastrukturen im Untergrund zu revolutionieren? Inwieweit verbessern technologische Neuerungen unser Verständnis für Daten und deren Nutzung für Betriebsoptimierung, Investitionsplanung und Erfolgskontrolle?
Haag, F. (2019). Advancing decision analysis methods for environmental management. Including stakeholder values in wastewater infrastructure planning and river assessment (Doctoral dissertation). doi:10.3929/ethz-b-000378014, Institutional Repository

Good decision-making requires the joint consideration of two aspects: knowledge about consequences of decision alternatives and knowledge about values, which can be expressed as decision objectives and preferences. Obtaining information on potential consequences and on stakeholder values, structuring this information, and integrating it in a meaningful way presents challenges for environmental decisions. Traditionally, natural and engineering sciences are concerned with improving the prediction of potential consequences. In this dissertation, the focus is on values, with the aim of a better integration of both aspects: How can we improve the inclusion of subjective values, expressed as objectives and preferences, in decision-making? [...]

Um gute Entscheidungen zu treffen, müssen zwei Aspekte betrachtet werden: Zum einen braucht es Wissen über die Konsequenzen der Entscheidungsalternativen, zum anderen müssen Werte, die in Form von Zielen und Präferenzen ausgedrückt werden können, einbezogen werden. Informationen zu den möglichen Konsequenzen und zu den Werten von Akteuren zu sammeln, sie zu strukturieren und schlussendlich zusammenzuführen, sind Herausforderungen für die Entscheidungsfindung im Umweltbereich. Natur- und Ingenieurswissenschaften bemühen sich traditionellerweise vor- wiegend darum, die Abschätzung von Konsequenzen zu verbessern. In dieser Dissertation liegt der Fokus auf den Werten, mit dem Ziel einer besseren Integration dieser beiden Aspekte für die Entscheidungsfindung: Wie können wir den Einbezug subjektiver Werte - Ziele und Präferenzen - in Entscheidungen verbessern? [...]
Haag, F., Reichert, P., Maurer, M., & Lienert, J. (2019). Integrating uncertainty of preferences and predictions in decision models: an application to regional wastewater planning. Journal of Environmental Management, 252, 109652 (16 pp.). doi:10.1016/j.jenvman.2019.109652, Institutional Repository

Decision-making in environmental management requires eliciting preferences of stakeholders and predicting outcomes of decision alternatives. Usually, preferences and predictions are both uncertain. Uncertainty of predictions can be tackled by multi-attribute utility theory, but the uncertainty of preferences remains a challenge. We demonstrate an approach for including both uncertainties in a multi-criteria decision analysis (MCDA), using utility theory and the concept of expected expected utility. For a decision regarding a regional merger of wastewater infrastructure in Switzerland, we constructed preference models for four stakeholders. These models also allowed for non-additive interactions between objectives. We evaluated the performance of eleven decision alternatives for which we predicted potential outcomes. Even though uncertainties were high, we could draw conclusions based on the expected expected utility of alternatives. Building a pipeline to discharge treated wastewater to a larger river emerged as a potential consensus alternative to mitigate the problem of micropollutants in a small stream. We investigated the robustness of the findings with sensitivity analysis regarding the preference parameters and the included objectives. In their actual decision, the stakeholders partly preferred other alternatives than those proposed by the model. Their choices could be explained by reduced decision models in which only few objectives were included. This may indicate the use of simplified choice heuristics by the stakeholders. The presented approach is feasible for supporting other difficult environmental or engineering decisions in practice, for which we give a number of recommendations.
Maurer, M., & Hoffmann, S. (2019). Eaux usées: des égouts à assainir. Volkswirtschaft, 89(6), 12-15. Retrieved from https://dievolkswirtschaft.ch/fr/2019/05/maurer-hoffmann-06-2019fr/, Institutional Repository

Avec une valeur de remplacement de 230 milliards de francs, les infrastructures d’approvisionnement en eau et d’élimination des eaux usées sont parmi les plus précieuses de Suisse. Les canalisations vieillissantes, l’évolution démographique et l’urbanisation croissante nécessitent d’investir 130 milliards de francs ces 30 prochaines années. Au niveau mondial, l’OCDE estime à 900 milliards de francs les fonds alloués chaque année à la gestion des eaux urbaines. Ce grand besoin d’investissements et la pression internationale accrue pour trouver de nouvelles approches favorisent des solutions innovantes. La recherche de pointe menée en Suisse dans ce domaine et la nécessité de renouveler les infrastructures confèrent un potentiel inexploité de marché pilote à notre pays. Un programme d’impulsion national permettant de coordonner les décisions d’infrastructure fragmentées des communes est néanmoins nécessaire.
Maurer, M., & Hoffmann, S. (2019). Sanierungsfall Abwassersystem. Volkswirtschaft, 89(6), 12-15. Retrieved from https://dievolkswirtschaft.ch/de/2019/05/hoffmann-maurer-06-2019/, Institutional Repository

Mit einem Wiederbeschaffungswert von 230 Milliarden Franken zählt die Wasserversorgung und Abwasserentsorgung in der Schweiz zu den wertvollsten Infrastrukturbauten. Alternde Leitungen, steigende Bevölkerungszahlen und zunehmende Urbanisierung verlangen in den nächsten 30 Jahren Investitionen von insgesamt 130 Milliarden Franken. Auf globaler Ebene schätzt die OECD die Investitionen in die Siedlungswasserwirtschaft auf jährlich 900 Milliarden Franken. Dieser hohe Investitionsbedarf und der global steigende Druck, neue Ansätze zu finden, bieten einen Spielraum für innovative Lösungen. Die Schweiz hat mit ihrer Spitzenforschung in diesem Bereich und dem aktuellen Bedarf an Infrastrukturerneuerung ein ungenutztes «Lead-Market»-Potenzial. Dazu braucht es aber ein gesamtschweizerisches Impulsprogram, das die fragmentierten Infrastrukturentscheide der Gemeinden koordiniert.
Moy de Vitry, M. (2019). Public surveillance and the future of urban pluvial flood modelling (Doctoral dissertation). doi:10.3929/ethz-b-000397587, Institutional Repository

Motivation and objective
Urban pluvial flooding is an issue of increasingly critical importance due to climate change and urbanization. However, the numerical models used for flood forecasting and risk mitigation suffer from a pronounced lack of monitoring data, which affects model accuracy. Monitoring data are necessary so the models, which contain undefined parameters, can be calibrated and validated against real flood events. In particular, it is important that the models are able to reproduce flood behavior in and around buildings, where the most damage is caused. However, conventional flow and water level sensors reach their limits in public spaces like streets due to irregular topography, moving obstacles, and the risk of vandalism. It has been suggested that surveillance cameras and social media could provide the necessary surface flooding data at a fraction of the cost of conventional sensors. The objective of this thesis is to explore how trend-like data can be extracted from surveillance footage and assimilated to boost the reliability of urban pluvial flood models. [...]

Motivation und Zielsetzung
Urbane regenbedingte Überschwemmungen sind aufgrund des Klimawandels und der Urbanisierung von immer größerer Bedeutung, aber den numerischen Modellen zur Hochwasservorhersage und Risikominderung mangelt es an Überwachungsdaten, was die Modellgenauigkeit einschränkt. Überwachungsdaten sind notwendig, damit die Modelle, welche unsichere Parameter enthalten, gegen echte Hochwasserereignisse kalibriert und validiert werden können. Insbesondere ist es wichtig, dass die Modelle das Überschwemmungsverhalten in und um Gebäude herum nachbilden können, wo die meisten Schäden verursacht werden. Herkömmliche Strömungs- und Wasserstandsensoren stoßen jedoch im öffentlichen Raum, wie Straßen, aufgrund unregelmäßiger Topographie, beweglicher Hindernisse und der Gefahr von Vandalismus an ihre Grenzen. Deswegen gibt es Interesse für alternative Datenquellen wie Überwachungskameras und soziale Medien, aus denen Oberflächenabflussdaten zu einem Bruchteil der Kosten herkömmlicher Sensoren gewonnen werden könnte. Das Ziel dieser Arbeit ist es, zu untersuchen, wie trendartige Daten aus Überwachungsbildern extrahiert und assimiliert werden können, um die Zuverlässigkeit von Überschwemmungsmodellen zu erhöhen. [...]
Mutzner, L., Vermeirssen, E. L. M., Mangold, S., Maurer, M., Scheidegger, A., Singer, H., … Ort, C. (2019). Passive samplers to quantify micropollutants in sewer overflows: accumulation behaviour and field validation for short pollution events. Water Research, 160, 350-360. doi:10.1016/j.watres.2019.04.012, Institutional Repository

Contaminants in sewer overflows can contribute to exceedances of environmental quality standards, thus the quantification of contaminants during rainfall events is of relevance. However, monitoring is challenged by i) high spatiotemporal variability of contaminants in events of hard-to-predict durations, and ii) a large number of remote sites, which would imply enormous efforts with traditional sampling equipment. Therefore, we evaluate the applicability of passive samplers (Empore styrene-divinylbenzene reverse phase sulfonated (SDB-RPS)) to monitor a set of 13 polar organic contaminants. We present calibration experiments at high temporal resolution to assess the rate limiting accumulation mechanisms for short events (<36 h), report parameters for typical sewer conditions and compare passive samplers with composite water samples in a field study (three locations, total 10 events). With sampling rates of 0.35–3.5 L/d for 1 h reference time, our calibration results indicate a high sensitivity of passive samplers to sample short, highly variable sewer overflows. The contaminant uptake kinetic shows a fast initial accumulation, which is not well represented with the typical first-order model. Our results indicate that mass transfer to passive samplers is either controlled by the water boundary layer and the sorbent, or by the sorbent alone. Overall, passive sampler concentration estimates are within a factor 0.4 to 3.1 in comparison to composite water samples in the field study. We conclude that passive samplers are a promising approach to monitor a large number of discharge sites although it cannot replace traditional stormwater quality sampling in some cases (e.g. exact load estimates, high temporal resolution). Passive samplers facilitate identifying and prioritizing locations that may require more detailed investigations.
Mutzner, L. Z. (2019). Spatiotemporal variability of micropollutants in sewer overflows (Doctoral dissertation). doi:10.3929/ethz-b-000349443, Institutional Repository

Motivation. Our surface water is impacted by a wide variety of contaminants released through human activities. One contaminant group of concern is micropollutants, which can have eco-toxicological effects in trace concentrations. Micropollutants, for example, include plant protection products and biocides, which are specifically designed to harm organisms. An important input pathway of micropollutants to surface water can be untreated sewer overflows (combined sewer overflows and stormwater outlets). However, the understanding of factors influencing the occurrence and levels of micropollutants is limited and challenged by: i) high spatial differences among sites, ii) a large number of discharge sites and iii) high temporal fluctuating discharge events.

Research objective. This thesis intends to enhance our understanding of micropollutants in sewer overflows. It aims to investigate efficient methods to prioritize sewer overflow sites, which can be potentially harmful for receiving waters. The presented work focuses on the development of model prediction and efficient monitoring approaches and includes the following: i) a Swiss-wide model to assess how many discharge sites may be critical (Chapter 2), ii) fundamentals to develop passive sampling as an alternative monitoring method for short duration sewer overflows (Chapter 3 and 4) and iii) an extended monitoring study covering 20 combined sewer overflows (CSOs) to explore spatial differences among sites (Chapter 5). The main findings of this thesis are presented in the following.

Model-based screening. A dynamic substance flow modeling approach was applied to 2,500 Swiss municipalities, considering micropollutant accumulation and wash-off on urban surfaces. The approach is based on the simplification, that there is one CSO and one stormwater outlet per municipality. The model allows for an estimation of the micropollutant concentration fluctuations in sewer overflows in 10-min resolution. The results show the importance of untreated discharges from sewer overflows as emission into receiving waters. The load contribution to sewer overflows of micropollutants in stormwater (e.g. plant protection products and biocides) is estimated to be considerably higher than of micropollutants in municipal wastewater (e.g. pharmaceuticals and other household chemicals). In addition, the results indicate that up to 83% of all urban catchments have sewer overflows that need to rely on upstream dilution in order to not exceed substance-specific environmental quality standards (EQS). Thus, this nationwide screening approach clearly highlights the need for a more detailed assessment of micropollutants in sewer overflows, and especially, the need for more measured data to allow the development of validated micropollutant prediction models.

Measuring. Difficulties of monitoring sewer overflows with traditional methods are i) high concentration fluctuations with unknown event durations which require a high temporal sampling resolution, ii) many discharge sites and iii) placement, operation, and maintenance of equipment. Hence, passive samplers for polar organic micropollutants are analyzed systematically as a viable alternative to monitor short duration sewer overflows. The main advantage of passive samplers is the continuous accumulation of contaminants from the water phase, with no need for external energy sources nor for immense water sample storage volume. In a first step, the impact of fluctuating concentrations on deviations from true time-weighted average (TWA) concentrations was studied. The results highlight that the deviations induced by fluctuating concentrations are similar or smaller than uncertainties arising from chemical analysis and environmental factors. Understanding the uptake mechanism of micropollutants is one of the most important issues that needs to be resolved to reduce uncertainties in passive sampling data. The uptake experiments in sewer conditions for short duration events (<36h) indicate that the mass transfer is either dominated by the sorbent, or, by a multi-step mechanism. Therefore, a new semi-empirical mixed rate control model is proposed, which can be directly used for future studies under similar conditions. A field validation (3 locations, 10 events) shows that TWA concentration estimates measured by passive samplers are within a factor of 0.4 to 3.1 compared to composite water samples. Hence, the use of upper limit TWA concentration estimates is recommended for compliance checking with EQS. The findings clearly show that passive samplers are suitable to estimate TWA concentration ranges in sewer overflows and, thus facilitate identification of potentially critical discharge sites.

Occurrence of micropollutants. Unique monitoring data from 20 CSO sites was collected with passive samplers. In total 13 polar organic micropollutants were analysed in 95 events (2-7 events per site). The results highlight indicator micropollutants, which were often found in the monitored CSOs and could be used in future monitoring studies: diclofenac, benzotriazole, carbamazepine, diazinon, diuron, carbendazim, mecoprop, metolachlor and terbutryn. Further, our results reveal that the spatial differences among CSO sites are bigger than the inter-event differences within a site for all studied micropollutants. Nevertheless, no significant correlation with land use data could be identified. The results, therefore, suggest that additional factors, most likely the contaminant usage pattern, have a considerable influence on the observed spatial differences. Both municipal wastewater and stormwater contributed to concentrations above the EQS in CSOs (not in the receiving water). In addition, the monitoring with passive samplers indicates that at least 13 out of 20 CSOs show concentrations above EQS in CSOs, and would rely on dilution by receiving waters to not exceed EQS.

Outlook. Overall, the thesis shows the relevance of sewer overflows as a source of micropollutants entering receiving water bodies. The findings can serve as a basis for the development of a systematic and stepwise approach to efficiently identify critical sites. The development of such an approach would require joint efforts by eco-toxicologists, analytical chemists, regulators and wastewater engineers. This approach could be based on a simplified modeling approach as a first indicator, followed by passive sampling to assess micropollutant levels. To enable the widespread application of passive samplers in monitoring programs, regulators’ and operators’ confidence in passive sampling needs to be strengthened with more field validation studies and common guidelines.
Penn, R., Maurer, M., Michalec, F. G., Scheidegger, A., Zhou, J., & Holzner, M. (2019). Quantifying physical disintegration of faeces in sewers: stochastic model and flow reactor experiments. Water Research, 152, 159-170. doi:10.1016/j.watres.2018.12.037, Institutional Repository

We present a novel stochastic model for quantifying gross solids (GS) physical disintegration under varying turbulent flow conditions and used a unique experimental setup for model calibration and validation. The stochastic deterioration model predicts faeces size evolution over time. It conceptually entails the two main processes of solid fragmentation, namely breakage and erosion. Model parameters were calibrated on synthetic faeces and validated with real human ones. A cylindrical reactor was used, where turbulent flow was forced by an array of water jets and the physical disintegration of the faeces was monitored using a high speed camera. Image analysis of breakage experiments obtained under backlight illumination allowed determination of the evolution of the solids’ size over time. The flow field in the reactor was characterised by particle image velocimetry (PIV) using tracer particles seeded into the water. We found different disintegration behaviours depending on turbulence intensity and water content of the solid. In conditions of low shear stress, dense solids hardly disintegrated. Generally, the model predictions mirrored the broad range in the solids disintegration rate imparted by the high variability in flow conditions and in solids characteristics. It is expected that, similar to our experiments, also in real sewer systems both flow conditions and solid characteristics are highly variable and the stochastic model can be tailored to capture this variability. We thus anticipate that the model can be integrated into existing sewer models predicting sewer flows and solids’ movement. From these, shear stress, flow velocities and transport of individual solids can be inferred. The integration of the present solids disintegration model may provide better predictions of hot-spots for solids accumulation and blockages in sewers.
Schneider, M. Y., Carbajal, J. P., Furrer, V., Sterkele, B., Maurer, M., & Villez, K. (2019). Beyond signal quality: the value of unmaintained pH, dissolved oxygen, and oxidation-reduction potential sensors for remote performance monitoring of on-site sequencing batch reactors. Water Research, 161, 639-651. doi:10.1016/j.watres.2019.06.007, Institutional Repository

Sensor maintenance is time-consuming and is a bottleneck for monitoring on-site wastewater treatment systems. Hence, we compare maintained and unmaintained sensors to monitor the biological performance of a small-scale sequencing batch reactor (SBR). The sensor types are ion-selective pH, optical dissolved oxygen (DO), and oxidation-reduction potential (ORP) with platinum electrode. We created soft sensors using engineered features: ammonium valley for pH, oxidation ramp for DO, and nitrite ramp for the ORP. Four soft sensors based on unmaintained pH sensors correctly identified the completion of the ammonium oxidation (89–91 out of 107 cycles), about as many times as soft sensors based on a maintained pH sensor (91 out of 107 cycles). In contrast, the DO soft sensor using data from a maintained sensor showed slightly better (89 out of 96 cycles) detection performance than that using data from two unmaintained sensors (77, respectively 82 out of 96 correct). Furthermore, the DO soft sensor using maintained data is much less sensitive to the optimisation of cut-off frequency and slope tolerance than the soft sensor using unmaintained data. The nitrite ramp provided no useful information on the state of nitrite oxidation, so no comparison of maintained and unmaintained ORP sensors was possible in this case. We identified two hurdles when designing soft sensors for unmaintained sensors: i) Sensors’ type- and design-specific deterioration affects performance. ii) Feature engineering for soft sensors is sensor type specific, and the outcome is strongly influenced by operational parameters such as the aeration rate. In summary, the results with the provided soft sensors show that frequent sensor maintenance is not necessarily needed to monitor the performance of SBRs. Without sensor maintenance monitoring smalls-scale SBRs becomes practicable, which could improve the reliability of unstaffed on-site treatment systems substantially.
Beutler, P., Kianfar, B., Blumensaat, F., & Maurer, M. (2018). Klimawandel und Starkregen. Führt der Klimawandel zu veränderten Starkregen in der Schweiz? Ein Statusbericht. Aqua & Gas, 98(10), 14-20. , Institutional Repository

Ist in der Zukunft ein Einfluss des Klimawandels auf die für die Dimensionierung der Siedlungsentwässerung relevanten Starkregen erkennbar? Untersuchungen zeigen kein erkennbares Klimasignal, weder für die nahe (2035–2064) noch für die ferne Zukunft (2070–2099). Dies gilt für die Wiederkehrintervalle 5, 10 und 30 Jahre mit je drei Dauerstufen (10 Min., 60 Min., 24 Std.) und für die vier Niederschlagsregionen in der Schweiz, repräsentiert durch 22 MeteoSchweiz-Wetterstationen.
Blumensaat, F., Scheidegger, A., Ebi, C., Dicht, S., Schaltegger, F., Rüst, A., … Maurer, M. (2018). Digitalization meets reality - concept and experiences from long-term wireless data collection with 50+ sewer monitors. In G. Mannina (Ed.), Proceedings of 11th international conference on urban drainage modelling (pp. 360-363). sine loco: IWA. , Institutional Repository

Blossoming visions foresee an ubiquitous availability of data enabled through emerging sensors, novel transmission technologies and revisited data analysis techniques. It is often expected that this likewise applies to urban water management (Kerkez et al., 2016; Eggimann et al., 2017). Contrary to the envisioned easiness to collect data, an in-creasing number of studies report about a declining effort to conduct experimental field re-search in catchment and urban hydrology, implying the risk of scientific advancement to be misdirected (Blume et al., 2017; van Emmerik et al., 2018). In this paper, we present re-sults from a unique sensor network that collects, transmits, and organizes very high resolu-tion status information from an urban drainage catchment. Our findings are based on a two-year operation at full-scale with more than 50 sensor nodes connected to a low-power wireless sensor network (LPWSN). In essence we i) illustrate the scalability of LPWSNs, ii) reveal telemetry limitations of the LoRaWAN standard (LoRa®Alliance 2015), iii) suggest a novel technique (LoRaMesh) to master this constraint, and iv) discuss challenges associ-ated with managing the amount of data collected from diverse sources. We find: 1. the proposed transmission technique considerably improves telemetry performance of the en-tire network without introducing additional gateway stations (total packet loss 2.2 %). 2. Dynamic and flexible data management solutions come at a price. 3. It is not the pure amount of data that is most challenging but the diversity of different signals. 4. Full metada-ta integration in the data warehouse is laborious but clearly consolidates data interpretation in the long-term run.
Eggimann, S., Truffer, B., Feldmann, U., & Maurer, M. (2018). Screening European market potentials for small modular wastewater treatment systems – an inroad to sustainability transitions in urban water management?. Land Use Policy, 78, 711-725. doi:10.1016/j.landusepol.2018.07.031, Institutional Repository

Urban water management represents a core economic sector exposed to global water-related challenges. Recently, small modular system configurations have been identified to enable a potential sustainability transition in this lasting and rather conservative sector. The identification of current market potentials of decentralised wastewater treatment is a first step to assess whether decentralised treatment technologies could potentially be deployed on a larger scale in Europe, which would allow current decentralised wastewater treatment technologies to develop and mature. The paper elaborates a method to assess the market potential for decentralised wastewater treatment systems by starting from a raster-based geospatial modelling framework, to determine the optimal degrees of centralisation for the case of Switzerland. The resulting market potential is shown to be twenty times higher than the current market share of decentralised systems. In order to extrapolate these findings to other countries, the calculated optimal degrees of centralisation were correlated with different spatial density measures to determine a reliable and widely available proxy: population density. Based on this indicator, the European market potentials for decentralised treatment systems are estimated to be about 100,000 units per annum serving around 35 million population equivalents. The paper concludes by discussing implications for future sustainability transitions in urban water management by large-scale installation of small modular wastewater treatment systems.
Maurer, M. (2018). Die Zukunft gestalten. Aqua & Gas, 98(10), 30-33. , Institutional Repository

Die Aufgaben der Siedlungsentwässerung werden immer komplexer und anspruchsvoller. Umso wichtiger ist es, engagierte Talente für die Siedlungswasserwirtschaft zu begeistern. Wie das gelingt, erklären sieben junge Forscherinnen und Forscher aus ihrer ganz persönlichen Sicht.
Penn, R., Ward, B. J., Strande, L., & Maurer, M. (2018). Review of synthetic human faeces and faecal sludge for sanitation and wastewater research. Water Research, 132, 222-240. doi:10.1016/j.watres.2017.12.063, Institutional Repository

Investigations involving human faeces and faecal sludge are of great importance for urban sanitation, such as operation and maintenance of sewer systems, or implementation of faecal sludge management. However, working with real faecal matter is difficult as it not only involves working with a pathogenic, malodorous material but also individual faeces and faecal sludge samples are highly variable, making it difficult to execute repeatable experiments. Synthetic faeces and faecal sludge can provide consistently reproducible substrate and alleviate these challenges. A critical literature review of simulants developed for various wastewater and faecal sludge related research is provided. Most individual studies sought to develop a simulant representative of specific physical, chemical, or thermal properties depending on their research objectives. Based on the review, a suitable simulant can be chosen and used or further developed according to the research needs. As an example, the authors present such a modification for the development of a simulant that can be used for investigating the motion (movement, settling and sedimentation) of faeces and their physical and biological disintegration in sewers and in on-site sanitation systems.
Spuhler, D., Scheidegger, A., & Maurer, M. (2018). Generation of sanitation system options for urban planning considering novel technologies. Water Research, 145, 259-278. doi:10.1016/j.watres.2018.08.021, Institutional Repository

The identification of appropriate sanitation systems is particularly challenging in developing urban areas where local needs are not met by conventional solutions. While structured decision-making frameworks such as Community-Led Urban Environmental Sanitation (CLUES) can help facilitate this process, they require a set of sanitation system options as input. Given the large number of possible combinations of sanitation technologies, the generation of a good set of sanitation system options is far from trivial.
This paper presents a procedure for generating a set of locally appropriate sanitation system options, which can then be used in a structured decision-making process. The systematic and partly automated procedure was designed (i) to enhance the reproducibility of option generation; (ii) to consider all types of conventional and novel technologies; (iii) to provide a set of sanitation systems that is technologically diverse; and (iv) to formally account for uncertainties linked to technology specifications and local conditions.
We applied the procedure to an emerging small town in Nepal. We assessed the appropriateness of 40 technologies and generated 17,955 appropriate system options. These were classified into 16 system templates including on-site, urine-diverting, biogas, and blackwater templates. From these, a subset of 36 most appropriate sanitation system options were selected, which included both conventional and novel options.
We performed a sensitivity analysis to evaluate the impact of different elements on the diversity and appropriateness of the set of selected sanitation system options. We found that the use of system templates is most important, followed by the use of a weighted multiplicative aggregation function to quantify local appropriateness. We also show that the optimal size of the set of selected sanitation system options is equal to or slightly greater than the number of system templates.
As novel technologies are developed and added to the already large portfolio technology options, the procedure presented in this work may become an essential tool for generating and exploring appropriate sanitation system options.
Wani, O. (2018). Statistical methods for better hydrologic predictions. Improving parameter and uncertainty estimation (Doctoral dissertation). doi:10.3929/ethz-b-000315756, Institutional Repository

Hydrologic systems are complex - constituting spatially distributed and temporally variable properties and processes. Such systems are generally modelled mathematically after some simplifying assumptions, for example, by aggregating certain variable properties and neglecting many subprocesses. These model structure deficits result in a mismatch between the real and the modelled system response, which entails uncertain predictions. In addition to model structure deficits, the presence of errors in model inputs and in the observations of system response contributes to the uncertainty in the estimation of model parameters. For risk-based decision making and for statistical hypothesis testing using these models, their uncertainties need to be adequately and explicitly stated. Furthermore, attempts need to be made to reduce these uncertainties. [...]

Hydrologische Systeme sind komplex - sie bilden räumlich verteilte und zeitlich veränderliche Eigenschaften und Prozesse ab. Solche Systeme werden mathematisch unter einigen vereinfachenden Annahmen modelliert, beispielsweise durch das Aggregieren bestimmter Variableneigenschaften und das Vernachlässigen einiger Teilprozesse. Diese Defizite in der Modellstruktur führen zu einer Diskrepanz zwischen realem und modelliertem System, was zu Vorhersagen mit grösserer Unsicherheiten führt. Weiterhin trägt das Auftreten von Fehlern in den Input-Parametern sowie in den simulierten Resultaten zu Unsicherheiten bei der Schätzung von Modellparametern bei. Für eine risikobasierte Entscheidungsfindung sowie für statistische Hypothesentests unter Verwendung der Modelle müssen Unsicherheiten angemessen und explizit angegeben und langfristig reduziert werden.
Blumensaat, F., Ebi, C., Dicht, S., Rieckermann, J., & Maurer, M. (2017). IoT driven low-power radio technology for highly distributed in-sewer monitoring - a data collection technique that shifts paradigms?. In 14th IWA/IAHR international conference on urban drainage. Conference proceedings (pp. 1542-1547). Prague: c-in. , Institutional Repository

Urban drainage systems traditionally lack adequate monitoring and evaluation technologies. Although weather radar and high-resolution remote sensing technologies promise vast advances for rainfall and land-use data collection, it is still challenging to deploy dense hydrological monitoring networks for sewers. Low-power data transmission technology, which is the communication backbone in the Internet-Of-Things (IoT), has the potential to contribute to a game change towards an evidence-based management of urban drainage systems. In this paper, we share our experiences with establishing and operating a wireless sensor network (WSN) at full-scale with approximately a 1 sensor per hectare connected catchment area and a monitoring frequency of 5 minutes or less. Specifically, we discuss i) the monitoring and deployment approach and ii) the adequacy of sensorand LoRaWANTM wireless data transmission technology for monitoring applications in sewer networks. A thorough evaluation of the telemetry performance provides evidence that the proposed technique allows a highly distributed monitoring of drainage capacity, sewer infiltration, performance of retention basins and overflows, with a far less effort compared to conventional methods. Remaining challenges concern the radio network architecture to allow better access to deep underground structures and efficient methods for automated data quality control to handle this type of data in the future.
Blumensaat, F., Ebi, C., Dicht, S., Rieckermann, J., & Maurer, M. (2017). Langzeitüberwachung der Raum-Zeit-Dynamik in Entwässerungssystemen mittels Niedrigenergiefunk. KA: Korrespondenz Abwasser Abfall, 64(7), 594-603. doi:10.3242/kae2017.07.001, Institutional Repository

Obgleich gegenwärtig mittels Regenradar und hochauflösender Fernerkundung immer effizienter Daten zu Niederschlag, Topographie und Landnutzung erhoben werden, ist es nach wie vor schwierig, eine hydrologische Überwachung für Entwässerungssysteme mit hinreichender Informationsdichte und -konsistenz zu realisieren. Ob und inwieweit die Technologie des Niedrigenergiefunks (LPWAN) – als Kommunikations-Backbone des Internet der Dinge (IoT) bekannt – das Potenzial hat, diese Lücke zu schließen, diskutieren wir in diesem Beitrag. Grundlage dafür sind unsere Erfahrungen beim Aufbau und dem bis dato einjährigen Betrieb eines Drahtlossensornetzwerks in einem mittelgroßen Schweizer Siedlungsentwässerungsnetz mit einer Sensordichte von über einem Sensor pro Hektar und einer Überwachungsfrequenz von fünf Minuten. Im Einzelnen erörtern wir i) das zugrundeliegende Monitoringkonzept, ii) die technische Spezifikation der Sensorik und der Datenübertragungstechnologie LoRaWANTM und iii) die bisherigen Erfahrungen zur Systemperformance, illustriert durch ein Anwendungsbeispiel.
Eggimann, S., Mutzner, L., Wani, O., Schneider, M. Y., Spuhler, D., Moy de Vitry, M., … Maurer, M. (2017). The potential of knowing more: a review of data-driven urban water management. Environmental Science and Technology, 51(5), 2538-2553. doi:10.1021/acs.est.6b04267, Institutional Repository

The promise of collecting and utilising large amounts of data has never been greater in the history of urban water management (UWM). This paper reviews several data-driven approaches which play a key role in bringing forward a sea change. It critically investigates whether data-driven UWM offers a promising foundation for addressing current challenges and supporting fundamental changes in UWM. We discuss the examples of better rain-data management, urban pluvial flood-risk management and forecasting, drinking water and sewer network operation and management, integrated design and management, increasing water productivity, wastewater-based epidemiology and on-site water and wastewater treatment. The accumulated evidence assembled from research documented in the literature points towards a future UWM that offers significant potential benefits thanks to increased collection and utilisation of data. The findings show that data-driven UWM allows us to develop and apply novel methods, to optimize the efficiency of the current network-based approach, and an extended functionality of today’s systems. However, generic challenges related to data-driven approaches (e.g. data processing, data availability, data quality, data costs) and the specific challenges of data-driven UWM need to be addressed, namely data access and ownership, current engineering practices and the difficulty of assessing the cost benefits of data-driven UWM.
Manny, L. A. D. (2017). Policy-Analyse im Bereich Gewässerschutz bei Regenwetter (Master thesis). 105 p. , Institutional Repository

Für einen effektiveren Gewässerschutz bei Regenwetter bedarf es nicht nur der Optimierung von Kläranlagen, sondern auch einem Verständnis über die hydraulische Funktionsweise von Sonderbauwerken, wie z.B. Regenüberlaufbecken (RÜB). RÜB, die bei grösseren Regenereignissen verdünntes Mischabwasser in die Gewässer einleiten, werden auf Grundlage von Simulationsmodellen dimensioniert. Ob die berechnete Entlastungshäufigkeit und -dauer auch der tatsächlichen entspricht, wird in der Schweizer Praxis kaum überprüft. Zur Überprüfung können RÜB mit Messgeräten ausgerüstet und wichtige Variablen, wie z.B. der Wasserstand im RÜB erfasst werden. Für Datenfernübertragung und die automatisierte Auswertung sind heute praxistaugliche Technologien verfügbar. Es besteht daher die Vermutung, dass der Einsatz vorhandener Messtechnik an RÜB nicht durch technische Deffizite zu begründen ist, sondern dass das Verständnis für den tatsächlichen Wert und Nutzen von Messdaten bei Betreibern und Behörden fehlt.

Das Ziel dieser Masterarbeit ist es, erstens den heutigen Zustand in der Schweiz in Bezug auf die Ausstattung von RÜB mit Messtechnik und den Umgang mit Messdaten zu erfassen und zu erklären. Davon werden zweitens Instrumente abgeleitet, die dazu beitragen könnten, dass Messdaten von allen Akteuren (Gemeinden, Abwasserverbänden, Kantone, Bund, Ingenieur- und Planungsbüros) genutzt werden. Zur gemeinsamen Untersuchung des technischen Systems und beteiligter Akteure werden methodische Ansätze aus der Policy-Analyse angewendet, wobei der Fokus auf die Abwasserverbände in der Schweiz gelegt wurde. Eine Online-Umfrage wurde durchgeführt und mit deskriptiven und erklärenden statistischen Analysemethoden (wie z.B. Regressionsanalysen) ausgewertet.

Mit der Online-Umfrage werden 73 % der Abwasserverbände in der Schweiz abgedeckt. Überraschend positiv ist, dass insgesamt bereits 84 % der RÜB, die sich im Betrieb von Abwasserverbänden befinden, mit einem Messgerät ausgerüstet sind. Defizite sind jedoch im Umgang mit den Messdaten vorhanden. In 34 % der Abwasserverbände werden Wasserstands-Daten aggregiert, was heute nicht mehr dem Stand der Technik entspricht. Daten werden in 47 % der Abwasserverbände nie oder nur unregelmässig ausgewertet und in 61 % weder an Ingenieurbüros (für Planungszwecke) noch an kantonale Fachstellen (zur Erfolgskontrolle) weitergeleitet. Das liegt vor allem daran, dass Abwasserverbände Messdaten hauptsächlich für die betriebliche Optimierung nutzen. Da Kosteneinsparungen eher im Hintergrund stehen, liegt nahe, dass Subventionen weniger bevorzugt sind. Vielmehr priorisieren Abwasserverbände und Kantone die Einführung von Zielvorgaben.

Die Ergebnisse aus der Online-Umfrage beschränken sich nur auf die Abwasserverbände, Gemeinden werden z.B. nicht untersucht. Da die Situation in der Schweiz sehr heterogen ist, sollten Instrumente regional angepasst werden. Um dies zu untersuchen, wären weitergehende statistische Verfahren, wie z.B. die Clusteranalyse, angebracht.

Die Ergebnisse deuten darauf hin, dass für eine volle Wertausschopfung von Messdaten regulative Instrumente ebenso erforderlich sind wie organisatorische Anpassungen. Dafür sollten Akteure (Bund, Kantone, VSA) zum Beispiel eine Verordnung entwickeln, die Zielvorgaben für RÜB definiert und betriebliche Kompetenzen klar verteilt.

Diese Masterarbeit stellt viel Material bereit, das sich ohne grosse Anpassungen auch für die Untersuchung in anderen Ländern (z.B. Deutschland, Österreich) anbietet.
Mutzner, L., Mangold, S., Maurer, M., Scheidegger, A., Singer, H., Vermeirssen, E., & Ort, C. (2017). Passive sampling: an efficient way to monitor micropollutants in sewer overflows? (pp. 10-17). Presented at the 14th IWA/IAHR international conference on urban drainage (ICUD). Prague: CZWA; Czech Technical University; IAHR/AIRH; IWA. , Institutional Repository

High spatio-temporal variability characterizes micropollutants discharged from separate and combined sewers. This challenges monitoring and prediction. We propose passive samplers (Chemcatcher® for polar, organic substances) as an alternative to active water sampling. Our results indicate sufficient sensitivity of passive samplers for short exposures so that typical rain event durations (<30 h) can be sampled integratively. Although time-weighted average concentrations estimated via passive sampling are higherthan in composite water samples -on average by a factor 2.7 - we conclude that passive sampling is a cost-effective approach to identify locations with critical concentration ranges.
Scholten, L., Maurer, M., & Lienert, J. (2017). Comparing multi-criteria decision analysis and integrated assessment to support long-term water supply planning. PLoS One, 12(5), e0176663 (30 pp.). doi:10.1371/journal.pone.0176663, Institutional Repository

We compare the use of multi-criteria decision analysis (MCDA)–or more precisely, models used in multi-attribute value theory (MAVT)–to integrated assessment (IA) models for supporting long-term water supply planning in a small town case study in Switzerland. They are used to evaluate thirteen system scale water supply alternatives in four future scenarios regarding forty-four objectives, covering technical, social, environmental, and economic aspects. The alternatives encompass both conventional and unconventional solutions and differ regarding technical, spatial and organizational characteristics. This paper focuses on the impact assessment and final evaluation step of the structured MCDA decision support process. We analyze the performance of the alternatives for ten stakeholders. We demonstrate the implications of model assumptions by comparing two IA and three MAVT evaluation model layouts of different complexity. For this comparison, we focus on the validity (ranking stability), desirability (value), and distinguishability (value range) of the alternatives given the five model layouts. These layouts exclude or include stakeholder preferences and uncertainties. Even though all five led us to identify the same best alternatives, they did not produce identical rankings. We found that the MAVT-type models provide higher distinguishability and a more robust basis for discussion than the IA-type models. The needed complexity of the model, however, should be determined based on the intended use of the model within the decision support process. The best-performing alternatives had consistently strong performance for all stakeholders and future scenarios, whereas the current water supply system was outperformed in all evaluation layouts. The best-performing alternatives comprise proactive pipe rehabilitation, adapted firefighting provisions, and decentralized water storage and/or treatment. We present recommendations for possible ways of improving water supply planning in the case study and beyond.
Barrett, R. (2016). Spatial modelling of rain-induced infiltration into sewers (Master thesis). 37 p. , Institutional Repository
Eggimann, S., Truffer, B., & Maurer, M. (2016). Economies of density for on-site waste water treatment. Water Research, 101, 476-489. doi:10.1016/j.watres.2016.06.011, Institutional Repository

Decentralised wastewater treatment is increasingly gaining interest as a means of responding to sustainability challenges. Cost comparisons are a crucial element of any sustainability assessment. While the cost characteristics of centralised waste water management systems (WMS) have been studied extensively, the economics of decentralised WMS are less understood. A key motivation for studying the costs of decentralised WMS is to compare the cost of centralised and decentralised WMS in order to decide on cost-efficient sanitation solutions. This paper outlines a model designed to assess those costs which depend on the spatial density of decentralised wastewater treatment plants in a region. Density-related costs are mostly linked to operation and maintenance activities which depend on transportation, like sludge removal or the visits of professionals to the plants for control, servicing or repairs. We first specify a modelled cost-density relationship for a region in a geometric two-dimensional space by means of heuristic routing algorithms that consider time and load-capacity restrictions. The generic model is then applied to a Swiss case study for which we specify a broad range of modelling parameters. As a result, we identify a ‘hockey-stick’-shaped cost curve that is characterised by strong cost reductions at high density values which level out at around 1 to 1.5 plants per km2. Variations in the cost curves are mostly due to differences in management approaches (scheduled or unscheduled emptying). In addition to the well-known diseconomies of scale in the case of centralised sanitation, we find a similar generic cost behaviour for decentralised sanitation due to economies of density. Low densities in sparsely populated regions thus result in higher costs for both centralised and decentralised system. Policy implications are that efforts to introduce decentralised options in a region should consider the low-density/high-cost problem when comparing centralised and decentralised options.
Eggimann, S., Truffer, B., & Maurer, M. (2016). The cost of hybrid waste water systems: a systematic framework for specifying minimum cost-connection rates. Water Research, 103, 472-484. doi:10.1016/j.watres.2016.07.062, Institutional Repository

To determine the optimal connection rate (CR) for regional waste water treatment is a challenge that has recently gained the attention of academia and professional circles throughout the world. We contribute to this debate by proposing a framework for a total cost assessment of sanitation infrastructures in a given region for the whole range of possible CRs. The total costs comprise the treatment and transportation costs of centralised and on-site waste water management systems relative to specific CRs. We can then identify optimal CRs that either deliver waste water services at the lowest overall regional cost, or alternatively, CRs that result from households freely choosing whether they want to connect or not. We apply the framework to a Swiss region, derive a typology for regional cost curves and discuss whether and by how much the empirically observed CRs differ from the two optimal ones. Both optimal CRs may be reached by introducing specific regulatory incentive structures.
Eggimann, S. J. (2016). The optimal degree of centralisation for wastewater infrastructures. A model-based geospatial economic analysis (Doctoral dissertation). doi:10.3929/ethz-a-010811248, Institutional Repository

Efficient infrastructure planning is essential to achieve a more sustainable future. This includes aiming for optimal and economically more efficient infrastructures in the field of urban water management (UWM). Especially network-based infrastructures need special attention as they are generally very cost intensive and have distinctly demanding planning characteristics. Today’s historically evolved UWM practices tend to be network-based as in the last century enormous investments have been made to build-up vast sewer networks and large central wastewater treatment plants which centrally connect very high population percentages in many countries. The construction of large network infrastructures has resulted in a dominant centralised planning paradigm and heavily centralised wastewater management systems (WMS). However, this strong central planning paradigm is increasingly being questioned with respect to sustainability challenges and the call is becoming louder for innovative and radical approaches to address future challenges in the field of UWM. One such innovative approach is the decentralised treatment of wastewater by decentralised WMS, although in countries with high central connection rates this has so far been seen mainly as a stopgap solution. Today, connection rates differ significantly across countries: Great differences exist not only between high-income and low-income countries but also within OECD countries. It is unclear to what degree centralised or decentralised WMS should be installed in a region from the point of view of economic efficiency. Whereas the UWM literature presents specific cost assessments, there is a paucity of tools and methods to assess the costs of WMS consisting of centralised and decentralised systems (hybrid WMS). There are also few cost assessments of decentralised WMS with respect to their operation and maintenance costs. This dissertation uses an economic geospatial model-based approach to address the challenging research question of the optimal degree of centralisation. Conceptually, especially the spatially explicit full-cost modelling and the socio-technical conceptualisation of WMS are of special relevance. The basic trade-off between wastewater transportation and treatment is modelled in a geographically explicit way, economies of density for decentralised systems are assessed and a framework is presented to assess different optimal connection rates for hybrid systems. This framework is then used to assess economically sustainable connection rates in order to promote the economic argumentation for a possible sustainability transition in UWM. [...]
FitzGerald, D. V. (2016). Taking into account future uncertainty when designing urban water supply systems: a flexible approach (Master thesis). 59 p. , Institutional Repository

Water supply networks have to be designed while taking into account the long-term future water demand. Given the difficulties in estimating the future water demand, a flexible approach for planning water supply systems was implemented. The flexibility in engineering design approach (de Neufville and Scholtes, 2011) is a procedure for designing systems in the face of an uncertain future. This approach was applied to a fictitious town, which is expected to expand in the near future and will need to extend its water supply network to the new areas.
To model the uncertain future water demand, 1000 scenarios were generated by randomly projecting the population of the town. A decision rule, which governs when the network must be modified, was defined based on the pressure that is required at the nodes of the network. Four different design alternatives were tested: the deterministic design, which is completely built in advance based on one single scenario, and three flexible designs, which consist in expanding the network as the water demand changes.
The design alternatives were simulated using the hydraulic solver EPANET and were evaluated in terms of costs, using the specific net present value, and in terms of performance based on the pressure and residence time of water in the network. The results showed that the flexible design alternatives provide a significant decrease in the specific costs compared to the deterministic design, thus demonstrating the value of flexible designs. By evaluating the designs over a range of water demand scenarios, different results were obtained compared to the case where only one scenario was used. This showed that the flexibility in engineering design approach is a helpful tool for designing water supply networks in the context of an uncertain future.
Keller, C. (2016). Understanding the urban drainage system of Fehraltorf. Enhancing the reliability of Fehraltorf’s SWMM model through calibration (Master thesis). 30 p. , Institutional Repository

The hydraulic behavior and the capacity of sewer systems are assessed through hydrodynamic modeling. They are widely used in drainage planning, although their parameters are mostly estimated and the models are only checked for general plausibility. The Master‘s Thesis assessed the effect of calibration on the model reliability on the basis of a case study, namely Fehraltorf.
Fehraltorf is located in the agglomeration of Zurich and Winterthur and is inhabited by 6’292 people. Most of the village of Russikon and Fehraltorf are connected to the WWTP of Fehraltorf. The DWF amounts up to 66 l/s, whereas the residual flow Q347 of the main receiving water (Luppmen) is 72 l/s. The infiltration of the groundwater is 30.1 l/s, as a significant share of the drainage system was built below the average groundwater table.
During the thesis the conversion of the Mike Urban model to SWMM was revised and further adjustments were implemented. The data for input and calibration was chosen depending on its reliability and further processed if necessary. Rain events were selected and split for calibration and validation. Parameters known to be changed in the calibrations were selected and in the sensitivity analysis the most sensitive, and thus, important parameters were determined. Then, the calibration was conducted manually as well as automatically with simulated annealing. The effect of calibration was assessed for the calibration and validation events visually and with various objective functions, viz. Nash-Sutcliffe Efficiency, total volume, peak flow and time to peak. The hydraulic performance of the sewer system was tested by simulating a 10-year design rainfall event in the uncalibrated and the calibrated model.
For the simulations, the data of the rain gauge on the WWTP had to be discarded because it showed high deviations to the ones installed by EAWAG. The rainfall data and flow data (of the FloDars) collected by EAWAG were assessed to be reliable, but as the measurements were installed recently, only four rain events were available for calibration and validation. The objective functions could be raised to a satisfying level in the manual calibration and were further improved in the automatic calibration. The validation confirmed that the reliability of the model could be increased with calibration. Furthermore, the assessment of the sewer system revealed that there are less capacity limits in the calibrated model then in the uncalibrated one, but further adjustments are needed due to numerical instabilities.
Even though the validation suggests that manual as well as automatic calibration enhance the reliability of the model because of improved goodness of fit assessed by different objective functions, further input data and reliable calibration data is needed to perform the calibration once more.
After all, calibration is strongly recommended by the author of this thesis to not only improve parameter values which were only estimated in the uncalibrated models but also to detect systematic errors in the data and the model structure.
Larsen, T. A., Hoffmann, S., Lüthi, C., Truffer, B., & Maurer, M. (2016). Emerging solutions to the water challenges of an urbanizing world. Science, 352(6288), 928-933. doi:10.1126/science.aad8641, Institutional Repository

The top priorities for urban water sustainability include the provision of safe drinking water, wastewater handling for public health, and protection against flooding. However, rapidly aging infrastructure, population growth, and increasing urbanization call into question current urban water management strategies, especially in the fast-growing urban areas in Asia and Africa. We review innovative approaches in urban water management with the potential to provide locally adapted, resource-efficient alternative solutions. Promising examples include new concepts for stormwater drainage, increased water productivity, distributed or on-site treatment of wastewater, source separation of human waste, and institutional and organizational reforms. We conclude that there is an urgent need for major transdisciplinary efforts in research, policy, and practice to develop alternatives with implications for cities and aquatic ecosystems alike.
Schegg, S. (2016). Modern receiving water protection using an integrated control system (Master thesis). 36 p. , Institutional Repository

A case study for an integrated real time control (RTC) in the catchment Wohlen-Villmergen, Switzerland is introduced. The RTC-based control was simulated for the inflows to the wastewater treatment plant Wohlen and the connecting sewer system using a conceptual model in CityDrain II. For evaluating the model performance, high-resolution routine data were available for the entire year of 2015.
The main goal of this thesis was to control the system with an aim to improve the receiving water quality. In urban drainage systems, combined sewer overflows (CSO) represent the main pollutant source. A load-based approach was introduced to further characterize CSO. Then, different static and dynamic control strategies were compared for reducing CSO number, volume and load.
It was found that a dynamically controlled RTC can avoid 25 % of CSO events that would have happened in a static controlled system in 2015. However, the reduction was much smaller for overall CSO volume (7 %) and load (9 %).
Schärer, N. (2016). Evaluation of the impact of presence / absence tests on safe water consumption (Master thesis). 30 p. , Institutional Repository

Nepal’s human development index ranks 145 among 188 countries. Even though 88 % of the Nepalese population had access to an improved drinking water source in 2011, a study in 2014 showed that 91 % of the households had detectable E.coli contamination in their stored drinking water at the household.
The aim of this study was to evaluate the impact of three different interventions on safe water consumption. The initial hypotheses were that groups with the opportunity to observe P/A water quality tests conducted during the intervention get a higher risk awareness on water quality than the group only receiving WASH information, which is expressed in more consistent water treatment and better hygiene, and leads to better water quality at household level. And that if P/A tests were conducted at household level people get a higher risk awareness on water quality than the group conducting P/A tests at community level, which is also expressed in more consistent water treatment and better hygiene that leads to better water quality at household level.
During a field study, questionnaires in households and water sampling at the households and at the points of collection were conducted to evaluate 3 different WASH education campaigns. All three sites received a promotion campaign focussing on providing WASH information, in addition P/A tests were conducted at household level in one site, another included P/A tests at community level while no water quality tests were conducted in the third site.
The results showed no significant difference in risk awareness, hygiene or microbiological water quality at household level between the three interventions. The WASH intervention was very effective, since the percentage of people treating their drinking water rose from 18 % in the baseline study to 86 % after the intervention. Also other hygiene behaviours improved. Even though 77 % of all households used ceramic candle filters as household water treatment, water quality did not improve compared to the baseline study (2014). Average water quality at the point of use was worse than at the point of collection indicating a high level of recontamination during transport, treatment and storage. The recontamination in the filter could be caused by wrong installation, handling and maintenance.
The initial set of hypotheses had to be rejected because no significant differences in WASH behaviour in the three groups could be observed neither any differences in water quality that were attributable to the intervention could be observed. The P/A tests therewith had no impact. Since the WASH information was so effective it is possible that the impact of P/A tests was relatively low and therefore not detectable any more. For further studies it is important to ensure that a careful training on the proper installation, the handling and the maintenance of the promoted household water treatment is included in the intervention.
Maurer, M., Rieckermann, J., Muschalla, D., Gruber, G., Schmitt, T. G., Kaufmann Alves, I., … Dittmer, U. (Eds.). (2016). "Miss es oder vergiss es!" - Daten, Wissen und Konzepte für den Gewässerschutz bei Regenwetter. Aqua Urbanica 2016. Dübendorf: Eawag. , Institutional Repository
Egger, C., & Maurer, M. (2015). Importance of anthropogenic climate impact, sampling error and urban development in sewer system design. Water Research, 73, 78-97. doi:10.1016/j.watres.2014.12.050, Institutional Repository

Urban drainage design relying on observed precipitation series neglects the uncertainties associated with current and indeed future climate variability. Urban drainage design is further affected by the large stochastic variability of precipitation extremes and sampling errors arising from the short observation periods of extreme precipitation. Stochastic downscaling addresses anthropogenic climate impact by allowing relevant precipitation characteristics to be derived from local observations and an ensemble of climate models. This multi-climate model approach seeks to reflect the uncertainties in the data due to structural errors of the climate models. An ensemble of outcomes from stochastic downscaling allows for addressing the sampling uncertainty. These uncertainties are clearly reflected in the precipitation-runoff predictions of three urban drainage systems. They were mostly due to the sampling uncertainty. The contribution of climate model uncertainty was found to be of minor importance. Under the applied greenhouse gas emission scenario (A1B) and within the period 2036–2065, the potential for urban flooding in our Swiss case study is slightly reduced on average compared to the reference period 1981–2010. Scenario planning was applied to consider urban development associated with future socio-economic factors affecting urban drainage. The impact of scenario uncertainty was to a large extent found to be case-specific, thus emphasizing the need for scenario planning in every individual case. The results represent a valuable basis for discussions of new drainage design standards aiming specifically to include considerations of uncertainty.
Egger, C., & Maurer, M. (2015). Kanalnetzbemessung unter Unsicherheit. Die Bedeutung des Klimawandels für die hydraulische Funktion von Kanalnetzen. Aqua & Gas, 95(11), 56-63. , Institutional Repository

Menschlich bedingte Einflüsse auf das Klimasystem und eine einhergehende Erhöhung von extremen Niederschlagsintensitäten (in diesem Zusammenhang sind Ereignisse mit Wiederkehrintervall von etwa mindestens einem Jahr von Bedeutung) haben mancherorts bereits zu Anpassungen der Entwässerungssysteme und den zugrunde liegenden Bemessungsregeln geführt. Im vorliegenden Artikel wird die Bedeutung des Klimawandels an einem Beispiel in der Schweiz analysiert und mit anderen niederschlagsbezogenen Unsicherheiten in Verhältnis gesetzt.
Egger, C., Scheidegger, A., Maurer, M., & Reichert, P. (2015). Schätzung der Kanalalterung. Modellbasierte Schätzung des Alterungsverhaltens von Kanalnetzen ohne Datenhistorie. Aqua & Gas, 95(11), 48-54. , Institutional Repository

Modellbasierte Prognosen über die Alterung von Kanalnetzen helfen (langfristige) Konsequenzen möglicher Sanierungsstrategien zu evaluieren. Die Schätzung von Modellparametern, basierend auf heute verfügbaren und oftmals limitierten Informationen, birgt Herausforderungen. Im vorliegenden Artikel wird das Problem fehlender historischer Leitungsdaten erläutert und ein Lösungsansatz dazu aufgezeigt.
Egger, C. S. (2015). Sewer rehabilitation planning under uncertainty (Doctoral dissertation). doi:10.3929/ethz-a-010532893, Institutional Repository

The need for renewal of sewer systems will increase in coming decades. However, efficient and effective rehabilitation involves substantial planning challenges. These challenges are due to the typically limited degree of documentation of existing infrastructure, variability of input data and deterioration processes, lack of knowledge on the current and indeed future structural condition of sewer systems and unpredictable external influences. Planning challenges are even more pronounced in small utilities as (i) the rehabilitation demand will increase more markedly and (ii) informational, personal and financial planning resources are typically more restricted. Furthermore, it is necessary to make the planning process transparent as a wide range of stakeholders is involved and affected by the planning decisions. [...]

Der Erneuerungsbedarf von Kanalisationen wird in den nächsten Jahren vielerorts ansteigen. Eine effiziente und effektive Umsetzung dieses Bedarfs beinhaltet jedoch substanzielle planerische Herausforderungen. Diese sind begründet in limitiertem Dokumentationsgrad bestehender Infrastruktur, Variabilität von Eingangsgrössen und Alterungsprozessen, fehlendem Wissen über den heutigen und zukünftigen baulichen Zustand der Infrastruktur, sowie in hohem Masse unbekannten äusseren Einflussfaktoren. Insbesondere kleine Kanalnetzbetreiber sind von diesen Herausforderungen betroffen, da im ländlichen Raum oftmals (i) der Erneuerungsbedarf ausgeprägter ansteigen wird und (ii) dessen Planung informationell, personell wie finanziell noch stärkeren Einschränkungen unterliegt. Weiterhin gilt es entsprechende Planungen transparent zu gestalten, da ein breites Spektrum an Akteuren an Entscheidungen beteiligt und betroffen ist. [...]
Eggimann, S., Truffer, B., & Maurer, M. (2015). To connect or not to connect? Modelling the optimal degree of centralisation for wastewater infrastructures. Water Research, 84, 218-231. doi:10.1016/j.watres.2015.07.004, Institutional Repository

The strong reliance of most utility services on centralised network infrastructures is becoming increasingly challenged by new technological advances in decentralised alternatives. However, not enough effort has been made to develop planning tools designed to address the implications of these new opportunities and to determine the optimal degree of centralisation of these infrastructures. We introduce a planning tool for sustainable network infrastructure planning (SNIP), a two-step techno-economic heuristic modelling approach based on shortest path-finding and hierarchical-agglomerative clustering algorithms to determine the optimal degree of centralisation in the field of wastewater management. This SNIP model optimises the distribution of wastewater treatment plants and the sewer network outlay relative to several cost and sewer-design parameters. Moreover, it allows us to construct alternative optimal wastewater system designs taking into account topography, economies of scale as well as the full size range of wastewater treatment plants. We quantify and confirm that the optimal degree of centralisation decreases with increasing terrain complexity and settlement dispersion while showing that the effect of the latter exceeds that of topography. Case study results for a Swiss community indicate that the calculated optimal degree of centralisation is substantially lower than the current level.
Lienert, J., Scholten, L., Egger, C., & Maurer, M. (2015). Additional information for "Structured decision-making for sustainable water infrastructure planning and four future scenarios". Working papers in environmental social sciences: Vol. Working paper 2014-3. Dübendorf, Switzerland: Eawag. , Institutional Repository

To support Sustainable Water Infrastructure Planning (SWIP), a participatory decision-making procedure was developed in the SWIP project at Eawag1. This procedure is based on Structured Decision Making (SDM)2, which guides stakeholders through different steps of the decision process: (1) clarify decision context (may include a stakeholder analysis); (2) define objectives and attributes; (3) develop alternatives; (4) estimate consequences; (5) evaluate trade-offs and select alternatives; and (6) implement, monitor and review.
The SDM application to water infrastructure planning was developed in close collaboration with stakeholders in a case study near Zürich, Switzerland. The experienced advantages and disadvantages of the first steps of the proposed procedure were discussed in a scientific publication by Lienert et al. (2014)3. We strongly encourage others to apply this SDM procedure for sustainable water infrastructure planning to their specific case. To this end, the approach was developed in a generalized way and we present more material covering the different steps of the SDM procedure in this working paper.
The here presented material includes different steps in the development of a comprehensive objectives hierarchy for water supply and wastewater management. The objectives are operationalized with attributes (indicators/ benchmarks), which are described in detail, including the ranges (best- and worst-possible case) and a description of the status quo. Four future scenarios were developed in a scenario planning workshop together with local stakeholders to capture socio-demographic uncertainty, which are again described in detail. Ten strategic decision alternatives were developed by stakeholders with help of a strategy generation table. These include the current system with central water supply and wastewater treatment plants, but also fully decentralized on-site options and different management strategies. The strategy generation table can be used to tailor decision alternatives for water infrastructure planning to other cases. Finally, we provide detailed feedback from the stakeholders for each step. We evaluate the proposed SDM approach and give recommendations for other applications.
Lienert, J., Scholten, L., Egger, C., & Maurer, M. (2015). Structured decision-making for sustainable water infrastructure planning and four future scenarios. EURO Journal on Decision Processes, 3, 107-140. doi:10.1007/s40070-014-0030-0, Institutional Repository

Water supply and wastewater infrastructures are vital for human well-being and environmental protection; they adhere to the highest standards, are expensive and long-lived. Because they are also aging, substantial planning is required. Climate and socio-economic change create large planning uncertainties and simple projections of past developments are no longer adequate. This paper presents the initial phases of a structured decision-making (SDM) procedure which is designed to increase the sustainability of water infrastructure planning and includes various stakeholders in an exemplary Swiss case study. We evaluate the SDM approach critically based on stakeholder feedback, give general recommendations and provide ample material to make it applicable to other settings. We carried out 27 interviews and two stakeholder workshops. We identified important objectives for water infrastructure planning, including all three sustainability pillars and their respective attributes (indicators, benchmarks) to measure how well the objectives are achieved. We then created strategic decision alternatives, including "business-as-usual" upgrades of the central water supply and wastewater system as well as semi- to fully decentralized alternatives. To tackle future uncertainty, we developed four socio-demographic scenarios. We used these to test the robustness of decision alternatives in a later Multi-Attribute Utility Theory analysis. Additionally, we contribute to the topical discussion of combining scenario planning with multi-criteria decision analysis and demonstrate how various scenarios can stimulate creativity when generating decision alternatives. Their internal consistency is ensured by rigorously specifying them using a strategy generation table. Our SDM procedure can be adapted to inform decisions about sustainable water infrastructures in other contexts.
Logar, I., Brouwer, R., Maurer, M., & Ort, C. (2015). Wert der Spurenstoffelimination. Eine ökonomische Analyse zum Ausbau Schweizer Abwasserreinigungsanlagen. Aqua & Gas, 95(2), 42-48. , Institutional Repository

Welchen Wert misst die Bevölkerung der Elimination von Mikroverunreinigungen in den Kläranlagen zu? Aus den Antworten von 1000 Deutschschweizern und Deutschschweizerinnen wurde der wirtschaftliche Nutzen des Ausbaus von Abwasserreinigungsanlagen abgeleitet. Der Vergleich mit den veranschlagten Kosten zeigt, dass der Ausbau in der Schweiz gerechtfertigt ist.
Hoffmann, S., Hunkeler, D., & Maurer, M. (2014). Approvisionnement en eau et assainissement des eaux usées durables en Suisse. Défis et mesures possibles. Synthèse thématique 3 dans le cadre du programme national de recherche PNR 61 «Gestion durable de l'eau». Retrieved from http://www.nfp61.ch/fr/actualites-media/publications, Institutional Repository
Hoffmann, S., Hunkeler, D., & Maurer, M. (2014). Nachhaltige Wasserversorgung und Abwasserentsorgung in der Schweiz. Herausforderungen und Handlungsoptionen. Thematische Synthese 3 im Rahmen des Nationalen Forschungsprogramms NFP 61 «Nachhaltige Wassernutzung». Retrieved from http://www.nfp61.ch/de/news-medien/publikationen, Institutional Repository
Logar, I., Brouwer, R., Maurer, M., & Ort, C. (2014). Cost-benefit analysis of the Swiss national policy on reducing micropollutants in treated wastewater. Environmental Science and Technology, 48(21), 12500-12508. doi:10.1021/es502338j, Institutional Repository

Contamination of freshwater with micropollutants (MPs) is a growing concern worldwide. Even at very low concentrations, MPs can have adverse effects on aquatic ecosystems and possibly also on human health. Switzerland is one of the first countries to start implementing a national policy to reduce MPs in the effluents of municipal sewage treatment plants (STPs). This paper estimates the benefits of upgrading STPs based on public’s stated preferences. To assess public demand for the reduction of the environmental and health risks of MPs, we conducted a choice experiment in a national online survey. The results indicate that the average willingness to pay per household is CHF 100 (US$ 73) annually for reducing the potential environmental risk of MPs to a low level. These benefits, aggregated over households in the catchment of the STPs to be upgraded, generate a total annual economic value of CHF 155 million (US$ 113 million). This compares with estimated annual costs for upgrading 123 STPs of CHF 133 million (US$ 97 million) or CHF 86 (US$ 63) per household connected to these STPs. Hence, a cost-benefit analysis justifies the investment decision from an economic point of view and supports the implementation of the national policy in the ongoing political discussion.
Maurer, M., & Lienert, J. (2014). La durabilité des infrastructures dans un avenir incertain. Eawag News [éd. fr.] (2), 1-9. Retrieved from http://newsletter.eawag.ch/e/8bbab41cc9ae86ac/nl/webversion/c55eed59e3a945f06c3247b5/fr.html, Institutional Repository

Les infrastructures d’eau potable et d’assainissement sont des biens pérennes appelés à être transmis de génération en génération. Leur gestion et leur planification s’inscrivent donc dans la durée. Mais comment assurer leur efficacité dans un avenir nécessairement incertain? Comment gérer les incertitudes? Comment quantifier la durabilité dans la planification? L’Eawag s’est penché sur ces questions dans le Programme national de recherche 61.
Maurer, M., & Lienert, J. (2014). Sustainable water infrastructure planning for an uncertain future. Eawag News [engl. ed.] (2), 1-8. Retrieved from http://newsletter.eawag.ch/e/8bbab41cc9ae86ac/nl/webversion/c55eed59e3a945f06c3247b5/en.html, Institutional Repository

Water supply and wastewater disposal networks have a long service life and thus require long planning horizons. How can the services they provide be assured for future generations? How are we to deal with the associated uncertainties? How can sustainability be included in our planning procedures using quantitative methods? These questions were addressed by Eawag as part of National Research Programme 61.
Maurer, M., & Lienert, J. (2014). Wasserinfrastrukturen nachhaltig in eine unsichere Zukunft führen. Eawag News [dtsch. Ausg.] (2), 1-8. Retrieved from http://newsletter.eawag.ch/e/8bbab41cc9ae86ac/nl/webversion/c55eed59e3a945f06c3247b5/de.html, Institutional Repository

Die Wasserversorgung und Abwasserentsorgung sind Generationenbauwerke mit langer Lebensdauer und entsprechend langen Planungshorizonten. Wie können wir ihre Leistungen nachhaltig in die Zukunft führen? Wie gehen wir mit den Unsicherheiten um? Wie beziehen wir die Nachhaltigkeit quantitativ in unsere Planungsansätze ein? Im Rahmen des nationalen Forschungsprogramms 61 ging die Eawag diesen Fragen nach.
Scholten, L., Scheidegger, A., Reichert, P., Mauer, M., & Lienert, J. (2014). Strategic rehabilitation planning of piped water networks using multi-criteria decision analysis. Water Research, 49(1), 124-143. doi:10.1016/j.watres.2013.11.017, Institutional Repository

To overcome the difficulties of strategic asset management of water distribution networks, a pipe failure and a rehabilitation model are combined to predict the long term performance of rehabilitation strategies. Bayesian parameter estimation is performed to calibrate the failure and replacement model based on a prior distribution inferred from three large water utilities in Switzerland. Multi criteria decision analysis (MCDA) and scenario planning build the framework for evaluating 18 strategic rehabilitation alternatives under future uncertainty. Outcomes for three fundamental objectives (low costs, high reliability, and high intergenerational equity) are assessed. Exploitation of stochastic dominance concepts helps to identify twelve non dominated alternatives and local sensitivity analysis of stakeholder preferences is used to rank them under four scenarios. Strategies with annual replacement of 1.5 2% of the network perform reasonably well under all scenarios. In contrast, the commonly used reactive replacement is not recommendable unless cost is the only relevant objective. Exemplified for a small Swiss water utility, this approach can readily be adapted to support strategic asset management for any utility size and based on objectives and preferences that matter to the respective decision makers.
Scholten, L., Maurer, M., & Scheidegger, A. (2014). Zustandsmodellierung kleiner Versorgungsnetze. Ergebnisse aus dem NFP-61-Projekt "Langfristige Planung nachhaltiger Wasserinfrastrukturen". Aqua & Gas, 94(6), 51-58. , Institutional Repository

Den zukünftigen Sanierungsbedarf abzuschätzen, ist eine der grossen Herausforderungen für viele Wasserversorger. Dabei haben insbesondere kleinere Netze mit viel Erfahrungswissen und wenigen Daten besondere Schwierigkeiten. Der Artikel gibt einen Überblick zur Vorhersage des Netzzustandes und über wichtige Aspekte bei der Wahl der entsprechenden Modelle. Ein Folgeartikel zeigt an einem Beispiel die Anwendung des an der Eawag neu entwickelten Schadensmodells.
Veronesi, M., Chawla, F., Maurer, M., & Lienert, J. (2014). Climate change and the willingness to pay to reduce ecological and health risks from wastewater flooding in urban centers and the environment. Ecological Economics, 98, 1-10. doi:10.1016/j.ecolecon.2013.12.005, Institutional Repository

Climate change scenarios predict an increase of extreme rain events, which will increase the risk of wastewater flooding and of missing legal water quality targets. This study elicits the willingness to pay to reduce ecological and health risks from combined sewer overflows (CSOs) in rivers and lakes, and wastewater flooding of residential and commercial zones under the uncertainty of climate change. We implement a discrete choice experiment on a large representative sample of the Swiss population. We find that about 71% of the respondents are willing to pay a higher annual local tax to reduce the risk of CSOs in rivers and lakes. Swiss households strongly value the protection of water bodies, and mostly, the avoidance of high ecological risks and health risks for children related to CSOs in rivers and lakes. Our findings also show that climate change perception has a significant effect on the willingness to pay to reduce these risks. These results are important to support policy makers' decisions on how to deal with emerging risks of climate change in the water sector and where to set priorities.
Egger, C., Honti, M., & Maurer, M. (2013). Einfluss des Klimawandels auf die Leistung der Siedlungsentwässerung. In Gewässerschutz bei Regenwetter – Gemeinschaftsaufgabe für Stadtplaner, Ingenieure und Ökologen (pp. 88-93). Dübendorf: Eawag. , Institutional Repository

Zukünftige, von regionalen Klimamodellen vorhergesagte Änderungen der Niederschlagseigenschaften müssen zuerst in die für die Siedlungsentwässerung relevanten räumliche und zeitliche Skalen übertragen werden. Dazu verwenden wir 'statistisches Downscaling', um synthetische Punktregenserien zu generieren. Diese können dann zur hydraulischen Analyse und Bemessung von Siedlungsentwässerungssystemen herangezogen werden. Wir analysierten damit den Einfluss des Klimawandels auf die hydraulische Leistungsfähigkeit eines ausgewählten Entwässerungssystems. Spezielles Augenmerk wurde dabei auf Unsicherheiten gelegt, welche (i) in der natürlichen Variabilität des Klimas und (ii) der Unsicherheit der Klimamodelle begründet sind. Die Analyse zeigt auf, dass die Leistungsfähigkeit von Entwässerungssystemen sowohl unter heutigem als auch zukünftigem Klima stark schwanken kann. Die Anteile von Schächten an denen das angewandte Bemessungskriterium nicht erfüllt wird, variiert zwischen 1,3 und 7,4 % (heutiges Klima) und 1,3 und 15,8 % (zukünftiges Klima). Damit zeigt sich eine Tendenz zu einer verschlechterten hydraulischen Leistungsfähigkeit unter zukünftigem Klima.
Egger, C., Scheidegger, A., Reichert, P., & Maurer, M. (2013). Sewer deterioration modeling with condition data lacking historical records. Water Research, 47(17), 6762-6779. doi:10.1016/j.watres.2013.09.010, Institutional Repository

Accurate predictions of future conditions of sewer systems are needed for efficient rehabilitation planning. For this purpose, a range of sewer deterioration models has been proposed which can be improved by calibration with observed sewer condition data. However, if datasets lack historical records, calibration requires a combination of deterioration and sewer rehabilitation models, as the current state of the sewer network reflects the combined effect of both processes. Otherwise, physical sewer lifespans are overestimated as pipes in poor condition that were rehabilitated are no longer represented in the dataset. We therefore propose the combination of a sewer deterioration model with a simple rehabilitation model which can be calibrated with datasets lacking historical information. We use Bayesian inference for parameter estimation due to the limited information content of the data and limited identifiability of the model parameters. A sensitivity analysis gives an insight into the model's robustness against the uncertainty of the prior. The analysis reveals that the model results are principally sensitive to the means of the priors of specific model parameters, which should therefore be elicited with care. The importance sampling technique applied for the sensitivity analysis permitted efficient implementation for regional sensitivity analysis with reasonable computational outlay. Application of the combined model with both simulated and real data shows that it effectively compensates for the bias induced by a lack of historical data. Thus, the novel approach makes it possible to calibrate sewer pipe deterioration models even when historical condition records are lacking. Since at least some prior knowledge of the model parameters is available, the strength of Bayesian inference is particularly evident in the case of small datasets.
Maurer, M., & Jordi, B. (2013). Besseres Management der Infrastruktur. Organisatorische, betriebliche und technische Anpassungen im Abwasserbereich. Aqua & Gas, 93(2), 24-32. , Institutional Repository

Die Abwasserinfrastruktur in der Schweiz ist weitgehend gebaut. In Zukunft soll die Leistungsfähigkeit der Kanalnetze und Kläranlagen gesichert und die Siedlungsentwässerung durch organisatorische, betriebliche und technische Anpassungen gezielt optimiert werden. Moderne Mess- und Regeltechnik sowie die Fernüberwachung erlauben heute die Anwendung anspruchsvollerer Verfahren. Dies ermöglicht Kanalisation und ARA als Einheit zu bewirtschaften und dadurch zum Beispiel bestehende Kapazitätsreserven besser zu nutzen. Der Eawag-Bericht «Abwasserentsorgung 2025» unterbreitet zahlreiche Vorschläge für ein besseres Management der Infrastruktur.
Maurer, M. (2013). Full costs (dis-)economies of scale and the price of uncertainty. In T. A. Larsen, K. M. Udert, & J. Lienert (Eds.), Source separation and decentralization for wastewater management (pp. 85-100). London: IWA Publishing. , Institutional Repository

The sewage systems of the 19th century were introduced as an emergency solution to a health crisis. In Britain, an average of 26% of children died before the age of five, in the cities this average was around 48% (Brown 2003). The draining of excrements and excess water in European cities improved the quality of life and health standards dramatically. The powerful sewer system also enabled a freshwater supply network which further improved the functions of the sewers. Since then, this successful solution has been continuously improved, but at its core it remains a conveyance system with some very important characteristics: [...]
Maurer, M., Scheidegger, A., & Herlyn, A. (2013). Quantifying costs and lengths of urban drainage systems with a simple static sewer infrastructure model. Urban Water Journal, 10(4), 268-280. doi:10.1080/1573062X.2012.731072, Institutional Repository

A generic model is introduced that is capable of quantitatively representing the combined sewer infrastructure of a settlement. It consists of a catchment area module, which calculates the length and size distribution of the needed sewer pipes on the basis of rain, housing densities and area size. These results are fed into the sewer construction costs module in order to estimate the combined sewer costs of the entire catchment area.
The model could be successfully fitted to existing Swiss sewer systems, indicating that it can emulate their principal characteristics. It could also identify fundamental differences in sewer designs in cities with historic roots. The results confirm that there are economies of scale for combined sewer systems in Switzerland. The modelling approach proved to be an effective tool for understanding the factors underlying the cost structure for water network infrastructures.
Rossboth, T. (2013). Model-based systems analysis of the collection management of source-separated urine in Ethekwini Municipality/South Africa (Master thesis). 51 p. , Institutional Repository

Source-separating sanitation technologies aim at handling urine separately from other wastewater streams. Source-separation is seen as a promising solution in terms of pollution control and allows the reuse of urine as a fertilizer. Recovery of these nutrients is one of the primary objectives of urine diversion toilets installed in developing regions. However, the economical operation of nutrient recovery reactors requires a medium to large scale urine collection system. Establishing such a system poses a challenge, especially in developing regions. The DeSaM model was developed to assist in the planning of a sanitation product transport scheme. It is a stochastic model used for calculating volume flows, mass flows and performing simple cost assessments.
For the work on this Master’s thesis DeSaM was applied to a case study for the first time. Two potential collection setups were defined for the situation in eThekwini Municipality; one setup is based on a centralized collection, while the other setup additionally includes local collection and intermediate storage. The performance of the setups and alternative schemes were assessed and compared. Systems analysis was employed to identify collection scheme constraints, limiting factors and the potential for improvement, achievable by varying the collection scheme input parameters and through the (conceived) effects of interventions. It was shown that the collection scheme performance is affected by conditions such as urine flow to toilet or working capacity. The base collection scheme of Setup A had more potential to improve the performance by increasing urine flow to toilet. However, collection schemes that allow the collection of urine at a lower price and with better performance (+80% collected urine) were identified.
The benefits of the DeSaM application for the collection scheme planning were demonstrated. It was shown that the simulation results support the refinement and subsequent selection of an optimum system.

Bei urinseparierenden Toiletten wird Urin getrennt von anderen Abwasserströmen gesammelt. Durch ein solches System wird eine separate Behandlung und die Wiederverwendung der im Urin enthaltenen Nährstoffe möglich. Um Reaktoren zur effizienten Nährstoffrückgewinnung ökonomisch betreiben zu können, bedarf es einer großen Menge an Urin. In Entwicklungsregionen kann der Bedarf und die Planung einer großflächigen Urinsammlung zur Herausforderung werden. Das stochastische Computermodel DeSaM wurde als unterstützendes Instrument für diesen Planungs- und Entscheidungsprozess entwickelt. In der vorliegenden Masterarbeit findet das Modell erstmals Anwendung.
Angelehnt an die Situation in der südafrikanischen Gemeinde eThekwini wurden zwei mögliche Sammelsysteme – eine zentrale Sammlung und eine Sammlung mit zusätzlicher lokaler Sammelaktivität und Zwischenspeichern – modelliert, analysiert und verglichen. Mit Hilfe einer Systemanalyse wurden die Grenzen und das Verbesserungspotential von bestimmten Sammelansätzen analysiert und die (fiktiven) Auswirkungen von Eingriffen in das Sammelsystem untersucht. Es wird aufgezeigt, dass die Leistung eines Sammelansatzes durch den Urinfluss zum Toilettentank und die Arbeitsleistung der Sammelteams beeinflusst werden kann. Der ursprüngliche Sammelansatz von System A (= Setup A) kann bei gesteigertem Urinfluss zu den Toilettentanks eine bessere Leistungssteigerung erzielen. Durch eine Anpassung des Sammelansatzes könnte jedoch deutlich mehr Urin (+80%) zu einem besseren Preis gesammelt werden.
Der Nutzen einer Anwendung von DeSaM im Planungsprozess wurde aufgezeigt und es wurde bewiesen, dass mit Hilfe der Simulationsergebnisse eine Identifikation des optimalen Systems erleichtert wird.
Scheidegger, A., Scholten, L., Maurer, M., & Reichert, P. (2013). Extension of pipe failure models to consider the absence of data from replaced pipes. Water Research, 47(11), 3696-3705. doi:10.1016/j.watres.2013.04.017, Institutional Repository

Predictions of the expected number of failures of water distribution network pipes are important to develop an optimal management strategy. A number of probabilistic pipe failure models have been proposed in the literature for this purpose. They have to be calibrated on failure records. However, common data management practices mean that replaced pipes are often absent from available data sets. This leads to a 'survival selection bias', as pipes with frequent failures are more likely to be absent from the data.
To address this problem, we propose a formal statistical approach to extend the likelihood function of a pipe failure model by a replacement model. Frequentist maximum likelihood estimation or Bayesian inference can then be applied for parameter estimation. This approach is general and is not limited to a particular failure or replacement model.
We implemented this approach with a Weibull-exponential failure model and a simple constant probability replacement model. Based on this distribution assumptions, we illustrated our concept with two examples. First, we used simulated data to show how replacement causes a 'survival selection bias' and how to successfully correct for it. A second example with real data illustrates how a model can be extended to consider covariables.
Scheidegger, A., Beutler, P., & Maurer, M. (2013). Prognosen zum Sanierungsbedarf. Schweizer Kanalisation – der Wert guter Daten für Einsichten in die Zukunft. Aqua & Gas, 93(1), 16-20. , Institutional Repository

Die Schweiz hat hervorragend ausgebaute Infrastrukturnetze. Dies gilt auch für die öffentliche Kanalisation, die einen geschätzten Wiederbeschaffungswert von rund 66,4 Mia. Franken hat (VSA 2011, [1]). In den letzten Jahren wurde vermehrt darauf hingewiesen, dass nicht ausreichend in den Unterhalt investiert wird und somit zukünftig mit einem grossen Anstieg des Sanierungsbedarfs zu rechnen ist. Im vorliegenden Artikel wird eine Prognose für den schweizweiten Sanierungsbedarf der Kanalisation vorgestellt.
Scholten, L., Scheidegger, A., Reichert, P., & Maurer, M. (2013). Combining expert knowledge and local data for improved service life modeling of water supply networks. Environmental Modelling and Software, 42, 1-16. doi:10.1016/j.envsoft.2012.11.013, Institutional Repository

The presented approach aims to overcome the scarce data problem in service life modeling of water networks by combining subjective expert knowledge and local replacement data. A procedure to elicit imprecise quantile estimates of survival functions from experts, considering common cognitive biases, was developed and applied. The individual expert priors of the parameters of the service life distribution are obtained by regression over the stated distribution quantiles and aggregated into a single prior distribution. Furthermore, a likelihood function for the commonly encountered censored and truncated pipe replacement data is formulated. The suitability of the suggested Bayesian approach based on elicitation data from eight experts and real network data is demonstrated. Robust parameter estimates could be derived in data situations where frequentist maximum likelihood estimation is unsatisfactory, and to show how the consideration of imprecision and in-between-variance of experts improves posterior inference.
Scholten, L. (2013). Multi-criteria decision analysis for water supply infrastructure planning under uncertainty (Doctoral dissertation). ETH Zürich, Zürich, 280 p. , Institutional Repository

Our centralized water supply systems are aging. Despite their success in reliably providing high quality drinking water, nowadays especially small utilities (e.g. less than 10’000 inhabitants supplied) are illprepared to face possible future challenges. The fragmented structure of the water supply sector leads to a lack of institutional, financial and personnel resources for professional management and planning of water supply systems. Current planning is furthermore challenged by insufficient knowledge and data about the prevailing water infrastructure condition and future rehabilitation demand. It usually ignores future dynamics and planning uncertainties, as well as alternatives to the perpetuation of the status quo. Infrastructure decision making is usually not transparent and only few stakeholders are included into the decision process.
This thesis presents an approach to overcome these shortcomings and support long-term water supply infrastructure planning under uncertainty in a multi-stakeholder context. Thereto, methods from multicriteria decision analysis (MCDA), strategic asset management (SAM), pipe failure modeling, and scenario planning were combined, adapted, and further developed. The suitability of the approach was validated in a case study in Switzerland. To improve the prediction of pipe service life in view of data scarcity, it was shown how the knowledge of experts can be quantitatively assessed and integrated into the calibration of pipe survival models by means of Bayesian inference. Similarly, knowledge gained from three mid-size to large Swiss water networks was used to improve calibration of a novel pipe failure model. It is demonstrated that this failure model is able to deal with the common data situation, and mitigate overestimation of the time to failure caused by the absence of data from already replaced pipes. The failure model was combined with a rehabilitation model to assess the performance of 18 rehabilitation strategies under four future scenarios for a small water utility. MCDA was used to compare these alternatives under different preferences concerning three objectives. The analysis revealed that the common strategy, purely reactive rehabilitation, is not recommendable in most cases and that annual replacement of 1–2 % of the network by condition might be a good strategy for the utility in question.
These findings were considered during the definition of alternatives for a second MCDA study aiming at identifying ‘good water supply infrastructure’ alternatives. Eleven alternatives and an objectives hierarchy consisting of 44 fundamental objectives and 30 attributes were developed together with stakeholders. The alternatives differ not only with regard to rehabilitation management, but also technical, managerial, and organizational aspects. The outcomes of all alternatives regarding these attributes were predicted under four future scenarios to account for uncertainties about the future development. The approach for the elicitation and modeling of preferences includes the imprecision of the stated preferences as well as uncertainties of preference parameters which were not elicited (the aggregation model, marginal value functions, risk attitude, and scaling factors). Preferences of ten selected stakeholders were then elicited and probability distributions of the ranking of alternatives based on these preferences were obtained. Despite differences in the individual rankings, a potential compromise solution could be proposed and ways for potential adaptation and improvement of other alternatives be indicated. In general, alternatives with good outcomes regarding groundwater protection, water quality, supply reliability, and realization of the rehabilitation demand received the highest ranks, as these were also among the most important objectives for the majority of the stakeholders. As operation and management do considerably contribute to the performance regarding the latter three objectives, the importance of a thorough infrastructure and rehabilitation management cannot be neglected. In view of the possible ranges of the outcomes, the objectives of ‘high social acceptance’ (e.g. disturbance by unnecessary road works, resources autonomy), and to some extent also ‘low costs’ were judged less important.
Multi-criteria decision analysis proved useful to support the long-term planning of water infrastructures under uncertainty and in a multi-stakeholder framework. The usual extrapolation of the status quo was overcome. Future dynamics and uncertainties could be incorporated by combining decision making and modeling with scenario planning, besides the quantitative consideration of uncertainties in making predictions, and evaluating the results. With the presented approaches for the modeling of pipe failures and rehabilitation, the methods and tools for the assessment of the current condition and future rehabilitation demand of small water networks despite a difficult data situation are now available.
von Horn, J., Maurer, M., Londong, J., Lautenschläger, S., Steinmetz, H., Hillenbrand, T., & Dockhorn, T. (2013). Welche neuartigen Sanitärsysteme (NASS) sind für Deutschland besonders Erfolg versprechend?. KA: Korrespondenz Abwasser Abfall, 60(8), 673-683. doi:10.3242/kae2013.08.002, Institutional Repository

The paper summarizes the current state of knowledge regarding novel sanitation systems. It is based on the outcomes of a DWA workshop in June 2012, at which the most important drivers for implementing novel sanitation systems in Germany were identified and at which participants determined those novel sanitation systems that were most promising for Germany in the next 15 years. In addition to the outcomes of the workshop itself, the paper also contains additional material from reference literature and thus provides a comprehensive overview of the current situation.
Maurer, M., Rieckermann, J., Muschalla, D., Gruber, G., Schmitt, T. G., Kaufmann Alves, I., … Dittmer, U. (Eds.). (2013). Gewässerschutz bei Regenwetter - Gemeinschaftsaufgabe für Stadtplaner, Ingenieure und Ökologen. Aqua Urbanica 2013. Retrieved from https://www.tugraz.at/events/aquaurbanica/aquaurbanica-2022/weitere/archiv/au-2013/programm-und-beitraege, Institutional Repository
Hering, J. G., Hoehn, E., Klinke, A., Maurer, M., Peter, A., Reichert, P., … Wehrli, B. (2012). Moving targets, long-lived infrastructure, and increasing needs for integration and adaptation in water management: an illustration from Switzerland. Environmental Science and Technology, 46(1), 112-118. doi:10.1021/es202189s, Institutional Repository
Hug, T., & Maurer, M. (2012). Stochastic modeling to identify requirements for centralized monitoring of distributed wastewater treatment. Water Science and Technology, 65(6), 1067-1075. doi:10.2166/wst.2012.945, Institutional Repository

Distributed wastewater treatment is increasingly considered as an alternative to the predominantly transport based combination of sewer network and centralized wastewater treatment plant. If substantial amount of wastewater of a particular area is processed in small distributed treatment units, the sum of these units must be considered as one system providing an overall service. This paper focuses on the monitoring for centralized operation of such distributed units. We present a simple stochastic model to calculate probability distributions of process performance. We thereby simulated a fleet of simple treatment units with stochastic failure rates, unreliable sensors and regular routine inspections. All calculated performance indicators exhibit a considerable difference between the true performance and the perceived that is based on sensor observations. The results also show that there is a trade-off between investing into more reliable technology or into more frequent human interventions to achieve a certain performance. The simulations can quantify both effects and thereby support the identification of requirements for centralized monitoring of distributed treatment units. The model approach is generic and can be extended and applied to various distributed wastewater treatment technologies and contexts.
Koch, G., Lienert, J., & Maurer, M. (2012). Judit Lienert: "Wir arbeiten mit einer multikriteriellen Entscheidungsanalyse.". Aqua & Gas, 92(5), 8-9. , Institutional Repository

Das Nationale Forschungsprogramm NFP 61 will wissenschaftlich fundierte Grundlagen zum künftigen Umgang mit Wasser bereitstellen. Es verfügt über einen Finanzrahmen von zwölf Millionen Franken und dauert ab Januar 2010 vier Jahre. Die Praxisrelevanz wird im Programm stark gewichtet. Aqua & Gas stellt an dieser Stelle jeweils ein Projekt vor. In diesem Beitrag geben Judit Lienert und Max Maurer vom NFP-61-Projekt «Langfristige Planung nachhaltiger Wasserinfrastrukturen» (SWIP) Einblick in ihre Projektarbeit.
Maurer, M., Bufardi, A., Tilley, E., Zurbrügg, C., & Truffer, B. (2012). A compatibility-based procedure designed to generate potential sanitation system alternatives. Journal of Environmental Management, 104(Aug), 51-61. doi:10.1016/j.jenvman.2012.03.023, Institutional Repository

Regarding multi-criteria decision analysis (MCDA), the problem of generating alternatives has not received the attention it deserves. Most research is currently devoted to the problem of alternative selection, where it is assumed that a set of appropriate alternatives is already given. This paper addresses the generation of potential alternatives in the domain of sanitation systems planning and decision-making. A compatibility assessment procedure is proposed to determine the set of technically feasible or potential sanitation system alternatives. This is based on a clear definition of such an alternative containing sub-processes that include a user interface, storage, conveyance treatment and reuse/disposal. A newly developed compatibility matrix is applied to identify incompatibilities between the options of the sub-processes.
A potential sanitation system alternative is therefore defined by the absence of two-by-two incompatibility between all its options.
The compatibility assessment acts as a first filter on the set of sanitation system alternatives to eliminate those that are inoperable before the feasibility assessment. The objective of both steps is to obtain a set of alternatives that are of reasonable and manageable size from which the final solution may be selected.
Maurer, M., Chawla, F., von Horn, J., & Staufer, P. (2012). Abwasserentsorgung 2025 in der Schweiz. Schriftenreihe der Eawag: Vol. 21. Retrieved from http://www.lib4ri.ch/institutional-bibliography/eawag/schriftenreihe-der-eawag.html, Institutional Repository
Scheidegger, A., & Maurer, M. (2012). Identifying biases in deterioration models using synthetic sewer data. Water Science and Technology, 66(11), 2363-2369. doi:10.2166/wst.2012.471, Institutional Repository

The assessment and validation of sewer deterioration models is difficult because reliable data are missing. This makes it hard to find the most suitable model for a particular application. A network condition simulator (NetCoS) is used to generate synthetic sewer data for defined test scenarios. Thereby, the deterioration and replacement of pipes, the expansion of the sewer network, and classification errors are considered. Based on such synthetic data, deterioration models are calibrated and their results compared with the predefined scenario. While this approach is not capable of proving that a model performs correctly on a real application, it highlights the strengths and weaknesses of a model. The influence of condition classification errors and the age of the sewer system is investigated for two deterioration models. The results show, that classification errors can introduce substantial biases in the parameter estimation of the Markov model while in comparison the applied cohort model is fairly robust. Young sewer systems with fewer pipes in bad condition states on the other hand, have a very strong influence on the parameter uncertainties of the cohort model while the Markov model proved to be less sensitive.
Arreaza Bauer, A. S. (2011). Robust elicitation of imprecise expert knowledge for water infrastructure management (Master thesis). 32 p. , Institutional Repository

A project lead by SWIP (Sustainable Water Infrastructure Planning) at Eawag is working on the development of probabilistic pipe decay models to support mid- and longterm infrastructure management and rehabilitation planning. Lack of data is one of the diculties this group is facing, but methods exist to collect information of experienced experts with the help of elicitation. To develop an appropriate elicitation procedure was the goal of this thesis, especially comparing the imprecise method of elicitation, which is in development, with the traditional precise method.
First, a brieng was developed for the experts to be informed about the intention and the procedure of the elicitation. The interview itself was conducted with 15 experts in water infrastructure management, eight in the drinking water sector and seven in the wastewater sector. The interviews were designed to elicit pipe lifetime distributions of dierent pipe types. Important psychological and statistical aspects as the basic axioms of probability theory, possible pitfalls, calibrating the expert and give feedback to recognize inconsistencies in the experts answers, are some among the important considerations.
To evaluate if experts have a distinct preference regarding the precise and imprecise method of elicitation, subjective questions were posed to the experts after the elicitations. To additionally see if the choice of the method had an inuence on the time needed for elicitation or the adaptations done for each probability, these were measured and compared. Finally, to recognize if both methods expressed the same information with regard to the lifetime of the pipes, the elicited precise and imprecise estimates for each pipe type were compared. The intention of this work was to evaluate if the imprecise method is equal or even better than the precise method. If this case was conrmed, then the imprecise method could be recommended for future elicitations.
The answers given for the questions posed after the elicitation, state a preference of the imprecise method (8 experts out of 14). Most experts also found it easier (9 out of 14). Interestingly, a majority thought in a precise way (8 out of 14), but this did not seem to infuence the preference of the method as half of those experts prefered the imprecise method. The results showed that the methods had no inuence on time nor on adaptation. The comparison of the methods with regard to the elicited pipe types showed, that the inuence factors of the dierent areas in Switzerland or the experience of the experts were dominating the elicited estimations.
To sum up, the imprecise method can be recommended for future elicitations, as it is considered equal or better than the precise method. More than half of the experts preferred this method. This is also supported by the easiness of doing the elicitation.
Brombach, H., Gruber, G., & Maurer, M. (2011). Kanalisation – Status quo und quo vadis?. In Schriftenreihe zur Wasserwirtschaft: Vol. 62. Niederschlags- und Mischwasserbewirtschaftung im urbanen Bereich (p. A (42 pp.). Graz: TU Graz. , Institutional Repository

Obwohl die statistische Datenbasis in den drei D-A-CH Nachbarländern sehr unterschiedlich ist, wird im Beitrag für den Bereich der öffentlichen Kanalisation der Versuch unternommen, die historische Entwicklung und den aktuellen Stand der Siedlungsentwässerung in diesen drei Ländern vergleichend gegenüberzustellen, sowie aktuelle Trends zu beleuchten. Während das Mischsystem in den südlichen deutschen Bundesländern und in der Schweiz klar vorherrscht, kommt es historisch bedingt in Österreich vor allem in den größeren Städten zur Anwendung, wogegen im ländlichen Raum fast nur noch Schmutzwasserkanäle errichtet wurden. Die einwohnerspezifischen durchschnittlichen Kanallängen sind in Deutschland und der Schweiz in etwa gleich lang, in Österreich deutlich länger. Generell lässt sich in den drei Nachbarländern ein Trend weg vom Mischsystem und hin zu den modifizierten Systemen feststellen, wo insbesondere im ländlichen Raum sehr oft nur noch Schmutzwasserkanäle errichtet werden. Aktuelle Probleme betreffen vor allem das Fremdwasser in der Kanalisation sowie den Mikroschadstoffaustrag aus der Kanalisation. Generell ist ein Harmonisierungsbedarf für die Zusammenstellung vergleichbarer Kennzahlen festzustellen.
Chawla, F., Veronesi, M., Maurer, M., & Lienert, J. (2011). Ökonomische Bewertung und Wahrnehmung von persönlichen und Umwelt-Risiken im Abwasserbereich: Beispiel aus einer repräsentativen „Conjoint-Analyse“- Umfrage in der Schweiz. Economic valuation and perception of personal and environmental risks in the wastewater sector: Evidence from a representative stated preference survey in Switzerland. Dübendorf: Eawag. , Institutional Repository

Scientists expect an increase in heavy rainfalls in Switzerland in the future because of climate change. During heavy rainfall, the wastewater system might not be able to cope with all the rainwater anymore, leading to surcharges of wastewater in combined sewer systems. Untreated wastewater can therefore reach surface waters, which is known as combined sewer overflows (CSOs). Wastewater can also overflow from manholes or sewers, thus flooding streets or cellars. With climate change, these events are expected to occur more often. It is possible to improve the wastewater system with structural measures to cope with such events, but the costs are high. Ultimately, this would result in an increase of the wastewater taxes paid by the population. [...]

Die Wissenschaft erwartet, dass Starkregen aufgrund des Klimawandels in Zukunft häufiger auftreten werden. Während eines Starkregens kann das Abwassersystem nicht immer das gesamte anfallende Regenwasser ableiten, was in einer Überlastung des Mischwassersystems resultiert. Ungereinigtes Mischwasser muss entlastet werden, was als Mischwasserentlastung (oder Abwasserüberlauf) bekannt ist. Das Mischwasser kann auch aus Schächten überlaufen und Strassen und Keller überfluten. Im Zuge des Klimawandels ist zu erwarten, dass diese Ereignisse häufiger auftreten werden. Es ist möglich, bauliche und damit kostenintensive Massnahmen zu treffen, um das Abwassersystem dem Klimawandel anzupassen. Damit würden die Abwassergebühren, die von der Bevölkerung bezahlt werden, ansteigen. [...]
Dockhorn, T., Hillenbrandt, T., Langergraber, G., Londong, J., Maurer, M., Niederste-Hollenberg, J., … Thaler, S. (2011). Bedarf für Forschung und Entwicklung im Bereich Neuartiger Sanitärsysteme (NASS). Arbeitsbericht der DWA-Arbeitsgruppe KA-1.8 „F+E-Bedarf" im Fachausschuss „Neuartige Sanitärsysteme". KA: Korrespondenz Abwasser Abfall, 58(6), 646-655. doi:10.3242/kae2011.07.002, Institutional Repository

Need for Research and Development in the Field of Novel Sanitation Systems
Report by DWA Working Group KA-1.8 “R&D Needs” within the Technical Committee “Novel Sanitation Systems”
Within DWA Technical Committee KA-1 “Novel sanitation systems”, working group KA-1.8 “R&D needs” has elaborated the present report on the need for R&D in the field of novel sanitation systems. The term novel sanitation systems comprises two basic approaches that promise to extent the limits and possibilities of “conventional” urban drainage systems. On the one hand, the goal is to utilize sewage ingredients (nutrients, organic substances, etc.), and on the other hand, the intention is to do without the complex and expensive transport of sewage in large pipes. The basic principle of resource-oriented sanitation systems is the separate collection and treatment of partial flows. Currently, novel sanitation systems are not in conformity with generally accepted engineering standards. The report identifies existing deficits and necessary developments in the affected technical areas (above all capturing of material flow and separation, collection, transport and discharge as well as treatment of material flow) and illustrates relevant, cross-system aspects (e.g. legal framework conditions, drivers and obstacles, acceptance and evaluation). A systematic status analysis has shown a great need for further research and development. Among other things, research, development, and pilot projects are necessary for a successful introduction of novel sanitation systems. Politicians must create effective incentives and control mechanisms.
Hug, T., & Maurer, M. (2011). Stochastic modeling to identify requirements for centralized monitoring of distributed wastewater treatment (p. (8 pp.). Presented at the SSS 4 water small sustainable solutions. Venice, Italy. , Institutional Repository

Distributed wastewater treatment is increasingly considered as an alternative to the predominantly transport based combination of sewer network and centralized wastewater treatment plant. If substantial amount of wastewater of a particular area is processed in small distributed treatment units, the sum of these units must be considered as one system providing an overall service. This paper focuses on the monitoring for centralized operation of such distributed units. We present a simple stochastic model to calculate probability distributions of process performance. We thereby simulated a fleet of simple treatment units with stochastic failure rates, unreliable sensors and regular routine inspections. All calculated performance indicators exhibit a considerable difference between the true performance and the perceived that is based on sensor observations. The results also show that there is a trade-off between investing into more reliable technology or into more frequent human interventions to achieve a certain performance. The simulations can quantify both effects and thereby support the identification of requirements for centralized monitoring of distributed treatment units. The model approach is generic and can be extended and applied to various distributed wastewater treatment technologies and contexts.
Larsen, T. A., & Maurer, M. (2011). Source separation and decentralization. In P. Wilderer (Ed.), Vol. 4. Treatise on water science (pp. 203-229). doi:10.1016/B978-0-444-53199-5.00083-X, Institutional Repository

Toward the end of the 1990s, a special issue on sustainable sanitation was published by Water Science and Technology, a journal of the International Water Association (IWA). In this issue, several authors discussed the issue of source-separation technologies in the area of wastewater management (Henze, 1997). All major sources of combined wastewater were covered: industrial wastewater (Visvanathan and Hufemia, 1997), storm water (Boller, 1997), gray water (domestic wastewater without toilet waste; Jeffrey et al., 1997), urine (Hanäus et al., 1997; Larsen and Gujer, 1997), and black water (combined toilet waste; Otterpohl et al., 1997).
Whereas separate discharge of storm water and separate treatment of industrial wastewater were already well-known concepts, source separation for domestic wastewater was at that time primarily recognized as an inexpensive sanitation technology for poor, rural areas. For urban areas, only sewer-based wastewater management was considered suitable. The above-mentioned special issue challenged this conventional wisdom with the idea that source separation could potentially compete with end-of-pipe technologies for all wastewaters, even in urban areas. The main concepts behind this idea were that, on the one hand, it would be more resource efficient to treat very concentrated solutions such as urine (Larsen and Gujer, 1997) and that, on the other hand, local recycling of (gray) water would increase flexibility of the urban water management system (Jeffrey et al., 1997). [...]
Maurer, M. (2011). Die zukünftige Wasserinfrastruktur planen. Eawag News [dtsch. Ausg.], 70, 22-25. , Institutional Repository

Eine nachhaltige Zukunftsplanung der Schweizer Trinkwasserversorgung und Abwasserentsorgung muss auch zukünftige Bedürfnisse und Unsicherheiten berücksichtigen. Gute Lösungen zeichnen sich dabei weniger durch möglichst geringe Kosten aus, sondern berücksichtigen den optimalen Nutzen über die gesamte Lebensdauer und sind lokal angepasst. Eine Standardlösung für die Schweiz gibt es nicht.
Maurer, M. (2011). Strategic planning of urban water infrastructure. Eawag News [engl. ed.], 70, 22-25. , Institutional Repository

Sustainable strategic planning of Switzerland's drinking water supply and wastewater management infrastructure has to take future demand and uncertainties into account. Rather than aiming to reduce costs as far as possible, sound solutions seek to optimize benefits over the entire lifespan and are adapted to local conditions. There is no "one-size-fits-all" solution for the country as a whole.
Scheidegger, A., & Maurer, M. (2011). Identifying biases in deterioration models using synthetic sewer data (p. (9 pp.). Presented at the Leading edge conference on strategic asset management (LESAM 2011). Mülheim an der Ruhr, Germany. , Institutional Repository

The assessment and validation of sewer deterioration models is difficult because reliable data are missing. This makes it hard to find the most suitable model for a particular application. A network condition simulator (NetCoS) is used to generate synthetic sewer data for defined test scenarios. Thereby, the deterioration and replacement of pipes, the expansion of the sewer network, and classification errors are considered. Based on such synthetic data, deterioration models are calibrated and their results compared with the predefined scenario.
Using this approach, the influence of condition classification errors and the age of the sewer system is investigated for two deterioration models. The results show, that classification errors can introduce substantial biases in the parameter estimation of the Markov model while in comparison the applied cohort model is fairly robust. Young sewer systems with fewer pipes in bad condition states on the other hand, have a very strong influence on the parameter uncertainties of the cohort model while the Markov model proved to be less sensitive.
Scheidegger, A., Hug, T., Rieckermann, J., & Maurer, M. (2011). Network condition simulator for benchmarking sewer deterioration models. Water Research, 45(16), 4983-4994. doi:10.1016/j.watres.2011.07.008, Institutional Repository

Anaccurate description of aging and deterioration of urban drainage systemsis necessary for optimal investment and rehabilitation planning. Due to a general lack of suitable datasets, network condition models are rarely validated, and if so with varying levels of success. We therefore propose a novel network condition simulator (NetCoS) that produces a synthetic population of sewer sections with a given condition-class distribution. NetCoS can be used to benchmark deterioration models and guide utilities in the selection of appropriate models and data management strategies. The underlying probabilistic model considers three main processes: a) deterioration, b) replacement policy, and c) expansions of the sewer network. The deterioration model features a semi-Markov chain that uses transition probabilities based on user-defined survival functions. The replacement policy is approximated with a condition-class dependent probability of replacing a sewer pipe. The model then simulates the course of the sewer sections from the installation of the first line to the present, adding new pipes based on the defined replacement and expansion program. We demonstrate the usefulness of NetCoS in two examples where we quantify the influence of incomplete data and inspection frequency on the parameter estimation of a cohort survival model and a Markov deterioration model. Our results show that typical available sewer inventory data with discarded historical data overestimate the average life expectancy by up to 200 years. Although NetCoS cannot prove the validity of a particular deterioration model, it is useful to reveal its possible limitations and shortcomings and quantifies the effects of missing or uncertain data. Future developments should include additional processes, for example to investigate the long-term effect of pipe rehabilitation measures, such as inliners.
Vollenweider, S., Bukowiecki, A., Dominguez, D., & Maurer, M. (2011). Management kommunaler Netzinfrastruktur. Standortbestimmung und Handlungsbedarf am Beispiel des Wassersektors. GWA Gas, Wasser, Abwasser, 91(5), 309-314. , Institutional Repository

Management of Municipal Network. Infratructures. Status Assessment and Requirement for Action using the Example of the Water Sector. Municipal authorities manage a substantial infrastructure portfolio, which includes safe supply in line with demand, drainage from residential areas, transport and communications. These municipal authority network infrastructures have a replacement value of CHF 460 billion. Long-term maintenance of the services associated with them is an important public duty. A working group from Wasser-Agenda 21 (Water Agenda 21) analysed the deficits which threaten the fulfilment of this duty using the example of the water sector. The article summarises the group’s findings, highlights areas where action needs to be taken and discusses appropriate countermeasures.
Hug, T., Dominguez, D., & Maurer, M. (2010). The cost of uncertainty and the value of flexibility in water and wastewater infrastructure planning. Proceedings of the Water Environment Federation. (pp. 487-500). Presented at the Cities of the future/urban river restoration 2010. doi:10.2175/193864710798284832, Institutional Repository

Planning of urban water and wastewater infrastructures is based on assumptions about the longterm future of the service area. Important factors, such as demand development, carry large uncertainties and have a substantial impact on plant size and ultimately on costs. In this paper we attempt to quantify the economic consequences of these uncertainties for wastewater treatment plants. As a measure for the specific costs we applied the specific net present value (SNPV) as introduced by Maurer (2009). Based on an exponential growth rate model we simulated random scenarios with different demand development and their economic effect. The results demonstrate that the SNPV rises with increasing rate of demand growth or decline, as well as with increasing uncertainty about the future demand. This indicates that ignoring uncertainty in an engineering economic analysis, may considerably under-estimate specific costs. Over-sizing plants as one strategy to cope with future demand uncertainty increases the specific costs even further. Implementing flexible systems as another strategy, however, reduces such additional costs as they can follow the actual demand more closely than large centralized plants. Consequently, there is an economic value of flexibility. We discuss its role in strategic planning of urban water infrastructure.
Hug, T., & Maurer, M. (2010). The economic value of flexibility in sewer infrastructure planning (p. (9 pp.). Presented at the 7th IWA leading-edge conference on water and wastewater technologies (LET2010). Phoenix, Arizona, USA. , Institutional Repository

Urban water and wastewater systems consist of capital intensive and long-lived infrastructure elements. The currently prevailing paradigm of centralized wastewater treatment requires large upfront investments into wastewater treatment plants and sewers that can satisfy the demand of the next decades. Planning the design capacity of these infrastructures is based on forecasting the long-term future demand of the catchment area. However, important factors, such as demand development, carry large uncertainties and have a substantial impact on system size and ultimately on costs. In this paper we attempt to quantify the effect of population growth and its uncertainty on the specific costs of a combined sewer system. The study is based on simulated random population growth scenarios. The results demonstrate that growth and uncertainty have both an increasing effect on costs due to idle capacity. The presented methodology suggests that there is an economic value in flexibility that can be quantified: The more flexible a system is, i.e. the closer its capacity can follow the actual demand, the lower are its specific costs. The results show that the presented simulation approach is an appropriate methodology to identify the value of enhancing the flexibility of a system.
Larsen, T. A., Maurer, M., Eggen, R. I. L., Pronk, W., & Lienert, J. (2010). Decision support in urban water management based on generic scenarios: the example of NoMix technology. Journal of Environmental Management, 91(12), 2676-2687. doi:10.1016/j.jenvman.2010.07.032, Institutional Repository

Urine source separation (NoMix technology) followed by processing the concentrated nutrient solution has the potential to become a cost-efficient alternative to conventional end-of-pipe nutrient elimination. A choice of processing technologies can only be made for specific scenarios, and there is currently no methodology for analyzing generic situations. In setting up a formalized decision-support methodology (based on STEEPLED analysis), we discuss how to create such generic scenarios, how to couple them with process engineering objectives, how to define the technology requirements, and finally how to produce a realistic subset of technology alternatives. The methodology is tested in five real scenarios. We also touch on the criteria for a final choice of technology taking into account large uncertainties about the performance of real technologies. We conclude that technology development is one of the most important requirements for implementing urine source separation in practice. There is an urgent need to develop cost-efficient processing technologies that satisfy the requirements of stakeholders.
Maurer, M., Wolfram, M., & Anja, H. (2010). Factors affecting economies of scale in combined sewer systems. Water Science and Technology, 62(1), 36-41. doi:10.2166/wst.2010.241, Institutional Repository

A generic model is introduced that represents the combined sewer infrastructure of a settlement quantitatively. A catchment area module first calculates the length and size distribution of the required sewer pipes on the basis of rain patterns, housing densities and area size. These results are fed into the sewer-cost module in order to estimate the combined sewer costs of the entire catchment area. A detailed analysis of the relevant input parameters for Swiss settlements is used to identify the influence of size on costs. The simulation results confirm that an economy of scale exists for combined sewer systems. This is the result of two main opposing cost factors: (i) increased construction costs for larger sewer systems due to larger pipes and increased rain runoff in larger settlements, and (ii) lower costs due to higher population and building densities in larger towns. In Switzerland, the more or less organically grown settlement structures and limited land availability emphasise the second factor to show an apparent economy of scale. This modelling approach proved to be a powerful tool for understanding the underlying factors affecting the cost structure for water infrastructures.
Ronteltap, M. (2010). Phosphorus recovery from source-separated urine through the precipitation of struvite (Doctoral dissertation). doi:10.3929/ethz-a-006042150, Institutional Repository

Background and Objectives
Domestic wastewater is built up of several components. One of the smallest components in terms of volume is urine, making up for less than 1% of the total wastewater stream. Despite this small volume, urine is a significant contributor of nutrients: it contains 85–90% nitrogen, 50–80% phosphorus, and 80–90% potassium excreted by humans. This aspect offers the opportunity to extract the nutrients and make them available for recovery and reuse. The project Novaquatis, within which this research was carried out, took up this opportunity as its starting point. NOVAQUATIS was a transdisciplinary research project concerned with urine source separation as a new element in wastewater management. In 2008, it won the “td‐net award for transdisciplinary research" from the Swiss Academies of Arts and Sciences.

Aim of the thesis
This thesis focuses on the recovery of phosphorus from urine. It aims at providing insight into struvite precipitation as a method to sustainably remove phosphorus from urine. The main scientific contribution to wastewater treatment and phosphorus removal is threefold. First, it provides insights into the thermodynamic aspects of struvite precipitation and develops the necessary tools to conduct calculations within the complexity of the urine matrix. Second, it examines the fate of pharmaceuticals, hormones and heavy metals during struvite precipitation. Third, by assessing how process parameters affect phosphorus removal efficiency and crystal growth, it provides insights that will be of help for practical implementation. [...]

Einleitung
Häusliches Abwasser ist aus mehreren Einzelkomponenten zusammengesetzt. Mit einem Anteil von weniger als 1 % stellt Urin eine der kleinsten Komponenten des gesamten Abwasservolumens dar. Trotz dieses geringen Volumens trägt Urin einen bedeutenden Anteil an Nährstoffen bei. So enthält Urin 85–90% des vom Menschen ausgeschiedenen Stickstoffs, 50–80% des Phosphors und 80–90% des Kaliums. Diese Gegebenheit stellt eine gute Möglichkeit dar, um Nährstoffe aus dem Abwasserstrom zu extrahieren und sie für die Rückgewinnung und Wiederverwendung verfügbar zu machen. Diese Möglichkeit war der Ausgangspunkt des Projektes Novaquatis, innerhalb dessen diese Forschungsarbeit durchgeführt wurde. Novaquatis ist ein transdisziplinäres Forschungsprojekt, welches sich mit der Urinseparierung als neues Element der Siedlungswasserwirtschaft beschäftigt.

Ziel der Arbeit
Der Fokus dieser Arbeit liegt auf der Rückgewinnung von Phosphor aus Urin. Zielsetzung ist die Bereitstellung von Erkenntnissen über die Ausfällung von Struvit, als eine Methode der nachhaltigen Entfernung von Phosphor aus Urin. Der wesentliche wissenschaftliche Beitrag zur Abwasserreinigung und zur Eliminierung von Phosphor kann in drei Bereiche aufgeteilt werden: Erstens werden Erkenntnisse zu thermodynamischen Aspekten der Fällung von Struvit aufgezeigt, und die notwendigen Werkzeuge zur genauen Berechnung innerhalb der komplexen Urin‐Matrix entwickelt. Zweitens werden die Rückstände von Arzneimitteln, Hormonen und Schwermetallen während der Fällung von Struvit untersucht. Drittens werden durch die Beurteilung der Einflüsse von Prozessparametern auf die Wirksamkeit der Phosphoreliminierung und des Kristallwachstums, Richtlinien für die praktische Anwendung bereitgestellt. [...]
Ronteltap, M., Maurer, M., Hausherr, R., & Gujer, W. (2010). Struvite precipitation from urine - influencing factors on particle size. Water Research, 44(6), 2038-2046. doi:10.1016/j.watres.2009.12.015, Institutional Repository

Struvite crystallisation is a fast and reliable phosphorus removal and recovery process for concentrated waste streams – such as hydrolysed human urine. In order to optimise P-elimination efficiency, it is beneficial to obtain larger particle sizes: they are easier to separate and less prone to wash-out than smaller particles. This paper presents the results of a study on the effect of process parameters on particle size in a single step struvite precipitation. Crystals formed in batch experiments with real hydrolysed urine were shown to have an average size of >90 μm at pH 9 and 20 °C. This is reduced to 45 μm when changing stirrer type. Particle size increases with lower supersaturation. The results showed that under otherwise constant conditions, particle size decreases with lower temperature and has a minimum between pH 9 and 10. Deviating trends are observed at pH <8. Struvite formation in a CSTR (continuously stirred tank reactor) process was shown to be a reliable stable process that does not require any pH control. A method based on conductivity measurement is presented to estimate ionic strength, which is needed for equilibrium calculations.
Truffer, B., Störmer, E., Maurer, M., & Ruef, A. (2010). Local strategic planning processes and sustainability transitions in infrastructure sectors. Environmental Policy and Governance, 20(4), 258-269. doi:10.1002/eet.550, Institutional Repository

Sustainability transitions have repeatedly been demanded in various economic sectors to confront global environmental problems. The present paper analyses the role of strategic planning processes for improving the prospects of achieving sustainable transitions in infrastructure sectors. Current planning approaches in these sectors tend to perpetuate the established socio-technical configurations by neglecting context uncertainties, by ignoring radical system alternatives and by focusing on narrow value considerations. In order to improve the prospects for sustainable transitions, more reflexive and discursive strategic planning methods are needed. We present the Regional Infrastructure Foresight methodology as a specific procedural proposal and analyse results from its application to a case study in the Swiss sanitation sector.
Hug, T., & Maurer, M. (2009). The cost of uncertainty in water and wastewater treatment planning (p. (16 pp.). Presented at the 2nd international symposium on wastewater recycling. Braunschweig, Germany. , Institutional Repository

Planning of water and wastewater infrastructures is based on assumptions about the long-term future of the catchment area. Important factors, such as demand development, carry large uncertainties and have a substantial impact on plant size and ultimately on costs. In this paper we attempt to quantify the economic consequences of these uncertainties for wastewater treatment plants. As a measure for the specific costs we applied the specific net present value (SNPV) as introduced by Maurer [1]. Based on an exponential growth rate model we simulated random scenarios with different demand development and their economic effect. The results demonstrate that the SNPV rises with increasing rate of demand growth or decline, as well as with increasing uncertainty about the future demand. This indicates that ignoring uncertainty in an engineering economic analysis, leads to considerably under-estimated specific costs. Over-sizing plants as one strategy to cope with future demand uncertainty increases the specific costs even further. Implementing flexible systems as another strategy, however, reduces such additional costs as they can follow the actual demand more closely than large centralized plants.
Kunz, Y., von Gunten, U., & Maurer, M. (2009). Wasserversorgung 2025. Vorprojekt Standortbestimmung im Auftrag des BAFU. Schriftenreihe der Eawag: Vol. 22. Retrieved from http://www.lib4ri.ch/institutional-bibliography/eawag/schriftenreihe-der-eawag.html, Institutional Repository

The present report reviews the state of knowledge on water supply in Switzerland. It focuses on the public water supply and on the identification of knowledge gaps in this field.
Larsen, T. A., Alder, A. C., Eggen, R. I. L., Maurer, M., & Lienert, J. (2009). Source separation: Will we see a paradigm shift in wastewater handling?. Environmental Science and Technology, 43(16), 6121-6125. doi:10.1021/es803001r, Institutional Repository
Maurer, M. (2009). Approvisionnement en eau 2025. Sécurité de l’approvisionnement. GWA Gas, Wasser, Abwasser, 89(9), 741-747. , Institutional Repository

In Switzerland, the public waterworks do not even use two percent of the annual rainfall for drinking water supply. In view of the available reserves in lakes and ground water deposits, the country will not be threatened in the foreseeable future with supply shortages. Primarily during longer dry periods supply shortfalls can definitely occur on a local or regional level, as was shown in the hot summer of 2003. However, possible shortages are absorbed by highly capable technical and organisational networking among water suppliers.
Maurer, M. (2009). Decentralised versus centralised water treatment: the impact of growth (pp. 633-640). Presented at the 2nd international conference on water economics, statistics, and finance. Alexandroupolis, Thrace, Greece. , Institutional Repository

A specific net present value (SNPV) approach is introduced as a criterion in economic engineering decisions. The SNPV expresses average costs, including the growth rate and plant utilisation over the planning horizon, factors that are excluded from a standard net present value approach. The use of SNPV favours alternatives that are cheaper per service unit and are therefore closer to the costs that a user has to cover. It also shows that demand growth has a similar influence on average costs as an economy of scale. In a high growth scenario, solutions providing less idle capacity can have higher present value costs and still be economically favourable. The SNPV approach is applied in a case to calculate comparable costs for on-site treatment (OST). The calculations show that: (i) The SNPV approach is suitable for quantifying the comparable costs of an OST system in a different scenario and (ii) small systems with projected high demand growth rates and high real interest rates are the most probable entry market for OST water treatment systems.
Maurer, M., Wolfram, M., & Herlyn, A. (2009). Factors affecting economy of scale in combined sewer systems (pp. 523-531). Presented at the 2nd international conference on water economics, statistics, and finance. Alexandroupolis, Thrace, Greece. , Institutional Repository

A generic model is introduced that is capable of representing the combined sewer infrastructure of a settlement quantitatively. It consists of a catchment area module, which calculates based on rain, housing densities and area size the length and the size distribution of the needed sewer pipes. These results are fed into the sewer construction costs module in order to estimate the combined sewer costs of the entire catchment area. A detailed analysis of the relevant input parameters for Swiss settlements is used to identify the influence of size on costs. The simulation results show that that there is indeed an economy of scale for combined sewer systems. This is the result of two main opposing cost factors: (i) increased construction costs for larger sewer systems due to larger pipes and increased rain runoff in larger settlements, and (ii) higher population and building densities in larger towns decreasing costs. In Switzerland, the more or less organically grown settlement structure and the limited land availability emphasises the second factor so that there is an apparent economy of size visible. The modelling approach proofed to be a strong tool to understand the underlying factors affecting the cost structure for water infrastructures.
Maurer, M. (2009). Ganzheitliches Einzugsgebietsmanagement (GEM). Schlussfolgerungen aus dem Expertenworkshop vom 1.– 3. Oktober 2008 in Emmetten. GWA Gas, Wasser, Abwasser, 89(3), 197-202. , Institutional Repository

Integrales oder Ganzheitliches Einzugsgebietsmanagement (GEM) ist eine der aktuellen Forderungen an die moderneWasserwirtschaft. Politische, organisatorische und fachtechnische Grenzen sollen überwunden werden, um die Gewässer, die Wasserressourcen und die Infrastrukturen ganzheitlich und kosteneffizient zu bewirtschaften. Wie aber soll dies konkret in der Schweiz aussehen? Wird die Wasser-Rahmenrichtlinie der EU übernommen oder gilt es, eine schweizerische Version zu erarbeiten? Der VSA Expertenworkshop vom 1.–3. Oktober 2008 in Emmetten nahm sich dieser Frage an, entwickelte gangbare Ideen und lotete den Handlungsbedarf für die Umsetzung von GEM in der Schweiz aus.
Maurer, M. (2009). Ganzheitliches Einzugsgebietsmanagement: Ansätze und Formen. Ingenieurbiologie: Mitteilungsblatt, 19(2), 3-7. , Institutional Repository

Ganzheitliches oder integrales Einzugsgebietsmanagement (IEM) ist eine der aktuellen Forderungen an die moderne Wasserwirtschaft. Wie das IEM in der Schweiz konkret aussehen könnte, wurde im VSA-Expertenworkshop vom 1. bis 3. Oktober 2008 in Emmetten diskutiert. Vielversprechende Ansätze für IEM sind in der Schweiz bereits vorhanden, die aber alle im Moment auch noch substantielle Schwächen zeigen. Deutlich wurde, dass das ganzheitliche Einzugsgebietsmanagement für die schweizerische Siedlungswasserwirtschaft ein zentrales Thema wird. Als Konsequenz dieser Veranstaltung hat der VSA-Vorstand das IEM als Kernthema in seine Arbeiten und Bestrebungen aufgenommen.
Maurer, M. (2009). Specific net present value: an improved method for assessing modularisation costs in water services with growing demand. Water Research, 43(8), 2121-2130. doi:10.1016/j.watres.2009.02.008, Institutional Repository

A specific net present value (SNPV) approach is introduced as a criterion in economic engineering decisions. The SNPV expresses average costs, including the growth rate and plant utilisation over the planning horizon, factors that are excluded from a standard net present value approach. The use of SNPV favours alternatives that are cheaper per service unit and are therefore closer to the costs that a user has to cover. It also shows that demand growth has a similar influence on average costs as an economy of scale. In a high growth scenario, solutions providing less idle capacity can have higher present value costs and still be economically favourable.
The SNPV approach is applied in two examples to calculate acceptable additional costs for modularisation and comparable costs for on-site treatment (OST) as an extreme form of modularisation. The calculations show that: (i) the SNPV approach is suitable for quantifying the comparable costs of an OST system in a different scenario; (ii) small systems with projected high demand growth rates and high real interest rates are the most probable entry market for OST water treatment systems; (iii) operating expenses are currently the main economic weakness of membrane-based wastewater OST systems; and (iv) when high growth in demand is expected, up to 100% can be additionally invested in modularisation and staging the expansion of a treatment plant.
Maurer, M. (2009). Wasserversorgung 2025. Aspekte der Versorgungssicherheit. GWA Gas, Wasser, Abwasser, 89(1), 7-12. , Institutional Repository

In Switzerland, the public waterworks do not even use two percent of the annual rainfall for drinking water supply. In view of the available reserves in lakes and ground water deposits, the country will not be threatened in the foreseeable future with supply shortages. Primarily during longer dry periods supply shortfalls can definitely occur on a local or regional level, as was shown in the hot summer of 2003. However, possible shortages are absorbed by highly capable technical and organisational networking among water suppliers.
Störmer, E., Truffer, B., Dominguez, D., Gujer, W., Herlyn, A., Hiessl, H., … Ruef, A. (2009). The exploratory analysis of trade-offs in strategic planning: lessons from regional infrastructure foresight. Technological Forecasting and Social Change, 76(9), 1150-1162. doi:10.1016/j.techfore.2009.07.008, Institutional Repository

The sustainable transformation of infrastructure sectors represents a challenge of prime importance worldwide. Due to long life times of infrastructures, strategic decision making has to explicitly consider uncertainties in context conditions, value considerations and available technological alternatives. However currently, strategic infrastructure planning is often carried out in a very narrow perspective. The present paper argues that foresight informed strategic planning, allows addressing trade-offs related to context uncertainties, value conflicts and sustainability deficits in a structured way. The paper introduces a specific procedural proposal, the Regional Infrastructure Foresight method (RIF) and illustrates its potential virtues through an application to urban water management planning in a Swiss region (Kiesental).
Zurbrügg, C., Bufardi, A., Tilley, E., Maurer, M., & Truffer, B. (2009). Decision-making for sanitation systems. Sandec News, 10, 20-21. , Institutional Repository

This Eawag project addresses the various decision-making aspects in sanitation system and technology selection as a support tool for choosing the best available options to secure sustainable sanitation systems.
Borsuk, M. E., Maurer, M., Lienert, J., & Larsen, T. A. (2008). Charting a path for innovative toilet technology using multicriteria decision analysis. Environmental Science and Technology, 42(6), 1855-1862. doi:10.1021/es702184p, Institutional Repository

Practical and theoretically sound methods for analyzing innovative environmental technologies are needed to inform public and private decisions regarding research and development, risk management, and stakeholder communication. By integrating scientific assessments with a characterization of values, multicriteria decision analysis (MCDA) supports the ranking of alternative technology pathways on the basis of technical, financial, and social concerns. We applied MCDA to evaluate the use of NoMix urine separating toilets for managing environmental risk and postponing expensive upgrades to a large wastewater treatment plant near Zürich, Switzerland. Results indicate that, given current priorities, no single, fixed course of action (including the status quo) will be desirable to all stakeholders over the considered time horizon. However, a path forward is suggested that is not significantly disadvantageous to any stakeholder now and leaves open future options, allowing society to achieve overall greater benefits if priorities change, new environmental risks are revealed, or technology improves. While our analysis focuses on a particular catchment in Switzerland, many communities worldwide are faced with an aging and inefficient wastewater treatment infrastructure while also experiencing growth and development. Our framework can help these communities balance the conflicting objectives of diverse stakeholders and gain insight into the role that urine separation can play in transitioning to a more comprehensive and sustainable urban water management system.
Störmer, E., Dominguez, D., Maurer, M., Ruef, A., & Truffer, B. (2008). Nachhaltige Planungen zur Erneuerung der Siedlungswasserwirtschaft in der Schweiz (p. (5 pp.). Presented at the 64. VSA-Hauptmitgliederversammlung. Aarau, Switzerland. , Institutional Repository
Störmer, E., Truffer, B., Ruef, A., Dominguez, D., Maurer, M., Klinke, A., … Markard, J. (2008). Nachhaltige Strategieentwicklung für die regionale Abwasserwirtschaft. Handbuch zur Methode «Regional Infrastructure Foresight». Handbuch des NFP 54. Retrieved from http://www.eawag.ch/de/abteilung/ess/projekte/regional-infrastructure-foresights-rif/, Institutional Repository
Störmer, E., Klinke, A., Maurer, M., Ruef, A., & Truffer, B. (2008). Regional Infrastructure Foresight. Partizipative Strategieentwicklung für eine nachhaltige regionale Abwasserwirtschaft. GWA Gas, Wasser, Abwasser, 88(11), 843-850. , Institutional Repository

The Swiss sanitation sector has to face high reinvestment needs after over thirty years of operation time. Solutions have to be detected which work properly under changing framework conditions during the entire constructions' Iifetime of at least 25 years. Solutions have to be integrated in an efficient and effective sanitation system from the source of the waste water producer to the receiving water. The regional urban water management system needs an integrative strategy to tackle this requirements. The strategy frames the design of the whole system and its elements. Strategy development has to handle complexities and uncertainties of long living infrastructures. This paper presents the participative planning approach «Regional Infrastructure Foresight - RIF›› with the help of one case study.
Herlyn, A., & Maurer, M. (2007). Status quo der Schweizer Abwasserentsorgung. Kosten, Zustand und Investitionsbedarf. GWA Gas, Wasser, Abwasser, 87(3), 171-176. , Institutional Repository

The Swiss waste water is treated in 759 central treatment plants with more than 500 population equivalents. The replacement value is CHF 10.1 billion. In total, the annual costs of waste water treatment are CHF 875 million. 47,400 km public sewers remove waste- and stormwater with an estimated value of CHF 55.2 billion. CHF 875 million are spent for operation costs and capital expenditures every year. Two thirds of the sewage system was built within the last 50 years, whereas cities have significantly older facilities than rural communities. About 23 % of the investigated sewers show sewere damages. In addition, more than 3,400 individual sewage treatment plants, about 42,000 km private sewers and estimated 1,700,000 house connections contribute to the high level of sanitation service.
Herlyn, A., & Maurer, M. (2007). Was ARA und Kanalisation kosten. Umwelt-Perspektiven, 2007(1), 2-3. , Institutional Repository

Die Abwasserentsorgung gehört auf kommunaler Ebene zu den anlagenintensivsten Dienstleistungen mit hohen langfristig gebundenen Kapitalbeträgen. Für eine strategische Investitionsplanung in der Schweiz fehlte bis anhin eine umfassende Datengrundlage, die jetzt vorliegt.
Herlyn, A., & Maurer, M. (2007). Zustand und Investitionsbedarf der Schweizer Abwasserentsorgung. Schweizer Gemeinde, 44(11), 14-17. Retrieved from http://www.wifpartner.ch, Institutional Repository

Der Gesamtwert der schweizerischen Abwasserentsorgung kann insgesamt auf knapp 100 Milliarden Franken geschätzt werden. Gemeinden, Zweckverbände und die anderen beteiligten Körperschaften stehen vor der Herausforderung, das hohe Dienstleistungsniveau der Abwasserentsorgung zu halten, indem sie sorgfältig den Werterhalt, die Erweiterung und die Modernisierung der bestehenden lnfrastrukturen sicherstellen.
Larsen, T. A., Maurer, M., Udert, K. M., & Lienert, J. (2007). Nutrient cycles and resource management: implications for the choice of wastewater treatment technology. Water Science and Technology, 56(5), 229-237. doi:10.2166/wst.2007.576, Institutional Repository

We look at the most important issues of the global nitrogen and phosphorus cycle and conclude that the nutrients from human metabolism are of no importance for the global nitrogen cycle and of minor importance for the global phosphorus cycle. However, for water pollution control, N and P from the human metabolism are of extreme importance. Nitrogen is mainly an issue for coastal waters, whereas P is an issue for freshwater and coastal areas alike. It is by now generally recognised that coastal ecosystems are exceedingly important for human well-being and at the same time highly endangered. The recycling issue is of high importance in areas where nutrient application is low due to economic constraints. NoMix technology (urine source separation) holds a large promise to become an efficient mainstream technology. The largest short-term potential is found in densely populated areas in coastal areas without existing infrastructure and in areas with nutrient deficiency, especially in urban areas with a large nutrient potential. We believe, however, that these technologies will, with time, also become competitive in Europe.
Maurer, M., Escher, B. I., Richle, P., Schaffner, C., & Alder, A. C. (2007). Elimination of β-blockers in sewage treatment plants. Water Research, 41(7), 1614-1622. doi:10.1016/j.watres.2007.01.004, Institutional Repository

β-Blockers are used to treat high blood pressure as well as patients recovering from heart attacks. In several studies, they were detected in surface water, thus indicating incomplete degradability of these substances in sewage treatment plants (STPs). In this study, we determined the sorption coefficients (KD) and degradation rates of the four β-blockers sotalol, atenolol, metoprolol and propranolol in sludge from an STP operating with municipal wastewater.
The sorption coefficients (KD, standard deviations in brackets) were determined as 0.04(+/-0.035), 0.04(+/-0.033), 0.00(+/-0.023) and 0.32(+/-0.058) L g-1COD, and the pseudo-first-order degradation rate constants were estimated to be 0.29(+/-0.02), 0.69(+/-0.05), 0.58(+/-0.05) and 0.39(+/-0.07) L d-1 g-1COD for sotalol, atenolol, metoprolol and propranolol, respectively.
These values translate into a typical elimination in STPs (sludge concentrations of 4 gCOD L-1 and a hydraulic retention time of 6 h) of 25%, 37%, 44% and 50% for sotalol, propranolol, metoprolol and atenolol, respectively. These results are also confirmed by measurements in two municipal STPs for atenolol, sotalol and propranolol. The estimated eliminations are slightly too high for metoprolol.
Maurer, M. (2007). Urine treatment - absolute flexibility. Eawag News [engl. ed.], 63, 14-16. , Institutional Repository

What happens to urine after it has been collected? The particular characteristics of this liquid permit a wide range of treatment methods. These can be used to modify the unusual resource as required - e. g. to remove specific pollutants or to produce a fertilizer. The suitability of a number of processes has been assessed by Eawag.
Ronteltap, M., Maurer, M., & Gujer, W. (2007). Struvite precipitation thermodynamics in source-separated urine. Water Research, 41(5), 977-984. doi:10.1016/j.watres.2006.11.046, Institutional Repository

Struvite (MgNH4PO4·6H2O) precipitation eliminates phosphate efficiently from urine, a small but highly concentrated stream in the total flux of domestic wastewater. Precipitation experiments with hydrolysed urine evaluated the solubility product of struvite. The stored and fully hydrolysed urine had an ionic strength of between 0.33 and 0.56 M and required the estimation of activity coefficients. From our data, we identified the Davies approximation with the two constants A=0.509 and B=0.3 as agreeing best with our laboratory results. The standard solubility product Ks0=f1[NH4+]f2[Mg2+]f3[PO43−] ([ ]=concentration of the species; fx=corresponding activity coefficient) of struvite in urine was found to be 10−13.26±0.057 at 25 °C and the enthalpy of struvite formation ΔH was 22.6(±1.1) kJ mol−1. The equilibrium calculations required the following dissolved complexes: [MgCO3]aq, [MgHCO3]+, [MgPO4]−, [NH4HPO4]−, and [NaHPO4]− and to a lesser extent [MgSO4]aq and [NH4SO4]−. Organic complexes do not seem to influence the solubility product substantially.
For practical purposes, a conditional solubility product Kscond=[Mgaq]·[NH4++NH3]·[Portho]=10−7.57 M3 was derived to calculate struvite solubility in urine at 25 °C, pH=9.0 and ionic strength I=0.4 M directly from measured concentrations.
Ronteltap, M., Maurer, M., & Gujer, W. (2007). The behaviour of pharmaceuticals and heavy metals during struvite precipitation in urine. Water Research, 41(9), 1859-1868. doi:10.1016/j.watres.2007.01.026, Institutional Repository

Separating urine from wastewater at the source reduces the costs of extensive wastewater treatment. Recovering the nutrients from urine and reusing them for agricultural purposes adds resource saving to the benefits. Phosphate can be recovered in the form of struvite (magnesium ammonium phosphate). In this paper, the behaviour of pharmaceuticals and heavy metals during the precipitation of struvite in urine is studied.
When precipitating struvite in urine spiked with hormones and non-ionic, acidic and basic pharmaceuticals, the hormones and pharmaceuticals remain in solution for more than 98%.
For heavy metals, initial experiments were performed to study metal solubility in urine. Solubility is shown to be affected by the chemical conditions of stored and therefore hydrolysed urine. Thermodynamic modelling reveals low or very low equilibrium solute concentrations for cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), nickel (Ni) and lead (Pb). Experiments confirmed Cd, Cu and Pb carbonate and hydroxide precipitation upon metal addition in stored urine with a reaction half-life of ca. 7 days.
For all metals considered, the maximum specific metal concentrations per gram phosphate or nitrogen showed to be typically several orders of magnitudes lower in urine than in commercially available fertilizers and manure. Heavy metals in struvite precipitated from normal stored urine could not be detected.
Phosphate recovery from urine over struvite precipitation is shown to render a product free from most organic micropollutants and containing only a fraction of the already low amounts of heavy metals in urine.
Escher, B. I., Pronk, W., Suter, M. J. F., & Maurer, M. (2006). Monitoring the removal efficiency of pharmaceuticals and hormones in different treatment processes of source-separated urine with bioassays. Environmental Science and Technology, 40(16), 5095-5101. doi:10.1021/es060598w, Institutional Repository

Urine can be collected separately from the general wastewater with the aim of recycling the nutrients. Urine source-separation not only prevents wasting nutrients but also prevents potentially hazardous micropollutants from entering the wastewater stream and tainting a final fertilizer product. We assessed various urine treatment technologies for their performance to remove micropollutants such as pharmaceuticals, natural and synthetic steroid hormones, and their human biotransformation products. Removal efficiencies were determined with a combination of bioassays and chemical target analysis. The yeast estrogen screen yielded information on estrogenicity. Specific phytotoxicity and nonspecific baseline toxicity was determined with an algae chlorophyll fluorescence test. Filtration methods, such as nanofiltration and electrodialysis, were highly efficient with respect to toxicity reduction. Micropollutant degradation during biological treatment in a sequencing batch reactor was very compound specific. Ozonation removed the target analytes and the estrogenicity completely, but the baseline toxicity was only reduced by 50-60% depending on the ozone doses. Struvite precipitation produced a very "clean" fertilizer product that is ready to use. The examples show that bioassays and chemical analysis yield complementary information, but are very useful to monitor treatment efficiencies and to assess the ecotoxicological potential of byproducts of urine treatment processes. The results of this study present a method to assess the micropollutant removal efficiency, and therefore, support the choice of an appropriate urine processing technique for real-world applications.
Gianella, S., & Maurer, M. (2006). Infrastrukturmanagement. Internationale Standortbestimmung für den Wasser- und Abwassersektor. GWA Gas, Wasser, Abwasser, 86(9), 733-742. , Institutional Repository

In the last years, many Swiss municipalities developed extensive information systems for the collection and use of manifold infrastructure data. Facing the high investments for the realization of these systems and the data value for an optimal infrastructure management, the municipalities must define a suitable data maintenance strategy. The experiences of different municipalities are used in this article to illustrate a procedure for the development of data maintenance strategies. The problems to solve are described and the goals and success factors of a data maintenance strategy are defined.
Maurer, M., Rothenberger, D., & Larsen, T. A. (2006). Decentralised wastewater treatment technologies from a national perspective: At what cost are they competitive?. Water Science and Technology: Water Supply, 5(6), 145-154. doi:10.2166/ws.2005.0059, Institutional Repository

In this paper we estimate at what cost decentralised wastewater treatment can be competitive compared with conventional centralised technologies. For the current wastewater infrastructure in Western Europe and North America, typical replacement costs are 2,600 US$/cap for large countries and 4,800 US$/cap for small ones. In the same literature, average annual operating costs are reported to be 3.8% of replacement costs. However, if a long-term interest rate of 3% is consistently applied, this value increases to 4.7% for small countries and 5.5% for large ones. Assuming that alternative wastewater systems will only be accepted if their costs are similar to existing ones, the possible investments for alternative wastewater treatment technologies are calculated. Between 640 and 2,170 US$/cap can be invested in new technologies for scenarios without a sewer system. The corresponding figures for scenarios with sewer systems are between 260 and 680 US$/cap. Acceptable maintenance requirements are calculated on the basis of unit size. Transition periods are not accounted for.
Maurer, M., Pronk, W., & Larsen, T. A. (2006). Treatment processes for source-separated urine. Water Research, 40(17), 3151-3166. doi:10.1016/j.watres.2006.07.012, Institutional Repository

The separate collection and treatment of urine has attracted considerable attention in the engineering community in the last few years and is seen as a viable option for enhancing the flexibility of wastewater treatment systems. This comprehensive review focuses on the status of current urine treatment processes and summarises the properties of collected urine. We distinguish between seven main purposes of urine-treatment processes: hygienisation (storage), volume reduction (evaporation, freeze-thaw, reverse osmosis), stabilisation (acidification, nitrification), P-recovery (struvite formation), N-recovery (ion treatment exchange, ammonia stripping, isobutylaldehyde-diurea (IBDU) precipitation), nutrient removal (anammox) and handling of micropollutants (electrodialysis, nanofiltration, ozonation). The review shows clearly that a wide range of technical options is available to treat collected urine effectively, but that none of these single options can accomplish all seven purposes. Depending on the overall goal of the treatment process, a specific technical solution or a combination of solutions can be found to meet the requirements. Such combinations are not discussed in this paper unless they are explicitly presented in the literature. Except for 'evaporation' and 'storage', none of the processes described have so far advanced beyond the laboratory stage. Considerable development work remains to be done to optimise urine-processing techniques in order to create marketable products.
Maurer, M., & Herlyn, A. (2006). Zustand, Kosten und Investitionsbedarf der schweizerischen Abwasserentsorgung. Dübendorf: Eawag. , Institutional Repository

Ziel und Vorgehen
Ziel des Projekts ist es, die konzeptionellen Grundlagen zu schaffen, um die Kostensituation, den Zustand der Infrastruktur und den Investitionsbedarf in der schweizerischen Abwasserreinigung systematisch zu analysieren. Es soll eine Datengrundlage entstehen, die unter Berücksichtigung von qualitativen, quantitativen, organisatorischen und räumlichen Kenngrössen den Ist-Zustand darstellt.
Eine repräsentative Erhebung stellt eine grosse methodische und daten-technische Herausforderung dar, die den vorgegebenen Finanzrahmen der Ausschreibung bei weitem übersteigen würden. Das hier vorgestellte Projekt soll wesentliche konzeptionelle, empirische und methodische Vorarbeit leisten, um den Aufwand einer systematischen Erhebung substantiell zu reduzieren. [...]
Escher, B. I., Bramaz, N., Maurer, M., Richter, M., Sutter, D., von Känel, C., & Zschokke, M. (2005). Screening test battery for pharmaceuticals in urine and wastewater. Environmental Toxicology and Chemistry, 24(3), 750-758. doi:10.1897/04-091R.1, Institutional Repository

A test battery for identifying ecotoxicological hazards was applied to six pharmaceuticals (carbamazepine, diclofenac, ethinylestradiol, ibuprofen, propranolol, and sulfamethoxazole), to their mixtures, and to urine spiked with pharmaceuticals to test the suitability of biotests for screening urine and wastewater and for monitoring the efficiency of wastewater treatment. The test battery comprised the bioluminescence inhibition test with Vibrio fischeri, the yeast estrogen screen, and a photosynthesis inhibition assay in algae based on chlorophyll fluorescence measurements. Mixture and additional experiments with a cocktail of pharmaceuticals added to urine confirmed the applicability of the test systems as an integrated measure of the overall micropollutant burden. Because the concentration of pharmaceuticals in wastewater is low and the nutrients and salts may have a negative impact on the bioassays, urine and wastewater samples were cleaned and concentrated by solid-phase extraction (SPE). The compounds of interest ranged from polar to nonpolar and from positively charged to neutral and negatively charged. Consequently, the SPE method was optimized for universality rather than for specificity. Results of preliminary experiments with raw and treated urine and wastewater indicate the suitability of the proposed test battery for screening urine and wastewater.
Larsen, T. A., Lienert, J., Maurer, M., & Gujer, W. (2005). Ökologische Infrastrukturinnovationen in der Siedlungswasserwirtschaft. Ansätze und Perspektiven. In R. Loske & R. Schaeffer (Eds.), Ökologie und Wirtschaftsforschung: Vol. 57. Die Zukunft der Infrastrukturen. Intelligente Netzwerke für eine nachhaltige Entwicklung (pp. 347-367). Retrieved from https://www.metropolis-verlag.de/Die-Zukunft-der-Infrastrukturen/502/book.do, Institutional Repository

Die Infrastrukturen der Siedlungswasserwirtschaft (Trinkwasserversorgung und Abwasserreinigung) sind teuer, langlebig und weitgehend unsichtbar. Ursprünglich durch nationale Subventionen ermöglicht, müssen sie heute in den meisten Fällen lokal unterhalten und erneuert werden. Ist die heutige Gesellschaft überhaupt dazu bereit, gibt es bessere Organisationsformen als die heute vorherrschende und technische Alternativen, die mit weniger Infrastruktur auskommen? Solche Fragen werden heute intensiv diskutiert, und man stößt, je nach fachlichem Hintergrund und politischem Standpunkt der Diskussionsteilnehmer, auf viele verschiedene Antworten.
Typischerweise rechnet man bei den Infrastrukturen der Abwasserreinigung in Europa mit Wiederbeschaffungswerten von 2.500 - 5.500 Euro pro Person, wobei die Kanalisation allein ca. 80% der Investitionen ausmacht (Maurer et al.). Die Situation in der Wasserversorgung ist ähnlich (Lehmann 1994). Sprechen wir also von den Infrastrukturen der Siedlungswasserwirtschaft, meinen wir vor allem den unsichtbaren Teil, die Rohrleitungen im Untergrund. Sowohl die Wasserversorgung als auch die Kanalisation sind mit den Siedlungen gewachsen, und ihre Komponenten haben eine Lebensdauer von bis zu 100 Jahren. Sie müssen dauernd erneuert und unterhalten werden, damit das System als Ganzes funktioniert.
In diesem Aufsatz werden wir ökologische Infrastrukturinnovationen in der Abwasserreinigung diskutieren. Weil das Kapital vor allem an die Kanalisation gebunden ist, heißt das nichts anderes als eine Diskussion über Sinn und Zweck der Schwemmkanalisation und mögliche Alternativen dazu.
Maurer, M. (2005). Vom Transportsystem zum Gewässerschutzelement. Schweizer Gemeinde, 42(6), 25-26. , Institutional Repository

Die Abwasserentsorgung befindet sich im Wandel vom Transportsystem zu einem Instrument des Gewässerschutzes. Wissenschaft und Praxis suchen nach Lösungen, um die bestehenden Strukturen zu optimieren. Entwickelt werden neue Ansätze für eine nachhaltige Siedlungsentwässerung. Die Gemeinden spielen dabei eine wichtige Rolle.
Langergraber, G., Rieger, L., Winkler, S., Alex, J., Wiese, J., Owerdieck, C., … Maurer, M. (2004). A guideline for simulation studies of wastewater treatment plants. Water Science and Technology, 50(7), 131-138. doi:10.2166/wst.2004.0436, Institutional Repository

A guideline for simulation studies of wastewater treatment plants is proposed. The aim of the HSG-guideline is to define a reference quality level that helps to make the results of simulation studies comprehensible and comparable and therefore increases the quality and reliability of mathematical modelling in wastewater treatment. The paper gives a summary of the HSG-guideline, written by a group of university members from Germany, Austria and Switzerland.
Maurer, M., & Rittmann, B. E. (2004). Formulation of the CBC-model for modelling the contaminants and footprints in natural attenuation of BTEX. Biodegradation, 15, 419-434. doi:10.1023/B:BIOD.0000044589.40735.b0, Institutional Repository

This paper provides the details of the Coupled Biological and Chemical (CBC) model for representing in situ bioremediation of BTEX. The CBC model contains novel features that allow it to comprehensively track the footprints of BTEX bioremediation, even when the fate of those footprints is confounded by abiotic reactions and complex interactions among different kinds of microorganisms. To achieve this comprehensive tracking of all the footprints, the CBC model contains important new biological features and key abiotic reactions. The biological module of the CBC-model includes these important new aspects: (1) it separates BTEX fermentation from methanogenesis, (2) it explicitly includes biomass as a sink for electrons and carbon, (3) it has different growth rates for each biomass type, and (4) it includes inhibition of the different reactions by other electron acceptors and by sulfide toxicants. The chemical module of the CBC-model includes abiotic reactions that affect the footprints of the biological reactions. In particular, the chemical module describes the precipitation/dissolution of CaCO3, Fe2O3, FeS, FeS2, and S°. The kinetics for the precipitation/dissolution reactions follow the critical review in Maurer & Rittmann (2003a).
Maurer, M., & Rittmann, B. E. (2004). Modeling intrinsic bioremediation for interpret observable biogeochemical footprints of BTEX biodegradation: the need for fermentation and abiotic chemical processes. Biodegradation, 15, 405-417. doi:10.1023/B:BIOD.0000044590.23221.b1, Institutional Repository

The intrinsic bioremediation of BTEX must be documented by the stoichiometric consumption and production of several other compounds, called ‘footprints’ of the biodegradation reaction. Although footprints of BTEX biodegradation are easy to identify from reaction stoichiometry, they can be confounded by the stepwise nature of the biodegradation reactions and by several abiotic chemical reactions that also produce or consume the footprints. In order to track the footprints for BTEX biodegradation, the following reactions need to be considered explicitly: (1) fermentation and methanogenesis as separate processes, (2) precipitation and dissolution of calcite, (3) precipitation and dissolution of amorphous iron monosulfide (FeS), (4) conversion of FeS into the thermodynamically stable pyrite (FeS2) with loss of sulfide and abiotic formation of H2, and (5) reductive dissolution of solid iron(III) by oxidation of sulfide. We critically review the research that underlies why these mechanisms must be included and how to describe them quantitatively. A companion manuscript develops and applies a mathematical model that includes these reactions.
Maurer, M. (2003). Du système de transport à l’outil de protection des eaux. Eawag News [éd. fr.], 57, 3-6. , Institutional Repository

L’assainissement se trouve en plein bouleversement et ce que l’on considérait plutôt comme un système de transport est en train de devenir un instrument important de la protection des eaux. Ce changement de fonction ne se fait cependant pas sans mal car certaines caractéristiques inhérentes au système actuel de traitement des eaux constituent des points faibles fondamentaux. Ainsi, par exemple, la capacité d’épuration du système d’assainissement est limitée par les déversoirs d’orage, par les fuites dans les canalisations et par la trop forte dilution des polluants. Dans un tel contexte, les scientifiques cherchent des solutions visant une optimisation des structures existantes et envisagent de nouvelles stratégies pour un assainissement de haut niveau placé dans une optique de durabilité.
Maurer, M. (2003). From transport to water protection. Eawag News [engl. ed.], 57, 3-6. , Institutional Repository

Urban drainage is in transition from functioning simply as a transport system to becoming an important element of water protection; however, this transition has been only partially successful since certain properties of today's sewage system represent inherent weaknesses. The cleaning efficiency of the sewage system as a whole, for example, is limited due to significant dilution with grey water and leaky sewage pipes. It is with this background that science is looking for ways to optimize existing structures and develop alternative approaches bringing sustainable urban drainage to a higher level.
Maurer, M., & Gujer, W. (2003). Ist unsere Abwasserentsorgung nachhaltig?. In R. Biedermann (Ed.), Wasser: Lebensquell und Wirtschaftskraft. Tagungsdokumentation VSA-Symposium (p. 1 (5 pp.). sine loco: VSA Verband Schweizer Abwasser- und Gewässerschutzfachleute. , Institutional Repository

Die Siedlungsentwässerung hat sich vom Transportsystem zu einem wichtigen Instrument des Gewässerschutzes gewandelt. Dieser Funktionswandel gelingt nur bedingt, da einige der systeminhärenten Eigenschaft der heutigen Abwasserbehandlung prinzipielle Schwachpunkte darstellen. So ist z. B. der Reinigungskapazität der Siedlungsentwässerung aufgrund von Mischwasserentlastungen, undichten Kanälen und der grossen Verdünnung der Schmutzstoffe eingeschränkt. Neue Lösungen müssen gefunden werden um eine nachhaltige Siedlungsentwässerung auf hohem Niveau garantieren zu können.
Maurer, M., Fux, C., & Siegrist, H. (2003). Nitrifikation, Denitrifikation und Energieeffizienz des Wirbelbettverfahrens in der kommunalen Abwasserreinigung. KA: Korrespondenz Abwasser Abfall, 50(9), 1142-1151. , Institutional Repository

Different aspects of the fluidised-bed process in municipal wastewater treatment were studied in detail in a full-scale plant with a tank volume of 850 m3. Kaldnes™ (KMT) was used as a substrate.
The maximum nitrification rate in all tanks was relatively constant and on average amounted to 107 gNm-3 d-1 (5 gO2m-3, 10°C and a filling ratio of 60 %). As a function of the tank volume, the average denitrification rate, with sewage as a substrate, amounted to approximately 210 gN m-3 d-1 (10 °C, 60 % filling ratio, and without taking account of oxygen transfer). Under realistic operating conditions, some 30 to 40 % of COD can be removed in the denitrification stage.
Experiences gained with the oxygen transfer in fluidised beds with Kaldnes are very different. Oxygen transfer in coarsebubble aeration can be of the same order of magnitude as in fine-bubble aeration (αOU* Te-1 == 10,1 gO2 Nm-3 m-1 ). The oxygen utilisation rate found during trial operation (αOU* Te-1), however, only amounted to 4,1 gO2 Nm-3 m-1.
Maurer, M., Schwegler, P., & Larsen, T. A. (2003). Nutrients in urine: energetic aspects of removal and recovery. Water Science and Technology, 48(1), 37-46. doi:10.2166/wst.2003.0011, Institutional Repository

The analysis of different removal and recovery techniques for nutrients in urine shows that in many cases recovery is energetically more efficient than removal and new-production from natural resources. Considering only the running electricity and fossil energy requirements for the traditional way of wastewater treatment and fertiliser production, the following specific energy requirements can be calculated: 45 MJ kg–1 N for denitrification in a WWTP, 49 MJ kg–1 P for P-precipitation in a WWTP, 45 MJ kg–1 N for N-fertiliser and 29 MJ kg–1 P for P-fertiliser production. These numbers are higher than the values derived for thermal volume reduction of urine (35 MJ kg –1 N for eliminating 90% water) or production of struvite (102 MJ kg–1 N, including 2.2 kg P). Considering only the electricity and fossil energy for the traditional way of wastewater treatment and fertiliser production, the energy value of 1 PE urine is 0.87 MJ PE–1d–1 (fertiliser value: 0.44, wastewater treatment: 0.43 MJ PE–1d–1).
A more detailed life cycle assessment (LCA) of the entire urine collection system, including the required materials and the environmental burden, support the energy analysis. The LCA compares conventional denitrification in a wastewater treatment plant with collecting urine in households, reducing the volume by evaporation and using it as a multi-nutrient fertiliser. The primary energy consumption for recovery and reuse of urine, including the nutrients N, P and K, is calculated with 65 MJ kg–1 N, compared with 153 MJ kg–1 N derived for the conventional 'recycling over the atmosphere'.
Maurer, M. (2003). Nährstoffrecycling in der Siedlungsentwässerung. Thema Umwelt, 2, 6-7. , Institutional Repository

Unser heutiges System der Schwemmkanalisation ist ein optimiertes Transportsystem. Die starke Verdünnung erschwert den Gewässerschutz und ist für einen nachhaltigen Umgang mit Nährstoffen denkbar ungeeignet. Möchte man diesen Umstand verbessern, sind tief greifende Veränderungen mit Massnahmen an der Quelle wie belspielsweise der Urinseparation nötig. Stickstoff könnte so in Form von Struvit, Ammoniumsulfat oder Ammoniumnitrat zurückgewonnen und als Dünger eingesetzt werden. Phosphor könnte zudem als Kalziumphosphat in die Phosphatindustrie zurückgeführt werden.
Maurer, M. (2003). Vom Transportsystem zum Gewässerschutzelement. Eawag News [dtsch. Ausg.], 57, 3-6. , Institutional Repository

Die Siedlungsentwässerung befindet sich im Wandel vom Transportsystem zu einem wichtigen Instrument des Gewässerschutzes. Dieser Funktionswandel gelingt jedoch nur bedingt, da einige der systeminhärenten Eigenschaften der heutigen Abwasserbehandlung prinzipielle Schwachpunkte darstellen. So ist z.B. die Reinigungskapazität der Siedlungsentwässerung aufgrund von Mischwasserentlastungen, undichten Kanälen und der grossen Verdünnung der Schmutzstoffe limitiert. In diesem Umfeld sucht die Wissenschaft nach Lösungen, um die bestehenden Strukturen zu optimieren, und entwickelt neue alternative Ansätze für eine nachhaltige Siedlungsentwässerung auf hohem Niveau.
Ronteltap, M., Biebow, M., Maurer, M., & Gujer, W. (2003). Thermodynamics of struvite precipitation in source separated urine. In C. Werner, V. Avedaño, S. Demsat, I. Eicher, L. Hernández, C. Jung, … M. Wafler (Eds.), Ecosan - closing the loop. Proceedings of the 2nd international symposium, 7th - 11th April 2003, Lubeck, Germany (pp. 463-470). Eschborn: Deutsche Gesellschaft fur Technische Zusammenarbeit (GTZ). , Institutional Repository

The thermodynamics of struvite (MgNH4PO4) precipitation in source separated and artificial urine under controlled addition of magnesium chloride (MgCl2), magnesium oxide (MgO) and magnesium hydroxide (Mg(OH)2) were investigated. The solubility product of struvite in source separated and artificial urine was identified by use of experimental results in a precipitation potential model designed for working with urine. A conditional solubility product of 10-11.7±0.51 was determined, which can be used for solutions comparable to source separated urine. With the precipitation model the inorganic complexes MgPO4-, MgHPO4, NH4HPO4-, NaHPO4-, MgSO4, MgHCO3+, MgCO3, and NH4SO4- were determined as significant in urine and they exert influence on the solubility of struvite. Ionic strength and formation of dissolved complexes were considered in calculating the average value of the standard solubility product of struvite in urine, which is 10-13.41±0.31. This value is slightly smaller but agrees well with the solubility products reported recently in the literature. Organic complexing agents do not influence the solubility of struvite.
Sutter, D., & Zschokke, M. (2003). Abbau von Östrogenen und Pharmaka in Urinbioreaktoren (Master thesis). 102 p. , Institutional Repository

Immer häufiger werden Rückstände von Pharmazeutika in der Umwelt in messbaren Konzentrationen nachgewiesen. Vor allem unterhalb von Kläranlagenausläufen aber auch in anderen Oberflächengewässern wurden Pharmazeutika in erheblichen Konzentrationen gemessen. Selbst im Trinkwasser konnten eine Reihe von Pharmazeutika in nicht unbeträchtlichen – für den Menschen aber gemäss Risikoabschätzungen noch unbedenklichen – Mengen nachgewiesen werden. Der Haupteintragsweg von Humanpharmaka in die Umwelt führt über die menschliche Ausscheidung ins Abwasser. Über Abwasser und Kläranlage gelangen Pharmaka so in die Oberflächengewässer und das Grundwasser. Da ein grosser Teil dieser Stoffe über den Urin in die Umwelt gelangt, könnte eine Urinseparation an der Quelle diese Einträge massiv reduzieren.
Um den so gesammelten Urin allerdings als Rohstoff (beispielsweise als Dünger) weiter verwenden zu können, sind weitere Massnahmen an der Quelle nötig.
Die vorliegende Arbeit untersuchte daher, ob Mikroverunreinigungen im Urin mit Hilfe eines Urin-Bioreaktors abbaubar sind. Exemplarisch wurden fünf Substanzen ausgewählt, welche als Mikroverunreinigungen im Urin bzw. im Abwasser auftreten und bereits in Oberflächengewässern nachgewiesen worden sind. Es sind dies die natürlichen Östrogene Estradiol und Estron, das synthetische Östrogen Ethinylestradiol, sowie die beiden Pharmaka Ibuprofen und Propranolol. [...]
Wilsenach, J. A., Maurer, M., Larsen, T. A., & van Loosdrecht, M. C. M. (2003). From waste treatment to integrated resource management. Water Science and Technology, 48(1), 1-9. doi:10.2166/wst.2003.0002, Institutional Repository

Wastewater treatment was primarily implemented to enhance urban hygiene. Treatment methods were improved to ensure environmental protection by nutrient removal processes. In this way, energy is consumed and resources like potentially useful minerals and drinking water are disposed of. An integrated management of assets, including drinking water, surface water, energy and nutrients would be required to make wastewater management more sustainable. Exergy analysis provides a good method to quantify different resources, e.g. utilisable energy and nutrients. Dilution is never a solution for pollution. Waste streams should best be managed to prevent dilution of resources. Wastewater and sanitation are not intrinsically linked. Source separation technology seems to be the most promising concept to realise a major breakthrough in wastewater treatment. Research on unit processes, such as struvite recovery and treatment of ammonium rich streams, also shows promising results. In many cases, nutrient removal and recovery can be combined, with possibilities for a gradual change from one system to another.
Biebow, M. (2002). Optimierung der Phosphatausfällung in urinhaltigen Lösungen (Master thesis). 61 p. , Institutional Repository

In der Vergangenheit wurde die Struvitfällung bereits in der Abwasserbehandlung zur Elimination von Stickstoff oder Phosphor als Magnesium-Ammonium-Phosphat (Struvit) eingesetzt. Im Projekt NOVAQUATIS an der EAWAG soll die Fokussierung auf den Einsatz der Struvitfällung aus gering verdünntem Urin zur Düngerproduktion erfolgen. Mit Orientierung auf den Einsatz als Klein- oder Kleinstanlagen wurden zunächst zwei einfache kontinuierliche Reaktoren ( 1)durchmischter Reaktor, 2)Festbett) betrieben. Die Systeme basierten auf einer Fällungsmittelvorlage in Form eines Magnesiumoxid/-hydroxid-Granulates. Nachdem eine Optimierung beider Reaktorsysteme im Rahmen dieser Arbeit nicht möglich war, wurden Batchversuchsreihen in den Vordergrund der Untersuchungen gestellt. Sie sollten erste Ansätze zur Evaluierung zentraler Prozesse und Einflüsse liefern soiwe deren mathematische Beschreibung ermöglichen.
Die Auswertung von Konzentrationsmessungen resultierte in der Erkenntnis zweier Bereiche der Struvitfällung. Während in Urin die P-Konzentration im ersten Bereich spontan auf bis zu 15 mg P/l abgesenkt wird (ausgehend von etwa 250 mg P/l im Zulauf: 94% P-Fällung), wird die Fällungsrate im zweiten Bereich unterhalb 15 mg P/l sehr stark reduziert. Es konnte keine Absenkung der P-Konzentration unter 2,6 mg P/l erfolgen.
Für beide Bereiche wurden hypothetisch anhand der erkannten Prozesse mathematische Ansätze evaluiert, welche jedoch wegen unzureichender Datenmengen nicht nachgewiesen werden konnten. In zukünftigen Untersuchungen sollte eine Vervollständigung der Erkenntnisse über ablaufende Prozesse sowie eine Präzisierung ihrer mathematischen Beschreibung stattfinden.
Maurer, M., Muncke, J., & Larsen, T. A. (2002). Technologies for nitrogen recovery and reuse. In P. Lens, L. Hulshoff Pol, P. Wilderer, & T. Asano (Eds.), Integrated environmental technology series. Water recycling and resource recovery in industry. Analysis, technologies and implementation (pp. 491-510). Retrieved from https://iwaponline.com/ebooks/book/143/Water-Recycling-and-Resource-Recovery-in-Industry, Institutional Repository

In industrial countries traditional waste management treats nitrogen as a waste. Discharged into our environment they boost nutrient cycles and lead to adverse effects such as over-fertilisation and eutrophication of lakes or ecotoxicological problems in river waters caused by ammonia and nitrite. On the other hand, significant amount of synthetic nitrogen fertiliser is produced and used in agriculture. In order to cut down the environmental burden from N-pollution and fertiliser production it would be beneficial to recover nitrogen from wastes and reuse it.
The following paragraphs give an overview over the currently available techniques to recover nitrogen from waste streams. The examples focus mainly on municipal wastewater. This is one of the biggest point sources of nitrogen and has a major impact on aquatic systems in many areas. For N-containing liquid industrial waste (e.g. pig manure or polyurethane production) treatment options are very similar.
Larsen, T. A., Peters, I., Alder, A., Eggen, R., Maurer, M., & Muncke, J. (2001). Re-engineering the toilet for sustainable wastewater management. Could one answer be a new toilet that separates urine from wastewater streams?. Environmental Science and Technology, 35(9), 192A-197A. doi:10.1021/es012328d, Institutional Repository
Larsen, T., Alder, A., Eggen, R., Maurer, M., Muncke, J., & Peters, I. (2001). Testlauf im KraftWerk1. Unimagazin. Zeitschrift der Universität Zürich / Bulletin. Magazin der ETH Zürich, 281, 47-49. Retrieved from https://www.magazin.uzh.ch/de/issues/unimagazin-01-1.html, Institutional Repository

Bitte nehmen Sie Platz! - Die Koevolution des umweltbewussten Menschen und des intelligenten WCs findet im KraftWerk1 in Zürich statt. Ein neues Sanitärkonzept könnte die traditionelle Abwasserreinigung revolutionieren.
MacGregor, B. J., Moser, D. P., Baker, B. J., Alm, E. W., Maurer, M., Nealson, K. H., & Stahl, D. A. (2001). Seasonal and spatial variability in Lake Michigan sediment small-subunit rRNA concentrations. Applied and Environmental Microbiology, 67(9), 3908-3922. doi:10.1128/AEM.67.9.3908-3922.2001, Institutional Repository

We have used molecular biological methods to study the distribution of microbial small-subunit rRNAs (SSU rRNAs), in relation to chemical profiles, in offshore Lake Michigan sediments. The sampling site is at a depth of 100 m, with temperatures of 2 to 4°C year-round. RNA extracted from sediment was probed with radiolabeled oligonucleotides targeting bacterial, archaeal, and eukaryotic SSU rRNAs, as well as with a universal probe. The coverage of these probes in relation to the present sequence database is discussed. Because ribosome production is growth rate regulated, rRNA concentrations are an indicator of the microbial populations active in situ. Over a 1-year period, changes in sedimentary SSU rRNA concentrations followed seasonal changes in surface water temperature and SSU rRNA concentration. Sedimentary depth profiles of oxygen, reduced manganese and iron, and sulfate changed relatively little from season to season, but the nitrate concentration was approximately fivefold higher in April and June 1997 than at the other times sampling was done. We propose that sediment microbial SSU rRNA concentrations at our sampling site are influenced by seasonal inputs from the water column, particularly the settling of the spring diatom bloom, and that the timing of this input may be modulated by grazers, such that ammonia becomes available to sediment microbes sooner than fresh organic carbon. Nitrate production from ammonia by autotrophic nitrifying bacteria, combined with low activity of heterotrophic denitrifying bacteria in the absence of readily degradable organic carbon, could account for the cooccurrence of high nitrate and low SSU rRNA concentrations.
Maurer, M., Fux, C., Graff, M., & Siegrist, H. (2001). Moving-bed biological treatment (MBBT) of municipal wastewater: denitrification. Water Science and Technology, 43(11), 337-344. doi:10.2166/wst.2001.0700, Institutional Repository

Denitrification in a full-scale installation and a pilot plant for moving-bed biological treatment (MBBT) was subject to detailed investigation. Two different types of carriers were used in conventional activated sludge reactors: Foam cubes and plastic tubes (Kaldnes®).
Both investigated carriers showed the same behavior with regard to denitrification capacity, temperature dependency and maximum COD and nitrate turnover. In contrast to the plastic tubes (Kaldnes®), the sponge cubes stored remarkable amounts of substrate. The maximum denitrification rate with acetate as a substrate was 420 gNm–3d–1 at 10°C and 730 gNm–3d–1 at 20°C. An average denitrification rate of 240 gNm–3d–1 (10°C) was achieved with wastewater. A maximum of 37% of the COD in the influent was denitrified with a volumetric loading rate in the anoxic zone of 2.2 kgCODm–3d–1.
Fux, C., Maurer, M., & Siegrist, H. (1999). Nitrifikation und Denitrifikation im Wirbelbett. In VSA-Fortbildungskurse. Nährstoffelimination auf Kläranlagen (p. 13 (40 pp.). Zürich: Verband Schweizer Abwasser- und Gewässerschutzfachleute. , Institutional Repository
Maurer, M., Abramovich, D., Siegrist, H., & Gujer, W. (1999). Kinetics of biologically induced phosphorus precipitation in waste-water treatment. Water Research, 33(2), 484-493. doi:10.1016/S0043-1354(98)00221-8, Institutional Repository

In waste-water treatment plants with enhanced biological phosphorus removal (EBPR), a part of the phosphorus can be eliminated by chemical precipitation. In experiments with inactivated sludge containing relatively high concentrations of dissolved calcium (≈1.5 mol m-3) and phosphorus (≈1 mol m-3), a pH-sensitive and partly reversible precipitation of calcium phosphates was observed at pH values below 8.0. A dynamic model was formulated on the basis of these observations. It contains, in addition to equilibrium equations for the deprotonation(s) of phosphoric acid, carbonic acid and water, the following reactions: (1) Fully reversible precipitation of hydroxydicalcium phosphate (Ca2HPO4(OH)2, HDP) as an intermediate. (2) Formation of hydroxyapatite (Ca5(PO4)3OH, HAP) from HDP. HAP is regarded as a kinetically stable product. A parameter estimation performed for the surface complex HDP predicts a solubility product of 10-22.6 M5 (20 °C) and a heat of dissolution (ΔH298) of -88.4 kJ molP-1. If the solubility of HDP is exceeded, then inorganic calcium phosphate (HAP) is fixed irreversibly in the sludge with a rate of 0.5 molP-3 d-1.
Maurer, M., Fux, C., Lange, D., & Siegrist, H. (1999). Modelling denitrification in a moving bed of porous carriers from a low-loaded wastewater treatment plant. Water Science and Technology, 39(7), 251-259. doi:10.1016/S0273-1223(99)00175-4, Institutional Repository

A model was developed to describe hydrolysis in a moving bed with polyurethane foam carriers under anoxic conditions. It is formulated as a two-box model and structured into bulk and carrier compartments linked by mass transfer processes for solutes and particles. The biological processes consist of the anoxic growth and decay of heterotrophic organisms and hydrolysis of the slowly biodegradable substrate. Kinetic and stoichiometric parameters are taken from Activated Sludge Model No. 2 (Henze et al., 1995). Parameter estimations based on 24 batch experiments resulted in anoxic hydrolysis rates of 3.9 d−1 (at 20°C) and 2.6 d−1 (at 10°C).
The mass transfer coefficient for solutes was determined from the mixing of an inert tracer to be 0.3 m d−1. Measurements of the enzymatic activity of α-, β-glucosidase and esterases confirmed that 90% of the activity involves the carriers. In conjunction with the finding that the absorption capacity of the carriers for slowly biodegradable substrate is high, it can be concluded that the hydrolysis takes place principally within the carriers.
Maurer, M., & Boller, M. (1999). Modelling of phosphorus precipitation in wastewater treatment plants with enhanced biological phosphorus removal. Water Science and Technology, 39(1), 147-163. doi:10.1016/S0273-1223(98)00784-7, Institutional Repository

Solubility equilibrium models and/or adsorption models enable the prediction of phosphorus residuals in an effluent of a wastewater treatment plant over a wide range of operating conditions. A generally valid model cannot be given because the model parameters depend on wastewater composition, e.g. on dissolved and particulate water constituents, above all on phosphorus speciation.
Chemical precipitation is able to bind ortho-phosphates proportionally to added chemicals and polyphosphates to a great extent. The P-residuals consist mainly of organically bound phosphorus and some residual polyphosphate. In wastewater treatment plants with enhanced biological phosphorus removal (EBPR), an extensive use of precipitation chemicals could suppress the EBPR-ability of the sludge.
In EBPR-plants a part of the phosphorus can also be eliminated by chemical precipitation without added chemicals. In experiments with inactivated sludge derived from a wastewater treatment pilot plant, a pH-sensitive and partly reversible precipitation of calcium phosphates was observed at pH values below 8.0.
A dynamic model was formulated on the basis of these observations. It contains the following reactions:
- Fully reversible precipitation of hydroxydicalcium phosphate (Ca2HPO(OH)2, HDP) as an intermediate, with a solubility product of 10−22.6 (kmole m−3)5 (20°C).
- Formation of hydroxyapatite (Ca5(PO4)3OH, HAP) from HDP. HAP is regarded as a kinetically stable endproduct.
If the solubility of HDP is exceeded, then 15.5 gpm−3d−1 of inorganic calcium phosphate (HAP) is fixated irreversibly in the sludge.
Maurer, M., Siegrist, H., & Becher, D. (1999). Nitrifikation und Denitrifikation im Wirbelbett. Biologische Reinigungsleistung in der kommunalen Abwasserreinigung. Mitteilungen zum Gewässerschutz: Vol. 36. Bern: Bundesamt für Umwelt, Wald und Landschaft (BUWAL). , Institutional Repository

Use of a moving bed biofilm system in municipal wastewater treatment was investigated in a pilot and full-scale plant. Kaldnes (small polyethylene elements, specific biofilm surface at 60% filling ratio: 275 m2m–3) and sponge cubes (based on the Linpor process) were used as carrier material. Without the addition of COD, the maximum nitrification rate for Kaldnes was almost identical in all compartments and averaged 107 gNm–3d–1 (at 5 gO2m–3 volume, 10 °C and 60% filling ratio). Nitrification of the Sponge cubes is significantly influenced by their distance from the inlet, with rates ranging between 137 and 300 gNm–3d–1 (same environmental conditions as above).
With wastewater as a substrate, denitrification rate with both carrier materials amounted to 210 gNm–3d–1 (at 10 °C and 60% filling ratio, neglecting the oxygen input). Roughly 30-40% of the COD load is degraded during denitrification. Compared to Kaldnes, the sponge cubes stored surprisingly large amounts of particulate substrate.
The energy demand for aeration with Kaldnes as a carrier material is greatly dependent on reactor configurations and wastewater conditions. Under favourable conditions, the oxygen utilization efficiency in the course bubble aeration is similar to that of a fine bubble aeration in activated sludge systems. Under unfavourable conditions, the energy demand can also be two to three times higher.
Experiments conducted over a period of six months in a large-scale system with Kaldnes revealed an apparent yield coefficient of Y' = 0.51 gCODg–1COD. The use of sponge cubes yielded a Y' equal to 0.36 gCODg–1COD. In an activated sludge system, the yield lies in between these two values.
Maurer, M., & Gujer, W. (1998). Dynamic modelling of enhanced biological phosphorus and nitrogen removal in activated sludge systems. Water Science and Technology, 38(1), 203-210. doi:10.1016/S0273-1223(98)00405-3, Institutional Repository

A dynamic model for the description of enhanced biological phosphorus removal is presented. Model approach and structure were mainly adopted from the ‘Activated Sludge Model (ASM) No 2’ (Henze et al., 1995). Two additional processes for the anoxic growth of phosphorus accumulating organisms (PAO) and anoxic storage of polyphosphate were included. The model was further enhanced with three processes describing biologically induced phosphorus precipitation. Stoichiometric coefficients for anoxic conditions are modified under the consideration of a 35% reduction of energy yield compared with oxygen as electron acceptor. In addition, a ratio for the anaerobic P-release per substrate taken-up is introduced, which depends on pH, glycogen and substrate. With the aid of 18 batch-experiments and measurements from a WWT pilot plant, a set of kinetic parameter was estimated, that was able to reproduce satisfactorily the nutrient removal behaviour of the investigated sludge.
Maurer, M., & Siegrist, H. (1998). Nitrifikation und Denitrifikation im Wirbelbettverfahren. VSA Verbandsbericht, 522, 6-17. , Institutional Repository

Biofilmverfahren erleben in den letzten Jahren eine Art Wiederentdeckung. Insbesondere verspricht der Umbau von überlasteten Belebtschlammanlagen zum sogenannten Wirbelbettverfahren die Abbauleistungen zu verbessern.
Dieses Verfahren zeigt eine Reihe von attraktiven Vorteilen: bestehende Belebungsbecken können einfach umgenutzt werden, eine Nitrifikation kann in relativ kleinen Becken etabliert werden und der fehlende Rücklaufschlamm entlastet die Nachklärbecken. Die Nachteile sind die hohen nötigen Mischenergien, die Abhängigkeit der Nitrifikationsleistung von der relativ hohen Sauerstoff-Betriebskonzentration (Energie), das kleine Spitzen- zu Durchschnitts-Lastverhältnis der einzelnen Becken und die fehlenden Möglichlkeiten zur biologischen Phosphoreliminalion.
Der Artikel beschreibt die theoretischen Grundlagen um die Leistung und den Energieverbrauch von Wirbelbettanlagen mit anderen Verfahren vergleichen zu können.
Maurer, M., Gujer, W., Hany, R., & Bachmann, S. (1997). Intracellular carbon flow in phosphorus accumulating organisms from activated sludge systems. Water Research, 31(4), 907-917. doi:10.1016/S0043-1354(96)00369-7, Institutional Repository

A biochemical model for the anaerobic and aerobic carbon flow in phosphorus accumulating organisms (PAO) is discussed. It is based on the assumption that for the anaerobic poly(hydroxyalcanoates) (PHA) storage the reduction power is delivered by glycogen and the energy is supplied with hydrolysis of glycogen or polyphosphate. These have to be regenerated under aerobic or anoxic conditions which requires energy and releases carbon dioxide. Batch experiments with activated sludge from a pilot plant fed with domestic wastewater were performed. 13C (in the form of acetate) was added and traced with solid state carbon NMR. The anaerobic formation of intracellular PHA from metabolised acetate together with degraded glycogen and the aerobic conversion of PHA to glycogen could be detected. The low ratio of acetate to carbohydrate conversion and the detection of poly(hydroxyvalerate) formed from glycogen shows that there is a substantial anaerobic breakdown of glycogen for energy production. The results from the NMR spectra also indicate that glycogen is degraded via the Entner-Doudoroff pathway. From the model it can be concluded that the maintenance of a glycogen and polyphosphate pool reduces the growth yield on substrate. This reduction depends on the type of substrate. It is estimated that for acetate there is a loss of biomass yield of about 12% as compared to strictly aerobic conditions. The model also shows that glycogen as well as polyphosphate may serve for anaerobic energy supply, however with acetate as the only carbon source, polyphosphate is essential for growth.
Maurer, M., & Gujer, W. (1996). Erhöhte biologische Phosphorelimination. GWA Gas, Wasser, Abwasser, 76(11), 867-876. , Institutional Repository

Prerequisite for the enhanced biological phosphorus removal in activated sludge plants are temporary anaerobic (nitrate and oxygen-free) conditions. The carbon substrates absorbed during this period are, under anoxic or aerobic conditions, utilised by the corresponding organisms for growing. Parallel to this, under anaerobic conditions, a large increase in the phosphorus concentration can be observed which decreases again during growth. The phosphorus-netto elimination obtained depends on the substrate available in the anaerobic phase. A pilot plant in Zurich operated with communal sewage showed an average phosphorus elimination capacity of 5.6 gP/m3influence. Detailed investigations with artificially increased phosphorus pattern resulted in characteristic weekly pattern, with distinct phosphorus discharge peaks after weekends or rainy periods. Combined with the enhanced biological phosphorus removal was a good denitrification performance.
A prerequisite for the integration of an enhanced biological phosphorus removal in a sewage treatment plant is due to the biologic character of the process, a good understanding of the processes and their interactions. Economic advantages will result, above all, through the reduced amount of sludge produced (30-60% compared with the chemical precipitation) but also through the distinctly reduced chemicals requirement.
Maurer, M. (1996). Erhöhte biologische Phosphorelimination. Modellierung der biologischen und chemischen Prozesse (Doctoral dissertation). Retrieved from https://doi.org/10.3929/ethz-a-001755939, Institutional Repository

Die erhöhte biologische Phosphorelimination (EBPE) in kommunalen Abwasserreinigungsanlagen stellt eine attraktive Alternative zur chemischen Phosphorfixierung dar. Dabei wird die Eigenschaft gewisser Organismen ausgenutzt, unter anaeroben Bedingungen Kohlenstoffverbindungen im Austausch gegen intrazelluläre Phosphate zu speichern. Steht anschliessend ein Elektronenakzeptor wie Nitrat oder Sauerstoff zur Verfügung, dann können diese organischen Substanzen für das Biomassewachstum genutzt werden. Ein Teil der dabei anfallenden Energie wird für die Aufnahme von Phosphaten und die Speicherung als Polyphosphat verwendet. In dieser Phase kann diese zusätzliche Phosphorfraktion mit dem Überschussschlamm entfernt werden. [...]

Enhanced biological phosphorus removal (EBPR) is an attractive possibility to remove phosphorus from waste water. The process uses the ability of certain organisms to store organic compounds under anaerobic conditions in exchange for intracellular phosphate. Providing there is an electron acceptor such as nitrate or oxygen afterwards available, the organisms are able to utilise the stored organic substances for growth. A part of the produced energy is employed to take up phosphate again and store it as polyphosphate. This phosphorus fraction can be removed together with the excess sludge. [...]
Maurer, M., & Gujer, W. (1995). Monitoring of microbial phosphorus release in batch experiments using electric conductivity. Water Research, 29(11), 2613-2617. doi:10.1016/0043-1354(95)00146-C, Institutional Repository

The ionic conductivity of an enhanced biological phosphorus removing (EBPR) sludge shows a clear behavior during the non-aerated phase. It decreases during denitrification and increases under anaerobic conditions proportionally to the phosphate concentration. The absolute value of this increase related to the release of phosphorus was determined between 1.66 × 10−4 to 1.99 × 10−4 S m2 gP−1 (at 293 K and an ionic strength of about 650 × 10−4 S m−1). Theoretical calculations are in good agreement with these results. Potassium, magnesium, calcium and phosphate show a positive, whereas acetate and pH show a negative correlation to the ionic conductivity. This method is an easy and inexpensive in-line method providing more information about phosphorus release. Under some circumstances (low salinity, sequencing batch reactor) it may be used to estimate the anaerobic increase of phosphorus concentration.
Bernhard, J., Wehrli, B., Bundi, U., Müller, E., Gujer, W., Siegrist, H., … Boller, M. (Eds.). (1995). Nährstoffelimination in der biologischen Abwasserreinigung. VSA-Fortbildungskurse. VSA-Fortbildungskurse 1993. Zürich: Verband Schweizer Abwasser- und Gewässerschutzfachleute. , Institutional Repository

Der VSA führt Fortbildungskurse mit jährlich wechselnden aktuellen Themen durch. lm Jahr 1993 wurde der Kurs "Nâhrstoffelimination in der biologischen Abwasserreinigung", beschränkt auf das Belebtschlammsystem, angeboten.

Der Kurs richtete sich an erfahrene Ingenieure, welche sich mit der Projektierung und dem Betrieb von Abwasserreinigungsanlagen mit Nährstoffelimination befassen müssen (Nitrifikation, Denitrifikation, Phosphorelimination). Es wurden die Grundlagen für das Verständnis der chemischen und biologischen Nährstoffeliminartlon in der kommunalen Abwasserreinigung vermittelt. Der Kurs führte in die Dimensionierung und Gestaltung der Verfahren unter Berücksichtigung der Schlammbehandlung ein und vermittelte Einsichten in praktische Probleme.

Nachdem die beschränkte Auflage der eigentlichen Kursdokumentation seit einiger Zeit vergriffen war, sollen die wertvollen Kursunterlagen mit dem vorliegenden Nachdruck einem breiten Anwenderkreis zugänglich gemacht werden. Aus Kostengründen wurde auf die Erarbeitung einer einheitlichen Darstellung und einer durchgehend systematischen Nomenklatur verzichtet. Trotzdem ist der Inhalt anschaulich gegeben und der Gesamtzusammenhang gut nachvollziehbar. Die gesetzlichen Grundlagen entsprechen dem Stand September 1993.
Maurer, M., & Gujer, W. (1994). Prediction of the performance of enhanced biological phosphorus removal plants. Water Science and Technology, 30(6), 333-343. doi:10.2166/wst.1994.0284, Institutional Repository

A static model is introduced, which allows for the estimation of the performance of a full scale EBPR plant The model is based on the assumption that the readily biodegradable substrate from the influent and the total COD-turnover in the anaerobic zone determine the amount of phosphorus contained within phosphorus accumulating organisms. Model predictions are based on wastewater composition,operating temperature, effects of oxygen and nitrate addition to the anaerobic reactor, solids retention time and anaerobic mass fraction of the activated sludge. The model is calibrated with full scale experience and may be useful for the analysis of plant performance as well as the design of new treatment plants.
Maurer, M., & Gujer, W. (1993). Grundlagen der biologischen Phosphorelimination in Belebungsanlagen. In VSA-Fortbildungskurse. Nährstoffelimination in der biologischen Abwasserreinigung (p. 10 (26 pp.). Zürich: Verband Schweizer Abwasser- und Gewässerschutzfachleute. , Institutional Repository

Lena Mutzner

Cavadini, G. B., Mutzner, L., Cook, L., Rodriguez, M., & Poggioli, M. (2024). BGI reduzieren Gewässerbelastung. Modellstudien zu Entlastungen und Wasserqualität sowie Auswirkungen des Klimawandels. Aqua & Gas, 104(10), 46-52. , Institutional Repository

Indem blau-grüne Infrastrukturen die Mischwasserentlastungen reduzieren, werden auch die Einträge von Mikroverunreinigungen verkleinert. Besonders Versickerungsflächen senken die eingeleiteten Volumina und Frachten in Oberflächengewässer. Klimawandelprognosen lassen eine Zunahme von Entlastungen erwarten. Blau-grüne Infrastrukturen können daher einen wichtigen Beitrag leisten, um unerwünschte Effekte zu vermeiden oder zu reduzieren.
Jensen, D. M. R., Mutzner, L., Wei, Y., Mikkelsen, P. S., & Vezzaro, L. (2024). Temporal variations in micropollutant inlet concentrations matter when planning the design and compliance assessment of stormwater control measures. Journal of Environmental Management, 356, 120583 (10 pp.). doi:10.1016/j.jenvman.2024.120583, Institutional Repository

Stormwater Control Measures (SCMs) contribute to reducing micropollutant emissions from separate sewer systems. SCM planning and design are often performed by looking at the hydrological performance. Assessment of pollutant removal and the ability to comply with discharge concentration limits is often simplified due to a lack of data and limited monitoring resources. This study analyses the impact of using different time resolutions of input stormwater concentrations when assessing the compliance of SCMs against water quality standards. The behaviour of three indicator micropollutants (MP - Copper, Diuron, Benzo[a]pyrene) was assessed in four SCM archetypes, which were defined to represent typical SCM removal processes. High resolution MP data were extrapolated by using high resolution (2 min) measurements of TSS over a long period (343 events). The compliance assessment showed that high resolution input concentrations can result in a different level of compliance with water quality standards, especially when discharged concentrations are close to the limit values. This study underlines the importance of considering the high temporal variability of stormwater micropollutants when planning and designing SCMs to identify the most effective solutions for stormwater pollution management and to ensure a thorough consideration of all the environmental implications.
Poggioli, M., Cavadini, G. B., Zheng, Z., Rodriguez, M., & Mutzner, L. (2024). The impact of blue-green infrastructure on trace contaminants: a catchment-wide assessment. Water Research X, 25, 100261 (11 pp.). doi:10.1016/j.wroa.2024.100261, Institutional Repository

Blue-green infrastructure (BGI) reduce urban combined sewer overflows (CSOs) and stormwater outlets (SWOs). However, most conventional BGI are not designed to remove trace organic contaminants. Little is known about the potential of conventional BGI to improve surface water quality by reducing the discharge of trace organic contaminants. We derived wash-off loads for street runoff (6PPD-q, DPG, and HMMM), construction materials (diuron), and wastewater-derived contaminants (diclofenac) based on measurements in the combined sewer system. Subsequently, the performance of four BGI types (bioretention cells, green roofs, porous pavements, and urban wetlands) to reduce the discharge of trace organic contaminants via SWOs and CSOs was quantified with a hydrodynamic SWMM model. Moreover, the catchment-wide impact of SWOs and CSOs on surface water was assessed using risk quotients. We found that the annually discharged load can be considerably reduced by implementing BGI. Among the studied BGI types, bioretention cells are the most effective, with a load reduction of up to 80% to surface waters, mainly due to a larger suitable implementation area and a substantial stormwater infiltration. BGI implemented in the separate sewer system are more effective in reducing stormwater contaminant loads than BGI in the combined system. The assessment of the risk quotient in the surface water showed that the concentrations during SWO and CSO discharges exceed the acute environmental threshold in the surface water for 6PPD-q, DPG, diuron, and diclofenac during several events. The implementation of BGI reduced the hours of exceeded risk quotient in the surface water by 93% for bioretention cells. These findings underscore the need for a catchment-wide assessment of future BGI implementations to quantify, manage, and mitigate the impacts of urban pollution.
Zhang, K., Zheng, Z., Mutzner, L., Shi, B., McCarthy, D., Le-Clech, P., … Deletic, A. (2024). Review of trace organic chemicals in urban stormwater: concentrations, distributions, risks, and drivers. Water Research, 258, 121782 (11 pp.). doi:10.1016/j.watres.2024.121782, Institutional Repository

Urban stormwater, increasingly seen as a potential water resource for cities and towns, contains various trace organic chemicals (TrOCs). This study, conducted through a comprehensive literature review of 116 publications, provides a detailed report on the occurrence, concentration distribution, health, and ecological risks of TrOCs, as well as the impact of land use and rainfall characteristics on their concentrations. The review uncovers a total of 629 TrOCs detected at least once in urban stormwater, including 228 pesticides, 132 pharmaceutical and personal care products (PPCPs), 29 polycyclic aromatic hydrocarbons (PAHs), 30 per- and polyfluorinated substances (PFAS), 28 flame retardants, 24 plasticizers, 22 polychlorinated biphenyls (PCBs), nine corrosion inhibitors, and 127 other industrial chemicals/intermediates/solvents. Concentration distributions were explored, with the best fit being log-normal distribution. Risk assessment highlighted 82 TrOCs with high ecological risk quotients (ERQ > 1.0) and three with potential health risk quotients (HQ > 1.0). Notably, 14 TrOCs (including six PAHs, five pesticides, three flame-retardants, and one plasticizer) out of 68 analyzed were significantly influenced by land-use type. Relatively weak relationships were observed between rainfall characteristics and pollutant concentrations, warranting further investigation. This study provides essential information about the occurrence and risks of TrOCs in urban stormwater, offering valuable insights for managing these emerging chemicals of concern.
Furrer, V., Mutzner, L., Ort, C., & Singer, H. (2023). Micropollutant concentration fluctuations in combined sewer overflows require short sampling intervals. Water Research X, 21, 100202 (8 pp.). doi:10.1016/j.wroa.2023.100202, Institutional Repository

Combined sewer overflows (CSOs) are an important pathway of organic micropollutants from urban areas to open water bodies. Understanding the temporal dynamics of these micropollutants during overflow events is crucial for applying appropriate sampling methods and implementing effective management strategies. Yet, little is known about the dynamics of micropollutants in CSOs, because most studies report concentrations from single grab samples or event mean concentrations (EMCs). With unique high temporal resolution measurements (3 min), we show the real dynamics of polar organic micropollutants in CSOs of one small (2,700 people: P) and one large (159,000 P) urban catchment, for two micropollutant categories: (i) 33 micropollutants in municipal wastewater and (ii) 13 micropollutants from urban surface runoff. The concentration dynamics depend on the substance source and the catchment size. Indoor substances such as pharmaceuticals show high temporal dynamics with changes of 1 to 2 orders of magnitude within 9 min in the CSO of the small catchment. In contrast, outdoor substances at the small catchment and all substances at the large catchment display considerably lower variation. We tested various time-proportional sampling strategies to assess the range of error when estimating EMCs. We recommend an interval of 3 min to capture the dynamics of indoor substances in CSOs from small catchments. The results highlight that both future monitoring campaigns and the planning and management of urban wet-weather treatment systems will benefit from high temporal sampling resolutions, not only to understand dynamics but also to minimize errors of estimated EMCs.
Mutzner, L., Zhang, K., Luthy, R. G., Arp, H. P. H., & Spahr, S. (2023). Urban stormwater capture for water supply: look out for persistent, mobile and toxic substances. Environmental Science: Water Research and Technology, 9, 3094-3102. doi:10.1039/D3EW00160A, Institutional Repository

Urban stormwater was traditionally managed for flood control and property protection. But this view is changing as urban stormwater is increasingly recognized as an underused water resource. As cities implement stormwater capture, treatment, and use practices, there is a growing need to address water quality criteria beyond traditional pollutants such as nutrients, total suspended solids, pathogens, and metals. Current use practice and regulations are lacking on the occurrence of persistent, mobile and toxic (PMT) and very persistent, very mobile (vPvM) organic substances. These substances are poorly removed in conventional stormwater treatment systems, e.g., urban blue-green infrastructure, and, thus, may pose a risk when urban runoff is used to augment drinking water sources or discharged to surface waters. We reviewed 97 stormwater monitoring studies and identified 49 PMT/vPvM substances detected in urban stormwater. Although detection does not equate with risk, this highlights the potential importance of urban stormwater as a source of PMT/vPvM substances released to water resources. There is a lack of surveillance data on PMT/vPvM substances in urban stormwater and their fate in stormwater control measures, which hinders reliable risk assessments of stormwater capture. Unified guidelines are needed to (i) monitor PMT/vPvM substances in urban stormwater runoff, (ii) assess the human and environmental risks PMT/vPvM substances may pose for urban stormwater capture and use, and (iii) establish improved stormwater management and use criteria to ensure safe stormwater capture for water supply.
Mutzner, L., Furrer, V., Castebrunet, H., Dittmer, U., Fuchs, S., Gernjak, W., … Vezzaro, L. (2022). A decade of monitoring micropollutants in urban wet-weather flows: what did we learn?. Water Research, 223, 118968 (14 pp.). doi:10.1016/j.watres.2022.118968, Institutional Repository

Urban wet-weather discharges from combined sewer overflows (CSO) and stormwater outlets (SWO) are a potential pathway for micropollutants (trace contaminants) to surface waters, posing a threat to the environment and possible water reuse applications. Despite large efforts to monitor micropollutants in the last decade, the gained information is still limited and scattered. In a metastudy we performed a data-driven analysis of measurements collected at 77 sites (683 events, 297 detected micropollutants) over the last decade to investigate which micropollutants are most relevant in terms of 1) occurrence and 2) potential risk for the aquatic environment, 3) estimate the minimum number of data to be collected in monitoring studies to reliably obtain concentration estimates, and 4) provide recommendations for future monitoring campaigns. We highlight micropollutants to be prioritized due to their high occurrence and critical concentration levels compared to environmental quality standards. These top-listed micropollutants include contaminants from all chemical classes (pesticides, heavy metals, polycyclic aromatic hydrocarbons, personal care products, pharmaceuticals, and industrial and household chemicals). Analysis of over 30,000 event mean concentrations shows a large fraction of measurements (> 50%) were below the limit of quantification, stressing the need for reliable, standard monitoring procedures. High variability was observed among events and sites, with differences between micropollutant classes. The number of events required for a reliable estimate of site mean concentrations (error bandwidth of 1 around the "true" value) depends on the individual micropollutant. The median minimum number of events is 7 for CSO (2 to 31, 80%-interquantile) and 6 for SWO (1 to 25 events, 80%-interquantile). Our analysis indicates the minimum number of sites needed to assess global pollution levels and our data collection and analysis can be used to estimate the required number of sites for an urban catchment. Our data-driven analysis demonstrates how future wet-weather monitoring programs will be more effective if the consequences of high variability inherent in urban wet-weather discharges are considered.
Mutzner, L., Bohren, C., Mangold, S., Bloem, S., & Ort, C. (2020). Spatial differences among micropollutants in sewer overflows: a multisite analysis using passive samplers. Environmental Science and Technology, 54(11), 6584-6593. doi:10.1021/acs.est.9b05148, Institutional Repository

Untreated sewer overflows can contaminate receiving waters with micropollutants. Although concentrations of discharged micropollutants can be ecotoxicologically relevant, only limited data is available to assess occurrence and spatial differences among sewer overflow catchments. Therefore, we present an innovative type of data obtained with passive samplers at 20 combined sewer overflow sites (2-7 events per site; 95 events in total). The data sheds light on concentration ranges for 13 representative polar organic micropollutants and shows that micropollutants in both municipal wastewater and stormwater can be relevant sources of contaminants. We identify indicator micropollutants for further studies: benzotriazole (80% interquantile of time-weighted average concentration: 250–4800 ng/L), carbamazepine (33-910 ng/L), diclofenac (78-1000 ng/L), carbendazim (21-900 ng/L), diazinon (2.1-53 ng/L), diuron (22-1100 ng/L), mecoprop (98–5300 ng/L), metolachlor (6-230 ng/L), and terbutryn (29-810 ng/L). These concentration estimates are assumed to be on the safe side for comparison with environmental quality standards (EQS). A majority of sewer overflow sites (13 of 20) show discharge concentrations above acute EQS for at least one micropollutant and thus would have to rely on dilution by receiving waters to not exceed any EQS. The intersite variability among sewer overflows exceed the within-site variability. Hence, future monitoring studies should cover more sewer overflow sites. No correlation could be found with event durations, specific storage volume or land use data, thus showing the complexity of micropollutant occurrence and indicating that other factors led to the observed high spatial variability. In conclusion, our results clearly show the potential relevance of micropollutants in sewer overflows and the need to assess site-specific measures.
Mutzner, L., Mangold, S., Dicht, S., Bohren, C., Vermeirssen, E. L. M., Scheidegger, A., … Ort, C. (2019). Mikroverunreinigungen aus Siedlungen. Messungen in 20 Mischabwasserentlastungen mit Passivsammler. Aqua & Gas, 99(10), 28-35. , Institutional Repository

Niederschlags- und Mischabwasserentlastungen aus Siedlungen tragen zu Mikroverunreinigungen in Gewässern bei. Mit Passivsammlern wurden erstmals Konzentrationsbereiche an 20 Standorten für insgesamt 95 Ereignisse bestimmt, was die Analyse von Unterschieden zwischen Standorten sowie die Identifikation relevanter Eintragspfade unterstützt. An 13 Standorten waren bei mindestens einer Substanz die Konzentrationen im Mischabwasser höher als akute Qualitätskriterien.
Mutzner, L., Vermeirssen, E. L. M., & Ort, C. (2019). Passive samplers in sewers and rivers with highly fluctuating micropollutant concentrations – Better than we thought. Journal of Hazardous Materials, 361, 312-320. doi:10.1016/j.jhazmat.2018.07.040, Institutional Repository

Considerable pollutant loads can enter surface waters during rain events. Three factors challenge quantification of these pollutant fluxes using traditional sampling methods: (i) concentration fluctuations; (ii) unknown event duration; and (iii) placement, operation, and maintenance of equipment. Passive samplers offer the advantage of sampling in a continuous mode without power supply. However, variable uptake rates due to environmental factors and desorption in the case of fluctuating concentrations can affect the accuracy of time-weighted average (TWA) concentration estimates. While uncertainties related to environmental factors could be accounted for with additional effort, we can neither control nor quantify the concentration variability. We present measured and modelled concentration profiles at high temporal resolution and provide a systematic approach to assessing deviations from true TWA concentration due to fluctuating concentration profiles. We evaluate sampling of sewer overflows (0.3–14 h) with Chemcatcher and 1-week sampling in rivers. The uncertainty due to fluctuating concentrations is small, and other factors such as chemical analyses and sampler calibration have a similar or higher impact. The uncertainty due to fluctuations clearly increases with the sampling duration, particularly when exceeding the half-life of equilibrium. We conclude that passive sampling can also be used in wastewater systems with potentially high concentration variations.
Mutzner, L., Vermeirssen, E. L. M., Mangold, S., Maurer, M., Scheidegger, A., Singer, H., … Ort, C. (2019). Passive samplers to quantify micropollutants in sewer overflows: accumulation behaviour and field validation for short pollution events. Water Research, 160, 350-360. doi:10.1016/j.watres.2019.04.012, Institutional Repository

Contaminants in sewer overflows can contribute to exceedances of environmental quality standards, thus the quantification of contaminants during rainfall events is of relevance. However, monitoring is challenged by i) high spatiotemporal variability of contaminants in events of hard-to-predict durations, and ii) a large number of remote sites, which would imply enormous efforts with traditional sampling equipment. Therefore, we evaluate the applicability of passive samplers (Empore styrene-divinylbenzene reverse phase sulfonated (SDB-RPS)) to monitor a set of 13 polar organic contaminants. We present calibration experiments at high temporal resolution to assess the rate limiting accumulation mechanisms for short events (<36 h), report parameters for typical sewer conditions and compare passive samplers with composite water samples in a field study (three locations, total 10 events). With sampling rates of 0.35–3.5 L/d for 1 h reference time, our calibration results indicate a high sensitivity of passive samplers to sample short, highly variable sewer overflows. The contaminant uptake kinetic shows a fast initial accumulation, which is not well represented with the typical first-order model. Our results indicate that mass transfer to passive samplers is either controlled by the water boundary layer and the sorbent, or by the sorbent alone. Overall, passive sampler concentration estimates are within a factor 0.4 to 3.1 in comparison to composite water samples in the field study. We conclude that passive samplers are a promising approach to monitor a large number of discharge sites although it cannot replace traditional stormwater quality sampling in some cases (e.g. exact load estimates, high temporal resolution). Passive samplers facilitate identifying and prioritizing locations that may require more detailed investigations.
Mutzner, L. Z. (2019). Spatiotemporal variability of micropollutants in sewer overflows (Doctoral dissertation). doi:10.3929/ethz-b-000349443, Institutional Repository

Motivation. Our surface water is impacted by a wide variety of contaminants released through human activities. One contaminant group of concern is micropollutants, which can have eco-toxicological effects in trace concentrations. Micropollutants, for example, include plant protection products and biocides, which are specifically designed to harm organisms. An important input pathway of micropollutants to surface water can be untreated sewer overflows (combined sewer overflows and stormwater outlets). However, the understanding of factors influencing the occurrence and levels of micropollutants is limited and challenged by: i) high spatial differences among sites, ii) a large number of discharge sites and iii) high temporal fluctuating discharge events.

Research objective. This thesis intends to enhance our understanding of micropollutants in sewer overflows. It aims to investigate efficient methods to prioritize sewer overflow sites, which can be potentially harmful for receiving waters. The presented work focuses on the development of model prediction and efficient monitoring approaches and includes the following: i) a Swiss-wide model to assess how many discharge sites may be critical (Chapter 2), ii) fundamentals to develop passive sampling as an alternative monitoring method for short duration sewer overflows (Chapter 3 and 4) and iii) an extended monitoring study covering 20 combined sewer overflows (CSOs) to explore spatial differences among sites (Chapter 5). The main findings of this thesis are presented in the following.

Model-based screening. A dynamic substance flow modeling approach was applied to 2,500 Swiss municipalities, considering micropollutant accumulation and wash-off on urban surfaces. The approach is based on the simplification, that there is one CSO and one stormwater outlet per municipality. The model allows for an estimation of the micropollutant concentration fluctuations in sewer overflows in 10-min resolution. The results show the importance of untreated discharges from sewer overflows as emission into receiving waters. The load contribution to sewer overflows of micropollutants in stormwater (e.g. plant protection products and biocides) is estimated to be considerably higher than of micropollutants in municipal wastewater (e.g. pharmaceuticals and other household chemicals). In addition, the results indicate that up to 83% of all urban catchments have sewer overflows that need to rely on upstream dilution in order to not exceed substance-specific environmental quality standards (EQS). Thus, this nationwide screening approach clearly highlights the need for a more detailed assessment of micropollutants in sewer overflows, and especially, the need for more measured data to allow the development of validated micropollutant prediction models.

Measuring. Difficulties of monitoring sewer overflows with traditional methods are i) high concentration fluctuations with unknown event durations which require a high temporal sampling resolution, ii) many discharge sites and iii) placement, operation, and maintenance of equipment. Hence, passive samplers for polar organic micropollutants are analyzed systematically as a viable alternative to monitor short duration sewer overflows. The main advantage of passive samplers is the continuous accumulation of contaminants from the water phase, with no need for external energy sources nor for immense water sample storage volume. In a first step, the impact of fluctuating concentrations on deviations from true time-weighted average (TWA) concentrations was studied. The results highlight that the deviations induced by fluctuating concentrations are similar or smaller than uncertainties arising from chemical analysis and environmental factors. Understanding the uptake mechanism of micropollutants is one of the most important issues that needs to be resolved to reduce uncertainties in passive sampling data. The uptake experiments in sewer conditions for short duration events (<36h) indicate that the mass transfer is either dominated by the sorbent, or, by a multi-step mechanism. Therefore, a new semi-empirical mixed rate control model is proposed, which can be directly used for future studies under similar conditions. A field validation (3 locations, 10 events) shows that TWA concentration estimates measured by passive samplers are within a factor of 0.4 to 3.1 compared to composite water samples. Hence, the use of upper limit TWA concentration estimates is recommended for compliance checking with EQS. The findings clearly show that passive samplers are suitable to estimate TWA concentration ranges in sewer overflows and, thus facilitate identification of potentially critical discharge sites.

Occurrence of micropollutants. Unique monitoring data from 20 CSO sites was collected with passive samplers. In total 13 polar organic micropollutants were analysed in 95 events (2-7 events per site). The results highlight indicator micropollutants, which were often found in the monitored CSOs and could be used in future monitoring studies: diclofenac, benzotriazole, carbamazepine, diazinon, diuron, carbendazim, mecoprop, metolachlor and terbutryn. Further, our results reveal that the spatial differences among CSO sites are bigger than the inter-event differences within a site for all studied micropollutants. Nevertheless, no significant correlation with land use data could be identified. The results, therefore, suggest that additional factors, most likely the contaminant usage pattern, have a considerable influence on the observed spatial differences. Both municipal wastewater and stormwater contributed to concentrations above the EQS in CSOs (not in the receiving water). In addition, the monitoring with passive samplers indicates that at least 13 out of 20 CSOs show concentrations above EQS in CSOs, and would rely on dilution by receiving waters to not exceed EQS.

Outlook. Overall, the thesis shows the relevance of sewer overflows as a source of micropollutants entering receiving water bodies. The findings can serve as a basis for the development of a systematic and stepwise approach to efficiently identify critical sites. The development of such an approach would require joint efforts by eco-toxicologists, analytical chemists, regulators and wastewater engineers. This approach could be based on a simplified modeling approach as a first indicator, followed by passive sampling to assess micropollutant levels. To enable the widespread application of passive samplers in monitoring programs, regulators’ and operators’ confidence in passive sampling needs to be strengthened with more field validation studies and common guidelines.
Zheng, Y., Mutzner, L., Ort, C., Kaegi, R., & Gottschalk, F. (2019). Modelling engineered nanomaterials in wet-weather discharges. NanoImpact, 16, 100188 (8 pp.). doi:10.1016/j.impact.2019.100188, Institutional Repository

The impacts of the unintended release of engineered nanomaterials (ENMs) and the resulting exposure to the ecosystems are still poorly understood and intensively debated. In current mass flow models, a global transfer coefficient is used to account for ENMs discharged from sewer systems to surface waters during rain events.
However, different types of sewer systems and specific ENM applications likely require a more elaborate approach to quantify ENM loads entering surface waters during rain events. Therefore, we evaluated the impact of distinguishing between different application areas of ENMs (indoor/outdoor) and different types of sewer systems (combined/separate) on the loads of selected ENMs passing through wastewater systems and reaching the surface water. We applied a dynamic mass flow analysis to eight substances (TiO2, ZnO, Ag, SiO2, FeOx, CuO, CeO2 and carbon black) for six different sewer system configurations. To estimate the runoff from streets and facades, we used a hydrological model developed for dissolved substances. For areas with separate sewer systems only and ENMs predominantly used in and released from outdoor applications (e.g. CuO, carbon black), up to ~80% of the annual loads entering the sewer systems never reach a sewage treatment plant. Those ENMs are directly discharged to surface waters via stormwater outlets. For combined sewer systems and ENMs mainly applied indoors (e.g. Ag, ZnO), the percentage of ENM bypassing sewage treatment plants remains below 2%. Although the model is setup for Switzerland and other geographical areas will show for example different rain characteristics, the relative importance of the different release pathways will broadly remain the same and the results should, therefore, be transferrable to other countries.
Eggimann, S., Mutzner, L., Wani, O., Schneider, M. Y., Spuhler, D., Moy de Vitry, M., … Maurer, M. (2017). The potential of knowing more: a review of data-driven urban water management. Environmental Science and Technology, 51(5), 2538-2553. doi:10.1021/acs.est.6b04267, Institutional Repository

The promise of collecting and utilising large amounts of data has never been greater in the history of urban water management (UWM). This paper reviews several data-driven approaches which play a key role in bringing forward a sea change. It critically investigates whether data-driven UWM offers a promising foundation for addressing current challenges and supporting fundamental changes in UWM. We discuss the examples of better rain-data management, urban pluvial flood-risk management and forecasting, drinking water and sewer network operation and management, integrated design and management, increasing water productivity, wastewater-based epidemiology and on-site water and wastewater treatment. The accumulated evidence assembled from research documented in the literature points towards a future UWM that offers significant potential benefits thanks to increased collection and utilisation of data. The findings show that data-driven UWM allows us to develop and apply novel methods, to optimize the efficiency of the current network-based approach, and an extended functionality of today’s systems. However, generic challenges related to data-driven approaches (e.g. data processing, data availability, data quality, data costs) and the specific challenges of data-driven UWM need to be addressed, namely data access and ownership, current engineering practices and the difficulty of assessing the cost benefits of data-driven UWM.
Mutzner, L., Mangold, S., Maurer, M., Scheidegger, A., Singer, H., Vermeirssen, E., & Ort, C. (2017). Passive sampling: an efficient way to monitor micropollutants in sewer overflows? (pp. 10-17). Presented at the 14th IWA/IAHR international conference on urban drainage (ICUD). Prague: CZWA; Czech Technical University; IAHR/AIRH; IWA. , Institutional Repository

High spatio-temporal variability characterizes micropollutants discharged from separate and combined sewers. This challenges monitoring and prediction. We propose passive samplers (Chemcatcher® for polar, organic substances) as an alternative to active water sampling. Our results indicate sufficient sensitivity of passive samplers for short exposures so that typical rain event durations (<30 h) can be sampled integratively. Although time-weighted average concentrations estimated via passive sampling are higherthan in composite water samples -on average by a factor 2.7 - we conclude that passive sampling is a cost-effective approach to identify locations with critical concentration ranges.
Mutzner, L., Staufer, P., & Ort, C. (2016). Model-based screening for critical wet-weather discharges related to micropollutants from urban areas. Water Research, 104, 547-557. doi:10.1016/j.watres.2016.08.003, Institutional Repository

Wet-weather discharges contribute to anthropogenic micropollutant loads entering the aquatic environment. Thousands of wet-weather discharges exist in Swiss sewer systems, and we do not have the capacity to monitor them all. We consequently propose a model-based approach designed to identify critical discharge points in order to support effective monitoring.
We applied a dynamic substance flow model to four substances representing different entry routes: indoor (Triclosan, Mecoprop, Copper) as well as rainfall-mobilized (Glyphosate, Mecoprop, Copper) inputs. The accumulation on different urban land-use surfaces in dry weather and subsequent substance-specific wash-off is taken into account. For evaluation, we use a conservative screening approach to detect critical discharge points. This approach considers only local dilution generated onsite from natural, unpolluted areas, i.e. excluding upstream dilution.
Despite our conservative assumptions, we find that the environmental quality standards for Glyphosate and Mecoprop are not exceeded during any 10-min time interval over a representative one-year simulation period for all 2500 Swiss municipalities. In contrast, the environmental quality standard is exceeded during at least 20% of the discharge time at 83% of all modelled discharge points for Copper and at 71% for Triclosan. For Copper, this corresponds to a total median duration of approximately 19 days per year. For Triclosan, discharged only via combined sewer overflows, this means a median duration of approximately 10 days per year. In general, stormwater outlets contribute more to the calculated effect than combined sewer overflows for rainfall-mobilized substances. We further evaluate the Urban Index (Aurban,impervious/Anatural) as a proxy for critical discharge points: catchments where Triclosan and Copper exceed the corresponding environmental quality standard often have an Urban Index >0.03.
A dynamic substance flow analysis allows us to identify the most critical discharge points to be prioritized for more detailed analyses and monitoring. This forms a basis for the efficient mitigation of pollution.
Faust, V. (2013). Aufenthaltszeit von Urin in einem Urinsammelsystem (Bachelor thesis). 16 p. , Institutional Repository

Im Forum Chriesbach der Eawag ist ein NoMix-System installiert, das den Urin sammelt und getrennt vom restlichen Abwasser abführt. Da der Urin einen Grossteil an Nährstoffen wie Stickstoff enthält, kann er separat aufbereitet und anschliessend als landwirtschaftlicher Dünger genutzt werden. Im Leitungssystem wird der Harnstoff, welcher die grösste Stickstoffkomponente im Urin bildet, durch Bakterien abgebaut. Für ein besseres Verständnis der Harnstoffhydrolyse muss bekannt sein, wie lange der Urin im Leitungssystem verweilt. Um die Aufenthaltszeit von Urin zu quantifizieren wurden in dieser Arbeit Tracerversuche mit Bromid durchgeführt. Dabei wurden neben einer mittleren Aufenthaltszeit auch der Einfluss der Benutzerfrequenz und der Distanz, also dem Stockwerk aus dem der Urin kommt, untersucht. Zusätzlich wurde die Aufenthaltszeit mit Hilfe einer Urinbilanz berechnet, bei der die summierten Input und Output Kurven des Urins aufgezeichnet wurden. Die zeitliche Verschiebung der beiden Kurven beschreibt eine mittlere Verweilzeit.
Die Tracerversuche zeigten, dass sich die Aufenthaltszeit des Bromids und des eigentlichen Urins deutlich unterscheiden. Der Tracer repräsentiert somit nicht wie ursprünglich angenommen den Grundstrom. Wie aus der Urinbilanz hervorging hat der Urin eine mittlere Verweilzeit von 31 Minuten mit einer Standartabweichung von 12 Minuten. Die mittlere Aufenthaltszeit des Bromids ist gemäss den Tracerversuchen etwa viermal grösser. Das unterschiedliche Verhalten ist dadurch zu erklären, dass das Bromid im Leitungsrohr in den Biofilm diffundiert und deshalb mehr Zeit als der Urin benötigt. Mit zunehmender Benutzerfrequenz gleichen sich die beiden Aufenthaltszeiten an, da mehr Urin vorhanden ist, in welches das Bromid zurückdiffundieren kann. Das Stockwerk beeinflusst die Aufenthaltszeit des Urins und des Bromids. Der Einfluss auf das Bromid ist jedoch grösser, da die Diffusion in den Biofilm in den vertikalen Leitungen grösser ist als in den horizontalen.
Auf die Verweilzeit des Harnstoffs konnte aus den Ergebnissen auf Grund der Diffusion nicht geschlossen werden, da weder der Urin noch das Bromid repräsentativ sind. Es kann aber mit grosser Wahrscheinlichkeit gesagt werden, dass auch der Harnstoff und weitere gelöste Stoffe in den Biofilm diffundieren und damit eine grössere Aufenthaltszeit als der Urin besitzen.
Mutzner, L. (2011). GIS based assessment of the fate of micropollutants in combined sewerages (Master thesis). 45 p. , Institutional Repository

Only little is known about the micropollutants from urban areas discharged via combined sewer overflows during rain events. In urban catchments various sources of micropollution
occur that change over time and with different kind of land uses. In Switzerland different rain regions and various land use types have to be considered to characterise the large variability of urban drainage systems. Thus a geographical information system based analysis of the urban areas in Switzerland combined with the modelling of the amount of pollutants released via combined sewer over flows during rain events is feasible to asses the dominant sources. Therefore a model was developed to determine the combined sewer over flow emissions loads of micropollutants for Switzerland. This model accounts for the main urban sources of micropollutants and the variation in the urban area of Switzerland.
The overall model results show, that combined sewer over flow emissions of urban areas are an important contribution to the pollutant load in surface water. Especially for pollutants
washed-off impervious areas, such as roofs or traffic surfaces, the load discharged via combined sewer over flow was estimated to be in the same range as the load discharged to the wastewater treatment plant. Thus the discharge via combined sewer over flow can result in acute effects on the environment. The result also emphasizes the importance of mitigation measures at the pollutant source rather then end-of-pipe measures.

Christoph Ort

Julian, T. R., Devaux, A. J., Brülisauer, L., Conforti, S., Rusch, J. C., Gan, C., … Ort, C. (2024). Monitoring an emergent pathogen at low incidence in wastewater using qPCR: Mpox in Switzerland. Food and Environmental Virology, 16, 269-279. doi:10.1007/s12560-024-09603-5, Institutional Repository

Wastewater-based epidemiology offers a complementary approach to clinical case-based surveillance of emergent diseases and can help identify regions with infected people to prioritize clinical surveillance strategies. However, tracking emergent diseases in wastewater requires reliance on novel testing assays with uncertain sensitivity and specificity. Limited pathogen shedding may cause detection to be below the limit of quantification or bordering the limit of detection. Here, we investigated how the definition of limit of detection for quantitative polymerase chain reaction (qPCR) impacts epidemiological insights during an mpox outbreak in Switzerland. 365 wastewater samples from three wastewater treatment plants in Switzerland from 9 March through 31 October 2022 were analyzed for mpox DNA using qPCR. We detected mpox DNA in 22% (79 of 365) wastewater samples based on a liberal definition of qPCR detection as any exponentially increasing fluorescence above the threshold. Based on a more restrictive definition as the lowest concentration at which there is 95% likelihood of detection, detection was 1% (5 of 365). The liberal definition shows high specificity (90%) and accuracy (78%), but moderate sensitivity (64%) when benchmarked against available clinical case reporting, which contrasts with higher specificity (98%) but lower sensitivity (10%) and accuracy (56%) of the 95% likelihood definition. Wastewater-based epidemiology applied to an emergent pathogen will require optimizing public health trade-offs between reporting data with high degrees of uncertainty and delaying communication and associated action. Information sharing with relevant public health stakeholders could couple early results with clear descriptions of uncertainty. Impact Statement: When a novel pathogen threatens to enter a community, wastewater-based epidemiology offers an opportunity to track its emergence and spread. However, rapid deployment of methods for to detect a novel pathogen may rely on assays with uncertain sensitivity and specificity. Benchmarking the detection of mpox DNA in Swiss wastewaters with reported clinical cases in 2022, we demonstrate how definitions of detection of a qPCR assay influence epidemiological insights from wastewater. The results highlight the need for information sharing between public health stakeholders that couple early insights from wastewater with descriptions of methodological uncertainty to optimize public health actions.
Nadeau, S., Devaux, A. J., Bagutti, C., Alt, M., Hampe, E. I., Kraus, M., … Stadler, T. (2024). Influenza transmission dynamics quantified from RNA in wastewater in Switzerland. Swiss Medical Weekly, 154(1), 3503 (20 pp.). doi:10.57187/s.3503, Institutional Repository

INTRODUCTION: Influenza infections are challenging to monitor at the population level due to many mild and asymptomatic cases and similar symptoms to other common circulating respiratory diseases, including COVID-19. Methods for tracking cases outside of typical reporting infrastructure could improve monitoring of influenza transmission dynamics. Influenza shedding into wastewater represents a promising source of information where quantification is unbiased by testing or treatment-seeking behaviours. METHODS: We quantified influenza A and B virus loads from influent at Switzerland's three largest wastewater treatment plants, serving about 14% of the Swiss population (1.2 million individuals). We estimated trends in infection incidence and the effective reproductive number (Re) in these catchments during a 2021/22 epidemic and compared our estimates to typical influenza surveillance data. RESULTS: Wastewater data captured the same overall trends in infection incidence as laboratory-confirmed case data at the catchment level. However, the wastewater data were more sensitive in capturing a transient peak in incidence in December 2021 than the case data. The Reestimated from the wastewater data was roughly at or below the epidemic threshold of 1 during work-from-home measures in December 2021 but increased to at or above the epidemic threshold in two of the three catchments after the relaxation of these measures. The third catchment yielded qualitatively the same results but with wider confidence intervals. The confirmed case data at the catchment level yielded comparatively less precise R_e estimates before and during the work-from-home period, with confidence intervals that included one before and during the work-fromhome period. DISCUSSION: Overall, we show that influenza RNA in wastewater can help monitor nationwide influenza transmission dynamics. Based on this research, we developed an online dashboard for ongoing wastewater-based influenza surveillance in Switzerland.
Salgueiro-Gonzalez, N., Béen, F., Bijlsma, L., Boogaerts, T., Covaci, A., Baz-Lomba, J. A., … Castiglioni, S. (2024). Influent wastewater analysis to investigate emerging trends of new psychoactive substances use in Europe. Water Research, 254, 121390 (11 pp.). doi:10.1016/j.watres.2024.121390, Institutional Repository

Wastewater-based epidemiology (WBE) can provide objective and timely information on the use of new psychoactive substances (NPS), originally designed as legal alternatives of internationally controlled drugs. NPS have rapidly emerged on the global drug market, posing a challenge to drug policy and constituting a risk to public health. In this study, a WBE approach was applied to monitor the use of more than 300 NPS, together with fentanyl and its main metabolite norfentanyl, in influent wastewater collected from 12 European cities during March-June 2021. Quantitative and qualitative analysis of NPS in composite 24 h influent wastewater samples were based on solid phase extraction and liquid chromatography-mass spectrometry. In-sample stability tests demonstrated the suitability of most investigated biomarkers, except for a few synthetic opioids, synthetic cannabinoids and phenetylamines. Fentanyl, norfentanyl and eight NPS were quantified in influent wastewater and at least three substances were found in each city, demonstrating their use in Europe. N,N-dimethyltryptamine and 3-methylmethcathinone (3-MMC) were the most common NPS found, with the latter having the highest mass loads (up to 24.8 mg/day/1000 inhabitants). Seven additional substances, belonging to five categories of NPS, were identified in different cities. Spatial trends of NPS use were observed between cities and countries, and a changing weekly profile of use was observed for 3-MMC. WBE is a useful tool to rapidly evaluate emerging trends of NPS use, complementing common indicators (i.e. population surveys, seizures) and helping to establish measures for public health protection.
Van Wichelen, N., Burgard, D., Campos-Mañas, M. C., Simarro-Gimeno, C., Hernández, F., Ort, C., … Bijlsma, L. (2024). A key factor in monitoring cannabis consumption trends through wastewater analysis: partitioning of THC[sbnd]COOH between the liquid and solid phase of influent wastewater. Water Research, 267, 122462 (9 pp.). doi:10.1016/j.watres.2024.122462, Institutional Repository

Current wastewater-based epidemiology (WBE) studies are predominantly focused on the analysis of urinary biomarkers present in the liquid phase of influent wastewater (IWW). This approach systematically underestimates less polar metabolites, such as cannabis biomarkers. These biomarkers can potentially sorb to and desorb from suspended particulate matter (SPM) present in IWW. This study investigates the bidirectional partitioning of THC[sbnd]COOH between the liquid phase and SPM of IWW by performing multiple sorption experiments using THC[sbnd]COOH-D9 as a surrogate due to the unavailability of blank SPM and blank IWW. In addition, this study involves the analysis of IWW collected from eight wastewater treatment plants (WWTP) (n = 56) across four European countries, where raw IWW, the liquid phase and SPM were separately analysed to identify potential trends in the fraction of THC[sbnd]COOH in the SPM between and withing the examined locations. Based on the performed sorption experiments, bidirectional partitioning of THC[sbnd]COOH between the liquid phase and SPM was noted, showing partition between both phases when only one of the two phases was spiked. It was illustrated that the concentration of SPM had a notable influence on the THC[sbnd]COOH partitioning between both phases. In addition to the inter location variability (average THC[sbnd]COOH present in the SPM ranged 31–59 %), a substantial intra location variation was also observed, e.g., in one location ranged 17–58 %. While the determination of a correction factor for the amount of THC[sbnd]COOH present in SPM would be ideal, this is challenging, since the amount of SPM is not fixed in all IWW samples. Although SPM has influence on the THC[sbnd]COOH partition, no correlation (p value Spearman correlation = 0.3160) was observed between the SPM concentration and the fraction of THC[sbnd]COOH in the solid phase. Moreover, the collection of homogenized samples is difficult, and the time required to reach an equilibration in partitioning of THC[sbnd]COOH between both IWW phases remains unclear. Due to i) the large inter-and intra-location variation of THC[sbnd]COOH present in the SPM, ii) the variability in SPM concentration in IWW samples, and iii) the time required to reach a partitioning equilibration, an analytical procedure based on liquid-liquid extraction (LLE) that considers both the liquid phase and SPM of IWW is recommended to reduce the overall uncertainty for THC[sbnd]COOH measurement in IWW. It was illustrated that this extraction method is capable to recover the total concentration of THC[sbnd]COOH in both phases.
Furrer, V., Mutzner, L., Ort, C., & Singer, H. (2023). Micropollutant concentration fluctuations in combined sewer overflows require short sampling intervals. Water Research X, 21, 100202 (8 pp.). doi:10.1016/j.wroa.2023.100202, Institutional Repository

Combined sewer overflows (CSOs) are an important pathway of organic micropollutants from urban areas to open water bodies. Understanding the temporal dynamics of these micropollutants during overflow events is crucial for applying appropriate sampling methods and implementing effective management strategies. Yet, little is known about the dynamics of micropollutants in CSOs, because most studies report concentrations from single grab samples or event mean concentrations (EMCs). With unique high temporal resolution measurements (3 min), we show the real dynamics of polar organic micropollutants in CSOs of one small (2,700 people: P) and one large (159,000 P) urban catchment, for two micropollutant categories: (i) 33 micropollutants in municipal wastewater and (ii) 13 micropollutants from urban surface runoff. The concentration dynamics depend on the substance source and the catchment size. Indoor substances such as pharmaceuticals show high temporal dynamics with changes of 1 to 2 orders of magnitude within 9 min in the CSO of the small catchment. In contrast, outdoor substances at the small catchment and all substances at the large catchment display considerably lower variation. We tested various time-proportional sampling strategies to assess the range of error when estimating EMCs. We recommend an interval of 3 min to capture the dynamics of indoor substances in CSOs from small catchments. The results highlight that both future monitoring campaigns and the planning and management of urban wet-weather treatment systems will benefit from high temporal sampling resolutions, not only to understand dynamics but also to minimize errors of estimated EMCs.
Keshaviah, A., Diamond, M. B., Wade, M. J., Scarpino, S. V., Ahmed, W., Amman, F., … Ort, C. (2023). Wastewater monitoring can anchor global disease surveillance systems. Lancet Global Health, 11(6), e976-e981. doi:10.1016/S2214-109X(23)00170-5, Institutional Repository

To inform the development of global wastewater monitoring systems, we surveyed programmes in 43 countries. Most programmes monitored predominantly urban populations. In high-income countries (HICs), composite sampling at centralised treatment plants was most common, whereas grab sampling from surface waters, open drains, and pit latrines was more typical in low-income and middle-income countries (LMICs). Almost all programmes analysed samples in-country, with an average processing time of 2·3 days in HICs and 4·5 days in LMICs. Whereas 59% of HICs regularly monitored wastewater for SARS-CoV-2 variants, only 13% of LMICs did so. Most programmes share their wastewater data internally, with partnering organisations, but not publicly. Our findings show the richness of the existing wastewater monitoring ecosystem. With additional leadership, funding, and implementation frameworks, thousands of individual wastewater initiatives can coalesce into an integrated, sustainable network for disease surveillance—one that minimises the risk of overlooking future global health threats.
Caduff, L., Dreifuss, D., Schindler, T., Devaux, A. J., Ganesanandamoorthy, P., Kull, A., … Julian, T. R. (2022). Inferring transmission fitness advantage of SARS-CoV-2 variants of concern from wastewater samples using digital PCR, Switzerland, December 2020 through March 2021. Eurosurveillance: bulletin européen sur les maladies transmissibles, 27(10), 2100806 (20 pp.). doi:10.2807/1560-7917.ES.2022.27.10.2100806, Institutional Repository

BackgroundThroughout the COVID-19 pandemic, SARS-CoV-2 genetic variants of concern (VOCs) have repeatedly and independently arisen. VOCs are characterised by increased transmissibility, increased virulence or reduced neutralisation by antibodies obtained from prior infection or vaccination. Tracking the introduction and transmission of VOCs relies on sequencing, typically whole genome sequencing of clinical samples. Wastewater surveillance is increasingly used to track the introduction and spread of SARS-CoV-2 variants through sequencing approaches.AimHere, we adapt and apply a rapid, high-throughput method for detection and quantification of the relative frequency of two deletions characteristic of the Alpha, Beta, and Gamma VOCs in wastewater.MethodsWe developed drop-off RT-dPCR assays and an associated statistical approach implemented in the R package WWdPCR to analyse temporal dynamics of SARS-CoV-2 signature mutations (spike Δ69-70 and ORF1a Δ3675-3677) in wastewater and quantify transmission fitness advantage of the Alpha VOC.ResultsBased on analysis of Zurich wastewater samples, the estimated transmission fitness advantage of SARS-CoV-2 Alpha based on the spike Δ69-70 was 0.34 (95% confidence interval (CI): 0.30-0.39) and based on ORF1a Δ3675-3677 was 0.53 (95% CI: 0.49-0.57), aligning with the transmission fitness advantage of Alpha estimated by clinical sample sequencing in the surrounding canton of 0.49 (95% CI: 0.38-0.61).ConclusionDigital PCR assays targeting signature mutations in wastewater offer near real-time monitoring of SARS-CoV-2 VOCs and potentially earlier detection and inference on transmission fitness advantage than clinical sequencing.
Campos-Mañas, M. C., Van Wichelen, N., Covaci, A., van Nuijs, A. L. N., Ort, C., Béen, F., … Bijlsma, L. (2022). Analytical investigation of cannabis biomarkers in raw urban wastewater to refine consumption estimates. Water Research, 223, 119020 (8 pp.). doi:10.1016/j.watres.2022.119020, Institutional Repository

Wastewater analysis of Δ9-tetrahydrocannabinol (THC) biomarkers can provide essential information on trends in cannabis consumption. Although analysis is mostly focused on the aqueous phase, previous studies have illustrated the need of improving the measurements of raw influent wastewater (IWW) considering also suspended solids. This is important for cannabis biomarkers, because a substantial part of them is expected to be found in the suspended solids due to their more lipophilic character compared with other metabolites/drugs included in these types of studies. However, it remains open to which extent trend estimates might be affected by solely analysing the liquid phase. To investigate this aspect, robust analytical methodologies are required to measure both the liquid and solid phases of IWW. In this work, we firstly tested liquid-liquid extraction (LLE) for THC and its major metabolites (THC-OH, and THC-COOH). Using LLE, no filtration or centrifugation step was required for raw IWW analysis, and the three analytes were extracted from both the liquid and the solid phase simultaneously. In parallel, the raw IWW was centrifuged and the obtained solid and liquid phases were analyzed separately: the liquid phase by both LLE and solid phase extraction (SPE) for comparison of data, and the suspended solids by solid-liquid extraction (SLE). The separate analysis of both phases in a number of samples revealed that a significant amount of cannabis biomarkers (ranging from 42 to 90%) was found in the suspended solids. In addition, the total amount of cannabis biomarkers obtained by analysing raw IWW on the one hand, and by separate analysis of the liquid and the solid phases, on the other hand, was in good agreement. Data from this study show that the sole analysis of the liquid phase would lead to a notable underestimation of cannabis biomarkers concentrations in IWW.
Cariti, F., Tuñas Corzon, A., Fernandez-Cassi, X., Ganesanandamoorthy, P., Ort, C., Julian, T. R., & Kohn, T. (2022). Wastewater reveals the spatiotemporal spread of SARS-CoV-2 in the Canton of Ticino (Switzerland) during the onset of the COVID-19 pandemic. ACS ES&T Water, 2(11), 2194-2200. doi:10.1021/acsestwater.2c00082, Institutional Repository

Wastewater-based epidemiology (WBE) has emerged as an effective tool for monitoring SARS-CoV-2 dynamics during the COVID-19 pandemic. Here, we add a spatial component to WBE and use it to investigate SARS-CoV-2 spread in the canton of Ticino during the onset of the pandemic in Switzerland (end of February 2020 to beginning of March 2020). Ticino is located at the border to Northern Italy, where a large COVID-19 outbreak occurred in February 2020. Not surprisingly, Ticino was the site of the first clinically confirmed COVID-19 case in Switzerland. We retrospectively analyzed daily influent samples from nine wastewater treatment plants in Ticino that jointly cover an area of 20 km × 60 km and 351,000 people (>99% of the population). Our result is a fine-grained view of the spatiotemporal evolution of the COVID-19 pandemic in this canton. The wastewater analysis revealed that by February 29, 2020, SARS-CoV-2 had already spread to all catchments. At the same time, only four individual cases had been clinically confirmed across the region served by the treatment plants investigated. Our results demonstrate that WBE could serve as a versatile tool to monitor the introduction and spread of an infectious agent on a regional scale. To fully exploit its utility, WBE should be implemented in real time and become an integral part of future disease surveillance efforts.
Huisman, J. S., Scire, J., Caduff, L., Fernandez-Cassi, X., Ganesanandamoorthy, P., Kull, A., … Julian, T. R. (2022). Wastewater-based estimation of the effective reproductive number of SARS-CoV-2. Environmental Health Perspectives, 130(5), 057011 (12 pp.). doi:10.1289/EHP10050, Institutional Repository

BACKGROUND: The effective reproductive number, Re, is a critical indicator to monitor disease dynamics, inform regional and national policies, and estimate the effectiveness of interventions. It describes the average number of new infections caused by a single infectious person through time. To date, Re estimates are based on clinical data such as observed cases, hospitalizations, and/or deaths. These estimates are temporarily biased when clinical testing or reporting strategies change.
OBJECTIVES: We show that the dynamics of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA in wastewater can be used to estimate Re in near real time, independent of clinical data and without the associated biases.
METHODS: We collected longitudinal measurements of SARS-CoV-2 RNA in wastewater in Zurich, Switzerland, and San Jose, California, USA. We combined this data with information on the temporal dynamics of shedding (the shedding load distribution) to estimate a time series proportional to the daily COVID-19 infection incidence. We estimated a wastewater-based Re from this incidence.
RESULTS: The method to estimate Re from wastewater worked robustly on data from two different countries and two wastewater matrices. The resulting estimates were as similar to the Re estimates from case report data as Re estimates based on observed cases, hospitalizations, and deaths are among each other. We further provide details on the effect of sampling frequency and the shedding load distribution on the ability to infer Re.
DISCUSSION: To our knowledge, this is the first time Re has been estimated from wastewater. This method provides a low-cost, rapid, and independent way to inform SARS-CoV-2 monitoring during the ongoing pandemic and is applicable to future wastewater-based epidemiology targeting other pathogens.
Jahn, K., Dreifuss, D., Topolsky, I., Kull, A., Ganesanandamoorthy, P., Fernandez-Cassi, X., … Beerenwinkel, N. (2022). Early detection and surveillance of SARS-CoV-2 genomic variants in wastewater using COJAC. Nature Microbiology, 7, 1151-1160. doi:10.1038/s41564-022-01185-x, Institutional Repository

The continuing emergence of SARS-CoV-2 variants of concern and variants of interest emphasizes the need for early detection and epidemiological surveillance of novel variants. We used genomic sequencing of 122 wastewater samples from three locations in Switzerland to monitor the local spread of B.1.1.7 (Alpha), B.1.351 (Beta) and P.1 (Gamma) variants of SARS-CoV-2 at a population level. We devised a bioinformatics method named COJAC (Co-Occurrence adJusted Analysis and Calling) that uses read pairs carrying multiple variant-specific signature mutations as a robust indicator of low-frequency variants. Application of COJAC revealed that a local outbreak of the Alpha variant in two Swiss cities was observable in wastewater up to 13 d before being first reported in clinical samples. We further confirmed the ability of COJAC to detect emerging variants early for the Delta variant by analysing an additional 1,339 wastewater samples. While sequencing data of single wastewater samples provide limited precision for the quantification of relative prevalence of a variant, we show that replicate and close-meshed longitudinal sequencing allow for robust estimation not only of the local prevalence but also of the transmission fitness advantage of any variant. We conclude that genomic sequencing and our computational analysis can provide population-level estimates of prevalence and fitness of emerging variants from wastewater samples earlier and on the basis of substantially fewer samples than from clinical samples. Our framework is being routinely used in large national projects in Switzerland and the UK.
Julian, T. R., Fernandez, X., Ort, C., & Kahn, T. (2022). How wastewater informs COVID-19 policy in Switzerland. Water Science Policy (3 pp.). doi:10.53014/BHET9151, Institutional Repository
Fernandez-Cassi, X., Scheidegger, A., Bänziger, C., Cariti, F., Tuñas Corzon, A., Ganesanandamoorthy, P., … Kohn, T. (2021). Wastewater monitoring outperforms case numbers as a tool to track COVID-19 incidence dynamics when test positivity rates are high. Water Research, 200, 117252 (9 pp.). doi:10.1016/j.watres.2021.117252, Institutional Repository

Wastewater-based epidemiology (WBE) has been shown to coincide with, or anticipate, confirmed COVID-19 case numbers. During periods with high test positivity rates, however, case numbers may be underreported, whereas wastewater does not suffer from this limitation. Here we investigated how the dynamics of new COVID-19 infections estimated based on wastewater monitoring or confirmed cases compare to true COVID-19 incidence dynamics. We focused on the first pandemic wave in Switzerland (February to April, 2020), when test positivity ranged up to 26%. SARS-CoV-2 RNA loads were determined 2–4 times per week in three Swiss wastewater treatment plants (Lugano, Lausanne and Zurich). Wastewater and case data were combined with a shedding load distribution and an infection-to-case confirmation delay distribution, respectively, to estimate infection incidence dynamics. Finally, the estimates were compared to reference incidence dynamics determined by a validated compartmental model. Incidence dynamics estimated based on wastewater data were found to better track the timing and shape of the reference infection peak compared to estimates based on confirmed cases. In contrast, case confirmations provided a better estimate of the subsequent decline in infections. Under a regime of high-test positivity rates, WBE thus provides critical information that is complementary to clinical data to monitor the pandemic trajectory.
Stravs, M. A., Stamm, C., Ort, C., & Singer, H. (2021). Transportable automated HRMS platform "mS2field" enables insights into water-quality dynamics in real time. Environmental Science and Technology Letters, 8(5), 373-380. doi:10.1021/acs.estlett.1c00066, Institutional Repository

Tracking the occurrence of a broad variety of chemicals in the aquatic environment at a high temporal resolution over extended time periods is challenging. Here, we present a transportable platform integrating sample preparation, liquid chromatography-high-resolution mass spectrometry measurement, automated data processing, and remote control and surveillance. The system is capable of quantifying pollutants at 20 min intervals with high sensitivity (limit of quantification down to 10 ng/L) and operated stably on-site over prolonged periods (<3 ppm mass drift over two weeks, <0.3 min retention time drift over six weeks). Field campaigns under different conditions demonstrated unprecedented insights into pollutant dynamics. Time-resolved measurements in a small creek revealed concentration peaks with up to 10-fold exceedances of environmental quality standards. The quantification of illicit drugs and their metabolites in raw wastewater distinguished fractions of consumed and discarded cocaine. Frequency analyses and data mining showed clusters of diurnal, episodic, and possibly industry-related pollutants, including newly identified substances. With this enabling technology the potential for researching and managing chemicals in natural and technical environments can be significantly expanded beyond our current capabilities, for example, real-time control in process engineering and sewer operation (water management and environmental toxicology), industrial surveillance, and wastewater-based epidemiology.
Bijlsma, L., Burgard, D. A., Been, F., Ort, C., Matias, J., & Yargeau, V. (2020). The estimation of cannabis consumption through wastewater analysis. In I. Ferrer & E. M. Thurman (Eds.), Comprehensive analytical chemistry. Analysis of Cannabis (pp. 453-482). doi:10.1016/bs.coac.2020.04.005, Institutional Repository
Dax, A., Stravs, M., Stamm, C., Ort, C., la Cecilia, D., & Singer, H. (2020). MS2field: Mikroverunreinigungen mobil messen. Aqua & Gas, 100(12), 14-19. , Institutional Repository

Konzentrationsspitzen von Pestiziden können von grosser biologischer und regulatorischer Bedeutung sein, werden aber selten und nur mit hohem Aufwand erfasst. Die neue MS2field-Plattform ist eine der ersten mobilen Messinfrastrukturen, die kontinuierliche und zeitlich hochaufgelöste Messungen von Mikroverunreinigungen in umweltrelevanten Konzentrationen im Feld erlaubt. Wie vielfältig Konzentrationsdynamiken von Pestiziden sein können und in welchem Ausmass Spitzenkonzentrationen mit konventionellen Probenahme- und Messtechniken bisher unterschätzt wurden, macht eine Messkampagne in einem landwirtschaftlich stark geprägten Bach sichtbar.
González‐Mariño, I., Baz‐Lomba, J. A., Alygizakis, N. A., Andrés‐Costa, M. J., Bade, R., Barron, L. P., … Ort, C. (2020). Spatio‐temporal assessment of illicit drug use at large scale: evidence from 7 years of international wastewater monitoring. Addiction, 115(1), 109-120. doi:10.1111/add.14767, Institutional Repository

Background and aims Wastewater‐based epidemiology is an additional indicator of drug use that is gaining reliability to complement the current established panel of indicators. The aims of this study were to: (i) assess spatial and temporal trends of population‐normalized mass loads of benzoylecgonine, amphetamine, methamphetamine and 3,4‐methylenedioxymethamphetamine (MDMA) in raw wastewater over 7 years (2011-17); (ii) address overall drug use by estimating the average number of combined doses consumed per day in each city; and (iii) compare these with existing prevalence and seizure data. Design Analysis of daily raw wastewater composite samples collected over 1 week per year from 2011 to 2017. Setting and Participants Catchment areas of 143 wastewater treatment plants in 120 cities in 37 countries. Measurements Parent substances (amphetamine, methamphetamine and MDMA) and the metabolites of cocaine (benzoylecgonine) and of Δ9‐tetrahydrocannabinol (11‐nor‐9‐carboxy‐Δ9‐tetrahydrocannabinol) were measured in wastewater using liquid chromatography-tandem mass spectrometry. Daily mass loads (mg/day) were normalized to catchment population (mg/1000 people/day) and converted to the number of combined doses consumed per day. Spatial differences were assessed world‐wide, and temporal trends were discerned at European level by comparing 2011-13 drug loads versus 2014-17 loads. Findings Benzoylecgonine was the stimulant metabolite detected at higher loads in southern and western Europe, and amphetamine, MDMA and methamphetamine in East and North-Central Europe. In other continents, methamphetamine showed the highest levels in the United States and Australia and benzoylecgonine in South America. During the reporting period, benzoylecgonine loads increased in general across Europe, amphetamine and methamphetamine levels fluctuated and MDMA underwent an intermittent upsurge. Conclusions The analysis of wastewater to quantify drug loads provides near real‐time drug use estimates that globally correspond to prevalence and seizure data.
Mutzner, L., Bohren, C., Mangold, S., Bloem, S., & Ort, C. (2020). Spatial differences among micropollutants in sewer overflows: a multisite analysis using passive samplers. Environmental Science and Technology, 54(11), 6584-6593. doi:10.1021/acs.est.9b05148, Institutional Repository

Untreated sewer overflows can contaminate receiving waters with micropollutants. Although concentrations of discharged micropollutants can be ecotoxicologically relevant, only limited data is available to assess occurrence and spatial differences among sewer overflow catchments. Therefore, we present an innovative type of data obtained with passive samplers at 20 combined sewer overflow sites (2-7 events per site; 95 events in total). The data sheds light on concentration ranges for 13 representative polar organic micropollutants and shows that micropollutants in both municipal wastewater and stormwater can be relevant sources of contaminants. We identify indicator micropollutants for further studies: benzotriazole (80% interquantile of time-weighted average concentration: 250–4800 ng/L), carbamazepine (33-910 ng/L), diclofenac (78-1000 ng/L), carbendazim (21-900 ng/L), diazinon (2.1-53 ng/L), diuron (22-1100 ng/L), mecoprop (98–5300 ng/L), metolachlor (6-230 ng/L), and terbutryn (29-810 ng/L). These concentration estimates are assumed to be on the safe side for comparison with environmental quality standards (EQS). A majority of sewer overflow sites (13 of 20) show discharge concentrations above acute EQS for at least one micropollutant and thus would have to rely on dilution by receiving waters to not exceed any EQS. The intersite variability among sewer overflows exceed the within-site variability. Hence, future monitoring studies should cover more sewer overflow sites. No correlation could be found with event durations, specific storage volume or land use data, thus showing the complexity of micropollutant occurrence and indicating that other factors led to the observed high spatial variability. In conclusion, our results clearly show the potential relevance of micropollutants in sewer overflows and the need to assess site-specific measures.
Blumensaat, F., Leitão, J. P., Ort, C., Rieckermann, J., Scheidegger, A., Vanrolleghem, P. A., & Villez, K. (2019). How urban storm- and wastewater management prepares for emerging opportunities and threats: digital transformation, ubiquitous sensing, new data sources, and beyond – a horizon scan. Environmental Science and Technology, 53(15), 8488-8498. doi:10.1021/acs.est.8b06481, Institutional Repository

Ubiquitous sensing will create many opportunities and threats for urban water management, which are only poorly understood today. To identify the most relevant trends, we conducted a horizon scan regarding how ubiquitous sensing will shape the future of urban drainage and wastewater management. Our survey of the international urban water community received an active response from both the academics and the professionals from the water industry. The analysis of the responses demonstrates that emerging topics for urban water will often involve experts from different communities, including aquatic ecologists, urban water system engineers and managers, as well as information and communications technology professionals and computer scientists. Activities in topics that are identified as novel will either require (i) cross-disciplinary training, such as importing new developments from the IT sector, or (ii) research in new areas for urban water specialists, for example, to help solve open questions in aquatic ecology. These results are, therefore, a call for interdisciplinary research beyond our own discipline. They also demonstrate that the water management community is not yet prepared for the digital transformation, where we will experience a data demand, i.e. a “pull” of urban water data into external services. The results suggest that a lot remains to be done to harvest the upcoming opportunities. Horizon scanning should be repeated on a routine basis, under the umbrella of an experienced polling organization.
Devasia-Metzger, J. R., Rieckermann, J., Ort, C., & Burkhardt, M. (2019). Vorhersage der Mecoprop-Dynamik im urbanen Regenwasserabfluss mit einem gekoppelten prozess-basierten Schmutzfrachtmodel. In M. Burkhardt & C. Graf (Eds.), Regenwasser weiterdenken - Bemessen trifft Gestalten. Tagungsband - Aqua Urbanica 2019 (pp. 46-53). Rapperswil: HSR Hochschule für Technik Rapperswil. , Institutional Repository

Bei Regenwetter werden viele potenziell toxische Schadstoffe aus Aussenhüllen von Gebäuden ausgewaschen und in die Gewässer eingetragen. Unklar ist allerdings, ob einfache lineare Auswaschfunktionen für Mikroschadstoffe aus Gebäudehüllen für Schmutzfrachtsimulationen ausreichend sind. Um Auswaschungen aus beregneten Gebäudehüllen dynamisch zu berechnen, wurde das "COnstruction Material LEAching Model" (COMLEAM) entwickelt, mit dem Mikroverunreinigungen prozess-basiert beschrieben werden. COMLEAM berücksichtigt allerdings keine Transportprozesse in der Siedlungsentwässerung, so dass es bislang nicht möglich ist, Umwelteinflüsse von Gebäudehüllen abzubilden. In dieser Studie wurde daher COMLEAM an das hydrodynamische Niederschlags-Abfluss Modell SWMM gekoppelt. Insbesondere wurden die Unterschiede von dynamischen und linearen Auswaschmodellen untersucht. Für die Verknüpfung der Modelle wurde eine neue Schnittstelle für COMLEAM programmiert, die sowohl einen Export von SWMM-kompatiblen Schmutzfracht-Zeitreihen, als auch Batch-Simulationen ermöglicht. Die Ergebnisse für eine Fallstudie in Fehraltorf (CH), wo Schmutzfrachten und Konzentrationen des Durchwurzelungsschutzmittels Mecoprop vorhergesagt wurden, zeigen grundsätzlich eine befriedigende Übereinstimmung mit zeitlich hochaufgelösten Daten aus einer Messkampagne. Langzeitprognosen mit dem dynamischen COMLEAM Modell liefern in unserem Fall signifikant unterschiedliche Ergebnisse als lineare Auswaschfunktionen. Allerdings sind diese Unterschiede, in unserem Fallbeispiel, ab einem Gebäudealter von 10 Jahren allerdings vernachlässigbar. Sensitivitätsanalyse deuten weiterhin darauf hin, dass Informationen zum Gebäudebestand, und insbesondere das Alter der Gebäude, sehr sensitiv auf die Simulationsresultate sind.
Gao, J., Li, J., Jiang, G., Shypanski, A. H., Nieradzik, L. M., Yuan, Z., … Thai, P. K. (2019). Systematic evaluation of biomarker stability in pilot scale sewer pipes. Water Research, 151, 447-455. doi:10.1016/j.watres.2018.12.032, Institutional Repository

Transformation of biomarkers (or their stability) during sewer transport is an important issue for wastewater-based epidemiology (WBE). Most studies so far have been conducted in the laboratory, which usually employed unrealistic conditions. In the present study, we utilized a pilot sewer system including a gravity pipe and a rising main pipe to investigate the fate of 24 pharmaceutical biomarkers. A programmable logic controller was used to control and monitor the system including sewer operational conditions and wastewater properties. Sequential samples were collected that can represent hydraulic retention time (HRT) of up to 8 h in a rising main and 4 h in a gravity sewer. Wastewater parameters and biomarker concentrations were analysed to evaluate the stability and transformation kinetics. The wastewater parameters of the pilot system were close to the conditions of real sewers. The findings of biomarker transformation were also close to real sewer data with seventeen biomarkers reported as stable while buprenorphine, caffeine, ethyl-sulfate, methadone, paracetamol, paraxanthine and salicylic acid degraded to variable extents. Both zero-order and first-order kinetics were used to model the degradation of unstable biomarkers and interestingly the goodness of fit R2 for the zero-order model was higher than the first-order model for all unstable biomarkers in the rising main. The pilot sewer system simulates more realistic conditions than benchtop laboratory setups and may provide a more accurate approach for assessing the in-sewer transformation kinetics and stability of biomarkers.
Mutzner, L., Mangold, S., Dicht, S., Bohren, C., Vermeirssen, E. L. M., Scheidegger, A., … Ort, C. (2019). Mikroverunreinigungen aus Siedlungen. Messungen in 20 Mischabwasserentlastungen mit Passivsammler. Aqua & Gas, 99(10), 28-35. , Institutional Repository

Niederschlags- und Mischabwasserentlastungen aus Siedlungen tragen zu Mikroverunreinigungen in Gewässern bei. Mit Passivsammlern wurden erstmals Konzentrationsbereiche an 20 Standorten für insgesamt 95 Ereignisse bestimmt, was die Analyse von Unterschieden zwischen Standorten sowie die Identifikation relevanter Eintragspfade unterstützt. An 13 Standorten waren bei mindestens einer Substanz die Konzentrationen im Mischabwasser höher als akute Qualitätskriterien.
Mutzner, L., Vermeirssen, E. L. M., & Ort, C. (2019). Passive samplers in sewers and rivers with highly fluctuating micropollutant concentrations – Better than we thought. Journal of Hazardous Materials, 361, 312-320. doi:10.1016/j.jhazmat.2018.07.040, Institutional Repository

Considerable pollutant loads can enter surface waters during rain events. Three factors challenge quantification of these pollutant fluxes using traditional sampling methods: (i) concentration fluctuations; (ii) unknown event duration; and (iii) placement, operation, and maintenance of equipment. Passive samplers offer the advantage of sampling in a continuous mode without power supply. However, variable uptake rates due to environmental factors and desorption in the case of fluctuating concentrations can affect the accuracy of time-weighted average (TWA) concentration estimates. While uncertainties related to environmental factors could be accounted for with additional effort, we can neither control nor quantify the concentration variability. We present measured and modelled concentration profiles at high temporal resolution and provide a systematic approach to assessing deviations from true TWA concentration due to fluctuating concentration profiles. We evaluate sampling of sewer overflows (0.3–14 h) with Chemcatcher and 1-week sampling in rivers. The uncertainty due to fluctuating concentrations is small, and other factors such as chemical analyses and sampler calibration have a similar or higher impact. The uncertainty due to fluctuations clearly increases with the sampling duration, particularly when exceeding the half-life of equilibrium. We conclude that passive sampling can also be used in wastewater systems with potentially high concentration variations.
Mutzner, L., Vermeirssen, E. L. M., Mangold, S., Maurer, M., Scheidegger, A., Singer, H., … Ort, C. (2019). Passive samplers to quantify micropollutants in sewer overflows: accumulation behaviour and field validation for short pollution events. Water Research, 160, 350-360. doi:10.1016/j.watres.2019.04.012, Institutional Repository

Contaminants in sewer overflows can contribute to exceedances of environmental quality standards, thus the quantification of contaminants during rainfall events is of relevance. However, monitoring is challenged by i) high spatiotemporal variability of contaminants in events of hard-to-predict durations, and ii) a large number of remote sites, which would imply enormous efforts with traditional sampling equipment. Therefore, we evaluate the applicability of passive samplers (Empore styrene-divinylbenzene reverse phase sulfonated (SDB-RPS)) to monitor a set of 13 polar organic contaminants. We present calibration experiments at high temporal resolution to assess the rate limiting accumulation mechanisms for short events (<36 h), report parameters for typical sewer conditions and compare passive samplers with composite water samples in a field study (three locations, total 10 events). With sampling rates of 0.35–3.5 L/d for 1 h reference time, our calibration results indicate a high sensitivity of passive samplers to sample short, highly variable sewer overflows. The contaminant uptake kinetic shows a fast initial accumulation, which is not well represented with the typical first-order model. Our results indicate that mass transfer to passive samplers is either controlled by the water boundary layer and the sorbent, or by the sorbent alone. Overall, passive sampler concentration estimates are within a factor 0.4 to 3.1 in comparison to composite water samples in the field study. We conclude that passive samplers are a promising approach to monitor a large number of discharge sites although it cannot replace traditional stormwater quality sampling in some cases (e.g. exact load estimates, high temporal resolution). Passive samplers facilitate identifying and prioritizing locations that may require more detailed investigations.
Mutzner, L. Z. (2019). Spatiotemporal variability of micropollutants in sewer overflows (Doctoral dissertation). doi:10.3929/ethz-b-000349443, Institutional Repository

Motivation. Our surface water is impacted by a wide variety of contaminants released through human activities. One contaminant group of concern is micropollutants, which can have eco-toxicological effects in trace concentrations. Micropollutants, for example, include plant protection products and biocides, which are specifically designed to harm organisms. An important input pathway of micropollutants to surface water can be untreated sewer overflows (combined sewer overflows and stormwater outlets). However, the understanding of factors influencing the occurrence and levels of micropollutants is limited and challenged by: i) high spatial differences among sites, ii) a large number of discharge sites and iii) high temporal fluctuating discharge events.

Research objective. This thesis intends to enhance our understanding of micropollutants in sewer overflows. It aims to investigate efficient methods to prioritize sewer overflow sites, which can be potentially harmful for receiving waters. The presented work focuses on the development of model prediction and efficient monitoring approaches and includes the following: i) a Swiss-wide model to assess how many discharge sites may be critical (Chapter 2), ii) fundamentals to develop passive sampling as an alternative monitoring method for short duration sewer overflows (Chapter 3 and 4) and iii) an extended monitoring study covering 20 combined sewer overflows (CSOs) to explore spatial differences among sites (Chapter 5). The main findings of this thesis are presented in the following.

Model-based screening. A dynamic substance flow modeling approach was applied to 2,500 Swiss municipalities, considering micropollutant accumulation and wash-off on urban surfaces. The approach is based on the simplification, that there is one CSO and one stormwater outlet per municipality. The model allows for an estimation of the micropollutant concentration fluctuations in sewer overflows in 10-min resolution. The results show the importance of untreated discharges from sewer overflows as emission into receiving waters. The load contribution to sewer overflows of micropollutants in stormwater (e.g. plant protection products and biocides) is estimated to be considerably higher than of micropollutants in municipal wastewater (e.g. pharmaceuticals and other household chemicals). In addition, the results indicate that up to 83% of all urban catchments have sewer overflows that need to rely on upstream dilution in order to not exceed substance-specific environmental quality standards (EQS). Thus, this nationwide screening approach clearly highlights the need for a more detailed assessment of micropollutants in sewer overflows, and especially, the need for more measured data to allow the development of validated micropollutant prediction models.

Measuring. Difficulties of monitoring sewer overflows with traditional methods are i) high concentration fluctuations with unknown event durations which require a high temporal sampling resolution, ii) many discharge sites and iii) placement, operation, and maintenance of equipment. Hence, passive samplers for polar organic micropollutants are analyzed systematically as a viable alternative to monitor short duration sewer overflows. The main advantage of passive samplers is the continuous accumulation of contaminants from the water phase, with no need for external energy sources nor for immense water sample storage volume. In a first step, the impact of fluctuating concentrations on deviations from true time-weighted average (TWA) concentrations was studied. The results highlight that the deviations induced by fluctuating concentrations are similar or smaller than uncertainties arising from chemical analysis and environmental factors. Understanding the uptake mechanism of micropollutants is one of the most important issues that needs to be resolved to reduce uncertainties in passive sampling data. The uptake experiments in sewer conditions for short duration events (<36h) indicate that the mass transfer is either dominated by the sorbent, or, by a multi-step mechanism. Therefore, a new semi-empirical mixed rate control model is proposed, which can be directly used for future studies under similar conditions. A field validation (3 locations, 10 events) shows that TWA concentration estimates measured by passive samplers are within a factor of 0.4 to 3.1 compared to composite water samples. Hence, the use of upper limit TWA concentration estimates is recommended for compliance checking with EQS. The findings clearly show that passive samplers are suitable to estimate TWA concentration ranges in sewer overflows and, thus facilitate identification of potentially critical discharge sites.

Occurrence of micropollutants. Unique monitoring data from 20 CSO sites was collected with passive samplers. In total 13 polar organic micropollutants were analysed in 95 events (2-7 events per site). The results highlight indicator micropollutants, which were often found in the monitored CSOs and could be used in future monitoring studies: diclofenac, benzotriazole, carbamazepine, diazinon, diuron, carbendazim, mecoprop, metolachlor and terbutryn. Further, our results reveal that the spatial differences among CSO sites are bigger than the inter-event differences within a site for all studied micropollutants. Nevertheless, no significant correlation with land use data could be identified. The results, therefore, suggest that additional factors, most likely the contaminant usage pattern, have a considerable influence on the observed spatial differences. Both municipal wastewater and stormwater contributed to concentrations above the EQS in CSOs (not in the receiving water). In addition, the monitoring with passive samplers indicates that at least 13 out of 20 CSOs show concentrations above EQS in CSOs, and would rely on dilution by receiving waters to not exceed EQS.

Outlook. Overall, the thesis shows the relevance of sewer overflows as a source of micropollutants entering receiving water bodies. The findings can serve as a basis for the development of a systematic and stepwise approach to efficiently identify critical sites. The development of such an approach would require joint efforts by eco-toxicologists, analytical chemists, regulators and wastewater engineers. This approach could be based on a simplified modeling approach as a first indicator, followed by passive sampling to assess micropollutant levels. To enable the widespread application of passive samplers in monitoring programs, regulators’ and operators’ confidence in passive sampling needs to be strengthened with more field validation studies and common guidelines.
O'Brien, J. W., Grant, S., Banks, A. P. W., Bruno, R., Carter, S., Choi, P. M., … Mueller, J. F. (2019). A national wastewater monitoring program for a better understanding of public health: a case study using the Australian census. Environment International, 122, 400-411. doi:10.1016/j.envint.2018.12.003, Institutional Repository

Wastewater contains a large range of biological and chemical markers of human activity and exposures. Through systematic collection and analysis of these markers within wastewater samples it is possible to measure the public health of whole populations. The analysis of effluent and biosolids can also be used to understand the release of chemicals from wastewater treatment plants into the environment. Wastewater analysis and comparison with catchment specific data (e.g. demographics) however remains largely unexplored. This manuscript describes a national wastewater monitoring study that combines influent, effluent and biosolids sampling with the Australian Census. An archiving program allows estimation of per capita exposure to and consumption of chemicals, public health information, as well as per capita release of chemicals into the environment. The paper discusses the study concept, critical steps in setting up a coordinated national approach and key logistical and other considerations with a focus on lessons learnt and future applications. The unique combination of archived samples, analytical data and associated census-derived population data will provide a baseline dataset that has wide and potentially increasing applications across many disciplines that include public health, epidemiology, criminology, toxicology and sociology.
Tscharke, B. J., O’Brien, J. W., Ort, C., Grant, S., Gerber, C., Bade, R., … Mueller, J. F. (2019). Harnessing the power of the census: characterizing wastewater treatment plant  catchment populations for wastewater-based epidemiology. Environmental Science and Technology, 53(17), 10303-10311. doi:10.1021/acs.est.9b03447, Institutional Repository

Wastewater studies that provide per capita estimates of consumption (influent) or release (effluent) via wastewater systems rely heavily on accurate population data. This study evaluated the accuracy of Wastewater Treatment Plant (WWTP) reported populations, as well as hydrochemical parameters, against accurate populations from a population census. 104 catchment maps were received from WWTPs, geolocated in geospatial software and overlaid with the smallest area unit of the Australian census, equating to 14.9 million Australians or 64% of the national population. We characterized each catchment for population counts, as well as by age profile, income profile, and education level. For a subset of sites, population estimates using hydrochemical parameters BOD, COD, and dissolved ammonia were evaluated for accuracy against census populations. Population estimates provided by WWTP personnel were on average 18% higher than census-based populations. Furthermore, hydrochemical-based population estimates had high RSD (>44%) for BOD, COD, and ammonium between sites, suggesting that their applicability for use in population estimation may not be appropriate for every WWTP. Catchment age distributions were evaluated and 46% of catchments had skewed age distributions: 6% were skewed older, and 40% were skewed younger. Through this process WWTP catchment populations can be characterized in a way that will enhance the interpretations of per capita estimates.
Zheng, Y., Mutzner, L., Ort, C., Kaegi, R., & Gottschalk, F. (2019). Modelling engineered nanomaterials in wet-weather discharges. NanoImpact, 16, 100188 (8 pp.). doi:10.1016/j.impact.2019.100188, Institutional Repository

The impacts of the unintended release of engineered nanomaterials (ENMs) and the resulting exposure to the ecosystems are still poorly understood and intensively debated. In current mass flow models, a global transfer coefficient is used to account for ENMs discharged from sewer systems to surface waters during rain events.
However, different types of sewer systems and specific ENM applications likely require a more elaborate approach to quantify ENM loads entering surface waters during rain events. Therefore, we evaluated the impact of distinguishing between different application areas of ENMs (indoor/outdoor) and different types of sewer systems (combined/separate) on the loads of selected ENMs passing through wastewater systems and reaching the surface water. We applied a dynamic mass flow analysis to eight substances (TiO2, ZnO, Ag, SiO2, FeOx, CuO, CeO2 and carbon black) for six different sewer system configurations. To estimate the runoff from streets and facades, we used a hydrological model developed for dissolved substances. For areas with separate sewer systems only and ENMs predominantly used in and released from outdoor applications (e.g. CuO, carbon black), up to ~80% of the annual loads entering the sewer systems never reach a sewage treatment plant. Those ENMs are directly discharged to surface waters via stormwater outlets. For combined sewer systems and ENMs mainly applied indoors (e.g. Ag, ZnO), the percentage of ENM bypassing sewage treatment plants remains below 2%. Although the model is setup for Switzerland and other geographical areas will show for example different rain characteristics, the relative importance of the different release pathways will broadly remain the same and the results should, therefore, be transferrable to other countries.
Castrignanò, E., Yang, Z., Bade, R., Baz-Lomba, J. A., Castiglioni, S., Causanilles, A., … Kasprzyk-Hordern, B. (2018). Enantiomeric profiling of chiral illicit drugs in a pan-European study. Water Research, 130, 151-160. doi:10.1016/j.watres.2017.11.051, Institutional Repository

The aim of this paper is to present the first study on spatial and temporal variation in the enantiomeric profile of chiral drugs in eight European cities. Wastewater-based epidemiology (WBE) and enantioselective analysis were combined to evaluate trends in illicit drug use in the context of their consumption vs direct disposal as well as their synthetic production routes. Spatial variations in amphetamine loads were observed with higher use in Northern European cities. Enantioselective analysis showed a general enrichment of amphetamine with the R-(−)-enantiomer in wastewater indicating its abuse. High loads of racemic methamphetamine were detected in Oslo (EF = 0.49 ± 0.02). This is in contrast to other European cities where S-(+)-methamphetamine was the predominant enantiomer. This indicates different methods of methamphetamine synthesis and/or trafficking routes in Oslo, compared with the other cities tested. An enrichment of MDMA with the R-(−)-enantiomer was observed in European wastewaters indicating MDMA consumption rather than disposal of unused drug. MDA's chiral signature indicated its enrichment with the S-(+)-enantiomer, which confirms its origin from MDMA metabolism in humans. HMMA was also detected at quantifiable concentrations in wastewater and was found to be a suitable biomarker for MDMA consumption. Mephedrone was only detected in wastewater from the United Kingdom with population-normalised loads up to 47.7 mg 1000 people−1 day−1. The enrichment of mephedrone in the R-(+)-enantiomer in wastewater suggests stereoselective metabolism in humans, hence consumption, rather than direct disposal of the drug. The investigation of drug precursors, such as ephedrine, showed that their presence was reasonably ascribed to their medical use.
Hernández, F., Castiglioni, S., Covaci, A., de Voogt, P., Emke, E., Kasprzyk-Hordern, B., … Bijlsma, L. (2018). Mass spectrometric strategies for the investigation of biomarkers of illicit drug use in wastewater. Mass Spectrometry Reviews, 37(3), 258-280. doi:10.1002/mas.21525, Institutional Repository

The analysis of illicit drugs in urban wastewater is the basis of wastewater-based epidemiology (WBE), and has received much scientific attention because the concentrations measured can be used as a new non-intrusive tool to provide evidence-based and real-time estimates of community-wide drug consumption. Moreover, WBE allows monitoring patterns and spatial and temporal trends of drug use. Although information and expertise from other disciplines is required to refine and effectively apply WBE, analytical chemistry is the fundamental driver in this field. The use of advanced analytical techniques, commonly based on combined chromatography—mass spectrometry, is mandatory because the very low analyte concentration and the complexity of samples (raw wastewater) make quantification and identification/confirmation of illicit drug biomarkers (IDBs) troublesome. We review the most-recent literature available (mostly from the last 5 years) on the determination of IDBs in wastewater with particular emphasis on the different analytical strategies applied. The predominance of liquid chromatography coupled to tandem mass spectrometry to quantify target IDBs and the essence to produce reliable and comparable results is illustrated. Accordingly, the importance to perform inter-laboratory exercises and the need to analyze appropriate quality controls in each sample sequence is highlighted. Other crucial steps in WBE, such as sample collection and sample pre-treatment, are briefly and carefully discussed. The article further focuses on the potential of high-resolution mass spectrometry. Different approaches for target and non-target analysis are discussed, and the interest to perform experiments under laboratory-controlled conditions, as a complementary tool to investigate related compounds (e.g., minor metabolites and/or transformation products in wastewater) is treated. The article ends up with the trends and future perspectives in this field from the authors’ point of view.
Kinyua, J., Negreira, N., McCall, A. K., Boogaerts, T., Ort, C., Covaci, A., & van Nuijs, A. L. N. (2018). Investigating in-sewer transformation products formed from synthetic cathinones and phenethylamines using liquid chromatography coupled to quadrupole time-of-flight mass spectrometry. Science of the Total Environment, 634, 331-340. doi:10.1016/j.scitotenv.2018.03.253, Institutional Repository

Recent studies have demonstrated the role of biofilms on the stability of drug residues in wastewater. These factors are pertinent in wastewater-based epidemiology (WBE) when estimating community-level drug use. However, there is scarce information on the biotransformation of drug residues in the presence of biofilms and the potential use of transformation products (TPs) as biomarkers in WBE.
The purpose of this work was to investigate the formation of TPs in sewage reactors in the presence of biofilm mimicking conditions during in-sewer transport. Synthetic cathinones (methylenedioxypyrovalerone, methylone, mephedrone) and phenethylamines (4-methoxy-methamphetamine and 4-methoxyamphetamine) were incubated in individual reactors over a 24 h period. Analysis of parent species and TPs was carried out using liquid chromatography coupled to quadrupole time-of-flight mass spectrometry (LC-QToFMS). Identification of TPs was done using suspect and non-target workflows.
In total, 18 TPs were detected and identified with reduction of β-keto group, demethylenation, demethylation, and hydroxylation reactions observed for the synthetic cathinones. For the phenethylamines, N- and O-demethylation reactions were identified. Overall, the experiments showed varying stability for the parent species in wastewater in the presence of biofilms. The newly identified isomeric forms of TPs particularly for methylone and mephedrone can be used as potential target biomarkers for WBE studies due to their specificity and detectability within a 24 h residence time.
Novic, A. J., Ort, C., O'Brien, D. S., Lewis, S. E., Davis, A. M., & Mueller, J. F. (2018). Understanding the uncertainty of estimating herbicide and nutrient mass loads in a flood event with guidance on estimator selection. Water Research, 132, 99-110. doi:10.1016/j.watres.2017.12.055, Institutional Repository

The aim of this study was to understand the uncertainty of estimating loads for observed herbicides and nutrients during a flood event and provide guidance on estimator selection. A high-resolution grab sampling campaign (258 samples over 100 h) was conducted during a flood event in a tropical waterway in Queensland, Australia. Ten herbicides and three nutrient compounds were detected at elevated concentrations. Each had a unique chemograph with differences in transport processes (e.g. dependence on flow, dilution processes and timing of concentration pulses). Resampling from the data set was used to assess uncertainty. Bias existed at lower sampling efforts but depended on estimator properties as sampling effort increased: the interpolation, ratio and regression estimators became unbiased. Large differences were observed in precision and the importance of sampling effort and estimator selection depended on the relationship between the chemograph and hydrograph. The variety of transport processes observed and the resultant variability in uncertainty suggest that useful load estimates can only be obtained with sufficient samples and appropriate estimator selection. We provide a rationale to show the latter can be guided across sampling periods by selecting an estimator where the sampling regime or the relationship between the chemograph and hydrograph meet its assumptions: interpolation becomes more correct as sampling effort increases and the ratio becomes more correct as the r2 correlation between flux and flow increases (e.g. > 0.9); a stratified composite sampling approach, even with random samples, is a promising alternative.
Ort, C., Bijlsma, L., Castiglioni, S., Covaci, A., de Voogt, P., Emke, E., … Kasprzyk-Hordern, B. (2018). Wastewater analysis for community-wide drugs use assessment. In H. H. Maurer & S. D. Brandt (Eds.), Handbook of experimental pharmacology: Vol. 252. New psychoactive substances. Pharmacology, clinical, forensic and analytical toxicology (pp. 543-566). doi:10.1007/164_2018_111, Institutional Repository

Wastewater-based epidemiology (WBE) complements existing epidemiologybased estimation techniques and provides objective, evidence-based estimates of illicit drug use. After consumption, biomarkers drugs and their metabolites - excreted to toilets and flushed into urban sewer networks can be measured in raw wastewater samples. The quantified loads can serve as an estimate for the collective consumption of all people contributing to the wastewater sample. This transdisciplinary approach, further explained in this chapter, has developed, matured and is now established for monitoring substances such as cocaine and amphetamine-type stimulants. Research currently underway is refining WBE to new applications including new psychoactive substances (NPS).
van Nuijs, A. L. N., Lai, F. Y., Been, F., Andres-Costa, M. J., Barron, L., Baz-Lomba, J. A., … Ort, C. (2018). Multi-year inter-laboratory exercises for the analysis of illicit drugs and metabolites in wastewater: development of a quality control system. Trends in Analytical Chemistry, 103, 34-43. doi:10.1016/j.trac.2018.03.009, Institutional Repository

Thirty-seven laboratories from 25 countries present the development of an inter-laboratory testing scheme for the analysis of seven illicit drug residues in standard solutions, tap- and wastewater. Almost 10 000 concentration values were evaluated: triplicates of up to five samples and 26 laboratories per year. The setup was substantially improved with experiences gained across the six repetitions (e.g. matrix type, sample conditions, spiking levels). From this, (pre-)analytical issues (e.g. pH adjustment, filtration) were revealed for specific analytes which resulted in formulation of best-practice protocols for inter-laboratory setup and analytical procedures. The results illustrate the effectiveness of the inter-laboratory setup to assess laboratory performance in the framework of wastewater-based epidemiology. The exercise proved that measurements of laboratories were of high quality (>80% satisfactory results for six out of seven analytes) and that analytical follow-up is important to assist laboratories in improving robustness of wastewater-based epidemiology results.
Aymerich, I., Acuña, V., Ort, C., Rodríguez-Roda, I., & Corominas, L. (2017). Fate of organic microcontaminants in wastewater treatment and river systems: an uncertainty assessment in view of sampling strategy, and compound consumption rate and degradability. Water Research, 125, 152-161. doi:10.1016/j.watres.2017.08.011, Institutional Repository

The growing awareness of the relevance of organic microcontaminants on the environment has led to a growing number of studies on attenuation of these compounds in wastewater treatment plants (WWTP) and rivers. However, the effects of the sampling strategies (frequency and duration of composite samples) on the attenuation estimates are largely unknown. Our goal was to assess how frequency and duration of composite samples influence uncertainty of the attenuation estimates in WWTPs and rivers. Furthermore, we also assessed how compound consumption rate and degradability influence uncertainty. The assessment was conducted through simulating the integrated wastewater system of Puigcerdà (NE Iberian Peninsula) using a sewer pattern generator and a coupled model of WWTP and river. Results showed that the sampling strategy is especially critical at the influent of WWTP, particularly when the number of toilet flushes containing the compound of interest is small (≤100 toilet flushes with compound day-1), and less critical at the effluent of the WWTP and in the river due to the mixing effects of the WWTP. For example, at the WWTP, when evaluating a compound that is present in 50 pulses.d-1 using a sampling frequency of 15-min to collect a 24-h composite sample, the attenuation uncertainty can range from 94% (0% degradability) to 9% (90% degradability). The estimation of attenuation in rivers is less critical than in WWTPs, as the attenuation uncertainty was lower than 10% for all evaluated scenarios. Interestingly, the errors in the estimates of attenuation are usually lower than those of loads for most sampling strategies and compound characteristics (e.g. consumption and degradability), although the opposite occurs for compounds with low consumption and inappropriate sampling strategies at the WWTP. Hence, when designing a sampling campaign, one should consider the influence of compounds' consumption and degradability as well as the desired level of accuracy in attenuation estimations.
Bade, R., Bijlsma, L., Sancho, J. V., Baz-Lomba, J. A., Castiglioni, S., Castrignanò, E., … Hernández, F. (2017). Liquid chromatography-tandem mass spectrometry determination of synthetic cathinones and phenethylamines in influent wastewater of eight European cities. Chemosphere, 168, 1032-1041. doi:10.1016/j.chemosphere.2016.10.107, Institutional Repository

The popularity of new psychoactive substances (NPS) has grown in recent years, with certain NPS commonly and preferentially consumed even following the introduction of preventative legislation. With the objective to improve the knowledge on the use of NPS, a rapid and very sensitive method was developed for the determination of ten priority NPS (N-ethylcathinone, methylenedioxypyrovalerone (MDPV), methylone, butylone, methedrone, mephedrone, naphyrone, 25-C-NBOMe, 25-I-NBOMe and 25-B-NBOMe) in influent wastewater. Sample clean-up and pre-concentration was made by off-line solid phase extraction (SPE) with Oasis MCX cartridges. Isotopically labelled internal standards were used to correct for matrix effects and potential SPE losses. Following chromatographic separation on a C18 column within 6 min, the compounds were measured by tandem mass spectrometry in positive ionization mode. The method was optimised and validated for all compounds. Limits of quantification were evaluated by spiking influent wastewater samples at 1 or 5 ng/L. An investigation into the stability of these compounds in influent wastewater was also performed, showing that, following acidification at pH 2, all compounds were relatively stable for up to 7 days. The method was then applied to influent wastewater samples from eight European countries, in which mephedrone, methylone and MDPV were detected. This work reveals that although NPS use is not as extensive as for classic illicit drugs, the application of a highly sensitive analytical procedure makes their detection in wastewater possible. The developed analytical methodology forms the basis of a subsequent model-based back-calculation of abuse rate in urban areas (i.e. wastewater-based epidemiology).
Besmer, M. D., Hammes, F., Sigrist, J. A., & Ort, C. (2017). Evaluating monitoring strategies to detect precipitation-induced microbial contamination events in karstic springs used for drinking water. Frontiers in Microbiology, 8, 2229 (12 pp.). doi:10.3389/fmicb.2017.02229, Institutional Repository

Monitoring of microbial drinking water quality is a key component for ensuring safety and understanding risk, but conventional monitoring strategies are typically based on low sampling frequencies (e.g., quarterly or monthly). This is of concern because many drinking water sources, such as karstic springs are often subject to changes in bacterial concentrations on much shorter time scales (e.g., hours to days), for example after precipitation events. Microbial contamination events are crucial from a risk assessment perspective and should therefore be targeted by monitoring strategies to establish both the frequency of their occurrence and the magnitude of bacterial peak concentrations. In this study we used monitoring data from two specific karstic springs. We assessed the performance of conventional monitoring based on historical records and tested a number of alternative strategies based on a high-resolution data set of bacterial concentrations in spring water collected with online flow cytometry (FCM). We quantified the effect of increasing sampling frequency and found that for the specific case studied, at least bi-weekly sampling would be needed to detect precipitation events with a probability of >90%. We then proposed an optimized monitoring strategy with three targeted samples per event, triggered by precipitation measurements. This approach is more effective and efficient than simply increasing overall sampling frequency. It would enable the water utility to (1) analyze any relevant event and (2) limit median underestimation of peak concentrations to approximately 10%. We conclude with a generalized perspective on sampling optimization and argue that the assessment of short-term dynamics causing microbial peak loads initially requires increased sampling/analysis efforts, but can be optimized subsequently to account for limited resources. This offers water utilities and public health authorities systematic ways to evaluate and optimize their current monitoring strategies.
Causanilles, A., Baz-Lomba, J. A., Burgard, D. A., Emke, E., González-Mariño, I., Krizman-Matasic, I., … Bijlsma, L. (2017). Improving wastewater-based epidemiology to estimate cannabis use: focus on the initial aspects of the analytical procedure. Analytica Chimica Acta, 988, 27-33. doi:10.1016/j.aca.2017.08.011, Institutional Repository

Wastewater-based epidemiology is a promising and complementary tool for estimating drug use by the general population, based on the quantitative analysis of specific human metabolites of illicit drugs in urban wastewater. Cannabis is the most commonly used illicit drug and of high interest for epidemiologists. However, the inclusion of its main human urinary metabolite 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (THC-COOH) in wastewater-based epidemiology has presented several challenges and concentrations seem to depend heavily on environmental factors, sample preparation and analyses, commonly resulting in an underestimation. The aim of the present study is to investigate, identify and diminish the source of bias when analysing THC-COOH in wastewater. Several experiments were performed to individually assess different aspects of THC-COOH determination in wastewater, such as the number of freeze-thaw cycles, filtration, sorption to different container materials and in-sample stability, and the most suitable order of preparatory steps. Results highlighted the filtration step and adjustment of the sample pH as the most critical parameters to take into account when analysing THC-COOH in wastewater. Furthermore, the order of these initial steps of the analytical procedure is crucial. Findings were translated into a recommended best-practice protocol and an inter-laboratory study was organized with eight laboratories that tested the performance of the proposed procedure. Results were found satisfactory with z-scores ≤ 2.
McCall, A. K., Palmitessa, R., Blumensaat, F., Morgenroth, E., & Ort, C. (2017). Modeling in-sewer transformations at catchment scale – implications on drug consumption estimates in wastewater-based epidemiology. Water Research, 122, 655-668. doi:10.1016/j.watres.2017.05.034, Institutional Repository

To which extent illicit drugs are transformed during in-sewer transport, depends on a number of factors: i) substance-specific transformation rates, ii) environmental conditions, iii) point of discharge (location of drug user) and iv) sewer network properties, primarily hydraulic residence time (HRT) and the ratio of biofilm contact area to wastewater volume (A/Veq).
Assessing associated uncertainties typically requires numerous simulations. Therefore, we propose a new two-step modeling framework: 1) Quantify hydrodynamic conditions. This computationally demanding step was performed once in SWMM to derive HRT and A/Veq for each potential point of discharge (node) in three catchments of different size. 2) Estimate biomarker loss. In this step, Monte Carlo simulations were performed for defined scenarios. Depending on assumptions about drug user distribution and prevalence, a number of nodes was sampled. For each node an empirical first-order transformation model was applied with flow-path-corresponding HRT and A/Veq from step 1. Biotic and abiotic transformation rates were sampled from distributions combining variability of different biofilms.
In our modeling study, median losses were >30% for amphetamine, 6-monoacetylmorphine and 6-acetylcodeine in all three catchments with high uncertainty (5%–100% loss), which would imply a systematic underestimation of consumption when neglecting in-sewer processes. Median losses for 21 other investigated biomarkers were <10% with different uncertainty ranges – “no substantial transformation” was confirmed for nine substances in a real sewer segment with a 2-h residence time. Transferability of these results must be tested for other catchments. To further reduce uncertainty, mainly additional knowledge on transformation rates, particularly in biofilm, and their distribution across a sewer network is needed to update model input objectively. Our approach allows efficient testing and, furthermore, can be expanded for many other human biomarkers. Accounting for biomarker stability during in-sewer transport will avoid biased estimates and further improve wastewater-based epidemiology.
Mutzner, L., Mangold, S., Maurer, M., Scheidegger, A., Singer, H., Vermeirssen, E., & Ort, C. (2017). Passive sampling: an efficient way to monitor micropollutants in sewer overflows? (pp. 10-17). Presented at the 14th IWA/IAHR international conference on urban drainage (ICUD). Prague: CZWA; Czech Technical University; IAHR/AIRH; IWA. , Institutional Repository

High spatio-temporal variability characterizes micropollutants discharged from separate and combined sewers. This challenges monitoring and prediction. We propose passive samplers (Chemcatcher® for polar, organic substances) as an alternative to active water sampling. Our results indicate sufficient sensitivity of passive samplers for short exposures so that typical rain event durations (<30 h) can be sampled integratively. Although time-weighted average concentrations estimated via passive sampling are higherthan in composite water samples -on average by a factor 2.7 - we conclude that passive sampling is a cost-effective approach to identify locations with critical concentration ranges.
O’Brien, J. W., Banks, A. P. W., Novic, A. J., Mueller, J. F., Jiang, G., Ort, C., … Thai, P. K. (2017). Impact of in-sewer degradation of pharmaceutical and personal care products (PPCPs) population markers on a population model. Environmental Science and Technology, 51(7), 3816-3823. doi:10.1021/acs.est.6b02755, Institutional Repository

A key uncertainty of wastewater-based epidemiology is the size of the population which contributed to a given wastewater sample. We previously developed and validated a Bayesian inference model to estimate population size based on 14 population markers which: (1) are easily measured and (2) have mass loads which correlate with population size. However, the potential uncertainty of the model prediction due to in-sewer degradation of these markers was not evaluated. In this study, we addressed this gap by testing their stability under sewer conditions and assessed whether degradation impacts the model estimates. Five markers, which formed the core of our model, were stable in the sewers while the others were not. Our evaluation showed that the presence of unstable population markers in the model did not decrease the precision of the population estimates providing that stable markers such as acesulfame remained in the model. However, to achieve the minimum uncertainty in population estimates, we propose that the core markers to be included in population models for other sites should meet two additional criteria: (3) negligible degradation in wastewater to ensure the stability of chemicals during collection; and (4) < 10% in-sewer degradation could occur during the mean residence time of the sewer network.
Banta-Green, C. J., Brewer, A. J., Ort, C., Helsel, D. R., Williams, J. R., & Field, J. A. (2016). Using wastewater-based epidemiology to estimate drug consumption—statistical analyses and data presentation. Science of the Total Environment, 568, 856-863. doi:10.1016/j.scitotenv.2016.06.052, Institutional Repository

Aim: Analysis of wastewater samples can be used to assess population drug use, but reporting and statistical issues have limited the utility of the approach for epidemiology due to analytical results that are below the limit of quantification or detection. Unobserved or non-quantifiable—censored—data are common and likely to persist as the methodology is applied to more municipalities and a broader array of substances. We demonstrate the use of censored data techniques and account for measurement errors to explore distributions and annual estimates of the daily mean level of drugs excreted per capita.
Measurements: Daily 24-hour composite wastewater samples for 56 days in 2009 were obtained using a random sample stratified by day of week and season for 19 municipalities in the Northwest region of the U.S.
Methods: Methamphetamine, benzoylecgonine (cocaine metabolite), 3,4 methylenedioxymethamphetamine (MDMA), methadone, oxycodone and hydrocodone were identified and quantified in wastewater samples. Four statistical approaches (reporting censoring, Maximum Likelihood Estimation, Kaplan-Meier estimates, or complete data calculations) were used to estimate an annual average, including confidence bounds where appropriate, dependent upon the amount of censoring in the data.
Findings: The proportion of days within a year with censored data varied greatly by drug across the 19 municipalities, with MDMA varying the most (4% to 94% of observations censored). The different statistical approaches each needed to be used given the levels of censoring of measured drug concentrations. Figures incorporating confidence bounds allow visualization of the data that facilitates appropriate comparisons across municipalities.
Conclusions: Results from wastewater sampling that are below detection or quantification limits contain important information and can be incorporated to create a more complete and valid estimate of drug excretion.
Baz-Lomba, J. A., Salvatore, S., Gracia-Lor, E., Bade, R., Castiglioni, S., Castrignanò, E., … Thomas, K. (2016). Comparison of pharmaceutical, illicit drug, alcohol, nicotine and caffeine levels in wastewater with sale, seizure and consumption data for 8 European cities. BMC Public Health, 16, 1035 (11 pp.). doi:10.1186/s12889-016-3686-5, Institutional Repository

Background: Monitoring the scale of pharmaceuticals, illicit and licit drugs consumption is important to assess the needs of law enforcement and public health, and provides more information about the different trends within different countries. Community drug use patterns are usually described by national surveys, sales and seizure data. Wastewater-based epidemiology (WBE) has been shown to be a reliable approach complementing such surveys.
Method: This study aims to compare and correlate the consumption estimates of pharmaceuticals, illicit drugs, alcohol, nicotine and caffeine from wastewater analysis and other sources of information. Wastewater samples were collected in 2015 from 8 different European cities over a one week period, representing a population of approximately 5 million people. Published pharmaceutical sale, illicit drug seizure and alcohol, tobacco and caffeine use data were used for the comparison.
Results: High agreement was found between wastewater and other data sources for pharmaceuticals and cocaine, whereas amphetamines, alcohol and caffeine showed a moderate correlation. methamphetamine and 3,4-methylenedioxymethamphetamine (MDMA) and nicotine did not correlate with other sources of data. Most of the poor correlations were explained as part of the uncertainties related with the use estimates and were improved with other complementary sources of data.
Conclusions: This work confirms the promising future of WBE as a complementary approach to obtain a more accurate picture of substance use situation within different communities. Our findings suggest further improvements to reduce the uncertainties associated with both sources of information in order to make the data more comparable.
Been, F., Bijlsma, L., Benaglia, L., Berset, J. D., Botero-Coy, A. M., Castiglioni, S., … Ort, C. (2016). Assessing geographical differences in illicit drug consumption—a comparison of results from epidemiological and wastewater data in Germany and Switzerland. Drug and Alcohol Dependence, 161, 189-199. doi:10.1016/j.drugalcdep.2016.02.002, Institutional Repository

Background: Wastewater analysis is an innovative approach that allows monitoring illicit drug use at the community level. This study focused on investigating geographical differences in drug consumption by comparing epidemiological, crime and wastewater data.
Methods: Wastewater samples were collected in 19 cities across Germany and Switzerland during one week, covering a population of approximately 8.1 million people. Self-report data and consumption offences for the investigated areas were used for comparison and to investigate differences between the indicators.
Results: Good agreement between data sources was observed for cannabis and amphetamine-type stimulants, whereas substantial discrepancies were observed for cocaine. In Germany, an important distinction could be made between Berlin, Dortmund and Munich, where cocaine and particularly amphetamine were more prevalent, and Dresden, where methamphetamine consumption was clearly predominant. Cocaine consumption was relatively homogenous in the larger urban areas of Switzerland, although prevalence and offences data suggested a more heterogeneous picture. Conversely, marked regional differences in amphetamine and methamphetamine consumption could be highlighted.
Conclusions: Combining the available data allowed for a better understanding of the geographical differences regarding prevalence, typology and amounts of substances consumed. For cannabis and amphetamine-type stimulants, the complementarity of survey, police and wastewater data could be highlighted, although notable differences could be identified when considering more stigmatised drugs (i.e. cocaine and heroin). Understanding illicit drug consumption at the national scale remains a difficult task, yet this research illustrates the added value of combining complementary data sources to obtain a more comprehensive and accurate picture of the situation.
Brewer, A. J., Banta-Green, C. J., Ort, C., Robel, A. E., & Field, J. (2016). Wastewater testing compared with random urinalyses for the surveillance of illicit drug use in prisons. Drug and Alcohol Review, 35(2), 133-137. doi:10.1111/dar.12185, Institutional Repository

Introduction and Aims. Illicit drug use is known to occur among inmate populations of correctional (prison) facilities. Conventional approaches to monitor illicit drug use in prisons include random urinalyses (RUA). Conventional approaches are expected to be prone to bias because prisoners may be aware of which days of the week RUAs are conducted. Therefore, we wanted to compare wastewater loads for methamphetamine and cocaine during days with RUA testing and without. Design and Methods. We collected daily 24-h composite samples of wastewater by continuous sampling, computed daily loads for 1 month and compared the frequency of illicit drug detection to the number of positive RUAs. Diurnal data also were collected for 3 days to determine within-day patterns of illicit drugs excretion.Results. Methamphetamine was observed in each sample of prison wastewater with no significant difference in daily mass loads between RUA testing and non-testing days. Cocaine and its major metabolite, benzoylecgonine, were observed only at levels below quantification in prison wastewater. Six RUAs were positive for methamphetamine during the month while none were positive for cocaine out of the 243 RUAs conducted.Discussion and Conclusions. Wastewater analyses offer data regarding the frequency of illicit drug excretion inside the prison that RUAs alone could not detect.
Burdon, F. J., Reyes, M., Alder, A. C., Joss, A., Ort, C., Räsänen, K., … Stamm, C. (2016). Environmental context and magnitude of disturbance influence trait-mediated community responses to wastewater in streams. Ecology and Evolution, 6(12), 3923-3939. doi:10.1002/ece3.2165, Institutional Repository

Human land uses and population growth represent major global threats to biodiversity and ecosystem services. Understanding how biological communities respond to multiple drivers of human-induced environmental change is fundamental for conserving ecosystems and remediating degraded habitats. Here, we used a replicated ‘real-world experiment’ to study the responses of invertebrate communities to wastewater perturbations across a land-use intensity gradient in 12 Swiss streams. We used different taxonomy and trait-based community descriptors to establish the most sensitive indicators detecting impacts and to help elucidate potential causal mechanisms of change. First, we predicted that streams in catchments adversely impacted by human land-uses would be less impaired by wastewater inputs because their invertebrate communities should be dominated by pollution-tolerant taxa (‘environmental context’). Second, we predicted that the negative effects of wastewater on stream invertebrate communities should be larger in streams that receive proportionally more wastewater (‘magnitude of disturbance’). In support of the ‘environmental context’ hypothesis, we found that change in the Saprobic Index (a trait-based indicator of tolerance to organic pollution) was associated with upstream community composition; communities in catchments with intensive agricultural land uses (e.g., arable cropping and pasture) were generally more resistant to eutrophication associated with wastewater inputs. We also found support for the ‘magnitude of disturbance’ hypothesis. The SPEAR Index (a trait-based indicator of sensitivity to pesticides) was more sensitive to the relative input of effluent, suggesting that toxic influences of wastewater scale with dilution. Whilst freshwater pollution continues to be a major environmental problem, our findings highlight that the same anthropogenic pressure (i.e., inputs of wastewater) may induce different ecological responses depending on the environmental context and community metrics used. Thus, remediation strategies aiming to improve stream ecological status (e.g., rehabilitating degraded reaches) need to consider upstream anthropogenic influences and the most appropriate indicators of restoration success.
Gao, J., O'Brien, J., Du, P., Li, X., Ort, C., Mueller, J. F., & Thai, P. K. (2016). Measuring selected PPCPs in wastewater to estimate the population in different cities in China. Science of the Total Environment, 568, 164-170. doi:10.1016/j.scitotenv.2016.05.216, Institutional Repository

Sampling and analysis of wastewater from municipal wastewater treatment plants (WWTPs) has become a useful tool for understanding exposure to chemicals. Both wastewater based studies and management and planning of the catchment require information on catchment population in the time of monitoring. Recently, a model has been developed and calibrated using selected pharmaceutical and personal care products (PPCPs) measured in influent wastewater for estimating population in different catchments in Australia. The present study aimed at evaluating the feasibility of utilizing this population estimation approach in China. Twenty-four hour composite influent samples were collected from 31 WWTPs in 17 cities with catchment sizes from 200,000–3,450,000 people representing all seven regions of China. The samples were analyzed for 19 PPCPs using liquid chromatography coupled to tandem mass spectrometry in direct injection mode. Eight chemicals were detected in more than 50% of the samples. Significant positive correlations were found between individual PPCP mass loads and population estimates provided by WWTP operators. Using the PPCP mass load modeling approach calibrated with WWTP operator data, we estimated the population size of each catchment with good agreement with WWTP operator values (between 50–200% for all sites and 75–125% for 23 of the 31 sites). Overall, despite much lower detection and relatively high heterogeneity in PPCP consumption across China the model provided a good estimate of the population contributing to a given wastewater sample. Wastewater analysis could also provide objective PPCP consumption status in China.
Humphries, M. A., Bruno, R., Lai, F. Y., Thai, P. K., Holland, B. R., O’Brien, J. W., … Mueller, J. F. (2016). Evaluation of monitoring schemes for wastewater-based epidemiology to identify drug use trends using cocaine, methamphetamine, MDMA and methadone. Environmental Science and Technology, 50(9), 4760-4768. doi:10.1021/acs.est.5b06126, Institutional Repository

Wastewater-based epidemiology is increasingly being used as a tool to monitor drug use trends. To minimize costs, studies have typically monitored a small number of days. However, cycles of drug use may display weekly and seasonal trends that affect the accuracy of monthly or annual drug use estimates based on a limited number of samples. This study aimed to rationalize sampling methods for minimizing the number of samples required while maximizing information about temporal trends. A range of sampling strategies were examined: (i) targeted days (e.g., weekends), (ii) completely random or stratified random sampling, and (iii) a number of sampling strategies informed by known weekly cycles in drug use data. Using a time-series approach, analysis was performed for four drugs (MDMA, methamphetamine, cocaine, methadone) collected through a continuous sampling program over 14 months. Results showed, for drugs with weekly cycles (MDMA, methamphetamine and cocaine in this sample), sampling strategies which made use of those weekly cycles required fewer samples to obtain similar information as sampling 5 days per week and had better accuracy than stratified random sampling techniques.
Kuroda, K., Itten, R., Kovalova, L., Ort, C., Weissbrodt, D. G., & McArdell, C. S. (2016). Hospital-use pharmaceuticals in Swiss waters modeled at high spatial resolution. Environmental Science and Technology, 50(9), 4742-4751. doi:10.1021/acs.est.6b00653, Institutional Repository

A model to predict the mass flows and concentrations of pharmaceuticals predominantly used in hospitals across a large number of sewage treatment plant (STP) effluents and river waters was developed at high spatial resolution. It comprised 427 geo-referenced hospitals and 742 STPs serving 98% of the general population in Switzerland. In the modeled base scenario, domestic, pharmaceutical use was geographically distributed according to the population size served by the respective STPs. Distinct hospital scenarios were set up to evaluate how the predicted results were modified when pharmaceutical use in hospitals was allocated differently; for example, in proportion to number of beds or number of treatments in hospitals. The hospital scenarios predicted the mass flows and concentrations up to 3.9 times greater than in the domestic scenario for iodinated X-ray contrast media (ICM) used in computed tomography (CT), and up to 6.7 times greater for gadolinium, a contrast medium used in magnetic resonance imaging (MRI). Field measurements showed that ICM and gadolinium were predicted best by the scenarios using number of beds or treatments in hospitals with the specific facilities (i.e., CT and/or MRI). Pharmaceuticals used both in hospitals and by the general population (e.g., cyclophosphamide, sulfamethoxazole, carbamazepine, diclofenac) were predicted best by the scenario using the number of beds in all hospitals, but the deviation from the domestic scenario values was only small. Our study demonstrated that the bed number-based hospital scenarios were effective in predicting the geographical distribution of a diverse range of pharmaceuticals in STP effluents and rivers, while the domestic scenario was similarly effective on the scale of large river-catchments.
Lai, F. Y., O'Brien, J. W., Thai, P. K., Hall, W., Chan, G., Bruno, R., … Mueller, J. F. (2016). Cocaine, MDMA and methamphetamine residues in wastewater: consumption trends (2009–2015) in South East Queensland, Australia. Science of the Total Environment, 568, 803-809. doi:10.1016/j.scitotenv.2016.05.181, Institutional Repository

Wastewater analysis, or wastewater-based epidemiology, has become a common tool to monitor trends of illicit drug consumption around the world. In this study, we examined trends in cocaine, 3,4-methylenedioxymethamphetamine (MDMA) and methamphetamine consumption by measuring their residues in wastewater from two wastewater treatment plants in Australia (specifically, an urban and a rural catchment, both in South East Queensland) between 2009 and 2015. With direct injection of the samples, target analytes were identified and quantified using liquid chromatography-mass spectrometry. Cocaine and MDMA residues and metabolites were mainly quantifiable in the urban catchment while methamphetamine residues were consistently detected in both urban and rural catchments. There was no consistent trend in the population normalised mass loads observed for cocaine and MDMA at the urban site between 2009 and 2015. In contrast, there was a five-fold increase in methamphetamine consumption over this period in this catchment. For methamphetamine consumption, the rural area showed a very similar trend as the urban catchment starting at a lower baseline. The observed increase in per capita loads of methamphetamine via wastewater analysis over the past six years in South East Queensland provides objective evidence for increased methamphetamine consumption in the Australian population while the use of other illicit stimulants remained relatively stable.
McCall, A. K., Bade, R., Kinyua, J., Lai, F. Y., Thai, P. K., Covaci, A., … Ort, C. (2016). Critical review on the stability of illicit drugs in sewers and wastewater samples. Water Research, 88, 933-947. doi:10.1016/j.watres.2015.10.040, Institutional Repository

Wastewater-based epidemiology (WBE) applies advanced analytical methods to quantify drug residues in wastewater with the aim to estimate illicit drug use at the population level. Transformation processes during transport in sewers (chemical and biological reactors) and storage of wastewater samples before analysis are expected to change concentrations of different drugs to varying degrees. Ignoring transformation for drugs with low to medium stability will lead to an unknown degree of systematic under- or overestimation of drug use, which should be avoided. This review aims to summarize the current knowledge related to the stability of commonly investigated drugs and, furthermore, suggest a more effective approach to future experiments. From over 100 WBE studies, around 50 mentioned the importance of stability and 24 included tests in wastewater. Most focused on in-sample stability (i.e., sample preparation, preservation and storage) and some extrapolated to in-sewer stability (i.e., during transport in real sewers). While consistent results were reported for rather stable compounds (e.g., MDMA and methamphetamine), a varying range of stability under different or similar conditions was observed for other compounds (e.g., cocaine, amphetamine and morphine). Wastewater composition can vary considerably over time, and different conditions prevail in different sewer systems. In summary, this indicates that more systematic studies are needed to: i) cover the range of possible conditions in sewers and ii) compare results more objectively. To facilitate the latter, we propose a set of parameters that should be reported for in-sewer stability experiments. Finally, a best practice of sample collection, preservation, and preparation before analysis is suggested in order to minimize transformation during these steps.
McCall, A. K., Scheidegger, A., Madry, M. M., Steuer, A. E., Weissbrodt, D. G., Vanrolleghem, P. A., … Ort, C. (2016). Influence of different sewer biofilms on transformation rates of drugs. Environmental Science and Technology, 50(24), 13351-13360. doi:10.1021/acs.est.6b04200, Institutional Repository

To estimate drug consumption more reliably, wastewater-based epidemiology would benefit from a better understanding of drug residue stability during in-sewer transport. We conducted batch experiments with real, fresh wastewater and sewer biofilms. Experimental conditions mimic small to medium-sized gravity sewers with a relevant ratio of biofilm surface area to wastewater volume (33 m2 m–3). The influences of biological, chemical, and physical processes on the transformation of 30 illicit drug and pharmaceutical residues were quantified. Rates varied among locations and over time. Three substances were not stable—that is, >20% transformation, mainly due to biological processes—at least for one type of tested biofilm for a residence time ≤2 h: amphetamine, 6-acetylcodeine, and 6-monoacetylmorphine. Cocaine, ecgonine methyl ester, norcocaine, cocaethylene, and mephedrone were mainly transformed by chemical hydrolysis and, hence, also unstable in sewers. In contrast, ketamine, norketamine, O-desmethyltramadol, diclofenac, carbamazepine, and methoxetamine were not substantially affected by in-sewer processes under all tested conditions and residence times up to 12 h. Our transformation rates include careful quantification of uncertainty and can be used to identify situations in which specific compounds are not stable. This will improve accuracy and uncertainty estimates of drug consumption when applied to the back-calculation.
Mutzner, L., Staufer, P., & Ort, C. (2016). Model-based screening for critical wet-weather discharges related to micropollutants from urban areas. Water Research, 104, 547-557. doi:10.1016/j.watres.2016.08.003, Institutional Repository

Wet-weather discharges contribute to anthropogenic micropollutant loads entering the aquatic environment. Thousands of wet-weather discharges exist in Swiss sewer systems, and we do not have the capacity to monitor them all. We consequently propose a model-based approach designed to identify critical discharge points in order to support effective monitoring.
We applied a dynamic substance flow model to four substances representing different entry routes: indoor (Triclosan, Mecoprop, Copper) as well as rainfall-mobilized (Glyphosate, Mecoprop, Copper) inputs. The accumulation on different urban land-use surfaces in dry weather and subsequent substance-specific wash-off is taken into account. For evaluation, we use a conservative screening approach to detect critical discharge points. This approach considers only local dilution generated onsite from natural, unpolluted areas, i.e. excluding upstream dilution.
Despite our conservative assumptions, we find that the environmental quality standards for Glyphosate and Mecoprop are not exceeded during any 10-min time interval over a representative one-year simulation period for all 2500 Swiss municipalities. In contrast, the environmental quality standard is exceeded during at least 20% of the discharge time at 83% of all modelled discharge points for Copper and at 71% for Triclosan. For Copper, this corresponds to a total median duration of approximately 19 days per year. For Triclosan, discharged only via combined sewer overflows, this means a median duration of approximately 10 days per year. In general, stormwater outlets contribute more to the calculated effect than combined sewer overflows for rainfall-mobilized substances. We further evaluate the Urban Index (Aurban,impervious/Anatural) as a proxy for critical discharge points: catchments where Triclosan and Copper exceed the corresponding environmental quality standard often have an Urban Index >0.03.
A dynamic substance flow analysis allows us to identify the most critical discharge points to be prioritized for more detailed analyses and monitoring. This forms a basis for the efficient mitigation of pollution.
Ryu, Y., Barceló, D., Barron, L. P., Bijlsma, L., Castiglioni, S., de Voogt, P., … Thomas, K. V. (2016). Comparative measurement and quantitative risk assessment of alcohol consumption through wastewater-based epidemiology: an international study in 20 cities. Science of the Total Environment, 565, 977-983. doi:10.1016/j.scitotenv.2016.04.138, Institutional Repository

Quantitative measurement of drug consumption biomarkers in wastewater can provide objective information on community drug use patterns and trends. This study presents the measurement of alcohol consumption in 20 cities across 11 countries through the use of wastewater-based epidemiology (WBE), and reports the application of these data for the risk assessment of alcohol on a population scale using the margin of exposure (MOE) approach. Raw 24-h composite wastewater samples were collected over a one-week period from 20 cities following a common protocol. For each sample a specific and stable alcohol consumption biomarker, ethyl sulfate (EtS) was determined by liquid chromatography coupled to tandem mass spectrometry. The EtS concentrations were used for estimation of per capita alcohol consumption in each city, which was further compared with international reports and applied for risk assessment by MOE. The average per capita consumption in 20 cities ranged between 6.4 and 44.3 L/day/1000 inhabitants. An increase in alcohol consumption during the weekend occurred in all cities, however the level of this increase was found to differ. In contrast to conventional data (sales statistics and interviews), WBE revealed geographical differences in the level and pattern of actual alcohol consumption at an inter-city level. All the sampled cities were in the "high risk" category (MOE < 10) and the average MOE for the whole population studied was 2.5. These results allowed direct comparisons of alcohol consumption levels, patterns and risks among the cities. This study shows that WBE can provide timely and complementary information on alcohol use and alcohol associated risks in terms of exposure at the community level.
Ryu, Y., Gracia-Lor, E., Bade, R., Baz-Lomba, J. A., Bramness, J. G., Castiglioni, S., … Thomas, K. V. (2016). Increased levels of the oxidative stress biomarker 8-iso-prostaglandin F2α in wastewater associated with tobacco use. Scientific Reports, 6, 1-7. doi:10.1038/srep39055, Institutional Repository

Wastewater analysis has been demonstrated to be a complementary approach for assessing the overall patterns of drug use by a population while the full potential of wastewater-based epidemiology has yet to be explored. F2-isoprostanes are a prototype wastewater biomarker to study the cumulative oxidative stress at a community level. In this work, 8-iso-prostaglandin F2α (8-iso-PGF2α) was analysed in raw 24 h-composite wastewater samples collected from 4 Norwegian and 7 other European cities in 2014 and 2015. Using the same samples, biomarkers of alcohol (ethyl sulfate) and tobacco (trans-3′-hydroxycotinine) use were also analysed to investigate any possible correlation between 8-iso-PGF2α and the consumption of the two drugs. The estimated per capita daily loads of 8-iso-PGF2α in the 11 cities ranged between 2.5 and 9.9 mg/day/1000 inhabitants with a population-weighted mean of 4.8 mg/day/1000 inhabitants. There were no temporal trends observed in the levels of 8-iso-PGF2α, however, spatial differences were found at the inter-city level correlating to the degree of urbanisation. The 8-iso-PGF2α mass load was found to be strongly associated with that of trans-3′-hydroxycotinine while it showed no correlation with ethyl sulfate. The present study shows the potential for 8-iso-PGF2α as a wastewater biomarker for the assessment of community public health.
Thomaidis, N. S., Gago-Ferrero, P., Ort, C., Maragou, N. C., Alygizakis, N. A., Borova, V. L., & Dasenaki, M. E. (2016). Reflection of socioeconomic changes in wastewater: licit and illicit drug use patterns. Environmental Science and Technology, 50(18), 10065-10072. doi:10.1021/acs.est.6b02417, Institutional Repository

The economic crisis plaguing Greece was expected to impact consumption of pharmaceuticals and illicit drugs – a priori to an unknown extent. We quantified the change of use for various classes of licit and illicit drugs by monitoring Athens’ wastewater from 2010 to 2014. A high increase in the use of psychoactive drugs was detected between 2010 and 2014, especially for antipsychotics (35-fold), benzodiazepines (19-fold), and antidepressants (11-fold). This directly reflects the perceived increase of incidences associated with mental illnesses in the population, as a consequence of severe socioeconomic changes. Other therapeutic classes, like antiepileptics, hypertensives, and gastric and ulcer drugs also showed an increase in use (from 2-fold increase for antiepileptics to 13-fold for hypertensives). In contrast, the overall use of antibiotics and NSAIDs decreased. For mefenamic acid, an almost 28-fold decrease was observed. This finding is likely related to the reduction in drug expenditure applied in public health. A 2-fold increase of methamphetamine use was detected, associated with a cheap street drug called ″sisa″ (related to marginal conducts), which is a health concern. MDMA (5-fold) and methadone (7-fold) use showed also an increase, while cocaine and cannabis estimates did not show a clear trend.
Van Dyken, E., Lai, F. Y., Thai, P. K., Ort, C., Bruno, R., Hall, W., … Prichard, J. (2016). Challenges and opportunities in using wastewater analysis to measure drug use in a small prison facility. Drug and Alcohol Review, 35(2), 138-147. doi:10.1111/dar.12156, Institutional Repository

Introduction and Aims. Wastewater analysis (WWA) is intended to be a direct and objective method of measuring substance use in large urban populations. It has also been used to measure prison substance use in two previous studies. The application of WWA in this context has raised questions as to how best it might be used to measure illicit drug use in prisons, and whether it can also be used to measure prescription misuse. We applied WWA to a small regional prison to measure the use of 12 licit and illicit substances. We attempted to measure the non-medical use of methadone and buprenorphine and to compare our findings with the results of the prison's mandatory drug testing (MDT). Design and Methods. Representative daily composite samples were collected for two periods of 12 consecutive days in May to July 2013 and analysed for 18 drug metabolites. Prescription data and MDT results were obtained from the prison and compared with the substance use estimates calculated from WWA data. Results. Daily use of methamphetamine, methadone, buprenorphine and codeine was detected, while sporadic detection of ketamine and methylone was also observed. Overall buprenorphine misuse appeared to be greater than methadone misuse. Discussion and Conclusions. Compared with MDT, WWA provides a more comprehensive picture of prison substance use. WWA also has the potential to measure the misuse of medically prescribed substances. However, a great deal of care must be exercised in quantifying the usage of any substance in small populations, such as in prisons.
Lai, F. Y., Anuj, S., Bruno, R., Carter, S., Gartner, C., Hall, W., … Ort, C. (2015). Systematic and day-to-day effects of chemical-derived population estimates on wastewater-based drug epidemiology. Environmental Science and Technology, 49(2), 999-1008. doi:10.1021/es503474d, Institutional Repository

Population size is crucial when estimating population-normalized drug consumption (PNDC) from wastewater-based drug epidemiology (WBDE). Three conceptually different population estimates can be used: de jure (common census, residence), de facto (all persons within a sewer catchment), and chemical loads (contributors to the sampled wastewater). De facto and chemical loads will be the same where all households contribute to a central sewer system without wastewater loss. This study explored the feasibility of determining a de facto population and its effect on estimating PNDC in an urban community over an extended period. Drugs and other chemicals were analyzed in 311 daily composite wastewater samples. The daily estimated de facto population (using chemical loads) was on average 32% higher than the de jure population. Consequently, using the latter would systemically overestimate PNDC by 22%. However, the relative day-to-day pattern of drug consumption was similar regardless of the type of normalization as daily illicit drug loads appeared to vary substantially more than the population. Using chemical loads population, we objectively quantified the total methodological uncertainty of PNDC and reduced it by a factor of 2. Our study illustrated the potential benefits of using chemical loads population for obtaining more robust PNDC data in WBDE.
Logar, I., Brouwer, R., Maurer, M., & Ort, C. (2015). Wert der Spurenstoffelimination. Eine ökonomische Analyse zum Ausbau Schweizer Abwasserreinigungsanlagen. Aqua & Gas, 95(2), 42-48. , Institutional Repository

Welchen Wert misst die Bevölkerung der Elimination von Mikroverunreinigungen in den Kläranlagen zu? Aus den Antworten von 1000 Deutschschweizern und Deutschschweizerinnen wurde der wirtschaftliche Nutzen des Ausbaus von Abwasserreinigungsanlagen abgeleitet. Der Vergleich mit den veranschlagten Kosten zeigt, dass der Ausbau in der Schweiz gerechtfertigt ist.
O'Brien, J. W., Thai, P. K., Brandsma, S. H., Leonards, P. E. G., Ort, C., & Mueller, J. F. (2015). Wastewater analysis of Census day samples to investigate per capita input of organophosphorus flame retardants and plasticizers into wastewater. Chemosphere, 138, 328-334. doi:10.1016/j.chemosphere.2015.06.014, Institutional Repository

The use of organophosphate esters (PFRs) as flame retardants and plasticizers has increased due to the ban of some brominated flame retardants. There is however some concern regarding the toxicity, particularly carcinogenicity and neurotoxicity, of some of the PFRs. In this study we applied wastewater analysis to assess use of PFRs by the Australian population. Influent samples were collected from eleven wastewater treatment plants (STPs) in Australia on Census day and analysed for PFRs using gas chromatography coupled with mass spectrometry (GC-MS). Per capita mass loads of PFRs were calculated using the accurate Census head counts. The results indicate that tris(2-butoxyethyl) phosphate (TBOEP) has the highest per capita input into wastewater followed by tris(2-chloroisopropyl) phosphate (TCIPP), tris(isobutyl) phosphate (TIBP), tris(2-chloroethyl) phosphate (TCEP) and tris(1,3-dichloroisopropyl) phosphate (TDCIPP). Similar PFR profiles were observed across the Australian STPs and a comparison with European and U.S. STPs indicated similar PFR concentrations. We estimate that approximately 2.1 mg person−1 day−1 of PFRs are input into Australian wastewater which equates to 16 tonnes per annum.
Been, F., Rossi, L., Ort, C., Rudaz, S., Delémont, O., & Esseiva, P. (2014). Population normalization with ammonium in wastewater-based epidemiology: application to illicit drug monitoring. Environmental Science and Technology, 48(14), 8162-8169. doi:10.1021/es5008388, Institutional Repository

Fluctuations in ammonium (NH4 +), measured as NH 4-N loads using an ion-selective electrode installed at the inlet of a sewage treatment plant, showed a distinctive pattern which was associated to weekly (i.e., commuters) and seasonal (i.e., holidays) fluctuations of the population. Moreover, population size estimates based on NH4-N loads were lower compared to census data. Diurnal profiles of benzoylecgonine (BE) and 11-nor-9-carboxy-δ9-tetrahydrocannabinol (THC-COOH) were shown to be strongly correlated to NH4-N. Characteristic patterns, which reflect the prolonged nocturnal activity of people during the weekend, could be observed for BE, cocaine, and a major metabolite of MDMA (i.e., 4-hydroxy-3- methoxymethamphetamine). Additional 24 h composite samples were collected between February and September 2013. Per-capita loads (i.e., grams per day per 1000 inhabitants) were computed using census data and NH4-N measurements. Normalization with NH4-N did not modify the overall pattern, suggesting that the magnitude of fluctuations in the size of the population is negligible compared to those of illicit drug loads. Results show that fluctuations in the size of the population over longer periods of time or during major events can be monitored using NH4-N loads: either using raw NH4-N loads or population size estimates based on NH 4-N loads, if information about site-specific NH4-N population equivalents is available.
Logar, I., Brouwer, R., Maurer, M., & Ort, C. (2014). Cost-benefit analysis of the Swiss national policy on reducing micropollutants in treated wastewater. Environmental Science and Technology, 48(21), 12500-12508. doi:10.1021/es502338j, Institutional Repository

Contamination of freshwater with micropollutants (MPs) is a growing concern worldwide. Even at very low concentrations, MPs can have adverse effects on aquatic ecosystems and possibly also on human health. Switzerland is one of the first countries to start implementing a national policy to reduce MPs in the effluents of municipal sewage treatment plants (STPs). This paper estimates the benefits of upgrading STPs based on public’s stated preferences. To assess public demand for the reduction of the environmental and health risks of MPs, we conducted a choice experiment in a national online survey. The results indicate that the average willingness to pay per household is CHF 100 (US$ 73) annually for reducing the potential environmental risk of MPs to a low level. These benefits, aggregated over households in the catchment of the STPs to be upgraded, generate a total annual economic value of CHF 155 million (US$ 113 million). This compares with estimated annual costs for upgrading 123 STPs of CHF 133 million (US$ 97 million) or CHF 86 (US$ 63) per household connected to these STPs. Hence, a cost-benefit analysis justifies the investment decision from an economic point of view and supports the implementation of the national policy in the ongoing political discussion.
O'Brien, J. W., Thai, P. K., Eaglesham, G., Ort, C., Scheidegger, A., Carter, S., … Mueller, J. F. (2014). A model to estimate the population contributing to the wastewater using samples collected on census day. Environmental Science and Technology, 48(1), 517-525. doi:10.1021/es403251g, Institutional Repository

An important uncertainty when estimating per capita consumption of, for example, illicit drugs by means of wastewater analysis (sometimes referred to as "sewage epidemiology") relates to the size and variability of the de facto population in the catchment of interest. In the absence of a day-specific direct population count any indirect surrogate model to estimate population size lacks a standard to assess associated uncertainties. Therefore, the objective of this study was to collect wastewater samples at a unique opportunity, that is, on a census day, as a basis for a model to estimate the number of people contributing to a given wastewater sample. Mass loads for a wide range of pharmaceuticals and personal care products were quantified in influents of ten sewage treatment plants (STP) serving populations ranging from approximately 3500 to 500 000 people. Separate linear models for population size were estimated with the mass loads of the different chemical as the explanatory variable: 14 chemicals showed good, linear relationships, with highest correlations for acesulfame and gabapentin. De facto population was then estimated through Bayesian inference, by updating the population size provided by STP staff (prior knowledge) with measured chemical mass loads. Cross validation showed that large populations can be estimated fairly accurately with a few chemical mass loads quantified from 24-h composite samples. In contrast, the prior knowledge for small population sizes cannot be improved substantially despite the information of multiple chemical mass loads. In the future, observations other than chemical mass loads may improve this deficit, since Bayesian inference allows including any kind of information relating to population size.
Ort, C., Eppler, J. M., Scheidegger, A., Rieckermann, J., Kinzig, M., & Sörgel, F. (2014). Challenges of surveying wastewater drug loads of small populations and generalizable aspects on optimizing monitoring design. Addiction, 109(3), 472-481. doi:10.1111/add.12405, Institutional Repository

Aims. Quantifying illicit drug loads through wastewater analysis (WWA) is an alternative approach to estimating population drug use. This study investigated the variability of daily drug loads in wastewater and their relationships to environmental factors over an extended period to: (i) explore the suitability of WWA in small populations and (ii) optimize the monitoring design for future studies.
Design, Setting, Participants. Daily wastewater samples (n = 1369 consecutive days) from a German village with approximately 7160 inhabitants.
Measurements. Samples were analysed for cocaine and benzoylecgonine with liquid chromatography-tandem mass spectrometry. Time-series analysis was used to explore the effects of weather and other factors on daily cocaine loads. Subsampling was used to assess monitoring design.
Findings. Cocaine loads [mean = 652 mgCOC/day, standard deviation (SD) = 498 mgCOC/day] increased over the study period, with higher values during winter and spring. Despite high day-to-day variation, loads were significantly higher during weekends [+161 mgCOC/day, 95% confidence interval (CI) = 115–207 mgCOC/day, P < 10−4] and days with frost (+114 mgCOC/day, 95% CI = 6–223 mgCOC/day, P = 0.039) or snow (+150 mgCOC/day, 95% CI = 46–253 mgCOC/day, P = 0.005). Annual means estimated from 1-week periods were subject to approximately 60% relative error. Increasing sample size and changing sampling from consecutive days to stratified random decreased this uncertainty.
Conclusions. Day-to-day variation and seasonality of drug loads from the few long-term wastewater studies available to date suggest that up to 56 stratified random samples are required to obtain reliable (expected uncertainty around 10%) annual estimates of drug loads. Successfully assessing changes in consumption patterns or relationships to external factors requires larger sample sizes than estimating annual means, which holds true for high-prevalence drugs in small communities and low-prevalence drugs in big cities.
Ort, C., Banta-Green, C. J., Bijlsma, L., Castiglioni, S., Emke, E., Gartner, C., … van Nuijs, A. L. N. (2014). Sewage-based epidemiology requires a truly transdisciplinary approach. GAIA: Ecological Perspectives for Science and Society, 23(3), 266-268. doi:10.14512/gaia.23.3.12, Institutional Repository

If asked whether you had consumed illicit drugs recently, would you admit it? If yes, could you precisely recall types of drug, times and amounts used? If you were the person commissioned with the task of quantifying drug use, what approach would you use given the social stigma attached with such behavior? We measure drug residues in sewage, which represents urine of entire populations, to provide an objective estimate of total drug use in a region. In transdisciplinary projects, sewage-based results provide valuable information at unrivaled spatiotemporal resolution complementing traditional data.
Ort, C., van Nuijs, A. L. N., Berset, J. D., Bijlsma, L., Castiglioni, S., Covaci, A., … Thomas, K. V. (2014). Spatial differences and temporal changes in illicit drug use in Europe quantified by wastewater analysis. Addiction, 109(8), 1338-1352. doi:10.1111/add.12570, Institutional Repository

Aims. To perform wastewater analyses to assess spatial differences and temporal changes of illicit drug use in a large European population.
Design. Analyses of raw wastewater over a 1-week period in 2012 and 2013.
Setting and Participants. Catchment areas of wastewater treatment plants (WWTPs) across Europe, as follows: 2012: 25 WWTPs in 11 countries (23 cities, total population 11.50 million); 2013: 47 WWTPs in 21 countries (42 cities, total population 24.74 million).
Measurements. Excretion products of five illicit drugs (cocaine, amphetamine, ecstasy, methamphetamine, cannabis) were quantified in wastewater samples using methods based on liquid chromatography coupled to mass spectrometry.
Findings. Spatial differences were assessed and confirmed to vary greatly across European metropolitan areas. In general, results were in agreement with traditional surveillance data, where available. While temporal changes were substantial in individual cities and years (P ranging from insignificant to <10−3), overall means were relatively stable. The overall mean of methamphetamine was an exception (apparent decline in 2012), as it was influenced mainly by four cities.
Conclusions. Wastewater analysis performed across Europe provides complementary evidence on illicit drug consumption and generally concurs with traditional surveillance data. Wastewater analysis can measure total illicit drug use more quickly and regularly than is the current norm for national surveys, and creates estimates where such data does not exist.
van Dyken, E., Thai, P., Lai, F. Y., Ort, C., Prichard, J., Bruno, R., … Mueller, J. F. (2014). Monitoring substance use in prisons: assessing the potential value of wastewater analysis. Science and Justice, 54(5), 338-345. doi:10.1016/j.scijus.2014.06.006, Institutional Repository

Prison substance use is a major concern for prison authorities and the wider community. Australia has responded to this problem by implementing the National Corrections Drug Strategy. Across Australia, the true extent of prison substance use cannot be determined. As a result, the effectiveness of the interventions employed as part of this strategy cannot be properly assessed. This has important implications for the allocation of corrective services resources and future policy development. This article explores the benefits and limitations, as well as the ethical and practical issues in using wastewater analysis (WWA) to measure levels of substance use in prisons. It reports results from the first application of WWA to an Australian prison, which supports the use of WWA in this context. Given the increasing concern for prescription misuse in prisons, we also highlight the novel use of WWA to measure the extent of prescription misuse by prisoners. The article concludes that as a result of its objectivity, sensitivity and cost-effectiveness, the use of WWA in prisons warrants further consideration in Australia.
Castiglioni, S., Bijlsma, L., Covaci, A., Emke, E., Hernández, F., Reid, M., … Zuccato, E. (2013). Evaluation of uncertainties associated with the determination of community drug use through the measurement of sewage drug biomarkers. Environmental Science and Technology, 47(3), 1452-1460. doi:10.1021/es302722f, Institutional Repository

The aim of this study was to integrally address the uncertainty associated with all the steps used to estimate community drug consumption through the chemical analysis of sewage biomarkers of illicit drugs. Uncertainty has been evaluated for sampling, chemical analysis, stability of drug biomarkers in sewage, back-calculation of drug use (specific case of cocaine), and estimation of population size in a catchment using data collected from a recent Europe-wide investigation and from the available literature. The quality of sampling protocols and analytical measurements has been evaluated by analyzing standardized questionnaires collected from 19 sewage treatments plants (STPs) and the results of an interlaboratory study (ILS), respectively. Extensive reviews of the available literature have been used to evaluate stability of drug biomarkers in sewage and the uncertainty related to back-calculation of cocaine use. Different methods for estimating population size in a catchment have been compared and the variability among the collected data was very high (7–55%). A reasonable strategy to reduce uncertainty was therefore to choose the most reliable estimation case by case. In the other cases, the highest uncertainties are related to the analysis of sewage drug biomarkers (uncertainty as relative standard deviation; RSD: 6–26% from ILS) and to the back-calculation of cocaine use (uncertainty; RSD: 26%). Uncertainty can be kept below 10% in the remaining steps, if specific requirements outlined in this work are considered. For each step, a best practice protocol has been suggested and discussed to reduce and keep to a minimum the uncertainty of the entire procedure and to improve the reliability of the estimates of drug use.
Clouzot, L., Choubert, J. M., Cloutier, F., Goel, R., Love, N. G., Melcer, H., … Vanrolleghem, P. A. (2013). Perspectives on modelling micropollutants in wastewater treatment plants. Water Science and Technology, 68(2), 448-461. doi:10.2166/wst.2013.272, Institutional Repository

Models for predicting the fate of micropollutants (MPs) in wastewater treatment plants (WWTPs) have been developed to provide engineers and decision-makers with tools that they can use to improve their understanding of, and evaluate how to optimize, the removal of MPs and determine their impact on the receiving waters. This paper provides an overview of such models, and discusses the impact of regulation, engineering practice and research on model development. A review of the current status of MP models reveals that a single model cannot represent the wide range of MPs that are present in wastewaters today, and that it is important to start considering classes of MPs based on their chemical structure or ecotoxicological effect, rather than the individual molecules. This paper identifies potential future research areas that comprise (i) considering transformation products in MP removal analysis, (ii) addressing advancements in WWTP treatment technologies, (iii) making use of common approaches to data acquisition for model calibration and (iv) integrating ecotoxicological effects of MPs in receiving waters.
Kaegi, R., Voegelin, A., Ort, C., Sinnet, B., Thalmann, B., Krismer, J., … Mueller, E. (2013). Fate and transformation of silver nanoparticles in urban wastewater systems. Water Research, 47(12), 3866-3877. doi:10.1016/j.watres.2012.11.060, Institutional Repository

Discharge of silver nanoparticles (Ag-NP) from textiles and cosmetics, todays major application areas for metallic Ag-NP, into wastewater is inevitable. Transformation and removal processes in sewers and wastewater treatment plants (WWTP) will determine the impact of Ag-NP on aquatic and terrestrial environments, via the effluents of the WWTP and via the use of digested sludge as fertilizer. We thus conducted experiments addressing the behavior of Ag-NP in sewers and in WWTP.
We spiked Ag-NP to a 5 km long main trunk sewer and collected 40 wastewater samples after 500 m, 2400 m and 5000 m each according to the expected travel times of the Ag-NP. Excellent mass closure of the Ag derived by multiplying the measured Ag concentrations times the volumetric flow rates indicate an efficient transport of the Ag-NP without substantial losses to the sewer biofilm. Ag-NP reacted with raw wastewater in batch experiments were sulfidized to roughly 15% after 5 h reaction time as revealed by X-ray absorption spectroscopy (XAS). However, acid volatile sulfide (AVS) concentrations were substantially higher in the sewer channel (100 μM) compared to the batch experiments (3 μM; still sufficient to sulfidize spiked 2 μM Ag) possibly resulting in a higher degree of sulfidation in the sewer channel. We further investigated the removal efficiency of 10 nm and 100 nm Ag- and gold (Au)-NP coated with citrate or polyvinylpyrrolidone in activated sludge batch experiments. We obtained very high removal efficiencies (∼99%) irrespective of size and coating for Ag- and Au-NP, the latter confirming that the particle type was of minor importance with respect to the degree of NP removal. We observed a strong size dependence of the sulfidation kinetics. We conclude that Ag-NP discharged to the wastewater stream will become sulfidized to various degrees in the sewer system and are efficiently transported to the WWTP. The sulfidation of the Ag-NP will continue in the WWTP, but primarily depending on the size the Ag-NP, may not be complete. Very high removal efficiencies in the WWTP will divert most of the Ag-NP mass flow to the digester and only a small fraction of the Ag will be released to surface waters.
Lai, F. Y., Bruno, R., Leung, H. W., Thai, P. K., Ort, C., Carter, S., … Mueller, J. F. (2013). Estimating daily and diurnal variations of illicit drug use in Hong Kong: a pilot study of using wastewater analysis in an Asian metropolitan city. Forensic Science International, 233(1-3), 126-132. doi:10.1016/j.forsciint.2013.09.003, Institutional Repository

The measurement of illicit drug metabolites in raw wastewater is increasingly being adopted as an approach to objectively monitor population-level drug use, and is an effective complement to traditional epidemiological methods. As such, it has been widely applied in western countries. In this study, we utilised this approach to assess drug use patterns over nine days during April 2011 in Hong Kong. Raw wastewater samples were collected from the largest wastewater treatment plant serving a community of approximately 3.5 million people and analysed for excreted drug residues including cocaine, ketamine, methamphetamine, 3,4-methylenedioxymethamphetamine (MDMA) and key metabolites using liquid chromatography coupled with tandem mass spectrometry. The overall drug use pattern determined by wastewater analysis was consistent with that have seen amongst people coming into contact with services in relation to substance use; among our target drugs, ketamine (estimated consumption: 1400–1600 mg/day/1000 people) was the predominant drug followed by methamphetamine (180–200 mg/day/1000 people), cocaine (160–180 mg/day/1000 people) and MDMA (not detected). The levels of these drugs were relatively steady throughout the monitoring period. Analysing samples at higher temporal resolution provided data on diurnal variations of drug residue loads. Elevated ratios of cocaine to benzoylecgonine were identified unexpectedly in three samples during the evening and night, providing evidence for potential dumping events of cocaine. This study provides the first application of wastewater analysis to quantitatively evaluate daily drug use in an Asian metropolitan community. Our data reinforces the benefit of wastewater monitoring to health and law enforcement authorities for strategic planning and evaluation of drug intervention strategies.
Lai, F. Y., Bruno, R., Hall, W., Gartner, C., Ort, C., Kirkbride, P., … Mueller, J. F. (2013). Profiles of illicit drug use during annual key holiday and control periods in Australia: wastewater analysis in an urban, a semi-rural and a vacation area. Addiction, 108(3), 556-565. doi:10.1111/add.12006, Institutional Repository

Aims: To examine changes in illicit drug consumption between peak holiday season (23 December-3 January) in Australia and a control period two months later in a coastal urban area, an inland semi-rural area and an island populated predominantly by vacationers during holidays. Design: Analysis of representative daily composite wastewater samples collected from the inlet of the major wastewater treatment plant in each area. Setting: Three wastewater treatment plants. Participants: Wastewater treatment plants serviced approximately 350 000 persons in the urban area, 120 000 in the semi-rural area and 1100-2400 on the island. Measurements: Drug residues were analysed using liquid chromatography coupled to a tandem mass spectrometer. Per capita drug consumption was estimated. Changes in drug use were quantified using Hedges' g. Findings: During the holidays, cannabis consumption in the semi-rural area declined (g=-2.8) as did methamphetamine (-0.8), whereas cocaine (+1.5) and ecstasy (+1.6) use increased. In the urban area, consumption of all drugs increased during holidays (cannabis +1.6, cocaine +1.2, ecstasy +0.8 and methamphetamine +0.3). In the vacation area, methamphetamine (+0.7), ecstasy (+0.7) and cocaine (+1.1) use increased, but cannabis (-0.5) use decreased during holiday periods. Conclusions: While the peak holiday season in Australia is perceived as a period of increased drug use, this is not uniform across all drugs and areas. Substantial declines in drug use in the semi-rural area contrasted with substantial increases in urban and vacation areas. Per capita drug consumption in the vacation area was equivalent to that in the urban area, implying that these locations merit particular attention for drug use monitoring and harm minimisation measures.
Lai, F. Y., Thai, P. K., O'Brian, J., Gartner, C., Bruno, R., Kele, B., … Mueller, J. F. (2013). Using quantitative wastewater analysis to measure daily usage of conventional and emerging illicit drugs at an annual music festival. Drug and Alcohol Review, 32(6), 594-602. doi:10.1111/dar.12061, Institutional Repository

Introduction and Aims. Wastewater analysis provides a non-intrusive way of measuring drug use within a population. We used this approach to determine daily use of conventional illicit drugs [cannabis, cocaine, methamphetamine and 3,4-methylenedioxymethamphetamine (MDMA)] and emerging illicit psychostimulants (benzylpiperazine, mephedrone and methylone) in two consecutive years (2010 and 2011) at an annual music festival. Design and Methods. Daily composite wastewater samples, representative of the festival, were collected from the on-site wastewater treatment plant and analysed for drug metabolites. Data over 2 years were compared using Wilcoxon matched-pair test. Data from 2010 festival were compared with data collected at the same time from a nearby urban community using equivalent methods. Results. Conventional illicit drugs were detected in all samples whereas emerging illicit psychostimulants were found only on specific days. The estimated per capita consumption of MDMA, cocaine and cannabis was similar between the two festival years. Statistically significant (P < 0.05; Z = −2.0–2.2) decreases were observed in use of methamphetamine and one emerging illicit psychostimulant (benzyl piperazine). Only consumption of MDMA was elevated at the festival compared with the nearby urban community. Discussion and Conclusions. Rates of substance use at this festival remained relatively consistent over two monitoring years. Compared with the urban community, drug use among festival goers was only elevated for MDMA, confirming its popularity in music settings. Our study demonstrated that wastewater analysis can objectively capture changes in substance use at a music setting without raising major ethical issues. It would potentially allow effective assessments of drug prevention strategies in such settings in the future.
Plósz, B. G., Benedetti, L., Daigger, G. T., Langford, K. H., Larsen, H. F., Monteith, H., … Vanrolleghem, P. A. (2013). Modelling micro-pollutant fate in wastewater collection and treatment systems: status and challenges. Water Science and Technology, 67(1), 1-15. doi:10.2166/wst.2012.562, Institutional Repository

This paper provides a comprehensive summary on modelling of micro-pollutants' (MPs) fate and transport in wastewater. It indicates the motivations of MP modelling and summarises and illustrates the current status. Finally, some recommendations are provided to improve and diffuse the use of such models. In brief, we conclude that, in order to predict the contaminant removal in centralised treatment works, considering the dramatic improvement in monitoring and detecting MPs in wastewater, more mechanistic approaches should be used to complement conventional, heuristic and other fate models. This is crucial, as regional risk assessments and model-based evaluations of pollution discharge from urban areas can potentially be used by decision makers to evaluate effluent quality regulation, and assess upgrading requirements, in the future.
Strähl, S., Ort, C., Siegrist, H., Thomann, M., Obrecht, J., & Kurz, E. (2013). Stickstoffelimination in Schweizer ARA. Weitere Entlastung der Oberflächengewässer. Aqua & Gas, 93(5), 74-84. , Institutional Repository

Mit dem Abwasser gelangen pro Jahr rund 41 000 t Stickstoff (N) in die Schweizer Kläranlagen. Davon werden heute etwa 18 000 t in den ARA eliminiert. Mit Hilfe einer Kombination von neu entwickelten Reinigungsverfahren, die zum Teil bereits gut etabliert und auf dem Stand der Technik sind, liessen sich die Oberflächengewässer im Inland um weitere 6600 t Stickstoff entlasten, wie die vorliegende Studie zeigt. Bei Ausschöpfung des Reduktionspotenzials in den 160 grösseren ARA ist mit Gesamtinvestitionen von 344 Mio. Franken und jährlichen Betriebskosten von 27 Mio. Franken zu rechnen.
Williams, M., Kumar, A., Ort, C., Lawrence, M. G., Hambly, A., Khan, S. J., & Kookana, R. (2013). The use of multiple tracers for tracking wastewater discharges in freshwater systems. Environmental Monitoring and Assessment, 185(11), 9321-9332. doi:10.1007/s10661-013-3254-8, Institutional Repository

The assessment of potential impacts of wastewater effluent discharges in freshwater systems requires an understanding of the likely degrees of dilution and potential zones of influence. In this study, four tracers commonly present in wastewater effluents were monitored to compare their relative effectiveness in determining areas in freshwater systems that are likely to be impacted by effluent discharges. The four tracers selected were the human pharmaceutical carbamazepine, anthropogenic gadolinium, fluorescent-dissolved organic matter (fDOM), and electrical conductivity (EC). The four tracers were monitored longitudinally in two distinct freshwater systems receiving wastewater effluents, where one site had a high level of effluent dilution (effluent <1 % of total flow) and the other site had a low level of effluent dilution (effluent ∼50 % of total flow). At both sites, the selected tracers exhibited a similar pattern of response intensity downstream of discharge points relative to undiluted wastewater effluent, although a number of anomalies were noted between the tracers. Both EC and fDOM are non-specific to human influences, and both had a high background response, relative to the highly sensitive carbamazepine and anthropogenic gadolinium responses, although the ease of measuring EC and fDOM would make them more adaptable in highly variable systems. However, the greater sensitivity and selectivity of carbamazepine and gadolinium would make their combination with EC and fDOM as tracers of wastewater effluent discharges highly desirable to overcome potential limitations of individual tracers.
Brewer, A. J., Ort, C., Banta-Green, C. J., Berset, J. D., & Field, J. A. (2012). Normalized diurnal and between-day trends in illicit and legal drug loads that account for changes in population. Environmental Science and Technology, 46(15), 8305-8314. doi:10.1021/es202447r, Institutional Repository

Drug concentrations in composite municipal wastewater samples and census-based estimates of population are used to derive daily loads of illicit substances that are indexed to population. However, such estimates do not provide information on the diurnal trends of substance excretion nor can they account for changes in population. To address these limitations, a series of 1 h composites created by sampling wastewater influent at 6 min intervals was collected over four consecutive days at a single wastewater treatment plant. Creatinine (a urinary indicator), caffeine, methamphetamine, benzoylecgonine (BZE), and cocaine were analyzed by liquid chromatography/tandem mass spectrometry (LC-MS/MS). Diurnal trends and between-day trends were substance specific and related to the number of estimated doses and excretory half-life. Normalization to creatinine yielded trends in substances that differed significantly from non-normalized trends by accounting for changes in population within the municipality studied. Increases in normalized substance excretion observed during early morning hours originate from individuals among the resident population of the municipality due to the absence of commuters.
Götz, C., Kase, R., Ort, C., Singer, H., & Bergmann, S. (2012). Mikroschadstoffe aus kommunalem Abwasser. Stoffflussmodellierung, Situationsanalyse und Reduktionspotenziale für Nordrhein-Westfalen. sine loco: sine nomine. , Institutional Repository

Mit 17,8 Millionen Einwohnern ist Nordrhein-Westfalen das bevölkerungsreichste Bundesland in Deutschland. Durch die hohe Besiedlungsdichte, insbesondere in industriellen Ballungsgebieten wie dem Ruhrgebiet, ist der Druck auf die Gewässer durch die Wassernutzung und Abwas-sereinleitung verhältnismäßig groß. Bei Niedrigwasser führen viele Gewässer einen Abwasseranteil (gereinigtes Abwasser aus kommunalen Kläranlagen) von mehr als 10%.
Mit dem gereinigten kommunalen Abwasser werden Rückstände von Arzneimitteln, Bioziden und Haushaltschemikalien, sogenannte Mikroschadstoffe, in die Oberflächengewässer einge-tragen. Aufgrund der hohen Abwasserbelastung der nordrhein-westfälischen Fliessgewässer, ist auch die Problematik der Mikroschadstoffe für Nordrhein-Westfalen von besonderer Rele-vanz. In diesem Projekt wurde für Arzneimittel und weitere Mikroschadstoffe aus kommunalen Kläranlagen mit einem Stoffflussmodell eine flächendeckende Übersicht zur Belastungslage erstellt und der aktuelle Handlungsbedarf aufgezeigt. Es wurden dabei rund 650 Kläranlagen mit einer Größe >50 Einwohnerwerten (EW) berücksichtigt. Mit dem Stoffflussmodell wurden sowohl die Stoffflüsse als auch die Konzentrationen im Gewässer direkt unterhalb der Einleit-stellen der Kläranlagen berechnet. [...]
Hall, W., Prichard, J., Kirkbride, P., Bruno, R., Thai, P. K., Gartner, C., … Mueller, J. F. (2012). An analysis of ethical issues in using wastewater analysis to monitor illicit drug use. Addiction, 107(10), 1767-1773. doi:10.1111/j.1360-0443.2012.03887.x, Institutional Repository

Aims: To discuss ethical issues that may arise in using WWA to monitor illicit drug use in the general population and in entertainment precincts, prisons, schools and work-places. Method: Review current applications of WWA and identify ethical and social issues that may be raised with current and projected future uses of this method. Results: Wastewater analysis (WWA) of drug residues is a promising method of monitoring illicit drug use that may overcome some limitations of other monitoring methods. When used for monitoring purposes in large populations, WWA does not raise major ethical concerns because individuals are not identified and the prospects of harming residents of catchment areas are remote. When WWA is used in smaller catchment areas (entertainment venues, prisons, schools or work-places) their results could, possibly, indirectly affect the occupants adversely. Researchers will need to take care in reporting their results to reduce media misreporting. Fears about possible use of WWA for mass individual surveillance by drug law enforcement officials are unlikely to be realized, but will need to be addressed because they may affect public support adversely for this type of research. Conclusions: Using wastewater analysis to monitor illicit drug use in large populations does not raise major ethical concerns, but researchers need to minimize possible adverse consequences in studying smaller populations, such as workers, prisoners and students.
Le Corre, K. S., Ort, C., Kateley, D., Allen, B., Escher, B. I., & Keller, J. (2012). Consumption-based approach for assessing the contribution of hospitals towards the load of pharmaceutical residues in municipal wastewater. Environment International, 45(1), 99-111. doi:10.1016/j.envint.2012.03.008, Institutional Repository

Hospitals are considered as major sources of pharmaceutical residues discharged to municipal wastewater, but recent experimental studies showed that the contribution of hospitals to the loads of selected, quantifiable pharmaceuticals in sewage treatment plant (STP) influents was limited. However such conclusions are made based on the experimental analysis of pharmaceuticals in hospital wastewater which is hindered by a number of factors such as access to suitable sampling sites, difficulties in obtaining representative samples and availability of analytical methods. Therefore, this study explores a refined and extended consumption-based approach to predict the contribution of six selected Australian hospitals to the loads of 589 pharmaceuticals in municipal wastewater. In addition, the possibility that hospital-specific substances are present at levels that may pose a risk for human health was evaluated. For 63 to 84% of the pharmaceuticals investigated, the selected hospitals are not a major point source with individual contributions likely to be less than 15% which is in line with previous experimental studies. In contrast, between 10 and 20% of the pharmaceuticals consumed in the selected hospitals are exclusively used in these hospitals. For these hospital-specific substances, 57 distinct pharmaceuticals may cause concerns for human health as concentrations predicted in hospital effluents are less than 100-fold lower than effect thresholds. However, when concentrations were predicted in the influent of the corresponding STP, only 12 compounds (including the antineoplastic vincristine, the antibiotics tazobactam and piperacillin) remain in concentration close to effect thresholds, but further decrease is expected after removal in STP, dilution in the receiving stream and drinking water treatment. The results of this study suggest that risks of human exposure to the pharmaceuticals exclusively administered in the investigated hospitals are limited and decentralised wastewater treatment at these sites would not have a substantial impact on pharmaceutical loads entering STPs, and finally the environment. Overall, our approach demonstrates a unique opportunity to screen for pharmaceuticals used in hospitals and identifying priority pollutants in hospital wastewater explicitly accounting for site-specific conditions. Being based on consumption and loads discharged by hospitals into municipal wastewater, it is not limited by 1) the big effort to obtain representative samples from sewers, 2) the availability of sensitive chemical analysis or 3) a pre-selection of consumption data (e.g. consumption volume).
McArdell, C. S., Ort, C., Kuroda, K., Singer, H., & Berg, M. (2012). Mass flux studies of polar organic micropollutants in water (pp. 30-32). Presented at the 10th United Nation University & Gwangju Institute of Science and Technology joint programme symposium "Southeast Asian transboundary environmental issues – contaminants and challenges". Bangkok, Thailand. , Institutional Repository

Two projects will be presented within this talk. First, a national wide model will be discussed for the prediction of mass flows of pharmaceuticals within the river system of Switzerland. Second, a mass flux study of organic micropollutants performed in rivers downstream of the Megacity Beijing will be presented.
Ort, C., & Scheidegger, A. (2012). Optimize sampling for micropollutants in urban drainage systems with pump stations - a conceptual hydraulic model. In D. Prodanović & J. Plavšić (Eds.), Urban drainage modelling. Proceedings of the ninth international conference on urban drainage modelling (p. (8 pp.). Belgrade: Faculty of Civil Engineering, University of Belgrade. , Institutional Repository

To date it is unknown how pumps in sewer systems influence micropollutant loads at the scale of minutes to hours. This is important to design sampling campaigns: i) collecting representative composite samples, ii) experimentally determining peak loads or iii) dynamically evaluating wastewater treatment plant performance.
Hydrodynamic models which could simulate pollutographs become available for an increasing number of catchments. However, computationally it remains demanding to run simulations at high temporal resolution for a large number of conduits. Furthermore, also in complex models pumps are typically only modelled as one conceptual node, i.e. no spatial differentiation only volume. Furthermore, particularly for micropollutants, long measured input time series at sufficiently high temporal resolution are missing. In this paper we present a conceptual model to assess any combination of sub-catchments and lift stations. In gravity systems the number of wastewater packets containing the substance of interest generated at the source - i.e. toilets and other household appliances - determines the variability of the pollutograph. However, in the effluent of sub-catchments with pumps, the variability is independent of the number of generated wastewater packets but heavily depending on the properties and operation of the lift station.
Prichard, J., Lai, F. Y., Kirkbride, P., Bruno, R., Ort, C., Carter, S., … Mueller, J. F. (2012). Measuring drug use patterns in Queensland through wastewater analysis. Trends & Issues in Crime and Criminal Justice, 442, 1-8. Retrieved from https://www.aic.gov.au/publications/tandi/tandi442, Institutional Repository

Illicit drug use results in considerable social and economic costs to Australia (Collins & Lapsley 2008) but the magnitude of use is inherently difficult to measure. Besides being a clandestine behaviour, drug use in the community is not static and can peak at certain events (such as music festivals; Hesse, Tutenges & Schliewe 2010) or celebratory times of the year (such as New Year Eve; van Nuijs et al. 2011). Drug trends are triangulated across monitoring systems that employ different research methods and a mix of strengths with respect to, among other things, timeliness, reliability, drug-specificity and sample size (see Griffith & Mounteney 2010).
Staufer, P., & Ort, C. (2012). Diffuse Einträge aus Siedlungen. Ergebnisse einer Situationsanalyse. Aqua & Gas, 92(11), 42-50. , Institutional Repository

Regenwassereinleitungen und Mischwasserentlastungen tragen erheblich zu den Frachten im Gewässer bei. Die Situationsanalyse charakterisiert diese Emissionen für Mikroverunreinigungen aus dem häuslichen Abwasser und dem Regenabfluss. Die Modellergebnisse weisen substanzabhängig auf kritische Stellen in kleinen und mittelgrossen Gewässern in verdichteten Siedlungsräumen hin.
Staufer, P., Mutzner, L., & Ort, C. (2012). Dynamic substance flow analysis of rainfall-mobilized micropollutants. In D. Prodanović & J. Plavšić (Eds.), Urban drainage modelling. Proceedings of the ninth international conference on urban drainage modelling (p. (14 pp.). Belgrade: Faculty of Civil Engineering, University of Belgrade. , Institutional Repository

Certain rainfall mobilized micropollutants have been found in relevant concentrations in various water bodies across Switzerland. To distinguish contributions by sewage treatment plants and combined sewer overflows, extensive and expensive measurement campaigns would be necessary. Indicators could be used to optimize such campaigns if they are able to give a sound estimate of the local emission. In this framework a dynamic substance flow analysis was carried out. It is able to use information on land-use to calculate the loads discharged via combined sewer overflows (CSOs). The overall model results show, that combined sewer overflow emissions of urban areas are an important contribution to the pollutant load in surface waters. Especially for pollutants washed off from impervious areas, such as roofs or facades, loads were estimated to be in the same range as the loads discharged towards the sewage treatment plants. E.g. for Mecroprop, which originates primarily from buildings and gardens, it was found, that CSOs are a major contributor to urban emissions. Referring to the load entering the sewer more than 70% of the load from buildings and more than 60% of the load originating from gardens leave the sewer systems via CSOs. Furthermore, the results showed that size of the population indicates the emission of Triclosan and Copper while the impervious area is an indicator for the release of Mecoprop and Glyphosat.
Staufer, P., & Ort, C. (2012). Mikroverunreinigungen aus diffusen Quellen. Faktenblatt „Diffuse Mikroverunreinigungs-Emissionen aus Siedlungen (DIMES)“. Dübendorf: Eawag. Das Wasserforschungs-Institut des ETH-Bereichs. , Institutional Repository

Dieses Faktenblatt hat die Ziele (i) den heutigen Kenntnisstand zu diffusen Emissionen von Mikroverunreinigungen aus Siedlungen zusammenzufassen und (ii) die Relevanz der Niederschlagswassereinleitungen auf lokaler und nationaler Ebene zu beurteilen. Dazu wurde Literatur ausgewertet und eine System- und Stoffflussanalyse durchgeführt. Die Untersuchung fokussiert auf diffuse urbane Stoff- und Quellenkombinationen, die über Mischwasserentlastungen und Regenwassereinleitungen (zusammen nachstehend als „Niederschlagswassereinleitungen“ bezeichnet) in die aquatische Umwelt gelangen. [...]
Sägesser, D. (2012). Transformation von Mikroverunreinigungen in der Kanalisation. Erstellung eines hydraulischen Modells als Grundlage (Bachelor thesis). 32 p. , Institutional Repository

Über die Transformation von Mikroverunreinigungen in Kanalisationssystemen ist bislang wenig bekannt. Aus diesem Grund will die vorliegende Bachelorarbeit aufzuzeigen, wie gross Abbauraten von solchen anthropogenen Stoffen sein müssten, damit am Ende eines Versuchskanals ein Abbau messbar ist. Dazu wurden mehrere Tracerexperimente ausgewertet. Die Tracerexperimente waren vorgängig von der EAWAG durchgeführt worden. Als Versuchskanal diente der fünf Kilometer lange Glattstollen, welcher das Abwasser durch den Zürichberg zur Abwasserreinigungsanlage Werdhölzli transportiert. Der Abwasserkanal ist für die Experimente ideal, da keine seitlichen Zuflüsse vorhanden sind.
Für die Auswertung der Tracerexperimente wurde das Computerprogramm Aquasim 2.1 verwendet. Der Abwasserkanal wurde sowohl als Advective-Diffusive Reactor Compartment (Modell 1) als auch als River-Section Compartment (Modell 2) modelliert. Anschliessend wurden die Modelle mittels Daten aus den Tracerexperimenten kalibriert. Als Grundlage dazu diente das Massenerhaltungsgesetz. Für die hydraulische Kalibrierung wurde bei beiden Modellen die Dispersion geschätzt. Zusätzlich wurde beim Modell 1 die Geschwindigkeit und beim Modell 2 der hydraulischen Widerstandsbeiwert nach Strickler ermittelt. Anschliessend wurde ein linearer Abbauprozess hinzugefügt. Durch das Variieren verschiedener Abbauraten konnte die verbleibende Konzentration fünf Kilometer nach Zudosierung berechnet und verglichen werden.
Das Modell 1 und 2 unterscheiden sich prinzipiell in der Wahl des Kompartiments. Gewisse Variablen müssen dadurch unterschiedlich definiert werden. Die Resultate zum Abbau indizieren, dass das Modell 2 genauere Ergebnisse liefert. Beide Modelle zeigen bei der Parameterschätzung ähnliche Resultate. Dies zeigt, dass auch die Modellierung des Kanals als Advektive-Diffusive Reactor Compartment (Modell 1) für eine solide Abschätzung der Parameter sowie zur Quantifizierung des Abbaus verwendet werden kann. Modell 1 ist insbesondere vorzuziehen, falls Angaben zum Durchmesser oder Gefälle fehlen.
Die Auswertung der Tracerversuche ergab, dass sich der Dispersionskoeffizient zwischen 0.11 – 0.29 m2/s befindet. Nach Rieckermann et al. (2005) ist in Abwasserkanälen ein mittlerer Dispersionskoeffizient von 0.16 m2/s üblich. Die ermittelten Werte sind somit durchaus realistisch.
Für die Quantifizierung des Abbaus wurden Abbauraten zwischen 0.1/d und 24/d betrachtet. Die Berechnungen ergaben, dass bei einer Abbaurate von 24/d am Ende des Versuchskanals etwa 90 % der Zudosiermenge abgebaut werden. Allerdings sind die Abbauraten von Mikroverunreinigungen viel geringer. Eine Abbaurate von 0.1/d oder noch kleiner ist realistischer (Joss et al., 2006). Dabei würden ungefähr 1.2 % abgebaut werden. Dies entspricht keinem erheblichen Abbau und könnte, je nach Substanz und Genauigkeit des Messinstruments, knapp oder gar nicht registriert werden.
Bei der Transformation von Mikroverunreinigungen in Abwasserkanälen spielt, neben dem Abbau, auch die Sorption eine Rolle. Durch die Erweiterung der Modelle mit einem Biofilm - Reaktor sowie einem Prozess, der die Sorption beschreibt, könnte das Verhalten der Mikroverunreinigungen in Kanalisationssytemen noch detaillierter betrachtet werden.
Thomas, K. V., Bijlsma, L., Castiglioni, S., Covaci, A., Emke, E., Grabic, R., … de Voogt, P. (2012). Comparing illicit drug use in 19 European cities through sewage analysis. Science of the Total Environment, 432, 432-439. doi:10.1016/j.scitotenv.2012.06.069, Institutional Repository

The analysis of sewage for urinary biomarkers of illicit drugs is a promising and complementary approach for estimating the use of these substances in the general population. For the first time, this approach was simultaneously applied in 19 European cities, making it possible to directly compare illicit drug loads in Europe over a 1-week period. An inter-laboratory comparison study was performed to evaluate the analytical performance of the participating laboratories. Raw 24-hour composite sewage samples were collected from 19 European cities during a single week in March 2011 and analyzed for the urinary biomarkers of cocaine, amphetamine, ecstasy, methamphetamine and cannabis using in-house optimized and validated analytical methods. The load of each substance used in each city was back-calculated from the measured concentrations. The data show distinct temporal and spatial patterns in drug use across Europe. Cocaine use was higher in Western and Central Europe and lower in Northern and Eastern Europe. The extrapolated total daily use of cocaine in Europe during the study period was equivalent to 356. kg/day. High per capita ecstasy loads were observed in Dutch cities, as well as in Antwerp and London. In general, cocaine and ecstasy loads were significantly elevated during the weekend compared to weekdays. Per-capita loads of methamphetamine were highest in Helsinki and Turku, Oslo and Budweis, while the per capita loads of cannabis were similar throughout Europe. This study shows that a standardized analysis for illicit drug urinary biomarkers in sewage can be applied to estimate and compare the use of these substances at local and international scales. This approach has the potential to deliver important information on drug markets (supply indicator).
Gottschalk, F., Ort, C., Scholz, R. W., & Nowack, B. (2011). Engineered nanomaterials in rivers - exposure scenarios for Switzerland at high spatial and temporal resolution. Environmental Pollution, 159(12), 3439-3445. doi:10.1016/j.envpol.2011.08.023, Institutional Repository

Probabilistic material flow analysis and graph theory were combined to calculate predicted environmental concentrations (PECs) of engineered nanomaterials (ENMs) in Swiss rivers: 543 river sections were used to assess the geographical variability of nano-TiO2, nano-ZnO and nano-Ag, and flow measurements over a 20-year period at 21 locations served to evaluate temporal variation. A conservative scenario assuming no ENM removal and an optimistic scenario covering complete ENM transformation/deposition were considered. ENM concentrations varied by a factor 5 due to uncertain ENM emissions (15%–85% quantiles of ENM emissions) and up to a factor of 10 due to temporal river flow variations (15%–85% quantiles of flow). The results indicate highly variable local PECs and a location- and time-dependent risk evaluation. Nano-TiO2 median PECs ranged from 11 to 1′623 ng L−1 (conservative scenario) and from 2 to 1′618 ng L−1 (optimistic scenario). The equivalent values for nano-ZnO and nano-Ag were by factors of 14 and 240 smaller.
Lai, F. Y., Ort, C., Gartner, C., Carter, S., Prichard, J., Kirkbride, P., … Mueller, J. F. (2011). Refining the estimation of illicit drug consumptions from wastewater analysis: co-analysis of prescription pharmaceuticals and uncertainty assessment. Water Research, 45(15), 4437-4448. doi:10.1016/j.watres.2011.05.042, Institutional Repository

Wastewater analysis is a promising monitoring tool to estimate illicit drug consumption at the community level. The advantage of this technique over traditional surveys and other surveillance methods has been emphasized in recent studies. However, there are methodological challenges that can affect reliability. The objectives of this study were to systematically reduce and assess uncertainties associated with sampling (through a stringent optimization of the sampling method) and the back calculation of per capita drug consumption (through a refined estimation of the number of people actively contributing to the wastewater in a given period). We applied continuous flow-proportional sampling to ensure the collection of representative raw wastewater samples. Residues of illicit drugs, opioids, prescription pharmaceuticals and one artificial sweetener were analyzed by liquid chromatography coupled with tandem mass spectrometry. A parameter estimating the number of people actively contributing to wastewater over a given period was calculated from the measured loads of prescription pharmaceuticals, their annual consumption and relative excretion data. For the calculation of substance loads in sewage, uncertainties were propagated considering five individual components: sampling, chemical analysis, flow measurements, excretion rates and the number of people contributing to the wastewater. The daily consumption per 1000 inhabitants was estimated to be almost 1000 mg for cannabis and several hundred mg for cocaine, methamphetamine and ecstasy. With the best sampling practice and current chemical analysis, we calculated the remaining uncertainty to be in the range of 20–30% (relative standard deviation, RSD) for the estimation of consumed drug masses in the catchment; RSDs for the per capita consumption were lower (14–24%), as one of the biggest uncertainty components (i.e. error in flow measurements) cancels out in the proposed method for the estimation of the number of people contributing to the daily wastewater volume. In this study, we provide methodological improvements that substantially enhance the reliability of the estimation method – a prerequisite for the application of this technique to meaningfully assess changes in drug consumption and the success of drug intervention strategies in future studies.
Rieckermann, J., Anta, J., Scheidegger, A., & Ort, C. (2011). Assessing wastewater micropollutant loads with Approximate Bayesian Computations. Environmental Science and Technology, 45(10), 4399-4406. doi:10.1021/es1030432, Institutional Repository

Wastewater production, like many other engineered and environmental processes, is inherent stochastic in nature and requires the use of complex stochastic models, for example, to predict realistic patterns of down-the-drain chemicals or pharmaceuticals and personal care products. Up until now, a formal method of statistical inference has been lacking for many of those models, where explicit likelihood functions were intractable. In this Article, we investigate Approximate Bayesian Computation (ABC) methods to infer important parameters of stochastic environmental models. ABC methods have been recently suggested to perform model-based inference in a Bayesian setting when model likelihoods are analytically or computationally intractable and have not been applied to environmental systems analysis or water quality modeling before. In a case study, we investigate the performance of three different algorithms to infer the number of wastewater pulses contained in three high-resolution data series of benzotriazole and total nitrogen loads in sewers. We find that all algorithms perform well and that the uncertainty in the inferred number of corresponding wastewater pulses varies between 6% and 28%. In our case, the results are more sensitive to substance characteristics than to catchment properties. Although the application of ABC methods requires careful tuning and attention to detail, they have a great general potential to update stochastic model parameters with monitoring data and improve their predictive capabilities.
Zimmermann, S. G., Wittenwiler, M., Hollender, J., Krauss, M., Ort, C., Siegrist, H., & von Gunten, U. (2011). Kinetic assessment and modeling of an ozonation step for full-scale municipal wastewater treatment: micropollutant oxidation, by-product formation and disinfection. Water Research, 45(2), 605-617. doi:10.1016/j.watres.2010.07.080, Institutional Repository

The kinetics of oxidation and disinfection processes during ozonation in a full-scale reactor treating secondary wastewater effluent were investigated for seven ozone doses ranging from 0.21 to 1.24 g O3 g−1 dissolved organic carbon (DOC). Substances reacting fast with ozone, such as diclofenac or carbamazepine (kP,O3 > 104 M−1), were eliminated within the gas bubble column, except for the lowest ozone dose of 0.21 g O3 g−1 DOC. For this low dose, this could be attributed to short-circuiting within the reactor. Substances with lower ozone reactivity (kP,O3 < 104 M−1 s−1) were only fully eliminated for higher ozone doses.
The predictions of micropollutant oxidation based on coupling reactor hydraulics with ozone chemistry and reaction kinetics were up to a factor of 2.5 higher than full-scale measurements. Monte Carlo simulations showed that the observed differences were higher than model uncertainties. The overestimation of micropollutant oxidation was attributed to a protection of micropollutants from ozone attack by the interaction with aquatic colloids. Laboratory-scale batch experiments using wastewater from the same full-scale treatment plant could predict the oxidation of slowly-reacting micropollutants on the full-scale level within a factor of 1.5. The Rct value, the experimentally determined ratio of the concentrations of hydroxyl radicals and ozone, was identified as a major contribution to this difference.
An increase in the formation of bromate, a potential human carcinogen, was observed with increasing ozone doses. The final concentration for the highest ozone dose of 1.24 g O3 g−1 DOC was 7.5 μg L−1, which is below the drinking water standard of 10 μg L−1. N-Nitrosodimethylamine (NDMA) formation of up to 15 ng L−1 was observed in the first compartment of the reactor, followed by a slight elimination during sand filtration. Assimilable organic carbon (AOC) increased up to 740 μg AOC L−1, with no clear trend when correlated to the ozone dose, and decreased by up to 50% during post-sand filtration. The disinfection capacity of the ozone reactor was assessed to be 1–4.5 log units in terms of total cell counts (TCC) and 0.5 to 2.5 log units for Escherichia coli (E. coli). Regrowth of up to 2.5 log units during sand filtration was observed for TCC while no regrowth occurred for E. coli. E. coli inactivation could not be accurately predicted by the model approach, most likely due to shielding of E. coli by flocs.
Abegglen, C., Escher, B., Hollender, J., Siegrist, H., von Gunten, U., Zimmermann, S., … Schärer, M. (2010). Ozonung von gereinigtem Abwasser zur Elimination von organischen Spurenstoffen. Großtechnischer Pilotversuch Regensdorf (Schweiz). KA: Korrespondenz Abwasser Abfall, 57(2), 155-160. doi:10.3242/kae2010.02.004, Institutional Repository

Within the framework of the “Micropoll Strategy” project of the Swiss Federal Environmental Agency, the suitability of ozonation as an additional treatment stage for the removal of organic trace elements was tested at the Regensdorf wastewater treatment plant. With ozone doses of 0.60 g O3/g DOC already, a large portion of the organic trace elements could no longer be detected in the plant run-off. Only for a few, very persistent compounds (like iodized radio-opaque substances or atrazine), the removal rates amounted to only about 50 percent, even with high ozone doses (1.16 g O3 /g DOC). Eco-toxicological methods were used to prove that a clear reduction in summary effects (like e.g. oestrogen effects or the effect of insecticides) took place. In two tests, negative effects were measured directly after ozonation, but they disappeared again after the final sand filter. Oxidation by-products (such as assimilable organic carbon or N-Nitrosodimethylamine [NDMA]) were also reduced through sand filtration. This underlines the importance of a biologically active stage downstream of the ozonation stage, for example a sand filtration stage. The pilot operation also showed that an ozonation stage at a municipal wastewater treatment plant is technically feasible and economically reasonable.
Ort, C., Lawrence, M. G., Rieckermann, J., & Joss, A. (2010). Sampling for pharmaceuticals and personal care products (PPCPs) and illicit drugs in wastewater systems: are your conclusions valid? A critical review. Environmental Science and Technology, 44(16), 6024-6035. doi:10.1021/es100779n, Institutional Repository

The analysis of 87 peer-reviewed journal articles reveals that sampling for pharmaceuticals and personal care products (PPCPs) and illicit drugs in sewers and sewage treatment plant influents is mostly carried out according to existing tradition or standard laboratory protocols. Less than 5% of all studies explicitly consider internationally acknowledged guidelines or methods for the experimental design of monitoring campaigns. In the absence of a proper analysis of the system under investigation, the importance of short-term pollutant variations was typically not addressed. Therefore, due to relatively long sampling intervals, potentially inadequate sampling modes, or insufficient documentation, it remains unclear for the majority of reviewed studies whether observed variations can be attributed to “real” variations or if they simply reflect sampling artifacts. Based on results from previous and current work, the present paper demonstrates that sampling errors can lead to overinterpretation of measured data and ultimately, wrong conclusions. Depending on catchment size, sewer type, sampling setup, substance of interest, and accuracy of analytical method, avoidable sampling artifacts can range from “not significant” to “100% or more” for different compounds even within the same study. However, in most situations sampling errors can be reduced greatly, and sampling biases can be eliminated completely, by choosing an appropriate sampling mode and frequency. This is crucial, because proper sampling will help to maximize the value of measured data for the experimental assessment of the fate of PPCPs as well as for the formulation and validation of mathematical models. The trend from reporting presence or absence of a compound in “clean” water samples toward the quantification of PPCPs in raw wastewater requires not only sophisticated analytical methods but also adapted sampling methods. With increasing accuracy of chemical analyses, inappropriate sampling increasingly represents the major source of inaccuracy. A condensed step-by-step Sampling Guide is proposed as a starting point for future studies.
Abegglen, C., Escher, B., Hollender, J., Koepke, S., Ort, C., Peter, A., … Rensch, D. (2009). Ozonung von gereinigtem Abwasser. Schlussbericht Pilotversuch Regensdorf. Dübendorf: Eawag. , Institutional Repository

Ozonation as an advanced treatment for micropollutant removal was tested full-scale on the wastewater treatment plant (WWTP) Regensdorf during 16 months. This experiment has been conducted within the project „Strategy Micropoll“ of the Swiss Federal Office for the Environment (FOEN). Ozonation eliminated a broad range of organic micropollutants and various ecotoxicological effects. The pilot study also showed that the implementation of an ozonation step in an existing WWTP is feasible, both technically and economically. [...]

Auf der Abwasserreinigungsanlage (ARA) Regensdorf wurde im Rahmen des Projekts „Strategie Micropoll“ des Bundesamts für Umwelt (BAFU) während 16 Monaten die Eignung der Ozonung als zusätzliche Reinigungsstufe für die Entfernung von Mikroverunreinigungen getestet. Dabei konnte ein breites Spektrum problematischer organischer Spurenstoffe entfernt werden. Gleichzeitig wurden verschiedene unerwünschte ökotoxikologische Wirkungen eliminiert. Der Versuchsbetrieb zeigte, dass eine Ozonungsstufe auf einer kommunalen ARA technisch machbar und wirtschaftlich vertretbar ist. [...]
Abegglen, C., Rosenstiel, R., Ort, C., & Schärer, M. (2009). Weitergehende Verfahren zur Elimination von organischen Spurenstoffen bei kommunalen Abwasserreinigungsanlagen. KA: Korrespondenz Abwasser Abfall, 56(6), 584-592. doi:10.3242/kae2009.06.003, Institutional Repository

Der Eintrag von organischen Spurenstoffen aus der Siedlungsentwässerung ist aktuell eine besondere Herausforderung für den Gewässerschutz. Im Rahmen des Projekts "Strategie Micro-Poll" des Schweizer Bundesamts für Umwelt werden weitergehende Maßnahmen auf Kläranlagen zur Reduktion des Eintrags problematischer Stoffe diskutiert. Dabei stehen zurzeit die Ozonung und die Behandlung mit Pulveraktivkohle im Vordergrund. In einer Teilstudie des Projekts wurden für sechs ausgewählte Kläranlagen unterschiedlicher Größe die Kosten für Bau und Betrieb dieser zwei Verfahren berechnet sowie die Kosten für Kläranlagen anderer Größen interpoliert. Die Mehrkosten gegenüber der herkömmlichen Reinigung belaufen sich, je nach Anlagengröße, auf 5 bis 25 Prozent. Anschließend wurden die Gesamtkosten für die Schweiz für verschiedene Szenarien bestimmt. Die Gesamtkosten für den Ausbau der größten Anlagen sowie der Ausbau aller Anlagen, bei denen das Qualitätsziel für Diclofenac im Gewässer überschritten ist, würden für die Schweiz auf 115 bis 180 Millionen Schweizer Franken pro Jahr oder 15 bis 24 Schweizer Franken pro Einwohner jährlich geschätzt. Die Mehrkosten werden somit als vertretbar angesehen. Für eine konkrete Umsetzung müssen im Einzelfall jedoch sorgfältige Kosten-Nutzen-Betrachtungen vorgenommen werden.
Escher, B. I., Bramaz, N., & Ort, C. (2009). JEM Spotlight: monitoring the treatment efficiency of a full scale ozonation on a sewage treatment plant with a mode-of-action based test battery. Journal of Environmental Monitoring, 11(10), 1836-1846. doi:10.1039/b907093a, Institutional Repository

Tertiary treatment of wastewater with ozone is a promising technique for removing residual micropollutants that remain after secondary biological treatment. We monitored the performance of a full-scale ozonation reactor on a sewage treatment plant in Switzerland with a screening battery of bioassays. Six toxicity endpoints were selected that covered non-specific toxicity, as well as selected receptor-mediated modes of action and reactive toxicity. Non-specific toxicity was assessed with two bioassays, the bioluminescence inhibition of the marine luminescent bacterium Vibrio Fischeri and the growth inhibition of the green algae Pseudokirchneriella subcapitata. Treatment efficiency was around 90% for the secondary treatment, but only 65% and 76% for the ozonation step in the two non-specific endpoints, respectively. This finding is consistent with this type of oxidation reaction because ozone only modifies the organic molecules but does not mineralize them fully leaving residual toxicity of the transformation products. In contrast, the specific receptor-mediated endpoints of inhibition of photosystem II in algae and estrogenicity were largely reduced by ozonation. While compounds inhibiting photosynthesis proved to be rather recalcitrant toward biological treatment with only 47% removal, an additional 86% removal by ozonation yielded an overall treatment efficiency in the entire treatment chain of 89%. The effect on estrogenicity, quantified with the yeast estrogen screen, was even more significant: A treatment efficiency of 95% in the secondary treatment, 86% during ozonation plus a small effect by biological sand filtration yielded an overall treatment efficiency of 99.5%. Insecticides that inhibit acetylcholinesterase were fairly resistant to degradation, but an overall treatment efficiency of 91% was achieved in two steps: 72% in biological treatment and 60% during ozonation. Finally, no significant genotoxicity was observed with the umuC test after ozonation, while the influent showed a genotoxic response when it was enriched by a factor of 15 to 60. Treatment efficiency increased with the ozone dose and remained virtually unchanged over ozone doses above 500 g ozone per kg dissolved organic carbon. The reduction of toxicity can be rationalized by the chemical oxidation processes likely to occur for each group of chemicals that are typical for a given mode of toxic action. For comparison, tertiary treatment with powdered activated carbon was also evaluated, which poses a viable alternative to ozonation with respect to removal of micropollutants.
Gälli, R., Schmidt-Kleikemper, J., Ort, C., & Schärer, M. (2009). Mikroverunreinigungen in den Gewässern. Bewertung und Reduktion der Schadstoffbelastung aus der Siedlungsentwässerung. Umwelt-Wissen: Vol. 0917. Retrieved from https://www.bafu.admin.ch/bafu/de/home/themen/wasser/publikationen-studien/publikationen-wasser/mikroverunreinigungen-in-den-gewaessern.html, Institutional Repository

Over the past few years a situation analysis on micropollutants in watercourses has been carried out on the initiative of the FOEN through various research projects. This report summarises the results of these studies.
The research groups obtained more detailed knowledge of the pollution situation, enabling them to make reliable model predictions and indicate possible options for action, their anticipated effects and the resultant costs –
with particular focus on the technical optimization of municipal waste water treatment. It became evident that significant reductions in micropollutant levels can only be made by combining a number of measures on multiple levels.
Hollender, J., Zimmermann, S. G., Koepke, S., Krauss, M., McArdell, C. S., Ort, C., … Siegrist, H. (2009). Elimination of organic micropollutants in a municipal wastewater treatment plant upgraded with a full-scale post-ozonation followed by sand filtration. Environmental Science and Technology, 43(20), 7862-7869. doi:10.1021/es9014629, Institutional Repository

The removal efficiency for 220 micropollutants was studied at the scale of a municipal wastewater treatment plant (WWTP) upgraded with post-ozonation followed by sand filtration. During post-ozonation, compounds with activated aromatic moieties, amine functions, or double bonds such as sulfamethoxazole, diclofenac, or carbamazepine with second-order rate constants for the reaction with ozone >104 M−1 s−1 at pH 7 (fast-reacting) were eliminated to concentrations below the detection limit for an ozone dose of 0.47 g O3 g−1 dissolved organic carbon (DOC). Compounds more resistant to oxidation by ozone such as atenolol and benzotriazole were increasingly eliminated with increasing ozone doses, resulting in >85% removal for a medium ozone dose (0.6 g O3 g−1 DOC). Only a few micropollutants such as some X-ray contrast media and triazine herbicides with second-order rate constants <102 M−1 s−1 (slowly reacting) persisted to a large extent. With a medium ozone dose, only 11 micropollutants of 55 detected in the secondary effluent were found at >100 ng L−1. The combination of reaction kinetics and reactor hydraulics, based on laboratory- and full-scale data, enabled a quantification of the results by model calculations. This conceptual approach allows a direct upscaling from laboratory- to full-scale systems and can be applied to other similar systems. The carcinogenic by-products N-nitrosodimethylamine (NDMA) (≤14 ng L−1) and bromate (<10 μg L−1) were produced during ozonation, however their concentrations were below or in the range of the drinking water standards. Furthermore, it could be demonstrated that biological sand filtration is an efficient additional barrier for the elimination of biodegradable compounds formed during ozonation such as NDMA. The energy requirement for the additional post-ozonation step is about 0.035 kWh m−3, which corresponds to 12% of a typical medium-sized nutrient removal plant (5 g DOC m−3).
Krauss, M., Longrée, P., Dorusch, F., Ort, C., & Hollender, J. (2009). Occurrence and removal of N-nitrosamines in wastewater treatment plants. Water Research, 43(17), 4381-4391. doi:10.1016/j.watres.2009.06.048, Institutional Repository

The presence of nitrosamines in wastewater might pose a risk to water resources even in countries where chlorination or chloramination are hardly used for water disinfection. We studied the variation of concentrations and removal efficiencies of eight N-nitrosamines among 21 full-scale sewage treatment plants (STPs) in Switzerland and temporal variations at one of these plants. N-nitrosodimethylamine (NDMA) was the predominant compound in STP primary effluents with median concentrations in the range of 5–20 ng/L, but peak concentrations up to 1 μg/L. N-nitrosomorpholine (NMOR) was abundant in all plants at concentrations of 5–30 ng/L, other nitrosamines occurred at a lower number of plants at similar levels. From concentrations in urine samples and domestic wastewater we estimated that human excretion accounted for levels of <5 ng/L of NDMA and <1 ng/L of the other nitrosamines in municipal wastewater, additional domestic sources for <5 ng/L of NMOR. Levels above this domestic background are probably caused by industrial or commercial discharges, which results in highly variable concentrations in sewage. Aqueous removal efficiencies in activated sludge treatment were in general above 40% for NMOR and above 60% for the other nitrosamines, but could be lower if concentrations were below 8–15 ng/L in primary effluent. We hypothesize that substrate competition in the cometabolic degradation explains the occurrence of such threshold concentrations. An additional sand filtration step resulted in a further removal of nitrosamines from secondary effluents even at low concentrations. Concentrations released to surface waters were largely below 10 ng/L, suggesting a low impact on Swiss water resources and drinking water generation considering the generally high environmental dilution and possible degradation. However, local impacts in case a larger fraction of wastewater is present cannot be ruled out.
Ort, C., & Siegrist, H. (2009). Assessing wastewater dilution in small rivers with high resolution conductivity probes. Water Science and Technology, 59(8), 1593-1601. doi:10.2166/wst.2009.174, Institutional Repository

Installation and maintenance of flow gauging stations to assess wastewater dilution in small creeks is expensive. The method outlined in this paper provides a flexible and cheap alternative for situations with dilution factors smaller than 10 and unambiguous flow direction. It is shown that conductivity profiles from three sampling locations enable accurate identification of the dilution factor with an uncertainty of ±10–30%. Furthermore, much insight can be gained on the temporal behavior of both, the receiving water and the wastewater treatment system by combined analysis of conductivity and temperature data. In this case study the data also enabled identification and tracking down of illegal polluters.
Ort, C., Hollender, J., Schaerer, M., & Siegrist, H. (2009). Model-based evaluation of reduction strategies for micropollutants from wastewater treatment plants in complex river networks. Environmental Science and Technology, 43(9), 3214-3220. doi:10.1021/es802286v, Institutional Repository

A model based on graph theory was developed to efficiently evaluate the impact of the effluent from 742 wastewater treatment plants (WWTPs) on micropollutant loading throughout all river catchments in Switzerland. Model results agree well with measured loads for 12 compounds in river water samples, revealing mean predictive accuracy factors between 0.8 and 3.4. Subsequently, pollutant concentrations were predicted for river sections downstream from 543 WWTPs where hydrological information was available, and compared with recent recommendations for water quality criteria. At base flow conditions, carbamazepine concentrations (parent compound only) are ubiquitously below a water quality criterion of 0.5 μg L−1. In contrast, the sum of diclofenac and its metabolites is expected to exceed the corresponding water quality criterion of 0.1 μg L−1 in 224 river sections. If diclofenac cannot be eliminated at the source, the model suggests a directed upgrade of 173 WWTPs to meet the condition that concentrations are never to exceed this water quality criterion.
Weissbrodt, D., Kovalova, L., Ort, C., Pazhepurackel, V., Moser, R., Hollender, J., … McArdell, C. S. (2009). Mass flows of X-ray contrast media and cytostatics in hospital wastewater. Environmental Science and Technology, 43(13), 4810-4817. doi:10.1021/es8036725, Institutional Repository

Little is known about the significance of hospitals as point sources for emission of organic micropollutants into the aquatic environment. A mass flow analysis of pharmaceuticals and diagnostics used in hospitals was performed on the site of a representative Swiss cantonal hospital. Specifically, we analyzed the consumption of iodinated X-ray contrast media (ICM) and cytostatics in their corresponding medical applications of radiology and oncology, respectively, and their discharge into hospital wastewater and eventually into the wastewater of the municipal wastewater treatment plant. Emission levels within one day and over several days were found to correlate with the pharmacokinetic excretion pattern and the consumed amounts in the hospital during these days. ICM total emissions vary substantially from day to day from 255 to 1259 g/d, with a maximum on the day when the highest radiology treatment occurred. Parent cytostatic compounds reach maximal emissions of 8−10 mg/d. A total of 1.1%, 1.4%, and 3.7% of the excreted amounts of the cytostatics 5-fluorouracil, gemcitabine, and 2′,2′-difluorodeoxyuridine (main metabolite of gemcitabine), respectively, were found in the hospital wastewater, whereas 49% of the total ICM was detected, showing a high variability among the compounds. These recoveries can essentially be explained by the high amount administered to out-patients (70% for cytostatics and 50% for ICM); therefore, only part of this dose is expected to be excreted on-site. In addition, this study emphasizes critical issues to consider when sampling in hospital sewer systems. Flow proportional sampling over a longer period is crucial to compute robust hospital mass flows.
Huset, C. A., Chiaia, A. C., Barofsky, D. F., Jonkers, N., Kohler, H. P. E., Ort, C., … Field, J. A. (2008). Occurrence and mass flows of fluorochemicals in the Glatt Valley watershed, Switzerland. Environmental Science and Technology, 42(17), 6369-6377. doi:10.1021/es703062f, Institutional Repository

Fluorochemicals are persistent contaminants that are globally distributed in air, water, sediments, and biota. Wastewater treatment plants (WWTPs) play an important role in mitigating pollutant releases from municipalities to aquatic and terrestrial environments. However, because WWTPs are point sources of fluorochemicals, it is important to understand their contribution to fluorochemical burdens in the greater context of watersheds. To this end, over a 1 week period, the mass flows of 11 fluorochemicals from seven WWTPs that discharge effluent into the Glatt River in Switzerland were measured and compared to the measured mass flows within the Glatt River. Overall, the fluorochemicals were not removed efficiently during wastewater treatment. Effluents from WWTPs and Glatt River water were dominated by perfluorooctane sulfonate, which was detected in all samples, followed by perfluorohexane sulfonate and perfluorooctanoate. The mass flows of fluorochemicals emanating from WWTPs were found to be conserved within the 35 km Glatt River, which indicates that input from the WWTPs is additive and that removal within the Glatt River is not significant. Per capita discharges of fluorochemicals were calculated from the populations served by the WWTPs studied; the values determined also account for the fluorochemical content of Lake Greifen (Greifensee), which is a lake at the headwaters of the Glatt River that also receives treated wastewater.
Ort, C., & Gujer, W. (2008). Sorption and high dynamics of micropollutants in sewers. Water Science and Technology, 57(11), 1791-1797. doi:10.2166/wst.2008.309, Institutional Repository

Down-the-drain household chemicals are mostly discharged intermittently (i.e. with water pulses, e.g. pharmaceuticals from toilet flushing) and well soluble micropollutants can, therefore, be subject to significantly high short-term fluctuations. It is not known how these fluctuations are attenuated by sorption to sewer sediments or biofilm. First, we investigated in this paper the effect of sorption for substances with high, medium and low affinity to particulate matter based on computational experiments. For substances with high Koc we found that the additional attenuation of a load pattern due to sorption is in the same order of magnitude as caused by dispersion in a typical main sewer. The mass flux between wastewater and the first biofilm layer was identified as the most sensitive parameter. Furthermore, the interplay of systematic, slow diurnal variations does not affect short-term fluctuations. Second, during rain events partial erosion of the biofilm can lead to increased micropollutant loads for substances with high Koc. This increase is in the same order of magnitude as diurnal variations of the loads in the liquid phase and the TSS.
Stamm, C., Alder, A. C., Fenner, K., Hollender, J., Krauss, M., McArdell, C. S., … Schneider, M. K. (2008). Spatial and temporal patterns of pharmaceuticals in the aquatic environment: a review. Geography Compass, 2(3), 920-955. doi:10.1111/j.1749-8198.2008.00104.x, Institutional Repository

In recent years, human and veterinary pharmaceuticals have received much attention as pollutants of water bodies or drinking water resources due to possible negative effects on humans or the ecosystem even at very low concentrations. Over the last 10 years, considerable progress has been made regarding the knowledge of the exposure of water bodies to those drugs. This review summarizes the present understanding in this broad and interdisciplinary field incorporating contributions ranging from trace analytics to spatially distributed modelling of point-source and diffuse pollution. It discusses the main factors and processes controlling the environmental fate of pharmaceuticals from their usage to their spatial and temporal occurrence in water bodies. The current research is still rather phenomenological and further advancement of the field requires more integrated, quantitative mass flux analyses. Such analyses should also consider the explicit incorporation of uncertainties that appropriately reflect the current limited understanding and data availability.
Ort, C., Siegrist, H., Hosbach, H., Studer, C., Morf, L., & Scheringer, M. (2007). Mikroverunreinigungen. Nationales Stoffflussmodell. GWA Gas, Wasser, Abwasser, 87(11), 853-859. , Institutional Repository

Sampling and analytical chemistry are costly, and therefore, measurements can only provide limited information in space and time on the occurrence of micropollutants in surface waters. What would the picture look like, if one measured in rivers downstream of all wastewater treatment plants? To make a prediction of pollutant loads from urban drainage a national mass flux model has been developed. For more than 100 wastewater treatment plants, the dilution factor of treated wastewater during dry weather conditions is smaller than 10. For specific substances, this can lead to the exceedance of critical concentrations in rivers. Furthermore, the model allows the calculation of different scenarios. Whole river catchments are taken inter consideration.
Ort, C., & Gujer, W. (2006). Sampling for representative micropollutant loads in sewer systems. Water Science and Technology, 54(6-7), 169-176. doi:10.2166/wst.2006.591, Institutional Repository

Most commercially available auto-sampling devices do not support a continuous flow-proportional sampling mode, which would conceptually be the best for collecting representative composite samples. Instead different discrete sampling modes are available. Household chemicals can show considerable random short-term variations. With the anticorrosive benzotriazole, relating to a middle-frequent household activity, we show that, besides an accurate flow meter, mainly three factors are decisive for the representativeness of a substance's average load: the substance's load pattern, the sampling frequency and the length of the composite sample. When the sampling intervals are 10 minutes or longer, errors in the order of ±40% (standard deviation) or more have to be accepted, if the substance of interest is contained in a low number of wastewater pulses (i.e. the level of household activity). This particularly holds true for specific pharmaceuticals e.g. carbamazepine. Ammonium would be less critical, because it relates to a larger number of sources in the same catchment.
Ort, C. (2006). Short-term dynamics of micropollutants in sewer systems (Doctoral dissertation). doi:10.3929/ethz-a-005256570, Institutional Repository

Introduction
A large number of substances, contained in pharmaceuticals, personal care products and other household chemicals, are comfortably disposed of in sanitary appliances. Collected in the sewer system and partly eliminated in wastewater treatment plants they are then released to a certain extent into the aquatic environment. Many of these compounds belong to the category of micropollutants, which can have adverse effects on living organisms already in very low concentrations. Since no clear causal relationship between observed changes of ecosystems and the presence of micropollutants could be established, scientists combine monitoring with laboratory data. While experiments in the laboratory can be performed under controlled conditions it is very difficult to assess the complex situation in the environment. It is not only a hand full of micropollutants, but rather hundreds. To measure environmental concentrations of all these compounds over a relevant period of time is impossible. Therefore, predictive models are needed to forecast environmental concentrations. The input to these kinds of models, are emission data. Their acquisition is a tedious task. [...]

Einleitung
Medikamente, Körperpflegemittel und viele andere Haushaltprodukte enthalten eine grosse Anzahl chemischer Substanzen. Diese werden nach ihrer Anwendung bequem in sanitären Einrichtungen wie Toilette, Bad, Geschirrspül- oder Waschmaschine entsorgt. Mit dem Abwasser werden sie in der Kanalisation gesammelt und in die Kläranlagen transportiert. Einige werden gut eliminiert, andere hingegen können nur teilweise oder gar nicht abgebaut werden und gelangen so in die natürlichen Gewässer. Viele dieser chemischen Verbindungen gehören zu Kategorie der so genannten „Mikroverunreinigungen“, welche bereits in tiefsten Konzentrationen negative Auswirkung auf aquatische Lebewesen haben können. Bis heute konnten keine eindeutigen Zusammenhänge zwischen dem Auftreten von Mikroverun-reinigungen und beobachteten Veränderungen aquatischer Populationen aufgezeigt werden. Deshalb kombinieren Wissenschaftler Laborergebnisse mit Umweltdaten. Während Labor-experimente unter weitest gehend kontrollierten Bedingungen durchgeführt werden können, ist es äusserst schwierig, die komplexe Situation in der Umwelt zu erfassen. Es handelt sich bei den Mikroverunreinigungen nicht nur um eine Hand voll, sondern eher um hunderte von kritischen Substanzen. Das Messen von Umweltkonzentrationen all dieser Stoffe über eine genügend lange Periode ist unmöglich. Darum braucht es Modelle, um diese Umwelt konzentrationen abschätzen zu können. Die Eingangsgrössen zu solchen Modellen sind Emissionsdaten. Diese zu erheben ist eine mühsame Aufgabe. [...]
Schärer, M., Müller, S., Carrard, M., Ort, C., Siegrist, H., Escher, B., … McArdell-Bürgisser, C. (2006). Projekt "Strategie MicroPoll". Strategie zur Reduktion von Mikroverunreinigungen. GWA Gas, Wasser, Abwasser, 86(7), 551-555. , Institutional Repository

In urbanized areas large quantities of synthetic organic compounds are being used which can inevitably enter both municipai waste water end receiving water bodies. Many of these substances can be detected in aqueous systems at very low concentrations (nano- to microgram per litre). These so-called rnicropollutants are seen as a further challenge tor the field of water protection. The new project «Strategy MicroPoll» of the Swiss Federal Office tor the Environment (FOEN) is gathering evidence to determine a basis for policy decision-making with regard to micropollutants in municipal waste water.
Neumann, M. B., Ort, C., Daebel, H., & Gujer, W. (2005). Legal criteria, variability and uncertainty in the design of CSO detention. In Vol. 1. Proceedings of the 5th international conference on sustainable techniques and strategies in urban water management (NOVATECH 2004) (pp. 391-398). sine loco: sine nomine. , Institutional Repository

The legal criteria for the design of CSO structures can be set at different levels of sophistication. Applying emission based criteria the performances of three design alternatives are compared by using different strategies to account for variability and parameter uncertainty. The importance of separating these two effects is highlighted and the decision processes are explored. Additionally, the consequences of different kind of criteria are discussed with respect to the stakeholders involved.

Les critères légaux pour le dimensionnement de bassins de rétention peuvent être placés à différents niveaux de sophistication. En appliquant un critère d'émission, trois alternatives de dimensionnement sont comparées en employant différentes stratégies de prise en compte de la variabilité et de l'incertitude de paramètre. L'importance de séparer ces deux effets est accentuée et les procédés de décision sont explorés. En outre, les conséquences de différents critères sont examinées en ce qui concerne les stakeholders.
Ort, C., Schaffner, C., Giger, W., & Gujer, W. (2005). Modeling stochastic load variations in sewer systems. Water Science and Technology, 52(5), 113-122. doi:10.2166/wst.2005.0122, Institutional Repository

In wastewater treatment and environmental risk assessments increasing attention is paid to the fate of micropollutants. These are time-consuming, expensive and difficult to detect and quantify. If a substance's load or concentration is subject to high dynamic fluctuations, it is demanding to take representative samples, especially when the "variation" is unknown. Therefore, we developed a concept to model stochastic load variations in sewer systems. We gathered readily available information from existing databases (population and consumption data) and combined it with the characteristics of household activities and appliances. We succeeded in predicting realistic short-term variations of benzotriazole (contained in dishwasher detergents) and validated them with a high-frequency measuring campaign. Benzotriazole stands as an example for other household chemicals, which cannot be measured so easily. All required information used within this case study is also available for other substances and catchments. This allows the forecast of stochastic load variations for many chemical compounds of interest. It helps to plan measuring campaigns, to estimate discharged loads from combined sewer overflows and to have a characteristic input for modeling purposes.
Rieckermann, J., Neumann, M., Ort, C., Huisman, J. L., & Gujer, W. (2005). Dispersion coefficients of sewers from tracer experiments. Water Science and Technology, 52(5), 123-133. doi:10.2166/wst.2005.0124, Institutional Repository

In this paper, 60 tracer experiments in 37 different sewer reaches have been analyzed for longitudinal dispersion under dry weather flow conditions. It was found that dispersion coefficients of sewers are two to three orders of magnitude smaller than those measured in rivers and do not differ much from system to system. Suitable equations were identified to predict reasonable dispersion coefficients in sewer reaches with uniform geometry and stable flow conditions, For engineering applications that require a high degree of accuracy the performance of tracer measurements is recommended.
Twerenbold, S. (2005). Charakterisierung von Abwasser – Fingerabdruck der Gesellschaft. Modellierung der Urinfracht-Schwankungen in der Kanalisation (Master thesis). 30 p. , Institutional Repository

In der vorliegenden Diplomarbeit geht es darum, die Schwankungen der Urinfracht in der Kanalisation zu untersuchen. Dazu wurde mittels eines mathematischen Modells ein Bezug zwischen der menschlichen Aktivität „urinieren“ und der Urinfracht in der Kanalisation hergestellt. Es geht dabei nicht darum den Tagesgang zu modellieren, sondern vielmehr aufzuzeigen, dass die Urinfracht in der Kanalisation starken kurzfristigen Schwankungen unterliegt und dass diese mit relativ geringem Aufwand vorhergesagt werden können. Mit einer Messkampagne soll überprüft werden, ob die modellierte Ganglinie mit der Realität übereinstimmt. Als Einzugsgebiet wurde das Dorf Wangen ZH gewählt. Beim gewählten Punkt in der Kanalisation sind 1063 Einwohner angeschlossen und die Fliessdistanz beträgt zwischen 52 und 965 Meter. Zur Modellierung der Urinfracht wurde ein bewusst einfach gehaltenes Advektions-Dispersions-Modell verwendet. Urin wird dabei durch den Parameter Stickstoff modelliert und gemessen. Dies ist möglich, da über 80% des in der Kanalisation vorhandenen Stickstoffs aus dem Urin stammt. Jeder Person wurde zufällig ein Zeitpunkt für den Toilettengang, eine Fliessdistanz, eine Urin-Stickstoff-Menge und eine Zeitdauer für den Urinpuls zugeteilt. Die Werte für diese Eigenschaften wurden aus der Literatur, einfachen Messungen und anderen Daten bestimmt. Die Urinpulse wurde dann um die Fliesszeit verschoben, einer Dispersion unterworfen und beim gewählten Punkt in der Kanalisation aufsummiert. Mit einer Monte Carlo Simulation wurden 200 Frachten-Ganglinien modelliert.
An einem Wochentag wurden zwischen 8:10 und 9:20 Uhr die Stickstoffkonzentration und der Durchfluss, im Abstand von 45 Sekunden, gemessen. Daraus wurde die Zeitreihe für die Urinfracht berechnet. Um die Messunsicherheiten zu berücksichtigen wurde ein mathematisches Modell erstellt, das jedem Wert der Zeitreihe zufällig eine Messabweichung zuteilt. Mit einer Monte Carlo Simulation wurden wiederum 200 Frachten-Ganglinien modelliert.
Anhand eines optischen Vergleiches und mit statistischen Kennwerten wurden die je 200 Frachten-Ganglinien miteinander verglichen. Sie zeigten optisch sowie für den Mittelwert, und damit für die Massenbilanz, eine sehr gute Übereinstimmung. Als weitere statistische Kennwerte dienten die Standardabweichung, die Anzahl der Nulldurchgänge sowie die Autokorrelation. In einem weiteren Analyse-Schritt wurden die Differenzen zwischen sich folgenden Werten der Ganglinien gebildet. Auch die Differenzen-Ganglinien wurden mit denselben statistischen Kennwerten untersucht. Für keinen dieser Kennwerte zeigten die gemessene und die modellierten Ganglinien eine starke Abweichung und für die meisten war die Übereinstimmung sehr gut.
Mit dieser Arbeit konnte gezeigt werden, dass das Muster der Urinfracht in der Kanalisation mit einem einfachen mathematischen Modell vorausgesagt werden kann. Für die Bestimmung der Parameter genügt es Angaben aus der Literatur und anderen vorhandenen Daten, sowie Werte aus einfachen Messungen zu verwenden. Die zeitintensivste Arbeit ist dabei die Literaturrecherche. Da das Modell einfach gehalten wurde, kann es ohne Probleme auf andere Einzugsgebiete oder Stoffe übertragen werden.
Für ein kleines Einzugsgebiet von gut 1000 Einwohnern konnte gezeigt werden, dass die Urinfracht starken kurzfristigen Schwankungen unterliegt. Innerhalb von gut 2 Minuten wurde eine Frachtzunahme um den Faktor 3 beobachtet. Diese kurzfristigen Frachten-Änderungen müssen bei Messkampagnen berücksichtigt werden, um grosse Fehler bei der Frachtenbestimmung zu vermeiden.

Jörg Rieckermann

Lechevallier, P., Neuenhofer, N., & Rieckermann, J. (2024). Die kontinuierliche Messung der Abwasserqualität mit Kameras – erste Erfahrungen aus Pilotversuchen. In Aqua Urbanica 2024. Urbanes niederschlagswassermanagement Herausforderungen - Möglichkeiten - Grenzen (pp. A1-A14). Graz: Aqua Urbanica. , Institutional Repository

Die kontinuierliche Überwachung von Abwassermenge und -qualität ist entscheidend für den Betrieb und die Optimierung von Abwassersystemen. Aktuelle Messtechniken zur Wasserqualitätsbestimmung, insbesondere im Rohabwasser, sind sehr wartungsintensiv und teuer. Hyperspektralkameras, die in der Fernerkundung und der Industrie eingesetzt werden, könnten eine vielversprechende Alternative zu herkömmlichen spektrometrischen oder ionenselektiven Sensoren darstellen. In einer sechsmonatigen Pilotstudie haben wir Abwasser in einem kleinen Einzugsgebiet mit einer industrietauglichen Hyperspektralkamera (VNIR) und getauchten Spektrometern (UV Vis) überwacht. Beide Systeme wurden anhand von Trübungsmessungen eines Online-Sensors und 467 Stichproben für Ammonium (NH4), Phosphat (PO4) sowie gelöstem organischen Kohlenstoff (DOC) kalibriert. Die Kalibrierung erfolgte mit einem Partial-Least-Squares-Modell. Die Hyperspektralkamera lieferte zufriedenstellende Trübungswerte (RMSE = 14,9 NTU), vergleichbar mit dem Spektrometer (11,7 NTU). Allerdings waren die Ergebnisse für NH4 (7.1 mg/l), PO4 (0.7 mg/l) und DOC (39.3 mg/l) jedoch weniger genau. Interessanterweise lieferte die Spektrometersonde präzisere Resultate für NH4 (4.3 mg/l). Die Studie zeigt das Potenzial der hyperspektralen Technologie für die kontinuierliche Abwasserqualitätsmessung. Vor allem bei der Hardware und den mechanistischen Modellen für den Lichttransport sehen wir Verbesserungspotenzial.
Lechevallier, P., Villez, K., Felsheim, C., & Rieckermann, J. (2024). Towards non-contact pollution monitoring in sewers with hyperspectral imaging. Environmental Science: Water Research and Technology, 10(5), 1160-1170. doi:10.1039/D3EW00541K, Institutional Repository

Monitoring water quality in sewers is challenging, particularly because state-of-the-art technologies require contact with the raw wastewater. The presence of fat, oil, grease, and solids makes automated grab sampling difficult and causes sensor fouling. To overcome these limitations, non-contact methods based on light reflectance, such as hyperspectral imaging (HSI), are gaining attention. However, HSI has never been tested for raw wastewater. To assess its accuracy for measuring pollution, we developed a laboratory setup and performed targeted experiments with a combination of raw and diluted wastewater, as well as synthetic turbidity stock solutions. We measured seven pollution variables: chemical oxygen demand, turbidity, dissolved organic compounds, ammonium, total nitrogen, phosphate, and sulphates. We used automated pixel selection and partial least squares regression to retrieve pollution information from the hyperspectral images. Our results, based on 144 samples, suggest that HSI can estimate pollution levels with a precision in the range of state-of-the-art absorbance spectrophotometric methods. Additionally, we found that the combination of pixel and wavelength selection, enabled by the hyperspectral data structure, significantly influences the performance of partial least square modelling. Overall, our findings indicate that HSI is a promising technology for non-contact monitoring of water quality in raw wastewater.
Micev, K., Steiner, J., Aydin, A., Rieckermann, J., & Delbruck, T. (2024). Measuring diameters and velocities of artificial raindrops with a neuromorphic event camera. Atmospheric Measurement Techniques, 17(1), 335-357. doi:10.5194/amt-17-335-2024, Institutional Repository

Hydrometers that measure size and velocity distributions of precipitation are needed for research and corrections of rainfall estimates from weather radars and microwave links. Existing optical disdrometers measure droplet size distributions, but underestimate small raindrops and are impractical for widespread always-on IoT deployment. We study the feasibility of measuring droplet size and velocity using a neuromorphic event camera. These dynamic vision sensors asynchronously output a sparse stream of pixel brightness changes. Droplets falling through the plane of focus of a steeply down-looking camera create events generated by the motion of the droplet across the field of view. Droplet size and speed are inferred from the hourglass-shaped stream of events. Using an improved hard disk arm actuator to reliably generate artificial raindrops with a range of small sizes, our experiments show maximum errors of 7% (mean absolute percentage error) for droplet sizes from 0.3 to 2.5mm and speeds from 1.3 to 8.0ms-1. Measurements with the same setup from a commercial PARSIVEL disdrometer show similar results. Both devices slightly overestimate the small droplet volume with a volume overestimation of 25% from the event camera measurements and 50% from the PARSIVEL instrument. Each droplet requires processing of 5000 to 50000 brightness change events, potentially enabling low-power always-on disdrometers that consume power proportional to the rainfall rate. Data and code are available at the paper website https://sites.google.com/view/dvs-disdrometer/home .
Regueiro-Picallo, M., Langeveld, J., Wei, H., Bertrand-Krajewski, J. L., & Rieckermann, J. (2024). Combining a daily temperature pattern analysis and a heat-pulse system to estimate sediment depths in sewer systems. Environmental Science: Water Research and Technology, 10(4), 922-935. doi:10.1039/d3ew00825h, Institutional Repository

Sediments in urban drainage systems (UDS) significantly impact their operation, so effective strategies are required to reduce their negative effects. Monitoring sediment accumulation provides valuable insights into sediment characteristics, sediment transport dynamics, and system performance. However, the effectiveness of monitoring systems is limited due to cost constraints and installation challenges. This study describes the development and application of a new system based on temperature dynamics to measure sediment depths in sewer systems. The methodology involves the analysis of temperature time series under dry weather flow conditions to identify harmonic patterns between wastewater and sediment-bed temperatures. These patterns are increasingly attenuated by increasing sediment depth. This study combines a system called MONitoring Temperatures in SEdiments (MONTSE), which integrates a dual-probe heat-pulse (DPHP) method to characterize sediment thermal properties, and a surrogate model, which includes temperature pattern analysis, to estimate sediment depths. Likewise, laboratory-scale experiments were performed to validate the temperature monitoring system and the surrogate model performance. The maximum absolute errors in measured sediment depths were less than 22 mm, and the uncertainty of the system was estimated at ±7.3 mm. Groundbreaking measurements of thermal properties of UDS sediments were also reported. Reliable information on sediment depths and properties was provided, so the system could significantly optimize sewer system operation and cleaning strategies.
Sitzenfrei, R., Annus, I., Langeveld, J., Rieckermann, J., & Rauch, W. (2024). Editorial: Developments and applications of IoT-based sensors for wastewater and drainage systems. Water Science and Technology, 89(4), iii-v. doi:10.2166/wst.2024.058, Institutional Repository
Preitner, K., Blanc, S., Honzatko, D., Kündig, C., Pad, P., Saeedi, S., … Dunbar, L. A. (2023). Intelligent multispectral vision system for non-contact water quality monitoring for wastewater. In B. Jalali & Kichi Kitayama (Eds.), Proceedings of SPIE: Vol. 12438. AI and optical data sciences IV (p. 124380V (13 pp.). doi:10.1117/12.2649921, Institutional Repository

Water quality monitoring in sewer networks remains a technical challenge even though water pollution and control are high priorities since decades. Current water quality monitoring usually analyzes samples in laboratories, allowing only sporadic measurements, or uses immersed sensors in the wastewater, leading to clogging and sensor fouling resulting in expense due to intensive maintenance. Both techniques thus have serious limitations.
Previous research showed that UV-Vis reflectance spectrometry can be used for non-contact monitoring of turbidity (TUR) and Chemical Oxygen Demand (COD), which are two key water quality indicators. Although spectrometer achieve high spectral resolution their limited spatial field of view is problematic for highly inhomogeneous surfaces as is the case wastewater.
In this study, we obtain beyond state-of-art measurement accuracies by combining machine learning techniques with increased spatial field-of-view Multi-Spectral Imaging (MSI) whilst substantially reducing the spectral resolution. We designed and built a dedicated setup with a monochromatic camera and an active illumination of thirteen LEDs covering the spectrum range of 200-700 nm. We acquired and calibrated data on 27 samples with different concentrations of TUR and COD. Machine learning regression models were trained and evaluated with the extracted spectra. We tested the Partial Least Square (PLS), Support Vector Machine (SVM) and Random Forest (RF). PLS regression performed best with excellent correlation coefficients (R2) of the 0.99 for TUR and 0.93 for COD. We obtained similar results with the SVM algorithm (R2 = 0.99 and 0.92), whilst RF had lower scores (R2 = 0.96 and 0.71).
Regueiro-Picallo, M., Anta, J., Naves, A., Figueroa, A., & Rieckermann, J. (2023). Towards urban drainage sediment accumulation monitoring using temperature sensors. Environmental Science: Water Research and Technology, 9, 3200-3212. doi:10.1039/d2ew00820c, Institutional Repository

Sewer sediments are among the main concerns related to urban drainage system management as they represent the largest contribution of suspended solid loads during rainfall events due to their resuspension. This study presents a novel methodology to detect and assess bed deposits in urban drainage systems based on temperature monitoring by using well-known thermodynamics and sediment properties. To illustrate the heat transfer processes in a liquid–sediment system and their relation to accumulation, a lab-scale experimental campaign was performed using sewer sediments and simulating water temperature gradients in sewers. Wastewater temperatures showed a marked daily pattern, while the presence of sediment dampened dynamics. Sediment thickness could therefore be estimated from the time evolution of the temperature differences measured between the bottom of the sediment bed and the water phase. Likewise, experimental data were used to calibrate a 1D heat transfer model, from which several sediment accumulation scenarios were simulated by using real wastewater temperature series. Thus, the influence of sediment properties on accumulation processes was assessed, and the range of potentially measurable sediments within an optimal range of [5–20] cm was identified. As a conclusion, temperature measurements and heat transfer model analysis can be used to approximate and monitor the sediments deposited in urban drainage systems. Future studies will extend the method to spatially-resolved sediment monitoring and active temperature sensing to improve sediment accumulation monitoring capabilities.
Tondera, K., Brelot, E., Fontanel, F., Cherqui, F., Ellerbæk Nielsen, J., Brüggemann, T., … Anta, J. (2023). European stakeholders' visions and needs for stormwater in future urban drainage systems. Urban Water Journal, 20(7), 831-843. doi:10.1080/1573062X.2023.2211559, Institutional Repository

Transitioning urban drainage systems to serve water-smart societies requires the involvement of different disciplines and stakeholders. However, stakeholders have different visions and needs from the transitioning process (e.g in terms of financing, policy adaptation and system management) these also vary between regions and countries. Identifying such different needs for stakeholders is necessary to propose practical adaptation strategies. Therefore, evidence of needs as reflected in policy papers and legislation in seven European countries was collected. Knowledgeable individuals in the urban drainage community were asked about their visions. Results show that whilst there is consensus on the challenges, visions on how to transition are diverse, indicating that more interaction between the different stakeholder groups is required to develop consensus. Additionally, organisational and legislative structures often slow down the necessary change processes.
Disch, A., Brupbacher, A., Lükewille, F., Manz, C., Kramer, S., Dürrenmatt, D., & Rieckermann, J. (2022). "RICHIE" - the virtual sewer worker for improved monitoring data quality, network maintenance and operation (p. (4 pp.). Presented at the 12th urban drainage modeling conference. Retrieved from https://udm2022.org/2021/11/09/richie-the-virtual-sewer-worker-for-improved-monitoring-data-quality-network-maintenance-and-operation/, Institutional Repository

We conclude that the data literacy gap is serious and will even be more difficult to overcome, when skilled workforce is missing due to over aging. Automating repetitive task does not only support high-level operator employees, but helps everyone who cannot program and does not intend to spend working time in front of a computer. This requires moving RICHIE away from a classical computer interface towards a mobile application. We will validate the acceptance and performance in a broad-based test including many operators.
Manny, L. (2022). Socio-technical challenges towards smart urban water systems (Doctoral dissertation). doi:10.3929/ethz-b-000578852, Institutional Repository

Globally, urbanization, climate change, and ageing assets affect urban water management. One potential solution is recognized in smart urban water systems, which rely on monitoring data from infrastructure elements, e.g., combined sewer overflows (CSOs). Such monitoring data provides evidence on system functioning and performance and allows a dynamic control to exploit all existing infrastructure capacities, for example during heavy rainfalls. As a result, smart urban water systems hold the potential to improve performance outcomes, to reduce environmental impacts on surface waters, and to manage infrastructures more efficiently.
However, despite the availability of digital technologies for monitoring, data transfer, and control, only few examples of smart urban water systems exist. Where monitoring data is already obtained, it is often not optimally handled. Potential reasons cannot be found at the technical level only, but require an understanding of smart urban water systems in their social and socio-technical dimensions. To achieve smart urban water systems, not only technical innovation, but also adaptations of the surrounding social system are needed. [...]
Manny, L., Angst, M., Rieckermann, J., & Fischer, M. (2022). Socio-technical networks of infrastructure management: network concepts and motifs for studying digitalization, decentralization, and integrated management. Journal of Environmental Management, 318, 115596 (14 pp.). doi:10.1016/j.jenvman.2022.115596, Institutional Repository

Networked infrastructure systems - including energy, transportation, water, and wastewater systems — provide essential services to society. Globally, these services are undergoing major transformative processes such as digitalization, decentralization, or integrated management. Such processes not only depend on technical changes in infrastructure systems but also include important social and socio-technical dimensions. In this article, we propose a socio-technical network perspective to study the ensemble of social actors and technical elements involved in an infrastructure system, and their complex relations. We conceptualize structurally explicit socio-technical networks of networked infrastructure systems based on methodological considerations from network analysis and draw on concepts from socio-technical system theories and social-ecological network studies. Based on these considerations, we suggest analytical methods to study basic network concepts such as density, reciprocity, and centrality in a socio-technical network. We illustrate socio-technical motifs, i.e., meaningful sub-structures in socio-technical networks of infrastructure management. Drawing on these, we describe how infrastructure systems can be analyzed in terms of digitalization, decentralization, and integrated management from a socio-technical network perspective. Using the example of urban wastewater systems, we illustrate an empirical application of our approach. The results of an empirical case study in Switzerland demonstrate the potential of socio-technical networks to promote a deeper understanding of complex socio-technical relations in networked infrastructure systems. We contend that such a deeper understanding could improve management practices of infrastructure systems and is becoming even more important for enabling future data-driven, decentralized, and more integrated infrastructure management.
Mathis, S., Gruber, J. M., Ebi, C., Bloem, S., Rieckermann, J., & Blumensaat, F. (2022). Energy self-sufficient systems for monitoring sewer networks. In ITG-Fachberichte: Vol. 303. Sensoren und Messsysteme. Beiträge der 21. ITG/GMA-Fachtagung (pp. 523-530). Berlin: VDE. , Institutional Repository

Underground infrastructure networks form the backbone of vital supply and disposal systems. However, they are under-monitored in comparison to their value. This is due, in large part, to the lack of energy supply for monitoring and data transmission. In this paper, we investigate a novel, energy harvesting system used to power underground sewer infrastructure monitoring networks. The system collects the required energy from ambient sources, such as temperature differences or residual light in sewer networks. A prototype was developed that could use either a thermoelectric generator (TEG) or a solar cell to capture the energy needed to acquire and transmit ultrasonic water level data via LoRaWAN. Real-world field trials were satisfactory and showed the potential power output, as well as, possibilities to improve the system. Using an extrapolation model, we proved that the developed solution could work reliably throughout the year.
Pastorek, J., Fencl, M., Rieckermann, J., & Bares, V. (2022). Precipitation estimates from commercial microwave links: practical approaches to wet-antenna correction. IEEE Transactions on Geoscience and Remote Sensing, 60, 4104409 (9 pp.). doi:10.1109/TGRS.2021.3110004, Institutional Repository

An inadequate correction for wet-antenna attenuation (WAA) often causes a notable bias in quantitative precipitation estimates (QPEs) from commercial microwave links (CMLs) limiting the usability of these rainfall data in hydrological applications. This article analyzes how WAA can be corrected without dedicated rainfall monitoring for a set of 16 CMLs. Using data collected over 53 rainfall events, the performance of six empirical WAA models was studied, both when calibrated to rainfall observations from a permanent municipal rain gauge network and when using model parameters from the literature. The transferability of WAA model parameters among CMLs of various characteristics has also been addressed. The results show that high-quality QPEs with a bias below 5% and root-mean-square error (RMSE) of 1 mm/h in the median could be retrieved, even from subkilometer CMLs where WAA is relatively large compared to raindrop attenuation. Models in which WAA is proportional to rainfall intensity provide better WAA estimates than constant and time-dependent models. It is also shown that the parameters of models deriving WAA explicitly from rainfall intensity are independent of CML frequency and path length and, thus, transferable to other locations with CMLs of similar antenna properties.
Regueiro-Picallo, M., Anta, J., Naves, A., & Rieckermann, J. (2022). Monitoring sewer sediment deposits with temperature sensors. In Proceedings of the IAHR world congress. IAHR world congress (pp. 1852-1857). doi:10.3850/IAHR-39WC2521711920221141, Institutional Repository

Sediment accumulation in urban drainage systems (UDS) is a serious problem, which requires costly maintenance and cleaning programmes. These tasks are often linked to previous experience, but there is no control strategy, nor a complete knowledge of the sediment transport processes. Attempts so far to monitor these processes have been based on techniques that require exhaustive work in their installation or in taking punctual field measurements. Therefore, sediment monitoring in UDS remains challenging. In this work, a new approach based in heat transfer processes is shown. For this purpose, high-resolution temperature data are used to detect sediments from changes in temperature dynamics between the fluid and the sediment bed deposits. A series of batch tests were carried out in adiabatic boxes with different thicknesses of real sewer sediments filled with water. Temperature sensors were installed in the water layer over the sediments and at the bottom of the sediment deposits. An additional sensor was deployed to control room temperature. Heat-cool pulses were programmed in the water layer to simulate water temperature oscillations. As a result, the temperature time series at the bottom of the sediment deposits were attenuated and time-shifted depending on the accumulated thickness above it. These results demonstrate the potential to monitoring sediment accumulation in UDS with passive temperature sensors. Further extensions to distributed temperature monitoring with fibre-optical sensors and active heating are currently being investigated.
Wani, O., Maurer, M., Rieckermann, J., & Blumensaat, F. (2022). Does distributed monitoring improve the calibration of urban drainage models? (p. (3 pp.). Presented at the 12th urban drainage modeling conference. Retrieved from https://udm2022.org/2021/11/09/does-distributed-monitoring-improve-the-calibration-of-urban-drainage-models/, Institutional Repository

We conclude that while distributed sensing of discharge and water level helps understanding the dynamics of the stormwater runoff, it is not always straightforward to make better predictive models of complex urban drainage networks using this data. This analysis - by delineating the bottlenecks towards informative inference - provides via-negativa recommendations for the placement of distributed sensors, when improved model performance is also one of the motivating factors for such data collection campaigns.
Disch, A., & Rieckermann, J. (Eds.). (2022). Grün statt grau. Mit Blau-Grünen Infrastrukturen gemeinsam die Siedlungsentwässerung der Zukunft planen. Aqua Urbanica 2022. Dübendorf: Eawag. , Institutional Repository
Barth, L., & Rieckermann, J. (2021). Messdatenbasierte Leistungsanalyse von Abflussregelungen. Aqua & Gas, 101(10), 42-50. , Institutional Repository

Abflussregelungen können oft kostengünstige Massnahmen sein, um den Gewässerschutz bei Regenwetter durch die bessere Auslastung der vorhandenen Infrastruktur zu verbessern. In Zukunft könnte die tatsächliche Leistung von Abflussregelungen mit Betriebsdaten und statistischen Methoden beurteilt werden. Eine verlässliche messdatenbasierte Leistungsanalyse von Regelungssystemen muss Variabilität und Unsicherheiten in den Messdaten berücksichtigen. Der «Potential Outcome»-Ansatz und flexible Regressionsmethoden, wie z. B. Random Forest, scheinen vielversprechende Lösungen zu sein, um den Effekt einer Abflussregelung zu schätzen.
Figueroa, A., Hadengue, B., Leitão, J. P., Rieckermann, J., & Blumensaat, F. (2021). A distributed heat transfer model for thermal-hydraulic analyses in sewer networks. Water Research, 204, 117649 (11 pp.). doi:10.1016/j.watres.2021.117649, Institutional Repository

Thermal-hydraulic considerations in urban drainage networks are essential to utilise available heat capacities from waste- and stormwater. However, available models are either too detailed or too coarse; fully coupled thermal-hydrodynamic modelling tools are lacking. To predict efficiently water-energy dynamics across an entire urban drainage network, we suggest the SWMM-HEAT model, which extends the EPA-StormWater Management Model with a heat-balance component. This enables conducting more advanced thermal-hydrodynamic simulation at full network scale than currently possible. We demonstrate the usefulness of the approach by predicting temperature dynamics in two independent real-world cases under dry weather conditions. We furthermore screen the sensitivity of the model parameters to guide the choice of suitable parameters in future studies. Comparison with measurements suggest that the model predicts temperature dynamics adequately, with RSR values ranging between 0.71 and 1.1. The results of our study show that modelled in-sewer wastewater temperatures are particularly sensitive to soil and headspace temperature, and headspace humidity. Simulation runs are generally fast; a five-day period simulation at high temporal resolution of a network with 415 nodes during dry weather was completed in a few minutes. Future work should assess the performance of the model for different applications and perform a more comprehensive sensitivity analysis under more scenarios. To facilitate the efficient estimation of available heat budgets in sewer networks and the integration into urban planning, the SWMM-HEAT code is made publicly available.
Manny, L., Duygan, M., Fischer, M., & Rieckermann, J. (2021). Barriers to the digital transformation of infrastructure sectors. Policy Sciences, 54, 943-983. doi:10.1007/s11077-021-09438-y, Institutional Repository

Digital technologies can be important to policy-makers and public servants, as these technologies can increase infrastructure performance and reduce environmental impacts. For example, utilizing data from sensors in sewer systems can improve their management, which in turn may result in better surface water quality. Whether such big data from sensors is utilized is, however, not only a technical issue, but also depends on different types of social and institutional conditions. Our article identifies individual, organizational, and institutional barriers at the level of sub-states that hinder the evaluation of data from sewer systems. We employ fuzzy-set Qualitative Comparative Analysis (fsQCA) to compare 23 Swiss sub-states and find that two barriers at different levels can each hinder data evaluation on their own. More specifically, either a lack of vision at the individual level or a lack of resources at the organizational level hinder the evaluation of data. Findings suggest that taking into account different levels is crucial for understanding digital transformation in public organizations.
Špačková, A., Bareš, V., Fencl, M., Schleiss, M., Jaffrain, J., Berne, A., & Rieckermann, J. (2021). A year of attenuation data from a commercial dual-polarized duplex microwave link with concurrent disdrometer, rain gauge, and weather observations. Earth System Science Data, 13(8), 4219-4240. doi:10.5194/essd-13-4219-2021, Institutional Repository

Commercial microwave links (CMLs) in telecommunication networks can provide relevant information for remote sensing of precipitation and other environmental variables, such as path-averaged drop size distribution, evaporation, or humidity. The CoMMon field experiment (COmmercial Microwave links for urban rainfall MONitoring) mainly focused on the rainfall observations by monitoring a 38 GHz dual-polarized CML of 1.85 km path length at a high temporal resolution (4 s), as well as a co-located array of five disdrometers and three rain gauges over 1 year. The dataset is complemented with observations from five nearby weather stations. Raw and pre-processed data, which can be explored with a custom static HTML viewer, are available at https://doi.org/10.5281/zenodo.4923125 (Špačková et al., 2021). The data quality is generally satisfactory for further analysis, and potentially problematic measurements are flagged to help the analyst identify relevant periods for specific study purposes. Finally, we encourage potential applications and discuss open issues regarding future remote sensing with CMLs.
Nagel, J. B., Rieckermann, J., & Sudret, B. (2020). Principal component analysis and sparse polynomial chaos expansions for global sensitivity analysis and model calibration: application to urban drainage simulation. Reliability Engineering and System Safety, 195, 106737 (16 pp.). doi:10.1016/j.ress.2019.106737, Institutional Repository

This paper presents an efficient surrogate modeling strategy for the uncertainty quantification and Bayesian calibration of a hydrological model. In particular, a process-based dynamical urban drainage simulator that predicts the discharge from a catchment area during a precipitation event is considered. The goal of the case study is to perform a global sensitivity analysis and to identify the unknown model parameters as well as the measurement and prediction errors. These objectives can only be achieved by cheapening the incurred computational costs, that is, lowering the number of necessary model runs. With this in mind, a regularity-exploiting metamodeling technique is proposed that enables fast uncertainty quantification. Principal component analysis is used for output dimensionality reduction and sparse polynomial chaos expansions are used for the emulation of the reduced outputs. Sobol’ sensitivity indices are obtained directly from the expansion coefficients by a mere post-processing. Bayesian inference via Markov chain Monte Carlo posterior sampling is drastically accelerated.
Naves, J., Rieckermann, J., Cea, L., Puertas, J., & Anta, J. (2020). Global and local sensitivity analysis to improve the understanding of physically-based urban wash-off models from high-resolution laboratory experiments. Science of the Total Environment, 709, 136152 (15 pp.). doi:10.1016/j.scitotenv.2019.136152, Institutional Repository

Physically-based urban wash-off models are a promising means of studying the transport of finer suspended solids and their associated pollutants during rain events, considering spatial and temporal heterogeneities. This study contributes to the understanding of these models through an in-depth sensitivity analysis to provide the necessary information to simplify the model and deal with parameter identifiability. First, based on twelve tailored high-resolution experiments, the accurate measurement of input variables was used to study the parameters of the Hairsine-Rose sediment transport model through a global sensitivity analysis. Using Standardized Regression Coefficients (SRC) and Extended Fourier Amplitude Sensitivity Test (EFAST) methods, the analysis showed that both the total washed-off mass and the TSS peaks concentration are highly sensitive to the critical mass, which considers the reduction in the detachment of particles when the sediment available decreases and is scattered over the surface. In addition, the rain- and flow-driven detachment parameters were presented as key for smaller and larger sediment particles, respectively. Then, those uncertainties that are associated in field studies with the determination of the model input variables were also considered by conducting a local sensitivity analysis. The initial load of sediment and the mean grain size were seen to be the most important variables, thus underlining the need for very accurate measurements here. Moreover, a precise definition of Harsine-Rose parameters is also necessary to achieve reliable results in order to work on treatment and management techniques to minimize the impact of urban surface contaminants on urban environments.
Rieckermann, J., Wettstein, M., Fritzsche, C., & Villez, K. (2020). Optimierung des Betriebs der ARA Basel und des Entwässerungsnetzes zur Reduktion von Entlastungen in den Rhein. Abschlussbericht für die ProRheno AG im Rahmen eines F&E-Projekts. Dübendorf: Eawag – Swiss Federal Institute of Aquatic Science and Technology. , Institutional Repository

Im Einzugsgebiet der ARA Basel haben sich in den letzten Jahren grundlegende Veränderungen in Bezug auf die ARA und das Kanalnetz ergeben. Dies eröffnet neue Handlungsoptionen, vor allem in Bezug auf fortgeschrittene Verfahrenstechniken, sowie Automations- und Regelungsstrategien. [...]
Villez, K., Del Giudice, D., Neumann, M. B., & Rieckermann, J. (2020). Accounting for erroneous model structures in biokinetic process models. Reliability Engineering and System Safety, 203, 107075 (8 pp.). doi:10.1016/j.ress.2020.107075, Institutional Repository

In engineering practice, model-based design requires not only a good process-based model, but also a good description of stochastic disturbances and measurement errors to learn credible parameter values from observations. However, typical methods use Gaussian error models, which often cannot describe the complex temporal patterns of residuals. Consequently, this results in overconfidence in the identified parameters and, in turn, optimistic reactor designs. In this work, we assess the strengths and weaknesses of a method to statistically describe these patterns with autocorrelated error models. This method produces increased widths of the credible prediction intervals following the inclusion of the bias term, in turn leading to more conservative design choices. However, we also show that the augmented error model is not a universal tool, as its application cannot guarantee the desired reliability of the resulting wastewater reactor design.
Blumensaat, F., Leitão, J. P., Ort, C., Rieckermann, J., Scheidegger, A., Vanrolleghem, P. A., & Villez, K. (2019). How urban storm- and wastewater management prepares for emerging opportunities and threats: digital transformation, ubiquitous sensing, new data sources, and beyond – a horizon scan. Environmental Science and Technology, 53(15), 8488-8498. doi:10.1021/acs.est.8b06481, Institutional Repository

Ubiquitous sensing will create many opportunities and threats for urban water management, which are only poorly understood today. To identify the most relevant trends, we conducted a horizon scan regarding how ubiquitous sensing will shape the future of urban drainage and wastewater management. Our survey of the international urban water community received an active response from both the academics and the professionals from the water industry. The analysis of the responses demonstrates that emerging topics for urban water will often involve experts from different communities, including aquatic ecologists, urban water system engineers and managers, as well as information and communications technology professionals and computer scientists. Activities in topics that are identified as novel will either require (i) cross-disciplinary training, such as importing new developments from the IT sector, or (ii) research in new areas for urban water specialists, for example, to help solve open questions in aquatic ecology. These results are, therefore, a call for interdisciplinary research beyond our own discipline. They also demonstrate that the water management community is not yet prepared for the digital transformation, where we will experience a data demand, i.e. a “pull” of urban water data into external services. The results suggest that a lot remains to be done to harvest the upcoming opportunities. Horizon scanning should be repeated on a routine basis, under the umbrella of an experienced polling organization.
Devasia-Metzger, J. R., Rieckermann, J., Ort, C., & Burkhardt, M. (2019). Vorhersage der Mecoprop-Dynamik im urbanen Regenwasserabfluss mit einem gekoppelten prozess-basierten Schmutzfrachtmodel. In M. Burkhardt & C. Graf (Eds.), Regenwasser weiterdenken - Bemessen trifft Gestalten. Tagungsband - Aqua Urbanica 2019 (pp. 46-53). Rapperswil: HSR Hochschule für Technik Rapperswil. , Institutional Repository

Bei Regenwetter werden viele potenziell toxische Schadstoffe aus Aussenhüllen von Gebäuden ausgewaschen und in die Gewässer eingetragen. Unklar ist allerdings, ob einfache lineare Auswaschfunktionen für Mikroschadstoffe aus Gebäudehüllen für Schmutzfrachtsimulationen ausreichend sind. Um Auswaschungen aus beregneten Gebäudehüllen dynamisch zu berechnen, wurde das "COnstruction Material LEAching Model" (COMLEAM) entwickelt, mit dem Mikroverunreinigungen prozess-basiert beschrieben werden. COMLEAM berücksichtigt allerdings keine Transportprozesse in der Siedlungsentwässerung, so dass es bislang nicht möglich ist, Umwelteinflüsse von Gebäudehüllen abzubilden. In dieser Studie wurde daher COMLEAM an das hydrodynamische Niederschlags-Abfluss Modell SWMM gekoppelt. Insbesondere wurden die Unterschiede von dynamischen und linearen Auswaschmodellen untersucht. Für die Verknüpfung der Modelle wurde eine neue Schnittstelle für COMLEAM programmiert, die sowohl einen Export von SWMM-kompatiblen Schmutzfracht-Zeitreihen, als auch Batch-Simulationen ermöglicht. Die Ergebnisse für eine Fallstudie in Fehraltorf (CH), wo Schmutzfrachten und Konzentrationen des Durchwurzelungsschutzmittels Mecoprop vorhergesagt wurden, zeigen grundsätzlich eine befriedigende Übereinstimmung mit zeitlich hochaufgelösten Daten aus einer Messkampagne. Langzeitprognosen mit dem dynamischen COMLEAM Modell liefern in unserem Fall signifikant unterschiedliche Ergebnisse als lineare Auswaschfunktionen. Allerdings sind diese Unterschiede, in unserem Fallbeispiel, ab einem Gebäudealter von 10 Jahren allerdings vernachlässigbar. Sensitivitätsanalyse deuten weiterhin darauf hin, dass Informationen zum Gebäudebestand, und insbesondere das Alter der Gebäude, sehr sensitiv auf die Simulationsresultate sind.
Disch, A., Scheidegger, A., Wani, O., & Rieckermann, J. (2019). Impact of different sources of precipitation data on urban rainfall-runoff predictions: a comparison of rain gauges, commercial microwave links and radar. In N. Peleg & P. Molnar (Eds.), Rainfall monitoring, modelling and forecasting in urban environments. Conference Proceedings UrbanRain18 (pp. 27-32). Zurich: ETH Zurich. , Institutional Repository

In this study, we investigate whether commercial microwave links (CML) can bridge the gap between rain gauge and radar. We performed a rainfall-runoff monitoring experiment with rain gauges, CMLs and weather radar in a small urbanized catchment during several months. The results of comparing rainfall data and resulting sewer flows suggest that quantitative precipitation estimates from CMLs require adjustment to local rain gauges to produce satisfactory results in a similar fashion as weather radar. In our study, CML with baseline removal and wet-antenna correction, but without adjustment, lead to substantial bias and underestimate rainfall-runoff ratios by more than 48% (Radar: ca. 40%). In contrast, adjusted CML produced results very similar to those from a dense rain gauge network and underestimated rainfall-runoff by about 11%. Further work is needed to better understand influential factors on the data quality of QPEs from CML. In addition, incentives are needed to motivate both telecommunication companies to provide CML data and weather service companies to use them in their products, i.e. commercializing information from opportunistic sensors.
Hopper, H., Dittmer, U., Gruber, G., & Rieckermann, J. (2019). Datenbasierte Planungs-, Betriebs- und Vollzugskonzepte zur nachhaltigen Regenwasserbehandlung. In J. Pinnekamp (Ed.), Gewässerschutz - Wasser - Abwasser: Vol. 250. 52. Essener Tagung für Wasserwirtschaft “Wasser und Gesundheit“ 20. bis 22. März 2019 im Eurogress Aachen (p. 26 (16 pp.). Aachen: Gesellschaft zur Förderung des Instituts für Siedlungswasserwirtschaft an der RWTH Aachen. , Institutional Repository
Manny, L., Fischer, M., Staufer, P., & Rieckermann, J. (2019). Saubere Gewässer dank Messdatenmanagement. Instrumente für einen guten Umgang mit Messdaten in der Schweizer Siedlungsentwässerung. Aqua & Gas, 99(1), 58-65. , Institutional Repository

Mit der fortschreitenden Digitalisierung gilt es heute als Stand der Technik, Messdaten über das Abwassersystem zu erheben, auszuwerten und zu archivieren. Wie der Wert von Messdaten für Betrieb, Planung und Leistungsüberprüfung ausgeschöpft werden kann, ist jedoch unklar. Um einen einheitlichen Einsatz von Messtechnik, z.B. an Regenüberlaufbecken, sowie einen guten Umgang mit erfassten Messdaten in der Schweizer Praxis zu schaffen, sind Anpassungen auf organisatorischer Ebene notwendig.
Pastorek, J., Fencl, M., Rieckermann, J., & Bareš, V. (2019). Commercial microwave links for urban drainage modelling: the effect of link characteristics and their position on runoff simulations. Journal of Environmental Management, 251, 109522 (11 pp.). doi:10.1016/j.jenvman.2019.109522, Institutional Repository

Commercial microwave links (CMLs), radio connections widely used in telecommunication networks, can provide path-integrated quantitative precipitation estimates (QPEs) which could complement traditional precipitation observations. This paper assesses the ability of individual CMLs to provide relevant QPEs for urban rainfall-runoff simulations and specifically investigates the influence of CML characteristics and position on the predicted runoff. The analysis is based on a 3-year-long experimental data set from a small (1.3 km2) urban catchment located in Prague, Czech Republic. QPEs from real world CMLs are used as inputs for urban rainfall-runoff predictions and subsequent modelling performance is assessed by comparing simulated runoffs with measured stormwater discharges. The results show that model performance is related to both the sensitivity of CML to rainfall and CML position. The bias propagated into the runoff predictions is inversely proportional to CML path length. The effect of CML position is especially pronounced during heavy rainfalls, when QPEs from shorter CMLs, located within or close to catchment boundaries, better reproduce runoff dynamics than QPEs from longer CMLs extending far beyond the catchment boundaries. Interestingly, QPEs averaged from all available CMLs best reproduce the runoff temporal dynamics. Adjusting CML QPEs to three rain gauges located 2–3 km outside of the catchment substantially reduces the bias in CML QPEs. Unfortunately, this compromises the ability of the CML QPEs to reproduce runoff dynamics during heavy rainfalls. More experimental case studies are necessary to provide specific recommendations on CML preprocessing methods tailored to different water management tasks, catchments and CML networks.
Wani, O., Scheidegger, A., Cecinati, F., Espadas, G., & Rieckermann, J. (2019). Exploring a copula-based alternative to additive error models—for non-negative and autocorrelated time series in hydrology. Journal of Hydrology, 575, 1031-1040. doi:10.1016/j.jhydrol.2019.06.006, Institutional Repository

Inaccurate description of uncertainty in the error models can cause biases in parameter estimation. When the parameters of the deterministic model and the error model are inferred jointly from the observations, the posterior converges to regions that reflect the processes in both high and low flows. If the nature of errors in low and high flows is different to the extent that the same error description cannot be used for both, biases in inference are introduced. In such cases, the parameter posterior will adjust to the region of the hydrograph with longer proportionate presence in the calibration time series. In this paper we demonstrate that the autoregressive order 1 (AR1) description of errors can lead to sub-optimally performing predictive models if the calibration period has substantial sections of inadequately modelled flows. Inference is performed within the Bayesian framework. We show this for a synthetic example as well as a case study. We also see that the predictive uncertainty bands that we get using the AR1 description can be overconfident and also admit negative values. To mitigate this, we analyze an alternative to additive error models. We use a distribution with a non-negative support, gamma in this study, reflecting the uncertainty in the system response at every time step. The gamma distribution is conditioned on the deterministic model output, which determines its mode and standard deviation. We capture autocorrelation in time using copulas. Given that copulas can capture dependence between different marginals, we use different specifications of the marginal distribution for high and low flows. The results show that 1) biases in parameter estimation can be reduced if a representative error description is attained using the flexibility of a copula-based likelihood. 2) The non-negative support allows to make more realistic uncertainty intervals for low flows. 3) However, the autocorrelation parameter in copulas severely interacts with the model and heteroscedasticity parameters. 4) While the formulation, in principle, should be of added value for parameter inference, in case of less informative priors, the flexibility of this description can produce non-robust inference.
Gresch, M., Manz, C., Hesse, K., & Rieckermann, J. (2018). Praxistaugliche Regelung von Entwässerungsnetzen - das Projekt INKA (pp. 1-12). Presented at the 3. Expertenforum Regenüberlaufbecken. Stuttgart: DWA-Landesverband Baden-Württemberg. , Institutional Repository

Im Rahmen eines Umwelttechnologieförderungsprojekts des Schweizerischen Bundesamts für Umwelt (BAFU) wurden verschiedene Werkzeuge für die bessere Ausnutzung der vorhandenen Abwasserinfrastruktur entwickelt. Als Kernstück des Projektes wurde ein generischer Abflussregler für die Bewirtschaftung von Entwässerungssystemen entwickelt und durch den Praxispartner eine Entwicklungsumgebung für konkrete Umsetzungen von Abflussregelungen geschaffen. Es stehen dabei verschiedene Zielfunktionen für die Abflussregelung zur Verfügung, darunter auch eine selbst-adaptierende Funktion. Des Weiteren wurden konkrete Software-Werkzeuge entwickelt, welche die praktische Projektierung und Implementation unterstützen. Dazu gehören zum Beispiel ein Screening-Tool zur Potenzialabschätzung und zur automatischen Datenanalyse von Betriebsdaten. Die Ergebnisse deuten auf ein beträchtliches Potential für Abflussregelungen in der Schweiz hin. Eher wissenschaftlich-orientierte Untersuchungen zeigen erstens, dass Schmutzfracht-basierte Regelung anhand von Ersatzparametern wie beispielswiese Temperatur oder Leitfähigkeit möglich sein können. Zweitens scheinen zur Leistungsüberprüfung von Abflussregelungen die Reduktion von Entlastungsvolumen alleine ungeeignet, da sie die Wirkung der Behandlungsanlagen auf den Gewässerschutz vermutlich unterschätzen.
Leitão, J. P., Carbajal, J. P., Rieckermann, J., Simões, N. E., Sá Marques, A., & de Sousa, L. M. (2018). Identifying the best locations to install flow control devices in sewer networks to enable in-sewer storage. Journal of Hydrology, 556, 371-383. doi:10.1016/j.jhydrol.2017.11.020, Institutional Repository

The activation of available in-sewer storage volume has been suggested as a low-cost flood and combined sewer overflow mitigation measure. However, it is currently unknown what the attributes for suitable objective functions to identify the best location for flow control devices are and the impact of those attributes on the results. In this study, we present a novel location model and efficient algorithm to identify the best location(s) to install flow limiters. The model is a screening tool that does not require hydraulic simulations but rather considers steady state instead of simplistic static flow conditions. It also maximises in-sewer storage according to different reward functions that also considers the potential impact of flow control device failure. We demonstrate its usefulness on two real sewer networks, for which an in-sewer storage potential of approximately 2,000 m3 and 500 m3 was estimated with five flow control devices installed.
Machac, D., Reichert, P., Rieckermann, J., Del Giudice, D., & Albert, C. (2018). Accelerating Bayesian inference in hydrological modeling with a mechanistic emulator. Environmental Modelling and Software, 109, 66-79. doi:10.1016/j.envsoft.2018.07.016, Institutional Repository

As in many fields of dynamic modeling, the long runtime of hydrological models hinders Bayesian inference of model parameters from data. By replacing a model with an approximation of its output as a function of input and/or parameters, emulation allows us to complete this task by trading-off accuracy for speed. We combine (i) the use of a mechanistic emulator, (ii) low-discrepancy sampling of the parameter space, and (iii) iterative refinement of the design data set, to perform Bayesian inference with a very small design data set constructed with 128 model runs in a parameter space of up to eight dimensions. In our didactic example we use a model implemented with the hydrological simulator SWMM that allows us to compare our inference results against those derived with the full model. This comparison demonstrates that iterative improvements lead to reasonable results with a very small design data set.
Manny, L., Fischer, M., & Rieckermann, J. (2018). Policy analysis for better protection of receiving waters during wet weather. Presented at the 11th international conference on urban drainage modelling (UDM 2018). Palermo, Italy. , Institutional Repository

Although CSOs are expensive infrastructures, which are important to reduce pollution from urban areas during wet weather, they are often not operated effectively. Despite of technical difficulties, major problems in CSO monitoring and performance assessment are caused by non-technical bottlenecks. Through a policy analysis we identified organisational and political problems as the biggest obstacles to the effective operation of CSOs. In addition, we investigated effective measures or incentives to overcome organisational and political obstacles. Our results suggest that a surprisingly high 84% of the CSOs operated by Swiss wastewater associations are monitored. In most cases the information is used to improve operation, but not for better planning or for regulatory performance assessment. The most desirable instrument seem to be legislative performance targets, which is preferred by both wastewater associations and cantonal stakeholders. From a political point of view, the cantonal authorities also consider a transfer of competences from the municipalities to the wastewater associations to be effective, i.e. wastewater associations should operate CSOs instead of municipalities. In contrast, Swiss associations prefer financial incentives, such as a one-off subsidy for the installation of CSO monitoring equipment. Before implementing certain instruments, and in particular regulatory instruments, we highly recommend to assess their impact on overall policy processes and individual stakeholders. In the long term, only the implementation of a carefully balanced, uniform strategy can overcome organizational and political barriers and thus can lead to effective success in water protection.
Manny, L., Fischer, M., & Rieckermann, J. (2018). Policy-Analyse für einen besseren Gewässerschutz bei Regenwetter. In T. G. Schmitt (Ed.), Schriftenreihe Wasser Infrastruktur Ressourcen: Vol. 1. Regenwasser in urbanen Räumen. aqua urbanica trifft RegenwasserTage 2018. Tagungsband (pp. 139-151). Kaiserslautern: Institut Wasser Infrastruktur Ressourcen. , Institutional Repository

Während für Kläranlagen gesetzlich festgelegte Einleitbedingungen existieren und Betreiber umfangreiche Jahresberichte an Behörden weiterleiten, sind über die Leistungsfähigkeit der Entwässerungsnetze und Sonderbauwerke in der Schweiz, trotz technischer Möglichkeiten durch die fortschreitende Digitalisierung, kaum Informationen vorhanden. Da es keine Eigenkontrollverordnungen gibt, wird der Einfluss von Mischwasserentlastungen aus Regenüberlaufbecken (RÜB) auf die Gewässerqualität bisher hauptsächlich modelliert und nur selten anhand von Messdaten tatsächlich überprüft. In dieser Studie fragen wir deshalb Abwasserverbände und kantonale Fachstellen, welche Informationen in der Schweiz vorhanden sind und wie sie mit Messdaten umgehen. Wir untersuchen zuerst, welche organisatorischen und politischen Hindernisse einem effektiveren Betrieb von RÜB entgegenstehen. Zweitens diskutieren wir wirksame Maßnahmen oder Anreize zur Überwindung dieser Hindernisse. Unsere Ergebnisse deuten darauf hin, dass in der Schweiz bereits 84% der RÜB, die sich im Betrieb von Abwasserverbänden befinden, messtechnisch überwacht werden. Leider werden diese Messdaten hauptsächlich zur Betriebsoptimierung erhoben und weder als Entscheidungsgrundlage verwendet, z.B. in dem sie ausgewertet, geprüft und anschließend archiviert werden, noch zur Erfolgskontrolle an Behörden weitergeleitet. Um langfristig eine vollständige Ausschöpfung des Werts von Messdaten zu erreichen, sollte eine einheitliche Strategie, wie z.B. die Einführung von Zielvorgaben für das Entlastungsverhalten von RÜB, entwickelt werden, damit keine „Daten-Müllberge" entstehen, sondern Messdaten sinnvoll genutzt und so zu einem verbesserten Gewässerschutz bei Regenwetter beitragen können.
Moy de Vitry, M., Schindler, K., Rieckermann, J., & Leitão, J. P. (2018). Sewer inlet localization in UAV image clouds: improving performance with multiview detection. Remote Sensing, 10(5), 706 (18 pp.). doi:10.3390/rs10050706, Institutional Repository

Sewer and drainage infrastructure are often not as well catalogued as they should be, considering the immense investment they represent. In this work, we present a fully automatic framework for localizing sewer inlets from image clouds captured from an unmanned aerial vehicle (UAV). The framework exploits the high image overlap of UAV imaging surveys with a multiview approach to improve detection performance. The framework uses a Viola–Jones classifier trained to detect sewer inlets in aerial images with a ground sampling distance of 3–3.5 cm/pixel. The detections are then projected into three-dimensional space where they are clustered and reclassified to discard false positives. The method is evaluated by cross-validating results from an image cloud of 252 UAV images captured over a 0.57-km2 study area with 228 sewer inlets. Compared to an equivalent single-view detector, the multiview approach improves both recall and precision, increasing average precision from 0.65 to 0.73. The source code and case study data are publicly available for reuse.
Wani, O. (2018). Statistical methods for better hydrologic predictions. Improving parameter and uncertainty estimation (Doctoral dissertation). doi:10.3929/ethz-b-000315756, Institutional Repository

Hydrologic systems are complex - constituting spatially distributed and temporally variable properties and processes. Such systems are generally modelled mathematically after some simplifying assumptions, for example, by aggregating certain variable properties and neglecting many subprocesses. These model structure deficits result in a mismatch between the real and the modelled system response, which entails uncertain predictions. In addition to model structure deficits, the presence of errors in model inputs and in the observations of system response contributes to the uncertainty in the estimation of model parameters. For risk-based decision making and for statistical hypothesis testing using these models, their uncertainties need to be adequately and explicitly stated. Furthermore, attempts need to be made to reduce these uncertainties. [...]

Hydrologische Systeme sind komplex - sie bilden räumlich verteilte und zeitlich veränderliche Eigenschaften und Prozesse ab. Solche Systeme werden mathematisch unter einigen vereinfachenden Annahmen modelliert, beispielsweise durch das Aggregieren bestimmter Variableneigenschaften und das Vernachlässigen einiger Teilprozesse. Diese Defizite in der Modellstruktur führen zu einer Diskrepanz zwischen realem und modelliertem System, was zu Vorhersagen mit grösserer Unsicherheiten führt. Weiterhin trägt das Auftreten von Fehlern in den Input-Parametern sowie in den simulierten Resultaten zu Unsicherheiten bei der Schätzung von Modellparametern bei. Für eine risikobasierte Entscheidungsfindung sowie für statistische Hypothesentests unter Verwendung der Modelle müssen Unsicherheiten angemessen und explizit angegeben und langfristig reduziert werden.
Zheng, F., Tao, R., Maier, H. R., See, L., Savic, D., Zhang, T., … Popescu, I. (2018). Crowdsourcing methods for data collection in geophysics: state of the art, issues, and future directions. Reviews of Geophysics, 56(4), 698-740. doi:10.1029/2018RG000616, Institutional Repository

Data are essential in all areas of geophysics. They are used to better understand and manage systems, either directly or via models. Given the complexity and spatiotemporal variability of geophysical systems (e.g., precipitation), a lack of sufficient data is a perennial problem, which is exacerbated by various drivers, such as climate change and urbanization. In recent years, crowdsourcing has become increasingly prominent as a means of supplementing data obtained from more traditional sources, particularly due to its relatively low implementation cost and ability to increase the spatial and/or temporal resolution of data significantly. Given the proliferation of different crowdsourcing methods in geophysics and the promise they have shown, it is timely to assess the state of the art in this field, to identify potential issues and map out a way forward. In this paper, crowdsourcing-based data acquisition methods that have been used in seven domains of geophysics, including weather, precipitation, air pollution, geography, ecology, surface water, and natural hazard management, are discussed based on a review of 162 papers. In addition, a novel framework for categorizing these methods is introduced and applied to the methods used in the seven domains of geophysics considered in this review. This paper also features a review of 93 papers dealing with issues that are common to data acquisition methods in different domains of geophysics, including the management of crowdsourcing projects, data quality, data processing, and data privacy. In each of these areas, the current status is discussed and challenges and future directions are outlined.
Blumensaat, F., Ebi, C., Dicht, S., Rieckermann, J., & Maurer, M. (2017). IoT driven low-power radio technology for highly distributed in-sewer monitoring - a data collection technique that shifts paradigms?. In 14th IWA/IAHR international conference on urban drainage. Conference proceedings (pp. 1542-1547). Prague: c-in. , Institutional Repository

Urban drainage systems traditionally lack adequate monitoring and evaluation technologies. Although weather radar and high-resolution remote sensing technologies promise vast advances for rainfall and land-use data collection, it is still challenging to deploy dense hydrological monitoring networks for sewers. Low-power data transmission technology, which is the communication backbone in the Internet-Of-Things (IoT), has the potential to contribute to a game change towards an evidence-based management of urban drainage systems. In this paper, we share our experiences with establishing and operating a wireless sensor network (WSN) at full-scale with approximately a 1 sensor per hectare connected catchment area and a monitoring frequency of 5 minutes or less. Specifically, we discuss i) the monitoring and deployment approach and ii) the adequacy of sensorand LoRaWANTM wireless data transmission technology for monitoring applications in sewer networks. A thorough evaluation of the telemetry performance provides evidence that the proposed technique allows a highly distributed monitoring of drainage capacity, sewer infiltration, performance of retention basins and overflows, with a far less effort compared to conventional methods. Remaining challenges concern the radio network architecture to allow better access to deep underground structures and efficient methods for automated data quality control to handle this type of data in the future.
Blumensaat, F., Ebi, C., Dicht, S., Rieckermann, J., & Maurer, M. (2017). Langzeitüberwachung der Raum-Zeit-Dynamik in Entwässerungssystemen mittels Niedrigenergiefunk. KA: Korrespondenz Abwasser Abfall, 64(7), 594-603. doi:10.3242/kae2017.07.001, Institutional Repository

Obgleich gegenwärtig mittels Regenradar und hochauflösender Fernerkundung immer effizienter Daten zu Niederschlag, Topographie und Landnutzung erhoben werden, ist es nach wie vor schwierig, eine hydrologische Überwachung für Entwässerungssysteme mit hinreichender Informationsdichte und -konsistenz zu realisieren. Ob und inwieweit die Technologie des Niedrigenergiefunks (LPWAN) – als Kommunikations-Backbone des Internet der Dinge (IoT) bekannt – das Potenzial hat, diese Lücke zu schließen, diskutieren wir in diesem Beitrag. Grundlage dafür sind unsere Erfahrungen beim Aufbau und dem bis dato einjährigen Betrieb eines Drahtlossensornetzwerks in einem mittelgroßen Schweizer Siedlungsentwässerungsnetz mit einer Sensordichte von über einem Sensor pro Hektar und einer Überwachungsfrequenz von fünf Minuten. Im Einzelnen erörtern wir i) das zugrundeliegende Monitoringkonzept, ii) die technische Spezifikation der Sensorik und der Datenübertragungstechnologie LoRaWANTM und iii) die bisherigen Erfahrungen zur Systemperformance, illustriert durch ein Anwendungsbeispiel.
Carbajal, J. P., Leitão, J. P., Albert, C., & Rieckermann, J. (2017). Appraisal of data-driven and mechanistic emulators of nonlinear simulators: the case of hydrodynamic urban drainage models. Environmental Modelling and Software, 92, 17-27. doi:10.1016/j.envsoft.2017.02.006, Institutional Repository

System identification, sensitivity analysis, optimization and control, require a large number of model evaluations. Accurate simulators are too slow for these applications. Fast emulators provide a solution to this efficiency demand, sacrificing unneeded accuracy for speed. There are many strategies for developing emulators but selecting one remains subjective. Herein we compare the performance of two kinds of emulators: mechanistic emulators that use knowledge of the simulator's equations, and purely data-driven emulators using matrix factorization. We borrow simulators from urban water management, because more stringent performance criteria on water utilities have made emulation a crucial tool within this field. Results suggest that naive data-driven emulation outperforms mechanistic emulation. We discuss scenarios in which mechanistic emulation seems favorable for extrapolation in time and dealing with sparse and unevenly sampled data. We also point to advances in Machine Learning that have not permeated yet into the environmental science community.
Fencl, M., Dohnal, M., Rieckermann, J., & Bareš, V. (2017). Gauge-adjusted rainfall estimates from commercial microwave links. Hydrology and Earth System Sciences, 21(1), 617-634. doi:10.5194/hess-21-617-2017, Institutional Repository

Increasing urbanization makes it more and more important to have accurate stormwater runoff predictions, especially with potentially severe weather and climatic changes on the horizon. Such stormwater predictions in turn require reliable rainfall information. Especially for urban centres, the problem is that the spatial and temporal resolution of rainfall observations should be substantially higher than commonly provided by weather services with their standard rainfall monitoring networks. Commercial microwave links (CMLs) are non-traditional sensors, which have been proposed about a decade ago as a promising solution. CMLs are line-of-sight radio connections widely used by operators of mobile telecommunication networks. They are typically very dense in urban areas and can provide path-integrated rainfall observations at sub-minute resolution. Unfortunately, quantitative precipitation estimates (QPEs) from CMLs are often highly biased due to several epistemic uncertainties, which significantly limit their usability. In this manuscript we therefore suggest a novel method to reduce this bias by adjusting QPEs to existing rain gauges. The method has been specifically designed to produce reliable results even with comparably distant rain gauges or cumulative observations. This eliminates the need to install reference gauges and makes it possible to work with existing information. First, the method is tested on data from a dedicated experiment, where a CML has been specifically set up for rainfall monitoring experiments, as well as operational CMLs from an existing cellular network. Second, we assess the performance for several experimental layouts of "ground truth" from rain gauges (RGs) with different spatial and temporal resolutions. The results suggest that CMLs adjusted by RGs with a temporal aggregation of up to 1 h (i) provide precise high-resolution QPEs (relative error <7%, Nash–Sutcliffe efficiency coefficient >0.75) and (ii) that the combination of both sensor types clearly outperforms each individual monitoring system. Unfortunately, adjusting CML observations to RGs with longer aggregation intervals of up to 24 h has drawbacks. Although it substantially reduces bias, it unfavourably smoothes out rainfall peaks of high intensities, which is undesirable for stormwater management. A similar, but less severe, effect occurs due to spatial averaging when CMLs are adjusted to remote RGs. Nevertheless, even here, adjusted CMLs perform better than RGs alone. Furthermore, we provide first evidence that the joint use of multiple CMLs together with RGs also reduces bias in their QPEs. In summary, we believe that our adjustment method has great potential to improve the space–time resolution of current urban rainfall monitoring networks. Nevertheless, future work should aim to better understand the reason for the observed systematic error in QPEs from CMLs.
Garbani-Marcantini, L., Cereghetti, G., Muschalla, D., Regneri, M., Schegg, S., & Rieckermann, J. (2017). Playing the rain: a chess-based rating algorithm for the performance assessment of real-time control in urban drainage networks (p. (8 pp.). Presented at the 14th IWA/IAHR International conference on urban drainage (ICUD). Prague: CZWA; CTU. , Institutional Repository

Existing urban drainage networks are often operated in a sub-optimal manner. Real-Time Control (RTC) can improve network performance, but its implementation in the real world is not trivial. Here, we suggest two new methods to predict the performance of RTC applied to urban water networks. Specifically, we propose using rainfall information and a robust overflow metric with a classification algorithm to assess RTC performance. Furthermore, we investigate the usage of chess-based rating systems to better predict and assess the efficiency of existing catchments. The results from two case studies suggest that it is possible to achieve fast and robust assessments with one year of data or less.
Honti, M., Schuwirth, N., Rieckermann, J., & Stamm, C. (2017). Can integrative catchment management mitigate future water quality issues caused by climate change and socio-economic development?. Hydrology and Earth System Sciences, 21(3), 1593-1609. doi:10.5194/hess-21-1593-2017, Institutional Repository

The design and evaluation of solutions for integrated surface water quality management requires an integrated modelling approach. Integrated models have to be comprehensive enough to cover the aspects relevant for management decisions, allowing for mapping of larger-scale processes such as climate change to the regional and local contexts. Besides this, models have to be sufficiently simple and fast to apply proper methods of uncertainty analysis, covering model structure deficits and error propagation through the chain of sub-models. Here, we present a new integrated catchment model satisfying both conditions. The conceptual "iWaQa" model was developed to support the integrated management of small streams. It can be used to predict traditional water quality parameters, such as nutrients and a wide set of organic micropollutants (plant and material protection products), by considering all major pollutant pathways in urban and agricultural environments. Due to its simplicity, the model allows for a full, propagative analysis of predictive uncertainty, including certain structural and input errors. The usefulness of the model is demonstrated by predicting future surface water quality in a small catchment with mixed land use in the Swiss Plateau. We consider climate change, population growth or decline, socio-economic development, and the implementation of management strategies to tackle urban and agricultural point and non-point sources of pollution. Our results indicate that input and model structure uncertainties are the most influential factors for certain water quality parameters. In these cases model uncertainty is already high for present conditions. Nevertheless, accounting for today's uncertainty makes management fairly robust to the foreseen range of potential changes in the next decades. The assessment of total predictive uncertainty allows for selecting management strategies that show small sensitivity to poorly known boundary conditions. The identification of important sources of uncertainty helps to guide future monitoring efforts and pinpoints key indicators, whose evolution should be closely followed to adapt management. The possible impact of climate change is clearly demonstrated by water quality substantially changing depending on single climate model chains. However, when all climate trajectories are combined, the human land use and management decisions have a larger influence on water quality against a time horizon of 2050 in the study.
Manny, L. A. D. (2017). Policy-Analyse im Bereich Gewässerschutz bei Regenwetter (Master thesis). 105 p. , Institutional Repository

Für einen effektiveren Gewässerschutz bei Regenwetter bedarf es nicht nur der Optimierung von Kläranlagen, sondern auch einem Verständnis über die hydraulische Funktionsweise von Sonderbauwerken, wie z.B. Regenüberlaufbecken (RÜB). RÜB, die bei grösseren Regenereignissen verdünntes Mischabwasser in die Gewässer einleiten, werden auf Grundlage von Simulationsmodellen dimensioniert. Ob die berechnete Entlastungshäufigkeit und -dauer auch der tatsächlichen entspricht, wird in der Schweizer Praxis kaum überprüft. Zur Überprüfung können RÜB mit Messgeräten ausgerüstet und wichtige Variablen, wie z.B. der Wasserstand im RÜB erfasst werden. Für Datenfernübertragung und die automatisierte Auswertung sind heute praxistaugliche Technologien verfügbar. Es besteht daher die Vermutung, dass der Einsatz vorhandener Messtechnik an RÜB nicht durch technische Deffizite zu begründen ist, sondern dass das Verständnis für den tatsächlichen Wert und Nutzen von Messdaten bei Betreibern und Behörden fehlt.

Das Ziel dieser Masterarbeit ist es, erstens den heutigen Zustand in der Schweiz in Bezug auf die Ausstattung von RÜB mit Messtechnik und den Umgang mit Messdaten zu erfassen und zu erklären. Davon werden zweitens Instrumente abgeleitet, die dazu beitragen könnten, dass Messdaten von allen Akteuren (Gemeinden, Abwasserverbänden, Kantone, Bund, Ingenieur- und Planungsbüros) genutzt werden. Zur gemeinsamen Untersuchung des technischen Systems und beteiligter Akteure werden methodische Ansätze aus der Policy-Analyse angewendet, wobei der Fokus auf die Abwasserverbände in der Schweiz gelegt wurde. Eine Online-Umfrage wurde durchgeführt und mit deskriptiven und erklärenden statistischen Analysemethoden (wie z.B. Regressionsanalysen) ausgewertet.

Mit der Online-Umfrage werden 73 % der Abwasserverbände in der Schweiz abgedeckt. Überraschend positiv ist, dass insgesamt bereits 84 % der RÜB, die sich im Betrieb von Abwasserverbänden befinden, mit einem Messgerät ausgerüstet sind. Defizite sind jedoch im Umgang mit den Messdaten vorhanden. In 34 % der Abwasserverbände werden Wasserstands-Daten aggregiert, was heute nicht mehr dem Stand der Technik entspricht. Daten werden in 47 % der Abwasserverbände nie oder nur unregelmässig ausgewertet und in 61 % weder an Ingenieurbüros (für Planungszwecke) noch an kantonale Fachstellen (zur Erfolgskontrolle) weitergeleitet. Das liegt vor allem daran, dass Abwasserverbände Messdaten hauptsächlich für die betriebliche Optimierung nutzen. Da Kosteneinsparungen eher im Hintergrund stehen, liegt nahe, dass Subventionen weniger bevorzugt sind. Vielmehr priorisieren Abwasserverbände und Kantone die Einführung von Zielvorgaben.

Die Ergebnisse aus der Online-Umfrage beschränken sich nur auf die Abwasserverbände, Gemeinden werden z.B. nicht untersucht. Da die Situation in der Schweiz sehr heterogen ist, sollten Instrumente regional angepasst werden. Um dies zu untersuchen, wären weitergehende statistische Verfahren, wie z.B. die Clusteranalyse, angebracht.

Die Ergebnisse deuten darauf hin, dass für eine volle Wertausschopfung von Messdaten regulative Instrumente ebenso erforderlich sind wie organisatorische Anpassungen. Dafür sollten Akteure (Bund, Kantone, VSA) zum Beispiel eine Verordnung entwickeln, die Zielvorgaben für RÜB definiert und betriebliche Kompetenzen klar verteilt.

Diese Masterarbeit stellt viel Material bereit, das sich ohne grosse Anpassungen auch für die Untersuchung in anderen Ländern (z.B. Deutschland, Österreich) anbietet.
Rieckermann, J. (2017). Mischwasserbehandlung in der Schweiz - Stand der Technik und aktuelle Entwicklungen. In Herausforderungen der Mischwasserbewirtschaftung. Erfahrungen aus 10 Jahren Anwendung des ÖWAV-Regelblattes 19 (p. (11 pp.). Vienna, Austria: ÖWAV. , Institutional Repository

Seit ca. 10 Jahren folgt die Planung von Anlagen zur Mischwasserbehandlung in der Schweiz den imissionsorientierten Vorgaben des Gewässerschutzgesetzes. Positiv wird beurteilt, dass Handlungsbedarf auf Basis von Gewässeruntersuchungen identifiziert wird und eine breite Evaulation von Massnahmen nicht nur zum besseren Verständnis der Abwassersysteme, sondern oft zu kostengünstigen Lösungen führt. Aufgrund von sich überlappenden Regelwerken und neuem Wissen, u.a. zu Spurenstoffen, wird zurzeit die neue Richtlinie zur „Abwasserbewirtschaftung bei Regenwetter“ erarbeitet, die vor allem auch den Vollzug erleichtern soll. Dazu stellt sie 4 neue Elemente vor: i) die vereinfachte Zulässigkeitsprüfung, ii) Bewertung von Einleitungen in stehende Gewässer, iii) schmutzfrachtbasierte Mindestanforderungen und iv) die Möglichkeit eines Probebetriebs mit Überwachung. Die Erfahrung in der Schweiz zeigt, dass die immissionsbasierte Bewirtschaftung von Abwassersystemen anspruchsvoll ist, aber teilweise zu innovativen Lösungen führt. Der „Preis“ solcher komplexer Planungsinstrumente sind hohe fachliche Anforderungen bei Betreibern, Planern und Regulatoren, um inadequate Massnahmen zu verhindern. Ein guter Wissensstand in der Praxis kann neben Weiterbildungen gegebenenfalls über fachspezifische „Nachbarschaften“ nach dem Modell von Baden-Württemberg erreicht werden. Offene Fragen sind, wie kleine Gewässerschutz-Behörden am besten bei der Bewilligung von Massnahmen unterstützt werden können und wie zukünftige Entwicklungen zum vermehrten Einsatz von Messtechnik den Gewässerschutz bei Regenwetter verbessern können.
Rieckermann, J., Gruber, G., & Hoppe, H. (2017). Zukunftsfähige Systeme zur Regenwasserbehandlung brauchen datenbasierte Betriebs-, Planungs- und Vollzugskonzepte. In G. Krebs & G. Gruber (Eds.), Schriftenreihe zur Wasserwirtschaft: Vol. 75. Urbanes Niederschlagswassermanagement zwischen zentralen und dezentralen Maßnahmen (p. C (30 pp.). Graz: TU Graz. , Institutional Repository

In der Siedlungsentwässerung in Deutschland, Österreich und der Schweiz basieren viele Massnahmenplanungen nicht auf Messdaten, sondern auf Annahmen und auf Vorhersagen von Simulationsmodellen. Ausserdem werden Messdaten sehr wenig zur Leistungsbeurteilung und Erfolgskontrolle eingesetzt. In diesem Beitrag vergleichen wir deshalb zum ersten Mal den aktuellen Stand zur Verwendung von Messdaten im deutschsprachigen Raum, den wir in einem Diskurs-Prozess anhand von neun konkreten Fallbeispielen erarbeitet haben. Grundsätzlich zeigt sich eine grosse Variabilität im Umgang mit datenbasierten Konzepten, auch innerhalb der Länder. Sowohl in Österreich als auch in der Schweiz wird die Leistung von Entwässerungsnetzen praktisch nicht anhand von Messdaten überwacht und bewertet. Zur Qualitätssicherung scheint das deutsche Prüfstellen-Modell sehr interessant. Unsere Ergebnisse deuten darauf hin, dass gute Messdaten nicht nur zur sicheren Abwasserableitung und zum Gewässerschutz beitragen, sondern eine sehr breite positive Wirkung auf fast alle Ziele einer nachhaltigen Siedlungswasserwirtschaft haben. Ein datenbasiertes Management benötigt jedoch weitere Entwicklungen im politischen und organisatorischen Bereich sowie in der Ausbildung.
Wani, O., Scheidegger, A., Carbajal, J. P., Rieckermann, J., & Blumensaat, F. (2017). Parameter estimation of hydrologic models using a likelihood function for censored and binary observations. Water Research, 121, 290-301. doi:10.1016/j.watres.2017.05.038, Institutional Repository

Observations of a hydrologic system response are needed to accurately model system behaviour. Nevertheless, often very few monitoring stations are operated because collecting such reference data adequately and accurately is laborious and costly. It has been recently suggested to use observations not only from dedicated flow meters but also from simpler sensors, such as level or event detectors, which are available more frequently but only provide censored information. Binary observations can be considered as extreme censoring. It is still unclear, however, how to use censored observations most effectively to learn about model parameters. To this end, we suggest a formal likelihood function that incorporates censored observations, while accounting for model structure deficits and uncertainty in input data. Using this likelihood function, the parameter inference is performed within the Bayesian framework. We demonstrate the implementation of our methodology on a case study of an urban catchment, where we estimate the parameters of a hydrodynamic rainfall-runoff model from binary observations of combined sewer overflows. Our results show, first, that censored observations make it possible to learn about model parameters, with an average decrease of 45% in parameter standard deviation from prior to posterior. Second, the inference substantially improves model predictions, providing higher Nash-Sutcliffe efficiency. Third, the gain in information largely depends on the experimental design, i.e. sensor placement. Given the advent of Internet of Things, we foresee that the plethora of censored data promised to be available can be used for parameter estimation within a formal Bayesian framework.
Barrett, R. (2016). Spatial modelling of rain-induced infiltration into sewers (Master thesis). 37 p. , Institutional Repository
Del Giudice, D., Albert, C., Rieckermann, J., & Reichert, P. (2016). Describing the catchment-averaged precipitation as a stochastic process improves parameter and input estimation. Water Resources Research, 52(4), 3162-3186. doi:10.1002/2015WR017871, Institutional Repository

Rainfall input uncertainty is one of the major concerns in hydrological modeling. Unfortunately, during inference, input errors are usually neglected, which can lead to biased parameters and implausible predictions. Rainfall multipliers can reduce this problem but still fail when the observed input (precipitation) has a different temporal pattern from the true one or if the true nonzero input is not detected. In this study, we propose an improved input error model which is able to overcome these challenges and to assess and reduce input uncertainty. We formulate the average precipitation over the watershed as a stochastic input process (SIP) and, together with a model of the hydrosystem, include it in the likelihood function. During statistical inference, we use “noisy” input (rainfall) and output (runoff) data to learn about the “true” rainfall, model parameters, and runoff. We test the methodology with the rainfall-discharge dynamics of a small urban catchment. To assess its advantages, we compare SIP with simpler methods of describing uncertainty within statistical inference: (i) standard least squares (LS), (ii) bias description (BD), and (iii) rainfall multipliers (RM). We also compare two scenarios: accurate versus inaccurate forcing data. Results show that when inferring the input with SIP and using inaccurate forcing data, the whole-catchment precipitation can still be realistically estimated and thus physical parameters can be “protected” from the corrupting impact of input errors. While correcting the output rather than the input, BD inferred similarly unbiased parameters. This is not the case with LS and RM. During validation, SIP also delivers realistic uncertainty intervals for both rainfall and runoff. Thus, the technique presented is a significant step toward better quantifying input uncertainty in hydrological inference. As a next step, SIP will have to be combined with a technique addressing model structure uncertainty.
Garbani Marcantini, L., Schegg, S., Gresch, M., Mischler, B., & Rieckermann, J. (2016). Ein hierarchischer Regelungsalgorithmus. Praxistaugliche Abflussregelung von Entwässerungsnetzen. Aqua & Gas, 96(10), 48-53. , Institutional Repository

Für einen effektiven Betrieb eines Abwassersystems bietet sich vielerorts eine Abflussregelung an. Dazu empfiehlt sich ein regelbasierter, selbstadaptiver und hierarchischer Regelungsalgorithmus, der allgemein anwendbar ist. Bei der ARA Wohlen steigerte er die Leistung des Entwässerungsnetzes im Mittel um 10–20% und kann ca. 25% der Entlastungsereignisse verhindern.
Gosset, M., Kunstmann, H., Zougmore, F., Cazenave, F., Leijnse, H., Uijlenhoet, R., … Hoedjes, J. (2016). Improving rainfall measurement in gauge poor regions thanks to mobile telecommunication networks. Bulletin of the American Meteorological Society, 97(3), ES49-ES51. doi:10.1175/BAMS-D-15-00164.1, Institutional Repository

Eighty-seven participants from 18 countries met to discuss the prospect for rainfall measurement and high-resolution mapping based on commercial microwave links in Africa. Experts from Europe and Israel provided training to African students, scientists, and meteorologists on this innovative method.
Keller, C. (2016). Understanding the urban drainage system of Fehraltorf. Enhancing the reliability of Fehraltorf’s SWMM model through calibration (Master thesis). 30 p. , Institutional Repository

The hydraulic behavior and the capacity of sewer systems are assessed through hydrodynamic modeling. They are widely used in drainage planning, although their parameters are mostly estimated and the models are only checked for general plausibility. The Master‘s Thesis assessed the effect of calibration on the model reliability on the basis of a case study, namely Fehraltorf.
Fehraltorf is located in the agglomeration of Zurich and Winterthur and is inhabited by 6’292 people. Most of the village of Russikon and Fehraltorf are connected to the WWTP of Fehraltorf. The DWF amounts up to 66 l/s, whereas the residual flow Q347 of the main receiving water (Luppmen) is 72 l/s. The infiltration of the groundwater is 30.1 l/s, as a significant share of the drainage system was built below the average groundwater table.
During the thesis the conversion of the Mike Urban model to SWMM was revised and further adjustments were implemented. The data for input and calibration was chosen depending on its reliability and further processed if necessary. Rain events were selected and split for calibration and validation. Parameters known to be changed in the calibrations were selected and in the sensitivity analysis the most sensitive, and thus, important parameters were determined. Then, the calibration was conducted manually as well as automatically with simulated annealing. The effect of calibration was assessed for the calibration and validation events visually and with various objective functions, viz. Nash-Sutcliffe Efficiency, total volume, peak flow and time to peak. The hydraulic performance of the sewer system was tested by simulating a 10-year design rainfall event in the uncalibrated and the calibrated model.
For the simulations, the data of the rain gauge on the WWTP had to be discarded because it showed high deviations to the ones installed by EAWAG. The rainfall data and flow data (of the FloDars) collected by EAWAG were assessed to be reliable, but as the measurements were installed recently, only four rain events were available for calibration and validation. The objective functions could be raised to a satisfying level in the manual calibration and were further improved in the automatic calibration. The validation confirmed that the reliability of the model could be increased with calibration. Furthermore, the assessment of the sewer system revealed that there are less capacity limits in the calibrated model then in the uncalibrated one, but further adjustments are needed due to numerical instabilities.
Even though the validation suggests that manual as well as automatic calibration enhance the reliability of the model because of improved goodness of fit assessed by different objective functions, further input data and reliable calibration data is needed to perform the calibration once more.
After all, calibration is strongly recommended by the author of this thesis to not only improve parameter values which were only estimated in the uncalibrated models but also to detect systematic errors in the data and the model structure.
Leitão, J. P., Moy de Vitry, M., Scheidegger, A., & Rieckermann, J. (2016). Assessing the quality of digital elevation models obtained from mini unmanned aerial vehicles for overland flow modelling in urban areas. Hydrology and Earth System Sciences, 20(4), 1637-1653. doi:10.5194/hess-20-1637-2016, Institutional Repository

Precise and detailed digital elevation models (DEMs) are essential to accurately predict overland flow in urban areas. Unfortunately, traditional sources of DEM, such as airplane light detection and ranging (lidar) DEMs and point and contour maps, remain a bottleneck for detailed and reliable overland flow models, because the resulting DEMs are too coarse to provide DEMs of sufficient detail to inform urban overland flows. Interestingly, technological developments of unmanned aerial vehicles (UAVs) suggest that they have matured enough to be a competitive alternative to satellites or airplanes. However, this has not been tested so far. In this study we therefore evaluated whether DEMs generated from UAV imagery are suitable for urban drainage overland flow modelling. Specifically, 14 UAV flights were conducted to assess the influence of four different flight parameters on the quality of generated DEMs: (i) flight altitude, (ii) image overlapping, (iii) camera pitch, and (iv) weather conditions. In addition, we compared the best-quality UAV DEM to a conventional lidar-based DEM. To evaluate both the quality of the UAV DEMs and the comparison to lidar-based DEMs, we performed regression analysis on several qualitative and quantitative metrics, such as elevation accuracy, quality of object representation (e.g. buildings, walls and trees) in the DEM, which were specifically tailored to assess overland flow modelling performance, using the flight parameters as explanatory variables. Our results suggested that, first, as expected, flight altitude influenced the DEM quality most, where lower flights produce better DEMs; in a similar fashion, overcast weather conditions are preferable, but weather conditions and other factors influence DEM quality much less. Second, we found that for urban overland flow modelling, the UAV DEMs performed competitively in comparison to a traditional lidar-based DEM. An important advantage of using UAVs to generate DEMs in urban areas is their flexibility that enables more frequent, local, and affordable elevation data updates, allowing, for example, to capture different tree foliage conditions.
Machac, D., Reichert, P., Rieckermann, J., & Albert, C. (2016). Fast mechanism-based emulator of a slow urban hydrodynamic drainage simulator. Environmental Modelling and Software, 78, 54-67. doi:10.1016/j.envsoft.2015.12.007, Institutional Repository

Gaussian process (GP) emulation is a data-driven method that substitutes a slow simulator with a stochastic approximation. It is then typically orders of magnitude faster than the simulator at the costs of introducing interpolation errors. Our approach, the mechanism-based GP emulator, uses knowledge of the simulator mechanisms in addition to the information gained from previous simulator runs, so called design data. In this study, we investigate how the degree of incorporating mechanisms into the design of the GP emulator influences emulation accuracy. Similarly to the previous results, we get a significant gain in accuracy already when using the simplest approximation of the mechanisms by a single linear reservoir. However, in this case, we again considerably improve emulation accuracy when using the next two approximations. This allows us to decreases the required number of design data to achieve a similar accuracy as a non-mechanistic emulator.
Rieckermann, J. (2016). "Wir müssen mit Nichtwissen und Unsicherheiten leben und trotzdem schon entscheiden.". Aqua & Gas, 96(10), 10-13. , Institutional Repository

In der schönen Bergwelt von Rigi Kaltbad fand die von Eawag und VSA organisierte Aqua Urbanica 2016 statt. Jörg Rieckermann (Eawag) und seine Mitorganisatoren Günter Gruber (TU Graz), Ulrich Dittmer (Universität Stuttgart) und Michael Burkhardt (HSR Hochschule für Technik Rapperswil) diskutieren im Interview die Themen und Hintergründe der Tagung. Unter anderem unterhalten sie sich über den Wert von guten Messdaten und Modellen, den Umgang mit Spurenstoffen und Unsicherheiten in der Planung sowie die fortschreitende Digitalisierung der Siedlungsentwässerung.
Schegg, S. (2016). Modern receiving water protection using an integrated control system (Master thesis). 36 p. , Institutional Repository

A case study for an integrated real time control (RTC) in the catchment Wohlen-Villmergen, Switzerland is introduced. The RTC-based control was simulated for the inflows to the wastewater treatment plant Wohlen and the connecting sewer system using a conceptual model in CityDrain II. For evaluating the model performance, high-resolution routine data were available for the entire year of 2015.
The main goal of this thesis was to control the system with an aim to improve the receiving water quality. In urban drainage systems, combined sewer overflows (CSO) represent the main pollutant source. A load-based approach was introduced to further characterize CSO. Then, different static and dynamic control strategies were compared for reducing CSO number, volume and load.
It was found that a dynamically controlled RTC can avoid 25 % of CSO events that would have happened in a static controlled system in 2015. However, the reduction was much smaller for overall CSO volume (7 %) and load (9 %).
Maurer, M., Rieckermann, J., Muschalla, D., Gruber, G., Schmitt, T. G., Kaufmann Alves, I., … Dittmer, U. (Eds.). (2016). "Miss es oder vergiss es!" - Daten, Wissen und Konzepte für den Gewässerschutz bei Regenwetter. Aqua Urbanica 2016. Dübendorf: Eawag. , Institutional Repository
Del Giudice, D., Löwe, R., Madsen, H., Mikkelsen, P. S., & Rieckermann, J. (2015). Comparison of two stochastic techniques for reliable urban runoff prediction by modeling systematic errors. Water Resources Research, 51(7), 5004-5022. doi:10.1002/2014WR016678, Institutional Repository

In urban rainfall-runoff, commonly applied statistical techniques for uncertainty quantification mostly ignore systematic output errors originating from simplified models and erroneous inputs. Consequently, the resulting predictive uncertainty is often unreliable. Our objective is to present two approaches which use stochastic processes to describe systematic deviations and to discuss their advantages and drawbacks for urban drainage modeling. The two methodologies are an external bias description (EBD) and an internal noise description (IND, also known as stochastic gray-box modeling). They emerge from different fields and have not yet been compared in environmental modeling. To compare the two approaches, we develop a unifying terminology, evaluate them theoretically, and apply them to conceptual rainfall-runoff modeling in the same drainage system. Our results show that both approaches can provide probabilistic predictions of wastewater discharge in a similarly reliable way, both for periods ranging from a few hours up to more than 1 week ahead of time. The EBD produces more accurate predictions on long horizons but relies on computationally heavy MCMC routines for parameter inferences. These properties make it more suitable for off-line applications. The IND can help in diagnosing the causes of output errors and is computationally inexpensive. It produces best results on short forecast horizons that are typical for online applications.
Del Giudice, D. (2015). Improving output and input statistical error descriptions in urban hydrological modeling (Doctoral dissertation). doi:10.3929/ethz-a-010536371, Institutional Repository

Hydrological or drainage models can be valuable tools to support water management in urban environments. They can help to assess the characteristics of a catchment and to make predictions about its response (e.g. discharge). Unfortunately, parameters and results of these models are not perfect. These inaccuracies manifest themselves as model discrepancy, the so-called bias. Model bias represents the systematic deviation between model output and the real system response. There are two main causes of bias. First, there are errors in the input estimates, e.g. due to the insufficient coverage of pluviometers. Second, there are deficits in the model structure, e.g. due to the use of oversimplified empirical equations. Besides model bias, there are output measurement errors, e.g. due to imprecise flowmeters.
Until now, a large proportion of hydrological studies implicitly neglected input and structural errors. Neglecting these can lead to: i) misrepresented output measurement errors, ii) incorrect parameter estimates which compensate for model discrepancy, and iii) predictions which underestimate the uncertainty. Furthermore, these approaches do not provide guidance for finding the reasons for bias. Therefore, they cannot support its reduction. This inappropriate error consideration can finally lead to faulty risk assessment, flawed evaluation of decision alternatives, and, consequently, impaired urban water management. More advanced error assessment techniques are therefore called for.
The main goal of this thesis is to better represent input, structural, and output measurement errors. This can meliorate parameter estimation and prediction generation. The main thesis contributions are two. The first is a realistic description of the uncertainties in stormwater, wastewater, and sediment transport predictions. The second is a sound representation of errors in the rainfall inputs. Additionally, we discuss and compare different statistical methods used for hydrological inference. Finally, we also present a new tool to improve sewer flow monitoring. [...]
Del Giudice, D., Reichert, P., Bareš, V., Albert, C., & Rieckermann, J. (2015). Model bias and complexity - understanding the effects of structural deficits and input errors on runoff predictions. Environmental Modelling and Software, 64, 205-214. doi:10.1016/j.envsoft.2014.11.006, Institutional Repository

Oversimplified models and erroneous inputs play a significant role in impairing environmental predictions. To assess the contribution of these errors to model uncertainties is still challenging. Our objective is to understand the effect of model complexity on systematic modeling errors. Our method consists of formulating alternative models with increasing detail and flexibility and describing their systematic deviations by an autoregressive bias process. We test the approach in an urban catchment with five drainage models. Our results show that a single bias description produces reliable predictions for all models. The bias decreases with increasing model complexity and then stabilizes. The bias decline can be associated with reduced structural deficits, while the remaining bias is probably dominated by input errors. Combining a bias description with a multimodel comparison is an effective way to assess the influence of structural and rainfall errors on flow forecasts.
Fencl, M., Rieckermann, J., Sýkora, P., Stránský, D., & Bareš, V. (2015). Commercial microwave links instead of rain gauges: fiction or reality?. Water Science and Technology, 71(1), 31-37. doi:10.2166/wst.2014.466, Institutional Repository

Commercial microwave links (MWLs) were suggested about a decade ago as a new source for quantitative precipitation estimates (QPEs). Meanwhile, the theory is well understood and rainfall monitoring with MWLs is on its way to being a mature technology, with several well-documented case studies, which investigate QPEs from multiple MWLs on the mesoscale. However, the potential of MWLs to observe microscale rainfall variability, which is important for urban hydrology, has not been investigated yet. In this paper, we assess the potential of MWLs to capture the spatio-temporal rainfall dynamics over small catchments of a few square kilometres. Specifically, we investigate the influence of different MWL topologies on areal rainfall estimation, which is important for experimental design or to a priori check the feasibility of using MWLs. In a dedicated case study in Prague, Czech Republic, we collected a unique dataset of 14 MWL signals with a temporal resolution of a few seconds and compared the QPEs from the MWLs to reference rainfall from multiple rain gauges. Our results show that, although QPEs from most MWLs are probably positively biased, they capture spatio-temporal rainfall variability on the microscale very well. Thus, they have great potential to improve runoff predictions. This is especially beneficial for heavy rainfall, which is usually decisive for urban drainage design.
Fencl, M., Rieckermann, J., Stránský, D., Sýkora, P., & Bareš, V. (2015). Dynamic bias correction of commercial microwave links. In P. Molnar & N. Peleg (Eds.), Rainfall in urban and natural systems. Proceedings (pp. UR15-19 (4 pp.). Zürich: ETH Zurich. , Institutional Repository

Urban storm water management requires rainfall data of high spatial and temporal resolution which are often not available (Schilling, 1991). Path-integrated rain rate information from cellular microwave links (MWLs) has potential to aid in this regard (Messer et al., 2006) as MWL network are very dense in urban areas and rain rate information can be at virtually no cost polled from each single MWL with sub minute temporal resolution. Unfortunately MWL rainfall is often significantly biased (Fencl et al., 2015). In this investigation we proposed method to dynamically correct MWL rain rates by remote rain gauges (RGs) with hourly temporal resolution, i.e. RGs often operated by national weather services. Our results show that although these RGs have unsufficient resolution for most of the urban storm water management applications they can be conveniently used to calibrate MWL attenuation-rain rate model. Such calibrated model provides unbiased high-res quantitative precipitation estimates.
Neumann, M. B., Rieckermann, J., Hug, T., & Gujer, W. (2015). Adaptation in hindsight: dynamics and drivers shaping urban wastewater systems. Journal of Environmental Management, 151, 404-415. doi:10.1016/j.jenvman.2014.12.047, Institutional Repository

Well-planned urban infrastructure should meet critical loads during its design lifetime. In order to proceed with design, engineers are forced to make numerous assumptions with very little supporting information about the development of various drivers. For the wastewater sector, these drivers include the future amount and composition of the generated wastewater, effluent requirements, technologies, prices of inputs such as energy or chemicals, and the value of outputs produced such as nutrients for fertilizer use. When planning wastewater systems, there is a lack of methods to address discrepancies between the timescales at which fundamental changes in these drivers can occur, and the long physical life expectancy of infrastructure (on the order of 25–80 years). To explore these discrepancies, we take a hindsight perspective of the long-term development of wastewater infrastructure and assess the stability of assumptions made during previous designs. Repeatedly we find that the drivers influencing wastewater loads, environmental requirements or technological innovation can change at smaller timescales than the infrastructure design lifetime, often in less than a decade. Our analysis shows that i) built infrastructure is continuously confronted with challenges it was not conceived for, ii) significant adaptation occurs during a structure's lifetime, and iii) "muddling-through" is the pre-dominant strategy for adaptive management. As a consequence, we argue, there is a need to explore robust design strategies which require the systematic use of scenario planning methods and instruments to increase operational, structural, managerial, institutional and financial flexibility. Hindsight studies, such as this one, may inform the development of robust design strategies and assist in the transition to more explicit forms of adaptive management for urban infrastructures.
Sikorska, A. E., Del Giudice, D., Banasik, K., & Rieckermann, J. (2015). The value of streamflow data in improving TSS predictions - Bayesian multi-objective calibration. Journal of Hydrology, 530, 241-254. doi:10.1016/j.jhydrol.2015.09.051, Institutional Repository

The concentration of total suspended solids (TSS) in surface waters is a commonly used indicator of water quality impairments. Its accurate prediction remains, however, problematic because: i) TSS build-up, erosion, and wash-off are not easily identifiable; ii) calibrating a TSS model requires observations of sediment loads, which are rare, and streamflow observations to calculate concentrations; iii) predicted TSS usually deviate systematically from observations, an effect which is commonly neglected. Ignoring systematic errors during calibration can lead to overconfident (i.e. unreliable) uncertainty estimates during predictions. In this paper, we therefore investigate whether a statistical description of systematic model errors makes it possible to generate reliable predictions for TSS. In addition, we explore how the reliability of TSS predictions increases when streamflow data are additionally used in model calibration. A key aspect of our study is that we use a Bayesian multi-output calibration and a novel autoregressive error model, which describes the model predictive error as a sum of independent random noise and autocorrelated bias. Our results show that using a statistical description of model bias provides more reliable uncertainty estimates of TSS than before and including streamflow data into calibration makes TSS predictions more precise. For a case study of a small ungauged catchment, this improvement was as much as 15%. Our approach can be easily implemented for other water quality variables which are dependent on streamflow.
Tokarczyk, P., Leitao, J. P., Rieckermann, J., Schindler, K., & Blumensaat, F. (2015). High-quality observation of surface imperviousness for urban runoff modelling using UAV imagery. Hydrology and Earth System Sciences, 19(10), 4215-4228. doi:10.5194/hess-19-4215-2015, Institutional Repository

Modelling rainfall–runoff in urban areas is increasingly applied to support flood risk assessment, particularly against the background of a changing climate and an increasing urbanization. These models typically rely on high-quality data for rainfall and surface characteristics of the catchment area as model input.
While recent research in urban drainage has been focusing on providing spatially detailed rainfall data, the technological advances in remote sensing that ease the acquisition of detailed land-use information are less prominently discussed within the community. The relevance of such methods increases as in many parts of the globe, accurate land-use information is generally lacking, because detailed image data are often unavailable. Modern unmanned aerial vehicles (UAVs) allow one to acquire high-resolution images on a local level at comparably lower cost, performing on-demand repetitive measurements and obtaining a degree of detail tailored for the purpose of the study.
In this study, we investigate for the first time the possibility of deriving high-resolution imperviousness maps for urban areas from UAV imagery and of using this information as input for urban drainage models. To do so, an automatic processing pipeline with a modern classification method is proposed and evaluated in a state-of-the-art urban drainage modelling exercise. In a real-life case study (Lucerne, Switzerland), we compare imperviousness maps generated using a fixed-wing consumer micro-UAV and standard large-format aerial images acquired by the Swiss national mapping agency (swisstopo). After assessing their overall accuracy, we perform an end-to-end comparison, in which they are used as an input for an urban drainage model. Then, we evaluate the influence which different image data sources and their processing methods have on hydrological and hydraulic model performance. We analyse the surface runoff of the 307 individual subcatchments regarding relevant attributes, such as peak runoff and runoff volume. Finally, we evaluate the model's channel flow prediction performance through a cross-comparison with reference flow measured at the catchment outlet.
We show that imperviousness maps generated from UAV images processed with modern classification methods achieve an accuracy comparable to standard, off-the-shelf aerial imagery. In the examined case study, we find that the different imperviousness maps only have a limited influence on predicted surface runoff and pipe flows, when traditional workflows are used. We expect that they will have a substantial influence when more detailed modelling approaches are employed to characterize land use and to predict surface runoff. We conclude that UAV imagery represents a valuable alternative data source for urban drainage model applications due to the possibility of flexibly acquiring up-to-date aerial images at a quality compared with off-the-shelf image products and a competitive price at the same time. We believe that in the future, urban drainage models representing a higher degree of spatial detail will fully benefit from the strengths of UAV imagery.
Tokarczyk, P., Leitao, J. P., Rieckermann, J., Schindler, K., & Blumensaat, F. (2015). Nutzung von Drohnen und Luftbildern in der Siedlungswasserwirtschaft. Geomatik Schweiz, Géomatique Suisse, Geomatica Svizzera, 113(9), 346-350. doi:10.5169/seals-513919, Institutional Repository

Vor dem Hintergrund von zunehmender Urbanisierung, Klimawandel und alternder Infrastrukturen gewinnt die Analyse und Bewertung von Überflutungen im urbanen Raum aufgrund von Starkregenereignissen zunehmend an Bedeutung. Dazu sind Modelle erforderlich, die das Niederschlag-Abflussverhalten in einem angemessenen zeitlichen und räumlichen Detail beschreiben. Neben Daten zur Menge und Verteilung des Niederschlags gehen in die Modellierung auch Oberflächeneigenschaften ein, insbesondere der Versiegelungsgrad und die Flächennutzung. In dieser Studie untersuchen wir erstmals die Möglichkeit, hochauflösende Landnutzungskarten städtischer Gebiete aus Drohnen(UAV)-Bildern abzuleiten und die Eignung solcher Karten als Datengrundlage für Modellanwendungen in der Siedlungswasserwirtschaft. Wir zeigen, dass die aus UAV-Bildern (automatisch) abgeleiteten Karten zum Versiegelungsgrad hinsichtlich ihrer Genauigkeit mit Karten auf Basis konventioneller Luftbilder vergleichbar sind. Darüber hinaus zeigt sich in unseren Experimenten, dass sich die Genauigkeit der Versiegelungskarten bedeutend steigern lässt, indem man diskriminative Lernverfahren in Verbindung mit Bildinformation aus einer grösseren Nachbarschaft benutzt.
Ort, C., Eppler, J. M., Scheidegger, A., Rieckermann, J., Kinzig, M., & Sörgel, F. (2014). Challenges of surveying wastewater drug loads of small populations and generalizable aspects on optimizing monitoring design. Addiction, 109(3), 472-481. doi:10.1111/add.12405, Institutional Repository

Aims. Quantifying illicit drug loads through wastewater analysis (WWA) is an alternative approach to estimating population drug use. This study investigated the variability of daily drug loads in wastewater and their relationships to environmental factors over an extended period to: (i) explore the suitability of WWA in small populations and (ii) optimize the monitoring design for future studies.
Design, Setting, Participants. Daily wastewater samples (n = 1369 consecutive days) from a German village with approximately 7160 inhabitants.
Measurements. Samples were analysed for cocaine and benzoylecgonine with liquid chromatography-tandem mass spectrometry. Time-series analysis was used to explore the effects of weather and other factors on daily cocaine loads. Subsampling was used to assess monitoring design.
Findings. Cocaine loads [mean = 652 mgCOC/day, standard deviation (SD) = 498 mgCOC/day] increased over the study period, with higher values during winter and spring. Despite high day-to-day variation, loads were significantly higher during weekends [+161 mgCOC/day, 95% confidence interval (CI) = 115–207 mgCOC/day, P < 10−4] and days with frost (+114 mgCOC/day, 95% CI = 6–223 mgCOC/day, P = 0.039) or snow (+150 mgCOC/day, 95% CI = 46–253 mgCOC/day, P = 0.005). Annual means estimated from 1-week periods were subject to approximately 60% relative error. Increasing sample size and changing sampling from consecutive days to stratified random decreased this uncertainty.
Conclusions. Day-to-day variation and seasonality of drug loads from the few long-term wastewater studies available to date suggest that up to 56 stratified random samples are required to obtain reliable (expected uncertainty around 10%) annual estimates of drug loads. Successfully assessing changes in consumption patterns or relationships to external factors requires larger sample sizes than estimating annual means, which holds true for high-prevalence drugs in small communities and low-prevalence drugs in big cities.
Ort, C., Banta-Green, C. J., Bijlsma, L., Castiglioni, S., Emke, E., Gartner, C., … van Nuijs, A. L. N. (2014). Sewage-based epidemiology requires a truly transdisciplinary approach. GAIA: Ecological Perspectives for Science and Society, 23(3), 266-268. doi:10.14512/gaia.23.3.12, Institutional Repository

If asked whether you had consumed illicit drugs recently, would you admit it? If yes, could you precisely recall types of drug, times and amounts used? If you were the person commissioned with the task of quantifying drug use, what approach would you use given the social stigma attached with such behavior? We measure drug residues in sewage, which represents urine of entire populations, to provide an objective estimate of total drug use in a region. In transdisciplinary projects, sewage-based results provide valuable information at unrivaled spatiotemporal resolution complementing traditional data.
Bianchi, B., Rieckermann, J., & Berne, A. (2013). Quality control of rain gauge measurements using telecommunication microwave links. Journal of Hydrology, 492, 15-23. doi:10.1016/j.jhydrol.2013.03.042, Institutional Repository

Accurate rain rate measurements are essential for many hydrological applications. Although rain gauge remains the reference instrument for the measurement of rain rate, the strong spatial and temporal variability of rainfall makes it difficult to spot faulty rain gauges. Due to the poor spatial representativeness of the point rainfall measurements, this is particularly difficult where their density is low. Taking advantage of the high density of telecommunication microwave links in urban areas, a consistency check is proposed to identify faulty rain gauges using nearby microwave links. The methodology is tested on a data set from operational rain gauges and microwave links, in Zürich (Switzerland). The malfunctioning of rain gauges leading to errors in the occurrence of dry/rainy periods are well identified. In addition, the gross errors affecting quantitative rain gauge measurements during rainy periods, such as blocking at a constant value, random noise and systematic bias, can be detected. The proposed approach can be implemented in real time.
Del Giudice, D., Honti, M., Scheidegger, A., Albert, C., Reichert, P., & Rieckermann, J. (2013). Berücksichtigung von systematischen Modellabweichungen in der Kanalnetzsimulation. In Gewässerschutz bei Regenwetter – Gemeinschaftsaufgabe für Stadtplaner, Ingenieure und Ökologen (pp. 166-170). Dübendorf: Eawag. , Institutional Repository

Hydrodynamische Kanalnetzmodelle sind für die Entwässerungsplanung unersetzlich.Obwohl sie den komplexen Niederschlags-Abfluss Prozess niemals exakt abbilden können, liefern sie oft akzeptable Ergebnisse. Es ist jedoch schwierig, plausible Schätzungen der Unsicherheit von Kanalnetzberechnungen zu erhalten, da die gängigen statistischen Verfahren auf sehr starken Annahmen über die Fehlerverteilung beruhen, wie z.B. unabhängige, und identisch verteilte Zufallseffekte, welche praktisch nie erfüllt sind. In diesem Artikel stellen wir deshalb eine Methode vor, um i) zuverlässigere Schätzungen der Unsicherheit von Kanalnetzsimulationen zu berechnen und ii) die Vorhersageunsicherheit in einzelne Komponenten zu trennen. Zu diesem Zweck werden neben dem deterministischen Modell und zufälligen Messfehlern auch systematische Modellabweichungen berücksichtigt. Diese systematischen Modellabweichungen werden durch einen autoregressiven Zufallsprozess beschrieben und erfassen die Effekte von Unsicherheiten in den Eingangsdaten und der Modellstruktur. Zur Kalibration wird Bayessche Parameterschätzung verwendet. Wir zeigen an einem Fallbeispiel, dass die Berücksichtigung der Modellabweichung die Zuverlässigkeit der Berechnungsergebnisse stark verbessert. Ausserdem wird deutlich, dass systematische Modellabweichungen die Vorhersageunsicherheit dominieren und weit grösser sind, als Unsicherheit in den Modellparametern oder Messfehler. Abgesehen von den langen Rechenzeiten ergeben sich gewisse Limitierungen aus der subjektiven Formulierung des Vorwissens über die Parameter des Fehlermodells. Die statistische Berücksichtigung von systematischen Modellabweichungen liefert jedoch eine zuverlässige Schätzungen der Unsicherheit als herkömmliche Methoden und scheint daher für Kanalnetzsimulationen sehr interessant.
Del Giudice, D., Honti, M., Scheidegger, A., Albert, C., Reichert, P., & Rieckermann, J. (2013). Improving uncertainty estimation in urban hydrological modeling by statistically describing bias. Hydrology and Earth System Sciences, 17(10), 4209-4225. doi:10.5194/hess-17-4209-2013, Institutional Repository

Hydrodynamic models are useful tools for urban water management. Unfortunately, it is still challenging to obtain accurate results and plausible uncertainty estimates when using these models. In particular, with the currently applied statistical techniques, flow predictions are usually overconfident and biased. In this study, we present a flexible and relatively efficient methodology (i) to obtain more reliable hydrological simulations in terms of coverage of validation data by the uncertainty bands and (ii) to separate prediction uncertainty into its components. Our approach acknowledges that urban drainage predictions are biased. This is mostly due to input errors and structural deficits of the model. We address this issue by describing model bias in a Bayesian framework. The bias becomes an autoregressive term additional to white measurement noise, the only error type accounted for in traditional uncertainty analysis. To allow for bigger discrepancies during wet weather, we make the variance of bias dependent on the input (rainfall) or/and output (runoff) of the system. Specifically, we present a structured approach to select, among five variants, the optimal bias description for a given urban or natural case study. We tested the methodology in a small monitored stormwater system described with a parsimonious model. Our results clearly show that flow simulations are much more reliable when bias is accounted for than when it is neglected. Furthermore, our probabilistic predictions can discriminate between three uncertainty contributions: parametric uncertainty, bias, and measurement errors. In our case study, the best performing bias description is the output-dependent bias using a log-sinh transformation of data and model results. The limitations of the framework presented are some ambiguity due to the subjective choice of priors for bias parameters and its inability to address the causes of model discrepancies. Further research should focus on quantifying and reducing the causes of bias by improving the model structure and propagating input uncertainty.
Dürrenmatt, D. J., Del Giudice, D., & Rieckermann, J. (2013). Dynamic time warping improves sewer flow monitoring. Water Research, 47(11), 3803-3816. doi:10.1016/j.watres.2013.03.051, Institutional Repository

Successful management and control of wastewater and storm water systems requires accurate sewer flow measurements. Unfortunately, the harsh sewer environment and insufficient flow meter calibration often lead to inaccurate and biased data. In this paper, we improve sewer flow monitoring by creating redundant information on sewer velocity from natural wastewater tracers. Continuous water quality measurements upstream and downstream of a sewer section are used to estimate the travel time based on i) cross-correlation (XCORR) and ii) dynamic time warping (DTW). DTW is a modern data mining technique that warps two measured time series non-linearly in the time domain so that the dissimilarity between the two is minimized. It has not been applied in this context before. From numerical experiments we can show that DTW outperforms XCORR, because it provides more accurate velocity estimates, with an error of about 7% under typical conditions, at a higher temporal resolution. In addition, we can show that pre-processing of the data is important and that tracer reaction in the sewer reach is critical. As dispersion is generally small, the distance between the sensors is less influential if it is known precisely. Considering these findings, we tested the methods on a real-world sewer to check the performance of two different sewer flow meters based on temperature measurements. Here, we were able to detect that one of two flow meters was not performing satisfactorily under a variety of flow conditions. Although theoretical analyses show that XCORR and DTW velocity estimates contain systematic errors due to dispersion and reaction processes, these are usually small and do not limit the applicability of the approach.
Fencl, M., Rieckermann, J., Schleiss, M., Stránský, D., & Bareš, V. (2013). Assessing the potential of using telecommunication microwave links in urban drainage modelling. Water Science and Technology, 68(8), 1810-1818. doi:10.2166/wst.2013.429, Institutional Repository

The ability to predict the runoff response of an urban catchment to rainfall is crucial for managing drainage systems effectively and controlling discharges from urban areas. In this paper we assess the potential of commercial microwave links (MWL) to capture the spatio-temporal rainfall dynamics and thus improve urban rainfall-runoff modelling. Specifically, we perform numerical experiments with virtual rainfall fields and compare the results of MWL rainfall reconstructions to those of rain gauge (RG) observations. In a case study, we are able to show that MWL networks in urban areas are sufficiently dense to provide good information on spatio-temporal rainfall variability and can thus considerably improve pipe flow prediction, even in small subcatchments. In addition, the better spatial coverage also improves the control of discharges from urban areas. This is especially beneficial for heavy rainfall, which usually has a high spatial variability that cannot be accurately captured by RG point measurements.
Schleiss, M., Rieckermann, J., & Berne, A. (2013). Quantification and modeling of wet-antenna attenuation for commercial microwave links. IEEE Geoscience and Remote Sensing Letters, 10(5), 1195-1199. doi:10.1109/LGRS.2012.2236074, Institutional Repository

Data from a new experimental setup deployed in Dübendorf (Switzerland) are used to quantify and model the magnitude and dynamics of the wet-antenna attenuation (WAA) affecting a 1.85-km commercial microwave link at 38 GHz. The results show that the WAA exhibits the following properties: 1) It is bounded by a maximum value of about 2.3 dB; 2) it increases exponentially toward 2.3 dB during the first 5-20 min of rainfall; and 3) it decreases exponentially as soon as the rain stops. A new dynamic WAA model that reproduces these three features and can be calibrated using solely link measurements is proposed. Its performance is evaluated at different temporal resolutions and compared with other wet-antenna models from the literature. The results show that the dynamic model outperforms all other models and significantly reduces the uncertainty of the retrieved path-averaged rain rates.
Sikorska, A. E., Scheidegger, A., Banasik, K., & Rieckermann, J. (2013). Considering rating curve uncertainty in water level predictions. Hydrology and Earth System Sciences, 17(11), 4415-4427. doi:10.5194/hess-17-4415-2013, Institutional Repository

Streamflow cannot be measured directly and is typically derived with a rating curve model. Unfortunately, this causes uncertainties in the streamflow data and also influences the calibration of rainfall-runoff models if they are conditioned on such data. However, it is currently unknown to what extent these uncertainties propagate to rainfall-runoff predictions. This study therefore presents a quantitative approach to rigorously consider the impact of the rating curve on the prediction uncertainty of water levels. The uncertainty analysis is performed within a formal Bayesian framework and the contributions of rating curve versus rainfall-runoff model parameters to the total predictive uncertainty are addressed. A major benefit of the approach is its independence from the applied rainfall-runoff model and rating curve. In addition, it only requires already existing hydrometric data. The approach was successfully demonstrated on a small catchment in Poland, where a dedicated monitoring campaign was performed in 2011. The results of our case study indicate that the uncertainty in calibration data derived by the rating curve method may be of the same relevance as rainfall-runoff model parameters themselves. A conceptual limitation of the approach presented is that it is limited to water level predictions. Nevertheless, regarding flood level predictions, the Bayesian framework seems very promising because it (i) enables the modeler to incorporate informal knowledge from easily accessible information and (ii) better assesses the individual error contributions. Especially the latter is important to improve the predictive capability of hydrological models.
Maurer, M., Rieckermann, J., Muschalla, D., Gruber, G., Schmitt, T. G., Kaufmann Alves, I., … Dittmer, U. (Eds.). (2013). Gewässerschutz bei Regenwetter - Gemeinschaftsaufgabe für Stadtplaner, Ingenieure und Ökologen. Aqua Urbanica 2013. Retrieved from https://www.tugraz.at/events/aquaurbanica/aquaurbanica-2022/weitere/archiv/au-2013/programm-und-beitraege, Institutional Repository
Blumensaat, F., Staufer, P., Heusch, S., Reußner, F., Schütze, M., Seiffert, S., … Rieckermann, J. (2012). Water quality-based assessment of urban drainage impacts in Europe - where do we stand today?. Water Science and Technology, 66(2), 304-313. doi:10.2166/wst.2012.178, Institutional Repository

Traditionally, design and optimisation of urban drainage systems was mainly driven by cost efficiency, surface flood prevention, and later by emission reduction. More recent procedures explicitly include ecological conditions of the receiving water in the definition of acceptable pollutant discharges via sewer system and treatment plant outlets. An ambient Water Quality based impact Assessment (WQA) principle therefore requires an integrative system optimisation. However, a broad range of mostly national WQA protocols exist across Europe varying in structure and complexity, assessment concept, spatial and temporal scope and handling of uncertainty. This variety inherently implies a considerable risk of subjectivity in the impact assessment with highly variable outcomes. The present review identifies differences and similarities of WQA protocols in use and discusses their strengths and weaknesses through: (i) a systematic comparison of WQA protocols by selected attributes, (ii) a review of real-life cases reported in the literature and expert interviews, and (iii) an illustration of our main findings by applying selected WQA in an instructive example. The review discusses differences in structure and concept, which are mainly identified for simplistic WQA protocols. The application of selected protocols to an example case shows a wide variety of numerical results and conclusive decisions. It is found that existing protocols target different questions within the decision making process, which users should be more aware of. Generally, to make assessments more reliable, further fundamental research is required to fully understand the relationship between stressors and stream ecosystem responses which will make assessments more reliable. Technically, tools suggested in WQA protocols show severe deficiencies and an uncertainty assessment should be mandatory.
Dürrenmatt, D. J., Del Giudice, D., & Rieckermann, J. (2012). Dynamic time warping improves sewer flow monitoring. In D. Prodanović & J. Plavšić (Eds.), Urban drainage modelling. Proceedings of the ninth international conference on urban drainage modelling (p. (13 pp.). Belgrade: Faculty of Civil Engineering, University of Belgrade. , Institutional Repository

Successful supervision and control of wastewater and storm water systems requires accurate sewer flow measurements. Unfortunately, the harsh sewer environment and missing flow meter calibration often lead to inaccurate and biased data. In this manuscript, we improve sewer flow monitoring by creating redundant information on sewer velocity from wastewater quality measurements. Continuous observations upstream and downstream of a sewer section are used to estimate the travel time based on dynamic time warping (DTW). DTW is a modern data mining technique that warps two measured time series non-linearly in the time domain so that the dissimilarity between the two is minimized. We first explore the characteristics of the method using numerical experiments. Our results demonstrate that the error in velocity estimates from DTW under typical conditions is about 7%. Second, we apply DTW in a case study to check the performance of two different sewer flow meters using temperature measurements. This enables us to detect that one of two flow meters was not performing satisfactorily under a variety of flow conditions. Although theoretical analyses show that DTW velocity estimates contain systematic errors due to dispersion and reaction processes, these are usually small and do not limit the applicability of the approach.
Fencl, M., Rieckermann, J., Stránský, D., & Bareš, V. (2012). Improving urban drainage modelling with path-average rainfall from telecommunication microwave link. In D. Prodanović & J. Plavšić (Eds.), Urban drainage modelling. Proceedings of the ninth international conference on urban drainage modelling (p. (10 pp.). Belgrade: Faculty of Civil Engineering, University of Belgrade. , Institutional Repository

Incomplete knowledge about spatio-temporal rainfall dynamics causes input uncertainty in rainfall - runoff modelling. This is especially critical in urban areas, where subcatchments are small and runoff is generated extremely fast on the impervious areas. Networks of telecommunication microwave links (MWL) are very dense in urban areas and therefore could provide novel rainfall information which has the potential to reduce input uncertainty in urban drainage modelling. In this study, we therefore investigate how the better information on spatio-temporal rainfall variability from MWL observations improves pipe flow predictions. Specifically, we perform numerical experiments with virtual rainfall fields and compare the results of MWL rainfall reconstructions to those of rain gauge observations. For a case study of a suburb in Prague, Czech Republic, we are able to show that MWL networks in urban areas are sufficiently dense to provide good information on spatio-temporal rainfall variability. Total rainfall volumes are reproduced very well, with errors of about 6 %. Although peak rainfall intensities are still systematically underestimated by approximately 30%, this clearly outperforms rain gauge observations. Also, we find that peak flows from MWL observations are only biased by -6 %, whereas rain gauge observations cause a bias of 16 %. In our study, we did not include effects of uncertainties in both MWL and rain gauge measurements, which, arguably, can be high. Nevertheless, MWL networks could provide hundreds of rainfall sensors, which would be available at virtually no cost. As demonstrated, MWLs can significantly reduce input uncertainties in future rainfall-runoff modeling and thus improve discharge predictions.
Fencl, M., Rieckermann, J., Stránský, D., Fidranská, H., & Bareš, V. (2012). Telecommunication microwave links as a source of rainfall information for urban rainfall-runoff modelling. In P. Molnar, P. Burlando, & T. Einfalt (Eds.), Urban challenges in rainfall analysis (pp. 188-192). Zurich: ETH Zurich. , Institutional Repository

In this paper we investigate potential of commercial microwave links (MWL) to capture the spatio-temporal rainfall dynamics and thus improve rainfall-runoff modelling in urban areas. Specifically, we perform numerical experiments with virtual rainfall fields and compare the results of MWL rainfall reconstructions to those of rain gauge (RG) observations. For a case study of a small sewer system, we are able to show that MWL networks in urban areas are sufficiently dense to provide good information on spatio-temporal rainfall variability and can thus considerably improve pipe flow prediction. This is especially beneficial for high-intensity rainfalls, which usually have a high spatial variability that cannot be accurately captured by RG point measurements.
Rieckermann, J., Fencl, M., & Bareš, V. (2012). Rainfall estimation with telecommunication microwave links - influence of reference rainfall observations. In P. Molnar, P. Burlando, & T. Einfalt (Eds.), Urban challenges in rainfall analysis (pp. 208-212). Zurich: ETH Zurich. , Institutional Repository

In this paper, we investigate how rainfall observations from telecommunication microwave links improve when the link is adjusted against different reference rainfall data from rain gauges or distrometers. Based on field data and numerical experiments we assess the performance of four different rainfall retrieval models, which require different levels of precipitation information.
Schatzmann, A., Scheidegger, A., Rieckermann, J., & Ruckstuhl, A. (2012). Robust extraction of rain-induced attenuation from microwave link observations using local regression. In P. Molnar, P. Burlando, & T. Einfalt (Eds.), Urban challenges in rainfall analysis (pp. 218-222). Zurich: ETH Zurich. , Institutional Repository

Recently, the rain-induced attenuation of microwave links (MWL) has been suggested as a novel tool to monitor rainfall in urban areas. However, this requires robust methods to identify and remove baseline attenuation during dry weather, which is not trivial. In this paper, we present a novel statistical method to identify the baseline attenuation based on robust local regression (REBS) offline and in real-time. To test the correct baseline removal, we were able to test the algorithm on an extraordinary dataset of a dense network of rain gauges and disdrometers that provides an unrivalled ground truth reference rain fall and avoids uncertainties due to scaling effect between the path-average MWL measurements and point rain gauge observations. Our results show that the robust regression algorithms predict the path-average rainfall intensities from MWL signal levels that are practically unbiased and match the reference rainfall well. Although the scatter for 1-min rainfall intensities can vary up to 80% of the reference measurements, this it reduced to about 20% for 10min average intensities.
Sikorska, A. E., Scheidegger, A., Banasik, K., & Rieckermann, J. (2012). Bayesian uncertainty assessment of flood predictions in ungauged urban basins for conceptual rainfall-runoff models. Hydrology and Earth System Sciences, 16(4), 1221-1236. doi:10.5194/hess-16-1221-2012, Institutional Repository

Urbanization and the resulting land-use change strongly affect the water cycle and runoff-processes in watersheds. Unfortunately, small urban watersheds, which are most affected by urban sprawl, are mostly ungauged. This makes it intrinsically difficult to assess the consequences of urbanization. Most of all, it is unclear how to reliably assess the predictive uncertainty given the structural deficits of the applied models. In this study, we therefore investigate the uncertainty of flood predictions in ungauged urban basins from structurally uncertain rainfall-runoff models. To this end, we suggest a procedure to explicitly account for input uncertainty and model structure deficits using Bayesian statistics with a continuous-time autoregressive error model. In addition, we propose a concise procedure to derive prior parameter distributions from base data and successfully apply the methodology to an urban catchment in Warsaw, Poland. Based on our results, we are able to demonstrate that the autoregressive error model greatly helps to meet the statistical assumptions and to compute reliable prediction intervals. In our study, we found that predicted peak flows were up to 7 times higher than observations. This was reduced to 5 times with Bayesian updating, using only few discharge measurements. In addition, our analysis suggests that imprecise rainfall information and model structure deficits contribute mostly to the total prediction uncertainty. In the future, flood predictions in ungauged basins will become more important due to ongoing urbanization as well as anthropogenic and climatic changes. Thus, providing reliable measures of uncertainty is crucial to support decision making.
Sikorska, A. E., Scheidegger, A., Chiaia-Hernandez, A. C., Hollender, J., & Rieckermann, J. (2012). Tracing of micropollutants sources in urban receiving waters based on sediment fingerprinting. In D. Prodanović & J. Plavšić (Eds.), Urban drainage modelling. Proceedings of the ninth international conference on urban drainage modelling (p. (14 pp.). Belgrade: Faculty of Civil Engineering, University of Belgrade, , Institutional Repository

Micropollutants in urban receiving waters typically origin from many sources, such as wastewater effluents, combined sewer overflows, stormwater discharges and diffuse inputs from arable land. To design effective pollution management strategies in watersheds with mixed land use, we suggest a screening method that pinpoints the origin of pollutants and identifies relevant flow paths. This takes advantage of the fact, that medium polar micropollutants sorb to sediments. The core of the approach is an expert system based on Bayesian probabilities that updates the experts’ knowledge on potential micropollutant sources in a catchment using monitoring data from a single sediment sample. We are able to demonstrate the feasibility of the approach on a real-world case study in the Mönchaltorfer Aa catchment, where micropollutants most probably origin from wastewater and stormwater influents and not from agriculture. Limitations arise from the analytical cost and labour-intensive analysis, which limits the number of samples and, inscreening mode, only provides qualitative information on the observed compounds.
Staufer, P., Scheidegger, A., & Rieckermann, J. (2012). Assessing the performance of sewer rehabilitation on the reduction of infiltration and inflow. Water Research, 46(16), 5185-5196. doi:10.1016/j.watres.2012.07.001, Institutional Repository

Inflow and Infiltration (I/I) into sewer systems is generally unwanted, because, among other things, it decreases the performance of wastewater treatment plants and increases combined sewage overflows. As sewer rehabilitation to reduce I/I is very expensive, water managers not only need methods to accurately measure I/I, but also they need sound approaches to assess the actual performance of implemented rehabilitation measures. However, such performance assessment is rarely performed. On the one hand, it is challenging to adequately take into account the variability of influential factors, such as hydro-meteorological conditions. On the other hand, it is currently not clear how experimental data can indeed support robust evidence for reduced I/I. In this paper, we therefore statistically assess the performance of rehabilitation measures to reduce I/I. This is possible by using observations in a suitable reference catchment as a control group and assessing the significance of the observed effect by regression analysis, which is well established in other disciplines. We successfully demonstrate the usefulness of the approach in a case study, where rehabilitation reduced groundwater infiltration by 23.9%. A reduction of stormwater inflow of 35.7%, however, was not statistically significant. Investigations into the experimental design of monitoring campaigns confirmed that the variability of the data as well as the number of observations collected before the rehabilitation impact the detection limit of the effect. This implies that it is difficult to improve the data quality after the rehabilitation has been implemented. Therefore, future practical applications should consider a careful experimental design. Further developments could employ more sophisticated monitoring methods, such as stable environmental isotopes, to directly observe the individual infiltration components. In addition, water managers should develop strategies to effectively communicate statistically not significant I/I reduction ratios to decision makers.
Staufer, P., Scheidegger, A., & Rieckermann, J. (2012). Statistical performance evaluation in urban drainage – an example of groundwater infiltration. In D. Prodanović & J. Plavšić (Eds.), Urban drainage modelling. Proceedings of the ninth international conference on urban drainage modelling (p. (11 pp.). Belgrade: Faculty of Civil Engineering, University of Belgrade. , Institutional Repository

Inflow and infiltration (I/I) have a number of negative effects on the operation of drainage systems. Measures to reduce I/I are applied in many municipalities. However, the effect is only assessed on rare occasions. While a number of guidelines and studies exist on how to quantify I/I, only little is known about the effect of the measures. To one part this results from limiting the quality assurance to the actual measure, e.g. leak-tightness of rehabilitated sewers. For a second part, this is due to lacking methods to separate the effect from external factors ike rainfall or hydrological conditions. This study presents the paired use of a reference catchment and regression analysis to illicit the effect of rehabilitation on groundwater infiltration. Comparing the results of the novel approach to the performance assessment in an ad-hoc manner revealed for the case study a crude overestimation of the effect for the traditional approach. While the regression analysis evaluated the effect to 24%, the traditional approach assesses the performance in the range between 38% and 61% depending on the season during the monitoring.
Thomas, K. V., Bijlsma, L., Castiglioni, S., Covaci, A., Emke, E., Grabic, R., … de Voogt, P. (2012). Comparing illicit drug use in 19 European cities through sewage analysis. Science of the Total Environment, 432, 432-439. doi:10.1016/j.scitotenv.2012.06.069, Institutional Repository

The analysis of sewage for urinary biomarkers of illicit drugs is a promising and complementary approach for estimating the use of these substances in the general population. For the first time, this approach was simultaneously applied in 19 European cities, making it possible to directly compare illicit drug loads in Europe over a 1-week period. An inter-laboratory comparison study was performed to evaluate the analytical performance of the participating laboratories. Raw 24-hour composite sewage samples were collected from 19 European cities during a single week in March 2011 and analyzed for the urinary biomarkers of cocaine, amphetamine, ecstasy, methamphetamine and cannabis using in-house optimized and validated analytical methods. The load of each substance used in each city was back-calculated from the measured concentrations. The data show distinct temporal and spatial patterns in drug use across Europe. Cocaine use was higher in Western and Central Europe and lower in Northern and Eastern Europe. The extrapolated total daily use of cocaine in Europe during the study period was equivalent to 356. kg/day. High per capita ecstasy loads were observed in Dutch cities, as well as in Antwerp and London. In general, cocaine and ecstasy loads were significantly elevated during the weekend compared to weekdays. Per-capita loads of methamphetamine were highest in Helsinki and Turku, Oslo and Budweis, while the per capita loads of cannabis were similar throughout Europe. This study shows that a standardized analysis for illicit drug urinary biomarkers in sewage can be applied to estimate and compare the use of these substances at local and international scales. This approach has the potential to deliver important information on drug markets (supply indicator).
Wang, Z., Schleiss, M., Jaffrain, J., Berne, A., & Rieckermann, J. (2012). Using Markov switching models to infer dry and rainy periods from telecommunication microwave link signals. Atmospheric Measurement Techniques, 5(7), 1847-1859. doi:10.5194/amt-5-1847-2012, Institutional Repository

A Markov switching algorithm is introduced to classify attenuation measurements from telecommunication microwave links into dry and rainy periods. It is based on a simple state-space model and has the advantage of not relying on empirically estimated threshold parameters. The algorithm is applied to data collected using a new and original experimental set-up in the vicinity of Zürich, Switzerland. The false dry and false rain detection rates of the algorithm are evaluated and compared to 3 other algorithms from the literature. The results show that, on average, the Markov switching model outperforms the other algorithms. It is also shown that the classification performance can be further improved if redundant information from multiple channels is used.
Mathieu, C., Rieckermann, J., Berset, J. D., Schürch, S., & Brenneisen, R. (2011). Assessment of total uncertainty in cocaine and benzoylecgonine wastewater load measurements. Water Research, 45(20), 6650-6660. doi:10.1016/j.watres.2011.09.049, Institutional Repository

To check the effectiveness of campaigns preventing drug abuse or indicating local effects of efforts against drug trafficking, it is beneficial to know consumed amounts of substances in a high spatial and temporal resolution. The analysis of drugs of abuse in wastewater (WW) has the potential to provide this information. In this study, the reliability of WW drug consumption estimates is assessed and a novel method presented to calculate the total uncertainty in observed WW cocaine (COC) and benzoylecgonine (BE) loads. Specifically, uncertainties resulting from discharge measurements, chemical analysis and the applied sampling scheme were addressed and three approaches presented. These consist of (i) a generic model-based procedure to investigate the influence of the sampling scheme on the uncertainty of observed or expected drug loads, (ii) a comparative analysis of two analytical methods (high performance liquid chromatography–tandem mass spectrometry and gas chromatography–mass spectrometry), including an extended cross-validation by influent profiling over several days, and (iii) monitoring COC and BE concentrations in WW of the largest Swiss sewage treatment plants. In addition, the COC and BE loads observed in the sewage treatment plant of the city of Berne were used to back-calculate the COC consumption. The estimated mean daily consumed amount was 107 ± 21 g of pure COC, corresponding to 321 g of street-grade COC.
Rieckermann, J., Anta, J., Scheidegger, A., & Ort, C. (2011). Assessing wastewater micropollutant loads with Approximate Bayesian Computations. Environmental Science and Technology, 45(10), 4399-4406. doi:10.1021/es1030432, Institutional Repository

Wastewater production, like many other engineered and environmental processes, is inherent stochastic in nature and requires the use of complex stochastic models, for example, to predict realistic patterns of down-the-drain chemicals or pharmaceuticals and personal care products. Up until now, a formal method of statistical inference has been lacking for many of those models, where explicit likelihood functions were intractable. In this Article, we investigate Approximate Bayesian Computation (ABC) methods to infer important parameters of stochastic environmental models. ABC methods have been recently suggested to perform model-based inference in a Bayesian setting when model likelihoods are analytically or computationally intractable and have not been applied to environmental systems analysis or water quality modeling before. In a case study, we investigate the performance of three different algorithms to infer the number of wastewater pulses contained in three high-resolution data series of benzotriazole and total nitrogen loads in sewers. We find that all algorithms perform well and that the uncertainty in the inferred number of corresponding wastewater pulses varies between 6% and 28%. In our case, the results are more sensitive to substance characteristics than to catchment properties. Although the application of ABC methods requires careful tuning and attention to detail, they have a great general potential to update stochastic model parameters with monitoring data and improve their predictive capabilities.
Scheidegger, A., Hug, T., Rieckermann, J., & Maurer, M. (2011). Network condition simulator for benchmarking sewer deterioration models. Water Research, 45(16), 4983-4994. doi:10.1016/j.watres.2011.07.008, Institutional Repository

Anaccurate description of aging and deterioration of urban drainage systemsis necessary for optimal investment and rehabilitation planning. Due to a general lack of suitable datasets, network condition models are rarely validated, and if so with varying levels of success. We therefore propose a novel network condition simulator (NetCoS) that produces a synthetic population of sewer sections with a given condition-class distribution. NetCoS can be used to benchmark deterioration models and guide utilities in the selection of appropriate models and data management strategies. The underlying probabilistic model considers three main processes: a) deterioration, b) replacement policy, and c) expansions of the sewer network. The deterioration model features a semi-Markov chain that uses transition probabilities based on user-defined survival functions. The replacement policy is approximated with a condition-class dependent probability of replacing a sewer pipe. The model then simulates the course of the sewer sections from the installation of the first line to the present, adding new pipes based on the defined replacement and expansion program. We demonstrate the usefulness of NetCoS in two examples where we quantify the influence of incomplete data and inspection frequency on the parameter estimation of a cohort survival model and a Markov deterioration model. Our results show that typical available sewer inventory data with discarded historical data overestimate the average life expectancy by up to 200 years. Although NetCoS cannot prove the validity of a particular deterioration model, it is useful to reveal its possible limitations and shortcomings and quantifies the effects of missing or uncertain data. Future developments should include additional processes, for example to investigate the long-term effect of pipe rehabilitation measures, such as inliners.
Ort, C., Lawrence, M. G., Rieckermann, J., & Joss, A. (2010). Sampling for pharmaceuticals and personal care products (PPCPs) and illicit drugs in wastewater systems: are your conclusions valid? A critical review. Environmental Science and Technology, 44(16), 6024-6035. doi:10.1021/es100779n, Institutional Repository

The analysis of 87 peer-reviewed journal articles reveals that sampling for pharmaceuticals and personal care products (PPCPs) and illicit drugs in sewers and sewage treatment plant influents is mostly carried out according to existing tradition or standard laboratory protocols. Less than 5% of all studies explicitly consider internationally acknowledged guidelines or methods for the experimental design of monitoring campaigns. In the absence of a proper analysis of the system under investigation, the importance of short-term pollutant variations was typically not addressed. Therefore, due to relatively long sampling intervals, potentially inadequate sampling modes, or insufficient documentation, it remains unclear for the majority of reviewed studies whether observed variations can be attributed to “real” variations or if they simply reflect sampling artifacts. Based on results from previous and current work, the present paper demonstrates that sampling errors can lead to overinterpretation of measured data and ultimately, wrong conclusions. Depending on catchment size, sewer type, sampling setup, substance of interest, and accuracy of analytical method, avoidable sampling artifacts can range from “not significant” to “100% or more” for different compounds even within the same study. However, in most situations sampling errors can be reduced greatly, and sampling biases can be eliminated completely, by choosing an appropriate sampling mode and frequency. This is crucial, because proper sampling will help to maximize the value of measured data for the experimental assessment of the fate of PPCPs as well as for the formulation and validation of mathematical models. The trend from reporting presence or absence of a compound in “clean” water samples toward the quantification of PPCPs in raw wastewater requires not only sophisticated analytical methods but also adapted sampling methods. With increasing accuracy of chemical analyses, inappropriate sampling increasingly represents the major source of inaccuracy. A condensed step-by-step Sampling Guide is proposed as a starting point for future studies.
Rieckermann, J., Borsuk, M. E., Sydler, D., Gujer, W., & Reichert, P. (2010). Bayesian experimental design of tracer studies to monitor wastewater leakage from sewer networks. Water Resources Research, 46(8), 1-14. doi:10.1029/2009WR008630, Institutional Repository

Despite more than a decade of research, the magnitude of wastewater leakage from defective sewer systems into groundwater supplies is still largely unknown, partly because reliable measurement methods are lacking. Although recently suggested in-sewer tracer studies present a promising solution, it is unclear how to optimally design such studies in network settings. In this study we present a formal experimental design procedure, which uses Bayesian data analysis to improve the diagnosis of sewer leakage by combining tracer test data with prior knowledge on network topology and condition. From a simulation study, we show that (1) if a single sewer section is expected to have high leakage, that section should be distinguished in measurement layouts through isolated tests or appropriate overlapping of multiple tests; (2) if multiple sections are expected to have high leakage, layouts with tests that cover more than one high-leakage section should be avoided; and (3) if a robust experimental design is desired, a balanced layout of tests that overlap multiple sections of high leakage, yet minimizes stretch length, should be chosen. This design will have the additional benefit of inducing covariance in the posterior distribution of exfiltration estimates, which can be used to advantage in subsequent studies. We apply these guidelines to a case study of a catchment in Zurich, Switzerland, and find that optimal layout design can improve the anticipated gain of information substantially relative to designs based on practical considerations alone. Remaining concerns regarding the procedure include (1) the generally poor understanding of the mechanisms governing sewer leakage, which can hamper reliable prior information on exfiltration; (2) the currently low measurement precision of sewer tracer studies, which might only allow for the detection of large leaks; and (3) the need for numerical implementation of the Bayesian inference procedure, which requires careful tuning and long computation times. In general, we were able to demonstrate that the incorporation of prior information through a Bayesian procedure adds significant value to experimental design, especially in situations with few "hard" data but good site-specific knowledge, which is common in water resources research.
Lüscher, R. (2009). Precipitation monitoring using mobile phone networks (Master thesis). 53 p. , Institutional Repository

Nowadays, mobile phone antennas can be found almost everywhere. We can see many of them in urban regions and also in very remote areas. Where the service provider is lacking a sufficient cable network, point-to-point radio systems are normally used to connect one antenna to the next or to the a nearby access point of the telephone network. The network of radio links has become very dense in the last years, especially in urban areas. But this kind of transmission is only possible if there is direct line of sight between the sender and the receiver. As soon as it starts to rain, the signal strength is lowered because the rain drops hamper the propagation of the electromagnetic waves. This attenuation of the signal depends on the intensity of the rainfall and can be measured at the receiver. By means of a widely accepted empirical relationship it is possible to estimate the average rain rate along the link from the attenuation measurements at the receiver.
An urban area of about 150km2 in Greater Zurich is subject to this thesis. Measurements from 23 microwave links are provided by a local network operator and reference data from 13 rain gauges, two disdrometers and a weather radar were available. A total of 128 calibrations were conducted to estimate the parameters for the empirical relationship and two different types of the necessary pre-processing of the data were compared to each other. It could be shown that 50 per cent of the predictions made by means of a constant parameter set, are afflicted with a mean error of less than 1.2mm/h. Differences in the drop size distribution of rain events and the quality of the received signal were identified as important influence factors for reliable model predictions.

Mobilfunkantennen findet man heutzutage fast überall. Wir begegnen vielen davon in den städtischen Gebieten aber auch in abgelegenen Regionen. Überall dort, wo es den Mobilfunkanbietern an einem ausreichend dichten Kabelnetz mangelt, wird Richtfunk eingesetzt um die einzelnen Antennen mit einander zu verbinden und ans Telefonnetz anzuschliessen. Dieses Netz von Richtstrahlverbindungen ist in den letzten Jahren vor allem in den städtischen Gebieten immer dichter geworden. Diese Art der Informationsübertragung ist jedoch nur möglich, wenn zwischen dem Sender und dem Empfänger eine direkte Sichtverbindung besteht. Sobald es zu regnen beginnt, wird das Signal abgeschwächt, da die Regentropfen die Ausbreitung der elektromagnetischen Wellen behindern. Diese Dämpfung des Signals hängt von der Niederschlagsintensität ab und kann am Empfänger gemessen werden. Mithilfe einer gängigen empirischen Beziehung ist es möglich, aus den Dämpfungsmessungen am Empfänger die mittlere Regenintensität entlang der Verbindung zu bestimmen.
Diese Arbeit bezieht sich auf ein ungefähr 150km2 grosses städtisches Gebiet im Grossraum Zürich. Es wurden Messungen von 23 Mikrowellenverbindungen eines lokalen Mobilfunkanbieters zur Verfügung gestellt und es waren Referenzdaten von 13 Regenschreibern, zwei Tropfenspektrometern und einem Wetterradar verfügbar. Insgesamt wurden 128 Kalibrierungen durchgeführt um geeignete Parameter für die empirische Beziehung zu schätzen und es wurden zwei unterschiedliche Varianten der nötigen Vorverarbeitung der Daten miteinander verglichen. Es konnte gezeigt werden, dass 50 Prozent der Vorhersagen, die mit einem konstanten Parameterset durchgeführt wurden, mit einem mittleren Fehler von weniger als 1.2mm/h behaftet sind. Unterschiede in den Tropfengrössenverteilung von Regenereignissen und die Qualität des gemessenen Signals wurden als wichtige Einflussfaktoren für zuverlässige Ergebnisse der Modellierung identifiziert.
Rutsch, M., Rieckermann, J., Cullmann, J., Ellis, J. B., Vollertsen, J., & Krebs, P. (2008). Towards a better understanding of sewer exfiltration. Water Research, 42(10–11), 2385-2394. doi:10.1016/j.watres.2008.01.019, Institutional Repository

This paper gives a full review of the importance of sewer leakage, which has received increased attention throughout the last decades. Despite the intensive interdisciplinary research that has been invested, its magnitude is still unclear and a comprehensive solution for the assessment of sewer exfiltration does not seem to be at hand. However, given that mechanisms of exfiltration and the factors influencing its extent are similar all over the world, it seems possible to develop a generic leakage approach. Several methods for modelling sewer leakage are reviewed and the available measuring techniques are critically evaluated. Based on this evaluation, we suggest a unifying framework to facilitate focused model building. Specifically, we identify open research questions and propose to (i) standardise measurement results to enable better understanding, (ii) perform more long-term experiments under realistic field conditions, and (iii) assess the uncertainty of measurement and model results so that findings are not over-interpreted.
Rieckermann, J., Bareš, V., Kracht, O., Braun, D., & Gujer, W. (2007). Estimating sewer leakage from continuous tracer experiments. Water Research, 41(9), 1960-1972. doi:10.1016/j.watres.2007.01.024, Institutional Repository

Direct measurements of sewer leakage with continuous dosing of tracers are often considered too imprecise for practical applications. However, no mathematical framework for data analysis is reported in literature. In this paper, we present an improved experimental design and data analysis procedure together with a comprehensive framework for uncertainty assessment. Test runs in a 700 m-long watertight sewer showed no significant bias and a very high precision of the methodology. The standard error in the results was assessed to 2.6% of the labeled flow with a simplified model. It could be reduced to 1.2% when a dynamic data analysis procedure was applied. The major error contribution was caused by transient transport phenomena, which suggests that careful choosing of the experimental time is more important than the choice of a very specific tracer substance. Although the method is not intended to replace traditional CCTV inspections, it can provide complementary information for rational rehabilitation planning.
Rieckermann, J., Daebel, H., Ronteltap, M., & Bernauer, T. (2006). Assessing the performance of international water management at Lake Titicaca. Aquatic Sciences, 68(4), 502-516. doi:10.1007/s00027-006-0863-0, Institutional Repository

In this article, we study the performance of international water management at Lake Titicaca in order to assess the empirical applicability of a new concept for measuring policy performance. This performance measurement concept (PER) is a function of three variables: optimum performance (OP), actual performance (AP), and counterfactual performance (CP). In examining the joint management of Lake Titicaca by Bolivia and Peru, we identify practical difficulties in applying PER and suggest extensions of the concept to assess uncertainty. We find that this measurement concept has several advantages: it takes into account counterfactual performance; the analysis can be performed in a structured, standardized, and transparent manner; and the formal framework allows for an assessment of uncertainty. Problems in applying the concept include: choice of attributes, identification of optimum performance, time-scale, and subjectivity of information. We conclude that, on balance, this approach is superior to other policy performance assessment measures developed to date.
Rieckermann, J., Borsuk, M. E., & Gujer, W. (2006). Using decision analysis to determine optimal experimental design for monitoring sewer exfiltration with tracers. Water Science and Technology, 54(6-7), 161-168. doi:10.2166/wst.2006.615, Institutional Repository

The tracer methods developed to assess exfiltration from sewers in the European project APUSS (assessment of the performance of sewer systems) have a high degree of freedom with regard to the choice of tracer and the dosing strategy. These can lead to very different degrees of uncertainty in the measured exfiltration ratio. In this study, we demonstrate how to select an optimal experimental design using decision analysis, which accounts for this uncertainty and its associated costs. Although the results are site-specific, we can conclude generally that, when NaCl is used as the tracer, the accuracy of the exfiltration estimate is most sensitive to the amount of tracer used and the starting time of the experiment.
Rutsch, M., Rieckermann, J., & Krebs, P. (2006). Quantification of sewer leakage: a review. Water Science and Technology, 54(6-7), 135-144. doi:10.2166/wst.2006.616, Institutional Repository

One of the goals of the APUSS project (assessing infiltration and exfiltration on the performance of urban sewer systems) is to assess sewer exfiltration, in order to support cities and operators to define problem-oriented rehabilitation strategies. In this paper, we review various methods currently used for the estimation of exfiltration and discuss data needs and applicability for rehabilitation planning. Although each approach has its individual advantages and drawbacks, we identified pressure tests and tracer methods to have the highest potential for decision support in rehabilitation planning. With regard to future challenges (e.g. micropollutants) such methods might play a key role in integrated sewer management.
Rieckermann, J., Borsuk, M., Reichert, P., & Gujer, W. (2005). A novel tracer method for estimating sewer exfiltration. Water Resources Research, 41(5), W05013 (11 pp.). doi:10.1029/2004WR003699, Institutional Repository

A novel method is presented to estimate exfiltration from sewer systems using artificial tracers. The method relies upon use of an upstream indicator signal and a downstream reference signal to eliminate the dependence of exfiltration estimates on the accuracy of discharge measurement. An experimental design, a data analysis procedure, and an uncertainty assessment process are described and illustrated by a case study. In a 2-km reach of unknown condition, exfiltration was estimated at 9.9 ± 2.7%. Uncertainty in this estimate was primarily due to the use of sodium chloride (NaCl) as the tracer substance. NaCl is measured using conductivity, which is present at nonnegligible levels in wastewater, thus confounding accurate identification of tracer peaks. As estimates of exfiltration should have as low a measurement error as possible, future development of the method will concentrate on improved experimental design and tracer selection. Although the method is not intended to replace traditional CCTV inspections, it can provide additional information to urban water managers for rational rehabilitation planning.
Rieckermann, J., Neumann, M., Ort, C., Huisman, J. L., & Gujer, W. (2005). Dispersion coefficients of sewers from tracer experiments. Water Science and Technology, 52(5), 123-133. doi:10.2166/wst.2005.0124, Institutional Repository

In this paper, 60 tracer experiments in 37 different sewer reaches have been analyzed for longitudinal dispersion under dry weather flow conditions. It was found that dispersion coefficients of sewers are two to three orders of magnitude smaller than those measured in rivers and do not differ much from system to system. Suitable equations were identified to predict reasonable dispersion coefficients in sewer reaches with uniform geometry and stable flow conditions, For engineering applications that require a high degree of accuracy the performance of tracer measurements is recommended.
Rieckermann, J., Kracht, O., & Gujer, W. (2003). How "tight" is our sewer system?. Eawag News [engl. ed.], 57, 29-31. , Institutional Repository

Urban sewer systems are subjected to constant stress by traffic and soil movement. Combined with natural fatigue of materials, these conditions lead to damage to underground pipes, causing exfiltration of sewage into the ground water as well as infiltration of ground water into the sewer pipes. EAWAG is currently developing a new method to quantify these processes by using both natural and artificial tracers, which will help us in planning more efficient remedial action.
Rieckermann, J., Kracht, O., & Gujer, W. (2003). L’étanchéité de nos égouts. Eawag News [éd. fr.], 57, 29-31. , Institutional Repository

Les réseaux d’égouts urbains sont constamment soumis à des contraintes liées à la circulation automobile et aux mouvements du sol. Se surajoutant à la fatigue naturelle des matériaux, elles causent des dommages coûteux à l’infrastructure souterraine provoquant des exfiltrations d’eaux usées et des infiltrations d’eaux souterraines. L’EAWAG est actuellement en train de développer de nouvelles méthodes permettant de quantifier ces processus indésirables à l’aide de traceurs naturels et artificiels. Les informations obtenues sur l’étendue des infiltrations et exfiltrations doivent permettre d’établir un plan de réhabilitation plus efficace des égouts urbains.
Rieckermann, J., Bareš, V., Kracht, O., Braun, D., & Gujer, W. (2003). Quantifying exfiltration with continuous dosing of artificial tracers. In P. Hlavínek, P. Prax, & V. Šulcová (Eds.), Hydrosphere 2003. Sborník přednášek konference s mezinárodní účastí optimalizace návrhu a provozu stokových sítí a ČOV (p. (4 pp.). Brno, CZ: NOEL. , Institutional Repository

In this paper the authors present a method to quantify the exfiltration from sewers with artificial tracers. In an application study Lithium and Bromide were used as ionic tracers. The results from an error analysis indicate that the main problems with the application of the method originate from the time-varying sewer flow. Accurate information on exfiltration could be used in innovative sewer operation and maintenance strategies.
Rieckermann, J., Kracht, O., & Gujer, W. (2003). Wie dicht ist unser Kanalnetz?. Eawag News [dtsch. Ausg.], 57, 29-31. , Institutional Repository

Städtische Kanalnetze sind ständigen Belastungen durch Verkehr und Bodenbewegungen ausgesetzt. In Kombination mit der natürlichen Ermüdung des Materials entstehen kostspielige Schäden an der unterirdischen Infrastruktur, die die Exfiltration von Abwasser sowie die Infiltration von Grundwasser zur Folge haben. Die EAWAG entwickelt zurzeit neue Methoden, die es ermöglichen, diese unerwünschten Prozesse mit künstlichen und natürlichen Tracern zu quantifizieren. Die Informationen über das Ausmass von Ex- und Infiltration sollen eine effiziente Sanierungsplanung ermöglichen.

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