Department Urban Water Management

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.

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.

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.

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.

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.

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. [...]

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.

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.

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.

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.

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.

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.

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.

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 1/10^th to 1/50^th 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.

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. [...]

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. [...]

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.

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. [...]

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? [...]

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.

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.

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.

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.

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.

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.

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.

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).

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.

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.

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. [...]

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).

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.

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. [...]

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?

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? [...]

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.

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.

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.

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. [...]

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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. [...]

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.

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.

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.

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 %).

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.

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.

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.

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.

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. [...]

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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: [...]

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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. [...]

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.

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.

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). [...]

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.

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.

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.

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.

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.

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.

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.

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.

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.

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. [...]

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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).

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.

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.

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.

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.

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.

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.

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.

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 (K_D) 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 (K_D, 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^-1_COD, 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^-1_COD for sotalol, atenolol, metoprolol and propranolol, respectively.
These values translate into a typical elimination in STPs (sludge concentrations of 4 g_COD 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.

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.

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 K_s⁰=f₁[NH₄⁺]f₂[Mg²⁺]f₃[PO₄³⁻] ([ ]=concentration of the species; f_x=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 K_s^cond=[Mg_aq]·[NH₄⁺+NH₃]·[P_ortho]=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.

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.

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.

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.

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.

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.

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. [...]

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.

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.

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.

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.

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).

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.

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.

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.

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.

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 g_Nm^-3 d^-1 (5 g_O2m^-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 g_N 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* T_e^-1 == 10,1 g_O2 Nm^-3 m^-1 ). The oxygen utilisation rate found during trial operation (αOU* T_e^-1), however, only amounted to 4,1 g_O2 Nm^-3 m^-1.

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'.

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.

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.

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.

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. [...]

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.

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.

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.

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.

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.

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 g_Nm^–3d^–1 at 10°C and 730 g_Nm^–3d^–1 at 20°C. An average denitrification rate of 240 g_Nm^–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 kg_CODm^–3d^–1.

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 mol_P^-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 mol_P^-3 d^-1.

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.

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 g_pm⁻³d⁻¹ of inorganic calcium phosphate (HAP) is fixated irreversibly in the sludge.

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 g_Nm^–3d^–1 (at 5 g_O2m^–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 g_Nm^–3d^–1 (same environmental conditions as above).
With wastewater as a substrate, denitrification rate with both carrier materials amounted to 210 g_Nm^–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 g_CODg^–1_COD. The use of sponge cubes yielded a Y' equal to 0.36 g_CODg^–1_COD. In an activated sludge system, the yield lies in between these two values.

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.

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.

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.

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 g_P/m³_influence. 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.

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. [...]

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 g_P⁻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.

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.

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.