Abwasser

Hu, Y., Morgenroth, E., & Jacquin, C. (2025). Online monitoring of greywater reuse system using excitation-emission matrix (EEM) and K-PARAFACs. Water Research, 268, 122604 (13 pp.). doi:10.1016/j.watres.2024.122604, Institutional Repository

A currently increasing interest in water reuse is met with the concern about water quality. Excitation-emission matrix (EEM) measurements, which are widely implemented in laboratory analysis, emerge as a promising tool for characterizing both microbial and chemical water qualities in the online monitoring of water reuse systems. However, the robustness of EEM measurements has been rarely validated in actual online monitoring campaigns where predictions are made for new samples independent of those used to establish EEM analysis models, including the popular parallel factor analysis (PARAFAC). In this study, two strategies of conducting PARAFAC were examined for the online monitoring of a greywater reuse system using two EEM datasets from two monitoring periods for model establishment and model testing respectively. With the first strategy that is commonly used in laboratory analyses, an entire EEM datasets from one period was used to establish one PARAFAC model, and the maximum fluorescence intensity (F_max) of a PARAFAC component was used to predict total cell count (TCC) in another period. However, under the disturbance of dissolved organic matter (DOM) fluorescence in the background, F_max gave unreliable predictions in model testing. To address this problem, a second and novel strategy was proposed using an EEM clustering and PARAFAC component shift mining technique. This unsupervised algorithm, named K-PARAFACs, automatically groups EEMs into K clusters and on each cluster establishes a cluster-specific PARAFAC model with distinct component shapes. With this method, multiple PARAFAC models were established on one EEM dataset, with each model representing samples with certain TCC ranges and DOM compositions. In model testing, these cluster-specific PARAFAC models served as EEM classifiers. A new sample was not characterized by F_max but by the cluster-specific model that best fitted the EEM signal of the sample with the least numerical error. The proposed strategy demonstrates its robustness by successfully predicting the TCC trend in test datasets. Our findings suggest that K-PARAFACs is a promising tool that enables robust qualitative monitoring of water reuse systems with background DOM variability.

Binz, C., Sedlak, D., O’Callaghan, P., Truffer, B., Nesi, M., Morgenroth, E., … Wellauer, S. (2024). Mainstreaming decentralized urban water management solutions for sustainable cities. doi:10.55408/eawag:33039, Institutional Repository

Bou-Sarkis, A., Paul, E., Bessiere, Y., Derlon, N., & Girbal-Neuhauser, E. (2024). Impact of biochemical properties on the gelation of EPS extracted from aerobic granules. Journal of Environmental Chemical Engineering, 12(5), 113648 (10 pp.). doi:10.1016/j.jece.2024.113648, Institutional Repository

Fau, Z., Damien, T., Azais, A., Derlon, N., Chazarenc, F., & Gillot, S. (2024). Towards a standardised analysis of experimental Threshold Of Flocculation (TOF) curves. Water Science and Technology, 90(7), 2103-2113. doi:10.2166/wst.2024.308, Institutional Repository

Fumasoli, A., Probst, M., Wett, B., Derlon, N., Wenger, R., & Rérolle, M. (2024). Indense - Verfahren für Granulierten Schlamm. Erfahrungen und Erkenntnisse aus einem ein jährigen Pilotenversuch auf der ARA Gossau-Grüningen. Aqua & Gas, 104(1), 32-39. , Institutional Repository

Ganesanandamoorthy, P., Joss, A., Gruber, W., Bührer, T., & Thomann, M. (2024). Online-Nitritmessung. Vergleich von Online-Nitritsensoren für die Abwassereinigung. Aqua & Gas, 104(1), 26-31. , Institutional Repository

Gruber, W., Niederdorfer, R., Ganesanandamoorthy, P., Bürgmann, H., Morgenroth, E., & Joss, A. (2024). Nitrit-Akkumulation auf Nitrifizierenden Belebtschlammanlagen. Wie kann der NO₂^– - Richtwert eingehalten werden?. Aqua & Gas, 104(1), 18-24. , Institutional Repository

Knabl, M., Rist, B., & Morgenroth, E. (2024). Wasserwiederverwendung in der Schweiz. Bedarf, Chancen, Risiken und abgeleitete Handlungsempfehlungen für Verantwortliche. doi:10.55408/eawag:32884, Institutional Repository

Die geplante Wiederverwendung von gereinigtem Abwasser kann konventionelle Wasserressourcen entlasten und den Wasserverbrauch senken. Sie ist eine mögliche Handlungsoption im integralen Wasserressourcenmanagement, wenn der Nutzen im lokalen Kontext den notwendigen Aufwand (zusätzliche Aufbereitung, Infrastruktur, Kosten, Energie) überwiegt. Im vorliegenden Projekt wurde untersucht, ob die Wasserwiederverwendung eine relevante Option für das Wasserressourcenmanagement in der Schweiz sein könnte. Dazu wurden bestehende Daten zur Wasserverfügbarkeit und zum -Verbrauch analysiert und eine Umfrage zum Thema bei den kantonalen Umweltfachstellen durchgeführt. Aufgrund des Klimawandels kommt es in der Schweiz bereits heute häufiger zu Trockenheitsperioden, insbesondere im Sommer. Die damit verbundenen Hitzeereignisse führen zu einem Anstieg des Wasserbedarfs für verschiedene Anwendungen (Bewässerung in der Landwirtschaft und in den Städten, Kühlwasser etc.). Auf lokaler Ebene haben Vertretende von 19 der 26 Kantone einen Bedarf für die Wasserwiederverwendung für verschiedene Anwendungen, besonders für die Bewässerung, festgestellt. Zudem wird erwartet, dass dieser Bedarf mit dem fortschreitenden Klimawandel ansteigen wird. Ausserdem weist die Wasserwiederverwendung Synergien mit anderen Massnahmen im Wasserressourcenmanagement auf, z.B. mit der Speicherung von Wasser für Zeiten mit erhöhtem Bedarf. Für die Wiederverwendung von Wasser müssen klare Vorgaben bezüglich Qualität, nutzbarer Menge und technischer Rahmenbedingungen definiert werden, um Mensch und Umwelt nicht zu gefährden. Um Wasserwiederverwendungsprojekte langfristig erfolgreich umzusetzen zu können, muss zudem die soziale Akzeptanz gewährleistet sein. Derzeit ist die Wasserwiederverwendung im Schweizer Recht nicht explizit geregelt; im Prinzip ist nur die Bewässerung implizit verboten, während alle anderen Anwendungen grundsätzlich erlaubt sind, jedoch ohne Vorgaben zur Umsetzung oder Qualität. Zudem fehlen in der Schweiz Erfahrungen, Wissen und Kompetenzen für ihre Umsetzung. Daher wird empfohlen, in praktischen Pilotprojekten Erfahrungen zu sammeln und projektspezifische Informationen zu ermitteln (Kosten, benötigte Infrastruktur etc.). Parallel dazu sollte ein koordinierter Gesetzesanpassungsprozess stattfinden, der einen sicheren Umsetzungsrahmen für die Praxis in der Schweiz schafft. Damit wird sichergestellt, dass die Wasserwiederverwendung als sichere und kontrollierte Massnahme im zukünftigen Wasserressourcenmanagement zur Verfügung steht.

La réutilisation planifiée des eaux usées épurées peut soulager les ressources en eau conventionnelles et réduire la consommation d'eau. Elle constitue une option d'action possible dans la gestion intégrée des ressources en eau, si les avantages dans le contexte local l'emportent sur les dépenses nécessaires (traitement supplémentaire, infrastructure, coûts, énergie). Le présent projet a cherché à savoir si la réutilisation de l'eau pouvait être une option pertinente pour la gestion des ressources en eau en Suisse. Pour ce faire, les données existantes sur la disponibilité et la consommation d'eau ont été analysées et une enquête sur le sujet a été menée auprès des services cantonaux de l'environnement. En raison du changement climatique, les périodes de fortes chaleurs sont de plus en plus fréquentes en Suisse, notamment en été. Les épisodes de sécheresse qui en découlent entraînent une augmentation des besoins en eau pour différentes applications (irrigation pour l'agriculture et dans les villes, eau de refroidissement, etc.). Au niveau local, les représentants de 19 des 26 cantons ont identifié un besoin de réutilisation de l'eau pour diverses applications, en particulier pour l'irrigation. De plus, on s'attend à une augmentation de ces besoins avec le changement climatique en cours. En outre, la réutilisation de l'eau présente des synergies avec d'autres mesures de gestion des ressources en eau, par exemple le stockage de l'eau pour les périodes où les besoins sont plus importants. Bien entendu, la réutilisation de l'eau doit être soumise à des exigences claires en termes de qualité et de quantité utilisable et des directives techniques doivent être établies, afin de ne pas mettre en danger l'homme et l'environnement. De plus, pour que les projets de réutilisation de l'eau puissent être mis en oeuvre avec succès à long terme, l'acceptation sociale doit être garantie. Actuellement, la réutilisation de l'eau n'est pas explicitement réglementée dans le droit suisse ; seule l'irrigation est implicitement interdite, alors que toutes les autres applications sont autorisées, mais sans directives concernant la mise en oeuvre ou la qualité. En outre, la Suisse manque d'expérience, de connaissances et de compétences pour la mise en place de la réutilisation de l’eau. Il est donc recommandé d’acquérir de l’expérience par le biais de projets pilotes et d’évaluer les informations spécifiques au projet (coûts, infrastructure nécessaire, etc.). En parallèle, un processus coordonné d'adaptation de la législation est nécessaire pour encadrer une mise en oeuvre sûre de la pratique en Suisse. Cela permettra de garantir que la réutilisation de l'eau soit une mesure fiable et contrôlée pour la gestion future des ressources en eau.

The planned reuse of treated wastewater can relieve the pressure on conventional water resources and reduce water consumption. It is a possible option for action in integrated water resource management if the benefits in the local context outweigh the necessary effort (additional treatment, infrastructure, costs, energy). This project analysed whether water reuse could be a relevant option for water resource management in Switzerland. To this end, existing data on water availability and consumption were analysed and a survey on the topic was conducted among the cantonal environmental agencies. Due to climate change, Switzerland is already experiencing more frequent periods of drought, particularly in summer. The associated heat events lead to an increase in water demand for various applications (irrigation in agriculture and cities, cooling water, etc.). At local level, representatives from 19 of the 26 cantons have identified a need for water reuse for various applications, particularly irrigation. This demand is also expected to increase as climate change progresses. In addition, water reuse has synergies with other water resource management measures, such as storing water for times of increased demand. Clear specifications regarding quality, usable quantity and technical framework conditions must be defined for the reuse of water so as not to jeopardise people and the environment. In order to successfully implement water reuse projects on the long term, social acceptance must also be guaranteed. Currently, water reuse is not explicitly regulated in Swiss law; in principle, only irrigation is implicitly prohibited, while all other applications are permitted in principle, but without specifications regarding implementation or quality. In addition, there is a lack of experience, knowledge and expertise for their implementation in Switzerland. It is therefore recommended to gather experience in practical pilot projects and to determine project-specific information (costs, required infrastructure, etc.). At the same time, a coordinated legislative amendment process should take place to create a secure implementation framework for water reuse in Switzerland. This will ensure that water reuse is available as a safe and controlled measure in future water resource management.

Meynet, P., Joss, A., Davenport, R. J., & Fenner, K. (2024). Impact of long-term temperature shifts on activated sludge microbiome dynamics and micropollutant removal. Water Research, 258, 121790 (10 pp.). doi:10.1016/j.watres.2024.121790, Institutional Repository

Pechaud, Y., Derlon, N., Queinnec, I., Bessiere, Y., & Paul, E. (2024). Modelling biofilm development: the importance of considering the link between EPS distribution, detachment mechanisms and physical properties. Water Research, 250, 120985 (16 pp.). doi:10.1016/j.watres.2023.120985, Institutional Repository

In industry, treatments against biofilms need to be optimized and, in the wastewater treatment field, biofilm composition needs to be controlled. Therefore, describing the biochemical and physical structures of biofilms is now required to better understand the influence of operating parameters and treatment on biofilms. The present study aims to investigate how growth conditions influence EPS composition, biofilm physical properties and volume detachment using a 1D biofilm model. Two types of EPS are considered in the present model, proteins and polysaccharides. The main hypotheses are that: (i) the production of polysaccharides occurs mainly under strong nutrient limitation(s) while the production of proteins is coupled to both the substrate uptake rate and the lysis process; (ii) the local biofilm porosity depends on the local biofilm composition. Both volume and surface detachment occur in biofilms and volume detachment extent depends on the biofilm local cohesion and thus on the local composition of biofilms for a given shear stress.
The model is based on experimental trends and aims to represent these observations on the basis of biochemical and physical processes. Four case studies covering a wide range of contrasting growth conditions such as different COD/N ratios, applied SOLR and shear stresses are investigated. The model predicts how the biochemical and physical biofilm structures change as a result of contrasting growth conditions. More precisely simulation results are in good agreement with the main experimental observations reported in the literature, such as: (i) a strong nitrogen limitation of growth induces an important accumulation of polysaccharides leading to a more porous and homogenous biofilm, (ii) a high applied surface organic loading load allows to obtain a high biofilm thickness, (iii) a strong shear stress applied during the biofilm growth leads to a reduction of the biofilm thickness and to a consolidation of the biofilm structure. Overall, this model represents a relevant decision tool for the selection of appropriate enzymatic treatments in the context of negative biofilm control. From our results, it appears that protease based treatments should be more appropriate for biofilms developed under low COD/N ratios (about 20 gCOD/gN) whereas both glucosidases and proteases based treatments should be more appropriate for biofilms developed under high COD/N ratio (about 70 gCOD/gN). In addition, the model could be useful for other applications such as resource recovery in biofilms or granules, and help to better understand biological membrane fouling.

Reynaert, E., Nagappa, D., Sigrist, J. A., & Morgenroth, E. (2024). Ensuring microbial water quality for on-site water reuse: importance of online sensors for reliable operation. Water Research X, 22, 100215 (8 pp.). doi:10.1016/j.wroa.2024.100215, Institutional Repository

Reynaert, E., Sylvestre, É., Morgenroth, E., & Julian, T. R. (2024). Greywater recycling for diverse collection scales and appliances: enteric pathogen log-removal targets and treatment trains. Water Research, 264, 122216 (13 pp.). doi:10.1016/j.watres.2024.122216, Institutional Repository

In light of increasingly diverse greywater reuse applications, this study proposes risk-based log-removal targets (LRTs) to aid the selection of treatment trains for greywater recycling at different collection scales, including appliance-scale reuse of individual greywater streams. An epidemiology-based model was used to simulate the concentrations of prevalent and treatment-resistant reference pathogens (protozoa: Giardia and Cryptosporidium spp., bacteria: Salmonella and Campylobacter spp., viruses: rotavirus, norovirus, adenovirus, and Coxsackievirus B5) in the greywater streams for collection scales of 5-, 100-, and a 1000-people. Using quantitative microbial risk assessment (QMRA), we calculated LRTs to meet a health benchmark of 10^–4 infections per person per year over 10′000 Monte Carlo iterations. LRTs were highest for norovirus at the 5-people scale and for adenovirus at the 100- and 1000-people scales. Example treatment trains were designed to meet the 95 % quantiles of LRTs. Treatment trains consisted of an aerated membrane bioreactor, chlorination, and, if required, UV disinfection. In most cases, rotavirus, norovirus, adenovirus and Cryptosporidium spp. determined the overall treatment train requirements. Norovirus was most often critical to dimension the chlorination (concentration × time values) and adenovirus determined the required UV dose. Smaller collection scales did not generally allow for simpler treatment trains due to the high LRTs associated with viruses, with the exception of recirculating washing machines and handwashing stations. Similarly, treating greywater sources individually resulted in lower LRTs, but the lower required LRTs nevertheless did not generally allow for simpler treatment trains. For instance, LRTs for a recirculating washing machine were around 3-log units lower compared to LRTs for indoor reuse of combined greywater (1000-people scale), but both scenarios necessitated treatment with a membrane bioreactor, chlorination and UV disinfection. However, simpler treatment trains may be feasible for small-scale and application-scale reuse if: (i) less conservative health benchmarks are used for household-based systems, considering the reduced relative importance of treated greywater in pathogen transmission in households, and (ii) higher log-removal values (LRVs) can be validated for unit processes, enabling simpler treatment trains for a larger number of appliance-scale reuse systems.

Sylvestre, É., Jahne, M. A., Reynaert, E., Morgenroth, E., & Julian, T. R. (2024). A critical evaluation of parametric models for predicting faecal indicator bacteria concentrations in greywater. Microbial Risk Analysis, 26, 100297 (8 pp.). doi:10.1016/j.mran.2024.100297, Institutional Repository

Bou-Sarkis, A., Paul, E., Girbal-Neuhauser, E., Derlon, N., & Bessiere, Y. (2023). Detection of gel-forming polymers via calcium crosslinking, applied to the screening of extracellular polymeric substances extracted from biological aggregates. Gels, 9(2), 157 (14 pp.). doi:10.3390/gels9020157, Institutional Repository

Brison, A., Rossi, P., & Derlon, N. (2023). Single CSTR can be as effective as an SBR in selecting PHA-storing biomass from municipal wastewater-derived feedstock. Water Research X, 18, 100165 (13 pp.). doi:10.1016/j.wroa.2023.100165, Institutional Repository

A key step for the production of polyhydroxyalkanoates (PHAs) from organic waste streams is the selection of a biomass with a high PHA-storage capacity (selection-step), which is usually performed in sequencing batch reactors (SBR). A major advancement would be to perform such selection in continuous reactors to facilitate the full-scale implementation of PHA production from municipal wastewater (MWW)-derived feedstock. The present study therefore investigates to what extent a simple continuous-flow stirred-tank reactor (CSTR) represents a relevant alternative to anSBR. To this end, we operated two selection reactors (CSTR vs. SBR) on filtered primary sludge fermentate while performing a detailed analysis of the microbial communities, and monitoring PHA-storage over long-term (∼150 days) and during accumulation batches. Our study demonstrates that a simple CSTR is as effective as an SBR in selecting biomass with high PHA-storage capacity (up to 0.65 gPHA gVSS⁻¹) while being 50% more efficient in terms of substrate to biomass conversion yields. We also show that such selection can occur on VFA-rich feedstock containing nitrogen (N) and phosphorus (P) in excess, whereas previously, selection of PHA-storing organisms in a single CSTR has only been studied under P limitation. We further found that microbial competition was mostly affected by nutrient availability (N and P) rather than by the reactor operation mode (CSTR vs. SBR). Similar microbial communities therefore developed in both selection reactors, while microbial communities were very different depending on N availability. Rhodobacteraceae gen. were most abundant when growth conditions were stable and N-limited, whereas dynamic N- (and P-) excess conditions favoured the selection of the known PHA-storer Comamonas, and led to the highest observed PHA-storage capacity. Overall, we demonstrate that biomass with high storage capacity can be selected in a simple CSTR on a wider range of feedstock than just P-limited ones.

Böhler, M. A., Carl, F., Zhu, M., McArdell, C. S., Frömelt, A., & Joss, A. (2023). Spurenstoffelimination bei stark verdünnter Abwassermatrix – Erfahrungen, Kenntnisstand und Herausforderungen. In M. Wessling & T. Wintgens (Eds.), 15. Aachener Tagung Wassertechnologie. Verfahren der Abwasserbehandlung und Wasseraufbereitung (pp. 14-23). Aachen: RWTH Aachen University. , Institutional Repository

Daigger, G. T., Kuo, J., Derlon, N., Houweling, D., Jimenez, J. A., Johnson, B. R., … Boltz, J. P. (2023). Biological and physical selectors for mobile biofilms, aerobic granules, and densified-biological flocs in continuously flowing wastewater treatment processes: a state-of-the-art review. Water Research, 242, 120245 (13 pp.). doi:10.1016/j.watres.2023.120245, Institutional Repository

Derlon, N., & Villez, K. (2023). Editorial: water resource recovery modelling 2021 (WRRmod2021 conference). Water Science and Technology, 87(12), III-IV. doi:10.2166/wst.2023.175, Institutional Repository

Dieziger, C., Freimann, R., Durisch-Kaiser, E., & Joss, A. (2023). Lachgasemissionen aus Faulwasserbehandlung. Beprobung und Einordnung 12 Schweizer Anlagen. Aqua & Gas, 103(3), 50-54. , Institutional Repository

Faust, V. (2023). Effects of pH on urine nitrification: from microbial selection to process performance (Doctoral dissertation). doi:10.3929/ethz-b-000648527, Institutional Repository

Separation of urine at the source allows for the efficient recovery of nitrogen, phosphorus and other nutrients and reduces the load of these nutrients on wastewater treatment plants. Before urine can be used as a fertilizer, a treatment for nitrogen stabilization is required. Nitrification is a well-suited process for urine stabilization and is also the targeted approach in bioregenerative life support systems for Space such as in the MELiSSA project. However, due to the limited alkalinity and the high residual ammonium concentration, urine nitrification without alkalinity addition is very pH sensitive, which can compromise stable urine nitrification. Usually, the pH is controlled with the influent. Nevertheless, process failures can occur, namely nitrite accumulation, complete cessation of nitrification, and the growth of acid-tolerant ammonia-oxidizing bacteria (AOB), which can further lower the pH during periods of limited urine and lead to the emission of harmful nitrogen oxide gases. [...]

Die Urinseparierung ermöglicht eine effiziente Rückgewinnung von Stickstoff, Phosphor und anderen Nährstoffen und führt zur Entlastung der Kläranlagen. Bevor Urin als Düngemittel verwendet werden kann, ist jedoch eine Stickstoffbehandlung erforderlich. Dafür bietet sich die Nitrifikation an, welche auch im Rahmen der bioregenerative Lebenserhaltungssysteme für Weltraumanwendungen wie das MELiSSA Projekt untersucht werden. Aufgrund der begrenzten Alkalinität und der hohen Ammoniumkonzentration ist die Nitrifikation von Urin ohne Erhöhung der Alkalinität jedoch sehr pH-empfindlich, was die Stabilität der Urinnitrifikation gefährdet. Normalerweise wird der pH-Wert mit dem Zufluss geregelt. Dennoch kann es zu Prozessstörungen kommen, wie zur Akkumulation von Nitrit, zum vollständigen Erlegen der Nitrifikation und zum Wachstum säuretoleranter Ammoniakoxidierenden Bakterien (AOB), die den pH-Wert bei geringem Urinzuflus weiter senken und zur Emission schädlicher Stickoxidgase führen können. [...]

Friedel, M., Chiodo, G., Sukhodolov, T., Keeble, J., Peter, T., Seeber, S., … Josse, B. (2023). Weakening of springtime Arctic ozone depletion with climate change. Atmospheric Chemistry and Physics, 23(17), 10235-10254. doi:10.5194/acp-23-10235-2023, Institutional Repository

In the Arctic stratosphere, the combination of chemical ozone depletion by halogenated ozone-depleting substances (hODSs) and dynamic fluctuations can lead to severe ozone minima. These Arctic ozone minima are of great societal concern due to their health and climate impacts. Owing to the success of the Montreal Protocol, hODSs in the stratosphere are gradually declining, resulting in a recovery of the ozone layer. On the other hand, continued greenhouse gas (GHG) emissions cool the stratosphere, possibly enhancing the formation of polar stratospheric clouds (PSCs) and, thus, enabling more efficient chemical ozone destruction. Other processes, such as the acceleration of the Brewer–Dobson circulation, also affect stratospheric temperatures, further complicating the picture. Therefore, it is currently unclear whether major Arctic ozone minima will still occur at the end of the 21st century despite decreasing hODSs. We have examined this question for different emission pathways using simulations conducted within the Chemistry-Climate Model Initiative (CCMI-1 and CCMI-2022) and found large differences in the models' ability to simulate the magnitude of ozone minima in the present-day climate. Models with a generally too-cold polar stratosphere (cold bias) produce pronounced ozone minima under present-day climate conditions because they simulate more PSCs and, thus, high concentrations of active chlorine species (ClO_x). These models predict the largest decrease in ozone minima in the future. Conversely, models with a warm polar stratosphere (warm bias) have the smallest sensitivity of ozone minima to future changes in hODS and GHG concentrations. As a result, the scatter among models in terms of the magnitude of Arctic spring ozone minima will decrease in the future. Overall, these results suggest that Arctic ozone minima will become weaker over the next decades, largely due to the decline in hODS abundances. We note that none of the models analysed here project a notable increase of ozone minima in the future. Stratospheric cooling caused by increasing GHG concentrations is expected to play a secondary role as its effect in the Arctic stratosphere is weakened by opposing radiative and dynamical mechanisms.

Huang, K., Eschenbach, W., Wei, J., Hausherr, D., Frey, C., Kupferschmid, A., … Mohn, J. (2023). Simultaneous ¹⁵N online analysis in NH₄⁺, NO₂^-, NO₃^-, and N₂O to trace N₂O production pathways in nitrogen-polluted aqueous environments. ACS ES&T Water, 3(11), 3485-3495. doi:10.1021/acsestwater.3c00216, Institutional Repository

Joss, A., Kipf, M., Morgenroth, E., Baggenstos, M., & Salzgeber, D. (2023). Modifiziertes Anammox-Verfahren. Faulwasserbehandlungen mit stabiler Prozessführung. Aqua & Gas, 103(1), 24-29. , Institutional Repository

Kizgin, A., Schmidt, D., Joss, A., Hollender, J., Morgenroth, E., Kienle, C., & Langer, M. (2023). Application of biological early warning systems in wastewater treatment plants: Introducing a promising approach to monitor changing wastewater composition. Journal of Environmental Management, 347, 119001 (12 pp.). doi:10.1016/j.jenvman.2023.119001, Institutional Repository

Wastewater treatment plants (WWTPs) are a major source of micropollutants to surface waters. Currently, their chemical or biological monitoring is realized by using grab or composite samples, which provides only snapshots of the current wastewater composition. Especially in WWTPs with industrial input, the wastewater composition can be highly variable and a continuous assessment would be advantageous, but very labor and cost intensive. A promising concept are automated real-time biological early warning systems (BEWS), where living organisms are constantly exposed to the water and an alarm is triggered if the organism's responses exceed a harmful threshold of acute toxicity. Currently, BEWS are established for drinking water and surface water but are seldom applied to monitor wastewater. This study demonstrates that a battery of BEWS using algae (Chlorella vulgaris in the Algae Toximeter, bbe Moldaenke), water flea (Daphnia magna in the DaphTox II, bbe Moldaenke) and gammarids (Gammarus pulex in the Sensaguard, REMONDIS Aqua) can be adapted for wastewater surveillance. For continuous low-maintenance operation, a back-washable membrane filtration system is indispensable for adequate preparation of treated wastewater. Only minor deviations in the reaction of the organisms towards treated and filtered wastewater compared to surface waters were detected. After spiking treated wastewater with two concentrations of the model compounds diuron, chlorpyrifos methyl, and sertraline, the organisms in the different BEWS showed clear responses depending on the respective compound, concentration and mode of action. Immediate effects on photosynthetic activity of algae were detected for diuron exposure, and strong behavioral changes in water flea and gammarids after exposure to chlorpyrifos methyl or sertraline were observed, which triggered automated alarms. Different types of data analysis were applied to extract more information out of the specific behavioral traits, than only provided by the vendors algorithms. To investigate, whether behavioral movement changes can be linked to impact other endpoints, the effects on feeding activity of G. pulex were evaluated and results indicated significant differences between the exposures. Overall, these findings provide an important basis indicating that BEWS have the potential to act as alarm systems for pollution events in the wastewater sector.

Kollmann, J., Nath, S., Singh, S., Balasubramanian, S., Reynaert, E., Morgenroth, E., & Contzen, N. (2023). Acceptance of on-site wastewater treatment and reuse in Bengaluru, India: the role of perceived costs, risks, and benefits. Science of the Total Environment, 895, 165042 (11 pp.). doi:10.1016/j.scitotenv.2023.165042, Institutional Repository

Larivé, O., Torii, S., Derlon, N., & Kohn, T. (2023). Selective elimination of enterovirus genotypes by activated sludge and chlorination. Environmental Science: Water Research and Technology, 9(6), 1620-1633. doi:10.1039/d3ew00050h, Institutional Repository

Niederdorfer, R., Gruber, W., Joss, A., & Bürgmann, H. (2023). MicROcensus: zeitnahe Mikrobiom-Analysen auf ARA. Aqua & Gas, 103(9), 54-59. , Institutional Repository

Reynaert, E., Steiner, P., Yu, Q., D'Olif, L., Joller, N., Schneider, M. Y., & Morgenroth, E. (2023). Predicting microbial water quality in on-site water reuse systems with online sensors. Water Research, 240, 120075 (13 pp.). doi:10.1016/j.watres.2023.120075, Institutional Repository

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

Reynaert, E., Nagappa, D., & Morgenroth, E. (2023). Research brief: using sensors and automated chlorination to improve the microbial water quality of on-site sewage treatment plants in Bengaluru. doi:10.3929/ethz-b-000603755, Institutional Repository

Reynaert, E., Gretener, F., Julian, T. R., & Morgenroth, E. (2023). Sensor setpoints that ensure compliance with microbial water quality targets for membrane bioreactor and chlorination treatment in on-site water reuse systems. Water Research X, 18, 100164 (13 pp.). doi:10.1016/j.wroa.2022.100164, Institutional Repository

Sam, S. B., Morgenroth, E., & Strande, L. (2023). Changes in organic fractions, cations, and stabilization from feces to fecal sludge: implications for dewatering performance and management solutions. Journal of Water Sanitation and Hygiene for Development, 13(9), 699-710. doi:10.2166/washdev.2023.086, Institutional Repository

Schäfer, R., Dönni, A., Thomann, M., Gulde, R., Eugster, F., Joss, A., & Piazzoli, A. (2023). Entwicklung des AIA-Tests. Alternativer inhärenter Abbautest für Industrieabwasser. Aqua & Gas, 103(4), 68-75. , Institutional Repository

Stoffel, D., Derlon, N., Traber, J., Staaks, C., Heijnen, M., Morgenroth, E., & Jacquin, C. (2023). Gravity-driven membrane filtration with compact second-life modules daily backwashed: an alternative to conventional ultrafiltration for centralized facilities. Water Research X, 18, 100178 (12 pp.). doi:10.1016/j.wroa.2023.100178, Institutional Repository

Gravity-driven membrane (GDM) filtration is a strategic alternative to conventional ultrafiltration (UF) for the resilient production of drinking water via ultrafiltration when resources become scarce, given the low dependency on energy and chemicals, and longer membrane lifetime. Implementation at large scale requires the use of compact and low-cost membrane modules with high biopolymer removal capacity. We therefore evaluated (1) to what extent stable flux can be obtained with compact membrane modules, i.e., inside-out hollow fiber membranes, and frequent gravity-driven backwash, (2) whether we can reduce membrane expenses by effectively utilizing second-life UF modules, i.e., modules that have been discarded by treatment plant operators because they are no longer under warranty, (3) if biopolymer removal could be maintained when applying a frequent backwash and with second-life modules and (4) which GDM filtration scenarios are economically viable compared to conventional UF, when considering the influence of new or second-life modules, membrane lifetime, stable flux value and energy pricing. Our findings showed that it was possible to maintain stable fluxes around 10 L/m²/h with both new and second-life modules for 142 days, but a daily gravity-driven backwash was necessary and sufficient to compensate the continuous flux drop observed with compact modules. In addition, the backwash did not affect the biopolymer removal. Costs calculations revealed two significant findings: (1) using second-life modules made GDM filtration membrane investment less expensive than conventional UF, despite the higher module requirements for GDM filtration and (2) overall costs of GDM filtration with a gravity-driven backwash were unaffected by energy prices rise, while conventional UF costs rose significantly. The later increased the number of economically viable GDM filtration scenarios, including scenarios with new modules. In summary, we proposed an approach that could make GDM filtration in centralized facilities feasible and increase the range of UF operating conditions to better adapt to increasing environmental and societal constraints.

Ward, B. J., Nguyen, M. T., Sam, S. B., Korir, N., Niwagaba, C. B., Morgenroth, E., & Strande, L. (2023). Particle size as a driver of dewatering performance and its relationship to stabilization in fecal sludge. Journal of Environmental Management, 326, 116801 (12 pp.). doi:10.1016/j.jenvman.2022.116801, Institutional Repository

Bou-Sarkis, A., Pagliaccia, B., Ric, A., Derlon, N., Paul, E., Bessiere, Y., & Girbal-Neuhauser, E. (2022). Effects of alkaline solvents and heating temperatures on the solubilization and degradation of gel-forming Extracellular Polymeric Substances (EPS) extracted from aerobic granular sludge. Biochemical Engineering Journal, 185, 108500 (9 pp.). doi:10.1016/j.bej.2022.108500, Institutional Repository

Braun, D., von Känel, L., Biolley, L., Bauer, H., Gahler, D., Gruber, W., … Morgenroth, E. (2022). Dynamische Regelung der ARA Hofen. Infrawatt-Innovationspreis für mehr Leistung und weniger Emissionen. Aqua & Gas, 102(1), 26-31. , Institutional Repository

Brison, A., Rossi, P., & Derlon, N. (2022). Influent carbon to phosphorus ratio drives the selection of PHA-storing organisms in a single CSTR. Water Research X, 16, 100150 (11 pp.). doi:10.1016/j.wroa.2022.100150, Institutional Repository

Brison, A., Rossi, P., Gelb, A., & Derlon, N. (2022). The capture technology matters: composition of municipal wastewater solids drives complexity of microbial community structure and volatile fatty acid profile during anaerobic fermentation. Science of the Total Environment, 815, 152762 (13 pp.). doi:10.1016/j.scitotenv.2021.152762, Institutional Repository

The production of volatile fatty acids (VFAs) represents a relevant option to valorize municipal wastewater (MWW). In this context, different capture technologies can be used to recover organic carbon from wastewater in form of solids, while pre-treatment of those solids has the potential to increase VFA production during subsequent fermentation. Our study investigates how VFA composition produced by fermentation is influenced (i) by the choice of the capture technology, as well as (ii) by the use of thermal alkaline pre-treatment (TAP). Therefore, the fermentation of solids originating from a primary settler, a micro-sieve, and a high-rate activated sludge (HRAS) system was investigated in continuous lab-scale fermenters, with and without TAP. Our study demonstrates that the capture technology strongly influences the composition of the produced solids, which in turn drives the complexity of the fermenter's microbial community and ultimately, of the VFA composition. Solids captured with the primary settler or micro-sieve consisted primarily of polysaccharides, and led to the establishment of a microbial community specialized in the degradation of complex carbohydrates. The produced VFA composition was relatively simple, with acetate and propionate accounting for >90% of the VFAs. In contrast, the HRAS system produced biomass-rich solids associated with higher protein contents. The microbial community which then developed in the fermenter was therefore more diversified and capable of converting a wider range of substrates (polysaccharides, proteins, amino acids). Ultimately, the produced VFA composition was more complex, with equal fractions of isoacids and propionate (both ~20%), while acetate remained the dominant acid (~50%). Finally, TAP did not significantly modify the VFA composition while increasing VFA yields on HRAS and sieved material by 35% and 20%, respectively. Overall, we demonstrated that the selection of the technology used to capture organic substrates from MWW governs the composition of the VFA cocktail, ultimately with implications for their further utilization.

Böhler, M. A., Joss, A., & McArdell, C. S. (2022). GAK-Filter für die Spurenstoffentfernung. Erfahrungen und Betriebsergebnisse der Pilotstudien ARA Furt/Bülach und Glarnerland. Aqua & Gas, 102(1), 48-54. , Institutional Repository

Carles, L., Wullschleger, S., Joss, A., Eggen, R. I. L., Schirmer, K., Schuwirth, N., … Tlili, A. (2022). Wastewater microorganisms impact microbial diversity and important ecological functions of stream periphyton. Water Research, 225, 119119 (13 pp.). doi:10.1016/j.watres.2022.119119, Institutional Repository

Derlon, N., Desmond, P., Rühs, P. A., & Morgenroth, E. (2022). Cross flow frequency determines the physical structure and cohesion of membrane biofilms developed during gravity-driven membrane ultrafiltration of river water: implication for hydraulic resistance. Journal of Membrane Science, 643, 120079 (10 pp.). doi:10.1016/j.memsci.2021.120079, Institutional Repository

Derlon, N., Garcia Villodres, M., Kovács, R., Brison, A., Layer, M., Takács, I., & Morgenroth, E. (2022). Modelling of aerobic granular sludge reactors: the importance of hydrodynamic regimes, selective sludge removal and gradients. Water Science and Technology, 86(3), 410-431. doi:10.2166/wst.2022.220, Institutional Repository

Desiante, W. L., Carles, L., Wullschleger, S., Joss, A., Stamm, C., & Fenner, K. (2022). Wastewater microorganisms impact the micropollutant biotransformation potential of natural stream biofilms. Water Research, 217, 118413 (13 pp.). doi:10.1016/j.watres.2022.118413, Institutional Repository

Gruber, W., Joss, A., von Känel, L., Biolley, L., Braun, D., & Morgenroth, E. (2022). Abluftmessungen in der biologischen Abwasserreinigung. Aqua & Gas, 102(1), 24-25. , Institutional Repository

Gruber, W., Niederdorfer, R., Bürgmann, H., Joss, A., von Känel, L., Braun, D., … Morgenroth, E. (2022). Lachgasemissionen aus ARA. Reduktionsmassnahmen zeichnen sich ab. Aqua & Gas, 102(1), 14-22. , Institutional Repository

Gruber, W., Magyar, P. M., Mitrovic, I., Zeyer, K., Vogel, M., von Känel, L., … Mohn, J. (2022). Tracing N₂O formation in full-scale wastewater treatment with natural abundance isotopes indicates control by organic substrate and process settings. Water Research X, 15, 100130 (11 pp.). doi:10.1016/j.wroa.2022.100130, Institutional Repository

Nitrous oxide (N₂O) dominates greenhouse gas emissions in wastewater treatment plants (WWTPs). Formation of N₂O occurs during biological nitrogen removal, involves multiple microbial pathways, and is typically very dynamic. Consequently, N₂O mitigation strategies require an improved understanding of nitrogen transformation pathways and their modulating controls. Analyses of the nitrogen (N) and oxygen (O) isotopic composition of N₂O and its substrates at natural abundance have been shown to provide valuable information on formation and reduction pathways in laboratory settings, but have rarely been applied to full-scale WWTPs.
Here we show that N-species isotope ratio measurements at natural abundance level, combined with long-term N₂O monitoring, allow identification of the N₂O production pathways in a full-scale plug-flow WWTP (Hofen, Switzerland). Heterotrophic denitrification appears as the main N₂O production pathway under all tested process conditions (0-2 mgO₂/l, high and low loading conditions), while nitrifier denitrification was less important, and more variable. N₂O production by hydroxylamine oxidation was not observed. Fractional N₂O elimination by reduction to dinitrogen (N₂) during anoxic conditions was clearly indicated by a concomitant increase in site preference, δ¹⁸O(N₂O) and δ¹⁵N(N₂O). N₂O reduction increased with decreasing availability of dissolved inorganic N and organic substrates, which represents the link between diurnal N₂O emission dynamics and organic substrate fluctuations. Consequently, dosing ammonium-rich reject water under low-organic-substrate conditions is unfavorable, as it is very likely to cause high net N₂O emissions.
Our results demonstrate that monitoring of the N₂O isotopic composition holds a high potential to disentangle N₂O formation mechanisms in engineered systems, such as full-scale WWTP. Our study serves as a starting point for advanced campaigns in the future combining isotopic technologies in WWTP with complementary approaches, such as mathematical modeling of N₂O formation or microbial assays to develop efficient N₂O mitigation strategies.

Hadengue, B., Morgenroth, E., & Larsen, T. A. (2022). How to get your feet wet: Integrating urban water and building engineering for low-energy domestic hot water systems. Energy and Buildings, 271, 112318 (6 pp.). doi:10.1016/j.enbuild.2022.112318, Institutional Repository

Hadengue, B., Morgenroth, E., Larsen, T. A., & Baldini, L. (2022). Performance and dynamics of active greywater heat recovery in buildings. Applied Energy, 305, 117677 (13 pp.). doi:10.1016/j.apenergy.2021.117677, Institutional Repository

Hadengue, B., Morgenroth, E., & Larsen, T. A. (2022). Screening innovative technologies for energy-efficient domestic hot water systems. Journal of Environmental Management, 320, 115713 (9 pp.). doi:10.1016/j.jenvman.2022.115713, Institutional Repository

Hausherr, D., Niederdorfer, R., Bürgmann, H., Lehmann, M. F., Magyar, P., Mohn, J., … Joss, A. (2022). Successful mainstream nitritation through NOB inactivation. Science of the Total Environment, 822, 153546 (11 pp.). doi:10.1016/j.scitotenv.2022.153546, Institutional Repository

Hausherr, D., Niederdorfer, R., Bürgmann, H., Lehmann, M. F., Magyar, P., Mohn, J., … Joss, A. (2022). Successful year-round mainstream partial nitritation anammox: assessment of effluent quality, performance and N₂O emissions. Water Research X, 16, 100145 (11 pp.). doi:10.1016/j.wroa.2022.100145, Institutional Repository

For two decades now, partial nitritation anammox (PNA) systems were suggested to more efficiently remove nitrogen (N) from mainstream municipal wastewater. Yet to date, only a few pilot-scale systems and even fewer full-scale implementations of this technology have been described. Process instability continues to restrict the broad application of PNA. Especially problematic are insufficient anammox biomass retention, the growth of undesired aerobic nitrite-oxidizers, and nitrous oxide (N₂O) emissions. In this study, a two-stage mainstream pilot-scale PNA system, consisting of three reactors (carbon pre-treatment, nitritation, anammox - 8 m³ each), was operated over a year, treating municipal wastewater. The aim was to test whether both, robust autotrophic N removal and high effluent quality, can be achieved throughout the year. A second aim was to better understand rate limiting processes, potentially affecting the overall performance of PNA systems. In this pilot study, excellent effluent quality, in terms of inorganic nitrogen, was accomplished (average effluent concentrations: 0.4 mgNH₄-N/L, 0.1 mgNO₂-N/L, 0.9 mgNO₃-N/L) even at wastewater temperatures previously considered problematic (as low as 8 °C). N removal was limited by nitritation rates (84 ± 43 mgNH₄-N/L/d), while surplus anammox activity was observed at all times (178 ± 43 mgN/L/d). Throughout the study, nitrite-oxidation was maintained at a low level (<2.5% of ammonium consumption rate). Unfortunately, high N₂O emissions from the nitritation stage (1.2% of total nitrogen in the influent) were observed, and, based on natural isotope abundance measurements, could be attributed to heterotrophic denitrification. In situ batch experiments were conducted to identify the role of dissolved oxygen (DO) and organic substrate availability in N₂O emission-mitigation. The addition of organic substrate, to promote complete denitrification, was not successful in decreasing N₂O emission, but increasing the DO from 0.3 to 2.9 mgO₂/L decreased N₂O emissions by a factor of 3.4.

Lamprecht, O., Wagner, B., Derlon, N., & Tlili, A. (2022). Synthetic periphyton as a model system to understand species dynamics in complex microbial freshwater communities. npj Biofilms and Microbiomes, 8, 61 (14 pp.). doi:10.1038/s41522-022-00322-y, Institutional Repository

Layer, M., Brison, A., Garcia Villodres, M., Stähle, M., Házi, F., Takács, I., … Derlon, N. (2022). Microbial conversion pathways of particulate organic substrate conversion of aerobic granular sludge systems: limited anaerobic conversion and the essential role of flocs. Environmental Science: Water Research and Technology, 8(6), 1236-1251. doi:10.1039/D1EW00841B, Institutional Repository

Particulate organic substrate (X_B) represents the major fraction of organic substrate in low-strength municipal wastewater (MWW) but its hydrolysis, conversion and utilisation in aerobic granular sludge (AGS) are not well understood. We systematically analysed through modelling the microbial conversion pathways of X_B in AGS systems operated as sequencing batch reactors and treating municipal wastewater. Based on our current understanding of AGS systems, we developed an AGS model in Sumo® to better understand (1) during which phases of the SBR cycle (anaerobic plug-flow feeding or aerobic fully-mixed conditions), (2) by what biomass fraction (granules or flocs) and (3) via which microbial processes X_B is converted into soluble organic substrate (S_B) and volatile fatty acids (S_VFA) and further utilised. The validity of all our results was evaluated by assessing the sensitivity of findings on the biomass distribution (floc fraction) (SCENARIO #1), SBR cycle (SCENARIO #2), and biofilm properties (SCENARIO #3). Our results indicate that only 20% of influent X_B was hydrolysed and 11% of influent X_B was then used for internal carbon-storage during 90 min anaerobic plug-flow feeding. The major fraction of influent X_B (80%) leaked into the aerobic SBR phase, where X_B was then hydrolysed and oxidised aerobically by ordinary heterotrophic organisms (OHOs). Under aerobic fully-mixed conditions, the flocs successfully competed for X_B with the granules. Aerobic X_B hydrolysis and its further utilisation by OHOs occurred mainly in flocs despite their minor biomass fraction (13% of total suspended solids), preventing excessive OHO growth on granules and demonstrating that flocs are beneficial for AGS systems treating MWW. Also, the model allowed us to better understand that the SBR sequence can be optimised to make better use of X_B under anaerobic conditions and to reduce the leakage of X_B to aerobic conditions. The introduction of a 60 min anaerobic idle phase after a 60 min plug-flow feeding phase almost doubled the anaerobic X_B hydrolysis and internal carbon-storage by phosphorus and glycogen accumulating organisms (PAOs and GAOs), respectively, compared to 90 min plug-flow feeding. Nonetheless, most influent X_B was still utilised by OHOs during the aerobic SBR phase.

Morgenroth, E., & Derlon, N. (2022). Entwicklung der biologischen Abwasserreinigung: Belebtschlamm vs Biofilmsysteme. In T. Wintgens & J. Pinnekamp (Eds.), Gewässerschutz, Wasser, Abwasser. 55. Essener Tagung für Wasserwirtschaft. Wasserwirtschaft im Klimawandel (p. 31 (12 pp.). Aachen: Gesellschaft zur Förderung des Instituts für Siedlungswasserwirtschaft an der RWTH Aachen. , Institutional Repository

Sam, S. B., Ward, B. J., Niederdorfer, R., Morgenroth, E., & Strande, L. (2022). Elucidating the role of extracellular polymeric substances (EPS) in dewaterability of fecal sludge from onsite sanitation systems, and changes during anaerobic storage. Water Research, 222, 118915 (12 pp.). doi:10.1016/j.watres.2022.118915, Institutional Repository

Stoffel, D., Rigo, E., Derlon, N., Staaks, C., Heijnen, M., Morgenroth, E., & Jacquin, C. (2022). Low maintenance gravity-driven membrane filtration using hollow fibers: effect of reducing space for biofilm growth and control strategies on permeate flux. Science of the Total Environment, 811, 152307 (13 pp.). doi:10.1016/j.scitotenv.2021.152307, Institutional Repository

The implementation of centralized drinking water treatment systems necessitates lower operational costs and improved biopolymer removal during ultrafiltration (UF), which can be afforded by gravity-driven membrane (GDM) filtration. However, prior to implementing GDM filtration in centralized systems, biofilm growth in compacted membrane configurations, such as inside-out hollow fiber (HF), and its impact on permeate flux need to be investigated. To this end, we operated modules with distinct limits on available space for biofilm growth: (1) outside-in 1.5 mm 7-capillary HF (non-limited), (2) inside-out 1.5 mm 7-capillary HF (limited), and (3) inside-out 0.9 mm 7-capillary HF (very limited). Here, we observed that the lower the space available for biofilm growth, the lower the permeate flux. To improve GDM performance with inside-out HF, we applied daily shear stress to the biofilm surface with forward flush (FF) or combined relaxation and forward flush (R+FF). We showed that applying shear stress to the biofilm surface was insufficient for controlling flux loss due to low available space for biofilm growth. At the experimental endpoint, we backwashed with a stepwise transmembrane pressure (TMP) increase or a single TMP on all inside-out HF modules, which removed the biofilm from its base. Afterwards, higher fluxes were yielded. We also showed that all modules exhibited a gradual increase in biopolymer removal followed by stabilization between 70 and 90%. Additionally, control of biofilm growth with surface shear stress did not affect biopolymer removal. In summary, the implementation of inside-out HF with GDM filtration is challenged by low available space for biofilm growth, but may be remedied with a regular backwash to remove biofilm from its base. We showed that a wider range of GDM applications are available; making GDM potentially compatible with implementation in centralized systems, if space limitation is taken into consideration for operation optimization.

Walpen, N., Joss, A., & von Gunten, U. (2022). Application of UV absorbance and electron-donating capacity as surrogates for micropollutant abatement during full-scale ozonation of secondary-treated wastewater. Water Research, 209, 117858 (11 pp.). doi:10.1016/j.watres.2021.117858, Institutional Repository

Ozonation of secondary-treated wastewater for the abatement of micropollutants requires a reliable control of ozone doses. Changes in the UV absorbance of dissolved organic matter (DOM) during ozonation allow to estimate micropollutant abatement on-line and were therefore identified as feed-back control parameter. In this study, the suitability of the electron-donating capacity (EDC) as an additional surrogate parameter which is independent of optical DOM properties was evaluated during full-scale ozonation. For this purpose, a recently developed EDC analyzer was enhanced to enable continuous on-line EDC and UV absorbance measurements. During a multi-week monitoring campaign at the wastewater treatment plant of Zurich, Switzerland, specific ozone doses were varied from 0.13 to 0.91 mg_O3⋅mg_DOC^-1 and selected micropollutants with different ozone reactivities were analyzed by LC-MS in conjunction with bromate analysis by IC-MS. In agreement with previous laboratory studies, the relative residual UV absorbance and EDC both decreased exponentially as a function of the specific ozone dose and, in comparison to the residual UV absorbance, residual EDC values showed a more pronounced decrease at low specific ozone doses ≤0.34 mg_O3⋅mg_DOC^-1. Logistic regression models allowed to estimate relative residual micropollutant concentrations in the ozonation effluent using either the residual UV absorbance or EDC as explanatory variable. Averaging those models along the explanatory variables allowed to estimate target values in relative residual UV absorbances and EDC for specific micropollutant abatement targets. In addition, both parameters allowed to identify conditions with elevated conversions of bromide to bromate. Taken together, these findings show that the integration of relative residual EDC values as a second control parameter can improve existing absorbance-based ozonation control systems to meet micropollutant abatement targets, particularly for treatment systems where low ozone doses are applied.

Ward, B. J. (2022). Settling and dewatering of fecal sludge: building fundamental knowledge for improved global sanitation (Doctoral dissertation). ETH Zurich, Zurich, 206 p. , Institutional Repository

Benstöm, F., Meda, A., Baumann, P., Derlon, N., Lackner, S., Layer, M., … Wichern, M. (2021). Aerobe Verfahren mit granuliertem Schlamm zur Abwasserbehandlung - Arbeitsbericht der DWAArbeitsgruppe KA6.3. "Biofilmverfahren"*⁾ - Teil 1. KA: Korrespondenz Abwasser Abfall, 68(4), 281-288. , Institutional Repository

Brander, A., Böhler, M., McArdell, C., & Joss, A. (2021). Hinweise zur Planung und Auslegung von diskontinuierlich gespülten GAK-Filtern zur Elimination organischer Spurenstoffe aus kommunalem Abwasser unter besonderer Berücksichtigung der Anforderungen und Erfahrungen in der Schweiz (p. (6 pp.). Presented at the 14. Aachener Tagung Wassertechnologie. Verfahren der Wasseraufbereitung und Abwasserbehandlung. Aachen, Deutschland. , Institutional Repository

Carles, L., Wullschleger, S., Joss, A., Eggen, R. I. L., Schirmer, K., Schuwirth, N., … Tlili, A. (2021). Impact of wastewater on the microbial diversity of periphyton and its tolerance to micropollutants in an engineered flow-through channel system. Water Research, 203, 117486 (14 pp.). doi:10.1016/j.watres.2021.117486, Institutional Repository

Wastewater treatment plants (WWTPs) play an important role in retaining organic matter and nutrients but to a lesser extent micropollutants. Therefore, treated wastewater is recognized as a major source of multiple stressors, including complex mixtures of micropollutants. These can potentially affect microbial communities in the receiving water bodies and the ecological functions they provide. In this study, we evaluated in flow-through channels the consequences of an exposure to a mixture of stream water and different percentages of urban WWTP effluent, ranging from 0% to 80%, on the microbial diversity and function of periphyton communities. Assuming that micropollutants exert a selective pressure for tolerant microorganisms within communities, we further examined the periphyton sensitivity to a micropollutant mixture extracted from passive samplers that were immersed in the wastewater effluent. As well, micropollutants in water and in periphyton were comprehensively quantified. Our results show that micropollutants detected in periphyton differed from those found in water, both in term of concentration and composition. Especially photosystem II inhibitors accumulated in periphyton more than other pesticides. Although effects of other substances cannot be excluded, this accumulation may have contributed to the observed higher tolerance of phototrophic communities to micropollutants upon exposure to 30% and 80% of wastewater. On the contrary, no difference in tolerance was observed for heterotrophic communities. Exposure to the gradient of wastewater led to structural differences in both prokaryotic and eukaryotic communities. For instance, the relative abundance of cyanobacteria was higher with increasing percentage of wastewater effluent, whereas the opposite was observed for diatoms. Such results could indicate that differences in community structure do not necessarily lead to higher tolerance. This highlights the need to consider other wastewater constituents such as nutrients and wastewater-derived microorganisms that can modulate community structure and tolerance. By using engineered flow-through channels that mimic to some extent the required field conditions for the development of tolerance in periphyton, our study constitutes a base to investigate the mechanisms underlying the increased tolerance, such as the potential role of microorganisms originating from wastewater effluents, and different treatment options to reduce the micropollutant load in effluents.

Gauthier, J., Boulain, H., van Vugt, J. J. F. A., Baudry, L., Persyn, E., Aury, J. M., … Drezen, J. M. (2021). Chromosomal scale assembly of parasitic wasp genome reveals symbiotic virus colonization. Communications Biology, 4(1), 104 (15 pp.). doi:10.1038/s42003-020-01623-8, Institutional Repository

Gruber, W., Joss, A., Luck, M., Kupper, T., Bühler, M., & Bührer, T. (2021). Elaboration of a data basis on greenhouse gas emissions from wastewater management - Final report N2OklimARA. Bern: Federal Office for the Environment (FOEN). , Institutional Repository

Gruber, W., von Känel, L., Vogt, L., Luck, M., Biolley, L., Feller, K., … Joss, A. (2021). Estimation of countrywide N₂O emissions from wastewater treatment in Switzerland using long-term monitoring data. Water Research X, 13, 100122 (12 pp.). doi:10.1016/j.wroa.2021.100122, Institutional Repository

Gruber, W., Niederdorfer, R., Ringwald, J., Morgenroth, E., Bürgmann, H., & Joss, A. (2021). Linking seasonal N₂O emissions and nitrification failures to microbial dynamics in a SBR wastewater treatment plant. Water Research X, 11, 100098 (13 pp.). doi:10.1016/j.wroa.2021.100098, Institutional Repository

Gruber, W. J. (2021). Long-term N₂O emission monitoring in biological wastewater treatment: methods, applications and relevance (Doctoral dissertation). doi:10.3929/ethz-b-000537321, Institutional Repository

Nitrous oxide (N₂O) emissions substantially contribute to global, environmental issues: climate change and stratospheric ozone depletion. Wastewater treatment plants (WWTPs) are potent point sources and significant contributors to anthropogenic N₂O emissions. However, emissions are currently underestimated in most greenhouse gas inventories due to overly simplified emission processes of WWTPs in the IPCC guidelines. Key limitations towards more realistic estimations are the low availability of representative monitoring campaigns and a limited understanding of N₂O formation mechanism during biological nitrogen removal in WWTPs. In particular, N₂O emission patterns assessed in long-term full-scale monitoring campaigns have shown strong seasonal variations, highlighting the requirement for long-term monitoring campaigns as basis for representative emission factor estimation. But underlying causes for the seasonal dynamics are unclear. Therefore, this thesis investigated (i) methods for long-term emission monitoring and the assessment of representative emission factors (EFs), (ii) methodologies for a more realistic estimation of countrywide N₂O emissions and (iii) causes of the seasonal emission pattern to ultimately propose mitigation measures. [...]

Lachgasemissionen (N₂O) tragen substantiell zu bedeutenden, globalen Umweltproblemen bei: dem Klimawandel und der stratosphärischen Zerstörung von Ozon. Kläranlagen (ARAs) sind relevante N₂O Punktquellen und verursachen einen relevanten Teil der anthropogenen Emissionen. Gegenwärtig werden die N₂O Emissionen aus ARAs in den meisten Treibhausgasinventaren jedoch unterschätzt, da die Emissionsprozesse in den üblicherweise verwendeten IPCC Richtlinien unzureichend abgebildet werden. Die Hauptgründe dafür sind eine limitierte Verfügbarkeit an repräsentativen Langzeitdaten und ein fehlendes Verständnis der N₂O Bildung während der biologischen Stickstoffelimination auf ARAs. Insbesondere die Ursachen für die saisonale Variabilität der Emission sind unbekannt. Die hohe Variabilität im Jahresverlauf unterstreicht die Notwendigkeit von Langzeitmess-kampagnen als Grundlage für eine repräsentative Schätzung der Emissionsfaktoren. Deshalb hatte die vorliegende Doktorarbeit folgende Zielsetzung: (i) Entwicklung und Anwendung einer Methode zur langfristigen Emissions-überwachung und zur Abschätzung repräsentativer Emissionsfaktoren (EFs), (ii) Erarbeitung eine Methode für eine realistischere Abschätzung der landesweiten N₂O Emissionen ARAs sowie (iii) Charakterisierung von ursächlichen Faktoren für die saisonale Variabilität, um schließlich Maßnahmen zur Emissionsminderung vorzuschlagen. [...]

Hausherr, D., Niederdorfer, R., Morgenroth, E., & Joss, A. (2021). Robustness of mainstream anammox activity at bench and pilot scale. Science of the Total Environment, 796, 148920 (11 pp.). doi:10.1016/j.scitotenv.2021.148920, Institutional Repository

New technologies and processes, such as mainstream anammox, aim to reduce energy requirements of wastewater treatment and improve effluent quality. However, in municipal wastewater (MWW) anammox system are often unstable due to process control disturbance, influent variability, or unwanted nitrite oxidizing bacteria (NOB). This study examines the anammox system by focusing on anammox activity and its robustness in a mainstream environment. An 8 m³ pilot-scale sequencing batch reactor (SBR) receiving pretreated MWW (with external nitrite addition) was seeded with pre-colonized carriers. Within six months at 12–20 °C an anammox activity of 200 gN·m⁻³·d⁻¹ was achieved. After the startup an anammox activity of 260 ± 83 gN·m⁻³·d⁻¹ was maintained over 450 days. The robustness of the anammox activity was analyzed through three disturbance experiments. Anammox biofilm on carriers were exposed to dissolved oxygen (DO = 1.6 mg·L⁻¹, intermittent aeration), organic loading rate (OLR, C/N increased from 2:1 to 5:1) and temperature disturbances (20 °C to 12 °C) in triplicate 12 L bench scale reactors. The anammox activity and microbial community was monitored during these disturbances. The DO and OLR disturbance experiments were replicated at pilot scale to investigate upscaling effects. Bench and pilot scale anammox activity were unaffected by the DO disturbance. Similarly, an increase in OLR did not deteriorate the bench and pilot scale anammox activity, if nitrate was available. When, at bench scale, the reactor temperature was reduced from 20 °C to 12 °C overnight, anammox activity decreased significantly, this was not the case for the slow seasonal temperature changes (12–25 °C) at pilot scale where no strong temperature dependency was detected in winter. Metagenomic analysis revealed a broad range of Brocadiaceae species with no single dominant anammox species. Anammox thrive under mainstream conditions and can withstand typical process disruptions.

Hess, A., & Morgenroth, E. (2021). Biological activated carbon filter for greywater post-treatment: Long-term TOC removal with adsorption and biodegradation. Water Research X, 13, 100113 (9 pp.). doi:10.1016/j.wroa.2021.100113, Institutional Repository

Hess, A., Baum, C., Schiessl, K., Besmer, M. D., Hammes, F., & Morgenroth, E. (2021). Stagnation leads to short-term fluctuations in the effluent water quality of biofilters: a problem for greywater reuse?. Water Research X, 13, 100120 (9 pp.). doi:10.1016/j.wroa.2021.100120, Institutional Repository

Magyar, P. M., Hausherr, D., Niederdorfer, R., Stöcklin, N., Wei, J., Mohn, J., … Lehmann, M. F. (2021). Nitrogen isotope effects can be used to diagnose N transformations in wastewater anammox systems. Scientific Reports, 11(1), 7850 (12 pp.). doi:10.1038/s41598-021-87184-0, Institutional Repository

Moraes Schambeck, C., Ribeiro da Costa, R. H., & Derlon, N. (2021). Phosphate removal from municipal wastewater by alginate-like exopolymers hydrogels recovered from aerobic granular sludge. Bioresource Technology, 333, 125167 (10 pp.). doi:10.1016/j.biortech.2021.125167, Institutional Repository

Niederdorfer, R., Fragner, L., Yuan, L., Hausherr, D., Wei, J., Magyar, P., … Bürgmann, H. (2021). Distinct growth stages controlled by the interplay of deterministic and stochastic processes in functional anammox biofilms. Water Research, 200, 117225 (14 pp.). doi:10.1016/j.watres.2021.117225, Institutional Repository

Niederdorfer, R., Hausherr, D., Palomo, A., Wei, J., Magyar, P., Smets, B. F., … Bürgmann, H. (2021). Temperature modulates stress response in mainstream anammox reactors. Communications Biology, 4(1), 23 (12 pp.). doi:10.1038/s42003-020-01534-8, Institutional Repository

Reynaert, E., Hess, A., & Morgenroth, E. (2021). Making waves: why water reuse frameworks need to co-evolve with emerging small-scale technologies. Water Research X, 11, 100094 (5 pp.). doi:10.1016/j.wroa.2021.100094, Institutional Repository

Riechmann, M. E., Ndwandwe, B., Greenwood, E. E., Reynaert, E., Morgenroth, E., & Udert, K. M. (2021). On-site urine treatment combining Ca(OH)₂ dissolution and dehydration with ambient air. Water Research X, 13, 100124 (12 pp.). doi:10.1016/j.wroa.2021.100124, Institutional Repository

We present the results of three field tests and three laboratory tests of a new physical-chemical urine treatment system, which can recover all nutrients, while pathogens are inactivated. The system consists of two steps. In the first reactor, biological processes including urea hydrolysis are prevented by mixing fresh urine with calcium hydroxide (Ca(OH)₂). Due to the high pH value and the high availability of calcium, phosphate can be recovered by precipitation. The high pH value also fosters the inactivation of microorganisms, including pathogens. In the second reactor, water is evaporated at low energy consumption by blowing unheated ambient air over the stabilized urine. Stabilization in the first reactor was successful in all field and laboratory tests. The pH value remained between 12 and 13, except for short dips due to shortages of Ca(OH)₂. Nearly all phosphorus (92-96%) precipitated and could be recovered as calcium phosphate in the first reactor, while nitrogen and potassium overflowed with the urine into the evaporation reactor. The efficiency of the second treatment step was very different for field and laboratory experiments and depended on the duration of the experiment. During a four-day laboratory test, nitrogen recovery was 98%. In contrast, nitrogen recovery was only around 20% in the long-term field experiments. The high nitrogen losses occurred, because biological urea hydrolysis was not inhibited anymore, when the pH value in the second reactor decreased due to the dissolution of high amounts of carbon dioxide from the ambient air. Potassium was not subject to any significant loss, and the measured recovery in the solid evaporation product was 98%. Evaporation rates ranged between 50 g m^-2 h^-1 (RH = 82±13%, T = 12±6°C) and 130 g m^-2 h^-1 (RH = 60±19%, T = 24±5°C) in the three field tests. Apart from some disturbances due to low supply of Ca(OH)₂, the urine module functioned without any substantial failures and was simple to maintain. The minimum consumption of Ca(OH)₂ at full capacity was 6 g·L^-1 urine and the electricity demand was 150 Wh kg^-1 water evaporated from urine, resulting in operational costs of 0.05 EUR pers^-1 d^-1.

Russo, S., Besmer, M. D., Blumensaat, F., Bouffard, D., Disch, A., Hammes, F., … Villez, K. (2021). The value of human data annotation for machine learning based anomaly detection in environmental systems. Water Research, 206, 117695 (10 pp.). doi:10.1016/j.watres.2021.117695, Institutional Repository

Sutherland, C., Reynaert, E., Sindall, R. C., Riechmann, M. E., Magwaza, F., Lienert, J., … Udert, K. M. (2021). Innovation for improved hand hygiene: field testing the Autarky handwashing station in collaboration with informal settlement residents in Durban, South Africa. Science of the Total Environment, 796, 149024 (13 pp.). doi:10.1016/j.scitotenv.2021.149024, Institutional Repository

Sutherland, C., Reynaert, E., Dhlamini, S., Magwaza, F., Lienert, J., Riechmann, M. E., … Sindall, R. C. (2021). Socio-technical analysis of a sanitation innovation in a peri-urban household in Durban, South Africa. Science of the Total Environment, 755, 143284 (12 pp.). doi:10.1016/j.scitotenv.2020.143284, Institutional Repository

Tang, X., Pronk, W., Traber, J., Liang, H., Li, G., & Morgenroth, E. (2021). Integrating granular activated carbon (GAC) to gravity-driven membrane (GDM) to improve its flux stabilization: respective roles of adsorption and biodegradation by GAC. Science of the Total Environment, 768, 144758 (10 pp.). doi:10.1016/j.scitotenv.2020.144758, Institutional Repository

Ward, B. J., Andriessen, N., Tembo, J. M., Kabika, J., Grau, M., Scheidegger, A., … Strande, L. (2021). Predictive models using "cheap and easy" field measurements: can they fill a gap in planning, monitoring, and implementing fecal sludge management solutions?. Water Research, 196, 116997 (12 pp.). doi:10.1016/j.watres.2021.116997, Institutional Repository

Wielinski, J., Gogos, A., Voegelin, A., Müller, C. R., Morgenroth, E., & Kaegi, R. (2021). Release of gold (Au), silver (Ag) and cerium dioxide (CeO₂) nanoparticles from sewage sludge incineration ash. Environmental Science: Nano, 8(11), 3220-3232. doi:10.1039/D1EN00497B, Institutional Repository

Wielinski, J., Voegelin, A., Grobéty, B., Müller, C. R., Morgenroth, E., & Kaegi, R. (2021). Transformation of TiO₂ (nano)particles during sewage sludge incineration. Journal of Hazardous Materials, 411, 124932 (14 pp.). doi:10.1016/j.jhazmat.2020.124932, Institutional Repository

Zhang, L., Graham, N., Derlon, N., Tang, Y., Siddique, M. S., Xu, L., & Yu, W. (2021). Biofouling by ultra-low pressure filtration of surface water: the paramount role of initial available biopolymers. Journal of Membrane Science, 640, 119740 (9 pp.). doi:10.1016/j.memsci.2021.119740, Institutional Repository

Ziemba, C., Sharma, P., Ahrens, T., Reynaert, E., & Morgenroth, E. (2021). Disruptions in loading and aeration impact effluent chlorine demand during biological greywater recycling. Water Research X, 11, 100087 (10 pp.). doi:10.1016/j.wroa.2020.100087, Institutional Repository

Bogler, A., Packman, A., Furman, A., Gross, A., Kushmaro, A., Ronen, A., … Bar-Zeev, E. (2020). Rethinking wastewater risks and monitoring in light of the COVID-19 pandemic. Nature Sustainability, 3, 981-990. doi:10.1038/s41893-020-00605-2, Institutional Repository

Burdon, F. J., Bai, Y., Reyes, M., Tamminen, M., Staudacher, P., Mangold, S., … Stamm, C. (2020). Stream microbial communities and ecosystem functioning show complex responses to multiple stressors in wastewater. Global Change Biology, 26(11), 6363-6382. doi:10.1111/gcb.15302, Institutional Repository

Multiple anthropogenic drivers are changing ecosystems globally, with a disproportionate and intensifying impact on freshwater habitats. A major impact of urbanization are inputs from wastewater treatment plants (WWTPs). Initially designed to reduce eutrophication and improve water quality, WWTPs increasingly release a multitude of micropollutants (MPs; i.e., synthetic chemicals) and microbes (including antibiotic‐resistant bacteria) to receiving environments. This pollution may have pervasive impacts on biodiversity and ecosystem services. Viewed through multiple lenses of macroecological and ecotoxicological theory, we combined field, flume, and laboratory experiments to determine the effects of wastewater (WW) on microbial communities and organic‐matter processing using a standardized decomposition assay. First, we conducted a mensurative experiment sampling 60 locations above and below WWTP discharges in 20 Swiss streams. Microbial respiration and decomposition rates were positively influenced by WW inputs via warming and nutrient enrichment, but with a notable exception: WW decreased the activation energy of decomposition, indicating a "slowing" of this fundamental ecosystem process in response to temperature. Second, next‐generation sequencing indicated that microbial community structure below WWTPs was altered, with significant compositional turnover, reduced richness, and evidence of negative MP influences. Third, a series of flume experiments confirmed that although diluted WW generally has positive influences on microbial‐mediated processes, the negative effects of MPs are "masked" by nutrient enrichment. Finally, transplant experiments suggested that WW‐borne microbes enhance decomposition rates. Taken together, our results affirm the multiple stressor paradigm by showing that different aspects of WW (warming, nutrients, microbes, and MPs) jointly influence ecosystem functioning in complex ways. Increased respiration rates below WWTPs potentially generate ecosystem "disservices" via greater carbon evasion from streams and rivers. However, toxic MP effects may fundamentally alter ecological scaling relationships, indicating the need for a rapprochement between ecotoxicological and macroecological perspectives.

Böhler, M., Hernandez, A., McArdell, C. S., Siegrist, H., Joss, A., & Baggenstos, M. (2020). Elimination von Spurenstoffen durch granulierte Aktivkohle-Filtration (GAK). Grosstechnische Untersuchungen auf der ARA Furt, Bülach. Schlussbericht. Dübendorf: Eawag. , Institutional Repository

Böhler, M., Joss, A., McArdell, C., & Meier, A. (2020). Hinweise zur Planung und Auslegung von diskontinuierlich gespülten GAK-Filtern zur Elimination organischer Spurenstoffe aus kommunalem Abwasser. Konsenspapier zum Ergebnis des Workshops vom 9.12.2019 an der Eawag. Dübendorf: Eawag; VSA. , Institutional Repository

Böhler, M., Joss, A., McArdell, C., & Meier, A. (2020). Notice explicative pour la planification et le dimensionnement de filtres à charbon actif en grains (CAG) rétrolavés discontinuellement pour l'élimination des composés traces organiques dans les eaux usées communales. Document de synthèse suite au workshop du 9.12.2019 à l'Eawag. Dübendorf: Eawag; VSA. , Institutional Repository

Doll, C., Larsen, T. A., Strande, L., Udert, K. M., & Morgenroth, E. (2020). Water Hub im NEST-Gebäude. Eine Plattform zum Testen von innovativen ressourcenorientierten Sanitärsystemen. Aqua & Gas, 100(2), 52-57. , Institutional Repository

Hadengue, B., Scheidegger, A., Morgenroth, E., & Larsen, T. A. (2020). Modeling the water-energy nexus in households. Energy and Buildings, 225, 110262 (10 pp.). doi:10.1016/j.enbuild.2020.110262, Institutional Repository

Helleshøj Sørensen, K., & Morgenroth, E. (2020). Biofilm reactors. In G. Chen, G. A. Ekama, M. C. M. van Loosdrecht, & D. Brdjanovic (Eds.), Biological wastewater treatment: principles, modeling and design (pp. 813-839). London: IWA Publishing. , Institutional Repository

Hess, A., Bettex, C., & Morgenroth, E. (2020). Influence of intermittent flow on removal of organics in a biological activated carbon filter (BAC) used as post-treatment for greywater. Water Research X, 9, 100078 (10 pp.). doi:10.1016/j.wroa.2020.100078, Institutional Repository

Hoffmann, S., Feldmann, U., Bach, P. M., Binz, C., Farrelly, M., Frantzeskaki, N., … Udert, K. M. (2020). A research agenda for the future of urban water management: exploring the potential of non-grid, small-grid, and hybrid solutions. Environmental Science and Technology, 54(9), 5312-5322. doi:10.1021/acs.est.9b05222, Institutional Repository

Jacquin, C., Yu, D., Sander, M., Domagala, K. W., Traber, J., Morgenroth, E., & Julian, T. R. (2020). Competitive co-adsorption of bacteriophage MS2 and natural organic matter onto multiwalled carbon nanotubes. Water Research X, 9, 100058 (12 pp.). doi:10.1016/j.wroa.2020.100058, Institutional Repository

A leading challenge in drinking water treatment is to remove small-sized viruses from the water in a simple and efficient manner. Multi-walled carbon nanotubes (MWCNT) are new generation adsorbents with previously demonstrated potential as filter media to improve virus removal. This study therefore aimed to evaluate the field applicability of MWCNT-filters for virus removal in water containing natural organic matter (NOM) as co-solute to viruses, using batch equilibrium experiments. Contrary to previous studies, our results showed with MS2 bacteriophages single-solute systems that the affinity of MWCNT for MS2 was low, since after 3 h of equilibration only 4 log₁₀ reduction value (LRV) of MS2 (20 mL at an initial concentration of 10⁶ PFU MS2/mL) were reached. Single solute experiments with Suwannee river NOM (SRNOM) performed with environmentally-relevant concentrations showed MWCNT surface saturation at initial SRNOM concentrations between 10 and 15 mgC/L, for water pH between 5.2 and 8.7. These results suggested that at NOM:virus ratios found in natural waters, the NOM would competitively suppress virus adsorption onto MWCNT, even at low NOM concentrations. We confirmed this expectation with SRNOM-MS2 co-solute experiments, which showed an exponential decrease of the MS2 LRV by MWCNT with an increase in the initial SRNOM concentration. More interestingly, we showed that pre-equilibrating MWCNT with a SRNOM solution at a concentration as low as 0.4 mgC/L resulted in a LRV decrease of 3 for MS2, due to the formation of a negatively charged SRNOM adlayer on the MWCNT surface. Complementary batch experiments with natural NOM-containing waters and competition experiments with SRNOM in the presence of CaCl₂ confirmed that the presence of NOM in waters challenges virus removal by MWCNT-filters, irrespective of the concentration and type of NOM and also in the presence of Ca²⁺. We therefore conclude that MWCNT-filters produced with commercially available pristine MWCNT cannot be considered as a viable technology for drinking water virus removal.

Jimenez, J., Charnier, C., Kouas, M., Latrille, E., Torrijos, M., Harmand, J., … Steyer, J. P. (2020). Modelling hydrolysis: simultaneous versus sequential biodegradation of the hydrolysable fractions. Waste Management, 101, 150-160. doi:10.1016/j.wasman.2019.10.004, Institutional Repository

Layer, M., Garcia Villodres, M., Hernandez, A., Reynaert, E., Morgenroth, E., & Derlon, N. (2020). Limited simultaneous nitrification-denitrification (SND) in aerobic granular sludge systems treating municipal wastewater: mechanisms and practical implications. Water Research X, 7, 100048 (13 pp.). doi:10.1016/j.wroa.2020.100048, Institutional Repository

Simultaneous nitrification-denitrification (SND) is, in theory, a key advantage of aerobic granular sludge systems over conventional activated sludge systems. But practical experience and literature suggests that SND and thus total nitrogen removal are limited during treatment of municipal wastewater using AGS systems. This study thus aims at quantifying the extent and understanding the mechanisms of SND during treatment of municipal wastewater with aerobic granular sludge (AGS) systems. Experiments (long-term and batch-tests) as well as mathematical modelling were performed. Our experimental results demonstrate that SND is significantly limited during treatment of low-strength municipal wastewater with AGS systems (14-39%), while almost full SND is observed when treating synthetic influent containing only diffusible substrate (90%). Our simulations demonstrate that the main mechanisms behind limited SND are (1) the dynamics of anoxic zone formation inside the granule, (2) the diffusibility and availability of electron-donors in those zones and (3) the aeration mode. The development of anoxic zones is driven by the utilisation of oxygen in the upper layers of the granule leading to transport limitations of oxygen inside the granule; this effect is closely linked to granule size and wastewater composition. Development of anoxic zones during the aerobic phase is limited for small granules at constant aeration at bulk dissolved oxygen (DO) concentration of 2 mgO₂ L^-1, and anoxic zones only develop during a brief period of the aerated phase for large granules. Modelling results further indicate that a large fraction of electron-donors are actually utilised in aerobic rather than anoxic redox zones - in the bulk or at the granule surface. Thus, full SND cannot be achieved with AGS treating low strength municipal wastewater if a constant DO is maintained during the aeration phase. Optimised aeration strategies are therefore required. 2-step and alternating aeration are tested successfully using mathematical modelling and increase TN removal to 40-79%, without compromising nitrification, and by shifting electron-donor utilisation towards anoxic redox conditions.

Layer, M., Bock, K., Ranzinger, F., Horn, H., Morgenroth, E., & Derlon, N. (2020). Particulate substrate retention in plug-flow and fully-mixed conditions during operation of aerobic granular sludge systems. Water Research X, 9, 100075 (11 pp.). doi:10.1016/j.wroa.2020.100075, Institutional Repository

Particulate substrate (X_B) is the major organic substrate fraction in most municipal wastewaters. However, the impact of X_B on aerobic granular sludge (AGS) systems is not fully understood. This study evaluated the physical retention of X_B in AGS sequencing batch reactor (SBR) during anaerobic plug-flow and then aerobic fully-mixed conditions. The influence of different sludge types and operational variables on the extent and mechanisms of X_B retention in AGS SBR were evaluated. X_B mass-balancing and magnetic resonance imaging (MRI) were applied. During the anaerobic plug-flow feeding, most X_B was retained in the first few cm of the settled sludge bed within the interstitial voids, where X_B settled and accumulated ultimately resulting in the formation of a filter-cake. Sedimentation and surface filtration were thus the dominant X_B retention mechanisms during plug-flow conditions, indicating that contact and attachment of X_B to the biomass was limited. X_B retention was variable and influenced by the X_B influent concentration, sludge bed composition and upflow feeding velocity (v_ww). X_B retention increased with larger X_B influent concentrations and lower v_ww, which demonstrated the importance of sedimentation on X_B retention during plug-flow conditions. Hence, large fractions of influent X_B likely re-suspended during aerobic fully-mixed conditions, where X_B then preferentially and rapidly attached to the flocs. During fully-mixed conditions, increasing floc fractions, longer mixing times and larger X_B concentrations increased X_B retention. Elevated X_B retention was observed after short mixing times < 60 min when flocs were present, and the contribution of flocs towards X_B retention was even more pronounced for short mixing times < 5 min. Overall, our results suggest that flocs occupy an environmental niche that results from the availability of X_B during aerobic fully-mixed conditions of AGS SBR. Therefore, a complete wash-out of flocs is not desirable in AGS systems treating municipal wastewater.

Moraes Schambeck, C., Girbal-Neuhauser, E., Böni, L., Fischer, P., Bessière, Y., Paul, E., … Derlon, N. (2020). Chemical and physical properties of alginate-like exopolymers of aerobic granules and flocs produced from different wastewaters. Bioresource Technology, 312, 123632 (11 pp.). doi:10.1016/j.biortech.2020.123632, Institutional Repository

Morgenroth, E. (2020). Modelling biofilms. In G. H. Chen, M. C. M. van Loosdrecht, G. A. Ekama, & D. Brdjanovic (Eds.), Biological wastewater treatment. principles, modeling and design (pp. 757-812). London: IWA Publishing. , Institutional Repository

Ranzinger, F., Matern, M., Layer, M., Guthausen, G., Wagner, M., Derlon, N., & Horn, H. (2020). Transport and retention of artificial and real wastewater particles inside a bed of settled aerobic granular sludge assessed applying magnetic resonance imaging. Water Research X, 7, 100050 (9 pp.). doi:10.1016/j.wroa.2020.100050, Institutional Repository

The removal or degradation of particulate organic matter is a crucial part in biological wastewater treatment. This is even more valid with respect to aerobic granular sludge and the impact of particulate organic matter on the formation and stability of the entire granulation process. Before the organic part of the particulate matter can be hydrolyzed and finally degraded by the microorganism, the particles have to be transported towards and retained within the granulated biomass. The understanding of these processes is currently very limited. Thus, the present study aimed at visualizing the transport of particulate organic matter into and through an aerobic granular sludge bed. Magnetic Resonance Imaging (MRI) was successfully applied to resolve the different fractions of a granular sludge bed over time and space. Quantification and merging of 3D data sets allowed for a clear determination of the particle distribution within the granular sludge bed. Dextran coated super paramagnetic iron oxide nanoparticles (SPIONs, d_p = 38±10 nm) served as model particles for colloidal particles. Microcrystalline cellulose particles (d_p = 1-20 μm) tagged with paramagnetic iron oxide were applied as a reference for toilet paper, which is a major fraction of particulate matter in domestic wastewater. The results were supplemented by the use of real wastewater particles with a size fraction between 28 and 100 μm. Colloidal SPIONs distributed evenly over the granular sludge bed penetrating the granules up to 300 μm. Rinsing the granular sludge bed proved their immobilization. Microcrystalline cellulose and real wastewater particles in the micrometer range accumulated in the void space between settled granules. An almost full retention of the wastewater particles was observed within the first 20 mm of the granular sludge bed. Moreover, the formation of particle layers indicates that most of the micrometer-sized particles are not attached to the biomass and remain mobile. Consequently, these particles are released into the bulk phase when the granulated sludge bed is resuspended.

Reynaert, E., Greenwood, E. E., Ndwandwe, B., Riechmann, M. E., Sindall, R. C., Udert, K. M., & Morgenroth, E. (2020). Practical implementation of true on-site water recycling systems for hand washing and toilet flushing. Water Research X, 7, 100051 (13 pp.). doi:10.1016/j.wroa.2020.100051, Institutional Repository

Schambeck, C. M., Magnus, B. S., de Souza, L. C. R., Leite, W. R. M., Derlon, N., Bittencourt Guimarães, L., & Ribeiro da Costa, R. H. (2020). Biopolymers recovery: dynamics and characterization of alginate-like exopolymers in an aerobic granular sludge system treating municipal wastewater without sludge inoculum. Journal of Environmental Management, 263, 110394 (11 pp.). doi:10.1016/j.jenvman.2020.110394, Institutional Repository

Wielinski, J. J. (2020). Investigations into the fate of engineered transition metal nano particles during sewage sludge incineration (Doctoral dissertation). doi:10.3929/ethz-b-000473625, Institutional Repository

Engineered nanoparticles (ENP) are applied in consumer products and industrial processes to increase profitability and sustainability through reduced resource consumption, e.g., TiO₂-NP in sun screens, ZnO-NP in cosmetics and paints or Ag-NP and CuO-NP as anti-microbial agents. However, critical discussions about unintended, adverse effects of ENP on humans, soil- and aquatic organisms have always accompanied their usage. Therefore, investigations into the fate of ENP after their use phase are necessary to enable a reliable assessment of the risks associated with the use of such novel materials. Previous research efforts showed that after usage, large shares of ENP applied in consumer products are discharged to wastewater and transported to wastewater treatment plants (WWTPs). WWTPs retain > 95% of ENP leading to their accumulation in sewage sludge. In Switzerland, sewage sludge is incinerated preferably in mono-combustion fluidized bed reactors (FBRs) and the resulting ashes are landfilled for resource recovery in the future. To contribute to a better understanding of the fate and behavior of ENP in the urban environment, the following research questions were addressed: (i) how can the kinetics of sewage sludge devolatilization be quantified, (ii) what chemical and physical transformations of ENP occur during the sewage sludge combustion, (iii) what are the possibilities of synchrotron hard X-ray chemical imaging to study transformation products of ENP, and lastly (iv) to what extent are ENP released from sewage sludge ash landfill sites? [...]

Künstlich produzierte Nanopartikel (NP) werden in Konsumgütern und industriellen Prozessen zur Steigerung von Effizienz und Nachhaltigkeit durch reduzierten Ressourceneinsatz verwendet, z.B. TiO₂-NP in Sonnencreme, ZnO-NP in Kosmetika und Farbe oder Ag-NP und CuO-NP zu antimikrobiellen Zwecken. Allerdings ist stets vor ungewollten, nachteiligen Effekten solcher NP gegenüber Menschen, sowie Boden- und Wasserorganismen gewarnt worden. Daher sind Studien über die Transformation und den Verbleib von NP nach ihrer Nutzungsphase notwendig um die oben genannten Risiken der Nutzung solcher neuartigen Materialen zuverlässig abschätzen zu können. Vorangegangene Studien haben gezeigt, dass ein grosser Teil der NP in Konsumgütern in Abwasserkanäle entlassen wird und in Abwasserreinigungsanlangen (ARAs) gelangt. ARAs halten über 95% der einkommenden NP zurück, welche folglich im Faulschlamm aufkonzentriert werden. In der Schweiz wird Faulschlamm vorzugsweise in speziell dafür errichteten Wirbelbettreaktoren verbrannt und die anfallende Asche wird von Asche aus anderen Brennstoffen getrennt deponiert um daraus in der Zukunft Ressourcen rückzugewinnen.
Um ein besseres Verständnis des Verhaltens von NP in städtischen Abwassersystemen und insbesondere während der Klärschlammverbrennung zu gewinnen, wurden die folgenden Forschungsfragen adressiert: (i)Wie lässt sich die Verbrennungskinetik von Klärschlamm quantifizieren, (ii) welche physikalischen und chemischen Transformationsprozesse unterlaufen NP während der Klärschlammverbrennung, (iii) wie können Transformationsprodukte von NP mithilfe synchrotronbasierter, chemische Bildgebung identifiziert werden und (iv) wie gross ist das Freisetzungspotential von NP aus Klärschlammaschedeponien? [...]

Wielinski, J., Marafatto, F. F., Gogos, A., Scheidegger, A., Voegelin, A., Müller, C. R., … Kaegi, R. (2020). Synchrotron hard X-ray chemical imaging of trace element speciation in heterogeneous samples: development of criteria for uncertainty analysis. Journal of Analytical Atomic Spectrometry, 35, 567-579. doi:10.1039/C9JA00394K, Institutional Repository

Ziemba, C., Larivé, O., Reynaert, E., Huisman, T., & Morgenroth, E. (2020). Linking transformations of organic carbon to post-treatment performance in a biological water recycling system. Science of the Total Environment, 721, 137489 (8 pp.). doi:10.1016/j.scitotenv.2020.137489, Institutional Repository

Burdon, F. J., Munz, N. A., Reyes, M., Focks, A., Joss, A., Räsänen, K., … Stamm, C. (2019). Agriculture versus wastewater pollution as drivers of macroinvertebrate community structure in streams. Science of the Total Environment, 659, 1256-1265. doi:10.1016/j.scitotenv.2018.12.372, Institutional Repository

Water pollution is ubiquitous globally, yet how the effects of pollutants propagate through natural ecosystems remains poorly understood. This is because the interactive effects of multiple stressors are generally hard to predict. Agriculture and municipal wastewater treatment plants (WWTPs) are often major sources of contaminants for streams, but their relative importance and the role of different pollutants (e.g. nutrients or pesticides) are largely unknown. Using a 'real world experiment' with sampling locations up- and downstream of WWTPs, we studied how effluent discharges affected water quality and macroinvertebrate communities in 23 Swiss streams across a broad land-use gradient.
Variation partitioning of community composition revealed that overall water quality explained approximately 30% of community variability, whereby nutrients and pesticides each independently explained 10% and 2%, respectively. Excluding oligochaetes (which were highly abundant downstream of the WWTPs) from the analyses, resulted in a relatively stronger influence (3%) of pesticides on the macroinvertebrate community composition, whereas nutrients had no influence. Generally, the macroinvertebrate community composition downstream of the WWTPs strongly reflected the upstream conditions, likely due to a combination of efficient treatment processes, environmental filtering and organismal dispersal. Wastewater impacts were most prominently by the Saprobic index, whereas the SPEAR index (a trait-based macroinvertebrate metrics reflecting sensitivity to pesticides) revealed a strong impact of arable cropping but only a weak impact of wastewater.
Overall, our results indicate that agriculture can have a stronger impact on headwater stream macroinvertebrate communities than discharges from WWTP. Yet, effects of wastewater-born micropollutants were clearly quantifiable among all other influence factors. Improving our ability to further quantify the impacts of micropollutants requires highly-resolved water quality and taxonomic data with adequate spatial and temporal sampling. These improvements would help to better account for the underlying causal pathways that drive observed biological responses, such as episodic contaminant peaks and dispersal-related processes.

Böhler, M. A., Remy, C., Löwenberg, J., Hagemann, N., Hernandez, A., Joss, A., & McArdell, C. S. (2019). Kann die Kohle nachhaltig sein? – Einsatz von Aktivkohle zur Elimination von Spurenstoffen aus kommunalem Abwasser. In M. Wessling & J. Pinnekamp (Eds.), 13. Aachener Tagung Wassertechnologie. Verfahren der Wasseraufbereitung und Abwasserbehandlung (pp. 51-62). Aachen: RWTH Aachen. , Institutional Repository

Fumasoli, A., Bützer, S., Kraft, T., Derlon, N., Lüdin, K., Behl, M., & Maissen, B. (2019). Trommelsieb als Vorklärbecken-Ersatz. Erkenntnisse aus einem Pilotversuch auf der ARA Sihltal. Aqua & Gas, 99(10), 76-82. , Institutional Repository

Gruber, W., Villez, K., Kipf, M., Wunderlin, P., Siegrist, H., Vogt, L., & Joss, A. (2019). N₂O emission in full-scale wastewater treatment: proposing a refined monitoring strategy. Science of the Total Environment, 699, 134157 (9 pp.). doi:10.1016/j.scitotenv.2019.134157, Institutional Repository

Nitrous oxide (N₂O) emissions from wastewater treatment contribute significantly to greenhouse gas emissions. They have been shown to exhibit a strong seasonal and daily profile in previously conducted monitoring campaigns. However, only two year-long online monitoring campaigns have been published to date. Based on three monitoring campaigns on three full-scale wastewater treatment plants (WWTPs) with different activated sludge configurations, each of which lasted at least one year, we propose a refined monitoring strategy for long-term emission monitoring with multiple flux chambers on open tanks. Our monitoring campaigns confirm that the N₂O emissions exhibited a strong seasonal profile and were substantial on all three plants (1-2.4% of the total nitrogen load). These results confirm that N₂O is the most important greenhouse gas emission from wastewater treatment. The temporal variation was more distinct than the spatial variation within aeration tanks. Nevertheless, multiple monitoring spots along a single lane are crucial to assess representative emission factors in flow-through systems. Sequencing batch reactor systems were shown to exhibit comparable emissions within one reactor but significant variation between parallel reactors. The results indicate that considerable emission differences between lanes are to be expected in cases of inhomogeneous loading and discontinuous feeding. For example, N₂O emission could be shown to depend on the amount of treated reject water: lanes without emitted <1% of the influent load, while parallel lanes emitted around 3%. In case of inhomogeneous loading, monitoring of multiple lanes is required. Our study enables robust planning of monitoring campaigns on WWTPs with open tanks. Extensive full-scale emission monitoring campaigns are important as a basis for reliable decisions about reducing the climate impact of wastewater treatment. More specifically, such data sets help us to define general emission factors for wastewater treatment plants and to construct and critically evaluate N₂O emission models.

Hadengue, B., Scheidegger, A., Morgenroth, E., & Larsen, T. A. (2019). The waterhub modules: material and energy flow analysis of domestic hot water systems. In A. Haumer (Ed.), Linköping Electronic Conference Proceedings: Vol. 157. Proceedings of the 13^th international modelica conference (pp. 639-646). doi:10.3384/ecp19157639, Institutional Repository

Horisberger, M., Casazza, R., Grelot, J., & Joss, A. (2019). Elimination von Mikroverunreinigungen. Pilotversuche: Einsatz von granulierter Aktivkohle im Wirbelbett auf der Ara Penthaz. Aqua & Gas, 99(1), 39-45. , Institutional Repository

Jafari, M., Derlon, N., Desmond, P., van Loosdrecht, M. C. M., Morgenroth, E., & Picioreanu, C. (2019). Biofilm compressibility in ultrafiltration: a relation between biofilm morphology, mechanics and hydraulic resistance. Water Research, 157, 335-345. doi:10.1016/j.watres.2019.03.073, Institutional Repository

Laureni, M., Weissbrodt, D. G., Villez, K., Robin, O., de Jonge, N., Rosenthal, A., … Joss, A. (2019). Biomass segregation between biofilm and flocs improves the control of nitrite-oxidizing bacteria in mainstream partial nitritation and anammox processes. Water Research, 154, 104-116. doi:10.1016/j.watres.2018.12.051, Institutional Repository

The control of nitrite-oxidizing bacteria (NOB) challenges the implementation of partial nitritation and anammox (PN/A) processes under mainstream conditions. The aim of the present study was to understand how operating conditions impact microbial competition and the control of NOB in hybrid PN/A systems, where biofilm and flocs coexist. A hybrid PN/A moving-bed biofilm reactor (MBBR; also referred to as integrated fixed film activated sludge or IFAS) was operated at 15 °C on aerobically pre-treated municipal wastewater (23 mg_NH4-N L^–1). Ammonium-oxidizing bacteria (AOB) and NOB were enriched primarily in the flocs, and anammox bacteria (AMX) in the biofilm. After decreasing the dissolved oxygen concentration (DO) from 1.2 to 0.17 mg_O2 L^–1 - with all other operating conditions unchanged - washout of NOB from the flocs was observed. The activity of the minor NOB fraction remaining in the biofilm was suppressed at low DO. As a result, low effluent NO₃^– concentrations (0.5 mg_N L^–1) were consistently achieved at aerobic nitrogen removal rates (80 mg_N L^–1 d^–1) comparable to those of conventional treatment plants. A simple dynamic mathematical model, assuming perfect biomass segregation with AOB and NOB in the flocs and AMX in the biofilm, was able to qualitatively reproduce the selective washout of NOB from the flocs in response to the decrease in DO-setpoint. Similarly, numerical simulations indicated that flocs removal is an effective operational strategy to achieve the selective washout of NOB. The direct competition for NO₂^– between NOB and AMX - the latter retained in the biofilm and acting as a "NO₂-sink" - was identified by the model as key mechanism leading to a difference in the actual growth rates of AOB and NOB (i.e., μ_NOB < μ_AOB in flocs) and allowing for the selective NOB washout over a broad range of simulated sludge retention times (SRT = 6.8–24.5 d). Experimental results and model predictions demonstrate the increased operational flexibility, in terms of variables that can be easily controlled by operators, offered by hybrid systems as compared to solely biofilm systems for the control of NOB in mainstream PN/A applications.

Layer, M., Adler, A., Reynaert, E., Hernandez, A., Pagni, M., Morgenroth, E., … Derlon, N. (2019). Organic substrate diffusibility governs microbial community composition, nutrient removal performance and kinetics of granulation of aerobic granular sludge. Water Research X, 4, 100033 (16 pp.). doi:10.1016/j.wroa.2019.100033, Institutional Repository

Basic understanding of formation of aerobic granular sludge (AGS) has mainly been derived from lab-scale systems with simple influents containing only highly diffusible volatile fatty acids (VFA) as organic substrate. This study compares start-up of AGS systems fed by different synthetic and municipal wastewaters (WW), characterised by increasing complexity in terms of non-diffusible organic substrate. Four AGS reactors were started with the same inoculum activated sludge and operated for one year. The development of AGS, settling characteristics, nutrient and substrate removal performance as well as microbial community composition were monitored. Our results indicate that the higher the content of diffusible organic substrate in the WW, the faster the formation of AGS. The presence of non-diffusible organic substrate in the influent WW led to the formation of small granules and to the presence of 20–40% (% of total suspended solids) of flocs in the AGS. When AGS was fed with complex influent WW, the classical phosphorus and glycogen accumulating organisms (PAO, GAO) were outcompeted by their fermentative equivalents. Substrate and nutrient removal was observed in all reactors, despite the difference in physical and settling properties of the AGS, but the levels of P and N removal depended on the influent carbon composition. Mechanistically, our results indicate that increased levels of non-diffusible organic substrate in the influent lower the potential for microbial growth deep inside the granules. Additionally, non-diffusible organic substrates give a competitive advantage to the main opponents of AGS formation – ordinary heterotrophic organisms (OHO). Both of these mechanisms are suspected to limit AGS formation. The presented study has relevant implications for both practice and research. Start-up duration of AGS systems treating high complexity WW were one order of magnitude higher than a typical lab-scale system treating VFA-rich synthetic WW, and biomass as flocs persisted as a significant fraction. Finally, the complex synthetic influent WW – composed of VFA, soluble fermentable and particulate substrate - tested here seems to be a more adequate surrogate of real municipal WW for laboratory studies than 100%-VFA WW.

Mansfeldt, C., Achermann, S., Men, Y., Walser, J. C., Villez, K., Joss, A., … Fenner, K. (2019). Microbial residence time is a controlling parameter of the taxonomic composition and functional profile of microbial communities. ISME Journal, 13(6), 1589-1601. doi:10.1038/s41396-019-0371-6, Institutional Repository

Nürenberg, G., Kunkel, U., Wick, A., Falås, P., Joss, A., & Ternes, T. A. (2019). Nontarget analysis: a new tool for the evaluation of wastewater processes. Water Research, 163, 114842 (11 pp.). doi:10.1016/j.watres.2019.07.009, Institutional Repository

Strategies to determine the removal efficiency of micropollutants in wastewater treatment plants (WWTPs) are widely discussed. Especially the evaluation of the potential benefit of further advanced treatment steps such as an additional tertiary treatment based on ozonation or activated carbon have come into focus. Such evaluation strategies are often based on the removal behavior of known micropollutants via target or suspected analysis. The utilization of nontarget analysis is considered to lead to a more comprehensive picture as also unknown or not expected micropollutants are analyzed. Here, the results of an evaluation via target and nontarget analysis were compared for biological treatment (BT) processes of eleven full-scale WWTPs and three different post-treatments (PTs): one sand filter (SF) and two granular activated carbon (GAC) filters. The similarity of the determined removals from target and nontarget analysis of the BTs increased significantly by excluding easily degradable "features" from the nontarget evaluation. A similar ranking of the removal trends for the BTs could also be achieved by comparing this new subset of nontarget features with a set of nine readily to moderately biodegradable micropollutants. This observation suggests that a performance ranking of BTs based either on target or nontarget analysis is plausible. In contrast to the BTs, the evaluation of the three PTs revealed that the difference of feature removal between SF and the two GACs was small, but large for the target analytes with substantially higher removal effciencies for the GACs compared to the SF. In addition to the removal behavior, the nontarget analysis provided further information about the number and quantity of transformation products (TPs) in the effluent from the BTs. For all BTs more than half (55–67%) of the features detected in the effluent were not found in the influent. A comparable proportion of TPs was also detected after GAC and sand filtration due to their microbial activities.

Pronk, W., Ding, A., Morgenroth, E., Derlon, N., Desmond, P., Burkhardt, M., … Fane, A. G. (2019). Gravity-driven membrane filtration for water and wastewater treatment: a review. Water Research, 149, 553-565. doi:10.1016/j.watres.2018.11.062, Institutional Repository

Purtschert, I., Gutmann, M., Bitterli, C., Joss, A., & Blumensaat, F. (2019). Abwasserentsorgung - Wie viel ist gut genug?. Aqua & Gas, 99(1), 85-86. , Institutional Repository

Seviour, T., Derlon, N., Simonsen Dueholm, M., Flemming, H. C., Girbal-Neuhauser, E., Horn, H., … Lin, Y. (2019). Extracellular polymeric substances of biofilms: suffering from an identity crisis. Water Research, 151, 1-7. doi:10.1016/j.watres.2018.11.020, Institutional Repository

Siegrist, H., Joss, A., Boehler, M., McArdell, C. S., & Ternes, T. (2019). Organic micropollutant control. In G. Mannina, G. Ekama, H. Ødegaard, & G. Olsson (Eds.), Advances in wastewater treatment (pp. 231-260). doi:10.2166/9781780409719_0231, Institutional Repository

Silva, M. O. D., Desmond, P., Derlon, N., Morgenroth, E., & Pernthaler, J. (2019). Source community and assembly processes affect the efficiency of microbial microcystin degradation on drinking water filtration membranes. Frontiers in Microbiology, 10, 843 (15 pp.). doi:10.3389/fmicb.2019.00843, Institutional Repository

Thürlimann, C. M. (2019). Soft-sensing, automation, and diagnosis for nitrification (Doctoral dissertation). doi:10.3929/ethz-b-000347049, Institutional Repository

Nitrification of wastewater requires control for the purposes of efficiency and of stability. However, first, the highly complex microbial community in wastewater treatment plants and very different compositions of wastewaters impede a complete understanding of nitrification. Second, the determination of the states of the process is seldom exact because sensors are subject to a high level of wear and tear. Consequently, instrumentation, control, and automation (ICA) of nitrification processes are a challenge. I hypothesize that soft-sensors - based on the signals of robust, physical sensors - and specially designed control loops, which do not need redundant information to correct for drift, can reduce the maintenance needs for the control of nitrification. Consequently, the econonomical application range for ICA of nitrification processes can be extended.
A large part of this thesis is dedicated to the stabilisation of urine nitrification as a pretreatment for nutrient recovery. To this end, an online nitrite detection and an according control of the process are required. Furthermore, the thesis comprises an ammonia aeration controller, which is based on pH signals, to be used in municipal wastewater. The four chapters of the thesis focus on the following topics.
The first chapter investigates calibration experiments for in-line UV-Vis sensors. Such sensors can serve as soft-sensors for numerous substances. With differently designed experiments, data for the calibration of UV-Vis based nitrite models in high strength wastewater was recorded. Online experiments executed in-situ allow calibrating similarly exact models like experiments which are conducted by spiking additional nitrite. The good performance of the models being based on online experiments is explained by the correlation of other light-absorbing substances in the process with nitrite.
The second chapter evaluates the potential of a stoichiometry-based soft-sensor for nitrite. The stoichiometry of nitrification theoretically allows distinguishing the ammonia and the nitrite oxidation rates by means of the derivatives of the dissolved oxygen and of the pH signal and in turn detecting nitrite accumulations. We show that under relatively ideal conditions the dynamics in the ratio of the two derivatives show similarities with the dynamics in the nitrite concentration. Factors that deteriorate this information quality are identified.
The third part of this thesis investigates how drifting sensor signals can be used as an input for a feedback controller without relying on redundant information to correct this drift. The controller shall prevent uncontrolled nitrite accumulation in a urine nitrification system. To this end, the controller does not use the absolute value of the nitrite signal, but its 1^st and 2^nd derivative as inputs. By controlled accumulation and degradation of nitrite, the controller can keep the derivatives continuously informative. The switch from substrate inhibition to substrate limitation of the nitrite oxidising bacteria can be identified by means of the inflection point in the signal. The developed controller is tested successfully on a lab-scale reactor.
The fourth chapter of this thesis describes an ammonia based aeration controller. These controllers usually require maintenance intensive instrumentation. Therefore a new ammonia soft sensor for continuously operated municipal wastewater treatment plants is developed. It relies on the 1^st derivative of a pH difference measured over the aerated zone. This soft sensor is successfully tested in a controller deployed on various municipal wastewater treatment plants. The controller was designed to increase its robustness towards drift in the pH signals.

Thürlimann, C. M., Udert, K. M., Morgenroth, E., & Villez, K. (2019). Stabilizing control of a urine nitrification process in the presence of sensor drift. Water Research, 165, 114958 (10 pp.). doi:10.1016/j.watres.2019.114958, Institutional Repository

Ward, B. J., Traber, J., Gueye, A., Diop, B., Morgenroth, E., & Strande, L. (2019). Evaluation of conceptual model and predictors of faecal sludge dewatering performance in Senegal and Tanzania. Water Research, 167, 115101 (13 pp.). doi:10.1016/j.watres.2019.115101, Institutional Repository

Wielinski, J., Gogos, A., Voegelin, A., Müller, C., Morgenroth, E., & Kaegi, R. (2019). Transformation of nanoscale and ionic Cu and Zn during the incineration of digested sewage sludge (biosolids). Environmental Science and Technology, 53(20), 11704-11713. doi:10.1021/acs.est.9b01983, Institutional Repository

Ziemba, C., Larivé, O., Deck, S., Huisman, T., & Morgenroth, E. (2019). Comparing the anti-bacterial performance of chlorination and electrolysis post-treatments in a hand washing water recycling system. Water Research X, 2, 100020 (10 pp.). doi:10.1016/j.wroa.2018.100020, Institutional Repository

Innovative solutions are necessary to enable the decentralized recycling of greywater for applications requiring high-quality water, such as hand washing. While physical barriers such as ultrafiltration membranes effectively prevent the passage of bacteria, and chemical and biological treatments can effectively reduce the carbon content of the treated water, there exists a knowledge gap regarding the application of anti-bacterial strategies to prevent the growth of harmful bacteria following treatment. In this study, the effluent water from a household-scale greywater treatment system was fed to seven parallel experimental post-treatment tanks: three receiving direct chlorination with free chlorine residuals of 0.2, 1 or 5 mg Cl₂/L, three with chlorine produced through electrolysis at the same residual concentrations, and one control with no chlorine added. For increasing concentrations of direct chlorination, the median total cell count (TCC) values were 9 × 10⁴, 2.9 × 10⁴ and 1.8 × 10³ cells/mL, respectively. Electrolysis treatment produced very similar TCC concentrations, 8.8 × 10⁴, 1.1 × 10⁴ and 2.3 × 10³ cells/mL. The TCC concentrations were lower than the concentration of the water entering each tank (~3 × 10⁵ cells/mL). Intact cell count (ICC) measurements indicated that the viable cell concentrations, were less than 10% of the TCC values. Though electrolysis treatment can produce powerful oxidants, such as hydroxyl radical, there was no evidence that electrolysis in this system provided additional benefits beyond chlorine production for control of total or intact cell counts. Oxidation of bacteria by chlorine was the dominant anti-bacterial mechanism in our system. Monitoring of dissolved organic carbon (DOC) and assimilable organic carbon (AOC) did not suggest that carbon-limitation significantly impacted cell counts when chlorination or electrolysis treatment was applied. This work demonstrates that either direct chlorination or electrolysis treatment are able to reduce bacteria concentrations over long-term operation of a hand washing water treatment system. We recommend selecting chlorine residual targets such that a chlorine residual is maintained during periods of challenging operating conditions. We observed that a target residual of 1 mg Cl₂/L, in our system, maintained the TCC below the concentration found in Zürich drinking water.

Achermann, S., Falås, P., Joss, A., Mansfeldt, C., Men, Y., Vogler, B., & Fenner, K. (2018). Trends in micropollutant biotransformation along a solids retention time gradient. Environmental Science and Technology, 52(20), 11601-11611. doi:10.1021/acs.est.8b02763, Institutional Repository

Carrel, M., Morales, V. L., Beltran, M. A., Derlon, N., Kaufmann, R., Morgenroth, E., & Holzner, M. (2018). Biofilms in 3D porous media: delineating the influence of the pore network geometry, flow and mass transfer on biofilm development. Water Research, 134, 280-291. doi:10.1016/j.watres.2018.01.059, Institutional Repository

Carrel, M., Morales, V. L., Dentz, M., Derlon, N., Morgenroth, E., & Holzner, M. (2018). Pore-scale hydrodynamics in a progressively bioclogged three-dimensional porous medium: 3-D particle tracking experiments and stochastic transport modeling. Water Resources Research, 54(3), 2183-2198. doi:10.1002/2017WR021726, Institutional Repository

Derlon, N., Layer, M., Morgenroth, E., Adler, A., Gelb, A., & Holliger, C. (2018). Boues granulaires aérobies. État de l'art de la recherche actuelle et future. Aqua & Gas, 98(1), 14-19. , Institutional Repository

Derlon, N., Pronk, W., & Morgenroth, E. (2018). Membranes d'ultrafiltration. La présence de biofilms: un avantage pour stabiliser le flux et augmenter la qualité du perméat. Aqua & Gas, 98(5), 30-35. , Institutional Repository

Desmond, P., Best, J. P., Morgenroth, E., & Derlon, N. (2018). Linking composition of extracellular polymeric substances (EPS) to the physical structure and hydraulic resistance of membrane biofilms. Water Research, 132, 211-221. doi:10.1016/j.watres.2017.12.058, Institutional Repository

The effect of extracellular polymeric substances (EPS) on the meso-scale physical structure and hydraulic resistance of membrane biofilms during gravity driven membrane (GDM) filtration was investigated. Biofilms were developed on the surface of ultrafiltration membranes during dead-end filtration at ultra-low pressure (70 mbar). Biofilm EPS composition (total protein, polysaccharide and eDNA) was manipulated by growing biofilms under contrasting nutrient conditions. Nutrient conditions consisted of (i) a nutrient enriched condition with a nutrient ratio of 100:30:10 (C: N: P), (ii) a phosphorus limitation (C: N: P ratio: 100:30:0), and (iii) a nitrogen limitation (C: N: P ratio: 100:0:10). The structure of the biofilm was characterised at meso-scale using Optical Coherence Tomography (OCT). Biofilm composition was analysed with respect to total organic carbon, total cellular mass and extracellular concentrations of proteins, polysaccharides, and eDNA. 2D-confocal Raman mapping was used to characterise the functional group composition and micro-scale distribution of the biofilms EPS. Our study reveals that the composition of the EPS matrix can determine the meso-scale physical structure of membrane biofilms and in turn its hydraulic resistance. Biofilms grown under P limiting conditions were characterised by dense and homogeneous physical structures with high concentrations of polysaccharides and eDNA. Biofilm grown under nutrient enriched or N limiting conditions were characterised by heterogeneous physical structures with lower concentrations of polysaccharides and eDNA. For P limiting biofilms, 2D-confocal Raman microscopy revealed a homogeneous spatial distribution of anionic functional groups in homogeneous biofilm structures with higher polysaccharide and eDNA concentrations. This study links EPS composition, physical structure and hydraulic resistance of membrane biofilms, with practical relevance for the hydraulic performances of GDM ultrafiltration.

Desmond, P. (2018). Linking hydraulic resistance to the physical structure of membrane biofilms (Doctoral dissertation). doi:10.3929/ethz-b-000296862, Institutional Repository

Gravity driven membrane (GDM) ultrafiltration is a continuous dead-end filtration process for potable and non-potable water production. GDM operates on the principle of tolerating biofilm development on the membranes surface for the benefit of minimum membrane maintenance, stable flux production, and improved permeate quality. The biological activity afforded by the tolerated biofilm allows degradation of foulants that would otherwise accumulate on the surface of the membrane, decreasing permeate flux. However, membrane biofilms are not without problems. The presence of a biofilm increases the hydraulic resistance, which exceeds the intrinsic resistance of the membrane, leading to low yet stable permeate flux. The purpose of the presented thesis is to evaluate what structural feature of the biofilm can exert a resistance to hydraulic passage and how hydraulic resistance is influenced by the biofilms mechanical response to changes in process operation (e.g., transmembrane pressure (TMP), cross-flow). Towards this goal, the approach taken to determine the link between hydraulic resistance and the biofilms structural and mechanical characteristics shall examine: (a) how different biofilm physical structures affect hydraulic resistance; (b) how compression affect physical structure and related hydraulic resistance; (c) how hydraulic resistance changes over the biofilms depth. A key advancement of the current study is evaluating the link between biofilm physical structure and resulting hydraulic resistance using in-situ and non-invasive methods for chemical, structural and mechanical characterization, using 2D confocal Raman microscopy and optical coherence tomography, respectively.

Results of the presented thesis indicate that the formation of GDM biofilms is influenced by the nutrient availability (carbon, nitrogen, and phosphorus), which determined composition and micro-scale spatial distribution of extracellular polymeric substances (EPS). High concentrations of anionic polymers, homogeneously distributed in space, led to the formation of thin dense homogenous physical structures which had a higher hydraulic resistance. Low concentration of anionic polymers, heterogeneously distributed in space, led to the formation of thick heterogeneous physical structures with a low hydraulic resistance. Taken together, it is demonstrated that thicker heterogeneous structures imposed less hydraulic resistance than thin dense homogeneous structure, indicating density rather than thickness is the structural determinant of a biofilms hydraulic resistance.

The hydraulic resistance of membrane biofilms is also linked to their structural response to perpendicular and parallel flow. With increasing perpendicular flow, heterogeneous biofilms became irreversibly compressed, while homogeneous biofilms were reversibly compressed. Irreversible compression results from the reduction of the biofilm roughness and porosity and led to an irreversible increase in hydraulic resistance. With increasing hydraulic shear stress (flow parallel to the membrane), we demonstrated stratification in the physical structure, cohesion and hydraulic resistance of GDM biofilms. Detachment of a thick surface layer roughness had limited impact on hydraulic resistance due to retention of a cohesive base layer with a high hydraulic resistance.

The presented thesis provides a fundamental understanding of how hydraulic resistance is linked to a biofilms composition, physical structure and mechanical strength. Our evaluation of biofilm physical structure and hydraulic resistance in GDM systems has demonstrated that heterogeneous physical structures exert limited hydraulic resistance and have a low mechanical strength. Greater hydraulic resistance is exerted by thin dense base layer at the surface of the membrane. We suggest GDM membrane operators (a) maintain constant transmembrane pressure to avoided compaction of heterogeneous structure, (b) avoid hydraulic shear due to limited effect on resistance due to retention of thin and dense cohesive base layer and (c) focus on efforts to decrease the hydraulic resistance by increasing structural heterogeneity "in-place" by way of predation and/or nutrient enrichment.

Desmond, P., Morgenroth, E., & Derlon, N. (2018). Physical structure determines compression of membrane biofilms during Gravity Driven Membrane (GDM) ultrafiltration. Water Research, 143, 539-549. doi:10.1016/j.watres.2018.07.008, Institutional Repository

Increasing transmembrane pressure (TMP) can compress and increase the hydraulic resistance of membrane biofilms. The purpose of the present study is to evaluate how compression of membrane biofilms occurs and how structural rearrangement can affect hydraulic resistance. Biofilms with heterogeneous and homogeneous physical structures were grown in membrane fouling simulators (MFS) in dead-end mode for 20 days with either (i) a nutrient enriched condition with a nutrient ratio of 100:30:10 (C: N: P), (ii) a phosphorus limitation (C: N: P ratio: 100:30:0), or (iii) river water (C: N: P ratio: ca. 100:10:1). The structural and hydraulic response of membrane biofilms to (a) changes in transmembrane pressures (0.06-0.1-0.5-0.1-0.06 bar) and (b) changes in permeate flux (10-15-20-15-10 L/m²/h) were investigated. Optical coherence tomography (OCT) was used to monitor biofilm structural response, and OCT images were processed to quantify changes in the mean biofilm thickness and relative roughness. Nutrient enriched and river water biofilms had heterogeneous physical structures with greater surface roughness (Ra' > 0.2) than homogeneous P limiting biofilms (Ra' < 0.2). Compression of biofilms with rough heterogeneous structures (Ra' > 0.2) was irreversible, indicated by irreversible decrease in surface roughness, partial relaxation in mean biofilm thickness and irreversible increase in hydraulic resistance. Compression of homogeneous biofilm (Ra' < 0.2) was on the other hand reversible, indicated by full relaxation of the biofilms structure and restoration of initial hydraulic resistance. Hydraulic response (i.e., change in the specific biofilm resistance) did not correspond with the change in physical structure of heterogeneous biofilms. The presented study provides a fundamental understanding of how biofilm physical structure can affect the biofilm's response to a change in TMP, with practical relevance for the operation of GDM filtration systems.

Desmond, P., Böni, L., Fischer, P., Morgenroth, E., & Derlon, N. (2018). Stratification in the physical structure and cohesion of membrane biofilms – implications for hydraulic resistance. Journal of Membrane Science, 564, 897-904. doi:10.1016/j.memsci.2018.07.088, Institutional Repository

Falås, P., Jewell, K. S., Hermes, N., Wick, A., Ternes, T. A., Joss, A., & Nielsen, J. L. (2018). Transformation, CO₂ formation and uptake of four organic micropollutants by carrier-attached microorganisms. Water Research, 141, 405-416. doi:10.1016/j.watres.2018.03.040, Institutional Repository

Horisberger, M., Casazza, R., Grelot, J., & Joss, A. (2018). Élimination des micropolluants. Essais pilotes: traitement par charbon actif en grain en lit fluidisé à la step de Penthaz. Aqua & Gas, 98(10), 44-50. , Institutional Repository

Jafari, M., Desmond, P., van Loosdrecht, M. C. M., Derlon, N., Morgenroth, E., & Picioreanu, C. (2018). Effect of biofilm structural deformation on hydraulic resistance during ultrafiltration: A numerical and experimental study. Water Research, 145, 375-387. doi:10.1016/j.watres.2018.08.036, Institutional Repository

Biofilm formation in membrane systems negatively impacts the filtration system performances. This study evaluated how biofilm compression driven by permeate flow increases the hydraulic resistance and leads to reduction in permeate flux. We analysed the effect of biofilm compression on hydraulic resistance and permeate flux through computational models supported by experimental data. Biofilms with homogeneous surface structure were subjected to step-wise changes in flux and transmembrane pressure during compression and relaxation tests. Biofilm thickness under applied forces was measured non-invasively in-situ using optical coherence tomography (OCT). A numerical model of poroelasticity, which couples water flow through the biofilm with biofilm mechanics, was developed to correlate the structural deformation with biofilm hydraulics (permeability and resistance). The computational model enabled extracting mechanical and hydrological parameters corresponding to the experimental data. Homogeneous biofilms under elevated compression forces experienced a significant reduction in thickness while only a slight increase in resistance was observed. This shows that hydraulic resistance of homogeneous biofilms was affected more by permeability decrease due to pore closure than by a decrease in thickness. Both viscoelastic and elastoplastic models could describe well the permanent biofilm deformation. However, for biofilms under study, a simpler elastic model could also be used due to the small irreversible deformations. The elastic moduli fitting the measured data were in agreement with other reported values for biofilm under compression. Biofilm stiffening under larger flow-driven compression forces was observed and described numerically by correlating inversely the elastic modulus with biofilm porosity. The importance of this newly developed method lies in estimation of accurate biofilm mechanical parameters to be used in numerical models for both membrane filtration system and biofouling cleaning strategies. Such model can ultimately be used to identify optimal operating conditions for membrane system subjected to biofouling.

Kassotaki, E., Pijuan, M., Joss, A., Borrego, C. M., Rodriguez-Roda, I., & Buttiglieri, G. (2018). Unraveling the potential of a combined nitritation-anammox biomass towards the biodegradation of pharmaceutically active compounds. Science of the Total Environment, 624, 722-731. doi:10.1016/j.scitotenv.2017.12.116, Institutional Repository

In the past few years, anaerobic ammonium oxidation-based processes have attracted a lot of attention for their implementation at the mainstream line of wastewater treatment plants, due to the possibility of leading to energy autarky if combined with anaerobic digestion. However, little is known about the potential degradation of micropollutants by the microbial groups responsible of these processes and the few results available are inconclusive. This study aimed to assess the degradation capability of biomass withdrawn from a combined nitritation/anaerobic ammonium oxidation (combined N/A) pilot plant towards five pharmaceutically active compounds (ibuprofen, sulfamethoxazole, metoprolol, venlafaxine and carbamazepine). Batch experiments were performed under different conditions by selectively activating or inhibiting different microbial groups: i) regular combined N/A operation, ii) aerobic (optimal for nitrifying bacteria), iii) aerobic with allylthiourea (an inhibitor of ammonia monooxygenase, enzyme of ammonia oxidizing bacteria), iv) anoxic (optimal for anaerobic ammonium oxidizing bacteria), v) aerobic with acetate (optimal for heterotrophic bacteria) and vi) anoxic with acetate (optimal for heterotrophic denitrifying bacteria). Ibuprofen was the most biodegradable compound being significantly degraded (49–100%) under any condition except heterotrophic denitrification. Sulfamethoxazole, exhibited the highest removal (70%) under optimal conditions for nitrifying bacteria but in the rest of the experiments anoxic conditions were found to be slightly more favorable (up to 58%). For metoprolol the highest performance was obtained under anoxic conditions favoring anammox bacteria (62%). Finally, carbamazepine and venlafaxine were hardly removed (≤ 10% in the majority of cases). Taken together, these results suggest the specificity of different microbial groups that in combination with alternating operational parameters can lead to enhanced removal of some micropollutants.

Rittmann, B. E., Boltz, J. P., Brockmann, D., Daigger, G. T., Morgenroth, E., Helleshøj Sørensen, K., … Vanrolleghem, P. A. (2018). A framework for good biofilm reactor modeling practice (GBRMP). Water Science and Technology, 77(5), 1149-1164. doi:10.2166/wst.2018.021, Institutional Repository

Ward, B. J., Sam, S., Andriessen, N., Morgenroth, E., & Strande, L. (2018). Research priorities and progress in faecal sludge dewatering. Sandec News, 19, 10-11. , Institutional Repository

Wielinski, J., Müller, C., Voegelin, A., Morgenroth, E., & Kaegi, R. (2018). Combustion of sewage sludge: kinetics and speciation of the combustible. Energy and Fuels, 32(10), 10656-10667. doi:10.1021/acs.energyfuels.8b02106, Institutional Repository

Ziemba, C., Larivé, O., Reynaert, E., & Morgenroth, E. (2018). Chemical composition, nutrient-balancing and biological treatment of hand washing greywater. Water Research, 144, 752-762. doi:10.1016/j.watres.2018.07.005, Institutional Repository

Bitterwolf, S., Böhler, M., Siegrist, H., & Joss, A. (2017). Elimination von Spurenstoffen durch granulierte Aktivkohle (GAK) Filtration: Grosstechnische Untersuchungen auf der ARA Furt-Bülach. Zwischenbericht. Dübendorf: Eawag. , Institutional Repository

Boltz, J. P., Johnson, B. R., Takács, I., Daigger, G. T., Morgenroth, E., Brockmann, D., … Derlon, N. (2017). Biofilm carrier migration model describes reactor performance. Water Science and Technology, 75(12), 2818-2828. doi:10.2166/wst.2017.160, Institutional Repository

Boltz, J. P., Smets, B. F., Rittmann, B. E., Van Loosdrecht, M. C. M., Morgenroth, E., & Daigger, G. T. (2017). From biofilm ecology to reactors: a focused review. Water Science and Technology, 75(8), 1753-1760. doi:10.2166/wst.2017.061, Institutional Repository

Biofilms are complex biostructures that appear on all surfaces that are regularly in contact with water. They are structurally complex, dynamic systems with attributes of primordial multicellular organisms and multifaceted ecosystems. The presence of biofilms may have a negative impact on the performance of various systems, but they can also be used beneficially for the treatment of water (defined herein as potable water, municipal and industrial wastewater, fresh/brackish/salt water bodies, groundwater) as well as in water stream-based biological resource recovery systems. This review addresses the following three topics: (1) biofilm ecology, (2) biofilm reactor technology and design, and (3) biofilm modeling. In so doing, it addresses the processes occurring in the biofilm, and how these affect and are affected by the broader biofilm system. The symphonic application of a suite of biological methods has led to significant advances in the understanding of biofilm ecology. New metabolic pathways, such as anaerobic ammonium oxidation (anammox) or complete ammonium oxidation (comammox) were first observed in biofilm reactors. The functions, properties, and constituents of the biofilm extracellular polymeric substance matrix are somewhat known, but their exact composition and role in the microbial conversion kinetics and biochemical transformations are still to be resolved. Biofilm grown microorganisms may contribute to increased metabolism of micro-pollutants. Several types of biofilm reactors have been used for water treatment, with current focus on moving bed biofilm reactors, integrated fixed-film activated sludge, membrane-supported biofilm reactors, and granular sludge processes. The control and/or beneficial use of biofilms in membrane processes is advancing. Biofilm models have become essential tools for fundamental biofilm research and biofilm reactor engineering and design. At the same time, the divergence between biofilm modeling and biofilm reactor modeling approaches is recognized.

Carr, G., Blanch, A. R., Blaschke, A. P., Brouwer, R., Bucher, C., Farnleitner, A. H., … Blöschl, G. (2017). Emerging outcomes from a cross-disciplinary doctoral programme on water resource systems. Water Policy, 19(3), 463-478. doi:10.2166/wp.2017.054, Institutional Repository

Carrel, M., Beltran, M. A., Morales, V. L., Derlon, N., Morgenroth, E., Kaufmann, R., & Holzner, M. (2017). Biofilm imaging in porous media by laboratory X-ray tomography: combining a non-destructive contrast agent with propagation-based phase-contrast imaging tools. PLoS One, 12(7), e0180374 (18 pp.). doi:10.1371/journal.pone.0180374, Institutional Repository

X-ray tomography is a powerful tool giving access to the morphology of biofilms, in 3D porous media, at the mesoscale. Due to the high water content of biofilms, the attenuation coefficient of biofilms and water are very close, hindering the distinction between biofilms and water without the use of contrast agents. Until now, the use of contrast agents such as barium sulfate, silver-coated micro-particles or 1-chloronaphtalene added to the liquid phase allowed imaging the biofilm 3D morphology. However, these contrast agents are not passive and potentially interact with the biofilm when injected into the sample. Here, we use a natural inorganic compound, namely iron sulfate, as a contrast agent progressively bounded in dilute or colloidal form into the EPS matrix during biofilm growth. By combining a very long source-to-detector distance on a X-ray laboratory source with a Lorentzian filter implemented prior to tomographic reconstruction, we substantially increase the contrast between the biofilm and the surrounding liquid, which allows revealing the 3D biofilm morphology. A comparison of this new method with the method proposed by Davit et al (Davit et al., 2011), which uses barium sulfate as a contrast agent to mark the liquid phase was performed. Quantitative evaluations between the methods revealed substantial differences for the volumetric fractions obtained from both methods. Namely, contrast agent—biofilm interactions (e.g. biofilm detachment) occurring during barium sulfate injection caused a reduction of the biofilm volumetric fraction of more than 50% and displacement of biofilm patches elsewhere in the column. Two key advantages of the newly proposed method are that passive addition of iron sulfate maintains the integrity of the biofilm prior to imaging, and that the biofilm itself is marked by the contrast agent, rather than the liquid phase as in other available methods. The iron sulfate method presented can be applied to understand biofilm development and bioclogging mechanisms in porous materials and the obtained biofilm morphology could be an ideal basis for 3D numerical calculations of hydrodynamic conditions to investigate biofilm-flow coupling.

Derlon, N., Thürlimann, C., Dürrenmatt, D., & Villez, K. (2017). Batch settling curve registration via image data modeling. Water Research, 114, 327-337. doi:10.1016/j.watres.2017.01.049, Institutional Repository

Fumasoli, A., Bürgmann, H., Weissbrodt, D. G., Wells, G. F., Beck, K., Mohn, J., … Udert, K. M. (2017). Growth of Nitrosococcus-related ammonia oxidizing bacteria coincides with extremely low pH values in wastewater with high ammonia content. Environmental Science and Technology, 51(12), 6857-6866. doi:10.1021/acs.est.7b00392, Institutional Repository

McCall, A. K., Palmitessa, R., Blumensaat, F., Morgenroth, E., & Ort, C. (2017). Modeling in-sewer transformations at catchment scale – implications on drug consumption estimates in wastewater-based epidemiology. Water Research, 122, 655-668. doi:10.1016/j.watres.2017.05.034, Institutional Repository

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

Nguyen, M. T., Allemann, L., Ziemba, C., Larivé, O., Morgenroth, E., & Julian, T. R. (2017). Controlling bacterial pathogens in water for reuse: treatment technologies for water recirculation in the Blue Diversion Autarky Toilet. Frontiers in Environmental Science, 5, 90 (13 pp.). doi:10.3389/fenvs.2017.00090, Institutional Repository

The Blue Diversion AUTARKY Toilet is a urine-diverting toilet with on-site treatment. The toilet is being developed to provide a safe and affordable sanitation technology for people who lack access to sewer-based sanitation. Water used for personal hygiene, hand washing, and flushing to rinse urine- and feces-collection bowls is treated, stored, and recycled for reuse to reduce reliance on external water supplies. The system provides an opportunity to investigate hygiene of water for reuse following treatment. Treatment in the toilet includes a Biologically Activated Membrane Bioreactor (BAMBi) followed by a secondary treatment technology. To identify effective secondary treatment, three options, including granular activated carbon (GAC) only, GAC+chlorine (sodium hypochlorite), and GAC+electrolysis are considered based on the bacterial inactivation and growth inhibition efficiency. Four different hygiene-relevant bacteria are tested: Escherichia coli, Enterococcus faecalis, Pseudomonas aeruginosa, and Salmonella typhimurium. Our evaluation demonstrates that—despite treatment of water with the BAMBi—E. coli, P. aeruginosa, and S. typhimurium have the potential to grow during storage in the absence of microbial competition. Including the indigenous microbial community influences bacterial growth in different ways: E. coli growth decreases but P. aeruginosa growth increases relative to no competition. The addition of the secondary treatment options considerably improves water quality. A column of GAC after the BAMBi reduces E. coli growth potential by 2 log₁₀, likely due to the reduction of carbon sources. Additional treatments including chlorination and electrolysis provide further safety margins, with more than 5 log₁₀ inactivation of E. coli. However, reactivation and/or regrowth of E. coli and P. aeruginosa occurs under in the absence of residual disinfectant. Treatment including the BAMBi, GAC, and electrolysis appear to be promising technologies to control bacterial growth during storage in water intended for reuse.

Schmitt, R. J. P., Morgenroth, E., & Larsen, T. A. (2017). Robust planning of sanitation services in urban informal settlements: an analytical framework. Water Research, 110, 297-312. doi:10.1016/j.watres.2016.12.007, Institutional Repository

Stamm, C., Burdon, F., Fischer, S., Kienle, C., Munz, N., Tlili, A., … Eggen, R. (2017). Einfluss von Mikroverunreinigungen. Aqua & Gas, 97(6), 90-95. , Institutional Repository

Tobias, R., O'Keefe, M., Künzle, R., Gebauer, H., Gründl, H., Morgenroth, E., … Larsen, T. A. (2017). Early testing of new sanitation technology for urban slums: the case of the Blue Diversion Toilet. Science of the Total Environment, 576, 264-272. doi:10.1016/j.scitotenv.2016.10.057, Institutional Repository

Völker, J., Vogt, T., Castronovo, S., Wick, A., Ternes, T. A., Joss, A., … Wagner, M. (2017). Extended anaerobic conditions in the biological wastewater treatment: higher reduction of toxicity compared to target organic micropollutants. Water Research, 116, 220-230. doi:10.1016/j.watres.2017.03.030, Institutional Repository

Extended anaerobic conditions during biological wastewater treatment may enhance the biodegradation of micropollutants. To explore this, we combined iron-reducing or substrate-limited anaerobic conditions and aerobic pilot-scale reactors directly at a wastewater treatment plant. To investigate the detoxification by these processes, we applied two in vitro bioassays for baseline toxicity (Microtox) and reactive toxicity (AREc32) as well as in vivo bioassays with aquatic model species in two laboratory experiments (Desmodesmus subspicatus, Daphnia magna) and two on-site, flow-through experiments (Potamopyrgus antipodarum, Lumbriculus variegatus). Moreover, we analyzed 31 commonly occurring micropollutants and 10 metabolites.
The baseline toxicity of raw wastewater was effectively removed in full-scale and reactor scale activated sludge treatment (>85%), while the oxidative stress response was only partially removed (>61%). A combination of an anaerobic pre-treatment under iron reducing conditions and an aerobic nitrification significantly further reduced the residual in vitro toxicities by 46–60% and outperformed the second combination consisting of an aerobic pre-treatment and an anaerobic post-treatment under substrate-limiting conditions (27–43%). Exposure to effluents of the activated sludge treatment did not induce adverse in vivo effects in aquatic invertebrates. Accordingly, no further improvement in water quality could be observed. Compared to that, the removal of persistent micropollutants was increased. However, this observation was restricted to a limited number of compounds and the removal of the sum concentration of all target micropollutants was relative low (14–17%).
In conclusion, combinations of strictly anaerobic and aerobic processes significantly enhanced the removal of specific and non-specific in vitro toxicities. Thus, an optimization of biological wastewater treatment can lead to a substantially improved detoxification. These otherwise hidden capacities of a treatment technology can only be uncovered by a complementary biological analysis.

Weissbrodt, D. G., Holliger, C., & Morgenroth, E. (2017). Modeling hydraulic transport and anaerobic uptake by PAOs and GAOs during wastewater feeding in EBPR granular sludge reactors. Biotechnology and Bioengineering, 114(8), 1688-1702. doi:10.1002/bit.26295, Institutional Repository

Wells, G. F., Shi, Y., Laureni, M., Rosenthal, A., Szivák, I., Weissbrodt, D. G., … Morgenroth, E. (2017). Comparing the resistance, resilience, and stability of replicate moving bed biofilm and suspended growth combined nitritation–anammox reactors. Environmental Science and Technology, 51(9), 5108-5117. doi:10.1021/acs.est.6b05878, Institutional Repository

Combined partial nitritation–anammox (PN/A) systems are increasingly being employed for sustainable removal of nitrogen from wastewater, but process instabilities present ongoing challenges for practitioners. The goal of this study was to elucidate differences in process stability between PN/A process variations employing two distinct aggregate types: biofilm [in moving bed biofilm reactors (MBBRs)] and suspended growth biomass. Triplicate reactors for each process variation were studied under baseline conditions and in response to a series of transient perturbations. MBBRs displayed elevated NH₄⁺ removal rates relative to those of suspended growth counterparts over six months of unperturbed baseline operation but also exhibited significantly greater variability in performance. Transient perturbations led to strikingly divergent yet reproducible behavior in biofilm versus suspended growth systems. A temperature perturbation prompted a sharp reduction in NH₄⁺ removal rates with no accumulation of NO₂^– and rapid recovery in MBBRs, compared to a similar reduction in NH₄⁺ removal rates but a high level of accumulation of NO₂^– in suspended growth reactors. Pulse additions of a nitrification inhibitor (allylthiourea) prompted only moderate declines in performance in suspended growth reactors compared to sharp decreases in NH₄⁺ removal rates in MBBRs. Quantitative fluorescence in situ hybridization demonstrated a significant enrichment of anammox in MBBRs compared to suspended growth reactors, and conversely a proportionally higher AOB abundance in suspended growth reactors. Overall, MBBRs displayed significantly increased susceptibility to transient perturbations employed in this study compared to that of suspended growth counterparts (stability parameter), including significantly longer recovery times (resilience). No significant difference in the maximal impact of perturbations (resistance) was apparent. Taken together, our results suggest that aggregate architecture (biofilm vs suspended growth) in PN/A processes exerts an unexpectedly strong influence on process stability.

Zöllig, H., Remmele, A., Morgenroth, E., & Udert, K. M. (2017). Removal rates and energy demand of the electrochemical oxidation of ammonia and organic substances in real stored urine. Environmental Science: Water Research and Technology, 3(3), 480-491. doi:10.1039/c7ew00014f, Institutional Repository

The separate collection and treatment of urine allows for an environmentally friendly and cost-efficient management of the nutrients contained in urine. The primary goal should be to recover all these nutrients. However, in some cases it will be economically or ecologically more sensitive to recover only the phosphorus, while nitrogen is removed together with organic substances (measured as chemical oxygen demand, COD) and pathogens. In this study, we investigated the use of galvanostatic electrolysis for the removal of nitrogen and COD from real stored urine. Non-active type boron-doped diamond (BDD) and active type thermally decomposed iridium oxide film (TDIROF) anodes were evaluated using batch experiments. On both anodes, ammonia was exclusively removed by indirect oxidation with active chlorine (AC: Cl₂, HClO, and ClO⁻). As a consequence, ammonia was not completely removed, if chlorine was consumed by competing processes. While COD was present, ammonia removal was faster on TDIROF (227 ± 16 gN m⁻² d⁻¹ at 20 mA cm⁻²) than on BDD (43 ± 20 gN m⁻² d⁻¹ at 20 mA cm⁻²). The reason for the slower ammonia removal on BDD was the enhanced reaction of AC with organic molecules. In fact, hydroxyl radicals broke organic molecules down to shorter chain molecules which reacted with most of the AC leaving only little AC for the oxidation of ammonia. This preferential oxidation of organics resulted in very high COD removal rates on BDD (above 420 gCOD m⁻² d⁻¹ at 20 mA cm⁻² for COD concentrations above 1000 mgCOD L⁻¹). A main drawback of electrolysis with both anodes was the high energy demand (BDD: 55 W h gCOD⁻¹ and 766 W h gN⁻¹ for 90% and 6% removal, respectively. TDIROF: 67 W h gCOD⁻¹ and 77 W h gN⁻¹ for 30% and 40% removal. All at 20 mA cm⁻²). It can be concluded that BDD and TDIROF anodes could be combined in series for a fast, complete, and more energy efficient electrochemical urine treatment: COD could be removed on BDD before the residual ammonia would be removed on TDIROF.

Bertram, K. (2016). Reverse osmosis of nitrified urine to concentrate the nutrients (Master thesis). 29 p. , Institutional Repository

Urine contributes a major part of the nitrogen, phosphorus and potassium in municipal wastewater. Since the concentrations are much lower than in commercial fertilizers, volume reduction can reduce costs for transport and storage. A combination of nitrification and distillation has been tested at Eawag and was found to produce a valuable fertilizer. The energy consumption of the process is high. Reverse osmosis is another option for volume reduction, which is expected to consume less energy. This thesis deals with the question, whether it is beneficial to use reverse osmosis as a preconcentration step before distillation.
Experiments were conducted in a lab-scale reverse osmosis system and the experimental observations were used to implement a model. The model was used to predict the concentration factor that can be reached with reverse osmosis and the ion loss that has to be expected.
The solution-diffusion model and the concentration polarization model with the equation of Schock and Miquel for the concentration polarization mass transfer coefficient were found to describe the experimental observations well and were used in the model. The parameters of the solution-diffusion model were determined experimentally.
In this study the model was not solved for each ion individually but only for the total ion concentration. This allowed a prediction of the overall concentration factor and ion loss but not for the individual ions.
It was found that a single-step reverse osmosis system can reach a concentration factor of 1.9 while losing about 5 % of the ions. For higher concentration factors, higher ion losses occur. Multi-stage systems have higher ion recovery and require less membrane area than single-stage systems. However, the recovery was found to improve only slightly with two- and three-stage systems. Two-pass systems lead to very high ion recoveries but require high membrane areas and consume more energy.
It was estimated that the energy consumption of the distillation process can be reduced to about 30 % when using a two-pass reverse osmosis system up to a concentration factor of about 4.8. However, about 4 % ion loss has to be expected in the reverse osmosis system.
In this study, the observations from the experiments were extrapolated to higher concentration factors and higher pressures. For the model assumptions and simplifications were made. Therefore, further research should be conducted to verify the model predictions from this study.
For the optimization of the process chain, all costs and benefits should be considered. A value would have to be assigned to the fertilizer produced and also to the ions that are lost. For this, it is important to predict the ion loss for each ion individually.

Burdon, F. J., Reyes, M., Alder, A. C., Joss, A., Ort, C., Räsänen, K., … Stamm, C. (2016). Environmental context and magnitude of disturbance influence trait-mediated community responses to wastewater in streams. Ecology and Evolution, 6(12), 3923-3939. doi:10.1002/ece3.2165, Institutional Repository

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

Cunningham, M. (2016). Particulate substrate (Xs) retention mechanisms during feeding of an aerobic granular sludge (AGS) system (Master thesis). 35 p. , Institutional Repository

Aerobic granular sludge (AGS) has been proposed as a lower cost alternative to activated sludge in municipal wastewater treatment. AGS has a settling velocity up to twenty times greater than activated sludge (Rocktaschel, 2013). Granules have multiple redox zones which potentially allows for carbon, nitrogen, and phosphorous removal to occur in a single reactor (Giesen et al., 2013). These benefits reduce AGS reactor tank volume, equipment and aeration requirements—resulting in cost savings. However, growing AGS with wastewater and other feed waters with high particulate substrate (Xs) results in undesirable fluffy less dense granules and floc growth (de Kreuk et al., 2010).
A proposed solution is maximizing Xs attachment, hydrolysis and consumption during the anaerobic plug flow feeding phase of a sequencing batch reactor (SBR) cycle (de Kreuk et al., 2010). This thesis aims to better understand how biomass composition (ratio of granules to flocs), Xs size, and feeding velocity influence Xs retention. The secondary objective is to compare Xs retention by flocs and granules under fully mixed conditions.
A column test was developed to compare cellulose and wastewater Xs attachment to granules, flocs and granular sludge under plug flow conditions. A feed velocity of 1.4 m/h resulted in greater Xs retention compared to 3 and 5 m/h by all types of biomass; the outlier scenario is wastewater fed at 3 m/h, which could be attributed to Xs wastewater concentration in those tests. Granules performed better than flocs, which was surprising given that in granular media filtration a smaller media diameter leads to better particle retention (Yao et al., 1971; Darby et al., 1990). Abrupt changes to the biomass bed structure through channel formation or fractioning into multiple segments is proposed as an explanation. Furthermore, channeling and fractioning affected the distribution of retained Xs in the bed. The hydrolysis rate is a function of biomass and Xs concentration; therefore, the distribution of retained Xs in the bed is an important topic for potential future research (Morgenroth et al., 2002).
The jar tests also further emphasize the importance of maximizing Xs retention and consumption by granules during the anaerobic phase. Flocs performed better than granules at capturing Xs in fully mixed conditions. This indicates that flocs are likely to survive on Xs that is available in the supernatant, or was retained by the bed of granules but becomes available during the aerobic cycle because it was not fully consumed.
Overall, this thesis provides a first step into understanding the fate of Xs in AGS systems treating municipal wastewater. This topic involves physical (Xs retention) and biological (Xs hydrolysis and degradation) processes. Previous research on granular media filtration and contact stabilization is helpful for developing experimental procedures. Continued research into this topic can help maximize the economic benefits of AGS for wastewater treatment by improving granule morphology and limiting floc growth.

Derlon, N., Wagner, J., Ribeiro da Costa, R. H., & Morgenroth, E. (2016). Formation of aerobic granules for the treatment of real and low-strength municipal wastewater using a sequencing batch reactor operated at constant volume. Water Research, 105, 341-350. doi:10.1016/j.watres.2016.09.007, Institutional Repository

This study aimed at evaluating the formation of aerobic granular sludge (AGS) for the treatment of real and low-strength municipal wastewater using a column sequencing batch reactor (SBR) operated in fill-draw mode (constant volume). The focus was on understanding how the wastewater upflow velocity (V_WW) applied during the anaerobic feeding influenced the sludge properties and in turn the substrate conversion. Two different strategies were tested: (1) washing-out the flocs by imposing high wastewater upflow velocities (between 5.9 and 16 m h⁻¹) during the anaerobic feeding (Approach #1) and (2) selective utilization of organic carbon during the anaerobic feeding (1 m h⁻¹) combined with a selective sludge withdrawal (Approach #2). A column SBR of 190 L was operated in constant volume during 1500 days and fed with real and low-strength municipal wastewater. The formation of AGS with SVI₃₀ of around 80 mL g_TSS⁻¹ was observed either at very low (1 m h⁻¹) or at high V_WW (16 m h⁻¹). At 16 m h⁻¹ the AGS was mainly composed of large and round granules (d > 0.63 mm) with a fluffy surface, while at 1 m h⁻¹ the sludge was dominated by small granules (0.25 < d < 0.63 mm). The AGS contained a significant fraction of flocs during the whole operational period. A considerable and continuous washout of biomass occurred at V_WW higher than 5.9 m h⁻¹ (Approach #1) due to the lower settling velocity of the AGS fed with municipal wastewater. The low sludge retention observed at V_WW higher than 5.9 m h⁻¹ deteriorated the substrate conversion and in turn the effluent quality. High solid concentrations (and thus solid retention time) were maintained during Approach #2 (V_WW of 1 m h⁻¹), which resulted in an excellent effluent quality. The study demonstrated that the formation of AGS is possible during the treatment of real and low-strength municipal wastewater in a SBR operated at constant volume. Low wastewater upflow velocities should be applied during the anaerobic feeding phase in order to ensure enough biomass retention and efficient substrate removal.

Derlon, N., Grütter, A., Brandenberger, F., Sutter, A., Kuhlicke, U., Neu, T. R., & Morgenroth, E. (2016). The composition and compression of biofilms developed on ultrafiltration membranes determine hydraulic biofilm resistance. Water Research, 102, 63-72. doi:10.1016/j.watres.2016.06.019, Institutional Repository

Ding, A., Liang, H., Li, G., Derlon, N., Szivak, I., Morgenroth, E., & Pronk, W. (2016). Impact of aeration shear stress on permeate flux and fouling layer properties in a low pressure membrane bioreactor for the treatment of grey water. Journal of Membrane Science, 510, 382-390. doi:10.1016/j.memsci.2016.03.025, Institutional Repository

Falås, P., Wick, A., Castronovo, S., Habermacher, J., Ternes, T. A., & Joss, A. (2016). Tracing the limits of organic micropollutant removal in biological wastewater treatment. Water Research, 95, 240-249. doi:10.1016/j.watres.2016.03.009, Institutional Repository

Removal of organic micropollutants was investigated in 15 diverse biological reactors through short and long-term experiments. Short-term batch experiments were performed with activated sludge from three parallel sequencing batch reactors (25, 40, and 80 d solid retention time, SRT) fed with synthetic wastewater without micropollutants for one year. Despite the minimal micropollutant exposure, the synthetic wastewater sludges were able to degrade several micropollutants present in municipal wastewater. The degradation occurred immediately after spiking (1–5 μg/L), showed no strong or systematic correlation to the sludge age, and proceeded at rates comparable to those of municipal wastewater sludges. Thus, the results from the batch experiments indicate that degradation of organic micropollutants in biological wastewater treatment is quite insensitive to SRT increases from 25 to 80 days, and not necessarily induced by exposure to micropollutants. Long-term experiments with municipal wastewater were performed to assess the potential for extended biological micropollutant removal under different redox conditions and substrate concentrations (carbon and nitrogen). A total of 31 organic micropollutants were monitored through influent-effluent sampling of twelve municipal wastewater reactors. In accordance with the results from the sludges grown on synthetic wastewater, several compounds such as bezafibrate, atenolol and acyclovir were significantly removed in the activated sludge processes fed with municipal wastewater. Complementary removal of two compounds, diuron and diclofenac, was achieved in an oxic biofilm treatment. A few aerobically persistent micropollutants such as venlafaxine, diatrizoate and tramadol were removed under anaerobic conditions, but a large number of micropollutants persisted in all biological treatments. Collectively, these results indicate that certain improvements in biological micropollutant removal can be achieved by combining different aerobic and anaerobic treatments, but that these improvements are restricted to a limited number of compounds.

Fumasoli, A., Etter, B., Sterkele, B., Morgenroth, E., & Udert, K. M. (2016). Operating a pilot-scale nitrification/distillation plant for complete nutrient recovery from urine. Water Science and Technology, 73(1), 215-222. doi:10.2166/wst.2015.485, Institutional Repository

Gold, M., Dayer, P., Faye, M. C. A. S., Clair, G., Seck, A., Niang, S., … Strande, L. (2016). Locally produced natural conditioners for dewatering of faecal sludge. Environmental Technology, 37(21), 1-13. doi:10.1080/09593330.2016.1165293, Institutional Repository

Habermacher, J., Benetti, A. D., Derlon, N., & Morgenroth, E. (2016). Degradation of the unbiodegradable particulate fraction (X_U) from different activated sludges during batch digestion tests at ambient temperature. Water Research, 98, 206-214. doi:10.1016/j.watres.2016.04.005, Institutional Repository

One strategy for the management of excess sludge in small wastewater treatment plants (WWTPs) consists in minimizing the excess sludge production by operating the WWTP at very long solids retention times (SRTs > 30 days). A number of recent studies have suggested that sludge minimization at very long SRT results from the degradation of the unbiodegradable particulate fraction (X_U) (influent unbiodegradable compounds and endogenous decay products). But the biodegradability of the unbiodegradable particulate fraction has only been evaluated during batch digestion test performed at ambient temperature with sludge fed with synthetic wastewaters. It is not clear to what extent observations made for sludge fed with synthetic influents can be transposed to sludge fed with real influent. The current study thus focused on evaluating the biodegradability of the unbiodegradable particulate fraction for sludge fed with real wastewater. Batch digestion tests (400 days, ambient temperature) were conducted with three different sludges fed with either synthetic or real influents and exposed to aerobic or intermittent aeration conditions. Our results indicate that volatile suspended solids (VSS) decreased even after complete decay of the active biomass (i.e., after 30 days of aerobic batch digestion) indicating that the unbiodegradable particulate fraction is biodegradable. However, very low degradation rates of the unbiodegradable particulate fraction were monitored after day 30 of digestion (0.7-1.7·10^-3 d^-1). These values were in the lower range of previously published values for synthetic wastewaters (1-7.5·10^-3 d^-1). The low values determined in our study indicate that the rate could decrease over time or that sludge composition influences the degradability of the unbiodegradable particulate fraction. But our results also demonstrate that extracellular polymeric substances (EPS) have a minor impact on the biodegradability of the unbiodegradable particulate fraction. Overall bound EPS were indeed biodegradable under all conditions and thus did not accumulate in the unbiodegradable particulate fraction. Different bound EPS pools (e.g., cation bound EPS) were associated with specific degradation behaviors. Besides improved mechanistic understanding of sludge degradation processes, our results have implications for the development of decentralized wastewater treatment technologies with on-site reduction of excess sludge.

Jewell, K. S., Castronovo, S., Wick, A., Falås, P., Joss, A., & Ternes, T. A. (2016). New insights into the transformation of trimethoprim during biological wastewater treatment. Water Research, 88, 550-557. doi:10.1016/j.watres.2015.10.026, Institutional Repository

Jewell, K. S., Falås, P., Wick, A., Joss, A., & Ternes, T. A. (2016). Transformation of diclofenac in hybrid biofilm–activated sludge processes. Water Research, 105, 559-567. doi:10.1016/j.watres.2016.08.002, Institutional Repository

The biotransformation of diclofenac during wastewater treatment was investigated. Attached growth biomass from a carrier-filled compartment of a hybrid-MBBR at the wastewater treatment plant (WWTP) in Bad Ragaz, Switzerland was used to test the biotransformation. Laboratory-scale incubation experiments were performed with diclofenac and carriers and high-resolution LC–QTof-MS was implemented to monitor the biotransformation. Up to 20 diclofenac transformation products (TPs) were detected. Tentative structures were proposed for 16 of the TPs after characterization by MS² fragmentation and/or inferring the structure from the transformation pathway and the molecular formula given by the high resolution ionic mass. The remaining four TPs were unambiguously identified via analytical reference standards. The postulated reactions forming the TPs were: hydroxylation, decarboxylation, oxidation, amide formation, ring-opening and reductive dechlorination. Incubation experiments of individual TPs, those which were available as reference standards, provided a deeper look into the transformation pathways. It was found that the transformation consists of four main pathways but no pathway accounted for a clear majority of the transformation. A 10-day monitoring campaign of the full-scale plant confirmed an 88% removal of diclofenac (from approximately 1.6 μg/L in WWTP influent) and the formation of TPs as found in the laboratory was observed. One of the TPs, N-(2,6-dichlorophenyl)-2-indolinone detected at concentrations of around 0.25 μg/L in WWTP effluent, accounting for 16% of the influent diclofenac concentration. The biotransformation of carriers was compared to a second WWTP not utilising carriers. It was found that in contact with activated sludge, similar hydroxylation and decarboxylation reactions occurred but at much slower rates, whereas some reactions, e.g. reductive dechlorination, were not detected at all. Finally, incubation experiments were performed with attached growth biomass from a third WWTP with a similar process configuration to Bad Ragaz WWTP. A similarly effective removal of diclofenac was found with a similar presence of TPs.

Klein, T., Zihlmann, D., Derlon, N., Isaacson, C., Szivak, I., Weissbrodt, D. G., & Pronk, W. (2016). Biological control of biofilms on membranes by metazoans. Water Research, 88, 20-29. doi:10.1016/j.watres.2015.09.050, Institutional Repository

Laureni, M., Falås, P., Robin, O., Wick, A., Weissbrodt, D. G., Nielsen, J. L., … Joss, A. (2016). Mainstream partial nitritation and anammox: long-term process stability and effluent quality at low temperatures. Water Research, 101, 628-639. doi:10.1016/j.watres.2016.05.005, Institutional Repository

The implementation of autotrophic anaerobic ammonium oxidation processes for the removal of nitrogen from municipal wastewater (known as “mainstream anammox”) bears the potential to bring wastewater treatment plants close to energy autarky. The aim of the present work was to assess the long-term stability of partial nitritation/anammox (PN/A) processes operating at low temperatures and their reliability in meeting nitrogen concentrations in the range of typical discharge limits below 2 mg_NH₄-N·L⁻¹ and 10 mg_Ntot·L⁻¹. Two main 12-L sequencing batch reactors were operated in parallel for PN/A on aerobically pre-treated municipal wastewater (21 ± 5 mg_NH₄-N·L⁻¹ and residual 69 ± 19 mg_CODtot·L⁻¹) for more than one year, including over 5 months at 15 °C. The two systems consisted of a moving bed biofilm reactor (MBBR) and a hybrid MBBR (H-MBBR) with flocculent biomass. Operation at limiting oxygen concentrations (0.15–0.18 mg_O₂·L⁻¹) allowed stable suppression of the activity of nitrite-oxidizing bacteria at 15 °C with a production of nitrate over ammonium consumed as low as 16% in the MBBR. Promising nitrogen removal rates of 20–40 mg_N·L⁻¹·d⁻¹ were maintained at hydraulic retention times of 14 h. Stable ammonium and total nitrogen removal efficiencies over 90% and 70% respectively were achieved. Both reactors reached average concentrations of total nitrogen below 10 mg_N·L⁻¹ in their effluents, even down to 6 mg_N·L⁻¹ for the MBBR, with an ammonium concentration of 2 mg_N·L⁻¹ (set as operational threshold to stop aeration). Furthermore, the two PN/A systems performed almost identically with respect to the biological removal of organic micropollutants and, importantly, to a similar extent as conventional treatments. A sudden temperature drop to 11 °C resulted in significant suppression of anammox activity, although this was rapidly recovered after the temperature was increased back to 15 °C. Analyses of 16S rRNA gene-targeted amplicon sequencing revealed that the anammox guild of the bacterial communities of the two systems was composed of the genus “Candidatus Brocadia”. The potential of PN/A systems to compete with conventional treatments for biological nutrients removal both in terms of removal rates and overall effluent quality was proven.

McCall, A. K., Scheidegger, A., Madry, M. M., Steuer, A. E., Weissbrodt, D. G., Vanrolleghem, P. A., … Ort, C. (2016). Influence of different sewer biofilms on transformation rates of drugs. Environmental Science and Technology, 50(24), 13351-13360. doi:10.1021/acs.est.6b04200, Institutional Repository

Meili, N. (2016). Improvement of permeate quality after gravity-driven membrane filtration (Master thesis). 42 p. , Institutional Repository

Niadiodava, H. (2016). Mechanisms governing simultaneous nitrification-denitrification in aerobic granular sludge (Master thesis). 28 p. , Institutional Repository

Aerobic granular sludge (AGS) is a new technology for biological treatment of wastewater. Simultaneous removal of organic matter, nitrogen and phosphorus is possible in an AGS reactor due to the large physical size of granules and their heterogeneous structure. While sufficient removal efficiencies of C and P have been achieved, N removal from municipal wastewaters using AGS still remains a challenge.
To address this knowledge gap, a model was developed in SUMO software to assess the mechanisms driving simultaneous nitrification and denitrification (SND) in a granular sludge reactor. Nitrification and denitrification can be accomplished in a single reactor due to coexistence of aerobic and anoxic zone in granules. Therefore, the objective of this master’s thesis is to evaluate the influence of oxygen concentration and anoxic volume in the granules on SND performance. Another objective is to evaluate the contribution of phosphorous accumulating organisms (PAO) on SND as PAOs are mainly responsible for the denitrification in AGS.
The granular sequenced batch reactor (SBR) module in SUMO was used to simulate mass transport and conversion processes occurring in the reactor. A low-strength influent with particulate organic carbon, which is typical for the municipal wastewater, was used in the study. A total COD concentration was 420 g_COD.m^-3. The model included growth and decay of nitrifiers, ordinary heterotrophs and PAO. Three case studies were analyzed with low, intermediate and high granulation. The simulations were performed under different airflow resulting in different dissolved oxygen concentration in the bulk.
The highest SND of 96% was achieved for the simulation with intermediate granulation and oxygen concentration in the bulk reaching 1.2 g_O2.m^-3. Complete nitrification occurred in this simulation. The fraction of anoxic volume in the granule reached 100% and remained high during most of the aerobic period, which is significantly higher than the anoxic volume in cases with low or high granulation. In case with intermediate granulation, high PHA concentrations are found in anoxic layers of the granule. Therefore, there is a sufficient amount of organic carbon for denitrification by PAOs. In cases with low and high granulation, most of the PHA was concentrated in the aerobic layers and was not available for denitrification by PAOs.
To conclude, this study shows that aerobic granular sludge can be an effective technology for treatment of municipal wastewater, achieving high nitrification and SND efficiencies. However, special consideration shall be paid to oxygen concentration, anoxic volume in the granule and organic carbon availability in the anoxic zone.

Shen, Y., Huang, C., Monroy, G. L., Janjaroen, D., Derlon, N., Lin, J., … Nguyen, T. H. (2016). Response of simulated drinking water biofilm mechanical and structural properties to long-term disinfectant exposure. Environmental Science and Technology, 50(4), 1779-1787. doi:10.1021/acs.est.5b04653, Institutional Repository

Mechanical and structural properties of biofilms influence the accumulation and release of pathogens in drinking water distribution systems (DWDS). Thus, understanding how long-term residual disinfectants exposure affects biofilm mechanical and structural properties is a necessary aspect for pathogen risk assessment and control. In this study, elastic modulus and structure of groundwater biofilms was monitored by atomic force microscopy (AFM) and optical coherence tomography (OCT) during three months of exposure to monochloramine or free chlorine. After the first month of disinfectant exposure, the mean stiffness of monochloramine- or free-chlorine-treated biofilms was 4 to 9 times higher than those before treatment. Meanwhile, the biofilm thickness decreased from 120 ± 8 μm to 93 ± 6–107 ± 11 μm. The increased surface stiffness and decreased biofilm thickness within the first month of disinfectant exposure was presumably due to the consumption of biomass. However, by the second to third month during disinfectant exposure, the biofilm mean stiffness showed a 2- to 4-fold decrease, and the biofilm thickness increased to 110 ± 7–129 ± 8 μm, suggesting that the biofilms adapted to disinfectant exposure. After three months of the disinfectant exposure process, the disinfected biofilms showed 2–5 times higher mean stiffness (as determined by AFM) and 6–13-fold higher ratios of protein over polysaccharide, as determined by differential staining and confocal laser scanning microscopy (CLSM), than the nondisinfected groundwater biofilms. However, the disinfected biofilms and nondisinfected biofilms showed statistically similar thicknesses (t test, p > 0.05), suggesting that long-term disinfection may not significantly remove net biomass. This study showed how biofilm mechanical and structural properties vary in response to a complex DWDS environment, which will contribute to further research on the risk assessment and control of biofilm-associated-pathogens in DWDS.

Shi, Y., Wells, G., & Morgenroth, E. (2016). Microbial activity balance in size fractionated suspended growth biomass from full-scale sidestream combined nitritation-anammox reactors. Bioresource Technology, 218, 38-45. doi:10.1016/j.biortech.2016.06.041, Institutional Repository

Stamm, C., Räsänen, K., Burdon, F. J., Altermatt, F., Jokela, J., Joss, A., … Eggen, R. I. L. (2016). Unravelling the impacts of micropollutants in aquatic ecosystems: interdisciplinary studies at the interface of large-scale ecology. In A. J. Dumbrell, R. L. Kordas, & G. Woodward (Eds.), Advances in ecological research: Vol. 55. Large-scale ecology: model systems to global perspectives (pp. 183-223). doi:10.1016/bs.aecr.2016.07.002, Institutional Repository

Thalmann, B., Voegelin, A., Morgenroth, E., & Kaegi, R. (2016). Effect of humic acid on the kinetics of silver nanoparticle sulfidation. Environmental Science: Nano, 3(1), 203-212. doi:10.1039/c5en00209e, Institutional Repository

Völker, J., Castronovo, S., Wick, A., Ternes, T. A., Joss, A., Oehlmann, J., & Wagner, M. (2016). Advancing biological wastewater treatment: extended anaerobic conditions enhance the removal of endocrine and dioxin-like activities. Environmental Science and Technology, 50(19), 10606-10615. doi:10.1021/acs.est.5b05732, Institutional Repository

Wu, S., Bhattacharjee, A. S., Weissbrodt, D. G., Morgenroth, E., & Goel, R. (2016). Effect of short term external perturbations on bacterial ecology and activities in a partial nitritation and anammox reactor. Bioresource Technology, 219, 527-535. doi:10.1016/j.biortech.2016.07.118, Institutional Repository

Bogler, A. (2015). Effect of a feed spacer on biofouling in a forward osmosis membrane system (Master thesis). 35 p. , Institutional Repository

Fresh water sources are getting scarcer and innovative technologies are necessary to treat other water sources, for example wastewater. Forward Osmosis (FO) has been met with increasing interest over the past decades as it shows different advantages over pressure driven membrane processes. One advantage is a lower fouling propensity that gives FO high potential in treating feed waters with high fouling capacity. Literature on biofouling in FO is sparse. The objective of this thesis was therefore to investigate the e ect of feed spacers on biofouling in a FO system.
Pseudomonas aerigunosa was used as a model strain to biofoul a closed-loop custom-made flow system with a polyamide thin-film composite FO membrane. Synthetic wastewater mimicking secondary effluent was circulated as the feed solution, while 0.5M sodium chloride solution was used on the draw side to generate an initial flux of 20L/m²/h. Baselines were recorded over 24h to account for dilution, followed by the biofouling run lasting again 24h. After the biofouling membrane and feed spacer were analyzed for bacterial concentration via plate counts, for total organic carbon and protein and with confocal laser scanning microscopy for further characterization of the biofilm.
Results show that flow rate and spacer configuration on the draw side infuence the flux decline due to dilution, which varied from 9% to 24% at 500mL cumulative volume. This effect was not captured by the calculation of the water flux and was attributed to changes in the mass transfer coecient on the draw side, which was used as a fitting parameter. Those changes could be caused by the used spacer type and stagnant zones between spacer laments, but more experiments are necessary to investigate this further.
No flux decline due to biofouling was observed and the application of a feed spacer did not lead to significant differences. Flux decline during the baseline and biofouling without a feed spacer was 23±2% at a cumulative volume of 600mL. With a feed spacer flux decline was 26±4% during the baseline and 251% during biofouling. There was no difference between the biofilm grown in experiments with and without a feed spacer.
An equation was developed for the estimation of water flux influenced by bio lm growth. It represents the biofilm analogously to the membrane support layer relying on the concept of cake-enhanced concentration polarization. The equation predicted a flux decline of 5% due to biofouling. Biofilm growth was probably reduced by high shear forces and short experiment durations and its effect on flux might have been lessened by low feed solution concentrations. The equation did not represent the biofilm or the mechanism correctly and again more experiments are necessary to nd out what caused the biofilm to be without influence on the flux and how it can be represented correctly.

Briner, K. (2015). Calibration of a UV-Vis spectrophotometer for simultaneous estimation of nitrate and nitrite in nitrified urine (Master thesis). 26 p. , Institutional Repository

Chomiak, A., Traber, J., Morgenroth, E., & Derlon, N. (2015). Biofilm increases permeate quality by organic carbon degradation in low pressure ultrafiltration. Water Research, 85, 512-520. doi:10.1016/j.watres.2015.08.009, Institutional Repository

We investigated the influence of biofouling of ultrafiltration membranes on the removal of organic model foulants and ultimately on the quality of permeate. Gravity Driven Membrane ultrafiltration (GDM) membrane systems were operated with modified river water during five weeks without control of the biofilm formation. Three GDM systems were studied: two systems with biofilms exposed to (A) variable or (B) constant load of organic foulants, and (C) one system operated without biofilm and exposed to constant foulant loading. Biodegradable dextran or non-biodegradable polystyrene sulfonate model foulants were tested. Substrate biodegradability was confirmed by Size Exclusion Chromatography (SEC) and by degradation batch tests (D). The GDM systems (A) and (B) were fed with pre-filtered river water supplemented with dextran (Dex) of 1, 150 or 2000 kDa, or polystyrene sulfonate (PSS) of 1 or 80 kDa at concentrations of 2–3.5 mgC L⁻¹. In exp. (C) the feed water consisted of deionized water with 25 mgC L⁻¹ of either PSS 1, 80 kDa or Dex 2000 kDa.
The biofilm formation on UF membrane surfaces controlled the foulant permeation and thus the permeate quality. Biofilms exposed to continuous foulant loading (exp. B) degraded low molecular weight (LMW) biodegradable foulants (1 kDa Dex), which improved the permeate quality. For high molecular weight (HMW) substrates (150, 2000 kDa Dex), the improvement of the permeate quality was observed after 7 days of biofilm formation, and resulted from the foulant hydrolysis followed by degradation. For non-biodegradable foulants, an improvement of 20% of the retention was observed for the polystyrene (1, 80 kDa PSS) due to the presence of biofilms on membrane surfaces. For variable foulant loading (exp. A) the biofilms hydrolysed the large biodegradable foulants but did not degraded them fully, which resulted a deterioration of the permeate quality (except for the LMW dextran (1 kDa) that was fully degraded). Overall, the “biofilm + membrane” composite retained a larger amount of biodegradable foulant than the membrane alone, due to the activity of the biofilm. However, this resulted in an increased biofilm accumulation and reduced flux. In presence of the biofilm, the highest fluxes were observed for control (no foulant) and for small non-biodegradable foulants (PSS 1 kDa). Low fluxes were observed for the accumulating on membrane surface or degradable foulants (exp. B). But, the lowest fluxes were observed in absence of the biofilm (exp. C) due to physical accumulation of the foulants (PSS 80 kDa and Dextran 2000 kDa). Overall our study demonstrates that the presence of biofilms on membrane surfaces has some benefits: (i) biofilm helps to increase the permeate quality and (ii) biofilms protect the membrane from further fouling. Permeate flux stabilizes in the case of biofilm-membrane composite, while it continuously declines in the case of the membrane only.

Chomiak, A. (2015). Influence of inorganic and organic matter in gravity driven membrane ultrafilatration (Doctoral dissertation). doi:10.3929/ethz-a-010453952, Institutional Repository

Del Giudice, D. (2015). Improving output and input statistical error descriptions in urban hydrological modeling (Doctoral dissertation). doi:10.3929/ethz-a-010536371, Institutional Repository

Hydrological or drainage models can be valuable tools to support water management in urban environments. They can help to assess the characteristics of a catchment and to make predictions about its response (e.g. discharge). Unfortunately, parameters and results of these models are not perfect. These inaccuracies manifest themselves as model discrepancy, the so-called bias. Model bias represents the systematic deviation between model output and the real system response. There are two main causes of bias. First, there are errors in the input estimates, e.g. due to the insufficient coverage of pluviometers. Second, there are deficits in the model structure, e.g. due to the use of oversimplified empirical equations. Besides model bias, there are output measurement errors, e.g. due to imprecise flowmeters.
Until now, a large proportion of hydrological studies implicitly neglected input and structural errors. Neglecting these can lead to: i) misrepresented output measurement errors, ii) incorrect parameter estimates which compensate for model discrepancy, and iii) predictions which underestimate the uncertainty. Furthermore, these approaches do not provide guidance for finding the reasons for bias. Therefore, they cannot support its reduction. This inappropriate error consideration can finally lead to faulty risk assessment, flawed evaluation of decision alternatives, and, consequently, impaired urban water management. More advanced error assessment techniques are therefore called for.
The main goal of this thesis is to better represent input, structural, and output measurement errors. This can meliorate parameter estimation and prediction generation. The main thesis contributions are two. The first is a realistic description of the uncertainties in stormwater, wastewater, and sediment transport predictions. The second is a sound representation of errors in the rainfall inputs. Additionally, we discuss and compare different statistical methods used for hydrological inference. Finally, we also present a new tool to improve sewer flow monitoring. [...]

Eckstein, D. T. (2015). Einfluss von biologisch abbaubarem Kohlenstoff auf die Aktivität und die räumliche Verteilung Nitrit oxidierender Bakterien im einstufigen Nitritations/Anammox-Prozess (Master thesis). 69 p. , Institutional Repository

Egger, C. S. (2015). Sewer rehabilitation planning under uncertainty (Doctoral dissertation). doi:10.3929/ethz-a-010532893, Institutional Repository

Fumasoli, A., Morgenroth, E., & Udert, K. M. (2015). Modeling the low pH limit of Nitrosomonas eutropha in high-strength nitrogen wastewaters. Water Research, 83, 161-170. doi:10.1016/j.watres.2015.06.013, Institutional Repository

Fux, C., Kienle, C., Joss, A., Wittmer, A., & Frei, R. (2015). Ausbau der ARA Basel mit 4. Reinigungsstufe. Pilotstudie: Elimination Mikroverunreinigungen und ökotoxikologische Wirkungen. Aqua & Gas, 95(7/8), 10-17. , Institutional Repository

Habermacher, J., Benetti, A. D., Derlon, N., & Morgenroth, E. (2015). The effect of different aeration conditions in activated sludge – side-stream system on sludge production, sludge degradation rates, active biomass and extracellular polymeric substances. Water Research, 85, 46-56. doi:10.1016/j.watres.2015.08.002, Institutional Repository

Harris, E., Joss, A., Emmenegger, L., Kipf, M., Wolf, B., Mohn, J., & Wunderlin, P. (2015). Isotopic evidence for nitrous oxide production pathways in a partial nitritation-anammox reactor. Water Research, 83, 258-270. doi:10.1016/j.watres.2015.06.040, Institutional Repository

Haupt, C. (2015). Feasibility of granular activated carbon (GAC) filtration as an alternative for electrolysis in the post-treatment of the Blue Diversion Toilet (Master thesis). 82 p. , Institutional Repository

The Blue Diversion Toilet (BDT) was developed as a possible answer to the sanita-tion crisis in urban slums. It is a urine-diverting dry toilet with an integrated water cycle that provides water for handwashing, personal hygiene and flushing the urine bowl. The recovery of the water happens in a so called water wall, based on a biolog-ically activated membrane bioreactor (BAMBi) together with an electrolysis module as the post-treatment. In order to primarily minimize the costs and the energy de-mand of the toilet, granular activated carbon (GAC) filters were investigated as an alternative to the electrolysis. For this purpose, four water walls with different post-treatments were monitored and compared: a control without any treatment, one drained and one flooded GAC bed and an electrolysis module. This study focused on the produced water quality from a hygienic point of view as well as with regard to the aesthetic, namely the colour. In order to investigate the possibility of the presence of pathogens in the recycled water, faecal indicators (E. coli and total coliforms) were monitored. Moreover, surrogates for organic content and therefore, the potential for microbial growth were investigated by measuring the amount of total organic carbon (TOC) and assimilable organic carbon (AOC). Further, a spiking experiment with a viral indicator (MS2) was conducted in order to examine the retention of vi-ruses within the water wall. Finally, the absorbance of the water was measured in order to investigate the colour removal. It was found that with both applications, GAC and electrolysis, the absence of E. coli in the effluent in most of the times was guaranteed and thus the risk of bacterial pathogens could be most probably excluded. While drained GAC and flooded GAC yielded to a significant TOC removal, no sig-nificant TOC removal by the electrolysis was observed. Further, no significant AOC removal by the post-treatments could be measured; neither for the electrolysis nor for GAC. All median AOC concentrations in the effluents exceeded the proposed limits for a biological stability at least for drinking water. In order to draw reliable conclu-sions of the impact of the post-treatments on the removal of viruses, further research is needed. With regard to the aesthetic, both, electrolysis and GAC, yielded to a sig-nificant reduction of absorbance of the water and did not significantly differ in their ability to reduce the colour. From those results it can be concluded that at the current settings of the electrolysis, GAC constitutes a feasible alternative. Due to the fact that both, electrolysis and GAC alone, only partly achieved a satisfying water quality, the combination of both should be considered, since this could achieve a better water quality and save energy.

Hubaux, N., Wells, G., & Morgenroth, E. (2015). Impact of coexistence of flocs and biofilm on performance of combined nitritation-anammox granular sludge reactors. Water Research, 68, 127-139. doi:10.1016/j.watres.2014.09.036, Institutional Repository

Nitrogen (N) removal from high-strength wastewater can be accomplished in single-stage combined nitritation-anammox reactors with suspended growth biomass composed of floccular sludge, granular sludge, or of any mix of these 2 different sludge fractions. To date, the influence of floccular biomass on granular sludge reactor performance and stability has not been investigated experimentally or numerically. To address this knowledge gap, two 1D multi-species models were developed in Aquasim to assess the importance of small levels of flocs in putatively granular sludge combined nitritation-anammox reactors for different bulk oxygen concentrations and organics loads. The models included the growth and decay of aerobic ammonium-oxidizing organism (AOO), nitrite-oxidizing organisms (NOO), heterotrophic organisms (OHO), and anammox organisms (AMO) in exclusively granular sludge reactors, and in granular sludge reactors with small levels (∼5% of total biomass) of flocs. While maximum N removal efficiencies were similar for both model structures, floc addition led to a lower optimal dissolved oxygen concentration (DO) as well as a narrower maximum N removal peak, suggesting that small levels of floccular material may decrease process robustness to bulk oxygen changes. For some DO levels, this led to drastic efficiency drops. Furthermore, floc addition also led to substantial segregation in activity and microbial population distribution, with AOO, NOO and OHO concentrated in flocs and AMO concentrated in granules. Increased organic loading (COD:N = 4:3) improved maximum N removal efficiency in both model structures, but yielded substantially different predictions for optimal DO setpoint and process robustness to variations in DO. Taken together, our results indicate that even small levels of floccular biomass in biofilm reactors can have profound implications for reactor performance and optimization and for segregation of linked microbial processes, and suggest that the common practice of neglecting small levels of floccular material in biofilm models and in practice may lead to erroneous predictions.

Künzle, R., Pronk, W., Morgenroth, E., & Larsen, T. A. (2015). An energy-efficient membrane bioreactor for on-site treatment and recovery of wastewater. Journal of Water Sanitation and Hygiene for Development, 5(3), 448-455. doi:10.2166/washdev.2015.116, Institutional Repository

Larsen, T. A., Gebauer, H., Gründl, H., Künzle, R., Lüthi, C., Messmer, U., … Ranner, B. (2015). Blue Diversion: a new approach to sanitation in informal settlements. Journal of Water Sanitation and Hygiene for Development, 5(1), 64-71. doi:10.2166/washdev.2014.115, Institutional Repository

Laureni, M., Weissbrodt, D. G., Szivák, I., Robin, O., Nielsen, J. L., Morgenroth, E., & Joss, A. (2015). Activity and growth of anammox biomass on aerobically pre-treated municipal wastewater. Water Research, 80, 325-336. doi:10.1016/j.watres.2015.04.026, Institutional Repository

Direct treatment of municipal wastewater (MWW) based on anaerobic ammonium oxidizing (anammox) bacteria holds promise to turn the energy balance of wastewater treatment neutral or even positive. Currently, anammox processes are successfully implemented at full scale for the treatment of high-strength wastewaters, whereas the possibility of their mainstream application still needs to be confirmed. In this study, the growth of anammox organisms on aerobically pre-treated municipal wastewater (MWW_pre-treated), amended with nitrite, was proven in three parallel reactors. The reactors were operated at total N concentrations in the range 5–20 mg_N∙L⁻¹, as expected for MWW. Anammox activities up to 465 mg_N∙L⁻¹∙d⁻¹ were reached at 29 °C, with minimum doubling times of 18 d. Lowering the temperature to 12.5 °C resulted in a marked decrease in activity to 46 mg_N∙L⁻¹∙d⁻¹ (79 days doubling time), still in a reasonable range for autotrophic nitrogen removal from MWW. During the experiment, the biomass evolved from a suspended growth inoculum to a hybrid system with suspended flocs and wall-attached biofilm. At the same time, MWW_pre-treated had a direct impact on process performance. Changing the influent from synthetic medium to MWW_pre-treated resulted in a two-month delay in net anammox growth and a two to three-fold increase in the estimated doubling times of the anammox organisms. Interestingly, anammox remained the primary nitrogen consumption route, and high-throughput 16S rRNA gene-targeted amplicon sequencing analyses revealed that the shift in performance was not associated with a shift in dominant anammox bacteria ("Candidatus Brocadia fulgida"). Furthermore, only limited heterotrophic denitrification was observed in the presence of easily biodegradable organics (acetate, glucose). The observed delays in net anammox growth were thus ascribed to the acclimatization of the initial anammox population or/and the development of a side population beneficial for them. Additionally, by combining microautoradiography and fluorescence in situ hybridization it was confirmed that the anammox organisms involved in the process did not directly incorporate or store the amended acetate and glucose. In conclusion, these investigations strongly support the feasibility of MWW treatment via anammox.

Mimoso, J., Pronk, W., Morgenroth, E., & Hammes, F. (2015). Bacterial growth in batch-operated membrane filtration systems for drinking water treatment. Separation and Purification Technology, 156, 165-174. doi:10.1016/j.seppur.2015.09.070, Institutional Repository

Morgenroth, E., Derlon, N., Pronk, W., & Larsen, T. A. (2015). Von der Grundlagenforschung zur Anwendung: Trinkwasseraufbereitung und Sanitärversorgung (p. (14 pp.). Presented at the 48. Essener Tagung für Wasser- und Abfallwirtschaft "Forschung trifft Praxis". Aachen, Germany. , Institutional Repository

Ravndal, K. T., Künzle, R., Derlon, N., & Morgenroth, E. (2015). On-site treatment of used wash-water using biologically activated membrane bioreactors operated at different solids retention times. Journal of Water Sanitation and Hygiene for Development, 5(4), 544-552. doi:10.2166/washdev.2015.174, Institutional Repository

Schielke-Jenni, S. (2015). Decentralised urine treatment with the nitritationammox process (Doctoral dissertation). doi:10.3929/ethz-a-010479901, Institutional Repository

Schielke-Jenni, S., Villez, K., Morgenroth, E., & Udert, K. M. (2015). Observability of anammox activity in single-stage nitritation/anammox reactors using mass balances. Environmental Science: Water Research and Technology, 1(4), 523-534. doi:10.1039/c5ew00045a, Institutional Repository

In nitritationammox reactors, several bacterial groups contribute to the overall nitrogen conversion. Knowing the activity of the main bacterial groups, especially of anaerobic ammonium-oxidising bacteria (AMX), is extremely helpful to understand the process and optimise its operation. Mass balances of dissolved compounds such as ammonium, nitrite and nitrate commonly allow the determination of bacterial activities in a nitritationammox process, but the activity of heterotrophic bacteria (HET) is usually neglected. However, even in wastewater with a low organic substrate content, heterotrophic denitrification can contribute substantially to nitrogen removal. The goal of this study was to critically evaluate the applicability of mass balances for the determination of the relevant bacterial activities in a nitritationammox process with high HET activity. We set up and solved mass balances of different degrees of complexity. Both linear equation systems, with catabolic reactions alone and with balances according to the activated sludge model stoichiometry, do not allow estimation of any of the considered bacterial activities. When kinetic rate expressions are included, it is possible to compute the concentrations of all considered bacterial groups, but the estimation uncertainty is far too high for practical purposes: the relative standard deviation for AMX is 5280%. In a completely autotrophic system, the relative standard deviation for AMX is only 5%, which proves that the high standard deviations are due to the complexity of the nitration–anammox process with HET activity. The high standard deviations of the calculated bacterial concentrations can be significantly reduced by adding an additional mass balance for the total biomass (standard deviation for AMX activity 1210%). The required number of measurements to achieve an acceptable precision, in our example about 600 conversion rate measurements to reach a 50% standard deviation for the AMX concentration, is still far too high though for practical purposes. To conclude, mass balances including kinetics theoretically allow the observation of the bacterial activities in nitritationammox reactors with high HET activity. However, the required precision of the calculated conversion rates, the uncertainty of stoichiometric and kinetic parameters and the reactor dynamics (unsteady conditions) make mass balances unsuitable for practical estimation of AMX activity. Due to high frequency and new online instruments, mass balances might become a suitable tool in the future.

Schönenberger, U. (2015). Data reconciliation and gross error detection for wastewater treatment processes (Master thesis). 34 p. , Institutional Repository

Shen, Y., Monroy, G. L., Derlon, N., Janjaroen, D., Huang, C., Morgenroth, E., … Nguyen, T. H. (2015). Role of biofilm roughness and hydrodynamic conditions in legionella pneumophila adhesion to and detachment from simulated drinking water biofilms. Environmental Science and Technology, 49(7), 4274-4282. doi:10.1021/es505842v, Institutional Repository

Stamm, C., Eggen, R. I. L., Hering, J. G., Hollender, J., Joss, A., & Schärer, M. (2015). Micropollutant removal from wastewater: facts and decision-making despite uncertainty. Environmental Science and Technology, 49(11), 6374-6375. doi:10.1021/acs.est.5b02242, Institutional Repository

Ternes, T., Joss, A., & Oehlmann, J. (2015). Occurrence, fate, removal and assessment of emerging contaminants in water in the water cycle (from wastewater to drinking water). Water Research, 72, 1-2. doi:10.1016/j.watres.2015.02.055, Institutional Repository

Thalmann, B., Voegelin, A., von Gunten, U., Behra, R., Morgenroth, E., & Kaegi, R. (2015). Effect of ozone treatment on nano-sized silver sulfide in wastewater effluent. Environmental Science and Technology, 49(18), 10911-10919. doi:10.1021/acs.est.5b02194, Institutional Repository

Thalmann, B. A. D. (2015). Transformations of silver nanoparticles in urban wastewater and water systems (Doctoral dissertation). doi:10.3929/ethz-a-010579189, Institutional Repository

Metallic silver nanoparticles (AgNP) are increasingly applied in consumer products from which they are probably released to the urban wastewater and water system. Due to the antimicrobial activity of AgNP, they are of high ecotoxicological concern and an engineered nanomaterial of priority for environmental risk assessment. Transformations of AgNP can have large efects on their toxicity toward aquatic organism. Most importantly, the sulidation of AgNP is known to reduce the toxicity of Ag by several orders of magnitude. Thus, a proper understanding of the sulidation of AgNP in the urban wastewater and water system is crucial for in-depth environmental risk assessments. Furthermore, the ozonation of the eluent of wastewater treatment plant (WWTP) to mitigate micropollutants is likely to further change the Ag speciation. he irst objective of this thesis was to understand the sulidation kinetics of AgNP with bisulide (HS-) and metal sulides. The second objective was to study the impact of ozone treatment on sulidized AgNP. [...]

Silber Nanopartikel (AgNP) werden vermehrt in Konsumgütern angewandt, von welchen die Partikel durch den Gebrauch in das urbane Abwasser und Wasser ausgewaschen werden können. Aufgrund ihrer antimikrobieller Wirkung stellen sie ein potentielles Risiko für die Umwelt dar, welches abgeschätzt werden sollte. Durch Umwandlung in der Umwelt ändert sich die Speziierung der AgNP was die Toxizität gegenüber aquatischen Organismen und Planzen beeinlusst. Die Reaktion von AgNP mit Suliden, genannt Sulidierung, zum Beispiel reduziert die Ag Toxizität um mehrere Grössenordnungen. Deshalb ist es für eine Risikoeinschätzung der AgNP in der Umwelt wichtig die Sulidierung im urbanen Abwasser und Wasser zu verstehen. Im Abwasser ist die dominante Sulid Quelle Bisulid (HS-), welches in erhöhten Konzentrationen zu inden ist. Für das Oberlächengewässer hingegen ist die Sulidierung mit Metallsuliden wahrscheinlicher, da sie persistenter gegen die Oxidation mit Sauerstof sind. Das erste Ziel dieser Dissertation war deshalb die Sulidierung von AgNP mit HS- und Metallsuliden zu verstehen. [...]

Trottmann, C. (2015). Simultaneous nitrification and denitrification with aerobic granules in municipal wastewater (Master thesis). 31 p. , Institutional Repository

This study aims at the question why SND is only working with very low efficiency for granules fed with municipal wastewaster. Therefore three hypotheses were set up: (i) Absence of anoxic zone within the aerobic granules due to deep penetration of oxygen, (ii) low availability of electron donor (carbon source) for denitrification and (iii) low denitrification rate as fraction of large granules is too small.
Experiments with batch reactors were performed, with aerobic granular sludge (40-60 % granules) from a column sequencing batch reactor fed with municipal wastewater, to verify the hypotheses.
To analyze the influence of a carbon source a distinction of two cases was done. In Case 1 the granules were fed with extra added acetate in a first anaerobic phase. Phosphate,- and glycogenaccumulating bacteria (PAOs and GAOs) stored this acetate intracellular as polyhydroxyalkanoates (PHA) before the aerobic phase started. For Case 2 only particular carbon stored in the matrix of the granules, as extracellular polymeric substances (EPS), was available.
Beside that the oxygen concentration was varied between 0.5-2.2 mg_O2l^-1 and separate tests with extra added nitrate were done to evaluate the denitrification rate.
For Case 1 the intracellular stored acetate (PHA) caused a stable simultaneous nitrification and denitrification process whereas for Case 2 unstable situations sometimes caused no denitrifaciton at all. The oxygen concentration was found to be a very important and sensitive parameter.
It has a direct impact to the anoxic volume in the granules due to its mass transport limitation by diffusion which is limiting the penetration depth (causing an aerobic surface were nitrification is performed and an anoxic core with denitrifying bacteria).
Highest SND ratios were found in Case 1 at an oxygen concentration level of 0.5-1.0 mg_O2l^-1 and completely taken up and intracellular stored acetate of 100 mg_CODl^-1. An average SND efficiency of 26.4±13.6 % was reached therefore.
Denitrification rates of 1.22±0.16 mg_N∙g_VSS^-1∙h^-1 (Case 1) and 0.89±0.05 mg_N∙g_VSS^-1∙h^-1 (Case 2) were observed.
The fraction of large granules (d>0.63 mm) of only 10 % by weight (g_VSS) was relatively low. Therefore it is affirmed that denitrification is low due to this, but not that the denitrification rate is lower than for smaller granules.

Vannecke, T. P. W., Wells, G., Hubaux, N., Morgenroth, E., & Volcke, E. I. P. (2015). Considering microbial and aggregate heterogeneity in biofilm reactor models: how far do we need to go?. Water Science and Technology, 72(10), 1692-1699. doi:10.2166/wst.2015.389, Institutional Repository

Wagner, J., Weissbrodt, D. G., Manguin, V., Ribeiro da Costa, R. H., Morgenroth, E., & Derlon, N. (2015). Effect of particulate organic substrate on aerobic granulation and operating conditions of sequencing batch reactors. Water Research, 85, 158-166. doi:10.1016/j.watres.2015.08.030, Institutional Repository

The formation and application of aerobic granules for the treatment of real wastewaters still remains challenging. The high fraction of particulate organic matter (X_S) present in real wastewaters can affect the granulation process. The present study aims at understanding to what extent the presence of X_S affects the granule formation and the quality of the treated effluent. A second objective was to evaluate how the operating conditions of an aerobic granular sludge (AGS) reactor must be adapted to overcome the effects of the presence of X_S. Two reactors fed with synthetic wastewaters were operated in absence (R1) or presence (R2) of starch as proxy for X_S. Different operating conditions were evaluated. Our results indicated that the presence of X_S in the wastewater reduces the kinetic of granule formation. After 52 d of operation, the fraction of granules reached only 21% in R2, while in R1 this fraction was of 54%. The granules grown in presence of X_S had irregular and filamentous outgrowths in the surface, which affected the settleability of the biomass and therefore the quality of the effluent. An extension of the anaerobic phase in R2 led to the formation of more compact granules with a better settling ability. A high fraction of granules was obtained in both reactors after an increase of the selection pressure for fast-settling biomass, but the quality of the effluent remained low. Operating the reactors in a simultaneous fill-and-draw mode at a low selection pressure for fast-settling biomass showed to be beneficial for substrate removal efficiency and for suppressing filamentous overgrowth. Average removal efficiencies for total COD, soluble COD, ammonium, and phosphate were 87 ± 4%, 95 ± 1%, 92 ± 10%, and 87 ± 12% for R1, and 72 ± 12%, 86 ± 5%, 71 ± 12%, and 77 ± 11% for R2, respectively. Overall our study demonstrates that the operating conditions of AGS reactors must be adapted according to the wastewater composition. When treating effluents that contain X_S, the selection pressure should be significantly reduced.

Wu, S., Weissbrodt, D. G., Morgenroth, E., & Goel, R. (2015). Resiliency of anammox against external stress factors – Effects of temperature and wastewater constituents. In Vol. 3. 88th annual water environment federation technical exhibition and conference (WEFTEC 2015) (pp. 1476-1483). doi:10.2175/193864715819540054, Institutional Repository

Wunderlin, P., Joss, A., Siegrist, H., Abegglen, C., & Schärer, M. (2015). Verfahrenstechnik Mikroverunreinigungen. www.micropoll.ch - Wissensplattform des VSA. Aqua & Gas, 95(2), 14-19. , Institutional Repository

Zöllig, H., Fritzsche, C., Morgenroth, E., & Udert, K. M. (2015). Direct electrochemical oxidation of ammonia on graphite as a treatment option for stored source-separated urine. Water Research, 69, 284-294. doi:10.1016/j.watres.2014.11.031, Institutional Repository

Electrolysis can be a viable technology for ammonia removal from source-separated urine. Compared to biological nitrogen removal, electrolysis is more robust and is highly amenable to automation, which makes it especially attractive for on-site reactors. In electrolytic wastewater treatment, ammonia is usually removed by indirect oxidation through active chlorine which is produced in-situ at elevated anode potentials. However, the evolution of chlorine can lead to the formation of chlorate, perchlorate, chlorinated organic by-products and chloramines that are toxic. This study focuses on using direct ammonia oxidation on graphite at low anode potentials in order to overcome the formation of toxic by-products. With the aid of cyclic voltammetry, we demonstrated that graphite is active for direct ammonia oxidation without concomitant chlorine formation if the anode potential is between 1.1 and 1.6 V vs. SHE (standard hydrogen electrode). A comparison of potentiostatic bulk electrolysis experiments in synthetic stored urine with and without chloride confirmed that ammonia was removed exclusively by continuous direct oxidation. Direct oxidation required high pH values (pH > 9) because free ammonia was the actual reactant. In real stored urine (pH = 9.0), an ammonia removal rate of 2.9 ± 0.3 gN·m⁻²·d⁻¹ was achieved and the specific energy demand was 42 Wh·gN⁻¹ at an anode potential of 1.31 V vs. SHE. The measurements of chlorate and perchlorate as well as selected chlorinated organic by-products confirmed that no chlorinated by-products were formed in real urine. Electrode corrosion through graphite exfoliation was prevented and the surface was not poisoned by intermediate oxidation products. We conclude that direct ammonia oxidation on graphite electrodes is a treatment option for source-separated urine with three major advantages: The formation of chlorinated by-products is prevented, less energy is consumed than in indirect ammonia oxidation and readily available and cheap graphite can be used as the electrode material.

Zöllig, H. (2015). Electrolysis for the treatment of stored source-separated urine (Doctoral dissertation). doi:10.3929/ethz-a-010549050, Institutional Repository

Zöllig, H., Remmele, A., Fritzsche, C., Morgenroth, E., & Udert, K. M. (2015). Formation of chlorination byproducts and their emission pathways in chlorine mediated electro-oxidation of urine on active and nonactive type anodes. Environmental Science and Technology, 49(18), 11062-11069. doi:10.1021/acs.est.5b01675, Institutional Repository

Zöllig, H., Morgenroth, E., & Udert, K. M. (2015). Inhibition of direct electrolytic ammonia oxidation due to a change in local pH. Electrochimica Acta, 165, 348-355. doi:10.1016/j.electacta.2015.02.162, Institutional Repository

Electrochemical ammonia oxidation has gained a lot of attention recently as an efficient method for ammonia removal from wastewater, for the use in ammonia-based fuel cells and the production of high purity hydrogen. Thermally decomposed iridium oxide films (TDIROF) have been shown to be catalytically active for direct ammonia oxidation in aqueous solutions if NH₃ is present. However, the process was reported to be rapidly inhibited on TDIROF. Herein, we show that this fast inhibition of direct ammonia oxidation does not result from surface poisoning by adsorbed elemental nitrogen (N_ads). Instead, we propose that direct ammonia oxidation and oxygen evolution can lead to a drop of the local pH at the electrode resulting in a low availability of the actual reactant, NH₃. The hypothesis was tested with cyclic voltammetry (CV) experiments on stagnant and rotating disk electrodes (RDE). The CV experiments on the stagnant electrode revealed that the decrease of the ammonia oxidation peaks was considerably reduced by introducing an idle phase at open circuit potential between subsequent scans. Furthermore, the polarization of the TDIROF electrode into the hydrogen evolution region (HER) resulted in increased ammonia oxidation peaks in the following anodic scans which can be explained with an increased local pH after the consumption of protons in the HER. On the RDE, the ammonia oxidation peaks did not decrease in immediately consecutive scans. These findings would not be expected if surface poisoning was responsible for the fast inhibition but they are in good agreement with the proposed mechanism of pH induced limitation by the reactant, NH₃. The plausibility of the mechanism was also supported by our numerical simulations of the processes in the Nernstian diffusion layer. The knowledge about this inhibition mechanism of direct ammonia oxidation is especially important for the design of electrochemical cells for wastewater treatment. The mechanism is not only valid for TDIROF but also for other electrodes because it is independent of the electrode material.

Chomiak, A., Mimoso, J., Koetzsch, S., Sinnet, B., Pronk, W., Derlon, N., & Morgenroth, E. (2014). Biofilm formation and permeate quality improvement in Gravity Driven Membrane ultrafiltration. Water Science and Technology: Water Supply, 14(2), 274-282. doi:10.2166/ws.2013.197, Institutional Repository

Chomiak, A., Sinnet, B., Derlon, N., & Morgenroth, E. (2014). Inorganic particles increase biofilm heterogeneity and enhance permeate flux. Water Research, 64, 177-186. doi:10.1016/j.watres.2014.06.045, Institutional Repository

Derlon, N., Mimoso, J., Klein, T., Koetzsch, S., & Morgenroth, E. (2014). Presence of biofilms on ultrafiltration membrane surfaces increases the quality of permeate produced during ultra-low pressure gravity-driven membrane filtration. Water Research, 60, 164-173. doi:10.1016/j.watres.2014.04.045, Institutional Repository

Eggen, R. I. L., Hollender, J., Joss, A., Schärer, M., & Stamm, C. (2014). Reducing the discharge of micropollutants in the aquatic environment: the benefits of upgrading wastewater treatment plants. Environmental Science and Technology, 48(14), 7683-7689. doi:10.1021/es500907n, Institutional Repository

Gruber, W. (2014). Modellierung der Lachgasemissionen aus der biologischen Abwasserreinigung (Master thesis). 34 p. , Institutional Repository

Lachgas (N₂O) ist ein Treibhausgas (ca. 300 Mal stärker als CO₂) und bedeutend an der Zerstörung der stratosphärischen Ozonschicht beteiligt. In der biologischen Stufe von Abwasserreinigungsanlagen (ARA) werden relevante Mengen an N₂O emittiert. Die N₂OBildung ist sehr komplex und nur ansatzweise verstanden. Es wird aber davon ausgegangen, dass hauptsächlich die Nitrifikation eine dominante Quelle darstellt.
In der vorliegenden Masterarbeit wurde anhand von qualitativen Modellierungen versucht die Dynamik der N₂O-Emissionen auf der ARA Real nachzuvollziehen und Strategien zur Reduktion der Emissionen zu entwickeln.
Anhand von Daten aus einer Langzeit Messkampagne auf der ARA Real über die N₂OEmissionen konnte gezeigt werden, dass die N2O-Emissionen im Winter und Frühling einen bedeutenden Einfluss auf die Treibhausgasbilanz der Anlage hat. Berechnungen ergaben, dass die Emissionen bei über 1.5% der Ammoniumfracht im Zulauf der Anlage liegen. Es wurde abgeschätzt, dass die Emissionen ca. je zur Hälfte auf die Haupt- und die Nachbelüftung der Anlage entfallen. Dieses Ergebnis ist erstaunlich, da üblicherweise vor allem in der Hauptbelüftung der Grossteil der N₂O-Emissionen ausgestossen wird.
Für die Entwicklung von N₂O reduzierenden Massnahmen auf Kläranlagen können Modellierungen wichtige Hilfestellungen bieten. Allerdings kann mit den bereits publizierten mechanistischen Modellen über die N₂O-Bildung nur ein Teil der N₂O-Dynamik erklärt werden. Daher wurde in der vorliegenden Studie die N₂O-Bildung basierend auf den Daten aus einer Langzeit-Messkampagne auf der ARA Real mit empirischen Ansätzen modelliert. Die N₂O-Emissionen zeigen starke Korrelationen zur NO₂^--Konzentration in der Belüftungszone, Temperatur und zum Niederschlag. Darauf aufbauend wurde das ASM3-Modell mit Stickstofferweiterung um die Lachgasbildung in der Nitrifikation durch die Nitrifikaten Denitrifikation und die hetrotrophe Denitrifikation erweitert und kalibriert. Der dritte bekannte Prozess zur N₂O-Bildung (Oxidation von NH₂OH) wurde weggelassen.
Die Resultate der Modellierungen zeigen, dass mit dem Modell die Emissionen im Winter qualitativ gut reproduziert und erklärt werden können. Im Sommer bei höheren Temperaturen sind die modellierten Konzentrationen zu hoch. Insbesondere für die Modell Prozesse der Denitrifikation sind Anpassungen möglicherweise vorzusehen.
Anhand des Modells wurden für den Winter Betriebsoptimierungen getestet. In Kombination mit den Resultaten aus der Analyse der Daten aus der Messkampange wurden verschiedene Optimierungsmassnahmen entwickelt. Am vielversprechendsten sind die Erhöhung der O₂-Konzentration in der Hauptbelüftung, die Verlängerung der Belüftungsphasen, ein dosierterer Betrieb der Belüftungseinheit der Nachbelüftung und die separate Behandlung von Rückläufen aus der Schlammbehandlung. Teilweise entstehen aber Konflikte mit anderen Zielgrössen, wie der Stickstoffelimination und dem Energieverbrauch der Anlage. Dabei kann das Modell in Zukunft interessante Hilfestellungen bieten und verbunden mit Ökobilanz-Tools könnten die gestellten Optimierungsprobleme gelöst werden.

Jenni, S., Vlaeminck, S. E., Morgenroth, E., & Udert, K. M. (2014). Successful application of nitritation/anammox towastewater with elevated organic carbon to ammonia ratios. Water Research, 49, 316-326. doi:10.1016/j.watres.2013.10.073, Institutional Repository

The nitritation/anammox process has been mainly applied to high-strength nitrogenous wastewaters with very low biodegradable organic carbon content (<0.5g COD·g N^–1). However, several wastewaters have biodegradable organic carbon to nitrogen (COD/N) ratios between 0.5 and 1.7g COD·g N^–1 and thus, contain elevated amounts of organic carbon but not enough for heterotrophic denitrification. In this study, the influence of elevated COD/N ratios was studied on a nitritation/anammox process with suspended sludge. In a step-wise manner, the influent COD/N ratio was increased to 1.4g COD·g N^–1 by supplementing digester supernatant with acetate. The increasing availability of COD led to an increase of the nitrogen removal efficiency from around 85% with pure digester supernatant to >95% with added acetate while the nitrogen elimination rate stayed constant (275 ± 40mg N·L^–1·d^–1). Anammox activity and abundance of anammox bacteria (AMX) were strongly correlated, and with increasing influent COD/N ratio both decreased steadily. At the same time, heterotrophic denitrification with nitrite and the activity of ammonia oxidising bacteria (AOB) gradually increased. Simultaneously, the sludge retention time (SRT) decreased significantly with increasing COD loading to about 15 d and reached critical values for the slowly growing AMX. When the SRT was increased by reducing biomass loss with the effluent, AMX activity and abundance started to rise again, while the AOB activity remained unaltered. Fluorescent in-situ hybridisation (FISH) showed that the initial AMX community shifted within only 40 d from a mixed AMX community to "Candidatus Brocadia fulgida" as the dominant AMX type with an influent COD/N ratio of 0.8 g COD·g N^–1 and higher. "Ca. Brocadia fulgida" is known to oxidise acetate, and its ability to outcompete other types of AMX indicates that AMX participated in acetate oxidation. In a later phase, glucose was added to the influent instead of acetate. The new substrate composition did not significantly influence the nitrogen removal nor the AMX activity, and "Ca. Brocadia fulgida" remained the dominant type of AMX. Overall, this study showed that AMX can coexist with heterotrophic bacteria at elevated influent COD/N ratios if a sufficiently high SRT is maintained.

Kohler, E., Villiger, J., Posch, T., Derlon, N., Shabarova, T., Morgenroth, E., … Blom, J. F. (2014). Biodegradation of microcystins during gravity-driven membrane (GDM) ultrafiltration. PLoS One, 9(11), e111794 (9 pp.). doi:10.1371/journal.pone.0111794, Institutional Repository

Lackner, S., Gilbert, E. M., Vlaeminck, S. E., Joss, A., Horn, H., & van Loosdrecht, M. C. M. (2014). Full-scale partial nitritation/anammox experiences – an application survey. Water Research, 55, 292-303. doi:10.1016/j.watres.2014.02.032, Institutional Repository

Martin, K. J., Bolster, D., Derlon, N., Morgenroth, E., & Nerenberg, R. (2014). Effect of fouling layer spatial distribution on permeate flux: a theoretical and experimental study. Journal of Membrane Science, 471, 130-137. doi:10.1016/j.memsci.2014.07.045, Institutional Repository

Ni, B. J., Joss, A., & Yuan, Z. (2014). Modeling nitrogen removal with partial nitritation and anammox in one floc-based sequencing batch reactor. Water Research, 67, 321-329. doi:10.1016/j.watres.2014.09.028, Institutional Repository

Renggli, S. (2014). Influence of dry phases on gravity-driven membrane performance (Master thesis). 63 p. , Institutional Repository

Sharma, K., Derlon, N., Hu, S., & Yuan, Z. (2014). Modeling the pH effect on sulfidogenesis in anaerobic sewer biofilm. Water Research, 49(1), 175-185. doi:10.1016/j.watres.2013.11.019, Institutional Repository

Thalmann, B., Voegelin, A., Sinnet, B., Morgenroth, E., & Kaegi, R. (2014). Sulfidation kinetics of silver nanoparticles reacted with metal sulfides. Environmental Science and Technology, 48(9), 4885-4892. doi:10.1021/es5003378, Institutional Repository

Uhlmann, C. (2014). Dynamics of complete and partial nitrification of source-separated urine (Master thesis). 32 p. , Institutional Repository

In this thesis the resilience of complete and partial nitrification of source-separated urine under dynamic conditions were investigated and compared. The process stability of nitrification reactors is important for their commercial application. In partial nitrification the alkalinity contained in urine allows nitrifying 50% of the ammonia whereas in complete nitrification the dosage of a base allows the nitrification of almost 100% of the ammonia. Due to considerations about Monod kinetic substrate limitation of Ammonia Oxidizing Bacteria (AOB) it was hypothesized that complete nitrification is more prone to nitrite accumulation and therefore less stable than partial nitrification. A computer model based on Monod kinetics should help to understand the processes and the resilience of urine nitrification reactors. Laboratory experiments were conducted in 7 L moving bed biofilm reactors (MBBR) to analyze the behavior of the two processes in respect to changes in temperature and inflow. The total ammonia concentration in the inflow was on average 1750±150 mg N L^-1. Complete nitrification has at same conditions a lower nitrification rate than partial nitrification due to the lower ammonia concentration in the reactor. In order to reach comparable nitrification rates complete and partial nitrification reactors were therefore operated at two different pH values of 7 and 6 respectively. The average nitrification rate in complete nitrification was 1.08±0.17 g N m-2 d-1 and in parital nitrification 0.90±0.25 g N m-2 d-1 with regard to biofilm carrier surface (Kaldnes^®). During all experiments no essential difference of process stability between complete and partial nitrification were observed. Both processes remained stable during temperature fluctuations between 20 °C and 32 °C when urine inflow was constant. pH-diven inflow control led to substantial nitrite accumulation and to a break down of nitrification due to an increase of the inflow caused by increasing AOB activity at higher temperatures. It could be shown that the dynamics of bacterial growth due to temperature changes are damped when pH is not controlled. Instantaneous increase of the inflow caused severe nitrite accumulations in both processes. A reliable process control should therefore consider the effects of temperature and restrict load fluctuations to a minimum. The developed model was able to describe the dynamics of nitrogen conversion due to temperature changes but failed in the prediction of process instabilities caused by increasing inflow.

Weissbrodt, D. G., Wells, G. F., Johnson, D. R., Bürgmann, H., Joss, A., Laureni, M., & Morgenroth, E. (2014). Towards community systems microbiology for the optimization of aerobic-anaerobic ammonium oxidation processes. In Vol. 1. 87th annual water environment federation technical exhibition and conference (WEFTEC 2014) (pp. 2645-2649). doi:10.2175/193864714815942567, Institutional Repository

Wunderlin, P., Siegrist, H., Kipf, M., Gruber, W., & Joss, A. (2014). Energieoptimierung um jeden Preis? – Potentielle Risiken für den Umweltschutz. In H. Steinmetz & C. Meyer (Eds.), Stuttgarter Berichte zur Siedlungswasserwirtschaft: Vol. 221. Energiepotenziale kommunaler Kläranlagen erkennen, nutzen und kritisch bewerten (pp. 1-26). München: DIV Deutscher Industrieverlag. , Institutional Repository

Lachgas (N₂O) ist ein starkes Treibhausgas und bedeutend an der Zerstörung der stratosphärischen Ozonschicht beteiligt. Seine Bildung und Freisetzung in die Atmosphäre hat deshalb eine grosse Umweltrelevanz. In der biologischen Abwasserreinigung kann N₂O sowohl während der Nitrifikation (Oxidation von Ammonium zu Nitrat), wie auch durch die heterotrophe Denitrifikation (Reduktion von Nitrat zu Luftstickstoff) gebildet werden. Diese Prozesse laufen häufig gleichzeitig ab. Daher lässt sich ihr individueller Beitrag zur N₂O Bildung nur schwer abschätzen. Für diese Studie wurde ein neuartiger Ansatz angewandt, der eine bessere Beurteilung der N₂O Bildung auf Abwasserreinigungsanlagen erlaubt. Anhand der Analyse der stabilen Stickstoffisotopen wurde gezeigt, dass unter aeroben Bedingungen die Nitrifikation die N₂O Bildung dominiert. Dabei fördern sowohl hohe Ammonium (NH₄⁺) wie auch Nitrit (NO₂^-) Konzentrationen die N₂O Bildung. Ausserdem ist zu beachten, dass die Entstehung von N₂O räumlich und zeitlich sehr variabel ist und durch viele Parameter beeinflusst wird. Die aktuellen Emissionsschätzungen sind daher mit einer grossen Unsicherheit verbunden, was eine Bestimmung von präzisen Emissionsfaktoren schwierig macht. Untersuchungen zeigen aber, dass die N₂O Emissionen die Treibhausgasbilanz der gesamten Anlage dominieren können, welche ansonsten vor allem durch die indirekten Emissionen der Belüftungenergie der biologischen Reinigungsstufe beeinflusst wird.
In Anbetracht der negativen Umweltauswirkungen von N₂O und der langen Aufenthaltszeit in der Atmosphäre (rund 120 Jahre) sollte unbedingt eine möglichst weitgehende Reduktion der Emissionen angestrebt werden. Das gegenwärtige Verständnis der relevanten Bildungsmechanismen deutet darauf hin, dass bei einer möglichst vollständigen Nitrifikation betrieben mit Sauerstoffkonzentrationen von mehr als 2 mgO₂/L und einer weitgehenden Denitrifikation unter Vermeidung von Sauerstoffeinträgen, gleichzeitig auch die Nitrit und damit die N₂O Bildung minimiert werden kann. Aus diesem Grund sollte sowohl bei der Auslegung wie auch bei der energetischen Optimierung und beim Betrieb von Belebtschlamm-Anlagen (z.B. Regelung der Belüftung, O₂-Sollwert) die N₂O Bildung mitberücksichtigt werden.

Böhler, M., Morgenroth, E., Siegrist, H., Haueter, R., Rensch, D., Sterkele, B., … Beurer, I. (2013). Machbarkeits‐ und Vergleichsstudie zur Umstellung der chemischen Phosphorelimination mittels Eisen‐ auf Aluminium‐Produkte auf kommunalen Abwasserreinigungsanlagen. Dübendorf: Eawag. , Institutional Repository

Carrel, M. (2013). Membrane ultrafiltration: a study of the combined use of iron chloride for coagulation and of hypochlorite for disinfection (Master thesis). 47 p. , Institutional Repository

Fouling is the main issue related to the use of ultrafiltration membranes, a promising technology arising in the drinking water field. The topic of this work was suggested by results of pilot tests performed by the Swiss company Membratec. This company holds a leading position in the water treatment field in Switzerland and is an industry partner of Eawag. They observed that the irreversible fouling caused by high waters with humic substances loads could almost be totally mitigated while combining inline iron chloride coagulation and hypochlorite disinfection twice a day. A further observation is that iron chloride had a positive effect regarding NOM retention.
Several experiments were performed at Eawag with Swiss natural waters in order to reproduce the results obtained by Membratec. The main focus of this work was to investigate whether the strong fouling mitigation observed was caused by the combination of optimal pre-treatment and disinfection processes, or whether these results were caused by direct chemical interactions occuring between iron chloride and hypochorite.
The results of these tests show that iron chloride is a powerful coagulant for the treatment of waters with high humic substances loads in terms of fouling mitigation (50 % hydraulically reversible fouling reduction when comparing with addition of iron chloride and without for short filtration experiments). Hypochlorite disinfection also allows important permability recovery. However, the fouling mitigation obtained here was not as strong as the one observed by Membratec. This could be explained by the higher NOM content of the water used in this work. With humic substances and biopolymers retention of more than 90 % respectively 80%, even at underdose, iron chloride can provide excellent and promising results in terms of NOM removal. Fouling quantification and analysis is a key step in order to compare different pre-treatments and cleaning strategies. Since the different fouling quantification approaches used in this work all represent limitations,the use of a multi-criteria analysis strategy combining them is suggested. Jar-tests showed that hypochlorite reacts with iron chloride flocs, suggesting that the cake layer produced by iron chloride coagulation can be removed very efficiently. These results underline the importance of understanding the mechanisms leading to the cake layer build up and of the necessity to adapt pre-treatment and disinfection to the water to be filtered.

Choubert, J. M., Rieger, L., Shaw, A., Copp, J., Spérandio, M., Sørensen, K., … Gillot, S. (2013). Rethinking wastewater characterisation methods for activated sludge systems - a position paper. Water Science and Technology, 67(11), 2363-2373. doi:10.2166/wst.2013.158, Institutional Repository

Derlon, N., Koch, N., Eugster, B., Posch, T., Pernthaler, J., Pronk, W., & Morgenroth, E. (2013). Activity of metazoa governs biofilm structure formation and enhances permeate flux during Gravity-Driven Membrane (GDM) filtration. Water Research, 47(6), 2085-2095. doi:10.1016/j.watres.2013.01.033, Institutional Repository

The impact of different feed waters in terms of eukaryotic populations and organic carbon content on the biofilm structure formation and permeate flux during Gravity-Driven Membrane (GDM) filtration was investigated in this study. GDM filtration was performed at ultra-low pressure (65 mbar) in dead-end mode without control of the biofilm formation. Different feed waters were tested (River water, pre-treated river water, lake water, and tap water) and varied with regard to their organic substrate content and their predator community. River water was manipulated either by chemically inhibiting all eukaryotes or by filtering out macrozoobenthos (metazoan organisms). The structure of the biofilm was characterized at the meso- and micro-scale using Optical Coherence Tomography (OCT) and Confocal Laser Scanning Microscopy (CLSM), respectively. Based on Total Organic Carbon (TOC) measurements, the river waters provided the highest potential for bacterial growth whereas tap water had the lowest. An increasing content in soluble and particulate organic substrate resulted in increasing biofilm accumulation on membrane surface. However, enhanced biofilm accumulation did not result in lower flux values and permeate flux was mainly influenced by the structure of the biofilm. Metazoan organisms (in particular nematodes and oligochaetes) built-up protective habitats, which resulted in the formation of open and spatially heterogeneous biofilms composed of biomass patches. In the absence of predation by metazoan organisms, a flat and compact biofilm developed. It is concluded that the activity of metazoan organisms in natural river water and its impact on biofilm structure balances the detrimental effect of a high biofilm accumulation, thus allowing for a broader application of GDM filtration. Finally, our results suggest that for surface waters with high particulate organic carbon (POC) content, the use of worms is suitable to enhance POC removal before ultrafiltration units.

Derlon, N., Coufort-Saudejaud, C., Queinnec, I., & Paul, E. (2013). Growth limiting conditions and denitrification govern extent and frequency of volume detachment of biofilms. Chemical Engineering Journal, 218, 368-375. doi:10.1016/j.cej.2012.11.061, Institutional Repository

Falås, P., Longrée, P., La Cour Jansen, J., Siegrist, H., Hollender, J., & Joss, A. (2013). Micropollutant removal by attached and suspended growth in a hybrid biofilm-activated sludge process. Water Research, 47(13), 4498-4506. doi:10.1016/j.watres.2013.05.010, Institutional Repository

Faust, V. (2013). Aufenthaltszeit von Urin in einem Urinsammelsystem (Bachelor thesis). 16 p. , Institutional Repository

Im Forum Chriesbach der Eawag ist ein NoMix-System installiert, das den Urin sammelt und getrennt vom restlichen Abwasser abführt. Da der Urin einen Grossteil an Nährstoffen wie Stickstoff enthält, kann er separat aufbereitet und anschliessend als landwirtschaftlicher Dünger genutzt werden. Im Leitungssystem wird der Harnstoff, welcher die grösste Stickstoffkomponente im Urin bildet, durch Bakterien abgebaut. Für ein besseres Verständnis der Harnstoffhydrolyse muss bekannt sein, wie lange der Urin im Leitungssystem verweilt. Um die Aufenthaltszeit von Urin zu quantifizieren wurden in dieser Arbeit Tracerversuche mit Bromid durchgeführt. Dabei wurden neben einer mittleren Aufenthaltszeit auch der Einfluss der Benutzerfrequenz und der Distanz, also dem Stockwerk aus dem der Urin kommt, untersucht. Zusätzlich wurde die Aufenthaltszeit mit Hilfe einer Urinbilanz berechnet, bei der die summierten Input und Output Kurven des Urins aufgezeichnet wurden. Die zeitliche Verschiebung der beiden Kurven beschreibt eine mittlere Verweilzeit.
Die Tracerversuche zeigten, dass sich die Aufenthaltszeit des Bromids und des eigentlichen Urins deutlich unterscheiden. Der Tracer repräsentiert somit nicht wie ursprünglich angenommen den Grundstrom. Wie aus der Urinbilanz hervorging hat der Urin eine mittlere Verweilzeit von 31 Minuten mit einer Standartabweichung von 12 Minuten. Die mittlere Aufenthaltszeit des Bromids ist gemäss den Tracerversuchen etwa viermal grösser. Das unterschiedliche Verhalten ist dadurch zu erklären, dass das Bromid im Leitungsrohr in den Biofilm diffundiert und deshalb mehr Zeit als der Urin benötigt. Mit zunehmender Benutzerfrequenz gleichen sich die beiden Aufenthaltszeiten an, da mehr Urin vorhanden ist, in welches das Bromid zurückdiffundieren kann. Das Stockwerk beeinflusst die Aufenthaltszeit des Urins und des Bromids. Der Einfluss auf das Bromid ist jedoch grösser, da die Diffusion in den Biofilm in den vertikalen Leitungen grösser ist als in den horizontalen.
Auf die Verweilzeit des Harnstoffs konnte aus den Ergebnissen auf Grund der Diffusion nicht geschlossen werden, da weder der Urin noch das Bromid repräsentativ sind. Es kann aber mit grosser Wahrscheinlichkeit gesagt werden, dass auch der Harnstoff und weitere gelöste Stoffe in den Biofilm diffundieren und damit eine grössere Aufenthaltszeit als der Urin besitzen.

Florin, A. (2013). Full nitrification of urine by adding a base (Master thesis). 38 p. , Institutional Repository

With the goal of nutrient recovery, full nitrification of human urine is investigated for its stabilization in simple, decentralized reactors. In a first part of this work, undiluted urine was completely nitrified in a laboratory-scale moving-bed biofilm reactor (MBBR), with automated dosage of a KHCO₃ solution keeping the pH at 7.0-7.1. The effluent contained up to 2706 mg-N/L of nitrate; on average > 99% of the total nitrogen. Maintaining low concentrations of ammonium and nitrite (generally below 1 ‰ and 4.7‰ respectively of the influent total ammonia) proved to reduce the risks of dramatic process instabilities due to inhibition with nitrous acid and free ammonia. Although full nitrification by adding a base presents several advantages, for decentralized applications, it is recommended to add alkalinity in a way requiring less expensive and complex material than by dosing a basic solution.
Hoping that calcite (CaCO₃) could be a simple alternative to buffer nitrification, in a second part we studied the dissolution of chalk powder in synthetic urine solutions, both in the presence and absence of phosphate. Experiments and simulations with PHREEQC verified the hypothesis that phosphate may precipitate on the surface of calcite, and thus slow down dissolution. In the absence of phosphate, calcite dissolved rapidly until saturation of the solution. By contrast, with the high phosphate concentrations in stored urine (around 200-250 mg_P/L), calcite dissolution was inhibited by the rapid formation of amorphous calcium-phosphate (ACP; eventually converting into hydroxyapatite, HAP) directly on the particle’s surface, as was revealed by XRD and REM analysis. To prevent calcite passivation, precipitation of struvite (MgNH₄PO₄•6H₂O) is suggested before the full nitrification reactor. In real urine, the effect of biofilm growth directly on calcite may be of advantage to compensate possibly too slow calcite dissolution, and should inform further work.

Guo, B., Zhang, Y., Yu, G., Lee, W. H., Jin, Y. S., & Morgenroth, E. (2013). Two-stage acidic-alkaline hydrothermal pretreatment of lignocellulose for the high recovery of cellulose and hemicellulose sugars. Applied Biochemistry and Biotechnology, 169(4), 1069-1087. doi:10.1007/s12010-012-0038-5, Institutional Repository

Janjaroen, D., Ling, F., Monroy, G., Derlon, N., Morgenroth, E., Boppart, S. A., … Nguyen, T. H. (2013). Roles of ionic strength and biofilm roughness on adhesion kinetics of Escherichia coli onto groundwater biofilm grown on PVC surfaces. Water Research, 47(7), 2531-2542. doi:10.1016/j.watres.2013.02.032, Institutional Repository

Martin, K. J., Derlon, N., Morgenroth, E., & Nerenberg, R. (2013). Fouling layer surface heterogeneity improves permeate flux. In 86th Annual Water Environment Federation Technical Exhibition and Conference, WEFTEC 2013: Vol. 1. 86th annual water environment federation technical exhibition and conference (WEFTEC 2013) (pp. 621-629). doi:10.2175/193864713813668079, Institutional Repository

Remmele, A. (2013). The influence of anode material and current density on the emissions of disinfection by-products (DBPs) during electrolytic treatment of stored urine (Master thesis). 33 p. , Institutional Repository

Wunderlin, P., Lehmann, M. F., Siegrist, H., Tuzson, B., Joss, A., Emmenegger, L., & Mohn, J. (2013). Isotope signatures of N₂O in a mixed microbial population system: constraints on N₂O producing pathways in wastewater treatment. Environmental Science and Technology, 47(3), 1339-1348. doi:10.1021/es303174x, Institutional Repository

Wunderlin, P., Siegrist, H., & Joss, A. (2013). Online N₂O measurement: the next standard for controlling biological ammonia oxidation?. Environmental Science and Technology, 47(17), 9567-9568. doi:10.1021/es402971p, Institutional Repository

Ye, X., Zhang, X., Morgenroth, E., & Finneran, K. T. (2013). Exogenous anthrahydroquinone-2,6-disulfonate specifically increases xylose utilization during mixed sugar fermentation by Clostridium beijerinckii NCIMB 8052. International Journal of Hydrogen Energy, 38(6), 2719-2727. doi:10.1016/j.ijhydene.2012.11.149, Institutional Repository

Zhang, X., Ye, X., Finneran, K. T., Zilles, J. L., & Morgenroth, E. (2013). Interactions between Clostridium beijerinckii and Geobacter metallireducens in co-culture fermentation with anthrahydroquinone-2, 6-disulfonate (AH₂QDS) for enhanced biohydrogen production from xylose. Biotechnology and Bioengineering, 110(1), 164-172. doi:10.1002/bit.24627, Institutional Repository

Zhang, X., Ye, X., Guo, B., Finneran, K. T., Zilles, J. L., & Morgenroth, E. (2013). Lignocellulosic hydrolysates and extracellular electron shuttles for H₂ production using co-culture fermentation with Clostridium beijerinckii and Geobacter metallireducens. Bioresource Technology, 147, 89-95. doi:10.1016/j.biortech.2013.07.106, Institutional Repository

Boehler, M., Zwickenpflug, B., Hollender, J., Ternes, T., Joss, A., & Siegrist, H. (2012). Removal of micropollutants in municipal wastewater treatment plants by powder-activated carbon. Water Science and Technology, 66(10), 2115-2121. doi:10.2166/wst.2012.353, Institutional Repository

Boltz, J. P., Morgenroth, E., Daigger, G. T., deBarbadillo, C., Murthy, S., Sørensen, K. H., & Stinson, B. (2012). Method to identify potential phosphorus rate-limiting conditions in post-denitrification biofilm reactors within systems designed for simultaneous low-level effluent nitrogen and phosphorus concentrations. Water Research, 46(19), 6228-6238. doi:10.1016/j.watres.2012.08.020, Institutional Repository

Water-quality standards requiring simultaneous low level effluent N and P concentrations are increasingly common in Europe and the United States of America. Moving bed biofilm reactors (MBBRs) and biologically active filters (BAFs) have been used as post-denitrification biofilm reactors in processes designed and operated for this purpose (Boltz et al., 2010a). There is a paucity of information describing systematic design and operational protocols that will minimize the potential for phosphorus rate-limited conditions as well as a lack of information describing the interaction between these post-denitrification biofilm reactors and unit processes that substantially alter phosphorus speciation (e.g., chemically enhanced clarification). In this paper, a simple mathematical model for estimating the threshold below which P becomes rate-limiting, and the model is presented and evaluated by comparing its predictions with operational data from post-denitrification MBBRs and BAFs. Ortho-phosphorus (PO₄–P), which is the dissolved reactive component of total phosphorus, was a primary indicator of P rate-limiting conditions in the evaluated post-denitrification biofilm reactors. The threshold below which PO₄–P becomes the rate-limiting substrate is defined: S_PO₄–P:S_{NO_x–N} = 0.0086 g P/g N and S_PO₄–P : S_M = 0.0013 g P/g COD. Additional analyses indicate J^avg_{NO_x-N} =0.48g/m²/d when S_PO₄–P:S_{NO_x–N} > 0.0086, and J^avg_{NO_x-N}=0.06g/m²/d when S_PO₄–P:S_{NO_x–N} < 0.0086. Effluent nitrate–nitrogen plus nitrite–nitrogen concentration (S_{NO_x–N})(S_{NO_x–N}) from the evaluated post-denitrification biofilm reactors began to rapidly increase when S_PO₄–P:S_{NO_x–N}:S_{NO_x–N} was 0.01, approximately (consistent with the rate-limitation threshold of S_PO₄–P:S_{NO_x–N} < 0.0086 predicted by the mathematical model described in this paper). Depending on the processes used at a given WWTP, optimizing chemically enhanced clarification to increase the amount of PO₄–P that remains in the clarifiers effluent stream, dosing phosphoric acid in the MBBR or BAF influent stream, and/or optimizing secondary process EBPR may overcome phosphorus rate-limitations in the biofilm-based post-denitrification process.

Derlon, N., Peter-Varbanets, M., Scheidegger, A., Pronk, W., & Morgenroth, E. (2012). Predation influences the structure of biofilm developed on ultrafiltration membranes. Water Research, 46(10), 3323-3333. doi:10.1016/j.watres.2012.03.031, Institutional Repository

Fritzsche, C. (2012). The formation of chlorinated organics during electrolytic urine treatment (Master thesis). 74 p. , Institutional Repository

Ghasemian, M., Amin, M. M., Morgenroth, E., & Jaafarzadeh, N. (2012). Anaerobic biodegradation of methyl tert-butyl ether and tert-butyl alcohol in petrochemical wastewater. Environmental Technology, 33(16), 1937-1943. doi:10.1080/09593330.2012.655313, Institutional Repository

Guo, B., Zhang, Y., Ha, S. J., Jin, Y. S., & Morgenroth, E. (2012). Combined biomimetic and inorganic acids hydrolysis of hemicellulose in Miscanthus for bioethanol production. Bioresource Technology, 110, 278-287. doi:10.1016/j.biortech.2012.01.133, Institutional Repository

Kazner, C., Joss, A., Ternes, T., van Houtte, E., & Wintgens, T. (2012). Membrane based treatment trains for managed aquifer recharge. In C. Kazner, T. Wintgens, & P. Dillon (Eds.), Water reclamation technologies for safe managed aquifer recharge (pp. 259-282). London: IWA Publishing. , Institutional Repository

Larsen, T., Gebauer, H., Künzle, R., Lüthi, C., McConville, J., Messmer, U., … Tumwebaze, I. K. (2012). Final report. Reinvent the toilet challenge. Round 1. Diversion for safe saniation. Dübendorf: Eawag. , Institutional Repository

Li, X., Yuen, W., Morgenroth, E., & Raskin, L. (2012). Backwash intensity and frequency impact the microbial community structure and function in a fixed-bed biofilm reactor. Applied Microbiology and Biotechnology, 96(3), 815-827. doi:10.1007/s00253-011-3838-6, Institutional Repository

Lotito, A. M., Wunderlin, P., Joss, A., Kipf, M., & Siegrist, H. (2012). Nitrous oxide emissions from the oxidation tank of a pilot activated sludge plant. Water Research, 46(11), 3563-3573. doi:10.1016/j.watres.2012.03.067, Institutional Repository

Menniti, A., Rieger, L., Boltz, J. P., Johnson, B., Daigger, G., Habermacher, J., … Morgenroth, E. (2012). Critical review on the degradability of endogenous decay products. In Vol. 12. 85th annual water environment federation technical exhibition and conference (WEFTEC 2012) (pp. 7406-7408). Virginia, USA: Water Environment Federation (WEF). , Institutional Repository

Rattier, M., Reungoat, J., Gernjak, W., Joss, A., & Keller, J. (2012). Investigating the role of adsorption and biodegradation in the removal of organic micropollutants during biological activated carbon filtration of treated wastewater. Journal of Water Reuse and Desalination, 2(3), 127-139. doi:10.2166/wrd.2012.012, Institutional Repository

Siegrist, H., & Joss, A. (2012). Review on the fate of organic micropollutants in wastewater treatment and water reuse with membranes. Water Science and Technology, 66(6), 1369-1376. doi:10.2166/wst.2012.285, Institutional Repository

Sägesser, D. (2012). Transformation von Mikroverunreinigungen in der Kanalisation. Erstellung eines hydraulischen Modells als Grundlage (Bachelor thesis). 32 p. , Institutional Repository

Über die Transformation von Mikroverunreinigungen in Kanalisationssystemen ist bislang wenig bekannt. Aus diesem Grund will die vorliegende Bachelorarbeit aufzuzeigen, wie gross Abbauraten von solchen anthropogenen Stoffen sein müssten, damit am Ende eines Versuchskanals ein Abbau messbar ist. Dazu wurden mehrere Tracerexperimente ausgewertet. Die Tracerexperimente waren vorgängig von der EAWAG durchgeführt worden. Als Versuchskanal diente der fünf Kilometer lange Glattstollen, welcher das Abwasser durch den Zürichberg zur Abwasserreinigungsanlage Werdhölzli transportiert. Der Abwasserkanal ist für die Experimente ideal, da keine seitlichen Zuflüsse vorhanden sind.
Für die Auswertung der Tracerexperimente wurde das Computerprogramm Aquasim 2.1 verwendet. Der Abwasserkanal wurde sowohl als Advective-Diffusive Reactor Compartment (Modell 1) als auch als River-Section Compartment (Modell 2) modelliert. Anschliessend wurden die Modelle mittels Daten aus den Tracerexperimenten kalibriert. Als Grundlage dazu diente das Massenerhaltungsgesetz. Für die hydraulische Kalibrierung wurde bei beiden Modellen die Dispersion geschätzt. Zusätzlich wurde beim Modell 1 die Geschwindigkeit und beim Modell 2 der hydraulischen Widerstandsbeiwert nach Strickler ermittelt. Anschliessend wurde ein linearer Abbauprozess hinzugefügt. Durch das Variieren verschiedener Abbauraten konnte die verbleibende Konzentration fünf Kilometer nach Zudosierung berechnet und verglichen werden.
Das Modell 1 und 2 unterscheiden sich prinzipiell in der Wahl des Kompartiments. Gewisse Variablen müssen dadurch unterschiedlich definiert werden. Die Resultate zum Abbau indizieren, dass das Modell 2 genauere Ergebnisse liefert. Beide Modelle zeigen bei der Parameterschätzung ähnliche Resultate. Dies zeigt, dass auch die Modellierung des Kanals als Advektive-Diffusive Reactor Compartment (Modell 1) für eine solide Abschätzung der Parameter sowie zur Quantifizierung des Abbaus verwendet werden kann. Modell 1 ist insbesondere vorzuziehen, falls Angaben zum Durchmesser oder Gefälle fehlen.
Die Auswertung der Tracerversuche ergab, dass sich der Dispersionskoeffizient zwischen 0.11 – 0.29 m²/s befindet. Nach Rieckermann et al. (2005) ist in Abwasserkanälen ein mittlerer Dispersionskoeffizient von 0.16 m²/s üblich. Die ermittelten Werte sind somit durchaus realistisch.
Für die Quantifizierung des Abbaus wurden Abbauraten zwischen 0.1/d und 24/d betrachtet. Die Berechnungen ergaben, dass bei einer Abbaurate von 24/d am Ende des Versuchskanals etwa 90 % der Zudosiermenge abgebaut werden. Allerdings sind die Abbauraten von Mikroverunreinigungen viel geringer. Eine Abbaurate von 0.1/d oder noch kleiner ist realistischer (Joss et al., 2006). Dabei würden ungefähr 1.2 % abgebaut werden. Dies entspricht keinem erheblichen Abbau und könnte, je nach Substanz und Genauigkeit des Messinstruments, knapp oder gar nicht registriert werden.
Bei der Transformation von Mikroverunreinigungen in Abwasserkanälen spielt, neben dem Abbau, auch die Sorption eine Rolle. Durch die Erweiterung der Modelle mit einem Biofilm - Reaktor sowie einem Prozess, der die Sorption beschreibt, könnte das Verhalten der Mikroverunreinigungen in Kanalisationssytemen noch detaillierter betrachtet werden.

Wunderlin, P., Mohn, J., Joss, A., Emmenegger, L., & Siegrist, H. (2012). Mechanisms of N₂O production in biological wastewater treatment under nitrifying and denitrifying conditions. Water Research, 46(4), 1027-1037. doi:10.1016/j.watres.2011.11.080, Institutional Repository

Nitrous oxide (N₂O) is an important greenhouse gas and a major sink for stratospheric ozone. In biological wastewater treatment, microbial processes such as autotrophic nitrification and heterotrophic denitrification have been identified as major sources; however, the underlying pathways remain unclear. In this study, the mechanisms of N₂O production were investigated in a laboratory batch-scale system with activated sludge for treating municipal wastewater. This relatively complex mixed population system is well representative for full-scale activated sludge treatment under nitrifying and denitrifying conditions.
Under aerobic conditions, the addition of nitrite resulted in strongly nitrite-dependent N₂O production, mainly by nitrifier denitrification of ammonia-oxidizing bacteria (AOB). Furthermore, N₂O is produced via hydroxylamine oxidation, as has been shown by the addition of hydroxylamine. In both sets of experiments, N₂O production was highest at the beginning of the experiment, then decreased continuously and ceased when the substrate (nitrite, hydroxylamine) had been completely consumed. In ammonia oxidation experiments, N₂O peaked at the beginning of the experiment when the nitrite concentration was lowest. This indicates that N₂O production via hydroxylamine oxidation is favored at high ammonia and low nitrite concentrations, and in combination with a high metabolic activity of ammonia-oxidizing bacteria (at 2 to 3 mgO₂/l); the contribution of nitrifier denitrification by AOB increased at higher nitrite and lower ammonia concentrations towards the end of the experiment.
Under anoxic conditions, nitrate reducing experiments confirmed that N₂O emission is low under optimal growth conditions for heterotrophic denitrifiers (e.g. no oxygen input and no limitation of readily biodegradable organic carbon). However, N₂O and nitric oxide (NO) production rates increased significantly in the presence of nitrite or low dissolved oxygen concentrations.

Ye, X., Zhang, X., Morgenroth, E., & Finneran, K. T. (2012). Anthrahydroquinone-2,6-disulfonate increases the rate of hydrogen production during Clostridium beijerinckii fermentation with glucose, xylose, and cellobiose. International Journal of Hydrogen Energy, 37(16), 11701-11709. doi:10.1016/j.ijhydene.2012.05.018, Institutional Repository

Arreaza Bauer, A. S. (2011). Robust elicitation of imprecise expert knowledge for water infrastructure management (Master thesis). 32 p. , Institutional Repository

A project lead by SWIP (Sustainable Water Infrastructure Planning) at Eawag is working on the development of probabilistic pipe decay models to support mid- and longterm infrastructure management and rehabilitation planning. Lack of data is one of the diculties this group is facing, but methods exist to collect information of experienced experts with the help of elicitation. To develop an appropriate elicitation procedure was the goal of this thesis, especially comparing the imprecise method of elicitation, which is in development, with the traditional precise method.
First, a brieng was developed for the experts to be informed about the intention and the procedure of the elicitation. The interview itself was conducted with 15 experts in water infrastructure management, eight in the drinking water sector and seven in the wastewater sector. The interviews were designed to elicit pipe lifetime distributions of dierent pipe types. Important psychological and statistical aspects as the basic axioms of probability theory, possible pitfalls, calibrating the expert and give feedback to recognize inconsistencies in the experts answers, are some among the important considerations.
To evaluate if experts have a distinct preference regarding the precise and imprecise method of elicitation, subjective questions were posed to the experts after the elicitations. To additionally see if the choice of the method had an inuence on the time needed for elicitation or the adaptations done for each probability, these were measured and compared. Finally, to recognize if both methods expressed the same information with regard to the lifetime of the pipes, the elicited precise and imprecise estimates for each pipe type were compared. The intention of this work was to evaluate if the imprecise method is equal or even better than the precise method. If this case was conrmed, then the imprecise method could be recommended for future elicitations.
The answers given for the questions posed after the elicitation, state a preference of the imprecise method (8 experts out of 14). Most experts also found it easier (9 out of 14). Interestingly, a majority thought in a precise way (8 out of 14), but this did not seem to infuence the preference of the method as half of those experts prefered the imprecise method. The results showed that the methods had no inuence on time nor on adaptation. The comparison of the methods with regard to the elicited pipe types showed, that the inuence factors of the dierent areas in Switzerland or the experience of the experts were dominating the elicited estimations.
To sum up, the imprecise method can be recommended for future elicitations, as it is considered equal or better than the precise method. More than half of the experts preferred this method. This is also supported by the easiness of doing the elicitation.

Boltz, J. P., Morgenroth, E., Brockmann, D., Bott, C., Gellner, W. J., & Vanrolleghem, P. A. (2011). Systematic evaluation of biofilm models for engineering practice: components and critical assumptions. Water Science and Technology, 64(4), 930-944. doi:10.2166/wst.2011.709, Institutional Repository

Dürrenmatt, D. J. (2011). Data mining and data-driven modelling approaches to support wastewater treatment plant operation (Doctoral dissertation). doi:10.3929/ethz-a-006717398, Institutional Repository

Houweling, D., Wunderlin, P., Dold, P., Bye, C., Joss, A., & Siegrist, H. (2011). N₂O emissions: modeling the effect of process configuration and diurnal loading patterns. Water Environment Research, 83(12), 2131-2139. doi:10.2175/106143011X13176499923775, Institutional Repository

Huber, S. J. (2011). Temperature dependent removal of sodium chloride (NaCl) from synthetic nitrified urine (Master thesis). 46 p. , Institutional Repository

Joss, A., Derlon, N., Cyprien, C., Burger, S., Szivak, I., Traber, J., … Morgenroth, E. (2011). Combined nitritation–anammox: advances in understanding process stability. Environmental Science and Technology, 45(22), 9735-9742. doi:10.1021/es202181v, Institutional Repository

Efficient nitrogen removal from wastewater containing high concentrations of ammonium but little organic substrate has recently been demonstrated by several full-scale applications of the combined nitritation–anammox process. While the process efficiency is in most cases very good, process instabilities have been observed to result in temporary process failures. In the current study, conditions resulting in instability and strategies to regain efficient operation were evaluated. First, data from full-scale operation is presented, showing a sudden partial loss of activity followed by recovery within less than 1 month. Results from laboratory-scale experiments indicate that these dynamics observed in full scale can be caused by partial inhibition of the ammonia oxidizing bacteria (AOB), while anammox inhibition is a secondary effect due to temporarily reduced O₂ depletion. Complete anammox inhibition is observed at 0.2 mg O₂·L^–1, resulting in NO₂^– accumulation. However, this inhibition of anammox is reversible within minutes after O₂ depletion. Thus, variable AOB activity was identified as the key to reactor stability. With appropriate interpretation of the online NH₄⁺ signal, accumulation of NO₂^– can be detected indirectly and used to signal an imbalance of O₂ supply and AOB activity (no suitable online NO₂^– electrode is currently available). Second, increased abundance of nitrite-oxidizing bacteria (NOB; competing with anammox for NO₂^–) is known as another cause of instability. Based on a comparison of parallel full-scale reactors, it is suggested that an infrequent and short-term increased O₂ supply (e.g., for maintenance of aerators) that exceeds prompt depletion of oxygen by AOB may have caused increased NOB abundance. The volumetric air supply as a proxy for O₂ supply thus needs to be linked to AOB activity. Further, NOB can be washed out of the system during regular operation if the system is operated at a sludge age in the range of 45 days and by controlling the air supply according to the NO₃^– concentration in the treated effluent. Early detection of growing NOB abundance while the population is still low can help guide process operation and it is suggested that molecular methods of quantifying NOB abundance should be tested.

Joss, A., Baenninger, C., Foa, P., Koepke, S., Krauss, M., McArdell, C. S., … Siegrist, H. (2011). Water reuse: >90% water yield in MBR/RO through concentrate recycling and CO₂ addition as scaling control. Water Research, 45(18), 6141-6151. doi:10.1016/j.watres.2011.09.011, Institutional Repository

Mutzner, L. (2011). GIS based assessment of the fate of micropollutants in combined sewerages (Master thesis). 45 p. , Institutional Repository

Shimada, T., Li, X., Zilles, J. L., Morgenroth, E., & Raskin, L. (2011). Effects of the antimicrobial tylosin on the microbial community structure of an anaerobic sequencing batch reactor. Biotechnology and Bioengineering, 108(2), 296-305. doi:10.1002/bit.22934, Institutional Repository

Shimada, T., Morgenroth, E., Tandukar, M., Pavlostathis, S. G., Smith, A., Raskin, I., & Kilian, R. F. (2011). Syntrophic acetate oxidation in two-phase (acid–methane) anaerobic digesters. Water Science and Technology, 64(9), 1812-1820. doi:10.2166/wst.2011.748, Institutional Repository

The microbial processes involved in two-phase anaerobic digestion were investigated by operating a laboratory-scale acid-phase (AP) reactor and analyzing two full-scale, two-phase anaerobic digesters operated under mesophilic (35 °C) conditions. The digesters received a blend of primary sludge and waste activated sludge (WAS). Methane levels of 20% in the laboratory-scale reactor indicated the presence of methanogenic activity in the AP. A phylogenetic analysis of an archaeal 16S rRNA gene clone library of one of the full-scale AP digesters showed that 82% and 5% of the clones were affiliated with the orders Methanobacteriales and Methanosarcinales, respectively. These results indicate that substantial levels of aceticlastic methanogens (order Methanosarcinales) were not maintained at the low solids retention times and acidic conditions (pH 5.2–5.5) of the AP, and that methanogenesis was carried out by hydrogen-utilizing methanogens of the order Methanobacteriales. Approximately 43, 31, and 9% of the archaeal clones from the methanogenic phase (MP) digester were affiliated with the orders Methanosarcinales, Methanomicrobiales, and Methanobacteriales, respectively. A phylogenetic analysis of a bacterial 16S rRNA gene clone library suggested the presence of acetate-oxidizing bacteria (close relatives of Thermacetogenium phaeum, ‘Syntrophaceticus schinkii,’ and Clostridium ultunense). The high abundance of hydrogen consuming methanogens and the presence of known acetate-oxidizing bacteria suggest that acetate utilization by acetate oxidizing bacteria in syntrophic interaction with hydrogen-utilizing methanogens was an important pathway in the second-stage of the two-phase digestion, which was operated at high ammonium-N concentrations (1.0 and 1.4 g/L). A modified version of the IWA Anaerobic Digestion Model No. 1 (ADM1) with extensions for syntrophic acetate oxidation and weak-acid inhibition adequately described the dynamic profiles of volatile acid production/degradation and methane generation observed in the laboratory-scale AP reactor. The model was validated with historical data from the full-scale digesters.

Ye, X., Morgenroth, E., Zhang, X., & Finneran, K. T. (2011). Anthrahydroquinone-2,6,-disulfonate (AH₂QDS) increases hydrogen molar yield and xylose utilization in growing cultures of Clostridium beijerinckii. Applied Microbiology and Biotechnology, 92(4), 855-864. doi:10.1007/s00253-011-3571-1, Institutional Repository

Ante, S., Böhler, M., Ellerhorst, S., Fink, G., Knacker, T., Joss, A., … Zwickenpflug, B. (2010). NEPTUNE. New sustainable concepts and processes for optimization and upgrading municipal wastewater and sludge treatment. A specific targeted research project under the thematic priority 'Global change and ecosystems'. Work packages 1 and 3. Deliverable 1.1 and 3.3 · Fate and occurrence of micropollutants, microorganisms and viruses and strategies to minimize their release in plant effluent. sine loco: Eawag. , Institutional Repository

Boltz, J. P., Morgenroth, E., & Sen, D. (2010). Mathematical modelling of biofilms and biofilm reactors for engineering design. Water Science and Technology, 62(8), 1821-1836. doi:10.2166/wst.2010.076, Institutional Repository

Brockmann, D., & Morgenroth, E. (2010). Evaluating operating conditions for outcompeting nitrite oxidizers and maintaining partial nitrification in biofilm systems using biofilm modeling and Monte Carlo filtering. Water Research, 44(6), 1995-2009. doi:10.1016/j.watres.2009.12.010, Institutional Repository

Corominas, Ll., Flores-Alsina, X., Joss, A., Lettl, W., Roels, J., Siegrist, H., … Vanrolleghem, P. A. (2010). NEPTUNE. New sustainable concepts and processes for optimization and upgrading municipal wastewater and sludge treatment. A specific targeted research project under the thematic priority 'Global change and ecosystems'. Work package 1 · Technologies for WWTP upgrading. Deliverable 1.2 · Strategies to improve nutrient removal. sine loco: Eawag. , Institutional Repository

Hug, A. (2010). Phosphate recovery from urine by electrocoagulation (Master thesis). 38 p. , Institutional Repository

Phosphorus is an essential compound for plants. But the major phosphorus source for fertilizers - phosphate rock - is a limited resource. To close the nutrient cycle, phosphorus should be recovered from waste streams. Urine has a high phosphate content, which can be recovered as struvite.
Struvite is a magnesium-ammonium-phosphate (NH₄MgPO₄ · 6 H₂O) and can be used as a slow release fertilizer in agriculture. As magnesium is the limited compound in urine, a magnesium source has to be added for struvite precipitation. Conventional methods consist in the dosage of a magnesium salt. Electrocoagulation on the other hand dissolves magnesium electrochemically from a magnesium electrode.
For electrocoagulation magnesium is oxidized to magnesium ions at the magnesium anode, water is reduced to hydrogen gas at the steel cathode. To enhance the reaction speed a voltage source can be added. The voltage source can either be applied between the magnesium and a reference electrode (magnesium potential, three electrode configuration) or between the magnesium and the steel electrode (cell voltage, two electrode configuration). The advantage of the three electrode configuration being that the magnesium potential determines directly the reactions that can take place at the magnesium electrode.
Two sets of experiments have been conducted: voltammetry and batch experiments. For voltammetry the applied magnesium potential was changed with time to detect electrode characteristics. For the batch experiments the voltage source (magnesium potential or cell voltage) was kept constant over time.
Voltammetry and batch experiments showed that the magnesium electrode is sensitive to layer formation at magnesium potentials below -800 mV. An electrode potential of -600 mV seemed to be a very appropriate potential concerning reaction speed and energy consumption. An electrocoagulation reactor can either be operated by applying an electrode potential or a cell voltage. Applying a cell voltage will be the easier configuration, as no potentiostat is needed. A cell voltage of at least 1000 mV should be applied to prevent layer formation.
The monitored cell voltage/electrode potential (depending on electrode configuration) showed a maximum/minimum as phosphate was removed from urine. It can therefore be used as a parameter to control the magnesium dissolution in order to not waste magnesium. A continuous reactor could then be operated in sequencing batch mode, using three tanks:
storage tank, electrocoagulation reactor and settling tank.
It has been shown that electrocoagulation is a very functional method to recover struvite from natural urine. The advantage of electrocoagulation against chemical dosing will be found in a high magnesium efficiency and in a high automation possibility.

Kapałka, A., Joss, L., Anglada, Á., Comninellis, C., & Udert, K. M. (2010). Direct and mediated electrochemical oxidation of ammonia on boron-doped diamond electrode. Electrochemistry Communications, 12(12), 1714-1717. doi:10.1016/j.elecom.2010.10.004, Institutional Repository

Li, X., Upadhyaya, G., Yuen, W., Brown, J., Morgenroth, E., & Raskin, L. (2010). Changes in the structure and function of microbial communities in drinking water treatment bioreactors upon addition of phosphorus. Applied and Environmental Microbiology, 76(22), 7473-7481. doi:10.1128/AEM.01232-10, Institutional Repository

Marti, B. (2010). Bioelectrochemical removal of sulfur from source-separated urine (Master thesis). 32 p. , Institutional Repository

All of the sulfur in human excreta ends up as dissolved sulfate in the urine. If released to the environment, sulfate is not problematic because it is stable. However, if it comes in contact with water containing a large amount of organics, sulfate transformation to sulfide starts as soon as the water is depleted of oxygen and nitrate, producing a bad smell and intoxicating the microbiology. The largest problem in wastewater treatment is probably the corrosion in anaerobic sewer systems due to sulfide oxidation. Another problem is the H2S production during biogas generation, which necessitates gas washing. Since it is an essential plant nutrient [18] and a widely applied element in industry [23], recovering sulfur from urine can be of interest. Within the scope of a master thesis of 16 weeks the bioelectrochemical sulfate removal from stored, source-separated urine was analyzed. The iodometric method was applied to urine in order to measure dissolved sulfide, thiosulfate, and sulfite. In a microbial electrolysis cell a sulfate load of 4.10 ± 0.17 g SO²⁻₄ -S m⁻² biofilm surface d⁻¹ was microbially transformed to sulfide which was subsequently oxidized to elemental sulfur at an anode potential of 0.06 V. Comparison between dissimilatory sulfate reduction with and without electrochemical sulfide oxidation showed an increase of the sulfate degradation rate of 30 % to 1.48 g SO²⁻₄ -S m⁻² biofilm surface d⁻¹ when sulfide was electrochemically oxidized. A mass balance of sulfur over the reactor showed that dissolved sulfur disappeared in the reactor. Based on the sulfur balance, a sulfide oxidation rate was estimated yielding 0.35 g SH⁻-S m⁻²d⁻¹. The process combination of biological sulfate reduction and subsequent partial sulfide oxidation to elemental sulfur was applied successfully to stored, source-separated urine. In a future work, the process parameters need to be improved, first of all the tradeoff between biofilm surface on the anode and free anode surface for sulfide oxidation. A separation of the biological and electrochemical processes would be suitable for further experiments on the bioelectrochemical sulfate reduction. Additionally a more throughout analysis of the conversion of the sulfur species in the reactor should be done. The limitations of the sulfate degradation need to be analyzed.

Menniti, A., & Morgenroth, E. (2010). Mechanisms of SMP production in membrane bioreactors: choosing an appropriate mathematical model structure. Water Research, 44(18), 5240-5251. doi:10.1016/j.watres.2010.06.040, Institutional Repository

Menniti, A., & Morgenroth, E. (2010). The influence of aeration intensity on predation and EPS production in membrane bioreactors. Water Research, 44(8), 2541-2553. doi:10.1016/j.watres.2009.12.024, Institutional Repository

Morgan-Sagastume, F., Karlsson, A., Werker, A., De Gussem, K., Roels, J., Weemaes, M., … Petrova, S. (2010). NEPTUNE. New sustainable concepts and processes for optimization and upgrading municipal wastewater and sludge treatment. A specific targeted research project under the thematic priority 'Global change and ecosystems'. Work package 5 · Dissemination. Deliverable 5.4 · Catalogue with criteria for evaluating technologies. sine loco: Eawag. , Institutional Repository

Morgenroth, E., Buergmann, H., & Udert, K. (2010). Functional diversity in wastewater treatment. Eawag News [engl. ed.], 69, 15-17. , Institutional Repository

Morgenroth, E., Bürgmann, H., & Udert, K. (2010). Funktionelle Vielfalt in der Abwasserreinigung. Eawag News [dtsch. Ausg.], 69, 15-17. , Institutional Repository

Obrecht, J. (2010). Online Überwachung biologischer Abwasserreinigungsprozesse (Master thesis). 75 p. , Institutional Repository

Der Anammox-Prozess (anaerobe Ammoniumoxidierung) ist eine Möglichkeit Stickstoff biologisch abzubauen. Anammox hat im Gegensatz zu Nitrifikation/Denitrifikation den Vorteil, dass kein leicht abbaubarer Kohlenstoff verbraucht wird. Die Anwendung dieses Prozesses in dezentralen Urinbehandlungsanlagen wird an der Eawag in Dübendorf seit 2008 in einer Pilotanlage getestet. Die Messungen mit einer Sauerstoff-, einer Leitfähigkeits- und einer pHSonde haben gezeigt, dass die Signale während eines Zyklus einen charakteristischen Verlauf aufweisen.
Das führte zur Vermutung, dass sich der Prozess anhand dieser drei Sondensignale überwachen lässt. Das Ziel war die Untersuchung folgender Frage: Können anhand einer Kombination der drei Parameter Sauerstoff, pH-Wert und Leitfähigkeit biologische Prozesse identifiziert und quantifiziert werden?
In der vorliegenden Arbeit werden folgende vier Hauptaufgaben vorgestellt:
• Tabelle zur quantitativen Bewertung der Sondensignale
• Quantifizierung des Stickstoffabbaus mittels der Leitfähigkeit
• Modellierung der Leitfähigkeit
• Unterscheidung von Anammox und heterotropher Denitrifikation anhand des pH-Werts und der Leitfähigkeit.
Die Tabelle zur qualitativen Bewertung der Sondensignale ist ein nützliches Mittel um rasch eine Aussage zum Zustand des Systems machen zu können. In der zur Verfügung stehenden Zeit, konnten nicht alle Störfälle beurteilt werden. Sie müssen noch modelliert werden, damit man die Tabelle vervollständigen kann.
Die Quantifizierung des Stickstoffabbaus durch die Leitfähigkeitsabnahme ist ein interessanter Ansatz. Bedingt durch einige Parameter - das Strippen von CO2 und der Abbau von organischen Stoffen zu Beginn des Zyklus - ist die Unsicherheit der Bestimmung des Stickstoffabbaus derzeit noch zu gross, um eine zuverlässige Aussage machen zu können. Es sind weitere Untersuchungen nötig um festlegen zu können, wie diese Parameter miteinzubeziehen sind.
Die Leitfähigkeit lässt sich mit der allgemeinen Formel gut berechnen. Werden bei der Berechnung alle gemessenen Ionen miteinbezogen, wird die Leitfähigkeit durch das Ergebnis der Modelle deutlich überschätzt. Ein besseres Resultat wird erzielt, wenn man die Leitfähigkeit mit der Aktivität modelliert.
Eine Unterscheidung von heterotropher Denitrifikation und Anammox ist zurzeit (noch) nicht möglich. Bei beiden Prozessen nimmt der pH-Wert zu und die Leitfähigkeit nimmt ab. Die modellierten Veränderungen sind so gering, dass die Sondensignale unter Einbezug der Messunsicherheit schwierig zu interpretieren sind. Zudem ist die Frage des Einflusses von Puffern noch nicht geklärt.
Zusammenfassend ist zu sagen, dass die Onlineüberwachung mit Sonden, die die beschriebenen drei Schlüsselsignale ermitteln, ein guter Ansatz ist. Dieses Vorgehen ermöglicht eine Prozessüberwachung ohne grossen Messaufwand. Der pH-Wert wird bereits heute für die Steuerung der Zykluslänge verwendet. Die Sauerstoffkonzentration gibt Auskunft über die Funktion der Belüftung und die Messdaten der Leitfähigkeit können evtl. in Zukunft für die Quantifizierung des Stickstoffabbaus verwendet werden.

Ort, C., Lawrence, M. G., Rieckermann, J., & Joss, A. (2010). Sampling for pharmaceuticals and personal care products (PPCPs) and illicit drugs in wastewater systems: are your conclusions valid? A critical review. Environmental Science and Technology, 44(16), 6024-6035. doi:10.1021/es100779n, Institutional Repository

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

Siegrist, H., Joss, A., & Miladinovic, N. (2010). NEPTUNE. New sustainable concepts and processes for optimization and upgrading municipal wastewater and sludge treatment. A specific targeted research project under the thematic priority 'Global change and ecosystems'. Final activity report. sine loco: Eawag. , Institutional Repository

Ternes, T., Joss, A., Knacker, T., Oehlmann, J., von Gunten, U., & Siegrist, H. (2010). NEPTUNE. New sustainable concepts and processes for optimization and upgrading municipal wastewater and sludge treatment. A specific targeted research project under the thematic priority 'Global change and ecosystems'. Work package 5 · Dissemination. Deliverable 5.2: Conclusions of the workshop about the revision of the WFD priority substances based on the Neptune outcome. sine loco: Eawag. , Institutional Repository

Zwickenpflug, B., Böhler, M., Sterkele, B., Joss, A., Siegrist, H., Traber, J., … Fink, G. (2010). Einsatz von Pulveraktivkohle zur Elimination von Mikroverunreinigungen aus kommunalem Abwasser. Dübendorf: Eawag. , Institutional Repository

Abegglen, C., Joss, A., & Siegrist, H. (2009). Eliminating micropollutants: wastewater treatment methods. Eawag News [engl. ed.], 67, 25-27. , Institutional Repository

Abegglen, C., Joss, A., & Siegrist, H. (2009). Eliminer des micropolluants: techniques d'épuration. Eawag News [éd. fr.], 67, 25-27. , Institutional Repository

Abegglen, C., Joss, A., Boehler, M., Buetzer, S., & Siegrist, H. (2009). Reducing the natural color of membrane bioreactor permeate with activated carbon or ozone. Water Science and Technology, 60(1), 155-165. doi:10.2166/wst.2009.331, Institutional Repository

Abegglen, C., Joss, A., & Siegrist, H. (2009). Spurenstoffe eliminieren: Kläranlagentechnik. Eawag News [dtsch. Ausg.], 67, 25-27. , Institutional Repository

Abegglen, C., Joss, A., McArdell, C. S., Fink, G., Schlüsener, M. P., Ternes, T. A., & Siegrist, H. (2009). The fate of selected micropollutants in a single-house MBR. Water Research, 43(7), 2036-2046. doi:10.1016/j.watres.2009.02.005, Institutional Repository

Membrane bioreactor (MBR) technology is an interesting option for single-house wastewater treatment or small communities. Because typically a very high effluent quality is achieved with respect to pathogens, suspended solids, organics and nitrogen, the permeate is well suited for reuse. Little is known about the fate of micropollutants in such small systems. The differences between centralized and decentralized biological wastewater treatment with respect to micropollutants are manifold: besides the operational parameters like hydraulic and sludge retention time, the main difference is in the load variation. While the influent load is expected to be more or less constant in large catchments, it varies strongly in small MBRs due to irregular consumption (e.g. of medication by individuals). Concentrations of micropollutants are higher by a factor 50–1000 than in centralized treatment. It is also unknown how reliable degradation of micropollutants is in case of irregular exposure.
In this study, two experiments were conducted in a small MBR treating the wastewater of a three-person household. During normal operation of the treatment plant, 25 pharmaceuticals (antibiotics, antiphlogistics, lipid regulators, iodinated contrast media and hormones) that had not been used by members of the household were added in concentrations typical for municipal wastewater. The removal of most substances was in the same range as for centralized wastewater treatment. It was shown that biological transformation was the main elimination process while adsorption to the activated sludge was negligible for most substances due to the low sludge production at high sludge retention time. No appreciable lag for inducing biological degradation was observed. The high hydraulic and sludge residence time had a positive effect on the elimination of slowly degradable substances, but this was partly compensated by the lower biological activity.
An experiment with antibiotics concentrations typical for decentralized treatment (between 500 and 1000 μg l⁻¹; sulfamethoxazole, sulfapyridine, trimethoprim, clarithromycin, roxithromycin) did not show an inhibitory effect on either nitrification or denitrification.

Boltz, J. P., Morgenroth, E., deBarbadillo, C., Dempsey, M. J., McQuarrie, J. P., Ghylin, T., … Nerenberg, R. (2009). Biofilm reactor technology and design. In T. L. Krause & A. B. Pincince (Eds.), WEF manual of practice No. 8 ASCE manuals and reports on engineering practice No. 76: Vol. 2. Design of municipal wastewater treatment plants. Liquid treatment processes (p. (238 pp.). Retrieved from https://www.accessengineeringlibrary.com/content/book/9780071663588/toc-chapter/chapter13/section/section1, Institutional Repository

Goosse, P., Steiner, M., & Joss, A. (2009). Safe and high quality food production using low quality waters and improved irrigation systems and management (SAFIR). A specific targeted research project under the thematic priority "Food quality and safety". Work package 1 · Water treatment and irrigation technology. D1_5(extra deliverable): evaluation of alternative water resources for irrigation in agriculture. sine loco: sine nomine. , Institutional Repository

Joss, A., Salzgeber, D., Eugster, J., König, R., Rottermann, K., Burger, S., … Siegrist, H. (2009). Full-scale nitrogen removal from digester liquid with partial nitritation and anammox in one SBR. Environmental Science and Technology, 43(14), 5301-5306. doi:10.1021/es900107w, Institutional Repository

Joss, A., Böhler, M., Wedi, D., & Siegrist, H. (2009). Proposing a method for online permeability monitoring in membrane bioreactors. Water Science and Technology, 60(2), 497-506. doi:10.2166/wst.2009.370, Institutional Repository

Menniti, A., Kang, S., Elimelech, M., & Morgenroth, E. (2009). Influence of shear on the production of extracellular polymeric substances in membrane bioreactors. Water Research, 43(17), 4305-4315. doi:10.1016/j.watres.2009.06.052, Institutional Repository

Morgenroth, E., & Milferstedt, K. (2009). Biofilm engineering: linking biofilm development at different length and time scales. Reviews in Environmental Science and Biotechnology, 8(3), 203-208. doi:10.1007/s11157-009-9163-1, Institutional Repository

Wick, A., Fink, G., Joss, A., Siegrist, H., & Ternes, T. A. (2009). Fate of beta blockers and psycho-active drugs in conventional wastewater treatment. Water Research, 43(4), 1060-1074. doi:10.1016/j.watres.2008.11.031, Institutional Repository

Brepols, C., Dorgeloh, E., Frechen, F. B., Fuchs, W., Haider, S., Joss, A., … Wozniak, T. (2008). Upgrading and retrofitting of municipal wastewater treatment plants by means of membrane bioreactor (MBR) technology. Desalination, 231(1–3), 20-26. doi:10.1016/j.desal.2007.11.035, Institutional Repository

Joss, A., Siegrist, H., & Ternes, T. A. (2008). Are we about to upgrade wastewater treatment for removing organic micropollutants?. Water Science and Technology, 57(2), 251-255. doi:10.2166/wst.2008.825, Institutional Repository

Siegrist, H., Salzgeber, D., Eugster, J., & Joss, A. (2008). Anammox brings WWTP closer to energy autarky due to increased biogas production and reduced aeration energy for N-removal. Water Science and Technology, 57(3), 383-388. doi:10.2166/wst.2008.048, Institutional Repository

Wedi, D., & Joss, A. (2008). Dimensioning of membrane bioreactors for municipal wastewater treatment. Water Science and Technology, 57(6), 829-835. doi:10.2166/wst.2008.117, Institutional Repository

Boehler, M., Joss, A., Buetzer, S., Holzapfel, M., Mooser, H., & Siegrist, H. (2007). Treatment of toilet wastewater for reuse in a membrane bioreactor. Water Science and Technology, 56(5), 63-70. doi:10.2166/wst.2007.557, Institutional Repository

De Wilde, W., Besancon, A., Joss, A., Sharma, S., Amy, G., Pollice, A., … Ng, H. Y. (2007). Reclaim water. A specific targeted research project under the thematic priority "Global change and ecosystems". Work package 1 assessment and development of water reclamation technology. Deliverable D 1.1 characterisation of unit operations for wastewater reclamation in terms of upgrading capability, reliability and flexibility. sine loco: sine nomine. , Institutional Repository

Göbel, A., McArdell, C. S., Joss, A., Siegrist, H., & Giger, W. (2007). Fate of sulfonamides, macrolides, and trimethoprim in different wastewater treatment technologies. Science of the Total Environment, 372(2–3), 361-371. doi:10.1016/j.scitotenv.2006.07.039, Institutional Repository

Jenni, S. (2007). Modellierung der autotrophen Deammonifikation (Master thesis). 98 p. , Institutional Repository

Mit dem Schlammwasser aus der anaeroben Schlammfaulung werden 15-20% der Gesamtstickstofffracht in den Zulauf der Abwasserreinigungsanlage zurückgeführt. Mit einer separaten Schlammwasserbehandlung kann die Stickstofffracht im Zulauf der Anlage verkleinert und somit die Stickstoffelimination signifikant gesteigert werden. Die autotrophe Deammonifikation bietet dabei eine Reihe von Vorteilen gegenüber der konventionellen Schlammwasserbehandlung mit Nitrifikation und Denitrifikation. In einem Sequencing Batch Reaktor (SBR) kann die autotrophe Deammonifikation in einem Reaktor kombiniert werden. Das Verfahren wurde so im Pilotmassstab an der EAWAG bereits über mehrere Monate erfolgreich betrieben. Ausstehend ist noch die Umsetzung des Verfahrens im Vollmassstab, die auf den Kläranlagen Werdhölzli (Zürich) und St. Gallen geplant ist.
In der vorliegenden Arbeit ist die Umsetzung des Verfahrens auf der Kläranlage Werdhölzli im Pilotmassstab getestet worden. Der 400L-Reaktor wurde dazu mit Schlamm aus der konventionellen Schlammwasserbehandlung des Werdhölzlis gefüllt und im Verhältnis 1:40 mit Anammoxschlamm aus der EAWAG angeimpft. Die Anammoxorganismen konnten allerdings nicht einwachsen, da der Schlamm eine zu hohe Nitritoxidationsaktivität aufwies. Innerhalb von vier Wochen konnte mit einer Substratlimitierung keine entscheidende Verminderung der Nitritoxidierer erreicht werden.
Für die Modellierung der einstufigen autotrophen Deammonifikation ist ein dynamisches Modell entwickelt und in AQUASIM implementiert worden. Experimentelle Untersuchungen einzelner kinetischer Parameter ergaben, dass der Nitritsättigungsbeiwert der Anammoxorganismen bei ungefähr 0.5 mgNO₂-N/L liegt und dass weder die Nitritoxidierer noch die Anammoxorganismen durch hohe Ammoniakkonzentrationen gehemmt werden. Das Modell ist mit Messdaten aus dem Betrieb der Pilotanlage kalibriert worden. Die beste Übereinstimmung zwischen den gemessenen und den modellierten Stickstoffzehrungsraten resultiert mit einer maximalen Wachstumsgeschwindigkeit der Anammoxorganismen von 0.083 d^-1.
Mit dem Modell wurde die Einwachsphase mit einer geringen Anfangsnitritoxidationsaktivität bei 35 und 25°C simuliert. Der Reaktor kann bei beiden Betriebstemperaturen problemlos eingefahren werden. Nach rund 30 bzw. 60 Tagen kann der Reak-tor mit einer hydraulischen Aufenthaltszeit von einem Tag und einem Schlammalter von rund 21 Tagen stabil betrieben werden. Die Konzentration der Nitritoxidierer nimmt dabei ab. Aus dieser und ähnlichen Simulationen lassen sich wichtige Erkenntnisse für den optimalen Betrieb eines Reaktors gewinnen.

Salzgeber, D., Joss, A., & Siegrist, H. (2007). Autotrophe Schlammwasserentstickung (Nitritation/Anammox). Im SBR-Verfahren (Sequencing batch reactor). GWA Gas, Wasser, Abwasser, 87(3), 205-209. , Institutional Repository

Salzgeber, D. (2007). Biologische Schlammwasserentstickung mit Anammox im einstufigen SBR (Master thesis). 59 p. , Institutional Repository

Die autotrophe Entstickung von ammoniumreichem Schlammwasser wird in einem 400L SBR-Reaktor während eines halben Jahres ohne Unterbruch betrieben. Dabei wird ein Teil des Ammoniums zu Nitrit oxidiert (Teilnitritation) und das restliche Ammonium mit Hilfe des gebildeten Nitrits zu molekularem Stickstoff oxidiert (Anammox: anaerob Ammoniumoxidation). Die Stickstoffeliminationsleistung liegt bei bis zu 680 gN m^-3 d^-1 bei einer Elimination von 90 % des Stickstoffs. Der Reaktor wird bei 30°C, 25°C und 20°C betrieben. Die tiefsten hydraulischen Aufenthaltszeiten (HRT) von unter einem Tag werden bei 30°C erreicht, wobei bei dieser Temperatur die Anammoxbakterien auch die höchsten Aktivitäten von über 2000 gN m^-3 d^-1 aufweisen. Der Betrieb kann bei 25°C und 20°C ebenfalls stabil aufrechterhalten werden, die HRT kann bei 20°C aber nicht mehr unter 1.5 Tage gesenkt werden. Während der ersten drei Monate kann für die Anammoxbakterien eine Wachstumsrate von 0.029 d^-1 beobachtet werden.
Der Ammoniumabbau kann sowohl in einem getakteten Betrieb durchgeführt werden, bei
dem auf jede 15-30 Minuten dauernde belüftete Phase eine unbelüftete Phase folgt, als auch
mit einer kontinuierlichen Belüftung, bei welcher die Ammoniumoxidation und die
Anammoxreaktion simultan ablaufen. Das Verfahren kann über das Leitfähigkeits-, pH- oder
Nitritsignal geregelt werden und wird im Sommer `07 in der ARA Werdhölzli in einem 1400
m³-Becken implementiert.

The autotrophic deammonification of ammonium-rich digester supernatant in a 400L SBR-reactor has been carried out for a half year without any interruptions. In this process a part of the ammonium is oxidized to nitrite. The remaining ammonium is oxidized under anoxic conditions with the formed nitrite to molecular nitrogen (Anammox: anaerobic ammonium oxidation). The nitrogen removal capacity is up to 680 gN m^-3 d^-1 with a elimination of 90 % of the nitrogen. The reactor is operated at 30°C, 25°C and 20°C. The shortest hydraulic
retention time (HRT) of less than one day is achieved at 30°C. At 30°C the Anammox-bacteria also exhibits the highest activity by removing over to 2000 gN m^-3 d^-1. Likewise, the operation can be stably maintained at 25°C and 20°C, but the HRT can not be shortened to less than 1.5 days at 20°C. Over the period of the first three months a growth rate of 0.029 d^-1 for the Anammox bacteria could be observed.
The ammonium degradation can be accomplished two ways: in an alternating mode where the reactor is aerated for a period of 15-30 minutes and then stirred, or in a continuous mode where the aeration is constant. The ammonium oxidation runs in this mode simultaneously to the Anammox-reaction. The procedure can be regulated using the conductivity, the pH-value or the nitrite concentration. This procedure will be implemented in the ARA Werdhoelzli/Zürich in the summer of 2007 in a 1400 m³-reactor.

Siegrist, H., Joss, A., & Ternes, T. (2007). Fate of micropollutants in drinking and wastewater treatment and consequences for process design (p. (8 pp.). Presented at the 4th leading edge conference on water and wastewater technologies. Singapore. , Institutional Repository

Siegrist, H., & Joss, A. (2007). Mikroverunreinigungen. Technische Verfahren zur Elimination. GWA Gas, Wasser, Abwasser, 87(11), 861-867. , Institutional Repository

de Mes, T. (2007). Fate of estrogens in biological treatment of concentrated black water (Doctoral dissertation). 154 p. , Institutional Repository

Sewage treatment plants (STPs) effluents were found to have estrogenic character which is mainly due to the presence of estrone (E1), 17β-estradiol (E2) and 17α-ethynylestradiol (EE2). E1 and E2 are natural hormones excreted by mammals in urine and faeces, whereas EE2 is a synthetic hormone present in the contraceptive pill. The largest part of the estrogens is excreted via urine as glucuronide or sulphate conjugate with no estrogenic properties. These conjugates can be cleaved back to their original form by bacterial enzymes, where deconjugation of glucuronide conjugates is faster than of sulphate conjugates.
Human excreted estrogens are insufficiently removed in conventional treatment systems designed to remove bulk organic matter and nutrients. Maximum reported concentrations in STP effluents are 76 ng/l for E1, 64 ng/l for E2 and 42 ng/l for EE2. Effects on fish were already prevalent at 3.3 ng E1/l, 1 ng E2/l and 0.03 ng EE2/l, values that are often exceeded in surface waters.
Present research focused on the fate of estrogens in sanitation concepts with source separated collection and treatment of domestic wastewater i.e. black water (toilet), grey water (personal hygiene, kitchen) and rain water. Source separated collection offer benefits in terms of energy and resource conservation. By applying vacuum toilets in these concepts, the black water volume containing estrogens is about 7 L per person per day, whereas in conventional sanitation concepts this volume (including rain water) is about 200 L per person per day.
Adsorption and biodegradation are considered the most important processes for the removal of estrogens in biological wastewater treatment systems, and therefore adsorption constants and first order degradation rates were determined. Besides, their fate was investigated in a concentrated black water pilot treatment system consisting of UASB septic tank, with aerobic post-treatment. Determination was established by HPLC with UV, fluorescence and diode array detection and GC-MS for environmental relevant concentrations.
The highest degradation rates were obtained under aerobic redox conditions for all three estrogens, with EE2 being the most persistent as was also confirmed in literature. Increasing sludge retention time had a positive effect on the biological removal rates, whilst nitrifiers did not contribute significantly to it. The results showed that reduced bioavailability, e.g. desorption of adsorbed estrogens, can suppress the conversion rate. During anaerobic conditions, a reduction of E1 to E2 was observed but no decline for the sum of E1 and E2 nor EE2 was observed in various types of sludge.
In the pilot UASB septic tank effluent, total concentrations of 4.02 μg E1/l and 18.69 μg E2/l, of which >70% for E1 and >80% for E2 were in conjugated form. EE2 concentrations were below the detection limit. In the effluent of the post-treatment E1 and E2 were present in concentrations of 1.37±1.45 μg/l and 0.65±0.78 μg/l, respectively. The limited deconjugation of conjugated estrogens during treatment was demonstrated when UASB septic tank was spiked with the sulphate conjugate of E2, revealing that 99% of the detected E2 in the final effluent is in conjugated form.
Even though the application of source separation can prevent storm water overflow and reduce the volume of the wastewater in which estrogens are present, high effluent concentrations after biological treatment necessitate additional treatment. Besides, there is a need for information on the deconjugation rates and the behaviour of conjugated estrogens in general.

Alder, A. C., Bruchet, A., Carballa, M., Clara, M., Joss, A., Löffler, D., … Ternes, T. A. (2006). Consumption and occurrence. In T. A. Ternes & A. Joss (Eds.), Human pharmaceuticals, hormones and fragrances. The challenge of micropollutants in urban water management (pp. 15-54). Retrieved from https://iwaponline.com/ebooks/book/19/Human-Pharmaceuticals-Hormones-and-Fragrances-The, Institutional Repository

Amy, G., Cheng, X., de Heyder, B., Hein, A., Jefferson, B., Joss, A., … Kazner, C. (2006). Reclaim water. A specific targeted research project under the thematic priority "Global change and ecosystems". Work package 1 · assessment and development of water reclamation technology. Milestone M 1.2 · Set up of all required analytical skills or contact to the corresponding labs. sine loco: sine nomine. , Institutional Repository

Fletcher, H., Kekre, K., Guihe, T., Seah, H., Guglielmi, G., Andreottola, G., … Siegrist, H. (2006). Design. In S. Judd & C. Judd (Eds.), The MBR Book. Principles and applications of membrane bioreactors in water and wastewater treatment (pp. 123-162). doi:10.1016/B978-185617481-7/50005-2, Institutional Repository

Joss, A., Zabczynski, S., Göbel, A., Hoffmann, B., Löffler, D., McArdell, C. S., … Siegrist, H. (2006). Biological degradation of pharmaceuticals in municipal wastewater treatment: proposing a classification scheme. Water Research, 40(8), 1686-1696. doi:10.1016/j.watres.2006.02.014, Institutional Repository

Joss, A., Klaschka, U., Knacker, T., Liebig, M., Lienert, J., Ternes, T. A., & Wennmalm, A. (2006). Source control, source separation. In T. A. Ternes & A. Joss (Eds.), Human pharmaceuticals, hormones and fragrances. The challenge of micropollutants in urban water management (pp. 353-384). Retrieved from https://iwaponline.com/ebooks/book/19/Human-Pharmaceuticals-Hormones-and-Fragrances-The, Institutional Repository

Joss, A., Carballa, M., Kreuzinger, N., Siegrist, H., & Zabczynski, S. (2006). Wastewater treatment. In T. A. Ternes & A. Joss (Eds.), Human pharmaceuticals, hormones and fragrances. The challenge of micropollutants in urban water management (pp. 243-292). London, UK: IWA Publishing. , Institutional Repository

Siegrist, H., & Joss, A. (2006). Leading-edge processes on urban wastewater treatment - presentation of the European Project NEPTUNE (p. (6 pp.). Presented at the 10a fiera internazionale del recupero di materia ed energia e dello sviluppo sostenibile (Ecomondo 2006). Rimini, Italy. , Institutional Repository

Siegrist, H., & Joss, A. (2006). Leistung der heutigen Abwasserreinigung und innovative Ansätze für das zukünftige Design (p. (9 pp.). Presented at the DWA Tagung "Elimination organischer Spurenstoffe und Mikroorganismen". Koblenz, Germany. , Institutional Repository

Heute sind in der Europäischen Union (EU) etwa 100'000 verschiedene Chemikalien gemeldet, von denen rund 30'000 in einer Menge von mehr als einer Tonne auf dem Markt vertrieben werden [1]. Es ist unvermeidlich, dass bei der Herstellung und Entsorgung sowie beim Gebrauch der Stoffe auch Anteile in die Umwelt gelangen.

Durch die sich die ständig verbessernde chemische Analytik findet man im Abwasser, in den Gewässern und im Klärschlamm vermehrt Verbindungen in sehr niedrigen Konzentrationsbereichen (Mikro- und Nanogramm pro Liter), die als Mikroverunreinigungen bezeichnet werden. Dazu gehören bekannte Vertreter wie das Pestizid Atrazin, der Kunststoffzusatz Bispenol A und das Benzinantiklopfmittel Methyl-tertiär-butylmethyläther. Weniger bekannt ist, dass sich darunter auch sehr viele Verbindungen für den täglichen Gebrauch wie z.B. Arzneimittel befinden. Heute werden in der EU ca. 3'300 verschiedene Stoffe als Arzneimittel verwendet. Mengenmässig bedeutsam sind Wirkstoffe, die u.a. als Analgetika, Antibiotika, Antidiabetika, Betablocker, Kontrazeptiva, Lipidsenker, Psychopharmaka oder Zytostatika eingesetzt werden.

Arzneimittel gelangen in der Regel über die natürlichen Ausscheidungen wie Urin oder Fäkalien in das Abwassersystem. Ein nicht zu vernachlässigender Anteil der im Abwasser enthaltenen Arzneimittel wird aber auch durch unsachgemässe Entsorgung über die Toilette eingetragen. Eine deutsche Studie [2] untersuchte das Vorkommen von 55 Arzneimittelwirkstoffen und 9 Metaboliten im Ablauf von 49 Kläranlagen sowie in den jeweiligen Gewässern, in die die geklärten Abwässer eingeleitet werden (Vorfluter). Dabei konnten in den Kläranlagenabläufen 36 Wirkstoffe und 5 Metaboliten in Konzentrationen bis zu mehreren μg/l nachgewiesen werden. In den Gewässern wurden noch Spitzenkonzentrationen von über 1 μg/l (z.B. Betablocker und Antiepileptika) gemessen.

Darüber hinaus machen in den letzten Jahren neuartige Umwelteffekte, wie die Verweiblichung von Fischen, von sich reden. Sie werden zum Teil auf den chronischen Eintrag hormonaktiver (endokriner) Substanzen zurückgeführt. Dazu gehören neben den körpereigenen Hormonen, die ebenso mit dem Urin ausgeschieden werden, auch diejenigen Arzneimittel, die aufgrund ihrer hormonellen Wirkung eingesetzt werden wie z.B. die Kontrazeptiva und Antidiabetika. Einigen anderen Arzneimittelwirkstoffen, wie z.B. β-Sitosterol (zur Senkung des Cholesterinspiegels) und Clenbuterol (Asthmamittel), wird zusätzlich zu ihrer nichthormonellen Hauptwirkung, eine hormonelle Nebenwirkung zugeschrieben. Für die meisten Arzneimittel sind jedoch keine endokrinen Wirkungen bekannt. Das mag aber auch daran liegen, dass sie niemals auf etwaige hormonelle Wirkungen getestet wurden. Es ist daher nicht ausgeschlossen, dass die Gruppe der Arzneimittelwirkstoffe mit ungewollten hormonellen Nebenwirkungen viel grösser ist als angenommen.

Der vorliegende Artikel gibt anhand ausgewahlter Beispiele einen Überblick über die Eliminationsprozesse und stellt mogliche Massnahmen zur Diskussion.

Wanner, O., Eberl, H., Morgenroth, E., Noguera, D., Picioreanu, C., Rittmann, B., & van Loosdrecht, M. (2006). Mathematical modeling of biofilms. Scientific and technical report: Vol. 18. doi:10.2166/9781780402482, Institutional Repository

Ternes, T. A., & Joss, A. (Eds.). (2006). Human pharmaceuticals, hormones and fragrances. The challenge of micropollutants in urban water management. doi:10.2166/9781780402468, Institutional Repository

Göbel, A., Thomsen, A., McArdell, C. S., Joss, A., & Giger, W. (2005). Occurrence and sorption behavior of sulfonamides, macrolides, and trimethoprim in activated sludge treatment. Environmental Science and Technology, 39(11), 3981-3989. doi:10.1021/es048550a, Institutional Repository

Huber, M. M., Göbel, A., Joss, A., Hermann, N., Löffler, D., McArdell, C. S., … von Gunten, U. (2005). Oxidation of pharmaceuticals during ozonation of municipal wastewater effluents: a pilot study. Environmental Science and Technology, 39(11), 4290-4299. doi:10.1021/es048396s, Institutional Repository

Joss, A., Goosse, P., Cao, T. A., & Siegrist, H. (2005). Langzeitverhalten der Permeabilität von getauchten Membranmodulen für die kommunale Abwasserreinigung. In T. Melin (Ed.), Membrantechnik in der Wasseraufbereitung und Abwasserbehandlung. Perspektiven, Neuentwicklungen und Betriebserfahrungen im In- und Ausland. Begleitbuch zur 6. Aachener Tagung Siedlungswasserwirtschaft und Verfahrenstechnik, 26. - 27.10.2005 (p. (15 pp.). Retrieved from https://www.avt.rwth-aachen.de/cms/AVT/Forschung/Sonstiges/Publikationen/~iavo/Details/?file=47592, Institutional Repository

Joss, A., Keller, E., Alder, A. C., Göbel, A., McArdell, C. S., Ternes, T., & Siegrist, H. (2005). Removal of pharmaceuticals and fragrances in biological wastewater treatment. Water Research, 39(14), 3139-3152. doi:10.1016/j.watres.2005.05.031, Institutional Repository

Siegrist, H., Joss, A., Ternes, T., & Oehlmann, J. (2005). Fate of EDCS in wastewater treatment and EU perspective on EDC regulation (pp. 3142-3165). Presented at the 78th annual technical exhibition and conference, Water Environment Federation, WEFTEC.05®. Alexandria, VA: Water Environment Federation. , Institutional Repository

Ternes, T., Joss, A., Kreuzinger, N., Miksch, K., Lema, J. M., von Gunten, U., … Siegrist, H. (2005). Removal of pharmaceuticals and personal care products - results of the poseidon project. Presented at the 78th Annual Technical Exhibition and Conference, Water Environment Federation WEFTEC. Washington DC, USA: 2005 Water Environment Federation. , Institutional Repository

Eberl, H. J., van Loosdrecht, M. C. M., Morgenroth, E., Noguera, D. R., Perez, J., Picioreanu, C., … Wanner, O. (2004). Modelling a spatially heterogeneous biofilm and the bulk fluid: selected results from Benchmark Problem 2 (BM2). Water Science and Technology, 49(11-12), 155-162. doi:10.2166/wst.2004.0829, Institutional Repository

Joss, A., Alder, A., Huber, M., Göbel, A., von Gunten, U., Keller, E., … Siegrist, H. (2004). Abbau von Mikroverunreinigungen in der kommunalen Abwasserreinigung. In Mikroverunreinigungen in der Abwasserreinigung (p. (18 pp.). Glattbrugg: Verband Schweizer Abwasser- und Gewässerschutzfachleute. , Institutional Repository

Zwei wichtige Aspekte haben dazu geführt, dass Mikroverunreinigungen in der aquatischen Umwelt gegenwärtig ein wichtiges Thema ist: Einerseits ist mit der Reduktion des Nährstoffeintrages in die Gewässer das Problem der Eutrophierung seit den 70er Jahre weitgehend entschärft worden. In der Folge konnte festgestellt werden, dass auch ohne Überdüngung der Gewässer einige Schadensbilder nicht aus unseren Fliessgewässern verschwunden sind (siehe Beitrag Patricia Holm). Andererseits haben die Weiterentwicklungen des letzten Jahrzehnts in der analytischen Chemie die Nachweisgrenze um etwa einen Faktor 1000 gesenkt. Dadurch konnten diese Stoffe nicht nur in der Umwelt, sondern teilweise auch im Trinkwasser quantifiziert werden und haben somit die Diskussion betreffend deren Bedeutung in Gang gesetzt. Abbildung 1 zeigt die gemessenen Arzneimittelkonzentration im Ablauf einer deutschen nährstoffeliminierenden Kläranlage (ARA Wiesbaden, 300'000 Einwohnergleichwerte, 11-13 Tage Schlammalter). Diese Daten zeigen exemplarisch, dass im gereinigten kommunalen Abwasser Arzneimittel typischerweise in Konzentrationen bis zu 5 μg L^-1 gemessen werden. Im vorliegenden Beitrag wird diskutiert, welchen Eliminationsbeitrag durch die kommunale Abwasserreinigung zu erwarten ist bzw. wie man diesen möglicherweise noch verbessern kann. Anhand der gegenwärtig vorliegenden Informationen zeichnet sich ab, dass Hochlastanlangen nur Stoffe mit guten Sorptionseigenschaften über den Schlamm entfernen, während bei nährstoffeliminierenden Anlagen zusätzlich eine bedeutende Anzahl Arzneimittel biologisch abgebaut werden. Das Schlammalter scheint hierfür die massgebende Grösse zu sein. Bei weiter steigendem Schlammalter scheint die Vielfalt an abgebauten Stoffen nur noch leicht zuzunehmen. Hingegen konnte gezeigt werden, dass mit Zusatzkosten von ~0.05 Fr m^-3_Abwasser durch Ozonierung eine breite Palette von Stoffen abgebaut wird. Obwohl die dabei entstehenden Abbauprodukte noch wenig bekannt sind, ist zu erwarten, dass dieser chemischen Nachbehandlung eine grosse Bedeutung zukommen wird, falls die Elimination bei der kommunalen Abwasserreinigung weiter verbessert werden soll.

Joss, A., Goosse, P., & Siegrist, H. (2004). Betriebliche Details von Membran Belebungsanlagen (MBR). Module für die kommunalen Abwasserreinigung. In MBR in der kommunalen Abwasserreinigung (p. (14 pp.). Glattbrugg: Verband Schweizer Abwasser- und Gewässerschutzfachleute. , Institutional Repository

Joss, A., Andersen, H., Ternes, T., Richle, P. R., & Siegrist, H. (2004). Removal of estrogens in municipal wastewater treatment under aerobic and anaerobic conditions: consequences for plant optimization. Environmental Science and Technology, 38(11), 3047-3055. doi:10.1021/es0351488, Institutional Repository

Larsen, T. A., Lienert, J., Joss, A., & Siegrist, H. (2004). How to avoid pharmaceuticals in the aquatic environment. Journal of Biotechnology, 113(1-3), 295-304. doi:10.1016/j.jbiotec.2004.03.033, Institutional Repository

Morgenroth, E., Eberl, H. J., van Loosdrecht, M. C. M., Noguera, D. R., Pizarro, G. E., Picioreanu, C., … Wanner, O. (2004). Comparing biofilm models for a single species biofilm system. Water Science and Technology, 49(11-12), 145-154. doi:10.2166/wst.2004.0826, Institutional Repository

Rieger, L., Thomann, M., Joss, A., Gujer, W., & Siegrist, H. (2004). Computer-aided monitoring and operation of continuous measuring devices. Water Science and Technology, 50(11), 31-39. doi:10.2166/wst.2004.0668, Institutional Repository

Rittmann, B. E., Schwarz, A. O., Eberl, H. J., Morgenroth, E., Perez, J., van Loosdrecht, M. C. M., & Wanner, O. (2004). Results from the multi-species Benchmark Problem (BM3) using one-dimensional models. Water Science and Technology, 49(11-12), 163-168. doi:10.2166/wst.2004.0831, Institutional Repository

Siegrist, H., & Joss, A. (2004). Membranverfahren in der Abwasserreinigung (p. (47 pp.). Presented at the 58. VSA Fortbildungskurs. Glattbrugg: Verband Schweizer Abwasser- und Gewässerschutzfachleute. , Institutional Repository

Ternes, T. A., Herrmann, N., Bonerz, M., Knacker, T., Siegrist, H., & Joss, A. (2004). A rapid method to measure the solid-water distribution coefficient (K_d) for pharmaceuticals and musk fragrances in sewage sludge. Water Research, 38(19), 4075-4084. doi:10.1016/j.watres.2004.07.015, Institutional Repository

Ternes, T. A., Joss, A., & Siegrist, H. (2004). Scrutinizing pharmaceuticals and personal care products in wastewater treatment. Environmental Science and Technology, 38(20), 392A-399A. doi:10.1021/es040639t, Institutional Repository

Wanner, O., & Morgenroth, E. (2004). Biofilm modeling with AQUASIM. Water Science and Technology, 49(11-12), 137-144. doi:10.2166/wst.2004.0824, Institutional Repository

Siegrist, H., Joss, A., Alder, A., McArdell-Bürgisser, C., Göbel, A., Keller, E., & Ternes, T. (2003). Micropolluants - le traitement des eaux usées face à un nouveau défi?. Eawag News [éd. fr.], 57, 7-10. , Institutional Repository

Siegrist, H., Joss, A., Alder, A., McArdell-Bürgisser, C., Göbel, A., Keller, E., & Ternes, T. (2003). Micropollutants - new challenge in wastewater disposal?. Eawag News [engl. ed.], 57, 7-10. , Institutional Repository

Siegrist, H., Joss, A., Alder, A., McArdell-Bürgisser, C., Göbel, A., Keller, E., & Ternes, T. (2003). Mikroverunreinigungen - Abwasserentsorgung vor neuen Anforderungen?. Eawag News [dtsch. Ausg.], 57, 7-10. , Institutional Repository

Joss, A., & Siegrist, H. (2002). Membranen - Material, Module, Betrieb. GWA Gas, Wasser, Abwasser, 82(1), 7-11. , Institutional Repository

Schmidt, T. C., Morgenroth, E., Schirmer, M., Effenberger, M., & Haderlein, S. B. (2002). Use and occurrence of fuel oxygenates in Europe. In A. F. Diaz & D. L. Drogos (Eds.), ACS symposium series: Vol. 799. Oxygenates in gasoline. Environmental aspects (pp. 58-79). doi:10.1021/bk-2002-0799.ch005, Institutional Repository

Fuchs, W., Braun, R., & Joss, A. (2001). Status and development of MBR-technology. H2O: Tijdschrift voor Watervoorziening en Waterbeheer, 34, 58-59. , Institutional Repository

Joss, A., Monti, A., Fux, C., Manser, R., Rozzi, A., & Siegrist, H. (2001). Anaerobic ammonia oxidation (anammox) with a submerged membrane system (p. (8 pp.). Presented at the International water conference on membrane technology for waste water reclaimation and reuse. London: IWA Publishing. , Institutional Repository

Joss, A. (2001). Mikroverunreinigungen. Umwelt-Focus, 27-31. , Institutional Repository

Joss, A., & Siegrist, H. (2001). Mikroverunreinigungen - brauchen wir neue Kläranlagen?. GWA Gas, Wasser, Abwasser, 81(3), 151-157. , Institutional Repository

Joss, A., & Siegrist, H. (2001). Mikroverunreinigungen: Brauchen wir neue Kläranlagen?. Kommunalmagazin, 18(12) (8 pp.). , Institutional Repository

Morgenroth, E., van Loosdrecht, M. C. M., & Wanner, O. (2000). Biofilm models for the practitioner. Water Science and Technology, 41(4-5), 509-512. doi:10.2166/wst.2000.0486, Institutional Repository

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