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No description available.

No description available.

According to estimates of the United Nations Environment Programme (UNEP), more than 1.8 billion people will be living in countries or regions with absolute water scarcity by 2025. The pressure on water resources is increased not only in arid and semiarid regions, but also in fast growing megacities around the world as a result of, amongst other factors, the changing nutritional and consumer behavior (rising living standards). Over 90 % of the annual water consumption of the newly industrializing and developing countries in the arid and semiarid climate zone is used for agricultural irrigation to ensure the nutrition of the population. Thus, since the beginning of the 20th century, the planned/controlled reuse of wastewater has developed into a central task of the sustainable water resources management. Wastewater represents a valuable resource in view of its composition (e. g. nutrients P, N for soil fertilizing) and its reliable, weather-independent availability in every household. The establishment of a closed-loop water management can enhance the efficiency of water usage. Therefore, activities in research and development are currently focused on decentralized and semi-centralized concepts, since their structures offer better conditions for the establishment of closed-loop systems and innovations in wastewater technology can be implemented more easily. In general, the hygienic quality requirements for wastewater reuse are predominantly oriented towards the planned usage. These are, in turn, regulated by thresholds and guidance values, e. g. for faecal indicator bacteria (e. g. faecal coliforms: E. coli), in widely differing norms and legal provisions specific to the respective countries. In Germany since 2005, small wastewater treatment plants can obtain the discharge class +H by the German Institute for Civil Engineering (DIBt: Deutsches Institut für Bautechnik) if secondary effluents contain less than 100 faecal coliforms (E. coli) per 100 mL. This ensures a safe effluent seepage in karst and water protection areas. Due to the infectious risk caused by a multitude of pathogens (bacteria, viruses, worm eggs, protozoa) which are still contained in wastewater after mechanical-biological treatment, specific disinfection methods are indispensable for their satisfactory reduction. Demands on disinfection methods for wastewater reclamation are quite complex. They should be characterized by a high and constant disinfection efficiency at low or moderate formation of disinfection by-products. The reclaimed wastewater should be able to be stored safely. Moreover, the disinfection method should be technically simple, scaleable, space-saving, subjected to low maintenance and realized at moderate investment and operating costs without applying external toxic chemicals. Established methods in decentralized wastewater disinfection are mainly based on membrane and UV technologies. However, these methods are currently working under high operating costs (high maintenance and cleaning efforts). Furthermore, the high investment costs of the membrane filtration are disadvantageous. In addition, both methods do not provide a disinfection residual. Thus, further research is required for the development and testing of alternative disinfection technologies. Against this background, the applicability of the electrolysis and UV/electrolysis hybrid technology for the decentralized wastewater reclamation was investigated and assessed in this dissertation. Results have shown that the electrochemical disinfection of biologically treated wastewater represents an efficient method at temperatures of > 6 °C, pH values of < 8.5 and DOC con-centrations of < 22 mg L-1. Under these conditions, an E. coli reduction of four log levels was achieved at a concentration of free chlorine ranging from 0.4 mg L-1 to 0.6 mg L-1 and at an after-reaction time of 15...20 min. However, it becomes simultaneously apparent that low temperatures, high pH values and high DOC concentrations are limiting parameters for this disinfection method to reclaim biologically treated wastewater. A high energy consumption of the electrolysis cell equipped with boron-doped diamond (BDD) electrodes (2...2.6 kWh m-3) represents a further unfavourable effect. Moreover, the undesired formation of chlorate (c = 1.3 mg L-1) and perchlorate (c = 18 mg L-1) at BDD electrodes can be considered as critical, since these disinfection by-products are, amongst others, human-toxicologically relevant. The concentration of adsorbable organically bound halogens (AOX) and trihalomethanes (THMs) proved to be marginal to moderate. Due to the synergistic effect of the combined application of UV irradiation (primary disinfection method) and electrolysis, the disadvantages of the single methods can be compensated. Decisive drawbacks of UV irradiation are photo and dark repair mechanisms of reversibly damaged bacteria. It was observed that the reactivation of reversibly UV-damaged E. coli even occurs at low temperatures (T = 10 °C) and strongly differing pH values (pH = 5.7...8.1) as well as at low light intensities and in darkness to an extent excluding a safe usage and storage of the reclaimed wastewater. The reactivation processes might be lowered by increased UV fluences. However, this is limited by high concentrations of total suspended solids (TSS). In spite of high UV fluences of > 400 J m-1, no complete removal of E. coli bacteria can be achieved at TSS concentrations of > 17 mg L-1. Therefore, it is indispensable to prevent bacterial reactivation caused by photo and dark repair processes. This topic was studied in the current work by electrochemically produced oxidants using an electrolysis cell positioned downstream of the UV unit. Results have shown that photo and dark reactivation were completely prevented by oxidants in a total concentration of 0.5...0.6 mg L-1 at a TSS concentration of 8...11 mg L-1, at pH values ranging from 5.7 to 8.1 and at temperatures ranging from 10 °C to 30 °C (t = 24....72 h). Even at a high TSS concentration of 75 mg L-1, the reactivation of E. coli (ctotal oxidants = 1.8 mg L-1) and, up to a TSS concentration of 32 mg L-1, the reactivation of total coliforms (except E. coli, ctotal oxidants = 1.0 mg L-1) can be prevented at a high initial germ concentration of 2…3 105 per 100 mL. The lowest energy consumption could be observed when mixed oxide electrodes (MOX electrodes) were applied. This result and the fact that no chlorate and perchlorate were observed at MOX electrodes argue for the application of these electrodes in practice. All in all, the UV/electrolysis hybrid technology represents an energy-efficient method for reclamation of biologically treated wastewater with TSS concentrations ranging from < 11 to 32 mg L-1 (E = 0.17…0.24 kWh m-3, MOX electrodes). Thereby, the reclaimed wastewater meet the hygienic quality requirements for a multitude of reuse categories starting from agricultural irrigation to urban and recreational reuse. Moreover, the requirements of the discharge class +H (100 faecal coliforms (E. coli) per 100 mL) are complied with reliably. The operational stability of the UV/electrolysis hybrid technology should also be ensured within the required maintenance intervals (t > 6 months). The undesired formation of coverings caused by biofouling processes on quartz glass surfaces could be prevented by electrochemically produced oxidants in a total concentration of 1 mg L-1 within an experimental duration of 5.5 months. However, the application of the UV/electrolysis hybrid technology is limited by increased particle concentrations and faecal loadings (initial E. coli concentration). The resulting enhanced demand of electrochemically produced oxidants for the prevention of bacterial reactivation results in a considerable increase of the electric charge input and energy consumption.

According to estimates of the United Nations Environment Programme (UNEP), more than 1.8 billion people will be living in countries or regions with absolute water scarcity by 2025. The pressure on water resources is increased not only in arid and semiarid regions, but also in fast growing megacities around the world as a result of, amongst other factors, the changing nutritional and consumer behavior (rising living standards). Over 90 % of the annual water consumption of the newly industrializing and developing countries in the arid and semiarid climate zone is used for agricultural irrigation to ensure the nutrition of the population. Thus, since the beginning of the 20th century, the planned/controlled reuse of wastewater has developed into a central task of the sustainable water resources management. Wastewater represents a valuable resource in view of its composition (e. g. nutrients P, N for soil fertilizing) and its reliable, weather-independent availability in every household. The establishment of a closed-loop water management can enhance the efficiency of water usage. Therefore, activities in research and development are currently focused on decentralized and semi-centralized concepts, since their structures offer better conditions for the establishment of closed-loop systems and innovations in wastewater technology can be implemented more easily. In general, the hygienic quality requirements for wastewater reuse are predominantly oriented towards the planned usage. These are, in turn, regulated by thresholds and guidance values, e. g. for faecal indicator bacteria (e. g. faecal coliforms: E. coli), in widely differing norms and legal provisions specific to the respective countries. In Germany since 2005, small wastewater treatment plants can obtain the discharge class +H by the German Institute for Civil Engineering (DIBt: Deutsches Institut für Bautechnik) if secondary effluents contain less than 100 faecal coliforms (E. coli) per 100 mL. This ensures a safe effluent seepage in karst and water protection areas. Due to the infectious risk caused by a multitude of pathogens (bacteria, viruses, worm eggs, protozoa) which are still contained in wastewater after mechanical-biological treatment, specific disinfection methods are indispensable for their satisfactory reduction. Demands on disinfection methods for wastewater reclamation are quite complex. They should be characterized by a high and constant disinfection efficiency at low or moderate formation of disinfection by-products. The reclaimed wastewater should be able to be stored safely. Moreover, the disinfection method should be technically simple, scaleable, space-saving, subjected to low maintenance and realized at moderate investment and operating costs without applying external toxic chemicals. Established methods in decentralized wastewater disinfection are mainly based on membrane and UV technologies. However, these methods are currently working under high operating costs (high maintenance and cleaning efforts). Furthermore, the high investment costs of the membrane filtration are disadvantageous. In addition, both methods do not provide a disinfection residual. Thus, further research is required for the development and testing of alternative disinfection technologies. Against this background, the applicability of the electrolysis and UV/electrolysis hybrid technology for the decentralized wastewater reclamation was investigated and assessed in this dissertation. Results have shown that the electrochemical disinfection of biologically treated wastewater represents an efficient method at temperatures of > 6 °C, pH values of < 8.5 and DOC con-centrations of < 22 mg L-1. Under these conditions, an E. coli reduction of four log levels was achieved at a concentration of free chlorine ranging from 0.4 mg L-1 to 0.6 mg L-1 and at an after-reaction time of 15...20 min. However, it becomes simultaneously apparent that low temperatures, high pH values and high DOC concentrations are limiting parameters for this disinfection method to reclaim biologically treated wastewater. A high energy consumption of the electrolysis cell equipped with boron-doped diamond (BDD) electrodes (2...2.6 kWh m-3) represents a further unfavourable effect. Moreover, the undesired formation of chlorate (c = 1.3 mg L-1) and perchlorate (c = 18 mg L-1) at BDD electrodes can be considered as critical, since these disinfection by-products are, amongst others, human-toxicologically relevant. The concentration of adsorbable organically bound halogens (AOX) and trihalomethanes (THMs) proved to be marginal to moderate. Due to the synergistic effect of the combined application of UV irradiation (primary disinfection method) and electrolysis, the disadvantages of the single methods can be compensated. Decisive drawbacks of UV irradiation are photo and dark repair mechanisms of reversibly damaged bacteria. It was observed that the reactivation of reversibly UV-damaged E. coli even occurs at low temperatures (T = 10 °C) and strongly differing pH values (pH = 5.7...8.1) as well as at low light intensities and in darkness to an extent excluding a safe usage and storage of the reclaimed wastewater. The reactivation processes might be lowered by increased UV fluences. However, this is limited by high concentrations of total suspended solids (TSS). In spite of high UV fluences of > 400 J m-1, no complete removal of E. coli bacteria can be achieved at TSS concentrations of > 17 mg L-1. Therefore, it is indispensable to prevent bacterial reactivation caused by photo and dark repair processes. This topic was studied in the current work by electrochemically produced oxidants using an electrolysis cell positioned downstream of the UV unit. Results have shown that photo and dark reactivation were completely prevented by oxidants in a total concentration of 0.5...0.6 mg L-1 at a TSS concentration of 8...11 mg L-1, at pH values ranging from 5.7 to 8.1 and at temperatures ranging from 10 °C to 30 °C (t = 24....72 h). Even at a high TSS concentration of 75 mg L-1, the reactivation of E. coli (ctotal oxidants = 1.8 mg L-1) and, up to a TSS concentration of 32 mg L-1, the reactivation of total coliforms (except E. coli, ctotal oxidants = 1.0 mg L-1) can be prevented at a high initial germ concentration of 2…3 105 per 100 mL. The lowest energy consumption could be observed when mixed oxide electrodes (MOX electrodes) were applied. This result and the fact that no chlorate and perchlorate were observed at MOX electrodes argue for the application of these electrodes in practice. All in all, the UV/electrolysis hybrid technology represents an energy-efficient method for reclamation of biologically treated wastewater with TSS concentrations ranging from < 11 to 32 mg L-1 (E = 0.17…0.24 kWh m-3, MOX electrodes). Thereby, the reclaimed wastewater meet the hygienic quality requirements for a multitude of reuse categories starting from agricultural irrigation to urban and recreational reuse. Moreover, the requirements of the discharge class +H (100 faecal coliforms (E. coli) per 100 mL) are complied with reliably. The operational stability of the UV/electrolysis hybrid technology should also be ensured within the required maintenance intervals (t > 6 months). The undesired formation of coverings caused by biofouling processes on quartz glass surfaces could be prevented by electrochemically produced oxidants in a total concentration of 1 mg L-1 within an experimental duration of 5.5 months. However, the application of the UV/electrolysis hybrid technology is limited by increased particle concentrations and faecal loadings (initial E. coli concentration). The resulting enhanced demand of electrochemically produced oxidants for the prevention of bacterial reactivation results in a considerable increase of the electric charge input and energy consumption.

[ES] El mundo se enfrenta a una profunda crisis asociada al agua y la reutilización de aguas residuales urbanas (UWW), especialmente en agricultura, se presenta como una posible solución para abordar este problema. No obstante, la reutilización se debe promover dentro de unos límites mínimos de calidad del agua, los cuales pueden alcanzarse mediante la implementación de eficientes tratamientos terciaros en las actuales plantas de tratamiento de aguas residuales urbanas. En las últimas décadas, los Procesos de Oxidación Avanzada (POA), basados en la generación de especies reactivas del oxígeno altamente oxidantes y no selectivas, se han planteado como alternativa a los tratamientos convencionales para desinfección y descontaminación de agua residual. El objetivo general de este estudio es, por tanto, la evaluación de nuevos POA para desinfección y descontaminación simultánea de agua, investigando: (i) fotocatálisis heterogénea solar con ZnO modificado (Ce, Yb y Fe) y TiO2-P25 de referencia, (ii) peroximonosulfato (PMS) bajo radiación solar natural (PMS/Solar), (iii) POA basados en radical sulfato utilizando PMS y radiación UV-C (PMS/UV-C) y (iv) combinación de ZnO modificado con PMS como estrategia de tratamiento. Los objetivos biológicos y químicos analizados en este estudio fueron: tres patógenos de impacto en salud humana (dos bacterias gram-negativas Escherichia coli, Pseudomonas spp y una gram-positiva Enterococcus spp) y tres Contaminantes de Preocupación Emergente (CE) (Diclofenaco-DCF, Sulfametoxazol-SMX y Trimetoprim-TMP). La fotoactividad de ZnO modificado con Ce, Yb o Fe se evaluó a escala de laboratorio (200 mL), obteniendo buenas cinéticas de inactivación bacteriana y degradación de CE. El ZnO-Ce mostró el mejor rendimiento, no obstante, se descartó el escalado de este proceso tanto su aplicación directa, considerando su similar eficiencia en comparación con TiO2-P25 y por el alto coste del tratamiento, como en combinación con PMS, por la la liberación de Zn2+ al agua tratada. El uso directo de PMS como agente oxidante para el tratamiento de agua y UWW se ha demostrado en este estudio, aumentado su eficiencia al ser el sistema irradiado tanto con lámparas UV-C como con luz solar natural. Se han postulado diferentes mecanismos de inactivación y degradación de CE para cada tipo de irradiación: activación de PMS para generar radicales (con fotones UV-C) y la no activación o mecanismo de oxidación directo (con luz solar natural). La capacidad de los procesos PMS/Solar y PMS/UV-C se evaluó en UWW a escala de planta piloto en un Colector Parabólico Compuesto (10 L) y en una planta piloto de UV-C (80 L), respectivamente. El mejor rendimiento de tratamiento se alcanzó con una concentración de PMS de 1 mM en ambos casos, logrando una inactivación exitosa de todos los objetivos microbianos (incluyendo bacterias resistentes a antibióticos), sin observar recrecimiento bacteriano tras 48 h y eliminando de manera eficiente los CE. Por otro lado, la eliminación eficiente de genes de resistentes a antibióticos y productos de transformación se obtuvo con PMS/UV-C, mientras que éstos parámetros siguen siendo un reto a abordar en el caso del proceso PMS/Solar. En ningún caso se observó toxicidad del agua tratada para Aliivibrio fischeri, excluyendo un efecto nocivo para el medio ambiente receptor del efluente, y solo un leve efecto fitotóxico en el crecimiento de dos de las tres semillas analizadas (L. sativum y S. alba), indicando la idoneidad del efluente para su reutilización en riego. Finalmente, el análisis de costes demostró que este factor clave podría ser una barrera importante para la implementación del proceso PMS/Solar en plantas centralizadas de tratamiento de UWW. No obstante, su consideración como sistemas descentralizados asociados a pequeños volúmenes de agua en zonas con alta incidencia de radiación solar, ahorrando costes energéticos mediante el aprovechamiento de la luz solar, podría ser una opción real y asequible. / [CA] El món s'enfronta a una profunda crisi associada a l'aigua i la reutilització d'aigües residuals urbanes (UWW), especialment en agricultura, es presenta com una possible solució per a abordar aquest problema. No obstant això, la reutilització s'ha de promoure dins d'uns límits mínims de qualitat de l'aigua, els quals poden aconseguir-se mitjançant la implementació d'eficients tractaments terciaris en les actuals plantes de tractament d'aigües residuals urbanes. En les últimes dècades, els Processos Avançats d'Oxidació (PAO), basats en la generació d'espècies reactives d'oxigen altament oxidants i no selectives, s'han plantejat com a alternativa als tractaments convencionals per a desinfecció i descontaminació d'aigua residual. L'objectiu general d'aquest estudi és, per tant, l'avaluació de nous POA per a desinfecció i descontaminació simultània d'aigua, investigant: (i) fotocatàlisi heterogènia solar amb ZnO modificat (Ce, Yb i Fe) i TiO2-P25 de referència, (ii) peroximonosulfat (PMS) baix radiació solar natural (PMS/Solar), (iii) POA basats en radical sulfat utilitzant PMS i radiació UV-C (PMS/UV-C) i (iv) combinació de ZnO modificat amb PMS com a estratègia de tractament. Els objectius biològics i químics analitzats en aquest estudi van ser: tres patògens d'impacte en salut humana (dos bacteris gram-negatius Escherichia coli, Pseudomonas spp i un gram-positiu Enterococcus spp) i tres Contaminants de Preocupació Emergent (CE) (Diclofenac-DCF, Sulfametoxazol-SMX i Trimetoprim-TMP). La fotoactivitat de ZnO modificat amb Ce, Yb o Fe es va avaluar a escala de laboratori (200 mL), obtenint bones cinètiques d'inactivació bacteriana i degradació de CE. El ZnO-Ce va mostrar el millor rendiment, no obstant això, es va descartar l'escalat d'aquest procés tant mitançant la seua aplicació directa o com en combinació amb PMS, considerant la seua similar eficiència en comparació amb TiO2-P25, l'alt cost del tractament i l'alliberament de Zn2+ a l'aigua tractada. L'ús directe de PMS com a agent oxidant per al tractament d'aigua i UWW s'ha demostrat en aquest estudi, augmentat la seua eficiència quan el sistema és irradiat tant amb llums UV-C com amb llum solar natural. S'han postulat diferents mecanismes d'inactivació i degradació de CE per a cada tipus d'irradiació: activació de PMS per a generar radicals (amb fotons UV-C) i la no activació o mecanisme d'oxidació directe (amb llum solar natural). La capacitat dels processos PMS/Solar i PMS/UV-C es va avaluar en UWW a escala de planta pilot en un Col·lector Parabòlic Compost (10 L) i en una planta pilot d'UV-C (80 L), respectivament. El millor rendiment de tractament es va aconseguir amb una concentració de PMS d'1 mm en tots dos casos, aconseguint una inactivació reeixida de tots els objectius microbians (incloent bacteris resistents a antibiòtics), sense observar recreixement bacterià després de 48 h i eliminant de manera eficient els CE. D'altra banda, l'eliminació eficient de gens de resistents a antibiòtics i productes de transformació es va obtindre amb PMS/UV-C, mentre que aquests paràmetres continuen sent un repte a abordar en el cas del procés PMS/Solar. En cap cas es va observar toxicitat a l'aigua tractada per a Aliivibrio fischeri, excloent un efecte nociu per al medi ambient receptor de l'efluent, i només un lleu efecte fitotòxic en el creixement de dos de les tres llavors analitzades (L. sativum i S. alba), indicant la idoneïtat de l'efluent per a la seua reutilització en reg. Finalment, l'anàlisi de costos va demostrar que aquest factor clau podria ser una barrera important per a la implementació del procés PMS/Solar en plantes centralitzades de tractament de UWW. No obstant això, la seua consideració com a sistemes descentralitzats associats a xicotets volums d'aigua en zones amb alta incidència de radiació solar, estalviant costos energètics mitjançant l'aprofitament de la llum solar, podria ser una opció real i assequible. / [EN] It is well recognized that the world is facing a water crisis and the reuse of urban wastewater (UWW) in agriculture, has been gaining attention as a reliable solution to address this problem. It is mandatory to promote the safe water reuse and minimum water quality limits could be achieved by upgrading the Urban Wastewater Treatment Plants, through the addition of an efficient tertiary treatment. In the last decades, Advanced Oxidation Processes (AOPs), relying on the potential generation of highly oxidant, reactive and non-selective Reactive Oxygen Species (ROS), have been raised as alternative to conventional treatments for both water disinfection and decontamination. The general aim of this study is the assessment of novel AOPs for the simultaneous disinfection and decontamination of water, investigating (i) solar heterogeneous photocatalysis, involving modified ZnO with Ce, Yb and Fe and the benchmark TiO2-P25, (ii) peroxymonosulfate (PMS) under natural solar radiation (PMS/Solar), (iii) Sulfate radical-based AOPs (SR-AOPs) involving PMS and UV-C radiation (PMS/UV-C) and (iv) combination of the best-performing photocatalytic material with PMS (PMS/modified ZnO). The involved biological and chemical targets in this study were: three human health impact pathogens (two gram-negative bacteria Escherichia coli, Pseudomonas spp. and the gram-positive Enterococcus spp.) and three Contaminants of Emerging Concern (CECs, Diclofenac-DCF, Sulfamethoxazole-SMX and Trimethoprim-TMP). Photoactivity of modified ZnO with Ce, Yb or Fe was assessed in 200-mL vessel reactors, attaining good target's removal kinetic rates. Best performing material was ZnO-Ce, but its feasibility for a further up-scaling was discarded both as photocatalyst alone, considering the similar performances obtained, compared to TiO2-P25 and the high treatment cost, and in combination with PMS, due to the release of high amount of Zn2+. PMS alone has been proven to be an effective oxidant agent for water and UWW treatment, increasing its effectiveness when illuminated with photons from UV-C lamps and natural sunlight. Nevertheless, different inactivation and CECs degradation mechanisms have been postulated for each type of irradiation, and according to the activation of PMS (with UV-C photons) or non-activation (under natural sunlight). The capability of PMS/Solar and PMS/UV-C processes were evaluated in actual UWW at pilot plant scale in 10-L Compound Parabolic Collector and in 80L UV-C pilot plant, respectively. Optimal load of PMS was found to be 1 mM in both cases, achieving successful inactivation of natural occurring bacteria and their antibiotic resistant counterparts, without observing bacterial regrowth after 48h and efficiently eliminating CECs. Efficient removal of antibiotic resistant genes (ARGs) and transformation products (TPs) was obtained by PMS/UV-C, while their elimination is still a challenge to be addressed in PMS/Solar process. Reclaimed UWW obtained by both PMS/Solar and PMS/UV-C process showed no toxicity towards Aliivibrio fischeri, excluding a harmful effect towards the receiving aquatic environment after effluent discharge, and a very slightly phytotoxic effect for growth of two out of the three tested seeds (L. sativum and S. alba), indicating the suitability of this water for its subsequent reuse for agriculture. The analysis of the treatment cost revealed that this key factor could be an important barrier for implementation of PMS/Solar process in large centralized UWW treatment plants. Nevertheless, its consideration as decentralized systems associated to small volume of water in areas with a high solar radiation incidence, saving energy costs by using natural solar radiation, could be a real and affordable option. / Berruti, I. (2022). Assessment of novel Advanced Oxidation Processes for the Simultaneous Disinfection and Decontamination of Water [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/183052

In dieser Dissertation wird der Einfluss von Transaktionen zur Wiederverwendung von Nährstoffen und gereinigtem kommunalen Abwasser auf die Wertschöpfungsketten der Abwasserbehandlung und Pflanzenproduktion untersucht. Ziel ist es, Kosten und Nutzen sowie die Wertschöpfung von Transaktionen in verknüpften Wertschöpfungsketten der Abwasserbehandlung und Pflanzenproduktion zu analysieren. Darüber hinaus wird untersucht, wie Transaktionen und Interdependenzen zwischen Akteuren in verknüpften Wertschöpfungsketten die lokalen Governance-Strukturen für die Wiederverwendung von Abwasser beeinflussen. Die Analyse wird hauptsächlich durch das Wertschöpfungskettenkonzept, das Konzept der Kreislaufwirtschaft und die Theorie der Transaktionskostenökonomie geleitet. Mit verschiedenen Methoden, wie der Kosten-Nutzen-Analyse, der Wertschöpfungskettenanalyse und der Transaktionskostenanalyse, werden zwei Fallstudien in Deutschland untersucht: (1) die Fällung von Struvit (Magnesium-Ammonium-Phosphat) und dessen Verwendung als Dünger in Berlin-Brandenburg und (2) das Modell der landwirtschaftlichen Abwasserwiederverwendung in Braunschweig. Die Ergebnisse zeigen, dass die Wiederverwendung von Nährstoffen und Abwasser zu geringeren Kosten für die Abwasserbehandlung, höherer Rentabilität und Wertschöpfung in der Pflanzenproduktion und zu einem hohen Anteil an regionaler Wertschöpfung führen. Die Ergebnisse verdeutlichen aber auch, dass die Wiederverwendung von Abwasser zu Einschränkungen, Verdrängungseffekten und Veränderungen in der Verteilung der Wertschöpfung führen kann. Des Weiteren zeigen die Ergebnisse, dass differenzierte Governance-Strukturen erforderlich sind, um den unterschiedlichen Eigenschaften der Transaktionen zwischen Abwasserbehandlung und der Pflanzenproduktion gerecht zu werden. Interdependenzen zwischen Abwasseranbietern und Landwirten erhöhen den Bedarf an hybriden und hierarchischen Elementen in den Governance-Strukuren für die Wiederverwendung von Abwasser. / This dissertation explores the impact of transactions for reusing nutrients and treated municipal wastewater on the value chains of wastewater treatment and crop production. It aims to analyze what costs and benefits and what added-value can result from transactions in linked value chains of wastewater treatment and crop production. Furthermore, it aims to analyze how transactions and interdependences between actors in linked value chains shape the governance structures for reusing wastewater at the local level. The analysis is mainly guided by the value chain concept, the concept of the circular economy and the theory of transaction costs economics. Different methods including cost-benefit analysis, value chain analysis and transaction cost analysis are used to investigate two case studies located in Germany: (1) the precipitation of struvite (magnesium ammonium phosphate) in the wastewater treatment plant in Waßmannsdorf and its application as fertilizer in Berlin-Brandenburg, and (2) the agricultural wastewater reuse scheme of the Wastewater Association Braunschweig. The results show that transactions for reusing nutrients and wastewater result in the development of linked regional value chains with lower costs of wastewater treatment, higher profitability and added-value in crop production, and a high share of regional added-value. However, the results also highlight that the reuse of wastewater can lead to restrictions (e.g., cultivation bans on certain crops), crowding out effects and changes in the distribution of the added-value. Furthermore, the findings suggest that different governance structures are needed to match the different properties of the transactions between wastewater treatment and crop production. Interdependences resulting from transactions between wastewater providers and farmers increase the need for hybrid and hierarchical elements in the governance structures for reusing wastewater.