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Over the last decade, more and more organic contaminants in trace level concentrations (µg/L to ng/L) have been detected ubiquitously in the aquatic environment and especially in urban water cycles. These so-called organic micropollutants are introduced into the environment by anthropogenic activities. They include pharmaceuticals, radiocontrast agents, household chemicals, food additives etc. These persistent compounds are discharged as part of municipal wastewater and cannot or only partly be retained in wastewater treatment plants. Thus, they end up in the receiving surface waters and spread in the aquatic environment. Furthermore, in closed or partially closed water cycles, which can often be found in urban areas, they can potentially end up in drinking water sources.
There is a lack of knowledge about the effects of the discharge of organic micropollutants. The processes that they undergo as well as the processes that they affect within the urban water cycle are only poorly investigated to date. These processes are studied in a multidisciplinary approach, with several projects focusing on different interfaces of the urban water cycle.
One aspect of research is the effect of organic micropollutants on the microbial metabolism with focus on the interface urban surface water - atmosphere. Hereby, extensive data are collected to understand the consequences of an organic micropollutant exposition on the emissions of CO2 (Project N4 ) and CH4 (Project N3 ). Further, investigating the sediment – surface water interface the impact of treated wastewaters (including micropollutants) on the hydraulics and water quality of urban lakes will be evaluated using numerical models (Project T4 ). The behavior of organic micropollutants at the interface of surface water and groundwater is also of special interest, from a natural as well as from a technical point of view. On the one hand, field as well as lab scale experiments are conducted to study the transport and retention of micropollutants in the hyporheic zone (Project N6 ). On the other hand, new information about the biotic and abiotic removal during bank filtration is gained, with a special focus on the behavior of radio-contrast agents (Project T6 ).
Moreover, the processes at solid-water interfaces are an important aspect which is studied in the research training group to understand micropollutant dynamics in urban water cycles. The degradation potential of microbial communities in biofilms is investigated in the lab as well as in the field (Project N1 ). Also the behavior in technical treatment systems is of interest. So far, there is only little knowledge about potential desorption effects of organic micropollutants in activated carbon processes. New findings will help to get a better understanding of this established technical application (Project T5 ).
All projects cover a wide range of research approaches and techniques, different zones and interfaces as well as different scales of interest. Combined with modern state-of-the-art analytical advices and methods improved knowledge about the effects and behavior of organic micropollutants in urban water cycles will be gained.
Robert Ladwig 
Clara Romero 
Sonia Herrero 
Marcella Nega 
Geert Aschermann (corresponding doctoral student) 
Jonas Schaper 
Fatima El-Athman 
- solid – water (N1 – Marcella Nega , T5 – Geert Aschermann )
- surface water – atmosphere (N3 – Sonia Herrero , N4 – Clara Romero )
- surface water – groundwater (N6 – Jonas Schaper , T6 – Fatima El-Athman )
- sediment – surface water (T4 – Robert Ladwig )
- Berliner Wasserbetriebe (BWB) 
- Helmholtz Centre for Environmental Research (UFZ), Leipzig 
- Senatsverwaltung für Stadtentwicklung und Umwelt, Berlin 
- Bundesanstalt für Materialforschung und -prüfung (BAM) 
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