The study “Trace pollutants in combined sewer overflows” provides an overview on the input of trace substances (organic or inorganic trace substances) to surface waters during combined sewer overflows (CSO). The study outlines substance pathways, types of substances, expected loads as well as possible impacts on the receiving water. The study shall aid the discussion and further handling of trace substances within the project Monitor-1, which is currently carried out at the Berlin Centre of Competence for Water (KWB). The study has identified more than 300 substances, which could reach the Berlin surface water bodies via CSO. Moreover, it is assumed that there is a large number of substances and metabolites, which are still unknown. Sewage-related substances in combined sewers can stem from: household products (e.g. surfactants from cleaning agents), leaching (e.g. amines from textile colours or Bisphenol A from plastic coatings), wash-off of cosmetic products (e.g. Benzophenone-3 from sunblocks) or health lotions, excretion of ingested products (e.g. the pain killer Diclofenac). Stormwater-related substances in combined sewers can stem from abrasion from car and railway traffic (e.g. cadmium from break lining abrasion), erosion of building materials (e.g. copper from eaves gutters), application (e.g. glyphosate for weed control on pavements) or atmospheric deposition (e.g. polychlorinated dibenzofurans from exhaust fumes). In the framework of this study available substance data was assembled, containing: general information like synonyms and CAS-No., chemical properties, elimination rate in wastewater treatment plant (WWTP), observed concentrations in surface waters and toxicity. A complete list of the substances as well as selected substance properties is attached in table A6 (Appendix). Some of these substances can be used as tracers to distinguish different pollution pathways to surface waters. Suitable indicators should enter surface waters mainly via one pathway, their half-life in surface waters should be sufficiently long, concentrations should show no seasonal fluctuations and they should be well-measurable. For instance, caffeine is a good indicator for inflows of untreated sewage via CSO, as it is very well degraded in WWTP. As an indicator for treated sewage the almost nondegradable anti-epileptic Carbamazepine could be used. Finally, polycyclic aromatic hydrocarbons (PAH) could be used as indicator for stormwater-related pollution. In road traffic, PAHs result from incomplete combustion processes, adsorb on atmospheric particles, deposit on the surface and are washed off by rainfall runoff. In this study the relevance of the path “CSO” for trace substance emissions from the Berlin wastewater system in comparison to the other paths (storm drainage and WWTP) was assessed. Therefore, a simple balance of the fraction of CSO in total emissions to the Berlin surface waters was carried out. The balance was based on the annual volumes of WWTP effluents, storm drainage and CSO. Due to a lack in substancespecific measurement information the balance was calculated dependent on the elimination rate of substances in WWTPs. Based on the resulting figures A, B, C, D and E the fraction of CSO in total loads to the Berlin surface waters can be assessed for each substance with known elimination rate in WWTPs. In the study we distinguished between: (i) sewage related substances / stormwater related substances, (ii) balance area „Berlin total“ (5 WWTPs with 622,000 m³/d, 97 km2 combined sewer system, 231 km2 storm drainage system) / balance area „Berlin city centre“ (60% of the WWTP Münchehofe with 39,000 m³/d, 83 km2 combined sewer system, 112 km2 storm drainage system) and (iii) total annual loads / event based loads.

In the rural and semi-rural environment many sources of contamination may impact surface water quality. In addition to nutrients from agricultural activities, contaminants occurring at low concentration so-called trace contaminants are a growing issue for water quality. To address this issue and investigate mitigation measures, the Berlin Centre of Competence for Water (KompetenzZentrum Wasser Berlin) developed a collaborative research project called Aquisafe, in association with the Indiana University – Perdue University Indianapolis (IUPUI), the German Federal Agency for the Environment “Umweltbundesamt” (UBA) and Veolia Water. The project aims at investigating mitigation zones such as constructed wetlands or riparian zones to improve the quality of surface water with respect to diffuse pollution. Before using models and conducting field experiments, the first part of the project is an extensive analysis of the nature, occurrence, and risks of source water contamination in rural and semi-rural areas. This is the subject of the poster. The objectives of this first part of the project are (i) to provide background information on surface water and its use in Europe, particularly regarding drinking water supply, (ii) to investigate the characteristics of the families of pollutants that are potentially of interest, and finally (iii) to select the most relevant trace contaminants to be investigated in future field experiments. To reach these objectives, an extensive literature review was carried out, using different criteria to select the relevant families of pollutants and then the individual substances. The screening process is currently in progress and includes a collection of substance characteristics that will be used for subsequent selection, such as toxicity or persistence in the environment. Key figures and information were collected concerning the nature, use and vulnerability of surface water in Europe that provides 70% of total water abstraction (drinking water, industry and agriculture) in Europe. The main pollutant families of interest for the screening process were the following: pesticides used in agriculture (e.g. glyphosate or isoproturon), pollutants coming from the spreading of animal waste on land (e.g. veterinary pharmaceuticals or hormones), pollutants coming from the spreading of sludge from wastewater treatment plants (e.g. heavy metals or hormones), pollutants from natural areas (e.g. flame retardants in forests), and pollutants from transportation networks (e.g. heavy metals from vehicles). Consequently in a rural or semi-rural area, the land use in the watershed plays a key role in the selection and assessment of priority pollutants coming from diffuse sources and entering surface waters. The work is still in progress concerning the review of pollutant families, and will lead to the final screening at substance level, providing a list of key contaminants for the other work packages within the Aquisafe project. Eventually, corresponding data for the same issues in the United States will be added and provide a comparison between the two continents.

The Aquisafe project assesses the effectiveness of natural mitigation zones in reducing diffuse pollution to surface waters. In one case study on a constructed wetland in agriculturally dominated Western France, nitrate concentrations from drainage inflows to a small river decreased up to tenfold on the way through an intermediary constructed wetland. However, only ~30 % of the total N-load is retained in the wetland, whereas ~70 % enters the river directly during high flow events as a result of low soil permeability. The study underlines the importance of flow paths and infiltration for nitrate removal in natural or constructed wetlands, which is often neglected in practice.

The Aquisafe project is a cooperation of the Indiana University Purdue University Indianapolis (IUPUI, USA), the German Federal Environment Agency (UBA, Germany) and the Berlin Centre of Competence for Water (KWB, Germany). The aim of the project is the development of a scheme for natural mitigation zones to protect surface waters from diffuse pollution in rural and semi-rural environments. In particular, key contaminants, applicable management and modelling tools and potential substance removal by constructed wetlands or riparian zones are being studied. Within these frameworks, two case studies are carried out in Brittany, the number one agricultural region in France. A hydrological model is currently being applied on the Ic catchment (92 km2) to test its capability of (i) understanding hydrological, basin-scale regimes, (ii) predicting the effect of mitigation measures and (iii) distinguishing diffusion pathways for different types of contaminants. In the second case study, a constructed wetland in Iffendic on the River Meu is monitored as an example of a natural and inexpensive mitigation option. On the way through the wetland nitrate concentrations from drainage inflows to the river decreased more than tenfold. In the ongoing monitoring, knowledge on hydrological flowpaths is improved to be able to quantify the retention potential of constructed wetlands in Brittany for nitrate and other agriculturally-based pollutants, such as pesticides.

In Berlin läuft seit April 2007 das BMBF-Forschungsprojekt SPREE2011, welches zum Ziel hat, eine neuartige Speichertechnologie für Mischwasserüberläufe zu entwickeln sowie Reinigungstechniken für die Mischwasserbehandlung zu erproben, die in Deutschland bisher nur aus anderen Anwendungsfällen bekannt sind. Auf diesem Wege soll ein direkter Beitrag geliefert werden zu den zukünftigen Zielen, die Stoffeinträge aus Misch- und Regenwasser in Gewässer zu minimieren.

The application of hydrodynamic sewer modelling allows for detailed description of complex hydraulic situations. However, for large systems long-term calculations with hydrodynamic models still require high computation times. This paper shows a possibility to overcome this problem by using a hybrid sewer model, which is a conjunction of conceptual and mechanistic modelling approaches to combine the calculating speed of conceptual models and the accuracy of mechanistic models in one model. The implementation of a hybrid sewer model was performed and tested in two case studies, in Berlin (Germany) for 6 representative catchments and in Herent (Flanders, Belgium) for one sewer system, using the hydrodynamic modelling software InfoWorks CS. Besides the motivation of the case studies on the sewer systems in Berlin and Herent this paper presents the methodologies developed for a hybrid simplification of the sewer network model, considering the calibration of the simplified network as well as the evaluation of the simplification performance. The use of a hybrid model for both case studies is then evaluated and the transferability of the methodologies is discussed.

The importance of integrated modelling of urban wastewater systems is ever increasing, also due to the European Water Framework Directive. In order to facilitate its practical application, the Central European Simulation Research Group (HSG) has prepared a guideline document, suggesting a seven-step procedure to integrated modelling. Findings of recent research and application projects in Central Europe have been integrated in the guideline. The present paper outlines this guideline document. The full guideline will be made available on the Internet.

The centre of Berlin, Germany, is drained by a combined sewer system. The receiving waters Havel and Spree are characterized by low flow velocities and an increased risk of eutrophication. High demands towards a reduction of the emission loads of combined sewer overflows (CSOs) down to 20 % of the mean annual runoff load of TSS, COD and BOD5 are formulated by the Berlin Water Authority. Therefore a pollution control plan will be carried out until the year 2020 that will lead to a storage enlargement of the combined sewer system by 100 %. To assess if these efforts will lead to the expected water quality of the receiving water regarding the objectives of the European Water Framework Directive, a method will be developed to evaluate in advance the achievable improvement. Starting from the actual status of the water body this model based method should allow for an estimation, if the good status will be achieved after the realization of the measures of storage upgrading in the sewer system. The study currently concentrates on the integrated water quality modelling of the high dynamic processes in the sewer system and the receiving water. The paper focuses on the simulation of oxygen concentration in the receiving water.