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.

Wet weather discharges from urban catchments are widely recognised as a major cause of unsatisfactory receiving water quality. Among stormwater discharges the impact from combined sewer overflows (CSO) plays a prominent role. The dynamic character of the discharge events lead to particular stress on the water bodies. Legal requirements for CSO follow the precautionary principle and usually set emission standards. Within the Urban Waste Water Treatment Directive 91/271/EEC of May 1991 it is written that “member states shall decide on measures to limit pollution from storm water overflows”. The directive does not give standards but solely proposes that “such measures could be based on dilution rates or capacity in relation to dry weather flow, or could specify a certain acceptable number of overflows per year”. The European Water Framework Directive 2000/60/EC of October 2000 goes beyond and asks for a combined approach to river basin management. On the source side, it requires that all existing technology-driven source-based controls must be implemented as a first step. On the effects side, it provides a new overall objective of good status for all waters, and requires that where the measures taken on the source side are not sufficient to achieve these objectives, additional ones are required. To assess the impact of CSO on the Berlin receiving water the research projects MONITOR and SAM-CSO are carried out in cooperation between Kompetenzzentrum Wasser Berlin, the Berliner Wasserbetriebe and the Senate Department of Environment Berlin. The objective of the projects is to identify and make available receiving water parameters (immission parameters) for the decision making process concerning the optimisation of the urban drainage system. Further on, a method for the evaluation of measures of combined water treatment on the basis of these immission criteria will be defined. The evaluation shall be based on both, available measurement data from the sewer system and the receiving water and simulations with an integrated model for the coupled drainage-river-system. The paper will present the methodology of the project. Special focus is on the description of the processes within the Berlin water bodies (stagnant lowland rivers) and the compilation of relevant physical-chemical and ecological parameters for the assessment of CSO.