In agricultural watersheds affected by diffuse pollution, limitation of fertilizer and pesticide application may not be sufficient to achieve good river water quality. After waterworks had to be closed in Brittany due to elevated nitrate concentrations in the river Ic (> 50 mg-NO3 L-1), the project Aquisafe has been initiated. The objective of Aquisafe is to reduce pollutant loads (nitrate and pesticides) from agricultural fields by implementation of near-natural mitigation zones at diffuse pollution hotspots at the head of watersheds. Simple and small solutions have to be designed in order to more efficiently reduce nitrate and pesticide concentrations in receiving rivers. In addition, a planning tool has to be developed to determine optimal locations to construct these systems. Finally, a tool to assess the effectiveness of these reactive zones on watershed water quality will be implemented. In order to reach the first objective, design features are tested on three scales: 1) laboratory scale, 2) technical scale and 3) field scale. 1) In the laboratory, column experiments were conducted with different organic substrates at short hydraulic residence times (HRT). The efficiency for parallel reduction of nitrate and two common herbicides in Europe, Bentazon and Isoproturon, was explored (Krause Camilo, 2012). 2) In technical scale, two parallel swales were filled with the most suitable material determined in (1) for a one year test. The influence of HRT and temperature was investigated. For nitrate, high reduction could be achieved at short HRT; results for herbicides still have to be confirmed. 3) One infiltration ditch and two simple wetlands were constructed in Brittany (France), taking into account experiences from other scales. These systems are now monitored to investigate the effects of upscaling. Site locations were chosen based on a validated and repeatable GIS-based overlay method that prioritises zones of potential contribution to nitrate pollution (Orlikowski et al, 2011). Additionally, a new wetland module is being developed for the Soil and Water Assessment Tool (SWAT). It allows to predict impacts of wetland constructions on nitrate concentrations in receiving rivers; the module is now implemented but still has to be calibrated with in situ monitoring results. The presentation will focus on results of the up-scaling approach, and will show how the tools of Aquisafe can be used for supporting the development of strategies at catchment scale.

Im Rahmen eines Forschungsprojektes wurden die Auswirkungen von Mischwasserentlastungen auf die Berliner Stadtspree untersucht und ein Planungsinstrument zur Reduzierung der Auswirkungen von Mischwasserüberläufen entwickelt.

Der Einsatz von Filtern zur Reduzierung von Stickstoff- und Phosphoreinträgen aus der Landwirtschaft in die Oberflächengewässer wurde in Deutschland bisher kaum untersucht. In einem Workshop wurde der Stand der Untersuchungen von Projekten in Polen, Dänemark, Deutschland und Frankreich vorgestellt. Um das Potential dieser Maßnahmen auszuschöpfen, sind die Entwicklung von Entscheidungsunterstützungssystemen für geeignete Einsatzorte und weitere Demonstrationsprojekte unter Feldbedingungen notwendig.

In the city of Berlin combined sewer overflows (CSO) can lead to severe depressions in dissolved oxygen (DO) of receiving urban rivers and hence to acute stress for the local fish fauna. To quantify CSO impacts and optimize sewer management strategies, a model-based planning instrument has been developed. It couples the urban drainage model InfoWorks CS which simulates hydraulics and pollutant transport in the sewer with the river water quality model QSim which simulates hydraulics, mass transport and various biogeochemical processes in the receiving water body. To identify simulated CSO impacts, concentration-durationfrequency-thresholds for DO are applied to river model results via an impact assessment tool. Two kinds of impacts are distinguished: i) suboptimal conditions and ii) critical conditions for which acute fish kills are possible. In the case of Berlin, suboptimal conditions are observed on up to 92 days per year, predominantly during periods of low discharge and high temperatures whereas critical conditions only occur after CSO. For model calibration and validation, continuous measurements in both river and sewer are used. First simulations show good accordance between simulated and measured DO concentration in the river with Nash-Sutcliffe efficiencies between 0.70 and 0.79 for an eight-month time period at three different river monitoring points. However, to assure satisfactory model performance for adverse DO conditions in particular, impact assessment results for measured and simulated data are compared. Regarding suboptimal DO conditions simulated and measured data show good agreement. Nevertheless model representation for critical conditions is poor for some river sections and requires further improvement for CSO conditions. The results underline the importance of combining different validation approaches when dealing with complex systems.

The urban stretch of the River Spree is a regulated lowland-river, which is affected by a number of anthropogenic pressures, most notably impacts from combined sewer overflows (CSO) of the Berlin sewer system. Collected data show that occurrence of CSO can be detected in the river through a combination of continuous monitoring data, such as specific conductivity, ammonium (NH4), chemical oxygen demand and dissolved oxygen (DO). Comparison with stormwater guidelines indicates that drops in DO from CSO lead to regular problematic conditions for the fish fauna. In contrast, observed NH4 peaks never reach fish-toxic levels. Mitigation measures are currently implemented to reduce these negative impacts during storm events. The effect of past and potential future CSO measures can be studied with a model tool, which has been tested and is currently calibrated based on the above monitoring data.

Vier verschieden-konfigurierte Multigas-Sensorsysteme (Elektronische Nasen) sind Gegenstand von Versuchen an einer Kanalforschungsanlage der Berliner Wasserbetriebe. Die Systeme werden 6 Monate verschiedenen realitätsnahen Prozessbedingungen ausgesetzt, um im Anschluss eine Aussage zur Einsetzbarkeit der Systeme auf derzeitigem Stand der Technik im Geruchsmanagement von Abwasserkanalisationen machen zu können. Momentan ist kein Standard zum Test und zur Bewertung von solchen technischen Messsystemen unter Praxisbedingungen verfügbar. Daher wurde eine Methode entwickelt, die eine anwendungs- und innovationsorientierte Bewertung zulässt. Bewertungskriterien werden aufgestellt, orientiert an Verfahrenskenngrößen laut DIN EN ISO 9169 [3]. Die Kriterien werden an das Messkonzept der Elektronischen Nasen, sowie an die Versuchsbedingungen angepasst und erweitert. Das Versuchsprogramm ist so konzipiert, dass verschiedene Zielanwendungsfälle (wie z. B. die Planung einer Dosierstrategie mit geruchsreduzierenden Additiven) abgedeckt sind. Das Vorhaben wird zusammen mit den Berliner Wasserbetrieben und Veolia Wasser sowie in Kooperation mit evado-engineering durchgeführt.

The effect of combined sewer overflow (CSO) control measures should be validated during operation based on monitoring of CSO activity and subsequent comparison with (legal) requirements. However, most CSO monitoring programs have been started only recently and therefore no long-term data is available for reliable efficiency control. A method is proposed that focuses on rainfall data for evaluating the effectiveness of CSO control measures. It is applicable if a sufficient time-series of rainfall data and a limited set of data on CSO discharges are available. The method is demonstrated for four catchments of the Berlin combined sewer system. The analysis of the 2000–2007 data shows the effect of CSO control measures, such as activation of in-pipe storage capacities within the Berlin system. The catchment, where measures are fully implemented shows less than 40% of the CSO activity of those catchments, where measures have not yet or not yet completely been realised.