Facilitating and improving decision-making in urban stormwater management is a key goal of the interdisciplinary research project “Concepts for urban rainwater management, drainage and sewage systems” (KURAS). By reinstating a more natural hydrological cycle, by increasing infiltration, evapotranspiration and stormwater reuse at the building or neighborhood level, e.g. via green roofs, pervious surfaces, swales and artificial ponds, to name but a few, stormwater management has the potential not only to reduce flooding and river degradation but also to improve landscape and habitat quality, the urban climate and resource efficiency, to reduce costs, and to respond more flexibly to uncertain future conditions. These multiple potential benefits have been valuated in a systematic way, thus providing a quantitative and comparative assessment of the effects of the various approaches to stormwater management as a basis for decision-making. An important element is the stakeholder involvement in planning in order to expose interests, resolve conflicts and to discuss existing financial, legal, administrative and knowledge-related barriers to adapted urban stormwater management. For two representative neighborhoods in Berlin, Germany, alternative and realistic stormwater management scenarios have been developed based upon an analysis of the current state and evaluated using the effect indicators. Central actors for stormwater management in Berlin are collaborating with other stakeholders in the sample neighborhoods to formulate and prioritize goals regarding the selection of measures, to discuss the evaluation results and to develop transition strategies. The presentation will focus on this experience of stakeholder participation in the design of stormwater management systems on the neighborhood scale. It will present preliminary findings to be translated into recommendations for policy makers and practitioners.

In view of existing and future challenges, such as the results of climate change and the changing manner of water usage, the overriding target of the joint research project KURAS (Concept for urban stormwater management and wastewater systems), sponsored by the German Federal Ministry for Education and Research, was to formulate recommendations for the operation, expansion and adjustment of urban wastewater and stormwater infrastructures to the future. To this end planning methods have been developed in KURAS, in which a consequent evaluation of measures interlink with local requirements and challenges. The basic methods were elaborated within the project for the topics wastewater systems and management of stormwater and applied for Berlin case studies at quarter and catchment area level. For both topic areas it shows that an integrated, scale overlapping planning of measures for stormwater management and wastewater management can achieve an increased level of usage. The methods developed in KURAS are suitable for supporting such a planning. A standard employment necessitates additional solutions of a technical as well as regulatory nature.

Im Rahmen eines Planspiels wurden für ein Stadtquartier Kombinationen der Regenwasserbewirtschaftung erstellt und wissenschaftlich bewertet. Die verwendete Methode kombiniert dazu lokale Bedingungen (Problemlage, Machbarkeit von Maßnahmen und lokale Ziele) mit einer Bewertung von 27 Einzelmaßnahmen hinsichtlich ihrer vielfältigen Effekte. Die Ergebnisse zeigen zunächst, dass eine skalenübergreifende Kombination von Maßnahmen vom Gebäude bis zum Kanaleinzugsgebiet ein großes Potenzial für die Verbesserung der städtischen Umwelt (Gewässer und Biodiversität) und Lebensqualität (Stadtklima, Freiraumqualität, Nutzen auf Gebäudeebene) hat. Die verwendete Methode erwies sich als gut geeignet für die Auswahl effektorientierter (und machbarer) Maßnahmen und für deren gezielte Platzierung in Problemräumen. Die Erfahrungen zeigen aber auch, dass die Methode optimiert werden muss, um eine bestimmte Zielerreichung (z.B. Kostenrahmen oder Einleitbeschränkung) während der Planung zu berücksichtigen.

A total of 27 existing measures of stormwater management were studied across scales from building level (vegetated buildings, rainwater use) to city quarter level (infiltration, de-paving, artificial lakes and streams, decentralised treatment) and catchment level (centralised treatment, storage). For each measure, the same performance indicators were quantified based on literature, monitoring and simulation results regarding six potential benefits (water/energy saving potential, improvement of landscape quality, increase in biodiversity, reduced urban heat exposure, improvement of groundwater and surface water bodies), indirect resource use (life cycle assessment) and direct cost. Results show that each measure has its strengths and weaknesses. Thus, it is expected that different combinations of measures will lead to increased benefits for different locations/settings. The developed measurebenefit/cost-matrix may support the finding of such improved combinations and is currently tested in a research project regarding its potential for problem-oriented urban planning in Berlin, Germany.

Swimming in urban surface waters is still an exception in European cities. At the same time there are numerous initiatives trying to achieve a quality of urban surface waters that allows recreational activities including swimming. In order to manage bathing waters properly the EU Bathing Water Directive (2006/7/EC) demands the elaboration of bathing water profiles in which sources of pollution have to be assessed. In order to investigate the relevance of stormwater as a source of microbial contamination as well as the influence of catchment characteristics on the faecal loading, E.Coli, intestinal Enterococci and colony counts have been measured in event related stormwater samples of three different catchment areas in Berlin. The catchment areas were chosen to be as homogeneous as possible representing catchments of old housing buildings (OLD), new housing buildings (NEW), and commercial areas (COM). N-Formylaminoantipyrine (FAA) was measured as a tracer for raw wastewater. Results showed elevated concentrations (1-2 log units) of faecal indicator organisms (FIO) in catchment OLD (104-105 in comparison to 103 cfu/100mL) suggesting illicit connections of wastewater discharges to rainwater drains, which is supported by elevated concentrations of FAA in the same catchment type. This underlines the relevance of these illicit connections as a source of hygienic contamination, which has to be considered when planning urban bathing water activities.

Untreated stormwater runoff can be an important source of pollutants affecting urban surface waters. To investigate the relevance of micropollutants in urban stormwater runoff for the city of Berlin, an event-based, one-year monitoring program for sampling of separate storm sewers was conducted. Monitoring points were selected in five homogeneous catchments of different urban structure types to consider catchment-specific differences. Volume proportional samples (one composite sample per event) were analysed for a comprehensive set of ~100 micropollutants determined from literature review (e.g. plasticisers [phthalates], biocides/pesticides, flame retardants [organophosphates, polybrominated diphenylethers], PAH, heavy metals) as well as standard parameters (TSS, total P, phosphate, ammonium, COD, BOD). For selected storm events, time resolved samples were analysed to investigate the concentration dynamics and evaluate first flush characteristics. Results of event mean concentrations show catchment-specific differences for the majority of detected micropollutants. Furthermore, results of time-resolved samples indicate that most parameters do not show clear first flush effects with concentrations of several micropollutants even remaining constant during the course of the storm event (e.g. mecoprop, carbendazim, TBEP).

Im Rahmen einer etwa zweijährigen Studie wurde für Berlin erstmals das Ausmaß der Belastung von Regenabfluss mit Spurenstoffen durch ein einjähriges Monitoringprogramm in Einzugsgebieten unterschiedlicher Stadtstrukturtypen (Altbau, Neubau, Gewerbe, Einfamilienhäuser, Straßen) untersucht. Insgesamt wurden über 90 volumenproportionale Mischproben auf etwa 100 Spurenstoffe analysiert (z.B. Phthalate, Pestizide/Biozide, Flammschutzmittel, PAK, Schwermetalle), von denen ein Großteil (>70) detektiert wurde. Die höchsten Konzentrationen an organischen Spuren- stoffen wurden für Phthalate gefunden (DIDP+DINP: Ø 12 µg/L), während Schwermetalle von Zink dominiert wurden (Ø 950 µg/L). Für die Mehrzahl der Stoffe gab es dabei signifikante Unterschiede zwischen den Stadtstrukturen. In einem Fließgewässer genommene Proben zeigen, dass für einige Substanzen (z.B. DEHP, Carbendazim, einige PAK) Umweltqualitätsnormen im Gewässer bei Regen überschritten werden können. Eine Hochrechnung der über das Regenwasser in die Gewässer gelangenden Spurenstofffrachten für Gesamt-Berlin hat ergeben, dass Frachten regenwasserbürtiger Spurenstoffe in der gleichen Größenordnung wie schmutzwasserbürtige Spurenstoffe liegen können.

Subsurface travel time from the area of recharge to the abstraction during Managed Aquifer Recharge (MAR) is a critical parameter to ensure sufficient attenuation for hygienic parameters and other undesired substances. This study investigates seasonal temperature fluctuations observed in recharge water and MAR wells as a proxy for cheap and reliable travel time control at a basin infiltration site in Berlin-Spandau (Germany). Based on a time series from seven years of manual measurements, temperature fluctuations observed in infiltration basins and abstraction wells were fitted to sinusoidal functions. Peak values represented as local maxima and local minima from the fitted curves were used for the approximation of travel times between infiltration basin and abstraction wells. Uncertainty was assessed by Monte Carlo simulation of fitted curves based on standard deviation (2s) from residuals. The calculated error propagation from 2s in infiltration basin and 2s in wells range from 7 to 19 days. This study indicates that travel time approximation based on biased manual measurements of temperature is associated with high uncertainty. Nevertheless, the water temperature method for estimating subsurface travel times shows encouraging results and if temperature can be accurately determined, this method can be readily applied at other sites with similar characteristics.

Ozonation is known as a suitable technical process to eliminate trace organic compounds (TrOC) in secondary effluent. To decide if ozonation is a suitable option as an upgrade of a specific wastewater treatment plant (WWTP), ozonation experiments in laboratory-scale can help to avoid the operation of expensive and labour intensive pilot plants. Such laboratory experiments should be conducted at similar conditions and by the same methods in order to achieve a better comparability of the results. In this study, potential impacts of sample dilution due to the addition of an ozone stock solution, water temperature, and concentration of suspended solids (TSS) on TrOC elimination and UVA254 reduction (delta UVA254) were investigated. The results show that a change in water temperature within a range of 10 to 30°C and sample dilution of less than 20% due to the addition of ozone stock solution at batch ozonation, respectively, does neither have a significant impact on achieved TrOC elimination nor or delta UVA254. Suspended solids affected the TrOC elimination and delta UVA254 at TSS concentrations of more than 30 mg/L, whereas at low TSS concentrations (< 4 mg/L), the impact of TSS was found to be neglectable.