Sludge treatment and disposal is one of the key positions of operating costs in large wastewater treatment plants (WWTPs). On large WWTPs, dewatering of digested sludge is mainly performed with centrifuges. The performance of the centrifuge and thus, the (cost-)efficiency of the whole sludge dewatering process, strongly depends on the operating parameters of the centrifuge and the properties/preparation and dosage of the polymer used as flocculation aid. The research project “Decamax” therefore mainly focuses on these aspects and their impact on the dewatering result, i.e. mainly the dry solid content of the sludge cake and the quality of the sludge liquor. Moreover, the impact of sludge pre-heating on sludge dewatering is assessed, because it is known that the dewatering temperature has a high influence on the process as well. Besides a technical study (Work Package 3) and full-scale trials at a WWTP in Berlin (WP 1), the project included trials with a 0.4 m³/h pilot-scale centrifugation unit in Braunschweig (Work Package 2). The results of this work package (performed by the Institute of Sanitary and Environmental Engineering, Technische Universität Braunschweig (ISWW)) are summarised in this report. Besides the ISWW, the pilot-scale trials were supported and evaluated by the Stadtentwässerung Braunschweig (SE|BS), the KompetenzZentrum Wasser Berlin (KWB) – also responsible for the overall project management and control – and Kläranlagenberatung Kopp (KBK). Moreover, the Decamax project team and technical committee include the Berliner Wasserbetriebe (BWB) and Veolia Wasser. The project is financially supported by Veolia Water and BWB.

Im Fokus des Projektes "Mikrobielle Verockerung in technischen Systemen" standen neutrophile und acidophile Eisenbakterien, die in Leitungen, Brunnen und an und in Pumpen vorkommen und dort Ablagerungen unlöslicher Eisenverbindungen verursachen. In Brunnen, werden diese Ablagerungsprozesse, die den Zustrom behindern und damit die Brunnenleistung mindern, auch als Brunnenalterung bezeichnet. Nach derzeitigem Stand des Wissens weisen in Deutschland dabei rund 80% der gealterten Brunnen biochemisch induzierte Eisenablagerungen auf (Houben & Treskatis 2002). Die Wiederherstellung der Brunnenleistung im Rahmen von Regenerierungen und präventiven Instandhaltungsmaßnahmen ist ressourcen- und energieintensiv, so dass ein besseres Verständnis der Schlüsselparameter und Lebensbedingungen der Eisenbakterien hilft, den Brunnenbetrieb und die Instandhaltungsmaßnahmen zu optimieren und die Brunnenalterung zu reduzieren. Das Kompetenzzentrum Wasser Berlin (KWB) war einer von insgesamt 14 Verbundprojektpartnern in dem interdisziplinären Team aus Wissenschaftlern, Ingenieuren und Technikern. In Teilprojekt 5 standen Probenahmen von Berliner Betriebsbrunnen und das Datenmanagement des Gesamtprojektes im Mittelpunkt der Arbeiten. Inhaltlich knüpften die Felduntersuchungen an das von den Berliner Wasserbetrieben (BWB) initiierte und am KWB koordinierte Forschungsprojekt WELLMA (für 'well management') an. Wesentliche Aufgabe des KWB war der frühzeitige Transfer der bei den Forschungspartnern erarbeiteten Ergebnisse in die Betriebspraxis bei den Berliner Wasserbetrieben (Teilprojekt 6). Dazu wurden Brunnen und Unterwassermotorpumpen aus der Trinkwassergewinnung der BWB durch die Projektpartner der TU Berlin (Teilprojekte 1a und 1b) hinsichtlich des Vorhandenseins und der Zusammensetzung biochemisch induzierter Eisenablagerungen untersucht. Neben Belagsproben von Pumpen bei Instandhaltungsarbeiten wurden dabei auch tiefenorientierte, zielgerichtete Proben aus dem Innenrohr (Vollrohr und Filterrohr) von Brunnen sowie Ablagerungsproben aus Steig- und Rohwassersammelleitungen entnommen und mikrobiologisch und chemisch untersucht. Eigene Feldarbeiten des KWB umfassten daneben in-situ-Messungen des Redoxpotentials im nahen Umfeld eines Brunnens sowie in-situ-Messungen der Feststofffracht (Trübung) in Abhängigkeit betrieblicher Randbedingungen. Wesentliche Ziele waren die Identifizierung von Schlüsselparametern zum Verständnis der Prozesse der Eisenverockerung und -rücklösung und die Quantifizierung des sich daraus ergebenden Verbesserungspotentials im Betrieb und der Instandhaltung aus dem Bezug der Untersuchungen auf die wasserchemischen, baulichen und betrieblichen Eigenschaften der untersuchten Brunnen. Im Ergebnis wurden von März 2012 bis September 2013 Pumpen aus 26 von geplanten 30 Brunnen beprobt. Zu deren Auswertung wurden drei Cluster unterschieden: (i) Brunnen, bei denen die Pumpen stark eisenverockert waren (ii) Brunnen ohne sichtbare Eisenverockerung, aber mit Biofilmen und (iii) Brunnen mit sauberen Pumpen. Der Abgleich mit im Rahmen von Instandhaltungsarbeiten erfolgten Kamerabefahrungen bestätigte einen Zusammenhang zwischen der Stärke der Verockerung der Pumpe und dem Vorhandensein und der Stärke von Ablagerungen im Filterrohrbereich.Schlüsselparameter aus statistisch belastbaren Zusammenhängen zwischen den Eisenbakterien-Gemeinschaften, den chemisch-mineralogischen Ockereigenschaften und den wasserchemischen, baulichen und betrieblichen Parametern konnten jedoch nicht herausgearbeitet werden, da die Diversität der beteiligten Eisenbakterien höher als vermutet war und sich selbst direkt benachbarte Brunnen mit ähnlichen Eigenschaften hinsichtlich der Ocker stark unterschieden. Auch stellten die Probenahmen immer nur Momentaufnahmen der zeitlich hochvariablen Anströmbedingungen dar.

Diffuse nitrate (NO3-) contamination from intense agriculture adversely impacts freshwater ecosystems, and can also pose a risk to human health if receiving surface waters are used for drinking water production. Implementation of near-natural mitigation zones such as reactive swales or wetlands have been proven to be promising measures to reduce nitrate loads in agricultural drainage waters. However, the behaviour of these systems at low temperatures and its dependence on system design is not well known until now. In this part of the Aquisafe project, the behaviour of a full scale (length: 45 m) infiltration ditch and two parallel wetlands (surface flow wetland and infiltration wetland) treating drainage water of two agricultural watersheds in Brittany (France) with high nitrate concentrations in the receiving river, were constructed and monitored for 3 flow seasons in 2011, 2012 and 2013 to evaluate field scale performance of these systems. As the flow in both sites is usually restricted to winter and spring months (December – May), systems usually operate at low water temperatures of 5°C - 10°C. Tracer tests revealed shorter than designed retention times (average values for whole flow season 2013: 1.1 h for infiltration ditch, 4.3 h for infiltration wetland and 8.4 h for surface wetland) due to high inflows and preferential flow. This likely is the main reason for observed low average retention of nitrate loads of 1.5-3% during the whole flow season. However, increase of relative nitrate retention to up to 80% during low flow conditions at the end of flow season in May with higher HRT and increasing temperatures show that investigated systems generally work. Results show a stronger correlation between residence time and nitrate reduction for all three systems compared to correlation with temperature. Retention times necessary in existing systems to achieve nitrate retention >30% were 1 day for infiltration ditch and 3 days for wetlands. Performance was compared to results of two technical scale reactive swales (length: 8 m) operated for 1.5 years at two different residence times (0.4 and 2.5 days), situated at a test site of the German Federal Environmental Agency (UBA) in Berlin (Germany). Similar nitrate reduction was observed for comparable temperature and HRT values (during low flow conditions at end of flow season 2013), showing that up-scaling is a suitable approach to transfer knowledge gathered from technical scale experiments to field conditions. For the design of new mitigation systems, expected inflow volumes have to be investigated carefully in advance to ensure a sufficient residence time for effective nitrate reduction at low temperatures.

The wash out of agricultural auxiliary chemicals like fertilizer and pesticides via surface run-off or subsurface leaching into drainage systems or ground waters, which discharge into surface waters, presents an increasing risk for drinking water production and biodiversity in rivers and lakes. Mitigation zones are important measures to attenuate contamination at the source and relieve surface waters downstream. Under high flow conditions, as they occur during rainy seasons and snow melt, the effectiveness of such facilities is restricted due to bypass of untreated waters or very short contact times. This study of the Aquisafe 2 project focus on drainage water decontamination and examines mitigation zone designs with organic substrates for their potential to reduce a set of herbicides and nitrate (NO3-), concurrently and efficiently, at short hydraulic residence times (0.2 to 2.5 days) to prepare their implementation in contamination hot spots. The herbicides bentazone, atrazine and isoproturon were classified as most relevant for drinking water production. On the basis of comprehensive literature studies the organic substrates bark mulch and straw and the design of bioretention swales emerged to be of high potential for decontamination of drainage waters in mitigation zones. In laboratory scale studies the substrates were tested in degradation-, sorption- and leaching-experiments at temperatures around 21 °C for their potential to ensure long- lasting hydraulic permeability, denitrification and attenuation of the selected herbicides. The selected organic substrates provide a high and long term stable permeable conductivity to realize and maintain high flow. The effective porosity yielded around 0.45 and reduced within 1.5 years by only 25 %. Straw is a readily available organic carbon source, which can support effective and efficient denitrification at short hydraulic residence times. Bark mulch contains more resistant carbon species, but contributes also to NO3- removal. In mixture with straw the performance of bark mulch as organic carbon source for denitrification increases (co-metabolic decomposition). Organic substrates are characterized by strong wash out of dissolved organic carbon (DOC) and high denitrification rates (15 to 45 g-N m-3 d-1) in the start phase and successive decrease of denitrification performance due to loss of readily available organic carbon. Despite decline of performance, denitrification rates stabilized after one year of operation at constant conditions at a level of 4 to 10 g-N m-3 d-1 (10 to 25 % of input). The potential of the organic substrate to retain the selected herbicides is very different for each compound and bases on different dissipation paths. Denitrifying conditions are in general disadvantageous for retention of the selected herbicides. Bentazone is too persistent and mobile to be considerably retained under high flow conditions. Atrazine can be substantially removed from drainage waters. It is suspected to be attenuated predominantly by formation of bound residues at the organic substrate, especially bark mulch, and partially by degradation to hydroxy-atrazine. Isoproturon seems to be effectively retained under suboxic conditions by degradation to metabolites. At technical scale parallel retention of NO3- and atrazine and NO3- and isoproturon was investigated. The potential of the organic carbon source (mixture of bark mulch and

Der Großteil der bundesdeutschen Binnengewässer wird bis 2015 nicht den guten ökologischen Zustand erreichen, der von der EU-Wasserrahmenrichtlinie gefordert wird. Bisher ging man davon aus, dass die Gewässergüte in erster Linie durch Phosphor bestimmt wird. In jüngster Zeit mehrten sich aber Hinweise, dass in vielen Gewässern auch Stickstoff eine entscheidende Steuergröße der Phytoplanktonentwicklung darstellt. Daher wird die Reduzierung von Stickstoffeinträgen gefordert. Die Kosten für Maßnahmen zur Reduktion der Stickstoffeinträge aus punktuellen (beispielsweise Kläranlagen) und diffusen Quellen (beispielsweise aus der Landwirtschaft) werden um ein Vielfaches höher geschätzt im Vergleich zu Maßnahmen zur Reduktion von Phosphoreinträgen. Ob Maßnahmen zur Stickstoffreduktion ökologisch wirksam werden, kann aufgrund unzureichender Kenntnisse zur Herkunft, Umsetzung und Wirkung von Stickstoff derzeit nicht eingeschätzt werden. Daher fordern öffentliche und wirtschaftliche Maßnahmenträger nachdrücklich eine Klärung des Nutzens von Stickstoffelimination. An diesem Punkt setzt NITROLIMIT an. Es sollte eine fundierte wissenschaftliche Grundlage zur Beurteilung des Einflusses von Stickstoff auf die Gewässergüte geschaffen, die Kosten und Nutzen von Maßnahmen zur Verringerung von Stickstoffeinträgen analysiert und darauf basierend Empfehlungen für eine nachhaltige Gewässerbewirtschaftung erarbeitet werden.

This report compiles the results of three consecutive work packages that have been worked on during the Aquisafe II project. The approach developed is based on the previous Aquisafe I project where the Soil Water Assessment Tool (SWAT) was used as an analytical instrument to develop mitigation strategies for N loads and concentrations in the Ic catchment. During Aquisage I we concluded that SWAT should include a wetland function with which the effect of artificially, constructed wetlands on solute N fluxes can be evaluated. Chapter 1 compiles results of an extensive literature review that was made to identify potential wetland routines and processes that can be included in SWAT. The SWAT add-on to be developed should allow to individually test the effect on single wetlands (e.g. in a given hydrological response unit or subcatchment) as well as the effect of multiple wetlands on the landscape scale. We therefore implemented a stand alone version of the new wetland module which is described in Chapter 2. Here we show the general functionality and individual components of the wetland module. The chapter ends with a virtual application of the modules using SWAT outputs copied from the Ic results. Additionally, a Monte Carlo based sensitivity analyses of the wetland module input parameters showed that the denitrification rate seems to be the most constrained parameter for the simulation of N turnover in the new wetland module. A full implementation of the new wetland module is described in chapter 3. Here, the structural embedment of the wetland module in the SWAT architecture is described. To proof the functionality of the SWAT wetland module model runs were compared to the stand alone version to make sure that the module was correctly implemented. We conclude that the SWAT wetland extension is ready to be tested in real world catchments. Such a full test of the SWAT wetland model was planned towards the end of Aquisafe II. However, as data from the wetlands constructed within Aquisafe II were not available in due time, this last test of the SWAT module was possible.

The final report of the project COSMA describes the modeling results of four different scenarios regarding the pressure build-up in shallow aquifers due to the injection of CO2 into the sandstone aquifers of the Detfurth Formation. It is based on the “Technical Report on hydrogeological and static structural geological model implementation” (D 2.1) which focuses on the compilation of geological and hydrogeological background data (average values) and the development of a simplified conceptual hydrogeological model for a setting typical for the Northern German Sedimentary Basin as well as the model selection, model parameterization, definition of boundary conditions and implementation in hydrogeological flow model software packages. The hydrogeological model of the Cenozoic includes Quaternary and Tertiary aquifers down to the layer beneath the Rupelian clay. Moreover, a concept for modeling the interaction between deep, consolidated, saline aquifers with unconsolidated freshwater aquifers was developed. This report describes scenario analyses by using the numerical hydraulic model of the Detfurth Formation (Middle Bunter) and the simplified numerical groundwater model of the Cenozoic. The numerical models can be used to assess the key parameters, having an impact on the upconing of deeper saline groundwater beneath the well fields of water works (in shallow aquifer) due to imposed pressure signals.

The export of agricultural contaminants from agricultural landscapes of the US Midwest has contributed to the impairment of surface waters throughout the Mississippi River Basin and has been linked to various human health concerns. Natural treatment systems (wetlands, bioswales, bioreactors) can capture agricultural runoff and significantly reduce nutrient loading to downstream waters but there is a paucity of data on the effectiveness of these treatment systems to attenuate the suite of pollutants (nutrients and synthetic organics) typically found in agricultural runoff. This understanding is important given that the degradation of different pollutants involves metabolic pathways that often require different redox environments. As part of the Aquisafe-2 project, a bioretention swale comprising two treatment cells (a subsurface cell in series with a surface cell) was monitored, and its performance evaluated over a three-year period (2011 - 2013). Results showed that the bioswale was moderately efficient with regard to nitrate (NO3-; retention range: 16-58 %). N removal averaging 30 % was measured during a series of wetting events during which the bioswale operated at an estimated average hydraulic retention time (HRT) of 0.97 day. Spatial analysis of the data showed that almost all the NO3- removal occurred in the subsurface cell; however, N removal was also measured in the surface cell under low flow conditions (estimated HRT: 2.5 days). The highest rates of N removal (~ 58 %) were measured when the bioswale stayed wet for several days probably due to the development of a more optimum environment for denitrifying microbes. Nitrate removal capacity was limited by NO3- availability, short retention times during high flows, and the frequent fluctuation between oxic and anoxic conditions, but not by water temperature (8.3-16.6 oC) and dissolved organic carbon (DOC; 1.9 - 29.2 mg C L-1). The bioswale performance with regard to soluble reactive phosphorus (SRP) and atrazine was more variable, with net retention during some periods and net release at other times. The bioswale was a net source of P during most sampling periods with an average SRP release corresponding to 13 % of input, probably due to desorption of water soluble P from the topsoil applied during construction. This interpretation is supported by the progressive decline in P release observed between the first and third year of monitoring. The subsurface and the surface cells contributed almost equally to the fate of P in the bioswale. Likewise, the bioswale was at times a small/moderate sink (13-31 % retention) for atrazine, and a net source (-38 % to -15 %) during periods when the bioswale received overland runoff from the adjacent crop field which bypassed the subsurface cell. Results suggested that competition between atrazine and DOC for sorption sites is a possible mechanism affecting atrazine removal efficiency. Additional work is needed to compare the efficiency of the subsurface and surface cells with regard to atrazine, and elucidate the biogeochemical factors controlling its fate in the bioswale.

Regenwasserabfluss ist die größte unbehandelte Quelle von potentiell hohen Spuren-stofffrachten in urbane Oberflächengewässer. In Berlin werden ca. 74% oder jährlich 44 Millionen m³ des Regenwasserabflusses weitgehend unbehandelt eingeleitet. Dies ent-spricht etwa 5% des jährlichen Abflusses der Stadtspree an der Mündung in die Havel. Erste Studien aus der Schweiz und Frankreich zu ausgewählten organischen Spurenstoffen (z.B. Biozide, Kunststoffinhaltsstoffe, Verbrennungsprodukte) im Regenwasserabfluss und Oberflächengewässern zeigen zum Teil hohe Konzentrationen von Substanzen mit möglicher Relevanz für aquatische Organismen oder die mensch-liche Nutzung.