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

To cope with occurring traces of organic contaminants in the effluent of waste water treatment plants, ozonation is a suitable technical treatment method. However, there is an ongoing discussion about the necessity of a posttreatment of ozonation effluents to remove possible toxic ozonation by-products. This study compares a dual media filter (DMF) and a biological activated carbon filter (BAC), which were used for ozonation post-treatment, and were also designed as coagulation filters for tertiary phosphor removal. The results of this study demonstrate that both rapid filters performed similarly in respect to DOC reduction and oxygen demand, and could also be used for tertiary phosphorus removal without any impairments. A comparison of a serial mode of the DMF and the BAC with a slow sand filter, which was used as a surrogate for an infiltration pond, showed that this two-stage process could increase the degradation of the DOC, but was not able to remove the entire biodegradable DOC.

Annually, about two million mega grams of dry solids (DS) of sewage sludge accumulate in wastewater treatment in Germany. According to the Statistical Federal Office (Destatis, 2013), 1,846,441 mega grams DS of sewage sludge were utilized in 2012. Besides incineration, the exploitation of sewage sludge in agriculture as fertilizer plays a significant role. In 2012, about 600,000 (544,065) mega grams of dry sewage sludge were applied on agriculturally or horticulturally used soils, which corresponds to 30.0 % of total amount (Bundesamt, 2011, AbfKlärV, 1992). Before disposing, the sewage sludge must be dewatered which is usually executed using synthetic flocculation aids like polyacrylamide (PAM) and its derivatives (Tuan et al., 2012). According to the fertilizer ordinance, as of 01/01/2017 20 % of all compounds as well as the end product of the used synthetic flocculation aids must be degraded two years after agricultural application (DüMV, 2012). Despite this regulation, an accumulation of polyacrylamide in the soil can be expected, since it is allowed to apply 5 mega grams DS of sewage sludge per hectare in 5 years (AbfKlärV, 1992). Seybold (1994) suggests that PAM is mostly resistant to microbial decomposition and mainly physically degraded. Not the PAM but its monomer (acrylamide) is known for its neurotoxicity (LoPachin and Gavin, 2012). Even if it does not permanently accumulate in soil, a potential toxicity exists. Therefore it is desirable to substitute the synthetic polyelectrolyte by a natural based and easily bio-degradable alternative flocculation aid. Several studies investigating the flocculation properties of cationic starch have been carried out (Rath and Singh, 1997, Khalil and Aly, 2001, Haack et al., 2002, Schwarz et al., 2006, Hebeish et al., 2010, Wang et al., 2013) but not in combination as nutrient incorporating fertilizer. The scarcity of phosphate rock sources has been an important issue in the last decades (Pinnekamp et al., 2007, Kabbe, 2013) as phosphate is a key nutrient for life on earth. As Kabbe (2013) states: “It is the key element in our genome, cellular membranes, skeleton and molecule adenosine triphosphate (ATP), the organism’s main energy storage.” Phosphorus is a non-substitutable nutrient in agriculture. An application of phosphorus fertilizer manufactured from non-renewable phosphate rock due to high crop yields is inevitable (Syers et al., 2011). Approximately 80 % of mined phosphorus are used for the fertilizer industry worldwide, in Germany even 85 % (Pinnekamp et al., 2007). Cordell et al. (2009) points out that the current global resources will be depleted in 50 to 100 years. For that reason, fostering of phosphorus recovery has become a current topic in the last years. So the European project P-REX – Sustainable Sewage Sludge Management fostering Phosphorus Recovery and Energy Efficiency was coined in September 2012. 16 European partners managed by project leader Dr Christian Kabbe from Berlin Centre of Competence for Water gGmbH work on 6 different working areas trying to close the phosphorus loop (shown in Fig. 1). Besides phosphorus recovery technologies from sludge processes or incineration ash out of sewage sludge, direct application on arable land is one branch of the phosphorus cycle. Within the working area 3 (WA3), the demonstration of applicability of green polymers for sludge dewatering step is one working package (P-REX, 2013). Within P-REX, this research attempts to combine phosphorus recovery and substitution of synthetic flocculation aids using natural based (green) polymers within sewage sludge treatment. The flocculation properties of a starch based cationic green polymer will be examined by measuring selected dewaterability indicators. Diverse sludge types from 3 different German wastewater treatment plants will be analysed after applying polyacrylamide/starch blends with defined ratios. As to phosphorus recovery, the phosphate contents of treated sludge water will be measured and a possible nutrient incorporation will be surveyed.

Intelligent gekoppeltes Regenwasser- und Abwassermanagement soll Abwasserentsorgung, Gewässerqualität und Stadtklima verbessern. Das Verbundforschungsprojekt KURAS ist ein durch das Bundesministerium für Bildung und Forschung gefördertes Vorhaben, das im Juni 2013 gestartet wurde. KURAS findet in enger Zusammenarbeit zwischen Fachpartnern aus Forschung und Praxis und Berliner Entscheidungsträgern statt. Die Projektkoordination liegt bei der TU Berlin und dem Kompetenzzentrum Wasser Berlin. Das Projekt hat ein Fördervolumen von 4,5 Mio. € und wird über drei Jahre durchgeführt.