Cyanobacteria of the order Nostocales – native species as well as alien species from tropical regions – were found to increase in many Brandenburg lakes while the formerly dominating microcystin (MC) producing cyanobacteria (Microcystis and Planktothrix) occurred less often and in lower amounts. As a consequence, lower MC concentrations were observed while the toxin cylindrospermopsin (CYN) that is produced by Nostocales was found to be widely distributed and to exceed sometimes the recommended guideline value for drinking-water of 1 µg L-1. Recent data on the occurrence of further neurotoxins (paralytic shellfish poisoningtoxin, PSP and anatoxin, ATX) produced by cyanobacteria of the order Nostocales did not exist. Nostocales are superior competitors under conditions of high light intensity and nitrogen depletion because they can fix molecular nitrogen. Their germination is regulated by temperature and the temporal starting point of the pelagic population determines the population size (the earlier the larger). Therefore, the following working hypothesis has been put forward: Combined effects of declining trophic state and global warming favor the development of Nostocales and cause a shift in the species composition as well as in the occurrences of cyanobacterial toxins. The NOSTOTOX project aimed to determine the present occurrence and future development of Nostocales and their toxins in waterbodies. Special emphasis was paid to answer the question, which Nostocales species and which toxins can be expected under conditions of a proceeding decline in trophic state and increasing water temperature. The outcome of the project aims to contribute to developing recommendations and guidelines for the management of inland waters and drinking water supplies.

Work package WP 5.2 “Combination of Managed Aquifer Recharge (MAR) and adjusted conventional treatment processes for an Integrated Water Resources Management“ within the European Project TECHNEAU (“Technology enabled universal access to safe water”) investigates bank filtration (BF) + post-treatment as a MAR technique to provide sustainable and safe drinking water supply to developing and newly industrialised countries. One of the tasks within this work package is to assess the costefficiency of BF systems. For this a comparative cost analysis (CCA) between groundwater waterworks using BF as natural pre-treatment step and surface water treatment plants (SWTPs) is performed. The CCA yielded that, under the assumption of equally low surface water quality, BF systems are more cost-efficient than SWTPs. This result is in line with the general water source priority of water suppliers, which prefer resources with the best water quality and security under the constraint of guaranteeing sufficient water availability. Furthermore the sensitivity analysis confirmed that the natural boundary condition 'pumping rate per production well' has a major impact on the specific total costs of BF systems. Lower pumping rates lead to increasing capital costs for the additional production wells, which are not fully compensated through pumping cost savings and thus lead to increasing total costs. In addition the result of the monitoring scenario clearly confirmed that for this aspect groundwater waterworks have a structural disadvantage compared to surface waterworks. Subsequently, if monitoring costs are taken into account, a higher critical pumping rate per production well is required to exceed the break-even-point. In a nutshell the CCA shall support water supply managers in the complex process of making rational investment decisions. However, since within this analysis only water abstraction and treatment process costs are considered, the CCA does not cover the total cost structure of a waterworks (e.g. costs of building sites). Thus the application of the CCA is only valid if both (i) neglected costs and (ii) benefits are in the same order of magnitude for all alternatives (exception: most cost-efficient alternative provides excess benefits). In case that the above stated prerequisites are not fulfilled, the CCA is only a first step in the economic assessment and more powerful evaluation methods (e.g. cost-benefit analysis) are needed.

Bank filtration (BF) and aquifer recharge (AR): aquifer storage recharge (ASR), aquifer storage transport recharge (ASTR); are natural and semi-natural methods for drinking water treatment and constitute a major barrier within water supply system. Recent investigations have shown that about 60 % of Berlin’s drinking water is produced via BF or AR (Zippel & Hannappel 2008). Most drinking water therefore originates from surface waters within the cities limits and is pumped from wells adjacent to it’s many lakes and rivers. Since more than 100 years this system has been supplying safe drinking water so that post-treatment is limited to aeration and subsequent sand filtration. Disinfection is usually not applied (SenStadtUm 2008). The research project NASRI (“Natural and Artificial Systems for Recharge and Infiltration”, KWB 2002 – 2006), funded by the Berliner Wasserbetriebe (BWB) and Veolia (VE) had the aim to characterize the specific hydraulic and hydrochemical conditions at selected BF and AR sites in Berlin and to assess the behaviour of major water constituents, trace organic substances, algal toxins and pathogens during subsurface passage. For this, field investigations at three transsects (Lake Tegel BFsite, Lake Tegel AR-site and Lake Wannsee), laboratory and technical scale experiments were carried out by 7 different working groups. The results of the investigations were documented in 6 extensive research reports and were the basis for nearly 50 scientific publications. In 2007 the IC-NASRI project (Integration & Consolidation of the NASRI outcomes) was initiated by VE and BWB in order to support the practical implementation and optimization of bank filtration and aquifer recharge for drinking water production with the experience gained during the NASRI project. The aim was to derive practical guidelines for design and operation of BF & AR systems by i) further interpretation of the NASRI data and ii) integrating experience from other BF / AR sites world wide. Although subsurface passage is characteristic to many systems of managed aquifer recharge (MAR) the investigations within IC-NASRI concentrated on systems where drinking water is produced by infiltration of surface water either from the banks of a lake / river or from infiltration ponds (or similar systems like ditches or irrigation fields). A transfer of the presented results to other MAR systems, which use different recharge methods (e.g. ASR) or different sources (e.g. treated wastewater) therefore needs to be considered carefully, even though many statements may be true for them as well. This reports aims at providing engineers and scientists involved in drinking water production by BF & AR with up-to-date information on settings of similar systems world wide and on the systems’ performance with regard to drinking water treatment. The aim was to give the reader a condensed overview of the topic whereas further details can be taken from the large number of references given in the bibliography.

Artificial groundwater recharge (AR) is used as semi-natural pre-treatment for drinking water production in Berlin and many other sites world-wide. Earlier research has focussed on the degradation of organic substances in these recharge systems (NASRI final reports 1 – 6), and has improved our knowledge of AR in the specific sites in Berlin. Nevertheless, a process understanding which might enable a transfer to other sites and boundary conditions is still lacking. Since biodegradation – which is assumed to be the main removal process of organic compounds – depends on the presence and activity of microorganisms, characterisation experiments with respect to biological activity will help to interpret results from soil column experiments simulating AR. In this stage of the OXIRED project, it will be of interest to link biological activity to degradation patterns in soil columns. Therefore, the following questions related to microorganisms could be necessary to answer: 1) How many are there? 2) How active are they? 3) Who is living there? A review of published literature yielded that in general, soils and sediments contain great numbers of microorganisms. Whereas in surface soils concentrations of culturable microorganisms can be found in the range of 108 per gram of dry soil, the number of culturable organisms in the subsurface are dependent on depth and are generally lower. In order to analyse them, adapted sampling methods and a sound sampling strategy are necessary for a reliable overview of microbial life. Another important aspect of microbial investigations is the detachment of organisms from biofilms for which enzymatic based methods have proven to be very useful. Different microbiological and biomolecular methods were described and assessed with respect to their suitability: 1) Cultivation: Since less than 1% of the microorganisms in natural environments can be cultured they will not be useful when one aims to get more insight into the microbial community. 2) Nucleic acid based techniques: Whereas DNA based primers can be used to detect specific species, general primers can be used to get a broad overview of the microbial life within a sample. Furthermore, active organisms can be detected by the use of RNA based primers. 3) Physiological technique: Microbial activity can be estimated indirectly based on AOC or BDOC measurements. To assess the micro-organisms present in soil columns and their activity the following methods are recommended: (i) Substrate degradation assessments by BDOC (or AOC) measurements (normally done in column studies) (ii) Direct counts (DAPI/ Acridine Orange) of direct extracted organisms and organisms present on buried slides. (iii) DGGE with universal primers (iv) qPCR (v) Direct counts with LIFE/DEAD staining and (vi) CTC redox dye o Clone libraries constructed from DGGE bands In addition to an extensive literature database of references for further details the results are summarized in a table with an overview of methods for detection, quantification and activity assessments of microbial communities in soils and sediments.

The project Aquisafe assesses the potential of selected near-natural mitigation systems, such as constructed wetlands or infiltration zones, to reduce diffuse pollution from agricultural sources and consequently protect surface water resources. A particular aim is the attenuation of nutrients and pesticides. Based on the review of available information and preliminary tests within Aquisafe 1 (2007-2009), the second project phase Aquisafe 2 (2009-2012) is structured along the following main components: (i) Development and evaluation of GIS-based methods for the identification of diffuse pollution hotspots, as well as model-based tools for the simulation of nutrient reduction from mitigation zones (ii) Assessment of nutrient retention capacity of different types of mitigation zones in international case studies in the Ic watershed in France and the Upper White River watershed in the USA under natural conditions, such as variable flow. (iii) Identification of efficient mitigation zone designs for the retention of relevant pesticides in laboratory and technical scale experiments at UBA in Berlin. The present report provides a review of the properties and existing mitigation experience of the two herbicides Atrazine and Bentazone, which will be examined exemplarily in (iii). Whereas Atrazine is clearly the pesticide of greatest concern in the USA, Bentazone is mainly an issue in Europe with an increasing tendency. The sorption of Atrazine and Bentazone on soils is moderate. Moderate sorption in combination with medium to high persistency makes these compounds relatively mobile; therefore they can usually be observed in surface waters in general and in ground waters near places of their application. First experiences show that mitigation systems can be effective measures to decrease their concentrations by supporting biotic and abiotic dissipation processes, mainly at high residence times. Adding organic matter can improve adsorption of Atrazine and Bentazone, an important dissipation process in these systems. Degradation rates for Atrazine and for Bentazone can be increased by implementing highly microbiologically active conditions which can usually be accomplished in the presence of external carbon sources. While mineralization of both herbicides is favoured in aerobic -environments significant degradation of Atrazine was also observed under anaerobic conditions. A great number of open questions remain on how to design a mitigation system which is adequate to reduce herbicides in drainage water. For instance, there is no specific information on the degradation of diluted and adsorbed forms of the herbicides, very little information about necessary residence times, adsorption constants, half lives and leaching behaviour in specific substrates or comparable designs. Moreover, the influence of nitrogen, which is present in drainage water at high concentrations, on degradation of Atrazine and Bentazone remains uncertain. Finally, the behaviour of Atrazine and Bentazone (contained in agricultural drainage water) in mitigation systems in general and in bioretention swales in particular is poorly studied. Realistically, mitigation systems would only be implemented if they also allow significant reduction of nitrates. Given the existing knowledge, systems with both aerobic and anoxic zones are likely to bring most successful results regarding both herbicides and nitrates; though they may be difficult to implement. Both for nitrates and pesticides, the presence of external organic carbon sources (with a combination of fast accessible and sustainable substrate partitions) seems to be a good basis for dissipation processes and effective reduction.

Work package WP 5.2 “Combination of Managed Aquifer Recharge (MAR) and adjusted conventional treatment processes for an Integrated Water Resources Management“ within the European Project TECHNEAU (“Technology enabled universal access to safe water”) investigates bank filtration (BF) + post-treatment as a MAR technique to provide sustainable and safe drinking water supply to developing and newly industrialised countries. One of the tasks within the project was the identification of state-of-the-art tools in the field of well field optimization modelling. Most of the currently used tools are process-driven simulation models like MODFLOW or FEFLOW. These are sometimes also combined with optimization models to reduce the computational demand and are utilized as strategic planning tools for water supply managers. However, in case of optimizing well field operation (i) under relatively constant boundary conditions and (ii) enough field data (temporal and spatial resolution dependent of the dynamics of the state parameter of interest, e.g. groundwater table, contaminant concentrations) data-driven approaches like support vector machines (SVM) can be used instead. If the water manager’s key interest is only a good predictive capability in combination with low computational demand, the application of this approach is more goal-orientated to simulate the dynamics of well field performance indicators efficiently. The contents of this report were presented to possible end-users, experts from Berliner Wasserbetriebe and Veolia. In agreement with their recommendations it was decided to focus further research within TECHNEAU on the empirical, data driven modelling approach. The selected approach is currently tested in the framework of a diploma thesis for a Berlin waterworks with the objective to analyse available production and observation well hydrographs by using modern statistical methods like principal component analysis and SVM (www.support-vector-machines.org).

Low-pressure membrane filtration of secondary effluents allows disinfection and, combined with chemical coagulation, advanced phosphorus removal. However, the loss of filtration performance due to membrane fouling is still a fundamental problem and has a strong impact on the costs of the process. Biopolymers as well as colloids in the range of 50 to 350 nm were identified as main foulants during ultrafiltration (UF). In this project the impact of a pre-treatment by ozonation (2-10 mg O3/L) and subsequent coagulation (FeCl3: 2-6 mg Fe3+/L) on the performance of a polymer UF membrane was studied. No free dissolved ozone was in contact with the membrane. Lab tests were performed using Amicon test cells in dead-end mode fed with 500 mL secondary effluent of the WWTP Ruhleben (Berlin) and the flux decline during filtration was measured. The effect of the two pre-treatment steps on the character of DOC, especially the biopolymer fraction, was investigated using size exclusion chromatography. The pre-treatment enables phosphorus removal of 75 up to 95 % with permeate concentrations of 30 to 50 µg P/L. In filtration tests pre-ozonation without flocculation leads to a less distinct flux decline (1-7 %). Coagulation without pre-ozonation increases the flux by 5 to 14 % compared to filtration of effluent without pre-tretament. The combination of both pretreatment steps improves the filtration performance up to 30 % and reduces the filtration time for 500 mL by 50 %. Different mechanisms are considered as reasons for the improved performance. It is known that coagulation partially removes the fouling-active biopolymers and humic substances. The pre-treatment with ozone, even at low dosages (2 mg/L), leads to a significant decrease of UV254 absorbance, pointing on a shift to more polar molecules. Higher ozone dosages (> 6 mg/L) additionally induce disintegration of biopolymers and a shift to smaller organic compounds. The interaction between ozonation and coagulation leads to a partial complexation of iron in solution. As a consequence, less iron is provided for the coagulation process. As the percentage of complexation of iron decreases with increasing coagulant dosage, the synergetic effect of pre-ozonation and coagulation on the filtration performance increases with increasing iron dosage. These results suggest that combining pre-ozonation and coagulation can be a promising pretreatment process to reduce the fouling of organic membranes, without the necessity of applying free dissolved ozone on the membrane surface.

The project Aquisafe assesses the potential of selected near-natural mitigation systems, such as constructed wetlands or infiltration zones, to reduce diffuse pollution from agricultural sources and consequently protect surface water resources. A particular aim is the attenuation of nutrients and pesticides. Based on the review of available information and preliminary tests within Aquisafe 1 (2007-2009), the second project phase Aquisafe 2 (2009-2012) is structured along the following main components: (i) Development and evaluation of GIS-based methods for the identification of diffuse pollution hotspots, as well as model-based tools for the simulation of nutrient reduction from mitigation zones. (ii) Assessment of nutrient retention capacity of different types of mitigation zones in international case studies in the Ic watershed in France and the Upper White River watershed in the USA under natural conditions, such as variable flow. (iii) Identification of efficient mitigation zone designs for the retention of relevant pesticides in laboratory and technical scale experiments at UBA in Berlin. The following report focuses on (ii), providing an overview of existing mitigation systems that may reduce transport of agricultural pollutants to surface waters, with a particular focus on nitrate. The report is based on an extensive review of scientific literature as well as practical guidelines. The review emphasizes on systems, which can treat pollutant loads from agricultural fields with surface or tile drainage. Such mitigation systems could play an important role in intensely used agricultural areas, where existing efforts in farm or crop management are not sufficient to reach water quality goals in receiving rivers. This is typically the case for agricultural catchments with high ratio of artificial drainage, which allows an almost complete transfer of water and contaminants, particularly during high flow events. For each identified mitigation system, its general approach, performance against nitrates and other contaminants, boundary conditions as well as expected cost are given. The systems are structured according to their place on the pathway between field and surface water into 1. systems which attempt to reduce contaminant loads in the drainage pipes and ditches (section 2), 2. systems, which can be placed between drainage system and surface water (section 3), 3. systems, which can be placed in the receiving surface water (section 4). The review shows that there are a number of feasible options with the potential to mitigate NO3 - pollution from drained agricultural land. The most promising approaches with high removal potential were found to be: - controlled drainage (section 2.2), - bioreactors at the tile level (section 2.3.2), - reactive swales (section 2.4.2), - constructed wetlands (section 3.2) and - river-diversion wetlands (section 4.2.2). Most practical experience exists for constructed wetlands with surface flow (globally) and for controlled drainage (mainly in the USA), whereas the other systems are currently at an experimental state. v For a model agricultural area, the above systems resulted in expected nitrate reduction between 14 and 82 % and cost efficiencies between 23 and 246 € kg-N-1. In terms of absolute nitrate removal, (i) wood chip walls parallel to tile drains and (ii) constructed wetlands with straw as carbon source were found to be most effective. However, for both systems there are relatively few experiences so further testing will be necessary. Regarding cost efficiency, (iii) constructed surface flow wetland with low construction cost (dam) and (iv) controlled drainage are most efficient. Whereas constructed surface flow wetlands can be implemented independently, drainage control structures need to be managed by farmers, which requires their active cooperation and proper training.

This report presented recent developments in the field on the UV-LED disinfection. This technological field is very recent and further interests - along with rapid and continuing improvements in performance (especially in terms of emission power) - are expected within the next years. After the physical characterisation of the few UV-LEDs - at 269 and 282 nm - that are currently available on the market, their disinfecting action was to be measured via biodosimetric tests. They show an increase of the inactivationwith an increasing fluence using different types of raw water, although some early static tests tend to highlight potential recontamination and inhomogeneous distribution of UV-light - which may be explained by the module configuration. Main other results indicate that UV-absorbing compounds in the various waters reduce the disinfection capacity. Morevoer, a more effective disinfection is observed at 269 nm than at 282 nm for a similar fluence. However, the emission output is better with 282 nm - UV-LEDs. Therefore, an interesting aspect, worth being investigated in the future is to ensure an optimized configuration, which balances the input power, which is necessay to run the UV-LED module, and its disinfecting action. With potential enhanced emission powers, new developments for UV-LED water purification applications would enable to perform larger-scale tests and shorten UV exposure times.