Numerous papers have been published studying the causes of fouling in membrane bioreactors (MBRs) and searching for a universal fouling indicator. Unfortunately, as these studies were performed using various set-ups and operating conditions (different membranes, sludge retention time (SRT), hydraulic conditions and diverse feed wastewaters, etc.), the results in terms of fouling rates and the infl uence of individual parameters rarely match up. In order to obtain a signifi cant database of comparable results from different plants, an intensive monitoring campaign of four MBR systems started in 2007 in Berlin. In these units, 14 parameters were monitored on a weekly basis over 10 months to characterise the mixed liquor and the corresponding permeability, including the novel parameter transparent exopolymer particles (TEP), which represent a specially sticky fraction of the extracellular polymeric substances (EPS). By performing statistical analyses it was demonstrated that there is no unique fouling indicator, and origins of fouling must be searched in the combination of several parameters using multivariable analysis. Applying a multiple regression the critical fl ux values could be correlated with four parameters (temperature, nitrate, bound and soluble TEP) measured in the activated sludge for 95% of the data.

Trinkwasserbrunnen unterliegen natürlichen Alterungsprozessen, unter anderem der Verockerung (Wiacek 2006). Es wurden mehrere Biofilmproben aus der Rohwasserleitung des Wasserwerks Stolpe-Berlin entnommen (Kapitel 1.4/ 2.2.1). Die Proben die von der TU-Berlin zur Verfügung gestellt wurden, wurden kultiviert und anschließend mit mikrobiologischen Methoden charakterisiert (Kapitel 3.4). Vier Stämme, die verstärkt Eisenablagerungen und dunkle Kolonien aufwiesen, wurden für Folgeversuche (Kapitel 3.2/ 3.3) eingesetzt. Alle Versuchsergebnisse deuten daraufhin, dass Eisenhydroxid einen großen Einfluss auf die Wirkung des H2O2 auf Biofilme hatte (Kapitel 3). Es hat sich ergeben, dass eisenoxidierende Bakterien und mit ihnen assoziierte Bakterien (Kapitel 3.6) effektiv zu bekämpfen sind, wenn die sie umgebenden Eiseninkrustierungen vorher gelöst werden (Kapitel 4.1.5). Sowohl in den Plattenversuchen, als auch in den Versuchen mit den Biofilmen, haben Oxalsäure und die EDTA-Lösung die besten Ergebnisse erzielt, in bezug auf die sich lösenden Eiseninkrustierung und der nachfolgenden Reduzierung der Zellzahlen mit H2O2. Auch wenn diese Stoffe nicht in verockerten Trinkwasserbrunnen eingesetzt werden können, dienten sie doch dazu, die negative Wirkung des Eisenhydroxids bei der Biofilmbehandlung mit H2O2 zu verdeutlichen.

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.

Enhanced nutrients removal in membrane bioreactors (ENREM) combines enhanced biological phosphorus removal (EBPR), post-denitrification without additional carbon supply, and membrane filtration in a relatively compact wastewater treatment process [Gnirss et al. 2003]. Since 2006, a demonstration plant of 10 m³ is serving a peripheral area of Berlin to treat the wastewater of about 250 people, following an anaerobic – aerobic – anoxic process scheme [Gnirss et al. 2008]. Post-denitrification without additional carbon supply is quite uncommon because the lack of carbon as electron donor usually results in low endogenous denitrification rates (DNR) below 0.6 mgNO3-N/(goTS h), leading to larger reactor volumes and thus higher investment costs [Kujawa & Klapwijk 1999]. In contrast to that, the ENREM process showed enhanced denitrification rates of 1-2 mgNO3-N/(goTS h), raising the question which carbon source is used to obtain these rates [Adam 2004; Lesjean et al. 2005; Vocks et al. 2005]. To address this question, several batch experiments were conducted using acetate as reactor feed, which is completely consumed by the biomass within the anaerobic phase. These experiments ruled out soluble carbon sources such as extracellular polymeric substances (EPS), lysis/hydrolysis products, or adsorption of acetate [Vocks et al. 2005; Bracklow et al. 2007]. The analysis of polyhydroxyalkanoates (PHAs) and glycogen as intracellular carbon storage compounds typical for EBPR systems showed no clear trend for the anoxic phase. Furthermore, the results showed a carbon recovery rate for the anaerobic phase of only 50-70 %, accounting for PHAs, glycogen, carbon dioxide, soluble COD, and acetate. The experiments also showed that the DNR can be increased by adding higher acetate dosages at the beginning of the process [Nicke 2005; Baumer 2006; Stüber 2007]. These observations led to the assumption that an unknown intracellular carbon storage compound might be formed during the anaerobic phase which serves as carbon source for enhanced denitrification [Lesjean et al. 2008; Vocks 2008]. This study was conducted to prove the theory of an unknown intracellular carbon storage compound used for enhanced denitrification and to identify this compound. In-vivo nuclear magnetic resonance spectroscopy (NMR) has proven to be an adequate tool to analyse metabolic pathways of microorganisms and to identify also unknown compounds [Pereira et al. 1996; Maurer et al. 1997; Jeon & Park 2000; Lemos et al. 2003]. However, NMR requires the use of a single carbon source (monosubstrate) which can be labelled by 13C isotopes. Hence, this study included the adaption of the ENREM process to acetate as monosubstrate in lab scale. A 6 L sequencing batch membrane bioreactor (SBMBR) was inoculated with sludge from the ENREM demonstration plant and stepwise adapted to acetate as single carbon source. The reactor was operated successfully for a period of 190 days and showed phosphorus and nitrogen dynamics typical for the ENREM process. Furthermore, carbon mass balances showed the same recovery rates of 50-70 % like in previous studies, and fluorescence in-situ hybridisation (FISH) showed a high abundance of phosphorus accumulating organisms (PAOs), thus indicating a successful adaption of all ENREM process characteristics to monosubstrate. The continuous long-term operation with a readily biodegradable monosubstrate rules out the presence of slowly biodegradable COD (sbCOD) as carbon source for denitrification.

Für die steigenden Anforderungen an die Ablaufqualität von Abwasserreinigungsanlagen sind Membranbelebungsanlagen (MBR-Anlagen) durch ihre hohen Reinigungsleistungen bezüglich den Nährstoffen wie Phosphor und Stickstoff sowie die Zurückhaltung von Bakterien eine geeignete Lösung. Ziel dieser Untersuchung war es, auf der Grundlage zweier in Berlin mit kommunalem Abwasser betriebenen MBR-Anlagen die Kosten semizentraler MBRAnlagen in Abhängigkeit von ihrer Größe und ihrer Reinigungsleistung zu vergleichen. Es handelt sich bei diesen Anlagen um eine Demonstrationsanlage für 130 EW und eine Pilotanlage für 50 EW, wobei sich die Technisierungsgrade und Reinigungsziele der beiden Anlagen stark unterscheiden. Ein Upscaling machte den Vergleich zwischen MBR-Anlagen mit Größen von 50 bis 5.000 EW möglich. Die Investitionskosten wurden anhand der einzelnen Anlagenteile aufgegliedert und für größere Anlagen mit Hilfe der Kapazitätsmethode abgeschätzt. In die Betrachtung der Betriebskosten gingen Personal-, Schlammentsorgungs-, Energie- und Chemikalienkosten sowie die Kosten für Wartung und Instandhaltung und die Abwasserabgabe ein. Aus den ermittelten Investitions- und Betriebskosten wurden mit einer dynamischen Kostenvergleichsrechnung die durchschnittlichen Jahreskosten berechnet. Um die Reinigungsleistung zu bewerten, wurde eine Einteilung in Reinigungsklassen mit unterschiedlichen Eliminationsraten für den chemischen Sauerstoffbedarf, Stickstoff und Phosphor vorgenommen, in die die MBR-Anlagen eingeordnet wurden. Die Untersuchung ergab, dass die vergleichsweise hohen spezifischen Kosten der betriebenen Anlagen mit zunehmender Anlagengröße stark abfallen. Sie sinken bei einer Anlagengröße von 1.000 EW auf ca. 2 €/m³. Die Erreichung einer hohen Ablaufgüte kann durch unterschiedliche Technologien erzielt werden. Es ist dafür bei den untersuchten MBR-Anlagen ein hoher Chemikalienaufwand oder ein hoher Energieaufwand nötig.

When mapping out strategies for an integrated water resource management in urban areas the precipitation-conditioned influences on the quality of waters available as resource are considered in an increasing manner. Amongst water discharges from urban areas, combined sewer overflows (CSO) represent a particular impact on waters due to their dynamic character. To assess CSO impacts, especially for an integrated modelling of sewer system and surface waters, quantity and quality data from the interface combined sewer overflow is needed. A monitoring concept for CSOs in Berlin was developed in the context of the project Monitor-1 by the KompetenzZentrum Wasser Berlin. In 2009, this concept will be realised in cooperation with the Berlin water authority and the utility Berliner Wasserbetriebe. When planning and preparing a monitoring an important aspect is, adjacent from the evaluation of possible locations, the selection of suitable measuring techniques. For this, extensive tests of different online measurement techniques from reputed manufacturers were accomplished at a test facility at the TU Berlin. Apart from questions such as accuracy, response behaviour at suddenly arising load peaks or dilutions and available measuring intervals, particularly aspects of calibration, cleaning and management of the sensors were evaluated. The influence of the calibration was especially examined with the ion-selective sensors (ISE). The question was pursued, how the sensors must be calibrated to offer the greatest possible accuracy for the generally very low concentrations in surface waters and the occurrence of a sudden and precipitous rise of concentration in the case of the start of the CSO. Ammonium and nitrate were also supplemented with chemicals besides the stockpiling with waste water. An important finding was that generally all sensors are applicable for the measurement task.

In the initial phase of the project "Organic Trace Substances Relevant for Drinking Water – Assessing their Elimination through Bank Filtration (TRACE)" the total herbicide glyphosate was classified as highly relevant for further investigations [Chorus & Wessel 2007]. Glyphosate is one of the most widely used and distributed herbicides in the world. Even though it has been on the market since 1974 its use increased with the expiry of the patent at the beginning of the 1990s, in the context of “soil conserving” agriculture (no ploughing) and with the introduction of glyphosate resistant, genetically manipulated cultures like corn, soy beans and cotton wool in 1997. To estimate the occurrence of glyphosate and its main metabolite AMPA in the surroundings of Berlin samples from 22 surface water sites were analysed within this study. In 5 samples the glyphosate concentration was above the European threshold for herbicides of 0.1 µg/L in drinking water. Up to 70 % of Berlin’s drinking water is produced via bank filtration and aquifer recharge characterized by comparatively low flow velocities (< 1 m/d), long contact times (3-6 months) and mainly anoxic redox conditions. To evaluate the potential of bank filtration to protect the drinking water from glyphosate contaminations an experimental study was conducted in the second phase of the TRACE project. Three enclosures at the UBA’s center for aquatic simulations were dosed with three different concentration levels (average concentration: 0.7, 3.5 and 11.6 µg/L) over a time period of 14 days. The effluent was sampled daily for 34 days. Glyphosate and AMPA were analysed applying the HPLC method according to the German Standard DIN 38407-22/2001. In parallel the applicability of the ELISA kit of the company Abraxis was tested without adequate results. The one-dimensional substance transport model VisualCXTFit was applied to obtain substance specific parameters of glyphosate and hydrodynamic parameters of the filter substrate from observed and measured breakthrough curves. The obtained results show that the breakthrough of glyphosate was retarded remarkably (retardation coefficient (R): 18.3 to 25) despite of the initially postulated low adsorption potential of the sandy filter substrate. Also a significant reduction, probably due to degradation was observed (1st order decay-rate (alpha): 0.069 to 0.092 d-1). In addition to the semi-technical scale enclosure experiments laboratory and lysemeter tests were carried out to investigate the processes responsible for glyphosate removal during subsurface passage. The laboratory experiments yielded a KF-value of 1.8998 mgLkg-1 and a Freundlich exponent of 0.4805, from which a retardation coefficient of 53.4 was calculated for a glyphosate concentration of 20 µg/L. Furthermore, delayed degradation under sub-oxic conditions could be observed. The lysemeter experiments ensured no glyphosate breakthrough in the effluent of a 2 m thick column of fine to medium sandy material within 7 months. The data obtained in this project prove that there is a potential of bank filtration to eliminate the herbicide glyphosate: Taking into account that glyphosate concentrations in surface water are highly variable a good protection of the drinking water source by bank filtration especially in respect to peak concentration is ensured. However, adsorption and degradation parameters obtained in the laboratory and semi-technical experiments vary significantly due to the difficulty to imitate natural conditions in the laboratory. Therefore the experimental study of the project TRACE emphasises the need to conduct semi-technical experiments in a near-natural environment to evaluate the risk of contamination.