A new method for the assessment of the filterability in membrane bioreactors was tested for five months in four MBR units in Berlin. The new method BFM (Berlin Filtration Method) for filterability assessment uses a small membrane filtration test cell which can be submerged directly in the biological tanks to determine the filterability of the activated sludge in-situ. The test cell contains an aerated flat-sheet membrane which operates at similar conditions as in the plant. Filterability is expressed in terms of critical flux obtained by performing flux-stepping experiments. The ultimate goal of monitoring the filterability with the device is to detect in real time fouling occurrences due to changes in sludge composition and to adapt accordingly the operating conditions. The usefulness of the device for this purpose was evaluated for five months after monitoring four MBR plants in Berlin with different activated sludge characteristics (MLSS from 5 to 21 g/L, SRT 12–35d and COD in the supernatant 30–400 mg/L). The first results show a good agreement between the filterability of the sludge with the portable filtration test cell and the filtration performance of the plant. Critical flux values varied between 3 and 30L/m2 h during the studied period. Useful information concerning the irreversibility of the fouling was provided by looking at the hysteresis curve of the flux-stepping experiments.

Membrane bioreactors (MBRs) have been increasingly employed for municipal and industrial wastewater treatment in the last decade. The efforts for modelling of such wastewater treatment systems have always targeted either the biological processes (treatment quality target) as well as the various aspects of engineering (cost effective design and operation). The development of Activated Sludge Models (ASM) was an important evolution in the modelling of Conventional Activated Sludge (CAS) processes and their use is now very well established. However, although they were initially developed to describe CAS processes, they have simply been transferred and applied to MBR processes. Recent studies on MBR biological processes have reported several crucial specificities: medium to very high sludge retention times, high mixed liquor concentration, accumulation of soluble microbial products (SMP) rejected by the membrane filtration step, and high aeration rates for scouring purposes. These aspects raise the question as to what extent the ASM framework is applicable to MBR processes. Several studies highlighting some of the aforementioned issues are scattered through the literature. Hence, through a concise and structured overview of the past developments and current state-of-the-art in biological modelling of MBR, this review explores ASMebased modelling applied to MBR processes. The work aims to synthesize previous studies and differentiates between unmodified and modified applications of ASM to MBR. Particular emphasis is placed on influent fractionation, biokinetics, and soluble microbial products (SMPs)/exo-polymeric substances (EPS) modelling

This paper deals with the performance and the optimisation of the hydraulic operating conditions of the A3 Water Solutions flat sheet membrane technology in a MBR pilot-plant to achieve a satisfying fouling control and also a reduction in the required aeration. Two vertically stacked modules were tested at pilot-scale at Anjou Recherche under typical biological operating conditions (mixed liquor suspended solids concentration (MLSS) = 10 g/l; sludge retention time (SRT) = 28 days; food to microorganism ratio (F/M) = 0.12 kg COD/kg MLSS/d). The use of a double-deck and of specific backwashes for this membrane technology enabled to achieve satisfying membrane performances for a net flux of 25 L h-1m-2, 20°C at a low specific aeration demand per membrane surface (SADm = 0.2Nm3 h-1m-2) which corresponds to a specific aeration demand per permeate volume unit (SADp) of 8Nm3 air/m3 permeate, which is lower than reported for many commercial membrane systems. The mixed liquor characteristics (foaming, MLSS concentration) appeared to influence the fouling behaviour of the membranes but no correlation was found with the fouling rate. However, with the new operating conditions, the system is robust and can cope with fouling resulting from biological stress and daily peak flows for MLSS concentrations in the membrane tank up to 18 g/l.

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).

Bank filtration (BF) is a well established and proven natural water treatment technology, where surface water is infiltrated to an aquifer through river or lake banks. Improvement of water quality is achieved by a series of chemical, biological and physical processes during subsurface passage. This paper aims at identifying climate sensitive factors affecting bank filtration performance and assesses their relevance based on hypothetical 'drought' and 'flood' climate scenarios. The climate sensitive factors influencing water quantity and quality also have influence on substance removal parameters such as redox conditions and travel time. Droughts are found to promote anaerobic conditions during bank filtration passage, while flood events can drastically shorten travel time and cause breakthrough of pathogens, metals, suspended solids, DOC and organic micropollutants. The study revealed that only BF systems comprising an oxic to anoxic redox sequence ensure maximum removal efficiency. The storage capacity of the banks and availability of two source waters renders BF for drinking water supply less vulnerable than surface water or groundwater abstraction alone. Overall, BF is vulnerable to climate change although anthropogenic impacts are at least as important.

Rver Bank Filtration (RBF) is a drinking water (pre-)treatment that can remove a wide variety of surface water contaminants . However, the efficiency of this natural treatment process depends on hydrochemical, aquifer- and operational characteristics. Therefore, complementary treatment options may be required in order to build up a multiple-barrier-system and obtain drinking water quality. As a follow-up to the TECHNEAU WP5.2 field investigations, this report aims at identifying potential post-treatment schemes for drinking water production at three river bank filtration sites in New Delhi - Palla, Nizamuddin and Najarfgarh – for which physicochemical parameters as well as levels of inorganic and trace organic substances and microbial contamination have been measured during field campaigns in 2007 and 2008 (see deliverables D5.2.2 and D5.2.6). The three investigated RBF sites in Delhi have distinctive geographical locations and contamination exposures. For each of them, critical water parameters were identified that present a challenge with regards to drinking water production, for which different treatment technologies are envisaged (see table below). For Palla and Najafgarh, one specific water component (fluoride and salinity, respectively) requires targeted treatment. For Nizamuddinm, however, where surface water is highly exposed to contamination from poorly treated waste water, theoretical post-treatment options are no longer efficient and extensive conventional wastewater treatment is recommended. One other possible option for Nizamuddin is the Oxidation / Biofiltration / Membrane technology (OBM process) developed by NTNU and SINTEF within the TECHNEAU project and a specific report on its application to Delhi is planned within TECHNEAU WP7.9. This report shows the theoretical post-treatment options for river bank filtration sites in Delhi. The strong technological requirements for Nizamuddin and Najafgarh seem inadequate to be currently implemented. The priority in Delhi would be to develop an integrated water and wastewater management, in order to reduce contamination in the surface water and thereby lower the technological requirements for drinking water production.

The Water Supply and Sanitation Technology Platform (WssTP) was initiated by the European commission in 2004 and developed by the European Water Industry, open to all stakeholders. The objective is to stimulate a collaborative, innovative, visionary and integrated research and technology development strategy for the European water sector. Within different pilot programmes of the WssTP Managed Aquifer Recharge (MAR) was identified as a topic of interest and area relevant for further research. For this reason a Task Force on MAR was initiated in 2009 with 36 representatives from European research institutes, industry partners and with participation of international experts. During a workshop conducted in Graz in June 2009 these experts developed the basis for a report that has now been submitted to the European Commission for consideration in future research calls. In this report MAR was identified as a possible countermeasure against degradation of groundwater resources in Europe, that has a history of more than 150 years of practical implementation in Europe. Although not generating “new” water resources, it enables the use of alternative resources that would not be used otherwise (e.g. storm-water, seasonal high water flow, recycled water) for drinking water and irrigation by buffering high variations in availability and demand. MAR also provides an additional purification step in the regional water cycle. Recharged water can also act as an hydraulic barrier to prevent saltwater intrusion or the spreading of contaminated groundwater and inhibit a regional decrease of groundwater tables. This is particularly important in the scope of achieving the goals of the EU water framework directive. Research needs were identified in the field of defining “Best Management Practices” and standards for MAR in Europe, modelling for transparent feasibility assessment and the investigation of MAR in karstic aquifers.

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.