Subsurface passage as utilized during river bank filtration and artificial groundwater recharge has shown to be an effective barrier for multiple substances present in surface waters during drinking water production. Additionally it is widely used as polishing step after wastewater treatment. However, there are limitations concerning the removal of DOC and specific trace organics. The project ”OXIRED“ aims at assessing possibilities to overcome these limitations by combining subsurface passage with pre-oxidation by ozone. In the first phase of the project, laboratory-scale column experiments were conducted in order to quantify removal for different settings under varying conditions. In a previous study different combinations of advanced oxidation and subsurface passage were evaluated concerning their potential removal efficiency and practical implementation on the basis of existing, published experiences and theoretical considerations. Two different scenarios were identified as promising for experiments in laboratory-scale columns with surface water and sewage treatment plant effluent: (A) surface water - oxidation - groundwater recharge and (B) surface water - short bankfiltration - oxidation - groundwater recharge. The investigations were designed to lead to recommendations for the implementation of a combined system of subsurface passage and advanced oxidation in pilot scale experiments that will be carried out in the second phase of the project. Prior to column experiments, batch tests following the RCT-concept by Elovitz and von Gunten (1999) were carried out to characterize the reaction of ozone with the investigated water qualities [1]. Additional batch ozonation tests with subsequent analysis of biodegradable dissolved organic carbon (BDOC) were conducted in order to determine optimal ozone doses for DOC removal in column experiments. For laboratory-scale experiments a set of 8 soil columns (length: 1 m; diameter: 0.3 m) was operated at TUB to evaluate the effects of pre-ozonation of different source waters (secondary effluent, surface water, bank filtrate). Ozonation was conducted with gaseous ozone in a 13-L stirred tank reactor. Specific ozone doses of 0.7 mg O3/mg DOC0 and 0.9 mg O3/mg DOC0 were investigated. Trace organic compounds to be targeted were identified in a prior literature study on existing data on subsurface removal. Results from laboratory-scale soil column experiments led to recommend specific ozone doses (z) of 0.7 mg O3/mg DOC0 for the following technical- and pilot-scale applications. Removal of surface water DOC in the soil columns was increased from 22% without ozonation to 40% (z = 0.7) and 45% (z = 0.9) with preozonation and the DOC in the column effluent reached the level of tap water in Berlin within less than one week of retention time. At bank filtration and artificial recharge sites in Berlin similar removal rates were only observed within 3 - 6 months of retention [2]. The transformation of many trace compounds was efficient with specific ozone doses of 0.6-0.7 mg O3/mg DOC0. Realistic surface water concentrations of carbamazepine,sulfamethoxazole, diclofenac and bentazone were reduced below the limits of quantification (LOQ). The pesticides diuron and linuron were reduced close to LOQ. The substances MTBE, ETBE and atrazine were only partly transformed during ozonation. For efficient transformation of these substances, higher ozone doses or an optimisation of the oxidation process, for example as advanced oxidation process (AOP), should be considered. Operating a preceding bank filtration (scenario B) will enhance the transformation efficiency of MTBE and ETBE. With similar ozone consumption the transformation of MTBE and ETBE was increased by 27-31% and 28-33% of the original removal, respectively. Other investigated compounds were efficiently transformed during ozonation of surface water independently of the preceding bank filtration step. For the removal of bulk organic carbon only little improvement was observed for scenario B. Overall DOC removal increased from 45% with direct ozonation of surface water to up to 50% with a preceding soil column. Despite the presence of relevant bromide concentrations (~ 100 µg/L) formation of the oxidation by-product bromate was not observed (< 5 µg/L). However, this could also be a result of analytical problems, as later spiking tests showed. Formation of brominated organic compounds was also not observed. Adsorbable organic bromide (AOBr) even decreased by 50 - 60% for secondary effluent and 80 - 90% for surface water. The reduction of AOBr concentrations was accompanied by an increase of inorganic bromide by up to 40 µg/L during ozonation of surface water. In the two conducted in vitro genotoxicity tests (Ames test, micronucleus assay) no genotoxicity caused by ozonation of water samples was observed. Testing for cytotoxicity (glucose consumption rate, ROS generation) showed positive results in several samples. However, a systematic attribution of toxic effects to ozonation or subsequent soil passage was not possible. Reasons for cytotoxic effects were not evaluated within the scope of this project but it is assumed that they were caused by unknown cofactors. These results show that the objectives of enhanced removal of trace organics and DOC by combining ozonation and subsurface passage are well met. Further investigations need to confirm this for the pilot scale, especially taking into account the formation, retention and toxicity of oxidation by-products.

Twelve years after the first full scale municipal application in Europe of the membrane bioreactor (MBR) technology, the process is now accepted as a technology of choice for wastewater treatment, and the market is showing sustained growth. However early misconceptions about the technology are persistent and false statements are commonly encountered in articles and conferences, generating unnecessary research efforts or even fuelling either fascination or scepticism with regards to the technology, which is ultimately detrimental to the perception of the process by water professionals. We try to provide some factual and rational clarifications on ten issues which are often wrongly reported about MBR technology.

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.