Two parallel membrane bioreactors (2m³ each) were operated over a period of 2 years. Both pilots were optimised for nitrification, denitrification, and enhanced biological phosphorous elimination, treating identical municipal waste water under comparable operating conditions. The only constructional difference between the pilots was the position of the denitrification zone (pre-denitrification in pilot 1 and post-denitrification in pilot 2). Despite identical modules and conditions, the two MBRs showed different permeabilities and fouling rates. The differences were not related to the denitrification scheme. In order to find an explanation for the different membrane performances, a one-year investigation was initiated and the membrane performance as well as the operating regime and characteristics of the activated sludge were closely studied. MLSS concentrations, solid retention time, loading rates, and filtration flux were found not to be responsible for the different performance of the submerged modules. These parameters were kept identical in the two pilot plants. Instead, the non-settable fraction of the sludges (soluble and colloidal material, i.e. polysaccharides, proteins and organic colloids) was found to impact fouling and to cause the difference in membrane performance between the two MBR. This fraction was analysed by spectrophotometric and size exclusion chromatography (SEC) methods. In a second step, the origin of these substances was investigated. The results point to microbiologically produced substances such as extracellular polymeric substances (EPS) or soluble microbial product.

Bank filtration and artificial recharge provide an important drinking water source to the city of Berlin. Due to the practice of water recycling through a semi-closed urban water cycle, the introduction of effluent organic matter (EfOM) and persistent trace organic pollutants in the drinking water is of potential concern. In the work reported herein, the research objectives are to study the removal of bulk and trace organics at bank filtration and artificial recharge sites and to assess important factors of influence for the Berlin area. The monthly analytical program is comprised of dissolved organic carbon (DOC), UV absorbance (UVA254), liquid chromatography with organic carbon detection (LC-OCD), differentiated adsorbable organic halogens (AOX) and single organic compound analysis of a few model compounds. More than 1 year of monitoring was conducted on observation wells located along the flowpaths of the infiltrating water at two field sites that have different characteristics regarding redox conditions, travel time, and travel distance. Two transects are highlighted: one associated with a bank filtration site dominated by anoxic/anaerobic conditions with a travel time of up to 4–5 months, and another with an artificial recharge site dominated by aerobic conditions with a travel time of up to 50 days. It was found that redox conditions and travel time significantly influence the DOC degradation kinetics and the efficiency of AOX and trace compound removal.

The secondary effluent of Berlin's sewage treatment plant Ruhleben was oxidized by dosages of 2.5-22 mg/L ozone and varying operation conditions to remove pharmaceutical compounds and disinfect water in parallel. The majority of analysed neutral and acidic drugs were efficiently removed to the detection limit at ozone consumptions equal to a dosage of < 10 mg/L O3. However, certain compounds like clofibric acid, ketaprofen and traced metabolites required higher dosages of > 10-15 mg/LO3 for complete removal. A series of four iodinated organic contrast media (ICM) persisted the ozone treatment even at high consumption rates. Related to disinfection, the legal requirements (EU bathing water directive) could be fulfilled by a consumption of < 10 mg/L O3. For a combined oxidation by ozone and H2O2 (perozone) higher conversion rates for clofibric acid, naproxen and ketaprofen could be obtained at lower dosage (6 mg/L O3). For two ICM, namely iopamidol and iohexol, this was the case at higher ozone consumption. The removal of adsorbable organic iodine (AOI) > 10% could not be achieved by any treatment. The initial genotoxicity of the secondary effluent was stated by four independent tests. Due to the application of ozone, this genotoxicity was completely removed. The presented results confirm that ozonation can be a suitable advanced wastewater treatment at varying operation conditions to lower effluent concentrations of pharmaceuticals and active micro-organsisms.

Investigations on the behavior of different bulk organics and trace organic compounds at a bank filtration site at Lake Tegel in Berlin, Germany, and in a long retention soil column system are reported. Objective of the research was to assess important factors of influence for the degradation of bulk and trace organics. More than two years of monitoring for the bulk parameter DOC proved that the redox conditions significantly influence the DOC-degradation kinetic but not necessarily the residual concentration. LC-OCD measurements confirmed that the change in character is comparable for aerobic and anoxic/anaerobic infiltration. Only the fraction of polysaccharides shows a better removal under aerobic conditions. Furthermore, adsorbable organic iodine (AOI) measurements revealed a more efficient degradation of AOI and AOBr under anoxic/anaerobic conditions. The monitoring of the single organic pollutants Iopromide, Sulfamethoxazole and naphthalenedisulfonic acids showed that the redox conditions have an influence on the degradation behavior of some of the monitored compounds. Iopromide was efficiently removed at all times, but no evidence for a dehalogenation under oxic conditions was found. Sulfamethoxazole showed a better removal under anoxic/anaerobic conditions. The very stable 1.5naphthalenesulfonic acid was not removed under either redox conditions.

At the Ruhleben wastewater treatment plant (WWTP) two membrane bioreactor (MBR) pilot plants have been operated since September 2001 by Veolia Water and Berliner Wasserbetriebe. The primary aim of the piloting is the investigation of biological phosphorus removal in conjunction with nitrification/denitrification in MBRs for later use in remote areas and small scale applications (WWTP serving a few thousand inhabitants) [Gnirss et al 2003a]. Both plants are fed with the same raw wastewater as it is treated in the conventional wastewater treatment plant. Instead of the mechanical treatment of the conventional plant, the raw wastewater passes a 1 mm punch hole screen prior to the biological treatment in the two MBR pilot plants. The two pilot plants are operated under parallel operating conditions (same raw wastewater, same sludge age and sludge concentration , etc.), but there are two different biological process configurations: pre-denitrification and postdenitrification without addition of a carbon source. Over the first year of operation, it has been observed that the unit with post-denitrification exhibited more rapid membrane fouling than the one with pre-denitrification. Preliminary LC-OCD (liquid chromatography-organic carbon detection) measurements carried out with the permeate compared to paper filtered sludge showed differences between the two units regarding the concentration of colloids and large macromolecules (as measured in the polysaccharide peak). Hence, an assessment and investigation of the fouling behaviour of the two MBR pilot plants was commenced. The results are presented in this report.

Bank fillration provides an important drinking water source to the city of Berlin. 56% of the drinking water is derived from bank filtration (the remainder is 14% replenished groundwater and 30% natural groundwater) [1]. At most bank filtration sites, the surface water contains portions of sewage treatment plant effluent (Lake Tegel 10-30%, [2]). Due to water recycling, the introduction of effluent organic matter (EfON) and persistent trace pollutants in the drinking water may be a concern. The project "Organic Substances in Bank filtration and Groundwater Recharge Process Studies" at the Department for Water Quality Control (DWQC) at the Technical University of Berlin is part of the "Natural and Artificial Systems for Recharge and lnfiltration (NASRI)' - project of the Berlin Centre of Competence for Water [3]. The research objectives of this part of the project are to study the removal of bulk organics (dissolved organic carbon (DOC) and EfOM) and trace organics at three field sites with different characteristics. Since the processes during bank filtration are very complex, it is difficult to predict bulk organic composition in the bank filtrale or to estimate important factors of influence for the degradation of trace compounds. For instance, it was shown in previous studies, that iodinated x-ray contrast medias are deiodinated under teductive conditions. Therefore, a bank filtration under anoxic or even anaerobic conditions would provide the removal of these trace pollutants. In addition to lhe redox state, factors such as retention time, initial degradable carbon . concentration, soil properties and hydrogeologlcal conditions may affect the final concentration. In order to be able to prevent the intrusion of persistent pollutants into the drinking water, lhe factors of influence are studied for a few model compounds that represent groups of trace pollutants. This will provide a tool that can be merged with hydrogeological models and soil properties to predict the removal efficiency of a given field site. To fulfill these objectives this research is presently investating: (i) the differences in bulk organic composition and trace organic concentration related to bank filtration conditions at three different field sites in Berlin, (ii) the simulation of a bank filtration site with a 30m soil column (elimination of hydrogeological variables).

Bank filtration and artificial recharge provides an important drinking water source to the city of Berlin. Due to water recycling, the introduction of persistent trace pollutants (e.g. pharmaceuticals) in the drinking water may be a concern. The project “Organic Substances in Bank filtration and Groundwater Recharge - Process Studies” at the Technical University of Berlin is part of the “Natural and Artificial Systems for Recharge and Infiltration (NASRI)”-project of the Berlin Centre of Competence for Water. The research objectives of this part of the project are to study the removal of bulk and trace organics at different field sites with different characteristics in Berlin. In Berlin’s public drinking water supply nearly 70% of the 220 Mio m3 per year originate from bank filtration and groundwater recharge (~56% from bank filtration and ~14% from groundwater recharge (BWB 2003)). Since the 19th century Berlin has relied on bank filtration with retention times of several months to produce “new” ground water. A semi-closed urban water cycle has been created with the growth of the city. At some bank filtration sites the surface water is strongly influenced by highly treated domestic waste water effluent (e.g. 15-30% in Lake Tegel) (Ziegler et al. 2002). Despite this indirect potable reuse, the bank filtration system continues to provide high quality water which is distributed without chlorination. This unique situation in Berlin was an interesting field site for a research project of the Berlin Center of Competence for Water. Recently, the break through of organic trace pollutants in bank filtration systems has been studied in various research projects. Especially, since improved analytical methods can detect in ranges below 1µg/l. Since the processes during bank filtration are very complex, it is difficult to predict the fate of trace organics during bank filtration or to estimate important factors of influence for their degradation. In addition to redox state, factors such as retention time, initial degradable carbon concentration, soil properties and hydrogeological conditions may affect the final concentration. Many studies revealed positive findings of pharmaceuticals, pesticides or industrial chemicals (Hiemstra et al. 2003, Heberer et al. 2001, Verstraeten et al. 2002) in bank filtrate. Compounds like carbamazepine and clofibric acid were reported to be partly recalcitrant during underground transport (Stan and Linkerhäger 1994, Ternes et al. 2002). Furthermore, Ternes and Hirsch (2000) reported the occurrence of x-ray contrast media in surface waters and in surface water influenced groundwaters, where they constitute a major fraction of the adsorbable organic iodine (AOI). The contrast media were found to be very polar, persistent and difficult to remove in wastewater treatment (Jekel and Wischnack 2000). Hartig (2000) reported the break through of antibiotic sulfonamides from surface water to monitoring wells more than 50 m off the lake front (residence time~3 months). But in most of the reported cases the concentration in the bank filtrate is much lower than in the surface water. Since this concentration decline is not only due to dilution, long term bank filtration appears to have the capability to reduce trace organic pollutant concentrations. It would be of great practical value to classify the important trace organic pollutants by degradability during bank filtration and to evaluate the conditions that are favorable for the removal of certain compounds. This study begins to clarify these issues for a few trace organic pollutants. The factors of influence for degradation are studied for model compounds that represent groups of trace pollutants. Additionally, the infiltration process is characterized by several bulk-organic parameters. The goal of the study is to provide a tool that can be merged with hydrogeological models and soil properties to predict the removal efficiency of a given field site.