The widespread application of the membrane-assisted activated sludge process is restricted by membrane fouling, which increases investment and operating costs. Soluble microbial products (SMPs) are currently considered as the major cause of membrane fouling in membrane bioreactors (MBRs). This study aims at elucidating and quantifying the effects of varying environmental conditions on SMP elimination and rejection based on findings in a pilot MBR and in well-defined lab trials. Several factors are thought to influence the concentration ofSMP and their fouling propensity in one way or the other, but findings are often inconsistent or even contradictory. Here, SMP loading rate was found to have the greatest effect on SMP elimination and thus on concentration in the MBR. The degree of elimination decreased at very lowDO and low nitrate concentrations. On average, 75% of influent SMP were eliminated in both pilot and lab trials, with the elimination of polysaccharides (PS) mostly above 80%. Rejection of SMP components by the used membrane (PAN, 37nm) ranged mainly from 20% to 70% for proteins and from 75% to 100% for PS. Especially protein rejection decreased at higher temperatures and higher nitrification activity. The increased fouling rates at lower temperatures might therefore partly be explained by this increased rejection. Apparently, mainly the nitrite-oxidising community is responsible for the formation for smaller SMP molecules that can pass the membrane.

MBR-technology is able to fulfil similar or even higher standard for nutrients removal than conventional activated sludge processes. This paper presents the optimisation of the membrane bioreactor technology, together with a low pressure sewer, to equip a remote and yet unsewered area of Berlin requiring high quality wastewater treatment. The hydraulic flow pattern of the entire system has to be studied carefully due to the small collection system (no time delay between wastewater discharge and treatment to minimise the daily profile). The pollutant concentrations in the wastewater exhibit also stronger variations. In order to flatten out the hydraulic and load profile, and therefore to reduce the size of the biological reactor and the membrane surface, an buffer tank was installed before the MBR-plant. A full analysis of the influent hydraulic flow and wastewater characterisation is provided for the demonstration MBR-plant.

Zentrale, konventionelle Wasserver- und Abwasserentsorgungskonzepte, in industrialisierten Ländern seit Jahrzehnten entwickelt und angewandt, sind aufgrund hoher Kosten, hohen Wasserverbrauches und geringer Wiederverwendung von Nährstoffen nicht hinreichend nachhaltig, insbesondere nicht für den Einsatz in Entwicklungsländer. Zielvorstellungen der nachhaltigen Konzepte sind eine weitgehende Wiederverwendung des gereinigten Abwassers, sowie der Nährstoffe, verbunden mit einem geringeren Energiebedarf bzw. einer Produktion von Energie. Alternative Konzepte und Techniken stehen bereits seit einiger Zeit zur Verfügung und werden auch angewendet, dennoch sind weitere Entwicklungen und Plausibilitätsprüfungen erforderlich. Aus diesem Grund hat das Kompetenzzentrum Wasser Berlin (KWB) zusammen mit den Berliner Wasserbetrieben (BWB) und Veolia Water ein entsprechendes EUDemonstrationsprojekt (Sanitation Concepts for Separate Treatment (SCST)) durchgeführt. Hierbei wurden zwei unterschiedliche Sanitärkonzepte in Gebäuden der BWB auf dem Gelände des Klärwerks Stahnsdorf erprobt. Ziel dieses Projektes war es zu erproben, ob diese neuen Sanitärkonzepte sowohl in ökologischer als auch in ökonomischer Hinsicht signifikante Vorteile gegenüber den konventionellen Sanitärsystemen mit Schwemmkanalistation und Kläranlage (end-ofpipe- system) bieten.

The removal of trace organic compounds through membrane bioreactors (MBR) in comparison to a conventional wastewater treatment plant (WWTP) in a long term study was investigated. Two MBR pilot plants were operated in parallel to a full-scale WWTP, fed with the same municipal raw waste water. Bulk organic parameters such as COD and TOC, high polar compounds (phenazone-type pharmaceuticals, their metabolites and carbamazepine), and less polar estrogenic steroids (estradiol, estrone and ethinylestradiol) were quantified. The removal rate of phenazone, propyphenazone and formylaminoantipyrine by the conventional WWTP was below 15 %. Significant higher removal rates (60-70 %) started to be clearly monitored with the pilot plants after about 5 months. The removal of the drug metabolite acetylaminoantipyrine during conventional treatment was below 30 % and reached 70 % in both pilot plant. Higher removal rates coincided here with higher temperatures at the summer time. Carbamazepine was not removed during conventional and membrane activated sludge treatment.The conventional WWTP removed in average more than 90 % of the natural steroids estrone and estradiol and about 80 % of the synthetic ethinylestradiol. The elimination of estradiol and estrone by the MBR processes were of about 99 % and Ethinylestradiol was removed by about 95 %.

The ENREM project aims at demonstrating a novel wastewater treatment process based on the technology of membrane bioreactor (MBR), set up in a configuration to enable enhanced biological elimination of nutrients. A new plant, and the related sewer system, was built in a unsewered periurban area of Berlin. The plant is to be operated over more than one year, and the process to be optimised. Performances and costs of the treatment system will be then assessed for the size 250 – 10,000pe, corresponding to semi-central schemes. The plant was started on 28 February 2006 with 8 month delay on the program identified in the LIFE proposal. As a consequence, a project extension request of 8 months will be lodged, in order to match the initial duration of 18 months for the optimisation, evaluation and dissemination phase. This delay incidentally caused also a 6 month delay for the preparation of this Interim Report. Despite these aspects, the management of the project has been achieved according to the organisation identified in the LIFE proposal. Annex 7.1 presents and discusses the key deliverables and milestones depending on the LIFE proposal and the current status. In relation to the technical content, Task 2 “Site and process definition” and Task 4 “Detailed design” were completed early 2005. Task 3 “Preliminary testing on representative site” was completed in September 2005 and enabled to validate the design, operation and start-up criteria of the MBR demonstration plant. The public tenders for the construction of the sewer network and the MBR container unit occurred during the first semester of 2005, and the construction of the scheme was completed by end 2006. In parallel, the required legal permits were acquired (for plant construction & operation, water discharge), as well as the parcel hosting the treatment unit. A relationship with the inhabitants of Margaretenhöhe was maintained in order to ensure a smooth construction phase, and a quick connection to the new sewer system. The dissemination activities covered several communication vectors (Tri-lingual website www.kompetenz-wasser.de, press-release and articles and bi-lingual KWB Newsletter, local press, scientific press, plant visits and inauguration, communication material etc). The project results will be widely communicated in the national and international medien, and a final project workshop will be organised in June 2007. The main task in 2006 will be the operation, optimisation and technical / economical evaluation of the low sewer system and the MBR demonstration plant. So far, the budget is generally in line with the expectations, or slightly below. The project finances allow the project extension of 8 months, required to achieve all announced technical outcomes of the project. After the 8 month extension the final project budget is expected to remain about 20% below the planned proposal, i.e. approx. € 600,000 savings on the total budget should be recorded, corresponding to a subvention reduction of approx. € 100,000 (also close to 20% reduction).

Extracellular polymeric substances (EPS) are considered as the major cause of membrane fouling in membranebioreactors. Recent studies have revealed a linear relationship between fouling rate (increase of filtration resistanceover time) and polysaccharide (PS) concentration [1]. Several factors like the type of wastewater, sludge loading rate, sludge age, MLSS concentration, and mechanical stress are known to influence the concentration of dissolved EPS. Also, unsteady states like intermittent feeding or shifts in the oxygen supply have been identified as additionalfactors leading to an increase in EPS formation or to a change in its fouling propensity. However, no systematicinvestigation to quantify such influences has been undertaken so far. This study is aimed at determining the influenceof discontinuous excess sludge withdrawal often applied in small decentralised plants and resulting unsteady loadingrates on EPS formation and filtration resistance. The general trend of increased fouling rate at higher PS concentrationsis confirmed but data show a larger scatter which could be due to a change in the PS structure and hence their fouling potential. The levels of dissolved oxygen and nitrate which also fluctuate more strongly in MBRs withirregular sludge wastage appear to have a profound impact on EPS uptake rate and thereby on EPS concentration.

Four international projects subsidised by the European Commission should push forward the development and application of membrane bioreactor processes in the municipal wastewater sector.

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.