As part of the EU-Life ENREM demonstration project the Department of Chemical Engineering, TU Berlin, was appointed to conduct the preliminary pilot trials in a representative site for verification of basic process design and operation criteria of the full-scale MBR demonstration plant. In addition to conception and construction of the pilot plant, this investigation consisted of two successive trial phases with distinct operation conditions. The first one was dedicated to the assessment of the “irregular sludge removal strategy” (the biomass is accumulating in the reactor, which is partly emptied when the sludge concentration reaches a given value). In the second trials phase normal operation conditions with daily sludge wastage were implemented with 28,5d SRT. The major outcome of the trials was that COD removal, enhanced biological phosphorus removal and the post-denitrification performed a similar way under both operational conditions. The denitrification rate was approximately 1 mgN/(h goTS). An influence of the anaerobic sludge loading on the post-denitrification rate was observed with higher rates (up to 4 mgN/(h goTS)) corresponding to higher organic loading. An influence of storage compounds built up in the anaerobic phase is assumed. Nitrification was better in the second phase when 4 mgN/(h goTS) were constantly reached while nitrification was unstable with an average of 2 mgN/(h goTS) in the phase of irregular sludge removal. The aerobic and anoxic reactors were enlarged during the regular sludge withdrawal phase by 23% resulting in 35d SRT. This led to a better COD removal and slightly better nitrogen removal. The enhanced SRT produced possibly a deterioration of biological P removal due to overloaded poly-P storage. A second possible reason is the massive reproduction of sludge worm Tubifex tubifex, which was observed after the plant enlargement. Different strategies to reduce the worm population were attempted. Ammonium dosing had no success. Copper dosing reduced the number of worms significantly but the population grew back after the dosing was stopped. The prolongation of SRT reduced the sludge yield from 0.23 gTS/gCOD at 28.5d to 0.18 gTS/gCOD at 35d.

As part of the EU-Life ENREM demonstration project the Department of Chemical Engineering, TU Berlin, was appointed to conduct the preliminary pilot trials in a representative site for verification of basic process designs and operation criteria of the full-scale MBR demonstration plant. In addition to conception and construction of the pilot plant, this investigation consists of two successive trial phases with distinct operation conditions: the first one being dedicated to the assessment of the “irregular sludge wastage strategy” (the biomass is accumulating in the reactor, which is partly emptied when the sludge concentration reaches a given value), and the second one being planned to verify normal operation conditions with daily sludge wastage. This progress report describes implementation and results of the first phase, for which a pilot plant of 140L was operated over 6 months with waste water of a decentralized area. The influent contained high concentrations of nitrogen (100-200 mg/L), phosphorus (10- 20 mg/l) and COD (1000-2000 mg/L). Also surprising were the high VFA concentrations (100-300 mg/L) which ensured a good EBPR process. The COD and also the enhanced biological phosphorus removal (EBPR) were not impacted by the irregular sludge wastage. COD effluent concentrations were around 50 mg/L and TP effluent was 0.1 to 0.3 mg/L. The high nitrogen influent concentrations were problematic. Due to changing TS concentrations and changing nitrification rates TN effluent was 10 to 30 mg/L with a NH4-N content of 0 to 20 mg/L. Denitrification rates were measured between 1 and 3 mgN/gVS h and were depending on TS concentration, with higher rates at lower TS concentrations. Polysaccharide concentrations in the sludge water phase were higher with low TS concentrations and low oxygen concentrations. Higher PS values led to faster fouling. Results of the trials suggest that the oxygen concentration should be kept above 2mg/L to ensure both sufficient nitrification and lower fouling. Since also high TS concentrations are needed to ensure complete nutrients removal the optimum TS range is relatively small and it must be concluded that the irregular sludge wastage strategy was not beneficial in this case and the demonstration plant should be run with regular sludge removal.

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, is to be built in a yet unsewered remote area of Berlin. The plant will be then operated over more than one year, and the process will 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 management of the project has been achieved according to the organisation identified in the LIFE proposal. No relevant modification has been required. Annex 3.1 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” are quasi-completed, with however a four month delay which will put back consequently the following actions, such as start of sewer and plant construction, and plant commissioning. Specifically, the following actions were completed, or are on the verge of completion: - Cost-comparison of decentralised treatment solutions to serve 20 unsewered areas of Berlin and selection of demonstration site (district of Margaretenhöhe); - Revision of cost evaluation for infrastructure; - Planning and specification of MBR plant; - Preparation and release of call for tender of MBR plant; - Planning and specification of low-pressure sewer; - Preparation and release of call for tender of low-pressure sewer construction; - Acquisition of legal permits (for plant construction & operation, water discharge); - Acquisition of parcel for MBR plant. In addition, the first trials phase of Task 3 “Preliminary testing on representative site” (period with irregular excess sludge withdrawal) was completed and enabled to validate the design criteria of the MBR demonstration plant. The relationship with the inhabitants of Margaretenhöhe was initiated in order to ensure a smooth construction phase, and a quick connection to the new sewer system. Dissemination activities were undertaken accordingly as shown in Annexes 7.1-7.3, and the project web-site in three languages was set up (see in www.kompetenz-wasser.de). The communications on project are expected to ramp up in 2005 and 2006, as more outcomes and results are getting available. The main task in 2005 will be the construction and commissioning of the low sewer system and the MBR demonstration plant. The start-up of the novel treatment scheme is now expected for October / November 2005. From the budget perspective, the total costs incurred over 2004 were 198,353€. This is 6% of the total budget of the LIFE proposal. The infrastructure costs and most of equipment costs (expected 62% of total budget) should occur in 2005 during the construction and commissioning phases of the scheme. No major budget deviation was noticed so far, and the re-evaluation of the infrastructure costs fit with those of the LIFE proposal.

Erfahrungen aus dem Betrieb einer Membranbelebung mit diskontinuierlichem Schlammabzug werden vorgestellt. Das Ziel ist, den Einfluss der Betriebsbedingungen auf Fouling und den Abbau extrazellulärer polymerer Substanzen zu bestimmen sowie mit bekannten Zusammenhängen aus Anlagen mit kontinuierlichem Abzug zu vergleichen.

In Berlin gibt es nur noch wenige abgelegene kleine Einzugsgebiete (<1%), die nicht an das zentrale Abwassersystem angeschlossen sind. Aber in den neuen EU-Ländern ist der Anteil an der Bevölkerung, die nicht an eine zentrale Abwasserreinigung angeschlossen sind, noch deutlich höher. Besonders in dünn besiedelten Gebieten gibt es immer noch sehr viele Abwassersammelgruben (abflusslos oder mit Versickerung). Für empfindliche Einzugsgebiete (Badeseen, Wassersport, Fremdenverkehr) könnte für die Einleitung von gereinigtem Abwasser eine über die Mindestanforderung in der Abwasserverordnung hinausgehende weitergehende Nährstoffentfernung von der zuständigen Behörde gefordert werden. Das Membranbelebungsverfahren (MBR) könnte eine technische und auch wirtschaftliche Lösung bieten, um eine semi-zentrale Erschließung in Gebieten mit einem sensitiven Vorfluter (Gewässer) zu realisieren. Mittels eines Membranprozesses kann die vollständige Desinfektion und weitgehende biologische Phosphorentfernung bis auf 0.1mgP/L oder niedriger ohne Fällmittel erreicht werden (Gnirss et al., 2003a, Gnirss et al., 2003b). Damit kann der Standard der EU-Richtlinie für Badegewässer direkt im Ablauf der kleinen Kläranlage erreicht werden und die Eutrophierung im Oberflächenge-wässer reduziert werden. Die Umsetzung von MBR-Anlagen in kleinen oder mittleren Einzugsgebieten ist mittels schlüsselfertiger Containereinheiten möglich, wodurch die Investitionskosten gesenkt und die üblichen Unannehmlichkeiten von Kläranlagen wie Geruchs- und Lärmemissionen vermieden werden können. Dieser Artikel stellt die Vorteile und die Kosten der MBRTechnologie für die dezentrale Erschließung eines Siedlungsgebietes im Norden von Berlin vor und vergleicht sie mit dem konventionellen Verfahren. Dabei werden die technischen Grundlagen der Demonstrationsanlage ausführlich erläutert, und die wichtigsten Designkriterien für die MBR-Anlage und das Druckentwässerungsnetz vorgestellt.

Given the important cost reduction of the membrane bioreactor technology in the last years, this advanced treatment process has now become cost-competitive with other conventional technologies. A cost estimation analysis undertaken with few remaining unsewered and remote areas of Berlin showed that the implementation of semi-central sanitation scheme with a local membrane bioreactor plant would lead to similar costs than the connection to the central sewer, but with a superior effluent quality. For such small systems, some design issues have to be considered in order to optimise the costs and the operation regime, such as plant capacity increase, buffer capacity, process configuration and membrane flux.