Die EU-Wasserrahmenrichtlinie (2000) verlangt bis zum Jahre 2015 für alle europäischen Gewässer die Wiederherstellung eines „guten ökologischen Zustands“. In Berlin muss zur Erfüllung dieses Ziels insbesondere der Phosphoreintrag aus Kläranlagen minimiert werden, da Phosphor als limitierender Nährstoff für die Eutrophierung der Gewässer hauptverantwortlich ist. Vor diesem Hintergrund wird die Einführung einer Membranfiltrationsstufe mit vorgeschalteter Phosphatfällung in der Berliner Kläranlage Ruhleben diskutiert (Gnirß 2008). Das Jahresmittel der Phosphorkonzentration im Ablauf der Kläranlage Ruhleben beträgt 0,3 - 0,4 mg P/L. Der Zielwert für die weitergehende Behandlung des Klarlaufes wurde mit 0,05 - 0,1 mg P/L festgelegt. Die Filtration von Klärwerksabläufen mit Niederdruckmembranen bietet in Kombination mit einer Flockungsstufe eine wirkungsvolle Möglichkeit für das Erreichen niedriger Phosphorkonzentrationen und einer zusätzlichen Entfernung von Pathogenen. Das Hauptproblem beim Betrieb von Niederdruckmembranen stellt jedoch nach wie vor der durch Fouling auftretende Verlust der Filtrationsleistung dar. Dieser entsteht durch das Verblocken der Membranporen mit organischem Material sowie Kuchenbildung auf der Membranoberfläche und schlägt sich entweder in der Verringerung des transmembranen Fluxes oder im Anstieg der transmembranen Druckdifferenz mit der Zeit nieder. Als Folge des Foulings müssen die Membranen regelmäßig physikalisch bzw. chemisch gereinigt werden, was zu einer Verringerung ihrer Standzeit führt. Lediglich 10 % der im Klarlauf enthaltenen organischen Substanzen leisten dabei einen Beitrag zum Fouling (Laabs 2004). Diese Substanzen eluieren bei einer Größenausschlusschromatographie im sogenannten Biopolymer-Peak, der sowohl Polysaccharide als auch organische Kolloide und Proteine umfasst. In Studien zum Fouling von Niederdruckmembranen wurden Biopolymere (BP) in Form von Proteinen und Polysacchariden sowie Partikel und Kolloide in der Größenordnung von 10 bis 450 nm als Hauptverursacher des Membranfoulings ermittelt (Zheng 2009, Poele 2006). Im Rahmen des Projekts „Oxeram“ (Technische Universität Berlin, KompetenzZentrum Wasser Berlin, Berliner Wasserbetriebe) wird untersucht, ob durch eine Ozonierung vor der Flockungsstufe das Fouling der nachgeschalteten Membran reduziert und somit die Leistungsfähigkeit der Membranfiltration verbessert werden kann und ob sich aus deKombination dieser Prozesse synergetische Effekte ergeben. Eine Ozonierung kann bei einem Einsatz von geringen Ozondosen (1 - 2 mg/O3/L) in Kombination mit einer Flockung aufgrund des Mikroflockeneffekts zu größeren, stabileren und robusteren Flocken führen. Diese können sich bei einer nachgeschalteten Membranfiltration positiv auf die Filtrationsleistung auswirken. Höhere Ozondosen (10 - 12 mg O3/L) dienen der Oxidation von organischen Wasserinhaltsstoffen und Spurenstoffen. Die hier dargestellten Ergebnisse beziehen sich auf Versuche, die in AmiconTestzellen im Labormaßstab durchgeführt wurden. Ziel war es zunächst, eine optimale Kombination von Ozoneintrag und Flockungsmittelkonzentration zu ermitteln.
The effect of combined sewer overflow (CSO) control measures should be validated during operation based on monitoring of CSO activity and subsequent comparison with (legal) requirements. However, most CSO monitoring programs have been started only recently and therefore no long-term data is available for reliable efficiency control. A method is proposed that focuses on rainfall data for evaluating the effectiveness of CSO control measures. It is applicable if a sufficient time-series of rainfall data and a limited set of data on CSO discharges are available. The method is demonstrated for four catchments of the Berlin combined sewer system. The analysis of the 2000-2007 data shows the effect of CSO control measures, such as activation of in-pipe storage capacities within the Berlin system. The catchment, where measures are fully implemented shows less than 40 % of the CSO activity of those catchments, where measures have not yet or not yet completely been realised.
The Berliner Wasserbetriebe are the largest water supply and wastewater disposal company in Germany. They are challenged to tackle various kinds of odour problems emerging from the sewer network. The continuous extension of sewer networks and a decrease in water consumption (in Berlin: ~ 20 % in the last 16 years, according to the statistical office BB, 2009) have led to elevated odour emissions arising from sewer systems. Together with growing public concern over odours from water treatment works, this has led to increasing numbers of odour complaints in urban catchments (Stuetz and Frechen, 2001; ATV-DVWK-M 154, 2003; Barjenbruch, 2003). Different odour abatement technologies are widely-used but often response only after consumer complaints and do not consider adequate identification of odour problems beforehand. An operational, together with a scientific approach is necessary in order to apply effective measures or combinations thereof. In Berlin annually almost 3 Mio € are spent by BWB to reduce odour emissions from the Berlin sewer system (BWB, 2006). Applied measures vary from dosing of nitrate or iron hydroxide sludge, flushing, or compensation by means of bio-filters or masking. The quantification of odour by means of continuous odour monitoring solutions such as electronic noses can contribute to minder economic and operational risks in odour management. The paper presents the research project ODOCO-ARTNOSE, dealing with the evaluation of electronic noses for the online application in sewer systems. The KompetenzZentrum Wasser Berlin (research centre) in cooperation with the Berlin water utilities Berliner Wasserbetriebe and Veolia Water will carry out bench tests with selected, commercially available chemosensor arrays to identify advanced applications of electronic noses in odour management in sewer networks. Objectives of the project are to analytically assess the online-ability of electronic noses by means of a multi-criteria methodology and to specify future odour control services based on the application of e-noses in sewer networks. The potential of electronic noses will be evaluated as tool to fulfil certain needs, namely (i) support for planning/designing of odour preventive measures and abatement strategies, (ii) support for real-time odour control and (iii) data acquisition tool to supervise and document (industrial) dischargers, document the effect of abatement measures and document legal compliance. Tests are possible to be carried out in the frame of a sewer research plant or within the sewer system of Berlin. A large-scale research plant was developed by Berliner Wasserbetriebe for investigating different odour and corrosion strategies. The plant consists of 2 independent gravity lines and is fed by combined wastewater from Berlin, pumped directly from the sewer. Various milieu conditions can be generated. The paper places current challenges within the city of Berlin into perspective and displays examples of odour abatement strategies of Berliner Wasserbetriebe. Expected outcomes and correlated benefits of the project will be presented. The methodological approach relies on a transparent selection of chemosensor array systems, on bench tests following a sophisticated measurement program and the evaluation of the electronic noses by clear defined criteria.
Due to their compact design and their high quality and reliable treatment, package or containerised membrane bioreactor (MBR) units are used for decentralised and semi-decentralised wastewater treatment plants. The operational availability, performance and economical viability of these MBR systems depend on the fi ltration performance of the membrane modules. Current chemical cleaning strategies of MBR modules, based on regular (weekly) maintenance cleanings and/or occasional (quarterly to biannual) intensive cleanings proved not to be adapted to semi-central MBR applications (100 up to 1000 p.e.): regular maintenance cleanings require automation and lead to too much care and personnel requirement. Occasional intensive cleanings increase the operational risk of membrane fouling and low cleaning recovery. In addition, semi-central MBR applications are often designed with at least two redundant fi ltration lines. An alternative chemical cleaning strategy was therefore proposed, implemented and assessed in a containerised MBR unit serving a population of about 250 p.e.: at a given time, only one fi ltration line is in operation while the other one soaks in a low-grade chemical solution. The modules are switched alternately on a monthly basis. To identify a cleaning strategy and an agent showing a good recovery, one of the modules was cleaned with H2O2, while the other was cleaned with NaOCl. A cleaning step with citric acid is added when necessary. These cleanings were tested over 16 months with the goal to minimise maintenance effort and chemicals used.
Two membrane bioreactor (MBR) plants were operated with a process which combines enhanced biological phosphorus removal (EBPR) and post-denitrification without external carbon dosing in the anoxic zone. An enhanced post-denitrification with denitrification rates (DNR) twice as high as the expected endogenous rate was observed. Batch tests revealed a linear correlation between the anaerobic acetate loading and the postDNR which is remarkable since the aerobic phase was located in-between the anaerobic and anoxic phase. An anaerobic build up of a carbon storage compound which can outlast the aerobic phase is postulated. Measurements showed that neither polyhydroxyalkanoates (PHAs) nor glycogen are used as carbon source for the enhanced post-denitrification. A carbon mass balance in the anaerobic phase strongly indicates the formation of a different so far unknown storage compound. This assumption is supported by literature data which show carbon recovery ratios of known storage compounds (PHAs and glycogen) in the anaerobic phase of EBPR systems often below 1 down to 0.3, in particular for trials performed with real wastewater. The potential of enhanced post-denitrification in conventional UCT systems is also demonstrated in full-scale non-MBR wastewater plants. When implemented in MBR process, enhanced nutrients elimination could be biologically achieved with 99% TP-removal and 90% TN-removal. A small full-scale unit is in operation in Berlin since March 2006 to demonstrate the process in real operation conditions with domestic wastewater.