Three different methods for fi ltration characterization in Membrane Bioreactor (MBR) systems were compared. These were the Delft Filtration Characterization Method (DFCm), the Berlin Filtration Method (BFM) and an ex situ side-stream fi ltration test cell for the determination of the critical fl ux. The ex situ fi ltration test cell and the DFCm fi lter activated sludge from a tank, while the BFM works in situ with a test cell directly submerged into the biological tank at similar operational conditions to a typical MBR plant. The mixed liquor of four different MBR units was characterised several times with the three fi ltration methods. The three tested methods seemed to agree in the classifi cation of the tested mixed liquors in terms of fi lterability except for one of the tested activated sludges. Additionally, three critical fl ux protocols were studied using the BFM fi ltration test cell. The fi rst consisted in the classical fl ux-step method, the second included relaxation between fi ltration steps and in the third protocol, 2 min fi ltration at a fi xed fl ux were performed before every fi ltration step. The last protocol was selected as the most representative of full scale MBR operation and the most interesting one for giving valuable information about the irreversibility of the fouling.

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.

Aim of this study is to evaluate the impacts of combined sewer overflows (CSO) on the Berlin Spree focussing on the intermittent effects of oxygen depletion on the aquatic biocenosis. The investigation bases on a long series of measurements carried out by Berliner Wasserbetriebe and the Berlin Senate for Health, Environment and Consumer Protection.

Waterborne diseases are frequent and recurrent episodes in developing countries with deficient sanitary conditions affecting drinking water. Waterborne epidemics might affect thousands of persons, like the Hepatitis-E-epidemics of Kuntra (Naik et al. 1992) and Delhi (Ramalingaswami and Purcell, 1988) with 79,000 and 25,000 ill persons respectively. It is not by chance that both epidemics occurred after drinking water treatment suffered a failure, allowing contaminated drinking water to reach the consumers. In order to ameliorate the consequences of water scarcity and poor sanitary conditions, systems for obtaining drinking water are needed which are efficient, robust, and require only low-cost technology. River Bank Filtration (RBF) is a process during which surface water is induced to infiltrate into the subsurface, either due to a natural hydraulic gradient or the depression cone of an abstraction well. During infiltration and soil passage, the quality of the surface water is substantially improved thanks to a combination of physical, chemical, and biological processes such as filtration, dilution with genuine groundwater, sorption and biodegradation of pollutants Apart from pathogens, organic trace compounds are widespread pollutants in rivers and lakes. The capacity of RBF to effectively or even completely remove both, pathogens and many organic contaminants has been confirmed in numerous investigations (e.g., Matthess et al. 1988). Its low costs in technology and labor makes RBF a very suitable drinking water treatment tool for developing countries. The aim of this study was to ascertain if RBF kept its power to remove pollutants and pathogens even in highly polluted waters as they are encountered in many urban agglomerations in developing countries.

Whilst the importance of integrated modelling of urban wastewater systems is ever increasing, there is still no concise procedure regarding how to carry out such modelling studies. After briefly discussing some earlier approaches, the guideline for integrated modelling developed by the Central European Simulation Research Group (HSG - Hochschulgruppe) is presented. This contribution suggests a six-step standardised procedure to integrated modelling. This commences with an analysis of the system and definition of objectives and criteria, covers selection of modelling approaches, analysis of data availability, calibration and validation and also includes the steps of scenario analysis and reporting. Recent research findings as well as experience gained from several application projects from Central Europe have been integrated in this guideline.

With increased computer performance and data-processing functionalities, there has been a tendency in the last few years to apply detailed hydrodynamic sewer modelling for long-term simulations, with long time series of rainfall. Although this is now fairly realistic for small networks, there is still a clear limit as to what can be done in the case of running bigger models for a long time, which need a lot more computational effort. Therefore, the idea has grown to investigate the possibilities of hybrid sewer modelling, a combination of conceptual and mechanistic modelling approaches to combine the advantages of both models, the speed of conceptual models and the accuracy of mechanistic models. Suggestions for hybrid model simplifications are presented in this paper within their application for two case studies.

Demonstrationsprojekt Berlin-Margaretenhöhe: Dezentrale Klärtechnik vor Ort erprobt und auf Wirtschaftlichkeit geprüft.

In Berlin, drinking water is exclusively abstracted from groundwater. For this reason, well monitoring is important to ensure a good water quality and a high well capacity. The project WellMa, which stands for well management, aims at the optimization of the operation and maintenance of drinking water abstraction wells. During the first work package of the preparatory project phase WellMa1, available data of 615 wells in Berlin were evaluated. Since ochre formations appear most frequently, the context between iron-related clogging and hydrochemistry, well construction and operation was examined. Based on the statistical analysis, TV camera inspections were identified to be the most reliable marker to indicate the iron-related clogging status of a well. The results were classified into four stages and set into relation to relevant chemical, operational and constructional parameters to determine trends and correlations. Outliers lie below or above the detected trends, as given by the generated boxplots. Seven parameters have to be taken into account: iron, manganese and nitrate-nitrogen concentrations, top of the first filter, distance to the next surface water, mean discharge rate and monthly operation hours. Wells, whose outlier parameter based on one of the following criteria, were excluded from further investigations: (i) clogging state 1, which should be lower according to the outlier parameter, at a high remaining specific capacity, (ii) nitrate-nitrogen values that should lead to higher clogging degrees lying slightly out of the range given by the boxplot, (iii) classification of the clogging degree shortly after construction, regeneration or H2O2 treatment and (iv) missing information about clogging state in the BWB well files and missing TV inspection videos to verify deviating values. The analysis demonstrates a complex interaction between the single parameters. High nutrient inflow because of river bank filtration, leakages of the casing, high discharge rates or unconfined conditions superimpose the distance to the surface of a deep screened well. Since the encrustations are mediated by bacteria, the composition and permeability of the biofilm varies depending on the engaged microorganism. Furthermore, the thickness and dimension are influenced by the available time for bacterial growth, the inflow velocity, number of switchings or position of the water levels.

Die Überwachung von Brunnen läuft nach Monitoringprogrammen, in denen der Ablauf der erforderlichen Maßnahmen geplant ist. Heutzutage werden zunehmend die Betriebsparameter kontinuierlich ermittelt und durch Fernübertragungssysteme zu zentralen Datenbanken übertragen. Basierend auf einem solchen System hat die Firma Veolia in Frankreich ein Software-Modul entwickelt, welches die Messdaten der Wasserstände, der gepumpten Wassservolumen und der Schaltungen der Pumpen in einer Datenbank ausliest und Bilanztabellen und Diagramme in Excel erstellt. Dies bildet die so genannten „Bilans Lerne“, die es ermöglichen, die Entwicklung der Brunnen kontinuierlich zu überwachen. Die Anwendung dieses Instruments an den Brunnen der Berliner Wasserbetriebe (BWB) wurde drei Monate lang beispielhaft an fünf Brunnen am Standort TegelHohenzollernkanal getestet. Ziel war es, zu prüfen, inwieweit sich die gegenseitigen Beeinflussungen zwischen den Brunnen und die für Berlin spezifischen Betriebspläne auf die Datenauswertung und Berechnungen des Moduls auswirken. Dazu sollte auch untersucht werden, ob das vorgegebene Messintervall, die Instabilitätskoeffizienten und die minimale Dauer für die Ermittlung der Betriebs- und Ruhewasserstände auf Berlin übertragen werden können oder ob Optimierungen notwendig sind. Dazu wurden zunächst einmal die gegenseitigen Beeinflussungen der Brunnen aufeinander geschätzt: Die Reichweiten der Absenkungstrichter erreichen mindestens 90 m und die betrachteten Brunnen sind ca. 50 m voneinander entfernt, so dass die Schaltungen eines Brunnens sich immer auf den Wasserstand in den unmittelbar benachbarten Brunnen auswirken. Dies ist auch auf den Gangliniendiagrammen der gemessenen Wasserstände deutlich zu sehen. In den dreimonatigen Messungen konnten die „Bilans Lerne“ für die fünf ausgewählten Berliner Brunnen erstellt werden. Allerdings sind die Ergebnisse der Modulanwendung teilweise unvollständig. Dies liegt vor allem daran, dass die Berliner Brunnen im Vergleich zu Brunnen in Frankreich sehr selten geschaltet werden, das Modul jedoch, um alle Parameter wie geplant ermitteln zu können, auf den Wechsel von Pump- und Auffüllungsphasen zurückgreift, um Fördermengen, Absenkungsbeträge und spezifische Ergiebigkeiten zu berechnen. So kann unter den Berliner Betriebsverhältnissen lediglich ein Wert der spezifischen Ergiebigkeit pro Monat berechnet werden, während für die französischen Brunnen i. d. R. ein Wert pro Tag berechnet wird. Da dies im Vergleich zum derzeitigen Stand der Praxis eine Verbesserung hinsichtlich der Häufigkeit der Ergiebigkeitsmessungen darstellt, kann die Benutzung eines solchen Instrumentes in Berlin empfohlen werden. Damit das Instrument in Berlin lückenlose Berechnungen durchführen kann, sind jedoch Anpassungen und Optimierungsschritte für die Makros erforderlich. Darüber hinaus könnte z. B. als eine Anpassung an die Betriebsbedingungen spezifisch für Berlin erwogen werden, die Messungen weniger häufig durchzuführen.