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.

The overall project WellMa, which stands for well management, aims at the optimization of the operation and maintenance of drinking water abstraction wells. For this purpose, in addition to a statistical analyses of well data (report D 1.2) and first field investigations to compare various diagnosis methods (report D 1.3), a review of literature during the preparatory phase WellMa1 should answer the following questions: (1) Which processes affecting the well performance and conditions can occur? (2) Which correlation exists between well ageing and well characteristics? (3) How can such well ageing be recognized at an early stage? (4) What is the state of the practice to restore a good performance and condition? (5) What can be done during well design and construction to prevent well ageing? (6) How can well operation be adjusted to slow-down well ageing processes? Based on textbooks, standards and professional articles published in large number since the middle of the nineties, the state of the art was gathered and compared to current practice at BWB and Veolia to identify possibilities for improvement and specify the need for further investigations to be proposed for WellMa2. 1) Three well ageing types involving different processes could be identified. These are chemical, biological and physical clogging. They are closely linked to the characteristics of the exploited aquifer, such as the physical properties of the formation or the chemical composition of the groundwater. 2) The evaluation of these site-specific aquifer characteristics, the impacts from well design and the observed effects on the well performance and condition and their development with time of operation should be used to specify the individual ageing potential for each well site. 3) The early recognition of well ageing implies the need to monitor wells (1) regularly and (2) with comparable methods. As suitable indicators, the development of water levels and discharge rates to calculate the specific drawdown and specific capacity, the pump surveillance and the visible condition of the well interior could be identified. 4) Both, the assessment of the ageing potential and the monitoring of a reference value describing the state of the well lead to the specification of maintenance requirements. Generally, three strategies could be identified, ranging from sheer operation, over reactive maintenance to regular condition assessment and preventive treatment. Concerning the choice of maintenance method, key criteria must always be the well design, its state of construction, the well ageing type and location. Up to now, patterns linking well characteristics and the success of maintenance could not be identified. Thus, maintenance relies on practical experience and the willingness to discuss limitations and disadvantages of methods as open as the advantages on side of the rehabilitation companies. 5) For well design and construction, the technical standards were summarized, describing the necessary steps for proper dimensioning, drilling, choice of materials and final well development. Not only the avoidance of nonconformities and the careful evaluation of the advantages, but also the restrictions of different well design alternatives, e.g. for the accessibility of rehabilitation, assure an optimal well ageing prevention and well operation. 6) Furthermore, well operation could be identified as a key element and critical factor codetermining the lifetime, but at the same time the economic efficiency of a well. It is always a compromise between demand, technical possibilities and economic considerations, for which reason general standards or technical guidance are not available so far. They need to be developed individually considering present well ageing processes and the quantification of impacts. Comparing the state of the art with current practice at BWB and Veolia, room for improvement could primarily be identified for monitoring and subsequent data processing for both, operational parameters (to assess well performance and condition), and maintenance (to evaluate the success of applied treatments). Based on the recommendations derived on this state of the art review, within WellMa2 the effects of measures for preventing and treating well ageing shall be quantified so that the benefits can be assessed for future optimized well management.

The study aims at validating the point-of-use investigations on long-term gravity-driven ultrafiltration for a scaled-up system, which could produce drinking water for a community of 100-200 inhabitants using natural surface water. Eawag, KWB and Opalium conceived a membrane-based small-scale system (SSS) which can operate without crossflow, backflush, aeration or chemical cleaning. Equipped with a biosand filter as pretreatment, it is designed to be robust, energy-sufficient (gravity-driven) and run with restricted chemical intervention (only residual chlorine). The containerised unit (10’) requires to be fed with raw water at a 2 m-height (energy-equivalent to ~8Wh/m3). As sole operational requirement, the membrane reactor is simply to be drained (i.e. emptied) on daily to weekly basis to superficially remove the material retained by the membrane and accumulated in the module. Otherwise, the system, which is only driven by a 40 cm differential pressure head (i.e. 40 mbar), is totally self-determined and autonomous. This report details the validation tests performed at Veolia Water Research Center in Annet-sur-Marne (France) from January to August 2009 : the gravity-driven UF compact unit showed promising results in regards to flux stabilization and flow capacity. Although early investigations take place in winter, an initial flux stabilization to 2.5 lmh is observed, which is below the reference results from the Eawag lab tests (i.e. 7-10 lmh, at 20 ± 2°C). However, the “scaled-up” system can benefit from a weekly drainage which seems to enhance the flux to 4-5 lmh, and thereby, the unit is to produce more than 4 m3/d, which is consistent with the design target of 5 m3/d. Moreover, the increase of the drainage frequency (to 3 times/week) along with warmer temperatures – leading to a better membrane permeability and biological activity - contribute to a further enhancement to 5-7 lmh. This is particularly relevant for South Africa, for which decentralized water supply is a burning issue and where the unit is to be further tested from November 2009. The investigations also highlighted the critical performance of the biosand filter as pretreatment. More than the UF step – whose membrane integrity was confirmed with bacterial analyses, the pretreatment step needed more frequent (i.e. monthly) O&M requirements. Therefore, the pretreatment necessity will be further assessed in South Africa where high turbidity peaks could represent an extra challenge for the unit.