The paper describes the planning process for the pilot implementation of a decision support system (dss) for global control of sewage pump stations in Berlin, which is going to be realised by the end of 2006. The objective of the control concept is to systematically manage in-pipe storage capacities in order to reduce cso. The paper presents the preliminary assessment of the system’s control potential based upon the analysis of operational figures and numerical simulations. Furthermore, the structure of the decision support systems procedure is illustrated.

In Berlin, Germany, the demand for enhanced protection of the environment and the growing economic pressure have led to an increased application of control concepts within the sewage system. A global control strategy to regulate the pumpage of the combined sewage system to the treatment plant was developed and evaluated in a theoretical study. The objective was to reduce CSO. In this paper an extension of the existing control algorithm by information from online rainfall measurement and radar nowcasting is described. The rainfall information is taken into account by two additive terms describing the predicted volume from rainfall runoff. On the basis of numerical simulation the potential of these two complementary forecast terms in the global control algorithm to further reduce CSO is evaluated. The investigations are based on long-time simulations that are conducted with the dynamic flow routing model InfoWorks for three subcatchments of the Berlin drainage system. The results show that at the current Berlin system a CSO reduction of only 0.8% is possible. The effect of the forecast terms is limited by operational constraints. Limits are set to both, the delivery from each individual pump station and the total pumpage to the treatment plant.

Im Oktober 2006 wurde das NASRI (Natural and Artificial Systems for Recharge and Infiltration) Projekt, ein Vorhaben der Kompetenzzentrum Wasser Berlin gGmbH, endgültig mit einer öffentlichen Präsentation der wichtigsten Ergebnisse abgeschlossen. In fast vier Jahren interdisziplinäre Forschungstätigkeit untersuchten mehr als 40 Wissenschaftler aus mehreren Berliner Universitäten und dem Umweltbundesland, gemeinsam mit den Berliner Wasserbetrieben die Prozesse während der Uferfiltration und künstlichen Grundwasseranreicherung. Es war ein Hauptziel des Projektes ein umfassendes Prozessverständnis zu entwickeln, um so die nachhaltige Nutzung der Uferfiltration und künstlichen Grundwasseranreicherung unter Berücksichtigung zukünftiger Anforderungen und Bedrohungen langfristig sicherzustellen.

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 %.

Recent research projects have shown a good suitability of the ozonation process to transform trace concentrations of most pharmaceuticals in wastewater treatment plant (WWTP) effluents. The concentrations of carbamazepine and 17a-ethinylestradiol, for instance, were reduced below their detection limits by use of ozone dosages resulting in a specific ozone consumption of 0.5 mg O3/ mg DOC0. At the same time a good disinfection performance was achieved. The given hygienic requirements of the EU bathing water directive (e.g. 2000 N / 100 ml faecal coliforms) are fulfilled without the formation of bromate (< 10 µg/L). As technical control parameter of the ozonation process usually the residual ozone in the liquid phase or in the off-gas are used. However, at very low specific ozone consumptions, ozone reacts instantaneously with dissolved compounds and can not be detected. Hence alternative parameters should be used for effective operation control. The present paper evaluates the relation between UVA decrease and the removal of different compounds (endocrine disrupting compounds, pharmaceuticals, iodinated Xray contrast media), microbial parameters and bromate formation. The results can be used as a guideline for the control of the oxidation performance at large scale ozonation units.

The development of the integrated control of sewage network and wastewater treatment plant has progressed during the last decade. Nevertheless, an operational implementation of the concepts for huge, complex systems has hardly been realised. That was an obvious reason to initiate the project "Integrated Sewage Management (ISM)". The ISM project aimed at the development of strategies for an integrated management of the Berlin sewage system consisting of sewer networks (both, combined and separate system), pump stations, pressure mains and wwtp. For these purposes a numerical model of the collection system has been built up. Those catchments have been chosen that have a significant quantity of wastewater and are connected to at least one of the three main wastewater treatment plants of Berlin (Ruhleben, Waßmannsdorf and Schönerlinde). To enable an evaluation of total emissions it was necessary to incorporate not only catchment area and collection system but also the wwtp into the model. Furthermore, the Berlin specific transport of wastewater through pressure mains had to be considered. Both, advective pollutant transport and the limiting pressure situation had to be taken into account. An integrated model of collection system, pressure mains and wwtp has been set up for the catchment of wwtp Ruhleben for the study of a global control concept. Those processes that were of particular importance for the control concepts or had a significant influence on the criteria (derived from the objectives) had to be simulated adequately. Hence, for the Berlin model the main attention was paid to an accurate reproduction of in-pipe storage activation and the transport of wastewater through the pressure pipes. A sufficient set of data was available to model the system structure. For process parameter estimation the necessary information was taken from the operational SCADA system. Some gaps in the data could be closed by additional measurement campaigns (Bln VII, 2001; Bln X, 2002; Heiligensee, 2003). For modelling the collection system the dynamic flow routing model InfoWorks CS of Wallingford Software Limited has been chosen due to its user-friendliness (window navigation, GIS) and comprehensiveness (pollutant load calculation, long-time simulation, spatial rainfall distribution, rtc module). A suitable approach to the simulation of the Berlin pressure mains was found to be based on EPANET 2 of the U.S. Environmental Protection Agency. The software SIMBA® 5 of ifak System GmbH has been used to simulate the dynamic treatment processes. For the activated sludge conversion part the Activated Sludge Model No. 1 (ASM 1) has been used. The three models have been coupled in sequence on the basis of simple input and output files. Further on, in the framework of three sub studies the ISM model has been applied to operational questions. The applicability of the ISM model for the assessment of the impact of the NPA control on the wwtp was tested. NPA stands for “new pump automatic (Neue Pumpen Automatik)” and signifies a control concept that is implemented in the framework of the LISA project (BWB). The inflow to wwtp Schönerlinde has been simulated for one rain event and the NPA control of the pump stations could be simulated well on the basis of the InfoWorks rtc module. Furthermore, the ISM model has been applied to evaluate a concept for a level dependant real-time control (Pegelgesteuerte Förderstromregelung) of sewage pump stations. The idea of the concept was to build an easy function that allowed continuously varying the pumpage and implicitly managing available inline storage capacities within the trunk sewers. The objective was to smooth the delivery towards the treatment plant to avoid peak loads. The evaluation showed that it is possible to manage available inline storage volume by applying the control function. But only if there is an adequate retention volume of around 60.0 m³/ha Aimp or more a significant improvement of the flow characteristic towards the wwtp is possible. Consequently, in Berlin only two catchments have the potential for the introduced control concept (Charlottenburg III und Ruhleben). Finally, the effects and the benefit from global pump station control in comparison to local control have been studied on the basis of the integrated model. The assessment of the Berlin drainage system that was carried out before arrived at the conclusion that there is a high potential for the control of the total system. The positive rating can partly be ascribed to the high storage volume that can be activated within the trunk sewers and the high number of pump stations that are used as actuators. However, this potential is already used by locally controlling the pump stations and storing sewage in the collectors. The potential of a global control of sewage pump stations arises from the non-uniform distribution of rainfall and the non-uniform distribution of storage volumes over the system. Those conditions usually lead to a non-uniform utilisation of storage capacities and further on to sewer overflows that cannot be balanced by local control. A look on the simulated total emissions showed that concerning discharged quantities the load from the wwtp is highly dominant, since most of the time (under dry weather conditions) wwtp effluents are the only impact on the receiving water. Furthermore, the global control concept only works during rain situation and does not have an influence on dry weather effluents. Consequently, the influence of global control on yearly total emissions is marginal. Nevertheless, it could be shown that global control can avoid peak load situations at the inflow to the wwtp and consequently reduce peak loads in the effluent. The control concepts had a significant influence on the emissions from combined sewer overflows. The reduction of sewer overflows plays a prominent role since they present a highly dynamic impact on the water body. The simulations showed that on average during periods of cso 2.5 t COD/h enter the receiving water. Compared to that load the continuous impact from the wwtp effluent was only 0.4 t COD/h. Moreover, due to the high fraction of biodegradable organic substrate the impact from combined sewer overflows is of special relevance. In contrary to the refractory COD from wwtp effluents, 60 % of the COD from combined sewer overflows are biodegradable leading to extreme oxygen depletion within the receiving water. It could be shown that under current conditions at the wwtp (rain weather capacity of wwtp Ruhleben = 6700 l/s) a local control (= local automation) of the pump stations has an adverse effect on the performance of the sewage system. In contrary to an optimum coordination of the pump stations local control leads to an overloading of the wwtp and an increase of emissions from combined sewer overflows by 9 % (volume), 15 % (COD) and 20 % (TKN). Due to that reason the current operation provides for manual interventions in case of rain events to coordinate the delivery of the pump stations. This necessity will persist under the LISA automation. Assuming a future upgrade of wwtp Ruhleben and an increase in rain weather capacity up to 7650 l/s, global pump station control will result in cso emissions that are 19 % (volume), 20 % (COD) and 25 % (TKN) below that under local control (= local automation). The major deliverable of the ISM project is the model for the Berlin collection system (18 combined and 29 separate sewer systems that are connected to the three main wastewater treatment plants Ruhleben, Waßmannsdorf and Schönerlinde). The further application and maintenance of the sewer model will take place at BWB, department NA-G. The scope of studies that will be supported by the model covers operational planning as well as general, conceptual and investment planning (storage optimisation, problem of parasite water). Concerning the implementation of the global control concept that has been developed in the framework of the ISM project first tests shall be carried out in 2006 and 2007. Therefore, the follow-up project EVA (Entscheidungshilfesystem zur Verbundsteuerung von Abwasserpumpwerken / Decision support system for global control of sewage pump stations) was planned at KWB to enable support and a further cooperation between KWB and BWB. The algorithm has to be adapted to the operational and technical boundary conditions and a detailed practical planning in terms of control engineering has to be carried out. The main prerequisite for an implementation of the introduced control concept is the technical ability of the pump stations to increase delivery beyond the value of 2 * Qd,16. Simultaneously, an authorisation is necessary to introduce a flexible regulation of the pump station’s rain weather delivery off the value of 2 * Qd,16 as demanded nowadays by the Berlin water authority. If the necessary data is available (usually given by the existing scada system of BWB) and if the used pumps can be controlled according to the above-stated technical requirements, thestudied control concept can be implemented without any further constructional investment.

Cyanobacterial toxins are substances produced by cyanobacteria that occur in surface waters world wide. The most common group of cyanobacterial toxins is the group of structurally similar microcystins (MCYST). Sand passage as used in slow sand filtration, artificial recharge and bank filtration has shown to be effective in eliminating microcystins in many cases. For secure drinking water production from surface waters infested by microcystins removal has to be ensured in a wide variety of cases met in the field. It was therefore the aim of experiments in technical and semitechnical scale on the UBA’s experimental field in Berlin to test some worst case scenarios for the reliability of microcystin elimination during sand passage. Experiments were conducted with virgin sand (no previous contact to MCYST) and high filtration rates as well as under anaerobic conditions. The results show that the greatest problem for MCYST elimination can be found under anaerobic conditions as degradation is not complete and may lead to harmful residual concentrations.

Microcystins (MCYST) are a group of toxic substances produced by cyanobacteria (‘blue-green-algae’). In case of cyanobacterial blooms microcystin concentrations in surface waters may reach values far above the value proposed as provisional guideline for drinking water by the WHO of 1 µg/L for MCYST-LR. For drinking water production via underground passage it is therefore necessary to ensure removal to a large extent. For this reason experiments with extracellular microcystins were conducted in the laboratory as well as in a natural setting on the UBA’s (German Federal Environmental Agency) experimental field for simulation of underground passage. Laboratory batch experiments showed that adsorption of microcystins can be neglected in sandy material (kd < 1 cm³/g). Batch and column experiments identified biodegradation as the predominant elimination process in these sediments. The degradation rates derived from laboratory column experiments as well as semi-technical scale enclosure experiments varied between 0.2 d–1 and 18 d–1. In the worst case this means a half life of 2.8 days, so that under aerobic conditions contact times of several days should be sufficient to eliminate MCYST to an extent safe for use as drinking water.