'Classical' real-time control (RTC) strategies in sewer systems are based on water level and flow measurements with the goal of activation of retention volume. The control system rule of 'clean (storm water) runoff into the receiving water - polluted runoff into the treatment plant' has been thwarted by rough operating conditions and lack of measurements. Due to the specific boundary conditions in the city of Wuppertal's separate sewer system (clean stream water is mixed with polluted storm water runoff) a more sophisticated--pollution-based--approach was needed. In addition the requirements to be met by the treatment of storm water runoff have become more stringent in recent years. To separate the highly-polluted storm water runoff during rain events from the cleaner stream flow a pollution-based real-time control (P-RTC) system was developed and installed. This paper describes the measurement and P-RTC equipment, the definition of total suspended solids as the pollution-indicating parameter, the serviceability of the system, and also gives a cost assessment. A sensitivity analysis and pollution load calculations have been carried out in order to improve the P-RTC algorithm. An examination of actual measurements clearly shows the ecological and economic advantages of the P-RTC strategy.

In some cities, industrial enterprises' discharges into municipal sewage systems have a major impact on the quantity and quality of inflows to the municipal treatment plants. In many cases, industrial discharges stand out on account of the great fluctuations in their volumetric rates of flow, pollution loads and temperatures. As a result, these discharges put a great strain on the sewage system, the treatment plant, and ultimately the receiving waters. The enterprises concerned have to pay the treatment plant operators fees based on the load and/or volume discharged. In most cases, qualitative monitoring operations merely consist of spot checks. This means that continuously surveillance is not possible and infringements of the permissible limit values are only discovered by accident. If impermissible discharges are carried out that may be susceptible to causing a treatment plant failure, the rapid initiation of countermeasures is not possible. Hence, spectrometer probes and mobile flowmeters were used in order to determine volumetric rates of flow, COD concentrations, and ultimately the loads discharged. The possibilities for, and limits to, online monitoring as well as shortcomings of spot-checks are discussed in the course of this paper, which also includes an uncertainty analysis.

As part of a research & development project commissioned by the Land of North Rhine-Westphalia's Ministry for the Environment and Nature Conservation, Agriculture and Consumer Protection (MUNLV) an examination is being carried out of the general possibilities for centralised and decentralised treatment storm water runoff to be discharged into (canalised) receiving waters and the costs ensuing from this. The examination of the different options is being carried out under real conditions, with the Briller Creek (Wuppertal/Germany) and Müggen Creek (Remscheid/Germany) catchment areas being used as models. The range of investigations deals with a comparison between 'decentralised, semicentralised, centralised' storm water treatment, centralised storm water treatment involving a separate sewer and parameter-specific pollution based storm water runoff control. In the framework of the research project each of the variants is to be elaborated and the costs are to be calculated so as to permit a comparison between the different system designs. In particular, the investigations are to take into account the actual requirements to be met by storm water drainage systems involving separate sewage systems.