Development of a Control Strategy to Reduce Combined Sewerage Overflows: The Case of Bremen – Left of the Weser

In recent years, the population and authorities in West Germany have become very concerned with water pollution. In this respect, combined sewage discharges have been pointed out as a major source. Various measures can be considered, which can be ordered into three categories: a redefinition of the objectives of the Urban Drainage System (UDS), the reshaping of the UDS (e.g. extension of the storage capacity) or the modification of its operation. Among the latter measures, Real-Time Control (RTC) constitutes the main option. It aims at a better exploitation of the existing storage potential. As the city of Bremen (Germany) decided, several years ago, to renew the on-line survey and monitoring system of its UDS, the determination of on-line strategies to operate the pumps came to the fore. Methods and tools to investigate the possibility to reduce the pollution loads through improved control strategies have been developed. Some results are presented.