Adaptation of CSOs to new regulation standards for a sewer system in Lower Austria

The area of the water association of 8 municipalities with 40.000 population equivalents with low industrial influence is located in the eastern part of Austria. The drainage area reaches from a steep sub-alpine part down to an alluvial sediment basin. The sewerage system consists of 1 main transportation sewer of about 24 km length (with a volume of 8000 m³) and more than 100 km of collecting combined municipal sewers and additional parts with sanitary sewers. Furthermore many of the roofs in combined areas are connected to piped receiving waters. The several take-over points between the communities and the transportation sewer are built as pumping stations, CSOs or gravity sewer connections. The combined sewer system with 42 CSOs without any retention basin up to now will be examined with an integrated view and will be modelled as one system for implementation of the upcoming new regulation standards in Austria. According to the new regulation the whole catchment area of the central WWTP has to be considered and no stand-alone CSOs.