In the catchment area of the Wilhelmshaven wastewater treatment plant, an integrated, fuzzy-based control system has been in place for more than a year now. The system’s essential elements are a sewer network control system to reduce stormwater overflow events and volumes at a sensitive sewage disposal point as well as the control of the wastewater treatment plant’s inflow as a function of measurement values during the treatment process in order to avoid critical load conditions. The accompanying monitoring shows that operating experiences are positive and it confirms a more than 25 % reduction in overall stormwater overflow volumes at the sensitive sewage disposal point only thanks to the implementation of the control system. Moreover, the safe operation of the wastewater treatment plant can be guaranteed by simple means without significantly increasing stormwater overflow discharges. Currently the concept, which up to now is partly based on values obtained by hand-held measuring devices, is broadened by installing additional on-line measurement technology in the wastewater treatment plant.