Small wastewater treatment plants play a very important role in German environmental politics. Presented here is a new system for biological wastewater treatment with simultaneous aerobic sludge stabilization. This system operates as a charge process and can be used in the range of 300 to 2000 population equivalents. Different modes of operation were tested in an experimental plant. The system is applicable for both separate sewerage systems and combined systems with large amounts of storm water. The quality of the purified water was good and even under the worst case conditions it met the demands of standard discharge consent conditions.
A theoretical simulation of the operation has not yet been started, because the system equations are very complex, due to the variable water volume.