Real time control for minimizing effluent concentrations during storm water events

Increased flow rates due to stormwater at the Klagshamn wastewater treatment plant occasionally cause hydraulic overloading of the activated sludge process resulting in sludge loss from the secondary clarifiers. To minimize these problems different operational strategies have been evaluated at the plant. Practical experiences have shown the benefits of using in-line storage for flow equalization even if the available volumes may seem small in comparison to the total daily flow rate during stormwater occasions. Step feed operation at the treatment plant can be used to further ease the problems with sludge loss. By-pass of primary treated wastewater can finally be used to avoid hydraulic overloading of the biological treatment process. By combining these strategies in a real time control system, the need for erecting off-line storage volumes can be minimized.