The Sewage Treatment plant of Koholmen

The Bypass of Sewage WaterAfter the mechanical handling, where all incoming sewage water passes, there is the possibility to lead thesewage water past the biological handling step. This is necessary at big flows, more than 2.000 cubicmeters per hour. Otherwise the biological processes will be damaged. A partial flow of the mechanicallypurified water is then led to the tank of sedimentation (by precipitation) for chemical handling and thefollowing sedimentation and filtration. If necessary a smaller part of the mechanically purified water canalso be led to the outlet pipe.Fortunately, bypassing of sewage water is most unusual and occurs on average only once year.The biological processes are dimensioned for a normal flow of about 700 cubic meters per hourand a maximum flow of 2.000 cubic meters per hour at the most. Should the flow be higher, theexcess part of the mechanically purified water will be led directly to chemical precipitation.Photo: Jan Andersson