Biological Effluent Treatment

In Germany's municipal wastewater treatment plants, biological treatment procedures are primarily driven by the activated sludge system, which consists of an activated sludge tank and a post-purification tank. The activated sludge tank contains a mixture of microorganisms attached to sludge particles and wastewater, which is rotated and ventilated to facilitate the decomposition of organic carbon compounds. In the post-purification tank, the activated sludge particles are separated from the purified wastewater by sedimentation.
Activated sludge reactors and the percolating filter and solid-state reactor processes are further used for biological purification of municipal and industrial wastewater. The structural engineering design of reactors has several advantages when compared with the tank method: it requires less space, makes more efficient use of oxygen, produces less noise and odour emission, as well as requiring less maintenance.
The CPG Databank contains a broad range of examples on this subject. They range from attempts to sterilise wastewater plant effluent using zebra mussels to the initiation of a German-Japanese cooperation project, in which a dynamic simulation program is being developed to describe processes for biological elimination of nitrogen and phosphorus.