ABSTRACT
The primary objective of the activated sludge process is the removal of biologically oxidizable materials. The organic pollutants present in municipal, industrial, or combined municipal-industrial wastewater streams are synthesized through microbiological action into insoluble cell mass or are oxidized into carbon dioxide and water. The biochemical reactions, however, only partially represent the success of meeting secondary effluent standards, as the separation of the resulting cell mass and other entrapped insoluble material (generally through sedimentation techniques) is of prime importance. Suspended solids removal, as well as residual organic pollutants, significantly affects the efficiency of activated sludge treatment because the carry-over of biological solids from the secondary clarifier increases effluent BOD. It is generally accepted that, even provided that hydraulic overloading does not occur, effluent suspended solids from a final clarification unit (sedimentation tank) will rarely be below 10 to 20 mg/l. It is therefore obvious that an integrated design philosophy must be adhered to in order to achieve desired effluent quality.
