Biological wastewater treating system

摘要

A modified activated sludge system is provided wherein wastewater containing BOD5 and phosphate values is admixed in an initial zone with biomass-containing recycled sludge to form a mixed liquor under conditions effecting sorption of BOD5 in the biomass. Subsequently, said mixed liquor is subjected to aeration in an oxidation zone under conditions for effecting oxidation of BOD5, such that oxidizing agent is incorporated into the oxidation zone at a rate not substantially exceeding the rate of oxidation. By such operation, considerable savings in power requirements for oxygen transfer to the mixed liquid are had, while developing and maintaining a dense non-bulking biomass having the properties of good removal of phosphate from the wastewater influent.