Biological wastewater treating system
AssigneeAir Products and Chemicals, Inc.
InventorsMichael S. K. Chen, Marshall L. Spector
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Abstract
A modified activated sludge system is provided wherein wastewater containing BOD.sub.5 and phosphate values is admixed in an initial zone with biomass-containing recycled sludge to form a mixed liquor under conditions effecting sorption of BOD.sub.5 in the biomass. Subsequently, said mixed liquor is subjected to aeration in an oxidation zone under conditions for effecting oxidation of BOD.sub.5, 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.
Claims9
In a method for operating an activated sludge system to produoe a non-bulking sludge having rapid settling characteristics and containing an activated biomass species capable of removing phosphate values which comprises:
- (a) forming a mixed liquor in a BOD sorption zone, said mixed liquor being formed by mixing an activated biomass with a soluble BOD.sub.5 containing wastewater influent under conditions such that at least 25% of the soluble BOD.sub.5 is sorbed by said biomass;
- (b) oxidizing the BOD.sub.5 in the mixed liquor, including at least part of the BOD.sub.5 sorbed in said biomass, in an oxidation zone by contacting the mixed liquor with an oxidizing agent, said oxidizing being effective for oxidizing at least 30% of the total influent BOD.sub.5 in the mixed liquor;
- (c) settling the resulting oxidized mixed liquor in a settling zone thereby forming a supernatent liquor and a dense sludge containing activated biomass;
- and
- (d) recycling at least a portion of the dense sludge to the BOD sorption zone;
- the improvement which comprises:
- incorporating oxidizing agent into said oxidation zone at a rate not substantially exceeding the rate of oxidation.
Dependencies are inferred from the claim text.