Production of non-bulking activated sludge
AssigneeAir Products and Chemicals, Inc.
InventorMarshall L. Spector
Life of this patent
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Abstract
A modified activated sludge system is provided wherein BOD-containing wastewater and recycled sludge are initially admixed under anaerobic conditions in the substantial absence of oxygen or oxidizing agents and subsequently subjected to aeration and clarification. By the disclosed operation the selective production of non-bulking biomass is favored while effective removal of phosphates is obtained. By a further alternative modification, nitrates and nitrites are also removed by interposing an anoxic treating zone between the anaerobic zone and the aerating zone.
Claims19
In the operation of an activated sludge system the method of inhibiting proliferation of filamentous biomass consisting essentially of:
- producing a mixed liquor by mixing in an initial contact zone recycled activated sludge with BOD-containing wastewater influent;
- said initial contact zone being maintained under anaerobic conditions such as to be substantially free of NO.sub.x.sup.- and to contain a concentration of less than 0.7 ppm dissolved oxygen;
- thereby effecting selective production of nonfilamentous microorganisms capable of sorbing BOD;
- oxidizing BOD in the mixed liquor in a subsequent oxygenated zone to cause removal of BOD by contact with oxygen-containing gas admitted to said oxygenated zone, said oxygenated zone having maintained therein a dissolved oxygen content of at least 1 ppm;
- transferring the oxidized mixed liquor from said oxygenated zone to a settling zone wherein purified supernatant liquid is separated from settled sludge;
- and returning a portion of said settled sludge to said initial contact zone to provide the activated sludge admixed therein with the wastewater influent.
In the operation of an activated sludge system to effect biological removal of phosphates from influent wastewater while inhibiting proliferation of filamentous biomass, the method consisting essentially of:
- producing a mixed liquor by mixing in an initial contact zone recycled activated sludge with wastewater influent containing BOD and phosphates;
- said initial contact zone being maintained under anaerobic conditions such as to be substantially free of NO.sub.x.sup.- and to contain a concentration of less than 0.7 ppm dissolved oxygen;
- thereby effecting selective production of nonfilamentous microorganisms capable of sorbing BOD and capable of storing polyphosphate under oxidizing conditions;
- oxidizing BOD in the mixed liquor in a subsequent oxygenated zone to cause removal of BOD by contact with oxygen-containing gas addmitted to said oxygenated zone, thereby simultaneously effecting storage of phosphates within said microorganisms;
- said oxygenated zone having maintained therein a dissolved oxygen content of at least 1 ppm;
- transferring the oxidized mixed liquor from said oxygenated zone to a settling zone wherein purified supernatant liquid is separated from settled sludge;
- and returning a portion of said settled sludge to said initial contact zone to provide the activated sludge admixed therein with the wastewater influent.
Dependencies are inferred from the claim text.