Dual-stage biological process for removing nitrogen from wastewa

Details Dual-stage biological process for removing nitrogen from wastewa Dual-stage biological process for removing nitrogen from wastewa

1995-09-08

1997-07-22

McCarthy, Neil

Liquid purification or separation

Processes

Treatment by living organism

210622, 210624, 210626, 210629, 210630, 210903, 210906, C02F 312, C02F 330

Patent

active

056500696

ABSTRACT:
A process for biologically removing nitrogen and other nutrients from wastewater using recycled activated sludge. A mixed liquor is formed from influent wastewater and recycled activated sludge and then treated in two successive nitrogen removal stages, each stage having an anoxic denitrification zone and an aerobic nitrification zone. The first nitrogen removal stage entails circulating the mixed liquor back and forth between the anoxic zone and the aerobic zone. The mixed liquor is then transferred to a final clarifier where activated sludge is separated from purified supernatant. To increase the NO.sub.x.sup.- reducing enzymatic activity of denitrification microorganisms, the activated sludge is retained in the final clarifier for a time period sufficient to permit adaptation of these microorganisms to a nitrate
itrite-respiring metabolic pathway. To maintain high levels of denitrifying microorganisms and thereby effectuate greater nitrogen removal than previously possible, a portion of the activated sludge is recycled from the final clarifier directly into the second nitrogen removal stage.

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patent: 5514278 (1996-05-01), Khudenko

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