초록 ▼

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 zo

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 NOx-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/nitrite-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.

대표청구항 ▼

An activated sludge process for biologically removing nitrogen from wastewater, comprising the steps of: a) forming mixed liquor from influent wastewater and activated sludge; b) treating the mixed liquor in a first nitrogen removal stage, including the substeps of: i) directing the mixed liquor int

An activated sludge process for biologically removing nitrogen from wastewater, comprising the steps of: a) forming mixed liquor from influent wastewater and activated sludge; b) treating the mixed liquor in a first nitrogen removal stage, including the substeps of: i) directing the mixed liquor into a first anoxic zone, ii) maintaining the mixed liquor under anoxic conditions within the first anoxic zone for a sufficient time period to permit denitrifying microorganisms to reduce nitrates and nitrites in the mixed liquor to elemental nitrogen, iii) transferring a portion of the mixed liquor from the first anoxic zone to a first aerobic zone, iv) aerating the mixed liquor within the first aerobic zone for a sufficient time period to permit nitrifying microorganisms to convert ammonia and organic nitrogen in the mixed liquor into nitrates and nitrites, and v) circulating the mixed liquor between the first anoxic zone and the first aerobic zone to effectuate denitrification and nitrification; c) treating the mixed liquor in a second nitrogen removal stage by passing the mixed liquor through a second anoxic zone and a second aerobic zone to effectuate further denitrification and nitrification; d) transferring the mixed liquor treated in the first and second nitrogen removal stages to a final clarifier where settled sludge is separated from purified supernatant; e) retaining the sludge in the final clarifier for a period of time sufficient to permit denitrifying microorganisms in the sludge to adapt to respiring nitrates and nitrites instead of oxygen; f) recycling a portion of the sludge from the final clarifier to form the mixed liquor; and g) recycling another portion of the sludge from the final clarifier into the mixed liquor between the first nitrogen removal stage and the second nitrogen removal stage so as to increase the population of microorganisms in the second nitrogen removal stage that have adapted to respiring nitrates and nitrites instead of oxygen.