Patent ID: 6372138
Filing Date: 2002-04-16
Classification: C02F,Y10S

Abstract:
A wastewater treatment method comprising the steps of:(a) denitrifying wastewater flowing into an anoxic tank by reducing the nitrate nitrogen into gaseous nitrogen using denitrifying bacteria being resident in the anoxic tank, and organic matter of the wastewater flowing into the anoxic tank; (b) making the carbon-to-nitrogen (C/N) ratio of the wastewater having undergone the step (a) suitable for a subsequent nitrification step after the wastewater flows into a first aeration tank by decomposing an excessive amount of organic matter using aerobic microorganisms attached to a carrier; (c) changing ammonia nitrogen of the wastewater having undergone the step (b) into nitrate nitrogen after the wastewater flows into a second aeration tank by using nitrifying bacteria attached to a carrier; (d) returning part of the wastewater having undergone the step (c) to the anoxic tank, while the remaining wastewater flows into a settling tank; and (e) returning part of the sludge discharged from the settling tank to the anoxic tank, discarding the remaining sludge as surplus sludge, and obtaining a supernatant separated from the sludge settled in the settling tank as the treated water.