Patent ID: 7195712

Claim:
A wastewater treatment apparatus for removing nitrogen and phosphorus having a pre-anoxic tank, an anaerobic tank, a denitrifying phosphorus accumulating organism (dPAO) tank, an anoxic tank, an aerobic tank, and a clarifier wherein: (a) sludge returned from the clarifier and some of the wastewater are introduced into the pre-anoxic tank, (b) wastewater treated by the pre-anoxic tank and some of the raw wastewater are introduced into the anaerobic tank in which a phosphorous release reaction by microorganisms occurs under anaerobic conditions, (c) wastewater treated by the denitrifying phosphorous accumulating organism (dPAO) tank and some raw wastewater are introduced into the anoxic tank in which denitrification of nitrate nitrogen occurs under anoxic conditions, (d) wastewater treated by the anoxic tank is introduced into the aerobic tank in which nitrification and luxury uptake of phosphorous occur with supply of oxygen, (e) the aerobic tank includes a baffle installed at one side thereof to form a dissolved oxygen reducing zone for reducing the concentration of dissolved oxygen contained in internally recycled wastewater returned from a dissolved oxygen reducing zone while increasing the concentration of dissolved oxygen contained in treated effluent supplied from a part other than the dissolved oxygen reducing zone of the aerobic tank to a clarifier in a subsequent stage, and (f) wastewater treated by the anaerobic tank and the wastewater treated by the dissolved oxygen reducing zone of the aerobic tank are introduced into the denitrifying phosphorous accumulating organism (dPAO) tank in which denitrification and removal of phosphorous occur at the same time by denitrifying accumulating organisms (dPAOs).