Patent ID: 7198716

Claim:
A system of vessels for the treatment of wastewater comprising: a reactor vessel holding a mixed liquor of activated sludge and wastewater, said reactor vessel in fluid communication with an anaerobic vessel and a separator; said reactor vessel in further communication with aeration equipment; said anaerobic vessel in fluid communication with said separator and receiving a fluid stream of thickened solids from said separator; said separator in fluid communication with said anaerobic vessel and said reactor vessel; said separator receiving as an influent a fluid stream of return activated sludge and discharging as effluent a supernatant and a fluid stream of thickened solids said reactor vessel receiving the effluent of said anaerobic vessel and said supernatant of said separator; wherein said reactor vessel is capable of being operated in an aerated phase with said aeration equipment on and in an anoxic phase with said aeration equipment off; wherein the effluent from said reactor vessel following solid/liquid separation has a total nitrogen concentration less than or equal to 3.0 mg/l.