Patent ID: 7172699
Filing Date: 2007-02-06
Classification: C02F,Y02W,Y10S

Abstract:
1. In a liquid side of a sewage treatment system for treating wastewater, a biological nutrient removal (BNR) configuration of high efficiency with minimal aeration requirements, comprising: at least four tanks or zones arranged for successive treatment of the wastewater, including simultaneous nitrification/denitrification, aerobic, anoxic and aerobic stages in sequence in the respective tanks or zones, a first simultaneous nitrification/denitrification stage being maintained essentially at less than 1 ppm oxygen, and with the oxygen level adjusted to maintain simultaneous nitrification/denitrification, so that ammonia is broken down to produce nitrate, and nitrate is broken down to release nitrogen gas, within a single tank or zone and simultaneously, a first aerobic stage being maintained essentially at greater than 1 ppm oxygen to promote nitrification, an anoxic stage after the first aerobic stage, being maintained essentially at less than 1 ppm oxygen, and with the oxygen level adjusted to maintain an anoxic condition at least in part of the wastewater or part of the time, to break down nitrate to release nitrogen gas, and a second aerobic stage being maintained essentially at greater than 1 ppm oxygen to promote nitrification.