Patent ID: 7473365

Claim:
A biological water or wastewater treatment process comprising: passing the water or wastewater into at least one biological tank, wherein the biological tank includes at least one free or mixed biomass; performing at least one separation step on the water or wastewater in the biological tank to generate sludge and treated effluent; measuring a nitrate content of the treated effluent or the water or wastewater; measuring a redox potential of the water or wastewater in the biological tank; aerating the water or wastewater in the biological tank until either (1) an elapsed aeration time exceeds a minimum aeration time and the measured nitrate exceeds a high nitrate set value or the measured redox exceeds a high redox set value; or (2) the elapsed aeration time exceeds a maximum aeration time and the measured nitrate is less than or equal to the high nitrate set value or the measured redox is less than or equal to the high redox set value; and subjecting the water or wastewater in the biological tank to anoxic treatment until either (1) an elapsed anoxic treatment time exceeds a minimum anoxic treatment time and the measured nitrate is less than or equal to a low nitrate set value; or (2) the elapsed anoxic treatment time exceeds a maximum anoxic treatment time and the measured nitrate exceeds the low nitrate set value.