Nitrification kinetics of a full-scale anaerobic/anoxic/aerobic wastewater treatment plant

Nitrification kinetics of a full-scale anaerobic/anoxic/aerobic wastewater treatment plant were investigated by considering the anaerobic ((A)) and anoxic reduction factors ((N)) on decay rate of nitrifying biomass (b(AUT)) for estimating minimum sludge age ((mc)). Ammonium nitrogen in the effluent was fluctuating seasonally with low nitrification efficiency from December to June. The measured b(AUT) values were 0.175, 0.092, and 0.077d(-1) under aerobic, anoxic, and anaerobic conditions, respectively. A low maximum specific growth rate at 20 degrees C (0.48d(-1)) and high temperature correction factor (1.208) were yielded in the range of 10-25 degrees C, indicating that the activity of nitrifying biomass was low and depended more sensitively on lower temperatures. At temperature below 12.1 degrees C, the decay rate of nitrifying biomass exceeded growth rate, and a negative (mc) was obtained. The extremely high (12.1-15.0 degrees C) or negative (<12.1 degrees C) (mc) indicated that prolonging sludge age was probably malfunctioned at cold temperature.