Nitrifying Treatment of Wastewater from Fertilizer Production in a Three‐Phase Flow Airlift Loop Bioreactor

Abstract

AbstractA 12‐L gas‐liquid‐solid three‐phase flow airlift loop bioreactor, in which biological membranes replace the activated sludge, was used in the nitrifying treatment of a real effluent in a Nanjing chemical fertilizer plant. The influences of temperature, pH, air flow rate and HRT on ammonia nitrogen reduction were investigated and discussed. The optimum operating conditions, such as temperature of 30–35 °C, pH value of 7–8, air influx of 0.3 m3/h, and hydraulic residence time (HRT) of 8 hours, were found. Under optimum operating conditions, the average removal efficiencies of COD and NH4‐N are higher than 95 % and 99 %, corresponding to the effluent COD < 50 mg/L and NH4‐N < 5 mg/L, which is far below the primary discharge standard for the chemical fertilizer industry of P.R. China – COD < 150 mg/L and NH4‐N < 60 mg/L (GWPB4–1999). In addition, the radial and axial positions have little influence on the local profiles of COD and NH4‐N.