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

A 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 HRTon 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 m 3 /h, and hydraulic residence time (HRT) of 8 hours, were found. Under optimum operating conditions, the average removal efficiencies of COD and NH 4 -N are higher than 95 % and 99 %, corresponding to the effluent COD < 50 mg/L and NH 4 -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 NH 4 -N < 60 mg/L (GWPB4-1999). In addition, the radial and axial positions have little influence on the local profiles of COD and NH 4 -N.