Short-Cut Nitrification and Denitrification Treatment for High Strengh Ammonium Wastewater Using a Pilot-Scale “Anoxic-Anaerobic-Microaerobic-Aerobic (A<sub>2</sub>O<sub>2</sub>)” System

Abstract

A pilot-scale nitrogen removal system composed of an anoxic area, an anaerobic area, a microaerobic area and an aerobic area (A2O2) was established to treat high strength ammonium wastewater from a nitrogenous fertilizer factory. The influences of key factors such as DO, pH, FA and temperature on partial nitrification in the microaerobic area were investigated. The results showed that in the DO concentration of 0.5~0.7mg/L, the stable and efficient nitrite accumulation could be realized. Meanwhile, the effluent NH3-N and TN quality was superior to the requirement of the《Synthetic ammonia industrial water contamination emission standard》(draft for comment). The optimal pH of 7.5~8.0 and the corresponding free ammonia (FA) concentration of around 0.95 mg/L limited the nitrobacteria activity selectively, thus favoring the stability of partial nitrification. The nitrite accumulation rate didn’t show obvious difference in wide temperature range (18~35°C) at given DO (0.5~0.7mg/L) and pH (7.5~8.0). But contrary to the usual partial nitrification obtained by high temperatures (>30°C), the effluent ammonium of A2O2system was substandard due to the inhibition of nitrobacteria activity caused by high temperature, which diminished the further removal of ammonium in the subsequent aerobic area.