China's water pollution comes mainly from two aspects, first, excessive discharge of industrial wastewater from industrial development, and second,a serious lack ofurban sewage treatment facilities after rapid urbanization which causes environmental pollution by discharging a large number of untreated sewage directly into water bodies . In recent years, despite the decrease of industrial wastewater after treatment,urban sewage accounting for 51% of water pollution still increases.
The design requires a stable and efficientA2 / O activated sludge processfor a capacity of 20000m3 / d of municipal wastewater. Due to different environmental conditions, different functions of the organic complex microbial communities, combined with anaerobic, anoxic units, in an A2O process some non-biodegradable organic matter (CODNB) can be open or broken, making the N, P, organic carbon could be removed simultaneously, and the removal of CODNB ¬ can be increased. It can simultaneously remove organic matter, conduct nitrification and denitrification, excessively intake of phosphorus and other functions.Nitrogen can be removed in anoxic tank on the premise of nitrification of NH3 - N which is completed by the aerobic tank. Combination of anaerobicand aerobic units undertakes phosphorus removal.