Study on Treatment Efficiency of City River Sewage by Anoxic/Anaerobic/Anoxic/Aerobic Process

A continuous-flow anoxic/anaerobic/anoxic/aerobic process was used in a pilot-scale reactor for treatment of Shenzhen Buji River sewage.The removal efficiency of COD,NH+4-N,TN and TP in different seasons was measured to provide operating parameters for a new wastewater treatment plant.During the summer rainy season,when the influent COD and TN were 36.4 to 195.5 mg/L and 13.7 to 29.5 mg/L,the effluent concentrations were 22.7 to 87.9 mg/L and 10.5 to 19.2 mg/L,respectively.The average removal rates were 72.1% and 26.0% respectively.During the winter dry season,when the influent COD and TN were 168.0 to 317.1 mg/L and 33.0 to 41.0 mg/L,the effluent concentrations were 20.2 to 58.0 mg/L and 13.0 to 22.5 mg/L,respectively.The average removal rates were 84.7% and 51.4% respectively.When the influent NH+4-N was 9.38 to 39.02 mg/L,the effluent concentration was 0.01 to 8.01 mg/L,and the average removal rate was 96.3%.Time to reach stable concentration was about three times higher for effluent ammonia than for COD and TN during the pilot-scale reactor recovery operation period.When the influent TP was 1.04 to 5.58 mg/L,the average effluent concentration was 0.97 mg/L.When 15 mg/L of PAC was dosed into the reactor,the average effluent TP was reduced to 0.30 mg/L,and the average removal rate was increased to 91.5%.The results reached the first level A criteria specified in Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant(GB 18918-2002).