Enhancing Nitrogen and Phosphorus Removal in Step-feed A/O Process

In order to improve the efficiency of simultaneous nitrogen and phosphorus removal, step-feed A / O process was used to treat high ammonia nitrogen domestic sewage. The removal efficiencies of COD,ammonia nitrogen,total nitrogen and total phosphorus were investigated under average COD / TN ratio of 3. 8,different aeration rates and chemical phosphorus removal. When the aeration rates were 0. 7,0. 5 and 0. 3 m3/ h,the average removal rates of COD were 87. 97%,90. 72% and 91. 27%,respectively. When the aeration rate was 0. 5 m3/ h,the ammonia nitrogen removal rate was more than 95% with optimal distribution of DO concentration in the aerobic tank. Moreover,the total nitrogen removal was higher at 0. 5 m3/ h because of aerobic denitrification. When carbon source was the factor limiting nitrogen and phosphorus removal,the average removal rates of phosphorus under the three aeration rates were 31. 76%,32. 84% and 44. 49%,respectively. Total phosphorus concentration in the effluent was about 0. 5 mg / L after adding mixed flocculant of PAC and Al 2( SO 4) 3.