Effect of Aeration Rate on Nitrogen and Phosphorus Removal in Step-feed SBR with Side-stream Phosphorus Removal

In order to solve the issue of poor efficiency of nitrogen removal especially phosphorus removal from low-carbon source wastewater(COD/TN5,COD 180 mg/L),the aeration rate of SBR operated under external sludge recycle for side-stream phosphorus removal,step feed and alternating aerobic-anoxic conditions was controlled to achieve a rational distribution of carbon source and good nitrogen and phosphorus removal effect.When the aeration rate is controlled at a level of 3.57 m3/(h·m3),and the average concentrations of COD,ammonia nitrogen,TN and TP are 121 mg/L,29 mg/L,31.4 mg/L and 4.6 mg/L respectively,the removal efficiencies of the pollutants are 86%,98.6%,61.7% and 93.6% respectively.The phosphorus storage balance in PAOs is broken by enhancing anaerobic phosphorus release with external sludge recycle.The once-a-day external sludge recycle for side-stream phosphorus removal can ensure the phosphorus removal effect and simplify the operation course of side-stream phosphorus removal process.