Optimization of Operation Parameters of CAST Process in Low Temperature Period
The microbial activity is significantly reduced at low temperature,which has a great influence on the efficiency of biological treatment process.CAST process is used in Chongqing Lijiatuo WWTP,and its operation pattern in low temperature period is as follows;influent 1 h,influent/aeration 2 h,slight aeration 1 h,sedimentation 1 h and decanting 1 h.The optimization of operation parameters was carried out to improve nitrogen removal efficiency.The result shows that optimal nitrogen removal efficiency can be achieved with an average nitrogen removal rate of 75%when DO during aeration period and slight aeration period is 2.0 to 3.0 mg/L and below 0.5 mg/L,MLSS is 3 500 to 4 000 mg/L,correspondingly, SRT of 15 to 20 d,and the sludge reflux ratio is 30%.