Treatment Of Municipal Sewage And Optimal Control In Combined BAF-MBR Process

Water scarcity is one of the major factors limiting the development of human civilization, especially in China. At present, people pay more and more attention on wastewater treatment and reuse. To improve the quality of effluent, we must strengthen management and transformation processes of the sewage treatment projects which have been completed. The purpose of the test was to combine MBR and BAF on the basis of the original project and to optimize the composite technology. Reducing energy consumption was another purpose besides meeting the I-A of the GB 18918-2002. Assembling, installing and starting the craft with its effectiveness research, optimizing operating parameters after the study on its influences and studying on simultaneous removal of phosphorus were the three contents of this project.Hanging biofilm on the BAF with composite inoculum costed 8 d in summar and 10 d in winter while vaccinating directly for the MBR. The effect was obvious of the combined system because of some shock loading, reaching the standard and reducing of pollution of the membrane. Optimum operating parameters in the BAF was 100 L/d for water flow, 2:1 for gas-water ratio, 200% for reflux ratio while the average concentration and removal rates of COD, ammonia, TN of BAF-MBR were 7.11 mg/L, 0.23 mg/L, 8.85 mg/L and 94%, 98%, 58%.Dosing ferrous salt in the MBR, aluminum salt in the MBR, ferrous salt in the BAF, aluminum salt in the BAF were all studied to remove phosphorus of which the optimum dosage and cost were 20 mg/L, 30 mg/L, 25 mg/L, 25 mg/L and ￥0.014/t, ￥0.036/t, ￥0.0175/t, ￥0.003/t.Dosing ferrous salt in the BAF was the best way because of no influences on the treatment effect and membrane fouling and lower cost. Dosing aluminum salt in the BAF were made adverse to remove TN and it increased the clogging of BAF filter. Dosing ferrous salt in MBR will increase the membrane fouling while dosing aluminum salt in MBR decreased that. However, high cost of chemicals and poor performance in sludge dewatering made aluminum salt in MBR not advantageous. It’s the best way that dosing ferrous salt in the BAF while setting coagulation sedimentation tank before the combined system, otherwise there needed a further comparative analysis.This paper pointed out the advantages of combined BAF-MBR process, studied and optimized the various factors affecting the system, found out the difference of ferrous and aluminum removing phosphorus in different places. This test was conductive to improving the level of effluent and the utilization of sewage. The results provided theoretical and technical guidance for sewage treatment plant renovation in the actual project application.