Study On Advanced Treatment For Domestic Sewage Using Biological Aerated Filter

The biological aerated filter (BAF) as a simple,low-consumptive,high-efficient new sewage treatment technology, corresponding to the situation of China, will have great development prospects in our country. In this paper, to solve the problem at the present time existing in the advanced treatment domestic sewage field, a method of domestic sewage treatment using BAF as a secondary treatment unit was proposed. Through treating the domestic sewage using BAF, experimental study and theoretical analysis was carried on. The removal performance and hydraulic retention time(HRT),gas-water ratio and the height of filter factors to influence the removal effect of pollutants was studied.It took 27 days to succeed in film hanging using of the method of the natural membrane. COD,ammonia nitrogen removal rate were at 45% and 96%.Trough experimental research on effects of removing contaminants of the BAF under the conditions of different HRT and gas-water ratio, the optimum parameters of the system were determined as follows: HRT was 2.2 hour, gas-water ratio was 5:1, and the height of filter was 105 cm. Under the optimum technological parameter conditions, the efficiency of removing COD,ammonia nitrogen and turbidity of the reactor was 44%,98%,62%, respectively; the concentration of COD,ammonia nitrogen and turbidity in effluent was 31 mg/L,0.8mg/L,5NTU, respectively. The effluent value met the demand of the A-level standard in the integrated wastewater discharge standard (18918-2002), and gained the ends of advanced treatment for municipal wastewater.The back wash is one of the key factors influencing the performance of the BAF. Trough experimental research, the fitting method of backwash was determined as follows: first, backwashing with air for 3 min, the backwash intensity was 18 L/(m~2·s); then, simultaneous backwashing of air and water for 8 min, the backwash intensity of air and water was 18 L/(m~2·s) and 4 L/(m~2·s), respectively; last, backwashing with water for 3 min, the backwash intensity of water was 4 L/(m~2·s). The backwash period was 7 days. By means of kinetics research on the mechanics of removing organic matters of the reactor, the kinetics model was built.Nitration kinetics research on bio-filter indicated that there were different characteristics of nitrification rate in the three kinetics regions which were DO control region, substrates and DO control regions, ammonia-nitrogen concentration control region.By means of kinetics research on the mechanics of removing ammonia-nitrogen of the reactor, the kinetics model was built, and as a coarse estimate model, the Nitration kinetics model will play an important role in the aspect of operation instruction for BAF.