Study On The Aerated Biological Filter For Municipal Wastewater Treatment

The Aerated Biological Filter (BAF) is a simples high-efficients low-consumptive for municipal sewage treatment correspond to the situation of china, developed rapidly in last ten years, will be one of the important technical approaches to solve the water pollution and shortage problem faced china. This paper focuses on the experimental study and mechanism analysis in which the upflow Aerated Biological Filter was adopted on treatment domestic waste water. The removal performance and gas-water ratio, hydraulic loading, pollutants volume loading and the height of filter etc factors to influence the removal effect of pollutants was studied.It take about 24 days to succeed in cultivating biofilm using of the method of continuous flow following seeding with activated sludge, and the removal ratios of COD, NH₃-N gets to 75% and 60%.The experimental results showed that the removal rate of COD, NH3-N and turbidity in BAF system comes up to 88.1%, 60.1% and 95.1% respectively.gas-water ratios hydraulic loading, pollutants volume loading and the height of filter etc factors will influence the removal rate in BAF system. The gas-water ratio has not evident effect on the removal of COD, but has much greater effect on the NH₃-N. When gas-water ratio at 5:1,the object of carbon oxygen and nitrification can be arrived. The result on studying the hydraulic loading influence the removal rate show that when gas-water ratio at 5:1 ,hydraulic loading from 0.21m /(m²h) to 0.63m /(m²-h),hydraulic loading has not evident effect on removal of COD, but has an evident effect on the NH3-N.With the hydraulic loading higher, the removal of NH3-N has an evident lower. To the BAF in which 120cm height filter bed is used, the optimal region of COD removal is 0-70cm,the optimal region of NH3-N removal is 40-100cm, at 40cm height ,the turbidity will be removed mostly.Backwash is one of an important factor influence BAF. Through the study of backwash regimes, backwash intensity and backwash interval ,the result show that backwash interval ofBAF can be determinated by head loss and effluent quality. Hydraulic loading has much greater effect on backwash interval, with the hydraulic loading higher, the backwash interval will be shorter. The backwash regimes of gas combined with water has a good backwash effect. The backwash parameters as follows: first,the backwash air-flow intensity was 10—12 L/(m2 ? s), time was 3 min;second, mixing backwash, air-flow intensity was 10—12 L/(m2 ? s), water-flow intensity was 4-5 L/(m2 ? s), time was 5 min;finally, backwash intensity was 10¹2 L/(m2 ? s), time was 10-12 min.