Study On Advanced Treatment Of Organic Wastewater By Biological Aerated Filter (BAF)

The pollution and shortage of the water resource makes the necessary of the advanced treatment and the reuse of the wastewater. Biological Aerated Filter (BAF) process, a new technology that combines Biological Contact Oxidation and supply filtration, will be one of the important methods to solve above problems.In this paper, low concentration dyestuff wastewater was advanced treated by two-stage UBAF which is filled with ceramic granule and active carbon. The main obtained results are as follows:1. It is demonstrated by the experiment of inoculation and cultivating biofiim on packings that it takes four weeks to succeed in cultivating biofiim on packings and the removal ratios of NH3-N gets to 30% , when gas-water ratio is no less than 3:1, HRT is1h, water temperature is above 15℃.2. It is demonstrated that gas-water ratio, hydraulic loading, HRT etc are important factors to influence the removal effect of pollutants. With gas-water ratio about 2:1, hydraulic loading about 0.39m3/m2-h, HRT about lh, average water temperature about 24℃, pH ranging 6.5-7.5, the removal effect of pollutants is very good: the removal ratios of NH3-N, COD_cr and SS reached 78.6%, 50.08% and 81.79% respectively, and the effluent value of NH3-N, COD_cr and SS below 5mg/L, 50mg/L, 10mg/L respectively, which satisfying the water quality criteria for resue.3. Alongside the depth of filter bed, the removal characteristics of pollutants differ each other: the main region of COD_cr removal is the first half of the filter bed(distance from water inlet to 60cm) ; Slightly differing from CODcr removal, the main region of NH3-N removal is 25cm to 50cm.4. Under the condition of low gas-water ratio, the experiment of denitrification ability of UBAF shows that: With gas-water ratio about 0.3:1, filtration velocity about 0.7m/h, average water temperature about 21.5℃, pH ranging 6.5~7.5, the inflow COD_cr about 69.10mg/L, the removal ratios of NH3-N, and TN reached 55.84% and 47.20% respectively.5. Performance cycle of UBAF ranges from 6d to 7d. The backwashing way is gas combined with water. Under the condition that backwashing intensity of gas is10~ 12 L/s m~2, mixing backwashing: gas intensity is 7~8 L/s m~2 and water intensity is 3 ~4 L/s m~2, backwashing intensity of water is 5~6 L/s-m2; backwashing time: gas backwashing is 5~6 min, mixing backwashing is 6 min, and gas backwashing is 6~8 min, UBAF has a good effect of backwashing.