Application of downflow-upflow biological aerated filter in the pretreatment of raw water containing high ammonia nitrogen

摘要

In a subtropical area, a downflow-upflow biological aerated filter (D-UBAF) was used in the pretreatment of raw water containing seasonal high levels of ammonia nitrogen (NH _3-N) and organic pollutants. Operating parameters for low-flow periods were as follows: filtration rate of 8 m/h and gas-water ratio of 0.51.5. In terms of water quality, the average concentrations of NH _3-N and permanganate index (COD _(Mn)) and the turbidity of the raw water were 5.02-9.45 ~(mg/L, 5.79-10.1)mg/L, and 19.7-63.1 NTU, respectively. The corresponding indexes of the D-UBAF effluent were 0.30-0.96 ~(mg/L, 3.24-5.85)mg/L, and 3.83-19.9 NTU, respectively. The removal efficiencies were 90.3%, 42.7%, and 66.3%, respectively. Operating parameters for high-flow periods were as follows: filtration rate of 12 m/h and gas-water ratio of 0.30.5. In terms of water quality, the average concentrations of NH _3-N and COD _(Mn) and the turbidity of the raw water were 2.19-3.41 ~(mg/L, 5.30-7.56)mg/L, and 27.3-40.1 NTU, respectively. The corresponding indexes of the D-UBAF effluent were 0.18-0.41 ~(mg/L, 2.87-4.50)mg/L, and 5.43-16.8 NTU, respectively. The removal efficiencies were 89.3%, 40.2%, and 65.0%, respectively. The D-UBAF with one DBAF and two UBAFs constituted a -shaped structure. The space among these three components was used as a common tube gallery. The UBAF is the principal component of the biological pretreatment process. The DBAF runs before the UBAF; it can ensure that the head loss in the UBAF does not exceed 0.2 m H _2O after filtration for 24h. This also satisfies the head loss control requirement for numerous UBAFs, which share a centralized aeration system to achieve uniform aeration.