Application of Downflow-Upflow Biological Aerated Filter in the Pretreatment of Raw Water Containing High Ammonia Nitrogen

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 (NH3-N) and organic pollutants. Operating parameters for low-flow periods were as follows: filtration rate of 8 m/h and gas-water ratio of 0.5:1.5. In terms of water quality, the average concentrations of NH3-N and permanganate index (CODMn) 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 0.3:0.5. In terms of water quality, the average concentrations of NH3-N and CODMn 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 "(sic)"-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 mH(2)O after filtration for 24 h. This also satisfies the head loss control requirement for numerous UBAFs, which share a centralized aeration system to achieve uniform aeration. DOI: 10.1061/(ASCE)EE.1943-7870.0000447. (C) 2011 American Society of Civil Engineers.