A Novel Approach to Remove Nitrogen in a Biological Aerobic Filter (BAF)

Abstract

Laboratory study on nitrogen removal was carried out using biological aerobic filter (BAF) fed with synthetic domestic wastewater in the temperature range of 20.5-26.5°C in order to gain insight into the mechanism and the influences of operation parameters on nitrite accumulation in the biological nitrogen removal process. Influent loading with 0.26-0.62 kg (m3 d−1) NH4 +-N, 0.28-0.63 kg (m3 d−1) TN, 1-2 m h−1 hydraulic loading and air/water ratio 3:1, resulted in the removal of NH4 +-N and TN by 0.15-0.52 kg (m3 d−1) and 0.18-0.42 kg (m3 d−1) respectively. Hence BAF seems to be a promising nitrogen removal technique. The investigation of nitrite concentrations in the bulk and effluent, the profiles of inorganic nitrogen compounds and the spatial distribution of microbial populations and activity indicated that the nitrite accumulation and shortcut nitrification-denitrification had taken place in the bioreactor. No clear relationships were observed between the nitrite accumulation with the influent loading, temperature and pH value except that nitrite concentrations in the bulk increased with high back washing frequency. The results suggested that the filter structure and operation pattern were the principal factors that cause the nitrite accumulation and shortcut nitrification-denitrification occurring in the biological aerobic filter.