Evaluation of denitrification performance and bacterial community of a sequencing batch reactor under intermittent aeration

Effects of operational parameters (initial nitrite concentration, initial nitrate concentration, carbon source, and COD/N ratio) on denitrification performance was evaluated using a sequencing batch reactor (SBR) under intermittent aeration. Complete denitrification was observed without N₂O accumulation when the initial nitrite concentration was 100–500 mg-N·L⁻¹. When the initial nitrate concentration was 75–300 mg-N·L⁻¹, 95–96% of NO₃ ⁻-N was completely reduced to N₂ gas. Acetate was the most effective sole carbon source for the complete denitrification of the SBR under intermittent aeration, and 99% of NO₃ ⁻-N was reduced to N₂ gas. The optimum COD/N ratio was 8–12 for the complete denitrification, while NO₂ ⁻ accumulation was observed at low COD/N ratios of 1 and 2. In this study, N₂O accumulation was not observed during the denitrification process regardless of operational condition. Paracoccus (15–68%), a representative aerobic denitrifying bacterium, was dominant in the SBR during the denitrification process, and the intermittent aeration condition could affect the abundance of Paracoccus in this study.