N₂O emission during short-cut nitrification of high ammonium containing wastewater

By controlling the aeration rate in a sequencing batch reactor (SBR), nitritation was achieved with the influent ammonium nitrogen (NH₄⁺-N) concentration gradually increased to 800 mg·L^-1. Within the typical SBR reaction cycle, factors such as low dissolved oxygen and high free ammonia concentrations caused low activity of ammonia oxidation bacteria (AOB), and nitrifiers denitrification was carried out by AOB with nitrite nitrogen (NO₂^--N) as the electron acceptor and the emission factor of nitrous oxide (N₂O) was 9.8%. During batch experiments, with the initial NH₄⁺-N concentration of 100 mg·L^-1 and varied aeration rates (0.22~0.88 L·min^-1), nitrifier activities increased with increasing dissolved oxygen concentrations and the N₂O emission factor was in the range of 0.51%~0.85%. With the initial NH₄⁺-N concentration of 100 mg·L^-1 and the aeration rate of 0.66 L·min^-1, the applied NO₂^--N concentration of 0~100 mg·L^-1 affected little on nitrifier activities and the N₂O emission factor was in the range of 0.50%~0.71%. By controlling suitable dissolved oxygen and free ammonia concentrations, high activity of AOB could be maintained, resulting in the inhibited aerobic nitrifier denitrification and the reduced N₂O emission.