N2O emission from nitrogen removal via nitrite in oxic-anoxic granular sludge sequencing batch reactor

Bionitrification is considered to be a potential source of nitrous oxide (N₂O) emissions, which are produced as a by-product during the nitrogen removal process. To investigate the production of N₂O during the process of nitrogen removal via nitrite, a granular sludge was studied using a lab-scale sequence batch reactor operated with real-time control. The total production of N₂O generated during the nitrification and denitrification processes were 1.724 mg/L and 0.125 mg/L, respectively, demonstrating that N₂O is produced during both processes, with the nitrification phase generating larger amount. In addition, due to the N₂O-N mass/oxidized ammonia mass ratio, it can be concluded that nitrite accumulation has a positive influence on N₂O emissions. Results obtained from PCR-DGGE analysis demonstrate that a specific Nitrosomonas microorganism is related to N₂O emission.