N₂O emission in short-cut simultaneous nitrification and denitrification process: dynamic emission characteristics and succession of ammonia-oxidizing bacteria

A sequencing batch airlift reactor was used to investigate the characteristics of nitrous oxide (N₂O) emission and the succession of an ammonia-oxidizing bacteria (AOB) community. The bioreactor could successfully switch from the complete simultaneous nitrification and denitrification (SND) process to the short-cut SND process by increasing the influent pH from 7.0–7.3 to 8.0–8.3. The results obtained showed that, compared with the complete SND process, the TN removal rate and SND efficiency were improved in the short-cut SND process by approximately 13 and 11%, respectively, while the amount of N₂O emission was nearly three times larger than that in the complete SND process. The N₂O emission was closely associated to nitrite accumulation. Analysis of the AOB microbial community showed that nitrifier denitrification by Nitrosomonas-like AOB could be an important pathway for the enhancement of N₂O emission in the short-cut SND process.