The accumulation characteristics of NO and N2O in A/O-SBR for treating ammonium-rich organic wastewater

Abstract

The emissions of NO and N2O during biological nitrogen removal harm the environment. In this study, a sequencing batch reactor (SBR) was used to treat ammonium-rich organic wastewater. The nitrogen transformation and characteristics of NO and N2O accumulation in typical cycles under different nitrification conditions were monitored, and the mechanisms of NO and N2O production in A/O-SBR were analyzed. The results showed that NO accumulated in the anoxic phase under a fixed concentration of organic carbon source during denitrification with nitrite as electron acceptor or nitrate as electron acceptor. NO production in the aerobic phase could be related to hydroxylamine oxidation and nitrite reduction caused by high ammonia nitrogen. The accumulation of N2O mainly occurred in the aerobic phase, and the cumulative concentration of N2O at the end of the four typical cycles was above 4.02 mg/L. N2O accumulation attributed to the inhibition of free nitrous acid (FNA) and NO, and electronic competition, which made N2O reductase (N2OR) activity insufficient, failing N2O reduction.