Decoding the response of complete autotrophic nitrogen removal over nitrite (CANON) performance and microbial succession to hydrazine and hydroxylamine: Linking performance to mechanism.

The influence of hydrazine (N2H4) and hydroxylamine (NH2OH) on performance and microbial community structures of complete autotrophic nitrogen removal over nitrite (CANON) process were assessed in this study. Experimental results demonstrated that CANON process was successfully started up and got total nitrogen removal efficiency (TNRE) of 53.6 % ± 9.8 % and 56.4 % ± 6.5 % under 1.0 and 0.5 mg L-1 N2H4 and NH2OH, respectively. N2H4 and NH2OH promoted activity of ammonia-oxidizing bacteria (AOB) and anaerobic ammonium oxidation bacteria (AnAOB), and inhibited activity of nitrite-oxidizing bacteria (NOB). Meanwhile, the stable operation of CANON process could be maintained without N2H4 auxiliary. While, performance assisted by NH2OH was fluctuated without NH2OH addition, suggesting that both N2H4 and NH2OH had a persistent and reversible inhibition on NOB. This study reveals new insights into influence of N2H4 and NH2OH on CANON performance.