Revealing the combined effect of hydroxylamine and hydrazine on nitrogen removal performance of completely autotrophic nitrogen removal over nitrite (CANON) process

This study explored capabilities of completely autotrophic nitrogen removal over nitrite (CANON) process under co-regulation of hydroxylamine (NH₂OH) and hydrazine (N₂H₄). Results indicated that granular (R₁) and flocculated (R₂) sludge CANON systems were started-up respectively on day 14 and day 17 by co-introduction of 0.50 + 1.00 mg/L and 1.00 + 5.00 mg/L NH₂OH and N₂H₄, with ammonia removal efficiency (ARE) of 53.75 % ± 8.30 % and 54.17 % ± 7.40 %, respectively. Furthermore, the relative abundance of Nitrosomonas, Nitrospira, Candidatus_Nitrotoga and Nitrobacter reduced after NH₂OH and N₂H₄ was supplied into R₁ and R₂ for 30 days, thereby inhibiting ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) activity. Nevertheless, the relative abundance of Candidatus_Kuenenia and Candidatus_Jettenia recovered once NH₂OH and N₂H₄ were absent, produced reversible inhibitory on anaerobic ammonia-oxidation bacteria (AnAOB) activity. Results will demystify the nitrogen elimination performance and mechanism of the CANON process from a novel viewpoint.