The feasibility of the completely autotrophic nitrogen removal over nitrite (CANON) process for removal of nitrogen from mainstream wastewater (~60 mg NH4+-N·L-1) at room temperature (25℃) was investigated using bio-augmentation batch enhanced (BABE) controlling strategy. The results indicated that through changing 40% sludge of the mainstream reactor from sidestream reactor every 7 d

the total nitrogen removal rate (TNRR) and the total nitrogen removal efficiency (TNRE) stabilized at about 80 g N·m-3·d-1 and 70%.The specific anammox activity in mainstream reactor increased continuously. 16S rDNA gene high-throughput sequencing results showed that the functional microorganisms involved in both mainstream and sidestream reactor were Candidatus Jettenia like anammox bacteria and Nitrosomonas like ammonia-oxidizing bacteria (AOB)

and the abundance of Nitrospira like nitrite-oxidizing bacteria (NOB) always maintained below 1% during 60 days' operation. It can be concluded that the operational mode of changing sludges between mainstream and sidestream every 7 d guarantees anammox activity and good nitrogen removal performance of mainstream CANON reactor under the experimental conditions herein.