Insight into partial nitrification of membrane aerated biofilm reactor (MABR): performance, microbial characteristic and mechanism

Nitrosospira (18.4%, 12.9% and 2.1%), unclassified_o__SBR1031 (8.2%, 11.2% and 8.9%), OLB13 (1.5%, 36.8% and 22.3%) and Nitrosomonas (2.5%, 0.8% and 4.1%) were all have relatively high abundance in R1, R2, and R3, which was also observed by the SEM (Fig. 2A3O-2C3O). Nitrosospira and Nitrosomonas belong to the common AOB and are devoted to PN. Unclassified_o__SBR1031 was considered as the symbiotic organism with the ability to cross-feed with AnAOB, which also had the ability to convert NH4+-N to NO2--N [39,40]. OLB13 could accumulate NO2--N by reducing NO3--N.