Biomass Types of Nitrate-Reducing Denitrifiers to Differentiate the Hybrid Community Allocation of Partial Denitrification (PD) and Anammox: IFAS Vs MBBR

•The difference of the dominant nitrate-reducing denitrifiers in MBBR and in IFAS reactor.•Nitrate-reducing denitrifiers selectively immigrate to the anammox biofilm.•The distribution of the microbial community in MBBR and IFAS reactors is different.•Aggregation and diversity of AnAOB in anammox biofilm higher in the IFAS reactor than MBBR.•Compared to MBBR, IFAS is a superior coupling mode in the PD/anammox process.