Denitrification performance and microbial versatility in response to different selection pressures.

•Aerobic and anoxic suspended biomass could remove diverse NOx− concentrations.•Denitrifying community significantly altered under different incubation conditions.•Interspecies interactions possibly limited aerobic denitrification capacity.•Granular biomass removed nitrogen via heterotrophic nitrification/denitrification.•Microbial selection and nitrogen removal pathway depend on nourishment condition.