The effects of microplastics and nanoplastics on nitrogen removal, extracellular polymeric substances and microbial community in sequencing batch reactor

•NPS and high-level MPS inhibited denitrification and induced NO3−-N accumulation.•NPS and MPS affected functional genes involved in nitrogen metabolism.•The NPS increased, but the MPS decreased the total amounts of EPS.•NPS and MPS increased PRO/PSR ratio and changed protein secondary structure in EPS.•Abundance of microbe related to nitrogen metabolism and EPS production was altered.