Responses of biofilm characteristics to variations in temperature and NH4+-N loading in a moving-bed biofilm reactor treating micro-polluted raw water

► The pilot-scale MBBR showed good performance for NH4+-N removal from raw water. ► PS, PN and PL are good indicators of biomass development and detachment. ► Temperature and NH4+-N loading affect the ratios of PS/VS, PN/VS, HS/VS and PL/VS. ► The competitiveness of AOB and NOB were promoted by increasing NH4+-N loading. ► The biofilm characteristics provide detailed insights into MBBR treating raw water.