Effect of polytetrafluoroethylene nanoplastics on combined inhibition of ciprofloxacin and bivalent copper on nitrogen removal, sludge activity and microbial community in sequencing batch reactor

• PTFE-NPs weaken the Cu(II) and CIP antagonism on sludge activities. • Nitrifier was more alive to Cu(II) and CIP than denitrifier with or without PTFE-NPs. • Adsorption of CIP and Cu(II) by PTFE-NPs was synergistic. • PN level in EPS was decreased by PTFE-NPs at mixed Cu(II)/CIP. • PTFE-NPs abated the binding of functional groups in PN and PS to mixed Cu(II)/CIP. The work aimed to explore effects of polytetrafluoroethylene nanoplastics on joint inhibitions of ciprofloxacin and bivalent copper on the nitrogen removal in a sequencing batch reactor and its potential mechanisms. The addition of bivalent copper and/or ciprofloxacin reduced the ammonia nitrogen elimination rate with or without polytetrafluoroethylene nanoplastics. Adsorption kinetics and thermodynamics showed the binary bivalent copper and ciprofloxacin promoted their adsorptions by polytetrafluoroethylene nanoplastics. Polytetrafluoroethylene nanoplastics enhanced combined toxicities of ciprofloxacin and bivalent copper to sludge activities and microbial community involved into nitrification and denitrification due to the adsorption of ciprofloxacin and bivalent copper by polytetrafluoroethylene nanoplastics. With or without polytetrafluoroethylene nanoplastics, bivalent copper and/or ciprofloxacin caused more obvious level changes of protein than polysaccharide. This study provides novel insights for understanding the effect of combined heavy metals and antibiotics on the performance in a sequencing batch reactor with the nanoplastics stress.