Effects of polystyrene nanoplastics on extracellular polymeric substance composition of activated sludge: The role of surface functional groups

Highlights: • Compared the effects of PS NPs with surface modification on EPS of activated sludge. • Three PS NPs inhibited the total production of EPS and protein after 12 h exposure. • C-(C, H) was involved in the interactions between PS NPs and EPS. • C=O and O-C-O were involved in the interactions between PS-NH₂ NPs and EPS. • Three PS NPs induced obvious increases in ROS generation and LDH release. Here we investigated the acute effects (12 h exposure) of three polystyrene nanoplastics (PS NPs, including PS, PS−COOH and PS−NH₂) on extracellular polymeric substance (EPS) composition of activated sludge. Three PS NPs exhibited the significant inhibition in total EPS and protein (PRO) production. The functional groups involved in the interactions between PS NPs and EPS were C-(C, H), and those between PS-NH₂ NPs and EPS were CO and O–C–O. In addition, the dewaterability of activated sludge were optimized by three PS NPs, especially PS-NH₂ NPs. Three PS NPs caused nonnegligible cellular oxidative stress and cell membrane damage in activated sludge (PS NPs exposure concentration: 100 mg/L). Among them, the cell membrane damage caused by PS-NH₂ was the most significant. Overall, the degree of influence on EPS and cytotoxicity of activated sludge varies with the surface functional groups of PS NPs.