Pre-oxidization-induced change of physicochemical characteristics and removal behaviours in conventional drinking water treatment processes for polyethylene microplastics

Microplastics (MPs), as emerging pollutants, have attracted worldwide attention due to their ecological and biological toxicity. As microplastics have been detected frequently in drinking water, it is essential to evaluate the physicochemical property change and removal behaviors of MPs in drinking water treatment processes. This study selected polyethylene microplastics (PE-MPs) as the representative, and investigated the variations in its physicochemical characteristics after oxidizing by several conventional pre-oxidants (potassium permanganate, sodium hypochlorite, and ozone). Furthermore, coagulation, sedimentation, and filtration experiments were conducted to verify whether pre-oxidization influenced the removal of microplastics. The results indicate that pre-oxidization indeed changed the hydrophobicity, specific surface area, and functional groups of PE-MPs surface exposing to water phase. These changes affected the adsorption of trace pollutants with different hydrophobicity (acesulfame, carbamazepine, and nitrobenzene). However, such changes showed a subtle effect on the removal of PE MPs by coagulation-sedimentation-filtration processes. Current findings suggest that pre-oxidization may increase the risk of pathogenic microorganisms due to the increasing oxidization-induced shelter ability of MPs towards microorganisms.