Secondary risks induced by polyethylene microplastics during the disinfection processes of chlorination, UV irradiation, and ozone treatment

ABSTRACT The presence of microplastics in surface waters poses potential hazards to both organisms and human health. Traditional water treatment processes have proven to be inadequate in effectively removing microplastics. Besides, previous studies have often utilized disinfectant dosages that surpass those commonly employed in drinking water treatment plants (DWTPs), and the biotoxicity changes induced by microplastics after disinfection remain largely unexplored. To address these knowledge gaps, our study aimed to investigate the impact of practical disinfectant dosages on the leaching of organic compounds from microplastics and the formation of disinfection byproducts (DBPs). Furthermore, the resulting acute and genetic toxicity was evaluated through bioassays. Our findings revealed an elevated release of dissolved organic matter (DOM) derived from microplastics. Additionally, both acute and genetic toxicity increased following various disinfection processes. Specifically, chlorination exhibited the highest level of toxicity in short-term disinfection, while the pretreatment of ozonation followed by residual chlorination demonstrated the highest toxicity in the long-term disinfection, which was correlated with the concentration of CHCl3 formed. These findings will advance our understanding of the potential risks associated with microplastics during various disinfection processes, with the ultimate goal of safeguarding water supplies.