Effects of microplastics on water disinfection and formation of disinfection by-products

The presence of microplastics (MPs) in water systems has emerged as a significant concern due to their persistence, ubiquity, and potential to interfere with treatment processes. While some studies have investigated the interactions of MPs with disinfectants and MPs’ potential to act as precursors for disinfection by-products (DBPs), most have relied on laboratory setups that employ unrealistically high concentrations of MPs and disinfectants doses. These conditions fail to replicate the complex effects of background chemistry, the presence of microbial communities, and other aspects of environmental dynamics typical of actual water treatment plants (WTPs) and wastewater treatment plants (WWTPs). The results from such studies cannot be used to unambiguously understand and predict the real-world scenarios of MP effects, thereby limiting real-world applicability of the model experiments. Another aspect of MP-associated effects is their role as carriers for pathogens, antibiotic-resistant genes (ARGs), and disinfectant resistant-genes (DRGs), along with their capacity to interfere with disinfection efficacy while forming a potential habitat for microbial communities. The study calls for a paradigm shift towards more realistic field-representative studies that are needed to bridge the gap between lab and field results and ultimately accurately assess the risks which MPs pose in water treatment contexts. • MPs interfere with disinfection and reduce the efficacy of chlorination and ozonation. • MPs can leach dissolved organic carbon and react with disinfectants, leading to formation of DBPs. • Real-world roles of MPs as DBP precursors and ARG/DRG carriers remain largely underexplored. • Laboratory experimental studies on MPs use unrealistic conditions, thereby limiting real-world applicability.