The effects of polypropylene microplastics on the DBP formation under the chlorination and chloramination processes

With the increased use of microplastics in modern society, tonnes of various microplastics (MPs) end up in natural and engineered water systems if not properly handled. Being a class of organics, the role of MPs during the disinfection of water treatment systems is still unclear at this stage. In the current experimental study, the formation of 6 typical disinfection by-products (DBPs) was investigated using varying concentrations of polypropylene (PP) MPs under various aquatic chemistry conditions and disinfectants. All investigated DBPs were detected, during the chlorination of PP, with an average CHCl3 concentration of 378 mu g/g, and other DBPs, including CHCl2Br, TCA, DCAN, 1,1-DCP, and TCNM, were present in less than 60 mu g/g, on average. When PP coexisted with Suwannee River Fulvic acid (SRFA), a suppression of DBP formation was observed with a 56% net reduction compared with a condition of PP alone. The dynamic balance of being a DBP precursor, or a scavenger, by absorbing the organics of PP is subjected to aquatic chemistry. Increasing the pH decreases the HOCl concentrations, reducing the PP oxidation capacity and DBP formation. As salinity increases, the aggregation of PP can reduce the reaction sites on the surface of PP and enhance the adsorption of SRFA, hence lowering the formation of DBPs.

Automated summary

With the increased use of microplastics, it is important to understand their role in water treatment systems. This study investigated the formation of disinfection by-products using polypropylene microplastics under different conditions. It was found that the presence of organic matter suppressed the formation of by-products, and the pH and salinity of the water affected the formation of the by-products.