Exploring the co-occurrence of microplastics, DOM and DBPs inside PVC pipes undergoing chlorination by correlation analysis and unsupervised learning

Drinking water distribution systems face a multifaceted emerging concern, including in situ microplastic (MP) generation, chemical leaching from plastic pipes, and the formation of disinfection by-products (DBPs). This study investigated the co-release of MPs and chemical leachates from polyvinyl chloride (PVC) pipes exposed to different chlorine concentrations on a lab scale, as well as the subsequent formation of DBP. Results highlighted significant evidence of PVC-derived dissolved organic matter (PVC-DOM) and microplastic (PVC-MP) leaching at higher chlorine concentrations. However, at chlorine residuals of 1 ppm, natural organic matter (NOM) retained its importance, with minimal release of PVC-DOM and PVC-MP from plastic pipes. Correlation analysis highlights the critical role of DOM, including both NOM and PVC-DOM, as a key intermediary between MPs and DBPs. This is evidenced by the strongest observed correlations within the DOM group and its significant associations with both MPs and DBPs. Conversely, the limited direct connections between MPs and DBPs further underscore the importance of DOM as the key link between these two targets. Using unsupervised learning techniques, including clustering and dimensionality reduction, further elucidated the influence of DOM in controlling the data patterns, enabling robust interpretation of complex datasets, and providing valuable insights. This study contributes to advancing understanding of the co-occurrence and behaviors of MP, DOM, and DBP within drinking water distribution systems, as well as propelling the associated risk in this intricate scenario.