Chlorination enhances the phthalates release and increases the cytotoxicity and bacterial functions related to human disease of drinking water in plastic pipes

Abstract

The interaction between water and pipe surfaces can deteriorate drinking water quality, thus threatening public health. However, uncertainties remain in the release mechanism of phthalates acid esters (PAEs) from plastic pipes and their effects on drinking water quality. Our study indicated that PAEs released from polyvinyl chloride (PVC) pipes was higher than polyethylene (PE) pipes. Chlorine disinfection increased the released PAEs concentration in effluents of PE-Cl₂ and PVCCl₂ pipes to 6.60∼7.87 μg/L and 7.45∼8.88 μg/L, respectively. PAEs release varied the CHO and tannins numbers in dissolved organic matter (DOM), increasing the cytotoxicity of water. Although chorine disinfection reduced the abundance of pathogenic bacteria, it upregulated the relative abundance of bacterial metabolic pathways related to human disease, such as drug resistance: antimicrobial and cancer: overview. In addition, various biofilm bacterial community compositions affected the interactions between bacteria and pipe surfaces, and the roughness of pipe surfaces increased after biofilm formation. The hydrophilicity of pipe surfaces also increased due to biofilm formation and chlorine disinfection. After five months of running, higher hydrophilicity of PVC pipe surface was observed than that of PE pipes, especially after chlorine disinfection, consequently enhancing PAEs release. In conclusion, chlorine disinfection accelerated PAEs release from plastic pipes by increasing the hydrophilicity of pipe surfaces, resulting in higher cytotoxicity and microbial risk of drinking water, especially in PVCCl₂ pipes. This study revealed the influence of chlorine disinfection on PAEs release and its potential risk to public health, which provided insightful visions for the future drinking water security monitoring.