Release of microplastics from pipe materials and their impact on stagnant water

This study examines the release of microplastics from four types of pipe materials polypropylene random copolymer (PPR), polyvinyl chloride (PVC), polyethylene (PE), and stainless steel , assessing their impact on water quality and microbial communities under varying residual chlorine concentrations in stagnant water . Significant differences were found in the amount of microplastic released from each material, with PVC pipes releasing the highest amount, reaching 1.14 × 10 5 particles/L, while PE pipes released the least, exhibiting no significant difference from stainless steel samples. Microplastic particles in water accelerates chlorine decay, increases turbidity , elevates total organic carbon (TOC) levels, and can lead to the release of smaller microplastic particles into the water. Microplastics facilitated microbial proliferation, as indicated by higher heterotrophic plate counts (HPC), particularly in samples with PPR microplastics . After 360 h of stagnation, the HPC in the PPR-containing sample was still 1.40 × 10 5 CFU/mL, while chlorine levels in other samples had dropped to near zero. Scanning electron microscopy (SEM) revealed considerable surface degradation of microplastics under higher chlorine concentrations, with distinct bacterial colonization patterns on different microplastic materials. Chlorine concentration influenced microbial composition , with Sphingomonas species dominating at 0.25 mg/L and Pseudomonas species at 1.5 mg/L. Kruskal-Wallis test, identified significant taxonomic and phylogenetic differences in microbial communities among stagnant water , microplastic particles, and tube wall biofilms . Initial chlorine residuals also shaped dominant species, with Sphingomonas prevailing at 0.25 mg/L and Pseudomonas at 1.5 mg/L.