Variation of microplastics and biofilm community characteristics along the long-distance raw water pipeline

The massive accumulation of microplastics (MPs) in aquatic environments and water treatment plants and their potential threat to human health have attracted widespread attention. The water quality indices, occurrence characteristics of MPs, and changes in the pipe wall biofilm structure along long-distance raw water pipelines in Jiangsu were studied, and the key factors influencing the variation in microbial community structure were revealed. The results demonstrated that the types of MPs detected in long-distance raw water pipelines were mainly polypropylene (PP), polyethylene (PE), polystyrene (PS), polyethylene terephthalate (PET), and polyvinyl chloride (PVC). The total abundance of MPs decreased significantly with an increase in the conveying distance, from 1570.8 n center dot L-1 at water intake to 377.0 n center dot L-1 at the end of the pipeline network. Small-scale MPs were the most abundant, maintaining the highest concentration of 300-700 n center dot L-1. The decrease along the pipeline was more obvious for MPs with larger densities and particle sizes. Physical sedimentation and biosorption by extracellular polymeric substances may be the means by which MPs are removed. The diversity of bacterial communities in the pipe wall biofilms changed significantly along the pipeline, but the predominant bacterial groups at each sampling point were similar at different taxonomic levels. RDA showed that the effects of DOC (41.6 %), CODCr (33.5 %), and MPs abundance (30.1 %) were comprehensive and were the top three key factors affecting the variation in the biofilm community characteristics along the pipeline.