Microplastics in wastewater treatment plant: Characterization of changes, influencing factors, and their impact on the spatial distribution of pathogenic bacteria

Wastewater treatment plants (WWTPs) have been proposed as pivotal convergence points for microplastics (MPs) and hotspots of bacterial pathogens. In this study, the characteristics of MPs and bacteria in the sewage/sludge were investigated and their relationship was formulated. Meanwhile, this study innovatively focused on the impact of MPs on microbial aerosolization process in WWTP. MPs and pathogenic bacteria were identified in sewage/sludge samples from all treatment steps, in which the levels and compositions of them vary. However, Bacillus, Planifilum, Achromobacter, and Geobacillus were the dominant genera in bioaerosol samples. The dominant shape of MPs was fibers and fragments. The main size range of MPs were 0.5 - 1 mm, with the primary type of polyethylene and polypropylene. White was the most prevalent color. Furthermore, a significant correlation between MPs and bacterial community structure in sewage/sludge was observed. The abundance and some characteristics of MPs showed positive correlations with the relative abundances of some potential pathogens, including Bacillus, Pseudomonas, Staphylococcus, Acinetobacter and Achromobacter. Aeration experiments demonstrated that the presence of MPs exerted an influence on the microbial aerosolization process. Collectively, this study provides a better understanding of the relationship between MPs and bacterial structures in a WWTP and offers new insights to the role of MPs on the microbial aerosolization process. The findings will provide a basis for the control and reduction of MPs and bacterial pathogens in WWTPs.