Abstract
Microplastics are ubiquitous contaminants in aquatic habitats globally, and wastewater treatment plants (WWTPs) are point sources of microplastics. Within aquatic habitats microplastics are colonized by microbial biofilms, which can include pathogenic taxa and taxa associated with plastic breakdown. Microplastics enter WWTPs in sewage and exit in sludge or effluent, but the role that WWTPs play in establishing or modifying microplastic bacterial assemblages is unknown. We analyzed microplastics and associated biofilms in raw sewage, effluent water, and sludge from two WWTPs. Both plants retained >99% of influent microplastics in sludge, and sludge microplastics showed higher bacterial species richness and higher abundance of taxa associated with bioflocculation (e.g. Xanthomonas) than influent microplastics, suggesting that colonization of microplastics within the WWTP may play a role in retention. Microplastics in WWTP effluent included significantly lower abundances of some potentially pathogenic bacterial taxa (e.g. Campylobacteraceae) compared to influent microplastics; however, other potentially pathogenic taxa (e.g. Acinetobacter) remained abundant on effluent microplastics, and several taxa linked to plastic breakdown (e.g. Klebsiella, Pseudomonas, and Sphingomonas) were significantly more abundant on effluent compared to influent microplastics. These results indicate that diverse bacterial assemblages colonize microplastics within sewage and that WWTPs can play a significant role in modifying the microplastic-associated assemblages, which may affect the fate of microplastics within the WWTPs and the environment.
Highlights
Microplastic particles are contaminants found in aquatic habitats throughout the world, including marine [1,2,3,4] and freshwater ecosystems [5,6,7,8,9]
There was no significant effect of plant on microplastic concentrations (p = 0.204) but there was a significant effect of sample type (p
Microplastic concentrations in untreated sewage ranged from 800–2,000 particles/m3, which is comparable to published data which ranged from 1,000 to > 50,000 particles/m3 [24,25,26]
Summary
Microplastic particles are contaminants found in aquatic habitats throughout the world, including marine [1,2,3,4] and freshwater ecosystems [5,6,7,8,9]. Consumer products, including personal care products (e.g., soaps, lotions, and cleansers that contain microplastic abrasives) and synthetic textiles (fabrics composed of polymers such as acrylic and polyester), are sources of microplastics to the environment [21,22,23]. Wastewater treatment alters microbial colonization of microplastics domestic wastewater (sewage) through normal use of these products (e.g. washing with soaps and laundering of textiles) and can enter the environment directly if untreated sewage is released through combined sewer overflows or leaking sewage infrastructure. WWTPs are point sources of microplastics to aquatic environments [6, 8, 30, 31]
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