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Response mechanisms of enhanced biological phosphorus removal systems to microplastics stress
Summary
Tiny plastic particles found in wastewater treatment plants actually help remove phosphorus (a pollutant that causes algae blooms) more effectively, but they make the plants worse at removing nitrogen. More concerning, the study found that harmful bacteria and antibiotic-resistant genes tend to stick to the surface of these microplastics, suggesting they could act as rafts that carry drug-resistant germs through our water systems and potentially back into the environment we live in.
Enhanced biological phosphorus removal (EBPR) systems play a vital role in wastewater treatment plants (WWTPs) for controlling phosphorus discharge into urban water bodies and mitigating eutrophication risks. The accumulation of microplastics (MPs) in WWTPs has raised concerns about their potential impact on EBPR performance. This study investigated the effects of polyethylene terephthalate (PET) and polybutylene adipate terephthalate (PBAT) MPs on EBPR functionality and associated microbial communities. The results demonstrate that MPs enhance EBPR stability and significantly improve phosphorus removal efficiency while simultaneously inhibiting nitrogen removal. Microbial community analysis and functional gene profiling revealed that MP-exposed groups exhibited higher ratios of polyphosphate accumulating organisms (PAOs) to glycogen accumulating organisms (GAOs) and reduced denitrification gene abundance, which collectively explain the observed enhancement in EBPR stability and decline in nitrogen removal. Furthermore, Candidatus Accumulibacter vicinus was identified as the dominant lineage in the EBPR system, challenging the conventional focus on Ca. Accumulibacter phosphatis. Notably, pathogens were enriched in free-living activated sludge (AS), whereas antibiotic resistance genes (ARGs) accumulated on microplastic surfaces. This study elucidates the response mechanisms and potential ecological risks of EBPR systems under microplastic stress.