Performance and bacterial community profiles of sequencing batch reactors during long-term exposure to polyethylene terephthalate and polyethylene microplastics.

Microplastics (MPs) are ubiquitous in wastewater treatment plants (WWTPs), but much remains to be learned about their roles in WWTPs. Herein, polyethylene terephthalate (PET) and polyethylene (PE) particles were added into sequencing batch reactors (SBRs), and the sole impacts and co-impacts of MPs with other pollutants (phenol and Cu) on wastewater treatment processes were evaluated. Results indicated that MPs did not significantly affect SBR performance, either alone or co-occurrence with phenol, but the co-exposure to MPs and Cu severely suppressed COD removal efficiency by 37.02%-64.70%. The functional groups of activated sludge had no changes after receiving MPs, but the MPs-Cu co-exposure could greatly promote the secretion of extracellular polymeric substances. Furthermore, MPs had no negative impacts on diversity, richness and structure of bacterial communities, and PET and PE showed different preferences for enrichment of bacterial populations. Moreover, the MPs-Cu co-exposure obviously reduced the overall abundances of Cu-related genes in SBRs.