Fate of per- and polyfluoroalkyl substances (PFAS) and microbial communities in wastewater treatment: Disinfection-driven changes in microbial dynamics and PFAS profiles

Municipal wastewater treatment plants (MWWTPs) are both sinks and sources of per- and polyfluoroalkyl substances (PFAS) due to limited removal efficiency in current treatment systems. However, the role of treatment processes, especially disinfection, in altering PFAS and microbial communities remains underexplored. In this study, we investigated the occurrence of 17 PFAS in two MWWTPs in Northwest China and characterized microbial communities through metagenomic sequencing. Results showed that total PFAS concentrations increased from 56.8 to 60.3 ng/L in MWWTP_A and from 5.1 to 19.1 ng/L in MWWTP_B, indicating ineffective removal. Perfluoropentanoic acid (PFPeA) and perfluorononanoic acid (PFNA) dominated the influent, accounting for 86.6% and 33.3% in MWWTP_A and MWWTP_B, respectively. In contrast, perfluorooctanesulfonic acid (PFOS, 46.8-52.4%) and perfluorooctanoic acid (PFOA, 5.1-8.9%) concentrations increased markedly in the effluent, becoming the predominant PFAS. Meanwhile, disinfection also altered microbial diversity and homogenized community structures between the two MWWTPs. Further analysis revealed strong associations (p < 0.01) between elevated PFAS levels and specific microbial taxa, including Actinomycetia and Thermoprotei, alongside increased relative abundance of genes annotated as haloacid dehalogenases, monooxygenases, and cytochrome P450. These associations may reflect potential influences on PFAS precursor dynamics. Overall, these findings highlight the importance of considering both chemical and microbial shifts when evaluating PFAS behavior during wastewater treatment.