Dissection of Denitrification Pathways and Synergistic Degradation Mechanisms of Functional Microbial Communities under per- and polyfluoroalkyl substances (PFAS) Exposure

This study investigated the effects of PFAS on nitrogen efficiency and the dynamics of microbial communities during wastewater treatment using a sequencing batch biofilm reactor.Synthetic wastewater containing 100 ug/L of emerging contaminants - hexafluoropropylene oxide dimer acid (HFPO-DA) and short-chain PFAS (PFHxA) - was compared with a control group.The results showed that the removal efficiencies of ammonium nitrogen, chemical oxygen demand, and nitrate nitrogen decreased by 28%, 10%, and 1%, respectively, under PFAS exposure. PICRUSt2-predicted gene abundances revealed that the introduction of PFAS promoted nitrification, inhibited ammonia assimilation, while denitrification remained relatively stable. The stress-induced secretion of extracellular polymeric substances indicated a high potential of microbial communities to tolerate PFAS toxicity. Microbial degradation contributed to the removal of 13.8% of PFHxA and 14.9% of GenX. Notably, the degradation intermediates, including PFPeA, PFBA, PFPrA, and TFA, were detected, providing insight into the potential degradation pathways of both GenX and PFHxA.