Impact of perfluorooctanoic acid on treatment wastewater by a tandem AnSBR-ASBR system: Performance, microbial community and metabolism pathway

The interaction of perfluorooctanoic acid (PFOA) with anaerobic and aerobic microorganisms was investigated to explore the effect of PFOA on microbial community evolution, carbon metabolism and nitrogen metabolism, and to a provide reference for treatment of wastewater containing PFOA. Compared with phase I (PFOA 0 mg L-1), the average COD removal rate of the anaerobic sequencing batch reactor (AnSBR) in phase II, III and IV (5-20 mg L-1) decreased by 8.85%, and that of the aerobic sequencing batch reactor (ASBR) decreased by 8.31%. However, PFOA had little effect on ammonia nitrogen (NH4+-N) removal at the preset concentrations and the average removal rate of NH4+-N in the system was 97.90 & PLUSMN; 0.59%. The average removal of PFOA in the AnSBR and ASBR decreased from 78.30% and 86.36% (phase I), to 18.77% and 19.25% (phase IV), respectively, indicating that the removal of PFOA was mainly dependent on the adsorption of microorganisms in the initial the experiment. 3D excitation-emission matrix results showed that PFOA affected the functional groups of extra cellular polymeric substances, especially the red shift of fulvic acids along the Em axis. Meanwhile, high concentration PFOA could reduce the activities of acetate kinase and coenzyme F420 in the sludge, thereby affecting the metabolism of carbon and methane by microorganisms. When the concentration of PFOA was 20 mg L-1, the abundances of hydrogenotrophic methanogens such as Methanospirillum (AnSBR phase I-IV: 24.07%-27.43%) and Methanobacterium (AnSBR phase I-IV: 15.06%-21.27%) exceeded that of methylotrophic methanogens, indicating that the existence of PFOA changed the methane metabolism pathway.