Occurrence and fate of perfluorinated acids in two wastewater treatment plants in Shanghai, China

Perfluorinated acids (PFAs) have drawn much attention due to their environmental persistence, ubiquitous existence, and bioaccumulation potential. The discharge of wastewater effluent from municipal wastewater treatment plants (WWTPs) is a significant source of PFAs to the environment. In this study, wastewater and sludge samples were collected from two WWTPs in Shanghai, China, to investigate the contamination level and fate of PFAs in different stages of processing. The total concentrations of PFAs (aPFAs) in influent from plants A and B were 2,452 and 292 ng L-1, respectively. Perfluoropentanoic acid (1,520 +/- 80 ng L-1 in plant A and 89.2 +/- 12.1 ng L-1 in plant B) was the predominant PFA in influent waters, followed by perfluorooctanoic acid. The concentration of aPFAs ranged from 75.0 to 126.0 ng g(-1) dry weight in sludge samples from plant B, with perfluorooctanesulfonic acid as the predominant contaminant. The concentrations and fate of PFAs in different WWTPs vary. The aPFAs entering plant A decreased significantly in the final effluent of activated sludge process, while that in plant B increased significantly in the final effluent of sequencing batch reactor system. The concentration changes could be due to the sorption onto sludge, or the degradation of PFAs precursors.