Perfluorooctanoic acid (PFOA), one of the most typical representatives of perfluoroalkyl surfactants (PASs), has relatively high detection rate and level of pollution, and the accumulation of PFOA in the environment has been a serious threat to human health and security of the whole ecological environment. Therefore, studies on anaerobic biodegradability of PFOA are very important for elucidation of its environmental fate. This study used anaerobic sludge from municipal sewage treatment plant (WWTP) and 5.0 mg·L-1 vitamin B12 (VB12) as catalysts for the degradation of PFOA in the anaerobic environment. The anaerobic biodegradability of PFOA was examined by liquid chromatography tandem mass spectrometry (LC-MS/MS) and ion chromatography while some indictors, such as molar recoveries of PFOA as well as concentrations of fluoride, acetate, 2H-PFOA (F(CF2)6CHFCOOH), and shorter chain (<C8) perfluorocarboxylates (PFCAs) etc., were selected according to the reductive degradation results reported by predecessors. The results indicated that the molar recoveries of PFOA significantly decreased from 101%±5% at the initial incubation (3 d) to 85.6%±3.9% at the end of incubation (250 d), while fluoride concentrations significantly increased from 0.59 mg·L-1±0.02 mg·L-1 at the initial incubation (3 d) to 0.63 mg·L-1±0.02 mg·L-1 at the end of incubation (250 d) in biodegradation samples. Meanwhile, certain amounts of acetate, 2H-PFOA, and short-chain PFCAs, the products of reductive degradation of PFOA reported by precursors, were detected in biodegradation samples. However, there was no significant difference between these indicators in biodegradation samples and their corresponding controls. Therefore, no evidences were found to certify the anaerobic biodegradability of PFOA under the conditions described in present study, though the microorganisms were able to obtain enough energy for growth from reductive defluorination of PFOA in the thermodynamic aspects.
Keywords: anaerobic sludge; biodegradability; degradation products; perfluorooctanoic acid; reductive degradation.