Biodegradation mechanism of perfluorooctane sulfonic acid (PFOS) in domestic sewage: Specific methanogenic activity, molecular biology, and ecotoxicological aspects

Among the perfluorinated compounds (PFCs), perfluorooctane sulfonic acid (PFOS) is one of the most used ones worldwide, specially in the textile industry as a surfactant. In addition, this contaminant is present in several products, such as: fire extinguisher foams, insecticides formulations, electronic devices, and kitchen products. PFOS is an endocrine disruptor, undergoes bioaccumulation, resists to biological degradation, and has been detected in human blood, animals, dusts, sediments, surface waters, and groundwater as well. Therefore, this research aimed at assessing the degradation of PFOS (100 μg L−1) in anaerobic conditions using simulated domestic sewage as co-substrate. After 10 days, at pH 6 and 35 °C, a 24 % PFOS degradation was achieved. In this period of time, inhibition of specific methanogenic activity (SMA) and changes to the microbial consortium (Archaea and Bacteria Domains) were not observed. The biodegradation products (BPs) were identified by high performance liquid chromatography coupled to high resolution mass spectrometry (HPLC-MS). One of them is reported here for the first time: C4F9CHO (2,2,3,3,4,4,5,5,5-nonafluoropentanal). BPs acute and chronic ecotoxicities for three aquatic organisms (fishes, daphnids, and green algae) and lipophilicity (log D, pH 7.4) were estimated using the ECOSAR 1.11 and Chemicalize software, respectively. Taken as a whole, they presented increased lipophilicities and ecotoxicities compared to PFOS. The present study showed, for the first time, that PFOS degradation is possible by a biological process in anaerobic conditions (although low efficiencies were achieved). Three possible degradation mechanisms were proposed.