0      0

3924884 - Anaerobic biotransformation of PFAS – Insights from batch systems and anaerobic membrane bioreactors

‐ Aug 15, 2023 2:45pm

Per and polyfluoroalkyl substances (PFAS) pose a severe risk to human health and the environment given their widespread use and recalcitrance, making their exposure unavoidable. Conventional aerobic wastewater treatment plants fail to remove PFAS via either biological or physicochemical means. Anaerobic biodegradation of PFAS is thermodynamically feasible and a few recent studies have found bacteria capable of reductive defluorination, implying that other microorganisms capable of a similar metabolism may yet to be discovered with potential use in anaerobic technologies such as anaerobic membrane bioreactors (AnMBRs). AnMBRs combine anaerobic treatment with membrane separation which allows for high solids retention time where slow biotransformation of PFAS may occur. A mass balance approach is needed to evaluate the fate of PFAS in AnMBRs, such as partitioning to biomass and by-product formation from biotransformation products. In this study, respirometry was performed for 100 days using anaerobic digester sludge inoculated with a high concentration of PFAS (10 mg/L and 100 mg/L). Samples were collected periodically to test for methane content, volatile fatty acids (VFAs), fluoride, PFAS concentration, and microbial community structure. Results showed volatile fatty acids depicted a differentiated metabolism for reactors exposed to 100 mg/L PFAS, particularly in the production of butyrate, valerate, and unknown compounds. PFAS concentration decreased for all reactors and showed a fluctuating pattern in sludge concentration indicating an adsorption-desorption behavior likely influenced by the partitioning coefficient. The microbial community analysis showed an increase in Firmicutes and Synergistetes bacterial phyla and enrichment of Methanomassiliicoccus and Methanosphaera archeal genera in 100 mg/L PFAS reactors. Two AnMBR reactors are currently operated with synthetic wastewater spiked with 100 ug/L PFAS to characterize biotransformation products and assess the “removal” efficiencies at various AnMBR conditions. To elucidate degradation pathways and allow for mass balance determination 19F NMR, high resolution LC-MS and F- analysis are being used.