Physical and Biological Release of Poly- and Perfluoroalkyl Substances (PFASs) from Municipal Solid Waste in Anaerobic Model Landfill Reactors

Abstract

A wide variety of consumer products that are treated with poly- and perfluoroalkyl substances (PFASs) and related formulations are disposed of in landfills. Landfill leachate has significant concentrations of PFASs and acts as secondary point sources to surface water. This study models how PFASs enter leachate using four laboratory-scale anaerobic bioreactors filled with municipal solid waste (MSW) and operated over 273 days. Duplicate reactors were monitored under live and abiotic conditions to evaluate influences attributable to biological activity. The biologically active reactors simulated the methanogenic conditions that develop in all landfills, producing ∼140 mL CH4/dry g refuse. The average total PFAS leaching measured in live reactors (16.7 nmol/kg dry refuse) was greater than the average for abiotic reactors (2.83 nmol/kg dry refuse), indicating biological processes were primarily responsible for leaching. The low-level leaching in the abiotic reactors was primarily due to PFCAs ≤C8 (2.48 nmol/kg dry refuse). Concentrations of known biodegradation intermediates, including methylperfluorobutane sulfonamide acetic acid and the n:2 and n:3 fluorotelomer carboxylates, increased steadily after the onset of methanogenesis, with the 5:3 fluorotelomer carboxylate becoming the single most concentrated PFAS observed in live reactors (9.53 nmol/kg dry refuse).

Anaerobic biotransformation of N‐methyl perfluorobutanesulfonamido ethanol and N‐ethyl perfluorooctanesulfonamido ethanol

“…Correct identification and monitoring of the actual PFAS constituents present in anaerobic environments such as sediments, groundwater, and leachates are of critical importance for properly assessing remediation efforts and for evaluating ecotoxicological impacts. The identification of MeFBSAA as an end product in anaerobic sludge cultures helps provide some clarity to the presence of MeFBSAA in leachate from anaerobic landfill simulation tests [34,35] and the recent detection of MeFBSAA and PFBSI in river sediments [23]. Similarly, the identification of EtFOSAA and PFOSI from EtFOSE can explain the determination of EtFOSAA as a major PFAS in sediment, soil, and sludge samples [32,33].…”

“…However, some researchers have found that under certain physiological conditions EtFOSE biotransformation is incomplete and exclusively yields N-ethyl perfluorooctanesulfonamido acetate (EtFOSAA) and perfluorooctane sulfinate (PFOSI) and not PFOS [31]. The analogous anticipated MeFBSE biotransformation product N-methyl perfluorobutanesulfonamido acetate (MeFBSAA) was recently identified in leachate from anaerobic landfill simulation tests with municipal solid wastes, and levels appeared to increase over time [34], suggesting that biotransformation of MeFBSE in anaerobic waste may occur. The analogous anticipated MeFBSE biotransformation product N-methyl perfluorobutanesulfonamido acetate (MeFBSAA) was recently identified in leachate from anaerobic landfill simulation tests with municipal solid wastes, and levels appeared to increase over time [34], suggesting that biotransformation of MeFBSE in anaerobic waste may occur.…”

“…More recently, the anaerobic biodegradation of 8:2 FTOH and its short-chain replacement 6:2 FTOH was shown to occur [36]. Interestingly, 6:2 FTCA, 6:2 FTUCA, and 5:3 acid were recently identified in leachates from anaerobic landfill simulation tests [34] and likely formed from anaerobic biotransformation of 6:2 FTOH-based fluoropolymer treatments. However, 8:2 FTCA, 8:2 FTUCA, 7:3 acid, and PFOA are observed in aerobic 8:2 FTOH incubations with sludge [37,38].…”

“…An abundant PFAS in marine sediments and soils contaminated with domestic sludge is N-Ethyl perfluorooctanesulfonamido acetate [32,33], and such environments may exist as low-oxygen conditions. The analogous anticipated MeFBSE biotransformation product N-methyl perfluorobutanesulfonamido acetate (MeFBSAA) was recently identified in leachate from anaerobic landfill simulation tests with municipal solid wastes, and levels appeared to increase over time [34], suggesting that biotransformation of MeFBSE in anaerobic waste may occur. Likewise MeFBSAA also formed in leachate from anaerobic landfill reactors loaded with only carpet and clothing [35], suggesting that MeFBSAA may come from disposed materials previously treated with MeFBSE-based products.…”

“…The 6:2 FTOH biodegrades faster than the 8:2 FTOH, with approximate anaerobic biodegradation half-life times of 37 and 145 d, respectively. Interestingly, 6:2 FTCA, 6:2 FTUCA, and 5:3 acid were recently identified in leachates from anaerobic landfill simulation tests [34] and likely formed from anaerobic biotransformation of 6:2 FTOH-based fluoropolymer treatments. Also, MeFBSAA was identified in those same leachates and possibly derived from MeFBSE-based treatments.…”