Topic Area: 5c. Emerging Contaminants: Detection, Degradation, Fate and Transport

Formatted Title:

Anaerobic Biodegradation of PFAS by a Dehalogenating Culture: Implications for Subsurface Fate and Bioremediation

Background/Objectives:

Per- and polyfluoroalkyl substances (PFAS) are widespread contaminants of emerging concern owing to their use in aqueous film-forming foams (AFFF) and a multitude of consumer and industrial products and applications. Perfluorooctane sulfonate (PFOS), a major component of legacy AFFF produced by electrochemical fluorination, is one of the most commonly detected PFAS in soil and groundwater. PFOS and other perfluoroalkyl acids (PFAAs) can also be produced from abiotic and biotic transformation of polyfluoroalkyl substances or their precursors, and are commonly believed to be recalcitrant, terminal end products. Understanding both PFAA and precursor fate is critical for site characterization and developing in situ remediation strategies. We conducted laboratory experiments to determine if the mixed anaerobic culture WBC-2, originally enriched and applied to dehalogenate chlorinated solvents, could be used to degrade PFOS through similar reductive dehalogenation pathways. Additional experiments with soil and sediment containing PFAAs and precursors were then used to evaluate biodegradation of a range of PFAS.

Approach/Activities:

The first experiment consisted of a set of anaerobic microcosms that were prepared with soil from a military installation and simulated groundwater. Target PFAS concentrations were low in the site soil, and the microcosms were amended with PFOS (100 micrograms per liter). Replicate treatments were prepared with and without bioaugmentation with the WBC-2 culture and with and without addition of chlorinated volatile organic compounds (cVOCs) (1,000 and 100 micrograms per liter of 1,1,2,2-tetrachloroethane and trichloroethylene, respectively) that the culture is able to completely dechlorinate. Additional microcosm experiments were then performed with soil or sediment from sites containing a mix of PFAS at relatively high concentrations. In an anaerobic chamber, homogenized soil was mixed with simulated or site groundwater with lactate added as a carbon donor. Killed controls and deionized water controls were also prepared. All treatments were prepared in duplicate or triplicate for sacrificial sampling at each time point. Microcosm water and solids were analyzed for targeted PFAS and total oxidizable precursors (TOP assay) to obtain total mass of PFAS over time. Microbial community compositions, dissolved organic carbon, anions, and redox constituents were also analyzed.

Zachary Hopkins

Affiliation

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Anaerobic Biodegradation of PFAS by a Dehalogenating Culture: Implications for Subsurface Fate and Bioremediation