A novel bacterium, Acidimicrobium Sp. Strain A6 (A6), has been shown to degrade PFAS during the Feammox process, defined as ammonium oxidation (NH₄⁺) coupled to iron (Fe³⁺) reduction under anaerobic conditions. A6 is an autotroph found in acidic, iron-rich environments. Previous experiments report defluorination of PFAS by A6; however, to facilitate mass balances and degradation product tracking, these experiments utilized high PFAS concentrations (> 0.1 ppm) that do not represent environmental levels. To study PFAS degradation at environmentally relevant conditions and environments where A6 is present, sediment and water samples were collected from the Neuse River, NC, which has ideal conditions for A6 growth, namely acidic, high Fe³⁺ and NH₄⁺ levels, and where low PFAS levels have been detected. Incubations with Neuse River water and sediment have been set up to explore the efficacy of A6 biodegradation of PFAS under natural conditions and for sediments amended with NH₄⁺, Fe³⁺, or both. Preliminary PFAS analyses of these incubations show a decrease in PFOA concentrations over time, accompanied by appearance of shorter-chain PFAS compounds. Samples augmented with PFOA also show a clear increase in fluoride concentration. Results show that augmentation of the sediments with NH₄⁺ and Fe³⁺ results in increased PFAS degradation. Analyses also show a correlation between the A6 numbers and PFAS removal. Samples from the Cape Fear River, NC, are also being studied to investigate the effect of pH on A6 biodegradation. The Cape Fear water and sediment are more alkaline than the Neuse River, but the PFAS levels are concerning to the public. A6 numbers in the Cape Fear sediments are much lower than in Neuse sediments, and preliminary results indicate less if any PFAS degradation in these sediments. The effect of lowering the pH in these sediments on the Feammox process and PFAS defluorination is currently being investigated.

Chiara Smorada

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