Stimulation of Acidimicrobium sp. Strain A6 Biodegradation of PFOS in AFFF-Impacted Sediment Columns Using PAA-Coated...

PFAS biodegradation at aqueous film-forming foam (AFFF)-impacted sites may be achieved by leveraging the native biogeochemical properties of the soil. Previous studies have shown that Acidimicrobium sp. strain A6 (A6), an ammonium-oxidizing iron reducer capable of Feammox, can be biostimulated to degrade PFOA and PFOS in sediment slurries under controlled laboratory incubations. However, implementing this biostimulation in the field requires distributing Fe-(III) throughout the sediment. To do so, we lowered the zeta potential of goethite by coating it with polyacrylic acid (PAA) and conducted column experiments under different iron levels across three experimental setups: AFFF-contaminated sediments, ¹²C₈-PFOS-spiked AFFF-contaminated sediments, and ¹³C₈-PFOS-spiked AFFF-contaminated sediments. Results show that PAA-coated goethite treatment decreased PFOS mobilization and enhanced A6 activity, as demonstrated by increased Feammox activity and increased A6 counts. This biostimulation promoted PFOS degradation, as evidenced by the production of F^- and shorter carbon-chain intermediates. Greater stimulation was observed in soils with high initial Fe-(III) content, indicating the importance of initial soil geochemical conditions for A6 activity. This stimulation of A6 in natural soils via the addition of PAA-coated goethite is highly promising for environmental remediation of PFAS-contaminated sediments and warrants further optimization and testing under field-relevant conditions.