Acidimicrobium sp. A6 (A6), which oxidizes ammonium while reducing iron - a process called Feammox - is capable of defluorinating per- and polyfluoroalkyl substances (PFAS) during this process, including the more recalcitrant perfluoroalkyl acids such as perfluorooctanoic acid, perfluorooctane sulfonic acid, and perfluorohexanesulfonic acid. A6 has been shown to exist in many acidic, iron-rich soils, including at several sites with soils impacted be aqueous film-forming foam (AFFF), although usually with low activity and numbers. The overall objective of this proof-of-concept project is to determine the conditions required to biostimulate A6 at selected AFFF-impacted sites for the purpose of biologically defluorinating AFFF-based PFAS. The project team will also determine conditions necessary to grow A6 at large scale for possible bioaugmentation applications.

This research will provide insights into how to stimulate A6 under field-relevant conditions to achieve PFAS defluorination, and how the activity of A6 might be affected as the general microbial community shifts in response to such stimulation. In the first task, the project team will conduct laboratory batch experiments with AFFF-impacted sediments from sites that are acidic and iron-rich with A6 enrichment cultures. These experiments will evaluate the effect of temperature, organic carbon supply, iron and ammonium dosing, and pH adjustment on A6 growth and activity. The second task will involve column experiments with site sediments to validate the data from the batch studies. 

Bioremediation can be a cost-effective method to remediate sites and has been successfully used for many different chemicals of concern such as chlorinated organics and hydrocarbons. This specific effort will be limited to sediments that are acidic and iron-rich, which are common throughout the Northern Atlantic Coastal Plain. If successful, the results of this project will ultimately bolster operational capabilities and warfighter preparedness of by mitigating the impacts of these chemicals. (Anticipated Project Completion - 2027)