Advances in Perfluoroalkyl Chemicals (PFCs) Characterization and Remediation
The U.S. Navy developed aqueous film-forming foam (AFFF), a synthetic foam to extinguish flammable liquid fuel fires, in the mid 60s. Since then, it has been used effectively in military and civilian operations. However, AFFF contains potentially harmful polyfluoroalkyl substances (PFASs) and studies suggest that PFCs are resistant to biodegradation, photo-oxidation, direct photolysis, and hydrolysis. Aggravating this issue, PFCs are mobile in soil and leach into groundwater. Therefore the Environmental Protection Agency (EPA) recently issued a Provisional Health Advisory value of 0.4 μg/L for perfluorooctanoic acid (PFOA) and 0.2 μg/L for perfluorooctane sulfonate (PFOS) in drinking water.
Since FY11, SERDP and ESTCP have sponsored a number of projects seeking to develop a better understanding of occurrence, fate and transport, potential remedial treatment, and toxicological effects.
Collectively, in response to an FY11 solicitation, results of fate and transport projects give us a better understanding of the behavior of PFCs in contaminated groundwater and the fate and transformation processes of these chemicals in the presence of other contaminants of concern commonly found at military installations. As part of SERDP project ER-2126, researchers at the Colorado School of Mines determined that in situ chemical oxidation (ISCO), as commonly applied to groundwater, is unlikely to degrade perfluoroalkyl acids (PFAAs), but will strongly impact their transport in the subsurface. In addition, research showed that, PFAAs recalcitrance could have adverse impacts on microbial processes used for bioremediation of co-mingled chlorinated solvents such as trichloroethene (TCE). Under project ER-2128, researchers at Oregon State University have identified the PFASs in the different AFFF formulations, determined the potential for biotransformation, and characterized sorption of PFASs to soils and sediments under conditions representative of military sites.
A follow on solicitation was released in FY14 to develop in situ remedial alternatives for groundwater contaminated with PFASs. Projects were selected to evaluate bioaugmentation ( ER-2422), ISCO ( ER-2423), electrocatalytic technologies ( ER 2424), a PFC-coagulant that retains the PFC sorbed for future destruction ( ER-2425) and in situ chemical reductive defluorination ( ER-2426). Although experiments are on going, interim results are encouraging.
In FY16, a solicitation was released to study ecotoxicity of PFASs. Projects selected will investigate ecotoxicity towards birds, fish, amphibians, reptiles, and invertebrates. These projects will begin shortly and will yield needed toxicological information within the next 3 to 4 years. Additional information on these projects can be found at the FY16 new start project description page.
Two projects have recently been selected under ESTCP. Dr. Jennifer Field from Oregon State University will be leading a team to develop online tools and documents intended to expedite the transfer of the knowledge base of both the types of PFASs that occur at military sites as well as how they can be reliably measured in environmental media. This project was initiated in 2015 and technology transfer products will become available in mid to late 2016 through 2017.
Dr. John Kornuc from NAVFAX EXWC is leading a team under project ER-201633 that will characterize the total footprint of PFAS contamination at field sites by total fluorine and individual PFAS analysis to enable fingerprinting of AFFF-based sources as compared to non-AFFF sources. In addition, the team will determine the nature and extent of PFAS source areas at Navy and other DoD sites as well as identify factors such as soil characteristics (organic carbon content and ion exchange capacity) and groundwater redox potential that affect the transport of PFASs that vary in carbon chain length and head group character. This project was recently initiated with final results due in 2018.