Superfund Research Program
Enhancing transport and delivery of ferrihydrite nanoparticles via polymer encapsulation in PFAS-contaminated sediments to simulate PFAS defluorination by Acidimicrobium sp. Strain A6
Per- and polyfluoroalkyl substances (PFAS) are ubiquitous in the environment and highly stable. They are present in many consumer products and over 4,000 different PFAS have been synthesized. Among the most common and of most concern are perfluorooctanoic acid (PFOA) and perfluoro octane sulfonate (PFOS). The EPA reports that these compounds can cause reproductive and developmental defects, liver and kidney damage, and immunological effects in laboratory animals, and that they may cause tumors in animal studies.
Due to the strong carbon-fluorine bond, no defluorination followed by mineralization of perfluorinated compounds has been reported so far, except PFAS defluorination by the recently discovered and isolated Feammox bacterium Acidimicrobium sp. Strain A6 (A6). A6 oxidizes ammonium (NH4+) while reducing ferric iron (Fe(III)), and it can during this process also transfer electrons to PFAS and defluorinate them. Bioremediation and biostimulation usually require achieving proper biogeochemical conditions via the supply of appropriate electron donors/acceptors, redox potential manipulation, and bioaugmentation if the required organism is not present. A6 is common in iron-rich acidic soils, indicating that biostimulation could be an appropriate technology in many cases to use this organism for PFAS bioremediation schemes. Under electron donor/acceptor limiting conditions, it is easy to supply NH4+ to an aquifer, while it is challenging to supply and spatially distribute solid-phase Fe(III), requiring novel methods to enhance the transport of Fe(III) phases.
The researchers hypothesize that polymer encapsulated nano-ferrihydrite can be delivered throughout a porous medium to stimulate the activity of A6 and its defluorination of PFAS. Hence, the aims of this project include:
- Develop polymer-encapsulated nano-ferrihydrite particles that have increased transport properties in a porous medium.
- Ascertain that the polymer-encapsulated nano-ferrihydrite is bioavailable and enhances PFAS defluorination by A6.
- Determine via soil column experiments how to supply the polymer-encapsulated nano-ferrihydrite to enhance the A6 activity and its defluorination of PFAS.
The outcome of this project will result in the first approach to design and operate a bioremediation scheme to defluorinate PFAS, which are of increasing health concern and for which drinking water is the main exposure for humans. This will be achieved by combining techniques and experimental methods from material science, microbiology, and hydrology/environmental engineering. The project will provide new knowledge on how to supply a Fe(III) source, which also has other remediation applications. Additionally, it will provide new insights on how to stimulate A6 for the bioremediation of PFAS and other pollutants and show how to integrate these findings for an effective PFAS bioremediation scheme that is able to operate for extended time periods to improve water quality.