Project Summary/Abstract
Per- and polyfluoroalkyl substances (PFAS) are ubiquitous in the environment and highly stable. They
are present in many consumer products and over 4000 different PFAS have been synthesized. Among
the most common and of most concern are perfluorooctanoic acid (PFOA) and perfluoro
octane sulfonate
(PFOS), for which 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 C-F 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/biostimulation usually requires
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. We
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: (1)
develop polymer-encapsulated nano-ferrihydrite particles that have increased transport properties in a
porous medium; (2) ascertain that the polymer-encapsulated nano-ferrihydrite is bioavailable and
enhances PFAS defluorination by A6; and (3) 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, 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 in order to achieve desired final concentration/water quality goals.
