Per‑ and polyfluoroalkyl substances (PFAS) are widely used chemicals known for extreme persistence. In fact, PFAS resist both biological and chemical degradation due to their strong carbon-fluorine bonds, which is why the public calls them “forever chemicals”. At ETEC, we are excited whenever we hear of promising breakthroughs in PFAS degradation via bioremediation, but we have not yet found any to be practical in the field. The slow progress towards a bioremediation solution is not surprising. Unique PFAS properties and challenges include:
- Novel chemicals: C-F bonds are not common in nature, leading to little microbial adaptation to utilize PFAS as a food source or as an electron acceptor.
- Widespread contamination: Used in everything from firefighting foam to nonstick cookware, PFAS have spread into groundwater, soil, and even dust across the globe.
- Toxic byproducts: When PFAS are defluorinated, the daughter products may be harmful.
- Regulatory goals: The regulatory goals for these compounds are either non-existent or prohibitively low, either of which causes confusion and difficulty with remediation.
Lab Studies vs. Field Application
In controlled lab studies, researchers have found a few microbes that can defluorinate PFAS. One study showed bacteria shortening PFOA/PFOS chains and releasing fluoride in a flask. These experiments prove it is possible to biodegrade PFAS under ideal conditions (special cultures, high PFAS concentrations, no other energy source available, etc.) In field conditions (heterogeneous soils, low PFAS levels, other available food and energy sources, etc.), the same defluorination process rarely happens or is orders of magnitude less productive. Lab success stories are encouraging, but reliable bioremediation methods in the field remain elusive.
Capture and Containment
The focus now has been on capturing and sequestering PFAS to prevent off-site contamination. Most are using fractionation, granular activated carbon (GAC) filters, ion exchange resins, high-pressure membranes, or pump-and-treat systems that essentially trap PFAS in filters or media. Another viable option for capturing and containing PFAS is using recirculation (such as ETEC’s systems) along with one of these pretreatment options. This approach offers many advantages such as customization of the system and hydraulic control in specific sub-surface areas.
This is a practical interim step as it stops PFAS from leaching deeper into groundwater or reaching sensitive receptors. However, it’s crucial to understand that such methods do not destroy PFAS without a secondary step. As stated by the EPA, “full-scale treatment of PFAS-impacted [media] is currently limited to sequestration technologies that remove or bind PFAS but do not destroy them.” epa.gov
Going Forward
ETEC is continuing to follow studies and conduct our own internal research until bioremediation of PFAS is proven to be successful in the field. We follow the research closely, but we do not yet have a field-validated PFAS biodegradation product or process. When consultants face PFAS-impacted sites, we support by informing them of the practices mentioned previously but we make it clear that there are trade-offs with the various approaches.
In the meantime, we continue advancing our proven bioremediation solutions for petroleum hydrocarbons, chlorinated solvents, and other “treatable contaminants” as usual. Our team can help assess any PFAS site and integrate bioremediation for co-contaminants, while advising on PFAS capture options. Ultimately, we hope future breakthroughs in PFAS bioremediation (possibly guided by those rare lab successes) will lead it to be a standard part of our remediation services. Until then, we emphasize realistic expectations.
By monitoring the science and educating stakeholders about the challenge and current solutions, we help ensure that PFAS-impacted sites are handled responsibly today – even as we anticipate better solutions tomorrow.
Sources: pmc.ncbi.nlm.nih.gov, epa.gov.