PFAS
What are poly and perfluoroalkyl substances?
Poly and perfluoroalkyl substances (PFAS) are characterized as carbon chains that contain multiple fluorine atoms. Typically, these compounds also have an end group, such as a carboxylic acid or sulfonate, that is capable of making them charged under environmental conditions. The surfactant nature of these compounds makes them both repellent to water as well as grease and suitable for a wide array of commercial and industrial applications
This family of compounds are considered “emerging contaminants.” That is, their toxicity to humans and the environment has only been characterized recently and the regulatory framework for their management is still evolving rapidly as new and improved science becomes available. Given the recent attention to these compounds, the methods to remediate them are still in development and there are few widely accepted standards. Fixed Earth’s knowledge of just how many chemicals of this class were used by industry is still evolving, with over 14,000 known and more being discovered. The structure of PFOS is shown above as a key example of a compound in this suite of chemicals. Their toxicity is typically measured in parts per trillion (ppt) as opposed to parts per million (ppm) normally used for other toxic compounds.
Where are they commonly found?
In short: Everywhere. The very strong nature of the carbon-fluorine bonds found in PFAS means they do not readily breakdown in the environment and can persist for decades following their release. This resilience has earned them the moniker “forever chemicals” in the press. These chemicals were, and still are, used in many commercial and industrial applications including common items such as shampoo, pots and pans, paper towel, electronics, plastics, receipts, pesticides, firefighting, and more.
It is estimated that PFAS can be found in the bloodstream of almost every living thing on earth.
It is estimated that 55% of drinking water in the USA contains PFAS.
PFAS may have impacted 20 million acres of farmland.
There are over 58,000 sites in the USA where PFAS contamination is suspected. More are found each day.
Industry is still using PFAS and PFAS-like compounds that are not yet regulated.
How are they currently remediated?
PFAS is notoriously difficult to remediate. The carbon-fluorine bond is one of the strongest known in organic chemistry and can be very difficult to successfully break. PFAS can contain numerous bonds of this type. As a result, most methods currently used to remediate PFAS utilize very high energies such as incineration of contaminated materials, super-critical water oxidation, or electrolysis using exotic electrodes. PFAS is often filtered from water using carbon filters that require frequent changes and destruction once contaminated. Few, if any, commercial technologies exist that can successfully treat impacted soil and water in-situ (in place).
How do you know the microbes are working?
PFAS are considered by the majority of the scientific community to be resistant to, if not impervious, to destruction by biological means. When the team identified their first microbe capable of consuming PFAS as a food source in 2019 Fixed Earth knew the burden of proof to show that destruction of these compounds by bacteria would be high and have worked since to demonstrate this possibility in the lab and field. Fixed Earth has performed the following tests in the lab and maintain a whitepaper providing greater technical details of these tests to demonstrate microbe efficacy:
The microbes utilized are capable of surviving on PFAS as a sole carbon source.
PFAS destruction rates, as measured by EPA 537, exceed 90% under lab conditions in 2-8 weeks.
Polyfluoro and precursors are consumed by the microbes, as measured by Total Oxidizable Precursor (TOPA) and Total Absorbable Fluorine (TAF/TOF).
When microbes are not given the required conditions PFAS degradation is not observed.
Sorptive losses to heat-killed biomass are negligible.
Fluorinated volatile compounds (VOCs) are not formed in measurable quantities.
Lab tests have shown the formation of fluoride by the microbes, indicating carbon-fluorine bond cleavage.
In addition to lab tests, the team has done multiple field pilots of these technologies and included case studies as part of this document. To our knowledge, they are the only commercial entity on Earth using bioremediation of PFAS successfully in the field.
Are the microbes invasive or genetically modified?
No microbes developed or deployed by the team are genetically modified in any way. Fixed Earth typically uses microbes that are derived from the site they are cleaning and are already present in the site in small amounts, making it unlikely that they are invasive.
What happens to the microbes when the job is done?
All of the microbes Fixed Earth deploys utilize oxygen. When they leave the site and remove the oxygen generation system the majority of the microbes will die off or become inactive.
What are the by-products of remediation and are they safe?
When broken down by microbes, polyfluoro compounds will become fluoride ions, carbon dioxide, and more bacterial cells. Fluoride ions, under typical environmental conditions, will quickly react with calcium or magnesium to form inert minerals like fluorite. These compounds are essentially inert and are not considered toxic to people or the environment.
Is this cost effective?
In situ bioremediation has the potential to be significantly cheaper than traditional remediation methods. The exact savings will depend on the specific site. Contact Fixed Earth today to get an estimate for your project.