A biotech firm is trialling the removal of PFAS 鈥渇orever chemicals鈥� from soil at a test site in Wisconsin by injecting chemical-eating bacteria and electrocuting the ground.
Perfluoroalkyl and polyfluoroalkyl substances, or PFAS, are a class of thousands of different synthetic chemicals that contain carbon and fluorine atoms linked by strong bonds. The chemicals 鈥� which repel grease and water 鈥� have been in widespread use since the 1940s in everything from firefighting foam at airports to dental floss.
But the same qualities that make PFAS useful stop the chemicals from degrading, so many of them are . They are often called forever chemicals, and have been found in drinking water and in people鈥檚 blood all over the world. like kidney disease, cancer and . In Maine, there are reports of due to PFAS contamination from fertiliser.
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Existing methods to deal with PFAS contamination are expensive and inadequate, says at the University of Minnesota. Contaminated soil or water can be removed and brought to a landfill site, but it can leach out from there. Incineration is another option, although this produces toxic hydrogen fluoride gas. Existing methods are especially impractical for sites with low concentrations of PFAS.听
Microbes could help. At an airport in Wisconsin, a start-up firm called is 10 weeks into a pilot 鈥渂ioremediation鈥� project using a bacterium it found living in the soil there.
By growing litres of bacteria in the lab, then injecting them back into the ground along with an absorbent material, some of the firm鈥檚 injection wells have seen a greater than 99 per cent reduction across all the PFAS chemicals the firm can measure at the site, including PFOS and PFOA, says , president of Fixed Earth. The absorbent material might be helping to concentrate the PFAS for the bacteria, says Repas.
Because the bacteria seem to perform better when oxygen is available, the company is also pulsing electricity through the soil at the injection wells. The electricity splits water molecules, releasing hydrogen and oxygen. The reduction in PFAS contamination at wells without the electrical treatment is around 60 per cent, says Repas.
The identity of the PFAS-eating bacterium, the method for identifying microbes that do this job and the absorbent material injected along with them 鈥� made by a company called ORIN Technologies 鈥� are all proprietary information, says Repas.
He doesn鈥檛 want to publish results until the firms are able to protect that intellectual property, and says more tests are needed 鈥� for instance, to show that the bacteria produce fluorine when degrading the PFAS, indicating they are breaking down the carbon-fluorine bonds. He says fluorine concentrations in real-world sites are too low to detect with standard methods.
Without more data, outside researchers say they can鈥檛 adequately evaluate the bacteria鈥檚 effectiveness, but 鈥渋f it was true as the company claimed, the PFAS problem would soon be solved鈥�, says at the University of California, Riverside. 鈥淚t would be phenomenal.鈥�
In June, the US Environmental Protection Agency tightened standards for safe levels of PFOS and PFOA in drinking water by more than a thousandfold, and to help states address PFAS contamination.
Bioremediation is already used to clean up other recalcitrant contaminants 鈥� for instance, trichloroethylene, or TCE 鈥� but , says Wackett. Carbon-fluorine bonds are relatively rare in nature, so it seemed unlikely that anything would have evolved the ability to break them down. 鈥淚f you look at the structure, it鈥檚 strange to bacteria,鈥� says Men.
But perhaps widespread PFAS contamination has led some bacteria to evolve the ability to metabolise PFAS, says Wackett. Many researchers working on the problem have had that could deal with PFAS, yet Fixed Earth says it has discovered bacteria that can do it 鈥� and even says they are pretty common.
In a test at a in 2021, Fixed Earth identified another bacterium in the soil that reduced some types of PFAS in water samples by an order of magnitude in laboratory tests, says Repas. He also claims to have found other PFAS-eating microbes in the Arctic and the Caribbean. People usually express great scepticism when told that, says Repas.
But some are being won over.听A spokesperson for the Wisconsin Air National Guard, which is funding the project in Wisconsin along with the Dane County Regional Airport, says the 鈥渙verwhelming success鈥� of an initial study using the same method in bins of contaminated water convinced them to support the project, which will be complete at the end of the year.
Wackett doesn鈥檛 think the results are impossible, but says 鈥渢here鈥檚 going to be scepticism until it鈥檚 proven鈥�.
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