The class of chemicals known as PFASs—per- and polyfluoroalkyl substances—poses a unique threat to public health that our chemical and environmental engineers are working to solve.
These include PFOA, PFOS, and more than 3,000 related chemicals, including the GenX variant known for polluting the Cape Fear River in southeastern North Carolina. Different variants have unique properties—such as repelling water or oil, or protecting against acid—that make them useful for a variety of purposes. Since the 1940s, they have been widely used in consumer products, such as nonstick coatings, food packages, cleaning products, and, notably, firefighting foams.
Unfortunately, PFASs are linked to cancer and disrupt the immune and endocrine systems. And unlike some other compounds, they can persist for decades in the environment. If they get into the water supply, they accumulate in the bodies of plants, animals, and people who consume them. Combined with their widespread use, this is why they remain a serious concern. Chemical companies have voluntarily phased out long-chained PFAS compounds but have replaced them with shorter-chained counterparts that have unknown effects.
PFASs present a risk no matter where they are found, but certain places introduce a more pressing threat. The U.S. Department of Defense owns more than 300 sites around the country where troops being trained to fight fires used countless gallons of PFAS-based firefighting foam over several decades. The chemical remnants of that foam now permeate the water supply near many of these sites.
The Department of Defense’s Strategic Environmental Research and Development Program (SERDP) is looking for a solution. In mid-2018, RTI began working with SERDP to investigate a method of breaking down PFASs.
Breaking Down PFASs In the Lab
Part of the reason PFAS contamination is so persistent is that these molecules contain a carbon-fluorine bond, one of the strongest in chemistry. Methods for removing PFAS from water already exist, but they don’t break apart the PFAS molecule. These methods leave behind a sludge with higher PFAS levels than the original source.
The process we are testing causes PFAS molecules to disintegrate. Our system uses a combination of ultraviolet light and a silicon-carbon and single atom catalyst (SAC) developed by researchers at Yale University. So far, we have demonstrated that the compound breaks down PFOA and PFOS. Drawing on our experience with scaling up promising technologies, we plan to experiment with other PFASs.
Our plans now include testing the method at contaminated sites. The ultimate goal is to create a system that allows users to pump contaminated water from the ground, treat it, and return it to the aquifer.
Once we are able to apply it at a larger scale, our method should make it much easier to achieve water quality targets. This will bring safe water to people near Department of Defense sites more quickly.
Restoring and Protecting Water Quality
A solution for PFAS contamination could have a major impact on human and environmental health. The reality is that most people in the United States already have trace amounts of PFASs in their bloodstream. The full extent of PFAS contamination in the United States is not fully understood or documented, but the Department of Defense is taking crucial steps toward addressing sites where its firefighting foams have potentially contaminated the groundwater.
Besides the hundreds of affected DoD sites, municipal water treatment plants may be interested in a technology to keep PFASs out of their customers’ tap water. Our system could be crucial to righting a longstanding environmental problem, preventing millions of people from being exposed to these harmful chemicals.