Per- and polyfluoroalkyl substances (PFAS) have been mass produced for decades in consumer products like frying pans, water-resistant clothing, food packaging and cosmetics. They have also been used in a range of industrial applications, including firefighting foam, metal coatings and mechanical lubricants. The ubiquity of these chemicals in groundwater, along with the strength of their unique covalent carbon-fluoride bond, has raised a critical question: how can we remediate the contaminated groundwater at hundreds of military, industrial, municipal and other sites across the country?
While previous research has demonstrated the potential to destroy selected PFAS in laboratory-based settings, a new study led by researchers from Brown University, the University of Minnesota, Jacobs Engineering, Arq Inc. and the U.S. Navy demonstrates a potential solution to the challenge of mitigating PFAS in real-world situations.
Specifically, researchers wanted to see whether a specially-engineered, ultra-fine carbon material called colloidal carbon product (CCP) could be injected underground to trap PFAS in groundwater. They tested this using a method called "push-pull" testing, which involves first pushing the carbon into the soil to create an underground filter and then pulling water back out to see if PFAS levels dropped after passing through the filter.
Researchers tested this approach both in a small lab model filled with soil from the site, then in a real-world test at a Navy training area where PFAS levels were extremely high. By comparing PFAS levels before and after CCP was injected, the researchers could tell how well the carbon trapped the chemicals and whether this simple, noninvasive method could work as a practical cleanup option.
The paper, published in The Journal of Hazardous Materials, found:
- PFAS concentrations dropped by up to four orders of magnitude in the field test, from more than 50,000 ng/L to below detection limits 10 months after injection.
- The treatment effectively removed both long-chain and short-chain PFAS, an important advancement because short-chain PFAS are typically more difficult to capture.
- A cost analysis found that long-term operating costs of CCP treatment would be less than half those of other PFAS-removal methods, making it a cost-effective alternative for sites requiring decades of remediation.
"This study shows that we can create an effective treatment zone underground that dramatically reduces PFAS levels with far lower long-term costs," said Matt Simcik, a professor in the School of Public Health and co-author. "The effectiveness of this method, combined with the fact that the system requires very little ongoing maintenance, makes this a promising option for real-world cleanup efforts. For communities facing PFAS contamination, this represents a major step forward toward practical, sustainable technologies that can protect drinking water and reduce long-term exposure risks."
"The project shows the importance of partnerships between practitioners, government and academia," said William Arnold, a professor in the College of Science and Engineering. "The expertise, experience and insight of the individuals that made up the team was needed for this lab-to-field project to succeed."
Additional research is needed to fully understand and optimize this cleanup method. The team recommends studying how long the underground carbon treatment zone can keep capturing PFAS, testing the approach in different soil and groundwater conditions, conducting larger and longer-term field trials and exploring whether CCP could be combined with technologies that actually destroy PFAS.
This work was conducted with support from the Navy Environmental Sustainability Development to Integration Program.
About the School of Public Health
The University of Minnesota School of Public Health improves the health and wellbeing of populations and communities around the world by bringing innovative research, learning, and concrete actions to today's biggest health challenges. We prepare some of the most influential leaders in the field, and partner with health departments, communities, and policymakers to advance health equity for all. Learn more at sph.umn.edu.
About the College of Science and Engineering
The University of Minnesota College of Science and Engineering brings together the University's programs in engineering, physical sciences, mathematics and computer science into one college. The college is ranked among the top academic programs in the country and includes 12 academic departments offering a wide range of degree programs at the baccalaureate, master's, and doctoral levels. Learn more at cse.umn.edu.
