Filtration method removes harmful ‘permanent chemicals’ from drinking water
A team of Johns Hopkins engineers have discovered a method to filter out a toxic industrial “forever chemical” commonly found in the country’s drinking water.
Called permanent chemicals because they last for thousands of years, per- and polyfluoroalkyl substances, commonly known as PFASs, are a group of synthetic organic contaminants used in many industrial processes and consumer products, including non-stick coatings for cookware, food wrapping, waterproof clothing, and interior textiles. When these products are improperly used, discarded or dumped, PFAS enters water system. Once there, they are extremely difficult to handle because of the unique chemical properties imparted by carbon-fluorine bonds – one of the strongest in chemistry.
The exact amount of PFAS in the country’s drinking water is unknown, but experts say it ranges from common to nearly universal.
Long-term, low-concentration exposure to PFAS may interfere with Immune System, interfere with hormones, and reduce the effectiveness of vaccines. It can also cause low birth weight and high cholesterol. People exposed to high doses of PFAS at work or because they live near a landfill are at increased risk of kidney cancer, liver damage, testicular cancer, and thyroid disease.
The team compared two of the most promising separation media – granular activated carbon and anion exchange resin – to remove PFAS. They systematically evaluated how well each of these resins performed against different types of PFAS in pilot municipal water treatment plants for 15 months, concluding that the resins were effective. more effective in removing most of the tested PFASs.
“You can think of treatments as large-scale versions of the filters that people use at home to filter their own drinking water. The water is fed continuously from above and we measure the time interval ahead of time. when PFAS was first discovered, says Steven Chow, a research associate in the Department of Engineering and Environmental Health at Johns Hopkins and first author of the study. Water Research.
The researchers say that the study is promising because it provides one of the most in-depth laboratory analyzes of a large-scale designed PFAS treatment system to date. Usually, laboratory research has limitations in terms of practical applicability because it is conducted on a small scale for a limited time. And many large-scale designed systems run by drinking Water utility Engineers say there is no luxury in in-depth analysis of their systems beyond regulatory requirements.
“Our collaboration between academia, industry and city partners allows the team to answer fundamental questions about how these separation vehicles work while demonstrating their effectiveness under real-world conditions.
Although the technical prospects for filtering PFAS from drinking water are promising, the researchers warn that there are caveats. Building and operating such systems can cost millions of dollars, in addition to the costs of existing water treatment operations. Once PFAS is removed, the contaminants and filters used to collect them must be properly handled and disposed of, and because PFAS molecules are so powerful, a significant amount of energy is required. amazing to destroy them.
Chow says that when it comes to PFAS, prevention can be the best cure.
“PFAS is a generational environmental problem that will take decades to manage and may never be fully resolved,” he said. “The key is forward-thinking policies that reduce the total amount of PFAS released into the environment and prevent the unfortunate replacement of known PFAS with chemicals that are unknown or potentially worse. .”
The research team also includes Kellogg J. Schwab, professor, and Carsten Prasse, assistant professor, both in the Department of Engineering and Environmental Health. The study was carried out in collaboration with the Canada-based environmental engineering company Stantec.
Steven J. Chow et al., Comparative investigation of PFAS adsorption onto activated carbon and anion exchange resins during long-term operation of a pilot treatment plant, Water Research (In 2022). DOI: 10.1016 / j.watres.2022.119198
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Johns Hopkins University
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