A novel, Stevens-innovated filter medium made from recycled water treatment by-products may offer protection against harmful and persistent chemicals seeping into the region's and nation's drinking water.
That's the conclusion of new Stevens research published in the Journal of Hazardous Materials Letters.
"This is an important public health challenge," says environmental engineering professor Dibyendu "Dibs" Sarkar, lead investigator for the effort, "and we may have achieved proof-of-concept for a scalable, environmentally friendlier solution."
Removing chemicals that can last 1,000 years
The U.S. Environmental Protection Agency (EPA) recently announced a new effort to more closely monitor perfluoroalkyl and polyfluoroalkyl chemicals, a class of more than 4,000 related manufactured substances collectively known as PFAS.
Those chemicals are created as products or by-products of dry cleaning operations and firefighting foams as well as the industrial manufacture of nonstick cookware, waterproof clothing, carpets, ski wax, paper plates, microwave popcorn bags, furniture and other items.
Because of their unusual structure and strong chemical bonds, PFAS chemicals degrade extremely slowly in the environment.
"Some forms of PFAS are believed to remain in the soil and water for as long as 1,000 years before they fully break down," notes Sarkar. "Even in the human body, which is better at breaking them down, they seem to remain for as long as eight years."
That's bad news, because a growing body of research suggests these chemicals appear to raise our cancer risk — as well as the potential for liver damage, kidney damage and infertility — when they're ingested in even very small quantities.
Northern New Jersey contains perhaps the highest concentration of PFAS-contaminated facilities and water supplies in the nation, according to the nonprofit Environmental Working Group.
"This makes our challenge even more urgent," says Sarkar. "We are right here in the heart of the problem."
Current technologies for removing and reducing PFAS from water supplies at large scales are mostly variations of either reverse-osmosis filtration technology or chemical adsorption using activated carbon. Both methods have drawbacks, however, and neither is particularly sustainable nor cost-effective.
That’s why Sarkar, with postdoctoral fellow Zhiming Zhang and researchers at Montclair State University and Michigan Technological University, has devised a novel filter material made from residuals produced incidentally by municipal treatment plants as they process and disinfect wastewater with aluminum-based salts.
"This is 'green' material, in a sense, because it would have been discarded anyway," notes Sarkar. "It is not toxic. It seems to adsorb the PFAS very effectively in our experiments, removing them from the water stream in a non-harmful and cost-effective way."
Indeed, in tests conducted in Sarkar’s lab, the filter material proved highly effective as a filter under certain conditions. When used to filter water with a pH of 3.0, for instance, more than 97% of PFOAs and more than 99% of PFOS (two sub-classes of PFAS chemicals) were adsorbed by the material. The materials also works relatively quickly, within about two hours of first contacting water — similar to powdered activated carbon.
Patent applications for the filter material are being prepared, says Sarkar, and research will continue.