Granular activated carbon is the main raw material for processing PFAS (short for perfluorinated and polyfluoroalkyl substances) and organic chemicals. In the simplest terms, the technology works when unwanted compounds are absorbed by the carbon.
In order to produce activated carbon made from coal, it must be subjected to relatively high temperatures. This process can release climate-changing carbon dioxide into the atmosphere.
Then, once activated carbon has been used to eliminate PFAS, these materials must be disposed of. This is usually done by incinerating it or sending it to landfill, which may release more carbon dioxide. Activated carbon can be recycled and reused, but it also requires a lot of energy.
The lower the MCL setting of PFAS in drinking water, the greater the potential for environmental impact because more work needs to be done to achieve lower levels of the compound.
But there is no magic number that strikes a balance.
“What is the right MCL that is also good for the planet? I don’t have that answer — I don’t think anyone has,” Coleman-Kammula said.
Currently, there is no federal MCL for PFAS in public drinking water. The Environmental Protection Agency does set a federal health advisory level of 70 parts per trillion for two PFAS compounds, PFOA and PFOS, but unlike the MCL, the advisory is not enforceable. Pennsylvania and Delaware are choosing their proposed MCLs based on the amount of chemicals a person can eat, drink or breathe each day without presenting a detectable risk to health. A spokesman for the Delaware Department of Public Health said the state does not take into account the impact on the environment simply because there is currently no solution to the carbon dilemma.
Drexel University has received funding from the U.S. Department of Defense’s Strategic Environmental Research and Development Program to study the use of non-thermal (or “cold”) plasma technology to degrade and destroy PFAS into benign products – carbon dioxide and fluoride. The technology, if successful, will address the current need to deal with remaining contaminated materials.
Christopher Sass, a professor of environmental engineering at the university’s college, said that while PFAS is considered a part-per-trillion health risk, the generation of part-per-trillion carbon dioxide and fluoride from the destruction of PFAS is not dangerous. engineering.
Fluoride is typically added to drinking water at levels around 1 milligram per liter (roughly 1 part per million), so the amount of fluoride from breaking PFAS should be negligible, sales say. Likewise, the amount of carbon dioxide produced is negligible—to put that in perspective, seawater typically has a dissolved carbon dioxide concentration of 40 milligrams per liter (40 parts per million), Sales said.
“We are in the early stages of demonstrating and optimizing a cold plasma system for PFAS degradation,” he said. “For destructive technologies, it is important to understand the mechanisms of how they are degraded, and the by-products they produce. Although the goal of these destructive technologies is to generate carbon dioxide and fluoride, we must ensure that they do not cause harmful toxic By-products. We want to make sure that we are optimizing destructive technologies so that they not only remove PFAS quickly, but also produce safe by-products as efficiently as possible.”
Dozens of other technologies are currently being studied, he said. “[The science community is] Now throw the kitchen sink at PFAS and see what works. ”
Aside from its environmental impact, granular activated carbon doesn’t work perfectly for all PFAS compounds, said Yanna Liang, professor and chair of the Department of Environmental and Sustainable Engineering at SUNY Albany. Although this technique works well in removing PFOA and PFOS, it is not as successful in removing other types of short-chain PFAS.
“Unfortunately, we don’t have a perfect solution to deal with PFAS. I think as researchers, we’re all trying to find a panacea,” she said.
Liang’s team is working on a technique that would use plants to absorb PFAS from contaminated soil, sediment or surface water and then use a thermal process to destroy the chemicals accumulated in plant biomass.
“We want to have a technology or technology that can remove all PFAS chemicals from water or soil. And, we want it to be cost-effective, environmentally sustainable and friendly,” she said. “So that’s our goal. But again, we’re still in the process of getting there, we’re not there yet.”