Colorado School of Mines researchers patent new process to destroy harmful PFAS "forever chemicals"

As water systems across Colorado, and the entire country, grapple with how to remove toxic "forever chemicals" from their drinking water supplies, researchers at the Colorado School of Mines have invented and patented a new process to eliminate them entirely. 

Per- and polyfluoroalkyl substances, or PFAS, are called forever chemicals, because of their tough durability and difficulty breaking down in the environment. PFAS are used in a variety of products, like nonstick cookware, waterproof clothing, and firefighting foam.

But the Environmental Protection Agency says they can cause health problems, including birth defects and cancer. This year, the EPA is working to create regulations for PFAS in drinking water for the very first time, but that's creating new challenges for many public water systems that have recently discovered levels above recommended safe limits. 

As public water systems install filtration systems to filter out the PFAS, the utilities will also need to decide what to do with the PFAS-concentrated toxic waste that is left behind. 

The new process invented by the School of Mines solves the problem of what to do with that waste -- it destroys it. 

Previously, the concentrated PFAS waste would get shipped to a landfill or sent to a facility to be incinerated, but those options could release the toxic chemicals back into the environment.

Instead, the School of Mine's process -- called Hydrothermal alkaline treatment, or HALT -- uses an extremely hot boiling sand with a chemical reactant to eliminate PFAS without emissions. It's a process that's been five years in the making. 

"Ultimately that would kind of close the cycle and actually remove PFAS from the environment, and not just transfer it somewhere where it has a chance to escape again in the future," said Timothy Strathmann, a civil and environmental engineering professor at Mines, and co-inventor of HALT. "Halt PFAS, stop the PFAS."

Researchers relate it to a pressure cooker.

"We heat the water to these high temperatures, usually 350 degrees Celsius, and then the second thing is that we add a simple chemical called a base, like sodium hydroxide, that historically was used to make soap and is used in a variety of consumer products," Strathmann said. "The way I explain it to people is that it's really a pressure cooker on steroids."

Strathmann said the breakthrough came when he and other researchers at Mines were using a similar process on algae. 

"It was a little bit serendipitous. We were working on biofuel research where we were using a similar process to convert algae into liquid fuels, and there was a call for proposals dealing with this important issue of PFAS that was emerging in the country, and we decided to just check whether or not the same conditions might also degrade PFAS," Strathmann said. "We tested the same kinds of reactions with lots of different chemicals that we added in the different ones and tested and found that the some of the very simple ones like these chemical bases, were able to promote destruction of the PFAS, and so we were very excited about that, and that led us down the road, and now it represents a major portion of what we work on in this lab."

Strathmann says he and other engineers are now analyzing how to make the process even more sustainable for the environment. 

"We're studying how HALT might be used not only to destroy PFAS and those biosolids, but also taking it full circle back to our biofuels research. Can we generate products like liquid fuels and recover fertilizer from those waste materials by these conditions?" Strathmann said. "So, we're trying to look at the value of destruction and producing valuable products from the process."

Asked about the limitations of the new process, Strathmann said, "it's a more of an emerging technology, so, there's less of a track record; anytime you have emerging technologies like we're developing, and others are developing, there's higher risks to utilities to adopt."

Despite that, Mines says the technology is considered by many in the field to be one of the most promising options for the destruction of PFAS ever invented, and a Washington-based cleantech startup just licensed it for commercialization.