GRAND RAPIDS, Mich. (WOOD) — A report from an environmental nonprofit organization estimates between 2 and 20 million acres of American farmland are contaminated with PFAS because of sewage sludge. Now, the U.S. Environmental Protection Agency is researching four methods to pull the chemicals out of sewage sludge and other contaminated material in hopes to slow down PFAS pollution.
PFAS — or per- and polyfluoroalkyl substances — is a giant group of chemical compounds. PFAS were first developed in the 1940s and incorporated into all sorts of products in the years that followed. You may have heard about PFAS being used in non-stick pans or firefighting foams, but the list of everyday products is much longer, including dental floss, shampoo, nail polish and eye makeup.
PFAS compounds are commonly called “everywhere chemicals” — because they are so commonly used that its impact is felt worldwide. A national test conducted between 2011 and 2012 found an estimated 97% of all Americans have some trace of PFAS in their blood.
The chemicals start with these products but spread across our environment in many ways, mostly through groundwater. Manufacturing sites are the primary polluter, with the chemical compound seeping into wastewater. Products containing PFAS are thrown away and end up in landfills, spreading to the groundwater.
Wastewater treatment plants can pull PFAS out of the water before cycling it back for drinking, but leftover biosolids still contain PFAS. When sold as a fertilizer, it is spread on farmland, once again contaminating groundwater but also the crops that grow, putting PFAS on your dinner plate.
A PROBLEM DECADES IN THE MAKING
According to documents released by the Environmental Working Group, researchers at chemical manufacturers 3M and DuPont found evidence that PFAS was harmful as early as the 1950s, including evidence that PFAS builds up in a person’s bloodstream. But that information was mostly kept private, and the development and use of the chemicals continued for decades.
According to a 1963 technical manual from 3M, the company considered the compounds toxic. In 1973, a study done by DuPont found that people could experience liver damage when exposed to the PFAS used in food packaging. In 1981, both 3M and DuPont started moving female employees away from certain departments after studies found a connection between PFAS and eye development issues in animal fetuses.
In 1989, a 3M study found a higher rate of cancers in employees who handled PFAS. A study conducted by DuPont three years later confirmed that finding. These studies eventually made their way outside of the business halls and into the public consciousness. By 1999, elevated levels of PFAS were found in blood banks around the country.
It wasn’t until 2000 that 3M announced they would stop producing PFAS chemicals and would stop selling products that contain PFAS by 2002.
In 2005, for the first time, an advisory panel for the EPA found that PFAS chemicals are a “likely human carcinogen,” meaning they can cause cancer.
BREAKING CHEMICAL BONDS
PFAS compounds are also referred to as “forever chemicals” because the bond between fluorine and carbon is extremely strong and will not break down naturally. However, scientists have developed some new techniques that can break those chemical bonds and separate them into the original elements.
The EPA has dedicated a group of experts to investigate ways to destroy PFAS, called the PFAS Innovation Treatment Team (PITT). Their research identified four promising treatments that could be used to break down the chemical bonds within PFAS: a mechanochemical process, an electrochemical process, pyrolysis and super-critical water oxidation.
The mechanochemical treatment involves ball milling — or using a machine to tightly compact and grind material along with an agent to break apart those bonds. Tests using alumina and potassium persulfate as the milling agents completely broke down the fluorine bonds.
Electrochemical oxidation is a process that uses electric currents passed through a solution to oxidize pollutants. Preliminary testing results were mixed, with researchers working with different materials and solutions to find the best fit. The process has yet to be proven fully effective, but some researchers are optimistic.
Pyrolysis is a process that decomposes polluted material at an extremely high temperature in an oxygen-free environment. The process can transform the material, like sewage sludge, into a char while separating out a hydrogen-rich synthetic gas. In early tests done by the EPA, the char showed no signs of PFAS after undergoing pyrolysis.
WHAT IS SUPER-CRITICAL WATER OXIDATION?
The fourth treatment is one that is fairly new and is the focus of new research: super-critical water oxidation.
We normally think of matter falling into one of three phases: solid, liquid or gas. Water, however, has a rarely seen fourth stage called super-critical water. Water stays liquid between 32- and 212-degrees Fahrenheit. When it dips below 32 degrees, it freezes and becomes a solid. When it passes 212 degrees, it turns into vapor gas. But if it continues to warm past 705 degrees Fahrenheit — or 374 degrees Celsius — it becomes super-critical water and takes on different properties.
Doug Hatler is the chief revenue officer of 374 Water, a company based out of Durham, North Carolina, that is looking to use this technology to recycle waste back into reusable resources that are safe to use. He says that while oil and water don’t mix, oil and super-critical water do.
“When you take water and you heat it above 705 degrees Fahrenheit … you take that above a pressure of 3,210 pounds per square inch. Think of your car tire, which is generally 35 PSI, imagine 100 times that pressure at a temperature of 705 degrees,” Hatler told News 8. “Water takes on very unique properties, its polarity is reversed. Typically, organic materials like oil and other organic compounds don’t mix in water, they separate. When you get into the super-critical state, the organics now become soluble and the inorganics, which are normally dissolved into ions, come out of the solution.”
Super-critical water flipping its polarity plays a key role, but it’s the oxidation process that breaks down PFAS.
“In that high pressure, high temperature state, there’s a tremendous amount of energy in there. It’s just very, very highly energized. So, now if you insert oxygen into that environment with the organic material, you get an exothermic oxidation reaction,” Hatler said. “That heat and energy is released. And that energy is much greater than the energy that holds those chemical bonds together.”
So, how can this process directly relate to cleaning sewage sludge?
“What happens is you break all the carbon bonds, carbon-hydrogen, carbon fluoride. If there’s any carbon-nitrogen, carbon whatever, they all break down and you mineralize things into their basic building blocks: carbon dioxide, water, you get nitrogen gas and then you get inorganic materials like manganese,” Hatler said. “These inorganics will either be as ions in the solution, or they’ll form precipitates and fall out as a mineral. (And then on top of all of that), you’ve got clean water that comes out.”
Hatler knows that the process works and can provide an environmental benefit. The question is whether super-critical water oxidation can provide an economic benefit. Hatler and his team are betting it can.
“As an environmental engineer, I started remediation 30-something years ago cleaning up hazardous waste sites,” Hatler told News 8. “I believe that if the free markets are allowed to operate, the markets will pick the technologies and pick the things that will work and will work most successfully.”
Only time will answer that question, but Hatler believes there is a way forward to a healthier environment and that super-critical water oxidation can play a key part.
“We, as a company, we still have a profit motive. But our vision is a world without waste,” Hatler said. “We want to be able to contribute to a circular economy. Our mission is to preserve a clean and healthy environment that sustains life.”
*Correction: A previous version of this article incorrectly identified the city in which 374Water is based. We regret the error, which has been fixed.