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Exploiting PFAS's Achilles Tendon: A Review of Remediation Techniques

Technology designed PFAS to withstand heat and water, enabling them to persist in nature for eons. How can technology eliminate them?

In The Growing Menace of PFAS, I explain how PFAS—perfluoroalkyl and polyfluoroalkyl substances—came to be perhaps one of the most ubiquitous pollutants humanity has ever created. Designed to be solid and nonreacting, this family of chemicals has countless industrial applications, like fracking, manufacturing, electronics, food packaging, and clothing.

The problem with PFAS is their resiliency. Unlike most things we buy, such as electronics, which fail after a few uses or years, PFAS keep going and going like the Energizer Bunny. Light and seemingly indestructible, they can become airborne, riding columns of air and mixing with clouds before hitching a ride back to earth in rain; they can also seep into the ground, leaching into our food and drinking water systems.

Despite their tenacity, PFAS molecules have weaknesses that scientists are learning to exploit. This knowledge is revisiting some older, trusted technologies while spurring new ones. Though the PFAS problem is immense, these multiple solutions might make it more manageable. This post explores a few of the solutions.

PFAS’s secret sauce

The secret to PFAS’s superhero strength is their carbon-fluorine bond, one of nature’s strongest bonds. A typical PFAS molecule consists of a chain of carbon atoms flanked by fluorine atoms. Tightly packed around the carbon, the fluorine protects it from reacting with anything that might weaken or break the chain. Moreover, this molecule has a hydrophilic (water-loving) head, and a hydrophobic (water-hating) chain, meaning one end is water soluble and the other oil soluble, features that magnify its toxicity.

But every superhero also has a weakness that renders them powerless and ineffective. PFAS is no different. If we exploit a chink in its armor, the molecule will crumble into smaller, more manageable bits. Unfortunately, each class of PFAS has its unique weakness, and because PFAS number in the thousands, the techniques to destroy them will require ingenuity and lots of trial and error.

Common PFAS capture methods

The most popular method, granular activated carbon (GAC), has been around since the early 1800s. It’s also one of the easiest ways because water passes through a filter of a porous material that captures pollutants. Used on US military bases, industrial sites, and water treatment facilities for over 15 years, GAC effectively removes several types of PFAS. When the activated carbon becomes too clogged, it’s either removed for permanent disposal or thermally reactivated for reuse. Reactivating GAC reduces remediation costs, but some drinking water agencies have regulations against reusing it. If sent for disposal, the PFAS-laced GAC is treated before being deposited in certified landfills.

In use since the 1930s for softening, demineralization, and selective contaminant removal, membrane filtration is another widely used method for PFAS removal. Two more common filtration processes are ion-exchange resin (IX) and reverse osmosis (RO). IX employs polarity to do the heavy lifting. As water passes through an IX filter, positively charged resins attract negatively charged PFAS molecules. With RO, water passes through a semipermeable membrane. RO’s simplicity means it can purify water for a single household or be scaled up to industrial applications, like desalination.

GAC and membrane filtration are passive ways to clean water. In contrast, treating contaminated soil is more arduous because it employs earthmoving equipment and trucks. Called excavation and disposal, it involves transporting the PFAS-contaminated soil to an off-site location for disposal while refilling the excavated area with clean backfill. Disposing of tainted soil poses challenges. The ideal location is a specially lined landfill that prevents PFAS from leaching into the underlying sediment and nearby aquifers. Unfortunately, few of these landfills exist in the US.

An alternative to burying is incineration. This requires heating the spent GAC, filter sludge, or soil to at least 1,800°F to break apart the PFAS molecules. Though effective, its effects on PFAS are not well understood. Incomplete combustion may result in smaller PFAS molecules. It’s also highly energy intensive given the scores of trucks needed to transport these materials to and from incinerators and the fuel to burn them properly and safely.

Experimental methods

Despite their effectiveness, filtration and excavation have limitations. Filtration eliminates PFAS from public utility systems but doesn’t address the root cause: PFAS-contaminated aquifers. Likewise, excavation works locally, like at a manufacturing compound, but what about farmland spanning hundreds of acres? This is where experimental methods step in.

An aquifer is an underground formation of sediment filled with groundwater. Some aquifers lie near the surface and cover a few acres. Others encompass whole regions and extend hundreds of feet underground, like the Ogallala aquifer, which stretches across eight High Plains states. This is where sorption treatment might help. With sorption, specially treated particles are injected directly into a contaminated aquifer, where they seek out and immobilize PFAS molecules.

One method, called colloidal activated carbon (CAC), employs superfine carbon molecules that coat the aquifer pore structure. Like activated charcoal, CAC pulls pollutants out of water. But because each activated carbon particle is a spaghetti junction of tunnels—just one pound has an equivalent surface area of 100 acres—it gobbles up more PFAS. Polymer-coated sand, zeolites/clay materials, and biochar work similarly for different applications. Sourced from volcanoes, zeolites carry a negative charge and a honeycomb structure, characteristics that make them highly absorbent. Biochar comes from organic waste like wood or manure partially combusted in a low-oxygen environment. Besides sequestering PFAS, it absorbs many other pollutants while making an excellent soil amendment.

Another technology is chemical oxidation, which zeros in on the heads and tails of PFAS molecules. When oxidants react with PFAS molecules, they transfer electrons to individual atoms within the PFAS molecule, which decreases their ability to cleave to other atoms. Among the explored systems are ozone, catalyzed hydrogen peroxide, and ultrasound. Already a highly reactive element, ozone, when coupled with other oxidants, aggressively decomposes PFAS molecules by creating free radicals, which are apparently as damaging to PFAS as they are to humans. Ultrasound uses pulses of acoustic waves that cause the water to cavitate, in which tiny bubbles form and suddenly collapse. The action of collapsing bubbles creates energy, in this case, heat and pressure. With just a few short pulses, PFAS degrades to fluoride, sulfate, and carbon dioxide—much more manageable elements.

Electricity plays a leading role in electrochemical, plasma, and electron beam treatments. With electrochemical oxidation, anodes zap water with electrical currents that cause PFAS to oxidize. Numerous studies show its effectiveness in destroying several types of PFAS and its low-energy costs, especially when compared with thermal incineration. With plasma, electricity and argon gas concentrate PFAS molecules in a liquid-gas phase and then blast them with plasma. Similarly, high-energy electron beams oxidate PFAS in both water and soil. Because it doesn’t produce any nasty by-products, this method may become a standard process for certain consumer packaged goods.

Two other methods that deserve mention are foam fractionation and bioremediation. With foam fractionation, oxygen or ozone bubbles pass through polluted water, grabbing hold of PFAS molecules on their way up. Once at the surface, bubbles form into a foam supersaturated with PFAS. Now separated from the water, the PFAS-foam concentrate is processed further and disposed of. Bioremediation utilizes enzymes from certain fungi and bacteria to erode the carbon-fluorine bond. With the bond broken, the enzyme feast on the PFAS molecule with abandon. One fungus that’s getting attention is white rot fungi. Because it degrades hydrocarbons and pesticides in a matter of weeks, scientists hope it does the same with PFAS.

All is not doom and gloom

Perhaps the most worrisome aspect of PFAS is their ability to bioaccumulate. As they move up the food chain, the molecules build up within the tissues of living organisms, becoming more concentrated and toxic as they move up the chain. High PFAS levels are believed to damage the liver and immune system and cause birth defects, low birth weight, and delayed development in animals. Their impact on humans is less specific, although studies show strong connections between PFAS and cancer and infertility. Current estimates suggest that 97 percent of the US population has PFAS in their blood.

To be sure, the PFAS problem that looms over us can’t be solved with a silver bullet. But, as the remediation methods highlighted in this post indicate, all is not doom and gloom. PFAS molecules are robust, but they also have an Achilles tendon, a realization we are only now beginning to explore.

Further reading

Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS).” National Institute of Environmental Health Sciences, July 29, 2022.

Per- and Polyfluoroalkyl Substances (PFAS).” US Environmental Protection Agency, August 26, 2022.

PFAS Physical & Chemical Properties.” Interstate Technology and Regulatory Council, January 24, 2020.

Treatment Technologies.” Interstate Technology and Regulatory Council, June 2022.

Whelan, Sarah. Subset of “Forever Chemicals” Destroyed by Efficient New Method. Technology Networks, August 18, 2022.

Zimmer, Carl. “Forever Chemicals No More? PFAS Are Destroyed with New Technique.” New York Times, August 18, 2022.

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