Competition to destroy ‘forever chemicals’ heats up

Scientists once wrongly assumed that the carbon-fluorine bond was almost impossible to break. And that meant there was no practical way to completely destroy per- and polyfluoroalkyl substances (PFAS).

“They were truly thought to be ‘forever chemicals,’ ” says Julie Bliss Mullen, who began investigating technologies for removing PFAS from drinking water as an undergraduate in 2010. At the time, “destruction was not really on the table,” she recalls.

But Mullen was obsessed with breaking the carbon-fluorine bond. PFAS can be removed from water, but they just get transferred to another medium and eventually make their way back into the environment, she says. To stop that cycle, you have to destroy the molecules by breaking the “unbreakable” bond.

Around 2014, as a PhD student at the University of Massachusetts Amherst, Mullen got her hands on some electrodes and, as she puts it, “started playing around with electrochemical oxidation in the lab.” The process creates hydroxyl radicals and, unlike other advanced oxidation techniques, facilitates the direct transfer of electrons. “Those electrons will almost immediately break the carbon-fluorine bond if we’re able to get PFAS onto the anode surface,” she says.

Mullen won’t say how she attracts PFAS to the anode surface. But in 2017, she and the university filed for a patent and spun out a company, Aclarity, to commercialize the technology. Mullen never did finish her PhD. Today, as cofounder and CEO of the Massachusetts-based firm, she’s seeing big interest in the technology from landfill operators and wastewater treatment plants.

Aclarity is not the only company vying for a piece of the PFAS destruction market. Dozens of start-ups are working on technologies for destroying the chemicals, which have been linked to cancer and adverse effects on the liver and immune system. Some companies are already operating at full scale; others are not far behind. And it turns out that electrochemical oxidation is just one of many ways to break the carbon​-fluorine bond.

Companies are developing an array of approaches, including supercritical water oxidation, hydrothermal alkaline treatment, plasma destruction, ultraviolet light combined with photocatalysts, and sonolysis. They all claim to break down most PFAS into less harmful chemicals, such as carbon dioxide, fluoride ions, and water. But complete destruction of all PFAS, including short-chain PFAS and precursors, is a stretch for some techniques.

Many of these start-ups are partnering with companies specializing in technologies that remove PFAS from contaminated water and concentrate it. The PFAS destruction start-ups come in at the end and destroy the concentrated PFAS.

It’s early days for PFAS destruction and too soon to tell which technologies will succeed in the marketplace. But entrepreneurs who started these companies see the possibility of permanently ridding drinking water of the once-invincible “forever chemicals.”

Electrochemical oxidation comes of age

Aclarity is one of a handful of companies developing electrochemical oxidation for destroying PFAS. The technique, one of the more mature on the market, works by applying an electric current through a conductive liquid between an anode and a cathode. Direct oxidation occurs at the anode surface after the transfer of electrons from PFAS. Indirect oxidation involves the creation of oxidants, such as hydroxyl radicals, that break PFAS apart.

Electrochemical oxidation techniques can destroy over 99% of long-chain PFAS, which contain eight or more fully fluorinated carbons. But destroying shorter-chain PFAS, which can be present initially or be created by the incomplete degradation of long-chain PFAS, is more challenging. Several companies claim they have optimized their technologies to destroy all PFAS, but they tend to be short on details.

Aclarity says its ability to destroy both long- and short-chain PFAS is more than just about its electrodes. “We originally looked at so many different anode and cathode combinations,” Mullen says. “So while a portion of the secret sauce is certainly related to our electrodes, we’ve optimized the materials, the geometries of the reactor, the flow, and how we process water through.” That optimization process helps the PFAS get to the anode, improving the performance, she says.

Arizona-based OXbyEL Technologies also claims to destroy long- and short​-chain PFAS in one step. “We have the only electrochemical cell that is divided,” says Colleen Legzdins, the start-up’s vice president of technology. Rather than flow between the anode and the cathode, PFAS-contaminated water “only flows over the anode for oxidation,” she says. “We can provide a high-enough oxidation potential to destroy the PFAS to the end products. We are not producing the short-chain by-products.”

OXbyEL won’t disclose much about the electrode, but Legzdins says it is about one-seventh the price of traditional boron-doped diamond. A special catalyst coating and a 3D anode structure facilitate the migration of PFAS to the anode surface and minimize unwanted reactions, like the electrolysis of water, she says. “The energy consumption really is the electrolysis of water,” Legzdins says.

Electrochemical oxidation processes do not require high temperatures or high pressures, like some other techniques for destroying PFAS. OXbyEL claims that its process also does not require the addition of chemicals, such as a supporting electrolyte.

In April, OXbyEL plans to pilot test its system at the Davis-Monthan Air Force Base in Arizona, says OXbyEL cofounder and CEO Ed Ricci. PFAS in firefighting foam, which was used extensively in fire-training exercises on the base, contaminated a drinking-water well in the city of Tucson. “We are going to be evaluating treatment efficiencies around that well water,” Ricci says.

Supercritical water oxidation takes the stage

Sprawling along the Olentangy River, the immense Battelle Memorial Institute campus in Columbus, Ohio, could easily be mistaken for part of the Ohio State University, which sits across the street.

The heavily secured main entrance to the nonprofit research organization’s headquarters leads to a colorfully lit lobby that looks like a cross between a museum and a fancy hotel. A series of underground hallways connects the nearly 100-year-old buildings.

Inside, a Battelle spin-off named Revive Environmental is preparing to deploy a technology called the PFAS Annihilator. Battelle, in partnership with Viking Global Investors, launched Revive a little over a year ago to commercialize supercritical water oxidation (SCWO) for PFAS destruction. SCWO is a powerful oxidation technique that obliterates organic chemicals. Scientists have been using it for decades to destroy chemical weapons and other difficult-to-treat contaminants.

Each Annihilator system contains a series of wires, heat exchangers, flow valves, pumps, and pipes connected to a reactor box that looks somewhat like a coffin. PFAS-contaminated water is pumped through the reactor, where high temperature and high pressure, above the critical point of water, enable an oxidation reaction that breaks the carbon​-fluorine bond.

Revive and a few other firms pursuing SCWO offer full-scale, commercial systems that can be integrated into existing wastewater treatment facilities or transported in shipping containers to contaminated sites. Each company is targeting specific markets and developing ways to lower energy use, control corrosion, and eliminate the buildup of salts that commonly clog SCWO systems.

Energy is a big part of the operating cost. SCWO works by heating and compressing liquid waste to above 374 °C and 22 MPa, the critical point of water. In that supercritical state, an oxidizer drives a reaction that cleaves the carbon-fluorine bond.

Unlike some other destruction methods, SCWO does not create unwanted by-products, such as short-chain PFAS and precursors to PFAS. But in general, breaking the carbon-fluorine bond creates hydrofluoric acid, which has to be neutralized with a base like sodium hydroxide.

Battelle began developing the SCWO technology behind Revive in 2018. At the time, the organization committed nearly 100 staffers to destroying PFAS, says Amy Dindal, PFAS program manager at Battelle. “We set out with this more holistic view. Destruction was number 1, but we wanted to be able to augment that with other technologies and capabilities,” she says. These included accredited analytical methods for measuring specific PFAS, methods that screen for PFAS using high-resolution mass spectrometry, and a total organic fluorine assay used to verify that all PFAS are destroyed.

Battelle kept its analytical chemistry capabilities related to PFAS and now subcontracts those capabilities to Revive. Battelle also manufactures all the equipment and provides warehouse-size space for the start-up at its Columbus campus.

So far, Revive has installed a commercial PFAS Annihilator unit at a wastewater treatment facility in Michigan. But for PFAS destruction firms like Revive, “the hottest market right now is AFFF—aqueous film-forming foam,” says David Trueba, Revive’s CEO.

AFFF is the firefighting foam used by military bases, airports, and anywhere there’s a need to extinguish flammable liquid fires, such as those caused by oil and gas. The US Department of Defense and state agencies are transitioning to alternative firefighting foams that don’t contain PFAS, and they are seeking to destroy stockpiles of unused AFFF.

States are aggregating AFFF from fire departments. “We just were awarded the Ohio State take-back program,” which will involve destroying PFAS in nearly 200,000 L of AFFF over the next few months, Trueba says. Revive is also working with New Hampshire and a few other states, as well as airports, to destroy AFFF stockpiles. Trueba predicts that eliminating all the stockpiled AFFF will take at least 5 years.

Chemical manufacturers, the oil and gas industry, and industrial users of PFAS are the next big market for SCWO, Trueba says. Some companies are trying to eliminate AFFF, some are remediating groundwater, and others with fluorinated chemical production processes are seeking a remediation step that will allow them to stay in business, he says.

Here comes hydrothermal alkaline treatment

Hydrothermal alkaline treatment (HALT), like SCWO, was developed decades ago to destroy stockpiles of chemical weapons. It too recently hit the PFAS destruction scene.

Timothy Strathmann, a professor of civil and environmental engineering at the Colorado School of Mines, and colleagues were the first to optimize it for destroying PFAS. The Washington State–based start-up Aquagga has an exclusive license to the technology and is commercializing it at full scale.

HALT is like SCWO but with a catalyst and lower temperatures, says Brian Pinkard, Aquagga’s cofounder and chief technology officer. The firm’s system operates at about 350 °C, in the subcritical phase, he says. In addition to using less energy than SCWO, HALT can handle high levels of salts without any special treatment, he points out.

Pinkard says the first time he heard about PFAS was in 2019, when he joined entrepreneur Nigel Sharp in the Innovation Corps program of the US National Science Foundation (NSF). The program trains scientists and engineers on how to explore the commercial potential of technologies they are working on in the laboratory.

At the time, Pinkard was finishing up a PhD at the University of Washington, where he was investigating HALT for destroying chemical weapons. “I was curious whether what I was working on had any commercial relevance to anybody anywhere,” he says.

Pinkard entered the NSF program thinking he might have a technology that could destroy sewage sludge, solving wastewater issues around the world, he recalls. But when he and Sharp started interviewing people in the wastewater and environmental industries, PFAS came up over and over again.

“We kept hearing, ‘PFAS is this huge issue. Nobody knows how to deal with this stuff. Nobody knows how to destroy PFAS. It’s an impossible problem,’ ” Pinkard says. “It turned out the technology that I was working on was applicable for destroying PFAS.” Pinkard, Sharp, and their colleague Chris Woodruff launched Aquagga later in 2019 as a public benefit company.

The start-up conducted its first field test last summer at an airport in Fairbanks, Alaska. The site has a lined pond that collected runoff for decades from PFAS-laden foam used in firefighting training.

Aquagga teamed up with ECT2 (Emerging Compounds Treatment Technologies), a Maine-based start-up that specializes in PFAS removal techniques. Aquagga used ECT2’s foam fractionation method, which concentrates PFAS and reduces the volume of liquid that needs to be treated. The team successfully destroyed PFAS in the concentrate with a mobile HALT unit.

The field test showed the technology can run off a generator at a remote site. “You can hook it up to these totes filled with really nasty water, process the water through it, and produce something that’s much, much cleaner for discharge,” Pinkard says. The system can process about a full tote’s worth of water in a little over a day, he says. That’s a bit more than 1,000 L.

Plasma sparks interest

The start-up Onvector is pilot testing what it calls a plasma vortex. The technology rapidly destroys long-chain PFAS, such as perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS). But it takes longer for plasma to degrade short-chain PFAS, CEO and founder Daniel Cho says.

Onvector started out in 2013 in an industrial park on the outskirts of Philadelphia. The company’s main location is now nestled among other cleantech startups at the Greentown Labs incubator in Somerville, Massachusetts.

Scientists still conduct bench-scale tests in a small lab at the Pennsylvania site. A unit there, small enough to fit inside a shipping container, sits on metal scaffolding on wheels. Pipes, tubes, pumps, and valves connect PFAS-laden wastewater in a stainless steel tank to a plasma reactor housed inside a series of clear, block-shaped polycarbonate modules.

Argon gas is injected through an electrode in the bottom of the reactor. With the flick of a switch, a roaring flame appears inside.

The geometry of the reactor is similar to that of a cyclone separator used in industry to remove particles from a gas or a liquid, Cho says. “We’ve added an electrode at the bottom of the cyclone, through which we inject gas,” he says. The electrode generates high-energy electrons that ionize the gas, creating a plasma that stretches through the cyclone.

As the plasma rotates like a tornado, liquid waste containing PFAS flows in through the side of the device near the top. Gas and low-density material, like foam, flow to the center, “where you have a column of fire and lightning,” Cho says. PFAS interact with the plasma and break apart. Unreacted solids spin out and are collected for disposal.

Some short-chain PFAS could end up in the solid waste, but Cho considers it a de minimis amount of solid waste. “My view is that a huge liquid PFAS problem is worse than a tiny PFAS solids problem,” he says.

Argon is the preferred carrier gas for plasma PFAS destruction, Cho says. To reduce or eliminate any release of PFAS into the air, the device recirculates argon in a closed loop. At the end of the process, the gas passes through activated carbon to scrub out any remaining PFAS or other hazardous substances.

Onvector completed a pilot test of the technology on Joint Base Cape Cod under a grant from the US Air Force. The Air Force is now interested in testing plasma paired with technologies that concentrate PFAS before they are destroyed, Cho says. Onvector successfully combined its plasma vortex with regenerative ion-exchange technology developed by ECT2. It will soon test the plasma at the Cape Cod site with two other preconcentration technologies.

“We’re the caboose of the treatment train. As long as you provide us with high-enough PFAS waste, we’ll hit it with a heavy hammer,” Cho says.

Despite the fire-and-lighting appearance, a plasma reactor does not require large amounts of electricity, says Selma Mededovic Thagard, a professor of chemical engineering at Clarkson University. “It’s essentially like running a microwave or high-wattage heater at home.”

Thagard and her colleague Thomas Holsen cofounded New York–based Dmax Plasma in 2014 to commercialize a plasma technology for destroying PFAS using a reactor much different from that of Onvector.

The Dmax system pumps argon into the bottom of a large bath of PFAS-contaminated water. Gas bubbles rise to the surface, picking up PFAS along the way. A series of electrodes above and below the water surface generates plasma at the air-water interface. Electrons in the plasma break the carbon-fluorine bonds.

Thagard acknowledges that short-chain PFAS don’t always break down because they often don’t make it to the interface. “They are not surfactants, so they don’t attach to argon bubbles,” she says. But her team discovered that it can get short-chain PFAS to the interface by adding small amounts of surfactant (J. Hazard. Mater. 2023, DOI: 10.1016/j.jhazmat.2023.131691). PFAS attach to the surfactant, and argon bubbles carry the combo to the interface. The removal rate for short-chain PFAS is slower than for long-chain PFAS, but it is possible to remove them, Thagard says.

UV photocatalysis shines through

In Minnesota, Claros Technologies is commercializing a UV-photocatalytic approach for PFAS destruction that marries UV light systems, which are already used for water disinfection, with inorganic photocatalysts to break the carbon-fluorine bond.

“We see UV light as an inherently scalable technology for PFAS destruction,” says John Brockgreitens, the company’s vice president of R&D. “Through the use of photosensitizers, those initiating agents that are actually really doing the defluorination reaction, we can use a lot less energy than, say, an electrochemical process or supercritical water process.”

UV light has to be able to transmit through the sample, so one of the biggest challenges with the approach is dealing with background organic molecules that absorb in the UV range, Brockgreitens says. Suspended solids are also problematic. But many industrial customers have prescreening or prefiltration steps, he notes. “You may already have a pH adjustment or a coagulation process that’s getting out solids and some of these other background organics.”

Claros got its start making textiles with antimicrobial and other properties. In 2018, the company began creating a sorbent for capturing PFAS in water. Once the sorbent reaches capacity, “you incinerate it or you landfill it,” Claros CEO Michelle Bellanca says. “We quickly realized that although our sorbent was quite effective at capturing the PFAS, we were going to be perpetuating the problem” of PFAS in the environment, she says.

Claros abandoned the sorbent idea and set out to develop a method for destroying PFAS. The UV-photochemical process eliminates the need for a sorbent, Bellanca says.

The company also has years of experience developing PFAS analytical methods, including a total organofluorine assay and liquid chromatography/mass spectrometry methods. “Our tagline is ‘We became PFAS detection experts so that we can become PFAS destruction experts,’ ” Brockgreitens says.

Companies that find they must use PFAS chemicals, including pharmaceutical, medical, semiconductor, and aerospace firms, are coming to Claros for help managing their PFAS waste, Brockgreitens says. The company also sees drinking​-water facilities as potential customers.

Sonolysis goes underground

Predestruction steps such as granular activated carbon filtration, reverse osmosis, ion exchange, and foam fractionation can be used with nearly all PFAS destruction techniques to concentrate the chemicals. Groundwater cleanup will likely involve some combination of approaches.

Another option is to move the technology underground. “It costs a lot of money and energy to pump water out of the ground to treat it,” says Michelle Crimi, dean of the graduate school and professor of environmental engineering at Clarkson University. Crimi is cofounder of the New York–based start-up RemWell, which is seeking to commercialize underground sonolysis for PFAS destruction.

Sonolysis relies on sound waves in a certain frequency range—the ultrasonic and even the megasonic, Crimi says. At those frequencies, sound waves cause cavitation in water, she says. Tiny cavities that are too small to see grow until they implode, releasing energy.

PFAS like to hang out at surfaces, so they line up on these cavities, Crimi says. The high energy released from the cavities can be in the form of heat, which can break down contaminants by pyrolysis, she notes. The energy can also create free radicals that help degrade contaminants. “There’s a variety of mechanisms at play, all of which are very aggressive,” she says.

RemWell’s reactor is designed to go into a long horizontal well that is built underground at depths of up to 90 m. The reactor is about 30 cm in diameter and 45 cm long. Contaminated groundwater flows through the reactor slowly, taking 12 h or more to pass through, Crimi says.

RemWell is testing its technology on PFAS-contaminated groundwater at a Department of Defense (DOD) site. Later this year when the weather warms up, it plans to install the technology in Sweden for further testing. The governments of Australia and Sweden “were very quick to react to the PFAS problem,” Crimi says.

Looming regulations and liability

There’s a good chance that multiple technologies will play a role in cleaning up the PFAS that have found their way into landfills, wastewater, and sources of drinking water. PFAS have been used for decades in consumer products, firefighting foam, and the production of fluoropolymers. They are now widespread in the environment and in people.

Some PFAS are harmful to human health at parts-per-trillion levels. Attention has focused primarily on two of the most toxic ones: PFOA and PFOS. But for most PFAS—and there are nearly 15,000 of them—little is known about their effects on human health.

Although PFOA and PFOS are no longer used or produced in the US, they contaminate drinking-water sources across the country. Many municipal drinking-water utilities treat their water to remove the chemicals to comply with state or local regulations. Soon, they may have to meet even stricter limits under federal regulations.

But landfill operators, wastewater treatment plants, and chemical producers aren’t waiting for regulations. They don’t want the liability of being a source of PFAS pollution, so they are seeking to destroy the contaminants instead.

Experts agree there’s no one-size-fits-all approach for destroying PFAS. “It’s not going to be ‘May the best one win,’ ” RemWell’s Crimi says. “It’s going to be more like ‘Where is the best niche for this one? Where is the best niche for that one?’ ” She describes the PFAS destruction community as “pretty friendly; competitive yet collaborative.”

Later this year, Aquagga and three teams with full-scale SCWO systems—Revive, General Atomics, and a partnership of Arcadis, 374Water, and Clean Earth—will demonstrate their PFAS destruction technologies at a DOD site. In the so-called bake-off, the four teams will each destroy three different PFAS samples, each preconcentrated by a different method.

“The goal of the upcoming demonstrations is to assess cost and performance of the PFAS destruction technologies at a large scale in a relevant environment,” a DOD spokesperson says in an email. “These demonstrations will allow for a head-to-head comparison.”

The DOD is not seeking a single winner, the spokesperson says. “Earlier research indicates that multiple technologies have a high likelihood of success, and several technologies will be needed to address specific scenarios.”

“There is a lot of work out there to be done,” Aquagga’s Pinkard says. “Even if all of us are wildly successful, there’s still going to be more PFAS out in the world to treat,” he says. “There are cases where customers will come to us, and I’ll recommend other treatment technologies because maybe we’re not the best fit,” he says.

“Our mission is to end PFAS,” Aquagga CEO Sharp says, “not to beat the other guys who are ending PFAS.”