Getting PFAS out of drinking water

When scientists discovered three per- and polyfluoroalkyl substances (PFAS) at worrisome levels in the drinking water provided to about 450 people in rural Maysville, North Carolina, town officials sprang into action. It was 2019, and at the time, there were no guidelines or federal limits for PFAS in drinking water. Still, town leaders immediately shut down the water plant and began purchasing water from a facility in neighboring Jones County.

Five years later, Maysville is now preparing to reopen its water plant thanks to about $1 million in federal grant money. The town used the funds to install a filtration system that can remove PFAS, including both long- and short-chain compounds.

Long-chain PFAS are those with eight or more carbons, such as the commonly found and toxic perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS). Short-chain PFAS have four to seven carbons. Maysville is dealing with PFOA, PFOS, and perfluorohexanesulfonic acid in its water.

To remove all three PFAS, the town chose a system that uses both granular activated carbon (GAC) and ion-exchange resins. The water treatment services firm ECT2 designed and installed the technology.

Surrounded by fields of tobacco, soybeans, and corn, Maysville is not the kind of place one would expect to find such advanced water treatment technology. Many businesses on the main street are shuttered. The municipal building sits across the street from a Piggly Wiggly grocery store and Hardee’s fast-food restaurant. Visitors passing through the town on their way to coastal vacation spots might easily miss it.

But Maysville is one of the lucky towns that identified PFAS in its drinking water and secured grants to address the problem before the US Environmental Protection Agency set limits. The agency issued the stringent, low parts-per-trillion limits for six PFAS in drinking water in April, giving public water utilities 5 years to meet them. Now, tens of thousands of utilities big and small will be competing for government money to tackle the problem.

Public water utilities that find PFAS above the EPA limits have a range of options to remove the chemicals. Single-use ion-exchange resins and GAC are the most common ways. Neither approach is new to the water treatment industry.

What is new is the desire to regenerate spent filtration media to keep captured PFAS out of landfills. Sustainability goals, concerns about liability related to PFAS in waste, and potential supply chain issues from increased demand for PFAS removal media are pushing regenerable technologies forward.

Foam fractionation is also gaining traction as a simple way to remove PFAS from water, particularly industrial wastewater and highly contaminated groundwater.

Ultimately, the decision about how best to treat PFAS in drinking water will depend on each utility’s unique situation. Factors such as cost, building size, local regulations, water composition, and sustainability will all come into play. And it’s not clear how water utilities will pay for advanced treatment processes. The EPA estimates it will cost $15 billion over 10 years to build systems to meet the new limits. The American Water Works Association says the figure is likely to be three to four times as high.

Sorbents meet ion exchange

ECT2 was formed in 2013 in Portland, Maine, to develop technologies for treating emerging contaminants in water and vapor. Montrose Environmental Group acquired it in 2019. The company is known for its regenerable ion-exchange resins, but it offers several other PFAS removal technologies, including single-use ion-exchange resins, GAC, membrane filtration, and foam fractionation.

“The regenerable resin product is not the panacea that solves all situations,” says David Kempisty, director of emerging contaminants at ECT2. “We look at each case and each particular customer’s treatment objectives and preferences.”

ECT2 has designed and deployed systems for removing PFAS in water around the globe. It has helped clean up groundwater contaminated with PFAS from the use of firefighting foam on military bases in the US and Australia and at airports in Scandinavia. The company has also worked with a textile maker in the southeastern US, a refinery in Alaska, and the PFAS manufacturer 3M to remove PFAS from their wastewater.

The system installed at the Maysville water plant is tiny compared with 3M’s system, which takes up two US football field–size buildings, says Todd Grosshandler, chief commercialization officer at Montrose. 3M was attracted to ECT2 because of its regenerable ion-exchange technology, he says. Without that capability, 3M “would have to dispose of huge quantities of spent material.” Regenerable ion-exchange resins create one five-hundredth of the waste that GAC does, and it takes up about half the space.

To regenerate the resin, ECT2 scientists strip PFAS off the material with brine and a solvent such as methanol. “We recover the solvent, and then we take the very high-brine solution and pass it through a specialized sorbent at a very low flow rate,” says Mike Nickelsen, vice president of R&D at ECT2. The clean brine solution, solvent, and resin can all be reused.

It’s not easy to remove PFAS from ion-exchange resins, Nickelsen says, because the resin captures PFAS in two ways. The hydrophobic carbon-fluorine tails of PFAS adsorb to the resin’s hydrophobic backbone, and the negatively charged heads of PFAS are attracted to the resin’s positively charged sites.

The dual mechanism increases the technology’s effectiveness at capturing PFAS, including short-chain compounds. But it complicates removing the compounds from the resin. Using the solvent and brine together allows scientists to deal with both mechanisms simultaneously, Nickelsen says.

The economics of regenerating ion-exchange resins has historically not favored drinking-water applications because single-use resins can last for a year or more.

But the resin must be changed eventually, and that disposal poses a problem. The EPA designated PFOA and PFOS as hazardous substances under the Comprehensive Environmental Response, Compensation, and Liability Act, also known as the Superfund law, in April. At the same time, the agency issued an enforcement discretion policy to reassure water utilities, airports, landfills, and other secondary sources of PFAS that it plans to focus enforcement efforts on parties that contribute the most to PFAS pollution.

But even if the EPA doesn’t crack down on those secondary sources, there’s no guarantee that some affected entity won’t sue water utilities for PFAS contamination. To reduce the risk of liability, some facilities may choose not to landfill PFAS-laden media.

ECT2’s regenerated ion-exchange resins currently work for nonpotable applications, but the firm is considering ways to make them comply with the NSF/ANSI 61 standard, which governs materials that come into contact with drinking water. One possibility is to find a food-grade solvent to strip PFAS from the resins. Another option is a solvent-free approach, which “is going to require some new resins that haven’t been made yet,” Nickelsen says.

Tried-and-true GAC

Water providers have been using GAC to improve the taste of drinking water and remove odors since the early 1960s, according to Calgon Carbon, the world’s largest GAC producer. The firm has also been selling GAC to remove PFAS from drinking water for more than a decade. It offers activated carbon, equipment, installation, exchange services, and reactivation of spent carbon.

In the US, Calgon Carbon makes activated carbon by crushing and processing bituminous coal in low-temperature ovens and then heating the coal in high-temperature activation furnaces.

In anticipation of the EPA’s new PFAS drinking-water limits, the firm ramped up production at its Mississippi plant last year. It now produces more than 90 million kg of virgin activated carbon annually in the US, according to a press release.

GAC removes PFAS in water by adsorption. The fluorochemicals are attracted and stick to the surface of the GAC pores as contaminated water flows through a vessel or bed filled with the material. When all the pores are filled with PFAS, it is time to replace the carbon.

For effective PFAS removal, GAC needs to be in contact with the water longer than ion-exchange resins do. That means it takes up more space than ion-exchange resins. Space can be limited at drinking-water facilities, and there may not be money or room to construct new buildings.

It’s common to install GAC filtration systems in front of an ion-exchange resin, like the design at the Maysville water plant, ECT2’s Kempisty says. GAC removes organics and other chemicals that can destroy the resin, which is relatively expensive to replace. “We want to make sure we protect that resin,” he says.

GAC effectively captures long-chain PFAS targeted by the EPA’s drinking-water limits, but there’s debate over how well it removes short-chain PFAS. ECT2 scientists say ion-exchange resins do a better job than GAC at catching the short-chain PFAS. Calgon Carbon claims that its activated carbon product is effective at removing PFAS with four, six, and eight carbons to undetectable levels. GAC products made from coconut and lignite are ineffective at removing short-chain PFAS, the firm says on its website.

Calgon Carbon reactivates spent carbon by heating it for several hours in a high-temperature furnace under low-oxygen conditions. This step destroys PFAS and generates hydrogen as a by-product, according to research published by Calgon Carbon scientists (Remediation 2022, DOI: 10.1002/rem.21735). An abatement system handles the furnace’s air emissions, which contain hydrogen fluoride gas.

The company has five reactivation plants across the US, as well as facilities in Europe and Asia. It says the carbon dioxide footprint of reactivated carbon is significantly lower than that of virgin activated carbon. For drinking-water purposes, Calgon Carbon offers a custom reactivation service that complies with NSF/ANSI 61.

A new way to renew GAC

It takes a lot of effort to move spent carbon or other filtration media to regeneration facilities, says David Trueba, CEO of the Battelle Memorial Institute spin-off Revive Environmental.

Revive Environmental is commercializing a supercritical water oxidation (SCWO) system called the PFAS Annihilator for PFAS destruction. It’s also developing GAC Renew, a process to regenerate GAC on-site for potable and nonpotable water applications.

“We can take a solvent that is fit for human contact and pass it through the media. We extract the PFAS off of the media, and then that extract goes to our PFAS Annihilator for closed-loop destruction,” Trueba says.

Revive Environmental is optimizing a nonpotable-water version of the GAC Renew system at its R&D facility in Columbus, Ohio. It plans to be at large-volume scale later this year for nonpotable applications such as treating wastewater from metal plating and contaminated groundwater at military bases. The firm plans to bring a potable-water version of the system to market in the next 18 months.

That will be 2 years after the EPA finalized limits for PFAS in drinking water, and GAC in systems that were commissioned during those 2 years will start needing to be replaced. “We want to be ready for that wave of exchanges,” Trueba says.

The EPA predicts that thousands of public water utilities in the US will need to remove PFAS from their water to comply with the new limits. A typical drinking-water plant would need 9,000–45,000 kg of GAC to be effective, Trueba says. “That’s a lot of carbon.”

Plant-based media

The Chicago-based water purification company Cyclopure is looking beyond traditional activated carbon and ion-exchange resins. It uses β-cyclodextrins made from plant-based products like corn and potato starch to remove PFAS from water.

For the past 4 years, the company has been optimizing conditions for polymerizing, purifying, and granulating β-cyclodextrins, which it purchases in bulk from Wacker Chemie, Cyclopure CEO Frank Cassou says. The plant-based sorbent, sold under the name Dexsorb, has a high capacity for PFAS. It takes up less space than GAC and can be regenerated, Cassou says.

The fresh sorbent is compliant with the NSF 61 drinking-water standard, but the regenerated form is not. To make the regenerated sorbent available for drinking water, Cyclopure would have to add a few wash steps to rinse off any solvent that remains behind. For now, Cassou says, companies are using regenerated Dexsorb to remove PFAS from industrial wastewater, landfill leachate, and groundwater near military or firefighting training sites.

The company installed a full-scale Dexsorb system this year at a port in New Jersey to remove PFAS from industrial wastewater, and it established one in Pennsylvania to clean up stormwater at a Department of Defense site, Cassou says. At a northern Michigan facility, Cyclopure’s technology reduced a PFAS removal system’s footprint from four vessels to two and extended the filtration media’s life from 6 to 36 weeks, he says.

“We consistently outperform carbon, which works but has capacity limitations because the pore sizes are uneven,” Cassou says.

Cyclopure is also tapping into the consumer market. It launched a home PFAS water-testing kit in 2020 and a countertop filter resembling a Brita pitcher filter in 2022. According to Cassou, the company commercialized whole-home filtration systems for consumers earlier this year and is planning to launch an under-the-counter version to treat water from one source in a home in the fall.

“I love providing the service to consumers,” he says. “It’s so rewarding, but from a real big-impact and, also, a real value standpoint, these projects treating non-drinking-water sources are really our big markets.”

Bubbling up in foam

Foam fractionation, a method used by the aquaculture sector for skimming proteins off the surface of water, is another popular way to remove PFAS from water. It is suited for difficult-to-treat waters that contain high salts, organic matter, and other contaminants that can shorten the lives of resins and other filtration media.

Companies are seeking to bring foam fractionation to the drinking-water sector, possibly as a pretreatment step, but so far scientists have used it primarily to treat PFAS in landfill leachate and groundwater at military sites and airports affected by PFAS in firefighting foam.

Because PFAS have hydrophilic heads and hydrophobic tails, they like the air-water interface, ECT2’s Kempisty says. “We’ve designed units to introduce large amounts of air in a turbulent fashion in the bottom of a reactor. This violent mechanism creates a large number of small air bubbles,” he says. PFAS are attracted to the bubbles, which rise to the top as foam. The foam layer can be skimmed off the top and destroyed by methods like SCWO or electrochemical oxidation.

Remediation companies in Australia have used foam fractionation for about a decade to clean up PFAS in groundwater on military bases, says Jason Hnatko, engineering manager of emerging contaminants at Allonnia, a Massachusetts-based biotechnology and environmental engineering firm. Allonnia is the sole distributor in North America of a foam fractionation unit called SAFF (surface active foam fractionation), commercialized by the Australian firm Epoc Enviro.

The unit is self-contained in a shipping container. The process involves both the foam fractionation step and a secondary step to further concentrate the captured PFAS and reduce the volume of waste.

“It’s very important to find ways to concentrate the PFAS into a smaller volume,” Hnatko says, because methods for destroying PFAS are much more economical when applied to low volumes of highly concentrated samples. “Foam fractionation is one of those technologies that works very well to accomplish that task.”

After the first fractionation, the foam looks like dish soap bubbles, Hnatko says. After the secondary fractionation, it looks more like shaving cream, he says. “In that secondary fractionation, you get an additional 1,000 to 10,000 times concentration of PFAS and reduction in waste volume.”

Foam fractionation in general struggles to capture short-chain PFAS, Kempisty acknowledges, because the short-chain compounds are less hydrophobic and aren’t as attracted to the bubbles.

But foam fractionation eliminates the need for a lot of pretreatment steps. Samples like landfill leachate contain lots of organics that compete for sorption sites on activated carbon and ion-exchange resins. Foam fractionation can treat those samples directly.

Moreover, foam fractionation easily combines with PFAS destruction methods like SCWO and electrochemical oxidation.

The water technology provider Gradiant recently launched an all-in-one PFAS removal and destruction system targeting wastewater from the semiconductor and petrochemical industries. The system combines foam fractionation, electrochemical oxidation, and the firm’s artificial intelligence platform. “The AI platform constantly analyzes the water chemistry and adapts the functioning of the various components within the system,” Gradiant president Govind Alagappan says.

Drinking-water utilities are on the firm’s radar as potential clients, but the semiconductor and petrochemical industries have shown the most interest, Alagappan says. “As far as the US is concerned, the biggest pie is the drinking-water applications,” he says. “The ability to roll that out in different parts of the country boils down to the motivation and proactiveness of different states.” Some are more motivated than others to remove PFAS from their drinking water now rather than wait until the EPA’s deadline, he says.

Money crunch

Water utilities are challenging the EPA’s new limits for PFAS in drinking water. The American Water Works Association and the Association of Metropolitan Water Agencies filed a petition with the US Court of Appeals for the District of Columbia Circuit June 7, asking the court to review the rule.

“The rule significantly underestimates nationwide costs, does not take into account the latest PFAS data, and will add to affordability challenges for many households without achieving the public health outcomes we all seek,” the CEOs of the two water groups say in a joint statement.

Under a court settlement approved in April, 3M agreed to pay about $10.3 billion over 13 years to more than 11,000 public water systems to help them remove PFAS from drinking water.

The Bipartisan Infrastructure Law, enacted in 2021, provided another $9 billion to help communities deal with PFAS in drinking water. Of that money, $4 billion was set aside for state grants to help public water utilities pay for PFAS removal systems.

Water groups claim that the total amount from both sources won’t even be enough to install new equipment. And none of it is slated for maintaining such systems or disposing of and replacing used PFAS-laden media.

In Maysville, water plant operators don’t know how long it will be before they have to replace the filtration media in their new treatment system.

Five years after PFAS were discovered in Maysville’s water, the source is still a mystery. Unlike Wilmington, North Carolina, a community heavily affected by PFAS from decades of wastewater discharged by Chemours into the Cape Fear River, Maysville is not downstream of a chemical facility that produces or uses PFAS. Town officials speculate that the PFAS came from firefighting foam spilled onto the ground for years when firefighters filled up their truck tanks from a hydrant next to the water plant.

Thousands of towns across the US are facing the same predicament as Maysville. The EPA estimates that 4,100–6,700 water systems will need to install equipment to remove PFAS to meet the new drinking-water limits. Even if utilities are lucky enough to get the funding to establish advanced treatment processes, they will struggle in the years to come to find money to maintain those systems, replace spent media, and responsibly dispose of their PFAS-laden waste.