Warminster Township officials thought they had finally found the best way to remove toxic PFAS chemicals from the township’s drinking water: an ion-exchange treatment system.

Pilot tests showed that the system effectively got rid of the undesirable chemicals. Plus, the technology lasts longer than alternatives and requires less space, and the military, which is funding some of the water-contamination cleanup, paid for installing it.

Then state regulators reversed course, after giving their initial approval for it, local officials say. The Department of Environmental Protection now wants more testing — a move the Warminster water authority says could create more costs and further burden residents who are already paying higher water bills and worrying about the potential health impacts of decades of drinking water tainted by PFAS.

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Horsham and Warrington Townships, which like Warminster have water tainted by per- and polyfluoroalkyl substances that were in firefighting foam used at nearby military bases, had also hoped to rely on the ion-exchange systems. The chemicals have been linked to cancer and other health risks.

The reversal leaves the townships in limbo as they try to keep their water clean — and grapple with state bureaucracy over a question communities across the country are trying to answer: What’s the best and safest way to remove PFAS, the so-called forever chemical, from drinking water?

The DEP had previously approved pilot programs for the treatment systems in Warminster, Warrington, and Horsham. Now, it has effectively revoked the townships’ permit approvals and says further testing is needed as standard practice.

“It’s quite a setback,” said Tim Hagey, general manager of the Warminster Municipal Authority, which began using ion exchange systems on a non-potable well in 2018 and a drinking well in 2019.

He and other experts say they are more efficient, more cost-effective, and take up less space than granular activated carbon filters — which state regulators have approved and are more widely used.

All three townships have carbon filters operating on their other wells and also purchase water from North Wales to provide enough PFAS-free water to their residents. Though the Navy funded the installation of the treatment systems in all three townships, residents have still been paying millions a year in increased water bills or surcharges to cover the other costs of dealing with PFAS.

The ion exchange treatment system works by using resin made up of positively charged ions that attract negatively charged ions — like PFAS chemicals — and replace them with chloride as the water flows through. It is effective for removing all PFAS, according to the Environmental Protection Agency.

Officials in Warrington and Warminster are appealing the decision. Horsham’s permit for the treatment system is still in effect but expires Oct. 17.

The DEP’s decision was “a little bit of a curveball,” said Christian Jones, Warrington Township’s director of water and sewer. Officials there had received approval for plans to construct hybrid systems for two wells that combine ion exchange and carbon filtration. That construction could now be delayed.

“It’s kind of out of the blue, like, ‘You know what, we changed our minds,’” Jones said.

Warminster had begun using an ion exchange system on one drinking well. Horsham Township has run its ion exchange system on one of the township’s public wells, also funded by the military, for more than two years.

A DEP spokesperson said Thursday, in response to questions from The Inquirer, that “DEP plans to sit down with those townships to discuss the issue.”

Officials at the three township water authorities say the system has already been proven to work. Warminster Municipal Authority contends that it had provided sufficient testing data and technical information with its permit application. The authority alleged that regional DEP employees were told by the Harrisburg office “to, in effect, ignore” all pilot study data previously collected by the three townships and “chose to completely … disregard” their results and other statistics showing the treatment systems work, according to the municipal authority’s appeal to the Environmental Hearing Board.

The DEP is following state and federal standards by requiring more pilot testing, said DEP spokesperson Elizabeth Rementer, citing the lead contamination crisis in Flint, Mich., as an example of why testing before making changes to water supplies is critical.

“Pilot studies are necessary to ensure treatment efficacy and fully evaluate any secondary adverse impacts to water quality,” she said.

Granular activated carbon filters were developed first to deal with PFAS contamination, but ion exchange systems are growing in popularity, said Christopher Bellona, an assistant professor at the Colorado School of Mines. While ion exchange systems can be more expensive, he said, the less frequent replacement of materials makes up for the difference.

Warminster’s coconut-based carbon filters last for about a month before the carbon has to go through a five-week process of being changed out and tested, Hagey said, estimating that the resin used in ion systems lasts “10 to 20 times longer” than carbon.

“The ion exchange held a lot of promise for us,” said Tina O’Rourke, business manager of the Horsham Water and Sewer Authority.

Officials said the DEP’s recent decision could make it even more costly: In Warminster, the municipal authority will have to shut down a chlorine-booster station that operates from one of the resin-equipped wells, build a new chlorine station on a different well, and buy more water from North Wales to make up for the loss of the resin-equipped well.

“It’s more money that our ratepayers have to pay for cleanup of PFAS contamination that they shouldn’t have to pay,” Hagey said.

O’Rourke is concerned about what the fate of its system will be after the township’s permit expires next month.

“It’s a tough pill to swallow, especially after piloting this for two years,” she said.