“Forever chemicals” leave the op-ed page the day a water utility pours concrete, sets steel pressure vessels on it, and fills them with carbon or resin. PFAS — per- and polyfluoroalkyl substances, the family behind nonstick coatings, stain-proof fabric, and firefighting foam — are built around carbon–fluorine bonds that barely break down in nature, which is exactly why they turn up in rivers and wells decades later. The applied point is not a new molecule or a lab breakthrough. It is filtration chemistry that already exists, scaled to a city and run every hour of every day.
The engineering comes down to a short list. In its 2024 drinking-water rule, the U.S. Environmental Protection Agency named the best available technologies for PFAS: granular activated carbon, PFAS-selective ion exchange resin, and reverse osmosis or nanofiltration. Activated carbon is a porous material, often made from coal or coconut shells, with an enormous internal surface area; PFAS molecules stick to it as water trickles through until the bed fills up and contaminants start to “break through,” at which point the carbon is swapped out and sent to be reactivated or disposed of. Ion exchange resin works more like a magnet tuned for charged PFAS molecules, and it tends to do the same job in smaller, faster vessels. Reverse osmosis pushes water through membranes fine enough to reject PFAS, but it costs more and leaves a concentrated waste stream to deal with. Most big utilities pick carbon or resin, and they usually pilot several products for months before committing.
Delaware fills 42 tanks with carbon
Delaware shows the carbon route at full size. Veolia’s Stanton Water Treatment Plant near Wilmington opened its PFAS system in June 2025: a $35 million, 17,600-square-foot building wrapped around 42 pressure vessels, each about 22 feet tall and holding 40,000 pounds of granular activated carbon. The vessels went in first and the building was raised around them. Equipment maker Newterra supplied them as 21 paired “lead-lag” trains, so water passes through one vessel and then a backup; when the lead bed is spent, operators change its carbon while the second vessel keeps guarding the tap. The plant can treat up to 30 million gallons a day drawn from two nearby rivers for more than 100,000 New Castle County residents. Veolia’s 2024 water quality report had shown PFAS at Stanton averaging as high as 29 parts per trillion; the company says finished water now tests at non-detectable levels, years ahead of the federal deadline.
Colorado bets on resin
Colorado shows the resin route. South Adams County Water and Sanitation District cut the ribbon on its Klein Enhancement Project in Commerce City in late July 2026 — an $86 million ion exchange plant that raises the Klein facility’s PFAS treatment capacity to 18 million gallons a day, fed by 13 production wells and serving roughly 70,000 to 75,000 people. The district calls it the biggest infrastructure investment in its history and Colorado’s largest ion exchange PFAS plant. It was a seven-year effort through pilot testing, design, construction, and commissioning, finished ahead of schedule and under budget while customers kept getting water. Funding leaned on the Bipartisan Infrastructure Law and Colorado’s Drinking Water State Revolving Fund; design partner Brown and Caldwell says it helped the district line up nearly $90 million in low-interest loans and grants. In Southern California, the Orange County Water District and Yorba Linda Water District have run a 25-million-gallon-a-day ion exchange plant since late 2021, and the regional program has brought dozens of PFAS-contaminated wells back into service.
Parts per trillion became a budget line
Regulation is what turned these into budget lines. The EPA’s April 2024 rule set enforceable limits of 4 parts per trillion each for PFOA and PFOS, the two best-known PFAS, plus limits for four more, with compliance due in 2029. In May 2026 the agency proposed keeping the PFOA and PFOS limits while letting systems apply for two extra years, to 2031, and separately proposed dropping the limits for the other four. Neither proposal was final as of early October 2026. Plants like Stanton and Klein were designed against the stricter version and are already running, which is part of the story: once the vessels are full and the water is clean, a utility doesn’t switch them off because Washington moved a date. The open problem is the back end. Spent carbon and resin hold concentrated PFAS, and how to destroy those chemicals for good, rather than just move them, is still a live research and permitting fight.
For appliedscience.com, the hook is simple. Forever chemicals became an engineering problem with a price tag the moment limits were written in parts per trillion and utilities had to hit them. Stanton and Klein aren’t demonstrations. They are tanks of carbon and resin that tens of thousands of households already drink through every day. The science that already shipped is adsorption chemistry, pilot-tested media, lead-lag vessels, and a rate base that paid for it.
Sources
- Veolia — Stanton plant opening (June 2025)
- WHYY — Stanton PFAS levels and treatment
- Newterra — Stanton case study
- Smart Water Magazine — Klein, Commerce City
- Rocky Mountain Construction — Klein completion
- Yorba Linda Water District — ion exchange plant
- EPA — proposed PFOA/PFOS compliance extension (May 2026)
- EPA — proposed rescission for four other PFAS (May 2026)
- EPA — best available technologies for PFAS (2024)