PFAS in drinking water & groundwater.
The USGS estimates at least 45% of U.S. tap water contains PFAS. How it gets there, the contamination cases on the record, the technologies that remove it, and the utilities that have brought it to non-detect.
In your drinking water
PFAS reaches water supplies through industrial discharge, AFFF firefighting foam leaching from bases and airports, land-applied biosolids, and landfill leachate, and conventional wastewater treatment doesn't remove it, so it passes straight through. EPA ↗
A 2023 USGS study tested 716 sites and found PFAS in roughly 45% of U.S. tap water, ~75% likely in urban areas, ~25% rural, and it tested only 32 of the thousands of PFAS, so it's likely an underestimate. USGS ↗
In April 2024 the EPA set enforceable drinking-water limits (PFOA/PFOS at 4 ppt; PFHxS, PFNA, GenX at 10 ppt; a Hazard Index for mixtures). A May 2026 proposal would keep PFOA/PFOS but extend the deadline to 2031 and rescind the others, proposed, not final.See the regulations primer. EPA ↗
Groundwater plumes
PFAS is water-soluble, mobile, and doesn't biodegrade, so it spreads through aquifers and persists. The biggest sources are AFFF training and response sites (military bases, airports, refineries), fluorochemical plants, landfills, and biosolids. ITRC ↗
The contamination cases that defined the issue:
Cape Fear River. Chemours, NC
NC DEQ traced GenX in the Cape Fear River to the Chemours Fayetteville Works in 2017. A February 2019 consent order forced Chemours to stop discharging, supply replacement water, and build a barrier wall plus groundwater extraction and GAC.
Source ↗Parkersburg, WV. DuPont C8
DuPont's Washington Works released PFOA (C8) to air and the Ohio River for decades. The class-action settlement created the C8 Science Panel, which found PFOA 'probably linked' to six conditions including kidney and testicular cancer.
Source ↗Fountain–Widefield, CO. Peterson AFB
AFFF used at Peterson Air Force Base migrated into the Widefield Aquifer and contaminated municipal drinking-water wells south of Colorado Springs; CDPHE and ATSDR ran an exposure assessment.
Source ↗Oscoda, MI. Wurtsmith AFB
AFFF from the former Wurtsmith base migrated through groundwater into Clark's Marsh and surrounding lakes and rivers; a remedial investigation published in 2022, with 'do not eat' advisories for game and fish.
Source ↗Newburgh, NY. Stewart ANGB
PFOS-containing foam at Stewart Air National Guard Base contaminated Washington Lake, Newburgh's reservoir. The city switched water sources after EPA's 2016 advisory; the area was listed as a NY Superfund site, with the DoD named a responsible party.
Source ↗Hoosick Falls, NY. Saint-Gobain
PFOA from past plastics manufacturing contaminated the village water supply and private wells. NYSDEC added it to the state Superfund list in 2016, EPA to the federal list in 2017; GAC was installed on village wells and point-of-entry units on private wells.
Source ↗How PFAS is removed from water
EPA names four Best Available Technologies for the 2024 limits, granular activated carbon, anion exchange, reverse osmosis, and nanofiltration: EPA ↗
- Granular activated carbon (GAC). PFAS adsorbs onto porous carbon. Excellent for long-chain PFOA/PFOS; short-chain compounds break through faster. Spent carbon must be reactivated or disposed of.
- Ion exchange (IX) resin, anion resin grabs negatively-charged PFAS, smaller footprint, better on short-chain. Often run after GAC, in series.
- Reverse osmosis / nanofiltration, membranes physically separate PFAS, >90% across all chain lengths, but ~20% of the feedwater leaves as a concentrated waste stream.
Success stories
Water systems that have taken PFAS to non-detect, with the method and the result:
Sweeney WTP. Cape Fear PUA, Wilmington NC
Installed granular activated carbon (chosen over RO and IX in a pilot), online October 2022, ~3 million lbs of carbon, the largest GAC water plant in North Carolina. PFOA and PFOS now non-detect. $35.9M construction.
Source ↗Horsham Water & Sewer Authority, PA
After AFFF contamination from the former Willow Grove base, HWSA installed permanent GAC and ran early anion-exchange pilots. Reports meeting a 'Horsham Standard' of non-detect for PFAS since October 2019.
Source ↗Warminster Municipal Authority, PA
Two-stage train (GAC then ion-exchange resin) brings treated water to undetectable PFAS, one well had measured 251 ppt before treatment.
Source ↗Orange County Water District + City of Orange, CA
After a 2019 pilot testing 14 adsorbents, OCWD selected ion exchange and brought four treatment facilities online in October 2022 (~10.8 MGD combined).
Source ↗Wausau Water Works, WI
An anion-exchange system active December 2022 cut PFOA/PFOS below detectable levels; a permanent GAC system began operating November 2024.
Source ↗Hyannis (Barnstable), MA
GAC filtration begun in 2016 brought levels below the 2016 advisory; the Hyannis system reports no detectable PFAS as of early 2024.
Source ↗In progress, not yet finished: Brunswick County, NC (a low-pressure RO plant still under construction in 2025) and Tucson, AZ (GAC since 1994, with an advanced-oxidation upgrade due in 2026). Listed honestly as underway, not as completed wins.