Per- and polyfluoroalkyl substances (PFAS) are a group of over 12,000 synthetic chemicals that have been used in manufacturing and consumer products since the 1940s. They don’t break down in the environment — which is why they’re called “forever chemicals” — and they accumulate in drinking water supplies, human tissue, and wildlife. In 2024, the EPA set the first-ever enforceable maximum contaminant levels (MCLs) for PFAS in public drinking water, setting limits as low as 4 parts per trillion (ppt) for PFOA and PFOS. Reverse osmosis is one of the few treatment methods consistently shown to reduce PFAS concentrations to below detection limits.
What Are PFAS and Where Do They Come From?
PFAS include compounds like PFOA (perfluorooctanoic acid), PFOS (perfluorooctane sulfonate), PFNA, PFHxS, HFPO-DA (GenX), and thousands of related structures. Common sources of PFAS contamination in drinking water:
- AFFF firefighting foam — used at military bases and airports for decades; a primary source of PFAS in groundwater near these facilities
- Industrial discharge — from facilities manufacturing PFAS-containing products: non-stick cookware, food packaging, stain-resistant textiles, and semiconductors
- Landfill leachate — PFAS-containing products disposed in landfills leach into groundwater
- Agricultural land application — biosolids (sewage sludge) used as fertilizer can contain PFAS that migrate into soil and groundwater
- Consumer products — carpets, upholstery, food packaging, and clothing treated with stain-resistant coatings contain PFAS that enter wastewater systems
2024 EPA PFAS Drinking Water Regulations
The EPA’s April 2024 final rule established legally enforceable MCLs for six PFAS compounds in public water systems:
| Compound | MCL (2024) | Health Concern |
|---|---|---|
| PFOA | 4 ppt (0.004 µg/L) | Cancer (kidney, testicular), immune effects, thyroid disease |
| PFOS | 4 ppt (0.004 µg/L) | Cancer, cholesterol effects, immune suppression |
| PFNA | 10 ppt | Reproductive effects, thyroid, immune |
| PFHxS | 10 ppt | Thyroid effects |
| HFPO-DA (GenX) | 10 ppt | Liver, kidney, immune effects |
| PFBS | 2,000 ppt (mixture) | Thyroid, developmental effects |
Public water systems have until 2029 to comply with these MCLs. Private well owners are not covered by this regulation and are responsible for their own testing and treatment.
Does Reverse Osmosis Remove PFAS?
Yes — reverse osmosis is one of the most effective treatment technologies for PFAS removal available at the point-of-use and point-of-entry scale. Studies consistently show RO membranes achieve 90–99% rejection of PFOA, PFOS, and related long-chain PFAS compounds. The mechanism is size exclusion and charge repulsion: PFAS molecules are relatively large and negatively charged, and thin-film composite RO membranes physically block their passage through the membrane.
| Compound | Typical RO Rejection Rate | Source |
|---|---|---|
| PFOA (C8) | 96–99% | Multiple peer-reviewed studies, NSF P473 testing |
| PFOS (C8) | 95–99% | Multiple peer-reviewed studies, NSF P473 testing |
| PFNA (C9) | 95–98% | EPA/NSF testing data |
| PFHxS (C6) | 90–97% | Shorter chain; slightly lower rejection than long-chain |
| PFBS (C4) | 80–95% | Short-chain; lowest rejection among regulated PFAS |
| HFPO-DA (GenX) | 92–97% | EPA and university studies |
Important: short-chain PFAS (4-carbon chains like PFBS) are rejected at lower rates than long-chain PFAS. If your water has significant short-chain PFAS contamination, a two-pass RO system or RO combined with activated carbon may be appropriate for maximum removal.
Other Treatment Options vs. RO
Three technologies are consistently shown to reduce PFAS in drinking water: reverse osmosis, activated carbon (granular activated carbon or carbon block), and anion exchange resin. Comparing them:
| Technology | PFAS Removal | Also Removes | Limitations |
|---|---|---|---|
| Reverse osmosis | 90–99% (most PFAS) | TDS, heavy metals, nitrates, bacteria, viruses | Produces reject water; slower flow rate |
| Granular activated carbon (GAC) | 50–90% (variable) | Chlorine, VOCs, taste/odor | Breakthrough risk; lower rejection of short-chain PFAS; bed exhaustion unpredictable |
| Anion exchange resin (PFAS-selective) | 95–99% (most PFAS) | Some other anions | Higher cost; regeneration or disposal of PFAS-loaded resin |
RO is the most versatile choice for most residential and commercial applications because it removes PFAS plus a broad spectrum of other contaminants (heavy metals, nitrates, TDS) in a single treatment stage. For applications where only PFAS removal is needed and high flow rate is critical, PFAS-selective anion exchange is sometimes preferred.
Point-of-Use vs. Whole House RO for PFAS
Point-of-use RO (under-sink) treats only the drinking and cooking water at one tap. For most households, this covers the majority of ingestion risk. However, PFAS can also be absorbed through skin contact during showering and bathing — an exposure pathway that point-of-use filters don’t address.
If PFAS levels in your water are significantly above MCLs, or if household members have elevated health risk (children, pregnant women, immunocompromised individuals), a whole-house RO system treats all water entering the home — including shower, bath, and laundry water — not just the drinking tap.
AMPAC USA RO Systems for PFAS Removal
AMPAC USA residential and whole-house reverse osmosis systems use FILMTEC™ thin-film composite membranes rated for 95–99% rejection of long-chain PFAS compounds. Systems range from under-sink point-of-use units to whole-house systems rated for 200–1,000+ GPD.
If your municipality has disclosed PFAS contamination above EPA MCLs, or if your private well has tested positive for PFAS, our engineering team can specify the appropriate treatment system for your flow requirements, PFAS concentration, and budget. PFAS remediation for commercial and industrial facilities (above 1,000 GPD) is also available — contact us for a custom system design.
Know your PFAS level? Share your water test results with our team and we’ll recommend the right treatment approach. Contact AMPAC USA or use our free Water Quality Assessment to get started.
Related: RO Water Quality: TDS, pH, and Conductivity Guide | Residential RO Systems | Whole House RO Systems