{"id":89121,"date":"2026-06-22T08:40:53","date_gmt":"2026-06-22T08:40:53","guid":{"rendered":"https:\/\/www.ampac1.com\/blog\/does-reverse-osmosis-remove-pfas\/"},"modified":"2026-06-22T08:40:53","modified_gmt":"2026-06-22T08:40:53","slug":"does-reverse-osmosis-remove-pfas","status":"publish","type":"post","link":"https:\/\/www.ampac1.com\/blog\/does-reverse-osmosis-remove-pfas\/","title":{"rendered":"Does Reverse Osmosis Remove PFAS? What Commercial Operators Need to Know"},"content":{"rendered":"

If your facility draws from groundwater near a military base, airport, or agricultural area with a history of AFFF use, PFAS is no longer a theoretical concern \u2014 it’s a procurement decision. The question facility managers and water treatment engineers are asking right now: does reverse osmosis actually remove PFAS well enough to meet the new EPA limits? Short answer is yes, with caveats that matter at commercial scale.<\/p>\n

What PFAS Actually Are<\/h2>\n

Per- and polyfluoroalkyl substances (PFAS) are a family of roughly 12,000 synthetic chemicals used in industrial and consumer products since the 1940s \u2014 non-stick coatings, firefighting foam, food packaging, stain-resistant textiles. The carbon-fluorine bond is one of the strongest in organic chemistry, which is why PFAS persist in soil, water, and human tissue essentially indefinitely. The most studied compounds \u2014 PFOA (perfluorooctanoic acid) and PFOS (perfluorooctane sulfonic acid) \u2014 are linked to kidney and testicular cancer, thyroid disruption, and immune suppression at low concentrations. GenX chemicals (HFPO-DA) were introduced as PFOA replacements and are now under regulatory scrutiny for similar reasons.<\/p>\n

EPA’s April 2024 PFAS MCL Rule<\/h2>\n

In April 2024, EPA finalized the first federal maximum contaminant levels (MCLs) for PFAS in drinking water under the Safe Drinking Water Act. Public water systems have until 2029 to complete initial monitoring and until 2031 to achieve full compliance<\/strong>. The enforceable limits are tighter than most water treatment professionals expected:<\/p>\n\n\n\n\n\n\n\n\n\n\n
PFAS Compound<\/th>\nEPA MCL<\/th>\nTypical RO Rejection Rate<\/th>\nNotes<\/th>\n<\/tr>\n<\/thead>\n
PFOA<\/td>\n4 ppt (ng\/L)<\/td>\n95\u201399%<\/td>\nLonger-chain; well-rejected by quality membranes<\/td>\n<\/tr>\n
PFOS<\/td>\n4 ppt (ng\/L)<\/td>\n95\u201399%<\/td>\nLonger-chain; well-rejected by quality membranes<\/td>\n<\/tr>\n
HFPO-DA (GenX)<\/td>\n10 ppt (ng\/L)<\/td>\n90\u201397%<\/td>\nShorter-chain; rejection varies by membrane type<\/td>\n<\/tr>\n
PFNA<\/td>\n10 ppt (ng\/L)<\/td>\n95\u201399%<\/td>\nLonger-chain; similar behavior to PFOA<\/td>\n<\/tr>\n
PFHxS<\/td>\n10 ppt (ng\/L)<\/td>\n88\u201395%<\/td>\nShorter-chain; may require lower recovery rates<\/td>\n<\/tr>\n
PFBS<\/td>\n2,000 ppt (ng\/L)<\/td>\n80\u201392%<\/td>\nShort-chain; highest MCL, lowest rejection rates<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

The 4 ppt limit for PFOA and PFOS is effectively at the limit of detection for many labs. That means treatment systems need to be engineered for consistent, high-rejection performance \u2014 not just average performance.<\/p>\n

How RO Removes PFAS: The Mechanism<\/h2>\n

Size exclusion<\/strong> is the primary driver. RO membranes have pore sizes in the 0.0001\u20130.001 micron range. PFAS molecules \u2014 even shorter-chain compounds \u2014 are physically too large to pass through intact membrane material. Water molecules pass through; PFAS molecules do not.<\/p>\n

Charge repulsion<\/strong> adds a second layer of rejection. Most PFAS compounds are anionic (negatively charged) at drinking water pH. The polyamide membrane surface also carries a negative charge, creating electrostatic repulsion that pushes PFAS toward the concentrate stream. This is why PFAS rejection rates are higher at neutral-to-alkaline pH.<\/p>\n

Together, these mechanisms achieve 90\u201399% rejection for PFOA and PFOS with properly specified FILMTEC or equivalent membranes. Shorter-chain PFAS (PFBS, PFHxS) see lower rejection rates \u2014 typically 80\u201395% \u2014 because both the size exclusion and charge effects are weaker with smaller molecules.<\/p>\n

NSF\/ANSI 58 Certification: What Commercial Buyers Should Ask For<\/h2>\n

NSF\/ANSI 58 is the certification standard for point-of-use RO systems. It covers material safety and structural integrity, but the PFAS-specific testing protocol is an optional annex \u2014 vendors must explicitly test and pass the PFAS reduction claim to make it on their literature. This distinction matters for procurement.<\/p>\n

When evaluating commercial RO systems for PFAS removal, ask the manufacturer directly: does this system carry NSF\/ANSI 58 certification specifically for PFAS reduction, or does it carry general NSF\/ANSI 58 certification? They are not the same thing. AMPAC systems use FILMTEC membranes<\/strong>, which are among the most tested polyamide thin-film composite membranes for PFAS rejection in commercial literature.<\/p>\n

Pre-Treatment: The Part That Gets Underspecified<\/h2>\n

RO membranes are the last line of defense, not the first. PFAS-contaminated groundwater frequently carries co-contaminants that will foul or damage membranes before PFAS removal becomes the limiting factor.<\/p>\n

Common co-contaminants in PFAS-impacted wells include:<\/p>\n