Treatment Technology Performance at EPA MCL Levels
EPA’s 4 ng/L PFOA/PFOS MCLs require treatment technologies capable of reducing PFAS to very low concentrations. Performance comparison at these ultra-low levels is essential for technology selection, as efficiency can differ from performance at higher PFAS concentrations.
GAC Performance at Low Concentrations
Granular activated carbon achieves >90% PFAS removal in most applications, but breakthrough curves show PFAS emerging above MCLs well before GAC exhaustion indicators such as TOC. Carbon replacement frequency increases substantially to maintain compliance at 4 ng/L targets.
Ion Exchange Consistency
Strong-base anion exchange resins maintain more consistent PFAS removal efficiency across their service life compared to GAC, with sharp breakthrough curves predictable from column volume calculations. Single-use PFAS-selective resins achieve MCL compliance more reliably than GAC for very low target concentrations.
Reverse Osmosis Reliability
RO achieves the most consistent PFAS removal (>99%), providing the greatest margin of safety against MCL exceedances. However, RO costs, water waste ratios, and mineral reduction make it less attractive for whole-house treatment compared to targeted point-of-use applications.