PFAS Pilots: Strategic Planning

In April 2024, the U.S. Environmental Protection Agency (EPA) finalized a drinking water rule establishing maximum contaminant levels (MCLs) for six PFAS compounds — PFOA, PFOS, PFHxS, PFNA, HFPO-DA (GenX), and PFBS — plus a hazard index for certain PFAS mixtures. In May 2025, EPA announced it will retain only the MCLs for PFOA and PFOS (4 ppt each) while rescinding and reconsidering the others and extended the compliance deadline for PFOA and PFOS from 2029 to 2031.

Even with this narrower scope, utilities across the United States are still moving forward with treatment planning. PFOA and PFOS are among the most widely detected PFAS in drinking water sources, and the final limits remain among the most stringent in the world. In addition, many states are maintaining or pursuing their own PFAS limits beyond PFOA and PFOS, and future federal regulation of additional PFAS is still possible. As a result, utilities that design for flexibility now will be better positioned to meet both today’s and tomorrow’s requirements.

For utilities preparing treatment upgrades, the stakes are high. PFAS occur in a wide range of water sources and behave differently depending on their chemical structure. Short-chain compounds can be more difficult to capture than their long-chain counterparts, and sitespecific factors such as seasonal changes in water chemistry, co-contaminants, or operational constraints can influence treatment performance. Selecting a system without accounting for these variables can lead to costly mistakes, underperformance, and even non-compliance.