PA Issues New Rule for PFAS Drinking Water Standards

On January 14, 2023, PADEP published a new rule, 25 Pa. Code Chapter 109, setting drinking water standards for two of the most commonly used PFAS substances, PFOA and PFOS.  The maximum contaminant levels (MCLs) for PFOA is 14 parts per trillion (ng/l or ppt) with an MCL goal of meeting 8 ng/l or ppt and PFOS is 18 ng/l or ppt with an MCL goal of 14ng/l or ppt.  The new rule applies to all public water systems (PWS) with compliance obligations to monitor quarterly for 4 consecutive quarters during the calendar year at each entry point to the distribution system beginning January 1, 2024 for PWS of 350 people or more and sampling beginning January 1, 2025 for PWS serving less than 350 persons.   Depending on the results, there is different monitoring requiring after the initial sampling. Thereafter, there are different monitoring rules and frequency depending on those initial results.   The rule also sets forth monitoring methods and approved treatment technologies, including granular activated carbon, ion exchange and reverse osmosis.