New PFAS in Drinking Water Regulations

Allie Goldberg, PE, Project Manager II, Weston & Sampson

Since October 2020, Massachusetts water systems were required to comply with the Massachusetts Department of Environmental Protection (MassDEP) Maximum Contaminant Level (MCL) of 20 parts per trillion (ppt) for the sum of six per- and polyfluoroalkyl substances (PFAS) compounds in drinking water. These compounds include:

• Perfluorooctanoic acid (PFOA)
• Perfluorooctane sulfonic acid (PFOS)
• Perfluorononanoic acid (PFNA)
• Perfluorohexane sulfonic acid (PFHxS)
• Perfluoroheptanoic acid (PFHpA)
• Perfluorodecanoic acid (PFDA)

In April 2024, the U.S. Environmental Protection Agency (EPA) announced the final National Primary Drinking Water Regulation (NPDWR), establishing significantly lower allowable limits for individual PFAS compounds. The new federal limits are:

• PFOA: < 4 ppt
• PFOS: < 4 ppt
• PFNA: < 10 ppt
• PFHxS: < 10 ppt
• Hexafluoropropylene Oxide (HFPO) Dimer Acid (HFPO-DA, known as "GenX"): < 10 ppt
• Hazard Index for PFNA, PFHxS, perfluorobutane sulfonate (PFBS), and GenX

Communities across Massachusetts will be required to comply with these stricter federal regulations by 2029, implementing necessary actions to reduce PFAS concentrations in drinking water to meet the new standards. 

The Role of PFAS Pilot Programs
Recent pilot programs have demonstrated that the new and more stringent EPA regulations can have a significant impact on the cost and efficiency of PFAS treatment strategies. In particular, media replacement and operational costs are expected to increase as treatment requirements become more rigorous.

Understanding the interaction between existing upstream water treatment processes, overall water quality, and PFAS removal technologies is essential in designing an effective and cost-efficient solution. Conducting PFAS pilot studies before full-scale implementation can provide critical insights into:

• Estimating PFAS breakthrough based on regulatory limits.
• Evaluating the performance of different treatment media.
• Selecting the most cost-effective and efficient PFAS removal system for full-scale implementation.
• Estimating media replacement costs and frequencies to optimize long-term operations.

For a pilot study to be effective, it should be designed to simulate full-scale operational conditions, considering key parameters such as:

• Hydraulic Loading Rate (HLR)
• Empty Bed Contact Time (EBCT)
• Influent Water Quality

By closely replicating real-world conditions, pilot studies provide communities with projections of when PFAS compounds are expected to breakthrough, helping municipalities plan proactively for regulatory compliance and financial sustainability.