Understanding the PFAS MCLs, Part 2: Treatment and initial monitoring

In case you missed it, be sure to read the first article in our three-part series on the EPA’s draft PFAS MCLs. We’re asking: what does the MCL rule say and how will it impact drinking water utilities across the United States? 

In this second segment, I’m going to turn our focus to best-available treatment and initial monitoring requirements.

Best-available treatment

This one is kind of easy. For treatment technologies, EPA recognizes Granular Activated Carbon (GAC), Ion Exchange (IX), and high-pressure membranes – Reverse Osmosis (RO) or Nanofiltration (NF) – as best-available technologies (BAT). There are also non-treatment options which may be used for compliance such as replacing or blending a PFAS-contaminated drinking water source with a new uncontaminated source or purchasing compliant water from another system.

Some interesting items related to treatment: 

• First, there is no distinction between GAC, IX, RO, and NF.  EPA treats them as equally viable.  In my opinion, I would generally agree with that statement but site-specific water quality, flowrates, and criteria/constraints are best used to select the most appropriate technology.
• Second, the EPA specifically mentions reactivation of GAC as appropriate, along with thermal treatment (incineration) in general for all media.
• Third, the EPA suggests that potential hazardous waste disposal requirements may only increase public water system treatment costs marginally. This one may be the most questionable. With limited supply (locations and facilities), increased demand (quantity of media requiring disposal), and increasing transportation costs (fuel and labor), the qualifier of “marginal” may not be quite accurate.
• Lastly, very little is said about managing RO/NF concentrate.

What about Point of Use (POU) systems for households? 

GAC and IX have pre-existing certification through NSF/ANSI, however, POU RO is not currently listed as a compliance option because the ability for membranes to reduce to below proposed MCL values was not evaluated under the current NSF/ANSI certification standard.  Basically, the EPA is stating that they believe that through NSF/ANSI, or other certification, it is assumed that RO will become a compliance option for POU, but not right now.  And future standards may change the certification and required designs of such units. Not quite black-and-white.

Initial monitoring requirements

Of course, we know that the proposed MCL has been issued in the middle of the fifth Unregulated Contaminant Monitoring Rule (UCMR5). So, all large utilities and a number of smaller utilities are collecting PFAS data under that program. But the EPA is also recognizing that either through State-level requests or individual proactivity, other sampling efforts may have been or are being executed.

Initial monitoring requirements must be satisfied within the three years following rule promulgation.  However, we are all aware that if treatment is required, that will be too late. So, utilities should already be establishing initial monitoring.

Qualified data collected subsequent to January 1, 2019, from State-led or other appropriate occurrence monitoring using EPA methods 533 or 537.1 can be used to satisfy initial monitoring requirements. The data must be lower than the proposed rule trigger levels (more on this on Part 3, when I discuss Compliance Monitoring and trigger levels).

I want to emphasize that “or” – Method 533 or 537.1.  This is different than UCMR5 requirements.  Although UCMR5 is requiring both methods to obtain the largest number of PFAS for assessment purposes, the sampling under this proposed rule requires one or the other. User choice. Because the six proposed regulated compounds are analyzed by both methods.  

Groundwater systems serving greater than 10,000 connections and all surface water systems are initially required to monitor quarterly within a 12-month period for regulated PFAS. EPA is also proposing that smaller groundwater systems serving less than 10,000 connections are initially required to only monitor twice for regulated PFAS within a 12-month period, each sample at least 90 days apart.

In the final part of this series, I’ll discuss compliance monitoring and areas where the EPA is looking for feedback. Stay tuned.