The U.S. Environmental Protection Agency (EPA) recently announced its proposal for what would be the first-ever national drinking water standards for PFAS. This news likely triggered several questions about what this means to the drinking water industry. Here, we will address some of the most important ones.
What’s the first thing people need to know in general about these draft MCLs?
First, the EPA’s announcement is a draft regulation, so it is not yet enforceable by law. But these MCLs, or maximum contaminant levels, are slated to become formal regulations by year’s end. That’s not to say they will be immediately enforceable, as there will be a grace period. Adherence to the new rules is expected to begin no sooner than three years after the rule is finalized.
The limits are driven by health risks, so while they are small values — in the parts per trillion (ppt) — they do represent achievable targets.
What is meant by “achievable targets”?
The levels have been set at 4ppt for both PFOA and PFOS. The other four PFAS addressed by this regulation are PFNA, PFHxS, PFBS, and GenX, which follow an easy-to-understand blended Hazard Index. The good news is that these levels are achievable with the correct treatment technology under the appropriate design and implementation. And importantly, they are accurately measurable at these levels with existing analytical technology.
How many sites will be impacted across the U.S.?
The EPA estimates approximately 66,000 water providers will be subject to the rule and anticipates about 3,400 to 6,300 systems to exceed one or more MCL. Some water providers already have treatment systems in place. In fact, Calgon Carbon has been removing PFAS from water for more than 20 years, helping facilities to consistently achieve non-detectable PFAS levels. Providers with no treatment systems in place will have to treat the source water to remove PFAS or find an alternate, non-contaminated water source.
What treatment technologies are available?
There are three commonly accepted treatment technologies recommended by the EPA: granular activated carbon (GAC), ion exchange resin (IX), and high-pressure membranes, also referred to as reverse osmosis (RO) filtration. Each option comes with its own advantages and disadvantages, as noted below:
GAC – Granular activated carbon is a proven technology, having been in use for more than 20 years to remove PFAS. It’s generally the lowest-cost treatment option, and with proper reactivation of the spent carbon, the PFAS can be removed from the GAC and destroyed through a properly controlled, high-temperature thermal reactivation process. GAC also provides the additional benefit of removal of a wide array of other organic compounds from the water. The downside to GAC is that it has the largest physical footprint of the three treatment technologies.
IX – Ion exchange resin systems generally require a smaller footprint than GAC systems because they require less contact time and a have a higher capacity for PFAS. The downside, however, is that you don’t get removal of any other organics and many resins are not capable of withstanding disinfection; should one be necessary, it would destroy the resin. Resin is also more costly than GAC, both initially and on the back end with regard to disposal costs.
RO – Reverse osmosis is highly effective at removing particles greater than 0.1 nanometers, which includes PFAS. But it’s an expensive technology, consumes a lot of energy, creates a problematic concentrated waste stream, strips the water of many healthy minerals, and reduces the pH of the water, making it more corrosive to plumbing systems.
