Chemical	Maximum Contaminant Level Goal (MCLG)	Maximum Contaminant Level (MCL)
PFOA	0	4.0  PPT
PFOS	0	4.0 PPT
PFHxS	10 PPT	10 PPT
HFPO-DA (GenX Chemicals)	10 PPT	10 PPT
PFNA	10 PPT	10 PPT

When the Environmental Protection Agency (EPA) issued the Final Rule on regulation of poly-fluoro alkaline substances (PFAS) last week I had three questions. The first was: “Good grief 4.0 parts per trillion (PPT). Are there analytical methods that can even determine such a low number”. So I hopped on the EPA website and checked out EPA’s Technical Support Documents (TSD) for the new Rule. And yes indeed EPA says analytical methods can detect PFOA and PFOS to 4 PPT.

For purposes of regulation these numbers are referred to as the Minimum Reporting Level (MRL). An MRL is the minimum quantification level EPA has determined can be achieved with specified confidence by a large number of laboratories in the U.S. It is different from the Detection Limit (DL) which a lot of environmental professionals toss around in their daily lingo about sample analysis. Laboratory methods are so sensitive for PFAS chemicals that they can detect even lower levels than EPA is satisfied are actually real results. For those of you who are casual readers of this blog and are not familiar with analytical methods, EPA develops and maintains analytical standards for laboratories to use in testing for chemicals. EPA Methods 533 and 537.1 are required for analysis of the PFAS chemicals in the table above.

The table may look like a whole bunch of alphabet soup to you and you may be wondering what all these chemicals are. I have a previous blog post that you can read if you want to learn a little more about what the popular press have dubbed “Forever Chemicals.” Just check out this link here (https://waterblogger.org/category/contaminants/ ). Originally EPA was only planning on regulating PFOA and PFOS but in 2023 they decided to expand regulation to a couple other PFAS chemicals. Specifically, Hexaflurorpropylene Oxide Dimer Acid (HFPO-DA) and its ammonium salt known as Genx chemicals, Perfluorononanoic acid (PFNA) and Perfluorohexane sulfonic acid (PFHxS). Regulatory limits for drinking water were also placed on these chemicals in the Final Rule.

So my first question was answered. My second question was: “How big a problem is this anyway? Are there really that many drinking water systems out there that are contaminated with PFAS?” The EPA’s TSD supplied the answer to that as well.  Back between 2013 and 2015 EPA required public water systems to conduct PFAS testing under the Unregulated Contaminant Monitoring Rule. Public water systems were monitored semi-annually. The study included all large and very large water systems which serve greater than 10,000 people. EPA found that 2 % of these systems are contaminated with PFOA and PFOS.

My third question was: “Are there any technologies that can actually treat drinking water to these very low levels of 4 PPT? And how much is this all going to cost?” Indeed the TSD confirmed that there are a number of technologies that can treat PFAS chemicals to reach those levels.

There are three main treatment technologies that can treat drinking water to the new MCLS: Granular Activated Carbon (GAC), Ion Exchange, and Reverse Osmosis/Nano Filtration

GAC uses a specially preprepared carbon media such as lignite or wood to adsorb contaminants from water. GAC media has the unique distinction among these technologies of being reuseable. Ion exchange employs an ion bead resin treated with an anion (typically chloride) as the media to exchange a strong bonding ion (fluoride in the case of PFAS) in water for a weaker one (chloride). Unfortunately the media once depleted has to be disposed of as a hazardous waste. Reverse Osmosis removes contaminants through forcing water through a membrane at high pressure. There are two effluents produced from the process. One is the treated water and the other is a brine which must be disposed of. The spent media can’t be reused and also has to be disposed of.

Another option was looked at too. Just replace the contaminated drinking water with a different source. This could mean switching to a surface water source if you have contaminated groundwater or drilling outside of the contaminated area for groundwater replacement.

Cost for the different treatment systems was calculated for both the capital cost of constructing the system and for annual operation and maintenance costs. Below are approximate costs that I attempted to ferret out from the graphs EPA provided in their TSD. Everything is in 2022 dollars so add on the annual inflation costs if you must.

The cheapest thing to do of course, if it is available to you, is to replace your drinking water source. Capital costs are estimated to be about $500K to $4M for capital costs and $5K to $100K annually for operation and maintenance.

Treatment System	Capital Cost	Operation & Maintenance Cost
GAC Large System	$5 – $100 M	$100 K – $10 M
GAC Small System	$100K – $1 M	$10K – $100K
Ion Exchange Large System	$2M – $100 M	$100K – $10 M
Ion Exchange Small System	$100K – $1M	$10K – $100K
Reverse Osmosis/Nanofiltration Large System	$5M – $100M	$200K – $12M
Reverse Osmosis/Nanofiltration Small System	$1M – $3M	$70K – $200K

All three of my questions answered. Yes these very low MCLs for PFAS in the new Rule can be analyzed for using EPA Methods 533 and 537.1, yes there are a good number (2 %) of public water systems that are contaminated with PFAS, and yes there are treatment technologies that can achieve MCLs, although it looks like they are pretty costly. If you have questions about the new Rule, please feel free to reach out to me and I will see if I can provide you with an answer from EPA’s lengthy documentation.