Fairfax Water and PFAS

Last Friday the Potomac Watershed Roundtable resumed in person meetings with a meeting at the H.I. Mooney Wastewater Treatment plant in Woodbridge and hosted by the Prince William Service Authority. I’ve toured the plant a couple of times, so my real interest was the speakers. The talk from Fairfax Water- From Source to Tap: Fairfax Water’s Insights on PFAS and Source Water Protection was the big draw for me. Susie Miller the Manager of Public Affairs and Greg Prelewicz the Manager Planning gave a great presentation that really summed up the challenges facing Fairfax Water and all drinking water suppliers. Let me see if I can give you the highlights and do their talks justice.

Fairfax Water is the largest drinking water provider in the Commonwealth of Virginia and one of the  largest in the nation. They supply drinking water to 2 million residents (1.13 million retail customers and 988,000 residents through their wholesale customers like our very own PWSA). Fairfax Water owns and operates the two largest water treatment facilities in Virginia with an average daily water production of 167 million gallons and a combined maximum capacity of 376 million gallons per day. The James J. Corbalis Jr. treatment plant is at the northern tip of Fairfax County and the Frederick P. Griffith Jr. treatment plant is on the northern edge of the Occoquan Reservoir in Fairfax County.

Last summer the U.S. Environmental Protection Agency (EPA) announced drinking water interim health advisory levels for four contaminants widely found in drinking water that are part of a group of compounds called PFAS (per- and polyfluoroalkyl substances) commonly referred to a "forever chemicals" because they do not breakdown in the environment.  Drinking water health advisories provide information on contaminants but are non-enforceable and non-regulatory. EPA plans to propose a PFAS maximum contaminant level (MCL) for some or all these chemicals under the Safe Drinking Water Act in March 2023. That level will be enforceable.

As EPA develops this proposed rule, the agency is also evaluating additional PFAS beyond the chemicals in the health advisory and considering actions to address other groups of PFAS. This is a very dynamic environment. The health advisories addressed four PFAS chemicals: perfluorooctanoic Acid (PFOA) and Perfluorooctane Sulfonate (PFOS), and the chemicals that have replaced them in the United States in recent years, GenX and perfluorobutane sulfonate (PFBS). Fairfax Water along with all other water utilities in the United States is going to have to comply with the regulations when they go into effect.

As you can see in the chart below, the MRL, the minimum reportable level, is the minimum level that you can reliably detect a chemical using a specified analytical method. While scientists’ ability to detect lower and lower levels of chemicals is evolving very quickly, it still has not reached the level in the health advisory for PFOS and PFOA. Currently, the MRL of those chemicals is 4 parts per trillion (or nanograms per liter); and because PFAS is ubiquitous in our environment, it is extremely difficult to prevent contamination of a sample.

There are thousands of PFAS chemicals, and they are found in many different consumer, commercial, and industrial products. This category of chemical has been widely used for over 80 years mainly for their ability to repel oil, grease, water, and heat. We are all exposed to PFAS in everyday life. Stain-resistant carpeting, nonstick cookware, grease- and water-proof food packaging, fabric softeners, waterproof clothing, cosmetics, and through our diet and water. These forever chemicals have remained in the soil, been taken up into plants, and made their way into animals who eat those plants. Ms. Miller told us that diet is responsible for 66%-72% of exposures to PFOA and PFOS (the two chemicals that have been most widely studied). In some cases, they have also leached into both surface and groundwater. Water is responsible for 22%-25% of exposures.

In anticipation of future regulations, Fairfax Water hired an independent lab to test their water using current EPA-approved methods that can detect PFAS at much lower concentrations than previous methods. Fairfax Water also participated in the Virginia Department of Health (VDH) Occurrence Study that was completed in 2021. However, the practical quantitative limit was 4 ppt, significantly above the health advisory limit.

Some of Fairfax Water’s results for PFOS and PFAS were above the MRL and the ones below cannot be quantified down to the EPA’s Interim health advisory levels for PFOS and PFOA. Though, there is no knowing what the ultimate level for the EPA regulations will be, it is expected that EPA will propose both a non-enforceable Maximum Contaminant Level Goal (MCLG) and an enforceable standard, or Maximum Contaminant Level (MCL) or Treatment Technique.

PFAS dissolves in water, and combined with their chemical properties means that traditional drinking water treatment technologies used at water treatment plants are not designed to remove them, it is believed though, that carbon filtration does remove some. Activated carbon adsorption, ion exchange resins, and high-pressure membranes have been found to remove PFAS from drinking water, especially Perfluorooctanoic acid (PFOA) and Perfluorooctanesulfonic acid (PFOS), which have been the most studied of these chemicals.

Nanofiltration or reverse osmosis have been found to be extremely effective at removing PFAS. This technology depends on membrane permeability. Reverse osmosis membranes are tighter than nanofiltration membranes. A standard difference between the two is that a nanofiltration membrane will reject hardness to a high degree, but pass salts; whereas reverse osmosis membrane will reject salts to a high degree (which is why it’s used for desalinization).

According to Mr. Prelewicz, reverse osmosis, the most effective method, has a high capital cost (estimated to be $3 billion when all the other fixed assets of Fairfax Water are $2 billion) and is very energy intensive (has a high operating cost in the form of energy necessary to push the water through the membranes). In addition, about 20-25% of water would be lost as a waste stream. That would be up to 55 million gallons a day. In addition the waste stream containing the PFAS would have to be disposed of in a way that does not contribute of the problem. Fairfax Water is a passive receiver of PFAS.  They do not produce or manufacture PFAS.  Instead, these chemicals are present in source waters that are treated to produce drinking water.  However, if they need to dispose of PFAS removed from water they could be responsible for future contamination. 

Keeping PFAS out of the source water tis the real challenge when PFAS is in our diet and wastewater is reused in our drinking water supplies. Source water protection will have to part of the solution. With that in mind both Fairfax Water has developed an analytic framework which provides information about PFAS across the environment. This information will help them better understand potential PFAS sources in our communities and develop a road map to continue proving safe drinking water to Northern Virginia. Stay tuned for the EPA announcement and timeline coming in March 2023.