By Nick Nigro
By now, most water professionals have heard of PFAS, those pesky synthetic chemicals that can cause so much damage to human health but are so hard to get rid of. Thankfully, there are commonly available technologies that can remove them from tap water, but these solutions can be expensive, and not everybody has access to them. So how did PFAS get into the drinking water supply, and what can be done about them?
Why PFAS Are Here to Stay…for Now Anyway
The PFAS problem began in 1938 when DuPont researchers accidentally discovered polytetrafluoroethylene, a chemical that repels water and oil very effectively. It wasn’t until after World War II that the company got around to commercializing the discovery into a product called Teflon. Since then, other chemical manufacturers have developed a slew of PFAS to be used in everything from firefighting foams to waterproof clothing. PFAS are also frequently used in industry as a lubricant or surfactant.
What makes a PFAS a PFAS—and gives it such useful properties—is the chemical structure of the compound. The scientific name for the category of chemicals we refer to as PFAS is per- and polyfluoroalkyl substances. To belong to this group, a compound must have at least one carbon-fluorine bond. This bond is the strongest in nature and one of the reasons water professionals will be dealing with PFAS for many years to come. PFAS chemicals that were disposed of decades ago in long-forgotten landfills or wastewater ponds are still around today.
One of the most infamous examples of the problematic endurance of PFAS involves the Wolverine World Wide shoe manufacturer in Michigan. Wolverine used a PFAS compound supplied by 3M to waterproof the shoes and boots made in its Rockford, Michigan, facility. Sludge from the tannery was disposed of in a landfill owned by the company. Although the landfill was closed down decades ago, the tannery landfill was discovered much more recently to be a source of PFAS in the local water supply, leading to a slew of lawsuits, some of which are ongoing.
The PFAS Keep Coming
The other reason PFAS are here to stay is because they are so useful, and new PFAS can be produced to replace PFAS that are determined to be toxic. There are over 5,000 PFAS compounds known today, and since they are all similarly structured, it is generally believed that they all have a similar impact on human health and the environment. The question is, to what degree?
While all PFAS contain at least one carbon-fluorine bond, studies suggest that the number of bonds in a chemical has an impact on toxicity. In general, long-chain compounds are those that contain seven or more bonds. Short-chain compounds are those that contain fewer than seven. Available toxicity assessments indicate that long-chain PFAS compounds are likely to be more toxic than short-chain compounds.
Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS), for example, are two long-chain, highly toxic PFAS compounds that were voluntarily discontinued in the United States years ago. (These compounds are still imported into the U.S. via commercial and industrial products.) The original U.S. manufacturers of PFOA and PFOS have created short-chain compounds to replace their more toxic predecessors. PFOA was largely replaced with a compound referred to as GenX that contains six carbon-fluorine bonds, and PFOS was replaced with perfluorobutane sulfonic acid (PFBS), a compound that contains four carbon-fluorine bonds. The U.S. EPA recently completed toxicity assessments for GenX and PFBS. While these compounds are considered toxic, the resulting health advisories are set at much higher levels than those for PFOA and PFOS.
As consumers continue to want products that are waterproof, nonstick, and oil resistant, PFAS will continue to be used. As some PFAS are more tightly regulated, other PFAS will take their place. A few states are attempting to outlaw products that include PFAS—see California’s most recent ban on PFAS in textiles and cosmetics—but laws like this aren’t gaining much traction at the federal level, since not enough is known about the relative toxicity values of the PFAS family of compounds. So, PFAS are here to stay.
Why Wastewater Treatment Isn’t the Answer
Today’s water-treatment systems are highly sophisticated and can address contamination from a wide variety of chemicals and biological organisms. Unfortunately, traditional wastewater treatment does not remove PFAS from wastewater. If you’ve discovered PFOA or PFOS in your water and can’t find the source, work with your local wastewater treatment partners to look for PFAS precursors in wastewater influent. Here are a few sources to look for:
Local industry. The first place most think to look is at the businesses in the affected area. Chemical manufacturers are the obvious possible culprits, but other types of businesses, such as metal finishing and textile manufacturers, can be a source.
Storm water runoff. This runoff may be from an industrial site where PFAS is manufactured or used, but there are other sources to consider. For example, Boston has gone so far as to prohibit AstroTurf in public parks due to the potential of PFAS (and a variety of other compounds) in runoff from these sites.
Airports and military sites. Aqueous film-forming foam, the foam used to fight Class B chemical fires, often contains PFAS. Runoff from sites where this foam has been used, either in an emergency or training exercises, typically hits the storm sewer system and is then sent to the local wastewater treatment facility.
Landfill leachate. As liquid (e.g., rain, condensation, or liquid waste) passes through a landfill, it can leach PFAS from solid waste containing PFAS. This contaminated leachate is typically sent to the local wastewater treatment facility, where it can enter the water supply.
Testing Wastewater for PFAS
One of the other challenges with PFAS in wastewater is testing a liquid that contains varying degrees of solids. The test methods for drinking water (Method 533 and Method 537.1) validated by the U.S. Environmental Protection Agency (EPA) aren’t appropriate, so the agency is actively working on two test methods in conjunction with other organizations, including the U.S. Department of Defense and authorized labs:
- Draft Method 1633 can quantitate 40 unique PFAS compounds across a wide range of solid and aqueous matrices, including wastewater, and leachate.
- Draft Method 1621 is a screening method designed to quantify total organic fluorine at the parts-per-billion level in all aqueous matrices.
Once finalized, methods 1633 and 1621 will support a variety of EPA initiatives to monitor—and eventually regulate—PFAS in non-potable waters. In fact, even though Method 1633 has not yet passed the multi-lab validation phase, the EPA issued a memo requiring it for National Pollutant Discharge Elimination System permitting. Method 1621 may also be used.
Total oxidizable precursor (TOP) assay is another test method. Some wastewater treatment processes can convert PFAS precursors into terminal PFAS such as PFOA and PFOS. This method oxidizes these precursors to turn them into terminal PFAS compounds that can then be measured. The increase in PFAS measured after the TOP assay oxidation relative to preoxidation levels is a worst-case estimate of the total concentration of PFAS precursors present in a sample. This analysis is particularly useful in forensic studies designed to identify the source of elevated PFAS levels in finished drinking water.
Water Filtration’s Catch-22
Thankfully, there are solutions, such as granular activated charcoal (GAC) water filtration, that have been shown to remove PFAS from drinking water supplies. Some municipalities are spending thousands to implement such solutions locally.
However, while GAC filtration provides immediate protection for the public, it’s not without its drawbacks. It can be expensive. Moreover, activated carbon filters do not destroy PFAS; they only contain it. Municipalities are then faced with the problem of disposing of the contaminated filters. Incineration has been shown to spread PFAS particles through stack emissions, and sending the filters to the landfill just recycles the PFAS back into the water supply through the leachate.
However, many companies and research facilities are working on ways to destroy PFAS in the environment, including the cultivation of PFAS-eating microbes and chemical “decapitation.” Until then, water professionals will need to monitor their water supply and search for the source of PFAS when elevated levels are discovered. Testing wastewater influent and effluent is often the place to start your forensic effort.
About the author
Nick Nigro is a product manager at Pace Analytical, responsible for PFAS operations at seven emerging contaminant centers of excellence within Pace’s nationwide network of environmental testing laboratories.
About the company
Pace® has over four decades of experience in advancing science and informing decision-makers. Pace® people support our partners with data, expertise, and local-level service backed by a national laboratory network. To read more about our commitment to making the world a safer, healthier place through science, visit www.pacelabs.com.