Dyson and Smith detailed situations they are familiar with and the challenges they create, during a Webcast—Advancing PFAS Removal From Pilot to Plant—held on Sept. 3, 2028 that was hosted by the American Water Works Association (AWWA). The challenges outlined are:

The Right Absorbent

“There are a lot of technologies out there, many of them have been around for a long time,” said Dyson, who added that when “most people think about” PFAS removal, they focus on “absorbing different compounds out of the water” using granular activated carbon (GAC) to remove perfluorooctanesulfonic acid (PFOS). Anytime a carbon-based product like GAC is being used to remove PFOS it is being attached to the GAC absorbent material via the “hydrophobic tail” (which is a hydrophobic [water fearing] hydrocarbon chain of an amphiphilic molecule), and ion exchange via the ionized head that is present, Dyson said. Therefore, while it is important to consider how the PFOS is actually being removed, there are other matters to be aware of such as how GAC absorbent is going to react when a substance like PFOS is captured, according to Dyson.

PFOS has a higher solubility because they are “long-chain type products,” and “have a larger (hydrophobic) tail,” which is important because the hydrophobic tail is “one of the ways” absorbent materials removes those substances, Dyson said.

So, “it’s a little easier” for the absorbent materials “to pull those out of the water,” he said, quickly adding, there is also Perfluoropentanesulfonic acid (PFPS), “which was one of the constituents of the hazard index” (which is a method used by environmental agencies to evaluate potential non-cancer health risks). What is different about PFPS is it has “a smaller chain,” meaning “it's a little bit more soluble than PFOS or perfluorooctanoic acid (PFOA); so “it's a little harder to hold on to (and) retain within the absorbent material. In addition, when utilities “move actually over to that carboxylate side,” substances like PFOA and Perfluoropropionic acid (PFPA) and to its derivative, pentafluoropropionic acid are more difficult to remove. “So, removing these compounds and which ones will break through are really important to understand,” he said.

Furthermore, “there’s also reverse osmosis (RO),” which removes from 90 percent to over 99 percent of PFOS from drinking water, Dyson said. “But RO brings some unique challenges,” he said including dealing with “FORM fraction” (FORM frac) that is “more waste stream, (and) not really a drinking water aspect.”

There are also “short chain” substances the follow “the same rules,” but are “the harder ones to retain on the absorbent material,” he said. Nonetheless, there are “alternative(s) to GAC ion exchange and RO,” including a system called Aqua PRS technology developed by his company, Aqua-Aerobic Systems, Inc.

The Aqua PRS technology was developed to “be applied on a wide range of technologies to be an alternative to GAC ion exchange and RO” and “meet the needs across that large spectrum of industry and future markets,” Dyson said. What is unique about the Aqua PR PFOS removal system, and its absorbent material, is a microabsorbent is used, he said comparing it to utilization of GAC. “When GAC is used, they are large granules, but large portions of those granules are really unutilized,” he said.

Conversely, “powder activated carbon” is a much smaller particle than” GAC, so what Aqua-Aerobic Systems has done with its Aqua PRS technology is it has engineered “carbon-based material with some additives to it to be about one micron in size, and that does some major differences,” Dyson said. By creating a particle that is one micron, the surface area is increased “many, many times,” making that area from “hundreds, (to) thousands of times more available,” which makes one gram of GAC dramatically different” from one gram of air absorbent material, according to Dyson.

Unique Situations

Besides the effectiveness of absorbents, there are other situations that can impact water quality, according to Dyson who said, “There’s always something that you have to realize,” and cited some situations, including when contaminated water from a landfill is leaching into groundwater, a case he was involved with. He said “we knew their source was a landfill that was contributing to the contamination of their groundwater, so I decided that we should possibly analyze to see what other organic fluorine compounds were there.”

Dyson listed the actions taken such as data collection from absorbent material to determine contaminate levels and of removal. “The absorbent was loaded up,” and the PFOS collected was removed, but a “breakthrough” was not reached requiring the collection of additional data, he said

While the “absorbable organic fluorine test is not very sensitive, it does give an indication,” Dyson said. What was found there was over 2,000 parts per trillion of absorbable organic fluorine. In response, the absorbent implements decreased PFOS to non-detectable levels, meaning the PFOS was being absorbed out. “What’s important to realize is not only does the absorbent take out PFOS compound, but it’s taking out other constituents,” he said.

Furthermore, Smith of the CWWC discussed a unique situation he has experienced  in which PFAS substances and other contaminates might be present in water from blended water sources. The CWWC system contains 12,500 active water counts over 425 miles of water mains, said Smith adding the system is at “capacity now” and the CWWC purchase about six million gallons a day.

Of the plants operated by the CWWC, it is the Eton Water Plant that is now served by two sources—O'Neill Spring and Eton Spring—with Eton being the largest spring, but also the highest source of PFOS contaminate which fluctuates from 70 to 90 parts per trillion “depending on the weather,” Smith said. At those levels the CWWC decided to shut down its Eton plant “until we figured out what was what we were going to do moving forward,” he said.

However, it was Georgia’s Environmental Protection Division (EPD) that told the CWWC “blending” water from Eton Spring and O'Neill Spring “is an option” as long as the water produced remains below the 70 parts per trillion, said Smith. CWWC did as the EPD suggested and the bending has produced water with PFAS levels of below 40 parts per trillion, according to Smith.

Testing at that time recorded PFAS levels of about 40 parts per trillion. “Anything below 40 (parts per trillion) was non-detectable4, so pretty much all the other samples we got back from those systems were non-detectable,” he said.