“I’ve been doing research on water quality and treatment for about 20 years now, so I’ve worked with several different emerging contaminants,” said Kyle Doudrick, an associate professor in the Department of Civil and Environmental Engineering and Earth Sciences. “There have been several urgent contaminant issues throughout our history, but I think it is safe to say that PFAS is the worst one we have had to deal with. It’s a real mess—and my lab has pretty much shifted all our time to dealing with it.”
Doudrick specializes in physical-chemical treatment technologies of emerging contaminants including micro- and nanoplastics and per- and polyfluorinated alkyl substances, or PFAS. His research focuses on identifying viable, cost-effective solutions to treat emerging contaminants and improve conventional water treatment processes.
His lab is currently working on multiple PFAS-related projects with funding from the Department of Defense, including a study of the leaching of PFAS from contaminated pavements into the surrounding environment.
“If you look at what happened at military installations during firefighter training with aqueous film forming foams (AFFFs), the pavement acts like a sponge, but not a very good sponge,” Doudrick said. “It soaks up the PFAS and then, over time—when it rains, for example—the PFAS seeps out and runs off the pavement into the surrounding environment. Then more rain causes it to percolate down through the soil into the groundwater. The result is a massive, growing contaminated area.”
Doudrick uses several analytical techniques to measure PFAS concentrations, including using PIGE for rapid and cost-effective identification of PFAS hotspots. One of his goals is to develop a predictive model to estimate the environmental load—or the amount and rate at which PFAS leaches into the surrounding environment—of contaminated pavements. He’s also testing how different sealants could reduce leaching into the environment.
PFAS can enter the water supply from multiple sources. A significant contributor includes treated wastewaters, including those of municipalities, chemical manufacturing plants, paper and textile mills, and metal plating—a source Doudrick references often.
Metal plating is a process used in automotive, aerospace, and defense industries, as well as in appliances, medical and dental products, and electronics. “The fumes are harmful,” Doudrick explained, “so a fume suppressant is mixed into the solution, and the active ingredient in that suppressant is PFAS. Metal plating companies have been using this stuff for decades and several have been directly discharging the waste into the municipal wastewater treatment facilities.”
Doudrick and his lab are studying the use of adsorptive membranes as effective filters for PFAS in drinking water, which the EPA recently began regulating. This technology could also be used to manage PFAS contamination at wastewater treatment facilities, which produce one of Doudrick’s biggest concerns: biosolids.
“In the process of treating wastewater, you create a sludge,” Doudrick said. That sludge—the solid waste that separates from liquids and settles to the bottom of sedimentation tanks at wastewater treatment facilities—becomes biosolids.
Class A biosolids are considered “nutrient rich” and safe, because they are free of pathogens or hazardous contaminants. They’re packaged, sold, and marketed as organic fertilizer, Doudrick said.
And they’re contaminated with PFAS.
“We’re literally taking all of these sources of PFAS, concentrating it in biosolids, and then we’re spreading it everywhere,” Doudrick said. “These biosolids are considered a sustainable product and they’ve been offered for free to farmers, who go pick it up and put it all over their land, and I’m telling you, it’s the worst idea we’ve ever had. We’re going to regret it. It will be our mercury or lead.”
Use of PFAS-laden biosolids in agriculture contaminates the soil, the produce grown within that soil, the feed grown from that soil and fed to farm animals, and the groundwater that is used to irrigate crops or serve as a source of drinking water for humans and animals. Farmers have begun educating themselves on the dangers of PFAS, but they aren’t the only consumers of biosolids.
“You can go to Home Depot and buy a bag of it,” Doudrick said. “They market it as ‘green’ or organic fertilizer, which it is, but the problem is, it contains PFAS and you spread it all over your yard—and your kids go play in that yard.”
Still, the question remains: If we could pull all the PFAS-laden biosolids from store shelves, extract it from pavement, remove it from the soil ... How would we dispose of these wastes?
Doudrick is working on that too.
Incineration is a common, recommended method of hazardous waste disposal. Trash, soil, and even those chunks of pavement excavated from military installations and airports are fed into incinerators that break the material down at extremely high temperatures. Doudrick’s lab is studying how incineration can help treat contaminated pavement at its end-of-life.
But the process has proven to be tricky when it comes to waste contaminated with PFAS.
Even when incinerated at 1,000 degrees Celsius (1832 Fahrenheit)—or more—PFAS don’t always break down completely. Incinerators produce exhaust. Incomplete destruction means PFAS end up expelled into the atmosphere through that exhaust.
In some cases where air quality measurements were taken near incinerators used to dispose of waste containing PFAS, “the results showed elevated levels of PFAS in the atmosphere and in soil deposits,” Doudrick said.
His lab is taking a different approach.
Doudrick mixes hydrated lime with waste containing PFAS before incineration. Lime enhances the incineration process, fully breaking down PFAS at lower temperatures—fewer than 450 degrees Celsius (842 degrees Fahrenheit). It also works as a scrubber to clean the exhaust before it’s released into the atmosphere.
“We can completely destroy it at lower temperatures,” Doudrick said. “And with lime, what you end up with are harmless minerals. It works quick, and it scrubs any other byproducts produced during incineration as well, so there are multiple benefits to using it as an additive.”
Through the 2021 Bipartisan Infrastructure Law, the federal government has pledged $10 billion toward addressing emerging contaminants, including PFAS, in water, and the Department of Defense recently requested $1.6 billion to clean up PFAS-contaminated sites. Interest in and funding for PFAS research has increased exponentially in recent years, creating a competition for graduate students and postdocs.
There is plenty of work to do. Doudrick believes the range of expertise on campus, the capabilities of rapid PIGE analysis and mass spectrometry, and the use of specialized incineration techniques makes Notre Dame uniquely positioned to tackle the inherent challenges of PFAS now and in the future.
“We are well-situated as a university with unique tools and expertise,” Doudrick said. “What we can do with PIGE is unique. We’ve developed all of the methods for it, and we’ve been able to build on it with new techniques and the ability to measure PFAS in a variety of ways. We have a lot of momentum now.”