S7E4: How can we eliminate PFAS?

In recent years, communities across Maine and the U.S. have discovered the presence of toxic chemicals called per- and polyfluoroalkyl substances, or PFAS, in their land and water. Also known as forever chemicals because they are difficult to destroy, PFAS have been incorporated in various products, including food containers, clothing, rugs, teflon pans, fabrics and dental floss, for decades. Emerging research, however, has linked PFAS to several health issues, including weakened immune systems, increased risk of obesity and multiple cancers, developmental problems in children and harm to negative effects on reproduction.

Onur Apul, assistant professor of environmental engineering at the University of Maine, is researching how to eliminate PFAS. He is one of many UMaine faculty members studying these forever chemicals and ways to mitigate them, and providing technical assistance to Maine farmers and other stakeholders. In Episode 4 of Season 7 of “The Maine Question,” Apul elaborates on the origins of PFAS, the threats they pose and efforts to stop their widespread contamination.


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Onur Apul:  It’s everywhere. 200 million Americans are exposed to PFAS through drinking water. It’s in floss. It’s in nonstick pans. It’s in food containers. It is in nonstick fabric, nonstick carpets, firefighting foams. It has been used as a commercial product for a long time.

Ron Lisnet:  That’s Onur Apul, assistant professor of environmental engineering, talking about PFAS, also known as a forever chemical.

I’m Ron Lisnet. This is “The Maine Question” podcast.

PFAS. It’s an acronym for a wide range of chemicals that are all around us in today’s world. They became popular in a vast array of applications precisely because they are virtually indestructible. When it comes time to throw away that Teflon pan or the rug that’s treated with a fire resistant substance, that is when the trouble begins.

These toxic chemicals don’t break down. They get into our drinking water or into the air and cause serious health problems. Farmers are finding them on their land, and in some cases, have to cut back on their crop or animal production, or stop altogether.

Apul is one of many researchers at UMaine looking at PFAS. He and his team are researching ways to break down these chemicals into harmless byproducts and keep them out of the environment. His work is getting attention and funding to try and solve this intractable problem. More help may be on the way in this battle.

Congress is considering funding for a lab that will analyze PFAS contamination in Maine and provide guidance to farmers and others. The work is still in the early stages, but it does show promise, providing us a way to get yet another dangerous chemical out of our lives.

Thank you so much for taking the time to talk to us. It seems you can’t turn on a news report or open the newspaper and see something about PFAS these days. I imagine you’re pretty busy.

Onur:  Thank you for having me, Ron. Yes, PFAS is keeping me very busy nowadays.

Ron:  Maybe let’s start there, defining some terms. What is PFAS? How do you pronounce the name of what it actually is?

Onur:  PFAS is a good way to pronounce it. It’s an acronym. It’s a mouthful. It’s per‑and polyfluoroalkyl substances. It has substances in the definition. It’s a plural acronym. It’s unusual. PFAS stands for about 5,000, 6,000 different chemicals. It’s an umbrella term.

Anything that has a carbon fluoride bond in a chain‑like structure saturated with fluorine ion elements is PFAS.

Ron:  They’re known as forever chemicals. You maybe can talk about that. Why are they so dangerous? Why do they persist so much in our world? How do they affect our health?

Onur:  PFAS is a favorable compound because of its relatively hard to destroy chemical properties. They are thermally resistant. They are resistant to biodegradation. They are resistant to typical weathering processes in the environment. They stay around.

We like it so much because of its properties. Teflon pans or nonstick surfaces make them very favorable for everyday products. When it’s time to get rid of them, it becomes problematic. The chemical makeup of the class of chemicals making them so difficult to destroy and the toxicity of them, the public health hazards, the environmental implications still undergoing.

Every day, we are discovering new ways that the toxicity of these chemicals could harm people. So far, we know it causes kidney damage, testicular problems, cancer, damage to pregnant ladies. There is a lot of ongoing research on toxicity. It’s not my field, but we know it’s not good for us. We can see from the federal response from how we have to eliminate this from our bodies.

Ron:  You talked about Teflon pans, but this stuff is everywhere. I heard it’s even in dental floss, and certainly, in drinking water. Is it really pervasive in our world?

Onur:  It’s everywhere. 200 million Americans are exposed to PFAS through drinking water. It’s in floss. It’s in nonstick pans. It’s in food containers. It is in nonstick fabric, nonstick carpets, firefighting foams. It has been used as a commercial product for a long time. It’s been produced domestically even a few decades ago.

It is a very prevalent compound. It’s everywhere. It is not being produced domestically at massive scales anymore, but we still have it circulating around and in our daily lives.

Ron:  Give us the cocktail napkin pitch. What are your basic research questions you’re going after?

Ron:  I try to understand how these forever circular patterns of PFAS are. There is an engineering water system. We purify water, we flush it down the toilet, we use it. There’s a natural water cycle in rivers, lakes, rainwater, groundwater.

These circles, these circular motion of water coincide. Engineer‑built and natural water systems. PFAS is moving in those systems. Of course, we contribute through solid waste. We contribute through commercial products. Industry contributes. Firefighting foams contributes. There are point and nonpoint sources.

Long story short, I’m trying to understand where PFAS naturally accumulates because it’s much easier when something is concentrated on some medium. This could be a dead‑end street in a landfill leachate or it could be on a water filter that accumulates PFAS. Try to resolve the problem when the PFAS is concentrated on this particular medium.

Ron:  Are you looking to neutralize it, eliminate it, sequester it away? How do you hope to deal with it and get it out of our lives in this way?

Onur:  Removing it from water is not very difficult. It is just another chemical. We know how to deal with removing chemicals. The problem becomes its circular motion. If you remove it, then what happens to the filter medium you used? What happens to the membrane, the activated carbons that you used?

I focus on destroying PFAS when it’s adsorbed onto filter medium, particularly granular activated carbon.

Ron:  Your novel approach, how are you approaching this than other folks are doing?

Onur:  I’m trying to integrate PFAS destruction into the existing engineering systems. The regeneration of used activated carbon is an existing network of industrial operation. European companies are powerful in that realm. They regenerate carbon and then they compete with new materials so they can recover activated carbon and sell it as a product.

I’m trying to integrate this existing infrastructure of carbon recovery and regeneration into PFAS destruction. Particularly when PFAS is adsorbed onto activated carbon, we think there is a catalytic reaction that decreases the temperature of destruction for PFAS.

We want to exploit this, and while we are taking advantage of the existing carbon recovery infrastructure.

Ron:  Obviously, these chemicals are useful in many ways. Are there any less harmful alternatives or is this it for the applications that PFAS has?

Onur:  No. I think it’s a very good research question to find an alternative compound that is as good. We have made some mistakes and replaced PFAS with short‑chain PFAS, and then realized they may be also problematic. I think it’s an ongoing long‑term process to find safer alternatives.

The term safer shouldn’t be subjective. It should be also going through the same legislations and the procedures that are regulating the compounds in our environmental systems.

Ron:  What, if anything, can a homeowner do to protect themselves, filters or other ways to get it out of their lives? Anything?

Onur:  Water filters that we use, like the point‑of‑use type pitchers, carbon filters, under the sink type of filters generally work well. I would recommend being on top of replacing the cartridges, maintaining their water filters. They have a certain capacity. PFAS eventually will break through.

My advice would be being on top of your water quality.

Ron:  The other big project you’re involved with involves something called nanobubbles. What are they? What potential do they hold?

Onur:  The idea we had was we are dealing with these contemporary water problems. We have a lot more water demand, a very complicated water source. We have a cocktail of pollutants now. We still rely on technologies dating back to Victorian era.

The idea came to utilize this probably 10, 15 years old technology of using nanoscale bubbles to purify water. Nanobubbles are just tiny bubbles in water. They are very, very small. That makes them stable. You create a biphasic fluid, both gas and water. The bubbles don’t rise up to the surface. You create a permanently porous liquid.

We are trying to understand if we could remove PFAS or other pollutants from water with the use of nanobubbles. It’s a relatively new idea and a relatively new project aspiring to shift the paradigm of water treatment.

Ron:  Just for us non‑scientists that are listening, nano, how small is that?

Onur:  Nano is a unit that is one‑billionth of any metric quantity. Nanosecond is one‑billionth of a second. Nanometer is very, very small. If you compare the size of the Earth to a basketball, you’d be making a fairly similar comparison between the same basketball and a nano particle.

Ron:  How do the nanobubbles…What is it about their properties that allow them to remove and do the things you’re hoping it can do?

Onur:  They’re very tiny. When they are very tiny, the same amount of gas constitutes a lot of surface area. Their size and stability is promising. They also have a surface charge. They may contribute to the partitioning of these pollutants into gas phase.

Then if we find a way to remove bubbles, we are using ultrasonic cavitation, then we may be able to remove these pollutants. In brief, they’re miniscule size and high surface area.

Ron:  Regular bubbles can’t do the same thing.

Onur:  Regular bubbles are too buoyant and not stable enough to stay long enough in water.

Ron:  Talk a little bit about working with other folks on campus to do the work and testing you’re doing. There’s talk about high‑altitude balloons, satellite launches. How will those things help in your work?

Onur:  Nanobubble project, it’s a very futuristic idea. As I mentioned, we are trying to shift the paradigm from Victorian era technologies like sand filters into using nanotechnology in water treatment.

The idea was picked up by NASA. They are aspiring to utilize nanobubbles in water treatment systems in International Space Station, in space exploration. It’s a very forward‑looking technology.

NASA is interested in understanding the stability of these bubbles in rocket launch conditions. There is a lot of vibrations, zero gravity, microgravity, sudden shift in G‑force. That’s why we are utilizing the existing UMaine infrastructure for high‑altitude ballooning, as you mentioned.

We have a local aerospace company helping us to simulate rocket launchers. Eventually, we are getting advice from our NASA mentors to see if nanobubbles are applicable in space. Of course, I just want to reiterate, space exploration is the aspiration. Along the way, we may be making discoveries that are helpful for order treatment on Earth.

Ron:  This is just getting going. Do you anticipate putting experiments up into space? How far into the future is that going to happen?

Onur:  We have a pending project proposal with NASA. It’s a Zero‑G flight proposal. We put together the proposal today, actually. If the project is selected, then we’ll be sending a crew for a parabolic flight. It’s also known as Vomit Comet.

We’ll put these nanobubbles into the zero gravity conditions as they start to see if our initial testing in the laboratory is also valid in zero gravity in space.

Ron:  This all comes under the heading of environmental engineering. What drew you to this field? Why are you interested in it?

Onur:  Environmentalism was very popular in 1990s. It was a new thing. People were talking about, “We have to protect the environment, protect the planet.” I never realized that protecting the planet is a very ambitious goal. We have to protect our own species, let alone the planet.

I was drawn to the environmentalism pretty much in elementary school. I was recycling batteries for my classmates, recycling juice boxes. I’m talking about age six, seven. That’s how it started that I became the environmental advocate in my cohort.

When it was time to choose an engineering branch, I realized environmental engineering is utilizing the tools, technology, and science with a very noble cause, in my opinion, to help the environment.

Ron:  Are students involved with your research?

Onur:  Yes. We have graduate and undergraduate students. A relatively large number of students are helping us, of course.

Currently, the nanobubble project is hiring a new PhD student from Ghana. For the PFAS project, we have a few other graduate students that are already working in their degrees in UMaine.

Ron:  If all this goes the way you realistically hope it does, where do you see us in 5 to 10 years with this work you’re doing? Will PFAS be still as omnipresent in our lives or less of a danger? Are the nanobubbles going to be out there and doing their thing?

Onur:  It’s hard to predict the future. At the pace and the resources that are spent for PFAS mitigation, I see a light at the end of the tunnel. Meaning that we may be understanding the pathways better. We may find better mitigation technologies. We may be slowly phasing out the fear of PFAS with the knowledge‑building.

Of course, I’m assuming the investment and the resources are continuing in the next 5 to 10 years. Nanobubbles is very, very hard to predict. One, because it’s a baby technology. We did not believe nanobubbles could exist 20 years ago because of simple mathematical equations would predict their internal pressure extremely high and unstable.

About 10, 15 years ago, we were able to see them under a microscope. That shifted the paradigm. We didn’t really compute their surface curvature or electrostatic charges. Now we are accounting for them. They could actually be stable. Hard to predict.

I think they are going to take off, considering the needs of gas‑liquid mixing in aquaculture, gas‑liquid mixture mixing in industry, in agriculture, in horticulture, in wastewater treatment. There’s a lot of venues that this could take off. I view this is going to be the next chapter in water treatment.

Ron:  How do you make nanobubbles? I assume you don’t put a straw in the water and blow, right?

Onur:  Kind of. There are different ways. These companies who we work with are keeping their secrets trade secrets. For the most part, principally, either you could apply some energy by mixing or you could take advantage of the pressure jumps like a Venturi type system and create cavitation bubbles.

Either statically without putting any energy. Very similar to blowing bubbles with a straw, but straw is designed for nanobubble production. You can put a little bit energy. We have both static systems and dynamic systems. We can generate nanobubbles through mixing, through chemical addition, electrostatically.

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Onur:  Again, I’m not very comfortable with the way they are produced, but I’m comfortable with the principle to how they are produced.

Ron:  We wish you well in your research. Hope you have great success. Thank you for taking the time to talk to us.

Onur:  Thank you for having me, Ron.

Ron:  Thanks for joining us. As always, you can find all of our episodes on Apple and Google podcasts, Spotify, Stitcher, SoundCloud, UMaine’s Twitter, YouTube and Facebook pages, as well as Amazon and Audible. Questions or comments, send them along to mainequestion@maine.edu.

This is Ron Lisnet. We’ll catch you next time on The Maine Question.