Utah Water Research Lab Breaks Down Solutions to Plastic Pollution

The Utah Water Research Laboratory is conducting research at every stage of the plastic problem, from generation to degradation, to support a cleaner future.

The journey of a plastic bottle is a well-worn tale. Bought from a convenience store or snatched from a cafeteria, this little petroleum-based container is quickly emptied and thrown away, but its travels don’t end there.

Plastic in its myriad forms travels from trash bin to landfill, often skipping that journey altogether to land on the side of the road or in a stream. Wherever its final resting place, it is neither final nor resting. Weathering from wind and water and sun exposure slowly break down plastic into microplastics and eventually nanoplastics, leaching chemicals into water, soil and air.

Plastics aren’t sustainable, but use over decades have woven them into society. As long as people use plastics, they will always be breaking down and turning into the tiny particles that harm the health of both the environment and humans. This means solutions are needed not only to clean up the microplastic problem already upon us but also to find new alternatives to the toxic chemicals involved in production.

Generation

One of the ways plastics degrade and break down into harmful micro- and nanoplastics is through exposure to ultraviolet light from the sun. UV light can make plastic brittle or yellowed and more prone to breaking or leaching chemicals. To prevent this, plastics constantly exposed to the sun, like a car’s headlights or dashboard, have additives mixed in. These UV stabilizers keep those headlights looking new for years, but when they do eventually break down into the environment, they can impact human health.

“Plastics aren’t sustainable, but the plastic additives that are in use are also not sustainable,” said assistant professor Kyle Moor. As plastics break down, the UV stabilizers enter soils and surface waters and then can disrupt human endocrine systems and harm natural ecosystems. To address this problem in plastic creation, Moor is looking for safer alternatives for these additives.

Moor’s alternative takes a leaf out of the plant book. Plants, like car headlights, are exposed to UV light, and they have protection of their own in the form of flavones. Like the molecule quercetin in parsley, these flavones protect the plant from UV damage, and Moor believes they can be used in plastic production.

“The idea is we can replace those more harmful chemicals with ones that are found in plants that we consume through our diet already,” Moor said.

Using lasers to simulate UV exposure, Moor and his team are exploring how flavone chemistry controls its ability to act as a UV stabilizer.

Moor said sustainable chemistry as the idea behind all of his work.

“As we’re looking toward these new solutions, they need to be grounded in sustainable chemistry concepts to make sure we’re not impacting the environment or human health by these new materials or new additives we might be using,” he said.

Transport

As assistant professor Yiming Su said, “Plastics are everywhere.” They’re in our kitchen utensils and our favorite sweaters. They form containers and tools and grocery store packaging. And once they’re out in the environment, broken down into tiny plastic particles, they can start to pop up in unexpected places.

Su’s work on plastic focuses on its transport through water and soil, particularly the pieces that are too small to be filtered out. These are called nanoplastics, and they are less than one micron in size.

Su said we don’t really know the significance of plastic particles to human health, but the things attached to the plastics, like additives, per- and polyfluoroalkyl substances (PFAS), or heavy metals, can and do have health effects. This highlights the motivation to study the movement of plastics through our water, soil, and air.

For example, the pipes that bring water to a city can be either metal-based or plastic-based PVC pipe. In a joint study with professor Steve Barfuss, Su looked for the release of nanoplastics from PVC walls as water rushed through them, simulating the drinking water supply system. Anything larger than 20 microns can be effectively removed during drinking water treatment, but Su’s process allowed him to detect anything down to 100 nanometers.

His results showed no significant release of microplastics or nanoplastics — good news for PVC in drinking water systems.

But pipes aren’t the only avenue for plastic transport into our homes. Many plastics find their way into irrigation and drinking water systems from wastewater treatment plants. The plastic fibers of our clothing come off in the washing machine; the frayed edges of our plastic cooking utensils scour away in the dishwasher.

“Most of that will be removed in the sludge,” Su said, speaking of the wastewater treatment process, “but there is still quite a bit of plastic in the effluent after treatment.”

Wastewater effluent can be used as an irrigation water source downstream. To study how the microplastics in wastewater effluent can impact crops, Su and his students are growing lettuce in the lab.

Nanoplastics, which, again, are smaller than a single micron, can be taken up by plants. To simulate this, Su created nanoplastics and plated them with palladium as a tracer. Then he grew lettuce with the recycled water used on agriculture fields. After a month of exposure, he and his student analyzed the lettuce for palladium to see how much plastic the lettuce absorbed.

Su said he sees more nanoplastics in older leaves, so a preventative action for consumers is to strip those outer, older leaves before preparing food. He is also researching biochar as a possible soil amendment to keep nanoplastics in the soil and out of the plants. His research shows promising results with significantly lower nanoplastic levels in lettuce with biochar added to the soil.

Throughout his research, Su emphasized the importance of using precise and innovative methods to find the tiny plastic particles escaping treatment and working their way into our food and water.

Getting his research to the public to inform action is a core part of Su’s work. After a study detecting nanoplastic particles on the shores of Bear Lake in Utah, the Bear Lake community came together to host a plastic collecting event to lower the amount of microplastics released at the popular recreation spot. These are the kinds of outcomes Su hopes come from his projects, and he looks forward to future action on plastic pollution.

Degradation

Assistant professor Joanna (Liyuan) Hou started her research on plastics seven years ago on the heels of the New York City plastic bag ban. She saw how plastics broke down into microplastics and persisted in the environment, never degrading entirely. Hou didn’t see any way to end the story of plastics because we as humans are always using them.

“So how can we deal with it?” she asked.

With her expertise in environmental engineering and microbes, Hou started to look at the communities of microbes on microplastics in wastewater, surface water, ocean water, and soil to understand their role in biodegradation.

Wastewater in particular holds interest because of how the presence of microplastics can affect treatment. Hou saw that some pathogens and microbes could escape treatment by hiding under microplastics, using them like an umbrella.

“I felt this is important to look at,” Hou said. “Who is escaping and taking a ride?”

By identifying the specific microbes escaping treatment and how microplastics affect their fate, we can control harmful microbes in wastewater. But not all microbes are harmful. “Different microbes can actually provide benefits,” Hou said.

One of Hou’s many microbe-microplastic interaction projects involves a graduate student using machine learning to identify microbes that can actually degrade plastic.

“I’m trying to understand which microbes are on microplastics, what their role is, and how we can use the benefits of their metabolism pathways to make plastic finally biodegradable,” Hou said.

She and her team collected data from published papers about plastic-associated biofilms and analyzed them to look for plastic-degrading bacteria. They used three representative studies for wastewater, three for surface water, and three for ocean water to understand the diversity of microbes in different environments.

After comparison, they noticed consistent potential plastic-degrading bacteria had the highest concentrations in wastewater.

Plastic-degrading bacteria are linked with certain non-plastic-degrading bacteria, meaning that the different types help each other survive on the surface of plastics. When the plastic degraders chew the long polymers into short pieces, they leave behind organic matter byproducts for non-plastic degraders to use as an energy source, turning the whole piece of plastic into CO2 and leaving behind an empty dinner plate.

These bacteria, already at work, can be used to help the plastic pollution problem.

“If we can see more plastic-degrading bacteria, maybe in the future we can take advantage by isolating those bacteria from wastewater to do the degradation,” Hou said.

Alongside Hou’s microbial solutions, Moor is also working on projects at the tail of plastic pollution, exploring the role of UV light exposure in plastic degradation, specifically the fate of agricultural mulch films after season-long UV light exposure.

Mulch films are the long black plastic sheets laid on the fields of specialty crops like strawberries. New biodegradable mulch films are designed to replace polyethylene films (made of the same material found in grocery store bags) that release micro- and nanoplastics into soils. The new mulch films are intended to be tilled into the soil at the end of the growing season to naturally degrade, but Moor wants to see how season-long UV light exposure impacts the breakdown process. UV light generates a complex mixture of dissolved organics from plastic or plastic additives that could affect soil microorganisms, nearby surface waters from runoff, or the crops themselves.

Both Moor and Hou hope that, through research, we can solve the problem and finally give the plastic degradation story a period.

Not a Never-Ending Story

Plastics are pervasive and invasive in their impact on the environment. Every stage of the life cycle of a piece of plastic requires research to improve the design and disposal processes and mitigate negative effects.

The professors at the Utah Water Research Lab are acutely aware of the cycle and are working to break it.

Different applications for plastics require different solutions to the pollution problem, but the start is to reduce and reuse. From personal decisions to state action to national and global efforts, each step taken, each new discovery, is a step toward a sustainable future.