Science Friday - Can algae help pull microplastics out of our water supply?

Episode Date: April 6, 2026

Microplastics and nanoplastics have been found just about everywhere: in our soil, our bodies, and our water. Recent research involving bioengineered algae has had success in capturing and removing microplastics from water. Environmental reporter Kate Grumke joins Producer Kathleen Davis to talk about the latest approaches to addressing microplastics, and researcher Susie Dai discusses her work using algae to pull them out of wastewater. Guests:  Dr. Susie Dai is a professor of chemical and environmental engineering at the University of Missouri. Kate Grumke is a senior environmental reporter for St. Louis Public Radio. Transcripts for each episode are available within 1-3 days at sciencefriday.com. Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.

Hey, it's Science Friday producer Kathleen Davis, and you're listening to Science Friday. Microplastics and nanoplastics have been in the news a lot. These are teeny, tiny pieces of plastic fragments that are found pretty much everywhere. They've been found in the soil, in the water, in our bodies, even on the top of Mount Everest. And it all feels overwhelming and existential. But there's some good news, too. Just this week, the EPA announced it's taking the first step to regulate, microplastics in drinking water. And lots of scientists are looking for solutions for our microplastic malaise. And here to fill us in on some research happening in the Midwest is Kate Grumke, senior environmental reporter for St. Louis Public Radio. Hey, Kate, thanks for being here.

Hi, Kathleen. Thanks for having me. So Kate, as an environmental reporter, what's your level of personal concern on microplastics? Like, where do they rank on your list of topics that are big and scary that you cover? Oh, man. Well, we have a lot of scary weather events here. So I would say that those can be maybe bigger or more urgent feeling than microplastics. But the thing about microplastics is you can end up thinking about them quite a lot because there's so much plastic in our daily life. So I feel like I have just constant reminders of this issue because there's so much plastic around us. Right. So as I said, microplastics are everywhere. Has there been any? anything in your neck of the woods that has made you be like, okay, this is actually very freaky. Oh, definitely. So one story I wrote about was about a group of scientists at St. Louis University. They recently found microplastics in a cave around here that had been closed to the public for 30 years.

So there's a population of endangered bats in this cave. So people are generally not allowed to go in there. And they found a lot of microplastics. And they found it in both the water. water and in sediment in the cave. And one thing that was really interesting, they published a paper about this, that they found it even more during flooding. So the caves around St. Louis are generally kind of connected to the outside world. And so during flooding events, more of that outside world and the plastic inside of it is being washed into that cave. Okay, so let's talk about a story that you did recently. You reported on a lab in Missouri that's doing some pretty innovative stuff with algae. Tell me about this.

Yeah, so there is a professor at the University of Missouri who is working with engineered algae. And she recently worked with a team to see what this would do with microplastics. So this algae is essentially really hydrophobic. So it repels water and microplastics are also hydrophobic. So they basically found that these algae sort of clump onto the microplastics and then bring them down to the bottom of water. and they're really good at cleaning the microplastics out of the water. So they laid out this process in a new paper in nature communications where they can kind of clean up the microplastics this way and then maybe even recycle that sludge of algae

and microplastics into a new product. Okay, so you said it's effective. How effective is it? They found that it removed more than 90% of microplastics in the water that they were testing in a solution. So very, very good. And it's especially good at removing super, super tiny pieces of plastic. So sometimes it's easier to filter things that are bigger out, but they are really targeting those super extra small pieces of plastic with this process. And we'll talk to the lead researcher on that study in a little bit here.

But let's talk a little bit about other local efforts that you've reported on to tackle this microplastics problem. Does anything spring to mind? Yeah, there have been a few other projects. in St. Louis that are really interesting. One, I was especially interested in at St. Louis University. So there's a researcher there who is looking at creating something that kind of acts like whale baleen. So this is the sort of like fibrous, not teeth, but teeth like structure in a whale's mouth. And so this professor realized that plankton are kind of a similar size to microplastics. And if whales are really good at sucking up plankton, maybe they,

They could also use Baleen to suck up microplastics. So I thought that was a really interesting test case. And then at Washington University, they actually have a research center now that's working on creating plastic alternatives that are also kind of rude and a natural process. So I think that that is pretty interesting as well. They're targeting fibers, which is a big problem from our clothes, from plastic and the clothing. And so, yeah, there's a lot of people around here. who are trying to find a solution to this problem.

I mean, as a reporter who covers this, how does it make you feel to have some kind of promising things to talk about when it comes to microplastics? This is one of those issues where I talk to the scientists and they're really hopeful. They're really excited about what they're working on. They feel like they're finding solutions to a big problem in our lives. So I really think that this is a great area to look at.

If you're looking for some hope in an otherwise kind of stress, environment. Well, thanks so much, Kate. Thanks, Kathleen. Kate Gromke, senior environmental reporter for St. Louis Public Radio. We have to take a break, but don't go away. When we come back talking to the researcher behind this algae breakthrough, stay with us. Now, we're going to dive into some more detail on this bioengineered algae. We've learned that it can clump onto microplastics and make them easier to remove, but how could it actually work out in the world? Joining me now is Dr. Susie Day, Professor of Chemical and Biological Engineering at the University of Missouri. Thanks so much for being here.

Oh, it's my great pleasure. So this is a really exciting idea, right? And I know that you've gotten a lot of attention for this. But is it scalable? Like, how can we imagine this actually working effectively in the future? Yeah. And it's more than $1 million question, right? So we have to remember we're dealing with multiple things here.

one, we need to grow a stable culture in a container that's large enough for the treatment of our target of the water. And number two, and this is really a genetic modified organism, and many times people are concerned about those genetic modified organism. Then in my vision, we were not to freely release that back into the environment. So this will be done in a confined environment. So once you design a bioreactor, you can have this algae grow in a controlled manner, such as you can control the temperature, you can control the pH, you can control many things. So in this case, then we can cultivate at the optimized condition in the future in large containers that we can put in the field potentially or in a plant or in a facility.

That's supposed to be used together for other water treatment purposes. So we're talking about keeping this in like wastewater plants. Yes, and so waste water plant is one viable venue to operate this. But together, we can think of if you have other water body, that the algae can grow so that we can also use those water bodies potentially with other source of contamination. And then we can also integrate this reactor for other purposes. Because algae can use CO2 carbon dioxide as is a carbon source. So basically, you can grow it in a place once you have sunlight, right?

And then you can grow it with water that come in with extra of the nutrient that you want to remove. So definitely with the water plant is one designation that we can implement this platform. But there are other places maybe in the culture that we can do that too. So microplastics are everywhere. I think this is something that most people are aware of at this point. I mean, in the grand scale of this issue, how impactful would it be to be able to get microplastics out of wastewater? Like, how much of a dent do you think that could make on this overall problem? Yeah, and that's actually a question needs a multi-level analysis.

So I think right now people know we have the presence of those microplastics. And then we don't really know what's the final impact in our... ecosystem in, let's say, in the urban area, right? I think we know better in the sea and in those waters, but how much we know those microplastics are getting into our life, into our food system, into our drinking system. So together with treatment of those microplastics, I think another benefit we need to remember is this algae can also remove the extra nutrient from the wastewater water. Currently, most of the wastewater facility are designed to deal with the organic carbon and oxygen level. But most of the current infrastructure for wastewater treatment

is not dealing with extra nitrogen and phosphorus. So that's what I hope this platform is not only bring one benefit, but one stone for multiple birds. Then when we can manage microplastics, which is an emerging contaminant, still with a lot of research needs going on, we can also do at the same time remove those extra nutrients that are also not very good for our environment. Before I let you go, I want to ask you because I hear you did not necessarily originally intend to make an algae that could absorb microplastics. What was your original goal? Yes, that's a very good question. So I think this builds on years of the research when we're trying to work on algae in the very beginning.

At that time, we didn't have this beautiful imagination. We can apply the algae for this purpose. At that time, we're looking into using algae as a feta stock to produce high value products. So if you look at the structure, the chemical property of this compound coming from the algae, this is a wonderful compound. You can think of parallel to all those aviation fuel you can pump into the plane. And this compound has a higher energy density than ethanol. Nowadays, everybody pump about 10% of balkenol into our fuel tank for the car, right?

And then because the energy density for this molecule is higher than ethanol, it made that more ideal for the aviation fuel. And that's the original purpose. I mean, aviation fuel is so different from microplastic cleanup. How did you get from point A to point B? In parallel to that study process, we're looking to other means to remove those contaminants from the water, such as using the fungus biomass to remove. move those microplastics. So because those two research line are going on with each other in parallel, and when we saw that algae can self-precipricitate, then simultaneously were thinking, oh, what can we do is

it? So how about we apply that to the microplastics, and then can we observe the same phenomena? And bingo, it happened. I mean, this to me is such a perfect example of how random and unexpected scientific discovery can be sometimes. Yes, that's why I think as a scientist, we should not limit ourselves for the owning goal at that time for that one research project. I think very interesting about research is you have open mind, then you talk with people, then you collaborate, and then different minds come together, I think create a much better project than the one by the self in the very beginning.

Well, thank you so much, Susie. this was such a great conversation. I really appreciate the chance to talk to you about this. Yeah, thank you for your time. And it's my great pleasure talking to you. Dr. Susie Day is a professor of chemical and biological engineering at the University of Missouri. This episode was produced by me, Kathleen Davis. And if there's another good news story about a big environmental problem that you want us to talk about, give us a ring. 8774 SciFri. That's 8774 SciFri. Catch you next time. I'm Kathleen Davis.