Short Wave - Saving Water One Flush At A Time

Episode Date: November 19, 2019

Happy World Toilet Day! Flushing toilets can consume a lot of water, so Tak-Sing Wong, a biomedical engineer at Penn State University, is trying to minimize how much is needed. Wong developed a slippery coating for the inside of a toilet bowl. It can potentially move human waste more efficiently, leaving a cleaner bowl and using less water. Follow host Maddie Sofia on Twitter @maddie_sofia. Email the show at [e-mail] pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences.NPR Privacy Policy

You're listening to Shortwave from NPR. Hello and happy world toilet day. Yes, that's a thing. And here on Shortwave, we are taking it very literally and bringing you some toilet-based science. Imagine a toilet that can always keep itself clean without living streak of human waste that just makes it more appealing for people to use it. For example, in the case of public bathroom. I mean, I've definitely gone into a problem.

public bathroom and been like, I'm going no further. Yes, yeah. That's Taxing Wong. He's a biomedical engineer at Penn State University, and he's trying to solve what he is called a universal problem, a problem as old as time. Poop is sticky to the surfaces. So basically you're saying like that poop sticks to a toilet bowl is what you're saying. Yeah, when the poop sees this surface, it just stick on it. Here's the thing. Taxing isn't focused on this because he's an advocate for streak-free toilets.

It's that getting all this sticky poop off the sides of the toilet takes water. And in areas of the world that use flushable toilets, it's a lot of water. Everyone flushes multiple times every day, and each flush takes about a couple liters of water. And if you multiply this to global population who have access to this flushed toilet, it's a tremendous amount of water. It is estimated that there's over 140 billion liters of fresh water just fussed down the drink every day. Today on the show, we learned about a super slippery coating that could make toilets more efficient. Plus, a recipe for making synthetic poop.

You know, in case you need that. All right, you ready to talk about some toilet science? Yes, I'm ready. We're talking with researcher Taxing Wong today on the holiday of all holidays, World Toilet Day. Taxing has spent years developing a non-stick coating that can be used in toilet bowls. and his inspiration came from kind of an awesome place. The original inspiration is from this Caniffords plant called a pitcher plant. Oh, the pitcher plant, the one that eats bugs.

Exactly, yes. As their name suggests, pitcher plants kind of look like water pitchers. Think the Kool-Aid man, but without the creepy little face. There's an opening at the top of the plant, the shape of a teardrop. And on the rim of that opening, some pitcher plants have these microscopic little scales that can trap water or plant nectar. And that trapped layer of liquid acts as a slippery little lubricant. So this pitcher plant has evolved this really slippery coating that when box like ants walk on this surface, it just slide off from the slippery surface and got

digested by the plant. It's like a water slide. Taxing borrowed the idea of this lubricant-infused surface to create a slippery coating called Less. It's a spray that keeps poop and pee moving once they hit the toilet bowl. Can you just define what Les stands for? Yeah, less is an acronym stands for liquid-enched smooth surface. Liquid-entrenched smooth surface. That's correct. And by having this last coating, you use less water. You use less cleaning chemical to clean the surface. Yeah. I see what you did there. That was very clever there. The coating comes with two parts. The first layer is made up of microscopic little hair-like material. It's kind of like a

a hair or grass structure. You can imagine it's like a grass structure, but the size of this is about nanometer thick. Oh, so very small. The second layer is a lubricant made out of silicon that attaches to the tiny little hairs in the first layer. And in combination of these two materials, then it becomes super slippery.

Even poop doesn't stick on it. Taxing says it takes about five minutes to apply the whole shebang. And in order to test out the coating, they had to do some poop-based experiments. So in one test that I saw, you were kind of trying to look at how artificial feces stuck to a toilet with your new coding versus stuck to a commercially available toilet. That's right, yeah. So after we design this coding, we need to find some way to test it, right?

And of course, the best thing is we test with the real human waste. Right. But in the lab setting, if I asked my graduate student to do it, they probably wouldn't want to do it for a long time. Yeah, yeah. That's why we asked our collaborator from Cranfield University to see if there's a synthetic version of this human waste that we can emulate its property. And then they sent us this recipe. And this, what I call the synthetic poop, is a seven component materials that compose of peanut. oil, miso, yeast, and other materials. You mix them together, and we can control the property

such that it can simulate the actual physical property of real human waste. Taxing, when you were younger, were you like, one day, I'm going to make artificial poop in the name of science. Yeah, I am. Yes, in the names of science, that's right. So this wasn't a surprising turn in your career. for you at all. I wasn't expected that at one point in my career, we are making synthetic poop, but this is a very big problem. And as you mentioned in the name of science and global health, we're happy to do that.

Taxing sent me some videos of these experiments. And unfortunately, or very fortunately, for you, dear listener, the videos do not have sound. So I'm looking at two toilets. I'm watching somebody, I assume a graduate student, some poor graduate student, has flicked some of this artificial poop onto the commercially available toilet. And it's kind of it kind of sticks and it's like sliding

down towards the little toilet hole. But it's making its way slowly. And then when they flick the poop onto your toilet, it just slams down to the bottom. Like it's very impressive. It just like literally just goes right

down there immediately. Thank you. Yeah. It takes us some time to create such a powerful poop with pollen coating. After they went through the fake poop trials, it was time for the real thing. But you also did experiments with actual human feces, right? That's correct. And you, tell me if I'm wrong, basically, you compared it to a surface with your less coating on it. Ceramic, which is common toilet material, Teflon, which is, you know, historically not sticky, and silicon. Tell me about, like, the results of that experiment. So after we test with the synthetic poop,

we're very confident that this will work on the real human thesis. In this test, they collect this human thesis from three volunteers. They mix it, and then in the test, they have designed a setup where they put our coated surface, ceramic, taflon, and silicon. And what they do is they drop the human thesis, which they put it in a pancake shape, onto each of their surfaces. So what happened is that except our coded surfaces, which the human thesis doesn't stick on it, all the other surfaces, the human faces just

stick to it and cannot be removed easily. How do you calculate how much less stickier your coding is? So this goes back to our laboratory. We use an instrument that can measure the adhesion between the synthetic poop and the surface. And we compare this adhesion force with coded and uncoated surfaces. In our laboratory test, we find that the surfaces that is coated with our less coating is 19% less adhesive than the one that is without a coating. So in the U.S., an average toilet uses about 1.6 gallons per flush. And about half of that is used to get your waste off the sides of the bowl after you flush.

And the other half is used to propel the poop through the pipes. Taxing says his coating saves you the 50% you would normally need to clean the bowl. So you can save 50% of that flush water because you're saving the water that it's sticking or like helping get all the poop off the toilet ball. That's correct. All right. But you still need water to shoot it down the pipe. You still need that, yes, to transport the waste.

Yeah, that's right. The main downside of the coating is it doesn't last forever. The top layer needs to be reapplied fairly frequently. And for high traffic toilets like public restrooms, that's a problem. The second layer requires replenishment overuse. and if we can make it last longer, particular for high traffic toilet, I think that will be good.

But again, like we applying this coding is very simple and straightforward, everyone can do that. And we hope the benefit will be way exceeding the downside, definitely. Right now the coding is about $20 per kit. Taxing says that would last you a few months depending on how much you use your toilet. The technology is impressive. But before it can make a global impact,

it'll probably have to last longer and cost less. Taxing's results were published yesterday in the journal Nature Sustainability. And that's not all that was published there. We do have the formula, the recipe to create a synthetic proof in the paper published in Nature's Sustainability. If people are interested to make it at home, they're welcome to. I don't know why, but yeah, we do have the recipe there. It's really a public service you're doing there. Yes.

Okay, texting, this was really fun. I really appreciate you. Yeah, thank you, Maddie. Yeah, nice talking to you. Today's episode was produced by Britt Hansen and edited by Viet Leigh. I'm Maddie Safaya. Thanks for listening to Shortwave from NPR.