- There's a lot that divides us humans, but one thing we all learn from a young age is that everybody poops.

And for all our advances in technology, humans haven't really figured out how to handle our excreta efficiently.

For one, half the world's population doesn't have access to a bathroom that properly stores and clean sewage, so that's a problem.

And two, although you might be fond of your porcelain throne, it's wasteful by its nature.

Flushable toilets use a gallon and a half of treated, clean drinking water every time you flush.

That's why toilet engineers all over the world are trying to solve this most basic problem of what you with our pee and poo.

- I usually say I clean up [beep] water for a living which I know you can't use that.

So one of the big problems that we're trying to solve and one that I'm personally very interested in is we use drinking water to flush our toilets.

And as the climate continues to change and as water becomes more scarce and we have more droughts and more fires, we're gonna be using more and more drinking water and having less and less of it, so we really need to conserve that precious resource.

- The gold standard toilet is flushable and connected to some sort of water treatment, but it's expensive and takes an enormous amount of water, land and energy to lay pipes and build treatment plants.

And even then, modern sewage systems are far from perfect.

For example, every year, the US spends a billion dollars to remove fatbergs, which are essentially massive clogs made of wet wipes and cooking fats.

During the pandemic, these clogs went up by 50%.

Yup, everybody was using a lot more wipes and flushing them down the toilet.

But while our sewage system might not be the best, things could be crappier.

- In a lot of places, the toilet pipe just goes nowhere, out into the street or out into a creek or river.

- Toilets are absolutely a justice issue and a human rights issue.

So when you get contamination particularly of drinking water with untreated waste water, it spreads disease, most notably diarrhea, which kills about half a million children a year worldwide.

So digging a sewer under a city that already exists is tremendously expensive.

And when you look at a city like Mumbai or Kinshasa, they're huge.

Millions and millions of people live there.

The political will the money to go and dig a new sewer under those cities.

It's just not there.

It's very unlikely to happen.

- But that's where the toilet engineering comes in.

Brian, Lena and their team are working on a toilet they hope will use way less water and help communities that need access to affordable bathrooms that work.

It's called the Reclaimer.

And they're building it in this warehouse in the appropriately named Bay Number Two.

Sorry, I had to.

So this is a toilet?

- Well, this isn't exactly a toilet.

This is what we would call a backend unit.

So if you think of the toilet as your front end, everything that happens after the toilet in terms of treatment is the backend.

Ideally, we envision this or something like it being an appliance you would have in your house that your toilet would be plumbed to.

What that appliance does is it receives the waste water from the toilets and it treats it on site.

It's not potable.

You don't wanna drink it, but it's good enough for reuse.

We like to use it for flushing the toilets themselves, so you have just sort of a continual reuse of water locally.

- [Host] But how does it work?

First things first, separate the poop from the pee.

The Reclaimer filters out the poop, pushing it to a separate container so that bacteria can digest it over time.

- We then take the liquid fraction that's left, that goes to the inlet of the Reclaimer.

At the very bottom here, you have what we call our feed tank so that's where the dirty water comes in.

And you can see it's pretty, pretty dirty.

You can even see it through the tank.

- Disgusting.

- Yeah, absolutely.

So the very first stage is what we call ultra-filtration and that's exactly what it sounds like.

We force the liquid through those straws and the straw itself is what filters the liquid.

- [Host] The liquid travels through three more filtration chambers, one that uses granular activated carbon like you'd find in a Brita filter, one that removes ammonia, and one that zaps the water with chlorine to kill any foul-smelling bacteria.

And after that, the water can be used to flush the toilet again.

Brian's team is testing the Reclaimer in India at a cotton mill.

- A lot of the brunt of sourcing clean water for the family falls on women and girls.

And so women and girls can't have other jobs or they have to travel great distances and miss school just to provide clean water for their family.

And so if there's a way that we can again conserve drinking water so that those trips need to be made less frequently, women and girls can live fuller, richer lives doing other things besides going to the well.

- [Host] The team is also hoping the Reclaimer can be used in the US in places like Utah, California, or Nevada, all states experiencing record breaking droughts and huge population growth.

- Right now, we use a lot of water just to flush all of our waste to the treatment plant.

But if you're treating the water on site, you can use much less water and you can reuse it right where you need it.

I spend so much of my time in the lab and we often don't get to see our inventions and ideas out in the world.

And so that's been something that keeps me really motivated here.

But if you had told me two years ago I would be working with human waste and shoveling it into experimental toilets, I would not have believed you.

[laughter]