Half The World Lacks Proper Sanitation. Is It Possible To 'Transform The Toilet'?

Jun 30, 2021

The United Nations estimates that 4.2 billion people — more than half of the world's population — live without any access to safely managed sanitation. No septic systems. No waste treatment plants.

"Some people don't have any toilets at all. They practice what's known as open defecation," science writer Chelsea Wald says. "Other people — many, many people in the world — use pit latrines. And those pit latrines might be nice and functional or they might be in really bad shape."

In her new book, Pipe Dreams, Wald examines the health issues related to human waste — and what she calls the "urgent quest" to rethink the toilet. She says the tools Americans rely on to remove and process our bodily waste aren't available to billions of people across the globe.

"It's a massive infrastructure that requires a big upfront investment and it also requires large operating costs, as well as expertise and chemicals and constant electricity," Wald says. "For that reason, it's not a particularly appropriate technology for many cities in the world."

But Wald notes that there's a broad movement among scientists and philanthropists to find a more efficient way to handle human waste, including turning it into fuel and fertilizer.

"I am hopeful that some of these projects will eventually make it to the kind of scale that's needed to make a difference, to make progress on this on this really important global problem [and] provide people ... with an acceptable level of sanitation [and] allow them to kind of become leaders in showing a new way to do things," she says.


Interview highlights

On the health risks associated with untreated sewage

Simon & Schuster

The exposure to the pathogens and poop can cause diarrheal disease, which affects children disproportionately, causes a lot of suffering and death, especially among children, and it can lead to a condition called stunting, which has not just to do with height, but cognitive function that can persist throughout the life of the child and has effects [on] later generations as well. It's a multigenerational problem. There can be outbreaks of diseases like cholera and typhoid fever, which were common in London and in U.S. cities in the 19th century, but ended after the widespread installation of wastewater systems and drinking water systems.

On a localized sewage system in the Netherlands that could change systems worldwide

I was really interested in going to see this project in the north of the Netherlands because it provides a contrast to this conventional ... way of dealing with sewage [in which waste is treated at an off-site location]. Here in the Netherlands, some experts over the past couple of decades have worked on developing an alternative system which treats the toilet waste locally. [It's a housing] complex of about 200 units, where people use vacuum toilets.

So you might know vacuum toilets from an airplane. ... They use very little water. [In the complex,] the concentrated toilet waste then flows to a facility on site where it's made into biogas, which is used to heat the homes. And also fertilizer comes out of it and water that could be reused in the homes. Although the project doesn't reuse the water yet, it's something that is possible. So it's the idea of building, from the ground up, a system that recovers the resources that we put into the toilet. ...

It is a demonstration project. [The experts] have had some growing pains, and it's not to scale, but what they've determined is that at a larger scale, it really has the potential to be economically viable under certain conditions and it has the potential to be more environmentally friendly as well.

On an above-ground sewage system in Haiti

I went to Cap-Haïtien ... a port city [in Haiti] with a lot of poor areas where people have either no toilets or very low-quality toilets. And there's a program there called SOIL that is innovating in this area that's become known as container-based sanitation, with projects popping up all over the world, especially in these informal settlements with dense urban slum environments. ... The customers rent a toilet. Inside the toilet is a container. And then every so often they seal up the container and they put it outside where workers come and collect it. [The workers] transport it over ground. They're either using these little three-wheeled motorcycles with a flatbed on the back, or sometimes they have to use wheelbarrows because the streets are so narrow. [The workers] collect the containers and take them to a depot where they get loaded on larger trucks and taken to a processing center where it gets turned into compost, which is great for Haiti's depleted soils.

On using the larvae of the black soldier fly to break down waste

There's this animal called the black soldier fly that actually exists in much of the world. It's particularly good for processing waste, for the reason that it only likes to eat organic waste when it is in the larvae stage. ... There are many research projects and companies that are turning this fly — and in particular the maggot form the fly — into a kind of technology that will then eat organic waste, including feces, but also food waste and other kinds of organic waste. And as it grows into a plump maggot, it becomes a really good source of protein that can be fed to livestock. It could replace sources of livestock feed like fishmeal, which contributes to overfishing, so it's a more potentially sustainable source of livestock feed.

On blockages that plague modern sewer systems, like the massive "fatberg" that was found in the sewers of London in 2017

So sewer workers discovered this massive fatberg, which was 275 yards long and 140 tons, and they named it "Fatty McFatberg." ... These are massive agglomerations of fats, oils and grease mixed in with lots and lots of different kinds of trash and they clog sewers and cost a lot of money to clean out and are also a big problem for the workers who work in the sewers. This is an increasing problem as we put more of these oils into the sewers from cooking and also put more trash into them, like flushing wet wipes.

On what we can learn from analyzing waste

When you go to a doctor, they might ask for samples of urine or stool, but your toilet takes those samples every time you use it. And so your toilet could become a kind of medical device. There are teams of innovators who are working on that. And then the sewers also contain a kind of flow of information about the health of our cities, of all the people in the city, it's kind of a collective sample. And public health experts are working on collecting and analyzing that data in order to create policies that improve public health. ...

There's a team that has come up with a kind of box that goes into manholes, extracts samples from the sewage and then analyzes it. What they were working on before the pandemic was the opioid crisis. They were finding evidence of opioid use in sewage and analyzing it to try to figure out patterns in a city. And once the pandemic started, they pivoted along with many, many wastewater utilities around the world and started trying to analyze sewage for evidence of coronavirus infections in the cities. And that has really picked up in the past year. And it has taken this field of wastewater surveillance and epidemiology to a whole new place.

On overcoming the "yuck factor," especially as it relates to recycling wastewater into drinking water

Disgust is a very strong emotion, and it doesn't always keep up with our scientific understanding. So, for example, with recycled wastewater, which can be cleaned and purified into drinking water, there's still a kind of yuck factor that creates resistance in the public. And people are looking at how they can decrease that resistance so that this important technology can be implemented. And one of the ways is to explain it to them, give people information — another way is to reframe it. Branding has become a big issue in the topic of recycled wastewater. People really admire Singapore's branding of this reused water as "new water." Building trust seems to be very important. Americans have a problem with trust in their drinking water, and so building this trust between the water utilities and people, and involving communities in this decision are also very important [to] creating a kind of social acceptability of the products.

Sam Briger, Heidi Saman and Kayla Lattimore produced and edited the audio of this interview. Bridget Bentz, Molly Seavy-Nesper and Malaka Gharib adapted it for the web.

Copyright 2021 Fresh Air. To see more, visit Fresh Air.

DAVE DAVIES, HOST:

This is FRESH AIR. I'm Dave Davies, in for Terry Gross, who's off this week. If you're listening to this at home, you're probably just a couple of rooms away from a truly miraculous device, the flush toilet. Most people for nearly all of human history didn't have this convenience. With the flick of a handle, that stuff we don't want to smell or even think about gets carried to an underground sewer system where somebody does something with it.

Our guest, writer Chelsea Wald, says a lot of high-powered scientists, public health officials and philanthropists are thinking these days about new ways to handle our poop, partly because our current sewage systems are creaky and wasteful, plagued by problems like 100-ton fatbergs (ph), which you'll hear about shortly, and because these systems are out of reach for billions of people who need sanitary ways to dispose of what their bodies excrete. In a new book, Wald writes about new designs for toilets, new uses for our waste - like fuel, fertilizer, even food - and new ways to handle it all. Some are even designing high-tech toilets that can monitor our health by analyzing our deposits.

Chelsea Ward has been writing about science and the environment for 15 years. Her new book is "Pipe Dreams: The Urgent Global Quest To Transform The Toilet." Chelsea Wald, welcome to FRESH AIR.

CHELSEA WALD: Thanks so much for having me.

DAVIES: You know, sewers - that is to say pipes that carry rainwater and stormwater and, you know, human waste - date back to before Roman times. When did humans begin to have toilets in their homes that would flush contents away to a sewer?

WALD: Well, the start of the kind of modern era of the flush toilet was in the 16th century, when Sir John Harington invented a flush toilet, but it didn't really catch on until the late 18th century, when a new inventor improved on that design. And over the next century, further inventors improved it even further, and it became more widely adopted, in part thanks to the fact that people had access to running water. And so they could put these flush toilets into their homes, and the water served to not only carry the waste away, but it also cleaned out the bowl, and it also provided a seal at the bottom of the bowl in a kind of trap, a U trap under the bowl to prevent sewer gases from wafting back up the pipes into the house. So the water had a lot of purposes that were very useful and made things very - much more pleasant for the users. On the other hand, the water created the problem of wastewater outside of the home, and that was a problem then that sewers had to solve.

DAVIES: Right. It made things cleaner and more pleasant inside homes, and so what happened outside?

WALD: There was sort of a, you know, disorganized series of ditches and cesspools and waterways, you know, this - if you're thinking about London in the 19th century, where people would just direct their wastewater, and it all, you know, more or less ended up in the Thames, where it festered and created, you know, sort of a massive, stinky mess, which got so bad that the lawmakers in Parliament were affected by it. That was the Great Stink in the middle of the 19th century, and that's when they authorized the building of a comprehensive sewer system that would then take all of this wastewater away from the city.

DAVIES: Now, there are - there's a lot of need for sanitation throughout the world. Why is this system of flush toilets and big sewage systems and treatment plants not the best or most workable idea for the world's sanitation needs?

WALD: Yeah. It's a massive infrastructure that requires a big upfront investment, and it also requires large operating costs, as well as expertise and chemicals and constant electricity. And for that reason, it's not a particularly appropriate technology for many cities in the world. And in fact, where these plants have been installed, they have sometimes failed. So around the world, there are big wastewater treatment plants that are no longer in operation, and so sewers are discharging directly to water bodies without the sewage being treated.

DAVIES: Right. So there's a lot of innovative thinking going on about toilets and about the systems that connect to them. You write about visiting a housing development in the Netherlands. There's this particular housing development where residents all have toilets, but they don't connect to a sewer system, right? They handle it themselves.

WALD: Yeah. They handle it themselves. I was really interested in going to see this project in the north of the Netherlands because it provides a contrast to this conventional gold standard - which is not my term but an expert term - way of dealing with sewage the centralized way. Here in the Netherlands, some experts over the past couple decades have, you know, worked on developing a kind of alternative system which treats the toilet waste locally.

So there in the complex, which is 200 units, about 200 units, people use vacuum toilets. So you might know vacuum toilets from an airplane, and airplane toilets are gross, right? But these are actually pretty nice, and people don't mind using them. And they use very little water, and the concentrated toilet waste then flows to a facility on-site, where it's made into biogas, which is used to heat the homes. And also, fertilizer comes out of it and water that could be reused in the homes, although the project doesn't reuse the water yet. But it's something that is possible, so it's the idea of building from the ground up a system that recovers the resources that we put into the toilet.

DAVIES: Right. So it all happens there on - in this housing development. Most people don't want to live near a sewage plant. What's this like? Does it smell? Are people even aware of it?

WALD: They are aware of it because they're pretty famous. The king of the Netherlands, when he was still a prince, went to open this site. And then they have tourists, you know, kind of special kind of tourists like me, come from all over the world to see what's going on there. On the other hand, I think that it's a very normal housing complex. It's - there's nothing, you know, particularly special about the people who live there or, you know, that make them more open to this kind of alternative system. They - and they don't really have to do much other than sort of, you know, use slightly different toilets. So they kind of have, you know, accepted it and gotten on with life. As far as the researchers tell me, they, you know, don't complain about it.

DAVIES: And do the numbers work? Is it economically viable?

WALD: Yeah. I mean, that's a good question. I mean, it is a demonstration project, so they have had some growing pains. And it's not to scale, but what they've determined is that, at a larger scale, that it really has the potential to be economically viable under, you know, certain conditions and that it's, you know, has the potential to be more environmentally friendly as well.

DAVIES: Would some of the problems we have with our sewer systems be solved if we had dedicated pipes that just carried human waste and other things went to different pipes?

WALD: Yeah. I think, you know, one of the problems is that, you know, our pipe - that everything does get mixed together, and even some old pipes mix in storm water, which makes things even more difficult. So, you know, the extent to which we can separate it out, the - you know, just like we do with recycling bins - the more likely you can use the different streams and make better use of the different streams. So maybe it means separating out urine or, like in Sneek, it means concentrating just the toilet waste, and they add food waste. So it depends what you want to do with it, really. But, yeah, the idea of having more pipes is one that's very appealing to innovators (laughter) who want to make use of the waste.

DAVIES: Right. But I assume it makes the system more expensive, right? - (laughter) twice as many pipes?

WALD: Yeah. And we're already - you know, many places are already locked into this old system, so replacing it is very daunting. But if you're building a new building, that's - it's certainly something that can be considered.

DAVIES: And there's information in the stuff that we excrete from our bodies. What are some of the ideas that come from the idea that, by Analyzing our liquid and solid waste, we can get useful health information?

WALD: Yeah. So when you go to a doctor, they might ask for, you know, samples of urine or stool. But your toilet takes those samples (laughter) every time you use it. And so your toilet could become a kind of medical device, and there are teams of innovators who are working on that. And then the sewers also contain a kind of flow of information about the health of our cities, of all the people in the city, as kind of a collective sample. And public health experts are working on collecting and analyzing that data in order to create policies that improve public health.

DAVIES: Right. So what are some of the specific things we've come up with? Are - there are actually boxes that hang in sewers that monitor stuff, right?

WALD: Yeah, there's a team that has come up with a kind of box that goes into manholes, extracts samples from the sewage and then analyzes it. What they were working on before the pandemic was the opioid crisis. They were finding evidence of opioid use in sewage and analyzing it to try to figure out patterns in a city. And once the pandemic started, they pivoted, along with many, many wastewater utilities around the world, and started trying to analyze sewage for evidence of coronavirus infections in the cities. And that has really picked up in the past year, and it has taken this field of wastewater surveillance and epidemiology to a whole new place.

DAVIES: So they're actually getting useful data about patterns in COVID infections and opioid use from samples taken from sewers?

WALD: Yeah. Well, they - yeah, they are learning how to analyze the sewage for those patterns, and they're learning how to use the data to make policy. It's a nice complement to other sources of information, like - you know, like, testing of individuals, like PCR testing in the case of coronavirus. Yeah.

DAVIES: Let me reintroduce you again. We are speaking with Chelsea Wald. She's a science writer, and her new book is "Pipe Dreams: The Urgent Global Quest To Transform The Toilet." She'll be back after this short break. I'm Dave Davies, and this is FRESH AIR.

(SOUNDBITE OF FOTHERINGAY'S "THE SEA")

DAVIES: This is FRESH AIR. I'm Dave Davies, in for Terry Gross, who's off this week. Our guest is science writer Chelsea Wald, whose new book describes how scientists are exploring ways to redesign toilets, sewers and other systems that take care of our solid waste. The book is "Pipe Dreams: The Urgent Global Quest To Transform The Toilet."

If I remember this right from your book, 3.4 billion people in the world don't have what experts call safely managed sanitation, the kind of flush toilets and sewer systems that we take for granted. What are some of the ways people relieve themselves, and what happens to the waste that is generated?

WALD: Yeah, that's more than half the world's population doesn't have this kind of system or else a system where the waste is safely managed from an onsite system, like a septic tank, and then gets emptied and taken to a treatment plant. So it doesn't make it safely to treatment. Some people don't have any toilets at all. They practice what's known as open defecation. Other people - many, many people in the world use pit latrines, and those pit latrines might be nice and functional, or they might be in really bad shape. And when they fill up, especially in cities, which - where - when many people use them, they can fill up - and that can cause a problem because there might not be an emptying service or an emptying service that can come and take the waste safely to a treatment plant. There may not be a treatment plant.

DAVIES: So this waste that is undisposed of, that collects in streets and sewers and in pits in people's yards, what sort of health risks does this present?

WALD: So the exposure to the pathogens in poop can cause diarrheal disease, which affects children disproportionately - causes a lot of suffering and death, especially among children. And it can lead to a condition called stunting, which is not just to do with height, but cognitive function. That can persist throughout the life of the child and has effects in later generations, as well. It's a multigenerational problem. There can be outbreaks of diseases like cholera and typhoid fever, which were common, you know, in London and in U.S. cities in the 19th century, but ended after the widespread installation of wastewater systems and drinking water systems.

DAVIES: Bill Gates has identified this problem of bringing sanitation to more people in the world as a major focus of his philanthropy. What's he up to? What is he doing?

WALD: Yeah. So he is very active in this area, or the foundation is very active in this area. About a decade ago, they had the Reinvent the Toilet Challenge, which I think brought this issue to the attention of many people because it was an exciting challenge in which he asked research groups all over the world to come up with a new way to handle waste on-site without a infrastructure grid, a sort of high-tech toilet for an extremely low-resource context. And those have kind of been in development since then.

And on top of that, the foundation does a lot of other funding. They certainly haven't limited their investment to this kind of moonshot toilet approach. And they also fund the education of wastewater experts, sanitation experts from low- and middle-income countries all over the world. They fund projects that are creating new ways to empty pit latrines and to treat fecal sludge, which is the material - the name for the material inside pit latrines. They are coming - helping to support new business models and financial models for sanitation, which is a big problem, and, you know, even new, you know, odor-fighting chemicals, you know, to help make toilets smell better.

DAVIES: So the goal here is not just to get better toilets, but to find systems that people can use which will take care of the waste and dispose of it responsibly and in sanitary ways. You looked at a program in Haiti that looked pretty interesting that is effective at low cost. Do you want to describe this?

WALD: Yeah. So I went to Haiti, Cap-Haitien. It's a port city, really beautiful city with a lot of poor areas where people have either no toilets or very low-quality toilets. And there's a program there called SOIL that is innovating in this area that's become known as container-based sanitation, with projects popping up all over the world, especially in these informal settlements, sort of urban - dense urban slum environments.

And what they offer - it's a business. It's a social business. And the customers rent a toilet. Inside the toilet is a container. And then every so often, they seal up the container. It's a sealed - they seal up the container, and they put it outside, where workers come and collect it. And so they transport it over ground, so they're either using these little three-wheeled motorcycles, you know, with a flatbed on the back, or sometimes they have to use wheelbarrows 'cause the streets are so narrow. They collect the containers and take them to a depot, where they get loaded on larger trucks and taken to a processing center, where it gets turned into compost, which is great for Haiti's depleted soils.

DAVIES: So what you have here is something which is really a low-tech idea. I mean, it's a container that's in your house. It gets sealed, and then somebody picks it up and gives you an empty container. But it's a way of dealing with this without having to have a huge, massive, billion-dollar sewage system. Does it seem to be catching on? Do people like it?

WALD: Yeah. I went around with the team and met many of the customers who liked the system. It's private, which is something that these pit latrines often aren't. They're outside the house. You know, they might not have doors that lock. And it's not susceptible to the flooding that happens. When I was in Cap-Haitien, it rained, and the rain came down so hard. And the next day, the streets were completely flooded, which made it hard for the team of workers to go around and collect the toilet - to collect the containers. But also, pit latrines were flooded, and it was hard to get to them. But with these containers, they could - people could just take them and pick them up and put them on a table inside. And then they would have - they would still have a toilet.

DAVIES: Let me reintroduce you again. We are speaking with science writer Chelsea Wald. Her new book is "Pipe Dreams: The Urgent Global Quest To Transform The Toilet." We'll continue our conversation in just a moment. This is FRESH AIR.

(SOUNDBITE OF FRANK ZAPPA'S "BLESSED RELIEF")

DAVIES: This is FRESH AIR, and we're speaking with science writer Chelsea Wald. Her new book is "Pipe Dreams: The Urgent Global Quest To Transform The Toilet."

You know, programs that deal with our waste on a large scale have a better chance if the numbers work, if we actually find ways that our waste can be processed into things that have value and that people want to buy. You know, municipal sewage treatment plants, for a long time, have been turning this, you know, sludge into biosolids, essentially fertilizers. Are food growers and food companies comfortable using this for stuff that we eat, or does it go to - I don't know. What's it used for?

WALD: Well, it gets used in a lot of different ways. There's different classes of biosolids. And the class A biosolids can be used to grow just about anything, although there are some food companies that have sworn off using biosolids on foods. And there is a sense that there's an increasing sort of dissatisfaction among the public with biosolids. Some of this is that - you know, there's a history of people, you know, just being kind of grossed out by it, learning about it and saying, ew, that's gross. I don't want, you know, this stuff, you know, on my food. That's nasty.

But that's not the only part of the story. There - the problem with our sewers is that they really mix everything together. So it's not just toilet waste, but it's, you know, everything that you put down your drains in your household, that comes out of your washing machine. You know, there's plastics in there. There's industrial waste that ends up in the sewer. And all of that flows to the treatment plant. And some of it doesn't get completely taken care of by the treatment process. Treatment plants aren't designed to, you know, break down many of these molecules, and some of them persist and get embedded into the biosolids. And although they're regulated for certain things, there's increasing concern about, you know, these chemicals and plastics and other things in those biosolids. And so there's an interest in creating new technologies for making use of them, not just using it as a kind of fertilizer. Or the other two options that are very common is incinerating them or, you know, when neither of those is available, landfilling them.

DAVIES: There's a fascinating (laughter) idea here that involves the black soldier fly and letting their larva chew on sewage. And somehow this eventually ends up into - what? - a food for animals, maybe. Explain this. (Laughter).

WALD: Yeah. So there's this animal called the black soldier fly that actually exists in much of the world. It's - you know, it's already there. And it's particularly good for processing waste for the reason that it only likes to eat organic waste when it's in the larva stage - so when it's not in the fly stage. When flies land on waste to eat it, then they move to food. And then that way they transfer pathogens and are dangerous. But this fly won't do that because it doesn't eat in the fly stage. And so there are many research projects and companies who are turning this fly - and particularly the maggot form of the fly into a kind of technology that will then eat organic waste, including feces, but also food waste and other kinds of organic waste. And as it grows into a plump maggot, it becomes a really good source of protein, can be fed to livestock. And it could replace sources of livestock feed like fishmeal, which contributes to overfishing. So it's a more - potentially more sustainable source of livestock feed.

DAVIES: Wow. So the fly larva eats the sewage, they get fat on it. And then what - they're harvested and ground up. And what does the product look like? Is it pellets? Is it a meal?

WALD: Well, first let me just back up for a second and say that, you know, this is being really implemented more in places where you don't have sewers and sewage, but you have either a container-based system or potentially a kind of dry pit latrine waste. The larva can actually be fed directly to chickens, although, you know, when I've seen that done, it's been larva that have been, you know, raised on food waste (laughter). But a - you know, I talked to an animal nutritionist in Kenya who mixes feed for farmers, and he's taking larva from a project in Kenya, and he mixes it into animal feed. And he gives that to farmers who use it.

DAVIES: You know, one of the problems that afflicts sewage systems is clogging. And you tell this amazing story, in 2017, of workers in London discovering - well, you describe this. (Laughter).

WALD: So sewer workers discovered this massive fatberg, which was 275 yards long and 140 tons, and they named it Fatty McFatberg. And I mean, I'm laughing, but it's actually not funny, you know? These are massive agglomerations of fat, oils and grease mixed in with lots and lots of different kinds of trash. And they clog sewers and, you know, take a lot of - you know, cost a lot of money to clean out and are also a big problem for the workers who work in the sewers. You know, this is an increasing problem as we put more of these oils into the sewers from cooking and also put more trash into them, like flushing wet wipes.

DAVIES: Right. And just so I'm clear about this, this was in a big sewer pipe in London that they found this. It was clogged with this, you know, more than a hundred tons of fat and and other materials thrown together?

WALD: Yeah, it's in the sewer. Yeah, it's in the sewer.

DAVIES: Do we see this in the United States also?

WALD: Yes, absolutely. Especially in the older sewer systems, you see these fatbergs. And again, they're an increasing problem, and they cost cities, you know, really a lot of money every year to clean them out because people are abusing the sewers.

DAVIES: Yeah. How do you clean out a fat bird?

WALD: Yeah. I mean, sometimes with pickaxes or with power hoses and, you know, any way you can. It's very difficult. They can harden into very - almost, like, rock-like masses because of the sort of weird chemistry that goes on in them.

DAVIES: You know, there seems to be some uses for our human waste, but probably some psychological resistance just because it seems kind of creepy to people. Are people trying to figure out ways to - I don't know - make this more acceptable, talk about it in ways that give people comfort?

WALD: Yeah. This is the yuck factor or the ick factor, discusses a very strong emotion. And it's not always, you know, it doesn't always keep up with our scientific understanding. So for example, with recycled wastewater, which can be cleaned and purified into drinking water, the - you know, there's still a kind of yuck factor that creates resistance in the public. And people are looking at how we can - how they can decrease that resistance so that this important technology can be implemented. And, you know, one of the ways is to explain it to them, to give people information. Another way is to reframe it. And I think that, you know, branding has become a big issue in the topic of recycled wastewater. People really admire Singapore's branding of this reused water as new water. And also, building trust seems to be very important. So people, you know - Americans have a problem with trust in their drinking water. And so building this trust between the water utilities and people and involving communities in this decision are also very important, also creating a kind of social acceptability of the products.

DAVIES: You know, this issue of providing, you know, sanitary facilities in parts of the world where they don't exist seems like such an urgent problem. And like a lot of the serious problems facing us, there are interesting ideas and people of talent and good faith working on them. But the scale of the problem just seems so daunting. How encouraged or discouraged are you that we can make real progress on this?

WALD: I think I started out a bit skeptical in my research that these new technologies and these projects could really make a difference. But as I kept going in my research and found so many people devoted to this topic and working, you know, in a long-term way on developing their ideas and really implementing them in a practical way in the field, I started to believe in them a little more, I guess I would say, to believe in their potential to really make a difference. I am hopeful that some of these projects will eventually make it to the kind of scale that's needed to make it - to make a difference, to make progress on this really important, global problem - and to provide people, you know, not only with a kind of, you know, acceptable level of sanitation, but allow them to kind of become leaders in showing a new way to do things.

DAVIES: Well, Chelsea Wald, thank you so much for speaking with us.

WALD: Thank you so much for having me.

DAVIES: Chelsea Wald's new book is "Pipe Dreams: The Urgent Global Quest To Transform The Toilet." Coming up, John Powers reviews Joshua Cohen's new novel, "The Netanyahus," which John says is a genuinely funny book about serious things. This is FRESH AIR.

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