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
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.
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