Reclaiming Water from Waste

9/17/20 Podcast

Washing our hands with soap and running water for at least twenty seconds helps prevent the spread of pathogens. For areas of the world where water is scarce, ECE faculty member Brian Stoner and his colleagues at WaSH-AID are reclaiming usable water from an unlikely source.

podcast cover art: toilet
Reclaiming Water from Waste


Brian R. Stoner Profile Photo
Brian R. Stoner Profile Photo

Brian R. Stoner

Research Professor in the Department of Electrical and Computer Engineering


Miranda: This is Rate of Change, a podcast from Duke Engineering dedicated to the ingenious ways that engineers are solving society’s toughest problems. I’m Miranda Volborth.

Theme music: Leopard Print Elevator by Kevin MacLeod (License)

Among all the things we take for granted, one of the most important (toilet flushing) is the toilet. More broadly, I mean our access to safe, well-managed managed sanitation systems. When people who lack this access come into contact with water contaminated with human waste, the health effects are profound.

In the early spring of 2020, I asked Brian Stoner, the director of the Duke Center for Wash-AID- Water, Sanitation, Hygiene and infectious Disease, to record a conversation about those effects. And how Wash-AID engineers are trying to increase access to safe sanitation, through solutions developed at their lab in Durham, and field tested in India—solutions including a toilet system called the Reclaimer, which treats wastewater electrochemically to render it pathogen-free and generates clean water for reuse.

Then… (News clips that Duke’s campus has closed due to Covid-19.)

Miranda: When I finally caught up with Brian, it was April. And it via Zoom, so our conversation sounds pretty echo-ey. Thanks for bearing with us.

Miranda: How are you doing, and your team? Is everybody doing ok?

Brian: Team’s doing well, I mean as well as can be expected. Being a lab-based center, it’s a bit challenging, when you’re doing that without a lab.

Miranda: Yeah. What about your team in India? Have you—I mean, I assume you’ve been keeping tabs on them, how are they kind of dealing with everything?

Brian: India’s a challenge. It’s a challenge to say, “Here’s what the World Health Organization is telling us,”  and now trying to advise people to apply those procedures. For example, social distancing and hand washing is a middle-class luxury that we have. To say “wash your hands for 20 seconds” to people who live in an area where it’s been water-stressed for the last decade is… is not practical. You know, 20 seconds is a long time! I don’t know if you’ve tried to sing Happy Birthday twice, while washing your hands. I mean, we do that now, consciously, because we’re thinking about it, but that’s significantly longer than most people who have access to plenty of water would do.

Miranda: you know, as we’re talking about this… earlier, I was kind of thinking about it as very distinct from what’s going on right now, but it’s not. It’s sanitation and hygiene as related to infectious disease. So it is all…

Brian: Thank you for making that connection. We’ve been getting a lot of calls—I mean, there’s absolutely a lot of crossover. I think we’ve seeing it as well with Covid-19. I mean, what’s really sad about this most recent coronavirus is, it attacks those who… it attacks the poor. It attacks those who lack access to health care and a lot of what we are wrestling with on the toilet project and the global sanitation crisis—there’s a huge overlap in terms of— groups that are negatively impacted by the lack of safe and effective sanitation, are the most vulnerable in pandemics like this that are going to prey on areas that lack safe hygiene, sanitation,    access to health care, people packed into tight spaces… there’s a huge overlap.

Brian: It’s actually a sad statistic— in a world that has over seven billion people, you have probably more than four billion people in the world that lack access to what we call safely managed sanitation. And that means everything from no sanitation or no safe wastewater treatment directly, as well as infrastructure that is overburdened. This could be a waste treatment facility that was built 30 years ago, and now the city has grown by a factor of ten and it’s just overflowing. And so the water might go into a wastewater treatment facility, but it just goes out untreated. So that’s about 4.2 billion people in the world that lack access to properly managed sanitation. And the result is, you know, there are almost half a million diarrheal deaths every year, from lack of access to safe sanitation.

Miranda: yeah, that number—every time I hear it, it does not shock me any less. It’s still a staggering number.

(Music from

Miranda: WaSH-AID has been working on a solution called The Reclaimer, which is currently funded by the Bill and Melinda Gates Foundation, as part of its Reinvent the Toilet Challenge. These toilets have to not only remove pathogens from human waste, but reclaim resources: energy, nutrients, or water.

Brian: In areas that lack access to clean water… ideally, we want the ability to wash our hands. Or wash surfaces that we’re going to come into contact with. But in areas that are water-stressed, that’s a huge challenge. So if you have something like the Reclaimer, or more generally, the ability to treat wastewater and render it safe enough to be able to be used for non-potable applications, including handwash and other washing applications, that’s a huge bonus.

So the Reclaimer is a system that’s designed to take fecal-contaminated water and it treats that in such a way that it’s safe to discharge directly to the environment, so it meets certain international standards for discharge. It’s treated even sufficient for human contact, just non-potable use. So it’s up to—stopping short of—being able to create drinking water from it.

Miranda: I remember that when I went into your lab to meet you. That was one of the things that really stuck out to me, that I remembered, were the two vials on your windowsill. One was—the “before” vial—was just this murky, gray-brown kind of sludge, and the second was crystal-clear. It looked like rainwater.

Brian: Yep, and that is striking, yes. The brown, muddy-looking water, that is what comes in, and what comes out is indistinguishable from clean tap water. It would need to go through one more stage if treatment to remove some of the inorganic compounds, and some of the salts that exist from following the treatment process, but otherwise, optically, to the human eye, it’s indistinguishable from clean tap water.

Miranda: But… the end product didn’t look like clean tap water in 2014, when the Reclaimer was first put out into the field.  

Brian: In the beginning, our technology was able to clean and disinfect the liquid that met local discharge standards, but it was still slightly brown. When you see a brown liquid, and you know it came from a toilet, you know exactly what that brown liquid represents. You don’t want to touch it, you don’t want to smell it. Your goal is—your challenge, really, in converting that to something that is useful and something that someone would feel comfortable washing their hands with, is you have to first convince them that it’s ok. But then also I think there’s the challenge of turning it into something that looks and feels different. By this—and take the Reclaimer as an example—the Reclaimer uses the natural salts that exist in urine, and it converts them into chlorine. So we’ve been to pools—pools are treated with chlorine to prevent bacteria from building up. We know that smell. The smell of chlorine is often from bleach products and cleaning products—we associate that with something that’s been cleaned. We don’t associate that with something that is brown, fecal-contaminated water. And so part of our process —and I think one of the advantages is, as we take something that’s a brown smelly liquid and convert it to a clear liquid, you also end up with a residual amount of chlorine that’s dissolved in that liquid. So that when someone does smell it, they already perceive it as—and genuinely—as something that’s cleaner, and different, than what it came from.

Miranda: Fun fact. Brian Stoner’s father was also an engineer who worked on similar projects for use in Navy submarines. They developed a way to harvest the salts that occur naturally in urine, convert them to chlorine, and use them to treat wastewater.

Miranda: Brian says there’s no substitute for the feedback you can gather in the field.

 Brian: In the field we’ve gotten so much interesting feedback from how people are using it and experiencing  the system that forced us to go beyond just getting a technology and worked in the lab and met the engineering standard, but also had to meet some of the social and cultural standards.  Another interesting anecdote is, when we’re testing in the lab we don’t test all the ways someone can use, misuse, and abuse a system, and people get pretty creative. Cleaning solutions—standard cleaning solutions that we would use here in our labs at Duke are very different than what might be commonly available or typically used in India, for example. There’s a very aggressive acid-based solution that was being used in one village, and it was pretty common.

Miranda: Brian says that every time visitors associated with the project would go to the test site, the system would break down. They were flummoxed. Eventually, they discovered that to get the site super clean, people were swamping it with hydrochloric acid, which the components just couldn’t stand up to.

Brian: It just destroyed a number of the materials that we were using in our processes, and we never tested for that. We didn’t know about it, so we weren’t testing for it. By going out into the field you learn a lot of vulnerabilities to your system—we call it “stress-testing.” One of the challenges—you want your system to fail, meaning that you want to see how it fails and where it fails. And quickly feed that back to your engineering team, so you can design a system that becomes more robust to a broader set of use cases. If you develop something that can only survive when run continuously in your lab, you don’t have something that is useful when you start taking it out into the communities.

Miranda: Women have emerged as a really crucial stakeholder group in this feedback process. How are you incorporating their feedback into revisions and, you know, continuing to improve the design?

Brian: Thank you for bringing that up. It’s a sad fact that in many communities that lack safe and effective sanitation, that women and girls are disadvantaged in other ways. We consider women to be one of the more critical stakeholder groups for a number of reasons. Men, as we say, tend to go any way, anywhere, anyhow, with less constraints socially over how they use the bathroom. With women there are a lot more constraints. So for us it’s not just being able to provide a physical need, but it’s also a level of dignity—and in many cases, safety—that’s important. So in the very beginning, in 2014, we started working with a group called SEWA—it’s an acronym, S-E-W-A, Self-Employed Women’s Association—it grew out of the garment district in a state in India—they work with us to go into communities and establish a level of trust, especially with some of the female stakeholders, to understand what their needs are and to be able to talk about the safety and dignity portion of it, as well as the menstrual hygiene element. And so a lot of groups, people, or companies that try to develop sanitation solutions or toilet solutions for low-income communities neglect the need for safe disposal and replenishment of hygiene products, and that is a critical oversight.

Miranda: You can learn much more about how WaSH-AID is addressing this oversight in the next episode of Rate of Change.

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