Changing the world, one flush at a time | MEDICUS 2023 Issue 4

Changing the world, one flush at a time

By Michael Penn, Director of Communications, Marketing and Alumni Relations, Duke Global Health Institute

Dr Brian Hawkins (left) reviews water samples taken from different stages in the reclaiming process // Credit: Chris Hildreth, Rooster Media

In a small, cream-coloured building on the site of a cotton mill in Coimbatore, India, sits a toilet with a lot riding on it. Its mission is to stop the spread of deadly diseases, conserve dwindling fresh water and even keep girls in school.

Can a toilet change the world? Professor of Electrical and Computer Engineering Brian Stoner, who leads the Duke team behind the unit in Coimbatore, thinks this one could. “I certainly believe it has that potential,” said Stoner, who is also part of the Duke Global Health Institute.

Around 3.6 billion people—nearly 46 per cent of the global population—lack access to safe sanitation, according to the United Nations’ 2023 World Water Development report. Nearly 500 million relieve themselves in the open, while many more use pit latrines or septic systems that discharge untreated waste into the environment. It’s a problem that impacts people in remote villages and densely packed urban slums, in poor countries and in places where population growth outstrips infrastructure. And it kills: Drinking or bathing in water contaminated by waste is one of the main drivers of diarrhoeal diseases that cause the deaths of more than half a million children under age five each year.

Stoner’s team is one of a handful of groups working to tackle these issues through the “Reinvent the Toilet” challenge, an initiative launched in 2011 by the Bill & Melinda Gates Foundation to spark development of a new generation of toilets capable of treating waste on site. To be considered, projects had to remove pathogens and other harmful agents from waste without drawing external water or power. And they had to do it cheaply, costing no more than five cents (USD) per user per day.

Professor Brian Stoner (right) with Dr Sonia Grego, a WaSH-AID researcher from the Duke Smart Toilet Lab are part of the Duke team behind the project // Credit: Chris Hildreth, Rooster Media

“It’s arguably the hardest way to do it,” said Brian Hawkins, a scientist who leads technology development for Stoner’s team. “If you’ve got a lot of space and a lot of time, [wastewater treatment] isn’t hard. If you’re trying to get it done in a small space and very quickly, it gets exponentially more difficult.”

In 2018, Stoner’s team developed a prototype they call “the Reclaimer.” It’s a boxy unit the size of a skinny refrigerator that uses electrical current to generate chlorine from the salts in urine, one of several chemical processes it deploys to cleanse bacteria, viruses and other unsavory bits from wastewater. Solids proved too expensive to treat within the system, and so the current model filters them out for separate processing. The result is water that, while not quite pure enough to drink, is safe to cycle back into the toilet, creating a closed loop. The unit can be connected to any toilet and can be powered by a solar panel.

The team also developed a mobile Reclaimer that enabled them to take WaSH-AID into the community for demonstrations // Credit: Chris Hildreth, Rooster Media

But for all its fancy chemistry, the Reclaimer is one of those rare engineering projects that is informed as much by human nature as science. Before completing the prototype, the team engaged a local partner to conduct surveys and focus groups in several communities in India, gathering input on what users might expect from a reinvented toilet.

One of the team’s most profound insights speaks to the unique significance of a safe toilet space in the lives of women, especially those who live in poverty. While men may face no stigma for relieving themselves in the open, many women in low-income countries endure the daily stress of finding private spaces to take care of bodily functions. The perceived shame of acknowledging female biology is so strong that girls often skip or drop out of school when they start menstruating.

When the Duke engineers heard these stories, they realised they were creating more than an environmentally friendly toilet. At the cotton mill in Coimbatore, they designed the entire building, selecting lighting, fixtures and even the floor tiles to foster a sense of comfort and privacy.

“That’s an aspect we’re really proud of,” said Stoner. “We wanted to think not just about the traditional use of a toilet, but what would make a space safer, more secure and more attractive for women and girls.”

What the Reclaimer is not—at least not yet—is particularly affordable. Although operating costs are minimal, a prototype unit is around US$12,000 to manufacture, too steep to expect wide adoption in places like India. Stoner’s team believes the price will come down through economies of scale, but also by finding more profitable uses for their technology in wealthier countries.

Hawkins thinks technologies like the Reclaimer could find a market niche in wealthier countries that face an increasingly water-scarce future. Households and larger developments could use the system to recapture and reuse wastewater. Multiple companies have shown interest in commercialising the technology, he said, including businesses in India, China, the Middle East, Africa, Europe and North America.

The hope is to build a kind of waste evangelism, akin to the movements around renewable energy and sustainable agriculture, that can seed market opportunities. “The people who really believe in the technology and can afford it are always the early adopters,” said Stoner. “Those first customers can make it attractive for businesses, and that brings the price down for the countries that really need it.”