There are 2.5 billion people around the world who don’t have access to safe, affordable sanitation systems. That means every time they go to the bathroom they have to put themselves in an unhealthy or dangerous situation.
It’s a problem that the Bill and Melinda Gates Foundation believes can be solved by innovative technologies. And through their Reinvent The Toilet Challenge, they’ve recruited scientists and engineers from around the world to make new types of toilets and public sanitation systems for places that can’t afford modern upgrades. One of the companies they’ve funded, New Zealand-based Scion Research (a government-owned company), is developing a new type of toilet that used pressure and microwave technology to treat sewage right in people’s homes.
“We get to flush here and it gets out of our household and treated and discharged into the environment and we’re removed from the issue so we don’t have to handle it personally or live amongst it. In a large part of the developing world that’s not the case. Their proximity to their waste is constant and the risk of disease is high,” says Daniel Gapes, an environmental engineer working on the project.
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So why not just work on innovating infrastructure to help bring running water and sewage treatment facilities to places in the world that don’t have them? The Gates Foundation is working on innovating this as well, Gapes says, “but the fact is that in a lot of communities the infrastructure is so complex and the buildings and people are on top of one another and lack of access makes putting infrastructure in complex and unaffordable. Putting sewage into a city that doesn’t have it—the costs are mind-boggling,” he says.
So the Scion Research team turned to a technology that is fairly well known in large-scale applications (it’s used in mining and also sewage treatment), which they think could work well if innovative methods are used to downsize it. The method is called wet oxidation. Essentially, it works by taking waste and adding oxygen and then putting everything under pressure and gently heating it to about 400 degrees Fahrenheit.
“What would happen in that environment over a period of an hour is that organic material will oxidize. It gets converted to carbon dioxide and water. Just heating under oxygen pressure. It’s quite amazing,” says Gapes. The byproduct is completely sterile—a clear liquid that can be treated and passed through a filtration membrane to produce purified water and an ash that contains a high content of phosphorous, a chemical element used in fertilizer.
The challenge for the team is to find a way to create a small household system that contains heat and pressure in a way that is safe to have in a residence. Currently, the team is working on developing a microwave reactor that can quickly heat the unit, and they’re also looking at options for using electricity.
The end game is to make a toilet that looks familiar, is highly efficient, uses less water (because the regions it would be going into don’t have access to running water), and is very cheap. In fact, the Gates Foundation stipulates that the completed toilets should cost no more than 5 cents per person per day—and Gapes says ideally when finished it will cost even less than that. “It needs to feel like a regular toilet,” says Gapes. “The challenge is really high.”
There’s no guarantee it will work in the end. But Gapes says even if they’re not able to scale the technology all the way down to household size there will still be a benefit in the work. After all, even in the developed world much of the infrastructure is aging and the cost of replacing pipes and sewage systems can be astronomical (just look at the failures in Flint). If this research can find a way to decentralize sewage treatment on smaller scales then is currently necessary it could ultimately be a huge benefit.
“If working at the toilet scale is very very hard there are other scales. If you move to a bigger scale the cost might work and it’s still useful, it’s immediate, and remains exciting even if you didn’t quite crack the single toilet result,” he says.
