David Warsinger

David Warsinger thinks he’s found an innovation that could help combat one of the 21st century’s great environmental challenges: water shortages around the globe.

His fix is an improved form of reverse osmosis—the most common method of desalination. Today, an estimated 5% of the world’s population relies on desalinated water, drawn from the ocean or brackish inland sources, to meet at least some daily needs. This figure will continue to rise as aquifers are further squeezed by pollution, overuse, and shifting rainfall patterns linked to climate change. According to the United Nations, some 3.6 billion people live in areas that experience water scarcity at least one month of the year—and that number is likely to exceed five billion by 2050. “Globally, we are truly tapping out our water resources,” Warsinger says.

Yet desalination today has major limitations. Traditional reverse osmosis, in which pressurized water is forced through a salt-removing membrane, uses a lot of energy and is costly. It also leaves behind a large part of the water as brine—an especially big problem for inland plants, where source water is scarcer.

Warsinger’s system, which he developed with Emily Tow while they were both at MIT, is known as batch reverse osmosis, and it is designed to make the process more efficient. The technique allows desalination to occur in batches, with salinity and pressure varying over time. Whereas traditional reverse osmosis systems apply constant pressure, the batch system is engineered to apply less pressure to water that’s less salty, saving a considerable amount of energy. It also increases the rate of fresh water extraction by minimizing the build-up of salt on the membranes.

Warsinger’s lab at Purdue, where he’s now a professor of mechanical engineering, has since worked to refine the batch design. His team has developed a trailer-sized prototype it hopes to use for pilot plants in Peru and Kenya.