MIT has come up with a new way to remove salt from water, in a way that doesn’t filters (which eventually clog up) or require boiling (which uses too much energy to be sustainable). Instead, it uses a shockwave to slam the salt out of the water as it flows past.
The system, implemented by engineering and math professor Martin Bazant and his team, uses electricity. “[It is] a fundamentally new and different separation system,” he told MIT news. Saltwater flows through a “frit,” a material made of tiny glass particles. This is held in place by porous membranes on either side, but the water doesn’t flow through these membranes like it would in a filter system, but across them.
Instead, an electrical current is applied to the flow, and this “shock electrodialysis,” as it’s called, separates the water into ever saltier and fresher flows, running along next to each other in the pipe. Because the current affects the charged salt particles, they just move off to the side. At a certain current, a shockwave between the flows is generated, making the separation complete, like stripes in toothpaste. Then you just pipe off the fresh water.
The principal itself isn’t new, but its application is. “The breakthrough here is the engineering,” says Bezant. He took existing research, which achieved the same thing in non-flowing water and realized it could be used for desalination. And because there are no filters to clean and the system uses cheap, easy-to-find materials, scaling should also be easier. The electricity even kills some bacteria, which goes some way to sterilizing the water.
Right now, Bazant’s system is best suited to small-scale cleanup. In future, with more testing, it may rival conventional desalination systems, but currently the simplicity and portability make it ideal for emergency use, in disaster zones for example, where it could be used to clean contaminated water or to provide temporary freshwater supplies from seawater.
Who said electricity and water don’t mix?