Removing all the dangerous bacteria from drinking water would have enormous health benefits for people around the world.
The technologies exist for doing that, but there's a problem: cost.
Now a scientist at the Massachusetts Institute of Technology thinks he's on to a much less expensive way to clean up water.
MIT's Rohit Karnik is a mechanical engineer who works on water technologies. He says it's relatively easy to make membranes that can filter the bacteria out of water. But making membranes cheaply, he says, is not so easy.
One day a few years ago, he was at a meeting on plants and water flow when a light bulb went off in his head. Why not, he thought, use the xylem tissue in plants for water filtration?
Now if you remember your high school biology, you'll know that xylem is the stuff in plants that transports water in the form of sap from the roots to the leaves.
"And the way the water is moved is by evaporation from the leaves," says Karnik.
It's somewhat like what happens when you put a straw into a glass of liquid. Evaporation from the leaves has the same effect as sucking on the straw.
Pulling water up to the leaves this way creates a problem for the plant, but also an opportunity for an inventor.
The plant's problem is something called cavitation, or the growth of air bubbles, which makes it harder for water to reach the leaves. But Karnik says xylem has a way of getting rid of these bubbles.
Written By: Joe Palca
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