Students designed a way to know when water left in a plastic water bottle in the sun is safe to drink.

Disinfecting water with the sun is an old idea. But students at University of Washington have come up with a clever way of checking whether or not the water being disinfected is finally ready to drink. Using simple parts, their cheap set-up is a solution for safe drinking water in poor areas, and it won them a $40,000 prize.


Solar disinfection of water is an old idea, and one that has sparked the interests of many designers hoping to come up with interesting and practical solutions for low cost clean water. Using the sun’s rays to disinfect water is a primary way to minimize water-borne infections. But one problem with many systems is the user doesn’t know when the water is finally safe to drink. That’s where the students at University of Washington step in.

University of Washington reports that using parts from a keychain that blinks in response to light, they created a device that is similar to what you’d find in a solar powered calculator. The device monitors how much light is passing through a water-filled bottle and how many particulates are obstructing the light. When enough particulates are removed, the sensor indicates that the water is now safe to drink.

The solution could be retailed at just $3.40, the students estimate, making it a viable solution for many non-profits that provide this kind of support to communities.

Via Treehugger