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Simple Solar Water System Devised to Kill Pathogens

Water pouring into a glass

(Greg Riegler/Flickr)

Engineering and food science faculty at Purdue University in West Lafayette, Indiana  designed a solar device to kill waterborne bacteria that the inventors say can help provide clean drinking water to millions of people in developing countries. Civil and environmental engineering professor Ernest “Chip” Blatchley and food science biologist Bruce Applegate, with the help of students, built several prototypes, and Purdue’s technology commercialization office filed an international patent for the technology.

The device pumps water through a plastic pipe that’s transparent to ultraviolet (UV) rays, placed in a parabolic reflector. The U-shape of the reflector mirror concentrates the sun’s rays to make the UV radiation more intense inside the reflector than on the outside. As water flows through the pipe, the concentrated UV rays damage the DNA of the microorganisms in the water, so the microbes cannot grow or reproduce, thus ridding the water of disease-causing pathogens.

Blatchley and Applegate believe the device can work effectively in or near equatorial regions where solar exposure is plentiful. Their tested the system in West Lafayette with non-pathogenic bacteria similar to waterborne microbes causing cholera and typhoid. The results, say the researchers, can be applied to regions where these disease-causing microorganisms are prevalent — often from human or animal waste —  and also have similar or higher levels of UV radiation.

“We have information about how UV irradiance in West Lafayette compares to cities around the world including Port-au-Prince, Haiti, and the Kenyan cities of Eldoret and Mombasa,” says Blatchley in a university statement. “The maximum solar irradiance that occurs in West Lafayette is similar to the minimum values observed in these near-equatorial cities.”

The researchers built small-scale prototypes that produce clean water at rates of up to 20 milliliters (0.68 fluid ounces) a minute. The protoypes were built on a small scale to make testing economical, but they plan to scale up and demonstrate their device.

The following video tells more about the UV water system.

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