Disinfection system harnesses sunlight to produce safer drinking water

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WEST LAFAYETTE, IN, Oct. 24, 2013 -- Two professors at Purdue University -- Ernest "Chip" R. Blatchley III, professor of civil engineering and environmental and ecological engineering, and Bruce Applegate, associate professor of food science and biological sciences -- have developed prototypes of a water disinfection system to harness ultraviolet (UV) radiation from the sun.

Applegate said the Purdue water disinfection system pumps water through a UV-transparent pipe placed on a parabolic reflector. "The shape of the reflective mirror concentrates the sun's UV rays so the radiation inside the pipe is more intense than outside," he said. "The radiation damages the DNA in microorganisms; the microbes can no longer grow and the water is safe."

According to Blatchley, more than 800 million people do not have readily available, inexpensive access to a safe water supply. "Common problems include microbial pathogens, which are largely associated with human and animal waste," he said. "If you take a global view of people who have little or no access to safe water, you'll see that most live close to the equator. Solar UV radiation is abundant in equatorial and near-equatorial nations."

Blatchley said the results from experiments conducted in West Lafayette could translate to the field where higher levels of UV radiation exist. "The maximum solar irradiance that occurs in West Lafayette is similar to the minimum values observed in Port-au-Prince, Haiti and the Kenyan cities of Eldoret and Mombasa," he said. "The experiments we conduct here, where we have had success, should be at least as successful if they were conducted in these near-equatorial cities, and probably quite a bit more."

The researchers now are determining how to scale up production in the system, which currently produces water at a rate of about 10-20 milliliters per minute. "The original prototypes were intentionally built on a small scale so we could conduct experiments using a relatively modest amount of time and resources," Blatchley said. "We have ideas on how we expect it to scale up, and we plan to demonstrate those."

The Purdue Office of Technology Commercialization has filed an international application for patent of the innovation.

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