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How UV light in water disinfection works

This is Science Today. After sunlight, chlorine is one of the oldest disinfection methods for water supplies. Bassam Younis, a professor of civil and environmental engineering at the University of California, Davis, says the toxicity issues with chlorine are now well-known and so disinfection alternatives include filtering and the use of ultraviolet light.

Younis:            The UV light doesn't actually kill the microorganisms, what it does is through photochemical process, it disrupts part of their DNA, which means that that they can not reproduce. If they can not reproduce, they can not establish colonies and if they can not establish colonies, then they can not harm you. So, they are rendered harmless rather than destroyed by this process.

Narrator:        Younis has developed novel technology for water disinfection called UltraV, which does away with the current practice of using mercury lamps, which is expensive to dispose of. UltraV is currently being tested at the UC Davis wastewater treatment facility. For Science Today, I'm Larissa Branin.