[[Image:UV lamps.jpg|thumb|right|300px|In Bhupalpur, India, Ashok Gadgil's ultraviolet-light water purification system treats water from a public well. Photo: [http://web.mit.edu/invent/www/ima/gadgil_bio.html Ashok Gadgil.]]]
UV irradiation provides a quick and effective way of disinfecting water supply from harmful bacteria without leaving a chemical residue, like the one chlorine leaves. <ref>UV light has demonstrated efficacy against pathogenic organisms, including those responsible for cholera, polio, typhoid, hepatitis and other bacterial, viral and parasitic diseases.</ref>
Two alternative configurations or physical systems are used for UV disinfection of small or household water supplies, submerged lamps or lamps in air and mounted above a thin layer of the water to be irradiated. In the units with submerged lamps, the lamps are covered with a protective, UV-penetrable as protection from the electrical hazards associated with water. Water can be treated on a batch basis by placing the lamp in a container of water for several minutes or longer, or on a flow-through basis in a housing or channel, with the water flowing parallel or perpendicular to the lamp(s).
UV Waterworks systems have been used in India, South Africa, the Philippines, Honduras, and other countries. Since 1998, the Mexican government has installed about 100 in Guererro, a state on the Pacific in southwestern Mexico. The results have been very positive. In the summer of 2000, Gadgil reports, people from Water Health International returned with stories and data showing a dramatic decline in the incidence of diarrhea among children and adults. And preventing deaths and illness are just the most visible effects of purifying water—it also protects children from stunted physical and mental growth. "This is the kind of story that really makes my day, really makes me happy," Gadgil continues. "It makes me feel good when I get up in the morning."
==Reference manualsManuals, videos, and links==
[[Image:UV lamp unit.jpg|thumb|right|250|UV Waterworks commercial unit. Photo: [http://eetd.lbl.gov/l2m2/waterworks.html UV Waterworks.]]]
* Commercial UV units: [http://www.purestfilters.com/ultraviolet.htm Ultraviolet Water Purification Systems Available from Purest Filters.com.] Prices start at USD$ 365.
* Commercial UV unit: [http://eetd.lbl.gov/newsletter/cbs_nl/nl09/cbs-nl9-waterworks.html UV Waterworks: Reliable, Inexpensive Water Disinfection for the World.]
==References==
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==Acknowledgements==
* [http://www.who.int/water_sanitation_health/dwq/wsh0207/en/ Managing Water in the Home: Accelerated Health Gains from Improved Water Supply]. WHO, 2002.
* [http://web.mit.edu/invent/www/ima/gadgil_bio.html Courage: Ashok Gadgil.] From the book: Inventing Modern America: From the Microwave to the Mouse. David E. Brown. MIT Press.