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Industry: Email Alert RSS FeedA safe solution: disinfection at home could provide Africa with cheap and abundant potable water
Science News, March 1, 2003 by Ben Harder
RELATED ARTICLE: Do-it-yourself.
A grab bag of water treatments
Heat, ultraviolet radiation, filtration, or some combination of these can disinfect water, just as chlorine can. A few researchers consider these alternatives safer because chlorine can react with organic material in murky water and produce organochlorine compounds, which carry cancer risks. That hazard has elicited hesitation among some health workers in countries where the Atlanta-based Centers for Disease Control and Prevention (CDC) is promoting chlorination. However, most researchers agree that any risks from chlorination byproducts over a lifetime of drinking treated water are more than compensated for in developing countries by the reduced risk of death from diarrheal diseases at an early age.
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Straining water through a cloth or using some other method to remove sediments before adding chlorine mitigates the formation of potentially harmful byproducts and also reduces how much chlorine is required for treatment. Furthermore, according to a report by Rita R. Colwell and her colleagues in the Feb. 4 Proceedings of the National Academy of Sciences, cloth straining by itself can reduce cholera infections by 48 percent.
Some people use other low-tech disinfection methods to kill bacteria that can't be removed by straining water. Boiling kills pathogens, but fuels for heating often are too expensive or hard to obtain. Such fuels can also pose environmental and health risks.
Practitioners of solar disinfection put water into used soft-drink bottles or other clear containers--sometimes painted black on one side to improve heat absorption--and set them out in the sun. In strong sunlight, heat and ultraviolet radiation can render microbe-contaminated water potable in as little as 3 hours. Kenyan children who treated water this way suffered diarrhea 20 to 30 percent less often than did those who drank from bottles they left in the shade, Ronan M. Conroy and his colleagues at the Royal College of Surgeons in Dublin, Ireland, reported in 1996.
Filtering water through densely packed sand or storing it for several weeks also appears to improve water quality in certain conditions, says Conroy, but for many other alternatives in use, researchers "just don't have data on whether these things work."
Furthermore, such methods may purify water without preventing recontamination during storage, says CDC's Robert Tauxe. One advantage of chlorine is that some of the chemical remains in the water and continues to work as an antimicrobial agent. "If there is any recontamination, the chlorine will knock it out," says Tauxe.--B.H.
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