Germs Begone: New technology cleans dangerous water

An experimental mix of chemicals permits low-cost home treatment of highly contaminated water. The packet has been designed for use in developing countries, where some 5,000 children die each day from diarrheal disease–primarily because of poor sanitation and infected drinking water.

WHICH TO SIP? Some people drink organics-laden water (left three glasses) without boiling it. Treatment cleaned Kenyan dam water (leftmost) into clear, germfree water (rightmost). Procter and Gamble

The new treatment turns even dark, foul-smelling, germ-laden water into a drink as clean as most U.S. tap water, says Stephen Luby of the Centers for Disease Control and Prevention in Atlanta. The chemicals’ cost should run about a penny per liter of treated water, according to Greg Allgood of Procter and Gamble’s Health Sciences Institute in Cincinnati.

During tests in Guatemala, Kenya, Pakistan, and Bangladesh, residents were instructed to stir a 4-gram packet of the chemicals into a 10-liter jug of river or other water for 5 minutes, until dirt and other suspended materials settled out. Villagers then filtered out the sediment by pouring the water through tightly woven cloth. Over the next 20 minutes, the water’s residual chlorine bleach vanquished germs.

The first step of the method resembles the flocculation used to pull algae and their toxins out of seawater (SN: 11/30/02, p. 344: Available to subscribers at Taming Toxic Tides).

Although bleach alone is a good disinfectant (SN: 3/1/03, p. 136: Available to subscribers at A Safe Solution), dirt and other organic gunk can chemically disarm it. By first removing organics with clay and ferrous sulfate, the mix reserves its controlled-release bleach until the water clears. Flocculation also removes many metals and other poisons, providing an added benefit over bleach treatment alone.

Philip K. Souter of Procter and Gamble in Newcastle-upon-Tyne, England, designed the mix, which enters the company’s PUR line. The water-purifying mix is the company’s first product intended for consumers in the developing world.

In the June Journal of Water and Health, Souter’s team offers data on dirty water collected from sites around the world. The scientists spiked their samples with large quantities of pathogens, including 14 types of bacteria, 2 viruses, and 2 parasites. The PUR mix reduced bacterial loads to less than a hundred-millionth of starting concentrations, the viruses to less than a ten-thousandth, and the parasites to less than a thousandth of initial values. The flocculation also removed more than 99 percent of the naturally occurring arsenic in water from a Bangladesh well.

Final concentrations of these toxicants met World Health Organization guidelines for safe drinking water, Allgood notes. In unpublished studies, the PUR mix removed 95 percent of the DDT, at least 98 percent of lead, and more than 99 percent of chromium in water samples, Allgood told Science News.

Last March, Luby and his colleagues reported in the Journal of Water and Health that in a Guatemalan test, the PUR mix disinfected the fairly clear local water as well as bleach alone did. However, Luby says that the mix’s sedimentation of what had been barely detectable pollution offered a visual sign of the treatment’s activity. This encouraged many villagers to stick with the treatment long enough to see a decrease in diarrheal disease. In unpublished work, Luby’s group measured a 40 percent reduction in diarrheal disease among households tested over a 4-month period.

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Janet Raloff

Janet Raloff is the editor of Science News for Students, a daily online magazine for middle school students. She started at Science News in 1977 as the environment and policy writer.

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