Published on March 11th, 2009 | by Tina Casey8
Revved-Up Sand Could Purify Water
First there was the Life Straw. Then there was the Aquaduct Tricycle. Now ordinary sand could provide an answer to one of the thorniest problems of the future: how to purify drinking water for the many millions of people who don’t have access to a clean, disease-free source — and no means to pay for conventional water treatment.
Cryptosporidium and Waterborne Disease
Cryptosporidium is a genus of microscopic, chlorine-resistant parasite. It is one of the most common causes of waterborne disease, even in the U.S, where it is both a drinking problem and a recreational hazard. When they make that announcement that everyone has to clear the kiddie pool, that’s cryptosporidium.
Cryptosporidiosis is the potentially life-threatening diarrheal disease caused by the parasite.
Enter Sand Man
Dr. James Amburgey is assistant professor of Civil and Environmental Engineering at the University of North Carolina – Charlotte. Searching for a simple, low-tech, low cost way to treat water for crypto, he came upon a system that relies on sand, piping, and some common chemicals. The result is a stepped-up treatment system that works 30 to 50 times faster than conventional sand filtration.
Iron (III) chloride, also called ferric chloride, is the secret weapon that Dr. Amburgey deployed to rev up the process. Normally, the tiny crypto parasite slips easily between grains of sand. Both are negatively charged, exacerbating the slipperiness. By adding a ferric chloride pretreatment to the water, Amburgey neutralized the Cryptosporidium’s surface charge.
One important advantage of Amburgey’s process is simplicity. Instead of having to adjust the pretreatment chemicals for each water source, so far his tests have shown that the same dose is effective on local creeks, rivers, and wastewater. And, practically any local source of sand or crushed rock can be used.
Another interesting factoid: the process relies partly on recycled chemicals. Much of the ferric chloride in use today is recycled from the steel-making process.
Other new developments in water filtration, like carbon nanotubes, promise a high-tech fix. For the low-tech world, Amburgey’s approach could be just what the doctor ordered.