Ceramic filter makes water treatment easy

The technology sounds simple: fire a ceramic pot, perhaps coat it with a fine layer of silver, and let the water percolate through. In regions where water carries millions of microbes, this relatively inexpensive treatment method has its attractions. For about a decade, the nonprofit organization Potters for Peace has been teaching communities to manufacture their ceramic water filters, which retail for $5–15. Although they have been used widely from Nicaragua to Thailand, no scientific data have been published to prove their efficacy or to show how these ceramic filters work.

Now researchers from the University of Virginia report that clay water filters from Mexico and the U.S. can remove more than 98% of the test organism E. coli. With an added layer of silver, the filters remove all E. coli. "Without the silver—just the ceramic filter—it seems like it works well, but adding the silver further improves the performance," says coauthor James Smith.

"Until this report, there have been very little data on how [the filters] work and what the specific mechanisms are," says Kara Nelson, an environmental engineer who studies a variety of low-cost point-of-use water treatments at the University of California Berkeley. "Without an understanding of the fundamental mechanisms behind [a technology], we have to take a black-box approach," she says. "That's not efficient. There are so many different pathogens, so many environmental conditions, so many different things that could be in water."

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