Cheap colloidal silver filters.

ROBERT SIEGEL, host:

To Yemen now, where conflict, corruption and a burgeoning water crisis have foreigners leaving and tourists staying away. But at least one American businessman is thriving. He’s one of a few dozen producers of affordable, deceptively simple water filters.

As NPR’s Peter Kenyon reports, some believe these filters could revolutionize the struggle to bring drinking water to poor people in Yemen and around the world.

PETER KENYON: On the western edge of sun amid a scattering of ramshackled mud and stone houses, Ali Sala Soloman(ph) shows up to work at his pottery factory.

(soundbite of construction)

KENYON: He watches as workers mold and press round filters that are made of clay with a small amount of sawdust. He pauses before a large brick kiln fed by an array of gas burners. Soloman checks the slowly rising temperature and nods. After 16 years of making flower pots and stoves, Salman has devoted his factory to this simple but incredibly effective technology. He’s starting out approximately 100 filters a day and his work is suddenly saving lives.

Mr. SOLOMAN: (Translator) It looks very simple, but it has certain specifications that make it work. The water is being filtered and purified. The parasites are kept away. And bacteria and other problems remain inside the filter and what comes out is only pure water.

KENYON: Over several hours, the kiln is heated to 880 degrees Centigrade, more than 1600 degrees Fahrenheit. By that point, the sawdust that was mixed in with the clay will have burned away, leaving the tiny pores that allow water to seep out. Later the filters will be dipped into a solution of colloidal silver, the ingredient that scientists say kills many water borne impurities.

These filters sit inside plastic containers that resemble garbage cans with spigots at the base. Each filter is tested to make sure that it flows at a rate of one-and-a-half to three liters an hour, a rate that allows the purification to take place.

The man who hired Soloman to make these filters is Richard Bony(ph), a former Peace Corps volunteer, who like many visitors to Yemen, fell in love with this beautiful, troubled corner of the world. With the help of the group, Potters without Borders, Bony launched the silver filter business in 2007. He amazed himself by selling 20,000 of them last year. And as someone new to the world of pottery, he still gets a kick out of watching the kiln in operation.

Mr. RICHARD BONY: It’s not cool. It’s really hot. And it’s one of the most beautiful things. When we get up around 7 or 800 degrees, you can open this little porthole in the kiln door and you can look inside and it is just a mass of charged particles all red and the filters are there, they’re almost surreal, you know, just sitting inside. Potters around the world will say, oh, that’s not so hot, you know. ‘Cause they fire often at 1100, 1200 degrees for glazes and things like that. To me it’s awesome.

PETER CANYON: Despite the low tech feel of the operation, each filter is created according to exacting specifications. And everyone is tested before leaving the factory. According to the World Health Organization, 1.7 million people, mainly children under the age of five die each year from diarrhea due to unsafe drinking water. Six months after these silver filters were introduced to two Yemeni villages, a study by Care, International found infant and child diarrhea down nearly 80 percent.

The filters aren’t perfect. They don’t catch viruses, for example, although testing is underway elsewhere to determine if adding iron to the colloidal silver will enhance their effectiveness. Bony sells his filters for $25 each and they can last for at last two to three years. One study in Nicaragua found filters still working after seven years.

Mr. BONY: I can’t actually tell you why it worked for so long. To me it’s like magic, you know. The science, just tell me why it works and so on and so forth, but, you know, there’s just something else that colloidal silver, which has an electrical charge, just sits inside that filter while it just keeps killing bacteria and parasites. And it’s really unbelievable.

KENYON: In large doses, silver can be toxic to humans. Among other things, it can turn your skin blue. But these filters have been in use since the early 1980s and studied have shown no harmful effects from the trace amounts that may remain in the water. Bony hopes to build more kilns this yeah and increase production, not to boost profits, but so he can lower the price of the filters and get more of them where they’re needed most: into the homes of poor Yemeni famtoms(ph).

Peter Kenyon, NPR News.