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Drinking water infested with germs and parasites or steeped in toxic chemicals is the number-one health problem in the world.

It’s so big, in fact, that the United Nations has proclaimed 2005-2015 to be the “Water for Life” decade. The UN goal is to get its member nations to honor their commitments to halving the proportion of individuals without access to safe drinking water.

But such huge development programs run by international entities such as the UN are not the only way to approach the problem, say some technologists and investors. Helping local entrepreneurs to buy and operate their own water purifiers may be the most efficient way to bring fresh water to the poor, according to famed inventor Dean Kamen and international financier Iqbal Quadir, a fellow at Harvard University’s John F. Kennedy School of Government.

Kamen, inventor of the Segway personal transporter, described his design for a simple, energy-efficient water purifier at last week’s Emerging Technology Conference, hosted by Technology Review (see last week’s story).

The concept has just gotten a boost, according to Quadir, from the successful completion of a trial in two small villages outside of Dhaka, Bangladesh, using an electrical generator designed by Kamen that could power the water purifier.

While the generator and water purifier have not been tried out in tandem in a rural setting, the tests showed that the generator can produce enough power to run the purifier. And the trial proved that the generator can even be fueled by gas produced by local cows’ dung. What’s more, it was a local entrepreneur who gathered the fuel and sold the power to local villagers.

Kamen and Quadir’s hope is that the two machines can be manufactured at a price that thousands of local entrepreneurs in developing countries could afford through small loans. In Bangladesh, a microloan program founded by Quadir and run by Dhaka-based Grameen Bank, has already helped tens of thousands of rural citizens buy cell phones, bringing telephone service to 60 million rural Bangladeshis.

Other experts consider the plan promising, but note that many cultural, as well as technological, obstacles must be overcome.

“Should it work the way they say it will work, it will be huge,” says Amy Smith, an inventor, MacArthur fellow, and MIT instructor who co-founded MIT’s International Development Initiative. “But it will not be easy.”

The basic design behind Kamen’s generator is nothing new. It uses Kamen’s version of a Stirling engine, which works as air heated in one chamber expands and moves a piston. The air cycles between hot and cool chambers, keeping the piston moving.

Any fuel source can be burned to heat the engine from the outside. In the villages outside Dakha, propane is available, but only sporadically, according to Quadir. Instead, the local entrepreneur gathered cow dung, put it in a bio-digester, and harvested the resulting gases.

Bangladesh’s national electrical grid is unreliable, and doesn’t even extend into the villages where the generator was tested. The trial showed that under these conditions, villagers were willing to pay twice the cost of grid power for juice from Kamen’s generator. Kamen believes that it may be possible to manufacture his generators, given enough orders, for $1,000, excluding marketing and distribution costs. If the generators can be made available at this price, Quadir estimates that the rates villagers could pay for power would be enough to make a loan program viable.

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