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The US National Academy of Engineering has issued scientists with a million-dollar challenge: to develop a cheap and sustainable method of removing arsenic from contaminated water.

This is the first target of the US$1 million Grainger Challenge Prize for Sustainability, established by the academy this year to speed up the development of technologies that are socially and environmentally sustainable.

Tens of millions of people in Bangladesh have suffered arsenic poisoning through drinking contaminated water from the country's ten million tube-wells. Arsenic is present in dangerously high levels in other parts of the world too, but developed countries such as the United States have access to expensive methods of treating the water to make it safe. 

Developing countries, which lack access to — or the capacity for — Western technology, will need a cheap household or community-based system to purify their water.

According to the Grainger Challenge Prize website, the winning system must "be technically robust, reliable, maintainable, socially acceptable and affordable, be manufactured and serviced in a developing country, and must not degrade other water quality characteristics".

Last year, Mark Elless and colleagues found that a species of fern could draw arsenic out of tainted water, reducing levels of the toxin nearly 100-fold within 24 hours (See Ferns clean up poisoned water).

In a Nature news story about the research, biogeochemist Andrew Meharg commented that "the ferns may not be able to cope with the huge volumes of water used for irrigation" and that "Bangladesh probably lacks the infrastructure needed to maintain such treatment facilities".

Speaking to SciDev.Net this week, Elless, whose team intends to try for the prize, responded to Meharg's concerns by saying "We agree that most methods of water treatment are not practical for agriculture:  the volumes of water involved are simply too large for pretreatment to be cost-effective".

However, he added, that use of the ferns to treat water for cooking and drinking "appears very practical".

Research from scientists based at the University of Illinois, United States, whose work last year showed that adding an inexpensive mineral to contaminated water reduced its arsenic content could, in theory, also be a contender for the prize (See A cheap fix for arsenic-polluted water?).

Craig Bethke, who led the Illinois team, told SciDev.Net "it will be interesting to see whether the successful solution involves a device to treat water after it has been pumped, or a method to reduce arsenic [while it is still] in the aquifer by stimulating bacterial activity".

During the next few months, public input into the competition's design can be made through the Grainger Challenge Prize website. Detailed criteria for participating in the challenge will be made public in June 2005.

Applicants will then have until June 2006 to submit their ideas, and the prize will be awarded in February 2007.

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