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A quarter of the population of Bangladesh drinks water from tube wells--a cheap, low-tech way of accessing groundwater. Many of the country's estimated 10 million tube wells were built with international aid to provide an alternative to bacteria-tainted surface water. Unfortunately, these wells frequently tap into aquifers contaminated by arsenic from natural sources. The Grainger Challenge Prize's Gold Award-winning SONO filter is a point-of-use method for removing arsenic from drinking water. A top bucket is filled with locally available coarse river sand and a composite iron matrix (CIM). The sand filters coarse particles, while the CIM removes inorganic arsenic. The water then flows into a second bucket where it again filters through coarse river sand, then wood charcoal to remove organics, and finally through fine river sand and brick chips to remove fine particles and stabilize water flow. |
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