The contest recognized efforts to reduce arsenic levels in water, a problem for millions of people in developing countries.

The Gold Award, and 1 million dollars, went to Abul Hussam, a professor at George Mason Univ. He developed the Sono filter, a point-of-use method. A bucket is partially filled with locally available river sand and a composite iron matrix. Sand filters out coarse particles from water poured into the bucket, while iron removes inorganic arsenic. The water flows into a second bucket where it filters through sand again, and then through wood charcoal, which removes organics. Finally, the water goes through fine sand and brick chips to remove small particles. The filters are made and used in Bangladesh.

The Silver Award and $200,000 went to Arup Sengyupta, an engineering professor at Lehigh Univ., and two student assistants, John Greenleaf and Lee Blaney; and Owen Boyd, CEO of SolmeteX Co., Northborough, Mass., and Arunk Deb, a retired vice president of Weston Solutions Inc., Chester, Pa. They developed a system that removes arsenic at the well head. Water is pumped through a fixed-bed column where alumina or a hybrid anion exchanger removes arsenic. The water then flows over gravel to remove particulates and is ready to drink. The systems are used in 160 locations in West Bengal, India, where villagers operate and maintain them.

The Bronze Award and a $100,000 prize went to Proctor & Gamble Co., Cincinnati, for the Pur water purifier developed by its Children's Safe Water Program. The purifier, costing about 7¢, consists of a sachet with all the chemicals needed to purify 10 liters of water. The company has distributed 57 million sachets in more than 30 countries over the past three years.