“This should come out costing one to two cents a day for a family of four in the developing world,” said Mason B. Tomson, a professor of engineering at Rice who was a co-author of the report. Tomson added that the process would leave a small amount of arsenic-laced residue, enough to fill a cooking bowl in a year, that villagers would have to collect and dispose of, probably in landfills.

The researchers said further research was needed to determine whether the magnetite would be an improvement on other nanoscale minerals already used in such systems, including zirconium, aluminum, iron and manganese compounds.

Even if Tomson’s cost estimates are correct, researchers still have to demonstrate the technology can be used safely. For example, no one knows the risks of the arsenic residues’ being consumed by accident or of their leaching from landfills back into water supplies. The first field tests of the material are being planned for Brownsville, Texas, next year, as is a study in India, the researchers said. Competing technologies, including the use of plants to draw arsenic from the ground and specialised clay filters, are also being explored.

Experts in arsenic contamination who were not involved in the Rice research said it sounded intriguing. “All of the arsenic removal systems so far require filtration of some sort,” said Alexander van Geen, a senior research scientist at the Lamont-Doherty Earth Observatory at Columbia University. Such systems perform poorly if not properly maintained and may become infected with bacteria and other microbes, van Geen and others said.

... contd.