Iron file... ings

Sunday, May 24, 1998


Professor Nikolaos Nikolaidis of the department of environmental engineering, University of Connecticut has created an arsenic filter for drinking water supplies. A simple filter using iron filings and sand is being used to treat water contaminated with arsenic. People in countries like Bangladesh and Bengal, where the soil is contaminated with arsenic compounds are suffering from arsenic poisoning. Water from wells contains between 300 and 4000 micrograms of arsenic per litre. Bengalis working in the heat consume up to 20 litres of water a day. Symptoms of arsenic poisoning include skin lesions and kidney damage. A tube filled with iron filings, sand and barium sulphate, is fitted over the well outlet. The iron filings react with the arsenic to form arsenopyrite, a compound that contains iron, arsenic and sulphur. Arsenopyrite is insoluble and remains trapped in the filter. It is estimated that the cost of providing arsenic free drinking water would cost fifteen cents per year. A prototype filter capable of producing 5500 litres of water per day is being designed. This would provide clean drinking water for 150 people.

Excerpted from New Scientist, 28th March 1998.

Chlorinated organic compounds

For several years Dr. Robert Gillham of Waterloo's earth sciences department has been interested in remediating chemical contamination of groundwater. His interest was aroused when he noticed that unexpectedly, contaminated well-water samples which he had in his lab had come in contact with some metal components, subsequent to this contact, the contaminants simply disappeared. He concluded that the contact with the metal must have caused this breakdown, though at the time he did not understand the process. He has since developed a decontamination methodology that one journalist whimsically dubbed "magic sand"; it involves combining sand and iron filings and placing the mixture in the ground, in the path of a plume of groundwater that has been contaminated by chlorinated organic compounds (some known to be cancer-causing). The groundwater moves through the sand/iron barrier and the contaminating chemicals are rendered harmless.

Tests have shown it works . . . and that it is a very inexpensive way to treat certain types of contamination, particularly from chlorinated solvents used extensively in manufacturing activities. There is no need to pump the water to the surface to treat it. The sand/iron wall is "passive" -- you put it in the ground and more or less forget about it, and it goes on working year after year.

The technology is currently being tested in a number of locations in Canada and the United States and is being used in half a dozen full-scale treatment installations in the U.S. and Northern Ireland. Other installations are being developed in England and Germany.

Dr. Gillham has set up a company, EnviroMetal Technologies Inc., of Guelph, Ontario, to further the transfer of the technology. He has been awarded a special research chair in Waterloo's Department of Earth Sciences, supported by the federal government's Natural Sciences and Engineering Research Council (NSERC), by Motorola Canada Ltd., and by EnviroMetal Technologies. This will enable his research to continue at an accelerated pace.