New method clears nitrates from water

Press, 20 April 1982, Page 22

New method clears nitrates from water

NZPA staff correspondent Washington A Minnesota chemist has developed an old process to a point where it can help produce safe drinking water from sources polluted by nitrogenous fertilisers. The fertilisers form a nitrate in the soil which is relatively harmless but is converted by bacteria in the intestines of infants to nitrite, another negatively charged combination of nitrogen and oxygen. The nitrite interferes with the use of oxygen, and causes a small number of fatalities in the United States every

year among young children whose food is prepared with contaminated well water. The nitrite is suspected of causing cancer as well. It can also be produced by car engines and by coal-fired and oil-fired power stations. The method developed by Dr Maurice Kreevoy at the University of Minnesota uses a porous plastic membrane plus additives which attract nitrate ions from water more than they attract other negative ions, according to the National Science Foundation, which funded the research.. The membrane can skim off the very low coricentra-

tions usually found in the contaminated water.

Some problems remain, however. The process is slow and one of the chemicals used, trioctylphosphate, leaves a detectable trace in the water.

One way of improving the membrane, Dr Kreevoy said, might be to build several square metres of membrane into a device not much bigger than a toaster, a method used in artificial kidney machines.

“If the remaining problems can be solved, such a device could easily provide a family with a safe supply of drinking water,” he said.