14/10/2005
UNESCO Unveils Low Cost Arsenic Filter Made From Waste Product

Arsenic is well-known as a toxic by-product of mining, mineral extraction and coal-burning electricity production. It also occurs naturally. But if the poisonous substance finds its way into drinking water, great harm can result. Prevention is the only recourse since there is no medical treatment for intoxication by arsenic-contaminated water. And hitherto filters have been expensive. Great excitement was therefore generated this week by an announcement from UNESCO that they had succeeded in making a low-cost filter from an industrial waste product.

The UN World Health Organisation (WHO) sets the healthy maximum of arsenic in water at 0.01 milligrams per litre. But in Bangladesh, for example, levels as high as 1.8 milligrams per litre have been found in the groundwater. Arsenic is also a serious problem in many other countries, including Argentina, Chile, China, Ghana, Hungary, India, and Mexico and the United States.

Branislav Petrusevski, Director of the UNESCO-IHE Institute in Delft, The Netherlands, which offers post-graduate training and research programmes on water and the environment to developing country professionals explained that the technology is based on arsenic absorption by iron oxide coated sand. This is a natural waste product of a water purification process in which sand is used to remove iron from drinking water. "If you produce the material commercially it is very expensive and when its absorption capacity is exhausted, you have to replace it and dispose of the waste," said Mr Petrusevski.

Instead, the Institute team recycled iron oxide coated sand produced as a by-product in groundwater treatment plants. The filter is easy to use, requires no power and can be produced locally. The "family" filter produces 100 litres of arsenic-free water per day, enough to supply the needs of 20 people.

"Plants in many countries around the world use natural sand for iron removal and have to replace it after a certain number of years. We found that this material, now coated with iron oxides, is an excellent absorbent for removing arsenic from water. It is free of charge and consequently the technology based on its use is cheap," Mr. Petrusevski said.