Arsenic Rooted from Water

ENVIRONMENTAL SCIENCE

One of the most problematic weeds in the world could prove useful for cleaning up water supplies contaminated with arsenic.

Principal lecturer Parvez I. Haris and coworkers at De Montfort University, Leicester, England, have shown that dried roots of the water hyacinth, Eichhornia crassipes, rapidly reduce arsenic concentrations in water to levels less than the maximum value for drinking water recommended by the World Health Organization (J. Environ. Monit., published online March 7, http://xlink.rsc.org/?DOI=B500932D).

Naturally occurring arsenic contaminates drinking water in many parts of the world, especially in Bangladesh, where more than 60% of the groundwater contains arsenic concentrations in excess of the WHO guideline value. The water hyacinth grows prolifically in ponds, lakes, and rivers in tropical and subtropical regions and is notorious for clogging up waterways and causing other problems.

The De Montfort team took water hyacinth plants from a pond in Dhaka, Bangladesh; dried them in air; and prepared a fine powder from the dried roots. Using atomic absorption spectroscopy, they showed that more than 93% of arsenite [As(III)] and 95% of arsenate [As(V)] was removed from a solution containing 200 g of arsenic per L within 60 minutes of exposure to the powder. The concentration of arsenic remaining in solution was less than the WHO guideline value of 10 g per L.

"I'm delighted with the discovery that a plant, regarded as a nuisance, has been turned into a lifesaving material that can help some of the poorest people in the world, not only in Bangladesh, but also in India, Mongolia, Mexico, Chile, and Thailand," Haris says. "It is obvious that an affordable and effective solution to the problem of arsenic in drinking water has to be found using materials that are locally abundant."