Taking toxins out of the water

A researcher at the Washington University in St. Louis has discovered an effective way to remove a troubling new pollutant from water sources.

Pratim Biswas, PhD, the Stifel and Quinette Jens Professor of Environmental Engineering Science and director of the Environmental Engineering Science Program, has found a method for removing the toxin MTBE from water.

MTBE has been used in American fuels since 1979 - even more so in recent years in California - as an alternative to octane-enhancing lead additives because it helps fuel to be completely combusted. Thus, MTBE decreases the environmentally harmful by-products of incomplete burning without containing the toxic element lead.

The one drawback is that MTBE can be harmful to human health, too, through exposure via groundwater sources. Underground gas tanks consistently leak, and when gasoline leaks out, the MTBE is very soluble in water, and even localized leaks can allow MTBE to spread widely in a relatively short amount of time.

Biswas discovered that a nanostructured form of a compound called titanium dioxide causes MTBE to react with dissolved oxygen so that it yields the harmless gas carbon dioxide. This reaction proceeds via oxidation of MTBE on the surface of the titanium dioxide to produce a harmless end product.

Then, using the titanium dioxide catalyst, he developed a compact reactor for removing MTBE - his prototype was only 18 inches by 6 inches and held 3-4 gallons of water, yet it removed all of the MTBE within a few hours.

Now companies such as Salt Lake City, UT-based Ceramatec are collaborating with him to scale up the purifying unit, a process that he anticipates to be rather straightforward.

Biswas felt it was important to find a way to remove this pollutant because it "is a toxin and has been implicated as a carcinogen". Even more immediately obvious, the chemical's presence in water produces an offensive taste and a slight odour.