Natural sunlight can purify water.

At a time when water disinfection with chlorine is under attack because of potential health and ecological concerns, an environmentally friendlier way of cleansing drinking water may be on the horizon. The method, solar-assisted water disinfection, takes advantage of the ultraviolet (UV) component of natural sunlight to kill water-borne bacteria and break up undesirable chemical contaminants. It is particularly effective in remote and rural areas, scientists indicate, though more work needs to be done before the method could be applied for large-scale water disinfection.

Krishnan Rajeshwar and his colleagues at the University of Texas at Arlington confirmed during laboratory and outdoor tests that exposing H20 samples - which contained suspensions of E. coli and titanium dioxide (a photocatalyst that changes the rate of light-induced chemical reactions) - to the UV component of natural sunlight eliminated waterborne bacteria within minutes.

Although there are alternative water-disinfection technologies - such as chlorine dioxide, ozone, UV radiation (artificial light), and advanced filtration processes - solar-assisted water disinfection provides several positive and unique features. It only requires a cheap and safe oxidizing agent (atmospheric oxygen) and a nonhazardous and inexpensive catalyst (titanium dioxide). Also, since the UV component of natural sunlight is used, rather than artificial light, no power sources are required as in the UV irradiation approach, and system maintenance is essentially nil.

These also are the characteristics which make solar-assisted water disinfection attractive for use in remote...