Access to clean water is increasingly becoming the most important issue that faces people around the world. Worldwide, 1.2 billion people lack access to sufficient amounts of clean water, millions die every year from contaminated water, and hundreds of millions are sickened and disabled.^1,2 Industry, agriculture, livestock, mining, refining, and virtually every aspect of human activity depend on water. No other problem today is close in magnitude, and problems with water are expected to grow worse rapidly due to population growth imposing larger demands for domestic, industrial, agricultural, livestock, and energy uses.

In addition, water supplies are increasingly threatened by contamination of aquifers, the largest source of freshwater in the world, by toxic compounds and salts intruding from sea and saline sources. Salting and contamination of freshwater sources drive the need for new clean water, or more extensive water treatment. As the glaciers disappear on continents throughout the world, the major rivers that currently supply freshwater year-round may become intermittent, forcing the search for new water supplies.^3,4