Refreshing Ideas Entrepreneurs take on the world's growing demand for pure water.

Imagine your town has just been visited by a massive natural disaster. There's no electricity, and the water system is contaminated with sewage. What are you going to drink? At the six day disaster preparedness exercise called Strong Angel III, held last August in San Diego, the answer for the event's 800 participants was purified seawater from Aqua Genesis LLC. The 3-year-old Las Vegas company's desalination device can be powered by geothermal heat, so it will work even if the power grid goes down.

The easy-to-maintain device, which has few moving parts, is the brainchild of tire heir Doug Firestone, 56, and Ronald Newcomb, 53, who's also director of operations at the Center for Advanced Water Technologies at San Diego State University. Last fall, the entrepreneurs were in the process of securing roughly $4 million in private financing to build the first full-scale plant using their device, known as the Delta-T, in California's Imperial County. They plan to operate their own plants and sell water to municipalities around the Southwest, a market that Newcomb estimates at $1 billion. "We tried to estimate the potential size of our company," Newcomb says. "But the numbers became so big, we just stopped."

Newcomb isn't the only entrepreneur who thinks he's found a gold mine in water. With the world's popu-lation increasing about 2 percent each year, fresh water supplies are being exhausted in many locales. The World Health Organization estimates 1.1 billion people worldwide lack regular access to potable water today, some 17 percent of the world's population. Here in the U.S., growing population has put pressure on water supplies in California, Hawaii, parts of the Southwest and elsewhere as wells are contaminated or exhausted and river-water supplies become scarcer. Hurricane Katrina also raised public awareness about the problems of contaminated water. Experts believe there's boundless opportunity for creative inventors who can help meet the world's growing water needs.