Looking Downstream to "Troubled Waters".

• Position: Filtration

The Golden Age of Water--characterized by clean, abundant, and cheap H20--is ending, maintains Seth Darling, a nanoscientist at Argonne National Laboratory and a fellow at the Institute for Molecular Engineering at the University of Chicago (Ill). "This is going to reshape how we live, raise food, organize communities, and function in our entire economy," he contends.

Although water crises remain rare in the U.S., they are part of daily life around the world. Eighty percent of the world's sewage is discharged into waterways without treatment. Agricultural runoff is creating enormous algae blooms. In many developing countries, girls have to walk miles to fetch water, something that prevents them from attending school. Every 90 seconds, a child dies from a water-related disease--and, on the geopolitical scene, water is an issue in border disputes and used as a weapon of war.

The problem is a lack of fresh water, which makes up less than three percent of the Earth's water. Of that fresh water, the vast majority is tied up in icecaps, glaciers, and permafrost. Much of what is available to humans is being diminished by climate change, droughts, unsustainable utilization, and other factors.

While supply is diminishing, "demand for fresh water is skyrocketing due, in part, to population growth and development," Darling notes. "Global demand is projected to rise 55% in the next 35 years."

A big part of the problem is that water's role in the production of everyday consumer goods is overlooked. There are 37 gallons of water embedded in a cup of coffee, 634 in a hamburger, and 39,000 in a car. "We're moving a lot of virtual water around the world and not policing it in an efficient, organized way."

One of the most promising areas of water research is membrane technologies, which are used to filter and desalinate water. "We're developing all kinds of advanced technologies for membranes to clean themselves and effectively remove pathogens, metals, salt, and other impurities from...