V AROUND THE INSTITUTE
Clarifying Water’s
Murky Fate
SYMPOSIUM draws experts to discuss the state of our water by Steve Nadis
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ra dcl iffe ma ga zi ne Winter 2013
TONY RINALDO
bruce e. rittman i s exploring new ways to clean up pollution, treat water and wastewater, and improve human health.
it’s called—with good reason—the most precious substance on earth. We’re predominately made up of water, more than 70 percent of our planet’s surface is covered with it, and everything we eat depends on it. Life as we know it would not exist but for the extraordinarily special molecule composed of two parts hydrogen and one part oxygen. Yet this priceless commodity has forever been taken for granted, squandered, overused, and abused. We clearly need to do a better job of understanding and protecting our water resource while we still have the chance. Indeed, that was the main topic of conversation last October at the Radcliffe Institute’s Annual
Science Symposium, “Cloudy with a Chance of Solutions: The Future of Water.” In her introductory remarks to the crowd of some 350 people, Radcliffe Dean Lizabeth Cohen said she couldn’t think of a better subject than water to satisfy the Institute’s criteria for a theme that would benefit from a multidisciplinary approach. Challenges around the world include pollutants, deadly bacteria, overwhelmed governments, and fractious political disputes. “Fortunately,” she added, “we don’t have to look too far to find great minds focused on these problems.” To show how timely the symposium’s topic was, Joan Ruderman, Radcliffe’s senior science advisor, cited numerous headlines from recent newspapers, including one about plans for using desalinated seawater in San Diego. Menachem Elimelech of Yale followed on with that general topic, claiming that, in principle, seawater desalination could furnish practically an unlimited supply of water. The main drawback is that it takes three to four times as much energy to desalinate seawater as to treat water coming from, say, the Charles River. The key question, he said, is whether the energy efficiency of desalination can be improved enough to make this approach sustainable. Elimelech led the audience through a technical review of reverse osmosis and other water purification methods before concluding that desalination should be considered “a last resort.” Yet in some countries, such as in the Middle East, it may be the only way of adding to tightly constrained water supplies. Bruce E. Rittman of Arizona State University focused on energy conversion techniques modeled after nature, which use water frugally. Instead of growing “energy crops” like corn to produce biofuels—a dubious strategy given that agriculture already accounts for 70 percent of the world’s water consumption—Rittman proposed, we should employ photosynthetic bacteria, housed in slurries within transparent “photobioreactors,” to convert the sun’s energy into fuels. His approach, in contrast to fossil fuel combustion, emits no net carbon dioxide. Water recirculates within a “closed-loop system,” keeping consumption down. “In this way,” Rittman said, “we let water work for us rather than against us.”