Volume 3, Issue 4 May 2003

2003
2002
2001

Fresh Water by David Pescovitz Printer-friendly version This wasterwater stabilization pond treats the water from Xalostoc, Mexico, a few hours east of Mexico City. Courtesy Kara Nelson While we take clean drinking water for granted, more than a billion people around the world aren't so fortunate. As many as five million people, mostly in developing countries, die each year from diseases transmitted from tainted water, and over the next few decades, water-borne diseases are likely to rival the public health threat of AIDS, malaria, and tuberculosis. To fight this global grim reaper, UC Berkeley environmental engineer Kara Nelson is studying ways to measure water-based pathogens and knock them out of commission using nature's own processes. "We'd like to identify inactivation mechanisms that occur in natural environments and consider how you might employ those in a treatment plant for drinking and waste water," says Nelson, an assistant professor in the Department of Civil Engineering. A large part of Kara Nelson's NSF CAREER award is improving outreach and education for students. To that end, she recently founded "Engineers Without Borders," a group to help engineering students work in developing countries and collaborate with professional engineers on real-world projects. Nearly 100 students attended the first meeting. Courtesy Kara Nelson In March, Nelson received a National Science Foundation CAREER Award that recognizes "the early career development activities of those teacher-scholars who are most likely to become the academic leaders of the 21st century." Nelson's CAREER Award will support her research efforts aimed at understanding how sunlight may destroy pathogens in water. According to Nelson, sunlight may be the essential weapon against bacterial and viral pathogens in water. For starters, the ultraviolet (UV) radiation in sunlight has been shown to wreak havoc on the DNA and proteins inside a pathogen's cells. "If the DNA gets damaged, the organism simply can't reproduce," Nelson says. "Or if the proteins are damaged, the organism may not be able to complete tasks essential to its metabolism." Exposing municipal drinking water and wastewater — either in the natural environment, in treatment plants, or at household water stores — to UV radiation may be an ideal defense against the spread of water-based bacteria and viruses. But, while Nelson studies how effective UV disinfection is on specific pathogens and how quickly inactivation occurs, she's also evaluating two indirect mechanisms. Both involve photooxidation — a damaging chemical reaction that occurs either inside or outside the cell in the presence of a certain level of oxygen. The concentration of oxygen may be increased, Nelson says, by "designing pond systems to promote the growth of algae." More algae, she says, may provide a double whammy weapon against pathogens. Could the solution to water quality problems be found in light and oxygen? We want to hear from you... In addition to increasing the oxygen in the water, the photosynthesis of algae raises the pH in the water, making it even more difficult for pathogens to live. A better understanding of the conditions in which photooxidation occurs could lead not only to better treatment plant designs, but also to information about desired oxygen levels in bottles of drinking water treated by sunlight, she adds. Whatever combination of mechanisms proves most effective given the circumstance and specific pathogens, Nelson believes that the quality of drinking water is inextricably tied to improved sanitation. Safe drinking water is easily contaminated by improper disposal or treatment of human waste. "The two are intimately linked," she says. "Unless you work on both, you're shooting yourself in the foot." Kara L. Nelson's home page Nelson research projects NSF CAREER Awards Lab Notes is published online by the Public Affairs Office of the UC Berkeley College of Engineering. The Lab Notes mission is to illuminate groundbreaking research underway today at the College of Engineering that will dramatically change our lives tomorrow. Editor, Director of Public Affairs: Teresa Moore Writer, Researcher: David Pescovitz Designer: Robyn Altman Subscribe or send comments to the Engineering Public Affairs Office: lab-notes@coe.berkeley.edu. © 2003 UC Regents. Updated 5/1/03.