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A fresh look at water treatment
by David Pescovitz
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“California and Australia are pretty similar in terms of geography and climate,” says CEE professor David Sedlak, who won a Fulbright fellowship to spend a year in Australia investigating inexpensive, low-tech methods for reusing wastewater. In his spare time, he learned how to surf.
PEG SKORPINSKI PHOTO
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It's a do or dry situation for Australia's national water shortage. According to the Australian Water Services Association, the country is facing a 275-gigaliter shortage of drinking water in the next 10 years unless drastic conservation measures and new treatment methods are promptly put into place.
To CEE professor David Sedlak, the situation is similar to California's own water problems, only much worse. During a Fulbright fellowship last year at the University of New South Wales in Sydney, Sedlak worked on a novel treatment technique that could help in the purification of contaminated water and increase drinkable resources down under.
“There are a number of ways to treat groundwater or soil that’s contaminated with organic pollutants like pesticides,” Sedlak says. “The problem is that many of these methods are too expensive and relatively inefficient.”
When Sedlak arrived in Australia, he was introduced to a recent discovery by graduate student Sung Hee Joo that had the potential to dramatically improve a time-tested technique of water treatment. Joo had observed that nanoscale particles of iron, when exposed to oxygen in contaminated water, become a powerful oxidizing agent that completely degrades the pesticides.
Sprinkling contaminated water or soil with iron filings scavenged from industrial trash is nothing new, Sedlak says. The filings act as a reductant, transferring electrons to the pollutant and thereby reducing the toxicity of the contaminant. The process is commonly used to clean up groundwater tainted by dry cleaning chemicals. In Australia, the researchers found that the iron particles transfer electrons to the oxygen, producing a reactant that, in turn, oxidizes the contaminants and purifies the water much more effectively.
Now, Sedlak, Joo, and their collaborators are taking a deeper look at the reaction to understand the chemical mechanisms involved in hopes of using the technique with contaminants such as benzene, the gasoline additive MTBE (methyl tertiary-butyl ether), and in other similar applications.
Back at Berkeley, Sedlak has had time to reflect on the different ways Australians and Californians are dealing with a threatened shortage of life’s most precious fluid.
“In California, we prefer to solve our water problems with big approaches, like dams, high-tech treatment plants, and new water recycling facilities,” Sedlak says. “In Australia, the public thinks more locally, down to collecting roof runoff to water their gardens. In the near term, I hope we’ll also start thinking more about local solutions to our water shortage.”
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