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Environmental engineer takes on water woes

USC Viterbi professor makes desalination more energy-efficient

Pacific Ocean
The Pacific Ocean can potentially be used to solve Southern California’s water problems.

Los Angeles has a shortage of drinking water. The Pacific Ocean could help solve this problem, but salt water first needs to be purified through the process of desalination, which can be energy-intensive, expensive and harmful to the environment.

To the rescue: USC Viterbi School of Engineering Professor Amy Childress, who is working on a concept to make desalination more energy-efficient and environmentally friendly.

Childress and her colleagues are the first researchers in the country to pilot the RO-PRO, short for Reverse Osmosis-Pressure-Retarded Osmosis water desalination system, a process inspired by a similar system utilized in Norway by Statkraft, Europe’s largest renewable energy company.

Reverse osmosis is a water purification technology whereby water passes through a membrane that separates the water into two streams — a purified stream and a concentrate stream containing salt that must be disposed of.

Childress’ process has two benefits: While the energy needed for reverse-osmosis desalination is reduced, so is the concentration of the brine water going into the ocean. Excess salt can create an imbalance that could threaten the sea’s ecosystem.

RO-PRO offers more energy-efficient ways to desalinate water than other techniques. Bloomberg reports that up to 50 percent of costs for water desalination plants are related to energy use.

Childress’ research is particularly important in Southern California, which has unique water problems. Much of the region’s water — up to 66 percent, according to the West Basin Municipal Water District, which provides water to 17 cities in Southern California, including Los Angeles — comes from Northern California or the Colorado River. That process is both expensive and unsustainable. While Southern California does not currently take advantage of ocean water as a potential source of drinking water, Childress’ research could help change that.

Moreover, the Southland is currently vulnerable to suddenly losing access to its imported water in a major earthquake. Converting ocean water into potable water could help mitigate this risk and increase regional water independence.

“Seawater desalination and wastewater reclamation are highly relevant, especially in this part of the country,” Childress said of her decision to return to the city where the UCLA alumna earned her doctorate. “Southern California is the epicenter of environmental decision-making.”

Many water agencies are looking to research like this to help expand their water portfolios. The West Basin Water District wants to reduce its imported water more than one-third by 2020.

“For us in Southern California, we have always been looking at local supply alternatives,” said Shivaji Deshmukh, assistant general manager at West Basin. “We feel it is our responsibility to consider seawater desalination.”

Childress’ work has global implications, as water shortages affect numerous areas. In recent years, she has lectured around the world. Southern California, however, is often the testing ground for innovative new technologies.

“A lot of the innovation in water treatment has happened in Southern California because it has its own water problems,” Deshmukh said. “It’s very fitting, and we are very excited to have Dr. Childress here.”

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Environmental engineer takes on water woes

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