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Water remediation technology worth its salt

A Laboratory-developed desalination technology will be at the heart of a project to build experimental water-purification reactors for drought-plagued northeastern Australia.

An Australian-led collaboration is expected to announce the plan to use reactors employing capacitive deionization (CDI) — an electric field water remediation technology that has been under development at the Lab since the mid 1990s — according to an article published in the April edition of IEEE Spectrum online (Institute of Electrical and Electronics Engineers).

Bill Daily, a civil engineer in the Engineering Directorate, is building on Joe Farmer’s (now retired) early capacitive deionization (CDI) reactor research work to develop a design that is "more economical to get into the field."

"The goal is to have a system up and running this year," said Daily, who is an engineer for groundwater remediation at the Laboratory’s main site and Site 300.

CDI provides an alternative to the predominant reverse osmosis desalination technology, which removes impurities by pumping pressurized water through membrane filters that often need to be cleaned or replaced.

In contrast, CDI works by streaming water between pairs of oppositely charged porous electrodes and removing impurities such as salts, which dissolve in water as positively charged and negatively charged ions. Positive ions are drawn to the negatively charged porous electrodes and negative ions to the positive electrodes. CDI offers the advantage of a low-pressure system that is easily "rejuvenated," or cleaned, by reverse polarization of the porous electrodes, allowing impurities to then be flushed out of the system.

In an effort to improve the CDI reactor’s volume capacity and reduce system costs, Daily is using electrodes made of circuit board material and carbon aerogel — another Lab invention. Carbon aerogel’s huge surface area for its small volume allows pores to filter out large quantities of impurities.

Daily is working on the project with Sacramento-based Campbell Applied Physics through a cooperative research and development agreement. Fabrication of a reactor is to start at LLNL in the next month. After completion, the system will be shipped to Sacramento for further testing and, eventually, to Australia. Campbell Applied Physics is a scientific, technical, marketing and management consulting firm specializing in advanced technology-based infrastructure projects.

The company contacted Daily after learning of the technology through what was at the time the Laboratory’s Industrial Partnerships and Commercialization Office.

The CDI system will be used to treat the pressurized water used to extract gases trapped in northeastern Australia’s coal bed gas mines. Water released as a byproduct is currently too brackish for reuse in agriculture.

Daily says that this same technology can be applied to other kinds of water remediation and groundwater cleanup projects.

"It’s gratifying to apply Laboratory research and technology to a project that can make a difference in people’s quality of life," he said.

May 2, 2008

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Don Johnston
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