City’s Desalination Method Efficient

By Harry Saltzgaver
Executive Editor

More than two years after the first sea water was poured into the test facility at the edge of the city, the Long Beach Method of taking salt and minerals out of water has been deemed a success.

In a release Tuesday, the Long Beach Water Department announced that the Long Beach Method had proven 30% more energy efficient than the now-common reverse osmosis method. The testing is being conducted in conjunction with the U.S. Department of Interior, Bureau of Reclamation.

“The objectives of this major study phase are to determine, through extensive water quality monitoring, if the potable water products produced are comparable, and to scientifically determine and compare the energy requirements under each technology,” said Dr. Robert Cheng, assistant general manager for operations. “We’ve demonstrated that the Long Beach process is more energy efficient than reverse osmosis, with comparable water quality.”

The Long Beach Method is known as dual-stage nanofiltration, and was developed by Diem X. Vuong, Cheng’s predecessor. It has since been patented by the city.

The test facility is next to the Haynes Power Plant, on Long Beach’s eastern border. It cost $5.4 million to build.

The plant provides two parallel systems, with one using the Long Beach Method and the other using reverse osmosis, comparing the two using the same water source under the same circumstances. Energy consumption is measured, as is the quality of the water produced.

Energy is the largest cost in producing drinkable water from seawater. Under the old process, it can cost up to $1,200 an acre-foot to produce water.

The plant will continue operation, with tests focusing on the best possible membrane and shapes for the piping to further lower energy consumption. Tests also will be done to try out new methods for disinfection and fouling of the membranes.

In the meantime, the water department and the Bureau of Reclamation are building another test site for the other problems associated with desalination — biological and environmental damage where water is taken into the system and where the mineral-saturated brine is discarded.

That facility, at the east end of the Junipero Beach parking lot, is testing permeable pipe buried 300 feet out under the sea floor to use the sand to both filter the incoming water and diffuse the effluent. That testing could begin later this year.

It will be at least 2015 before Long Beach residents are drinking any desalinated water. It will take that long to build a full-scale plant, and even then, only 10% of the city’s water supply is expected to be generated from desalination.

Still, the effort has taken on added urgency in the last year with increased uncertainty of the city’s water supply from other sources.

The federal government is paying for half of the testing phase of the project.

Funding for a full-scale desalination plant has not been determined.

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