Desalination: Often overlooked in California’s water debate

Desalination is more than taking salt out of seawater and making it drinkable. It also means removing salt, other minerals or chemical compounds from impure water. As California looks around for new sources of water, desalination inevitably gets considered.

Desalination has been used on a major scale in the Middle East and in a limited fashion in a few California communities, with Santa Barbara as the best-known example.

But desalination is expensive: Capital investment in desalination plants is costly because of the special equipment required, and the process itself is relatively inefficient. For example, the state Water Resources Department says  that desalination efficiency typically runs between 15 percent and 50 percent, which means that 15 to 50 gallons of water are derived from every 100 gallons of sea water.
The desalination process typically uses the reverse osmosis, which is highly energy intensive. According to one report in the 1990s by the California Energy Commission, the energy required to make drinkable water from seawater by reverse osmosis is about 2,500 to 12,000 kilowatt-hours per acre foot.

Although figures are far from exact, that translates into $1,300 to about $2,200 per acre-foot – a price tag that depends on the cost of energy, which can fluctuate dramatically.

As a comparison, costs of water at the Metropolitan Water District of Southern California was far less – some $200 to $300 per acre-foot, depending on the classification of water.

Years later, that price disparity still exists, and it’s the major reason that desalination is not yet a major part of the debate over the statewide debate over California’s water issues.

But desalination always has piqued people’s interest – and sometimes their pocketbook.

In November 2002, California voters approved Proposition 50, known officially as the Water Security, Clean Drinking Water, Coastal and Beach Protection Act.

Among other things, Proposition 50 allocated $50 million for grants for brackish water and ocean water desalination projects. This grant program – administered by DWR – aimed to assist local public agency to develop new local water supplies through the construction of brackish water and ocean water desalination projects and help advance water desalination technology and its use by means of feasibility studies, research and development, and pilot and demonstration projects. Two rounds of funding were conducted (2004-2006) under this grant program investing about $50 million to support 48 desalination projects including: 7 construction projects, 14 research and development projects, 15 pilots and demonstrations, and 12 feasibility studies.

Seven years ago, the Legislature approved legislation requesting DWR to convene the California Water Desalination Task Force to look into potential opportunities and impediments for using seawater and brackish water desalination. The task force was asked to examine what role, if any, the state should play in furthering the use of desalination technology.

The bottom line: A primary finding of the Task Force is that economically and environmentally acceptable desalination should be considered part of a balanced water portfolio to help meet California’s existing and future water supply and environmental needs.