For several decades, lobe and multistage blowers were the tried-and-true blower technologies for wastewater treatment plants. Over the past 15...
Anticipating that new technology has increased the efficiency and lowered the cost of desalting the ocean for drinking water supplies, the Metropolitan Water District of Southern California today issued a request for proposals for seawater desalination projects that together could produce enough fresh water for up to 400,000 people a year.
"Although the Pacific Ocean lies at our doorstep, desalting seawater for drinking has in the past been far too expensive compared to our other sources of water," said Ronald R. Gastelum, Metropolitan's chief executive officer.
"Now, as Metropolitan expands its portfolio of resources to prepare Southern California's water supply for the next 20 years and beyond, we're anxious to see if advances in filtering processes have brought desalination into an acceptable price range.
"This could be an important step in dealing with growth projections, climate change, new water quality standards, drought and other variables," Gastelum said.
In a new approach, Metropolitan will be considering desalination projects from a different perspective. Rather than funding, constructing and operating a desalination plant itself, the district will pay up to $250 an acre-foot for potable water produced by plants built and operated through a sponsoring member public water agency.
"Metropolitan's board of directors recently adopted a program through which we will support seawater desalination in the same manner that we fund projects that are cleaning up contaminated groundwater or recycling wastewater throughout the Southland," Gastelum said.
Should proposals be submitted and accepted, Metropolitan estimates that one or more seawater desalination plants could be built and operating along Southern California's coastline by 2007. The district is seeking annual production of up to 50,000 acre-feet for 25 years, enough water for approximately 400,000 people annually.
By comparison, Metropolitan imports (from the Colorado River and Northern California) and wholesales approximately 2 million acre-feet annually to Southern California's water agencies. Local wells and other sources provide approximately another 2 million acre-feet.
Proposals, which must come from the regional wholesaler's 26 member public water agencies and may be in partnership with other public agencies and private firms, are due at Metropolitan's Los Angeles headquarters building by 4 p.m. Feb. 14, 2002.
Eight of Metropolitan's member agencies lie along the coast between Oxnard and San Diego, including the Calleguas, West Basin, and Orange County municipal water districts, the cities of Los Angeles, Santa Monica, Torrance and Long Beach, and the San Diego County Water Authority.
Due to high costs primarily due to the large amount of energy needed to operate them there are currently no plants converting seawater to drinking water known to be operating in California. Brackish, or salty, groundwater can be desalted far more economically because it is far less saline than seawater.
For instance, Metropolitan wholesales an acre-foot of treated water imported from the Colorado River and Northern California for $431. By comparison, an acre-foot of desalted seawater has recently cost two or more times that, depending on energy costs and the technology used.
Desalination is commonly divided into two basic technologies, distillation and reverse osmosis, commonly called R.O. In a distillation process seawater is boiled, with the steam skimmed off and cooled as drinking water and the salt and other minerals left behind. In R.O., saltwater is forced through filters that screen out the minerals.
The complete request for proposals for seawater desalination projects is posted on Metropolitan's Web site — www.mwdh20.com.
The Metropolitan Water District of Southern California is a cooperative of 26 cities and water agencies serving 17 million people in six counties. The District imports water from the Colorado River and Northern California to supplement local supplies, and helps its members to develop increased water conservation, recycling, storage, and other water-management programs.