Santa Barbara County Public Works Department

Process
History
Unit Cost

Process

Desalination is the process of removing salt from seawater. Desalination is used in many arid countries around the world to provide a reliable source of drinking water. The process dates back to the 4th century B.C. when Greek sailors used an evaporative process to desalinate seawater. Most United States desalination plants are used to clean brackish groundwater or to produce highly purified water for industrial use.

Desalination separates saline water into two products: fresh water and water containing the concentrated salts, or brine. Such separation can be accomplished by a number of processes. The three most common processes are distillation, electrodialysis, and reverse osmosis. Distillation works by heating salty water to produce water vapor that is then condensed to form fresh water. Both the electrodialysis and the reverse osmosis processes use membranes to separate salts from water.

The City of Santa Barbara Charles Meyer Desalination Facility, located at 525 E. Yanonali Street, was built in 1991-1992 as a temporary emergency water supply in response to the severe drought of 1986-1991. The facility is the largest seawater reverse osmosis desalination facility in the United States. First, ocean water is pumped at a very low pressure through a 2,500 foot seawater intake line to the facility. The incoming seawater is pretreated in round horizontal media filters. There are two sets of filters — primary, consisting of sand, gravel, and anthracite, and secondary consisting of the same media as primary, plus garnet. Next, the cartridge filters act as a check to catch any material that gets through the primary and secondary stages. At this point all particulate matter has been removed from the water; only dissolved salt remains. Then, pumps drive the water at 800 pounds per square inch (p.s.i.) through reverse osmosis membranes that separate the dissolved salt from the water. Approximately 45% of the pressurized seawater goes through membranes and becomes drinking water.The drinking water is pumped into the existing Yanonali Street water main for distribution to water customers. The remaining seawater and concentrated salts (brine) are combined with treated wastewater from the adjacent wastewater treatment plant, and discharged to the ocean at the end of the 1.5 mile long outfall line.

Electricity is used to operated the facility. At this facility, it takes approximately 6,600 kilowatt hours of electrical energy to produce one acre-foot (AF) (326,000 gallons) of desalted water. (This is approximately the amount of energy one family uses in a year.) Visit the City of Santa Barbara's website for more information on desalination in Santa Barbara County.

History

The 1986-1991 drought showed that the City of Santa Barbara’s pre-drought water supplies were inadequate. In 1990-91, an extensive analysis was done to determine which water supply alternatives would best ensure adequate water supplies for the future. The analysis showed that either desalination alone, at a capacity of 5,000 acre-foot per year (AFY), or the State Water Project at an entitlement of 3,000 AFY plus a desalination capacity of 3,000 AFY as a drought backup, were the best alternatives. In June 1991, City voters supported both the State Water Project and desalination as permanent water supplies and the City has included the combined State Water Project/desalination option in its Long-Term Water Supply Program (LTWSP).

As a result of the analysis in the LTWSP and the 1991 vote, the Santa Barbara City Council decided that the temporary facility would be converted to permanent status for use as a backup during future droughts. The facility also has the potential for use during non-drought periods, which would help meet regional or statewide needs for water by operating under a water exchange agreement.
To obtain permanent status the facility went through additional environmental review and permitting which was completed in December 1995. The facility was dedicated as the Charles Meyer Desalination Facility on December 11, 1995 in honor of Mr. Meyer’s long and dedicated service on the City Water Commission, and in recognition of the facility’s permanent role in the City’s water future.

The City’s facility was built by a private company, Ionics, Inc., under a “take or pay” contract. Over the 5-year contract period, the City, along with the Montecito and Goleta Water Districts, paid off the $34 million construction cost and either paid for water produced or paid to maintain the facility in standby mode. Due to abundant rainfall since 1991 the facility has been on standby since the initial testing period was completed in June 1992. The facility has permits to operate as a permanent part of the City’s water supply and all equipment is compatible with long-term use.

Unit Cost

Because a relatively high proportion of the cost of desalination is in operation rather than capital costs, savings accrue when the water is not needed. This means that desalination will be as cost effective as other new water supplies, such as State Water, for which costs remain relatively constant regardless of the amount of water delivered. The cost of desalted water is approximately $1,100 per AF including labor, chemicals, power, maintenance, and a sinking fund to replace worn components.

There are several other desalination facilities located in coastal communities throughout the state. These include Catalina Island and the City of Morro Bay. For communities in semiarid climates, desalinated ocean water provides a water source that is not dependent on rainfall. This gives the community the ability to provide fresh water as a backup for depleted surface water supplies, thereby easing the hardship of drought. As technology advances and other water sources become less available, desalination will become more cost-effective and more communities may turn to this as a viable source of water.

Last updated: January 22, 2007