Desalination

Seawater desalination is one of the Water Authority’s newest water supply diversification efforts. The concept is to convert seawater from the Pacific Ocean into a high quality and drought-proof local drinking water supply. Brackish water desalination is the treatment of saline groundwater extracted from underground aquifers.

In both the seawater and brackish water desalination process, fresh water is separated from the salty seawater using reverse osmosis. In the reverse osmosis process, seawater is forced through a tightly wrapped membrane under very high pressure.  The membrane allows the smaller water molecules to pass through. Salt and other remaining impurities are then discharged from the facility.
 

Seawater Desalination Process

The two projects currently in development within San Diego County are the Carlsbad Desalination Project and the Camp Pendleton Seawater Desalination Project. The Carlsbad Desalination Project is located at the Encina Power Station in Carlsbad, California. It is being developed by Poseidon Resources.

Carlsbad Desalination Project Site: Encina Power Station

The Water Authority is participating in the Carlsbad project as a potential purchaser of product water from the facility. In July 2010, the Water Authority Board of Directors approved a term sheet between the Water Authority and Poseidon. In November 2011, the Water Authority and Poseidon began direct negotiations on a draft water purchase agreement.  The Water Authority expects to complete a draft water purchase agreement in early 2012 and then circulate it for member agency and public review.  The project would involve a new pipeline connection to the Water Authority’s existing regional aqueduct system.

The Camp Pendleton Desalination Project is currently in the planning phase and is being led by the Water Authority, with participation from U.S. Marine Corps Base Camp Pendleton. Following the recent completion of a feasibility study the Water Authority intends to conduct further technical studies at the proposed facility site.

Camp Pendleton Seawater Desalination Feasibility Study Executive Summary Report

Camp Pendleton Seawater Desalination Feasibility Study Final Report – Volume 1

Camp Pendleton Seawater Desalination Feasibility Study Final Report – Volume 2  

The Water Authority also is participating in a binational feasibility study of a large-scale seawater desalination plant that would be constructed in Rosarito Beach in Baja California, Mexico.  The objective of this study is to evaluate the potential for constructing a  seawater desalination plant with a capacity of up to 75 million gallons per day.  The product water supply from this project could be made available to U.S. and Mexican water users, augmenting Colorado River supplies. Funding for this project is being shared among the Water Authority, Metropolitan Water District, Central Arizona Water Conservation District, and Southern Nevada Water Authority.  The study is comprised of four phases, the first of which was completed in May 2010.  The second phase is expected to begin in March 2011 and be complete by the end of the calendar year.