Project Phases

Pilot Plant Testing

The City of Santa Cruz initiated the Pilot Test Program in November 2005 which included the design and construction of a small-scale Reverse Osmosis Desalination Pilot Plant.

From March 2008 through April 2009, scwd² conducted a comprehensive pilot plant testing program to evaluate alternative treatment systems for a seawater reverse osmosis (SWRO) desalination plant. The pilot plant was located at the University of California Santa Cruz Long Marine Laboratory and treated up to 50 gallons per minute of seawater supplied from the Lab’s existing open ocean intakes. The goals of the pilot program were to:

• Demonstrate the best desalination technology. Data collected during seasonal variations, algal blooms, and storm events indicates that a robust pretreatment system is crucial to maintain reliable production while minimizing costs and energy use during desalination.
• Test any special treatment needs. Data collected during special studies indicates that the design of the desalination system will be determined by the concentrations of chloride, boron, and bromide in the seawater; achieving target water quality objectives for these parameters provides sufficient removal of other salts, minerals, regulated parameters, and selected unregulated parameters.
• Provide water quality data for regulatory approval and permitting for a potential full-scale plant. Extensive water quality monitoring and special studies indicate that the seawater off the coast of Santa Cruz is largely free of contamination, that the latest generation of RO membranes achieve regulatory and project-specific water quality goals, and that adding minerals after desalination provides a water that tastes similar to the existing supply and minimizes pipeline corrosion.

Pilot Program Concluded Seawater Desalination will be a Safe and Reliable Source of Supply

The pilot program results demonstrated that seawater off the coast of Santa Cruz can be treated to provide a safe and reliable supplemental source of drinking water supply.

Extensive water quality monitoring was conducted at the pilot plant and at the site of the proposed intake for the potential SWRO plant, which is located approximately 2,000 feet off the coast at a depth of 40 feet.  The monitoring included analysis of over 150 regulated and non-regulated water quality parameters to assess the quality of the source and treated waters.

The parameters included regulated indicators of contamination such as pathogens, radionuclides, and synthetic and volatile organic compounds; along with physical parameters; and unregulated parameters including selected emerging contaminants (7 pharmaceuticals and 27 steroids), harmful marine algal toxins (domoic acid and saxitoxin), and unregulated contaminants requiring monitoring by the California Department of Public Health.

The monitoring found that Monterey Bay water is high quality and largely free of contaminants. Computerbased modeling of the Bay performed by others for the project showed that the water quality impact of the San Lorenzo River and the City’s wastewater treatment plant outfall are negligible at the proposed open ocean intake location, because they are diluted by a factor of between 100,000 to one million (106) times depending upon tidal and weather conditions.

Comprehensive testing of the SWRO desalination treatment process found that the desalinated water meets all federal and state drinking water regulations, and that the treatment process removes potential contaminants including marine algal toxins. Taste-testing by the public, elected officials and members of the local media found that the taste of the desalinated water matches that of existing water supplies. Sixteen weeks of laboratory tests by university researchers found that the conditioned desalinated water would not be corrosive to the pipes in the SCWD and SqCWD delivery systems nor those of their customers.

The Pilot Test Program Final Report was issued April 2010.  For on-line viewing of the full report and the technical memos:

Final Report (6.5 MB, .pdf)

• Cover and Table of Contents
• Executive Summary
• Section 1- Introduction
• Section 2- Public Outreach
• Section 3- Source Water Monitoring and Treated Water Quality Objectives
• Section 4- Permeate  Water Quality Results and Special Treatment Studies
• Section 5- Pretreatment System Results
• Section 6- Performance of the RO System Alternatives
• Section 7- Treatment System Comparison
• Section 8- Recommended Treatment Process and Cost Estimates

Appendix A: Technical Memorandums (16.3 MB, .pdf)

Other Appendices are available upon request.  Please contact Heidi Luckenbach at hluckenbach@cityofsantacruz.com.

For More Information on our Pilot Test Program:

Tour Book Guide (.pdf)

Pilot Plant Update Sheets (.pdf) November 2008 | April 2009 | Pilot Plant Handout