Oxnard Saline Treatment Wetlands

Project ID: 9424
Principal Investigator: Katharine Dahm
Research Topic: Ecosystem Needs
Priority Area Assignments: 2012 (Advanced Water Treatment), 2013 (Advanced Water Treatment)
Funded Fiscal Years: 2012 and 2013
Keywords: salt marsh, saline, wetland, concentrate, treatment, brine

Research Question

Can coastal saline treatment wetlands be created and/or restored using advanced water treatment concentrate waste streams?

Alternative strategies for concentrate management must be developed to serve the anticipated growth in use of membrane technologies. One conceptual alternative is to remove contaminants from the concentrate with engineered treatment wetlands and create or restore brackish or salt marsh wetlands with treated concentrate.

The City of Oxnard's Ground Water Recharge Extraction and Treatment GREAT) program incorporated two desalting facilities treating either ground water or reclaimed water, which would yield concentrate qualities of highly varying composition and strength. The City's Water Division and CH2M HILL conducted mesocosm studies of wetland treatability of concentrate derived from membrane treatment of ground water between 2003 and 2006 and from reclaimed water between 2008 and 2009.

Key findings of the pilot wetland studies indicated that (1) the concentrates and the wetland treatment systems are not objectionable aesthetically (i.e., no odor ); (2) brackish marsh plant species grow normally in concentrate; (3) contaminants such as nitrate-nitrogen, selenium, and other metal pollutants are removed passively from the concentrate through natural wetland processes; (4) acute and chronic toxicity to brackish test organisms are significantly reduced, and (5) concentrate volume is reduced through evapo-transpiration. Collectively, these findings support the initial project hypothesis that concentrate can be used to help create and restore coastal salt marshes.

Need and Benefit

The City of Oxnard in studying the innovative use of advanced water treatment concentrate waste streams for the creation of saline marsh treatment wetlands. There is widespread local support for this study. Oxnard needs technical assistance and peer review from Bureau of Reclamation (Reclamation) staff on this study. Should the pilot saline wetlands prove successful as treatment wetlands, there is tremendous potential for widespread adoption of this strategy throughout Reclamation's coastal States. This innovative technique uses a "waste" product that would otherwise discharge to the ocean while creating much needed salt marsh habitat.

Contributing Partners

Contact the Principal Investigator for information about partners.

Research Products

Bureau of Reclamation Review

The following documents were reviewed by experts in fields relating to this project's study and findings. The results were determined to be achieved using valid means.

Oxnard Saline Treatment Wetlands: Monitoring Plan, Baseline Monitoring Results, and Supplemental Research Topics (final, PDF, 1.6MB)
By Dr. Katharine Dahm, Joan Daniels, Amy Witherall and Doug McPherson
Report completed on September 27, 2012

The goal of the Oxnard Saline Treatment Wetlands project is to demonstrate the use of wetlands as a natural treatment technology for advanced water treatment concentrate waste streams. The potential exists to remove contaminants from concentrate with engineered treatment wetlands and create or restore brackish or salt marsh wetlands with treated concentrate.

Presentation: Reclamation Research at the Oxnard Saline Demonstration Wetland (interim, PDF, 2.4MB)
By Dr. Katharine Dahm, Joan Daniels, Doug McPherson and Amy Witherall
Publication completed on April 30, 2013

On Tuesday April 30, 2013, the City of Oxnard Department of Public Works held an Applied Wetlands Research Workshop, "Investigating the Future Uses of Reverse Osmosis Concentrate for Wetlands Restoration", with Reclamation and CH2MHill. Consultants, environmental stewards, and researchers from California universities attended to discuss research collaboration at the facility. This presentation documents Reclamation's past, current, and future research objectives and collaborative efforts.

Saline Treatment for Salt Marsh Coastal Wetlands (final, PDF, 368KB)
By Katharine Dahm
Publication completed on September 30, 2013

This bulletin summarizes the research results and potential application to Reclamation's mission.

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Last Updated: 6/22/20