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Water Reuse Study E-Update - April 2006

The Water Reuse Study team has created this "E-Update" to keep you up-to-date on Study activities and provide news about the recycled water industry. Each issue will be posted on this website. We are sending e-mail announcements of new issues to persons who have expressed an interest in the Study. If you did not receive an e-mail announcement and would like to, please join our news group. If you did receive an announcement about this issue, you are automatically in the news group.

If you are new to the Water Reuse Study, the Study Overview will provide helpful background information. The Frequently Asked Questions section contains additional material that may also be of interest.

Reverse Osmosis Has A Variety of Water Treatment Uses

Reverse osmosis (R/O) can be used in several ways to purify water - for advanced treatment to tertiary level recycled water, seawater desalination and for groundwater demineralization or desalination.

For cities with access to the ocean, reverse osmosis can be used to remove salt and pollutants to make seawater drinkable. Another smaller-scale way to desalinate ocean water is to boil the water and condense the steam (distillation), a process used on some ocean-going ships and boats.

A seawater desalination project generally uses a pre-filter (such as microfiltration or ultrafiltration) to remove particles before the R/O process. Without a pre-filtration step, the R/O membranes would "clog" and need more frequent replacement. In Carlsbad, California, a proposed seawater desalination project using R/O is currently undergoing environmental review. The project could produce 50 million gallons of drinkable water each day from ocean water.

Reverse osmosis is also used to make poor quality or "salty" groundwater drinkable. Because R/O removes so many minerals, "helpful" minerals are added back in before distribution and use. The first large-scale groundwater desalination project in San Diego was the Sweetwater Authority?s Richard A. Reynolds Groundwater Desalination Facility, completed in 1999. The plant produces up to four million gallons of drinkable water each day by removing dissolved salts, microscopic compounds and unwanted minerals with reverse osmosis. A pre-filtering step with cartridge filters is needed before the R/O process.

Another local project where R/O is used to desalinate groundwater is the City of Oceanside?s Mission Basin Groundwater Purification Facility. The facility currently produces an average of 2.2 million gallons of drinking water per day by removing unwanted minerals (that discolor clothes when laundered) from the local groundwater. Microfiltration is used prior to the R/O process. When a new well begins production later this year, the facility will be able to produce 6.3 million gallons of desalinated groundwater per day.

A three-step advanced water treatment process: microfiltration or ultrafiltration, reverse osmosis, and advanced oxidation by ultraviolet light and hydrogen peroxide, can be used for certain water reclamation projects. These projects treat recycled water to a higher level so that it can be added to underground drinking water supplies or to open reservoirs that store untreated drinking water. Reservoir augmentation, one of the water reuse options researched in the Water Reuse Study, would require this additional three-step process to recycled water produced by the City?s water reclamation facilities.

The Orange County Water District?s Groundwater Replenishment Project facility will use these three steps to produce 70 million gallons of high quality recycled water per day (70,000 acre feet per year*) when the facility goes on-line in 2007. The water will be added to an underground aquifer that supplies drinking water to area residents.

*one acre foot of water equals 325,851 gallons, enough water to supply the needs of two average-size families with a house and yard for a year

Australian City Considering Reservoir Augmentation Project

The Queensland, Australia, city of Toowoomba is proposing a reservoir augmentation project that would produce three million gallons of advanced treated recycled water per day. Faced with low water levels in its reservoirs, high energy costs to pump water into the city and limited groundwater supplies, the Toowoomba government is considering using advanced treated recycled water to supplement a local water storage reservoir created by the Cooby Dam.

Toowoomba proposes using the same three-step advanced water treatment process that has been researched by the City of San Diego Water Department at the North City Water Reclamation Plant. The same process will be used by the Orange County Water District?s Groundwater Replenishment Project. The Toowoomba City Council has established an independent advisory panel and a community engagement strategy to educate and inform citizens about the treatment process and the project. With costs estimated at $49 million, funding from the Australian government is needed for the project. Source: Water Desalination Report, March 27, 2006.

Recycled Water Pipeline Installation Passes Halfway Mark

The Otay Water District is constructing a six-mile long pipeline connecting the City of San Diego?s South Bay Water Reclamation Plant to the District?s recycled water distribution system. The pipeline will be able to deliver up to 10 million gallons per day of recycled water. The main will connect to a new 12 million gallon recycled water reservoir (steel storage tank) located just south of Olympic Parkway in the Otay Water District service area.

The new 30-inch diameter pipeline passes underneath an I-805 overpass and will be encased in a tunnel under the Otay River. Since part of the installation will be in heavily traveled streets in San Diego and Chula Vista, some work is being done at night to decrease impacts to commuters. A new pump station will be built to complete the system. The pipeline installation is over 60% complete, and the reservoir is currently under construction.

The pipeline is scheduled to be completed November 2006 and the reservoir and pumping station in spring 2007. Once the facilities are on line, the City will sell recycled water produced at the South Bay Water Reclamation Plant to the Otay Water District on a wholesale basis. The Otay Water District will distribute the water to its existing and new recycled water customers for irrigating parks, street medians, golf courses and large open spaces in eastern Chula Vista communities that include Eastlake and Otay Ranch.

Recycled Water Customer Focus ? University of California, San Diego

The Water Department is pleased to have a number of well-known customers using recycled water. The University of California, San Diego campus in La Jolla has been using City of San Diego recycled water since 1998. There are three large City meters delivering an average of 100 to 120 acre feet* per year of recycled water produced at the North City Water Reclamation Plant. The water is used for irrigation in the east, southeast and northwest parts of campus, including university athletic fields. The North Field is visible in a portion of the Water Reuse Study?s educational video as a backdrop to comments by a facilities maintenance employee on the University?s use of recycled water on campus.

*one acre foot of water equals 325,851 gallons

In the News

News Articles of Interest - a chronological compilation with links to articles, materials and information about recycled water and related topics. Recent additions include:

Be sure to visit these and other areas of our website

  • Speakers Bureau information - how to contact the Study team for a presentation, a list of completed presentations, and a downloadable flyer on the Speakers Bureau.
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