Metropolitan Water District Switches To Ozone Treatment

Los Angeles, CA — The quality, taste and aroma of the tap water received by millions of Southland residents will be enhanced beginning Friday, July 1, as the Metropolitan Water District switches its largest treatment plant to a disinfection process that improves aesthetics and reduces potential health concerns.

The Joseph P. Jensen Water Treatment Plant in Granada Hills, which serves water agencies in Ventura, Los Angeles and Orange counties, will switch its primary disinfectant from chlorine to ozone. The largest of Metropolitan's five water treatment plants throughout the region, treating up to 750 million gallons per day, it is also the largest water treatment plant in the United States to employ ozone disinfection.

The retrofit is part of an ongoing capital improvement program to improve the quality of Metropolitan's water and to meet increasingly strict federal and state requirements. Metropolitan had committed to the state Department of Health Services that ozone disinfection would be on-line at Jensen by July 1, and is meeting that deadline.

"Ozone is a safe, colorless gas that is an excellent disinfectant--and, in fact, has been used as a water disinfectant in Europe since the 1800s," said Dr. Mic Stewart, Metropolitan's water quality manager.

Ozone destroys a wider range of organisms in drinking water, removes most objectionable tastes and odors, and produces fewer potentially harmful byproducts than the traditional chlorine treatment, Stewart said.

"Installing the ozone treatment process at the Jensen plant is a milestone in Metropolitan's $856.4 million program to install ozone disinfection at all five of our plants," said Metropolitan board Chairman Wes Bannister. "Now that Jensen and our Mills plant at Riverside are retrofitted, we move on to the Skinner treatment plant in southern Riverside County."

The Jensen plant treats water delivered by the state Department of Water Resources from northern California, via the State Water Project. That water contains dissolved organic materials, which cause potentially carcinogenic byproducts when the water is disinfected with chlorine.

Water from Jensen and Metropolitan's other treatment plants is piped to Metropolitan's member public water agencies, which, in turn, send it to retail water agencies or directly to homes and businesses. In most cases, local water agencies mix Metropolitan's water with supplies from local wells before sending it to consumers.

Additionally, while water from the Jensen plant has won first- and second-place awards in international water-tasting competitions, algae growths in the state's nearby Castaic Lake reservoir occasionally give Jensen's treated water an unpleasant taste and odor. Treating the water with ozone will substantially reduce unpleasant tastes and odors in the tapwater.

Indeed, recipients of Jensen water may already have noted a difference in their tapwater, as the ozone process has been tested over the past few weeks.

Retrofit of the Jensen plant required an extensive array of new buildings and equipment. Ozone is formed when oxygen gas is passes through an electrical field in a specially designed generator; a small portion of the oxygen--less than 10 percent--is converted into ozone. The ozone gas is immediately bubbled through the untreated water as it flows through a serpentine series of chambers.

Finally, the treated water is given a dose of chloramines--a combination of chlorine and ammonia--to maintain quality for the sometimes lengthy period between leaving the plant and flowing from a homeowner's faucet.

SOURCE: Metropolitan Water District of Southern California