Water Treatment

Every gallon of water that can be reused means that one more gallon can remain underground; or one more gallon doesn't need to be imported from Northern California or from the Colorado River. With about 25,000 acre-feet of recycled water sold annually by EMWD, recycled water is a significant resource. In comparison, domestic and agricultural customers take about 75,000 acre-feet a year of fresh water.

There are two grades of recycled water: tertiary water and secondary water.

Secondary Water
After having gone through a primary (mechanical) process using screens, settling tanks and skimmers, a higher (biological) treatment level incorporates bacteria which feed on nutrients. Primary treatment removes about 70% of suspended solids; secondary treatment removes 85-90% of the remaining suspended solids and other impurities.

Tertiary Water
Also known as Title 22 water, this is the most refined level. Tertiary treatment incorporates filters to "polish" and remove pathogens such as bacteria and viruses, and virtually all suspended solids. Chlorinating also helps in purification.

Who uses it?
Recycled water is in great demand. More than half of EMWD's production is sold to agricultural and irrigation customers. Schools, parks, a cemetery, more than a dozen golf courses and streetscapes will be using recycled water when planned pipelines are completed.

Uses for recycled water:
California's regulations allow use of EMWD's top quality tertiary water for swimming, boating and fishing, landscape irrigation for golf courses, parks, cemeteries, freeway landscapes, playgrounds and schoolyards.

Among the crops that can use tertiary water are potatoes, lettuce, carrots, tomatoes, strawberries, sugar beets, grain, citrus, avocado, grapes, sod and ornamental nursery stock.

Secondary treated water is used to irrigate pasture for milking animals, and for fodder, fiber and seed crops.

More About EMWD's Regional Water Reclamation Facilities

EMWD has five regional water reclamation facilities. The information about these facilities is provided in the form of Adobe Acrobat (pdf) files.

methane digester

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