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Recycled Water

Recycled Water Saves Money and Protects our Environment 

Delta Diablo (District) has been providing recycled water services for industrial and landscape customers since 2000. Using recycled water offers safe, reliable, and drought-tolerant supplies which protects the Sacramento-San Joaquin Delta System.  Our recycled water facility has generated 26 Billion gallons of recycled water to date.

Each day nearly six million gallons of recycled water is generated and used for cooling at two power-generating plants (90%), as well as landscape irrigation at two golf courses and 12 city parks (10%) in our service area.

The purchase price of recycled water per acre-foot costs less than purchasing potable water and makes it a wise investment for companies, cities, and school districts, which require large quantities of water for non-drinking purposes. 

What is it?

Recycled water is wastewater that has been processed through modern primary, secondary, and tertiary treatment for beneficial reuse following the strict standards of state and local agencies.  After residents and businesses have used the municipal water supply, it flows to our treatment plant in Antioch.  There it undergoes extensive cleansing through primary and secondary treatment processes before it is returned to the San Joaquin River.  Water that is recycled goes through an additional treatment step, a “tertiary” process that uses flocculation, filtration, and disinfection to further remove bacteria and viruses from the water.  The treatment processes at the District’s Recycled Water Facility accelerate and simulate Mother Nature’s cleansing processes, which are part of the natural hydrological cycle.

Why use it? 

Water is a precious natural resource that is in short supply in California.  Population increases and efforts to protect the environment have reduced the reliability of our water supply.  Without widespread development of additional water resources, the State Department of Water Resources predicts that by the year 2020 Californians will be short 7 million acre-feet of water per year during a drought and 2.9 million acre-feet in an average year.  The East County Water Management Association has estimated that east and central Contra Costa service areas could experience a shortfall of up to 25,000 acre-feet per year with currently available supplies.  The State of California has mandated that processes such as power plant cooling must use recycled water when readily available and economical so they do not rely on potable or other raw water supplies that would or could be used as potable water.  An acre-foot of water is enough to supply two families for a year. Recycled water projects, such as the Delta Diablo Recycled Water Program, are essential to the water resources management of the region and Contra Costa County. 

What is it used for?

Recycled water is most commonly used for irrigation of pastures and food crops, as well as landscape irrigation of school grounds, parks, and golf courses. More recently, however, recycled water also has been used for recreation purposes, habitat restoration, and commercial uses, such as carpet dying, paper production, heating, and cooling.  Recycled water produced by the District is used for cooling at two power plants, as well as landscape irrigation at several parks and golf courses in Antioch and Pittsburg.

Recycled water protects our environment. 

The Bay-Delta system comprises the largest estuary on the west coast of North America and is the source of drinking water for 2/3 of California (over 23 million people).  Over-allocation, court-ordered restrictions on Bay-Delta water withdrawals, and anticipated climate change impacts, means the demand for California’s water is increasing and putting a strain on our fresh water supplies and ecosystems.   

Recycled water projects from urban wastewater provide reliable, long-term, sustainable, and drought tolerant supplies. Reusing water helps improve reliability and preserve limited river and groundwater supplies.  San Francisco Bay Area recycled water projects, such as the District's recycled water facility, benefits the Bay-Delta by reducing water withdrawals and discharges, offering reliable supplies and protecting our wildlife, fish, and plants.

How safe is it?

In California, recycled water has been used safely for over four decades.  Although it frequently meets the same standards as drinking water, recycled water is not used or intended for consumption.  In fact, recycled water pipelines, which are colored purple, are entirely separate from drinking waterlines.  State and local regulations strictly guide the use of recycled water to protect public health and safety.  Extensive testing is performed on recycled water to ensure water quality standards are met.  Continual monitoring, testing, and treatment ensures that this water supply meets the highest quality standards set by state regulations for the intended uses.    
Some updated information regarding recycled water and Pharmaceuticals and Personal Care Products can be found below. 

Who regulates it?

The State Water Resources Control Board oversees production, conveyance, quality control, and proper use of recycled water. The California Department of Public Health, as well as local health agencies, has developed regulations “Title 22”, which establish the water reclamation health requirements.  The recycled water produced by Delta Diablo meets the most stringent standards established by Title 22 and is safe for all human contact, except drinking.    

History of Recycled Water.

Recycled water has been used throughout the State of California as far back as the turn of the century.  The founders of Golden Gate Park began irrigating with untreated sewage in 1889 to make the park soil more productive.  The first water reclamation plant was constructed there in 1932. The City and County of San Francisco continue today to include water reuse in their master plan for water resources management.  One agency in Orange County, California, has been using recycled water to form a groundwater barrier to stop salt water intrusion since the 1960’s.  Several agencies in Contra Costa County are endeavoring to develop and use recycled water for applications such as landscape irrigation, non-fodder irrigation, power plant cooling, and process water supplies.  Hundreds of other water and wastewater agencies statewide are also actively recycling our State’s “liquid gold”.

Additional information about recycled water can be found at

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