Recycled Water Study

Water Treatment Plant Operator holding a sample of recycled water
Water Treatment Plant Operator holding a sample of recycled water

In the U.S., many non-potable uses are served by potable water that has been treated to safe drinking water standards established by the federal Environmental Protection Agency and state and local agencies charged with protecting public health and safety.  Recycled water can be used to safely displace use of potable water for these types of non-potable uses such as toilet flushing, landscape irrigation, commercial car washing, and fire protection. 

Recycled water is produced by treating municipal wastewater.  California treated about 5 million acre-feet of municipal wastewater in 2002.  About half of that amount was recoverable as recycled water.  However, as much as 70% is discharged without beneficial use to natural waterways and to the ocean every year, representing a viable, untapped resource – a lost opportunity.

Recycled water could be used to enhance potable supplies after undergoing highly advanced treatment. Several water agencies in Southern California are taking advantage of advanced technologies to produce recycled water that exceeds California drinking water standards.  These agencies are using this recycled water to protect and replenish groundwater aquifers that serve as a major potable supply to the region. 

In May 2008, the Alliance released a study titled The Role of Recycled Water in Energy Efficiency and Greenhouse Gas Reduction that estimated the potential energy and carbon benefits of accelerating and increasing the development and use of recycled water in Southern California.

Results of the study show up to 580,000 acre-feet of existing recycled water supply in Southern California is currently being released to streams and the ocean without benefit.  This supply could meet all of Southern California’s projected increase in water use through 20301 . According to the study, every gallon of recycled water that is not used to offset potable water use is a missed opportunity for California to increase water and energy supplies and to reduce carbon emissions.

Download the full report for more information.  See the appendices for profiles of each of the participating water agencies.

1As projected by the Department of Water Resources under a Business As Usual scenario