Beneficial reuse of recycled water has been identified as a key component of the San Diego region’s water supply diversification strategy for more than 20 years. Since the 1990s, the San Diego County Water Authority has been supportive of its member agencies’ efforts to develop potable reuse projects. Beginning with the city of San Diego’s Clean Water Program, which investigated the option of augmenting surface water reservoirs in San Diego County with purified wastewater using similar treatment processes previously approved for groundwater injection projects, the Water Authority has worked in conjunction with its member agencies to promote the development of this valuable water resource.
As outlined in the diagram to the right, the water purification process, also referred to as potable reuse, employs advanced multi-barrier treatment technology. This separates pollutants from the water, purifying it to a drinking water level that fully complies with both federal and state drinking water quality standards. Purified water is continuously tested and is monitored by the State of California Division of Drinking Water.
As water resources are stressed around the state, it is critical for the San Diego region to continue its strategy to diversify water supply sources and to rely less on imported water. Purifying water is a cost-effective option that will provide a locally controlled, drought-proof water supply that is safe and reliable.
To facilitate project development, the Water Authority sponsored and actively supported legislation, SB 918 in 2010 and SB 322 in 2013 that expedited specific regulations for potable reuse through surface water augmentation. It also sought acknowledgement by the State of California that direct potable reuse could be a viable water supply option. Currently, Water Authority staff are working with its member agencies through the Potable Reuse Coordination Committee in three key areas to support development of potable reuse projects in the San Diego region. These areas include enhanced public outreach, regulatory engagement, and investigating opportunities to obtain outside funding for project development in our region.
Water Authority member agencies located throughout San Diego County have indicated a high level of interest in developing potable reuse projects. As of July 15, 2015, 11 member agencies have indicated their intent to implement potable reuse projects for a potential total production of 110,000 acre-feet of drinking water per year by 2035. Many of these agencies are preparing or have completed feasibility studies for purified water projects. Agencies that have the most progress in project development include the city of San Diego with its Pure Water Program. Pure Water is a multi-year phased program that at full build-out in 2035 will produce 83 million gallons per day, enough water supply. This program will use local reservoirs to blend purified water before delivery to downstream surface water to provide one third of the city’s treatment plants. The city is also conducting a study at its advanced water treatment to provide one third of the city's treatment plants.
The city is also conducting a study at its advanced water treatment demonstration facility to support direct potable reuse. Additionally, Padre Dam Municipal Water District, an East San Diego County agency, recently launched its pilot testing program of advanced treatment processes at its water reclamation facility. This work will help Padre Dam develop purified water through groundwater recharge in the Santee Basin, and potentially provide purified water to the Helix Water District for reservoir augmentation.