The San Diego County Water Authority’s Board of Directors on Thursday approved a formal resolution supporting the city of San Diego’s proposed large-scale water recycling project Pure Water San Diego, which the Water Authority has identified as the region’s most likely next source of local supply.
For more than two decades, the Water Authority has promoted the advancement of water recycling and reuse in San Diego County as part of the region’s water supply diversification strategy. It has done so by promoting ongoing scientific analysis and guidance by technical advisory panels, securing money to study related issues, conducting polling to measure public support for water recycling, and sponsoring state legislation to speed the adoption of regulations for potable reuse. The Water Authority also is assisting regional efforts to advance potable reuse through public outreach, technical collaboration and coordination on regulatory issues.
“Projects such as Pure Water San Diego are critical to the continued success of our regional water supply diversification strategy,” said Thomas V. Wornham, Chair of the Water Authority’s Board of Directors. “The city of San Diego is not only leading the way locally, but it’s blazing regulatory and scientific trails that one day could benefit all Californians. The Water Authority has long supported these efforts and will continue assisting San Diego and other member agencies that are pioneering potable reuse.”
Unplanned, or incidental, water reuse has occurred for hundreds of years as wastewater has been discharged to rivers or lakes, then withdrawn, treated and distributed through drinking water systems. Planned potable reuse involves blending safe, advanced-treated recycled water with other drinking water supplies.
Currently, the only permitted potable reuse projects in California are for “indirect” projects in which purified wastewater is exposed to the environment, for instance by injecting it into groundwater basins, before it’s used to augment drinking water supplies. Large-scale indirect potable reuse started in California in 1962, when groundwater in Los Angeles County was recharged with treated wastewater as part of the Montebello Forebay Project. Indirect potable reuse has become increasingly popular in California in recent years. For instance, the Groundwater Replenishment System in Orange County has been operating since 2008 with capacity to produce enough purified wastewater for nearly 600,000 people.
Direct potable reuse projects involve augmenting raw water supplies with advanced-treated water or putting advanced-treated water directly into drinking water supply systems without an environmental barrier. Such projects have not been given regulatory clearance in California. However, years of research have proven that technology is available to allow consideration of direct potable reuse as a safe and reliable treatment option. If approved by the state Department of Public Health, a direct potable reuse treatment protocol would permit water agencies in California to maximize the use of existing infrastructure and produce new water supplies while continuing to protect public health.
The San Diego region has a long history of safely recycling water for non-potable purposes dating to the early 1960s when Padre Dam Municipal Water District started using recycled water in Santee Lakes. Currently, 17 agencies in the region purvey or distribute more than 28,800 acre-feet of recycled water per year, enough to serve more than 57,000 typical single-family homes annually. (An acre-foot is about 325,900 gallons, enough to meet the needs of two average single-family households of four people for a year.)
Several Water Authority member agencies including the city of San Diego are developing or studying potable reuse projects. They include Padre Dam, Helix Water District, the city of Oceanside and the city of Escondido. Also, a large coalition of member agencies in North County is maximizing the region’s reuse potential by combining water recycling efforts, including potable reuse projects.
The Water Authority helped develop water reuse options starting in the mid-1990s, when it joined the city of San Diego to investigate the potential for augmenting surface water reservoirs with highly treated water. In a letter to the Water Authority, state health regulators approved the concept of reservoir augmentation in 1996. Two years later, the Water Authority funded a report on the on the issue by the National Research Council, which validated indirect potable reuse.
The Water Authority also sponsored state Senate Bill 322, signed by Gov. Jerry Brown in October 2013, to expedite a transparent and rigorous scientific assessment of potable reuse as a potential water source. In addition, the Water Authority supported a successful application from the WateReuse Research Foundation for $2.1 million from Proposition 84 to fund a potable reuse study at the city of San Diego’s demonstration facility. It’s designed to help provide the regulatory framework for direct potable reuse. WateReuse has raised an additional $5.8 million in research funding for a national effort to create a technical foundation for direct potable reuse and increase public acceptance.
Because of progress on San Diego’s potable reuse project, the Water Authority’s recently approved 2013 Water Facilities Optimization Study and Master Plan identified Pure Water San Diego as the most likely next increment of supply for the county. The city’s 2012 Recycled Water Study said a multi-phase potable reuse project could add up to 83 million gallons per day of highly reliable water to the region. It also would significantly reduce wastewater discharges to the ocean and help address regulatory compliance at the city’s Point Loma Wastewater Treatment Plant.
“There are many reasons that potable reuse is an attractive option not only for our region but for our entire state, especially in the face of a changing climate that likely will alter traditional water supplies,” said Ken Weinberg, director of Water Resources for the Water Authority. “Potable reuse is a renewable resource that can provide a cost-effective and sustainable supply of high-quality water. It will help the San Diego region continue to expand our water supply portfolio and improve supply reliability.”
The Water Authority’s long-term diversification strategy also includes water transfers that are part of the historic 2003 Colorado River Quantification Settlement Agreement. The Water Authority-Imperial Irrigation District water conservation-and-transfer agreement and related canal-lining projects will provide 180,000 acre-feet of highly reliable supplies to the San Diego region this year, enough to serve approximately 360,000 homes.
The Water Authority also has aggressively promoted water conservation as a way to stretch supplies. Per capita potable water use in San Diego County decreased about 27 percent between fiscal years 2007 and 2013, and local cities and water districts are on pace to meet their state-mandated water-use efficiency targets for 2020.
In addition, the Water Authority has invested $2 billion over the past decade in new, large-scale water infrastructure projects that are contributing to a more reliable water supply. The Carlsbad Desalination Project, now under construction, is another important element of the diversification plan. As early as fall 2015, the project could begin delivering up to 56,000 acre-feet of drought-proof, highly reliable water each year, enough for about 112,000 households.
For more information about water recycling in San Diego County, including the Water Authority’s Board resolution in support of the city’s project, go to page 89 of the Board packet at www.sdcwa.org/monthly-board-meeting-37. For more information about the city’s Pure Water project, go to www.purewatersd.org.