California city examining feasibility of recycled water treatment

(UC) — San Mateo, Calif., and nearby water agencies are studying the feasibility of a water facility project to expand recycled water supply, which could offset increased demand and drought conditions, The San Mateo Daily Journal reported.

The city, along with the San Francisco Public Utilities Commission, Bay Area Water Supply and Conversion Agency, Redwood City, Cal Water, and Silicon Valley Clean Water, are part of a Potable Reuse Exploratory Plan, the article states.

The agencies have reached the preliminary design and environmental documentation phase for an advanced water purification facility to treat wastewater from San Mateo and nearby areas and turn it into drinking water, according to the article. The SF-Peninsula Regional PureWater Project involves construction of a facility that could product up to 12 million gallons per day of potable water. It would cost about $700 million to build and $20 million annually to run, the Daily Journal reported.

“The city estimates the project timeline at over a decade,” the article states. “Questions remain about the role of each agency, who leads the project and how to fund it. San Mateo Public Works Director Azalea Mitch said the San Francisco Public Utilities Commission recently expressed interest in leading the project forward, putting it in a much better situation to be completed compared to previous years.”

California Gov. Gavin Newsom has called on residents and municipalities to build water resilience and look at innovative solutions in as the state enters its third consecutive year of drought. Last week, AP News reported that the California Senate took the first step toward lowering the standard for how much water people use in their homes from 55 gallons to 47 gallons, after a study revealed the median for indoor residential water use in the state is 48 gallons per person per day.

About 100 miles away from San Mateo, the Pure Water Monterey project takes wastewater from storm and sewer water and agricultural runoff from produce washing and treats it to potable standards, then injects it into underlying water basins for later extraction, the Monterey Herald reported. Monterey One Water, the Peninsula’s wastewater operator, operates the project.  

The Monterey Peninsula Water Management District and Monterey One Water have both recently said there is enough wastewater for Pure Water Monterey and its expansion to provide water supplies for the next three decades, in response to a group of businesses questioning the vulnerability of water sources, asking for details like the “projected and historical flow volumes of source waters available.”

The external affairs director for Pure Water said most of the information the businesses are seeking is available at

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