GrokSurf's San Diego

Local observations on water, environment, technology, law & politics

San Diego’s indirect potable reuse proposal without the hype

Posted by George J Janczyn on February 27, 2012

The City of San Diego is studying the feasibility of using purified recycled water to bolster its reservoir supply through its Water Purification Demonstration Project (originally called the Indirect Potable Reuse Reservoir Augmentation Demonstration Project).

Potable reuse has been a controversial and emotional topic in San Diego’s quest for new water resources. Provocative stands by certain politicians and pejorative headlines in some news media obscure a key underlying fact: for San Diego the real issue is unplanned vs. planned indirect potable reuse.

San Diego imports about 80% of its water from Northern California and the Colorado River. Imported water from these sources contains treated wastewater from over 345 municipal wastewater facilities [citation] — and when we get it, it only gets standard water treatment before delivery to customers. This is called unplanned indirect potable reuse. We’ve been doing it all along.

By contrast, under San Diego’s planned indirect potable reuse proposal, recycled water (aka treated wastewater) would subsequently go through a multi-staged advanced purification process rendering it similar in quality to distilled water. The purified water would be blended with our imported raw water in the San Vicente Reservoir. So, in fact we would actually improve the overall quality of the imported water before it goes to the final water treatment plant.

The goal, if the demonstration project is successful, is to produce 16 million gallons per day via the potable reuse process. That’s 16 million gallons per day less in imported water purchases, and 16 million gallons per day less in wastewater discharge into the ocean.

The Demonstration Project is also performing a limnology study to determine the reservoir mixing and dilution dynamics associated with adding the purified recycled water.

Over the last year the City of San Diego has been conducting educational presentations and guided tours of the advanced purification facility. The Water Reliability Coalition, a broad-based coalition of community organizations and groups has formed to further educate the public about potable reuse in San Diego. Polls indicate growing public acceptance of the process.


Reprinted from a page in the Topical Guide section of this blog. That page includes the latest news reports on the subject and a selected bibliography on potable reuse and related topics.


8 Responses to “San Diego’s indirect potable reuse proposal without the hype”

  1. merle Moshiri said

    And…….perhaps………16 million gallons less of Poseidon’ hyper expensive desalinated water? Is San Diego beginning to see the light? Not too late to throw in conservation and tiered rates. Reign in your big agriculture water users. Go for it!

    Merle Moshiri, President
    Residents for Resposible Desalination
    Huntington Beach, CA.

  2. E. Wolski said

    >>Imported water from these sources contains treated wastewater from over 345 municipal wastewater facilities [citation] — and when we get it, it only gets standard water treatment before delivery to customers<<

    Except that there is a lot of non-wastewater in both sources which heavily dilutes the municipal wastewater that enters the Colorado River Water and State Project Water. It is much more risky to start with 100% wastewater and treat it twice (once at the wastewater plant and then at a water treatment plant) than to have river water with a small quantity of municipally treated wastewater in it and only treat it once. So this statement is not necessarily true:

    "So, in fact we would actually improve the overall quality of the imported water before it goes to the final water treatment plant. "

    • Perhaps you didn’t read the part where it said that the 16 million gallons per day would be blended with the imported water in the San Vicente Reservoir. 16 mgd is only a small fraction of San Diego’s total water usage.

      Also, 4 years of experience with Orange County’s Groundwater Replenishment System, which produces 70 mgd, clearly demonstrates that the produced water is higher quality than either imported water or local groundwater. In Orange County’s case, they are improving the overall quality of the groundwater.

      • E Wolski said

        I’m familiar with both projects. I also know that the City is hoping to skip San Vicente reservoir eventually and pipe it directly to the water treatment plant. Yes it would probably also be blended at the plant with San Vicente or imported water at the plant. Right now the research on pharmaceuticals and other contaminants is in its infancy. Traditionally we have tried to pick water sources that are not known to be contaminated. But here we are purposely introducing a source of contaminants into drinking water. Hopefully most of them will be removed and as technology advances, we will be able to test for more of them and remove more of them. I’m not scared of wastewater reuse but I am worried when it gets back to me from the general public about how clean and great a source this is going to be. I think the hype has moved from over caution that killed the proposal years ago to one no caution at all about the project.

  3. @EWolski I’m not so sure the city is hoping to eventually skip San Vicente. A 15-mile pipeline needs to be built to transport water from the advanced treatment facility to San Vicente Dam so I’d be surprised if the city would be planning (or hoping) to abandon that investment before it’s even made.

    I’m more inclined to believe they _wish_ they could skip San Vicente now and go direct potable reuse, but that’s not going to even be up for discussion until the CA Department of Public Health issues guidelines for DPR (something they are only just gearing up to study).

    If direct potable reuse does become acceptable at some point, I would think a new advanced treatment facility elsewhere will make more sense. Indeed, the city hasn’t entirely ruled out a third tertiary treatment facility in Mission Valley to make recycled water available to Balboa Park and Mission Bay Park, among others. If that came about, an advanced treatment plant could be added on and then it would be a short pipeline to Alvarado Water Treatment Plant.

  4. […] we could have stronger conservation measures in place in our communities.  And, with our ability to turn wastewater into drinking water, we could supply our communities with even more water, all at a much cheaper cost than […]

  5. merle Moshiri said

    at a recent water conference sponsored by UCLA, the speaker from the CA Dept. of Health said his agency was working on reducing the amount of time it would take for compliance with Health Dept. standards, but even that would mean about 2 years. Well, its been 20? 30? years so 2 is looking good. And he also said he thought the technology required to detect pharmaceutical contamination was at hand. The water produced at the GWRS in Fountain Valley is there. As usual, it is a State agency dragging their feet while billions of gallons of water rush to the sea.

    Merle Moshiri
    Residents for Responsible Desalination
    Huntington Beach, CA

  6. merle Moshiri said

    Besides the steak dinners…… about MET’S Chairman “forgetting” to report hundreds of thousands of dollars on his 700’s statements, from his wife’s income as a consultant (desal, of course) and his own consulting fees? And…..maybe he “shouldn’t have voted on some of those projects.” Ya think?

    Merle Moshiri

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