How Clean Is Recycled Water?

We know all life depends on water. But it's the quality of that water that determines what can live/thrive on any particular mixture of H2O molecules and varying bits of other planetary elements, including some compounds humans invent.

In California’s rivers, anadramous fish species spawn in the fresh waters of their birthplace and later swim to the ocean to mature in the highly saline waters of the Pacific Ocean. Today, these same species struggle for their very existence amid our super-engineered water capture and diversion systems.

Water for commerce has varying quality requirements. Farmers can use almost anything wet, upstream of the tidal influence in the Delta.

Silicon Valley innovators finally realized reverse osmosis filters could turn tap water into the best solvent salt-free water. Pure water replaced the use of deadly organic solvents, used well into the 1980's, which resulted in unbearable grief and cost untold dollars.

For the last 50 years, Santa Clara County has been able to grow and prosper with water from remote watersheds. Fifteen percent comes from the snowmelt of Yosemite National Park's Hetch Hetchy Valley. The San Francisco Public Utilities Commission pipes it around the periphery of the Delta. Another 40 percent of our water comes out of the southern Delta near Tracy, using pumps built in the 1950s and ’60s by the state and federal governments. Our straws in this common pool, though essential to our survival in the past, are but pipettes compared to the cumulative draw of the San Joaquin Valley and the Metropolitan Water District of Southern California.

The quality of this imported water is of great concern to the Santa Clara Valley Water District and everyone else charged with getting adequate and safe water to your home or business. Over a hundred million dollars per year is spent capitalizing and operating water treatment plants, and transforming this downstream water to legal, potable quality. For this reason, local water officials generally support building new infrastructure to enable us to also get cleaner and less salty water further upstream, closer to Sacramento.

This year, with minimal storage remaining in the major reservoirs upstream of the Delta, our imported water is saltier than usual (300 vs. 200 mg/l). If it doesn't rain next winter, the Delta becomes the ocean, as the rivers run completely dry and tides move the salty water inland.

It's this pending catastrophe that has caused our local leaders to finally call for recharging our groundwater basins with water produced at the wastewater treatment plants, where currently 150 million gallons per day is wasted to South San Francisco Bay. Silicon Valley manufacturers have 30 years experience using reverse osmosis to rinse electronic components, and that same technology is at the heart of the recently completed Silicon Valley Advanced Water Purification Center.

There are sure to be loud-talking opponents who want to keep this sensible management from happening. But recycled water, produced with well-proven technology, can actually be cleaner than Hetch Hetchy snowmelt. It is a drought-proof water supply, and it is a faster and far more reliable solution than building a new dam north of the Delta. Recycled water is cheaper than desalination and it can be pumped upstream to groundwater recharge areas using existing transmission facilities (purple pipes). Santa Clara Mayor Jamie Matthews said we should accomplish this in a two-year period—the time it took to build the 49ers new stadium.

We can do this Silicon Valley. Our future may well depend on it.

Pat Ferraro served as an elected member of the Santa Clara Valley Water District from 1972-1995 and later served as executive director of the Silicon Valley Pollution Prevention Center. He is currently an adjunct professor at San Jose State University and Santa Clara University, lecturing on water law and policy and water resources management.


  1. Yes, through spending tax dollars on recycled water purification technology there’s no doubt we can meet the water needs of millions of new illegal aliens.

    • And which tribe are the Galt’s from John? We raise all boats or we all become water migrants. Hopefully others will extend a warm welcome to you upon your arrival somewhere else.

      • Whenever I travel abroad I try to remain extremely respectful of my host country’s culture, traditions, and laws.
        I can’t see myself sneaking into a foreign country, let alone sneaking in, then demanding my “rights” and my “fair share” of the resources.
        My allegiance to my “tribe” isn’t nearly as strong as my allegiance to my country, Mr. Ferraro. I wish I could say the same about the Democrat Tribe members who are in power around here.

  2. This is a conversation that is long overdue. Water resource professionals and researchers etc. have been working hard to find the best answers to our limited resources. We are stymied by the public perception of reusing water. This is a media and alarmist driven perception of uncleanliness that needs to be dispelled. Let open this convo now when we are mid drought.

      • In the liberal echo chamber known as San Jose State University, “wisdom” consists of one elitist academic persuading another that the only possible reason the unwashed, unenlightened masses could possibly hold a different opinion from ours, whether it’s about water, immigration, or feral cats, is that they are “uninformed” and have “misperceptions”.

      • I studied horticulture in uni at cal poly San Luis obispo. My focus was agribusiness and water issues. My thesis was reuse of saline irrigation water in the Middle East. My masters was at San Jose state in environmental studies. I’ve been advising best management practices for irrigation and particularly modified irrigation based on water quality for landscape and agriculture in California and Reno. I’m less involved with the politics of water source and delivery than I’d like.

        • You’ve chosen a valuable career and I’ve no doubt you can use your knowledge and growing experience to make California a better place. Recycling and conserving are sure better alternatives than more dams and aqueducts.
          In the future though, when our eco friendly measures turn out to still be inadequate, I just hope the water resource academics, whose expertise is subject to influence by politicians, have enough intellectual honesty to finally point out overpopulation as being the cause of our water shortage, and enforcement of immigration principles and laws as the obvious solution.

  3. Seriously, all water on earth has recycled for millions of years. Some of the H2O molecules in that fancy bottle you bought at a fancy restaurant could have passed through the Penis of Pontius Pilate. Get over it :))

  4. Pat I think you served when uncle Vincent “Crazy Horse” served.

    I’m a firm believer in science. If post reverse osmosis your scientists peer into a microscope, or vaporize water going into a gas chromatograph, and it comes out “Good enough to drink” then I’ll believe it. I think sir, you are a realist. It needs to happen. The bay area has way more people than sustainable resources, and we either have to start looking for new places to get our resources, or die.

    I don’t think I can be more blunt than that. Even after the last drought, our emergency measure (pipeline from San Luis to Calero) has failed us.

    Question is though, is there anyone on the water board with enough cajones to tell city leaders, “Hey, we can’t sustain this many people!” I think it’s time for a moratorium on building, at least until our water resources can meet the demand of an additional 6 million people estimated to move to the bay area over the next 20 years. What do you think Patrick?

    • Thanks for your comment, Robert. I did serve with your Uncle Vince, who is still a member of the Agricultural Advisory Committee. Your grandfather, Vincenzo, came to my home nearly forty years ago and gave me a lesson on grafting fruit trees.

      My first campaign for the Water Board in 1972 addressed population growth. I wanted to recycle water as an irrigation supply and preserve more agriculture to make use of the water, instead of paving the entire valley for urbanscape. That approach required expensive plumbing instead of tapping the groundwater as most of the farms outside of Evergreen could do. Most people believed that growth would happen anyway, even without additional supplies, but they didn’t want to force us into endless water shortages, so we built the San Felipe aqueduct. The year it was completed in 1987, we entered a six-year drought and had to spend all our cash reserves, $12 million, to buy water from the state-wide water bank in order to get water through the pipe. Recycled water, as an option, at least, delivers water rain or shine. It’s time to finally do this.

      • Ah you’re about a generation off :) Vincento was my great grandfather, Jerome was my grandfather.

        I’m glad to hear you were actively promoting sane growth with an eye on preserving agriculture. I’m sure you’re familiar with my families own water issues out in Evergreen, we pumped water to Cadawaller in the winter, so we could irrigate in the summer. At some point though we were told we can’t do that anymore.

        Sadly trees aren’t fans of chlorinated/flouridated water.

        Shame you couldn’t talk them into using recycled water for agriculture then. It would have been nice for the trees. Heh, not a day goes by where I don’t think about laying on top of a stack of fruit trays, watching the red shift sunset only visable from evergreen. We lost a lot choosing housing.

  5. When you say recycled water “can be pumped upstream to groundwater recharge areas using existing transmission facilities” do you mean to recharge reservoirs so the water can percolate into the aquifer? Or are you talking about injection wells?

    • Sr. Vaquero: The SCVWD owns and operates 600 acres of groundwater recharge ponds in the upper watersheds, which are currently completely empty since there is so little water available right now. The limited imported supplies we’re getting from the Delta is very salty this year, so we don’t want to put that into the basin.

      CA Dept. of Public Health could allow us to put recycled water in the reservoirs, but I don’t think it’s the best approach here since the Coyote Watershed can quickly generate large amounts of runoff that could “flush” any stored recycled water over the spillways and waste to to the Bay, losing all that effort to put it there in the first place. Injection wells are also an option we haven’t employed in the past, but are more expensive to operate than ponds.

  6. Paytrick, Thanks for leading in this fight!! One question: “Who Profits” from impeding the use of treated waste water for agriculture, for recharge, or for direct consumption? Could it be that the established water agencies don’t want an increased supply of water, so they can continue to charge higher rates (and keep paying off their bond-holders) by limiting the amount of water that is available?

  7. This just a puff piece to support his friend Brian Schmidt. Schmidt lost the endorsement of the Democratic Party, the Young Democrats, DAWN and the like. You should check out his opponent Gary Kremen – Gary4Water.Com who has been endorsed by over 100 elected and knows lots of water.

  8. This is long over due, and with the completion of the Advanced Water Purification Center in North San Jose, recycled water should not only be used to recharge ground water supplies, especially now, but to also augment stream flow of both Coyote Creek and Guadalupe River, both of which are currently bone dry. I am not aware of any subtle or organized opposition to this plan, but maybe it has not been delivered to the public for discussion. Other than just plain ignorance, it would be hard to fathom that anyone would seriously object to this plan, especially if our current drought were to extend into next year….landscaping would be a thing of the past.

    Also I believe that there is a significant process in which to obtain many level of approvals from the State to implement this idea, and this may not have even started yet.

    There are many questions: What is the status of obtaining State permits to allow groundwater recharge and stream augmentation, and what is the timeline to obtain this permitting? Locally, who should be starting this conversation with the public to educate them about using recycled water? If it’s our City of San Jose political leaders, then sadly this may be DOA, as there is no leadership to be found. But nonetheless, this really would be no different than folks and tourists in New Orleans, and many other communities along the Mighty Miss that rely on their drinking water from this great river…the same river that also receives treated waste water from upstream communities.

  9. John Galt. You make so much sense and then you drive a truck through it with your immigration soapbox. Are you seriously blaming the water issues on immigration flaws or do all roads lead back to immigration? I guess I’m wondering if you wouldn’t be more appropriate in a conservation about say….. Immigration or conspiracy theory or something like that.

    • Are you seriously suggesting that 5-10 million people don’t have an impact on the amount of water we use?
      I dunno Rachel. Just seems to me that no matter what problem our politicians are claiming to try to solve, whether it’s the education achievement gap, income inequality, health care, or in this case water shortages, there’s always an elephant in the room- a really big elephant. And everybody pretends it’s not there. And to me that makes all this high minded, serious political discourse a total farce.
      Sure I can confine my soapbox to the immigration discussion room but that won’t make the elephant leave the water shortage discussion room. But it will make it easier for everybody to pretend it did.

  10. There is no politics like water politics.

    There are hidden agendas inside of hidden agendas.

    Half truths piled on half truths.

    I confess, I am a babe in the woods when it comes to water politics.

    So, let me off up some simple solutions based on …. common sense.

    Solution 1:

    Using recycled water to replenish ground water? Makes sense to me, especially when it is purportedly purer than Hetchy Hetchy water.

    But, I’m wishy washy. Someone give me an argument why this ISN’T a good idea, and I might flip flop.

    Soluution 2.


    The ancient Egyptians knew how to move water. Archimedes knew how to move water. The Romans knew how to build aqueducts.

    I’m confident that even engineers from Cal or San Jose State could figure out how move water from the Pacific Northwest or Canada to the central valley.

    No need for energy wasting desalinization plants. Just get water from Pacific Northwest / British Columbia glaciers and use gravity to move it to Cali. It’s not rocket surgery.

    Droughts are caused be Mother Nature or Gaia.

    Water shortages are caused by politicians.

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