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The Key to San Diego's Water Independence: Sewage

The city’s ambitious Pure Water project aims to combat drought and harsh economics with reclaimed wastewater. But first, the public will have to get used to the idea.

Reverse-osmosis canisters like these at San Diego's Pure Water plant have the ability to detoxify former sewage. (City of San Diego)

What does water that once came from a toilet taste like?

Pretty bland, actually. “Our water goes through five different treatment steps, so it essentially purifies it,” says Brent Eidson, deputy director of external affairs at San Diego’s Public Utilities Department. “It almost strips the water of everything, so there’s not a whole lot of taste or anything left in it.”

If there is ever a city in need of water, it’s San Diego, where roughly 85 percent of its supply comes from sources often hundreds of miles away. The local government has developed a plan to secure its own water supply, using technology that will eventually transform 83 million gallons of former wastewater into fresh agua daily. The $3 billion project is called Pure Water, and it’s existed since 2011 in small form as a demonstration plant producing 1 million gallons a day. But the city recently voted to fast-track the program, with one council member declaring that if “we’re ever going to get self-sufficient on water, this is one part of a many-pronged approach.”

Pure Water technology now produces 1 million gallons of water a day; the city hopes to make it 30 million gallons by 2021. (City of San Diego)

Why the urgency? Well, start with geography: San Diego’s principal water sources are the Colorado River and Northern California Bay Delta. The Colorado River has been historically lashed by drought, and a new study estimates with the warming effects of climate change, its flow could drop by as much as 35 percent by 2100. The recent downpours that caused flooding across California have replenished many water supplies. But who knows when the next big storm train will arrive?

“If you’ve been aware of the hydrology over the last few years, it’s been stressful, it’s been strained,” says Eidson. “We know here in California droughts are cyclical in nature and become a little bit more longstanding and harder to predict when they’re going to break. We want to make sure we’re not at the whim of some atmospheric rivers that may or may not come this year.”

The Northern California delta has its own risks, a large one being the calamitous fallout from a natural disaster like a major earthquake (which will come, though nobody knows when). “The levees [along the San Francisco Bay] are definitely old and in need of infrastructure,” Eidson says. “If certain ones were to fail we could have significant seawater intrusion into the raw water supply, which means we would be cut off anywhere from six months to a year.”

This is a sliced-open view of a sample membrane filtration canister used at Pure Water. (City of San Diego)

There’s an environmental argument to be made, too, in that San Diego currently discharges most of its treated sewage into the ocean. Pure Water would make it a self-contained operation with little marine impact. And then there are economic justifications. The agencies the city buys its water from have their own costs, and these costs have risen significantly. In fact, imported water is three times as expensive in San Diego than it was 15 years ago, and it’s not likely to get cheaper anytime soon.

The prices of Pure Water’s liquid output is a little higher than the water San Diego imports. “But as we look at the projections of what imported water is likely to be in next 10 years, we expect our Pure Water costs to be on par with imported water,” says Eidson. “It’s just a matter of time before it’ll be less expensive.”

San Diego hopes to start construction next year on a beefed-up Pure Water facility in North City, which will scrub water with a buffeting of microfiltration, reverse osmosis, UV light, and hydrogen peroxide. In four years, it wants it to be recycling 30 million gallons of wastewater daily, and an additional 53 million gallons by 2035, representing about one-third of the area’s water supply.

A reverse-osmosis testing station at the demonstration plant. (City of San Diego)

So the looming question is: With the gears on this massive endeavor already turning—and despite thousands of tests proving the “pure water” meets all drinking standards—are locals psychologically prepared to imbibe what may have originated in a Carl’s Jr. urinal?

Eidson thinks they are. “There has been a sea change in the way people have accepted this program,” he says. He attributes that in part to education campaigns the city has staged—the demonstration Pure Water facility leads tours and offers free tastes, for instance. One visitor’s five-star Google review says that during her trip it “was a rainy day and the smell was not an issue at all.”

If that’s not convincing enough, just look to the other places in the world where it’s already an accepted practice. Singapore has ramped up its wastewater recycling as a matter of necessity to break away from its dependence on water from Malaysia, according to USA Today. The capital of Namibia has been doing the same since 1969, and Orange County, California, opened its own facility in 2008, according to Columbia University’s Earth Institute. But even as the technology advances to the level of what San Diego is using, projects elsewhere, including in Los Angeles, have fallen prey to the hostile whims of public opinion.

For any lingering skeptics, there’s one argument that has proven particularly effective in changing minds. It’s simply a map, showing all the entities that discharge sewage into the waters upstream of San Diego. “There are over 400 dischargers on those systems before we even put our straw into those rivers,” says Eidson. During presentations, he and his colleagues will pull up this map and say, “You all know the ad campaign for Las Vegas—what happens in Vegas stays in Vegas? Well, that's not really true.”

In other words, no matter where you live, you’re already drinking recycled toilet water.

“Las Vegas does treat and discharge their wastewater into Lake Mead, which is one of the areas where we pull our water,” he says. “Helping them realize this has been going on for a very long time helps them understand and accept this program.”

Visitors to the demonstration plant are offered tastes of crisp, demineralized Pure Water. (City of San Diego)

About the Author

  • John Metcalfe
    John Metcalfe is CityLab’s Bay Area bureau chief, based in Oakland. His coverage focuses on climate change and the science of cities.