Try driving up Morena Boulevard in Mission Valley, or north through Bay Park and Clairemont, and chances are you’ll be bottlenecked by an army of orange traffic cones demarking a huge construction project that will consume northern San Diego for years to come.
The city of San Diego is currently building a massive wastewater-to-drinking water recycling system – but it must tear up the streets to do it. The new pipe route tunnels from Morena Pump Station near the San Diego International Airport, then 10 miles north to University City and then another 8 miles to Miramar Reservoir, the final stop for all our transformed toilet water.
But wait – why is San Diego drinking its own sewage in the first place? And how is that even possible?
Right now, San Diego depends largely on water imported from hundreds of miles away, a plant in Carlsbad that makes ocean water drinkable and the small amount of rain that falls locally. But that imported water is growing less dependable as climate change and overuse zap the Colorado River and Sierra Nevada snowpack of its reliability.
That’s why San Diego is very proud of its recycling project, called Pure Water, which will turn 42 million gallons of wastewater into 34 million gallons of drinking water per day once the first phase is complete around 2027. But the project is actually a compromise the city made after years of wrangling over sewage, of which unlike drinkable water, the city often has too much.
A bit of history: In the 1930s, San Diego dumped its sewage into San Diego Bay which began to corrode the hulls of Navy ships and drove tourists away. In 1963, the city, with support from neighboring cities, opened the Point Loma Wastewater Treatment Plant which cleaned wastewater one way, but soon fell short of what the 1972 Clean Water Act required.
San Diego was on the hook to make billions of dollars in upgrades to Point Loma, even though it argued dumping treated wastewater should be OK because, as the saying goes, “the solution to pollution is dilution.” Congress agreed to give the city a pass on the Clean Water Act requirements for a decade until it failed to reapply for a waiver, setting off a wave of litigation. That’s about the time San Diego offered to do something different: Make its wastewater drinkable.
That seemed to settle qualms from environmentalists angered by Point Loma’s ocean pollution and the feds that were upset over continued Clean Water Act waivers. And here we are.
Pure Water officials told me the water produced on the other side of the multi-step recycling process is so clean, the city must add minerals back in at the end. And there’s the added bonus of San Diego having to buy less imported water – one of the city’s biggest monthly bills. Pure Water is supposed to provide over half the city’s water needs when it’s complete.
So instead of billions in upgrades to Point Loma, the city’s spending billions on Pure Water, about $1.5 billion just for the first of its two phases.
Beyond the miles of new pipeline and pumps yet to be built to round out the system, an expansion of the existing North City Water Reclamation Facility in Miramar is the heart of the purification process. Juan Guerreiro, the director of the city of San Diego’s Public Utilities Department, gave me and our social media journalist, Bella Ross, a tour of the construction.
The North City reclamation plant, and its sister plant in South Bay, were built about 25 years ago to divert some of the waste being sent to Point Loma, clean it, and use it for irrigation. The massive expansion effort is underway while the North City plant is still doing its 24/7 job.
“It’s like open heart surgery. You’re running the plant producing recycled water while it’s being expanded,” Guerreiro said.
That plant already strains out all the solids, adds bacteria to eat up bad gunk, chlorinates and then runs water through coal filters – like a big Brita filtration system. You could probably drink the end product, but it wouldn’t pass California’s drinking water standards. Pure Water adds five extra treatment steps, including shooting every water molecule through a filter membrane with pores that are 500,000 times smaller than a human hair.
After all that energy-intensive cleaning, the city dumps the purified water in the Miramar Reservoir where San Diego stores much of its untreated drinking water already. But wait, isn’t it kind of a shame to dump that extra-purified water into a reservoir filled with yet untreated drinking water, then treat it again?
In an abundance of caution, California requires the treated wastewater-turned-drinking water be stored in an “environmental buffer” like a reservoir or an underground aquifer, instead of pumping it straight to public taps. It’s a kind of “just in case” measure for a lot of these new recycling projects. Orange County built a similar wastewater-to-drinking water system in 2008 that injects the treated water into underground aquifers. San Diego doesn’t have many aquifers so the next best buffer is the reservoir.
Building Pure Water is a massive undertaking that involves building what officials called a “mega trench” artery connecting the North City Reclamation facility and the new Pure Water facility underneath Eastgate Mall road. But the city is also building a Pure Water education center on site to cure any skeptics of their suspicion of the process.
Now, students, don your lab goggles and learn how Pure Water is done:
- How it works now: Someone in the city of San Diego flushes their toilet. The waste flows through pipes in a building then out to the street into a large sewer main. Eventually it hits a pump station which shoots the sewage to its traditional final destination: The Point Loma Wastewater Treatment Plant.
- How it will work once Pure Water is complete: Everything is the same at the start, except a new pump station off Morena Boulevard and north of Interstate 8 will be responsible for diverting 32 million gallons of wastewater away from Point Loma and sending it northward to the reclamation plant.
- Once it makes its miles-long journey to the plant, the sewage moves through the first steps of a typical treatment process, starting with what’s called primary. That phase gets rid of the most obvious gross stuff. The water sits still in a settling tank so fats, oils, grease and plastic float to the top where that gunk is skimmed off and sent to disposal. Organic solids (fecal matter, etc.) sink to the bottom and separate from the water.
- That water is not ready to drink yet. Its next stop is secondary treatment, where the wastewater moves into huge concrete bathtubs and pumped through with air and microbes that eat up a lot of the organic stuff still floating around. The microbes burp out ammonia, carbon dioxide gases and water. If that bacteria begins to die during this process, it’s a signal to treatment plant staff that something toxic and unusual may have been illegally dumped into the sewage system. (That happened once back in 2016 when a port-a-potty company called Diamond Enviornmental Services got caught dumping its outhouse contents into the city’s wastewater system. The FBI raided the company’s offices. Some of its executives got prison time.)
- The wastewater moves to more settling tanks where that well-fed bacteria clump together, die and sink to the bottom. Cleaner water remains at the top inch of the surface, which then flows out onto the city’s prized Pure Water, five-step purification process – and reportedly exceed — drinking water standards.
- The reclaimed water first goes through ozone and biologically active carbon filtration. Any pharmaceuticals or personal care products one might worry survived the primary and secondary treatment get broken down by ozone and become food for additional biology in the carbon filter. Ozone, when dissolved in water, turns into a kind of biocide that kills bacteria, parasites, viruses and other bad stuff.
- By this stage, the water is ready to be shot at high speed through a membrane filter, which looks like a large PVC pipe filled with straws that contain ultra-small pores. The idea is any microscopic grime or grit still floating around won’t be able to make it through those pores.
- Next, the water goes through reverse osmosis, another kind of filter with even smaller pores, about the size of a water molecule. This helps remove any excess salts or minerals. “The water that comes through reverse osmosis is some of the cleanest we’ve seen compared to distilled water quality,” said Doug Campbell, the assistant director of the city’s Public Utilities Department’s wastewater branch. It cleans the water so well, Campbell said, minerals must be added back to the water later.
- There’s one more step, the water gets flashed by ultraviolet light at the most lethal wavelength for germs or microorganisms. “UV light is really good at harming organic things. So if any viruses, parasites or bacteria make it through the other steps, then the UV light will quickly destroy it,” said Campbell said.
Corrections: An earlier version of this article incorrectly stated that Orange County was building a similar treatment system. It’s been in operation since 2008. And San Diego’s Pure Water project will divert up to 32 million gallons of wastewater away from Point Loma wastewater treatment plant per day. Not 42 million.
How much more electricity is used for this new system and process? Are any renewable sources being used to produce the electricity?
Excellent question. They can start by figuring out how much SDG&E or SDCP electricity the city buys annually to pump wastewater near the airport uphill to the existing Miramar recycling facility. How much does that electricity cost now, and how much more will it cost to feed the new Pure Water repurification system? Does the city own any open land near its facilities that could be used to generate additional energy to feed the new system?
People feel alarmed when recycled water is referred to as “toilet to tap.” If not for San Diego’s news media slapping this label on it in the early 1990s, we would have been benefitting from recycled water for 20 years at a fraction of the price had it been built then. The fact is that EVERY drop of water on the planet has been through this cycle thanks to Mother Nature millions of times. You’re drinking dinosaur pee for that matter.
It was not the news media that slapped the phrase Toilet-to-Tap, it was opponents to reclamation of wastewater to develop a local source of water. Opposition to wastewater reclamation (purification) delayed City Council approval for the city’s Water Utilities Dept. to pursue studies for well over a decade.
I’m not alarmed. This is just another waste of money the city won’t maintain like infrastructure unless more taxes are attached to it.
The original plan was that North of I8 would flush and South of I8 would drink the reclaimed water, because the city didn’t have pipes to allow transfer of reclaimed water back to the northern reservoirs. That was a non-starter for everyone South of I8, as you might guess. That’s why it’s taken so long to be put in place – they had to re-pipe the system to allow for everyone in the city, not just those South of I8, to enjoy the “benefit” of drinking this experiment. While this seems like a good idea today, many past technologies seemed like a good idea, until the previously unknown side effects showed up, decades later. Things like CO2 from turn-of-the-20th-century internal combustion engines, lead pipes – as far back as the Roman Empire, asbestos, lead in paint, gasoline, and solder, etc. All of those things solved immediate problems and seemed like a long-term win, but they actually took a toll on everyone later and carried a huge cost to mitigate. Vigilant monitoring, not only of the water, but also the health of San Diegans, needs to be included in this project to ensure we don’t cause more problems than we solve.
“Some of its executives got prison time”. I was excited to hear that executives had for once been held responsible for atrocities committed by their companies. But it looks like he was accused of perjury, not criminal misconduct.
San Diego has a water problem from not investing in it’s dam system that is roughly 100 years old. Water levels were dropped for safety reasons. Billions of gallons were released from the rains. We can’t store water. The hydro plant at Hodges is inoperable and electricity is lost from this. Meanwhile, our misguided mayor, by this toilet water conversion, and negligence to infrastructure, has pushed up water rates while toilet water is 10 years away. This has been a costly mistake that will get even more costly as this thing progresses. This is a PR piece that doesn’t paint the entire picture.
The County Water Authority was too busy building new dams like Olivenhain, and raising San Vincente Dam to pay enough attention to the older dams needing maintenance.
Oh please. That’s not a reason.
Nice overview. Next step: follow the money… Who’s watching?
In twenty years, every municipality in the country that has a water scarcity issue will be using this technology. In thirty years, EVERY munciplaty in the country will be using this technology, not becuase of water scarcity, but because of PFAS contamination and also, instead of needing to maintain a Water Treatment Plant and a Waste Water Treament Plant and pay to staff to plants, you will only need to staff one. In fifty years, people will be astonished that we did it any other way.
I’m very glad we are two to three years away from making sewage our most reliable source of potable water. I’ve been to 2 or 3 tours of the existing Pure Water facility over the last 20 or so years and it always impresses me. Hopefully the water conservation agreements between the Colorado River Basin states can get us through to 2027.
Misguided Mayor is an understatement. He has been around WAY too long and need’s to be put out to pasture far, far, away.
She God save us all.
Gloria is another thief!
Will it reduce our water bills?
Technology/Green makes you pay more. There’s no competition. Water rates are going up now while waiting for toilet water construction. 1.5 billion spent and there’s more to follow.
San Diego wouldn’t have a water shortage if they hadn’t built housing for which there weren’t adequate resources.
I’m interested in the part about adding more minerals back into the purified water. Not sure why that is necessary. How cool would it be if that step didn’t have to be done and the purified water was actually more “soft” water than the current “hard” tap water that we currently have? Wouldn’t less minerals be better?
They tried that, but our existing water is so full of minerals that all the city’s water pipes are saturated with them. When they ran the repurified water through those pipes, the test water leeched all the minerals out of the pipes and many of them collapsed. Thus the step of adding back minerals before sending the repurified water through those pipes.
Excellent plain English explanation of a very complex process. Did your tour include any discussion of the city’s plans to establish very stringent monitoring and alarm systems that would show city staff if the system broke down anywhere along the way? The city’s water and wastewater department has a pretty miserable reputation for maintaining its systems (like stormwater drains and pipes) and it would only take one crisis or pandemic traced back to failed operation and maintenance of the Pure Water system to blow the credibility the city has spend a decade or so building up. If the department execs haven’t developed a very detailed plan to operate, monitor and maintain the new system, it could be a ticking timebomb.
All over the local news how city management for decades willfully failed to maintain our reservoirs, replace outdated ones. Lake Hodges dam releasing millions of gallons after the state said the dam was unsafe to hold the full amount.
Had all our reservoirs been correctly maintained to standard, the atmospheric rivers filling them, city would not be buying as much expensive water, need less from the expensive T2T system.
Especially with the city’s current top priority of empty bike lanes. You just can’t make this up.
It may sound gross, but they could actually harvest needed phosphate (used in fertilizers and other compounds) and other molecules from the waste. Right now, phosphate mining creates an ecological disaster. It would be great to collect these molecules from waste instead of destroying more of our earth.
And gee, the city getting sued 21M for not maintaining it’s dams. About dam time. 4-6 dams could have been fixed instead of toilet water.