For decades, water officials in San Diego, realizing the city was facing an ever-drier future, have worked to make the idea of what’s known as “direct potable reuse,” or DPR, more palatable to residents. In the 1990s, that turned into an uphill battle. The technology delivers purified wastewater to customers’ faucets without an environmental buffer—such as a groundwater aquifer, river, or other go-between—prior to distribution, so opponents labeled it “toilet-to-tap.” The epithet stuck and torpedoed the Southern California city’s water recycling plans.

But of course the water issues stuck around as well, leaving the city to continue looking for new sources of water, especially those that might be drought-proof.

And San Diego is just one city among many in the country’s most arid regions facing the ongoing threat of long-term drought. Western water agencies continue working to not only conserve water, but to also reuse as much wastewater as possible, including from the stable supply DPR promises. As San Diego discovered decades ago, making DPR a reality entails—along with regulatory and permitting changes—trying to overcome the “yuck factor.” Today, despite its “toilet-to-tap” hurdle, San Diego is now intent on becoming the first city in California to convey treated effluent directly from factory to faucet.

“We’re ahead right now, and it looks like we’ll be the first ones out of the gate,” says John Stufflebean, assistant director of the San Diego Public Utilities Department and executive lead for Pure Water San Diego, the name of the city’s latest water reuse project.

Watering the west

While DPR has faced backlash, indirect potable reuse—injecting treated effluent into a buffer such as a groundwater aquifer prior to distribution—has been watering the West for decades.

For nearly a century, Phoenix, Arizona, has been a model for water reclamation—and today recycles nearly all of its wastewater for indirect reuse. In addition to contributing water that helps cool the inland Palo Verde Nuclear Power Plant, Phoenix today supplies indirect-treated effluent for agricultural and turf irrigation. But as the Colorado River supply—which still accounts for 40% of Phoenician water—becomes more and more uncertain, officials are looking for new ways to avert a thirsty future.

“We are actually on the cusp of beginning some significant infrastructure investment in the northern part of the city,” says Cynthia Campbell, water resources management advisor for the City of Phoenix.

DPR will be a critical component of that investment, with Phoenix Water, as the city’s Water Services Department is known, planning to revive a dormant wastewater treatment plant built in the late 1990s, according to Campbell. The restored plant would serve customers in the northern part of the city and should be operational within 5 years, she says. The project would involve blending treated effluent with Colorado River water or groundwater before distributing it to customers.

Although this process—known as raw water augmentation—would involve blending the recycled water with another source, it still qualifies as DPR because the mix would head directly into the drinking water treatment plant, from which water flows to customers, as opposed to the necessary additional step indirect potable reuse requires, where the wastewater goes into a groundwater basin or other environmental system before the water can be reclaimed.

Describing the plans as “trailblazing,” Campbell explains that Arizona has signaled its willingness to consider DPR permits on a case-by-case basis, for projects of various scales. This approach is different from that of California, which will first need to approve the relevant regulations on a statewide level before individual projects can move forward.

Campbell notes that no one in the U.S. has augmented water in the way Phoenix is planning to. “We’ll probably be the guinea pigs for everyone,” she says.

Meanwhile, she does not foresee any public opposition to the project due to the longstanding Phoenician “culture of conservation.”

“They live in the Sonoran Desert,” she says. “They are under no illusions that there are unlimited sources of water here.”

Nonetheless, Campbell stressed that Phoenix Water wants to ensure that people are comfortable drinking their tap water, and she is therefore determined to show the public that water “that goes down the toilet is not in any way, shape or form what it is when it comes out of a modern, updated, sophisticated treatment system.”

‘The ability to filter out anything’

Campbell looks to Phoenix’s neighbors in nearby Scottsdale as leaders in demonstrating the safety of DPR. In a non-Covid yesteryear, curious Arizonans could venture to Scottsdale’s Advanced Water Treatment Plant to take a sip of treated water or attend the annual Canal Convergence arts festival to sample a beer—all originating from treated effluent.

“Using [the festival] to change public perception was really important and vital,” says David Walby, water reclamation services director for the City of Scottsdale.

Scottsdale was the first recipient of an Arizonan permit for DPR, and one of just a few nationwide. Although the water produced from the initiative doesn’t go into Scottsdale’s drinking water—instead the water will be available for taste testing at the Scottsdale Water Campus and will be provided to beverage companies for water-based beverages, according to the permit—it will be up to drinking water standards. The city acquired that permit after regulations changed in 2018, allowing people to consume highly treated effluent, Walby explains. Unlike Phoenix’s plan, Scottsdale’s DPR pilot doesn’t rely on raw water augmentation. Given the city’s 20-year history of using ultrafiltration, reverse osmosis and advanced oxidation for indirect potable reuse, Walby says that the transition to DPR “wasn’t a big leap” from a technological standpoint.

Campbell says the technology Scottsdale is using has “the ability to filter out anything,” adding that this “type of technology could turn out a quality far better than what we’re seeing in our raw water.”

Once the 2018 regulations were in place, Scottsdale and the Arizona Department of Environmental Quality decided to launch a program to demonstrate the viability of DPR. Their facility serves a maximum of only 1,500 visitors per year and is limited to producing 21,600 gallons (82,000 liters) per day — on a campus where a conventional treatment facility processes 70 million gallons (265 million liters) of water daily, according to Walby. Meanwhile, the Advanced Water Treatment Plant has the capacity to treat up to 20 million gallons per day to quality levels that exceed bottled drinking water standards.

While Scottsdale itself doesn’t have a need for a full-scale DPR water supply, due to its abundant surface water supply from the Central Arizona Project and the Salt River Project, Walby says the site could serve as a proof of concept for “outlying communities in northern Arizona solely dependent on groundwater,” or for utilities from other states.

Asked if implementing full-scale DPR would become practical any time soon, Walby says that cities must consider both their economic and water quality needs.

“Sometimes, those are on polar opposites,” he says. “From a financial standpoint, it’s not cheap. This stuff is really, really expensive.”

Walby says that while Scottsdale is able to maximize the equipment’s shelf life with careful maintenance, investing in such technology might be less practical for small northern Arizona communities. Suggesting that federal assistance could be one avenue toward solving this predicament, he cautions that using reclaimed water will never offset water demand— or every gallon of treated water he sends out, he only receives about 35% to 40% in return.

“The financial component is always the elephant in the room,” he says.

From “toilet-to-tap” to pure water

Unlike in Arizona, where permit approval for DPR occurs on a case-by-case basis, water agencies in Southern California are enthusiastically awaiting expected statewide regulations that will enable such projects across the board.

Jennifer West, managing director at the NGO WateReuse California, explains that the California State Legislature passed Assembly Bill 574 in 2017, requiring the State Water Resources Control Board to adopt regulations for DPR by 2023. The recommendation to develop these regulations also appears in Governor Gavin Newsom’s portfolio of water resiliency efforts, she adds.

“I am very optimistic that it can happen in the timeframe of the legislation,” West says. “With climate change, it’s extremely important that agencies diversify their water supply.”

As San Diego attempts to do just that, the city has needed to take a more creative approach toward wastewater reclamation, due to its minimal groundwater supplies. Pure Water San Diego, the city’s major water reuse initiative, will be occurring in multiple steps—a first phase focused on the northern part of the city and involving the use of a reservoir for indirect potable reuse, followed by second and third phases involving DPR, once California’s regulations are active, according to Stufflebean.

Construction recently began on phase 1, in which wastewater will be discharged into a reservoir and only later head to a treatment facility—generating about 30 million gallons (114 million liters) of potable water daily by 2025, according to Stufflebean. This phase qualifies as indirect potable reuse, Stufflebean explains, because the large reservoir provides some dilution and the long retention time allows some natural disinfection to take place, but implementing the plans required a change in regulations that deemed reservoirs an environmental barrier.

Phases 2 and 3 of the project, which will qualify as DPR, will involve injecting much more effluent into a smaller reservoir—too small to be considered a big enough buffer for indirect potable reuse—located upstream from the treatment plant, Stufflebean says. Assuming California’s DPR regulations move forward as expected, he anticipates that the second and third phases will begin supplying water by 2035.

In a city that was once appalled by the idea of DPR water, Stufflebean says most residents seem to be on board two decades later. Stressing the importance of public education on the issue, he points out that San Diegans are now well aware that they are already drinking treated wastewater through indirect injections upstream.

“There are 400 dischargers into the Colorado River and the water from Northern California that is right now the supply of San Diego—including the city of Las Vegas and city of Sacramento.” Stufflebean says. “They discharge their water into our water supply. The Pure [project] water is way cleaner than the Colorado River water.”

Different water for different uses

Another nearby agency working to integrate DPR into its portfolio is West Basin Municipal Water District, according to Barkev Meserlian, the agency’s executive manager of engineering and operations. West Basin provides water to 17 cities and unincorporated areas in Los Angeles County. After the region started experiencing drought in the late 1980s and early 1990s, West Basin set out to build a recycled water system, Meserlian says.

“There was a recognition around southern California that we need to do something to save every drop of potable water that was available,” he says.

But the project leaders recognized that different users required water treated to different standards. These discrepancies turned into an innovative recycling program that now offers five “designer waters,” as the program calls them, to meet diverse customer demands from one central location.

While all those distinct types of water come from indirect reuse projects, Meserlian describes West Basin as “a long proponent of pursuing DPR,” acknowledging that regulating the process will involve certain technical challenges such as defining what it would take to ensure that DPR passes safe drinking water regulations. He expresses optimism, however, that, with the passage of Assembly Bill 574 and Governor Newsom’s water resiliency portfolio, Californian officials will adopt plans soon, focusing on raw water augmentation.

‘A very clever project’

One such project, the city of Los Angeles’s $8 billion Operation NEXT, intends to recycle 100% of the water generated by the Hyperion Water Reclamation Plant—as much as 217 million gallons (821 million liters) per day—for beneficial reuse by 2035. The project directors are planning both indirect and direct reuse projects by replenishing the West Coast, Central and San Fernando groundwater basins with the purified water, as well as eventually injecting it directly into the Los Angeles Aqueduct Filtration Plant, a plant that treats 60-70% of the city’s water supply.

“We’re going to tilt the city of Los Angeles on its side and have water flow about 1,200 feet [366 meters] up to the headwaters at that filtration plant,” says Richard Harasick, the senior assistant general manager of the Water System for the Los Angeles Department of Water and Power (LADWP). From there, according to Harasick, because the treated effluent would be blended with raw water at the headwaters of the filtration plant, all residents would be receiving the same water—rather than some getting this water and others receiving surface water, as will occur in Phoenix.

Because of this, Campbell, from Phoenix Water, says she considers the Los Angeles plans to be “a very clever project.” She continues: “Everybody is effectively getting the same thing. … Having that blending, for some, takes away the yuck factor.”

Operation Next will first and foremost be a water supply program, as the city of Los Angeles has determined that relying on imported water is no longer a sustainable strategy, according to Harasick. Although he says that Los Angeles has reduced consumption from 700,000 acre-feet (863 million cubic meters; one acre-foot is about 326,000 gallons) to 500,000 acre-feet (617 million cubic meters) annually in the past 30 years, while increasing its population by 1 million, Harasick stresses the importance of generating a local source in order to continue managing demand.

As far as public understanding in Los Angeles is concerned, Harasick says that the city has been laying the groundwork for 20 years and also credited nearby Orange County for providing a positive example. Orange County has been using reverse osmosis to treat wastewater since the 1970s and now manages a groundwater basin that supplies 70% of the water supply to its 2.5 million people, according to Mike Markus, Orange County Water District general manager.

Although Orange County doesn’t have any DPR projects, “they’ve really plowed the ground for public acceptance,” Harasick says, because the municipality was responsible for implementing indirect reuse in the region on such a massive scale—a step that likely had to occur before anyone would be OK with DPR. Harasick adds that Los Angeles will be purifying its water to the same standards as those of Orange County.

Expressing similar confidence that direct potable reuse “is on the horizon,” Markus agrees that Los Angeles and San Diego would be ideal candidates for such ventures. Orange County, on the other hand, does not have the same need, Markus notes, due to the capacity of its large groundwater basin—the coastal aquifer—to store treated wastewater from the Orange County Sanitation District.

“For those that don’t have a groundwater basin or a reservoir, direct potable [reuse] is a key to opening up that additional [water] recycling,” Markus says.

In the short term, Markus continues, the most realistic—and more palatable—form of direct potable reuse will be raw water augmentation, similar to Los Angeles’ plans.

“When this is done,” Harasick adds, “along with our complete local resource portfolio, I’d like to say that the words ‘drought’ and ‘Los Angeles’ will never be in the same sentence again”—a desire shared by water managers across the U.S. West, as they look for more ways to secure their water supplies against an uncertain future.

Sharon Udasin is a staff reporter at The Hill whose work focuses on sustainability.