Phoenix to Build Multibillion Dollar Purification Plant to Make Wastewater Drinkable by 2030

Article originally posted on AZ Central on April 12, 2023

Phoenix wants to recycle wastewater into drinking water by the end of 2030 and share it with the Valley.

The plan is to build an advanced water purification facility and treat, then reuse millions of gallons of wastewater that would have otherwise been discharged into the Salt River.

The investment would provide Arizona cities a significant new drinking water supply, which is vital as they work to lessen their dependence on the shrinking Colorado River and diversify their water sources.

The multibillion-dollar technology, called direct potable reuse, or “tap to toilet,” by critics, cleans water that goes down a home’s drains and sends it back for reuse. It will be added to the 91st Avenue Wastewater Treatment Plant southwest of downtown and purify 60 million gallons per day — enough water for about 200,000 households per year.

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The new supply from the purification facility could replace half of what Phoenix gets from the Colorado River water each year, although Phoenix doesn’t intend to keep the water all for itself.

“It’s a new bucket for us,” Mayor Kate Gallego told The Arizona Republic in an exclusive interview. “For a lot of my life, I’ve been thinking about where you get that next bucket from, so it’s exciting.”

Finding new water sources is critical for central Arizona, which has long relied on the Colorado River for its drinking water — and heavily. It’s 40% of Phoenix’s and Mesa’s water portfolios.

But the river is shrinking, and climate change combined with overuse have led to historic water shortages that affect not only Arizona, but California and Nevada, too. Some Valley cities have raised water rates and have begun cutting back on water usage in response.

Politics exacerbates the issue, too. The federal agreement that manages the river’s allocation expires in 2026, and a new agreement could mean less water for the Phoenix area than before.

Without a new supply, Arizona cities would be short significant amounts of water and would likely have to dip into nonrenewable water supplies, like groundwater, which isn’t sustainable. Residents could be affected, as cities would likely enter into more severe phases of their water shortage plans.

Reliable and sustainable water is crucial to the Valley’s economic outlook.

Failure to shore up more potable water also affects regional growth. A gigantic master-planned community slated for the far west suburb of Buckeye is in jeopardy after a report showed inadequate water to support it.

Phoenix’s water outlook is not as dire as Buckeye’s, but the more it reduces its reliance on the Colorado River, the more breathing room it and other cities stand to potentially gain.

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While Scottsdale invested in an advanced water purification system in 2019, Phoenix is the first city to move to directly reuse effluent for drinking purposes on a mass scale. Scottsdale does not direct its purified wastewater into the drinking water system, according to its website.

Other cities, such as Peoria, engage in indirect reuse, which sends treated wastewater back into the ground for natural filtration before being pumped out for drinking purposes.

Arizonans have long been drinking purified wastewater, but Phoenix’s announcement means residents will drink wastewater solely purified by a plant, not a plant and the ground.

The advanced water purification technology in Phoenix, according to Water Resource Director Troy Hayes, would clean wastewater, or effluent, repeatedly to ensure it’s up to drinking standards set by the state.

It would undergo ozone treatment, which disinfects the water by killing “pathogenic organisms to prevent the spread of waterborne diseases,” according to the Environmental Protection Agency. Then the water would undergo granular activated carbon treatment, for odor, smell and chemicals. Lastly, it would go through ultra filtration or reverse osmosis for bacteria.

The water would be monitored by sensors and tested at the end to ensure quality and discharged to the river if it failed, Hayes said.

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Phoenix’s water resources management adviser Cynthia Campbell said unlike Colorado River water, which can be disrupted by drought and political agreements outside Phoenix’s control, direct potable reuse is a stable supply. That’s because residents’ indoor water usage has remained level the past five years, according to the city’s Water Resources Master Plan.

“We almost know with exact science exactly how much wastewater we’re going to get because it’s been so stable over the years,” Campbell said.

That doesn’t mean Phoenix isn’t encouraging conservation, Campbell says. She wants households to reduce their water use, but the focus is mostly on outdoor uses, like reducing grass or water-intensive plants.

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Hayes said the city’s next step is figuring out which cities want to buy in.

Mesa is one.

“Our (Colorado River) allotments are in jeopardy. The price of water is going up every year,” Mesa Mayor John Giles said. “Finding new buckets of water is a challenge that we all share. So we very much are in support of participating.”

Giles said Phoenix and Mesa could potentially pipe wastewater and purified water to each other, but a more likely scenario might be a water exchange, where Mesa buys into the plant but takes some of Phoenix’s Colorado River water instead of the purified water, which would then stay with Phoenix.

The 91st Avenue Wastewater Treatment Plant is co-owned by Phoenix, Mesa, Tempe, Glendale and Scottsdale. Hayes said as many as 10 Valley cities could benefit from the new facility.

Phoenix officials did not provide details on exact costs of the facility, saying only that it would be in the billions and that the size and number of municipalities that pay in will determine that.

Funding is expected to come from the federal government and the state Water Infrastructure Finance Authority, which received a $1 billion infusion last summer in an unsuccessful attempt by then-Gov. Doug Ducey to fund a desalination plant in Mexico.