Key Points:

• Rules in place for advanced water purification

• ADEQ surveys indicate strong public support

• State official predicts 100 million gallons a day

After a legislative directive and an extensive stakeholder and rulemaking process, Arizona now has the administrative infrastructure to start advanced water purification to transform wastewater into potable drinking water. 

With permit requirements now in place, the Arizona Department of Environmental Quality, the Arizona Department of Water Resources and municipal utilities hope potable reuse will create positive ripple effects in drought resilience, and water quality and security. 

“I wouldn’t be surprised at all if we weren’t seeing upwards of 100 million gallons of water a day reused through advanced water purification 10 years out from now,” Randall Matas, water quality division deputy director for ADEQ, said. “I think it really will be a game changer when we look at long-term water stability.”

The state first inched toward advanced water purification in 2018, with a rule change allowing for direct potable reuse, setting basic requirements, and eventually resulting in a single demonstration permit for Scottsdale Water to demonstrate at the city’s Advanced Water Treatment Facility. 

In 2022, the Legislature, as part of the environment budget bill, directed the Arizona Department of Environmental Quality to “adopt all rules necessary to establish and implement a direct potable reuse of treated wastewater program,” including the creation of a permit process. 

ADEQ created a technical advisory group composed of utilities, academics, local government, engineers, contractors and the general public to draft the new rules for the process. 

All in all, the change in administrative code sets up a permitting process, with checks to ensure any applicant can demonstrate the technical, managerial and financial capacity to operate and fund an advanced water purification project. 

Each applicant is held to a set of quality, monitoring and reporting standards, with required information and checks on the initial water source, a testing plan, and a response to off-specification water, or water that fails to meet standards. 

The rules for water quality require examining pathogens and chemicals, adhering to the same maximum contaminant levels set out in the federal Safe Drinking Water Act, and adding a list of advanced water project-specific contaminants. 

Matas said there is constant monitoring built into the process from the water source through each level of purification. 

“The whole thing is built on many safety steps along the way to ensure that the water is tested and verified at each step, and that all those barriers work together to give us this quality water,” Matas said. 

On March 4, the Governor’s Regulatory Review Council gave the proposed rules the greenlight, followed by a sign off by the secretary of state the same day. 

The road to securing a permit is long, as interested applicants must build the infrastructure necessary to qualify. However, efforts in Scottsdale and Phoenix are already underway.

Nazario Prieto, assistant water services director at the city of Phoenix, said the city took some “calculated risks” in beginning to build out an Advanced Water Purification facility at the shuttered Cave Creek Water Reclamation Plant, adjacent to the Union Hills Water Treatment Plant. 

Construction got underway last year amid the rulemaking process. 

“We put some forethought into how we leverage the existing infrastructure that’s there and the treatment plant that’s across the street,” Prieto said. “And, knowing that the rules were coming, how can we make the most out of this next design of that treatment plant to be able to set us up in a really good place for advanced purified water?” 

Beyond the Cave Creek plant, Phoenix plans to build a similar-sized facility north of the Central Arizona Project around I-17. Construction is expected to start sometime in the next five years. The city also plans to build another, much larger plant, by the 91st Avenue Wastewater Treatment Plant. 

As part of the rulemaking, ADEQ incorporated a provision requiring all water provider agencies to develop and implement a public communication plan to notify, address public concerns and garner greater confidence and acceptance of advanced water purification.  

Two statewide surveys conducted by ADEQ in 2023 and 2024 showed a fair amount of comfortability, with about 75% of respondents saying they would be willing to drink advanced water purification water, while about a quarter still had reservations given a lack of information or the “yuck factor” in considering its initial wastewater state. 

Though Prieto estimates that the city will be able to start producing potable drinking water at its Cave Creek plant by 2027, the facility will initially launch a pilot program. This program will involve sending purified water to recharge basins, demonstrating the plant’s capabilities and safety to the public through tours. 

“We want them to come if they have concerns, if they have questions. We want them to not only ask us questions, and we want them to tour the facility,” Prieto said. “After going and seeing what we’re doing, hopefully they’ll want to taste the water. I think that’s going to go a long way towards helping inform some of those customers that maybe aren’t so excited about this process.” 

After the pilot, the city would then seek the full permit to ADEQ dispense the water into the potable water system. 

“We think that this is a project that sets Phoenix up well into the future,” Prieto said. “Future generations will look back and say that it was great that they were able to move forward with this.”

Gretchen Baumgardner, water policy manager for Scottsdale, said the city is in the process of updating its existing purification plant to meet the new set of standards. 

But, in thinking about expanding the program in the future, Baumgardner stressed the importance of continuing to fund new areas of water innovation.

“We’re a desert city and a desert valley, and we can’t march through to the future doing the same things we’ve done in the past,” Baumgardner said. “If we want to continue to be a wonderful, smart, economically viable city and valley, we need to figure out and make sure that we all understand that that’s going to happen with infrastructure investment.”