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PHOENIX -- With dwindling water supplies, cities throughout Arizona are exploring multiple ways to meet residents� water needs.

In March, the Arizona Department of Environmental Quality gave municipalities a new tool: Wastewater treated by advanced purification can now flow directly from local water systems into residents� taps.

For years, cities have used advanced purified water as an indirect potable source, recharging it into aquifers or other water supplies, and later extracting it for purification and human consumption.

The new regulations enable cities to use advanced purified water immediately for direct consumption.

Advanced purified water is wastewater that has undergone a multi-step process to remove impurities and meet state drinking water standards. The treatment uses ultrafiltration, reverse osmosis, ultraviolet light disinfection and advanced oxidation. Together, they strip out contaminants and pathogens, creating a product that experts say is safe and cleaner than many traditional water sources.

Advanced purified water treatment wastes little water compared to a typical household, where for every gallon used, 4 to 5 gallons are wasted, said Bryan Cassens, director of water reclamation services for Scottsdale.

The new regulations are designed to ensure that water treatment systems are safe and flexible, allowing for different technologies and approaches to meet the same high bar, said Randy Matas, ADEQ’s Water Quality Division deputy director.

While the idea might sound new, the science and infrastructure have existed for decades and much of the water people drink today has, in some form, already been recycled, Matas said.

“All water is recycled water, so even in traditional water treatment, the water cycle exists,� he said. “Utilities purify wastewater and then historically have discharged it to the environment, either through groundwater or surface water. That groundwater or surface water is then reused as drinking water down the line.�

With the new regulations allowing advanced purified water to be used directly, safety and transparency are top priorities, Matas said. The new rules require rigorous, real-time testing and oversight at every advanced purification facility, he said.

“The most frequent testing required in this rule is continuous,� he said, with water quality reported every 15 minutes.

To further ensure that cities are following the new rules, ADEQ says it will conduct regular inspections and monitor the data submitted by each facility.

“We accomplish oversight in several ways: data reported to us and inspectors visiting facilities frequently to keep an eye on them and help where we can,� Matas said.

He said while ADEQ sets standards, the agency will not dictate the specific components of cities� water systems.

At least three cities already have plans to introduce advanced purified water in their systems: Phoenix, Scottsdale and Tucson.

Cassens said Scottsdale has explored the potential of advanced purified water for direct use since 2012, with plans to have their system meet the new standards by 2029.

At Scottsdale’s treatment facility, roughly 85% of the water processed through the purification system is recovered and put to use, he said.

While advanced water purification is efficient in terms of water recovery, it requires a considerable amount of energy, particularly during the reverse osmosis stage of the process, he said.

In Scottsdale, the treatment facility has implemented energy conservation policies onsite and in partnership with Arizona Public Service.

Cassens said securing Scottsdale’s future water supply is the priority over energy costs.

“The expectation is that Arizona is going to get less than what it currently gets,� Cassens said, “and so we have to be prepared to deal with getting less water.�

While advanced water purification is part of the solution for Arizona’s reduction in water supply, it is expected to make up just a part of municipal water supplies, officials said. Scottsdale officials view a diverse portfolio of water sources as the most effective strategy for ensuring long-term water security.

“As we progress toward the introduction of advanced purified water directly to customers, our intention is to always make it part of a blend of water,� said Bryan Bouchard, a Scottsdale public information officer. “This means that the water itself will not be the sole product being provided to customers, but rather blended with existing surface Central Arizona Project water, which we will continue to receive, albeit at a lower amount than what we are getting currently.�

Phoenix also uses advanced water purification indirectly by recharging treated water into aquifers for later recovery. The city plans to implement its first direct wastewater to drinking water process using advanced water purification technology at its Cave Creek water reclamation plant by 2030.

Tucson is developing a similar plant, with a target operation date of 2031.

Matas said interest in direct use is spreading, and smaller municipalities are expected to follow as infrastructure, public confidence and regulatory support grows.

For Bouchard, the work isn’t just about infrastructure, it’s about preparing for a future for Arizona’s next generations.

“We’re talking about not just our immediate future, but we’re talking about the future of our kids and our grandkids,� he said.