Against the backdrop of long-term drought and declining water levels in the Colorado River, the City of Phoenix and other water providers in the metropolitan area are investigating the possibility of implementing direct potable reuse (DPR). Although sure to be expensive, DPR offers a reliable source of water in a region that has limited options when it comes to boosting future water supplies.

Earlier this month, Phoenix hired the water engineering consulting firm Carollo Engineers to study options for implementing DPR in the Phoenix area, says Troy Hayes, the city’s water services director. To be completed this summer, the study will examine the possibility of constructing a regional advanced water purification facility to further cleanse treated effluent from the 91st Avenue Wastewater Treatment Plant (WWTP), which is owned by the cities of Phoenix, Mesa, Scottsdale, Glendale, and Tempe. 

“The thought is that we would pipe [effluent from the 91st Avenue WWTP] to an advanced water purification facility and to treat that to beyond drinking water standards and deliver that to customers,” Hayes says. Besides the five owners of the 91st Avenue WWTP, five other local governments have indicated an interest in potentially participating in the project, according to Hayes, who declined to name them because they have not entered into an agreement yet with Phoenix.

“The hope is that sometime this summer then we would have a fairly clear picture on the size and magnitude and scope of the project to be able to deliver high-quality drinking water to potentially the City of Phoenix as well as other water providers in our area,” Hayes says. “Once we get that accomplished, we would then be able to develop a financing plan to try to figure out how we can utilize either state or federal funds that are out there to help with drought situations. And that'll give a little bit clearer perspective to the different communities on what the local participation would be.”

Although the project’s estimated cost remains to be seen, it likely will be “in the billions,” Hayes says. “A lot of [the cost] depends on the size of the facility and the other infrastructure that would be needed to transport the finished water to participating cities,” he says. Other issues still to be determined concern ownership of the new facility and whether other cities might be able to contribute treated wastewater for the purpose of DPR.   

Drought is a significant factor in Phoenix’s decision to evaluate the possibility of DPR. Although recent major snowfalls in the Rocky Mountains are expected to boost water levels in Lake Powell and Lake Mead on the Colorado River this year, the long-term prognosis for the critical reservoirs remains grim.  

“We are having continuing struggles on the Colorado River system, which is putting stresses on our water supply,” though “not necessarily to a point at this time in which we don't have enough supplies,” Hayes says. “Because Phoenix has built a very robust and diverse water portfolio, we usually have large cushions. As we get cuts and things like that that happen, essentially those cushions are diminishing. So, we are actively looking for additional water supplies that can be added to the portfolio.”