Once mocked as “toilet to tap,” the practice of directly treating wastewater for drinking could be legal in Arizona by the end of this year.
The Arizona Department of Environmental Quality is likely to propose legalizing “direct potable reuse” in six months, its senior hydrologist Chuck Graf said this week. Better technology and safety measures now offer assurances the wastewater can be treated for drinking without ill effects, Graf and other officials said.
The first of a series of permitting rules and standards “hopefully can be approved by the end of this year,” Graf said in an interview. The ADEQ, which wants the change, will make the final decision.
Direct reuse has been illegal in Arizona since the state started regulating wastewater in 1982.
“Water reuse’s time has come. It’s a large theme taking place across the U.S. and the world,” Tucson Water director Tim Thomure told a state water recycling committee this week in Phoenix.
“We have had knowledge that this would be needed sooner rather than later. Later has become sooner,” he said.
But while water utility officials around the state are pushing for more liberal policies for treating wastewater for drinking, such treated water isn’t likely to be flowing from Tucson-area taps soon.
The practice is likely to begin first in places such as the Prescott Valley and mountainous or other less urban areas where water resources and the ability to recharge water for future use are limited, said Thomure, who chairs a statewide steering committee on the issue. In those areas, it will be at least two or three years before they’re ready to use it, he said.
In the Phoenix area, West Valley cities that lack access to Salt River Project water are also interested, Thomure said.
Thomure and Graf said they’re convinced that direct treatment of wastewater for drinking is safe. That’s even though more than 100 unregulated contaminants are showing up in various Arizona water supplies today at very low levels, such as parts per trillion, they say.
While traces of these compounds exist in drinking water supplies around the state and in surface water and groundwater, “frankly, if you go to direct potable reuse, the levels of treatment would rise immeasurably over what they are treating in drinking water. There will be multiple barriers, multiple safety factors,” Graf said.
Direct potable reuse involves piping wastewater from a conventional sewage treatment plant to another, more technologically advanced plant that treats the water to drinking quality. A reverse osmosis plant, which runs wastewater through membranes for treatment, is one of several technologies available.
This practice contrasts with indirect potable reuse, in which utilities recharge treated wastewater into the aquifer and pump it out for drinking. That happens along the Lower Santa Cruz River in the Tucson area, where two Pima County treatment plants discharge millions of gallons a day.
The idea of treating wastewater for drinking once was criticized by some environmentalists, who saw it as an effort to find more water to serve continued population growth rather than controlling or limiting growth.
Others, concerned about potential health impacts, mocked the practice as “toilet to tap.”
But in a new report last week, the environmental group Western Resource Advocates included direct potable reuse on a list of solutions to ease the pain of future Colorado River shortages.
With direct potable reuse, you don’t have to recharge the water underground or pump it back out, which saves money, said Linda Stitzer, a water policy adviser for Western Resource Advocates in Tucson.
“Right now, we’re limited to using (effluent) on golf courses and parks or recharging it,” Stitzer said. “By directly treating it to a higher standard … you have a whole new group of users.”
However, Tucson Water officials are no longer talking regularly, as they used to, of treating wastewater to drink possibly by the 2020s, to respond to population growth and drought pressures on the Colorado River.
Late last year, director Thomure said the utility now plans to put much of its effluent into the Santa Cruz through downtown Tucson as an amenity. With Tucson’s total water demand now at 1985 levels, the need for recycling wastewater has been delayed, he said. If that’s ever needed, the effluent put into the Santa Cruz will recharge the aquifer close enough to downtown that the utility can easily pump it out, he said.
Direct reuse’s potential would increase here “if our demand grows to the point where we exhaust Colorado River supplies or gets to the point where conditions on the Colorado are so debilitating that we have significant reductions in availability. At least from what we know today … this is decades out,” said Thomure.
Officials of the Marana, Oro Valley and Metro Water District water utilities say they also don’t expect to need direct potable reuse in the near future.
Marana’s treatment of its wastewater will be different, for instance. Starting in 2018, when it finishes construction of a sewage treatment plant along the Santa Cruz, it will recharge treated wastewater into the ground, said John Kmiec, Marana’s water director. That will provide water storage credits the town can draw upon to pump out water elsewhere, using existing wells.
But, “if a community wants to look at (direct reuse) when it may be more efficient in the future, it should have the option and not be prohibited,” said Kmiec, who chairs a statewide water recycling committee.
Direct reuse also isn’t likely to be needed soon for many Phoenix-area cities that have rights to Colorado and Salt River supplies, Thomure said.
Other Southwestern states and cities are looking at or even using direct potable reuse. After a crippling drought, Big Spring, Texas, put such a plant online in 2014 and still uses it. Wichita Falls used one for a while, then decommissioned it after heavy 2015 rains filled its reservoirs, Thomure said.
The village of Cloudcroft, New Mexico, has built such a plant and is preparing to start it up. In California, the State Water Resources Control Board published a major report last year that said direct potable reuse, “when implemented appropriately,” has the potential to provide a reliable water source that protects public health. The state plans to develop regulations allowing its use.
Many California environmentalists are pushing treating wastewater to drink as an alternative to building more costly desalination plants.
Drought is a key factor driving many states to consider direct potable reuse. In Arizona, a bigger factor may be that ADEQ is now revising what Graf calls its “pretty aged” overall water reuse regulations, unchanged since 2001. Water utilities want the direct reuse approved now because it may be years before the rules are revised again.
