Treated Wastewater For Drinking

Tucson Looks at Treating Wastewater for Drinking

Tucson is taking its first tentative dip into the sometimes turbulent waters of recycling treated sewage effluent for drinking.

Tucson Water has produced a detailed long-range plan and an accompanying timetable that calls for building a pilot project to recycle wastewater for potable use as soon as three years from now.

The timetable calls for starting construction of a full-scale wastewater recycling plant by the early 2020s. But the timing of these actions is very uncertain, with Tucson Water officials saying they could be stretched back as far as the 2050s, or done much more quickly, depending on how soon the water is needed.

While the plan hasn't won City Council approval, many council members gave it a relatively friendly reception at a study session discussion last month.

Mayor Jonathan Rothschild and two council members generally endorsed the idea of wastewater recycling for drinking in interviews last week. But they don't want to commit to building a plant until ensuring that the most advanced technology possible is used and that the public gets far more education about the treatment process.

Wastewater recycling is a very expensive, at times controversial, process, costing many times more than the delivery of Central Arizona Project water to Tucson.

It could, for instance, cost anywhere from $1,500 an acre-foot to $3,300 an acre-foot to treat effluent for drinking, the city's effluent recycling plan says. Pumping CAP water uphill for more than 300 miles from the Colorado River, by contrast, costs $146 an acre-foot for Tucson Water today, and could rise to $157 an acre-foot in 2015.

But as effluent's use for drinking grows around the arid Southwest, it's a water supply that many local officials say is inevitable, given the region's ongoing drought and population growth. They see it as the region's only sustainable, locally generated water supply, particularly given the strains on the Colorado River due to continued drought.

"I think it will happen sooner than the 2050s. The technological possibiilties, I know will happen sooner," Rothschild said. "But this is something you have to go to the community with and have people understand, and the technology has to be pretty good."

Recycled water has long been disdained by many residents here and elsewhere because of what's known as the "yuck factor" of drinking treated effluent. But while opponents denigrate the process as "toilet to tap," officials say they're confident that the water can be treated to quality as good or better than Tucson's current drinking water supplies.

One of the keys will be building public trust in whatever technology is employed, the master plan says.

In the coming year, Tucson Water will interview focus groups, make presentations to neighborhood associations and businesses and convene an expert panel to advise it on additional ways of educating the public about such treatment.

Utility officials will conduct studies of where the wastewater would be treated and where to build pipelines taking the water from Pima County's sewage treatment plants to recharge basins where it would be first placed, then pumped out.

A key unknown in the uncertainty of when such a plant would be built is the precarious state of Lake Mead and the Colorado River in general. They have suffered steadily declining water levels and flows since 2000 because of the drought and the Southwest's annual removal of about 1.2 million acre-feet more water from the lake than what the river delivers.

If those trends continue, Hoover Dam's power output eventually would be sharply curtailed, and Las Vegas would be unable to go deeply enough into the lake to get its water. Also, federal and state officials may have to consider reducing deliveries of river water to Arizona cities and Indian tribes in the 2020s to keep the lake from falling so low that it would reach "dead pool," in which no water could be pulled from it.

Source: Tucson

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• Treatment
• Sludge Separation
• Drinking Water