Treated sewer water to fill Tempe Town Lake

The idea of water in the desert is always appealing, but the murky stuff in Tempe Town Lake has never looked very alluring.

Yet now the city is planning to fill the man-made lake with something that sounds even less appealing — water from a sewage treatment plant.

City officials acknowledge the ick factor of the idea, but they say reclaimed water would actually be cleaner than what goes in now.

“Some people get a funny look on their face when you mention it, but I don’t have any comments from people who said out and out this is something they wouldn’t accept,” said Basil Boyd, a Tempe water resources hydrologist.

The city allows swimming at the lake only for special events, such as triathlons. Water quality is already a problem because high algae levels have pushed pH levels above federal standards at times.

John Hyte of Mesa said he’s competed in many events at the lake and gotten coldlike symptoms for a couple of days after each swim. Other triathletes have shared similar stories, he said.

“It’s common knowledge to expect to be sick after,” Hyte said.

The treated water is cleaner in every way, Boyd said. It’s clear, nearly meets standards for drinking water, has a low pH and doesn’t have any algae. An ultraviolet filter at the plant disinfects the water.

The only problem is a high level of phosphorous, which is a nutrient for algae. The city can control algae with chemicals, so city officials said that shouldn’t be a problem.

Because the lake would still meet safety standards, the biggest hurdle would likely be public perception, said Don Hawkes, Tempe’s water utilities manager.

“That’s something that we’ll need to educate people about,” Hawkes said.

It could take two years to put treated water in the lake. The city needs to install a $10.7 million, 5-mile pipeline from the plant to the lake. It also needs state environmental officials to sign off.

The city is pursuing the idea because of water conservation. The lake is now filled with groundwater or Colorado River water via the Central Arizona Project. Those sources can be used for drinking water. The treated water nearly meets drinking water standards but can’t be used for that, so switching sources would free up water for drinking.

The lake loses about 1.5 million gallons a day to evaporation. The city has enough surplus treated water to supply 60 percent to 80 percent of that, Boyd said.

The city’s water is now pumped into the Salt River and evaporates or seeps into aquifers. Some also goes to a golf course and a power plant.

Hyte has tested the pH himself and said he wants Tempe to ensure the water doesn’t get any worse.

“I don’t know what else they should do, but I think they should do everything they can,” Hyte said. “It’s a public safety thing, especially if they’re banking on swimming in it and to do events.”

People don’t refuse to swim in the lake despite its appearance, said Jeff Banas, head of the Arizona Triathlon Club. He suspects athletes would swim in the lake even if the reclaimed water were in it.

“I don’t think it would keep anybody from doing the event,” Banas said.