By Sara Jerome,
Recycled water is coming under scrutiny in Denver, where a major consumer is narrowing its use of this resource.
“The Denver Zoo has decided to stop feeding recycled water to elephants, rhinos and tapirs in its ‘crown jewel’ exhibit, the Toyota Elephant Passage,” Westword recently reported.
The city has a substantial recycled water program, according to the report:
Denver Water's program provides wastewater that’s been sufficiently treated for irrigation purposes at a fraction of the cost of potable water. Since its plant opened in 2004, numerous parks, schools and private entities, including golf courses and the Denver Country Club, have signed up for irrigation with water from the utility's "purple pipe."
But recently, the program has come under the scrutiny of some local residents, who are blaming recycled water for a recent die-off of trees in Washington Park.
Just ask Sonia John, a Friends and Neighbors of Washington Park member who wrote a guidebook about local plant life. She says trees on private property have remained healthy, and they receive potable water. The dying trees use recycled water, Westword reported.
Research undertaken at Denver Water’s request makes “a persuasive case that foliage and soils in city parks treated with Denver Water’s recycled product contain high amounts of sodium — which, over time, can be particularly lethal to conifers, since they draw water from their roots most of the year,” according to the report.
One such study is a 2010 report commissioned by Denver Water. The report “found high concentrations of sodium around trees in Denver Parks, which is irrigated with recycled water,” according to KUSA.
Here’s how the utility weighed in:
Over at Denver Water, officials said they've been working to reduce the amount of lye used to treat recycled water, which they say has helped lower salt levels. "It's been gradually decreasing, as treatment needs have changed based on the source water from metro," said Russell Plakke, Water Treatment Plant Supervisor for Denver Water.
Scott Gilmore, executive director of Denver Parks and Recreation, has questioned whether recycled water is acting alone in hurting the parks. "We have some challenges," he said. "There's weather factors and bugs and bees and pathogens and then we do have to work with reuse water."
For the latest developments in recycled water, visit Water Online’s Water Reuse Solutions Center.