Wastewater treated at one of El Paso’s four treatment plants is undergoing further purification at a pilot facility meant to clean it to drinking water standards. (Mónica Ortiz Uribe)
The search for new water sources is never-ending for growing cities in the desert Southwest. Traditional sources like rivers and underground aquifers are proving insufficient, so cities are turning to options that were once unthinkable — like “toilet to tap” recycling. A handful of cities in Texas are leading the way.
From above, the naked desert surrounding El Paso looks like a moonscape. It’s a treeless land of sand and shrubs that on average gets less than nine inches of rain per year. A century ago, the Rio Grande used to flood just east of downtown. Today growing regional demand has sucked the river bed dry.
When nature isn’t enough, people turn to technology.
A new purification system is being tested at one of El Paso’s wastewater treatment plants. For 50 years the city has used recycled wastewater, also known as purple pipe water, to irrigate parks, school yards and farms. Now the city wants to clean this water further and add it directly to the drinking supply.
“Basically it’s wastewater coming from homes, sinks, dishwashers, showers, toilets,” said Christina Montoya, marketing manager for El Paso Water Utilities.
Skeptics gave it the name “toilet to tap,” a phrase intended to provoke your gag reflex. But severe drought and dwindling water supplies across the Southwest are making the idea more palatable.
“In our very hot summer months, when people are really running their air conditioners, that’s when we get our highest water use,” Montoya said. “What happens is we come very close to not being able to meet that demand.”
Recycled wastewater could provide a 10 million gallon boost, about 6 percent of the city’s peak daily demand.
If approved by state regulators, El Paso’s project would be the largest in the country. Smaller Texas cities like Big Spring and Midland already have similar systems in place.
At its small pilot plant, the El Paso Water Utility runs greywater through a four step process known as direct potable reuse. It involves microfiltration, reverse osmosis, UV exposure and carbon filtration. It’s a quick process that can put recycled water back into the drinking supply in a matter of hours, so constant monitoring is crucial.
For Josiah Heyman, co-director of a federally funded water study at the University of Texas at El Paso, a big concern is keeping out potentially harmful elements — “small trace chemicals such as antibiotics, steroids and hormones that people use, caffeine,” he said.
There’s also the price tag. A full-scale purification plant could cost $100 million, which would increase people’s water bills. Rates have already risen 30 percent over the course of the past decade.
That’s partly due to the 2007 construction of the world’s largest inland desalination plant, which cleans up brackish groundwater and adds yet another source to El Paso’s drinking supply.
At a beauty salon on the city’s rapidly growing east side, stylist Iviana Monarrez clips purple extensions to a client’s hair. She’s more concerned about having a reliable water source than drinking purified toilet water.
“I wouldn’t think that it’s such a bad idea if it allows us to have more water,” she said. “I’m just thinking, my children in the future. Are they going to have water, are their children going to have water?”
El Paso Water Utilities conducted a phone survey of 1,087 households two years ago asking customers how they felt about drinking purified waste water — 77 percent said they strongly approved.
Treated wastewater is already put back into aquifers and man-made reservoirs across the Southwest. This adds an environmental filter of months or years before the water goes back to the tap. Direct potable reuse, which eliminates this environmental buffer, is far less common. Arizona currently prohibits it, but a stakeholder committee is currently exploring ways to change those regulations.
Heyman, the water scholar, said cities are quickly realizing that a diversified water portfolio is key.
“We need to think about many smart ways to use water more effectively in the future and restore some of our water,” he said.
If El Paso can prove to state regulators that its purification system is safe, the city can build and operate a full-scale plant as soon as 2020. And if that’s not enough, it hass also purchased land outside of town where it can take groundwater and pipe it back the city, 90 miles uphill.