LOS ANGELES – It’s a technology with the potential to ease California’s colossal thirst and insulate millions from the parched whims of Mother Nature, experts say.
But there’s just one problem: the “yuck factor.”
As a fourth year of drought continues to drain aquifers and reservoirs, California water managers and environmentalists are urging adoption of a polarizing water recycling policy known as direct potable reuse.
Unlike nonpotable reuse – in which treated sewage is used to irrigate crops, parks or golf courses – direct potable reuse takes treated sewage effluent and purifies it so it can be used as drinking water.
It’s a concept that might cause some consumers to wince, but it has been used for decades in Windhoek, Namibia – where evaporation rates exceed annual rainfall – and more recently in drought-stricken Texas cities, including Big Spring and Wichita Falls.
In California, however, similar plans have run into heavy opposition.
Los Angeles opponents coined the derisive phrase “toilet to tap” in 2000 before torpedoing a plan to filter purified sewage water into an underground reservoir – a technique called indirect potable reuse.
Despite defeats, proponents say the time has finally arrived for Californians to accept direct potable reuse as a partial solution to their growing water insecurity. With Gov. Jerry Brown ordering an unprecedented 25 percent cut in urban water usage because of drought, the solution makes particular sense for large coastal cities such as Los Angeles, they say.
Instead of flushing hundreds of billions of gallons of treated sewage into the Pacific Ocean each year, as they do now, coastal cities can capture that effluent, clean it and convert it to drinking water.
“That water is discharged into the ocean and lost forever,” said Tim Quinn, executive director of the Association of California Water Agencies. “Yet it’s probably the single largest source of water supply for California over the next quarter-century.”
To be sure, it will be years, or even a decade, before direct potable reuse systems begin operation in California.
One reason for this is that there is no regulatory framework for the approval of such a system. Currently, a panel of experts is preparing a report to the Legislature on the feasibility of creating such rules. That report is due in 2016.
Potable reuse advocates insist the public’s distaste for the concept is based on ignorance. They note that more than 200 wastewater treatment plants already discharge effluent into the Colorado River, which is a primary source of drinking water for Southern California.
“That’s what I call de facto potable reuse,” said George Tchobanoglous, a water treatment expert and professor emeritus at the University of California, Davis.
In an economic analysis last year, Tchobanoglous estimated that by 2020, potable reuse could yield up to 1.1 million acre-feet of water annually – somewhat less than the 1.3 million acre-feet of water the governor hopes to save through mandatory reductions, and enough to supply 8 million Californians, or one-fifth of the state’s projected population.
In an indirect potable reuse system, treated water is placed in an “environmental buffer,” such as an underground aquifer or surface water reservoir, where it is stored for a period of time before getting processed in a traditional water treatment plant. It is this type of system that was defeated in Los Angeles.
Although potable reuse advocates say opposition is often driven by a visceral response to the process, the so-called yuck factor, those who opposed the Los Angeles project said recently that they did so for a variety of reasons, including cost and the potential long-term effects of the trace quantities of drug compounds, hormones and personal care products found in wastewater and surface water.
“Personally I would not drink water that has been recycled through the toilet to tap process,” said Steven Oppenheimer, a biology professor at Cal State Northridge. However, Oppenheimer said he would use such water for irrigation, and even household cleaning and bathing.
The presence of so-called contaminants of emerging concern may prove to be one of the main barriers to direct potable reuse. Because of limited scientific knowledge, these compounds are unregulated, meaning that there are no government-prescribed methods for monitoring or removing them.
Tchobanoglous and others insist these substances exist in such small quantities that they don’t pose a significant issue.
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