Treated wastewater used for drinking supplies
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SAN DIEGO -- Almost hidden in the northern hills, the pilot water treatment plant here does not seem a harbinger of revolution. It cost $13 million, uses long-established technologies and produces 1 million gallons a day.
But the plant's very existence is a triumph over one of the most stubborn problems facing the nation's water managers: If they make clean drinking water from wastewater, will the "yuck" factor keep people from accepting it?
With climate change diminishing water supplies in the fast-growing Southwest, more cities are considering the potential of reclaimed water. A new report from the National Academy of Sciences said that if coastal communities used advanced treatment procedures on the effluent that is now sent out to sea, it could increase the amount of water available by as much as 27 percent.
San Diego's success, 12 years after its City Council recoiled from the toilet-to-tap concept, offers a blueprint for other districts considering wastewater reuse.
For most of the four decades beginning in 1970, the arid West was the fastest-growing region in the country; the population of Nevada quintupled in that period while Arizona's nearly quadrupled. Continued population growth, unmatched by growth in water storage capacity, makes this a "new era in water management in the United States," the science group's report said.
"The pressures on water supplies are changing virtually every aspect of municipal, industrial and agricultural water practice," it said.
Back in 1998, a branch of the National Academy of Sciences, the National Research Council, issued a study finding that supplementing stream flows or reservoirs with this water, a process called indirect potable reuse, was acceptable, although only as a last resort. Now, acceptance of reclaimed water for drinking is spreading, if slowly.
Still, just one-tenth of 1 percent of municipal wastewater nationally was recycled into local supplies in 2010. Only a handful of systems replenish their reservoirs or groundwater basins with treated wastewater.
The largest is in Orange County, Calif., about 100 miles north of San Diego, where a 4-year-old system replenishes the groundwater basin with 70 million gallons of treated effluent daily -- about 20 percent of the content of the aquifer. Other sites include El Paso and some areas around Los Angeles.
First Published February 12, 2012 12:00 am
