In January, public officials and residents of Orange County, California, toasted the culmination of a water supply project more than a decade in the making. But at these festivities champagne took a backseat to the beverage of choice as celebrants lifted glasses of recycled sewage water.
More than a billion people worldwide lack clean drinking water. While demand for freshwater access continues to increase—after tripling in the last 50 years—global supplies are becoming scarcer. Major rivers vital to surrounding populations are in danger of drying out. Groundwater reserves face a similar fate. The situation threatens to grow worse in the future as extreme droughts occur more often, according to the Intergovernmental Panel on Climate Change.
In the United States more than 2.1 trillion gallons of water are flushed down toilets every year. What most people think of as sewage is a freshwater reserve that, with a few steps of treatment, could provide drinking water for millions. Recognizing this, Orange County’s water and sanitation districts have begun recycling sewage into drinking water at the world’s largest plant of its kind, the $487 million Groundwater Replenishment System. The treated water, which exceeds state and federal heath standards, is being used to recharge the underground aquifer that feeds the taps of more than 2.3 million residents of the region. Other municipalities in California, Texas, Florida, Singapore, and Australia are exploring similar projects.
“We are, in essence, creating a new source of water,” says civil engineer Michael Markus, general manager of the Orange County Water District. “Right now we have severe challenges here,” he says, “where our imports have been reduced by about a third, and we’re sitting on an eight-year drought on the Colorado River.”
The treatment system, which began operation in January, purifies wastewater that would otherwise be dumped into the Pacific, creating 70 million gallons a day of clean water. “It’s a way to utilize an available resource instead of discarding it into the ocean, where it’s instantly no longer of use as freshwater,” says environmental health scientist Kellogg Schwab, who directs the Center for Water and Health at Johns Hopkins University.
Recycling starts with sewage treatment by the Orange County Sanitation District, which removes solid waste and uses microorganisms to break down organic materials. The water then heads to the recycling facility for purification. It passes at low pressure through an ultrafine filter that strains out particulate matter, bacteria, and the single-celled organisms known as protozoans (amoebas and their kin). Next comes reverse osmosis, in which the water is forced through a plastic membrane at high pressure to remove even tinier pollutants including viruses, salts, and pesticides. Treatment with hydrogen peroxide and ultraviolet light completes the process.
Half of the near-distilled-quality reclaimed water is injected into a saltwater barrier—an underground supply of freshwater that prevents brine from creeping inland from the sea and contaminating fresh reserves. The rest is pumped 13 miles north to a recharge basin in Anaheim, where it slowly percolates down into the ground to supplement the aquifer that provides drinking water to the community. Though all indications suggest that the water is safe the minute it emerges from filtration, direct recycling is not yet publicly accepted in the United States, according to the Environmental Protection Agency (EPA). A 2004 report from the agency found that people view recycled water that has passed through an aquifer or reservoir as being cleaner, though in some cases the recycled water is actually of higher quality than the natural sources it joins. Only one plant in the world, in Namibia, supplies recycled water directly to users without first mixing it with water from natural sources.