Officials in Orange County, Calif., will attend opening ceremonies today for the world's largest water-purification project, among the first "toilet-to-tap" systems in America. The Groundwater Replenishment System is designed to take sewage water straight from bathrooms in places like Costa Mesa, Fullerton, and Newport Beach and—after an initial cleansing treatment—send it through $490 million worth of pipes, filters, and tanks for purification. The water then flows into lakes in nearby Anaheim, where it seeps through clay, sand, and rock into aquifers in the groundwater basin. Months later, it will travel back into the homes of half a million Orange County residents, through their kitchen taps and showerheads.
It's a smart idea, one of the most reliable and affordable hedges against water shortages, and it's not new. For decades, cities throughout the United States have used recycled wastewater for nonpotable needs, like agriculture and landscaping; because the technology already exists, the move to potable uses seems a no-brainer. But the Orange County project is the exception. Studies show that the public hasn't yet warmed to the notion of indirect potable reuse (IPR)—or "toilet-to-tap," as its opponents would have it. Surveys like one taken last year in San Diego show that a majority of us don't want to drink water that once had poop in it, even if it's been cleaned and purified. A public outcry against toilet-to-tap in 2000 forced the city of Los Angeles to shut down a $55 million project that would have provided enough water for 120,000 homes. Similar reluctance among San Diego residents led Mayor Jerry Sanders to veto the city council's approval in November of a pilot program to use recycled water to supplement that city's drinking water. (A similar plan failed once before in 1999.)
But San Diego is in the midst of a severe water crisis. The city imports 90 percent of its water, much of that from the Colorado River, which is drying up. The recent legal decision to protect the ecosystem of the San Joaquin Delta in Northern California—San Diego's second-leading water source—will reduce the amount coming from there as well. Add to that rising population and an ongoing drought, and the situation looks pretty bleak: 3 million people in a region that has enough water, right now, for 10 percent of them.
We don't have enough water where we need it; if we don't learn to deal with drinking toilet water, we're going to be mighty thirsty. Only 2.5 percent of the water on Earth is freshwater, and less than 1 percent of that is usable and renewable. The Ogallala Aquifer—North America's largest, stretching from Texas to South Dakota—is steadily being depleted. And Americans are insatiable water consumers—our water footprint has been estimated to be twice the global average (PDF).
The ocean provides another source of potable water. Large-scale treatment of seawater already occurs in the Middle East, Africa, and in Tampa Bay, Fla. Construction of the largest desalination plant in the western hemisphere is supposed to begin this year in Carlsbad, Calif., which would convert 300 million gallons of seawater into 50 million gallons of drinking water each day. Taking the salt out of ocean water sounds like a good idea, but it's economically and environmentally far more expensive than sewage-water recycling. Orange County water officials estimate desalinated water costs between $800 and $2,000 per acre-foot to produce, while its recycled water runs about $525 per acre-foot. Desalination also uses more energy (and thus produces more greenhouse gas emissions), kills tiny marine organisms that get sucked up into the processing plant, and produces a brine byproduct laced with chemicals that goes back into the ocean.
What desalination doesn't have, though, is the "yuck" factor of recycled sewage water. But seawater, like other sources of nonrecycled water, is at least as yucky as whatever comes through a toilet-to-tap program. When you know how dirty all this water is before treatment, recycling raw sewage doesn't seem like a bad option. Hundreds of millions of tons of sewage are dumped into rivers and oceans, and in that waste are bacteria, hormones, and pharmaceuticals. Runoff from rainwater, watering lawns, or emptying pools is the worst, sending metals, pesticides, and pathogens into lakes, rivers, and the ocean. The water you find near the end of a river system like the Colorado or the Mississippi (which feeds big cities like San Diego and New Orleans) has been in and out of municipal sewers several times.
Whatever winds up in lakes and rivers used for drinking is cleaned and disinfected along with the rest of our water supply. Still, a recent analysis of San Diego's drinking water found several contaminants, including ibuprofen, the bug repellent DEET, and the anti-anxiety drug meprobamate. No treatment system will ever be 100-percent reliable, and skeptics who worry that pathogens in sewage water will make it past treatment and into our drinking water should worry about all drinking water, not just the water in a toilet-to-tap program. The fact is, supertreated wastewater is clean enough to drink right after treatment. It's been used safely this way (in a process known as direct potable reuse) for years in the African nation of Namibia. The EPA has conducted research in Denver and San Diego on the safety of direct potable reuse and found recycled water is often of better quality than existing drinking water. And although putting water into the ground, rivers, or lakes provides some additional filtering and more opportunities for monitoring quality, the benefits of doing it that way are largely psychological. In its 2004 report (PDF) on the topic, the EPA concluded that Americans perceive this water to be "laundered" as it moves through the ground or other bodies of water, even though in some instances, according to the report, "quality may actually be degraded as it passes through the environment."
Despite the public's concerns, a few U.S. cities have already started to use recycled wastewater to augment drinking water. In El Paso, Texas, indirect potable reuse supplies 2 percent of the city's drinking water; in Fairfax, Va., it supplies 5 percent. * Unless we discover a new source of clean, potable water, we're going to have to consider projects like these to make wastewater a reusable resource. The upfront costs for getting a system in place and educating the public may be steep, but it would save us the expense—both economic and environmental—of finding another river or lake from which we can divert water.
Correction, Aug. 3, 2011: This article originally stated that indirect potable reuse supplies 40 percent of El Paso's drinking water. That number was 20 times too high. (Return to the corrected sentence.)