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Orange County, Calif., has just opened 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.

Late last month, the first of this cleaned-up water was piped into lakes in nearby Anaheim, where it will seep through clay, sand and rock into aquifers in the groundwater basin. In six months to a year 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 - including St. Petersburg - 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. 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. 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 ocean provides another source of potable water. Large-scale treatment of seawater already occurs in the Middle East, Africa and right here in the Tampa Bay area, where water authorities officially opened the nation's largest seawater desalination plant late last month. The $158-million plant had been working in fits and starts for years, and is now finally supposed to realize its 25-million-gallons-a-day potential.

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 antianxiety 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. (In a mid-Pinellas neighborhood many years ago, a family got some direct experience with reclaimed water when a confused plumber hooked the reclaimed water up to the household plumbing and the drinking water line to the sprinkler system. The water was safe to drink but tasted awful.)

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, the benefits of doing it that way are largely psychological. In its 2004 report 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 40 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.

Eilene Zimmerman is a San Diego-based journalist who writes about business and political and environmental issues. Her work appears in the New York Times, the San Francisco Chronicle, Fortune Small Business,, Wired, the Christian Science Monitor and other publications.