I've been remiss in not linking to Elizabeth Royte's New York Times Magazine article from this past weekend, about her visit to Orange County's sewage treatment plant, by volume the largest indirect potable reuse ("toilet-to-tap") program in the world. Royte makes a very important, and often overlooked, point: It's not like ordinary freshwater is all that fresh.
To understand the basics of contemporary water infrastructure is to acknowledge that most American tap water has had some contact with treated sewage. Our wastewater-treatment plants discharge into streams that feed rivers from which other cities suck water for drinking. By the time New Orleans residents drink the Mississippi, the water has been in and out of more than a dozen cities; more than 200 communities, including Las Vegas, discharge treated wastewater into the Colorado River. ...
It’s one of the many pardoxes of indirect potable reuse that the water leaving the plant in Fountain Valley is far cleaner than the water that it mingles with. Yes, the water entering the sewage-treatment plant in Fountain Valley is 100 percent wastewater and has a T.D.S.--a measure of water purity, T.D.S. stands for total dissolved solids and refers to the amount of trace elements in the water--of 1,000 parts per million. But after microfiltration and reverse osmosis, the T.D.S. is down to 30. (Poland Spring water has a T.D.S. of between 35 and 46.) By contrast, the “raw” water in the Anaheim basins has a T.D.S. of 600.
There is some reputable opposition to indirect potable reuse--in particular, even if the process usually works fine, there's always the risk that human error or mechanical failure might result in occasional snafus, which could threaten public health. But most of the opposition, in cities like my own hometown of San Diego, results simply from the "yuck" factor. For some reason, reusing other cities' wastewater doesn't strike most people as nearly as objectionable as reusing your own wastewater. And the best solution to that is the market. If water from other sources becomes increasingly scarce and citizens are informed that their water bills would be, say, 40 percent higher in the absence of indirect potable reuse, my guess is the "yuck" factor wouldn't seem quite as compelling. (They may not like toilet-to-tap in Orange County, but what they really don't like is higher bills from governmental agencies.) In the meantime, though, we're likely to mostly just see more use of treated wastewater in industry, to water golf courses, and so on.