Drought-prone regions look to drink seawater, wastewater
by Daniel Simmons
Look into your toilet. Or gaze out to the sea. Likely, your first thought won't be, "I should take a swig."
But in a world of growing population and shrinking freshwater supplies, municipal water suppliers are looking to both as abundant, mostly untapped sources. Technology has improved enough, supporters say, that sticking a metaphorical straw into wastewater and seawater has become not only possible but economically viable, especially in the drought-prone Southeastern and Southwestern United States.
So will your next glass of tap water have once circled a shower drain or flushed a toilet? Or will it have been ladled from the ocean?
If you live in certain parts of the country, it already may have. Some regions draw a small amount of municipal supply from treated wastewater or lightly salted water. But two recently completed projects - a wastewater treatment plant in Orange County, Calif., and a seawater desalination plant in Tampa, Fla. - dwarf all that came before them. They provide water to hundreds of thousands of people. They cost hundreds of millions of dollars. And they stir up major controversies.
"They're the two bright lights in that they produce water that's new, and almost every other option has to do with conservation," says Rhodes Trussell, owner and consulting engineer with Trussell Technologies of Pasadena, Calif. He's been involved with water issues for 35 years and consulted on both projects. But each method faces stiff opposition, from people concerned with the safety and quality of wastewater and others concerned about upsetting the ocean's natural ecology.
Environmental concerns about desalination center around fish and microscopic sea life killed during the filtering process, the effect on ocean ecology of dumping the salty leftovers back in and the carbon footprint - treatment plants typically are very energy-intensive. "Collectively, we're really hurting the ocean already," says Maude Barlow, senior adviser to the United Nations on water issues. "We can't take care of our freshwater crisis by further harming the ocean."
But supporters point to the approximately 14,000 desalination plants operating in at least 150 countries and say that recent advances in technology have cut the cost and energy required to operate the plants.
The Tampa desalination plant opened in December 2007 and now supplies an average of 25 million gallons a day, or 10 percent of the region's water. Another desalination plant that will provide 50 million gallons a day to the San Diego area is slated to open in 2010. It will be the largest in the western hemisphere. The Orange County wastewater treatment plant opened in January 2008 and is transforming wastewater into up to 70 million gallons a day of purified drinking water, 15 percent of the region's water.
Supporters and opponents agree that more plants will likely follow. "They're both breakthroughs in that they're the first of their kind on that scale [in the U.S.]," Trussell says.
Angie's List members generally support both new approaches, although not as many are familiar with the so-called "toilet to tap" option. Eighty-five percent have heard about desalination, according to a recent online poll. Of them, nearly three-quarters approve. "It doesn't disturb the natural water cycle and doesn't impact nature as much," says member Elisabeth Wilkins of Suffolk, Va. "Damming up wild rivers wrecks ecosystems."
Wilkins tasted desalinated water while visiting her husband, who was in the U.S. Navy for 20 years stationed on ships that relied on desalinated seawater. "It tasted a lot better than the municipal water where we now live," she says.
But member Mary Taylor of Houston worries about potential damage to the ocean. "I think we're charging into destructive short-term solutions that may very well lead to making the natural environment collapse - or at least become a very inhospitable host," she says.
Angie's List members are less aware of treating wastewater than seawater, according to the poll. Fifty-seven percent of members have never heard of the approach. Among people who know about it, 79 percent expressed support, with 21 percent opposed.
Michael Shoffstall, of Hudson, Ohio, isn't bothered by the idea. "There's not really an ick factor for me - I understand it's part of nature's way," he says.
But others can't accept it. "I don't think I'd ever put purified, post-poo water in my body, not to mention let my kids bathe in it," says April Snyder of Indianapolis.
No similar yuck factor exists for desalinated water, but environmental concerns remain. An April 2008 National Academy of Sciences report urges caution going forward. While calling the potential water supply made possible by desalination "unlimited" - seawater accounts for an estimated 97 percent of the world's total water supply - the report's authors conclude that further study is needed. "Substantial uncertainty remains about the environmental impacts," they write.
The latest technology used in desalination, called reverse osmosis, relies on two sets of filters to remove large and small particles. Water must be pumped through at extremely high pressure, which requires a lot of energy. Yet the energy costs have dropped significantly over the last decade due to innovations that make filtering more efficient, Trussell says.
In 1992, a desalination plant went into operation in Santa Barbara, Calif., but was abandoned after just three months when the region's severe drought reportedly gave way to a "March miracle" of sustained, heavy rainfall. The desalinated water no longer was necessary, but the plant could start producing again if a serious enough drought returns, says Rebecca Bjork, water resources manager for the city. Producing the water there cost $2.10 in electricity for 1,000 gallons. By contrast, the same amount will cost $1.10 to produce at the plant expected to open in 2010 in the San Diego suburb of Carlsbad, Calif. "This technology is no longer just Research and Development curiosity," says Leon Awerbuch, a Boston-based chemical engineer and president of Leading Edge Technologies, developer of desalination plants worldwide. "It's been shown to be an economical and reliable source of water production."
However, the process still results in the death of fish and other ocean life, although it's estimated the daily fish kill is no more than what a pelican eats in a day. Both the Tampa Bay and the planned San Diego plants use water already drawn from the ocean to cool adjacent power plants. Concerns about the salty discharge causing further disruption upon re-entering the sea have been largely calmed at the Tampa Bay facility, says Fred Bloetscher, a civil engineer and assistant professor at Florida Atlantic University. State regulations require the water to be mixed with freshwater to dilute it before going back into the sea, he says, and the diluted water appears so far to be safe for sea life.
Desalination plants have been in operation in arid Middle Eastern countries for three decades and now supply more than three-quarters of the drinking water in countries such as Saudi Arabia, the United Arab Emirates and Kuwait, Awerbuch says. Many Caribbean island nations also rely on desalination, and plants have sprouted across Australia, including a Perth plant powered by wind.
The growth of desalination in the U.S. will only intensify, according to Awerbuch. "If you look long-term, the only possibility to feed demand for world water is to produce new water from the sea," he says.
Supporters of wastewater treatment, meanwhile, maintain there's plenty to tap in the existing supply, if people can get used to the idea of drinking wastewater purified to a level that exceeds state and federal drinking water standards. "It's locally supplied, locally controlled, and it lowers the demand for imported water," says Gina DePinto, an Orange County Water District spokesperson.
But public squeamishness has hampered other wastewater treatment projects. Trussell says that Orange County's approach - heavy on public outreach and communication - helped win over many reluctant residents and was a model for other regions considering a plant.
Last January, the OCWD, a state legislature-created agency that supplies water to 22 communities, powered up its $481 million Groundwater Replenishment System. Every day, up to 70 million gallons of it flows to reservoirs where it filters through the soil and mixes back into existing groundwater.
Retired engineer Clarke Lewis lives blocks from the plant and supports the approach. "We're going to have to figure out ways to get more miles out of the water we have, and reuse is an intelligent thing to do," he says. There's been "no difference whatsoever" in the taste, color or odor of his tap water since the plant opened, he says.
Meanwhile, many other people in Orange County interviewed agreed with Angie's List members Amy and Greg Ruth, who work in Irvine: They didn't realize anything had changed.
OCWD uses the groundwater basin beneath Orange County to supply its communities with about 70 percent of their water needs. The remainder is purchased from the Metropolitan Water District of Southern California, which imports water from the Colorado River and northern California.
Water officials in other California cities and in other water-starved Southeastern and Southwestern states also are exploring the idea. San Diego imports nearly all its water and already treats reclaimed wastewater to water crops and municipal gardens. In 2007, the city council approved a water reuse pilot project that would pump recycled wastewater into a drinking-water reservoir. The council approved an 8.4 percent increase in water rates, which began in January, to pay for it.
Last May, Los Angeles Mayor Antonio Villaraigosa proposed a 20-year water use strategy that included exploring groundwater replenishment similar to Orange County's. It's not the city's first foray. In 2000, L.A. opened and quickly shut down a $50 million plant due to public opposition. The current plan also is receiving criticism. "We believe the ratepayers should have a vote to do toilet-to-tap," says Gerald A. Silver, president of Homeowners of Encino, who opposed the 2000 plant.
Critics often cite the high cost to recycle wastewater, but proponents say it's actually cost-effective, particularly in areas that rely heavily on imported water. Treated wastewater in Orange County costs about $550 per acre-foot (326,000 gallons) to produce due to generous subsidies from the Metropolitan Water District, while imported water from northern California and Colorado costs about $650 per acre-foot.
However, groundwater drawn from natural sources such as rivers and rainfall costs half as much but is not plentiful enough to supply the region's water needs especially during droughts, DePinto says.
The next step may be supplying drinking water directly from treated wastewater without filtering it through groundwater. The only facility that currently does is in Africa. "It's a public perception people aren't quite ready to accept," DePinto says. "That will change."
- With additional reporting by Joshua Palmer, Paul F.P. Pogue and Conor Lee.