Anyone who has visited Disneyland recently and taken a sip from a drinking fountain there may have unknowingly sampled a taste of the future - a small quantity of water that once flowed through a sewer.
Orange County Water District officials say that's a good thing - the result of a successful, year-old project to purify wastewater and pump it into the ground to help restore depleted aquifers that provide most of the local water supply.
The $481 million (€376.334 million) recycling plant, the world's largest of its kind, uses microfiltration, reverse osmosis, ultraviolet light and hydrogen peroxide disinfection to treat 265 million litres of sewer water a day, enough to meet the drinking needs of 500,000 people.
Just don't call it "toilet-to-tap".
County officials prefer the term Groundwater Replenishment System, a name chosen after similar projects in Los Angeles and San Diego fell prey to public misconceptions, also known as the "yuck" factor," and local election-year politics.
Their experience underscores one of the great lessons facing municipal officials across the US West as they seek to bring purification and recycling technologies to bear against drought cycles expected to worsen with climate change.
Scientists, policymakers and investors agree ample know-how exists to solve the water crisis; the difficulties lie in energy constraints, economics and politics.
"We can solve most, if not all, of the world's biggest water problems with technology that exists today," said Stephan Dolezalek, who leads the clean-energy practice of Silicon Valley venture capital firm VantagePoint Venture Partners. "What we may not have is the willpower."
Experts say price distortions in the West, where government has long subsidized farm irrigation and the cost of pipelines and pumping stations to send fresh water from distant sources to cities, have discouraged the development of new supplies.
"The water that we use in the West is generally undervalued," said Tim Barnett, a marine research physicist for the Scripps Institution of Oceanography at the University of California, San Diego.
The math has changed as the region's water grows scarcer, its population swells and environmental pressures mount.
"This is a new day, and we have conditions which compel us to look to new water resources," said David Nahai, general manager of the Los Angeles Department of Water and Power, the nation's largest municipal utility.
He and other water managers see tremendous potential in stepped-up conservation, from encouraging more waste-conscious personal behaviour to installing low-flow showers, toilets, appliances and lawn sprinklers.
Such measures could add more than one million acre feet of water - enough for eight million people - to Southern California's regional supply alone, or about 25 per cent of current annual use, according to a report by the Los Angeles County Economic Development Corp.
Further gains are possible by replenishing groundwater basins with rainfall run-off that normally flows to sea.
Desalination, the process of converting salt water to fresh, has long been viewed as the holy grail in the quest to replace imported drinking supplies, said Jonas Minton of the environmental group Planning Conservation League.
But Mr Minton, who chaired a California state desalination task force earlier this decade, and other experts cite two major drawbacks.
One is a risk to marine life from intake pipes that suck water into the system and from a highly concentrated brine by-product that gets discharged back into the ocean.
The other is the relatively high cost of removing salt from ocean water, which contains roughly 30 times more dissolved impurities than sewer water and thus takes far more energy to distil. Energy demands become especially vexing in light of efforts to curb carbon emissions tied to global warming.
Desalination is common in parts of the Middle East, where freshwater sources are extremely scarce, oil is plentiful, and environmental laws are less stringent. But US ocean desal plants are rare. The biggest so far is in Tampa, Florida.
Six small-scale plants exist in California, and about 20 more are in various stages of planning or development.
The most ambitious, a $300 million facility to be built by the Connecticut-based company Poseidon Resources in Carlsbad, near San Diego, would produce 189 million litres of drinking water daily, enough for about 110,000 households.
The Poseidon plant, twice the size of the Tampa facility, would be the largest in the Western Hemisphere. It has yet to receive final approval for construction.
Once considered a less attractive alternative, wastewater recycling technology has proven more economically feasible and gained greater public acceptance.
"We're to a certain extent helping to drought-proof ourselves," said Michael Markus, general manager of the Orange County Water District and the chief engineer behind its Groundwater Replenishment System.
"Within three years, the price of imported water will be $800 per acre foot, and projects like this, even without outside funding, will become viable," he said. An acre foot of water is about a year's supply for two families.
By comparison, Orange County's recycling system currently produces water for $600 an acre foot, not including subsidies it received for the initial capital investment.
The plant takes pre-treated sewer water that otherwise would be discharged to the ocean and runs it through a three-step cleansing process - essentially the same technology used to purify baby food and bottled water.
Thousands of microfilters, hollow fibres covered in holes one-three-hundredth the width of a human hair, strain out suspended solids, bacteria and other materials.
The water then passes to a reverse osmosis system, where it is forced through semi-permeable membranes that filter out smaller contaminants, including salts, viruses and pesticides. Reverse osmosis also is the main process used in desalination.
Finally, the water is disinfected with a mix of ultraviolet light and hydrogen peroxide.
The resulting product exceeds all US drinking standards but gets additional filtration when it is allowed to percolate back into the ground to replenish the aquifer.
Much of the technology is supplied by private companies, including German-based Siemens AG, which makes the microfilters, and Danaher Corp, headquartered in Washington, DC, which furnishes the UV lamps.
The Orange County system is serving as a model for a project that Los Angeles plans to resurrect nearly 10 years after it was killed when local politicians disparaged the concept as "toilet-to-tap." San Diego's recycling project met a similar fate and also is back on the drawing board.
A recent study cited by LA County Economic Development Corp found more than 30 Southern California recycling projects with the potential of yielding over 450,000 acre feet of water within five years. That's about half the amount the region expects to import this year from the Colorado River.
Water managers say they now realise that an aggressive public education campaign is key to building support.
They want the public to understand that much of what comes from the tap today is recycled sewer water. The Colorado River, for example, contains large amounts of heavily treated waste discharged from cities upstream, including Las Vegas.
As the LA County Economic Development Corp study puts it, "What happens in Vegas doesn't stay in Vegas."
Key facts about water desalination
• The primary method of desalting water is reverse osmosis, which pushes water under high pressure through fine membranes that separate the salt. This uses high amounts of energy, the major cost.
• The top three desalination countries are Saudi Arabia with 17 per cent of global output, United Arab Emirates with 13.4 per cent, and the US with 13 per cent.
• Most of the world's high-capacity desalination projects are in the Middle East, where energy is cheaper and environmental regulations are more lax than in the US.
• Most of the US desalting plants process inland brackish water, accounting for 54 per cent of desalination. But seawater, which accounts for just 7.4 per cent and is more expensive to process, will be the main source of future growth as costs decrease and technology improves.
• In California, total capacity of desalination plants is 83,000 acre feet per year, equal to about 11 per cent of the water used in Los Angeles. An additional 475,000 acre feet per year in new capacity are in various stages of planning.
- A new desalination plant in San Diego County, using seawater, will be the biggest in the Western Hemisphere when it opens by 2012, with output of 56,000 acre feet per year.
• Environmental concerns include: the brine by-product that is much saltier than ocean water and must be processed before being put back in the ocean; and the impact of the suction intake pipes on sea life.
• Desalination will not be a major supply of California water until after 2025 due to the cost differential with conventional freshwater supplies.
• Desalinating seawater at major plants nearing construction in Southern California will cost between $950 to $1,100 per acre foot. It costs Southern California cities about $650 per acre foot for imported drinking water, which is to go up to $800 or more per acre foot in three years.
Note: An acre foot is the amount of water it takes to cover an acre 12 inches deep. It is enough water to serve two four-person US households.