Drinking water: Toilet to tap — get used to it!
In the future, your drinking water is going to be recycled from your toilet — believe it.
Surging population growth, climate change, reckless irrigation and chronic waste are placing the world’s water supplies at threat, a landmark UN report …
The global population is growing by 80 million people a year, 90 per cent of it in poorer countries. Demand for water is growing by 64 billion cubic metres per year, roughly equivalent to Egypt’s annual water demand today.
In the past 50 years, EXTRACTION from rivers, lakes and aquifers has tripled to help meet population growth and demands for water-intensive food such as rice, cotton, dairy and meat products. Agriculture accounts for 70 per cent of the withdrawals, a figure that reaches more than 90 per cent in some developing countries.
ENVIRONMENTAL DEGRADATION from water pollution and excessive extraction now costs many billions of dollars. Damage in the Middle East and North Africa, the world’s most water-stressed region, amounts to some $US9 billion ($A13.84 billion) a year, or between 2.1-7.4 per cent of GDP.
Yes, desalination will become much more widely used, but it is very energy intensive, creates its own environmental problems, and can’t easily be used everywhere (see “How dry I am: Droughts and desalination, another amplifying feedback” and below)
And that brings us to toilet to tap. Reuters has a good article on the subject I excerpt below:
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 recycling plant, the world’s largest of its kind, uses microfiltration, reverse osmosis, ultraviolet light and hydrogen peroxide disinfection to treat 70 million gallons (265 million liters) 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 U.S. 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.”
“A NEW DAY” FOR WATER
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 …
“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 behavior to installing low-flow showers, toilets, appliances and lawn sprinklers.
Such measures could add more than 1 million acre feet of water — enough for 8 million people — to Southern California’s regional supply alone, or about 25 percent 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 runoff that normally flows to sea.
THE HOLY GRAIL
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 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 byproduct 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 distill. 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 U.S. 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 50 million gallons (189 million liters) 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.
FROM THE GROUND AND BACK AGAIN
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 fibers 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 U.S. 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, D.C., 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 L.A. 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 realize 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 L.A. County Economic Development Corp study puts it, “What happens in Vegas doesn’t stay in Vegas.”