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 The recycling of wastewater for human consumption is gaining greater
credence in drought-stricken California, where scarce drinking
supplies, changing economics and a newly proven technology has led
more local leaders to embrace a concept once derided by critics as
"toilet-to-tap."
But experts warn that regulators and politicians must take care to
educate and reassure a wary public in casting wastewater as a
largely squandered resource.
"The yuck factor is still an issue," said Frances Spivy-Weber, vice
chair of the state Water Resources Control Board. "You have to be
quite straightforward with the public ... so they don't feel like
they're being tricked."
By all accounts, the tide of public opinion appears to be turning. A
number of cities, including Los Angeles and San Diego, have moved to
emulate Orange County's advanced purification system, the largest of
its kind in the world, which has been producing 70 million gallons
of fresh water daily from sewer effluent since 2008.
That system puts pre-treated waste discharge through a process of
microfiltration, reverse osmosis, ultraviolet light and hydrogen
peroxide disinfection to render enough potable water, nearly
distilled in quality, for over 500,000 people.
Yet this water does not go directly to homes. It is first pumped
into the county's groundwater basin to recharge depleted aquifers,
receiving another, natural level of filtration before being drawn
back to the surface for drinking and bathing.
In May, daily output was increased to 100 million gallons. The
groundwater basin as a whole, a third of it now derived from
recycled waste, is the principal drinking source for 2.4 million
people in northern and central Orange County.
INDIRECT VS. DIRECT
This "indirect potable reuse" of wastewater, in the parlance of
engineers and regulators, is seen as a promising new approach for
ensuring dependable water supplies as California struggles through a
fourth straight year of drought.
The state water board last year formalized the first regulations for
the type of recycling operation pioneered in Orange County.
The agency has until December 2016 to adopt new rules for indirect
potable reuse of highly purified wastewater that gets blended with
and stored in large freshwater surface basins, such as reservoirs or
lakes, rather than groundwater, before people drink it.
Even then, the water would make one last stop at a conventional
treatment plant en route to household taps, as it does now in Orange
County.
Regulators will turn next to "direct potable reuse," in which
purified wastewater would be fed straight into a traditional
treatment plant without first pausing in some kind of environmental
holding buffer. A feasibility study is due by the end of next year.
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Texas is the only U.S. state so far to approve direct potable
recycling, with two small-scale systems in towns that went online
last year amid severe drought and water shortages there.
The success of Orange County's Groundwater Replenishment System, a
name that conspicuously omits the words "waste" or "sewage," has
gone a long way toward winning greater support for potable reuse.
SUPPLY AND DEMAND
A record dry spell that has left reservoirs badly drained, forced
irrigation cutbacks by farmers and led to drastic new mandatory
conservation measures for homes and industry is also driving
support.
At the same time, the drought has raised the costs of piping in
fresh water from the Colorado River and elsewhere, making capital
investments in recycling plants more attractive by comparison.
"You can build one of these types of water plants for about the same
cost as purchasing imported water," said Michael Marcus, general
manager of the Orange County Water District.
Cost considerations also give recycled wastewater an edge over
desalination, the process of distilling fresh water from the sea, as
ocean water contains 30 times more dissolved impurities than
pre-treated sewer effluent and requires much more energy to purify.
The Pacific Ocean does offer a theoretically unlimited raw supply of
water. But the amount of unused wastewater currently flushed into
the ocean is staggering, an estimated 1.3 billion gallons daily off
Southern California alone, Marcus said.
For those who may still be squeamish, he points to an oft-overlooked
fact: The Colorado River has long contained large volumes of treated
waste discharged by Las Vegas and other cities upstream of Southern
California's water intakes.
"People have been drinking wastewater their entire lives; they just
haven't realized it," he said.
(Reporting by Steve Gorman; Editing by Cynthia Johnston and Leslie
Adler)
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