Current News |
From Sewage, Added Water
for Drinking
By RANDAL C. ARCHIBOLD
Published: November 27, 2007
http://www.nytimes.com/2007/11/27/us/27conserve.html?
FOUNTAIN VALLEY, Calif. — It used to be
so final: flush the toilet, and waste be
gone.
But on Nov. 30, for millions of people
here in Orange County, pulling the lever
will be the start of a long, intense
process to purify the sewage into
drinking water — after a hard scrubbing
with filters, screens, chemicals and
ultraviolet light and the passage of
time underground.
On that Friday, the Orange County Water
District will turn on what industry
experts say is the world’s largest plant
devoted to purifying sewer water to
increase drinking water supplies. They
and others hope it serves as a model for
authorities worldwide facing persistent
drought, predicted water shortages and
projected growth.
The process, called by proponents
“indirect potable water reuse” and
“toilet to tap” by the wary, is getting
a close look in several cities.
The San Diego City Council approved a
pilot plan in October to bolster a
drinking water reservoir with recycled
sewer water. The mayor vetoed the
proposal as costly and unlikely to win
public acceptance, but the Council will
consider overriding it in early
December.
Water officials in the San Jose area
announced a study of the issue in
September, water managers in South
Florida approved a plan in November
calling for abundant use of recycled
wastewater in the coming years in part
to help restock drinking water supplies,
and planners in Texas are giving it
serious consideration.
“These types of projects you will see
springing up all over the place where
there are severe water shortages,” said
Michael R. Markus, the general manager
of the Orange County district, whose
plant, which will process 70 million
gallons a day, has already been visited
by water managers from across the globe.
The finished product, which district
managers say exceeds drinking water
standards, will not flow directly into
kitchen and bathroom taps; state
regulations forbid that.
Instead it will be injected underground,
with half of it helping to form a
barrier against seawater intruding on
groundwater sources and the other half
gradually filtering into aquifers that
supply 2.3 million people, about
three-quarters of the county. The
recycling project will produce much more
potable water and at a higher quality
than did the mid-1970s-era plant it
replaces.
The Groundwater Replenishment System, as
the $481 million plant here is known, is
a labyrinth of tubing and tanks that
sucks in treated sewer water the color
of dark beer from a sanitation plant
next door, and first runs it through
microfilters to remove solids. The water
then undergoes reverse osmosis, forcing
it through thin, porous membranes at
high pressure, before it is further
cleansed with peroxide and ultraviolet
light to break down any remaining
pharmaceuticals and carcinogens.
The result, Mr. Markus said, “is as pure
as distilled water” and about the same
cost as buying water from wholesalers.
Recycled water, also called reclaimed or
gray water, has been used for decades in
agriculture, landscaping and by
industrial plants.
And for years, treated sewage, known as
effluent, has been discharged into
oceans and rivers, including the
Mississippi and the Colorado, which
supply drinking water for millions.
But only about a dozen water agencies in
the United States, and several more
abroad, recycle treated sewage to
replenish drinking water supplies,
though none here steer the water
directly into household taps. They
typically spray or inject the water into
the ground and allow it to percolate
down to aquifers.
Namibia’s capital, Windhoek, among the
most arid places in Africa, is believed
to be the only place in the world that
practices “direct potable reuse” on a
large-scale, with recycled water going
directly into the tap water distribution
system, said James Crook, a water
industry consultant who has studied the
issue.
The projects are costly and often face
health concerns from opponents.
Such was the case on Nov. 6 in Tucson,
where a wide-ranging ballot measure that
would have barred the city from using
purified water in drinking water
supplies failed overwhelmingly. The
water department there said it had no
such plans but the idea has been
discussed in the past.
John Kromko, a former Arizona state
legislator who advocated for the
prohibition, said he was skeptical about
claims that the recycling process
cleanses all contaminants from the water
and he suggested that Tucson limit
growth rather than find new ways to feed
it.
“We really don’t know how safe it is,”
he said. “And if we controlled growth we
would never have to worry about drinking
it.”
Mayor Jerry Sanders of San Diego, in
vetoing the City Council plan there,
said it “is not a silver bullet for the
region’s water needs” and the public has
never taken to the idea in the 15 years
it has been discussed off and on.
Although originally estimated at $10
million for the pilot study in San
Diego, water department officials said
the figure would be refined, and the
total cost of the project might be
hundreds of millions of dollars.
Although the Council wants to offset the
cost with government grants and other
sources, Mr. Sanders predicted it would
add to already escalating water bills.
“It is one of the most expensive kinds
of water you can create,” said Fred
Sainz, a spokesman for the mayor. “It is
a large investment for a very small
return.”
San Diego, which imports about 85
percent of its water because of a lack
of aquifers, asked residents this year
to curtail water use.
Here in Orange County, the project, a
collaboration between the water and
sanitation districts, has not faced
serious opposition, in part because of a
public awareness and marketing campaign.
Early on, officials secured the backing
of environmental groups, elected leaders
and civic groups, helped in part by the
fact the project eliminated the need for
the sanitation district to build a new
pipe spewing effluent into the ocean.
Orange County began purifying sewer
water in 1976 with its Water Factory 21,
which dispensed the cleansed water into
the ground to protect groundwater from
encroaching seawater.
That plant has been replaced by the new
one, with more advanced technology, and
is intended to cope with not only
current water needs but also
expectations that the county’s
population will grow by 500,000 by 2020.
Still, said Stephen Coonan, a water
industry consultant in Texas, such
projects proceed slowly.
“Nobody is jumping out to do it,” he
said. “They want to make sure the
science is where it should be. I think
the public is accepting we are
investigating it.”
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