Environmental Engineering Reference
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decided to replace Water Factory 21 with the larger, more advanced Groundwater Re-
plenishment System, which produces 70 million gallons of highly treated wastewater
per day, some of which is pumped into the aquifer and eventually added to Orange
County's drinking supply.
The practice remains highly controversial, but, said OCWD's Markus, “We got into
this out of necessity, not choice…. We live in a desert, but a lot of people here don't seem
to realize it. We have very little water, and the concern is that our periodic droughts will
grow more extended. We realized we needed to find a more reliable supply.”
By 2007, the population of Orange County was surging toward 3 million and facing
two related problems: soaring water demand and an increasing amount of sewage. In
2007, water consumption in the central and northern parts of the region was half a mil-
lion acre-feet a year. By 2020, the population is projected to increase by 20 percent, and
water consumption will climb to six hundred thousand acre-feet a year. (An acre-foot
of water is 325,851 gallons, which is the amount that would cover an acre of land with
one foot of water.) County managers solved their problems with one masterstroke: turn
the bothersome sewage into a new supply of drinking water.
In January 2008, Orange County opened the $481 million Groundwater Replenish-
ment System (GWRS), the world's most ambitious sewage-water purification project,
on the site of Water Factory 21. The GWRS collects wastewater from twenty-two cit-
ies—including Santa Ana, Newport Beach, Fullerton, and Costa Mesa—and, after an
initial cleansing at a conventional two-stage sewage treatment plant next door, pushes
the effluent through fine reverse-osmosis membranes, doses it with hydrogen peroxide
(an oxidizer), and disinfects it under ultraviolet light to kill any microbes and patho-
gens. The result is “the cleanest water there is,” said Mike Markus of OCWD.
The GWRS's treated water does not flow directly into people's taps, though it is clean
enough to do so. Instead, it is pumped fourteen miles north into a series of recharge
basins in Anaheim. There, it mixes with natural supplies, storm-water runoff, and water
diverted from the Santa Ana River, which eventually percolates down through layers of
sand, clay, and rock into deep aquifers. Months later, the mixture is pumped back up
and sent to 2.3 million customers.
The GWRS plant produces 23.5 billion gallons of water a year. “It's a water supply we
can't get anywhere else,” said Markus. “It's a big, big advance in water treatment.”
The toughest hurdle for reclaimed toilet-to-tap water is not microbial, financial, or tech-
nical: it is emotional. The “yuck factor” led to screaming headlines and became a divis-
ive political issue, especially in San Diego and Los Angeles, the state's two biggest cities.
Your golden retriever may drink out of the toilet with no ill effects. But that doesn't
mean humans should do the same,” declared the SanDiegoTribune.In 2006, the paper
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