From: Andy Soos, ENN
Published February 11, 2013 08:16 AM
Grey Water
There is only so much fresh water in the world of the kind people
need to drink to live. Recycled water, or gray water, is water that has
been used for household activities such as taking showers or washing
dishes. Then there is water that is a bit more dirty such as from the
toilet. There are or will be a time and a place where such water will
have to be used as is or will be treated so as to reuse once again. Even
now in places like Singapore and Namibia, limited supplies of freshwater
are being augmented by adding highly treated waste water to their
drinking water.
Over the last several decades, regional and local water shortages are
becoming increasingly common. Australia saw the worst droughts in its
settled history between 1995 and 2009. Droughts across the U.S. last
summer crippled farm crops in the midwest. Then there are people living
in the driest lands of the US such as Los Angeles, Las Vegas, and
Phoenix and these populations are growing and consuming every ounce of
water they can.
In the rest of the world countries in dry areas are arguing and
sometimes fighting over water supplies. Control of water resources is a
point of friction along already-contentious borders between Israel and
Jordan, India and Pakistan, and Turkey and Syria, for example. Fighting
over oil and religion is already happening. The war over water may be
even more immense.
Some grey water can be reused as is. Better is to collect the water at
a treatment plant. In some cases, the sewage systems already installed
are deviated to go to a toilet-to-tap treatment plant, instead of a
typical waste treatment plant. A typical plant would then release the
treated water, sometimes into rivers or the ocean, while other times it
is stored in large under ground lakes called aquifers, which clean the
water more as it slowly drips through layers of sand and rock to reach
underground streams. In either case the water is returned to a more
useful cycle.
There are many treatment schemes such as reverse osmosis, biological
aeration ultraviolet light and hydrogen peroxide to name a few to purify
water. There is also desalinization of sea water to consider ion the
mix. Treated grey water is just as good as any other water supply.
The advocates of reuse of grey water just want to take the treated water
and add it more directly to potable water supplies rather than to a
stream going to the sea. A variation of this is to use treated grey
water for irrigation as opposed to direct use.
There are many examples of communities that have safely used recycled
water for many years. Los Angeles County's sanitation districts have
provided treated waste water for landscape irrigation in parks and golf
courses since 1929. The first reclaimed water facility in California was
built at San Francisco's Golden Gate Park in 1932. The Irvine Ranch
Water District (IRWD) was the first water district in California to
receive an unrestricted use permit from the state for its recycled
water; such a permit means that water can be used for any purpose except
drinking. IRWD maintains one of the largest recycled water systems in
the nation with more than 400 miles serving more than 4,500 metered
connections.
Reclaimed water is highly engineered for safety and reliability so that
the quality of reclaimed water is more predictable than many existing
surface and groundwater sources. Reclaimed water is considered safe when
appropriately used. Reclaimed water planned for use in recharging
aquifers or augmenting surface water receives adequate and reliable
treatment before mixing with naturally occurring water and undergoing
natural restoration processes. Some of this water eventually becomes
part of drinking water supplies.
Singapore is a bit ahead of the curve in making grey water more
potable.
Cleaning waste water begins with conventional treatment. Microfiltration
is next, in which the water flows through a series of tubes containing
filters with microscopic pores, each 500 times smaller than the
thickness of a human hair. While water flows into the tubes and on to
the next step, microbes and all but the smallest solids are filtered
out.
Reverse osmosis is next and uses high pressure to force water through a
plastic membrane with pores so small that even dissolved salts typically
cannot get through. Although reverse osmosis is usually enough to
reliably remove all contaminants, the water flows past ultraviolet lamps
to ensure that it is completely sterilized in the last step at
Singapore.
Resistance to reuse is stronger in the us as opposed to the the
relatively isolated island nation of Singapore. Orange County, Calif.,
uses a process like Singapore’s, generating as much as 265 million
liters of clean water from waste water each day — enough to supply
20,000 average U.S. households. That recycled water is as pure as
distilled water and is injected into the aquifers that supply the
county’s drinking water. San Diego is also reusing treated waste water,
People do not like dirty water and have to be convinced it is clean
usually out of desperation in places where water is short.
For further information see
Toilet.
Sign image via Wikipedia.
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