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.
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