Environmental Engineering Reference
In-Depth Information
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A corollary to seasonal pricing is time-of-day pricing, in which prices
are higher during a utility's peak demand periods.
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A relatively new method for encouraging lower water use is a digital
water meter.
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Its heart is an electronic device called a water manager.
The water user buys a smart card at a local convenience store that,
like a long-distance telephone card, is programmed for a certain number
of credits. At home, the purchaser punches the card's code into a small
keyboard and pushes the LOAD key. The water manager automatically
sends a signal to the water company to supply water. When the user
runs out of credits, he or she pushes the LOAN key, and the utility
gives the user a bridge loan until he or she purchases another card.
Studies in the United Kingdom revealed that households using the water
manager reduced water use by 21 percent.
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The UK Environment
Agency said that a shift to widespread metering is essential for the
long-term sustainability of water resources.
More than 100 studies of the relationship between residential water
use and pricing indicate that a 10 percent increase in price lowers use
by 2 to 4 percent. In industry, a 10 percent increase in price lowers
demand by 5 to 8 percent. In economic terms, water demand is said to
be inelastic, meaning that when price increases, consumption decreases
at a smaller amount than the increase in price.
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Reusing Dirty Water
Through the natural water cycle, the earth has recycled and reused water
for billions of years. However, when used in discussions of water avail-
ability to consumers,
recycling
generally refers to projects that use tech-
nology to speed up natural processes. The number of such projects is
increasing dramatically in the United States because of increasing pres-
sure on freshwater resources. Recycled water can satisfy water demands
for irrigating crops, cooling water in power plants, mixing concrete in
construction work, watering a lawn, mopping a fl oor, or fl ushing a toilet.
Hundreds of American cities now use recycled water for nondrinking
purposes. Most irrigation of fruits and vegetables in California and
Florida is accomplished with recycled wastewater. In Israel, about one-
third of water needs is met by reclaimed and recycled municipal waste-
water, or sewage water. Water reuse and recycling is second only to
conservation as a means of boosting water supplies.
Water recycling is a three-step fi ltration process. When water enters
the treatment facility, solids are settled out, and the wastewater is sucked
