A Water-Covered Planet facing a Water Crisis seems Paradoxical
A water-covered planet facing a water crisis seems paradoxical. And yet that is exactly the reality on planet Earth, where 97 percent of the water is too salty to quench human thirst or to irrigate crops. Tackling water-shortage issues with desalination — drawing fresh, drinkable water out of salty seawater — is common in the desert nations of the Middle East, the Caribbean and the Mediterranean. But as the cost of desalination drops and the price and demand for water climb, countries in temperate regions are turning more and more to the sea.
(1) People have been pulling freshwater out of the oceans for centuries using technologies that involve evaporation, which leaves the salts and other unwanted constituents behind. Salty source water is heated to speed evaporation, and the evaporated water is then trapped and distilled. (2)This process works well but requires large Cartier Replica quantities of heat energy, and costs have been prohibitive for nearly all but the wealthiest nations, such as Kuwait and Saudi Arabia. To make the process more affordable, modem distillation “plans recycle heat from the evaporation step.
(3)A potentially cheaper technology called membrane desalination may expand the role of desalination worldwide, which today accounts for less than 0.2 percent of the water withdrawn from natural sources. Membrane desalination relies on reverse osmosis — a process in which a thin, semi permeable membrane is placed between a volume of saltwater and a volume of freshwater. The water on the salty side is highly pressurized to drive water molecules, but not salt and other impurities, to the pure side. In essence, this process pushes freshwater out of saltwater.
Most desalination research over the past few years has focused on reverse osmosis, because the filters and other components are much smaller than the evaporation chambers used in distillation plants. Reverse-osmosis plants are also more compact and energy-efficient.
Although reverse-osmosis plants can offer energy savings, the earliest membranes, made from either polyamide fibers or cellulose acetate sheets, were fragile and had short life spans, often no longer than three years. (4)These materials are highly susceptible to contaminants in the source water — particularly chlorine, which hardens the membranes, and microbes, which clog them. A new generation of so-called thin composite Cartier Replica Watches membranes, made from polyamide films, promises to eliminate these problems. Though still susceptible to contamination, these new membranes are sturdier, provide better filtration and may last up to 10 years.
Technical performance is important, but it alone does not drive the adoption of desalination as a source of clean water. (5) With or without technical improvements, the market for desalination equipment will very likely show healthy growth in the next 10 years as cities and other consumers realize the potential and favorable economics of existing equipment.
Hundreds of suppliers are already selling many thousands of pieces of equipment annually. These desalination units range in capacity from a few gallons a day (small emergency units for life rafts) to several million gallons a day (municipal systems).
Today the best estimate is that about 1 percent of the world’s drinking water is supplied by 12,500 desalination plants. No doubt, this is only the Replica Watches beginning. In the future, the water in your glass may have originated in the seas.
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