“Desalination is growing in arid regions,” said Tom Davis,Director, Center for Inland Desalination Systems, and Professor of Civil Engineering from the University of Texas at El Paso, reported www.cnn.com. “We are making progress in the USA, but the countries around the Persian Gulf are way ahead in the use of desalination, primarily because they have no alternative supplies of freshwater.”
Because of large droughts around the world, there have been major decreases in water sources. This has led people to search for other sources of fresh water.
Most of Earth’s mass is the ocean, large bodies of salt water. Of course, humans cannot consume salt water. However, scientists have discovered a method to provide freshwater from the ocean. This method is called “desalination.”
Salt water contains significant amounts of dissolved salts. In desalination, the concentration is the amount, in weight, of salt in water, which is expressed in “parts per million” (ppm), according to water.usgs.gov.
Fresh water – Less than 1,000 ppm
Slightly saline water – From 1,000 ppm to 3,000 ppm
Moderately saline water – From 3,000 ppm to 10,000 ppm
Highly saline water – From 10,000 ppm to 35,000 ppm
The ocean water contains about 35,000 ppm of salt.
There are two basic methods for desalinating saltwater:
Thermal cleansing and membrane separation. Thermal refinement involves heat: The workers of the plant will boil the water so that it becomes a vapor, which leaves all of the salt behind. Then it is collected and condensed back into water through cooling.
The most common type of desalination is called reverse osmosis. Seawater is forced through a semipermeable membrane that separates salt from water. Because the technology typically requires less energy than thermal distillation, most new plants, like Tampa’s, now use reverse osmosis.
Because salt easily dissolves in water, desalinated water will not be cheap; water taken from the ocean could cost up to 60 cents per cubic meter of water, according to www.scientificamerican.com.
Because small marine organisms, like plankton for example, can be sucked into the plants, they would be killed and upset the food chain. Also, the brine, or leftover salt and particles, will be discharged into the ocean, which will also ruin marine life and habitats. Reducing these impacts is possible, but it adds to the costs, reported www.scientificamerican.com.
As result of the costs, the Desalination Plant being created in Carlsbad has decided to dispose of the brine discharge into the San Diego Bay to create new habitats so marine life can reproduce there.
The Carlsbad Desalination Plant will be completed in 2016 and will become the Western Hemisphere’s largest desalination plant, creating 50 million gallons of freshwater a day. Constructing the plant will cost approximately $1 billion and use the energy of 70 homes in a single day, according to www.cnn.com.
“Whenever a drought exacerbates freshwater supplies in California, people tend to look toward the ocean for an answer,” said Jennifer Bowles, executive director of the California-based Water Education Foundation, according to www.cnn.com. “It is, after all, a seemingly inexhaustible supply.”