Desalination, also called desalinization, refers to the processes involved in removing excess sodium chloride (salt), excessive minerals and other impurities from sea and ocean water. Its purpose is to convert salt water into fresh water, to make it suitable for irrigation and human consumption. Water is desalinated using one (or more) methods, including distillation (vapor-compression or VC, multiple-effect evaporator or MEDIME, and multi-stage flash distillation or MSF), ion exchange, membrane processes (electrodialysis reversal or EDR), reverse osmosis or RO, nanofiltration or NF, and membrane distillation or MD), freezing, solar humidification, and high-grade water recycling. Desalination has numerous advantages, some of which are detailed below.
Availability of Water in Areas of Drought
The main purpose of desalination is to make water available in those areas that have limited resources of fresh water. It provides a reliable and safe supply of water to growing communities. An example of a desalination plant serving a low-rainfall area is the Kurnell Desalination plant located in Sydney, Australia. The Kurnell provides 250 megalitres of water per day and contributes 15 percent of the current water supply to Sydney. As of March 2009, the Kurnell plant is the largest desalination plant operating in Australia. The Aruba Island Desalination Plant has a capacity of producing 11.1 million gallons of fresh water daily.
Alternative Source of Water
Desalination provides a readily available and reliable alternative source of water in times of severe drought (like the drought of 2007 that hit most of the southeastern U.S.) and/or water shortages. According to the journal "Water Resources Research," there is a 50 percent chance of Lake Powell and Lake Mead running dry by 2021. The two lakes jointly supply water to more than 25 million people and seven states. Desalination becomes a necessity in the current climate of increasing global temperature, burgeoning populations, and unsustainable groundwater.
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Production of a High Yield of Water
The desalination process produces a high yield of consumable water. The Ashkelon desalination plant in Israel produces a minimum of 83.2 gallons of water on a daily basis and has a capacity of 315 megaliters of water. Another desalination plant in Israel, the Hadera plant, produces a minimum of 91.9 gallons of water per day and has a full capacity of 349 megaliters of water. The El Paso desalination plant located in Texas produces approximately 27.5 million gallons of water per day.