Water and Desalination

What is desalination? Desalination is the separation process of removing or reducing excess salts and other mineral from substances. 1 The process of desalination may be used on different substances however this paper will focus on the desalination of water. The desalination of water is very important to human and animal life. For centuries humans have used the process of desalination to obtain water safe for consumption.Various methods of desalination have been produced however only some of those methods are widely used today. Although there are numerous methods of desalination all of them involve three liquid streams: the saline feedwater (seawater or brackish water), low-salinity product water, and very saline concentrate (brine water). 1 The low salinity product water and the saline concentrate are output streams that are produced when the saline feedwater goes through the process of desalination.1 The desalination of the saline feedwater liquid can be divided into five classifications: distillation, membrane, humidification, freezing, and chemical . 2 The two main desalination processes used today are the desalination by distillation and the desalination by reverse osmosis. Within each method of desalination there are several other processes involved. Distillation processes are the most commonly used methods of desalination as well as some of the oldest methods.1 In 1869, the British Government built the first steam distillation process on land.2 There are various distillation processes they include the long-tube vertical distillation, Multistage flash distillation (MSF), Multiple Effect distillation (MED), Vapor Compression distillation (VC), and membrane distillation. Most of these methods produce freshwater by heating saline water to produce water vapor and then reducing the vapor pressure to allow the water to boil at a lower temperature so more heat will not be used up. All of these methods consume some type of thermal energy or electrical power

Bibliography: 1. Source Book of Alternative Technologies for Freshwater Augmentation in Latin America and the Caribbean;IETC Technical Publication Series by UNEP International Environmental Technology Centre, Osaka/Shiga, Japan, 1997. http://www.oas.org/dsd/publications/Unit/oea59e/begin.htm#contents 2. Popkin, Roy. Desalination: Water for the World’s Future. Frederick A. Praeger, Publishers: New York, 1968. 3. Betts, Kellyn. “Desalination, desalination everywhere.” Environmental Science and Technology: American Chemical Society. 2004, 246A-247A. 4. Levine, Sumner. Desalination and Ocean Technology. Dover Publications, INC: New York, 1968.