http://www.answers.com/topic/desalinizationDesalinization
A solution to hydrate the arid Middle East.
Desalinization, also referred to as desalination, is the removal of salts and dissolved solids from brackish water or seawater. In the past three decades, due to increasing water demand and increasing resource scarcity, desalinization has become a critical, relatively drought-proof, resource of potable, irrigation, and industrial water in arid regions of the globe. In the Arab countries, which have 5 percent of the world population but only 0.9 percent of the water resources, water shortages are a constant challenge, and desalinization is playing an increasing role. Once so prohibitively expensive and technologically troublesome as to be totally impractical, it is now often the solution of choice in conditions of unreliable water resources. Capital investments and costs of production are going down as innovations improve the technologies involved.
Of the more than 12,500 desalinization plants in operation or in construction worldwide, 60 percent are located in the Middle East and North Africa (MENA). The Shuʿayba Plant Phase II in Jeddah, Saudi Arabia, for a time the world's largest plant, supplies the daily water needs of 1.5 million people. Saudi Arabia, whose desalinization output exceeded one billion cubic meters in 2002 to provide 70 percent of its water needs, is the largest desalinated water producer in the world, contributing to 30 percent of global output. Desalinized seawater currently constitutes Saudi Arabia's main source for potable water. This water is transported in a network of 1,550-mile pipelines, 21 pumping stations, 131 depots, and 10 stations for mixing the desalinated water with underground water. Around 1972, the MENA region "ran out of water" as the consumption surpassed the rate of resource renewal. Since then, MENA has relied heavily on desalinization, and is poised to remain for the foreseeable future the largest desalinization market in the world.
Desalinization systems can be membrane-based, such as Reverse Osmosis (RO) and Electro-Dialysis Reversal (EDR), or thermal, such as multi-stage flash (MSF) and multiple-effect distillation (MED). Boiling, leading to desalinization through evaporation, a process of thermal distillation, was known and practiced from ancient times. However, now most desalinization plants use membrane-based reverse osmosis, a process that allows the separation of 99 percent of dissolved salts and impurities from water, by means of pressure exerted on a semi-permeable membrane. Between 15 and 50 percent
Bahrain's installed desalination capacity (July 2000)Facility Date of commissioning Capacity (MGD) Technology
SOURCE:Ministry of Electricity and Water, Bahrain.
TABLE BY GGS INFORMATION SERVICES, THE GALE GROUP.
Sitra power and water plant (I, II, III) 1974, 1984, 1985 27.5 MSF
Ras Abu Jarjur RO plant 1984 12.5 RO
Addur RO plant 1992 3 RO
Hidd power and water plant 2000 30 MSF
Total installed capacity - 73 -
of seawater intake into a plant is purified; the rest becomes brine, or high-salt water, in need of dilution, then dumping. Environmental regulations dealing with the impact of desalinization on the environment vary from country to country. In addition to brine, other effluents include discharged process chemicals used for defouling, and toxic metals, as well as small amounts of solid waste (spent pretreatment filters, filtered solid particles, etc.).
Energy requirements for desalinization are high, mostly to power machinery and to heat feed-water. RO and distillation plants are often located with energy generation plants to improve efficiency. In such cases, additional environmental impacts have to be taken into account on a case-by-case basis. Fortunately, many of the water-starved countries such as Saudi Arabia, Kuwait, the United Arab Emirates, and Libya are major oil and gas producers and have significant reserves. They have invested heavily in desalinization from early on. The first plant in Saudi Arabia was inaugurated in 1954. The Saline Water Corporation in Saudi Arabia is the largest investor in, and operator of, desalinization plants in the world.
Cost reduction is the single most important factor necessary to increase the implementation of desalination. Capital investment unit costs range from $1,000 to $2,000 per cubic meter of capacity, and can be amortized over 20 to 30 years. Unit production costs per cubic meter range from $0.50 for large plants to over $1.50 for small plants, or about one-half the cost of desalinated water in the recent past. It is not economical to operate a plant part time. Economies of scale play an important role in investment decision-making but are more easily achieved in distillation than in RO process. The Middle East Desalination Research Center (MEDRC), established in 1996 in Muscat, Oman, has been conducting basic and applied research to reduce the cost of water desalinization.
Bahrain, Jordan, and Kuwait were the only water-scarce countries in the region in 1950s. In 2003, twelve countries have water scarcity, and by 2023, six more countries will suffer the same vulnerability, including Israel and Palestine. If the participants in the Palestine - Israel conflict do not exploit water as a unilateral security issue and insist upon retaining control over water resources in the Occupied Territories, the desalinization option may contribute to a solution.
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