Water Desalination

Water Desalination is proving to be more and more important as time goes on. There is a serious need for fresh-water in the world. Knowledge about desalination could be the first step to a solution. This paper will educate people about desalination, by explaining the problem, the solution and background, and the procedures.

The water consumption rate has doubled every 20 years, outpacing the population rate by two-times. This issue could become a serious problem sooner than people think. It is projected that water demand will exceed supply by 56% by the year 2025. At this rate, four billion people will be affected by water shortages by 2050. Obviously, this is a serious issue. We need a solution fast and water desalination seems to be that solution.

Oceans make up 97% of the worlds water. Desalination is the process of removing salt and chemicals from water. If this process was used more often, we could drastically slow down or even stop the water shortage. The practical application of water desalination reaches all throughout the globe, particularly in coastal areas where the most accessible water is saline. We will look at two water desalination plants in construction that are on the forefront of the water desalination frontier. The first case is a General Electric product in the Ecomagination division. It is located in Algeria where the fresh water supply is diminishing due to overpopulation, rainfall that is unpredictable and an out of date pipeline system that inhibits much of the fresh water from getting where it needs to go. The GE Ecomagination project will supply twenty-five percent of the Capital city, Algiers with clean fresh desalinized seawater. As it is now, a typical Algerian only receives fresh water one out of every three days. The unit puts out two hundred thousand cubic meters of water per day easing the stress of water shortages. The project will also embody the first privately owned reverse osmosis water desalination unit. The financing of the desalination unit will fall only thirty percent onto the Algerian Energy Company and the General Electric Corporation will take seventy percent. The ultimate goal is to provide fresh water for industry, agriculture and drinking purposes while minimizing the impact on the already depleted fresh water supplies throughout the country. (GE Press Release, 2005)

Nigerian Desalination

Another case is that of the proposed water desalination plant in India. The plant would supply the very isolated island on Kavaratti, population 10,000 with much needed fresh water. Thirty percent of India’s entire population lives in coastal areas and that is a healthy sum of people to find fresh water for. Desalination is the only other known viable option. The island of Kavaratti presents a number of limiting factors for setting up a desalination plant. The first and foremost is that the only way to access the island is by boat or helicopter. Construction and maintenance is a bear due to the isolation and inaccessibility. Furthermore, the island has strict limits put on environmental pollution, which does not allow for the standard reverse osmosis desalination technique. Reverse osmosis leaves brine and the used membranes as chemical pollutants, which would not be allowed, on the island. A modification to the normal thermal desalination technique was added to this particular unit. The unit will draw cold water from an extreme depth in the ocean and flash evaporate the water at sea level. The process is quick and allows for minimal energy usage and pollution.

There are a many different ways of desalinating water. One way is a thermal process, which is pretty simple. It desalinates by boiling the water than then condensing the water vapor into fresh water. Multistage flash distillation is one of the most popular distillation processes. In this method they have many chambers. They put saltwater in the first chamber and then they lower the pressure to reduce the waters boiling point. Then they take the water vapor from the boiling and collect it in the form of fresh water. Each chamber also removes the brine. They do this in every chamber until the water is clean. Another way is called multi-effect distillation. In this method there are many long, thin tubes. These tubes are surrounded by high temperature steam that causes the water to boil as it falls. Part of the resulting steam creates fresh water. In vacuum freezing, seawater is frozen by reducing the pressure and temperature and when the water freezes the minerals and salt is removed from the ice crystals. They then wash the ice to make fresh water. Unfortunately this method has not been commercially effective. Finally, there is reverse osmosis.

In this method seawater is put through a semi-permeable membrane. It uses the natural process of osmosis to separate the salt and minerals from the fresh water. As you can see there are many different methods of desalination, some are more effective than others, and some are more widely used.

Desalination is seen by many as the future for clean drinkable water, but what many fail to look at is what will this product of tomorrow actually cost us? A study found on (http://www.owue.water.ca.gov) shows us the cost per unit of this new frontier of desalination. In this study they focused on the most commonly used method of desalination, reverse osmosis. They started accumulating the costs of the process with the costs to use the facility which in this study is very expensive due to the size of the plant needed and the energy used to power the several machines that run the plant. For some plants this is close to 44% of their total costs. The second amount added is the maintenance for the machines. This is a big problem mostly due to the fact that the several machines used in the plant are subjected to very high temperatures and are used for long hours of constant production. The next portion accounts for about 5% of the costs, this is the membrane replacement, this adds in the costs of the materials needed such as the water, the cost of transportation and the chemicals used in the process of membrane replacement. The next cost added is the labor and supervision used at the plant, this accounts for about 4% of the cost for the company. Ironically this is the smallest cost in the process of desalination. The upside is that the expenditures of production have been steadily declining since the 1990’s were the cost was close to $6 for every 1000 gallons and now the price for 1000 gallons is down to $1.50. These cost reductions have been made possible due to the technological developments, technological maturity, the increase in size of plants, the lowered finance rate, the lower energy costs, the changes in managing enterprise performance, and the growing and intense competition of equipment suppliers worldwide. One of the biggest percentages of cost reduction lies in the membrane; the amount that has been saved is close to 86% since 1990 and is still continuing to be reduced through new innovative techniques. These techniques include new pretreatment approaches such as using micro and ultra-filtration. Another technique that has turned how desalination is done upside down is the increase in the size of the membrane. Before the change in size of the membrane was suggested the most common size of membrane spiral was 8”x 40” surface area, which is about 440sq feet. The new mega magnum spiral is an incredible 17”x 60” which surface area is close to 2,400sq feet. This increase is close to 6 times the old common size of spiral element. This amazing leap for desalination has made many benefits such as space savings of 15%, the dropping need for manifolds and pressure vessels, and lastly it has cut costs in capital and civil workers by 20%. Further information found on this site (http://www.membranes-amta.org) helps us to understand the total costs of desalination on a larger scale fit for a population. Currently close to 1,300 desalination plants are operating in the United States and they are producing about 400 million gallons of water per day. This quantity has a cost, which is more than $10 billion dollars every year. Also this growing industry has already set aside almost 3 billion for investing and advancement in their product for just this next year. For an even bigger picture, worldwide, membrane and thermal desalination produces more than 11 billion gallons per day from over 1,200 plants this is worth $9.2 billion per year, growing by 12% each year. This Newly accessed technology will have to be further exploited in the future, for it opens up the oceans as an endless water supply.

Works Cited

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Clark C. K. Liu, Jae-Woo Park, “Water Desalination”, in AccessScience@McGraw-Hill, http://www.accessscience.com, DOI 10 .1036/1097-8542.598900

Water Desalination

Kathiroli, S. Jalihal, Purnima. "Up from the Deep." Up from the Deep Jan 2008 Apr 2008 http://web.ebscohost.com/ehost/pdf?vid=5&hid=5&sid=0d46b8a1-33fa-483f-a67d-0dac1f43c6a7%40sessionmgr3.

Up From The Deep

Mellody, Ellen. “GE announces plans for largest desalination plant in Africa.” GE announces plans for largest desalination plant in Africa 25 June 2005 04 Apr 2008 .

GE Press Release

“Desalination.” Desalination 2008 04 Apr 2008 http://www.gewater.com/what_we_do/water_scarcity/desalination.jsp.

Desalination

Chaudhry, Shahid. “Unit cost of desalination.” Department of Water Sources. 10 Apr 2008 http://www.owue.water.ca.gov/recycle/desal/Docs/UnitCostDesalination.pdf.

Unit Cost of Desalination