Fresh water is increasingly becoming a scarce resource in the world. An increase in its amount will be highly required in the future. This is due to the resultant increasing in the population, enhanced living standards and expansions experienced in the industrial sector and agricultural activities. Seawater technologies help in reducing the shortage of this vital resource.
Statistically the marine makes up 97% of the global aqua storage. Whereas the locked amount by the glaciers and ice caps amount to 2% of the total supply. The percentage available for human use is about 0.5%. Supplied by lakes and rivers. Water from the sea is neither suitable for consumption by humans nor industrial use. There by desalination being considered as an important alternative for sourcing out fresh water.
The desalination process involves separation of the resource into two streams. A fresh stream containing a low concentration of dissolved salts and a concentrated brime stream. The above process requires some form of energy to desalinate and several different technologies are utilized. Over the years a variety of innovations have been developed on the basis of thermal distillation, membrane separation, freezing, electro dialysis, etc. On commercial basis the two most important technologies are based on the MSF and RO technologies although it is viewed that the two processes together with MED (multiple effect distillation) will be dominant and competitive in the future.
Multiple stage flash distillation. One of the methods of desalination. It is built on flash evaporation principle. Where evaporation is induced by reduction of pressure instead of increasing of temperature. Its economic advantage is through the regenerative heating. Where the resource gives up its heat to its counterpart on every flash chamber it goes through.
Multiple effect distillation is the form of distillation process. And is also thermodynamically efficient. The process takes place in a series of evaporators called effects and uses the principle of reducing the ambient pressure in the various effects. The MED plant steam economy is proportional to the number of effects. MED plants can have 3 types of tubes, that is, horizontal, vertical or submerged. Most recent application have been in the Middle East. Although their number is still relatively small compared to MSF plants, their numbers have been increasing.
Another form of distillation is the vapor compression. Where compression of vapor is the means of heating the incoming aqua. This is made possible by application of two methods. Use of mechanical compressor hand in hand with steam jet. It is built in the principle that boiling point is reduced with reduction of pressure. In small scale units of desalination this method is highly used.
Reverse osmosis, commonly referred to as RO, is where the osmotic pressure is overcome by applying external pressure higher than the osmotic pressure on the sea water. Thus it flows in the reverse direction to the natural flow across the membrane leaving the dissolved salts behind with an increase in salt concentration. Over the past decade a number of developments have been made to help reduce the operating cost of RO plants. These are the development of membranes that can operate efficiently with longer duration and the use of energy recover devices.
Methods such as solar evaporation, freezing and potabilization are used but not as often as the ones described above.
Statistically the marine makes up 97% of the global aqua storage. Whereas the locked amount by the glaciers and ice caps amount to 2% of the total supply. The percentage available for human use is about 0.5%. Supplied by lakes and rivers. Water from the sea is neither suitable for consumption by humans nor industrial use. There by desalination being considered as an important alternative for sourcing out fresh water.
The desalination process involves separation of the resource into two streams. A fresh stream containing a low concentration of dissolved salts and a concentrated brime stream. The above process requires some form of energy to desalinate and several different technologies are utilized. Over the years a variety of innovations have been developed on the basis of thermal distillation, membrane separation, freezing, electro dialysis, etc. On commercial basis the two most important technologies are based on the MSF and RO technologies although it is viewed that the two processes together with MED (multiple effect distillation) will be dominant and competitive in the future.
Multiple stage flash distillation. One of the methods of desalination. It is built on flash evaporation principle. Where evaporation is induced by reduction of pressure instead of increasing of temperature. Its economic advantage is through the regenerative heating. Where the resource gives up its heat to its counterpart on every flash chamber it goes through.
Multiple effect distillation is the form of distillation process. And is also thermodynamically efficient. The process takes place in a series of evaporators called effects and uses the principle of reducing the ambient pressure in the various effects. The MED plant steam economy is proportional to the number of effects. MED plants can have 3 types of tubes, that is, horizontal, vertical or submerged. Most recent application have been in the Middle East. Although their number is still relatively small compared to MSF plants, their numbers have been increasing.
Another form of distillation is the vapor compression. Where compression of vapor is the means of heating the incoming aqua. This is made possible by application of two methods. Use of mechanical compressor hand in hand with steam jet. It is built in the principle that boiling point is reduced with reduction of pressure. In small scale units of desalination this method is highly used.
Reverse osmosis, commonly referred to as RO, is where the osmotic pressure is overcome by applying external pressure higher than the osmotic pressure on the sea water. Thus it flows in the reverse direction to the natural flow across the membrane leaving the dissolved salts behind with an increase in salt concentration. Over the past decade a number of developments have been made to help reduce the operating cost of RO plants. These are the development of membranes that can operate efficiently with longer duration and the use of energy recover devices.
Methods such as solar evaporation, freezing and potabilization are used but not as often as the ones described above.
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