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DESCRIBE THE PROCESS OF DESALINATION

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akim mansor

on 26 May 2014

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Transcript of DESCRIBE THE PROCESS OF DESALINATION

DESCRIBE THE PROCESS OF DESALINATION
Removing salt from water is a process that has been used for a long time, in the form of distillation. The natural process evaporation from the surface of the sea, to form clouds, which then result in rain, is the most widespread distillation process.
Boiling salty water and condensing the steam, or even just putting a dish of water in the sun and collecting the vapour on a clear cover are both very simple methods of distillation.
Commercial desalination plants have been operating now for decades, using the distillation process. When distilling large quantities of water, say for a town supply, there are practical problems to be dealt with: firstly, the energy needed to evaporate water is quite considerable, so the process can be very expensive, unless a cheap source of electricity or heat is available.
For instance, running a power station and a desalination plant together (commonly called cogeneration) can be cost effective, since the waste heat from a generator can be used, as well as cheap electricity.
Step 2 : Membrane processes:
A more recent development, and now more widely used, relies on what is called a semi-permeable membrane to separate salt from water. Simply put, a synthetic membrane is made, with pores so tiny that water molecules can pass through it, but other molecules, especially salts, cannot.

EVIDENCE:
This separation does not happen easily, though, and it requires very high pressures to force the water through the membrane. A natural process, called osmosis, operates in all living cells, to equalise the salt concentration on either side of the membrane.
Step 3 : Other processes:
There are other ways of removing salt from water, but they are not practical for community supplies.

EVIDENCE
Vapor phase, or evaporative processes are used
primarily for seawater conversion, and consist
of the following well established methods:
• Multistage flash evaporation (MSF)
• Multieffect distillation (MED)
• Vapor compression (VC)
MSF and MED require thermal input in
addition to electric power, and because they
handle hot seawater, materials selection
becomes a critical factor in design. VC uses
only electric power, with the thermal input
coming from heat of compression. VC is
generally the most economical evaporative
process, but the fan compressors that are used
limit the output capacity of the equipment.
Depending on the plant design, distilled
water produced from a thermal desalination
plant typically has salt concentrations of
between 5 to 50 parts per million (ppm) of
Total Dissolved Solids (TDS). Between 25
and 50 percent of the source water is
recovered by most distillation methods.
gROUP NAME
MUHAMMAD AFIF BIN SUHAIMI - UK30468
CHE ABDUL HAKIM BIN CHE MANSOR - UK 33092
MOHAMAD KHAROL AZLAN BIN HAROM - UK 33103
MUHAMAD AZHARI BIN YUSARI-UK30966
INTRODUCTION
Desalination (desal)
- The process of removing dissolved salts and minerals from seawater or brackish water.
- Desalination produces drinking water and concentrate (the water that contains the salts
that were removed in the desalination process, which is sometimes called brine).
-The dominant technology used in desalination today is
a)reverse osmosis
b)which involves forcing water through semi-
permeable membranes to remove salts
c) other impurities.

Most of the modern interest in desalination is focused on developing cost-effective ways of providing fresh water for human use in regions where the availability of fresh water is, or is becoming, limited.

Although seawater desalination projects often face some environmental and economical challenges, these challenges can be successfully addressed by carefully selecting the project site, by implementing state-of-the-art intake and concentrate discharge technologies, and by incorporating energy-efficient and environmentally sound equipment and systems.
STEP 1: Thermal (Distillation) Processes
CONCLUSION
Seawater desalination is ideal for arid coastal regions that need an additional source to augment drinking water supplies. Brackish desalination allows inland communities to take advantage of water sources that are too salty to treat with conventional methods. There are more than 15,000 desalination plants worldwide. Some locations currently using and/or considering desalination technology include:

Abu Dhabi, United Arab Emirates
Algeria
Aruba
Australia
Cyprus
Israel
Singapore
United Kingdom
United States, in states such as Florida, California, and Texas
Trinidad and Tobago
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