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1. Desalination
GROUP (16)
presented to prof.Khalid Ramzy 2025

2. Introduction

3. What is desalination?
It can be defined as any process which removes
excess salts and minerals from water (or) the chemical
process of changing seawater into potable water are
called desalination.

4. Why Desalination?
75% of the Earth’s surface is covered by water but 97.5% of that water is salty
Only 2.5% is fresh water
of the world’s population lives in countries with insufficient fresh water
resources
The existing fresh water resources are decreasing
Desalination can play a large role in increasing the supply of fresh water in both
developing and developed nations

5. Distribution of Water Supplies

6. Desalination technologies
The two major technologies that are mainly used for desalination are:
Thermal desalination technology
Membrane desalination technology
Both the technologies include a number of different processes

7. Desalination technologies
1. Thermal Desalination Processes
-changing saline water into vapor.
-This vapor is generally free of the salt and minerals.
-When condensed, this vapor forms a high-purity
distilled water.

8. Desalination technologies
2. Membrane Desalination Processes
-Saltwater is forced through membrane sheets at high
pressures.
-Membrane sheets are designed to catch salt ions.
-Process produces clean water and brine.

9. The dominant desalination processes in use today are
based on Reverse Osmosis (RO) and Multi Stage Flash
(MSF) which constitute 60.0% and 26.8% of the
worldwide capacity, respectively

10. Comparison between desalination technologies

11. multistage flash desalination
PRESENTED BY MOHAMED SAMY

12. Multi-stage flash distillation (MSF)
its a water desalination process that distills sea water by
flashing a portion of the water into steam in multiple stages
of what are essentially countercurrent heat exchangers
(thermal distillation) . Multi-stage flash distillation plants
produce about 26% of all desalinated water in the world,
but almost all of new desalination plants currently use
reverse osmosis due to much lower energy consumption

13. How does the multistage flash
distillation process work?
In an MSF distillation sea water vaporization takes place at low
temperatures in vacuum. The vapors condense to form fresh water. At vacuum pressures the boiling point of water is
low requiring less energy.
A brine heater heats the sea water to around 90 to 110 deg C.
Before reaching the brine heaters the cold sea water passes through condensing coils in the vacuum flash chambers.
This has the dual function of
• Preheating the cold sea water before entering the brine heater and
• Condensing the flashed steam in the chambers to produce fresh water.
The hot brine then enters the flash chamber which is at a vacuum. Since the entering water temperature is higher than
the boiling temperature at that vacuum pressure, a part of the water flashes to steam. The steam rises to the upper part
of the chamber and on contact with condensing coils condenses to form pure water. The salt and other impurities
remain with balance of the brine at the bottom of the chamber. Steam ejectors produce the necessary vacuum in the
flash chambers.
The balance brine goes to the next chamber where the process repeats. Multiple chambers increases the quantity of the
water product. The balance brine returns to the sea. A 20 % yield of fresh water is possible in MSF systems.
The energy requirement
• Electrical energy for pumping the water.
• Steam energy for heating the brine.

14. Performance aspects

15. Solar Desalination
PRESENTED BY/ AHMED MAGDY ISMAIL MOHAMED

16. Some Background Info

17. Direct solar desalination system
• Briefing

18. Single basin type solar still

19. Components & Process

20. Variants

21. Application

22. Limitations

23. Devices for Converting Solar
Radiation into Thermal Energy
Suitable for Desalination

25. Reverse Osmosis

26. To understand the purpose and process of Reverse Osmosis you must first understand the naturally
occurring process of Osmosis.
Osmosis :Osmosis is a naturally occurring phenomenon
and one of the most important processes in nature. It is
a process where a weaker saline solution will tend to
migrate to a strong saline solution.
Examples :
kidneys absorb water from our blood
plant roots absorb water from the soil

27. What is Reverse Osmosis?
Reverse Osmosis is a technology that is used to remove a large majority of contaminants from water
by pushing the water under pressure through a semi-permeable membrane.
semi-permeable membrane is a membrane that will allow some atoms or molecules to pass but not
others.
Example: screen door, It allows air molecules to pass
through but not pests or anything larger than the holes
in the screen door

28. How does Reverse Osmosis work?
Reverse Osmosis works by using a high pressure pump to increase the pressure on the salt side of the RO and
force the water across the semi-permeable RO membrane, leaving almost all (around 95% to 99%) of dissolved
salts behind in the reject stream.
The amount of pressure required depends on the salt concentration of the feed water. The more concentrated the
feed water, the more pressure is required to overcome the osmotic pressure.

29. What contaminants will Reverse
Osmosis remove from water?
Reverse Osmosis is capable of removing up to 99%+ of the dissolved salts (ions), particles,
colloids, organics, bacteria and pyrogens from the feed water.
Some examples of industries that use RO water
pharmaceutical
boiler feed water

30. Summary

31. Electrodialysis
PRESENTED BY : MOHAMED ABD ELHADY AHMED

32. WHAT IS
ELECTRODIALYSIS ?

33. ELECTRODIALYSIS
PROCESSES

36. ADVANTAGES AND
DISADVANTAGES

37. APPLICATION
S