sea water desalination process, distillation process, reverse osmosis process

1. S E A WAT E R
D E S A L I N AT I O N
P R O C E S S : P R I N C I P L E ,
M E C H A N I S M S , T R E N D S
A N D F U T U R E
P E R S P E C T I V E S
Fahim Shahriar Sakib – 0422022001
Safat Anam - 0423022104

2. C O N T E N T
Basic Principle Mechanisms
Trends Future Perspectives

3. I N T R O D U C T I O N
Desalination is a process that takes away mineral components from saline water.
Saltwater (especially sea water) is desalinated to produce water suitable for human
consumption or irrigation and the by-product of the desalination process is brine.
Due to its energy consumption, desalinating sea water is generally more costly than fresh
water from surface water or groundwater, water recycling and water conservation.
Desalination processes are using thermal methods (distillation), membrane-based methods
(reverse osmosis) energy types and elctro-oxireduction methods (electrodialysis).
Among them, reverse osmosis is majorly used due to its low operational cost rather than
others.

4. B A S I C C O N C E P T

5. P R O C E S S
D E S C R I P T I O N

7. P R I M A RY P R E T R E AT M E N T
Coagulation, Flocculation and
Dissolved Air Flotation (DAF)
• Primary treatment is needed to remove
suspended solids like sand, shell, small
particles etc.
• Coagulation need rapid mixing.
Flocculation need slow mixing.
• Fine air bubbles is used to float the
solids on the surface and to get the clear
water.

8. S E C O N D A RY P R E T R E AT M E N T
Ultrafiltration
• Ultrafiltration is used to remove fine particles
and it reduces Slit Density Index (SDI) < 3.
• Two types: Pressurized Membrane Systems
and Submerged Membrane. Mainly constructed
with PES, PVDF or both. Pore size around 0.02
micron.
• Four operational modes: Processing,
Backwash, Cleaning and Integrity Testing.

9. D E S A L I N AT I O N
Reverse Osmosis
• Rejects dissolved solids of the water and
fresh water passes from the membrane.
• Salt rejection rate 99.9% and recovery rate
around 40-50%.
• Spiral wound Poly Amide membrane is
used. Cartridge filter is used before RO
passing.
• High pressure pump (50-70 bar) is used to
pump the RO feed water.

10. P O S T T R E AT M E N T
Re Hardening
Calcium Carbonate, Carbon Dioxide,
Calcium Bicarbonate is used to increase the
hardness and alkalinity of the RO permeate
water.
Disinfection
Three types: Chlorination, UV, Ozonation.
Removes any types of viruses or bacteria.

11. G L O B A L
T R E N D S
The three trends that create impact on the
future of desalination projects.
 Climate change will exacerbate the problem
of water scarcity and increase global focus on
desalination as part of the solution.
 Technological innovation will continue to
reduce desalination’s specific energy
consumption and environmental impact.
 More desalination will be powered by
renewable energy.

12. C L I M AT E C H A N G E
Regions that are already dry are becoming
drier due to global climate change.
Disruptions of age-old precipitation patterns
and extreme weather events make some
regions wetter and others drier.
Desalination is increasingly seen as a partial
solution to water scarcity, especially for the
roughly 40% of the world’s population that live
in coastal communities.

13. T E C H N O L O G I C A L I N N O VAT I O N
Desalination’s specific energy consumption
(SEC) has dropped continuously for almost a
century.
Improved membrane technology reduces the
need for backwashing and chemicals to check
biofouling.
Innovation and competition will make ERDs and
high-pressure pumps both better and more
affordable.

14. R E N E WA B L E E N E R G Y
Renewable energies are the cheapest new
source of power.
The price disparity between clean renewable
energy and energy derived from fossil fuels will
most likely continue to expand.
This trend influences desalination’s financial and
environmental costs. Renewables’ share of total
electricity supply grows from a record 30% in
2021.

15. F U T U R E P E R S P E C T I V E
SWRO membranes today are many times smaller, more
productive and cheaper than the first working prototypes.
More efficient desalination membranes, innovative thermal
membranes or hybrid desalination technologies, and
equipment improvements, are released every few years.
Technology advances are expected to reduce the cost of
desalinated water by 20% in the next five years, and by up to
60% in the next 20 years.

16. F U T U R E P E R S P E C T I V E
Parameter for Best-in Class
Desalination Plants
Year 2016 Within 5 Years
Within 20 Years
Cost of Water
(US$/m3)
0.8 – 1.2 0.6 – 1.0 0.3 – 0.5
Construction Cost
(US$/MLD)
1.2 – 2.2 1.0 – 1.8 0.5 – 0.9
Electrical Energy Use
(kWh/m3)
3.5 – 4.0 2.8 – 3.2 2.1 – 2.4
Membrane Productivity
(m3/membrane)
28-47 35-55 95-120

17. C O N C L U S I O N
The desalination of brackish water and seawater proves to be a reliable source of fresh
water and is proves to be a solution for the world’s water shortage problem.
Desalination processes are normally used to produce drinking water in areas where only
seawater or brackish water is the source of water.
Several technologies have been developed and many more methods are under R&D for
desalination.
Though desalination costs seem to be progressively decreasing, but they are still costlier
than conventional drinking water processes.