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1. GOVERNMENT ENGINEERING COLLEGE,
BHARUCH
Department -Chemical Engineering (7th sem.)
SUBJECT : New Separation Techniques
TOPIC : Reverse Osmosis(R.O.)

2. OVERVIEW
 Different types of Membrane separation techniques
 Concept of osmosis
 Reverse Osmosis
 Different type of membrane
 Types of membrane module
 Advantage & Disadvantage of RO
 Application of RO

3. Different type of membrane process

4. OSMOSIS:FUNDAMENTAL
 Osmosis is a natural phenomenon that
provides water to all animal and vegetable
cells to support life.
 Water moves from a high concentration of
water to a low concentration of water
across a semi-permeable membrane.
 This means that water can cross a
selectively permeable membrane from a
dilute solution (less dissolved in it) to a
concentrated solution.

5. OSMOSIS: WHAT IS IT?
 A semi-permeable membrane is a
membrane which will allow only
certain molecules or ions to pass
through
 Osmosis is very important in biology
as it provides the primary means by
which water is transported in and out
of cells.

6. REVERSE OSMOSIS:WHAT IS IT?
 RO is a form of filtration using osmosis in reverse Water passes from a
more concentrated solution to a less concentrated solution.
 To accomplish this a force or pressure must be applied RO requires 1 psi
of pressure for every 100 ppm of TDS.
 RO is used to remove dissolved solids from water but it can also improve
taste, odor & color of water.
 RO membranes have the capability to remove particles as small as ions
i.e. magnesium ions or sodium ions.
 RO membrane will reject most compounds based largely on size
 Dissolved ions, such as salts, carry an electric charge and will also be
rejected by membrane.

7. REVERSE OSMOSIS:HOW IT WORKS
 Feed water flows into RO unit with the force of line pressure Water is forced
through membrane by cross flow filtration.
 Cross flow filtration is most commonly used in RO as it allows membrane to
continually clean itself Membrane then either rejects or repels contaminants.
Two exit streams generated: waste & product stream
 Waste stream consists of: A concentrate (reject) stream which carries
contaminants (compounds too large to pass through membrane)
 Permeate stream consists of: Product water which has been forced through the
membrane & is virtually free of TDS.

8. Reverse Osmosis Fundamentals:
 REJECT WATER: Portion of feed water which did not pass through membrane; carries
impurities to drain.
 MODULE: Combination of spiral round membrane element & pressure vessel.
 FEED WATER: Main flow of impure water to be treated.
 PRODUCT WATER: Portion of feed water which passes through membrane as
permeate.

9. (1)Asymmetric membrane :
 This type of membranes have a thin(-100 nm) permselective skin layer support on
a more porous sublayer of the same polymer.
 Dense skin layer determines the fluxes and selectivites of membrane ,whereas the
porous sublayer serves only as a mechanical support for the skin layer . its block
the passage of quite small solute molecules.
RO Membrane:

10. (2)Thin film composite membrane:
 TFC membranes are intolerant
to chlorine– will cause
deterioration of membrane.
 Must use a carbon pre-filter for
TFC membranes.
 TFC membranes have a much
higher rejection rate of many
chemicals than CTA membranes.
 Carbon pre filters are vital in the
life of this membrane & must be
changed regularly.

11. Membrane material and modules
 Although reverse osmosis membrane have been formed and tested using a
large number of different material.
 Two types of membrane material
(1)cellulosic acetate
(2) Aromatic Polyamide

12. (1)Cellulose acetate membranes
 Cellulose acetate has a higher flux and a smaller area of membrane is therefore
required. It is also resistant to small concentrations of free chlorine and may
therefore be kept free of bacteria and also produce a product with residual chlorine
in it to prevent subsequent re-growth.

13.  The polyamide membrane can be used at a higher temperature (35 oC) than
cellulose acetate (30 oC), it cannot tolerate chlorine but is not attacked by
bacteria whereas some bacteria which can occur in surface water in woodlands
actually destroy cellulose acetate. Finally, polyamides can be used over a much
wider pH range (4-11) than cellulose acetate (4-7.5)
(2)Polyamide membranes

15. MEMBRANE MODULES

16. TYPES OF MEMBRANE MODULE

17.  The permeate from each
pair of membranes can be
visually observed in the
plastic tubing coming from
each support plate.
 A gasket is used to
transform the flat plate into
a long tortuous narrow
channel.
 Replacement of membranes
on site is relatively easy.
PLATE AND FRAME MODULE

18. SPIRAL-WOUND MODULE
 Particles hang-up in the mesh
network, resulting in cleaning
problem.
 This makes it difficult to process
feeds containing suspended
particles. Spiral-wound modules
work best on relatively clean feed
streams with a minimum of
suspended matter

19. TUBULAR MODULE
 Tubular membranes are not self-supporting
membranes. They are located on the inside
of a tube, made of a special kind of material.
This material is the supporting layer for the
membrane.
 Because the location of tubular membranes
is inside a tube, the flow in a tubular
membrane is usually inside out. The main
cause for this is that the attachment of the
membrane to the supporting layer is very
weak.

20. HOLLOW FIBRE MODULE:
 A bundle of hollow fibers are
mounted in a pressure vessel and
open end of u shaped fibers is
plotted into head plate.
 In a hollow fiber module the
permeate water flow per unit area
of membrane is low and therefore
concentration polarization is not
high at the membrane surface .
 The net result is that hollow fibre
units operate in a non-tubulent
and laminar flow regime.

21. COMP. OF VARIOUS MODULES

22. Parameters that affect RO
 Pressure: The water flux is a function of the pressure differential between the
applied hydrostatic pressure and the osmotic pressure across the membrane.
Passage of water increased with increased in applied pressure, assuming
osmotic pressure constant. Solute rejection rises with pressure , since solvent
flux increase and solute diffusion doesn’t.
 Temperature: solvent flux increases with increase in temperature since
viscosity decrease.
 Solute concentration : flux declines with increasing solute concentration
because of increase is osmotic pressure difference. At low feed velocity past the
membrane , solute is ploarized at the membrane.
 Membrane packing density :This is expression of unit area of membrane ,
which can be placed per unit volume of pressure vessels.
 Recovery factor: The consideration of recovery factor of actually represents
 Plant capacity.
 Feed water stream velocity:The hydraulics of reverse osmosis system are such
that velocities in the range of 1.2 to 76.2 cm/s are common.

23. ADVANTAGES
 RO performs a separation without a phase change.
 RO system are compact and space requirement are less space other desalting
system. EX.-distillation.
 Simultaneous separation and concentration of both inorganic and organic
compounds are possible using RO process.
 RO eliminates 95% to 99% of total dissolved solids(TDS),reverse osmosis is
the best technology today for getting clean water free of contaminants.
 Today RO system provides such diverse uses as drinking water , rinse ,ice
making to so many industries that uses it.

24. DISADVANTAGES
 The small pores of the membrane block particles of large molecules but
pesticides and chlorine are molecularly smaller then water can pass through.
This is the why carbon filter must be used as supplement to the RO process
because it can remove chlorine in the water.
 As most minerals like iron , magnesium , calcium and solution are larger in size
than water molecules , semi permeable prevents them from passing on to other
side.so water actually gets de-mineralized.
 The systems needs professional for cleaning.

25. Applications for Reverse Osmosis Systems
The ideal applications for RO water filtration
equipment include:
 Boiler Feed Water
 Ion Exchange Pre-treatment
 Beverage Production
 Safe Drinking Water
 Spot Free Product Rinse

26. T
H
A
N
K
Y
O
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MAYUR GAMI
120140105008
HARDIK SUTARIYA
120140105019
PARVEJ CHAVDA
120140105046
AJAY KAMALIYA
110140105042
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