This is a basic introduction of Reverse osmosis (R O) Process including governing equations and engineering design parameters.

1. Reverse Osmosis
Group 1
Abhishek Patil
Piyush Hatwalne
Naman Shukla

2. Various Filtration Processes

3. Fundamental Equation Regarding Reverse Osmosis
• The basic and far most important equation is
π = CRT
Where π : Osmotic pressure.
C : Concentration of the solute.
R : Gas constant.
T : Temperature.

4. Flow Governing Equations
Water Transport:
Qw = ( ∆P - ∆Posm) * Kw * S/d
Salt Transport:
Qs = ∆C * Ks * S/d
Salinity:
Cp = Qs/Qw

5. Industrial Application - Desalination

6. Desalination Techniques Overview
• Electrodialysis.
• Multiple-effect distillation.
• Multi-stage flash distillation.

7. Performance limiting factors of reverse osmosis plant
• Concentration Polarization
– Caused due to particulate matter accumulating near the membrane
• Membrane Deterioration
– Fouling
• caused by deposition of organic matter on membrane
– scaling
• caused due to deposition of inorganic salts on membrane pores

8. Module Design
There are two major types
• Hollow fiber module
– The water flows from outside the fiber while permeate is processed inside the lumen.
• Spiral wound module(SWM)
– The SWM consist of several flat sheet membranes that are glued together to form a
membrane pocket.

9. Internal staging design
Desalination plants based on RO membrane technology are usually multiple stage processes. There
are three basic plant designs for straight-through operation and a selection of a proper design will
depend on plant capacity and production requirements

10. Pretreatment of feed water
• Chlorination
• pH Adjustment
• Anti-Scaling
• Dechlorination
Post Treatment
Untreated permeate from reverse osmosis plants does not conform with drinking water
standards. It is often corrosive due to lack of TDS. Rehardening of water is done to make
water potable.

11. Advantages and Disadvantages of R.O.
Advantages Disadvantages
Energy Requirement is low compared to
other thermal Processes
Pre-treatment is always required before
reverse osmosis
RO systems can be installed on very small
household basis, where other systems are not
portable
Low Chemical Compatibility-highly sensitive
to pH cannot be used with even traces of
oxidants like Cl2
Very High Salt rejection rate (>99%) Not compatible with micro organisms which
have acetate attacking enzymes
Excellent rejection of Microorganisms and
organic compounds

12. Suitable membrane should posses following properties:-
● High permeability to water.
● High impermeability to solutes.
● Ability to withstand high pressure without failure.
● Resistant to physical, chemical, and biological attacks.
● Tolerant of pH and temperature changes.
● Economical, to decrease the operating cost.
Examples:-
• Cellulose membrane.
• Polyamide.
Suitable Membrane Materials

13. Scope For Future Research
• Membranes
• Energy Recovery