Reverse OsmosisGroup 1

Abhishek PatilPiyush Hatwalne

Naman Shukla

Various Filtration Processes

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.

Flow Governing Equations

Water Transport:Qw = ( ∆P - ∆Posm) * Kw * S/d

Salt Transport:Qs = ∆C * Ks * S/d

Salinity: Cp = Qs/Qw

Industrial Application - Desalination

Desalination Techniques Overview

• Electrodialysis.

• Multiple-effect distillation.

• Multi-stage flash distillation.

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

Module DesignThere 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.

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

Pretreatment of feed water

• Chlorination

• pH Adjustment

• Anti-Scaling

• Dechlorination

Post TreatmentUntreated 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.

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

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

Scope For Future Research

• Membranes

• Energy Recovery