sewage treatment plant stp ernakulam In the Reverse Osmosis water purification systems process, water from a pressurized saline solution is separated from the dissolved salts by flowing through a water-permeable membrane. The permeate (the liquid flowing through the membrane) is encouraged to flow through the membrane by the pressure differential created between the pressurized feed water and the product water, which is at near-atmospheric pressure. The remaining feed water continues through the pressurized side of the reactor as brine. The major energy requirement is for the initial pressurization of the feed water. For brackish water desalination the operating pressures range from 250 to 400 psi, and for seawater desalination from 800 to 1000 PSI.

A Desalination R O Systemconsists of four major components/processes:

(1) Pretreatment, (2) Pressure Boosting, (3) Membrane separation (4) Post-treatment stabilization.

Pretreatment : The incoming feed water is pretreated to be compatible with the membranes by removing suspended solids, adjusting the pH, and adding a threshold inhibitor to control scaling caused by constituents such as calcium sulphate.

Pressure Boosting : The pump raises the pressure of the pretreated feed water to an operating pressure appropriate for the membrane and the salinity of the feed water. Now a days, Energy Recovery Devices are used in tandem with Pressure Booster so as to cut down the energy costs.

Separation : The permeable membranes stops the passage of dissolved salts while permitting the desalinated product water to pass through. Applying feed water to the membrane assembly results in a freshwater product stream and a concentrated brine reject stream. Because no membrane is perfect in its rejection of dissolved salts, a small percentage of salt passes through the membrane and remains in the product water. Reverse osmosis membranes come in a variety of configurations. Most common now a days are Thin Film Composite.

Post Treatment : The product water from the membrane assembly usually requires pH adjustment and degasification before being transferred to the distribution system for use as drinking water. The disinfection is also done if the water is being used for drinking purpose.

• Thermal and Membrane Process
• Multiple Effect Distillation (MED)
• Reverse Osmosis (RO)
• Multistage Flash (MSF)
• Hybrid Configurations
• Salt Recovery
• Packaged Plants

 

 

Read More about Thermal Desalination