Understanding Reverse Osmosis in Water Treatment

Osmosis is a natural process where solvent molecules move through a semi-permeable membrane from a dilute solution to a concentrated solution, driven by the pressure difference between the two solutions. Osmotic pressure is the force required on the concentrated solution side to halt the solvent flow through the membrane.

Reverse Osmosis Process:

Reverse osmosis (RO) is the reversal of this natural flow. It involves forcing water through a semi-permeable membrane from a concentrated solution to a dilute solution, resulting in the production of filtered water. This reversal is achieved by applying sufficient pressure to the concentrated solution, surpassing the osmotic pressure. Feed water pumps generate this pressure.

Concentrated contaminants (brine) are reduced from the high-pressure side of the RO membrane, while filtered water (permeate) is collected from the low-pressure side. Membrane modules can be configured in various designs to achieve the highest-quality permeate with minimal waste. Typically, about 95% of dissolved salts are removed from the brine, and all particulates are effectively filtered out. However, it’s important to note that RO membranes, due to their molecular porosity, do not remove dissolved gases like Cl2, CO2, and O2.

RO Membranes:

The two primary types of RO membranes used in industrial water treatment are cellulose acetate (CA) and polyamide (PA) composite. The prevailing configuration is the spiral wound design, although hollow fibre configurations are also available. In the spiral wound setup, a flat sheet membrane and spacers are wound around the permeate collection tube, creating flow channels for both permeate and feed water. This design optimizes flow while minimizing the size of the membrane module. Reverse osmosis stands as a powerful and widely used method in industrial water treatment, offering efficient removal of contaminants and providing high-quality filtered water for various applications.