Role of RO Membranes
Water is made to pass through the membrane at a very high speed, and pressure and when they pass through it, all the other contaminants are left behind on the surface of the membrane. There is something called a reject stream, which then removes the salts and the contaminants from the system. The water which is rejected is then thrown out or sent to the feedwater supply. This depends on the design of the system.
Unlike standard filters, RO uses cross filtration. In standard filters, all the contaminants get accumulated in the filter media. This is not the case in the case of RO. In the case of an RO system, the solution passes through the filter in two different ways. The contaminated water flows through one direction and the filtered water in the other. There is another significant advantage of cross-flow filtration. It cleans up the membrane of contaminants when it flows; hence the membrane is always clean.
What is the RO membrane, and how does it work?
In an RO membrane, there are many sheets or layers of a film that are bonded together and then rolled in a spiral configuration around a plastic tube. This whole thing is also known as the TFC membrane or Thin Film Composite. The material has pores of size 0.0001 micron, and it is semi-permeable. Hence, it allows water molecules to pass through as it acts as a barrier for insoluble impurities.
The water molecules pass along the surface of the membrane and penetrate through it and get collected in the center tube. The contaminants are then washed and removed.