Table of Contents
Advertisement
Appendix B Basic Principles
Reverse Osmosis
In order to understand reverse osmosis, we must first define osmosis. Osmosis is the passage of a liquid through a
semi-permeable membrane. A semi-permeable membrane is a membrane which allows one component of a solution to
pass through it and not the others. In osmosis, there is a tendency for a liquid to go from an area of less concentration to
an area of more concentration through a semi-permeable membrane. Figure 74 shows the osmotic process.
Figure 74.
Osmotic process.
If pressure is applied to the concentrated solution, reverse osmosis will take place. The pressure causes a flow through
the semi-permeable membrane into the dilute solution. The semi-permeable membrane acts as a barrier to ions and does
not allow them to pass through into the dilute solution. When applied to water, this means that the product water has a
reduced total dissolved solids content as a result of the passage of water molecules through the membrane while the
mineral ions are rejected. See Figure 75.
Figure 75.
Effect of pressure on reverse osmosis.
Rejection and Recovery
Feed water entering the system is split into two streams, a product stream and a concentrate stream. See Figure 76.
Figure 76.
Feed water product stream and concentrate stream.
During the process of reverse osmosis, some of the water has its dissolved solids content reduced by approximately 99%.
This high quality product water is sent to service.
The rest of the feed water contains the dissolved solids removed from the product water, in addition to the dissolved solids
already present in the feed water. This concentrate water is sent to drain.
Cat. No. 01021713
Basic Principles
121
Hide quick links:
Advertisement
Table of Contents
