Brackish water is water that has more salinity than freshwater, but not as much as seawater.
It may result from the mixing of seawater with fresh water, as in groundwater.
In this process brackish water is forced against semi-permeable membranes under pressure in a continuous flow condition. The low salt content of brackish water requires that the operating pressure for Reverse Osmosis must be between 20-25 bar. As the water permeates through the membrane most of the dissolved impurities are removed and 99% of the total salt is removed.
The impurities are left behind in the flowing water and the concentrated stream from the membranes is discharged. The design of the complete system must optimize the flows, the area of the membranes, and other conditions to keep the system operating at the highest efficiency possible.