Fresh water is an important resource that’s being used in increasing amounts as populations increase. As population grows, the usual fresh water sources like rivers and streams are not going to continue to meet that increasing demand. However, the largest source of water is still untapped: the ocean. The problem is the salt content of seawater or brackish water render them unusable for drinking and irrigation purposes. This is why a lot of countries needing fresh water resort to desalination.
Desalination is the process of removing salt from water. This can be accomplished via various means. One of the more popular ways to do so is to use efficient reverse osmosis systems. In such a system, there are three water streams involved: the input stream which is usually composed of seawater or brackish water, the product stream which is the low-salinity product water, and the discharge stream which is a high-saline water concentrate called brine.
Reverse osmosis works by pumping pressurized salt water into a closed container with a permeable membrane. The water is then separated from the salt by flowing through the membrane, encouraged by the pressure differences between the salt water and the fresh water behind the membrane.
The fresh water created thru this process only has 500 mg/1 dissolved solid and is useful enough for day-to-day use, while the brine is treated with effluent and often discharged to water golf courses and other open areas.