Desalination is a process that extracts mineral components from saline water. More generally, desalination refers to the removal of salts and minerals from a target substance, as in soil desalination, which is an issue for agriculture.

Saltwater is desalinated to produce water suitable for human consumption or irrigation. One by-product of desalination is salt. Desalination is used on many seagoing ships and submarines. Most of the modern interest in desalination is focused on cost-effective provision of fresh water for human use. Along with recycled wastewater, it is one of the few rainfall-independent water sources.

The world is getting thirstier and the global demand for fresh water is rising by 640bn litres a year.

Population growth is one factor, not only the need for drinking water and sanitation but also the need to produce more food. Agriculture accounts for 70% of water use.

More Info: en.wikipedia.org