In recent years, water desalination has increasingly been used throughout the whole world to produce potable water from brackish groundwater and seawater, to improve the quality of fresh water for drinking and industrial use and to treat industrial wastewater prior to discharge or reuse.
New technologies such as distillation, reverse osmosis,extracting , ion exchange and freezing processes are now widely applied to many countries to remove contaminates other than salt from freshwater supplies.
Currently, there are approximately 4,000 desalination plants in 120 countries worldwide with a combined capacity of over 3,500 million gallons per day (mgd). The use of desalination technologies will continue to increase because of the increasing shortage of use able surface and ground water in many parts of the world. Large-scale water desalination will probably be only cost-effective as a last resort when time comes.