Water treatment

Water treatment is treating water to make it suitable to be used. Providing drinking water is one of the main uses of water treatment. 
Many factories also need very clean water to make steam or to make high quality products. Some of this water has to be made very pure with almost no other chemicals dissolved in it.
Treating sewage so that it does not cause harm to the environment is another kind of water treatment.
Saline water can be treated by desalination to yield fresh water. Two main processes are used, reverse osmosis or distillation. Both methods require more energy than water treatment of local surface waters, and are rarely used where good fresh water is available.