72% of the earth's total surface is covered in water. 97% of this water is saltwater. Almost 40% of the world's population lives within 70 km from the coast.

These figures show the importance of seawater desalination techniques in meeting some of the world's water requirements. Furthermore, desalination plants mean that water is produced from a local resource (no need to transport distant resources).

There are two main desalination technologies:

• thermal desalination - by vaporizing the water in distillation facilities, the water is separated from the salts that it contains;
• membrane desalination - this consists of passing the pressurized water through a membrane which lets the water pass but retains not only the salts but also bacteria and viruses.