Desalination Seawater

72% of the earth's total surface is covered in water, of which 97% 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 allow water to be produced from a local resource with no need for transportation of distant resources.

There are two main desalination technologies:

• Thermal desalination - vaporizing water in distillation facilities, where water is separated from the salts that it contains
• Membrane desalination - pressurized water passes through a membrane, which lets water pass but retains the salts, bacteria and viruses.

EXAMPLE: Ashkelon, Israel

Seawater Desalination for an Alternative, Reliable Supply

Veolia Water and its two Israeli partners, Israel Desalination Engineering and Dankner, were awarded the BOT contract for a desalination plant with the capacity to produce 100 million m3 per year in Ashkelon, south of Tel Aviv. The Ashkelon region suffers from severe water shortages. Climate change and overexploitation have brought groundwater sources to their lowest level. To satisfy the growing demands for water, local authorities decided to turn to the sea. Desalination is an alternative resource that can provide large volumes of water. With its capacity of 320,000m3 a day, the Ashkelon plant is one of the world's largest desalination facilities.

Veolia Water's solutions:

• The production costs in Ashkelon for membrane desalination of seawater is among the lowest in the world. The production costs will only be half the cost of importing water for irrigation from regions in the eastern Mediterranean.
• The produced water is of outstanding quality. 32 reverse osmosis units capable of treating 10,000m3 a day gradually desalinate seawater. The salt concentration of the water is 30mg/l compared with 35,000mg/l in the raw water entering the plant. The standard for water for human consumption is 400mg/l.