Almost one quarter of the world's population lives within less than 25 kilometers of the coast. Seawater represents 97% of the world's water and covers 71% of earth's surface.
Desalination therefore presents an effective solution to the challenges of rapid population and economic growth that are leading to water shortages.
Veolia Water Solutions & Technologies has over 100 years of desalination experience dating back to the first VWS Westgarth thermal desalination units in 1890.
RO involves pushing water under pressure through a membrane that lets through the water but retains the salt and other impurities.
Osmosis is a natural phenomenon. When two aqueous solutions with a different saline concentration are separated by a membrane, the water moves spontaneously from the solution with the lower saline concentration to that with the higher saline concentration.
Reverse osmosis is based on the opposite principle. To reverse the natural principle, a high level of pressure is used on the salt water -requiring a lot of energy - to make it go through the membrane. The result is that only the water molecules go through the membrane and end up as freshwater. The membrane has a flat surface plane with selective permeability. It removes salt and unwanted elements in the water, such as microalgae, bacteria, some viruses, micro-organisms and micropollutants, thus producing purified water.
Veolia Water Solutions & Technologies' membrane desalination expertise covers all sizes of project and is provided through local VWS subsidiaries.
Water Reuse Symposium 2010: The 25th Annual WateReuse Symposium is the world's preeminent conference devoted to water reuse and desalination. The Symposium also features an exhibit hall, technical tours, an awards luncheon, and an array of networking opportunities.
Further Information
One of the oldest processes is distillation or thermal desalination.
The saline content is separated by evaporation of seawater in distillation systems. The principle of distillation is to reproduce the natural process of seawater evaporated by the heat of the sun and condensed into rainwater, but in a confined area and over a shorter period of time.
Thermal desalination can be applied to all types of seawater and requires only a limited amount of pre-treatment.
A process known as "multiple effect distillation" (MED) has been developed to reduce the high energy consumption required to heat the water. It economizes by reusing the energy generated during vapour condensation.
Veolia Water Solutions & Technologies' subsidiary, SIDEM, is world leader in Multi-Effect Distillation.