Different ways of desalination of seawater
Desalting can be done with different processes:
• Seawater desalination by an evaporation technique
A widespread possibility is evaporation technology. Here, the seawater is heated in large facilities. Afterwards, the water rises as steam. It cools down, drips into a pool and thus produces the drinking water, which contains no more salt. The water vapor is collected and cooled, so that it condenses again and the water vapor becomes liquid water without minerals. Minerals are added to the desalinated water afterwards.
• Gas or oil fired desalination plants
The drinking water can also be obtained by gas or oil fired desalination plants. Especially in the oil-rich Gulf states, this method is used.
• Seawater desalination by reverse osmosis
On the offshore island of Heligoland and the Canary Islands, drinking water is extracted through the reverse osmosis process. In this chemical process, the seawater is forced through membranes under very high pressure to reduce the salt content. The plastic membrane lets the water molecules through, but retains the salt components due to the tiny holes in the nanometer range. On the one hand, salt-free water is produced and the brine stays on the other side.
• Freezing process
The freezing process cools the seawater, forming ice crystals. These are free of salts. The problem, however, is that the ice crystals have to be washed, which in turn causes a great need for fresh water.