Improving the supply of potable waterWater from salt water
As the Earth鈥檚 population increases, the demand for potable water increases. Climate change could make finding water sources harder. The treatment needed to make the water safe depends upon the source.
Sources of fresh water are scarce in some regions of the world. If the area lies near the coast then it is possible to turn seawater into potableWater that is safe to drink. water.
The process used to remove the salt is called desalinationThe removal of salt from water. This is an energy-intensive process. Also known as desalinisation..
distillationA separation technique which involves a solution being heated so that the solvent evaporates before being cooled to form a pure liquid. is used to separate water vapour from the dissolved salt:
the water is evaporatedWhen a liquid changes state to a gas.
the water vapour is then condensedTurned from a gas or vapour into a liquid, usually as a result of cooling.
In the latest desalination plants, a new technique uses membraneA very thin layer of material that will only allow specific particles through.filtrationMethod used to separate an insoluble solid from a liquid using a physical barrier such as paper. to remove the salt. These use super-fine membranes. The membranes allow water moleculeA collection of two or more atoms held together by chemical bonds. to be forced through, but not the dissolved salts.
Chlorination
Chlorine is effective at killing any microorganismMicroscopic (too small to see) organisms, such as bacteria and viruses in water. However, chlorine is toxicPoisonous. so its use does have risks. For this reason the chlorinationThe controlled addition of chlorine to water in order to kill any microorganisms present. of water is subject to public regulation and often restricted in many countries.
In some parts of the world, chlorination is still not used. This leads to higher risks of waterborne diseases. In most countries it is believed that the benefits of chlorination outweigh the risks.