Throughout the universe, there is one molecule that mankind eagerly searches for, as the discovery of its presence at the surface or in the atmosphere of a distant planet would immediately unleash one of the human race’s wildest dreams: that of finding life on a planet other than our own.
The formula of this molecule can be written quite simply as H2O, resulting of the union of an oxygen atom with two hydrogen atoms: Water.
Behind the very word raises an image that resulting from the first voyages in space – that of the blue planet: Earth. Water is in fact the most widespread mineral substance on the earth’s surface. It forms its hydrosphere. It has an estimated volume of 1,385 million cubic kilometres:
- 97.4 % of which is in the various oceans which cover 71 % of the Earth’s surface
- 2 % is in the form of ice
- 0.6 % is continental fresh water including groundwater and moisture in soil
But first and foremost, water is synonymous with biological life.
It is the major component in living matter. On average it accounts for 80 % of its composition. In the higher animals, the percentage of water content is somewhere between 60 and 70 %. Extreme values of 98 % are encountered in marine organisms such as jellyfish and certain algae; to the contrary, sporulated bacteria, forms of resistance and suspended animation, have their water content reduced to 50 %.
Water, which is a major element in the mineral and biological world, is also fundamentally important for life and human activity.
Currently, global water use, with its various domestic, industrial and agricultural uses added up, accounts for an impressive figure of 250 m3 per person per year. And the disparities are still enormous, ranging from less than 100 m3 for developing countries to over 2,000 m3 for the United States. Consequently, it can be taken as read that mankind’s water needs will continue to grow. This means there is a pressing need to protect water and treat it, whether for the purpose of producing fresh water for human consumption, for specific industrial uses, or for limiting pollution discharged into the environment.
