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נושא המאמר: The global deficiency of fresh water, and its possible solution
מאת: Freddy Romm   שמור מאמר למועדפים

The deficiency of fresh water is one of the most serious problems of Mankind, it touches more and more countries. The list of countries suffering of this crisis includes the USA, Israel, Australia, Mexico, Spain, Italy, Ukraine, Russia, Greece, Cyprus, Singapore, the majority of African and Asian countries. This list is obviously incomplete, moreover – if any country (e.g., France) isn't included, it can very possibly appear there in next two-three years. This crisis is caused not only by global climatic changes but also by increase in water consumption cause of the growth of the population and the industry development.
Most of countries do not try to solve this problem only by the redistribution of water resources in their territory but also pay more attention to desalination of water unsuitable for the food, household and industrial purposes – first of all, sea water.
Among water desalination methods two approaches prevail: "evaporation-condensation" using heat coming from the sun rays or other source of heat, and membrane methods. These seem very technological, but have serious disadvantages, the main of which is the considerable consumption of electrical energy. In the light of the rise of prices of petroleum, this factor makes the desalinated water unreasonably expensive. Instead the problem of deficiency of fresh water, that aggravates the energy deficiency.
"Evaporation-condensation" systems of water desalination have much longer history than membrane desalination, because their prototype is water recycle in the nature, where the sea water is heated up by sun rays, therefore is evaporated, and then, in cool zones of atmosphere, - condensed providing fresh water in the form of rain. Originally desalination by "evaporation-condensation" was performed at temperatures above 100 degrees of Celsius (above – because the presence of salt in water raises the temperature of the boiling point, that is so-called ebulioscopic effect), however it is not easy to reach such temperatures, because of weather factors. For this reason, "evaporation-condensation" is usually performed at lower temperatures, while pressure is reduced to some vacuum. The first factor seriously enlarges the spectrum of the applicability of this method (e.g., it becomes suitable for the use on ships where the heat is taken from motor), but the second factor causes considerable expenses of the electric power. Therefore, the efficiency of this method is intermediate between those for the traditional "evaporation-condensation" and membrane methods.
New opportunities in water desalination are open due to the recent invention of the author – desalination by evaporation with aeration (with further condensation of vapor, of course). In this method, as in evaporation under low pressure, the evaporation is carried out at moderate temperatures (above 60 degrees) but that is reached due to injection of air into water. The consumption of electric power is negligible (in several situations, the aeration may be carried out by means of a manual pump), and this invention combines advantages of vacuum and traditional “evaporation-condensation”.
This invention may be successfully used in existing evaporation systems in which it can replace vacuum evaporation. Moreover: this invention is appropriate for private consumer, since water heating up is possible due to solar boilers. And, of course, this invention allows the use of the heat of burning combustible garbage. Fresh water instead garbage – is it not very good?
Freddy Romm, D.Sc
[email protected]