[gardeners] Re: desalinazation

George Shirley (gardeners@globalgarden.com)
Wed, 09 Aug 2000 20:38:01 -0500

They do do it for large cities. When we lived in Saudi Arabia all of our water
came from a large desal plant about 30 kilometers from where we lived. It
produced about 10 million gallons a day from water from the Red Sea. It didn't
use reverse osmosis though, that's only practical in small systems IIRC. The
plant was built by Mitsubishi and utilized flash evaporation, ie superheated
boilers. The steam was then condensed, cooled and put into the big tanks and
then to the pipes to where it was needed. The salt and other minerals remained
behind and were flushed back into the sea by the next load of water brought in
through standard filters. Since the Red Sea is about 10 percent more saline than
the other oceans and seas it didn't make much difference. Note: There are NO
fresh water streams running into the Red Sea at all. 

Flash evaporation on that scale is expensive unless you own half the oil in the
world. Many home filters run on reverse osmosis.

George, still posting via the archives