AThirstyWorld
Theworldisnotonlyhungry,itisalsothirsty.thismaysoundstrange,sincenearlyseventypercentoftheearth'ssurfaceiscoveredwithwater.butaboutninetypercentofthisisseawater.manandmostoftheanimalscanonlydrinkandusetheremainingpercentofwater——freshwater.theneedforwaterisincreasingdaybyday.onlystepsaretakentodealwiththisproblemimmediatelycanweavoidasevereworldwidewatershortagelateron.oneofthefirststepsistodevelopwaystoreuseit.
experimentshavealreadykeencarriedoutinthisfield.theusedwiterhasbeenpumpedtoawaterpurifyingplant.there,itcanbeseparatedfromwastematterandtreatedwithchemicalssothatitcanbeusedagain,justasifitwerefreshwaterfromaspring.