276 THE FUTURE OF ARID LANDS 
amount of salt to be removed, so that the application is practically 
restricted to brackish water. 
It may be possible to decrease the production cost by improving 
the regeneration process. To this end ion exchange can be prac- 
ticed in stages, several resin beds being used in succession, accom- 
panied by counterflow regeneration. Electric current can also be 
applied in regeneration to save chemicals. 
Much research has already been done in Algeria, since this 
method of demineralization is especially adapted to a country 
where skilled labor is scarce and power comparatively costly. 
France has set up a project for further research in Algeria and is 
willing to cooperate with other interested countries under the 
auspices of W.P.8. 
The experts group of W.P. 8 have estimated the total cost of 
desalting in the range from 1,000-300 ppm Cl’ at $1.60 per ton 
for a capacity of 10 tons per day. 
Solar Energy 
In the same way the French protectorate of Morocco intends 
to do more research in the field of distillation with solar energy, 
a process that must be restricted to small quantities in view of the 
large installations required. It is cheap in operation, as it does 
not require any fuel or electric energy, nor any chemicals. 
Factors Affecting Application 
In view of possible applications in the further development of 
arid regions, we must distinguish between: (a) water for human 
consumption, (4) water for animal husbandry, (c) water for 
agricultural purposes. Other factors are the availability of electric 
current and skilled labor. 
Human consumption asks for water of high quality (300-500 
ppm Cl’) in relatively small quantities, whereas production cost 
can be rather high. 
For cattle breeding the salt content may be 500-1000 ppm Cl’. 
For agricultural purposes large quantities of medium quality 
(750-1,000 ppm Cl’) must be available at a low price. 
It would seem that in the near future demineralization of 
brackish ground water in arid zones will become a practicable 
