DEMINERALIZATION OF SALINE WATERS 265 
For example, it is estimated that simple solar distillation appara- 
tus, located in the southwestern area of the United States, will 
produce water at a cost of from $1,600 or $1,700 per million 
gallons, or slightly less. It is believed that the design of solar 
stills can be improved to produce water from saline sources for 
one dollar per 1,000 gallons, or $1,000 per million gallons. Costs 
estimated recently for other desalting methods are $1.15 per 1,000 
gallons for vapor compression and $1.75 for a six effect flash 
evaporator. 
For many uses, the ultimate cost to the consumer can be re- 
duced by blending the distillate produced with the raw saline 
supply. For instance, if the raw water contained total dissolved 
solids of 4,000 parts per million, and if water of 2,000 parts per 
million were usable for certain requirements, then the cost of 
delivered water would be cut in half. 
The primary demand for fresh water in arid and semi-arid 
regions is to supply water for domestic use and for irrigation. It is 
the latter use of water which is of the greatest importance in the 
adaptation of treatment of saline supplies to make such water 
suitable for the growth of crops in regions where there is absence, 
or at least a shortage, of fresh water supply for irrigation. 
In many cases there is a lack of realistic evaluation of this 
phase of the problem. The quality of the water necessary for 
irrigation varies widely with a number of factors. These include 
total dissolved solids in the irrigation water and the ratio of 
various salts contained in the supply. Of great importance, also, 
is the soil condition in the selection of crops to be grown. In 
studying this problem, H. E. Hayward, in his many publications, 
has amassed and published voluminous data on the subject. 
In determining the cost of conversion of saline waters to produce 
water of satisfactory quality for irrigation purposes, one must 
evaluate all these factors, and the choice of crops grown will be 
influenced by the degree of treatment required in specific cases. 
It is important that permissible water quality be evaluated in the 
light of these limiting conditions. 
The research program financed by grants and aids made possible 
through the provisions of U. S. Public Law 448 is already highly 
