294 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1958 
Electrodialysis as a conversion process has developed rapidly from 
a laboratory phase to commercial operating units in about 6 years. 
Developments have been carried out in the Netherlands [28], Great 
Britain [29], South Africa [30], and the United States [31], and 
more recently in Japan, Soviet Russia [32], and Israel. 
One of the most advanced processes is that of Ionics, Inc., of 
Cambridge, Mass., developed partly through the Office of Saline 
Water. That process utilizes strong membranes having considerable 
durability, and a long tortuous flow path. Following laboratory tests 
that had highly favorable results, the process was incorporated in 
pilot tests [83]. The equipment, which was mounted in a trailer 
truck (pl. 4, fig. 2), was operated for some months on two naturally 
occurring saline waters in Arizona and South Dakota having salini- 
ties of 4,000 p.p.m. and 2,000 p.p.m. respectively. Operating difficul- 
ties such as fouling by scale were corrected by acid feed, and the 
process was in each location successfully carried to a residual 350 
p-p.m. concentration. High cost of equipment and membranes at 
present quoted prices accounts for about 80 percent of the cost of the 
water. With future increased production, these costs should be 
reduced. 
More than 20 Ionics., Inc., production plants are in use having 
capacities ranging from 500 gallons per day upward, with the largest 
plant of 86,400 gallons per day in the Middle East at Bahrein. The 
other well-advanced process is that of the Netherlands, TNO, also used 
in modified form in South Africa, in which thinner, less durable, but 
less expensive membranes are used in a continuous sheet-flow process. 
The one South African plant is reported to have a capacity of 
2,400,000 imperial gallons per day. 
The Office of Saline Water is conducting membrane evaluation 
and improved cell development at the laboratories of the Bureau of 
Reclamation in Denver, Colo. Membranes being tested are from 
American as well as other manufacturers. The electrodialysis units 
are from Ionics, Inc., and the Netherlands, TNO. The Texas Electric 
Service Co. of Fort Worth is developing improvements in the Ionics 
process. 
Osmionic—The second membrane process mentioned is known as 
osmionic, a term which was coined because of the osmotic and ionic 
forces involved in the process [34]. This is one of the new processes 
developed under the Saline Water Conversion Program of the United 
States and is somewhat similar to electrodialysis, except that it re- 
quires no outside electrical current and no electrodes. The driving 
force is obtained from the difference in concentration between a brine 
and the water to be demineralized. The power supply therefore 
might be obtained from salt deposits, brine wells, or by ponding saline 
water and allowing the sun to concentrate the water. 
