Evening star. [volume] (Washington, D.C.) 1854-1972, 1957-05-05
COSTS GO DOWN
Progress Is Made on Sea Water Conversion

eliminated" says Mr.. Jenkins, "a
l5-stage still could be feasible, one
that might produce fresh water
at between 30 and 40 cents per
1000 gallons"
. Solar DistillatiOn-This method
makes use of the evaporation prin-
ciple but employs the suns heat
to bring it about. Salt water in
nat containers is covered by slant
ing roofs" Of glass or plastic mem
brane. Heat from the sun evapo-
rates the water and the distilled
moisture collects on the covering
to be carried of to fresh water
storage. The method has much
promise for arid sections.
. ElectrOdialysis-A method Of
removing salt ions from water by
shooting an electric current through
salt water tanks divided by a sys-
tenn of permeable membranes. The
salt ions pass from one set Of
tanks to another, leaving fresh
water behind. The system looks
good for brackish waters, but so
far is too costly when applied to
sea water. The Dutch. employing
a lower scale of labor costs than
is possible in the United States,
think they are on the verge Of re-
filming this system to 80 cents or
less per 1000 gallons of brackish
water.
. Enthusiastically this Is q
system of reverse osmosis" in
which salt water ions are held back
by special types of membranes
while the pure water passes
through under mechanical pres
sure. A University of Florida team
has shown that 80 to IS per cent
Of the salt from sea water can be
removed this way, using cellulose
acetate membranes, in a single
operation. The problem now is
to get cheap membranes that will
hold up under extensive use while
increasing the rate of flow.
. Freezing-A system of de-salting
based on the idea of rapidly cooling
sea water and then getting the
pure water ice crystals washed free
or otherwise separated from the
brine. According to Secretary Sea-
ton, new freeze-evaporation proc
ess under study promises to pro-.
duce fresh water at q cost Of
between so cents and 81 per 1000
gallons.
. Solvent Extraction-Here the
idea is to get the salt out by dis
solving sea water in some kind Of
organic matter which will not dis
solve salt, then releasing the fresh
water from the solvent by q heat
separation process.
A Foregone Conclusion
Mr.. Jenkins emphasizes that
there are still q lot of "ifs" to be
overcome. Nevertheless, taking the
long view and in light Of the APP
parent rapidly accelerating need
for fresh water, 1t is hard to think
Of economical salt water CONVEX
sion as anything but a foregone
conclusion. Ei
It is reliably reported that the
coastal and gulf areas Of the
United States are being carefully
scrutinized by hundreds Of persons
who are thinking of what may hap
pen when the mass conversion Of
sea water to fresh water becomes
feasible.
In some coastal areas it is al
ready impossible to purchase sea-
side property. no matter how desc
late and remote the region may
be. Bay and inlet territory seems
likely to become equally desirable,
and not Just for recreational pur-
poses.
Tie all this in with the rising
atomic energy industry and its
voracious appetite for water-and
who can predict the industrial pro-
file or work-pattern Of such places
Is Maine and Florida q few. years
from now?