Water, Water Everywhere . . .
85
rather than overcome major difculties implicit in r«desaÏlting sea—‘water. And several of the methods currently being developed may
never go beyond the pilot plant stage. They will be left straddled
between laboratory and consumer, held back by problems inherent
in the process or created by the sea-wateritself. This abundance of
problems is conrmed in reports from the many laboratories
investigating desalination. Even the most ‘cursory glance attheir
pages shows that research aimed at improving presentcommercial .
methods of distillation and electrodialysis continues alongside the
development of other, as yet unproven, processes.
The calcium and magnesium salts dissolved ‘in sea—Water create
_
serious problems for distillati0n
When 'untreated sea—‘
Water is heated to about 70°C, the salts come out of solution and
encruSt the heat exchange
This mineral coating or scale
forms a barrier to the transfer tof—heat from the hot to the coder
water and therefore reduces the efciency of the plant.f‘Fla“sh
distillation avoids the worstproblems of scale fôrmation by operating
at comparatively low temperatures but it does not escape com—
pletely. The sea—water feed must be pre—treated toremove various
minerals and oxygen which increaSes the*corr0sive action of sea—‘water; Usually, acid is added to convert the chemical
makers into a harinless form, or the Calcium and magnesium may
be remd‘ved»from the sea—water by other chemical additives.
workers have even suggested that î the sediments from
sea—water might be used tomake chemical fertiliZers—one treatment
would produce 37 tons of fertilizer for
gallons‘of
-
,
‘
»
,
“
:
of mineral scale is“ not the only block to efcrency
as the steam condenses, a lm of water spreads‘bvef‘4themetätl
surfaces of the heat exchangers and acts “as an
slowrng
down
condensat‘t—ion:Thë“ôly Way to prevent‘tlîis
‘bfëak
the layer up into tiny
added to the :sea—Water—to promote this
icon—
—Ldensation but iris
mère *se‘tiäi‘sfact0ry if the surface itself can bring
“about this, more eicient type :*o‘f’ c0ndensat—ion.
years ago scientistS sh0Wed that a Very thin layer Ofwater—repellerit
material would increase acondensati0n,k «but only recentlyÏ7‘have
suitable surfacebbathgs such—as the plastic
been—discovered
Work along these lines arrhe Franklin Institutein'Philadelphiät‘has
led to. some rather remarkable”Suggestions.’ÏÏScie‘ntiSts>
‘
haVe
85
rather than overcome major difculties implicit in r«desaÏlting sea—‘water. And several of the methods currently being developed may
never go beyond the pilot plant stage. They will be left straddled
between laboratory and consumer, held back by problems inherent
in the process or created by the sea-wateritself. This abundance of
problems is conrmed in reports from the many laboratories
investigating desalination. Even the most ‘cursory glance attheir
pages shows that research aimed at improving presentcommercial .
methods of distillation and electrodialysis continues alongside the
development of other, as yet unproven, processes.
The calcium and magnesium salts dissolved ‘in sea—Water create
_
serious problems for distillati0n
When 'untreated sea—‘
Water is heated to about 70°C, the salts come out of solution and
encruSt the heat exchange
This mineral coating or scale
forms a barrier to the transfer tof—heat from the hot to the coder
water and therefore reduces the efciency of the plant.f‘Fla“sh
distillation avoids the worstproblems of scale fôrmation by operating
at comparatively low temperatures but it does not escape com—
pletely. The sea—water feed must be pre—treated toremove various
minerals and oxygen which increaSes the*corr0sive action of sea—‘water; Usually, acid is added to convert the chemical
makers into a harinless form, or the Calcium and magnesium may
be remd‘ved»from the sea—water by other chemical additives.
workers have even suggested that î the sediments from
sea—water might be used tomake chemical fertiliZers—one treatment
would produce 37 tons of fertilizer for
gallons‘of
-
,
‘
»
,
“
:
of mineral scale is“ not the only block to efcrency
as the steam condenses, a lm of water spreads‘bvef‘4themetätl
surfaces of the heat exchangers and acts “as an
slowrng
down
condensat‘t—ion:Thë“ôly Way to prevent‘tlîis
‘bfëak
the layer up into tiny
added to the :sea—Water—to promote this
icon—
—Ldensation but iris
mère *se‘tiäi‘sfact0ry if the surface itself can bring
“about this, more eicient type :*o‘f’ c0ndensat—ion.
years ago scientistS sh0Wed that a Very thin layer Ofwater—repellerit
material would increase acondensati0n,k «but only recentlyÏ7‘have
suitable surfacebbathgs such—as the plastic
been—discovered
Work along these lines arrhe Franklin Institutein'Philadelphiät‘has
led to. some rather remarkable”Suggestions.’ÏÏScie‘ntiSts>
‘
haVe