88
The Last Resource
In a scientic paper given in 1961 Hugh Simpson and Professor
Silver ranked it, together with reverse osmosis, as a process likely
to be cheaper than multi—stage ash distillation for desalting sea—
water. They arrived at this conclusion using a general theory based
on energy requirements and theoretical engineering costs. How—
ever, early experience was not encouraging and interest waned.
Only in the late 1960s did the process show signs of becoming a
successful commercial venture with several British companies
leading in its exploitation. We have here an example of yet another
problem area in desalination; the diñiculties of reliably assessing the
merits of the various processes when so few of them have reached
any sizeable productive capacity.
Dollars and pounds
We now have a working knowledge of the contenders in the
desalination race, but multi—stage ash distillation remains the
proven leader in large—scale desalination. In certain circumstances
electrodialysis competes favourably, but usually not in the context
of desalting the sea—the main concern here. In any race, the man
in search of a likely winner must have some basis for a choice, and
the desalination stakes are no exception. The decisive factor here is,
in a word, cheapness. In most countries water is a cheap raw
material, a gift from the heavens, which does not command any
great respect until time of shortage. Therefore, its price is usually
far below its real value to the community, a point well made by Dr
Roger Revelle in an amusing but relevant comparison of costs. In
the US., water costs $10 to $20 an acre—foot (325,872 U.S gallons),
compared With wholesale prices of $22,ooo for petroleum, $100,000
for milk and 31 million (not including taxes) for bourbon whiskey.
Making nancial comparisons between water from conventional
sources and that from desalination is not quite so easy. The pitfalls
are
many and Dr D. G. Miller of the British Water Research
Association has pointed out two sources of serious error. Unlike
water
rates, estimates for desalination do not usually include
distribution and storage, yet distribution costs may account for as
much as 50 per cent of the total. On the other hand, current costs
for conventional supplies are often based on old production plant
which would cost considerably more to replace than it originally did
to build. The only fair comparison, it seems, is between the total
cost of a completely new supply by each method. When this is done,
The Last Resource
In a scientic paper given in 1961 Hugh Simpson and Professor
Silver ranked it, together with reverse osmosis, as a process likely
to be cheaper than multi—stage ash distillation for desalting sea—
water. They arrived at this conclusion using a general theory based
on energy requirements and theoretical engineering costs. How—
ever, early experience was not encouraging and interest waned.
Only in the late 1960s did the process show signs of becoming a
successful commercial venture with several British companies
leading in its exploitation. We have here an example of yet another
problem area in desalination; the diñiculties of reliably assessing the
merits of the various processes when so few of them have reached
any sizeable productive capacity.
Dollars and pounds
We now have a working knowledge of the contenders in the
desalination race, but multi—stage ash distillation remains the
proven leader in large—scale desalination. In certain circumstances
electrodialysis competes favourably, but usually not in the context
of desalting the sea—the main concern here. In any race, the man
in search of a likely winner must have some basis for a choice, and
the desalination stakes are no exception. The decisive factor here is,
in a word, cheapness. In most countries water is a cheap raw
material, a gift from the heavens, which does not command any
great respect until time of shortage. Therefore, its price is usually
far below its real value to the community, a point well made by Dr
Roger Revelle in an amusing but relevant comparison of costs. In
the US., water costs $10 to $20 an acre—foot (325,872 U.S gallons),
compared With wholesale prices of $22,ooo for petroleum, $100,000
for milk and 31 million (not including taxes) for bourbon whiskey.
Making nancial comparisons between water from conventional
sources and that from desalination is not quite so easy. The pitfalls
are
many and Dr D. G. Miller of the British Water Research
Association has pointed out two sources of serious error. Unlike
water
rates, estimates for desalination do not usually include
distribution and storage, yet distribution costs may account for as
much as 50 per cent of the total. On the other hand, current costs
for conventional supplies are often based on old production plant
which would cost considerably more to replace than it originally did
to build. The only fair comparison, it seems, is between the total
cost of a completely new supply by each method. When this is done,