From: ronkean@juno.com
Date: Mon Nov 22 1999 - 01:33:54 MST
On Sun, 21 Nov 1999 11:25:06 -0600 "Billy Brown" <bbrown@transcient.com>
writes:
> On the same vessels the entire fresh water supply is extracted from
> sea
> water by mechanical systems. While this is a somewhat easier
> problem than
> extracting water from sewage, it illustrates that it is pretty easy
> to get a
> steady stream of potable water from a large uniform contaminated
> source. It
> should also be noted that this was accomplished in the '60s without
> a
> particularly large R&D investment - on can reasonably assume that a
> similar
> effort today could achieve similar results from a wider variety of
> inputs.
>
It is well known that pure water can be obtained from contaminated water
by a process of evaporation and condensation, which is sometimes called
distillation. When that is done as an intentional activity, the cost of
the resulting purified water is exorbitantly high relative to what people
are used to paying for tap water or agricultural/industrial water, since
the process is energy intensive. On a nuclear powered ship (submarine or
surface) there is plenty of energy available, so that technique could be
used. But still, it would probably be cheaper for a nuclear powered
surface ship to store fresh water obtained from on-shore sources than it
would be to make fresh water from seawater.
Almost all of the tap water and agricultural/industrial water consumed in
the world comes indirectly from the sea, and most of the purification is
accomplished by a process of evaporation and condensation. The trick is
that the evaporation and condensation step in the purification process is
accomplished free of cost since it happens naturally without any effort
on the part of man. Seawater evaporates and comes down as rain, and the
rainwater is collected in rivers, lakes, and groundwater. Nearly pure
water can be collected from those sources, and the additional processing
to make the water safe to drink can be done cheaply. Those processes are
settlement, filtration, and disinfecting (usually with chlorine).
Distribution is done under pressure to prevent the introduction of
contaminants during distribution.
Ron Kean
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.
.
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