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WATER,
next to air is the most important element to the sustenance of human
life. |
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What do we know about it ? |
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When we think about
water we usually visualize a crystal clean mountain stream flowing from
a beautiful waterfall.
Water is a universal solvent. No matter what it touches, water starts to
dissolve that substance, thereby contaminating itself.
Some contaminants are wanted, they are minerals essential to proper
nutrition. But most contaminants are unwanted, they are: |
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Pathogenic Bacteria
that cause disease
like hepatitis, typhoid, and cholera.
Natural Organics, like sediment, dirt,
decayed plant and animal matter.
Synthetic Organics, which are man-made
chemicals, trihalomethanes, pesticides, herbicides. |
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HYDROLOGIC CYCLE |
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The
hydrologic cycle is nature’s way of cleaning the air, ground, and water
on our planet.
During each
24 hour period, approximately one trillion tons of water
evaporates from the earth’s surface.
This vapor is attracted by particles of dirt in the air which become the
nuclei to form raindrops.
We see these accumulations of moisture as clouds. When clouds become
saturated, the moisture released as rain
either runs off into our streams, rivers, lakes and oceans, or it
percolates through the ground to become part of the underground water
tables. |
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WATER
DEMAND |
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The chief point to be
learned by examination of the hydrologic cycle is that the water supply
of the earth is fixed. Approximately 97.3% of the earth’s water is in
the oceans, of which a very tiny amount 0.007% is distributed annually
as precipitation over the land area. Much of the remainder is locked up
for the present in ice and snow; glaciers and ice caps cover 11 % of the
land area and pack ice and ice floes cover 25% OF THE OCEAN. The amount
of fresh water immediately available to people is a small fraction of
the total water found on earth. |
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Although composed of
about 65% water, man requires only a few liters a day for maintenance,
and, since much of this is supplied by food, often a liter or two is
adequate. This innate ability to conserve water evolved over a very long
time and probably had certain survival value where water was scarce, as
in desert areas inhabited by primitive man. |
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DRINKING WATER |
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Most of us are so accustomed to drawing
water from a tap that we quickly forget that our faucets are connected
by long miles of pipe to a supply somewhere.
A continuous flow of water is assumed to be an inalienable right. |
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Where does the water that is piped into your
homes come from? Because of the
absence of an abundant source of natural fresh water to meet the
domestic and industrial needs of St. Maarten’s economy, the need to
resort to seawater desalination has been practiced in St. Maarten for
over thirty(30) years. Formerly, this was achieved by the process of
distillation, nature’s way. Water in a boiling tank comes to a boil,
creating steam which rises leaving behind impurities. The steam then
enters condensing coils where it is cooled and converted back to water.
The liquid drops from the condenser into a collecting vessel. The
distillation plants of GEBE have become outdated and have been replaced
with a newer desalination technology, REVERSE OSMOSIS. |
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The reverse osmosis
(RO) process utilizes a water pressure differential to separate the
water from salt impurities that are normally in it. The cellulose
acetate membrane, which does all of the work, removes up to 95% of the
dissolved solids, all of the particulate matter, and most of the
dissolved compounds. The basic principal is that water molecules
dissolve in the thin cellulose acetate layer of a membrane and diffuse
through it molecule by molecule. Salt ions will also dissolve in the
cellulose acetate membrane and move through the thin layer by diffusion
except that the solubility of water in the acetate is greater. Hence,
the water moves through more rapidly with the result that a separation
occurs. The driving force is furnished by both the source water pressure
and the concentration differentials across the thin layer of cellulose
acetate.
It is interesting to
note that the dissolved oxygen of the source water penetrates the
membrane at about the same rate as the water molecules so that the
product produced has an oxygen content about the same as that of the
source water. This is very important to the taste consideration. Most
people believe that it is the high mineral content of water that makes
it taste good; however, this is not so. It is the degree of oxygen in
the water that gives it a good taste. RO water is high in oxygen which
gives it that “mountain spring” taste.
The RO unit is
designed so that it is continually self cleaning. As it flows through
the unit, the feed water is divided into two streams. One part is forced
through the membrane and emerges through the unit as product water. The
second stream serves as a blowdown and carries away the rejected salts
and particulate materials to the drain. Therefore, there is no
accumulation of debris on the high pressure side of the membrane as a
function of time. |
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