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Reverse osmosis is the finest water filtration method known. This process will
allow the removal of particles as small as ions from a solution. It is used
to purify water and remove salts and other impurities in order to improve the
color, taste or properties of the fluid. R.O. uses a membrane that is semi-permeable,
allowing the fluid that is being purified to pass through it, while rejecting
other ions and contaminants from passing.
This technology uses a process
known as crossflow to allow the r.o. membrane to continually clean itself. This
is the reason of why an r.o. element can last many years before clogging or
need replacement. This
water purification process requires a driving force to push the fluid through
the membrane, and the most common force is household water pressure or pressure
from a booster pump. The higher the pressure, the larger the driving force and
efficiency.
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FREE CAFRBON DIOXIDE IN WATER
Almost
all natural waters contain some carbon dioxide which they gain in several
ways. Carbon dioxide gas (CO,) is present in the air to the extent of
0.03 percent by volume and 0.05 percent by weight. As rain falls through
the air, it absorbs some of this gas.
Free
carbon dioxide.
Refers to carbon dioxide gas dissolved in water. The term is used to distinguish
a solution of the gas from the combined carbon dioxide present in bicarbonate
and carbonate ions.
On
reaching the earth, the rainwater now slightly acid will absorb additional
amounts of carbon dioxide if it flows through decaying vegetation. At
the same time, the carbon dioxide becomes carbonic acid. If the water
now passes through limestone formations, its carbonic acid content will
react with the limestone to form soluble calcium bicarbonate. In this
process the carbonic acid is partially neutralized.
Limestone. A sedimentary rock
formation wholly, or in large degree, composed of calcium carbonate. There
are many important varieties of limestone, such as chalk, travertine and
marble.
On
the other hand, if water passes through rock formations, such as granite,
no such reaction occurs. The carbonic acid is not neutralized. It continues
as carbonic acid until drawn to the surface where it can then cause corrosion
if not neutralized.
Granite. A type of rock that
consists primarily of quartz, alkali feldspar and mica. The quartz and
feldspar are always present in granite. Other minerals are sometimes present
as well. These are all silicates.
If nature or chemical
agents do not neutralize carbonic acid, it will cause corrosion of both
copper and galvanized plumbing systems . In those parts of the country
where the problem is prevalent it is serious, for it can lead to serious
damaging of plumbing equipment. Carbon dioxide, together with carbonic
acid, is primarily a problem in water containing relatively low concentrations
of minerals. In such water there are not sufficient alkaline salts to
buffer the effect of the carbonic acid.
The
simplest method for removal of carbonic acid is to pass the water through
a tank containing limestone chips. A neutralizing filter of this type
affects the carbonic acid just as does the underground limestone formation.
The limestone in the filter reacts with the carbonic acid to produce calcium
bicarbonate. In the same way, lesser amounts of magnesium bicarbonate
are formed. Note: Not all forms of limestone are suitable for this purpose.
Excessively soft material may break down to form a solid mass and block
the filter. The best types are hard, strong granules which
retain their physical structure, even as they are dissolved.
Another type of material
used in this neutralizing process is magnesium oxide. Although this procedure
does add hardness and alkaline salts to the water, it effectively neutralizes
a considerable amount of carbonic acid at a relatively low cost.
Where high carbon dioxide
concentrations are encountered, a solution of soda ash sodium carbonate
(Na2C03) may be fed into the water. The carbonic
acid and the sodium carbonate react directly to form sodium bicarbonate.
This method of treatment offers the advantage of not adding hardness to
the water. Also, it is especially effective where it is necessary to remove
carbonic acid from large volumes of water. This method, as we have seen,
has the disadvantage of requiring more attention in the preparation and
maintenance of proper feeds.
Where water is obtained
from a private well, a small positive displacement pump can be used to
feed the soda ash solution into the water. Normally such pumps are wired
to act in conjunction with the operation of the well pump. This permits
the proportioning of the solution with a good degree of accuracy.
Where a private water
system is not used to draw water to the household lines, some other type
of feeding device is necessary. However, the design of such devices is
limited only by the ingenuity of pump manufacturers and installation personnel.
It is important to feed soda ash solutions into the water in advance of some
type of tank or mixing device. This is necessary to provide for reasonably
consistent concentrations in the water to be treated. The type of pressure
tank utilized in
connection with most private water systems is adequate
for this purpose.
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