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you know?
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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Water Disinfection Methods. Part 2
VARIOUS
CHEMICAL DISINFECTANTS
The most common method
of treating water for contamination is to use one of the various chemical
agents available. Among these are chlorine, bromine, iodine, potassium
permanganate, copper and silver ions, alkalis, acids and ozone. Let us
review them briefly here.
BROMINE
Bromine
is an oxidizing agent that has been used quite successfully in the disinfecting
of swimming pool waters. It is rated as a good germicidal agent. Bromine
is easy to feed into water and is not hazardous to store. It apparently
does not cause eye irritations among swimmers, nor are its odors troublesome.
CHLORINE
One of the most widely
used disinfecting agents to insure safe drinking water is chlorine. Chlorine
in cylinders is used extensively by municipalities in water disinfection.
However, in this form, chlorine gas (Cl2) is far too dangerous
for any home purposes.
For use in the home,
chlorine is readily available as sodium hypochlorite (household bleach)
which can be used both for laundering or disinfecting purposes. This product
contains a 5.25% solution of sodium hypochlorite which is equivalent to
5% available chlorine.
Chlorine
is also available as calcium hypochlorite, which is sold in the form of
dry granules. In this form it is usually 70% available chlorine. When
calcium hypochlorite is used, this chlorinated lime should be mixed thoroughly
and allowed to settle, pumping only the clear solution. For a variety
of reasons, not the least of which is convenience, chlorine in the liquid
form (sodium hypochlorite) is more popular for household use. Chlorine
is normally fed into water with the aid of a chemical feed pump.
The first chlorine fed
into the water is likely to be consumed in the oxidation of any iron,
manganese or hydrogen sulfide that may be present. Some of the chlorine
is also neutralized by organic matter normally present in any supply,
including bacteria, if present. When the "chlorine
demand" due to these materials has been satisfied, what's left over
- the chlorine that has not been consumed - remains as a "chlorine
residual."
Chlorine.
There
are three basic terms used in the chlorination process: chlorine demand,
chlorine dosage and chlorine residual.
Chlorine
demand is
the amount of chlorine which will be reduced or consumed in the process
of oxidizing impurities in the water. Chlorine demand is the amount of
chlorine impurities in the water.
Chlorine dosage
is the amount of chlorine fed into the water.
And
chlorine residual is the amount of chlorine still remaining in
water after oxidation takes place.
For
example, if a water has 2.0 ppm chlorine demand, and a chlorine dosage
of 5.0 ppm is fed into the water, the chlorine residual would be 3.0 ppm.
The rate of feed is
normally adjusted with a chemical feed pump to provide a chlorine residual
of 0.5-1.0 ppm after 20 minutes of contact time. This is enough to kill
coliform bacteria, but may or may not kill any viruses or cysts which
may be present. Such a chlorine residual not only serves to overcome intermittent
trace contamination from coliform bacteria, but also provides for minor
variations in the chlorine demand of the water. The pathogens causing
such diseases as typhoid fever, cholera and dysentery succumb most easily
to chlorine treatment. Cyst-forming protozoa which cause amoebic dysentery
and giardiasis are most resistant to chlorine.
As
yet little is known about viruses, but some authorities place them at
neither extreme in resistance to chlorination.
IODINE
For emergency purposes
iodine may be used for treatment of drinking water. Much work at present
is being done to test the effect of iodine in destroying viruses, which
are now considered among the pathogens most resistant to treatment. Tests
show that 20 minutes exposure to 8.0 ppm of iodine is adequate to render
a potable water. As usual, the residual required varies inversely with
contact time. Lower residuals require longer contact time, while higher
residuals require shorter contact time. While such test results are encouraging,
not enough is yet known about the physiological effects of iodinetreated
water on the human system. For this reason its use must be considered
only on an emergency basis.
SILVER
Silver
in various forms has been used to inhibit the growth of microorganisms.
It is most frequently found combined with activated carbon in filters.
When some bacteria species come into contact with this silver, they are
rendered inactive. There is disagreement among the experts as to the effectiveness
of this process because silver ions in water kill E.coli very well and
probably also salmonella, shigella, and vibro bacteria, but it has found
lesser effect on viruses, cysts, and other bacteria species. Silver does
not produce offensive tastes or odors when used in water treatment. Further,
organic matter does not interfere with its effectiveness as is the case
with free chlorine. Its high cost, interferences by chlorides and sulfides,
need for long periods of exposure, and incomplete bactericidal action
have hindered its widespread acceptance.
COPPER
Copper ions are used
quite frequently to destroy algae in surface waters. But these ions are
relatively ineffective in killing bacteria. Copper sulfate, for example,
is also used to kill algae in reservoirs.
ALKALIES
AND ACIDS
Disease-bearing
organisms are strongly affected by the pH of a water. They will not survive
when water is either highly acid or highly alkaline. Thus treatment which
sharply reduces or increases pH in relation to the normal range of 6.5
to 7.5 can be an effective means of destroying organisms.
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Next)
According
to recent news and reports, most tap and well water in the U.S. are not
safe for drinking due to heavy industrial and environmental pollution.
Toxic bacteria, chemicals and heavy metals routinely penetrate and pollute
our natural water sources making people sick while exposing them to long
term health consequences such as liver damage, cancer and other serious
conditions. We have reached the point where all sources of our drinking
water, including municipal water systems, wells, lakes, rivers, and even
glaciers, contain some level of contamination. Even some brands of bottled
water have been found to contain high levels of contaminants in addition
to plastics chemical leaching from the bottle.
A good water
filtration system installed in your home is the only way to proactively
monitor and ensure the quality and safety of your drinking water. Reverse
osmosis water purification systems can remove 90-99% of all contaminants
from city and well water to deliver healthy drinking water for you and
your family.
Healthy and Convenient!
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