Did
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 3.
OTHER
AGENTS/ CHLORINATION
There are numerous
other agents which have proved to be successful in destroying pathogens.
Many of these must still be subjected to prolonged testing with regard
to their physiological effect on man. Among these are certain surfactants
and several types of surfactants which aid in destroying pathogens. The
cationic detergents readily kill pathogens. Anionic detergents are only
weakly effective in destroying pathogens. Because of their objectionable
flavor and possible toxic effects, however, surfactants have not been
seriously considered for treating drinking water.
Chlorine dioxide has
unusually good germ killing power. Up to the present time no valid tests
for its use have been developed because of the lack of means for determining
low residual concentrations of this agent. Because it is such a strong
oxidizing agent, a larger residual of chlorine dioxide would probably
be needed than is the case with chlorine.
At present, chlorination
in one form or another is regarded as the most effective disinfectant
available for all general purposes. It has full acceptance of health authorities.
Still there are certain factors which affect its ability to disinfect
waters. These should always be kept in mind. They are:
1.
"Free" chlorine residuals are more effective than "combined"
or "chloramine" residuals. Disinfection, regardless of the type
of chlorine, becomes more effective with increased residuals.
Chloramine.
The compound formed by feeding both chlorine and ammonia to the water.
This treatment has been used for controlling bacterial growth in long
pipe lines and in the applications where its slower oxidizing action is
of particular benefit.
2. A pH of 6.0 to
7.0 makes water a far more effective medium for chlorine as a disinfecting
agent than to higher pH values of around 9.0 to 10.0.
3. The effectiveness
of disinfection increases with the amount of contact time available.
4.
The effectiveness of chlorine residuals increases with higher temperatures
within the normal water temperature range.
5. All types of
organisms do not react in the same way under various conditions to chlorination.
6.
An increase in the chlorine demand of a water increases the amount of
chlorine necessary to provide a satisfactory chlorine residual.
In
order to insure the destruction of pathogens, the process of chlorination
must achieve certain control of at least one factor, and preferably two,
to compensate for fluctuations that occur. For this reason some authorities
on the subject stress the fact that the type and concentration of the
chlorine residual must be controlled to insure adequate disinfection.
Only in this way, they claim, can chlorination adequately take into account
variations in temperature, pH, chlorine demand, and types of organisms
in the water. While possible to increase minimum contact times, it is
difficult to do so. Five to ten minutes is normally all the time available
with the type of pressure systems normally used for small water supplies.
For this reason these authorities feel that satisfactory chlorine residual
alone can provide adequate control for disinfection. In their opinion,
therefore, superchlorination-dechlorination does the job best.
Briefly, what is this
technique, and how does it operate?
The success of superchlorination-dechlorination
depends on putting enough chlorine in the water to provide a residual
of 3.0 to 5.0 ppm. This is considerably greater than a chlorine residual
of 0.1 to 0.5 ppm usually found in municipal water supplies when drawn
from the tap. A superchlorination-dechlorination system consists of two
basic units. A chlorinator feeds chlorine into the raw water. This chlorine
feed is stepped up to provide the needed residual. A dechlorinator unit
then removes the excess chlorine from the water before it reaches the
household taps.
The chlorinator should
be installed so that it feeds the chlorine into the water before it reaches
the pressure tank. A general purpose chemical feed pump (such as described
in Lesson 5) will do the job. The size and the placement of the dechlorinator
unit depends on the type of treatment necessary. This will usually be
an activated carbon filter. If pathogen kill is all that is required,
a small dechlorinator can be installed at the kitchen sink.
Typical
layout of superchlorination-dechlorination equipment on a private water
system. With dechlorinator on main waterline, this arrangement can be
used where iron and/or manganese are present in the water.
This unit then serves to remove
chlorine from water used for drinking and cooking. Since many families
also drink water from bathroom taps, it may be necessary to install dechlorinators
at these locations as well. The advantage in dechlorinating only a part
of the water is obvious. A smaller filter unit does the job. And since
only a small portion of the total water is filtered under such conditions,
the unit lasts longer before either servicing or replacement is necessary.
Essentially dechlorination is not needed to insure a safe drinking water.
Once the water is chlorinated, the health hazard is gone. The chlorine
residual is removed merely to make the water palatable.
If the problem is compounded
due to the presence of iron and/or manganese, all the water must be filtered.
Under such conditions, a large central filter is necessary and should
be placed on the main line after the pressure tank.
The prime advantage
of the superchlorination-dechlorination process is that it saturates water
with enough chlorine to kill bacteria. Simple chlorination sometimes fails
its objective because homeowners may set the chlorine feed rate too low
in order to avoid giving their water a chlorine taste.
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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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