Activated Carbon Filters
Activated carbon filters are generally used to eliminate
undesirable odors and tastes, organic compounds and to remove residual chlorine.
These filters absorb impurities as they pass through a carbon cartridge. As
far as efficiency in terms of removal of contaminants is concerned - these filters
do not remove most inorganic chemicals, metals, microorganisms and nitrates.
However, carbon filters are very important and efficient in the removal of some
potentially hazardous contaminants such as radon gas, many
dissolved organic chemicals and tri-halo-methane. In case the water supply has
a low level of these contaminants, this filtration system can easily and effectively
be used as a whole-house unit. However, cases where the level of these contaminants
is persistently high, these filters are not the solution for removal and purification.
In these cases, or when contamination cannot be eliminated by usage of carbon
filters, it would be safest to choose an alternative water supply as the most
cost and health effective system.
When using a carbon filter, it must be remembered that these need to be replaced
periodically. With continued usage, as the filter gets saturated with contaminants,
it loses its effectiveness and must be replaced. Instead of replacing or delay
in replacement can result in contaminants
to be flushed into the drinking water. This can be unhealthy and must be avoided.
All these filters have a rated life beyond which they should not be used. Therefore,
it is important that before purchasing the unit, all information such as can
the filter can be replaced, the frequency of replacement, where replacement
filters may be purchased and how much they cost should be obtained from the
dealer. This factor may influence your decision on the model and type of system
being purchased.
A property of the material used in an activated carbon filter
that must be borne in mind is that it provides a growth surface for certain
bacteria. Therefore, if the filter has not been used for five or more days,
you must clean the surface. This can be achieved simply by running chlorinated
water through the filter for at least 30 seconds before use.
Because carbon filtering devices use carbon cartridges that have a porous surface,
it allows the cartridge to absorb a variety of substances that change the quality
of water, including THMs, odors and disagreeable tastes. This may not be
very agreeable. The effectiveness of a filter depends on the amount of carbon
that is in the unit and also on how long the water stays in the unit. As a norm,
the longer the water is in contact with the filter medium, the more time the
carbon has to remove impurities. Therefore, those filters that are packed with
a large volume of charcoal tend to remove more organic material at the beginning
of the cartridge life. However, the advantage is that the performance of these
high volume filters tends to decrease less rapidly over time than it does for
those containers with a small amount of charcoal.
• Faucet-mounted carbon filters attach to a faucet after the aerator is
removed.
• There are two basic designs of carbon filters. One
uses a by-pass valve that filters only water for cooking and drinking. The second
design has no by-pass valve and therefore, it filters all water flowing through
the faucet. Additionally there are those that are not permanently attached to
a faucet. These models are placed on a counter and have a hose running from
the faucet to a charcoal filter.
• Then there are pour-through (portable) filters. These are used effectively
to remove contaminants from water on recreational vehicles,
on boats or at campsites. However, in this case, you have to make sure that
the water started with is suitable for drinking (potable water). Water poured
through the filter flows into a container, is collected and consumed. This is
the simplest form of all carbon filters, especially if it is the non-powered
variety. There also exist models that are powered and operate on a 115-volt
current; there are some others that operate on a 12-volt line or battery. The
rate of filtration in the units that are powered is much higher when compared
to the non-powered filters. Some of those operating on a 12-volt battery can
filter up to 1-1/4 gallons (4.7 liters) in two minutes.
• Specialty-type filtering devices such as ice maker and scale filters
are placed on the cold water supply line to appliances. Ice maker filters are
attached to the cold water line to refrigerators or standard ice makers. Scale
filters are connected to the supply line of water heaters or humidifiers.
• A line by-pass filter may be installed in any one of the two locations.
The first location is beneath the sink where it is attached to a line leading
to a separate faucet at the kitchen sink. The second location is in the water
line after it enters the house. When installed in the water line after it enters
the house, it also requires installation of a valve in the water line ahead
of the filter in order for the water that is drawn from the regular faucet to
be shut off.
• A stationary water filter is installed
in the cold water line under the sink. All cold water flowing through the pipe
to the kitchen is thus filtered.
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