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Activated carbon (AC) filtration is most effective in removing organic contaminants from
water. Organic substances are composed of two basic elements, carbon and hydrogen. Because
organic chemicals are often responsible for taste, odor, and color problems, AC filtration can generally
be used to improve aesthetically objectional water. AC filtration will also remove chlorine. AC
filtration is recognized by the Water Quality Association as an acceptable method to maintain certain
drinking water contaminants within the limits of the EPA National Drinking Water Standards (See following Table).
AC filtration does remove some organic chemicals that can be harmful if present in
quantities above the EPA Health Advisory Level (HAL). Included in this category are trihalomethanes
(THM), pesticides, industrial solvents (halogenated hydrocarbons), polychlorinated biphenyls (PCBs),
and polycyclic aromatic hydrocarbons (PAHs).
THMs are a byproduct of the chlorination process that most public drinking water systems use
for disinfection. Chloroform is the primary THM of concern. EPA does not allow public systems to
have more than 100 parts per billion (ppb) of THMs in their treated water. Some municipal systems
have had difficulty in meeting this standard.
The Safe Drinking Water Act mandates EPA to strictly regulate contaminants in
community drinking water systems. As a result, organic chemical contamination of municipal drinking water
is not likely to be a health problem. Contamination is more likely to go undetected and untreated
in unregulated private water systems. AC filtration is a viable alternative to protect private
drinking water systems from organic chemical contamination.
Radon gas can also be removed from water by AC filtration, but actual removal rates of radon
for different types of AC filtration equipment have not been established.
Similar to other types of water treatment, AC filtration is effective for some contaminants and
not effective for others. AC filtration does not
remove microbes, sodium, nitrates, fluoride, and
hardness. Lead and other heavy metals are removed only by a very specific type of AC filter. Unless the manufacturer states that its product will remove heavy metals, the consumer should assume that the AC filter is not effective in removing them. Refer to the other circulars in the Treatment Systems for Household Water Supplies series for information on systems that do remove the contaminants listed above.
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