What Contaminants Do Activated Carbon Filters Remove From Water?
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 (Table 1).
Table 1. Water contaminants that
can be reduced to acceptable standards
by activated carbon filtration.
(Water Quality Association, 1989)
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Primary Drinking Water Standards
Contaminant *MCL, mg/L
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Inorganic Contaminants
Organic Arsenic Complexes 0.05
Organic Chromium Complexes 0.05
Mercury (Hg+2) Inorganic 0.05
Organic Mercury Complexes 0.002
Organic Contaminants
Benzene 0.005
Endrin 0.0002
Lindane 0.004
Methoxychlor 0.1
1,2-dichloroethane 0.005
1,1-dichloroethylene 0.007
1,1,1-trichloroethane 0.200
Total Trihalomethanes (TTHMs) 0.10
Toxaphene 0.005
Trichloroethylene 0.005
2,4-D 0.1
2,4,5-TP (Silvex) 0.01
Para-dichlorobenzene 0.075
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Secondary Drinking Water Standards
Contaminant **SMCL
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Color 15 color units
Foaming Agents (MBAS) 0.5 mg/L
Odor 3 threshold
odor number
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*Maximum Contaminant Level
**Secondary Maximum Contaminant Level
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.
Water Contaminants Not Removed by AC Filtration
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.
