Activated carbon can be very effective for treatment of a broad range of organic contaminants including solvents, pesticides, herbicides, DBPs, and other classes of organic compounds.

The activated carbon contains an internal pore structure of relatively large and small pores. The smaller pores contain less overall pore volume, but they have higher pore energy associated with them. It is the high energy pores that are most important in adsorption of trace concentrations of organic contaminants in water. In general, lower molecular weight, lower boiling point, and more water soluble organic compounds are more difficult for activated carbon to adsorb and thus require higher energy pores to adsorb them from the water.

There are several base materials used to produce activated carbon, most commonly coal and coconut shells. Both of these base materials can incorporate appropriate pore structures to be effective in adsorption of organic compounds, although not all coal based carbons have such a structure.

In addition to having an activated carbon with the correct pore structure, a system design that allows for adequate contact time between the dissolved organic contaminants and the activated carbon is important. Flow rates that are excessive or carbon beds without sufficient depth will severely limit system effectiveness, even if appropriate carbon is used.

Adsorptive capacity must be considered with activated carbon systems. As the high energy pores reach a certain degree of saturation, the effectiveness of the activated carbon is reduced and contaminant breakthrough begins to occur. For this reason, activated carbon systems are frequently designed with replaceable cartridges intended to be replaced at an interval recommended by the manufacturer. However, there are whole house type systems in use. These systems use a control valve to facilitate periodic backwashing to remove accumulated particulate matter from the system. Additionally, professional servicing is required to replace the carbon when it reaches its effective capacity.

The presence of natural organic matter in the drinking water will reduce the effective adsorptive capacity of the activated carbon because it will compete for adsorptive sites on the carbon with the organic contaminants.