Activated carbon is the most common method of treatment for dechlorination and removal of taste and odor from water, through adsorption of the compounds that cause these problems.

A wide variety of raw materials can be used to make activated carbon and they include wood, lignite, peat, coal, and coconut. The basic manufacturing process involves carbonisation, or conversion of the raw material to a char, and activation, or oxidation to develop the internal pore structure.

Activated carbon operates through adsorption. Adsorption is directly related to the surface area of the media. Activated carbon has tremendous surface area with most of this area being accounted for by the vast network of pores within each particle. Depending upon the carbon base, the surface area ranges from 900 to 1500m²/gram.

This great surface furnishes a huge adsorptive area for organic as well as chlorine molecules to attach themselves. This intermolecular attraction between the carbon surface and the substance that is being adsorbed can be altered by increasing the density of the carbon or by reducing the distance between the carbon surface and the substance being adsorbed.

Experience has shown that activated carbon has a very broad spectrum of adsorptive activity as most organic molecules are retained on its surface. Most difficult to retain are the short molecules and the least polar. Heavier molecules, such as aromatic compounds, substituted hydrocarbons volatile organic compounds (VOCs), which can cause taste, odour and appearance problems and halocarbons such as trihalomethane (THM) compounds and other process wastes, tend to be more firmly retained.

Once all of the surface area of the carbon has been exhausted through adsorption, the carbon can be regenerated in a number of different ways. The most common is offsite furnace re-activation, which involves heating the carbon up to drive off the organic materials that are adsorbed.