Activated carbon is a very mature technology that is designed to help remove taste and odor from water through adsorption of the compounds that cause problems.
There are a variety of different types of carbon that are used industry-wide. They include wood, lignite, coal, and coconut as the most common sources for activated carbon.
Activated carbon operates through adsorption. Adsorption is a surface phenomenon and is therefore directly related to the surface area of the media. In the case of activated carbon, the surface area is related to the pore structure of the raw materials. The cost of the media is also related to the raw materials, so there are other factors that must be taken into consideration besides the total surface area.
Adsorption takes place due to intramolecular attraction between the carbon surface and the substance that is being adsorbed. The force of the attraction can be altered by increasing the density of the carbon or by reducing the distance between the carbon surface and the substance being adsorbed (typically by reducing the median pore size). As the fluid (often water) passes over and through the carbon, the attractive forces between the compounds that are the most attracted to the carbon are adsorbed onto the surface. The compounds that are the most highly attracted are typically organic compounds (which can cause taste, odor and appearance problems), volatile organic compounds (VOCs) and halocarbons such as trihalomethane (THM) compounds and other process wastes.
Once all of the surface area of the carbon has been exhausted through adsorption, the carbon can be regenerated in a number of different manners. The most common is offsite furnace re-activation which involves heating the carbon up to drive off the organic materials that are adsorbed.