Activated carbon has been used for water treatment literally since ancient times and today, activated carbon is still used as the preferred media for purifying municipal water.
How Activated Carbon Works
Activated carbon is made from organic matter with a high level of natural carbon, such as peat, wood, or coal. The matter is slowly heated in a very low-oxygen environment to draw out water and impurities without allowing it to burn, creating a material known as char. The char is then activated through a series of chemical and physical processes to vastly increase its surface area and create a network of submicroscopic pores.
Through a process known as adsorption, the carbon attracts and traps a wide variety of compounds across its vast surface area. Activated carbon is capable of binding compounds in liquid, solid, and gas phases.
What It Removes
In water, activated carbon is most frequently used to remove organic compounds. These include a variety of bacteria and algae, as well as tannins and phenols. Tannins are produced when organic matter breaks down, and give water an unpleasant dark color. Phenols are naturally occurring compounds that may have some minor health benefits, but tend to create an odd smell. Activated carbon also breaks down chlorine into chloride, removing the strong odor and taste from chlorine-treated drinking water.
Pesticides, Herbicides, and Other Chemicals
Volatile organic compounds, or VOCs, are byproducts of common household products such as paints, solvents, and cleansers, as well as industrial and commercial processing. They enter the groundwater through runoff, spills, and improper containment procedures. At times, these VOCs can enter the drinking water supply. At other times, they evaporate into the air, causing airborne exposure that can result in severe respiratory distress in sensitive individuals.
What Is Not Removed
Activated carbon is a powerful water purifier, but it does not remove all possible contaminants. In particular, it is not effective against totally removing chloramines, the bi product of city disinfectants (chlorine and ammonia combination).
The decline in the use of just chlorine (versus the chlorine and ammonia blend) began with the relatively recent discovery of a group often carcinogenic spin-off chemicals called trihalomethanes (THMs) that are formed when chlorine combines with organic matter in water. To meet EPA standards for THMs, which once created are hard to remove, municipal suppliers are turning increasingly to disinfection with chloramines, which produce much lower levels of trihalomethanes.
Removing chloramine at the point of use, however, is more difficult than removing chlorine. Standard granular activated carbon (GAC) and carbon block products have limited capacity for chloramine reduction. The use of Catalytic carbon is an effective solution to addressing chloramines in the water.