Activated Carbon Filtration (GAC)
Activated carbon has been known as a miracle filter media by many researchers because of its unique ability to remove offensive tastes, odor, color, chlorine and volatile organic chemicals, pesticides and trihalomethanes (a group of suspected carcinogens). Briefly, activated carbon acts like a sponge, with a large surface area to absorb contaminants in the water. Many scientists believe this is a result of affinity that these chemicals have for carbon because of Van Der Waal forces.
Activated carbon is the preferred treatment and method recommended by the EPA to remove a host of potentially hazardous and possibly carcinogenic chemicals in drinking water. It does not add anything detrimental to the treated water, unlike chlorine which is used by municipalities to destroy bacteria.
Learn more about activated carbon on the USDA website.