Case Study: Granular Activated Carbon

Since the 1960s, GAC has been used to remove harmful organic compounds from water, as well as to remove unpleasant tastes and odors. Most recently, GAC has been identified as an effective means to allow municipal water utilities to comply with the EPA's Stage 2 Disinfection and Disinfection By-Products Rule (DBPR). GAC removes a wide variety of organic chemicals and chemical "groups," including DBP organic precursors, thereby forestalling the formation of DBPs when disinfectant chemicals such as chlorine and chloramines are introduced into the water. GAC has also been shown to be effective in removing contaminants of emerging concern, also identified as endocrine disrupting compounds, and pharmaceutical and personal care products (PPCP). In terms of groundwater treatment, GAC has been proven to be effective in removing a variety of VOCs, such as trichloroethylene and tetrachloroethylene.

GAC technology can be implemented by a typical U.S. water utility for a cost between $10 and $40 per year for a family of four. The range accounts for the size of the installation and population served, with the cost going down on a per capita basis as the size increases, due to economies of scale. Installing a DBP precursor technology such as GAC is considerably more affordable from the standpoint of the ratepayer than use of in-house filters (which can cost up to $100 per year) or bottled water (when purchased regularly, could cost between $950 to $1,800 per year).

Recycling of GAC is essentially recycling of exhausted activated carbon. The spent carbon is removed from the utilities' filters, transported to a reactivation facility, thermally reactivated to restore the carbon's capacity, and then returned and reinstalled into the utilities' filters. This approach can reduce the cost of the use of GAC by at least 20 percent, while reducing greenhouse gas emissions related to GAC by as much as 80 percent.