Microbiology of Activated Carbon

Abstract

Despite its long history of use, the microbiology of activated carbon and its impact on drinking water supplies has not been well characterized. A number of studies have shown that carbon particles coated with bacteria frequently penetrate treatment barriers and enter potable water supplies. The significance of bacteria released from GAC filters is unclear. Sand and anthracite carbon particles, as well as granular activated carbon (GAC) and powdered activated carbon (PAC) are filter materials released from treatment plants. Documentation of bacterial numbers in carbon adsorbers and in treated effluents is difficult to compare because of the variety of microbiological methods that have been used. Methods used to recover coliform bacteria in water from carbon filters may impact recovery efficiencies. Encouragement of bacterial growth on GAC media has been reported to increase the capacity of GAC filters for organic carbon removal, prolong bed-life of filters, remove nutrients for bacterial regrowth, and lower the chlorine demand of distribution water supplies. The role of bacterial antagonism on GAC has indicated that this phenomenon may be an important barrier to transport of pathogens into drinking water supplies. Studies have shown that bacteria attached to GAC were highly resistant to chlorine disinfection, but monochloramine may be valuable for the control of bacterial problems in GAC-treated water. Research needs to focus on maximizing the benefits of activated carbon, while minimizing its hazards. (See also W91-06194) (VerNooy-PTT)