Laboratory experiments showed that biodegradation of taste- and odor-causing compounds by biofilms grown on natural humic materials is feasible. Although the mineralization of peat fulvic acid (PFA) was relatively low (about 10 percent), long-term application of the PFA resulted in a significant amount of biofilm mass in the reactor and allowed the secondary utilization of trace levels of taste and odor compounds. These results suggest that biofilms grown on natural organic materials can play an important role in removing taste and odor compounds during water treatment. Examples of drinking water treatment processes that allow good biofilm accumulation are granular activated carbon, sand filters, river bank filtration, submerged fixed-bed reactors, and fluidized-bed reactors. (Copyright (c) Journal of American Water Works Association 79(7): 107-112, July 1987.)