Bottle point tests were conducted to evaluate granular activated carbon (GAC) adsorption capacities for various disinfection byproducts (DBPs). Using the adsorption isotherms, the GAC bed lives for these DBPs were estimated. Pilot studies were also conducted in a local water treatment plant to investigate the biological activity development in new GAC columns. The results of these studies indicated that GAC filters, or filter-adsorbers, could provide a long term (several years) removal for haloacetic acids (HAAs) after biological activity is developed and a short term (several months) removal for trihalomethanes (THMs) and trichloroacetic acid. To better utilize GAC adsorption for THM removal, GAC change should be conducted in early summer when high levels of THMs and trichloroacetic acid are expected for the rest of summer. This also coincides with high water temperatures which benefit biological activity development for HAA removal. Seeding 5% acclimated GAC could also expedite biological activity development for HAA removal in new GAC filters. Includes 9 references, tables, figures.