Results from pilot studies of the use of ozonation and biologically active GAC media to upgrade two existing direct filtration facilities are summarized. A comparison of preozonation followed by GAC filter media to post-filtration ozonation followed by a GAC contactor is made based on various aggregate measures of organic matter including DOC, THMFP, HAAFP, AOC and odors. The results show that ozonation and biologically active GAC media improve organic matter removal. For one plant, preozonation and post-ozonation at similar ozone to DOC ratios and GAC contact times produces very similar water quality while at the other plant, the post-ozonation option is significantly better. The choice of the location for ozonation and GAC at these facilities will ultimately depend on water quality goals and disinfection needs.