The study was conducted to determine the fate of C.I. Disperse Blue 79, one of the largest production volume dyes, and select biodegradation products in a conventionally operated activated sludge process and an anaerobic sludge digestion system. A pilot study was conducted from November 1987 to February 1989. The equipment operated included two continuous feed pilot-scale wastewater treatment systems, consisting of one control system and one experimental system. Screened, raw municipal wastewater fed to the experimental treatment system was dosed with a target concentration of 5 mg/L of active ingredient in the commercial formulation of C.I. Disperse Blue 79. The control system was fed only the screened, raw municipal waste-water. After acclimation and steady state conditions were reached, samples from each system were analyzed for the dye and related compounds. Volume I of the report presents the results regarding: the affect of the addition of C.I. Disperse Blue 79 on the operation of an activated sludge system and an anaerobic digester; the fate of the dye in the treatment systems; and the detection of any degradation products in the systems. Volume II contains the raw data.