A 0.3-million gal.//day, four-stage, fixed-bed, granular activated carbon pilot plant, complete with thermal regeneration facilities, continuously treated unfiltered, activated sludge wastewater treatment plant effluent for a four-year period. High-quality product water characterized by a COD of 10 mg./liter was produced on a routine basis. A 17% decrease in carbon capacity occurred between the first and fourth cycles (one cycle per year), at which time a steady state condition was established at a capacity between 45 to 50 lb. of dissolved COD per 100 lb. of carbon. Regeneration of the carbon was shown to be a feasible process and successful backwashing of the first stage carbon, which serves as a filter and an adsorber, made pretreatment of the wastewater treatment plant effluent unnecessary.