The world's largest installation of granular activated carbon to treat drinking water is scheduled to be put in operation by the city of Cincinnati, Ohio, in 1988. After five years of pilot studies, details of the design of the facility, including components for on-site regeneration of the carbon, have been developed. Twelve GAC contactors will provide an empty bed contact time of 15 minutes at a flow rate of 175 mgd (662 ML/d). The use of GAC is expected to remove the low concentrations of organic chemicals that are present in the Ohio River, the city's water source. Topics covered include: results of pilot-scale studies, GAC treatment design concepts, GAC contactors, carbon storage and transport, carbon regeneration, and plant controls. Includes 8 references, tables, figures.