Strongly basic ion-exchange resins have been shown to exhibit a preference for dichromate over many other anions in water solution. Laboratory studies were conducted to show that this ion preference could be used to remove chromate from waste waters which were discharged from a zinc yellow pigment manufacturing plant. It was also shown that the recovered chromate solution could be recycled into product manufacture without sacrificing product quality. From these laboratory studies, a full-scale ion-exchange treatment plant was designed, constructed, and demonstrated. The chromate composition of the plant effluent is being reduced from 2700 ppm to one to two ppm. The treatment system was designed to treat 60 gallons per minute of influent and to discharge an effluent which is within statutory limits for pH and for heavy metal content. The plant was designed to require minimal manual supervision. The steps in treatment and in resin regeneration are performed automatically and the control system is interlocked to make it fail safe.

Prepared by Mineral Pigments Corporation, Beltsville, Md., under project 12020 ERM, program element 1BB036. Includes appendices. Includes bibliographical references (pages 53-54).