The present invention provides a process for producing granular material useful as a phosphorus removal aggregate and involves the mixing of a pulverized calcium or magnesium oxide material with a dewatered clay waste material in a paddle or ribbon type mixer until reaching a state of a uniform consistency paste like material and then allowing such material to cure for several days while periodically mixing to expose new surface area thereof to the air to facilitate evaporation until the water content of the cured material is less than six percent.