Basic Study on Crystallization Process for High Concentration of Phosphorus

Abstract

Important factors for the crystallization of calcium phosphate are pH value and ratio of PO_4^-P and Ca²⁺ concentrations. Precipitation of calcium phosphate in the crystallization process reduces efficiency because the precipitate, which should be removed in settlement process, has no contribution to the crystallization. In order to get high removal efficiency in the crystallization, it is necessary to minimize the calcium phosphate precipitation. From this point of view, the optimum conditions for pH value and ratio of PO_4^-P and Ca²⁺ concentrations are examined in this study. Supersaturation conditions referring the crystallization and the precipitation are found from the experimental results. Promising approach for minimizing the precipitation is to control supersaturation by diluting PO_4^-P and Ca²⁺ concentrations with the effluent.