The focus in recent years has been on process improvements that lead to enhanced recovery of phosphorus from wastewater. This study was designed to develop a methodology based on the operating results of numerical simulations and laboratory experiments. The developed methodology is meant to determine the conditions favoring the maximum efficiency for the recovery of calcium phosphates. It concerns the modeling of chemical equilibria, for calculating the rate of conversion of phosphate depending on the pH and the reactant concentration of the developed reaction and their dependence on supersaturation. To measure the phosphate conversion rate, experiments were carried out in aqueous solution at different pH (from 9.5 to 11.5) for molar ratios of initial ion concentrations of Ca / P in different temperature (25 ° C). These conditions were chosen to cover the pH values at which calcium phosphate crystallizes easily. In order to achieve a visible precipitate and phosphorus removal efficiency close to 90%, 2 hours contact time was also required. The precipitation / crystallization process was then studied using the VISUAL MINTEQ program as a predictive tool to determine the conditions that affect the saturation index as a dependent function of the pH and the concentration of calcium, revealing the existence of three different stages.