Due to phosphorus impact on water pollution, a P-recovery process by calcium phosphate precipitation was developed. The reactor process is a fluidized bed in which phosphate precipitates continuously and coats sand grains. The pilot unit can treat synthetic wastewater flow rates ([P) = 50 mg/l) of about 0.1 m3/h. A two-stage methodology is proposed to understand the physicochemical phenomena. Fluidized bed precipitation modeling involves thermodynamical concepts taking into account the various calcium phosphates that can precipitate vs. operating conditions (PH, [P], [Ca], T). Coating modeling is performed by a first-order kinetics reaction between fines and sand grains, combined with a network of ideal reactors representing system hydrodynamics.