DEPHOSPHORIZATION DEVICE

PROBLEM TO BE SOLVED: To prevent the outflow of magnesium aluminum phosphate fine particles in a reaction column and the separation of scales in the column by providing a plurality of doping means on different site positions of the reaction column in a dephosphorization device with the doping means set on the reaction column. SOLUTION: Mg salt is doped into raw water such as phosphorus containing water, which is introduced onto the bottom of a magnesium aluminum phosphate(MAP) reaction column 1, and liquid flows are uniformized in a glass bead packed bed 4, and a MAP particle packed bed 5 is raised by plug flows. As an alkali agent is injected into the MAP particle packed bed 5, the MAP formation reaction proceeds on the surfaces of MAP particles to remove phosphorus and grow MAP crystals, and the grown particles are flowed down on the lower section of the packed bed 5 and taken out properly from a discharge pipe 6. At that time, injection pipings 11A-11C for injecting the alkali agent into the MAP particle packed bed 5 are formed on three sites in the height direction of the MAP reaction column 1. The phosphorus concentration difference is reduced to accelerate the growth of crystals by the arrangement.