Abstract: The present invention describes a process for the treatment of a precipitate starting material comprising magnesium ammonium phosphate, magnesium potassium phosphate or potassium phosphate, or any derivate thereof, or a mixture thereof, said process comprising dewatering of the precipitate starting material, wherein the dewatering is performed by use of a hydrocyclone followed by the removal of excess water by filtration, and wherein the product obtained is a powder product. Furthermore, the present invention also discloses a powder product comprising particles of magnesium ammonium phosphate and/or magnesium potassium phosphate, wherein at least 75% of the particles have a particle size of maximum 10 ?m and wherein at least 50% of the particles have a particle size in the range of 4-10 ?m.