Phosphorus recovery from wastewater by using natural and granulated apatite (Phosclean®) filters is studied. A mechanistic model describing P retention by means of adsorption and precipitation phenomena is being developed with the HP1® software. This tool is able to account for hydraulics into the porous media, as well as, chemical speciation by using its PHREEQC® package. Phosphorus retention capacity and kinetics of both materials seem to be significantly different mainly because the apatite's surface in the Phosclean® product is not readily accessible to act as seed for Ca-P precipitation. This may lead to two different retention mechanisms and therefore, to two different models.