The invention discloses a double-layer compound
biological filter material for an aerated
biological filter. The double-layer compound
biological filter material is formed by combining an inner layer and an outer layer, wherein the inner layer consists of attapulgite clay and
fly ash in a weight ratio of 4:6; and the outer layer consists of attapulgite clay, kieselguhr and
coal dust in a weight ratio of 7-10:9-12:1. The preparation method comprises the following steps of: uniformly mixing the attapulgite clay and the
fly ash, and forming inner cores of
solid spheres in a granulator; uniformly mixing the attapulgite clay, the kieselguhr and the
coal dust to obtain mixed
powder, continuously and slowly adding the mixed
powder into the granulator to coat the surfaces of the inner cores of the
solid spheres for
granulation to obtain the finished product spheres; and
drying the finished spheres naturally for 24 hours and in a constant-temperature fan
drying box at the temperature of 120 DEG C for 2 hours, taking the finished spheres out of the
drying box, directly putting the finished spheres in a box-typed resistance furnace to sinter the finished spheres at the temperature of between 950 and 1.050 DEG C for 20 minutes, and naturally cooling the finished spheres to obtain the double-layer compound biological
filter material. The double-layer compound biological
filter material obtained by the preparation method has the advantages of
rough surface, high
void ratio, good wearing resistance, high strength, easy film formation and high economy and practicability.