The invention relates to a preparing method of a lightweight ceramsite
biological filter material. The
filter material is prepared by subjecting clay mineral, a lightweight material, a pore forming agent and a binder which are adopted as raw materials to high-temperature calcinating, wherein the lightweight material adopts an inorganic material the true density of which is about 0.23 g / cm<3>. The method includes (1) a step of
raw material preparation, namely a step of inner core matching, outer shell matching and glue preparing, namely a step of mixing the clay, the lightweight material and the pore forming agent, mixing the clay and the pore forming agent, and mixing the binder and water, respectively, (2) a step of
granulation, namely a step of feeding the inner core matching material into a granulating
machine, granulating to obtain inner core granules, feeding the outer shell matching material into the granulating
machine, and granulating to obtain spherical granules, with the glue being sprayed at the same time of feeding of the outer shell matching material, (3) a step of
drying, namely a step of
drying the spherical granules to remove water, and (4) a step of calcinating, namely a step of calcinating the dried spherical granules to obtain the lightweight ceramsite
biological filter material.