INVERSE TUBULAR FILTER Russian patent published in 1997 - IPC

FIELD: water purification. SUBSTANCE: invention's objective is increasing efficiency of filtration of liquid when utilizing reverse tubular filter. The problem is solved with that, in reverse tubular filter containing ascending tube with radial openings and two-layer filtration coating wherein porosity and average pore size are greater than those values in inner layer, additional third large-pore layer is placed between surface of ascending tube and small-pore layer, its thickness being not less than 0.25 and thickness of small-pore coating not larger than 0.2 of that of the entire filtration coating. Filter may be utilized for biological purification of water. EFFECT: increased filtration capability. 2 dwg