To enhance the water quality improving efficiency of a biological filter bed.
A container 2 having a living waste water finflow port 4 and an outflow port 2 is opened upwardly and the width 9 of the container 2 is formed so as to become small from the upper part thereof to the lower part thereof and a plurality of cylindrical biological filter beds 17 formed from a fibrous material are arranged in the container 2 in a tiered state and the arranging density of these biological filter beds 7 is made gradually small from an upper tier to a lower tier and the bottom 11 of the container 2 is inclined low from one end thereof to the other end thereof and a discharge pipe 21 discharging a deposit and a drain valve 22 are provided to the bottom 1 on the other end side.
MIZOGUCHI TADAAKI
KAJIYAMA YOSUKE
FUJITA KAZUNORI
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