| 摘要 |
PROBLEM TO BE SOLVED: To provide a sewage septic tank equipped with a biological filter tank packed with a floatable filter material and constituted so that the uppermost water passing plate of the biological filter tank is certainly fixed and the replacing work of the floatable filter material, support or the like in the biological filter tank can be easily performed. SOLUTION: In a sewage septic tank equipped with a biological filter tank packed with a filterable filter material with a specific gravity of 1 or less, a loop-shaped inhibiting member 20 is arranged along the surface peripheral edge part of the water passing plate 19 positioned at the uppermost part of the biological filter tank and held by the water passing plate 19 and the projections 25 provided to the inner wall of the outer contour 11 of the sewage septic tank to suppress the flotation of the water passing plate 19. The loop- shaped inhibiting member 20 comprises almost horizontal U-shape hollow cylindrical bodies divided into two parts and the opening part of one cylindrical body is inserted into the opening part of the other cylindrical body 21 and the inhibiting member 20 is made stretchable and the diameter of the inhibiting member can be adjusted so as to become than the opening part of the sewage septic tank.
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