PURPOSE: To enable the execution of the assembly operation of the filter medium packed bed in a short period of time and to facilitate the operation for maintenance and management by constituting all of the assembly of the filter medium packed bed in such a manner that water permeable members and filter media are built into the filter medium packed bed by utilizing guide pipes from apertures at top ends.
CONSTITUTION: The structure of the filter medium packed bed of the sewage septic tank is constituted by erecting the plural guide pipes 1 in the filter medium packed bed, passing the planar water permeable members 2 having the area approximately equal to the inside area of the filter medium packed bed and having holes for insertion of the guide pipes into the guide pipes 1, then fixing the water permeable members 2 as to hold these members through pipes 4 for fixing and charging the filter media 5 onto the water permeable members 2. The operations to pass the water permeable members 2 and the pipes 4 for fixing into the guide pipes 1, to drop these pipes onto the filter medium packed parts and to charge the filter media 5 are repeated and finally, the water permeable members 2 are passed to close the filter medium packed parts in the case of formation of the plural filter medium packed parts. The filter medium packed parts of the single layer or double layers are thus constituted.
KATAGAI NOBUYOSHI
ONUMA MASAYA
