DOWN-FLOW FILTER TANK BODY, METHOD FOR MANUFACTURING DOWN-FLOW FILTER TANK BODY, AND METHOD FOR MODIFYING DOWN-FLOW FILTER TANK BODY

PROBLEM TO BE SOLVED: To provide a novel down-flow filter tank body capable of preventing the blowup of the fragments at a back washing time properly, even if a water collecting apparatus is broken, a method for the down-flow filter tank, and a method for modifying the down-flow filter tank.SOLUTION: A down-flow filter tank 1 comprises: a down-flow filter tank body 2; a water collecting apparatus 3 dispersed on the bottom of the down-flow filter tank body 2; and a filter layer 4 composed of granules deposited on the water collecting apparatus 3. Treatment water is filtered by passing it from the upper side to the lower side of the filter layer 4. A water-permeable sheet 5 is laid along the boundary between the upper face of the water collecting apparatus 3 and the filter layer 4. 【課題】本発明は、集水装置に破損が生じても、逆洗作業時における前記集水装置の破片の吹き上がりを好適に防止し得る新規な下向流濾過槽、下向流濾過槽の製造方法、及び、下向流濾過槽の改修方法を提供することを目的とする。【解決手段】濾過槽本体２と、前記濾過槽本体２の底部に設置された集水装置３と、前記集水装置３上に堆積させた粒状物からなる濾層４と、を具備してなり、被処理水を、前記濾層４の上側から下側に向かって通水させることによって、前記被処理水を濾過処理するための下向流濾過槽１において、前記集水装置３の上面と、前記濾層４との境界に沿って、通水性シート５を敷設する。【選択図】図１