FILTRATION DEVICE, BALLAST WATER TREATMENT METHOD, AND BALLAST WATER TREATMENT DEVICE USING SAID FILTRATION DEVICE

摘要

A filtering device includes, as a filter membrane, a pleated filter formed of a filter base having folds so as to repeat peak portions and valley portions, the pleated filter having a shape of a cylinder whose axial direction is a ridge line direction of the folds. In the filtering device, the pleated filter is rotatable about a cylindrical axis of the shape of the cylinder. The filtering device includes a nozzle that is provided so as to face an outer circumferential surface of the pleated filter and that ejects a liquid toward the outer circumferential surface. The relationships 4p ‰¤ W, and h/5 ‰¤ L ‰¤ h/2 are satisfied, where p represents a spacing between pleats and h represents a length in the ridge line direction, the length being effective for filtration, in the folds on the outer circumferential side of the pleated filter, and W represents an opening width in a direction perpendicular to the ridge line direction and L represents an opening length in the ridge line direction in an opening portion of the nozzle.