| CPC B01D 63/10 (2013.01) [B01D 69/02 (2013.01); C02F 1/44 (2013.01); B01D 65/08 (2013.01); B01D 2325/24 (2013.01)] | 10 Claims |

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1. A separation membrane element comprising at least a water collecting pipe, separation membranes, a supply-side channel member, and a permeation-side channel member, wherein:
the supply-side channel member is interposed between two surfaces of the separation membranes to form a supply-side channel;
the supply-side channel member has a net shape in which plural fibrous rows X comprising fibrous objects A and arranged in one direction and plural fibrous rows Y comprising fibrous objects B and arranged in a different direction than the fibrous rows X cross each other sterically to form intersections;
at least one of the fibrous objects A and the fibrous objects B have a large diameter portion and a small diameter portion along a longitudinal direction;
in a longitudinal cross section including an arbitrary fibrous row and taken along a longitudinal direction of the arbitrary fibrous row, at least one of the fibrous objects A and the fibrous objects B comprise a thread that is thinner at a central portion located between intersection portions of the fibrous rows X and the fibrous rows Y than at the large diameter portion;
a supply-side channel area ratio is in a range of 45% to 65% defined by A1/A2×100 where A1 is the average area of the entire space within the thickness of the intersection portions in a longitudinal cross section taken along a longitudinal direction of a fibrous row, and A2 is the average area within the thickness of intersection portions between two adjacent intersection portions in the longitudinal cross section; and
when a surface of the supply-side channel member is observed from a thickness direction, a fiber between an arbitrary intersection and an adjacent intersection is a tapered fiber whose diameter increases like a taper in a direction from one intersection to the other intersection.
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