[Claim 1]
A separation membrane element comprising:
a water collection tube;
a separation membrane having a feed-side face and a permeate-side face;
a feed-side channel material; and
a permeate-side channel material,
wherein the separation membrane, the feed-side channel material and the permeate-side channel material are spirally wound around the water collection tube,
the feed-side channel material comprises a plurality of fibrous materials crossing each other,
the feed-side channel material has a thickness of 0.15 mm to 0.50 mm, and
in a case where an aqueous sodium chloride solution having a concentration of 200 ppm and an aqueous NaCl solution having a pH of 6.5 are used as feed water, and filtration is performed under conditions of an operation pressure of 0.41 MPa and a temperature of 25°C, the separation membrane has a value of A3/B (m2/sec2/MPa3) of 8.0 × 10-8 or more, in which A (m/sec/MPa) is a solution permeation coefficient and B (m/sec) is a solute permeation coefficient. [Claim 2]
The separation membrane element according to claim 1, wherein, in a case where an aqueous sodium chloride solution having a concentration of 200 ppm and an aqueous NaCl solution having a pH of 6.5 are used as feed water, and filtration is performed under conditions of an operation pressure of 0.41 MPa and a temperature of 25°C, a permeate amount is 1.5 m3/m2/day or more. [Claim 3]
The separation membrane element according to claim 1 or 2, wherein the feed-side channel material has an intersection density of 3 or less per 100 mm2. [Claim 4]
The separation membrane element according to claim 1 or 2, wherein the feed-side channel material has an intersection density of 15 to 210 per 100 mm2. [Claim 5]

The separation membrane element according to any one of claims 1 to 4, wherein a feed-side flow channel formed by the feed-side channel material is formed in a direction perpendicular to a longitudinal direction of the water collection tube. [Claim 6]
The separation membrane element according to any one of claims 1 to 5, wherein the permeate-side channel material is a sheet on which a plurality of projections are formed or a sheet on which a plurality of projections are fixed. [Claim 7]
The separation membrane element according to claim 6, wherein the projections are continuous in the direction perpendicular to the longitudinal direction of the water collection tube. [Claim 8]
The separation membrane element according to any one of claims 1 to 7, wherein a cross section of the permeate-side channel material forms a plurality of permeate-side flow channels, and a cross-sectional area ratio of the permeate-side channel material is 0.4 to 0.75. [Claim 9]
A method for operating a separation membrane element, the method comprising: producing fresh water in an amount of 60% or more based on an amount of water fed, using the separation membrane element according to any one of claims 1 to 8. [Claim 10]
A method for operating a separation membrane element, the method comprising: producing fresh water in an amount of 40% or less based on an amount of water fed, using the separation membrane element according to any one of claims 1 to 8.