Abstract: The present invention relates to a dialysate regeneration method that reduces a urea concentration of a urea-containing aqueous solution, the method including a reverse osmosis process of obtaining, from the urea-containing aqueous solution, a concentrate having a higher urea concentration and a permeate having a lower urea concentration by using a reverse osmosis membrane element at an operating pressure of 0.5 MPa or more and 2.0 MPa or less, in which the urea concentration of the urea-containing aqueous solution is 0.5 g/L or more, the reverse osmosis membrane element includes a reverse osmosis membrane, and the reverse osmosis membrane has a pore diameter of 7.0 ? or less as measured by a positron annihilation lifetime measurement method.

Abstract: The present invention provides a filter which, even when raw water is subjected to high-speed treatment, enables achieving a high solute rejection ratio and a long solute filtration life and which exhibits a low water flow resistance. The present invention pertains to a filter obtained by laminating woven fabrics or knitted fabrics, the filter being characterized in that: said woven fabrics or knitted fabrics comprise a fiber capable of adsorbing components dissolved in liquid: said fiber has a diameter of 100-600 ?m; the woven fabrics or knitted fabrics have a porosity of 15-70%; and variation in area porosity in the thickness direction of the laminate is 15% or less.

Abstract: The present invention provides a filter which, even when raw water is subjected to high-speed treatment, enables achieving a high solute rejection ratio and a long solute filtration life and which exhibits a low water flow resistance. The present invention pertains to a filter obtained by laminating woven fabrics or knitted fabrics, the filter being characterized in that: said woven fabrics or knitted fabrics comprise a fiber capable of adsorbing components dissolved in liquid: said fiber has a diameter of 100-600 ?m; the woven fabrics or knitted fabrics have a porosity of 15-70%; and variation in area porosity in the thickness direction of the laminate is 15% or less.

Abstract: The present invention provides a composite semipermeable membrane which has practicable water permeability and high acid resistance. The present invention relates to a composite semipermeable membrane including a supporting membrane and a separation functional layer disposed on the supporting membrane, in which the separation functional layer includes a crosslinked aromatic polyamide and has a protuberance structure including protrusions and recesses, a proportion in number of protrusions each having a height of 100 nm or larger is 80% or larger in the protrusions of the protuberance structure, and the separation functional layer contains amino groups, carboxy groups, and amide groups and satisfies y/x?0.81, in which x is the molar ratio of carboxy groups/amide groups and y is the molar ratio of amino groups/amide groups.