A spiral cross-flow filter, comprising: an outer shell; a permeate tube having a blocked middle portion, wherein the permeate tube is coaxially-aligned within the outer shell and radially-offset therefrom, thereby forming an annular space between the outer shell and the permeate tube; and a pleated filter element located within the annular space between the outer shell and the permeate tube, the pleated filter element comprising a composite filter material comprising: a first layer of a membrane material adjacent the outer shell; and a second layer of a permeate spacer material adjacent the permeate tube, the pleats of the filter element defining a plurality of circumferentially spaced leaves; wherein the plurality of circumferentially spaced leaves wrap around the permeate tube in a uniform direction; characterized in that the permeate tube comprises: a hollow inlet portion comprising a first annular-shaped manifold formed by a perforated section of a cylindrical wall of the inlet portion, wherein the perforated section is radially-offset inwardly relative to an outer cylindrical surface of the blocked middle portion and an outer cylindrical surface of the inlet portion; and a hollow outlet portion comprising a second annular-shaped manifold formed by a perforated section of a cylindrical wall of the outer portion, wherein the perforated section is radially offset inwardly relative to an outer cylindrical surface of the blocked middle portion and an outer cylindrical surface of the outlet portion; wherein the filter is configured to direct fluid out of the permeate tube into the plurality of leaves and back into the permeate tube downstream of the blocked middle portion. an outer shell; a permeate tube having a blocked middle portion, wherein the permeate tube is coaxially-aligned within the outer shell and radially-offset therefrom, thereby forming an annular space between the outer shell and the permeate tube; and a pleated filter element located within the annular space between the outer shell and the permeate tube, the pleated filter element comprising a composite filter material comprising: a first layer of a membrane material adjacent the outer shell; and a second layer of a permeate spacer material adjacent the permeate tube, the pleats of the filter element defining a plurality of circumferentially spaced leaves; wherein the plurality of circumferentially spaced leaves wrap around the permeate tube in a uniform direction; a first layer of a membrane material adjacent the outer shell; and a second layer of a permeate spacer material adjacent the permeate tube, the pleats of the filter element defining a plurality of circumferentially spaced leaves; wherein the plurality of circumferentially spaced leaves wrap around the permeate tube in a uniform direction; characterized in that the permeate tube comprises: a hollow inlet portion comprising a first annular-shaped manifold formed by a perforated section of a cylindrical wall of the inlet portion, wherein the perforated section is radially-offset inwardly relative to an outer cylindrical surface of the blocked middle portion and an outer cylindrical surface of the inlet portion; and a hollow outlet portion comprising a second annular-shaped manifold formed by a perforated section of a cylindrical wall of the outer portion, wherein the perforated section is radially offset inwardly relative to an outer cylindrical surface of the blocked middle portion and an outer cylindrical surface of the outlet portion; wherein the filter is configured to direct fluid out of the permeate tube into the plurality of leaves and back into the permeate tube downstream of the blocked middle portion. a hollow inlet portion comprising a first annular-shaped manifold formed by a perforated section of a cylindrical wall of the inlet portion, wherein the perforated section is radially-offset inwardly relative to an outer cylindrical surface of the blocked middle portion and an outer cylindrical surface of the inlet portion; and a hollow outlet portion comprising a second annular-shaped manifold formed by a perforated section of a cylindrical wall of the outer portion, wherein the perforated section is radially offset inwardly relative to an outer cylindrical surface of the blocked middle portion and an outer cylindrical surface of the outlet portion; wherein the filter is configured to direct fluid out of the permeate tube into the plurality of leaves and back into the permeate tube downstream of the blocked middle portion.