Abstract: A membrane module is made from at least one pair of spaced membrane sheets that are interposed between spaced porous material sheets and all of the layers of sheets are in turn spirally wound around an axially positioned hollow mandrel that has at least one internal flow blocking means therein and side-wall openings connective to an internal portion of one of said porous sheets such that a first fluid flow can pass outwardly from a portion of the mandrel into a portion of the connecting porous layer and into the envelope resulting from the encompassing membranes and then back into another portion of the mandrel such that at least one out-to-in flow will be made through the membrane envelope, while a second fluid stream is passed through the next adjacent porous material layers to carry the fluid which has permeated through the membranes.