Membrane module and a method for its manufacture

A fluid purifier membrane module, comprising:

• a pair of flexible web portions of membrane material disposed face to face, with a layer of a first spacer sandwiched therebetween, said web portions being permetrically joined and also joined to one another along a plurality of longitudinally spaced transversally extending joints, thereby providing a plurality of membrane units disposed in a first line, each having a respective closed cavity enclosing a respective increment of said first spacer between increments of said pair of web portions;
• said line of membrane units being folded back and forth upon itself at respective folds so as to provide a stack of said membrane units;
• a second spacer having respective increments thereof disposed within said stack between each said fold in said stack;
• said flexible web portions being locally joined throughout said stack along a second line extending thicknesswise through said stack and said units so as to provide a passageway extending along said second line, whereby said first and second spacers form mutually alternating spacers in said stack for respectively receiving unpurified and purified portions of a fluid to be purified in a purifier using said membrane module.