Flat sheet membranes are conceived to satisfy particular intended applications requiring different configurations. Single layered flat sheet membranes are widely used in laboratory and research practice where the quantities of feed solutions are limited. While the industrial applications require treatment of much larger volumes. So flat sheet membranes are assembled to offer higher surface contact. In particular, flat sheets are either pleated and placed in a tubular shell or assembled in so-called spiral wound modules. Both these approaches allow greater productivity with lower footprint.
Flat sheet membranes
As the name foretells, flat sheet membranes are the semi-permeable barriers fabricated in the form of sheets. To ensure enhanced permeability these membranes have an asymmetric structure across its thickness. The top layer (also known as skin layer) possesses pores of smallest size, while the size of pores in underlying layers increase progressively. The part under the skin layer is inert and acts as a mechanical support to insure the integrity of the flat sheet device which is subjected to high pressures of the feed stream.