Flat sheet (FS) membranes have planar configuration and are mainly rectangular, though other geometries exist for membrane modules designed to rotate.
The element may be referred to as a ‘sheet’, ‘cartridge’ or, most commonly, a ‘panel’. Most of the rectangular panels are (semi-)rigid, though some of the thinner products are flexible and are mounted on a rigid frame.
Rigid panels have a plastic backing plate to which the membrane’s edge is welded on both sides. Water flows from outside to inside the panel and the permeate collected either from the permeate outlet tube(s) or side/central manifold(s). Sludge is air-lifted up through the membrane channels by air bubbles provided from a coarse-bubble aerator placed underneath the module.
Modules (ie collections of elements) may be stacked to provide a double deck, with further stacking possible for a few products.
Flat sheet membranes are used almost exclusively for immersed MBRs for both industrial and municipal applications, where they are sometimes favoured for smaller installations on the basis of their operational simplicity.