Abstract: A flat sheet membrane module is provided and includes a pair of laterally spaced membrane compartments formed therein for receiving and holding two sets of flat sheet membranes. A utility compartment is disposed between the membrane compartments and includes an air conduit for directing air downwardly through the module to air dispersers forming a part of the module or to a separate lower disposed module. Optionally, a permeate conduit may be provided in the utility compartment for channeling permeate from a lower disposed module. A support structure is disposed in each membrane compartment for receiving and holding a set of flat sheet membranes. The support structure includes a pair of plates that sandwich a set of flat sheet membranes together such that the flat sheet membranes of the set are disposed in a side-by-side relationship between the two end plates.