Abstract: A method and apparatus for uniformly distributing fluid across the entire cross section of a reaction medium and for compensating for volumetric changes in the reaction medium utilized a resilient membrane which cooperates with an adjacent fluid manifold distribution chamber. The combined operation of the manifold distribution chamber with the resilient membrane provides a low resistance to fluid flow in a direction transverse to fluid flow through the reaction medium and a higher resistance to fluid flow across the membrane in the direction of fluid flow through the reaction medium. In this way, fluid is evenly distributed across the cross section of the reaction medium prior to entering the reaction medium and after leaving the reaction medium. The resilient membranes have reserve expansion capabilities, when hydrated, to accommodate expansion in the reaction medium. The resilient membranes are also sufficiently resilient to accommodate expansion of the reaction medium when necessary.