Abstract: A filtration apparatus including a filtration module having an axially stacked plurality of filter membrane sheets with the module defining a stack of fluid flow chambers having multi-edged perimeters and disposed on opposite sides of and substantially coextensive with each membrane sheet. Also defined by the module are a plurality of feed passages communicating with alternating ones of the chambers adjacent first axially aligned edges thereof, a plurality of retentate passages communicating with the alternating chambers adjacent to second axially aligned edges thereof opposite to the first edges, and a plurality of filtrate passage means communicating with other ones of the chambers between the alternating ones thereof and with the filtrate passage means entering the other chambers adjacent to either the first or second aligned edges. Also included in the apparatus are a base frame and a pair of parallel plates supported by the frame and movable thereon relative to each other in directions normal thereto.