Abstract: A membrane module (100) has an upper header.(108) and multiple lower headers (110). A bundle of membranes (24) potted in the upper header is sub-bundled into the lower headers. The membranes (24) may be arranged in the upper header into a number of generally parallel sheets or planes and arranged into a lower header (110) into a lesser number of sheets or planes. Spaces between the multiple lower headers (110) help gas bubbles rise into the module (100) or water containing solids drain from the module (100). The module (100) may be used in batch or continuous filtration processes. In one specific process, water flows downwards through the module (100) and air bubbles are provided from near the bottom of the module (100).