Abstract: A novel spiral membrane arrangement is disclosed comprising opposing elongate filtration membrane units, spiraled about a base axis and separated by a novel lattice separator having spaced apart elongate primary laths which form fluid passageways, bridged by cross laths arranged to form a plurality of fluid shears spaced along the passageways which divide, deflect and/or disrupt gross fluid flow through the passageway, directing fluid against the membrane surface and creating a self cleaning functionality which improves the efficiency and the life of the life of the membrane arrangement.