Methods and apparatus for removing solids from a membrane module

A method of cleaning a plurality of membrane filtration modules comprising:

• performing a filtration operation with the plurality of filtration modules submersed in liquid in a vessel and having lower headers connected to a single open-ended plenum chamber including a as supply manifold disposed between the plurality of filtration modules and configured to direct as downward into the single open-ended plenum chamber between the plurality of filtration modules, each of the plurality of filtration modules including one or more membranes extending longitudinally between vertically spaced upper headers and the lower headers into which the ends of the membranes are potted, the lower headers having one or more openings, the single open-ended plenum chamber having an open lower end spaced from a port in the base of the vessel without any intervening structures therebetween, the membranes having permeable walls which are subjected to a filtration operation wherein the liquid is applied to one side of the membrane walls and filtrate is withdrawn from an other side of the membrane walls, and wherein the liquid is flowed through the one or more openings in the lower headers and the port in the base of the vessel;
• suspending the filtration operation;
• performing a cleaning process on the membrane walls to dislodge contaminant matter therefrom into liquid surrounding the membranes;
• removing the dislodged contaminant matter from the plurality of filtration modules in a direction substantially parallel to the longitudinally extending membranes, the dislodged contaminant matter flowing substantially parallel to the longitudinally extending membranes while exiting the plurality of filtration modules through the openings in the lower headers and proceeding through the open lower end of the single open-ended plenum chamber and the port in the base of the vessel, the dislodged contaminant matter not flowing perpendicular to the membranes and not exiting through side ports of the plurality of filtration modules or vessel during the removal from the plurality of filtration modules such that the membranes do not act as string filters;
• and
• recommencing the filtration operation.