Patent ID: 8114293

Claim:
A process for operating a water treatment plant comprising the steps of: (a) providing one or more process tanks containing water to be treated, (b) providing two or more trains of cassettes of membrane modules, each of the two or more trains being located in a separate membrane tank, (c) during a first period of time, operating each of the two or more trains in parallel, wherein the membrane tanks housing each of the two or more trains receive water in parallel from the one or more process tanks, the two or more trains are operated to remove permeate from the received water and mixed liquor is transferred from the membrane tanks housing each of the two or more trains to the one or more process tanks, and (d) during a second period of time, selecting one of the two or more trains, transferring sludge from the membrane tank housing a non-selected train to the membrane tank housing the selected train, and operating the selected train to thicken the transferred sludge, while the membrane tank or membrane tanks housing the non-selected train or trains continue to receive water from the one or more process tanks and the non-selected train or trains are operated to remove permeate from the received water and mixed liquor continues to be transferred from the membrane tank housing the non-selected train to the one or more process tanks.