Immersible rotary disc filtration device

Abstract

Rotary disc filtration devices and filtration processes using those devices are disclosed. The devices have one or more fluid filtration gaps into which fluid to be filtered into permeate and retentate is placed. Each fluid filtration gap is defined by a disc and a filter, one of which rotates with respect to the other. The filter is carried on a filter member. The discs and interleaved filter members may be suspended from the top of the device, the top may rest on a vessel containing the fluid to be filtered, the discs may be attached to a single shaft for rotation, and the filter members may be suspended from a sleeve around the shaft, which sleeve keeps the filters centered with respect to the discs. Removal of the device's top removes the discs and filter members together, facilitating maintenance. Each filter member may have a peripheral lip and the lips of adjacent filter members may be sufficiently close to one another to substantially restrict the flow of retentate out of the fluid filtration gap. Retentate flowing out of each fluid filtration gap may be directed into the vessel to counteract the tendency of the fluid in the vessel to rotate in the same direction as the discs are rotated, or the retentate may be recycled directly to the fluid filtration gaps. The liquid level in the vessel may be held constant using a dual-pipe system and three-head peristaltic pump.