This invention relates to a manifold system for a plurality of liquid filtration segments wherein a feed manifold is positioned to promote efficient liquid flow through the system. More particularly, this invention relates to a manifold system including a feed manifold positioned at an intermediate position within a manifold system of a plurality of stacked manifold segments.
Prior to the present invention, liquids, primarily aqueous liquids have been filtered by tangential flow filtration modules wherein a plurality of filters are stacked between two manifolds, one at the bottom of the stack and one at the top of the stack. The filtration module stack comprises a collection of one or more filtration modules and associated intermodule gaskets. The filters are separated by appropriate screens and liquid impervious layers to permit liquid flow, as well as filtrate and retentate flow into and from the stack. In addition, flow holes are provided through the layers within the stack. The holes are sealed appropriately to prevent admixture of filtrate with incoming liquid or retentate. The manifolds in each segment are designed so that the filtrate is removed from both the top and bottom manifolds while incoming liquid is introduced into one manifold and retentate is removed from the second manifold. This manifold arrangement necessitates fittings to both manifolds in order to supply and remove liquid to and from the stacks. This is undesirable since additional manipulative steps for removing and connecting the fittings are required when it is desirable to replace the filtration elements forming the stack. In addition, the use of two manifolds to remove filtrate from the stack undesirably increases the filtrate volume retained within the stack. Furthermore, the requirement of two manifolds is undesirably expensive.
It has been proposed in U.S. Pat. No. 4,849,102 to provide a manifold for a plurality of filtration modules. However, this manifold arrangement is limited since only two filtration modules can be accommodated while avoiding the need for conduits external the manifold. That is, when more than two filtration modules are utilized, external connecting conduits are required.
The manifold system disclosed in U.S. patent application Ser. No. 650,251, filed Feb. 4, 1991 comprises a manifold for a plurality of tangential flow filtration modules which utilizes only one manifold and which accommodates any number of a plurality of filtration modules without the need for conduits external of the manifold. This arrangement reduces the number of sealed fittings and reduces the required apparatus volume for processing a given volume of liquid as compared to the prior art systems. In this manifold system, the feed is introduced at one end of the stack so that the size of the feed is limited by and must be compatible with the size of the fixed liquid flow path within the manifold.