The graphic illustrates the flow
paths in a continuous, feed and bleed membrane filtration plant configuration
in spiral-wound membrane format. The feed product typically enters into a feed
balance tank. The product is picked up by a feed pump and transferred from the
feed balance tank into the first recirculation stage. The stage recirculation
pump is responsible for providing adequate flow and pressure conditions for
optimal membrane performance. Product is pumped through the vessel, or through
multiple vessels in parallel, and across the membrane surface. The permeate is
withdrawn from the vessel while simultaneously retentate exits the opposite end
of the vessel in a more concentrated state. The retentate flow is split between
that which is needed to satisfy the stage recirculation requirements while the
remainder progresses forward to the next stage in series. This step-wise
concentration progresses throughout a number of stages in series until the
final retentate is eventually withdrawn from the plant at the desired
concentration and composition.