A Word About


Filtration is the process of passing a material through a media to remove something from it. In biopharmaceutical manufacturing, both gases and liquids are filtered, but the process of filtration usually refers to liquid filtration. This can be done in one of two ways: direct flow filtration and cross-flow filtration.

Direct Flow Filtration

Direct flow filtration (aka. "dead end filtration") refers to any filtration operation in which the feed liquid is passed straight through the filtration media. Impurities are retained in the media. In prinicple, this is similar to removing sand from water by passing it through a cloth, except that in biopharmaceutical manufacturing, the particulates are often the cells and cell debris from the bioreactor. The two basic types of filter media are:

Cross Flow Filtration

cross-flow filtration diagram
Diagram of a typical cross-flow filtration process.

Cross Flow filtration is an operation in which the major flow of feed liquid runs across (not through) the membrane, with a relatively small fraction permeating through the membrane on each pass. What this does is to scrub the membrane with the liquid flowing across its surface to avoid the plugging of pores in the membrane.


Page updated 7/6/17


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