There are quite a few factors that could promote the masking of a filter by the feed stream. • The feed stream itself creates implication, meaning what product is filtered, for example Methylcellulose is known to foul filters rapidly • The type of foulant in the feed stream, the composition and behavior of the foulant, for example can the foulant create a collapsible, dense filter cake on top of the membrane • The filtration process conditions, like differential pressure can have an effect on masking as higher differential pressure could compact the filter cake. • The membrane constitution may have an effect on masking, as some of the membrane materials are highly adsorptive and foul faster than others. • The filter membrane combination can have an effect, as a heterogenous membrane combination with 0.45/0.2 micron layers, may have an advantage to protect the 0.2 micron membrane.
These are just a few factors, which require to be observed. However, all of these factors are tested during the filterability trials run to size the filtration system. The filterability trials will allow a judgment of the masking potential due to the fluid stream and filtration conditions.