ABSTRACT
Presented with the filtration results in Figure 6.4, of how a single filter paper performs under different conditions, how then do we come up with a performance rating? Obviously we cannot, since performance depends on the conditions of filtration. The only objective way to rate the filter paper is to address five properties (previously mentioned in Chapter 8):
• Material(s) of construction • Porosity • Permeability • Thickness • Whether one face is more porous than the other
The same is true of microporous membranes, Producers of microporous membranes, in essence, address these five points more than producers of paper or other nonwoven fibrous media. Yet users of membrane filters and governmental agencies want assurances that, in spite of variations in filtration conditions, a certain size microbe will indeed be stopped with great efficiency. This demand leads to the simple reasoning: build the membrane with pores smaller than the size of the microbes of interest. Then, these questions arise: What filtration efficiency is high enough? and What size microbes are of interest?
