Bacteria Retention and Bubble Point

RETENTION CHARACTERISTICS Bacteria Retention and Bubble Point 

In 1974-1976, Wallhausser wrote several controversial papers,10 11 showing that MF membranes may pass microbes at high challenge levels (see Table 2.2). Previously, membrane manufacturers had insisted that their membranes were absolute and many were skeptical of Wallhauser s data. 

Shortly thereafter, other data began to appear in the literature confirming Wallhausser s findings. Eventually the manufacturers collected their own data which showed that no membrane is truly absolute, for example, Table 2.312 shows that filtration time as well as challenge level is a factor. 

Pore size 0.2/tin (flow-rate 100 ml water in 22 sec) and 0.45 /tm (flow-rate 100 ml water in 13 sec). 

The manufacturers early recognized the discrepancy between theoretical and experimental bubble points. They introduced an experimental constant into equation (1) called a shape-factor which supposedly took into account the fact that tortuous pores are not cylindrical in shape. However, a shape factor of 0.25 cannot be justified from the capillary rise equations, as any good textbook on surface chemistry will attest. Indeed, for noncircular pores, equation (1) is adjusted to  

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