What is the formula for manually calculating the trans membrane pressure in micro-filtration?

The transmembrane pressure (TMP) in microfiltration can be calculated using the formula:

[ \text{TMP} = \frac{(P_{\text{feed}} + P_{\text{permeate}})}{2} - P_{\text{retentate}} ]

Where ( P_{\text{feed}} ) is the pressure of the feed solution, ( P_{\text{permeate}} ) is the pressure on the permeate side, and ( P_{\text{retentate}} ) is the pressure in the retentate stream. Typically, if the permeate is at atmospheric pressure, it can be simplified to:

[ \text{TMP} = P_{\text{feed}} - P_{\text{permeate}} ]