Laboratory Membrane Filter Technique

The Membrane Filter (MF) Technique was introduced in the late 1950s as an alternative to the Most Probable Number (MPN) procedure for microbiological analysis of water samples. The MF Technique offers the advantage of isolating discrete colonies of bacteria, whereas the MPN procedure only indicates the presence or absence of an approximate number or organisms (indicated by turbidity in test tubes). 

This membrane filtration method was accepted by the U.S. EPA for microbiological testing of potable water in the 11th edition of Standard Methods for the Examination of Water and Wastewater. In the 1978 publication, Microbiological Methods for Monitoring the Environment, the U.S. EPA stated that the MF Technique is preferred for water testing because it permits analysis of larger samples in less time.

Advantages of the Membrane Filter Technique:

• Permits testing of large sample volumes. 

• Reduces preparation time as compared to many traditional methods. 

• Allows isolation and enumeration of discrete colonies of bacteria.  

• Provides presence or absence information within 24 hours. 

• Effective and acceptable technique. Used to monitor drinking water in government laboratories. Useful for bacterial monitoring in the pharmaceutical, cosmetics, electronics, and food and beverage industries. 

• Allows for removal of bacteriostatic or cidal agents that would not be removed in Pour Plate, Spread Plate, or MPN techniques.