Explain Membrane Filtration Technique?

Another method used for determining the bacterial number is the filtration technique. The margain figure illustrates the membrane filter assembly. This technique can be used to know the microbial count in liquid samples containing relatively very small quantity of microbes. Both viable and total counts can be obtained. A known volume of the sample is passed through a special membrane filter having pores small enough to trap bacteria and other microbes. For viable count, the membrane filter is placed over the agar medium surface or over a pad soaked in liquid medium and incubated for 24 hours. Each cell trapped form a separate colony. The numbers of colonies, then formed, indicate the number of microbes present in the volume of sample, which is drawn through a membrane filter. The colonies are counted by hand or by using quebec colony counter.