This method of sterilization comes under the mechanical method of sterilization, whereby the microorganisms are physically removed by adsorption or by sieving mechanism onto the filter medium. Filtration sterilization can be effectively applied on heat-sensitive solutions. Filters that are available commercially come with various pore sizes. They are made up of thin plastic membranes of cellulosic esters with millions of pores per square inch. The pore sizes of these filters range from 0.025 μm to 14 μm. Other than the pore size, the important factors that influence the pore size are electrical charge on the filter and that of the microorganism, pH of the solution, temperature and the pressure of vacuum applied to the system.

The advantages of filtration sterilization are as follows:

1. It is inexpensive.
2. Speed in the filtration of small quantities of solution.
3. Thermolabile materials can be sterilized.
4. Complete removal of living and dead microorganisms and other particulate matter from the solution.

The following are the disadvantages:

1. Filters are fragile.
2. Filtration of large volume of liquids is time consuming.