Substances that are larger than the pores in the membranes are fully removed. Substances that are smaller than the pores of the membranes are partially removed, depending on the construction of a refuse layer on the membrane. .

Micro filtration is pressure-dependent processes, which remove dissolved solids and other substances from water to a lesser extent than nano filtration and Reverse Osmosis.

Membranes with a pore size of 0.1 – 10 µm perform micro filtration. Microfiltration membranes remove all bacteria. Only part of the viral contamination is caught up in the process, even though viruses are smaller than the pores of a micro filtration membrane. This is because viruses can attach themselves to bacterial biofilm.