The degree of removal of solids or contaminants depends on the type of filtration chosen. The different stages of filtration are microfiltration, ultrafiltration and nanofiltration. Some schools of thought include reverse osmosis in the filtration types, we will not include it in this article since the principle of separation by reverse osmosis is different.
Generally speaking, what is needed for filtration to work is a contaminated fluid, a pressure force (usually a pump) and a filter.
Microfiltration filters have pores with a size of 0.1 micron. Thanks to these pores, microfiltration membranes allow the extraction of bacteria, blood cells and anything larger than 0.1 micron.
Regarding ultrafiltration, the pores found on the membranes have dimensions of 0.01 micron. These pores allow the extraction of all the contaminants that can be extracted by the microfiltration membranes. In addition, ultrafiltration allows the extraction of dissolved metal ions, colloidal matter, viruses, and proteins from the water.
Nanofiltration is the type of filtration with the smallest filtration pores. With pores as small as 0.001 microns, nanofiltration membranes allow the extraction of aqueous salts, some pesticides, and some herbicides.
It is important to note that using a membrane with pores too small for the contaminants to be extracted is not advantageous since the membranes will tend to block quickly. Therefore, when nanofiltration is required, prefiltration steps are often added. In this way, the contaminants are extracted in a gradual way, and this allows optimizing the life span, the efficiency and the profitability of the membranes.