Multimedia filters, as their name suggests, use 2 or 3 media filters.
The most commonly used substances for multimedia filtration are anthracite, sand and garnet. Startification in the multimedia vessel is such that anthracite is positioned at the top, then comes a layer of sand and lastly a layer of garnet.
The difference in densites allows the particles to resettle into their former positions after the backwashing is complete.
Multimedia filters can remove particles as small as 10-25 microns.