How does filtration separate suspended solid particles from a liquid?

Filtration is a process used to separate suspended solid particles from a fluid (liquid or gas) by passing the mixture through a filter medium. This medium acts as a barrier that retains the solid particles while allowing the fluid to pass through.1

The separation relies on four basic requirements:
* Filter medium: A material, such as filter paper, cloth, or a thick bed of sand, that provides the barrier.12
* Suspended solids: The mixture containing the particles to be removed.1
* Driving force: A force, such as gravity, pressure, or vacuum, is necessary to push the fluid through the medium.13
* Mechanical device: The filter apparatus that holds the medium and contains the fluid.1

In thin media, particles are trapped because the pores are smaller than the particle size. In thick media, such as sand beds, particles are captured within the tortuous paths of the filter bed. If the solids are gelatinous or compressible, they may block the pores, a condition known as blinding; in such cases, filter aids may be added to maintain permeability.24