How does filtration separate suspended solids from liquids or gases?

Filtration is a process that separates solid particles from a liquid or gaseous fluid by passing the mixture through a filter medium. This medium acts as a barrier that retains the solids while allowing the fluid to flow through.1

The separation relies on four basic requirements: a filter medium, a fluid containing suspended solids, a driving force (such as a pressure difference or vacuum), and a mechanical device to hold the assembly.12

Filter media generally fall into two categories:
* Thin barriers: Materials like filter paper or cloth where the pores are smaller than the particles being removed.3
* Thick barriers: Materials like sand or porous ceramics where particles are trapped within the tortuous path of the medium, even if the pores are larger than the particles themselves.3

To prevent clogging—or "blinding"—when dealing with gelatinous or compressible solids, technicians may use filter aids to maintain permeability. Ultimately, the process yields either a clarified filtrate, a solid filter cake, or both.341