Filtration is the process of separating solids or undesirable fluids from the primary fluids by running the fluid through a medium through which only the primary fluid can pass. Filtration is a widely used operation in industrial plants.

Solids can be removed on the basis of size. This is accomplished by utilizing a medium with holes only large enough for allowable sized solids to flow through. Removing undesirable fluids from a fluid stream is usually accomplished through a process called coalescing. Coalescers are used to filter out fluid from gas streams or liquid streams.

Process filtration includes filters of the following type; bag, cartridge, clarifiers, cloth, coalescers, cyclones, leaf, membrane, sand, and sintered metal.