Fouling

the process in which undesirable foreign matter accumulates in a bed of filter media or ion exchanger, clogging pores and coating surfaces and thus inhibiting or retarding the proper operation of the bed.

Definitioner

Media: the selected materials in a filter that form the barrier to the passage of certain suspended solids or dissolved molecules.
Ion Exchanger: a permanent, insoluble material which contains ions that will exchange reversibly with other ions in a surrounding solution. Both cation and anion exchangers are used in water conditioning.
Ion: an atom, or group of atoms which function as a unit, and has a positive or negative electrical charge, due to the gain or loss of of one or more electrons.
Filter: specifically, a device or system for the removal of solid particles(suspended solids); in general, includes mechanical, adsorptive, oxidizing, and neutralizing filters.
Bed: the ion exchange or filter media in a column or other tank or operational vessel.