ABSOLUTE BARRIER: A filtration or separation technology that completely blocks a component(s) of a fluid from passing through. Ultrafiltration membranes, for instance, are an absolute barrier to bacteria and viruses.

BACKFLUSH: A type of cleaning procedure in filtration systems whereby fluid is pushed through the membrane in the opposite direction from usual process flow direction, helping to loosen accumulated particulates.

DEAD-END FILTRATION: A filtration process where all the feed is forced, either with pressure or vacuum, through the filter. Accumulated solids are deposited on the filter and all the feed is converted to permeate or filtrate during production.

FLUX: Flow rate through a membrane system per unit of membrane area, often measured in gallons of liquid per square foot of filter per day (GFD).

MEMBRANE: A semi-permeable material used in mechanical or osmotic filtration and separation, composed of a solid media with specific sized pores (see: PORES) designed to allow fluid to pass through unimpeded while solids are excluded.

MICROFILTRATION: Filtration process that allows some microorganisms and suspended solids to be removed from the process fluid.

NANOFILTRATION: Filtration process that allows bacteria, viruses, certain multivalent ions and suspended solids to be removed from the process fluid.

PARTICULATE: Small, often microscopic, solid particles suspended in process fluid.

PERMEATE: The filtered fluid allowed to flow through a membrane.

PORES: Holes in a membrane filter that allow the desired fluid to pass through while blocking all other media.

REJECTION: The exclusion of undesirable solids by a filter. Bacteria and viruses, for example, are rejected by drinking water filtration membranes.

REVERSE OSMOSIS: A filtration method typically associated with water desalination using the reversal of osmotic pressure in order to drive water away from dissolved material.

SPIRAL MEMBRANE: Flat sheet membranes that are wound around a hollow permeate tube to form a spiral.

TUBULAR MEMBRANE: Membranes in a tube form with the membrane casted on the inside diameter that are used for micro- and ultrafiltration.

ULTRAFILTRATION: Filtration process that allows bacteria, viruses, macromolecules and suspended solids to be removed from the process fluid.

Source: Koch Membrane Systems (KMS), a manufacturer of membrane filtration systems (www.kochmembrane.com).