ABSOLUTE: When referring to filters is used in reference to the micron rating indicating that all particles larger than a specified size will be trapped within or on the filter and will not pass through (typically 99.98%) 

ABSORPTION: The process of taking up a substance into the physical structure of a liquid or solid by physical or chemical action, but without chemical reaction 

ADSORPTION: The process by which molecules, colloids or particles adhere to the surfaces by physical action but without chemical reaction

BAR: Designation of pressure units. 1 bar = 14.5 psi

BUBBLE POINT: The differential gas pressure that when applied to a filter element submerged in the test fluid causes the first steady emission of gas (air) from the filter element being tested. This is a means of verifying the micrometer rating of the test element

CHANNELLING: Often associated with wound-string or granular carbon filters, is the phenomenon of liquid forcing a channel through the filter, thus meaning that the filtration does not occur

CHLORINE: Chemical used for its qualities as a bleaching, oxidising or disinfecting agent in water purification

EXTRACTABLES: Water-soluble matter, which can be eluted from a filter into the effluent

FDA CRITERIA: The Food and Drugs Administration issues criteria for the suitability of a material for use in human food or drugs production

FEED/FEEDWATER: The input solution to a treatment/purification system, including the raw water supply prior to any treatment

HEAVY METALS: Metals having a high density or specific gravity of approximately 5.0 or higher. The elemental weight is also high. A generic term used to describe contaminants such as cadmium, lead and mercury. In low concentrations are toxic to humans

HYDROPHILIC: Water-accepting

HYDROPHOBIC: Water-repelling

INTEGRITY TESTED: If a filter has been integrity tested then it has been checked after manufacture to ensure that it will perform to specification with regard to particulate and/or bacterial removal

LOG REDUCTION: A mathematical term for a tenfold (one decimal) or 90% reduction in microbes

LPH: Litres per hour

MG/L: Milligrams of an element per litre of water, approximately equal to ppm

MICRON: A metric unit of measurement equivalent to 10-6 metres, 10-4 centimeters. Symbol is µ

NOMINAL: In terms of filtration, a nominal rating describes the ability of the filter media to retain a percentage of particulate at the rated pore size

PORE: An opening in a membrane or filter matrix

POROUS: The ability of certain substances to pass fluids due to an open physical structure

PPM: Parts per million, commonly considered equivalent to milligrams per litre (mg/L 

PRESSURE DROP: the decrease in pressure from one point in a pipe or tube to another point downstream

RESINS (ION EXCHANGE): Specially manufactured polymer beads used in the ion exchange process to remove dissolved salts from water

REVERSE OSMOSIS: The separation of one component of a solution from another component by flowing the feed stream under pressure across a semipermeable membrane. RO concentrates ionized salts, colloids, and organics down to 150 molecular weight in the concentrate stream and provides a purified stream of water

SHARP CUT-OFF: A feature of a filter, which means that it will remove particles of a certain size, but will leave the vast majority of smaller particles in the effluent

TDS: Total Dissolved Solids

TOC: Total Organic Carbon – the amount of carbon bound in organic compounds in a water sample as determined by a standard laboratory test. The CO2 is measured when a water sample is atomised in a combustion chamber

VOC: Volatile Organic Compound – synthetic organic compounds that easily volatise. Many are suspected carcinogens