acid – A substance which releases hydrogen ions when dissolved in water. Most acids will dissolve the common metals, and will react with a base to form a neutral salt and water.
activated carbon – A granular material usually produced by the roasting of cellulose base substances, such as wood or coconut shells, in the absence of air. It has a very porous structure and is used in water conditioning as an adsorbent for organic matter and certain dissolved gases. Sometimes called “activated charcoal”.
adsorption – The process in which matter adheres to the surface of an adsorbent.
alkalinity – The quantitative capacity of a water or water solution to neutralize an acid. It is usually measured by titration with a standard acid solution of sulfuric acid, and expressed in terms of its calcium carbonate equivalent.
anion – A negatively charged ion in solution, such as bicarbonate, chloride or sulfate.
anion exchange – An ion exchange process in which anions in solution are exchanged for other anions from an ion exchanger. In demineralization, for example, bicarbonate, chloride and sulfate anions are removed from solution in exchange for a chemically equivalent number of hydroxide anions from the anion exchange resin.
aquifer – A layer or zone below the surface of the earth which is capable of yielding a significant volume of water.
attrition – The process in which solids are worn down or ground down by friction, often between particles of the same material. Filter media and ion exchange materials are subject to attrition during backwashing, regeneration and service.
backwash – The process in which beds of filter or ion exchange media are subjected to flow opposite to the service flow direction to loosen the bed and to flush suspended matter, collected during the service run, to waste.
bacteria – Unicellular micro-organisms which typically reproduce by cell division. Although usually classed as plants, bacteria contain no chlorophyll.
base – A substance which releases hydroxyl ions when dissolved in water. Bases react with acids to form a neutral salt and water.
bed – The exchange or filter media in a column or other tank or operational vessel.
bed depth – The height of the ion exchange or filter media in the vessel after preparation for service.
brine – A strong solution of salt (s), such as the sodium chloride brine used in the regeneration of ion exchange water softeners, but also applied to the mixed sodium, calcium and magnesium chloride waste solution from regeneration.
calcium – One of the principal elements making up the earth's crust, the compounds of which when dissolved make the water hard. The presence of calcium in water is a factor contributing to the formation of scale and insoluble soap curd which are a means of clearly identifying hard water.
capacity – An expression of the quantity of an undesirable material which can be removed by a water conditioner between cleaning regeneration or replacement, as determined under standard test conditions. For ion exchange water softeners, the capacity is expressed in grains of hardness removal between successive regenerations and is related to the pound of salt used in regeneration. For filters, the capacity may be expressed in the length of time or total gallons delivered between servicing.
carbon dioxide – A gas present in the atmosphere and formed by the decay of organic matter; the gas in carbonated beverages; in water it forms carbonic acid.
cation – An ion with a positive electrical charge, such as calcium, magnesium and sodium.
cation exchange – Ion exchange process in which cations in solution are exchanged for other cations form and ion exchanger.
caustic – Any substance capable of burning or destroying animal flesh or tissue.
caustic soda – The common name for sodium hydroxide.
chelate – To form a complex chemical compound in which an ion, usually metallic, is bound into a stable ring structure.
chlorine – A gas, C12, widely used in the disinfection of water and an oxidizing agent for organic matter, iron, etc.
coagulant – A material, such as alum, which will form a gelatinous precipitate in water, and cause the agglomeration of finely divided particles into larger particles which can then be removed by settling and/or filtration.
conductive – A measure of the ability of a solution to carry electricity; the reciprocal of the electrical resistance. The unit of conductance is the ohm (reciprocal ohm).
conductivity – The quality or power to carry electrical current; in water, the conductivity is related to the concentration of ions capable of carrying electrical current.
corrosion – The destructive disintegration of a metal by electrochemical means.
cycle – A series of events or steps which ultimately lead back to the starting point, such as the exhaustion- regeneration cycle of an ion exchange system; sometimes incorrectly used in reference to a single step of a complete cycle.