men on devices

Technical Terms


An expression of the concentration of hydrogen ions present in a solution.


A synthetic resin possessing the ability to attract and to hold charged particles.


The attachment of charged particles to the chemically active groups on the surface and in the pores of an ion exchanger.


The mingling of raw sugar with a warm, heavy syrup, which removes the molasses coating from the sugar crystal.


An expression of the total basic anions (hydroxyl groups) present in a solution. It also represents, particularly in water analysis, the bicarbonate, carbonate, and occasionally the borate, silicate, and phosphate salts which will react with water to produce the hydroxyl groups.

Amphiphilic Compound

A chemical compound possessing both hydrophilic and lipophilic properties.


Separation and measurement of component parts.


A negatively charged ion.

Anion Interchange

The displacement of one negatively charged particle by another on an anion exchange material.


Using water as a solvent.


The residual mineral content of resin after incineration at 800ºC. 


The rubbing of one particle against another in a resin bed; frictional wear that will affect the size of resin particles.

Back Pressure

Pressure exerted against a flow.


The upward flow of water through a resin bed (i.e. in at the bottom of the exchange unit, out at the top) to clean and reclassify the bed after exhaustion.


The hydroxyl form of a cation or a compound that can neutralize an acid.


The property of the trading of cations shown by certain insoluble natrually occurring materials (zeolites) and developed to a high degree of specificity and efficiency in synthetic resin adsorbents.

Batch Operation

The utilization of ion exchange resins to treat a solution in a container wherein the removal of ions is accompolished by agitation of the solution and subsequent decanting of the treated liquid. 


The ion exchange resin contained in a column.

Bed Depth

The height of the resinous material in the column after the exchanger has been properly conditioned for effective operation.

Bed Expansion

The effect produced during backwashing. The resin particles become separated and rise in the column. The expansion of the bed due to the increase in the space between resin particles may be controlled by regulating the backwash flow.

Bed Volumes per Hour (BV/h)

Flow rate expressed in relation to the volume of resin in the column.

Bicarbonate Alkalinity

The presence in a solution of hydroxyl (OH-) ions resulting from the hydrolysis of carbonates or bicarbonates. When these salts react with water, a strong base and a weak acid are produced and the solution is alkaline. The bicarbonate ion is the main alkaline factor in almost all water.


The amount of dissolved oxygen needed by aerobic biological organisms to break down organic material present in a given water sample at a certain termperature over a specific time period.


The first appearance in the solution flowing from an ion exchange unit of un-adsorbed ions similar to those which are depleting the activity of the resin bed. Breakthrough is an indication that regeneration of the resin is necessary. 


Any solution with an extremely high concentration of salts such as sodium chloride.

Brine Decalcification

Removal of hardness in saturated brine -- usually connected to chlorine production using membranes or mercury cells.


The ability of an ion exchange material to absorb ions. Usually expressed in kilograins per cubic foot or milliequivalents per milliliter.

Capacity, Operating

Also known as useful capacity; the number of ion exchange sites where exchange has taken place during the loading run. The portion of the total capacity utilized in practical ion exchange operation.

Capacity, Salt-Splitting

The portion of total capacity to split neutral salt; also known as "strong base" capacity.

Capacity, Total

The maximum theoretical quantity of ions that a resin can hold or the total number of exchange sites.

Carbonaceous Exchangers

Ion exchange materials of limited capacity prepared by the sulfonation of coal, lignite, peat, etc; helps to remove carbon from carbonaceous material.


A term describing a specific acidic group (COOH) that contributes cation exchange ability to some resins. As defined by Merriam-Webster, a monovalent functional group or radical -COOH typical of organic acids.


A positively charged ion.


Cleavage and furrowing of the bed due to faulty operational procedures, in which the solution being treated follows the path of least resistance, runs through these furrows, and fails to contact active groups in other parts of the bed.

Chemical Elution

The stripping of adsorbed ions from an ion exchange material by the use of solution containing other ions in relatively high concentrations; the process of extracting one material from another by washing with a solvent.

Chemical Stability

Resistance to chemical change. It is important for ion exchange resins to possess chemical stability despite contact with agressive solutions. 

Chromatographic Separation

Chromatography is a physical method of separation that distributes components to separate between two phases, one stationary, and the other moving in a definite direction.


By backwash to obtain a resin bed that is graduated in resin size from coarse on the bottom to fine on the top.

Coagulation or Coalesce

To bring together small particles into a single larger mass that can be filtered or settled out.


A collection of related parallel flows that occur typically between two stages of a multi-stage task in a network.


Composed of extremely small size particles which are not removed by normal filtration. Defined by Merriam-Webster as a substance that consists of particles dispersed throughout another substance which are too small for resolution with an ordinary light microscope but are incapable of passing through a semipermeable membrane.


Discoloration of the liquid passing through an ion exchange material; the flushing from the resin interstices of traces of colored organic reaction intermediates.

Column Operation

Conventional utilization of ion exchange resins in columns through which the solution to be treated passes (either upflow or downflow) through.

Condensate Polishers

Ion exchange resins being used to remove or exchange ions as well as to filter condensate for reuse in the steam cycle; resin-based ion exchange systems that are commonly used in power plant condensate systems to remove dissolved contaminants and suspended contaminants. 


The ability of electric current to flow through water as a measure of its ion content in mhos or micromhos.


The flow of a fluid in opposite directions.


Intermixing of one resin with another of opposite charge or of two water streams.


The degree of binding of a monomer or set of monomers to form an insoluble tri-dimensional resin matrix; a side bond that links two adjacent chains of atoms in a complex molecule.


A complete course of ion exchange operation. For instance, a complete cycle of cation exchange would involve: exhaustion of regenerated bed, backwash, regeneration and rinse to remove excess regenerant.

Day Tanks

Tanks used to hold diluted regenerant chemicals prior to being educted or pumped to the resin bed.


The removal from solution of inorganic salts by means of adsorption by ion exchange resins of both the cations and the anions that comprise the salts. See deionization.

Degasifier or Deaerator

A system to remove dissolved gas or gases from water.

Dehydration Degradation reaction

A conversion that involves the loss of water from reacting molecule or ion. Dehydration reactions are common processes, the reverse of a hydration reaction. 


Deionization, a more general term than deashing, embraces the removal of all charged constituents or ionizable salts (both inorganic and organic) from solution. See Deashing. 


The weight of a given volume of exchange material, backwashed and in place in the column.


The state of being spread out or transmitted especially by contact. For example, ions diffusing through ion exchange resin beads.


The process of ionization of an electrolyte or a salt upon being dissolved in water, forming ions of cation and anion. Defined by Merriam-Webster as being the process by which a chemical combination breaks up into similar constituents.

Divinylbenzene (DVB)

A difunctional monomer used to cross-link polymers.


Conventional direction of solutions to be processed in ion exchange column operation; in at the top, out at the bottom of the column.

Dry solids

The matter (usually expressed in weight percent) remaining after liquid removal. 


An ion exchange reaction taking place as the water moves past ion exchange resins.


Empty bed contact time, i.e., the hydraulic residence time in an empty bed of the same volume as the media including voids.


A device that, by flow of water through it creating a vacuum, draws a solution into the water stream.


The effectiveness of the operational performance of an ion exchanger. Efficiency in the adsoprtion of ions is expressed as the quantity of regenerant required to effect the removal of a specified unit weight of adsorbed material. e.g., pounds of acid per kilograin of salt removed.


The solution which emerges from (flows out of) an ion exchange column.


Conductive materials, placed in water solution, which have a positive or negative charge.


A chemical compound which dissociates or ionizes in water to produce a solution which will conduct an electric current; an acid, base or salt. Defined by Merriam-Webster as a substance that when dissolved in a suitable solvent or when fused becomes an ionic conductor. 


Where the positive charges equal the negative charges.

Electrophilic species

A positively charged or neutral species having vacant orbitals that are attracted to an electron rich center. It participates in a chemical reaction by accepting an electron pair in order to bond to a nucleophile.


The stripping of adsorbed ions from an ion exchange material by the use of solutions containing other ions in relatively high concentrates. More generally, the process of extracting one material from another by washing with a solvent.  

End Point

A preselected value or measurement used to determine when the service cycle is completed or that a breakthrough has occurred.

Equilibrium reactions

The interaction of ionizable compounds in which the products obtained tend to revert to the substances from which they were formed until a balance is reached in which both reactants and products are present in definite ratios. 

Equivalent weight

The molecular weight of any element or radical expressed as grams, pounds, etc. divided by the valence; according to Merriam-Webster, the mass of a particular substance especially in grams that combines with or is chemically equivalent to eight grams of oxygen or one gram of hydrogen.

Exchange Sites

The reactive (functional) groups of anions or cations on an ion exchange resin; situated throughout the polymer matrix.

Exchange Velocity

The rate with which one ion is displaced from an exchanger in favor of another. 


The state in which resin is no longer capable of useful ion exchange; the depletion of the exchanger's supply of available ions. The exhaustion point is determined arbitrarily in terms of:
(a) a value in parts per million of ions in the effluent solution
(b) the reduction in quality of the effluent water determined by a conductivity bridge which measures the electrical resistance to water.


Giving off heat in a reaction or solution of a substance.


Extending information beyond the point where proven data is available.


Extremely small particles of ion exchange materials.


Materials that can form gelatinous clouds of precipitate to enclose fine particles of suspended dirt to settle them from the water.

Flow Rate

The volume of solution passing through a given quantity of resin within a given time. Usually expressed in terms of gallons per minute per cubic foot of resin, as milliliters per minute per milliliter of resin, or as gallons per square foot of resin per minute.  The volume of solution passing through a given quantity of resin within a given time. Usually expressed in terms of gallons per minute per cubic foot of resin, as milliliters per minute per milliliter of resin, or as gallons per square foot of resin per minute.  


The free mineral acidity, or sum of the mineral acids.

Forced-draft degasifier

A tower in which water droplets descend through a flow of air blown upwards to remove gases such as carbon dioxide.


The accumulation of unwanted material on solid surfaces to the detriment of function. The fouling materials can consist of either living organisms or a non-living substance. Failing to clean a fouled resin will result in a significantly shorter resin life.

Free base

A regenerated form of a weakly basic anion resin.


The space provided above the resin bed in an ion exchange column to allow for expansion of the bed during backwashing.


Granular activated carbon.


Ion exchange resins that are made up of firm gel structure in a solid bead form, allowing for the diffusion of ions through the gel. 


A unit of mass, 0.0648 grams; typically used to measure the hardness of water.

Grains per Gallon

An expression of concentration of material in a solution, generally in terms of calcium carbonate; a unit of water hardness. One grain (as calcium carbonate) per gallon is equivalent to 17.1 parts per million. One grain per US gallon is equivalent to 0.017118061 kg/m3


The equivalent weight in grams, divided by 1000.


Granular Activated Carbon Adsorption

The activated carbon being retained on a 50-mesh sieve. Activated carbon is an effective adsorbent because it is a highly porous material and provides a large surface area to which contaminants may adsorb.


Measurement by weight.

Ground Remediation

Purification of water from a ground source, usually contaminated with metals etc. which need to be reduced. 


The scale-forming and lather-inhibiting qualities which water, high in calcium and magnesium ions, possesses. Temporary hardness, caused by the presence of magnesium or calcium bicarbonate, is so called because it may be removed by boiling the water to convert the bicarbonates to insoluble carbonates. Calcium Sulfate, Magnesium sulfate, and the chlorides of these two metals cause permanent hardness.

Hardness as calcium carbonate

The expression ascribed to the value obtained when the hardness forming salts are calculated in terms of equivalent quantities of calcium carbonate, a convenient method of reducing all salts to a common basis for comparison.


The reduction in liquid pressure associated with the passage of a solution through a bed of exchange material; a measure of the resistance of a resin bed to the flow of the liquid passing through it.

Hydraulic Classification

The rearrangement of resin particles in an ion exchange unit. As the backwash water flows up through the resin bed, the particles are placed in a mobile condition wherein the larger particles settle and the smaller particles rise to the top of the bed. Defined in Merriam-Webster as the sorting of small particles by allowing them to settle against rising currents of fresh water of different velocities.

Hydrogen Cycle

A complete course of cation exchange operation in which the adsorbent is employed in the hydrogen or free acid form. 


The splitting of a salt and water into its ions and formation of a weak acid or base, or both. As in ion exchange:
R-NH4+OH-R-H+ + NH4+OH- where R- is a WAC resin.


A device to measure specific gravity of fluids.


The term used to describe the anionic radical (OH-), which is responsible for the alkalinity of a solution and is present in alcohols and many other organic compounds. 

Hydroxymethylfurfural, HMF

An organic compound formed by the dehydration of certain sugars. 5 (hydroxymethyl) -2-furaldehyde, is a precursor of the coloring matter from decomposition of glucose and also thereby assisting in the color development in sugars. HMF is produced during contact with strong acid cation resins in the H+ form at elevated temperatures. 

Inert Media

A resin with no reactive groups.


The solution which enters (flows into) an ion exchange unit.

Interstitial Spaces

A compound that is formed when an atom of sufficiently small radius sits in an interstitial "hole" in a metal lattice. The smaller atoms become trapped in the spaces between the atoms in the crystal matrix, called the interstices.


An atom or molecule with a net electric charge due to the loss or gain of one or more electrons.

Ion Exchange

The interchange of one ion in solution with another ion on an insoluble material.


The process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons, often in conjunction with other chemical changes.

Ionization constant

An expression in absolute units of the extent of dissociation into ions of a chemical compound in solution; the equilibrium constant for a chemical reaction known as dissociation in the context of acid-base reactions. 

Also known as the dissociation constant, the ionization constant uses the symbol K to describe the equilibrium between ions and molecules that are not ionized in a solution or liquid. 

Kieselguhr Filtration

A filtration method in which diatomaceous earth is applied to precoat a mesh screen prior to each filter run. This method is most effective in water treatment. Effluent water quality of DE filtration depends on influent water quality and quality (or grade) of DE used.   

Kieselguhr (aka Diatomasceous earth) is a nonmetallic material or powder made of desiccated diatom material; used as a filtering agent, adsorbet, and abrasive in many chemical operations. 


A unit of weight; one thousand grains.


The effects of forces on the motion of matter, of concern with the velocity or speed of reactions.

layered bed

An ion exchange column with two different resins on top of each other, with a regenerant collector between them.

lead lag

When two vessels are used in series to achieve better quality and to maximize loading on a lead column (usually used in special applications).

lead lag merry-go-round

When operating lead lag having a third vessel in regeneration or on standby; when the column is fully exhausted and goes into regeneration, the lag column becomes the lead and the column in standby becomes the polisher.


The phenomenon in which some of the influent ions are not adsorbed or exchanged and appear in the effluent when a solution is passed through an under-regenerated exchange resin bed.

london forces

A temporary attractive force that results when the electrons in two adjacent atoms occupy positions that make the atoms form temporary dipoles. It is the weakest intermolecular force. 


Resins that have a rigid polymer porous network in which there exists a true pore structure even after drying. The pores are larger than atomic distances and are not part of the gel structure. 


A dense mass of sugar crystals mixed with mother liquor obtained by evaporation. 


Maximum contaminant level.


A slurry mixer used to commingle raw sugar and affination syrup to begin the process of transforming cane sugar into refined granulated product. Retention time and intense mixing are critical at this stage.

mixed bed

A method of filling a testing column, involving two resins intermingling with each other.

Moisture Content

The water loss of a fully hydrated resin under controlled drying conditions.

Molecular Weight

The relative weight of a molecule on a scale where oxygen has a given weight of 16.


The smallest particle of an element or compound retaining its characteristics.


A single reactive molecule capable of combining with another different monomer to form a polymer. Where two different monomers combine the resulting polymer is called a polymer.


Mass Transfer Zone.

negative charge

The electrical potential which an atom acquires when it gains one or more electrons; a characteristic of an anion.

packed bed

A method of filling a testing column such that the resin to be tested remains between 2 plates; an upper distributor and an underdrain (packing support).

permanent hardness

Hardness due to the prescence of minerals such as: chlorides, nitrates, and sulphates of calcium and magnesium, which will not be precipitated by boiling.


An expression of the acidity of a solution; the negative logarithm of the hydrogen ion concentration (pH I very acidic; pH 14, very basic; pH 7, neutral).

physical stability

The quality which an ion exchange resin must possess to resist changes that might be caused by attrition, high temperatures, and other physical conditions.


An expression of the degree of permeability in ion exchange resins to liquids and large organic molecules. Gel resins, even when referred to as highly porous, have a negligible porosity in comparison to the macropores inherent in the macroporous resins. Porosity is also defined as the ration of the volume of interstices of a material to the volume of its mass.  

positive charge

The electrical potential acquired by an atom which has lost one or more electrons; a characteristic of a cation. 

Potable water

Water suitable for drinking.

quaternary amine

A cationic amine salt in which the nitrogen atom has four groups bonded to it and carries a positive charge. They are used as oil-wetting agents, corrosion and shale inhibitors and bactericides.

quaternary ammonium

A specific basic group [-N(CH3)3+] on which depends the exchange activity of certain anion exchange resins. Any of numerous strong bases and their salts derived from ammonium by replacement of the hydrogen atoms with organic radicals.

raw water

Untreated water from wells, lakes, rivers, or from surface sources; natural minerals, ions, particles, bacteria, and parasites have not been removed.


A chemical compound solution used in the restoration of ion exchange system capacity. Acids are employed to restore a cation exchanger to its hydrogen form; brine solutions may be used to convert the cation exchanger to the sodium form. The anion exchanger may be rejuvenated by treatment with an alkaline solution.  


A chemical compound solution used in the restoration of ion exchange system capacity. Acids are employed to restore a cation exchanger to its hydrogen form; brine solutions may be used to convert the cation exchanger to the sodium form. The anion exchanger may be rejuvenated by treatment with an alkaline solution.  


The operation which follows regeneration; a flushing out of excess regenerant solution.


Strongly acidic cation (resin).


The conversion of salts to their corresponding acids or bases by passage through ion exchange resins containing strongly acidic or strongly basic functional groups. 


The maximum amount of a substance that can be put into solution (maximum capacity).


Strongly Basic Anion (resin).


The difference in attraction of one ion over another by an ion exchange resin. Ion exchange media have a greater affinity for certain ionic species than for others and are preferentially sorbed. 


One action occurring followed by others in a given order, as opposed to simultaneous actions.

Siliceous Gel Zeolite

A synthetic, inorganic exchanger produced by the aqueous reaction of alkali with aluminum salts. 


The process of replacing hardness with sodium by cation exchange.

Space Velocity

The flow per unit volume of resin, or gpm/ft3.

Specific Gravity

The ratio of the weight of a given volume of a substance to the weight of an equal volume of water at a fixed temperature.

Specific Resistance

The resistance between opposite faces of a one-centimeter cube of a given substance and expressed as ohm-cm3.


An apparatus for measuring the intensity of light in a part of the spectrum, especially as transmitted or emitted by particular substances. In the case of ion exchange resins, it is used to measure how much a chemical substance absorbs light by measuring the intensity of light as a beam of light passes through sample solution.


Relating to the spherical nature and whole bead content of a resin; the measure of how closely the shape of an object approaches tha of a mathematically perfect sphere. 


An ion exchange reaction occurring with a volume of liquid in continuous contact with a volume of resin.


A slotted or screened sieve to filter a flowing stream of water.


Relating to or denoting quantities of reactants in simple integral ratios, as prescribed by an equation or formula.

Strong Electrolyte Resin

The equivalent of strongly acidic or strongly basic resins and capable of splitting neutral salts. They're good conductors of electric current in a solution. 

Sulfonic Acid

A specific strong base acidic group (S03H) on which depends the exchange activity of certain cation exchange resins. They're frequently used as catalysts and for ion exchange.

Superficial Linear Velocity

Flow of water per unit of area, or gpm/ft2.


To contain more in solution than is normal for a given temperature.

Support Media

A graded-particle-size, high-density material such as gravel, anthrafil or quartz used to support the resin bed.


The expansion of an ion exchange bed which occurs when reactive groups on the resin are converted into certain forms. The amount of swelling partially depends on the elasticity of the resin. 

Tangential Filtration

A process where the feed stream flows parallel to the membrane face. Applied pressure causes one portion of the flow stream to pass through the membrane while the remainder is recirculated back to the feed reservoir. Particles smaller than the pore size are pushed out through the filrate.  


Total Dissolved Solids  TDS = TS - TSS.

Temporary Hardness

The hardness present in a water associated with the bicarbonate (alkalinity) and usually expressed in mg/l or ppm as CaCO3 or in meq/l.

Throughfare Regeneration

When regenerant is used on two vessels in series in one operation. For example, in a demin plant cation - anion - polishing cation, where the acid used to regenerate the main cation goes through the small polishing cation first (giving it in effect a free regeneration).


The amount of solution treated prior to the exhaustion of the ion exchange resin; the amount of material or items passing through a system or process.

throughput volume

The amount of solution passed through an exchange bed before exhaustion of the resin. 


To determine the amount of a substance in solution by adding a measured amount of another substance to produce a desired reaction or endpoint.


Total Mineral Acidity or anions.


Total Organic Carbon.

Total Dissolved Solids (TDS)

All the dissolved salts present in a feed supply.


A single ion exchange system, such as SAC and  SBA, capable of producing the treated water desired, with multiple trains being duplicates of the single system.


Total Suspended Solids.  TSS = TS - TDS.


Ultrafiltration or uncertainty factor.

Ultra-Filtration Membrane

A variety of membrane filtration in which forces like pressure or concentration gradients lead to a separation through a semipermeable membrane. Typically, these membranes will remove high molecular-weight substances, colloidal materials, and organic and inorganic polymeric molecules.

Ultrasonic Bath

Uses high-frequency, high-intensity sound waves in a liquid to facilitate or enhance the removal of foreign contaminants from surfaces submerged in an ultrasonically activated liquid. 


The operation of an ion exchange unit in which solutions are passed in at the bottom and out at the top of a container. 



Vacuum Degasifier

A tower to which a vacuum is applied and through which water droplets descend to remove dissolved gases.


The combining power of an element, as measured by the number of hydrogen atoms it can displace or combine with. 


The state of being thick, sticky, and semifluid in consistency due to internal friction. 


Volatile Organic Contaminant.

Void Volume

The space between particles of ion exchange resin in a settled bed, also called interstitial volume. Also used in ion exchange chromatography.


Weak Acid Cation. Refers to a cation exchange resin typically with carboxylic acid functionality.


The unrecycled portion of the water used in the backwash, regeneration and rinse cycles.

Water Hammer

Instantaneous surges of water pressure caused by sudden interruptions in water flow in pipe or tank systems.

Water Jacket

A water-filled casing surrounding a device, typically a metal sheath having intake and outlet vents to allow water to be pumped through and circulated. 

Water Softening

To exchange sodium for the hardness in water by ion exchange.


Weak Base Anion. Refers to an anion exchange resin with primary, secondary or tertiary amine functionality.

Weak Electrolyte

An electrolyte that gives a low percentage yield of ions when dissolved in water. 


A microporous, aluminosilicate mineral typically used as an ion-exchange bed in domestic and commercial water purification and softening. They have also been used as catalysts and sorbents.