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.
Resin that is made with an acrylic polymer instead of a styrene polymer. Acrylic resins can be activated with weakly
acidic, weakly basic, or strongly basic exchange groups.
A positively charged resin bead that exchanges negatively charged ions in the water.
The increase in volume of a bed of ion exchange resin or filter media during upflow operations such as backwashing,
due to lifting and separation of bed materials.
The amount of an element that resin will pick up before it needs to be regenerated. With softening resin, this usually
applies to hardness measured in kilograms per cubic foot of resin. Standard cation resins, once in service, will generally
remove 30,000 kilograms of hardness after it is regenerated with salt (sodium chloride). With nitrate removal, resin
calculations can be done to estimate the ppm (parts per million) of nitrate removal before the resin bed is exhausted and
another regeneration of salt is needed. Capacity is measured in many different ways and other elements can run interference
on a resin’s capacity.
A negatively charged resin bead that exchanges positively charged ions in the water. Cation resin is most often used for
removing calcium and magnesium (hardness) from water. (See ProSoft™)
The time that brine or other regenerant at the proper strength is moving through the resin bed.
A chemical bridge that connects the polymer chains of a resin bead; the glue that holds the resin beads together.
Generally, the higher the crosslink, the tougher the resin. For cation resins, higher crosslinking also means more
resistance to chlorinated water.
Stands for “Divinylbenzene.” Divinylbenzene is the chemical most commonly used to cross link polymers that are
used to make ion exchange resins.
Resin that is colored with a dye that is pH sensitive and changes color as the pH of the resin changes.
A measure of the size of particles of an ion exchange resin or filter media, defined as the diameter of a specific
particle in a bed, batch or lot which has ten percent smaller and 90 percent larger particles.
The stripping of ions from an ion exchange material by other ions, either because of greater affinity or because of
much higher concentration.
The process in which undesirable foreign matter accumulates in a bed of filter media, ion exchange resin or membrane
process, clogging pores and coating surfaces, thus inhibiting the proper operation of the system. This can be due to
the presence of suspended solids, precipitated salts or biological growth, and can cause a decrease in both the amount
of water produced and the quality of water.
The vertical distance between the top of a resin bed or filter media and the overflow or collector for backwash water.
This may be expressed either as a linear distance or a percentage of bed depth.
Resins that do not have discrete pores and are translucent in appearance. Gel resins generally have higher capacity
than macroporous resins.
Refers to the particular type of ion that is exchanged onto an ion exchange resin. (e.g. The ionic form of SWT’s
ProSelect™ Tannin is Cl (chloride) and the regenerant
used is salt (sodium chloride). This means that the chloride side of the salt is the exchanged ion.
The presence of a consistent concentration of ions in the effluent of an ion exchange system, due to incomplete removal of the ions.
Resins that have discrete pores and are opaque in appearance. Macroporous resins are generally stronger than gel resins.
The blending of cation and anion resins into a single bed. These resins are mostly used in D.I. or specialty applications.
By mixing and matching different resins and ratios, different results can be accomplished.
The quantity of ions that can be exchanged by a resin before leakage bleed-through of ions occurs. This term also refers
to resin in service, rather than resin fresh out of the bag.
At SWT, we believe it is the best anion resin you can buy.
At SWT, we believe it is the best cation resin you can buy.
This process includes the backwash, brine, and fresh water rinse steps necessary to prepare a water softener ion
exchange bed for service after exhaustion.
Selectivity (Relative Affinity)
A quantitative measure of a resin’s preference for various ions at equilibrium between the resin and water.
In general, an ion with greater selectivity will be removed preferentially to an ion with lower selectivity (as in
the case of “nitrate selective” resins).
Anion resins that are capable of splitting salts and can therefore operate in an alkaline environment and can
remove weakly ionized substances, such as carbon dioxide and silica.
The maximum quantity of ions that a resin is capable of exchanging.
Total Dissolved Solids (TDS)
The quantity of all the dissolved minerals in water.
Strong base anion resins that are activated with trimethylamine. These resins are relatively more stable and produce
higher water quantity, but have lower capacity and give off a “fishy” odor when used in the hydroxide form.
Strong base anion resins that are activated with dimethylethanolamine. These resins have a higher capacity and are
more easily regenerated, but do not produce as high of a water quality and generally have a shorter life.
Anion resins that can only function under acidic conditions, can only exchange for strong acids, and can not remove
weakly ionized substances.
A class of inorganic ion exchange materials that are based on aluminosilicate chemistry (e.g. — clay based
compounds). Zeolites have lower capacities than ion exchange resins, but are more selective for certain ions.