Glossary of Water Treatment Terms & Definitions
- Filter rating meaning that 99.9 % (or essentially
all) of the particles larger than a specified
micron rating will be trapped on or within the
- The process in which one substance penetrates
into the body of another substance, termed the
absorbent. An example is the absorption of water
- 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. An acid is the opposite
of an alkali, has a pH rating lower than 7.0,
will turn litmus paper red, and has a sour taste.
- The quantitative capacity of a water or water
solution to neutralize an alkali or base. It is
usually measured by titration with a standard
solution of sodium hydroxide, and expressed in
ppm or mg/L of its calcium carbonate equivalent.
- A medium made by treating aluminum ore so that it
becomes porous and highly adsorptive. Activated
alumina will remove several contaminants
including fluoride, arsenic, and selenium. It
requires periodic cleaning with a regenerant such
as alum, acid and/or caustic.
- A water treatment medium, found in block,
granulated, or powdered form, which is produced
by heating carbonaceous materials, such as coal,
wood, or coconut shells, in the absence of air,
creating a highly porous adsorbent material.
Activated carbon is commonly used for dechlorination,
organic chemical reduction and radon reduction, and is
recognized by the US EPA as the best available
technology for reduction of organic chemicals
from drinking water.
- A negatively charged colloidal substance
generally formed by combining a dilute sodium
silicate solution with a dilute acidic solution
(or other activant). Generally used as a
- Any substance that is or can be adsorbed. The
liquid, gas or solid substance which is adsorbed
as molecules, atoms, or ions.
- A water treatment medium, usually solid, capable
of the adsorption of liquids, gases, and/or
suspended matter. Activated alumina and activated
carbon are common adsorbents used in water
- The physical process occurring when liquids,
gases, or suspended matters adhere to the
surfaces of, or in the pores of, an adsorbent
media such as activated carbon. Adsorption is a
physical process which occurs without chemical
- The process in which air is brought into intimate
contact with water, often by spraying water
through air, or by bubbling air through water.
Aeration may be used to add oxygen to the water
for the oxidation of matter such as iron, or to
cause the release of dissolved gases such as
carbon dioxide or hydrogen sulfide from the
- An action or process conducted in the presence of
air, such as aerobic digestion of organic matter
- Air Check
- A device which allows water, but not air, to pass
through it. An air check is a typical component
of a treatment system using a regenerant eductor.
- Air Gap
- A clear vertical space through the free
atmosphere between the lowest opening of any pipe
or faucet conveying water or waste to a tank,
plumbing fixture receptor, or other device and
the flood level rim of the receptacle. An air gap
is used to prevent cross connection between a
water treatment device and a possible source of
wastewater thereby preventing a reverse flow of
water from the sewer into the water supply
system. Without an air gap, such reverse flow
could occur due to an increase in the pressure in
the sewer system or the creation of a negative
pressure in the water supply line. Local plumbing
codes usually require the air gap to be twice the
diameter of the inlet with a minimum width of 1
- A term usually applied to waters containing acid
or oxygen which hasten corrosion (rusting).
- Plant life (green scum) containing chlorophyll is
usually found in stagnant surface water.
Excessive growths may create taste and odor
problems, and consume dissolved oxygen during
decay. Sometimes it may be controlled in a pond
by the addition of Potassium Permanganate. In a
water supply system, chlorination followed by
dechlorination is often used.
- A substance which creates a bitter taste and a
slippery feel when dissolved in water and will
turn red litmus paper blue. An alkali has a pH
greater than seven and is the opposite of an
acid. Highly alkaline waters tend to cause drying
of the skin.
Alkalis may include the soluble hydroxide,
carbonate, and bicarbonate salts of calcium,
magnesium, potassium, and sodium. A hydroxide
alkali may also be called a base.
- The quantitative capacity of water to neutralize
an acid; that is, the measure of how much acid
can be added to a liquid without causing a
significant change in pH. Alkalinity is not the
same as pH because water does not have to be
strongly basic (high pH) to have high alkalinity.
In the water industry, alkalinity is expressed in
mg/l of equivalent calcium carbonate. There are
three kinds of alkalinity: carbonate,
bicarbonate, and hydroxide alkalinity. Total
alkalinity is the sum of all three kinds of
alkalinity. Different tests are used to determine
the quantity of the different kinds of
alkalinities present in water.
- As in the pressure in the sewer system or the
creation of a negative pressure in the water
supply line. Local plumbing codes usually require
the air gap to be twice the diameter of the inlet
with a minimum width of 1 1/2 inches.
- The common name for aluminum sulfate [Al2 (SO4) x
14H2 O] which is often used as a coagulant in
- A single celled protozoan that is widely found in
fresh and salt water. Some types of amoebas cause
diseases such as amoebic dysentery.
- An organism that can thrive in the absence of
oxygen (air), such as bacteria in a septic tank.
- Angstrom unit
- A unit of wavelength of light equal to .00001
millimeter or .0001 microns.
- A negatively charged ion in solution, such as
bicarbonate, chloride, or sulfate. An anion [such
as chloride (Cl-)] may result from the
dissociation of a salt, acid, or alkali.
- 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.
- The positive pole of an electrolytic system. The
metal which goes into solution in a galvanic
cell. Anodes of metals such as magnesium and zinc
are sometimes installed in water heaters or other
tanks to deliberately establish galvanic cells to
control corrosion of the tank through the
sacrifice of the anode.
- Abbreviation for American National Standards
- Containing water; watery.
- Natural underground reservoirs of porous layers
of sand, rock or gravel.
- Describes underground water trapped under
pressure between layers of impermeable rock. An
artesian well is one that taps artesian water.
- Abbreviation for American Society of Mechanical
- The process in which solids are worn 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.
water softener (or Automatic Filter)
- A water softener (or filter) that is equipped
with a clock timer, meter, or sensor which
automatically initiates the backwash and/or
regeneration process at the preset intervals of
time. A predetermined number of gallons of water
usage or as determined by a sensor. All
operations, including bypass of treated or
untreated water (depending upon design),
backwashing, brining, rinsing, and returning the
unit to service are performed automatically.
- Abbreviation for American Water Works
Association. Most municipal water treatment
plants hold membership in this association.
- Flow of water in a pipe or line in a
direction opposite to the normal flow;
often associated with back siphonage or
the flow of possibly contaminated water
into a potable water system.
- A device or system installed in a water
line to stop backflow from a non-potable
- Pressure which creates resistance against
the flow of water.
- The upflow or counter-current flow of
water through a filter or ion-exchange
medium, lifting the mineral bed and
flushing away to the drain the particles
of foreign matter that have been filtered
from the water supply during the service
- Unicellular microorganisms which
typically reproduce by cell division.
Although usually classed as plants,
bacteria contain no chlorophyll. Many
different types of bacterial organisms
are often found in drinking water. Most
municipally treated water is essentially
bacteria free due to the addition of
chlorine. Some forms of cyst type viruses
have a degree of immunity to chlorine due
to the cocoon-like shell around the
virus. These types of organisms such as
Giardia Cyst, Giardia Lamblia, and
Cryptosporidium have a physical size of
three to seven microns and can be
effectively removed by sub-micron
filtration. Some bacteria are helpful to
man, others harmful.
- Having the ability to inhibit the growth
of bacteria without destroying them. For
example, silver impregnated activated
carbon will limit bacterial colonization
but not eliminate it.
- Any substance or agent which kills
- A unit of pressure. One bar equals 14.5
pounds per square inch (psi) or about
0.987 standard atmospheres.
- An alkali that releases hydroxyl ions
when dissolved in water. Bases reset with
acids to form a neutral salt and water.
In general they taste bitter rather than
sour, and feel slippery and reverse the
color changes produced by acids in
indicators. For example, they turn litmus
- The utilization of ion exchange resins to
treat a solution in a container wherein
the removal of ions is accomplished by
agitation of the solution and subsequent
decanting of the treated liquid.
- A mass of ion exchange resin particles or
filter media contained in a column.
- Bed Depth
- The height of the resin or filter media
in the column after it has been properly
conditioned for effective operation,
usually expressed in inches. This depth
excludes any supporting bed.
- The effect produced during backwashing:
the resin particles become separated and
rise in the column. The expansion of the
bed due to the increase of the space
between resin particles may be controlled
by regulating backwash flow.
- 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 procured, and the
solution is alkaline.
- A chemical which can kill or inhibit the
growth of lining organisms such as
bacteria, fungi, molds, and slime.
Biocides can be harmful to humans.
- Subject to degradation into similar
substances by biological action .
Examples include detergents, sewage, and
other organic matter by bacteria.
- The trade name for a manganese dioxide
coated aluminum silicate used as an
oxidizing catalyst filter medium for iron
and manganese reduction.
- The withdrawal of water containing a high
concentration of solids or dissolved
solids or maintain a specified
solids-to-water concentration ratio.
- Abbreviation for Biochemical Oxygen
Demand. The amount of oxygen consumed in
the oxidation of organic matter by
biological action under specific standard
test conditions. Widely uses as a measure
of the strength of sewage and wastewater.
- Bone Char
- A black pigment substance with a carbon
content of about 10 percent, made by
carbonizing animal bones. It is used as a
selective anion exchanger for fluoride
and arsenic reduction.
- Water containing bacteria between 1.000
and 15,000 ppm of dissolved solids.
- The first appearance in the solution
flowing from an ion exchange unit of
unabsorbed ions similar to those which
are depleting the activity of the resin
bed. Breakthrough is an indication that
regeneration of the resin is necessary.
- A strong solution of salt(s), such as the
sodium chloride or potassium 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.
- A device used to draw a solution such as
brine from a storage tank and force it
into a cation or anion water treatment
- Brine Tank
- A tank which sits beside the softening
unit and acts as a salt storage and brine
- A chemical which causes a solution to
resist changes in pH, or to shift the pH
to a specific value.
- A connection or a valve system that
allows untreated water to flow to a water
system while a softener or filter is
being regenerated, backwashed or
serviced; also applied to a special water
line installed to provide untreated water
to a particular tap, such as a sill cock.
- Calcium carbonate (CaCO3). A trade name
for finely ground limestone, very high in
calcium carbonate, which is used to raise
the pH of acidic water.
- One of the primary elements of the
earth's crust commonly found in water as
a dissolved solid. The presence of
calcium in water is a factor contributing
to the formation of scale and insoluble
soap curds which are means of clearly
identifying hard water. It is sometimes
referred to as lime.
- All forms of water hardness and other
salts are commonly expressed in terms of
calcium carbonate equivalents. This is
necessary so that minerals of varying
weight can be expressed in chemically
- In a softener or deionizer it is the
adsorption activity possessed in varying
degree by ion exchange materials. This
quality may be expressed as kilograins
per cubic foot, gram-milliequivalents per
gram, pound-equivalents per pound,
gram-milliequivalents per milliliter,
etc., where the of these ratios represent
the weight of the ions adsorbed and the
denominators, the weight or volume of the
adsorbent. It can also refer to the
ability of any media to take up a
specific contaminant and is rated by time
over gallons. As to flow rates, it is the
maximum or minimum flow obtainable under
given conditions of media, temperature,
pressure, velocity, etc.
- Carbonaceous Exchangers
- Ion exchange materials of limited
capacity prepared by the sulfonation of
coal, lignite, peat, etc.
- Water with a low pH value usually
contains free carbon dioxide. Its
presence is caused generally by
absorption of carbon dioxide (CO2) from
the air as water falls as rain, or by
decay of organic matter in the earth.
Well water containing substantial
quantities of CO2 has a resultant low pH
and corrosive qualities. Carbon dioxide
in water forms a weak carbonic acid.
- A substance that can cause cancer.
- The control of the electrolytic corrosion
of an underground or underwater metallic
structure by the application of an
electric current is such a way that the
structure is made to act as the cathode
instead of anode of an electrolytic cell.
- A positively charged particle or ion.
- The common name for sodium hydroxide and
often used as a regenerant of anion resin in
- The flow of water or regenerant taking
the line of least resistance through a
media bed, as opposed to the usual
distributed flow through all passages of
the bed. Channeling may be due to fouling
of the bed, poor distribution design, low
flow rates, or insufficient backwash.
- A mechanical device designed to introduce
chemicals into a water system, more or
less accurately in proportion to water
Oxygen Demand (C.O.D.)
- The amount of matter, both organic and
inorganic, in a water or wastewater which
can be oxidized by boiling with a strong
oxidizing acid, and expressed as the
equivalent amount of oxygen. Often used
as a membrane of the strength of sewage.
- Resistance to chemical change which ion
exchange resins must posses despite
contact with aggressive solutions.
- Chemical complexes formed from the
reaction between ammonia and chlorine
being used to disinfect many municipal
water supplies. Does not combine with
organics to form triclomethanes.
- A mechanical device specifically designed
to feed chlorine gas or pellets, or
solutions such as hypochlorides, into a
water supply in proportion to the flow of
- Widely used in the disinfection of water
and as an oxidizing agent for organic
matter, iron, hydrogen sulfide, etc. It
is available as a gas, as a liquid in
sodium, hypochlorite, or as a solid in
calcium hypochlorite. In water chlorine
reacts with organics to form
trihalomethanes (THM) which can cause
- A measure of the amount of chlorine which
will be consumed by organic matter in a
water before a chlorine residual will be
- A material such as alum, which will form
a gelatinous precipitate in water, and
gather finely divided particles into
larger ones which can then be removed by
settling and/or filtration.
- Those regulations which the department
having jurisdiction may lawfully adopt.
- A group of organisms primarily found in
human and animal intestines and wastes,
and thus widely used as indicator
organisms to show the presence of such
wastes in water and the possible presence
of pathogenic (disease producing)
- Very finely divided solid particles
larger than molecules but small enough
that they will not settle out of a
solution; intermediate between a
dissolved particle and a suspended solid
which will settle out of solution.
Typically between 0.1 and 0.001 microns
in diameter, it usually requires
coagulation prior to filtration.
colloidal (heme) iron may be removed by
special anion resin.
- Color Throw
- Discoloration of the liquid passing
through a filtration or ion exchange
media. It may be flushing from the media
interstices of traces of colored organic
reaction intermediates. It could indicate
the presence of metallic ions, humus,
tannins, or industrial wastes.
- A calculated value based on the hardness,
the magnesium to calcium ratio, and the
sodium concentration of a water. It is
used to calculate the reduction in
hardness removal capacity of a softener
caused by these factors. No single method
of calculation has been widely accepted.
- Water which has liquefied from steam.
- The quality or power to carry electrical
current; in water, the conductivity is
related to the concentration of ions
capable of carrying electrical current.
The unit of measure is the mho, which is
the reciprocal of resistivity which is
- The actual time which water remains in
contact with an oxidizer, regenerant, or
water conditioning media within a water
treatment system. The amount of contact
time determines the effectiveness of the
system. Also called retention time.
- The addition of any physical, chemical,
biological or radiological substance to
water which reduces the value of the
water, or interferes with its intended
- A stopcock screwed into the street water
main to provide the house service
- The destructive disintegration of metals
by electromechanical means. Corrosion of
iron and steel is commonly called
- The minimum depth of an adsorbent bed
requited to contain the mass transfer
- Any physical connection between two
otherwise separated piping systems one of
which contains potable water and the
other of unknown or questionable safety,
whereby flow may occur from one system to
the other depending on the pressure
differential between the two systems.
- The bonding of linear polymers into a
resinous product with a material such as
divenylbenzene (DVB). The degree of
crosslinking is a factor of the resin's
ability to withstand chemical oxidation.
Softening resin is usually 8 percent
crosslinked, but can range from 6 percent
to 10 percent which is used in hot water
- A complete course of ion exchange
operation. For instance, a complete cycle
of cation exchange would involve:
regeneration of the resin, rinse to
remove excess regenerant, exhaustion,
backwash, and finally regeneration again.
- A waterborne protozoan that forms cysts
and causes acute illness in humans. This
type of organism is resistant to chlorine
and ultraviolet light but can be removed
by one micron filtration.
triacetate. Used to manufacture
reverse osmosis membranes.
- A process for the reduction of alkalinity
in a water supply. It is generally
accomplished by a chemical feed processor
combined cation and anion exchange
- 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.
- The removal of excess or free chlorine
from a water supply by adsorption with
activated carbon or by catalytic type
- The degradation of an ion exchange resin
structure by destruction of the crosslink
polymer as the result of aggressive
attack by chlorine, ozone, hydrogen
peroxide, or heat. Decrosslinking causes
increased moisture content in an ion
exchange resin and the physical swelling
of the beads.
- The removal of dissolved gasses from
water such as carbon dioxide, methane,
hydrogen sulfide, and oxygen. This can by
done by subjecting the water to below
atmospheric pressure, or by passing air
through the water at atmospheric
- The removal of the ionized minerals and
salts (both organic and inorganic) from a
solution by a two-phase ion exchange
procedure. First, positively charged ions
are removed by a cation exchange resin in
exchange for a chemically equivalent
amount of hydrogen ions. Second,
negatively charged ions are removed by an
anion exchange resin for a chemically
equivalent amount of hydroxide ions. The
hydrogen and hydroxide ions introduced in
this process unite to form water
molecules. The term is often used
interchangeably with demineralization.
The cation resin is regenerated with an
acid and the anion resin is regenerated
with sodium hydroxide (caustic soda).
- Delta P
- The pressure drop
or loss in psi between the inlet and the
outlet of a water conditioner as the
- Density, Apparent (Density, Bulk)
- The mass under specified conditions of a
unit volume of a solid sorbent including
its pore volume and inter-particle voids.
- The removal of dissolved inorganic solids
(salts) from a solution such as water to
make it free of dissolved salts.
Typically accomplished by reverse
osmosis, distillation, or
- Usually refers to synthetic detergent,
but can be any material with cleansing
powers such as soap, alkaline materials,
synthetic detergents, solvents, and
abrasives. Synthetic detergents are known
as surfactants which foam and act like
soap but are not made from fatty acids
- The separation of components of a
solution by diffusion through a
semi-permeable membrane which is capable
of passing certain ions or molecules
while rejecting others.
- A carbonate mineral of calcium and
magnesium found in nature in extensive
beds of compact limestone and marble that
are rich in carbonate.
- Drain Line
- A pipe or conduit from a water
conditioning unit used to carry backwash
water, regeneration wastes and/or rinse
water to a drain or waste system by
Primary Drinking Water Standards are
established by the U.S. Environmental
Protection Agency (EPA) are health
related and establish the maximum
contaminant levels (MCL's) for regulated
substances in drinking water. A MCL is
the highest permissible level of a
contaminant allowed in water delivered to
the consumer's tap. These standards
relate to public water systems. National
Secondary Drinking Water Standards
are also issued by the EPA and pertain to
aesthetic characteristics of water and
are recommended only.
Drinking Water Standards
- Abbreviation for Drainage, Waste, and
Vent. A name for copper or plastic tubing
used for drain, waste, or venting pipes.
- A venturi with an
opening at the throat used to educt (suck
in) air or liquid. The common method of
introducing brine into a water softener.
- The effectiveness of the operational
performance of an ion exchanger.
Efficiency in the adsorption 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
kilogram of salt removed.
- The outflow of a water treatment device.
Sometimes used to mean the product water
of a given water conditioning device or
- A dialysis process using semi-permeable
- A chemical compound which dissociates or
ionizes in water to produce a solution
which will conduct an electric current.
Could be an acid, base, or salt.
- The stripping of adsorbed ions from an
ion exchange material by the use of
solutions containing other ions in
concentrations higher than those of the
ions to be stripped. The process of
washing out adsorbed material, especially
by use of a solvent.
- The end point is that point in the
exhaustion run of a water conditioner
such as a softener or deionizer at which
the water quality has dropped below an
- The aging process of a body of water
caused by the depletion of available
oxygen. It can be accelerated by human
activities that add too many nutrients to
the water such as barn yard runoff or
- Locations on ion exchange resin beads
which hold mobile ions that are available
for exchange with other ions in a
solution passing through the bed. These
sites are also called functional groups.
- The rate with which one ion is displaced
from an exchanger in favor of another.
- The state of the adsorbent such as
activated carbon, a water softener, or a
deionizer that is no longer capable of
the removal of a specific pollutant or of
useful ion exchange. The exhaustion point
is determined arbitrarily in terms of:
(a) the presence or increase of an
adsorbent contaminant as chlorine; (b) a
value in parts per million of ions in the
effluent solution; (c) the reduction in
quality of the effluent water determined
by a conductivity bridge which measures
the resistance of the water to the flow
of an electric current.
- Ferric Iron
- Small solid iron particles containing
trivalent iron, usually as gelatinous
ferric hydroxide or ferric oxide (Fe2O3),
which are suspended in water and visible
as "rusty" water. Ferrous (iron
in solution) is readily converted to
ferric iron by exposure to oxygen found
both in water and air. Ferric iron can by
removed by filtration, but not by
- Usually ferrous hydroxide which when
dissolved in water produces a clear
solution. Often called clear water iron,
it can be removed by ion-exchange.
- A naturally occurring ore which serves as
a catalytic filter media in the removal
of iron, hydrogen sulfide and manganese.
It normally requires only backwashing,
but the use of oxidizers such as chlorine
or potassium permanganate enhances its
- A device used to clean water by removing
iron, silt, taste, odor, color, etc.,
before it is fed into the softener or
supply lines of the consumer. Includes
mechanical, adsorptive, oxidizing and
neutralizing filters. Available as media
beds in tanks or as cartridge
- The tradename for aluminum silicate
(pumicite) granular product used as a general purpose
filter medium. Lighter in weight, it requires a lower
backwash rate. Typically removed suspended solids down to
the 20-40 micron range.
- The process of passing water through a
porous substance to remove solids in
suspension. Available as media
beds in tanks or as cartridge
- Smaller than the specified size or
particles of ion exchange or filtration
materials. An excess of fines can create
undesirable pressure drop in the system.
- A count of the total number of plumbing
fixtures in a building to estimate peak
flow rates and the sizing of equipment,
especially for commercial buildings.
- An arbitrary unit assigned to different
type of plumbing fixtures, and used to
estimate flow rate and drain capacity
- A distillation process in which hot water
is introduced into a low pressure chamber
causing some of the water to flash or
quickly turn to steam.
- Materials added to water which can cause
gelatinous clouds of precipitate to
enclose fine particles of foreign
material in order to settle or filter
them from the water.
- An in-line self pressure adjusting or
orifice to regulate the flow of water or
regenerant through a water conditioner.
- Flow Rate
- The volume of solution which passes
through a given quantity of resin within
a given time. Flow rate is usually
expressed in terms of gallons per minute
per cubic foot of resin, or as
milliliters per minute per milliliter of
resin. If the flow rate is greater than
it should be, the water will not be
completely softened or filtered.
- Flush Valve
- A self closing valve used for flushing
urinals and toilets. This type of valve
allows flow rates of 15-20 gpm for up to
- In crossflow filtration, it is the
product flow rate through a reverse
osmosis, electrodialysis or
ultrafiltration membrane. It is usually
given in terms of volume unit per time
per membrane area.
- The vertical distance between a bed of
filter media or ion exchange material and
the overflow or collector for backwash
water; the height above the bed of
granular media available for bed
expansion during backwashing. It may be
expressed either as a linear distance or
a percentage of bed depth.
- A common unit of liquid volume; the US
gallon has a volume of 231 cubic inches
or 3.78533 liters; the British (Imperial)
gallon has a volume of 277.418 cubic
inches or 4.54596 liters.
- Granular Activated carbon.
- A form of corrosion which occurs when
dissimilar metals in contact with each
other and with an electrolyte causes on e
of the metals to dissolve and go into
solution. An example would be the result
of connection copper to steel without an
insulating (plastic) coupling or union.
The anode metal with the higher electrode
potential corrodes and the cathode is
- A common protozoan found in water and is
derived from animal droppings. It can
cause contagious waterborne disease
characterized by acute diarrhea. It is
resistant to disinfectants such as
chlorine, iodine, or ultraviolet light.
Giardia can be removed by filters of four
- (gr) A unit of weight equal to 1/7000th
of a pound or 0.0648 gram.
Per Gallon (GPG)
- An expression of concentration of
material in solution. One grain per
gallon is equivalent to 17.1 parts per
million. This is the common reference for
hardness of water.
- A layer or layers of graded gravel and
course sand placed around and above the
underdrain metalwork of a water treatment
system. It facilitates even distribution
and collection of both product water and
- A natural mineral, primarily composed of
complex silicates, which possess ion
exchange properties. Greensand was the
original material used in domestic and
commercial water softeners and is the
base product in the production of
- The term describing all subsurface water
and the source of well water. It can be
found in aquifers as deep as several
- A moderately insoluble calcium sulfate
containing 20.9 percent water. It is
often used to build soil structure and
- A geological term for rock salt, a
mineral which is more than 95 percent
sodium chloride. Also known as native or
- A family of elements that includes
bromine, chlorine, fluorine, astatine,
and iodine. They are very active
chemically. They are commonly found as
the ionic component in compounds with
various other elements.
- A characteristic of natural water due to
the presence of dissolved calcium and
magnesium; water hardness is responsible
for most scale formation in pipes and
water heaters, and forms insoluble
"curd" when it reacts with
soaps. Hardness is usually expressed in
grains per gallon, parts per million, or
milligrams per liter, all as calcium
carbonate equivalent. Temporary hardness,
caused by the presence of magnesium of
calcium bicarbonate, is so called because
it may be removed by boiling the water to
convert the bicarbonates to the insoluble
carbonates. Calcium sulfate, magnesium
sulfate, and the chlorides of these two
metals cause permanent hardness.
- The presence in the effluent of the type
of ions present in the water being
treated. Leakage may be caused by
incomplete regeneration, channeling,
excessive service water, low temperature,
high concentrations of sodium or
interfering TDS in the feedwater.
- Hard water
- Water with a total hardness of one grain
per gallon or more, as calcium carbonate
- A central piping system with two or more
side outlets located at the bottom of a
water conditioning system. It's purpose
is to both collect product water as well
as to distribute backwash water.
- Head loss
- The reduction on 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 glow of the liquid passing through
- Heme Iron
- Organically bound iron that can give
water a pinkish cast. It is found only in
groundwater supplies and cannot be
removed by filtration. Like soluble iron,
heme iron stains fixtures with a rust or
orange coloring. It may draw clear and
turn yellow or pink when exposed to
- The process of purifying a kidney
patients blood by means of a dialysis
membrane. In this process bodily waste is
transferred from the blood into a
hemodialysis grade water which is beyond
- Non-disease causing bacteria
- A chemical, such as sodium
hexametaphosphate, added to water to
increase the solubility of certain ions
and to inhibit precipitation of certain
chemicals. Known as a sequestering agent,
it forms a thin film that protects metals
- Hot Lime
- Partially softens water by adding lime
and soda ash at a water temperature of
about 212 degrees Fahrenheit. It
chemically precipitates calcium,
magnesium, iron, and silica. It also
drives away carbon dioxide.
- 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.
- A complete course of cation exchange
operation in which the cation medium is
regenerated with acid and them all
cations in the water are removed by
exchange with hydrogen ions.
Sulfide (H2 S)
- A corrosive and flammable gas produced
from decaying organic matter, commonly
known as "sulfur".
- The water cycle, including precipitation
of water from the atmosphere as rain or
snow, flow of water over or through the
earth, and evaporation or transpiration
to water vapor in the atmosphere. It is
natures great water conditioner since all
contaminants are left behind on the
- A measurement of structural strength and
ability to hold water pressure.
Hydrostatic pressure is more challenging
to a system than air pressure because air
will compress and absorb impact, whereas
water will not.
- The term used to describe the anionic
hydroxide radical (OH-) which is
responsible for the alkalinity of a
- The water entering a water treatment
- Matter which is not derived from living
organisms and contains no organically
produced carbon; includes rocks, minerals
- A piping arrangement which directs
separate streams through two or more
water treatment units in a balanced
manner, providing equal flow to each
device. The inlets of two or more units
are connected together and the outlets
are connected together such that water
will flow through the units
- A piping system in which all of the
effluent flow of one unit in a water
treatment system is fed to a second and
succeeding unit. This arrangement
achieves a greater reduction of
contaminants than can be obtained by the
passage through a single unit.
- An atom, or group of atoms in a solution
which function as a unit, and has a
positive or negative electrical charge,
due to the gain or loss of one or more
electrons. It is smaller than a colloid.
- A reversible process in which ions are
released from an insoluble permanent
material in exchange for other ions in a
surrounding solution; the direction of
the exchange depends upon the affinities
of the ion exchanger for the ions present
and the concentration of the ions in the
solution. The ion exchanger media is an
insoluble permanent solid medium.
for a product offering.
- A measure of the ability of activated
carbon to adsorb substances with low
molecular weights. It is the milligrams
of iodine that can be adsorbed on one
gram of activated carbon.
- The dissociation of molecules into
simpler, electronically charged
particles. It is related to the gaining
or losing of electrons causing the atoms
to become electronically charged.
- An element often found dissolved in
ground water (in the form of ferrous
iron) in concentrations usually ranging
from zero to 10 ppm (mg/l). It is
objectionable in water supplies because
of the staining caused after oxidation
and precipitation (as ferric hydroxide),
because of tastes, and because of
unsightly colors produced when iron
reacts with tannins in beverages such as
coffee and tea. As little as 0.3 ppm of
iron can cause staining. (See also
ferrous iron, ferric iron, and heme
- Organisms which are capable of utilizing
ferrous iron, either from the water or
from steel pipe, in their metabolism, and
precipitating ferric hydroxide in their
sheaths and gelatinous deposits. These
organisms tend to collect in pipe lines
and tanks during periods of low flow, and
to break loose in slugs of turbid water
to create staining, taste and odor
- The accumulation of iron on and within an
ion exchange resin or filter bed
resulting in a reduced capacity of the
Turbidity Unit (JTU)
- An arbitrary unit of turbidity originally
based on a suspension of specific type of
silica with the turbidity measured in a
Jackson Candle Turbidimeter. This has
been replaced by the nephelometric
turbidity unit (NTU).
- A water treatment media employing copper
and zinc alloy particulates which have a
redox potential. KDF does not support the
growth of bacteria and lasts up to twenty
times longer than activated carbon. KDF
55 granules are effective in removing
chlorine and other water-soluble heavy
metals such as lead. KDF 85 is the choice
for removing iron and hydrogen sulfide.
- A unit of weight; one thousand grains,
17100 ppm, or 0.1429 pounds.
- The study of the relationships between
temperature, motion, and the velocity of
very small particles. It is used to
describe the rate of ion exchange
- A calculated number that gives and
indication of the tendency of water to
form a protective film of calcium
carbonate scale, to dissolve it or be in
equilibrium with it. It does not take
into account the quantities of film
formed, the effect of velocities, oxygen,
carbon dioxide, ammonia, silicon or
natural inhibitors in the water.
Therefore, it is sometimes erroneously
assumed that any water that tends to
dissolve calcium carbonate is
- Leach Field
- Area where septic tank effluent is
distributed by underground piping for
natural leaching and percolation through
- The phenomenon in which some of the
influent ions are not adsorbed and appear
in the effluent. It is usually caused by
an under-regenerated exchange resin bed
or by excessive flow rate.
- A series of bacteria, including
legionella pneumophila, which can cause
pneumonia-like illness called
Legionnaires disease after the American
Legion convention in Philadelphia where
the disease first drew attention. These
bacteria have been found growing in hard
water scale and thrive below 140 degrees
Fahrenheit in water heaters, showers,
humidifiers, etc. Infection is obtained
- The common name for calcium oxide (CaO);
hydrated lime is calcium hydroxide,
- Lime Scale
- Hard water scale containing a high percentage of calcium
carbonate. Insoluble scale is commonly formed when water
containing calcium carbonate is heated. It also forms in
cold water but precipitates at a higher pH.
- Often used by municipalities for partial
reduction of water hardness. After the
addition of baked lime, soda ash is added
to form an insoluble precipitate which is
filtered from the water. This method
leaves five or more grains of hardness.
- Ion exchange resins produced in both
cation and anion versions with 12 percent
or higher cross-linkage. They offer a
higher resistance to oxidation and
- One of the elements making up the earth's
crust, the compounds of which when
dissolved in water make the water hard.
The presence of magnesium in water is a
factor contributing to the formation of
scale and insoluble soap curds.
- A element sometimes found dissolved in
ground water, usually with dissolved iron
but in lower concentrations. It causes
black stains in laundry and plumbing
fixtures at concentrations higher than
0.05 mg/l. It is removed the same way as
iron, by ion-exchange or oxidation and
- Greensand which has been processed to
incorporate in its pores and on its
surface the higher oxides of manganese.
The product has a mild oxidizing power,
and is often used in the oxidation and
precipitation of iron, manganese and/or
hydrogen sulfide, and their removal from
water. It is regenerated by the use of
two to four ounces of a weak solution of
potassium permanganate per cubic foot of
- Maximum Contaminant Level. A drinking
water standard. The maximum amount of a
contaminant allowed in drinking water.
- Maximum Contaminant Level Goal. The goal
set for the maximum amount of a
contaminant to be allowed in drinking
water. Has not been approved to become
- A filter primarily designed for the
removal of suspended solid particles, as
opposed to filters that remove
contaminants by chemical means.
- Also known as parts per billion (ppb).
The common symbol for microgram per liter
- One millionth of an ohm. A unit of
measurement used to test the electrical
resistance of water to determine its
purity. The purer the water, the greater
its resistance to conducting an
electrical current. Water of absolute
purity has a resistance of eighteen
million ohms across one centimeter at a
temperature of twenty-five degrees
- One millionth of a mho. Used to measure
the conductivity and the approximate TDS
content of water. Absolute pure water has
a conductivity of 0.055 micromhos per
centimeter at 25 degrees Celsius. Also
known as micro Siemens. The specific
conductance is the reciprocal of
resistance, therefore MHO is OHM spelled
- A linear measure equal to one millionth
of a meter, or .00003937 inch. The symbol
for the micron is the Greek letter
"µ". The smallest particle
visible to the human eye is 40 microns.
Most types of bacteria range from 0.05 to
10.0 microns in size.
- The term applied to a filter or filter
medium to indicate the particle size
above which all suspended solids will be
removed, throughout the rated capacity.
As used in industry standards, this is an
- (mg/l) A unit concentration of matter
used in reporting the results of water
and wastewater analyses. In dilute water
solutions, it is practically equal to the
part per million, but varies from the ppm
in concentrated solutions such as brine.
As most analyses are performed on
measured volumes of water, the mg/l is a
more accurate expression of the
concentration, and is the preferred unit
- A term applied to inorganic substances,
such as rocks and similar matter found in
the earth's strata, as opposed to organic
substances such as plant and animal
matter. Minerals normally have definite
chemical composition and crystal
structure. The term is also applied to
matter derived from minerals, such as the
inorganic ions found in water. The term
has been incorrectly applied to ion
exchangers, even though most of the
modern materials are organic ion exchange
- The simplest combination of atoms that
will form a specific chemical compound;
the smallest particle of a substance
which will still retain the essential
composition and properties of that
substance, and which can be broken down
only into atoms and simpler substances.
- A membrane process that treats water
between reverse osmosis and
ultrafiltration the filtration/separation
spectrum. It can remove particles in the
300 to 1,000 molecular weight range such
as humic acid and organic color found in
water. Nanofiltration may be used for
selective removal of hardness ions.
Turbidity Unit (NTU)
- The standard unit of measurement used to
measure turbidity in water. It makes use
of a light scattering effect of fine
suspended particles in a light beam. The
NTU has replaced the Jackson Turbidity
Unit (JTU) as the standard of
- A common designation for alkaline
materials such as calcite (calcium
carbonate) or magnesia (magnesium oxide)
used in the neutralization of acid
waters. Alkaline water can also be
neutralized by the addition of an acid.
The neutral point of the pH scale is 7.0,
indicating the presence of equal numbers
of free hydrogen and hydroxide ions.
- Abbreviation for National Sanitation
Foundation Testing Laboratory
- A unit of measure determining the
resistance to passage of an electrical
current. In a solution, it is related to
the electrolyte concentration in the
- The range of pressure, usually expressed
in pounds per square inch, over which a
water conditioning device or water system
is designed to function. Usually 30-100
- Having the characteristics of or being
derived from plant or animal matter, as
opposed to inorganic matter derived from
rocks and minerals. Organic matter is
characterized by its carbon-hydrogen
( i.e., Organic
- Term used to describe any or all of the
compounds with chemical structures based
on carbon. Examples are hydrocarbons,
wood, sugars, proteins, methane,
petroleum-based compounds, solvents,
pesticides, herbicides, trihalomethane
(THM) and trichloroethylene (TCE).
- A process of diffusion of a solvent such
as water through a semi-permeable
membrane which will transmit the solvent
but impede most dissolved substances. The
normal flow of solvent is from the dilute
solution to the concentrated solution.
Osmosis causes the stronger solution to
become more diluted and tends to equalize
the opposing solutions.
- The pressure and potential energy
difference that exists between solutions
on either side of a semi-permeable
membrane. This pressure is caused by the
tendency of water to flow in osmosis.
Every 100 ppm (mg/L) of TDS produces
about one pound per square inch of
osmotic pressure. Osmotic pressure must
first be overcome by water pressure in
the reverse osmosis process.
- Oxalic Acid
- Can be used for the removal of iron
stains from most washable fabrics. Oxalic
acid crystals can be obtained at most
drug stores. It is poisonous and a skin
irritant, therefore precautions must be
- A chemical process in which electrons are
removed from an atom, ion or compound.
The addition of oxygen is a speciform
of oxidation. Combustion is an extremely
rapid form of oxidation, while the
rusting of iron is a slow form. Oxidation
never occurs alone but always as a part
of the oxidation-reduction (redox)
- A chemical substance that brings about
the oxidation of other substances in
chemical oxidation and reduction
reactions. Examples of oxidizing agents
include oxygen, ozone, chlorine and
- A type of filter used to change the
valence state of dissolved molecules,
making them insoluble and therefore
filterable. For example, a filter that
oxidizes ferrous iron, manganous
manganese, and/or anionic sulfur by use
of a catalytic media such as manganese
oxide and then filters the oxidized
precipitant out of the water.
- An unstable form of oxygen (03), which
can be generated by sending a high
voltage electrical discharge through air
or regular oxygen. It is a strong
oxidizing agent and has been used in
water conditioning as a disinfectant. It
can be also produced by some types of
ultraviolet lamps and during lightning
- A term used to describe visible sediment
particles, used as both singular and
Per Billion (ppb)
- A basis for reporting the results of
water and wastewater analysis, indicating
the number of parts by weight of a
dissolved or suspended constituent, per
billion parts by weight of water or other
solvent. One part per billion is equal to
one microgram per liter, the preferred
Per Million (ppm)
- A common basis for reporting the results
of water and wastewater analysis,
indicating the number of parts by weight
of water or other solvent. In dilute
water solutions, one part per million is
practically equal to one milligram per
liter, which is the preferred unit. 17.l
ppm equals one grain per US gallon. One
ppm equals one pound per million pounds
- An expression of the acidity of a
solution; the negative logarithm of the
hydrogen ion concentration (pH 1 very
acidic; pH 14, very basic; pH 7,
neutral). e.g., pH 5 is 10 times the
acidity of 6 and 100 times the acidity of
7. pH is a measure of intensity and not
capacity. It is the logarithm of the
reciprocal of the hydrogen ion
concentration of a solution. The neutral
point of 7 indicates the presence of
equal concentrations of free hydrogen and
free hydroxide ions.
- The definition of six grades of water by
the U.S. Pharmacopoeia is as follows: 1.)
Purified water 2.) Water for injection
3.) Bacteriostatic water for injection
4.) Sterile water for inhalation 5.)
Sterile water for injection 6.) Sterile
water for irrigation.
- An acid-base indicator which produces no
color in an acid solution but turns pink
or red in an alkaline solution.
der Waals Adsorption)
- Binding of adsorbate to the surface of a
solid by forces whose energy levels
approximate those of condensation.
- The quality which an ion exchange resin
must possess to resist changes that might
be caused by attrition, high
temperatures, and other physical
- Point of
- A water treatment device which installs
at the main inlet to a building and acts
as centralized treatment.
- A water treatment system designed to
connect at the actual point-of-use for
water; countertop or undersink treatment
- A sequestering agent used to tie up
hardness and iron in solution. As a
coating agent, it forms a thin
passivating film on metal surfaces to
- The complex network of channels in the
interior of a particle of a sorbent.
- Water softeners, deionizers, and filters
which are designed for removal from its
point of application for transport to a
central station or plant for regeneration
- The electrical potential acquired by an
atom which has lost one or more
electrons; a characteristic of a cation.
- Water which is considered safe and fit
for human consumption, culinary and
domestic purposes and meets the
requirements of the health authority
- Activated carbon in particle sizes
predominantly smaller than 80 mesh.
- The abbreviation for "parts per
- The abbreviation for "parts per
- The application of chlorine to a water
prior to other water treatment processes.
- To cause a dissolved substance to form a
solid particle that can be removed by
settling or filtering. The term also
refers to the solid thus formed.
- Adsorption in which a certain component
or certain components are adsorbed to a
much greater extent than others.
- A decrease in water pressure during its
flow due to internal friction between
molecules of water, and external friction
due to irregularities or roughness in
surfaces past which the water flows.
- Any of a large group of mostly
microscopic, one celled animals living
chiefly in water. Many protozoa's are
parasitic and are higher on the food
chain than the bacteria they eat.
- A natural, glassy aluminum silicate
mineral from volcanic ash which is used
as a water treatment filtration media.
- The removal of undesirable matter from
water or wastewater. It is the
disinfection of water by the killing of
microbial contaminants, such as coliform
bacteria. A strict definition means the
removal from water of all contaminants.
- Biological decomposition of organic
matter by microbes with the production of
ill smelling products. Usually takes
place when there is a deficiency of
- Substances which produce fever when
introduced into humans. Being chemically
stable, pyrogens are not necessarily
destroyed by conditions that kill
bacteria. Pyrogenic means to cause heat.
- A super oxidation media serving as a catalyst in the
removal of iron, hydrogen sulfide and manganese. It works
best at or above a pH of 6.5 and requires no regeneration.
Adequate backwashing is necessary to provide at least 20 per
cent bed expansion of this 120 lb. per cubic foot media.
- Also called a quartz jacket, it is a
clear, pure quartz sleeve that is
installed around the high intensity
ultraviolet lamp in an ultraviolet
system. It retards less than 10 percent
of the radiation dosage in contrast to
the poorer results offered by glass.
- Naturally occurring radioactive elements
such as radium 226 and radium 228 created
in the decay of the uranium and thorium
series. It can be removed from water by
cation exchange softening.
- A short lived radioactive gas produced
from decaying uranium that is soluble in
water. Can be effectively removed by
activated carbon filtration or serration.
Radon is considered carcinogenic when
inhaled by humans.
- Raw Water
- Untreated water from wells or from
surface sources or any water before it
reaches a water treatment device or
- Oxidation processes for restoring the
adsorptive properties of a spent sorbent
such as activated carbon.
- A shortened term for oxidation-reduction.
A reaction where electrons are gained or
lost and new elements are formed.
- The solution used to restore the activity
of an ion exchanger. Acids are employed
to restore a cation exchanger to its
sodium form. The anion exchanger may be
rejuvenated by treatment with an alkaline
solution. Potassium permanganate is used
to regenerate a manganese greensand iron
and manganese iron and manganese removal
- The process of returning the sodium ions
to the mineral after it has exchanged all
its sodium ions for calcium and magnesium
from hard water. This is accomplished by
first back-washing the mineral bed to
free it of all foreign matter, them
passing salt brine through the mineral.
The sodium ions attach themselves to the
mineral, and the calcium and magnesium
combine with the chloride from the brine
to form calcium and magnesium chlorides,
which are rinsed down the drain. All
water softeners using the ion-exchange
process are regenerated with these basic
steps. In similar fashion cation and
anion components of a demineralizer as
well as manganese greensand are recharged
with comparable sequences.
- In crossflow membrane filtration and
deionization, it is the ability of the
membrane to reject the passage of
dissolved solids and other contaminants
into the product water.
- The amount of a specific material
remaining in the water following a water
treatment process. It may refer to
material remaining as the result of
incomplete removal such as hardness
leakage, or to a substance meant to
remain in the treated water such as
- Synthetic organic ion exchange material,
such as the high capacity cation exchange
resin widely used in water softeners.
Technical name- sulfonated co-polymer of
styrene and divinyl benzene.
- The ability of an adsorbent to resist
desorption of an adsorbate.
- The use of an anion exchange unit ahead
of a cation exchange unit- in that order-
in a deionization system.
- A process for the removal of dissolved
ions from water, in which pressure is
used to force the water through a
semi-permeable membrane, which will
transmit the water but reject most other
suspended and dissolved materials. It is
called reverse osmosis because mechanical
pressure is used to force the water to
flow in the direction that is the reverse
of natural osmosis, namely from the
dilute to the concentrated solution.
- The abbreviation for "reverse
- A reddish product of corrosion sometimes
found in water. Rust is formed as a
result of electrochemical interaction
between iron and oxygen in the presence
- An anode constructed of magnesium or
other suitable material and placed in a
water heater tank to accept the
electrolytic activity and to protect the
tank from corrosion.
- Sand Filter
- A treatment device or structure for
removing solid or colloidal material of a
type that cannot be removed by
sedimentation. Such filters can be
gravity rapid-rate or enclosed pressure
- The common name for the specific chemical
compound sodium chloride (NaCl), used in
the regeneration of ion exchange water
softeners. In chemistry, the term is
applied to a class of chemical compounds
which can be formed by the neutralization
of an acid with a base.
- A solution containing the maximum amount
of the dissolved substance that such a
solution can hold at this temperature.
- A polymer matrix or ion exchanger used to
remove organics from feedwater prior to a
- The second step in treating wastewater to
remove suspended and dissolved solids and
biochemical oxygen (BOD) after the
initial primary treatment.
- The use of a selective ion exchange
medium with the property of removing
specific ions from a solution.
- A chemical reaction in which certain ions
are bound into a stable, water soluble
compound, thus preventing undesirable
action by the ions. For example,
polyphosphates can sequester hardness and
prevent reactions with soap.
- Service Run
- That portion of the operating cycle of a
water conditioning unit during which
treated water is being delivered, as
opposed to the period when the unit is
being backwashed, recharged or
- A synthetic, inorganic exchanger produced
by the aqueous reaction of alkali with
- Soda Ash
- The common name for sodium carbonate, a
chemical compound used as an alkaline
builder in some soap and detergent
formulations, to neutralize acid water,
and in the lime- soda ash water treatment
- A strong reducing agent used as the main
ingredient of several resin cleaners used
to clean iron fouled in ion exchange
- Any water that is treated to reduce
hardness minerals to 1.0 GPG (17.1 mg/L)
or less, expressed as calcium carbonate.
- The liquid, such as water, in which other
materials (solutes) are dissolved.
- A yellowish solid chemical element. The
term is also used as a slang expression
to refer to water containing hydrogen
sulfide gas (H2 S).
- The expansion of an ion exchange bed
which occurs when the reactive groups on
the resin are converted from one form to
another. This property is reversible and
indeed, some resins shrink in the
- A toxic volatile organic chemical
typically used as an industrial solvent.
- The abbreviation for "total dissolved solids".
- A naturally occurring substance in wood,
grapeskins, seeds and stems. Is primarily
responsible for the basic
"bitter" component in wines.
Acts as a natural preservative, helping
the development and, in the right
proportion, balance of the wine.
Considered a pollutant when present in
- The third stage in the treatment of
sewage that in a high degree of
conditioning following the reduction of
pollutants accomplished by the primary
and secondary stages of treatment.
Composite Membrane (TFC)
- Reverse osmosis membrane produced with
polyamide-based polymer. It is resistant
to bacteria and can withstand a wide pH
range. However, it cannot tolerate
- The amount of solution passed through an
exchange bed before exhaustion of the
resin is reached.
- The total of all forms of acidity,
including mineral acidity, carbon
dioxide, and acid salts. Total acidity is
usually determined by titration with a
standard base solution to the
phenolphthalein endpoint (pH 8.3).
- The alkalinity of a water as determined
by titration with standard acid solution
to the methyl orange endpoint (pH
approximately 4.5); sometimes abbreviated
as "M alkalinity". Total
alkalinity includes many alkalinity
components, such as hydroxides,
carbonates, and bicarbonates.
- The total amount of chlorine is a
solution, which includes the combined
chlorine as well as the free available
- The weight of solids per unit volume of
water which are in true solution, usually
determined by the evaporation of a
measured volume of filtered water, and
determination of the residue weight. TDS
is expressed as ppm per unit volume of
water. An electrical conductivity test
provides only an estimate of the TDS
since non-conductive substances cannot be
measured by electrical means.
- The sum of all hardness components in a
water, expressed as their equivalent
concentration of calcium carbonate.
Primarily due to calcium and magnesium in
solution, but may include small amounts
of metals such as iron which can act like
calcium and magnesium in certain
reactions. These minerals are scale
forming, affect taste and color of
certain foods and react with soap to form
insoluble soap curds.
- The measurement of carbon dioxide
produced from organics when a water
sample is atomized into a combustion
chamber. The amount of carbon covalently
bound in organic compounds in a water
- The weight of all solids, dissolved and
suspended, organic and inorganic, per
unit volume of water; usually determined
by the evaporation of a measured volume
of water at 105 degrees Celsius in a
- A group of organic chemicals to known to
be carcinogenic in more than trace
amounts which are produced from
chlorination. They reduce the germicidal
activity of chlorine in alkaline water.
- A measure of the amount of finely divided
suspended matter in water, which causes
the scattering and adsorption of light
rays. Turbidity is usually reported in
arbitrary nephalometric turbidity units
(NTU) determined by measurements of light
scattering. NTU should not exceed 0.5 in
potable water. Turbidity can protect
bacteria from sterilization.
- A membrane type system that removes small
colloids and large molecules from
solutions. Ultrafiltration removes
particles in size range between 0.002 to
0.1 micron range. The process falls
between reverse osmosis and
microfiltration as far as the size of
particles removed is concerned.
- No standards exist describing ultrapure
water though it is not considered to be
sterile. It is water that has been
deionized and provides high resistivity
and contains no organics.
- Radiation having a wave length shorter
than 4000 angstroms (visible light) down
to 100 angstroms on the border of the
x-ray region. Ultraviolet light is used
as a disinfectant.
- The operation of an ion exchange unit in
which solutions are passed in at the
bottom and out at the top of the
- A radioactive metallic element found
naturally in combination with other
materials. Uranium 238 is the most common
- A tube with a tapered throat which causes
an increase in velocity thus a decrease
in pressure of the fluid passing through
it. It is the common item used to educt
or suck a regenerant into a water
- The smallest form of life known to be
capable of producing disease or
infection, usually considered to be of
large molecular size. They multiply by
assembly of component fragments in living
cells, rather than be cell division, as
do most bacteria. Being parasitic
infectious microbes, they are much
smaller than bacteria.
Organic Compounds (VOC's)
- Synthetic organic chemicals that vaporize
at relatively low temperatures.
- Void area
- The space between the resin beads in an
ion exchange bed or the space between the
particles of filter media bed. Also can
be defined as the space between the
chunks of salt in a brine tank.
- Virtually any form of water treatment
designed to improve the quality of water,
by neutralization, inhibition or removal
of undesirable substances.
- The shock wave produced by the abrupt
change of water flow through a piping
system. Water hammer produces an
instantaneous multiple increase in the
pressure normal to the system. The
installation of a water hammer arrestor
will absorb these shock waves.
- The reduction or removal of calcium and
magnesium ions which are the principle
cause of hardness in water.
- Water Quality Association. Many
participants in the POU and POE water
conditioning industry are members of this
- A volatile organic chemical (VOC)
commonly used in industry as a solvent.
- Naturally occurring or synthetic hydrated
sodium alumina silicate with ion exchange
properties. Zeolites have been largely
replaced with synthetic organic cation
ion exchange resins.
- Modified Zeolites can be selectively
charged with exchange minerals such as
potassium and used to remove undesirable
elements such as iron, hydrogen, sulfide,
- Zero Soft
- Water with a total hardness less than 1.0
grain per US Gallon (17.1 ppm), as