Water Glossary
ABS
Alkyl
Benzene Sulfonate. A type of surfactant, or surface
active agent, present in synthetic detergents in the United States
before 1965. ABS was especially troublesome because it caused
foaming and resisted breakdown by biological treatment processes.
ABS has been replaced in detergents by linear alkyl
sulfonate (LAS) which is biodegradable.
ACEOPS
See ALLIANCE OF CERTIFIED
OPERATORS, LAB ANALYSTS, INSPECTORS, AND SPECIALISTS
(ACEOPS).
atm
The abbreviation for
atmosphere. One atmosphere is equal to 14.7 psi or 100 kPa.
AWWA
AMERICAN WATER
WORKS ASSOCIATION.
ABANDONED (aBANdund)
No longer in use; a length,
section or portion of a collection system no longer in service and
left in place, underground. For example, when a house or building
is razed or removed the service connection may be left open and
unused.
ABATEMENT (aBAITment)
Putting an end to an
undesirable or unlawful condition affecting the wastewater
collection system. A property owner found to have inflow sources
connected to the collection system may be issued a "NOTICE OF
ABATEMENT." Such notices will usually describe the violation,
suggest corrective measures and grant a period of time for
compliance.
ABSORPTION (abSORPshun)
The taking in or soaking up
of one substance into the body of another by molecular or chemical
action (as tree roots absorb dissolved nutrients in the soil).
ABSORPTION CAPACITY
The amount of liquid which a
solid material can absorb. Sand, as an example, can hold
approximately onethird of its volume in water, or three cubic
feet of dry sand can contain one cubic foot of water. A denser
soil, such as clay, can hold much less water and thus has a lower
absorption capacity.
ABSORPTION RATE
The speed at which a measured
amount of solid material can absorb a measured amount of liquid.
Under pressure, water can infiltrate a given volume of gravel very
rapidly. The water will penetrate (or be absorbed by) sand more
slowly and will take even longer to saturate the same amount of
clay.
ACCOUNTABILITY
When a manager gives
power/responsibility to an employee, the employee ensures that the
manager is informed of results or events.
ACCURACY
How closely an instrument
measures the true or actual value of the process variable being
measured or sensed.
ACID
- A substance that tends to lose a proton.
- A substance that dissolves in water with the
formation of hydrogen ions.
- A substance containing hydrogen which may be
replaced by metals to form salts.
- A substance that is corrosive.
ACID RAIN
Precipitation which has been
rendered (made) acidic by airborne pollutants.
ACID REGRESSION STAGE
A time period when the
production of volatile acids is reduced during anaerobic
digestion. During this stage of digestion ammonia compounds form
and cause the pH to increase.
ACIDIC (uhSIDick)
The condition of water or
soil which contains a sufficient amount of acid substances to
lower the pH below 7.0.
ACIDIFIED (uhSIDuhFIEd)
The addition of an acid
(usually nitric or sulfuric) to a sample to lower the pH below
2.0. The purpose of acidification is to "fix" a sample so it won't
change until it is analyzed.
ACIDITY
The capacity of water or
wastewater to neutralize bases. Acidity is expressed in milligrams
per liter of equivalent calcium carbonate. Acidity is not the same
as pH because water does not have to be strongly acidic (low pH)
to have a high acidity. Acidity is a measure of how much base must
be added to a liquid to raise the pH to 8.2.
ACREFOOT
A volume of water that covers
one acre to a depth of one foot, or 43,560 cubic feet (1,233.5
cubic meters).
ACTIVATED CARBON
Adsorptive particles or
granules of carbon usually obtained by heating carbon (such as
wood). These particles or granules have a high capacity to
selectively remove certain trace and soluble materials from water.
ACTIVATED SLUDGE (ACKtaVATEed
sluj)
Sludge particles produced in
raw or settled wastewater (primary effluent) by the growth of
organisms (including zoogleal bacteria) in aeration tanks in the
presence of dissolved oxygen. The term "activated" comes from the
fact that the particles are teeming with bacteria, fungi, and
protozoa. Activated sludge is different from primary sludge in
that the sludge particles contain many living organisms which can
feed on the incoming wastewater.
ACTIVATED SLUDGE (ACKtaVATEed sluj) PROCESS
A biological wastewater
treatment process which speeds up the decomposition of wastes in
the wastewater being treated. Activated sludge is added to
wastewater and the mixture (mixed liquor) is aerated and agitated.
After some time in the aeration tank, the activated sludge is
allowed to settle out by sedimentation and is disposed of (wasted)
or reused (returned to the aeration tank) as needed. The remaining
wastewater then undergoes more treatment.
ACUTE HEALTH EFFECT
An adverse effect on a human
or animal body, with symptoms developing rapidly.
ADSORBATE (addSOREbait)
The material being removed by
the adsorption process.
ADSORBENT (addSOREbent)
The material (activated
carbon) that is responsible for removing the undesirable substance
in the adsorption process.
ADSORPTION (addSORPshun)
The gathering of a gas,
liquid, or dissolved substance on the surface or interface zone of
another material.
ADVANCED WASTE TREATMENT
Any process of water
renovation that upgrades treated wastewater to meet specific reuse
requirements. May include general cleanup of water or removal of
specific parts of wastes insufficiently removed by conventional
treatment processes. Typical processes include chemical treatment
and pressure filtration. Also called TERTIARY TREATMENT.
AERATION (airAshun)
The process of adding air to
water. Air can be added to water by either passing air through
water or passing water through air.
AERATION (airAshun)
The process of adding air to
water. In wastewater treatment, air is added to freshen wastewater
and to keep solids in suspension. With mixtures of wastewater and
activated sludge, adding air provides mixing and oxygen for the
microorganisms treating the wastewater.
AERATION (airAshun) LIQUOR
Mixed liquor. The contents of
the aeration tank including living organisms and material carried
into the tank by either untreated wastewater or primary effluent.
AERATION (airAshun) TANK
The tank where raw or settled
wastewater is mixed with return sludge and aerated. The same as
aeration bay, aerator, or reactor.
AEROBES
Bacteria that must have
molecular (dissolved) oxygen (DO) to survive. Aerobes are aerobic
bacteria.
AEROBIC (AIRObick)
A condition in which
atmospheric or dissolved molecular oxygen is present in the
aquatic (water) environment.
AEROBIC BACTERIA (AIRObick
backTEAReah)
Bacteria which will live and
reproduce only in an environment containing oxygen which is
available for their respiration (breathing), namely atmospheric
oxygen or oxygen dissolved in water. Oxygen combined chemically,
such as in water molecules (H2O), cannot be used for
respiration by aerobic bacteria.
AEROBIC (AIRObick) DECOMPOSITION
The decay or breaking down of
organic material in the presence of "free" or dissolved oxygen.
AEROBIC (AIRObick) DIGESTION
The breakdown of wastes by
microorganisms in the presence of dissolved oxygen. This digestion
process may be used to treat only waste activated sludge, or
trickling filter sludge and primary (raw) sludge, or waste sludge
from activated sludge treatment plants designed without primary
settling. The sludge to be treated is placed in a large aerated
tank where aerobic microorganisms decompose the organic matter in
the sludge. This is an extension of the activated sludge process.
AEROBIC (AIRObick) PROCESS
A waste treatment process
conducted under aerobic (in the presence of "free" or dissolved
oxygen) conditions.
AESTHETIC (esTHETick)
Attractive or appealing.
GE TANK
A tank used to store a known
concentration of chemical solution for feed to a chemical feeder.
Also called a DAY TANK.
AGGLOMERATION (aGLOMerAshun)
The growing or coming
together of small scattered particles into larger flocs or
particles which settle rapidly. Also see
FLOC.
AGRONOMIC RATES
Sludge application rates
which provide the amount of nitrogen needed by the crop or
vegetation grown on the land while minimizing the amount that
passes below the root zone.
AIR BINDING
The clogging of a filter,
pipe or pump due to the presence of air released from water. Air
entering the filter media is harmful to both the filtration and
backwash processes. Air can prevent the passage of water during
the filtration process and can cause the loss of filter media
during the backwash process.
AIR BINDING
The clogging of a pipe or
pump due to the presence of air released from water.
AIR BLOWER
A device used to ventilate
manholes and lift stations.
AIR GAP
An open
vertical drop, or vertical empty space, that separates a drinking
(potable) water supply to be protected from another water system
in a water treatment plant or other location. This open gap
prevents the contamination of drinking water by backsiphonage or
backflow because there is no way raw water or any other water can
reach the drinking water.
AIR GAP
An open
vertical drop, or vertical empty space, between a drinking
(potable) water supply and the point of use in a wastewater
treatment plant. This gap prevents the contamination of drinking
water by backsiphonage because there is no way wastewater can
reach the drinking water.
AIR GAP
An open vertical drop, or
vertical empty space, between a drinking (potable) water supply
and the point of use. This gap prevents backsiphonage because
there is no way wastewater can reach the drinking water. Air gap
devices are used to provide adequate space above the top of a
manhole and the end of the hose from the fire hydrant. This gap
ensures that no wastewater will flow out the top of a manhole,
reach the end of the hose from a fire hydrant, and be sucked or
drawn back up through the hose to the water supply.
AIR LIFT
A special type of pump. This
device consists of a vertical riser pipe submerged in the
wastewater or sludge to be pumped. Compressed air is injected into
a tail piece at the bottom of the pipe. Fine air bubbles mix with
the wastewater or sludge to form a mixture lighter than the
surrounding water which causes the mixture to rise in the
discharge pipe to the outlet. An airlift pump works like the
center stand in a percolator coffee pot.
AIR PADDING
Pumping dry air (dew point
-40°F) into a container to assist with the withdrawal of a liquid
or to force a liquified gas such as chlorine out of a container.
AIR PADDING
Pumping dry air (dew point
-40°F) into a container to assist with the withdrawal of a liquid
or to force a liquified gas such as chlorine or sulfur dioxide out
of a container.
AIR RELIEF
A type of valve used to allow
air caught in high spots in pipes to escape.
AIR STRIPPING
A treatment process used to
remove dissolved gases and volatile substances from water. Large
volumes of air are bubbled through the water being treated to
remove (strip out) the dissolved gases and volatile substances.
AIR STRIPPING
A physical treatment process
used to remove volatile substances from wastestreams. The process
transfers volatile pollutants from a high concentration in the
wastestream into an air stream with a lower concentration of the
pollutant. The process requires the wastestream containing the
volatile pollutant to come in contact with large volumes of air.
AIR TEST
A method of inspecting a
sewer pipe for leaks. Inflatable or similar plugs are placed in
the line and the space between these plugs is pressurized with
air. A drop in pressure indicates the line or run being tested has
leaks.
ALARM CONTACT
A switch that operates when
some preset low, high or abnormal condition exists.
ALGAE (ALgee)
Microscopic plants which
contain chlorophyll and live floating or suspended in water. They
also may be attached to structures, rocks or other submerged
surfaces. Excess algal growths can impart tastes and odors to
potable water. Algae produce oxygen during sunlight hours and use
oxygen during the night hours. Their biological activities
appreciably affect the pH, alkalinity, and dissolved oxygen of the
water.
ALGAE (ALgee)
Microscopic plants which
contain chlorophyll and live floating or suspended in water. They
also may be attached to structures, rocks, or other submerged
surfaces. Algae produce oxygen during sunlight hours and use
oxygen during the night hours. Their biological activities
appreciably affect the pH, alkalinity, and dissolved oxygen of the
water.
ALGAL (AL-gull) BLOOM
Sudden, massive growths of
microscopic and macroscopic plant life, such as green or
bluegreen algae, which develop in lakes and reservoirs.
ALGICIDE (ALjuhSIDE)
Any substance or chemical
specifically formulated to kill or control algae.
ALIGNMENT (aLINEment)
The proper positioning of
parts in a system. The alignment of a pipeline or other line
refers to its location and direction.
ALIPHATIC (ALuhFATick) HYDROXY
ACIDS
Organic acids with carbon
atoms arranged in branched or unbranched open chains rather than
in rings.
ALIQUOT (ALlikwot)
Portion of a sample. Often an
equally divided portion of a sample.
ALKALI (ALkalie)
Any of certain soluble salts,
principally of sodium, potassium, magnesium, and calcium, that
have the property of combining with acids to form neutral salts
and may be used in chemical water treatment processes.
ALKALI (ALkalie)
Any of certain soluble salts,
principally of sodium, potassium, magnesium, and calcium, that
have the property of combining with acids to form neutral salts
and may be used in chemical processes such as water or wastewater
treatment.
ALKALINE (ALkaLINE)
The condition of water or
soil which contains a sufficient amount of alkali substances to
raise the pH above 7.0.
ALKALINITY (ALkaLINittee)
The capacity of water to
neutralize acids. This capacity is caused by the water's content
of carbonate, bicarbonate, hydroxide, and occasionally borate,
silicate, and phosphate. Alkalinity is expressed in milligrams per
liter of equivalent calcium carbonate. Alkalinity is not the same
as pH because water does not have to be strongly basic (high pH)
to have a high alkalinity. Alkalinity is a measure of how much
acid must be added to a liquid to lower the pH to 4.5.
ALKALINITY (ALkaLINittee)
The capacity of water or
wastewater to neutralize acids. This capacity is caused by the
water's content of carbonate, bicarbonate, hydroxide, and
occasionally borate, silicate, and phosphate. Alkalinity is
expressed in milligrams per liter of equivalent calcium carbonate.
Alkalinity is not the same as pH because water does not have to be
strongly basic (high pH) to have a high alkalinity. Alkalinity is
a measure of how much acid must be added to a liquid to lower the
pH to 4.5.
ALLUVIAL (uhLOUveeul)
Relating to mud and/or sand
deposited by flowing water. Alluvial deposits may occur after a
heavy rainstorm.
ALLIANCE OF CERTIFIED OPERATORS,
LAB ANALYSTS, INSPECTORS, AND SPECIALISTS (ACEOPS)
A professional organization
for operators, lab analysts, inspectors, and specialists dedicated
to improving professionalism; expanding training, certification,
and job opportunities; increasiing information exchange; and
advocating the importance of certified operators, lab analysts,
inspectors, and specialists. For information on membership,
contact ACEOPS, 1810 Bel Air Drive, Ames, IA 50010, phone (515)
663-4128 or email: ACEOPS@aol.com.
ALLUVIAL (uhLOUveeul) DEPOSIT
Sediment (clay, silt, sand,
gravel) deposited in place by the action of running water.
ALTERNATING CURRENT (A.C.)
An electric current that
reverses its direction (positive/negative values) at regular
intervals.
ALTITUDE VALVE
A valve that automatically
shuts off the flow into an elevated tank when the water level in
the tank reaches a predetermined level. The valve automatically
opens when the pressure in the distribution system drops below the
pressure in the tank.
AMBIENT (AMbeeent)
Surrounding. Ambient or
surrounding atmosphere.
AMBIENT (AMbeeent) TEMPERATURE
Temperature of the
surrounding air (or other medium). For example, temperature of the
room where a gas chlorinator is installed.
AMBIENT (AMbeeent) TEMPERATURE
Temperature of the
surroundings.
AMERICAN WATER WORKS ASSOCIATION
A professional organization
for all persons working in the water utility field. This
organization develops and recommends goals, procedures and
standards for water utility agencies to help them improve their
performance and effectiveness. For information on AWWA membership
and publications, contact AWWA, 6666 W. Quincy Avenue, Denver, CO
80235. Phone (303) 7947711.
AMPERAGE (AMpurrage)
The strength of an electric
current measured in amperes. The amount of electric current flow,
similar to the flow of water in gallons per minute.
AMPERE (AMpeer)
The unit used to measure
current strength. The current produced by an electromotive force
of one volt acting through a resistance of one ohm.
AMPEROMETRIC (amPURRoMETrick)
A method of measurement that
records electric current flowing or generated, rather than
recording voltage. Amperometric titration is a means of measuring
concentrations of certain substances in water.
AMPEROMETRIC (am-PURR-o-MET-rick)
TITRATION
A means of measuring
concentrations of certain substances in water (such as strong
oxidizers) based on the electric current that flows during a
chemical reaction.
AMPHOTERIC (AMfuhTURick)
Capable of reacting
chemically as either an acid or a base.
AMPLITUDE
The maximum strength of an
alternating current during its cycle, as distinguished from the
mean or effective strength.
ANAEROBES
Bacteria that do not need
molecular (dissolved) oxygen (DO) to survive.
ANAEROBES
Bacteria that do not need
dissolved molecular oxygen (DO) to survive.
ANAEROBIC (ANairObick)
A condition in which
atmospheric or dissolved molecular oxygen is NOT present in
the aquatic (water) environment.
ANAEROBIC BACTERIA (ANairObick
backTEAReah)
Bacteria that live and
reproduce in an environment containing no "free" or dissolved
oxygen. Anaerobic bacteria obtain their oxygen supply by breaking
down chemical compounds which contain oxygen, such as sulfate (SO42-).
ANAEROBIC (ANairObick)
DECOMPOSITION
The decay or breaking down of
organic material in an environment containing no "free" or
dissolved oxygen.
ANAEROBIC (AN-air-O-bick) DIGESTER
A wastewater solids treatment
device in which the solids and water (about 5 percent solids, 95
percent water) are placed in a large tank where bacteria decompose
the solids in the absence of dissolved oxygen.
ANAEROBIC (ANairObick)
DIGESTION
Wastewater solids and water
(about 5% solids, 95% water) are placed in a large tank where
bacteria decompose the solids in the absence of dissolved oxygen.
At least two general groups of bacteria act in balance: (1)
SAPROPHYTIC bacteria break down complex solids to volatile
acids, the most common of which are acetic and propionic acids;
and (2) METHANE FERMENTERS break down the acids to methane,
carbon dioxide, and water.
ANAEROBIC SELECTOR
Anaerobic refers to the
practical absence of dissolved and chemically bound oxygen.
Selector refers to a reactor or basin and environmental conditions
(food, lack of DO) intended to favor the growth of certain
organisms over others.
ANALOG
The readout of an instrument
by a pointer (or other indicating means) against a dial or scale.
ANALOG
The readout of an instrument
by a pointer (or other indicating means) against a dial or scale.
Also the continuously variable signal type sent to an analog
instrument (for example, 4-20 mA).
ANALOG READOUT
The readout of an instrument
by a pointer (or other indicating means) against a dial or scale.
ANALYZER
A device which conducts
periodic or continuous measurement of some factor such as
chlorine, fluoride or turbidity. Analyzers operate by any of
several methods including photocells, conductivity or complex
instrumentation.
ANGLE OF REPOSE
The
angle between a horizontal line and the slope or surface of
unsupported material such as gravel, sand, or loose soil. Also
called the "natural slope."
Found in: 
O&M of
Wastewater Collection Systems, Vol I & II
ANGSTROM (ANGstrem)
A unit of length equal to
onetenth of a nanometer or onetenbillionth of a meter (1
Angstrom = 0.000 000 000 1 meter). One Angstrom is the approximate
diameter of an atom.
ANHYDROUS (anHIdrous)
Very dry. No water or
dampness is present.
ANIMAL WASTES
- Urine and fecal wastes of living animals.
- Wastes of animal tissue from meat processing
(feathers included), or hospital, surgical and clinical facility
wastes of animal types.
- Similar to (2) above, but cooked or prepared
wastes of animal tissues and bones from domestic or commercial
food preparation.
ANION (ANEYEen)
A negatively charged ion in
an electrolyte solution, attracted to the anode under the
influence of a difference in electrical potential. Chloride ion (Cl-)
is an anion.
ANIONIC (ANeyeONick) POLYMER
A polymer having negatively
charged groups of ions; often used as a filter aid and for
dewatering sludges.
ANNULAR (ANyouler) SPACE
A
ringshaped space located between two circular objects, such as
two pipes.
ANNULAR (ANyouler) SPACE
A
ringshaped space located between two circular objects. For
example, the space between the outside of a pipe liner and the
inside of a pipe.
ANODE (anOd)
The positive pole or
electrode of an electrolytic system, such as a battery. The anode
attracts negatively charged particles or ions (anions).
ANODIZING
An electrochemical process
which deposits a coating of an insoluble oxide on a metal surface.
Aluminum is the most frequently anodized material.
ANOXIC (anOXick)
Oxygen deficient or lacking
sufficient oxygen.
ANOXIC (anOXick)
A condition in which the
aquatic (water) environment does not contain enough dissolved
molecular oxygen, which is called an oxygen deficient condition.
Generally refers to an environment in which chemically bound
oxygen, such as in nitrate, is present.
ANOXIC DENITRIFICATION (deeNYEtruhfuhKAYshun)
A biological nitrogen removal
process in which nitrate nitrogen is converted by microorganisms
to nitrogen gas in the absence of dissolved oxygen.
ANTAGONISTIC REACTION
An interaction between two or
more individual compounds that produces an injurious effect upon
the body (or an organism) which is LESS than either of the
substances alone would have produced.
APARTMENT COMPLEX
One or more residential
buildings at a single location. An apartment building may contain
several residences with a single connection to the wastewater
collection system. A complex can have several buildings with a
single connection.
APPARENT COLOR
Color of the water that
includes not only the color due to substances in the water but
suspended matter as well.
APPROPRIATIVE
Water rights to or ownership
of a water supply which is acquired for the beneficial use of
water by following a specific legal procedure.
APPURTENANCE (uhPURRtennans)
Machinery, appliances,
structures and other parts of the main structure necessary to
allow it to operate as intended, but not considered part of the
main structure.
AQUEOUS (Akweeus)
Something made up of, similar
to, or containing water; watery.
AQUIFER (ACKwifer)
A natural underground layer
of porous, waterbearing materials (sand, gravel) usually capable
of yielding a large amount or supply of water.
AQUIFER (ACKwifer)
A porous, waterbearing
geologic formation. Usually refers only to materials capable of
yielding a substantial amount of water.
ARCH
- The curved top of a sewer pipe or conduit.
- A bridge or arch of hardened or caked
chemical which will prevent the flow of the chemical.
ARTESIAN (areTEEzhun)
Pertaining to groundwater, a
well, or underground basin where the water is under a pressure
greater than atmospheric and will rise above the level of its
upper confining surface if given an opportunity to do so.
ARTIFICIAL GROUNDWATER TABLE
A groundwater table that is
changed by artificial means. Examples of activities that
artificially raise the level of a groundwater table include
agricultural irrigation, dams and excessive sewer line
exfiltration. A groundwater table can be artificially lowered by
sewer line infiltration, water wells, and similar drainage
methods.
ASEPTIC (aSEPtick)
Free from the living germs of
disease, fermentation, or putrefaction. Sterile.
ASPHYXIATION (assFIXeeashun)
An extreme condition often
resulting in death due to a lack of oxygen and excess carbon
dioxide in the blood from any cause. Also called suffocation.
ASPIRATE (ASSperRATE)
Use of a hydraulic device
(aspirator or eductor) to create a negative pressure (suction) by
forcing a liquid through a restriction, such as a Venturi. An
aspirator (the hydraulic device) may be used in the laboratory in
place of a vacuum pump; sometimes used instead of a sump pump.
ASSOCIATION OF BOARDS OF
CERTIFICATION (ABC)
An international organization
representing over 150 boards which certify the operators of
waterworks and wastewater facilities. For information on ABC
publications regarding the preparation of and how to study for
operator certification examinations, contact ABC, 208 Fifth
Street, Ames, IA 500106259. Phone (515) 2323623.
ASYMMETRIC (AseeMETrick)
Not similar in size, shape,
form or arrangement of parts on opposite sides of a line, point or
plane.
ATOM
The smallest unit of a
chemical element; composed of protons, neutrons and electrons.
ATTACHED GROWTH PROCESSES
Wastewater treatment
processes in which the microorganisms and bacteria treating the
wastes are attached to the media in the reactor. The wastes being
treated flow over the media. Trickling filters and rotating
biological contactors are attached growth reactors. These reactors
can be used for BOD removal, nitrification and denitrification.
AUDIT, WATER
A thorough examination of the
accuracy of water agency records or accounts (volumes of water)
and system control equipment. Water managers can use audits to
determine their water distribution system efficiency. The overall
goal is to identify and verify water and revenue losses in a water
system.
AUGER (AWgrr)
A sharp tool used to go
through and break up or remove various materials that become
lodged in sewers.
AUTHORITY
The power and resources to do
a specific job or to get that job done.
AUTOIGNITION TEMPERATURE
The temperature at which a
material will spontaneously ignite and sustain combustion.
AUTOTROPHIC (autoTROFick)
Describes organisms (plants
and some bacteria) that use inorganic materials for energy and
growth.
AVAILABLE CHLORINE
A measure of the amount of
chlorine available in chlorinated lime, hypochlorite compounds,
and other materials that are used as a source of chlorine when
compared with that of elemental (liquid or gaseous) chlorine.
AVAILABLE EXPANSION
The vertical distance from
the sand surface to the underside of a trough in a sand filter.
This distance is also called FREEBOARD.
AVERAGE
A number obtained by adding
quantities or measurements and dividing the sum or total by the
number of quantities or measurements. Also called the arithmetic
mean.
Average = Sum of Measurements / Number of Measurements
AVERAGE DEMAND
The total demand for water
during a period of time divided by the number of days in that time
period. This is also called the average daily demand.
AXIAL TO IMPELLER
The direction in which
material being pumped flows around the impeller or flows parallel
to the impeller shaft.
AXIS OF IMPELLER
An imaginary line running
along the center of a shaft (such as an impeller shaft).