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A Dictionary of Technical and Legal Terms
Related to Drinking Water
Go to the concise consumer-friendly glossary.
A
ABC. See Association of Boards of Certification.
absorbed dose. The amount of a chemical that enters the body of an
exposed organism.
absorption. The uptake of water or dissolved chemicals by a cell
or an organism (as tree roots absorb dissolved nutrients in the soil).
absorption factor. The fraction of a chemical making contact with
an organism that is absorbed by the organism.
acceptable daily Intake (ADI). Estimate of the largest amount of
chemical to which a person can be exposed on a daily basis that is not
anticipated to result in adverse effects (usually expressed in mg/kg/day).
Same as RfD.
accuracy. How closely an instrument measures the true or actual
value of the process variable being measured or sensed.
acid mine drainage. Drainage of water from areas that have been
mined for coal of other mineral ores; the water has low pH, sometimes less
than 2.0 (is acid), because of its contact with sulfur-bearing material;
acid drainage is harmful because it often kills aquatic organisms.
acid rain. Precipitation which has been rendered (made) acidic by
airborne pollutants.
acidic (uh-SID-ick). The condition of water or soil which contains
a sufficient amount of acid substances to lower the pH below 7.0.
acidified (uh-SID-uh-FIE-d). 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
acre-foot A volume of water that covers one acre to a depth of one
foot, or 43,560 cubic feet (1233.5 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.
active transport. An energy-expending mechanism by which a cell
moves a chemical across the cell membrane from a point of lower
concentration to a point of higher concentration, against the diffusion
gradient.
action level. The concentration of lead or copper in water
specified at Code of Federal Regulations 141.80(c) which determines, in some
cases, the treatment requirements contained in subpart I of this part that a
water system is required to complete.
acute. Occurring over a short period of time; used to describe
brief exposures and effects which appear promptly after exposure.
acute exposure. A single exposure to a toxic substance which
results in severe biological harm or death. Acute exposures are usually
characterized as lasting no longer than a day.
acute toxicity. The ability of a substance to cause poisonous
effects resulting in severe biological harm or death soon after a single
exposure or dose. Also, any severe poisonous effect resulting from a single
short-term exposure to a toxic substance.
additive effect. Combined effect of two or more chemicals equal to
the sum of their individual effects.
adsorbate (add-SORE-bait). The material being removed by the
adsorption process.
adsorbent (add-SORE-bent). The material (activated carbon) that is
responsible for removing the undesirable substance in the adsorption
process.
adsorption. The process by which chemicals are held on the surface
of a mineral or soil particle (compare with Absorption).
aeration (air-A-shun). The process of adding air to water. Air can
be added to water by either passing air through water or passing water
through air.
aerobic (air-0-bick). A condition in which free" (atmospheric) or
dissolved oxygen is present in the water.
age tank. A tank used to store a chemical solution of known
concentration for feed to a chemical feeder. Also called a day tank.
aggregate. A mass or cluster of soil particles, often having a
characteristic shape.
agrochemical. Synthetic chemicals (pesticide and fertilizers) used
in agricultural production.
air binding. A situation where air enters the filter media. Air 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 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 padding. Pumping dry air into a container to assist with the
withdrawal of a liquid or to force a liquefied gas such as chlorine out of a
container.
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. Also see packed tower aeration.
alarm contact. A switch that operates when some pre-set low, high
or abnormal condition exists.
algae. Microscopic plants which contain chlorophyll and live
floating or suspended in water. They also may be attached to structures,
rocks or other submerged surfaces. They are food for fish and small aquatic
animals. 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 and dissolved
oxygen of the water.
algal bloom (AL-gull). Sudden, massive growths of microscopic
and macroscopic plant life, such as green or bluegreen algae, which
develop in lakes and reservoirs.
algicide (AL-gi-SIDE). Any substance or chemical specifically
formulated to kill or control algae.
aliphatic hydroxy acids (Al-uh-FAT-ick). Organic acids with carbon
atoms arranged in branched or unbranched open chains rather than in rings.
aliquot (AL-li-kwot). Portion of a sample.
alkali (AL-ka-lie). Various 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.
alkaline (Al-ka-LINE). The condition of water or soil which
contains a sufficient amount of alkali substances to raise the pH above 7.0.
alkalinity (AL-ka-LIN-it-tee). 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 can be added to a liquid without causing a great
change in pH.
alluvial (uh-LOU-vee-ul). Relating to mud and/or sand deposited by
flowing water. Alluvial deposits may occur after a heavy rain storm.
alternating current (A.C.). An electric current that reverses its
direction (positive/negative values) at regular intervals.
ambient. Environmental or surrounding conditions.
ambient temperature (AM-bee-ent). Temperature of the surrounding
air (or other medium). For example, temperature of the room where a gas
chlorinator is installed.
ammonium. One form of nitrogen that is usable by plants.
amperage (AM-purr-age). 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 (AM-peer). The unit used to measure current strength. The
current produced by electromotive force of one volt acting through a
resistance of one ohm
amperometric (am-PURR-o-MET-rick). Based on the electric current
that flows between two electrodes in a solution.
amperometric 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. See titrate.
anaerobic (AN-air-O-bick). A condition in which "free"
(atmospheric) or dissolved oxygen is NOT present in water.
analog. 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 turgidity.
Analyzers operate by any of several methods including photocells,
conductivity or complex instrumentation.
animal studies. Investigations using animals as surrogates for
humans, on the expectation that results in animals are pertinent to humans.
anion (AN-EYE-en). A negatively charged ion in an electrolyte
solution, attracted to the anode under the influence of a difference in
electrical potential. Chloride (CI-) is an anion.
anionic polymer (AN-eye-ON-ick). A polymer having negatively
charged groups of ions; often used as a filter aid and for dewatering
sludges.
annular space (AN-you-ler). A ring-shaped space located between
two circular objects, such as two pipes.
anode (an-0-d). The positive pole or electrode of an electrolytic
system, such as a battery. The anode attracts negatively charged
particles or ions (anions).
antagonism. Interference or inhibition of the effect of one
chemical by the action of another chemical.
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 (uh-PURR-ten-nans). 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.
aquatic. Plants of animal life living in, growing in, or adapted
to water.
aqueous (A-kwee-us). Something made up of, similar to, or
containing water; watery.
aquifer (ACK-wi-fer). A natural underground layer of porous,
water-bearing materials (sand, gravel) usually capable of yielding a large
amount or supply of water.
artesian (are-TEE-zhun - aquifer or well). Water held under
pressure in porous rock or soil confined by impermeable geologic
formations. An artesian well is free flowing. See confined aquifer .
aseptic (a-SEP-tick). Free from the living germs of disease,
fermentation or putrefaction. Sterile.
assay. A test for a particular chemical or effect.
Association of Boards of Certification. An international
organization representing over 150 boards which certify the operators of
waterworks and waste water facilities. For information on ABC publications
regarding the preparation of and how to study for operator certification
examinations, contact ABC, 4261/2 Fifth Street, P.O. Box 786, Ames, Iowa
50010-0786.
asymmetric (A-see-MET-rick). 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.
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.
axial to impeller. The direction in which material being pumped
flows around the impeller or flow parallel to the impeller shaft.
axis of impeller. An imaginary line running along the center of a
shaft (such as an impeller shaft).
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B
back pressure. A pressure that can cause water to backflow into
the water supply when a user's water system is at a higher pressure than the
public water system.
backflow. A reverse flow condition, created by a difference in
water pressures, which causes water to flow back into the distribution pipes
of a potable water supply from any source or sources other than an intended
source. Also see backsiphonage and cross-connection.
background level. In toxic substances monitoring, the average
presence of a substance in the environment, originally referring to
naturally occurring phenomena.
backsiphonage. A form of backflow caused by a negative or below
atmospheric pressure within a water system. Also see backflow and
cross-connection.
backwashing. The process of reversing the flow of water back
through the filter media to remove the entrapped solids.
bacteria (back-TEER-e-uh). Singular: bacterium. Microscopic
living organisms usually consisting of a single cell. Bacteria can aid in
pollution control by consuming or breaking down organic matter in sewage, or
by similarly acting on oil spills or other water pollutants. Some bacteria
in soil, water or air may also cause human, animal and plant health
problems.
baffle. A flat board or plate, deflector, guide or similar device
constructed or placed in flowing water or slurry systems to cause more
uniform flow velocities, to absorb energy, and to divert, guide, or agitate
liquids (water, chemical solutions, slurry).
bailer (BAY-ler). A 10- to 20-foot-long pipe equipped with a valve
at the lower end. A bailer is used to remove slurry from the bottom or the
side of a well as it is being drilled.
base metal. A metal (such as iron) which reacts with dilute
hydrochloric acid to form hydrogen. Also see noble metal.
batch process. A treatment process in which a tank or reactor is
filled, the water is treated or a chemical solution is prepared, and the
tank is emptied. The tank may then be filled and the process repeated.
best available technology (BAT). The best technology treatment
techniques, or other means which the Administrator finds, after
examination for efficacy under field conditions and not solely under
laboratory conditions, are available (taking cost into consideration). For
the purposes of setting MCLs for synthetic organic chemicals, any BAT must
be at least as effective as granular activated carbon.
best management practices (BMPs). Structural, nonstructural and
managerial techniques that are recognized to be the most effective and
practical means to control nonpoint source pollutants yet are compatible
with the productive use of the resource to which they are applied. BMPs are
used in both urban and agricultural areas.
bias. An inadequacy in experimental design that leads to results
or conclusions not representative of the population under study.
bioaccumulation. The retention and concentration of a substance by
an organism.
bioassay. Test which determines the effect of a chemical on a
living organism.
biochemical oxygen demand (BOD). The amount of oxygen consumed by
microorganisms (mainly bacteria) and by chemical reactions in the
biodegradation of organic matter.
bioconcentration. The accumulation of a chemical in tissues of an
organism (such as fish) to levels that are greater than the level in the
medium (such as water) in which the organism resides (see bioaccumulation).
biodegradation. Decomposition of a substance into more elementary
compounds by the action of microorganisms such as bacteria.
biological growth. The activity and growth of any and all living
organisms.
bioremediation. A process of adding nutrient to ground water to
speed up the natural process in which bacteria break down gasoline into
harmless compounds.
biotransformation. Conversion of a substance into other compounds
by organisms; includes biodegradation.
black water. Liquid and solid human body waste and the carriage
water generated through toilet usage.
blank. A bottle containing only dilution water or distilled water;
the sample being tested is not added. Tests are frequently run on a SAMPLE
and a BLANK and the differences are compared.
BOD. See biochemical oxygen demand.
bonnet (BON-it). The cover on a gate valve.
brackish. Mixed fresh and salt waters.
brake horsepower. 1) The horsepower required at the top or end of
a pump shaft (input to a pump). 2) The energy provided by a motor or other
power source.
breakpoint chlorination. Addition of chlorine to water until the
chlorine demand has been satisfied. At this point, further additions of
chlorine will result in a free residual chlorine that is directly
proportional to the amount of chlorine added beyond the breakpoint.
breakthrough. A crack or break in a filter bed allowing the
passage of floc or particulate matter through a filter. This will cause an
increase in filter effluent turbidity. A breakthrough can occur: 1) when a
filter is first placed in service, 2) when the effluent valve suddenly opens
or closes, and 3) during periods of excessive head loss through the filter
(including when the filter is exposed to negative heads).
brinelling (bruh-NEL-ing). Tiny indentations (dents) high on the
shoulder of the bearing race or bearing. A type of bearing failure.
buffer. A solution or liquid whose chemical makeup neutralizes
acids or bases without a great change in pH.
buffer capacity. A measure of the capacity of a solution or liquid
to neutralize acids or bases. This is a measure of the capacity of water for
offering a resistance to changes in pH.
buffer strips. Strips of grass or other close-growing vegetation
that separate a waterway (ditch, stream, creek) from an intensive land use
area (subdivision, farm); also referred to as filter strips, vegetated
filter strips, and grassed buffers.
bw. Body weight.
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C
C factor. A factor of value used to indicate the smoothness of the
interior of a pipe. The higher the C Factor, the smoother the pipe, the
greater the carrying capacity, and the smaller the friction or energy losses
from water flowing in the pipe. To calculate the C Factor, measure the flow,
pipe diameter, distance between two pressure gages, and the friction or
energy loss of the water between the gages. C Factor = Flow (GPM)/193.75
(Diameter, ft)2.63 (Slope)0.54
caisson (KAY-sawn). A structure or chamber which is usually sunk
or lowered by digging from the inside. Used to gain access to the bottom of
a stream or other body of water.
CAG. Carcinogen Assessment Group.
calcium carbonate (CACO3 ) equivalent. An expression of the
concentration of specified constituents in water in terms of their
equivalent value to calcium carbonate. For example, the hardness in water
which is caused by calcium, magnesium and other ions is usually described
as calcium carbonate equivalent.
calibration. A procedure which checks or adjusts an instrument's
accuracy by comparison with a standard or reference.
cancer. A disease characterized by the rapid and uncontrolled
growth of aberrant cells into malignant tumors.
capillary action. The movement of water through very small spaces
due to molecular forces.
capillary forces. The molecular forces which cause the movement of
water through very small spaces.
capillary fringe. The porous material just above the water table
which may hold water by capillarity (a property of surface tension that
draws water upwards) in the smaller void spaces.
capital costs. Costs (usually long-term debt) of financing
construction and equipment. Capital costs are usually fixed, one-time
expenses which are independent of the amount of water produced.
carcinogen (car-SIN-o-jen). Any substance which tends to produce
cancer in an organism.
carcinogenic. Cancer-producing.
CAS registration number. A number assigned by the Chemical
Abstracts Service to identify a chemical.
catalyst (CAT-uh-LIST). A substance that changes the speed or
yield of a chemical reaction without being consumed or chemically changed by
the chemical reaction.
catalyze (CAT-uh-LIZE). To act as a catalyst. Or, to speed up a
chemical reaction.
catalyzed (CAT-uh-LIZED). To be acted upon by a catalyst.
cathode (KA-thow-d). The negative pole or electrode of an
electrolytic cell or system. The cathode attracts positively charged
particles or ions (cations).
cathodic protection (ca-THOD-ick). An electrical system for
prevention of rust, corrosion, and pitting of metal surfaces which are in
contact with water or soil. A low-voltage current is made to flow through a
liquid (water) or a soil in contact with the metal in such a manner that the
external electromotive force renders the metal structure cathodic. This
concentrates corrosion on auxiliary anodic parts which are deliberately
allowed to corrode instead of letting the structure corrode.
cation (CAT-EYE-en). A positively charged ion in an electrolyte
solution, attracted to the cathode under the influence of a difference in
electrical potential. Sodium ion (Na+) is a cation.
cationic polymer. A polymer having positively charged groups of
ions; often used as a coagulant aid.
cavitation (CAV-uh-TAY-shun). The formation and collapse of a gas
pocket or bubble on the blade of an impeller or the gate of a valve. The
collapse of this gas pocket or bubble drives water into the impeller or gate
with a terrific force that can cause pitting on the impeller or gate
surface. Cavitation is accompanied by loud noises that sound like someone is
pounding on the impeller or gate with a hammer.
central nervous system. Portion of the nervous system which
consists of the brain and spinal cord; CNS.
centrate. The water leaving a centrifugal after most of the solids
have been removed.
centrifugal pump (sen-TRIF-h-gull). A pump consisting of an
impeller fixed on a rotating shaft that is enclosed in a casing, and having
an inlet and discharge connection. As the rotating impeller whirls the water
around, centrifugal force builds up enough pressure to force the water
through the discharge outlet.
centrifuge. A mechanical device that uses centrifugal or
rotational forces to separate solids from liquids.
check valve. A special valve with a hinged disc or flap that opens
in the direction of normal flow and is forced shut when flows attempt to go
in the reverse or opposite direction of normal flow.
chelation (key-LAY-shun). A chemical complexing (forming or
joining together) of metallic cations (such as copper) with certain organic
compounds, such as EDTA (ethylene diamine tetracetic acid). Chelation is
used to prevent the precipitation of metals (copper). Also see
sequestration.
chemical oxygen demand (COD). An indirect measure of the amount of
oxygen used by inorganic and organic matter in water. The measure is a
laboratory test based on a chemical oxidant and therefore does not
necessarily correlate with biochemical oxygen demand.
chisel plowing. Cropland preparation by a special implement
(chisel) that avoids complete inversion of the soil (as occurs with
conventional moldboard plowing). Chisel plowing can leave a protective cover
of crop residues on the soil surface that helps prevent erosion and improve
infiltration.
chloramines (KLOR-uh-means). Compounds formed by the reaction of
hypochlorous acid (or aqueous chlorine) with ammonia.
chlorination (KLOR-uh-NAY-shun). The application of chlorine to
water, generally for the purpose of disinfection, but frequently for
accomplishing other biological or chemical results (aiding coagulation and
controlling tastes and odors).
chlorinator (KLOR-uh-NAY-ter). A metering device which is used to
add chlorine to water.
chlorine-contact chamber. That part of a water treatment plant
where effluent is disinfected by chlorine.
chlorine demand. Chlorine demand is the difference between the
amount of chlorine added to water and the amount of residual chlorine
remaining after a given contact time. Chlorine demand may change with
dosage, time, temperature, pH, and nature and amount of the impurities in
the water. Chlorine Demand, mg/L = Chlorine Applied, mg/L - Residual, mg/L
chlorine requirement. The amount of chlorine which is needed for a
particular purpose. Some reasons for adding chlorine are reducing the number
of coliform bacteria (Most Probable Number), obtaining a particular chlorine
residual, or oxidizing some substance in the water. In each case a definite
dosage of chlorine will be necessary. This dosage is the chlorine
requirement.
chlorophenolic (klor-o-FEE-NO-lick). Chlorophenolic compounds are
phenolic compounds (carbolic acid) combined with chlorine.
chlorophenoxy (KLOR-o-fuh-KNOX-ee). A class of herbicides that may
be found in domestic water supplies and cause adverse health effects. Two
widely used chlorophenoxy herbicides are 2,4-D (2,4-Dichlorophenoxy acetic
acid) and 2,4,5-TP (2,4,5-Trichlorophenoxy propionic acid (silvex)).
chlororganic (klor-or-GAN-nick). Organic compounds combined with
chlorine. These compounds generally originate from, or are associated with,
life processes such as those of algae in water.
chronic. Occurring over a long period of time, either continuously or intermittently; used to describe ongoing exposures and effects that
develop only after a long exposure.
chronic exposure. Long-term, low-level exposure to a toxic
chemical.
circle of influence. The circular outer edge of a depression
produced in the water table by the pumping of water from a well. Also see
cone of influence and cone of depression.
circuit. The complete path of an electric current, including the
generating apparatus or other source; or, a specific segment or section of
the complete path.
circuit breaker. A safety device in an electrical circuit that
automatically shuts off the circuit when it becomes overloaded. The device
can be manually reset.
cistern (SIS-turn). A small tank (usually covered) or a storage
facility used to store water for a home or farm. Often used to store rain
water.
clarifer (KLAIR-uh-fire). A large circular or rectangular tank or
basin in which water is held for a period of time, during which the heavier
suspended solids settle to the bottom. Clarifiers are also called SETTLING
BASINS and SEDIMENTATION BASINS.
class (pipe and fittings). The working pressure rating of a
specific pipe for use in water distribution systems which i includes
allowances for surges. This term is used for cast iron, ductile iron,
asbestos cement and some plastic pipe.
clay. One type of soil particle with a diameter of approximately
one ten-thousandth of an inch.
clay soil. A soil containing more than 40 percent clay, but less
than 45 percent sand, and less than 40 percent silt.
clear well. A reservoir for the storage of filtered water of
sufficient capacity to prevent the need to vary the filtration rate with
variations in demand. Also used to provide chlorine contact time for
disinfection.
clinical studies. Studies of humans suffering from symptoms
induced by chemical exposure.
coagulant aid. Any chemical or substance used to assist or modify
coagulation.
coagulants (co-AGG-you-lents). Chemicals that cause very fine
particles to clump together into larger particles. This makes it easier to
separate the solids from the water by settling, skimming, draining or
filtering.
coagulation (co-AGG-yoo-LAY-shun). The clumping together of very
fine particles into larger particles caused by the use of chemicals
(coagulants). The chemicals neutralize the electrical charges of the fine
particles and cause destabilization of the particles. This clumping together
makes it easier to separate the solids from the water by settling, skimming,
draining, or filtering.
cohesion. Molecular attraction which holds two particles together.
coliform (COAL-i-form). A group of bacteria found in the
intestines of warm-blooded animals (including humans) also in plants, soil,
air and water. Fecal coliforms are a specific class of bacteria which only
inhibit the intestines of warm-blooded animals. The presence of coliform a
is an indication that the water is polluted and may contain pathogenic
organisms.
coliform organism. Microorganisms found in the intestinal tract of
humans and animals. Their presence in water indicates fecal pollution and
potentially dangerous bacterial contamination by disease-causing
microorganisms.
colloids (CALL-loids). Very small, finely divided solids
(particles that do not dissolve) that remain dispersed in a liquid for a
long time due to their small size and electrical charge. When most of the
particles in water have a negative electrical charge, they tend to repel
each other. This repulsion prevents the particles from clumping together,
becoming heavier, and settling out.
colorimetric measurement. A means of measuring unknown chemical
concentrations in water by measuring a sample's color intensity. The
specific color of the sample, developed by addition of chemical reagents, is
measured with a photoelectric colorimeter or is compared with "color
standards" using, or corresponding with, known concentrations of the
chemical.
combined available residual chlorine. The concentration of
residual chlorine which is combined with ammonia (NH3) and/or organic
nitrogen in water as a chloramine (or other chloro derivative) yet is still
available to oxidize organic matter and utilize its bactericidal properties.
combined residual chlorination. The application of chlorine to
water to produce combined available residual chlorine. This residual can be
made up of monochloramines, dichloramines, and nitrogen trichloride.
combined sewer. A sewer that transports surface runoff and human
domestic wastes (sewage), and sometimes industrial wastes. Wastewater and
runoff in a combined sewer may occur in excess of the sewer capacity and
cannot be treated immediately. The excess is frequently discharged directly
to a receiving stream without treatment, or to a holding basin for
subsequent treatment and disposal.
community water system (C.W.S.). A public water system which
serves at least 15 service connections used by yearround residents or
regularly serves at least 25 year-round residents. Also see non-community
water system, transient water system and non-transient non-community water
system.
complete treatment. A method of treating water which consists of
the addition of coagulant chemicals, flash mixing, coagulation -
flocculation, sedimentation and filtration. Also called CONVENTIONAL
FILTRATION.
compliance cycle. Thee nine-year calendar year cycle during which
public water systems must monitor. Each compliance cycle consists of three
three-year compliance periods. The first calendar year cycle begins January
1, 1993 and ends December 31, 2001; the second begins January 1, 2002 and
ends December 31, 2010; the third from January 1, 2011 to December 31, 2019,
etc.
compliance period. A three year calendar period within a
compliance cycle. Each compliance cycle has three three-year compliance
periods. Within the first compliance cycle, the first compliance period runs
from January 1, 1993 to December 31, 1995; the second from January 1, 1996
to December 31, 1998; the third from January 1, 1999 to December 31, 2001.
composite (proportional) samples (come-PAH-zit). A composite
sample is a collection of individual samples obtained at regular intervals,
usually every one or two hours during a 24-hour time span. Each individual
sample is combined with the others in proportion to the rate of flow when
the sample was collected The resulting mixture (composite sample) forms a
representative sample and is analyzed to determine the average conditions
during the sampling period.
composting. A controlled microbial degradation of organic waste
yield an environmentally sound, nuisance-free product of potential value as
a soil conditioner.
compound. A substance composed of two or more elements whose
composition is constant. For example, table salt (sodium chloride - NACl) is
a compound.
concentration polarization. 1) The ratio of the salt concentration in the membrane boundary layer to the salt concentration in the
bulk stream. The most common and serious problem resulting from
concentration polarization is the increasing tendency for precipitation of
sparingly soluble salts and the deposition of particulate matter on the membrane surface. 2) Used in corrosion studies to indicate a depletion of ions
near an electrode. 3) The basis for chemical analysis by a polarograph.
conductance. A rapid method of estimating the dissolved solids
content of a water supply. The measurement indicates the capacity of a
sample of water to carry an electrical current, which is related to the
concentration of ionized substances in the water. Also called SPECIFIC
CONDUCTANCE.
conductivity. A measure of the ability of a solution (water) to
carry an electric current.
conductor. A substance, body, device or wire that readily conducts
or carries electrical current.
cone of depression. The depression, roughly conical in shape,
produced in the water table by the pumping of water from a well. Also see
circle of influence and cone of influence.
cone of influence. The depression, roughly conical in shape,
produced in the water table by the pumping of water from a well. Also see
circle of influence and cone of depression
confined aquifer. An aquifer in which ground water is confined
under pressure which is significantly greater than atmospheric pressure. See
artesian aquifer.
confluent growth. A continuous bacterial growth covering the
entire filtration area of a membrane filter, or a portion thereof, in which
bacterial colonies are not discrete.
confounding factors. Variables other than chemical exposure level
which can affect the incidence or degree of a parameter being measured.
consumptive use. Water removed from available supplies without
direct return to a water resource system for uses such as manufacturing,
agriculture, and food preparation.
contactor. An electrical switch, usually magnetically operated.
contaminant Any physical, chemical, biological, or radio-logical
substance or matter that has an adverse effect on air, water, or soil.
contamination. The introduction into water of microorganisms,
chemicals, toxic substances, wastes, or wastewater in a concentration that
makes the water unfit for its next intended use.
continuous sample. A flow of water from a particular place in a
plant to the location where samples are collected for testing. This
continuous stream may be used to obtain grab or composite samples.
Frequently, several taps (faucets) will flow continuously in the laboratory
to provide test samples from various places in a water treatment plant.
contour farming. A conservation-based method of farming in which
all farming operations (for example, tillage and planting) are performed
across (rather than up and down) the slope. Ideally, each crop row is
planted at right angles to the ground slope.
contour strip farming. A kind of contour farming in which row
crops are planted in strips, between alternating strips of close-growing,
erosion resistant forage (grass, grain, hay) crops.
control loop. The path through the control system between the
sensor, which measures a process variable, and the controller, which
controls or adjusts the process variable.
control system. A system which senses and controls its own
operation on a close, continuous basis in what is called proportional (or
modulating) control.
controller. A device which controls the starting, stopping, or
operation of a device or piece of equipment.
conventional filtration. A method of treating water to remove
particulates. The method consists of the addition of coagulant chemicals,
flash mixing, coagulation - flocculation, sedimentation and filtration.
Also called COMPLETE TREATMENT. Also see direct filtration and in-line
filtration.
conventional filtration treatment A series of processes including
coagulation, flocculation, sedimentation, and filtration resulting in
substantial particulate removal.
conventional tillage. The traditional method of farming in which
soil is prepared for planting by completely inverting it with a moldboard
plow. Subsequent working of the soil with other implements is usually
performed to smooth the soil surface. Bare soil is exposed to the weather
for some varying length of time depending on soil and climatic conditions.
conventional treatment See conventional filtration Also called
COMPLETE TREATMENT.
conveyance loss. Water lost in conveyance (pipe, channel, conduit,
ditch) by leakage or evaporation.
corporation stop. A water service shutoff valve located at a
street water main. This valve cannot be operated from the ground surface
because it is buried and there is no valve box. Also called a CORPORATION
COCK.
corrosion. The gradual decomposition or destruction of a material
by chemical action, often due to an electrochemical reaction. Corrosion
may be caused by: 1) stray current electrolysis, 2) galvanic corrosion
caused by dissimilar metals, or 3) differential concentration cells.
Corrosion starts at the surface of a material and moves inward.
corrosion inhibitor. A substances that slows the rate of corrosion
of metal plumbing materials by water, especially lead and copper materials,
by forming a protective film on the interior surface of those materials.
corrosivity. An indication of the corrosiveness of a water. The
corrosiveness of a water is described by the water's pH, alkalinity,
hardness, temperature, total dissolved solids, dissolved oxygen
concentration, and the Langelier Index.
cost/beneflt analysis. A quantitative evaluation of the costs
which would be incurred versus the overall benefits to society of a proposed
action such as the establishment of an acceptable dose of a toxic chemical.
cost sharing. A publicly financed program through which society,
as the beneficiary of environment protection, shares part of the cost of
pollution control with those who must actually install the controls.
coulomb (COO-lahm). A measurement of the amount of electrical
charge conveyed in one second by an electric current of one ampere. One
coulomb equals about 6.25 x 1018electrons (6,250,000,000,000,000,000
electrons).
coupon. A steel specimen inserted into water to measure the
corrosiveness of water. The rate of corrosion is measured as the loss of
weight of the coupon (in milligrams) per surface area (in square decimeters)
exposed to the water per day. 10 decimeters = 1 meter = 100 centimeters
cover crop. A crop that provides temporary protection for delicate
seedlings and/or provides a canopy for seasonal soil protection and
improvement between normal crop production periods. Except in orchards
where permanent vegetative cover is maintained, cover crops usually are
grown for one year of less. When plowed under and incorporated into the
soil, cover crops are also referred to as gren manure crops.
crop rotation. A system of farming in which a regular succession
of different crops are planted on the same land area, as opposed to growing
the same crop time after time (monoculture).
cross connection. Any actual or potential connection between a
drinking (potable) water system and an unapproved water supply or other
source of contamination. For example, if you have a pump moving nonpotable
water and hook into the g water system to supply water for the pump seal, a
cross-connection or mixing between the two water systems can occur. This
mixing may lead to contamination of the drinking water. Also see backsiphonage and backflow.
CT or CTcalc. The product of "residual disinfectant concentration" (C) in mg/l determined before or at the first customer, and the
corresponding "disinfectant contact time" (T) in minutes, i.e., "C" x "T".
If a public water system applies disinfectants at more than one point prior
to the first customer, it must determine the CT of each disinfectant
sequence before or at the first customer to determine the total percent
inactivation or "total inactivation ratio".In determining the total
inactivation ratio, the public water system must determine the residual
disinfectant concentration of each disinfection sequence and corresponding
contact time before any subsequent disinfection application point(s).
"CT99.9" is the CT value required for 99.9 Percent (3-log) inactivation of
Giardia lamblia cysts. CT99.9 a variety of disinfectants and conditions
appear in Tables 1. l- 1.6, 2.1, and 3.1 of section 141.74(b)(3) in the code
of Federal Regulations. CT99.9 is the inactivation ratio. The sum of the
inactivation ratios, or total inactivation ratio shown as E = (CT calc) /
(CT99.9) is calculated by adding together the inactivation ratio for each
disinfection sequence. A total inactivation ratio equal to or greater than
1.0 is assumed to provide a 3-log inactivation of Giardia lamblia cysts.
cumulative exposure. The summation of exposures of an organism to
a chemical over a period of time.
curb stop. A water service shutoff valve located in a water
service pipe near the curb and between the water main and the building. This
valve is usually operated by a wrench or valve key and is used to start or
stop flows in the water service line to a building. Also called a "curb
cock."
curie. A measure of radioactivity. One Curie of radioactivity is
equivalent to 3.7 x 1010 or 37,000,000,000 nuclear disintegrations per
second.
current. A movement or flow of electricity. Water flowing in a
pipe is measured in gallons per second past a certain point, not by the
number of water molecules going past a point. Electric current is measured
by the number of coulombs per second flowing past a certain point in a
conductor. A coulomb is equal to about 6.25 x 1018 electrons
(6,250,000,000,000,000,000 electrons). A flow of one coulomb per second is
called one ampere, the unit of the rate of flow of current.
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D
dateometer (day-TOM-uh-ter). A small calendar disc attached to
motors and equipment to indicate the year in which the last maintenance
service was performed.
day tank. A tank used to store a chemical solution of known
concentration for feed to a chemical feeder. A day tank usually stores
sufficient chemical solution to properly treat the water being treated for
at least one day. Also called an AGE TANK.
dead end. The end of a water main which is not connected to other
parts of the distribution system by means of a connecting loop of pipe
decant To draw off the upper layer of liquid (water) after the
heavier material (a solid or another liquid) has settled.
dechlorination (dee-KLOR-uh-NAY-shun). The deliberate removal of
chlorine from water. The partial or complete reduction of residual chlorine
by any chemical or physical process.
decibel (
DES-uh-bull). A unit for expressing the relative intensity of
sounds on a scale from zero for the average least perceptible sound to about
130 for the average level at which sound causes pain to humans.
decomposition. The conversion of chemically unstable materials to
more stable forms by chemical or biological action. If organic matter decays
when there is no oxygen present (anaerobic conditions or putrefaction),
undesirable tastes and odors are produced. Decay of organic matter when
oxygen is present (aerobic conditions) tends to produce much less
objectionable tastes and odors.
defluoridation (de-FLOOR-uh-DAY-shun). The removal of excess
fluoride in drinking water to prevent the mottling (brown stains) of teeth.
degasification (DEE-GAS-if-uh-KAY-shun). A water treatment process
which removes dissolved gases from the water. The gases may be removed by
either mechanical or chemical treatment methods or a combination of both.
degradation. Chemical or biological breakdown of a complex
compound into simpler compounds.
demineralization (DEE-MIN-er-al-uh-ZAY-shun). A treatment process
which removes dissolved minerals (salts) from water.
denitrification. The biochemical conversion of nitrate; and
nitrite nitrogen in the soil dissolved in water to gaseous nitrogen.
density (DEN-sit-tee). A measure of how heavy a substance (solid,
liquid or gas) is for its size. Density is expressed in terms of weight per
unit volume, that is, grams per cubic centimeter or pounds per cubic foot.
The density of water is 1.0 gram per cubic centimeter or about 62.4 pounds
per cubic foot.
dermal exposure. Contact between a chemical and the skin.
desalinization (DEE-SAY-leen-uh-ZAY-shun). The removal of
dissolved salts (such as sodium chloride, NACI) from water by natural means
(leaching) or by specific water treatment processes.
desiccant (DESS-uh-kant). A drying agent which is capable of
removing or absorbing moisture from the atmosphere in a small enclosure.
desiccation (DESS-uh-KAY-shun). A process used to thoroughly dry
air; to remove virtually all moisture from air.
desiccator (DESS-uh-KAY-tor). A closed container into which heated
weighing or drying dishes are placed to coot in a dry environment. The
dishes may be empty or they may contain a sample. Desiccators contain a
substance, such as anhydrous calcium chloride, which absorbs moisture and
keeps the relative humidity near zero so that the dish or sample will not
gain weight from absorbed moisture.
destratification (de-STRAT-uh-fuh-KAY-shun).The development of
vertical mixing within a lake or reservoir to eliminate (either totally or
partially) separate layers of temperature, plant, or animal life. This
vertical mixing can be caused by mechanical means (pumps) or through the use
of forced air diffusers which release air into the lower layers of the
reservoir.
detention lag. The time period between the moment a change is made
and the moment when such a change is finally sensed by the associated
measuring instrument.
detention time. 1) The theoretical (calculated) time required for
a small amount of water to pass through a tank at a given rate of flow. 2)
The actual time in hours, minutes or seconds that a small amount of water is
in a settling basin, flocculating basin or rapid-mix chamber. In storage
reservoirs, detention time is the length of time entering water will be held
before being drafted for use (several weeks to years, several months being
typical). Detention Time (hr) = Basin Volume (gal.)(24 hr/day)t Flow
(gal/day)
dew point. The temperature to which air with a given quantity of
water vapor must be cooled to cause condensation of the vapor in the air.
d
ewater. 1) To remove or separate a portion of the water present in
a sludge or slurry. To dry sludge so it can be handled and disposed. 2) To
remove or drain the water from a tank or a trench.
diatomaceous earth. A fine, siliceous (made of silica) "earth"
composed mainly of the skeletal remains of diatoms, a type of
free-floating, microscopic plant found in the ocean.
diatomaceous earth filtration (DE filtration). A filtration method
resulting in substantial particulate removal, that uses a process in which:
1) a "precoat" cake of diatomaceous earth filter media is deposited on a
support membrane (septum), and 2) while the water is filtered by passing
through the cake on the septum, additional filter media, known as "body
feed," is continuously added to the feed water to maintain the permeability
of the filter cake.
diffusion. The movement of suspended or dissolved particles from a
more concentrated to a less concentrated region as a result of the random
movement of individual particles; the process tends to distribute them
uniformly throughout the available volume.
digital readout Use of numbers to indicate the value or
measurement of a variable. The readout of an instrument by a direct,
numerical reading of the measured value.
dilute solution. A solution that has been made weaker usually by
the addition of water.
dimictic (die-MICK-tick). Lakes and reservoirs which freeze over
and normally go through two stratification and two mixing cycles within a
year.
direct current (D.C.). Electrical current flowing in one direction
only and essentially free from pulsation.
direct filtration. A filtration method of treating water which
consists of the addition of coagulant chemicals, flash mixing, coagulation,
minimal flocculation, and filtration. The flocculation facilities may be
omitted, but the physical-chemical reactions will occur to some extent. The
sedimentation process is omitted. Also see conventional filtration and
in-line filtration.
direct runoff. Water that flows over the ground surface or through
the ground directly into streams, rivers, or lakes.
discharge head. The pressure (in pounds per square inch or psi)
measured at the centerline of a pump discharge and very close to the
discharge flange, converted into feet.
disinfectant. Any oxidant, including but not limited to chlorine,
chlorine dioxide, chloramines, and ozone, that is added to water in any part
of the treatment or distribution process and is intended to kill or
inactivate pathogenic microorganisms.
disinfectant contact time ("T" in CT calculations). The time in
minutes that it takes for water to move from the point of disinfectant
application or the previous point of disinfectant residual measurement to a
point before or at the point where residual disinfectant concentration (C)
Is measured. Where only one C is measured. T is the time in minutes that it
takes for water to move from the point of disinfectant application to a
point before or at where residual disinfectant concentration (C) is
measured. Where more than one C is measured, T is (a) for the first measurement of C, the time in minutes that it takes for water to move from the
first or only point of disinfectant application to a point before or at the
point where the first C+ is measured and (b) for subsequent measurements of
C, the time in minutes that it takes for water to move from the previous C
measurement point to the C measurement point for which the particular T is
being calculated - Disinfectant contact time in pipelines must be calculated
based on plug flow by dividing the internal volume of the pipe by the
maximum hourly flow rate through that pipe. Disinfectant contact time within
mixing basins and storage reservoirs must be determined by tracer studies or
an equivalent demonstration.
disinfection. The process designed to kill most microorganisms
in water, including essentially all pathogenic (disease causing) bacteria.
There are several ways to disinfect, with chlorine being most frequently
used in water treatment. Compare with sterilization.
disinfection by-product A compound formed by the reaction of a
disinfectant such as chlorine with organic material in the water supply.
dissolved oxygen (DO). Measure of water quality indicating free
oxygen dissolved in water.
distillate (DIS-tuh-late). In the distillation of a sample, a
portion is evaporated; the part that is condensed afterwards is the
distillate.
divalent (die-VAY-lent). Having a valence of two, such as the
ferrous ion, Fe2+.
diversion. 1) Use of part of a stream flow as a water supply. 2) A
structural conveyance (or ditch) constructed across a slope to intercept
runoff flowing down a hillside, and divert it to some convenient discharge
point.
Domestic or Other Non-distribution System Plumbing Problem. A
coliform contamination problem in a public water system with more than one
service connection that is limited to the specific service connection from
which the coliform positive sample was taken.
dosage. The quantity of a chemical administered to an organism. -
dose. The actual quantity of a chemical to which an organism is
exposed. See absorbed dose.
dose equivalent. The product of the absorbed dose from ionizing
radiation and such factors as account for differences In biological
effectiveness due to the " of radiation and is distribution in the body as
specified by the International Commission on Radiological Units and
Measurements (ICRU).
dose-response. A quantitative relationship between the dose of a
chemical and an effect caused by the chemical.
dose-response curve. A graphical presentation of the relationship
between degree of exposure to a chemical (dose) and observed biological
effect or response. -
dose-response evaluation. A component of risk assessment that
describes the quantitative relationship between the amount of exposure to a
substance and the extent of toxic injury or disease.
dose-response relationship. The quantitative relationship between
the amount of exposure to a substance and the extent of toxic injury
produced.
downgradients The direction that ground water flows; similar in
concept to: downstream for surface water, such as a river.
DPD (pronounce as separate letters). A method of measuring the
chlorine residual in water. The residual may be determined by either
titrating or comparing a developed color with color standards. DPD stands
for N,N-diethyl-p-phenylene-diamine.
draft 1) The act of drawing or removing water from a tank or
reservoir. 2) The water which is drawn or removed from a tank or reservoir.
drainage. A technique to improve the productivity of some
agricultural land by removing excess water from the soil; surface drainage
is accomplished with open ditches; subsurface drainage uses porous conduits
(drain tile) buried beneath the soil surface.
drainage basin. The area of land that drains water, sediment, and
dissolved materials to a common outlet at some point along a stream channel.
Also see watershed.
drawdown. 1) The drop in the water table or level of water in the
ground when water is being pumped from a well. 2) The amount of water used
from a tank or reservoir. 3) The drop in the water level of a tank or
reservoir.
DWEL (Drinking Water Equivalent Level). Estimated exposure (in
mg/L) which is interpreted to be protective for non carcinogenic endpoints
of toxicity over a lifetime of exposure. DWEL was developed for chemicals
that have a significant carcinogenic potential (Group B). Provides risk
manager with evaluation on non-cancer endpoints, but infers that
carcinogenicity should be considered the toxic effect of greatest concern.
dynamic pressure. When a pump is operating, the vertical distance
(in feet) from a reference point (such as a pump centerline) to the
hydraulic grade line is the dynamic head.
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E
eductor (e-DUCK-ter). A hydraulic device used to create a negative
pressure (suction) by forcing a liquid through a restriction, such as a
Venturi. An eductor or aspirator (the hydraulic device) may be used in the
laboratory in place of a vacuum pump. As an injector, it is used to produce
vacuum for chlorinators.
effective corrosion Inhibitor residual. A concentration of
corrosion inhibitor sufficient to form a protective coating on the interior
walls of a pipe, reducing its corrosion.
effective range. That portion of the design range (usually upper
90 percent) in which an instrument has acceptable accuracy. Also see range
and span
effective size (E.S.). The diameter of the particles in a granular
sample (filter media) for which 10 percent of the total grains are smaller
and 90 percent larger on a weight basis. Effective size is obtained by
passing granular material through sieves with varying dimensions of mesh and
weighing the material retained by each sieve. The effective size is also
approximately the average size of the grains.
effluent (EF-loo-ent). Water or some other liquid-raw, partially
or completely treated-flowing from a reservoir, basin, treatment process or
treatment plant.
ejector. A device used to disperse a chemical solution into water
being treated.
electrochemical reaction. Chemical changes produced by electricity
(electrolysis) or the production of electricity by chemical changes
(galvanic action). In corrosion, a chemical re-action is accompanied by
the flow of electrons through a metallic path. The electron flow may come
from. an external force and cause the reaction, such as electrolysis caused
by a D.C. (direct current) electric railway or the electron flow may be
caused by a chemical reaction as in the galvanic action of a flashlight dry
cell.
electrochemical sries. A list of metals with the standard
electrode potentials given in volts. The size and sip of the electrode
potential indicates how easily these elements will take on or give up
electrons, or corrode. Hydrogen is conventionally assigned a value of zero.
electrolysis (ee-leck-TRAWL-us-sis). The decomposition of material
by an outside electrical current.
electrolyte (ee.-LECK-tro-LIGHT). A substance which dissociates
(separates) into two or more ions when it is dissolved in water.
electrolytic cell (ee-LECK-tro-LIT-ick). A device in which the
chemical decomposition of material causes an electric current to flow. Also,
a device in which a chemical reaction occurs as a result of the flow of
electric current. Chlorine and caustic (NaOH) are made from salt (NACl in
electrolytic cells.
electromotive force (E.M.F.). The electrical pressure available to
cause a flow of current (amperage) when an electrical circuit is closed. See
voltage
electromotive series. A list of metals and alloys presented in the
order of their tendency to con-ode (or go into solution). Also called the
Galvanic Series. This is a practical application of the theoretical
ELECTROCHEMICAL SERIES.
electron. An extremely small, negatively charged particle; the
part of an atom that determines its chemical properties.
element. A substance which cannot be separated into its
constituent parts and still retain its chemical identity. For example,
sodium (Na) is an element.
end bells. Devices used to hold the rotor and stator of a motor in
position.
end point. Samples are titrated to the end point. This means that
a chemical is added, drop by drop, to a sample until a certain color change
(blue to clear, for example) occurs. This is called the END POINT of the
titration. In addition to a color change, an end point may be reached by the
formation of a precipitate or the reaching of a specified pH. An end point
may be detected by the use of an electronic device such as a pH meter.
endangerment assessment. A site-specific risk assessment of the
actual or potential danger to human health or welfare and the environment
from the release of hazardous substances or waste. The endangerment
assessment document is prepared in support of enforcement actions under
CERCLA or RCRA.
endemic (en-DEM-ick). Something peculiar to a particular people or
locality, such as a disease which is always present in the population.
endrin (EN-drin). A pesticide toxic to freshwater and marine
aquatic life that produces adverse health effects in domestic water
supplies.
energy grade line (E.G.L.). A line that represents the elevation
of energy head of water flowing in a pipe, conduit or channel. The line is
drawn above the hydraulic grade line (gradient) a distance equal to the
velocity head (V2/2g) of the water flowing at each section or point along
the pipe or channel. Also see hydraulic gradeline.
enteric. Of intestinal origin, especially applied to wastes or
bacteria.
entrain. To trap bubbles in water either mechanically through
turbulence or chemically through a reaction.
enzymes (EN-zimes). Organic substances (produced by living
organisms) which cause or speed up chemical reactions. Organic catalysts
and/or biochemical catalysts.
EPA United States Environmental Protection Agency.
epidemic. Widespread outbreak of a disease, or a large number of
cases of a disease in a single community or relatively small area. Disease
may spread from person to person, and/or by the exposure of many persons to
a single source, such as a water supply.
epidemiologic study. Study of human populations to identify causes
of disease. Such studies often compare the health status of a group of
persons who have been exposed to a suspect agent with that of a comparable
non-exposed group.
epidemiology (EP-uh-DE-me-ALL-o-gee). A branch of medicine which
studies epidemics (diseases which affect significant numbers of people
during the same time period in the same locality). The objective of
epidemiology is to determine the factors that cause epidemic diseases and
how to prevent them.
epilimnion (EP-ub-LIM-knee-on). The upper layer of water in a
thermally stratified lake or reservoir. This layer consists of the warmest
water and has a fairly uniform (constant) temperature. The layer is readily
mixed by wind action.
erosion. Wearing away of soil by timing water, wind, or ice;
erosion is the process by which the earth's surface is shaped and occurs
even in remote, uninhabited areas at a slow rate (geologic erosion); of more
concern is accelerated erosion caused by people's activities.
ester. A compound formed by the reaction between an acid and an
alcohol with the elimination of a molecule of water.
eutrophic (you-TRO-fick). Reservoirs and lakes which are rich in
nutrients and very productive in terms of aquatic animal and plant life.
eutrophication (you-TRO-fi-KAY-shun). The increase in the nutrient
levels of a lake or other body of water; this usually causes an increase in
the growth of aquatic animal and plant life.
evaporation. The process by which water or other liquid becomes a
gas (water vapor or ammonia vapor). Water from land areas, bodies of water,
and all other moist surfaces is absorbed into the atmosphere as a vapor.
evapotranspiration (ee-VAP-o-TRANS-purr-A-shun). The combined
processes of evaporation and transpiration. It can be defined as the sum of
water used by vegetation and water lost by evaporation.
exemption. A State with primacy may relieve a public water system
from a requirement respecting an MCL,treatment technique or both, by
granting an exemption if certain conditions exist. These are: 1) the system
cannot comply with a MCL or treatment technique due to compelling factors
which may include economic factors; 2) the system was in operation on the
effective date of the MCL or treatment technique requirement; and 3) the
exemption will not result in an unreasonable public health risk. Also see
variance.
exposure. Contact with a chemical or physical agent.
exposure assessment. The determination or estimation (qualitative
or quantitative) of the magnitude, frequency, duration, route, and extent
(number of people) of exposure to a chemical.
exposure coefficient. Term which combines information on the
frequency, mode, and magnitude of contact with contaminated medium to yield
a quantitative value of the amount of contaminated medium contacted per day.
exposure level (chemical). The amount (concentration) of a
chemical at the absorptive surfaces of an organism.
exposure scenario. A set of conditions or assumptions about
sources, exposure pathways, concentrations of toxic chemicals and
populations (numbers, characteristics and habits) which aid the investigator
in evaluating and quantifying exposure in a given situation.
extrapolation. Estimation of unknown values by extending or
projecting from known values.
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F
facultative (FACK-ul-TAY-tive). Facultative bacteria can use
either molecular (dissolved) oxygen or oxygen obtained from food material
such as sulfate or nitrate ions. In other words, facultative bacteria can
live under aerobic or anaerobic conditions.
fecal coliform bacteria. Bacteria found in the intestinal tracts
of animals. Their presence in water or sludge is an indicator of pollution
and possible contamination by pathogens.
feedback The circulating action between a sensor measuring a
process variable and the controller which controls or adjusts the process
variable .
filtration. A process for removing particulate matter from water
by passage through porous media.
finished water. Water that has passed through a water treatment
plant; all the treatment processes are completed or "finished". This water
is ready to be delivered to consumers. Also called PRODUCT WATER.
first draw. The water that immediately comes out when a tap is
first opened. This water is likely to have the highest level of lead
contamination from plumbing materials.
first draw sample. A one-liter sample of tap water, collected in
accordance with CFR Section 141.86(b)(2), that has been standing in plumbing
pipes at least 6 hours and is collected without flushing the tap.
fix, sample. A sample is fixed in the field by adding chemicals
that prevent the water quality indicators of interest in the sample from
changing before final measurements are performed later in the lab.
flagellates (FLAJ-el-LATES). Microorganisms that move by the
action of tail-like projections.
flame polished. Melted by a flame to smooth out irregularities.
Sharp or broken edges of glass (such as the end of a glass tube) are rotated
in aflame until the edge melts slightly and becomes smooth.
floc. Clumps of bacteria and particulate impurities that have come
together and formed a cluster. Found in flocculation tanks and settling or
sedimentation basins.
flocculation. The gathering together of fine particles in water by
gentle mixing after the addition of coagulant chemicals to form larger
particles.
floodplain. The flat or nearly flat land on the floor of a steam
valley or tidal area that is covered by water during floods.
fluidized (FLEW-id-i-zd). A mass of solid particles that is made
to flow like a liquid by injection of water or gas is said to have been
fluidized. In water treatment, a bed of filter media is fluidized by
backwashing water through the filter.
fluoridation (FLOOR-uh-DAY-shun).The addition of a chemical to
increase the concentration of fluoride ions in drinking water to a
predetermined optimum limit to reduce the incidence (number) of dental
caries (tooth decay) in children. Defluoridation is the removal of excess
fluoride in drinking water to prevent the mottling (brown stains) of teeth.
fluorosis. An abnormal condition caused by excessive intake of
fluorine, characterized chiefly by mottling of the teeth.
flush. I)To open a cold-water tap to clear out all the water which
may have been sitting for a long time in the pipes. m new homes, to flush a
system means to send large volumes of water gushing through the unused pipes
to remove loose particles of solder and flux. 2) To force large amounts of
water through liquid to clean out piping or tubing. storage or process
tanks.
flushing. A method used to clean water distribution lines.
Hydrants are opened and water with a high velocity flows through the pipes,
removes deposits from the pipes, and flows out the hydrants.
flux. A flowing or flow.
foot valve. A special type of check valve located at the bottom
end of the suction pipe on a pump. This valve opens when the pump operates
to allow water to enter the suction pipe but closes when the pump shuts off
to prevent water from flowing out of the suction pipe.
formation. A group of similar consolidation (that is, relatively
solid) rocks of unconsolidated (that is, relatively loose) minerals.
free available residual chlorine. That portion of the total
available residual chlorine composed of dissolved chlorine gas cl2),
hypochlorous acid (HOCl), and/or hypochlorite ion (OCl-) remaining in water
after chlorination. This does not include chlorine that has combined with
ammonia, nitrogen, or other compounds.
free residual chlorination. The application of chlorine to water
to produce a free available chlorine residual equal to at least 80 percent
of the total residual chlorine (sum of free and combined available chlorine
residual).
freeboard. 1) The vertical distance from the normal water surface
to the top of the confining wall. 2) The vertical distance from the sand
surface to the underside of a trough in a sand filter. This distance is also
called AVAILABLE EXPANSION
friction losses. The head, pressure or energy (they are the same)
lost by water flowing in a pipe or channel as a result of turbulence caused
by the velocity of the flowing water and the roughness of the pipe. channel
walls, and restrictions caused by fittings. Water flowing in a pipe loses
pressure or energy as a result of friction losses. Also see head loss.
fresh water. Water that generally contains less than 1,000
milligrams-per-liter of dissolved solids
fungi (FUN-ji). Mushrooms, molds, mildews, rusts, and smuts that
are small non-chlorophyll-bearing plants lacking roots, stems and leaves.
They occur in natural waters and grow best in the absence of light. Their
decomposition may cause objectionable tastes and odors in water.
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G
gage pressure. The pressure within a closed container or pipe as
measured with a gage. In contrast, absolute pressure is the sum of
atmospheric pressure (14.7 lbs/sq in) PLUS pressure within a vessel (as
measured by a gage). Most pressure gages read in gage pressure or psig
(pounds per square inch gage pressure).
galvnic call. An electrolytic cell capable of producing electrical
energy by electrochemical action. The decomposition of materials in the
cell causes an electric (electron) current to flow from cathode to anode.
galvanic series. A list of metals and alloys presented in the
order of their tendency to corrode (or go into solution). Also called the
ELECTROMOTIVE SERIES. This is a practical application of the theoretical
ELECTROCHEMICAL SERIES.
galvanize. To coat a metal (especially iron or steel) with zinc.
Galvanization is the process of coating a metal with zinc.
garnet (GAR-nit). A group of hard, reddish, glassy, mineral sands
made up of silicates of base metals (calcium, magnesium, iron and
manganese). Garnet has a higher density than sand.
gastroenteritis. An inflammation of the stomach and intestine
resulting in diarrhea, with vomiting and cramps when irritation is
excessive. When caused by an infectious agent, it is often associated with
fever.
gauge, pipe. A number that defines the thickness of the sheet used
to make steel pipe. The larger the number, the thinner the pipe wall.
gavage. Type of exposure in which a substance is administered to
an animal through a stomach tube.
geological log. A detailed description of all underground features
discovered during the drilling of a well (depth, thickness and type of
formations).
geophysical log. A record of the structure and composition of the
earth encountered when drilling a well or similar type of test hole or
boring.
germicide (GERM-uh-SIDE). A substance formulated to kill germs or
microorganisms. The germicidal properties of chlorine make it an effective
disinfectant.
Giardia lamblia. Flagellate protozoan which is shed during its
cyst stage into the feces of man and animals. When water containing these
cysts is ingested, the protozoan causes a severe gastrointestinal disease
called giardiasis.
giardiasis (gee-are-DYE-us-sis). Intestinal disease caused by an infestation
of Giardia flagellates.
glass, pipe and fittings. The working pressure rating of a
specific pipe for use in water distribution systems which includes
allowances for surges. This term is used for cast iron, ductile iron,
asbestos cement and some plastic pipe.
gooseneck A portion of a service connection between the
distribution system water main and a meter. Sometimes called a pigtail.
grab sample. A single sample collected at a particular time and
place which represents the composition of the water only at that time and
place.
grade. 1) The elevation of the invert of the bottom of a pipeline.
canal, culvert or similar conduit. 2) The inclination or slope of a
pipeline, conduit, stream channel, or natural ground surface; usually
expressed in terms of the ratio or percentage of number of units of vertical
rise or fall per unit of horizontal distance. A 0.5 percent grade would be a
drop of one-half foot per hundred feet of pipe.
gram. A unit of mass equivalent to one milliliter of water at 4
degrees Celsius. 1/454 of a pound.
gravimetric. A means of measuring unknown concentrations of water
quality indicators in a sample by WEIGHING a precipitate or residue of the
sample.
grey water. Wastewater other than sewage, such as sink drainage or
washing machine discharge.
ground water. The supply of fresh water found beneath the Earth's
surface. usually in aquifers. which is often used for supplying wells and
springs. Because ground water is a major source of drinking water there is
growing concern over areas where leaching agricultural or industrial pollutants or substances from leaking underground storage tanks are contaminating
ground water.
ground water under the direct influence (UDI) of surface water.
Any water beneath the surface of the ground with: 1) significant
occurrence of Insects or other macroorganisms algae. or large-diameter
pathogens such as Giardia lamblia or, 2) significant and relatively rapid
shifts in water characteristics such as turbidity, temperature,
conductivity, or pH which closely correlate to climatological or surface
water conditions. Direct influence must be determined for individual sources
in accordance with criteria established by the State. The State
determination of direct influence may be based on site-specific measurements
of water quality and/or documentation of well construction characteristics
and geology with field evaluation.
gross alpha particle activity. The total radioactivity due to
alpha particle emission as inferred from measurements on a dry sample.
gross beta particle activity. The total radioactivity due to beta
particle emission as inferred from measurements on a dry sample.
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H
half-life. The length of time required for the mass, concentration, or activity of a chemical or physical agent to be reduced by one-half.
halogen. One of the chemical elements chlorine, bromine, or
iodine.
hard water. Alkaline water containing dissolved salts that
interfere with some industrial processes and prevent soap from lathering.
Water may be considered hard if it has a hardness greater than the typical
hardness of water from the region. Some textbooks define hard water as water
with a hardness of more than 100 mgAL as calcium carbonate.
hardness, water. A characteristic of water caused mainly by the
salts of calcium and magnesium, such as bicarbonate, carbonate, sulfate,
chloride and nitrate. Excessive hardness in water is undesirable because it
causes the formation of soap curds, increased use of soap, deposition of
scale in boilers, damage in some industrial processes, and sometimes
causes objectionable tastes in drinking water.
hazard evaluation. A component of risk assessment that involves
gathering and evaluating data on the types of health injury or disease
(e.g., cancer) that may be produced by a chemical and on the conditions of
exposure under which injury or disease is produced.
head. The vertical distance (in feet) equal to the pressure (in
psi) at a specific point. The pressure head is equal to the pressure in psi
times 2.31 ft/psi.
head loss. The head, pressure or energy (they are the same) lost
by water flowing in a pipe or channel as a result of turbulence caused by
the velocity of the flowing water and the roughness of the pipe, channel
walls or restrictions caused by fittings. Water flowing in a pipe loses
head, pressure or energy as a result of friction losses. Also see friction
losses.
header. A large pipe to which a series of smaller pipes are
connected. Also called a MANIFOLD.
heat sensor. A device that opens and closes a switch in response
to changes in the temperature. This device might be a metal contact, or a
thermocouple which generates a minute electrical current proportional to the
difference in heat, or a variable resistor whose value changes in response
to changes in temperature. Also called a TEMPERATURE SENSOR.
heavy metals. Metallic elements with high atomic weights, e.g.,
mercury, chromium, cadmium, arsenic, and lead. They can damage living things
at low concentrations and tend to accumulate in the food chain.
hectare (HECK-tar). A measure of area in the metric system similar
to an acre. One hectare is equal to 10,000 square meters and 2.4711 acres.
hematopoiesis. The production of blood and blood cells;
hemopoiesis.
hepatic. Pertaining to the liver.
hepatitis (HEP-uh-TIE-this). Hepatitis is an inflammation of the
liver usually caused by an acute viral infection. Yellow jaundice is one
symptom of hepatitis.
hepatoma. A malignant tumor occurring in the liver.
herbicide (HERB-uh-SIDE). A compound, usually a man-made organic
chemical, used to kill or control plant growth.
hertz. The number of complete electromagnetic cycles or waves in
one second of an electrical or electronic circuit. Also called the frequency
of the current. Abbreviated Hz.
heterotrophic microorganisms. Bacteria and other microorganisms
that use organic matter synthesized by other organisms for energy and
growth.
heterotrophic plate count (HPC). The number of colonies of
heterotrophic bacteria grown on selected solid media at a given temperature
and incubation period, usually expressed in number of bacteria per
milliliter of sample.
high-line jumpers. Pipes or hoses connected to fire hydrants and
laid on top of the ground to provide emergency water service for an isolated
portion of a distribution system.
high-to-low-dose extrapolation. The process of prediction of low
exposure risks to rodents from the measured high exposure-high risk data.
histology. The study of the structure of cells and tissues;
usually involves microscopic examination of tissue slices.
hose bib. Faucet. A location in a water line where a hose is
connected.
HTH (pronounce as separate letters). High Test Hypochlorite.
Calcium hypochlorite or Ca(OCl)2
human equivalent dose. A dose which, when administered to humans,
produces an effect equal to that produced by a dose in animals.
human exposure evaluation. A component of risk assessment that
involves describing the nature and size of the population exposed to a
substance and the magnitude and duration of their exposure. The evaluation
could concern past exposures, current exposures, or anticipated exposures.
human health risk. The likelihood (or probability) that a given
exposure or series of exposures may have or will damage the health of
individuals experiencing the exposures.
humus. Organic portion of the soil remaining after prolonged
microbial decomposition.
hydrated lime. Limestone that has been burned and treated with
water under controlled conditions until the calcium oxide portion has been
converted to calcium hydroxide (Ca(OH)2). Hydrated lime is quicklime
combined with water. CaO + H20 --> Ca(OH)2. Also see quicklime.
hydraulic grade line. The surface or profile of water flowing of
hydraulic gradient The slope of the hydraulic grade line. is under pressure,
the hydraulic grade line is at the level water would rise to in a small
vertical tube connected to the pipe. Also see energy grade line
hydraulic gradient. The slope of the hydraulic grade line This is
the slope of the water surface in an open channel, the slope of the water
surface of the groundwater table, or the slope of the water pressure for
pipes under pressure.
hydrogeologic conditions. Conditions stemming from the interaction
of ground water and the surrounding soil and rock.
hydrogeologic cycle. The natural process recycling water from the
atmosphere down to (and through) the earth and back to the atmosphere again.
hydrogeology. The geology of ground water, with particular
emphasis on the chemistry and movement of water.
hydrogeologist (HI-dro-gee-ALL-uh-gist). A person who studies and
works with groundwater.
hydrograph. A graph of the rate of runoff plotted against time for
a point on a channel.
hydrologic cycle (HI-dro-LOJ-ick). Movement or exchange of water
between the atmosphere and the earth.
hydrology. The study of the occurrence, distribution and
circulation of the natural waters of the earth.
hydrolysis (hi-DROLL-uh-sis). A chemical reaction in which a
compound is converted into another compound by taking up water.
hydrophilic (Hi-dro-FILL-ick). Having a strong affinity (liking)
for water. The opposite of hydrophobic.
hydrophobic (Hi-dro-FOE-bick). Having a strong aversion (dislike)
for water. The opposite of hydrophilic.
hydropneumatic (Hi-dro-new-MAT-ick). A water system, usually
small, in which a water pump is automatically controlled (started and
stopped) by the air pressure in a compressed-air tank.
hydrostatic pressure (Hi-dro-STAT-ick). 1) The pressure at a
specific elevation exerted by a body of water at rest or, 2) In the case of
groundwater, the pressure at a specific elevation due to the weight of water
at higher levels in the same zone of saturation.
hydrochlorination (Hi-poe-KLOR-uh-NAY-shun). The application of
hypochlorite compounds to water for the purpose of disinfection.
hydrochlorinators (Hi-poe-KLOR-uh-NAY-tors). Chlorine pumps,
chemical feed pumps or devices used to dispense chlorine solutions made from
hypochlorites such as bleach (sodium hypochlorite) or calcium hypochlorite
into the water being treated.
hypochlorite (Hi-poe-KLOR-ite). Chemical compounds containing
available chlorine; used for disinfection. They are available as liquids
(bleach) or solids (powder, granules and pellets). Salts of hypochlorous
acid.
hypolimnion (Hi-poe-LIM-knee-on). The lowest layer in a thermally
stratified lake or reservoir. This layer consists of colder, more dense
water, has a constant temperature and no mixing occurs.
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I
imhoff cone. A clear. cone-shaped container marked with
graduations. The cone is used to measure the volume of settleable solids in
a specific volume (usually one liter) of water.
impeller. A rotating set of vanes in a pump designed to pump or
lift water.
impermeable (im-PURR-me-uh-BULL). Not easily penetrated. The
property of a material or soil that des not allow, or allows only with great
difficulty, the movement or passage of water.
incidence of tumors. Percentage of animals with tumors.
indicator (chemical). A substance that gives a visible change,
usually of color, at a desired point in a chemical reaction, generally at a
specified end point.
indicator (instrument). A device which indicates the result of a
measurement. Most indicators in the water utility field use either a fixed
scale and movable indicator (pointer) such as a pressure gage or a movable
scale and movable indicator like those used on a circular-flow recording
chart. Also called a RECEIVER.
infiltration. 1) The gradual flow or movement of water into and
through (to percolate or pass through) the pores of the soil. Also see
percolation. 2) the penetration of water from the soil into sewer or other
pipes through defective joints, connections or manhole walls.
infiltration gallery. A subsurface groundwater collection system,
typically shallow in depth, constructed with open-jointed or perforated
pipes that discharge collected water . into a water-tight chamber. From this
chamber the water is pumped to treatment facilities and into the
distribution system. Infiltration galleries are usually located close to
streams or ponds and may be under the direct influence of surface water.
infiltration rate. Quantity of water (usually measured in inches)
that will enter a particular type of soil per unit time (usually one hour).
influent (IN-flu-ent). Water or other liquid-raw or partially
flowing INTO a reservoir, basin, treatment process or treatment plant.
ingestion. Type of exposure through the mouth.
inhalation. Type of exposure through the lungs.
initial compliance period. The first full three-year compliance
period which begins at least 18 months after promulgation.
in-line filtration. The addition of chemical coagulants directly
to the filter inlet pipe. The chemicals are mixed by the flowing water.
Flocculation and sedimentation facilities are eliminated. This pretreatment
method is commonly used in pressure filter installations.
Also see conventional filtration and direct filtration.
inorganic. Material such as sand, salt, iron, calcium salts and
other mineral materials. Inorganic substances are of mineral origin, whereas
organic substances are usually of animal or plant origin. Also see organic.
input horsepower. The total power used in operating a pump and
motor. Input HP = (Brake HP)(100%)Motor Efficiency, %)
insecticide. Any substance or chemical formulated to kill or
control insects.
in situ. In place, the original location, in the natural environment.
instream uses. Water uses that can be carried out without removing
the water from its source, as in navigation and recreation.
integrated exposure assessment. A summation over time, in all
media, of the magnitude of exposure to a toxic chemical.
integrator. A device or meter that continuously measures and
calculates (adds) total flows in gallons, or million cubic feet. or some
other unit of volume measurement. Also called a TOTALIZER.
interface. The common boundary layer between two substances such
as water and a solid (metal); or between two fluids such as water and a gas
(air); or between a liquid (water) and another liquid (oil).
interflow. Lateral movement of water in the upper layer of soil.
interlock An electrical switch, usually magnetically operated.
Used to interrupt all (local) power to a panel or device when the door is
opened or the circuit exposed to service.
Internal friction. Friction within a fluid (water) due to cohesive
forces.
interspecies extrapolation model. Model used to extrapolate from
results observed in laboratory animals to humans.
Interstate carrier. Any vehicle or transport which conveys
passengers in interstate commerce.
interstice (in-TUR-stuhz). A very small open space in a rock or
granular material. Also called a void or void space. Also see pore.
invert The lowest point of the channel inside a pipe, conduit, or
canal.
in vitro. In glass; a laboratory experiment performed in a test
tube or other vessel.
in vitro studies. Studies of-chemical effects conducted in
tissues, cells or subcellular extracts from an organism (i.e., not in the
living organism).
in vivo. With in a living organism; a laboratory experiment
performed in which the substance under study is inserted into a living
organism.
in vivo studies. Studies of chemical effects conducted in intact
living organisms.
ion. An electrically charged atom, radical (such as SO42-), or
molecule formed by the loss or gain of one or more electrons.
ionic concentration. The concentration of any ion in solution,
usually expressed in moles per liter.
ionization (EYE-on-uh-ZAY-shun). The splitting or dissociation
(separation) of molecules into negatively and positively charged ions.
irreversible effect. Effect characterized by the inability of the
body to partially or fully repair injury caused by a toxic agent.
J
jar test A laboratory procedure that simulates a water treatment
plant's coagulation/flocculation units with differing chemical doses and
also energy of rapid mix, energy of slow mix, and settling time. The purpose
of this procedure is to ESTIMATE the minimum or ideal coagulant dose
required to achieve certain water quality goals. Samples of water to be
treated are commonly placed in six jars. Various amounts of chemicals are
added to each jar, and the settling of solids is observed. The dose of
chemicals that provides satisfactory settling removal of turbidity and/or
color is the dose used to treat the water being taken into the plant at that
time. When evaluating the results of a jar test, the operator should also
consider the floc quality in the flocculation area and the floc loading on
the filter.
jogging. The frequent starting and stopping of an electric motor.
joule (jewel). A measure of energy, work or quantity of heat. One
joule is the work done when a force of one newton is displaced a distance of
one meter in the direction of force.
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K
kilo. 1) Kilogram. 2) Kilometer. 3) A prefix meaning "thousand"
used in the metric system and other scientific systems of measurement.
kinetic energy. Energy possessed by a moving body of matter, such
as water, as a result of its motion.
kjeldahl nitrogen (KELL-doll). Nitrogen in the form of organic
proteins or their decomposition product ammonia, as measured by the Kjeldahl
Method.
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L
landfill Facility in which solid waste from municipal and/or
industrial sources is disposed; sanitary landfills are those that are
operated in accordance with environmental protection standards.
Langelier index (L.I.). An index reflecting the equilibrium pH of
a water with respect to calcium and alkalinity. This index is used in
stabilizing water to control both corrosion and the deposition of scale.
Langelier index = pH - pHs where pH = actual pH of the water, and pHs= pH at
which the water having the same alkalinity and calcium content is just
saturated with calcium carbonate.
large water system. A water system that serves more than 50,000
persons
latency. Time from the first exposure to a chemical until the
appearance of a toxic effect.
laundering weir (LAWN-der-ing weer). Sedimentation basin overflow
weir. A plate with V-notches along the top to assure a uniform flow rate and
avoid short-circuiting.
launders (LAWN-ders). Sedimentation basin and filter discharge
channels, consisting of overflow weir plates (in sedimentation basins) and
conveying troughs.
LC50. The concentration of a chemical in air or water which is
expected to cause death in 50% of test animals living in that air or water.
LD50. The dose of a chemical taken by mouth or absorbed by the
skin which is expected to cause death in 50% of the test animals so treated.
leachate. A liquid that results from water collecting contaminants as it trickles through wastes, agricultural pesticides or fertilizers.
Leaching may occur in farming areas, feedlots, and landfills, and may result
in hazardous substances entering surface water, ground water, or soil.
leaching. The process by which soluble substances are dissolved
and transported down through the soil by recharge.
lead(Pb). A heavy metal that is hazardous to health if breathed or
swallowed.
Its use in gasoline. paints, and plumbing compounds has been
sharply restricted or eliminated by federal laws and regulations. See heavy
metals.
lead service line. A service line made of lead which connects the
water main to the building inlet and any lead pigtail, gooseneck or other
fitting which is connected to such lead line.
legionella. A genus of bacteria, some species of which have caused
a type of pneumonia called Legionnaires Disease.
lesion. A pathological or traumatic discontinuity of tissue or
loss of function of a part.
lethal. Deadly; fatal.
level controls. A float device (or pressure switch) which senses
changes in a measured variable and opens or closes a switch in response to
that change. In its simplest form, this control might be a floating ball
connected mechanically to a switch or valve such as is used to stop water
flow into a toilet when the tank is full.
lifetime exposure. Total amount of exposure to a substance that a
human would receive in a lifetime (usually assumed to be 70 years).
lindane (LYNN-dane). A pesticide that causes adverse health
effects in domestic water supplies and also is toxic to freshwater and
marine aquatic life.
linearity (LYNN-ee-AIR-it-ee). How closely an instrument measures
actual values of a variable through its effective range; a measure used to
determine the accuracy of an instrument.
linearized multistage model. Derivation of the multistage model,
where the data are assumed to be linear at low doses.
littoral zone (LIT-or-al). 1)That portion of a body of fresh water
extending from the shoreline lakeward to the limit of occupancy of rooted
plants. 2) The strip of land along the shoreline between the high and low
water levels.
loading. The quantity of a substance entering the environment
(soil, water, or air).
LOAEL Lowest-observed-adverse-effect level; the lowest dose in an
experiment which produced an observable adverse effect.
logarithm (LOG-a-rith-m). The exponent that indicates the power to
which a number must be raised to produce a given number. For example: if B2
= N, the 2 is the logarithm of N (to the base B), or 102 =100 and log10 100
= 2. Also abbreviated to "log."
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M
macroscopic organisms (MACK-row-SKAWP-ick). Organisms big enough
to be seen by the eye without the aid of a microscope.
malignant Very dangerous or virulent, causing or likely to cause
death.
managerial controls Methods of nonpoint source pollution control
that are derived from managerial decisions, such as changes in application
times or rates for agrochemicals.
manifold. A large pipe to which a series of smaller pipes are
connected. Also called a HEADER.
man-made beta particle and photon emitting All radionuclides
emitting beta particles and/or photons listed in Maximum Permissible Body
Burdens and Maximum Permissible Concentration of Radionuclides in Air or
Water for Occupational Exposure, NBS Handbook 69, except the daughter
products of thorium-232, uranium-235 and uranium-238.
manometer (man-NAH-mut-ter). An instrument for measuring pressure.
Usually, a manometer is a glass tube filled with a liquid that is used to
measure the difference in pressure across a flow-measuring device such as an
orifice or Venturi meter. The instrument used to measure blood pressure is a
type of manometer.
margin of safety (MOS). Maximum amount of exposure producing no
measurable effect in animals (or studied humans) divided by the actual
amount of human exposure in a population.
mathematical model. Model used during risk assessment to perform
extrapolations.
maximum contaminant level (MCL). The maximum permissible level of
a contaminant in water which is delivered to the free flowing outlet of the
ultimate user of a public water system, except in the case of turbidity
where the maximum permissible level is measured at the point of entry to the
distribution system. Contaminants added to the water under circumstances
controlled by the user are excluded from this definition, except those
contaminants resulting from the corrosion of piping and plumbing caused by
water quality.
maximum contaminant level goal (MCLG). The maximum level of a
contaminant in drinking water at which no known or anticipated adverse
effect on the health of persons would occur, and which allows an adequate
margin of safety. Maximum contaminant level goals are non-enforceable health
goals .
maximum total trihalomethane potential (MTTP). The maximum
concentration of total trihalomethanes produced in a given water containing
a disinfectant residual, after 7 days at 25 degrees C or above.
MBAS. Methylene - Blue - Active Substances. These substances are
used in surfactants or detergents.
MCL See maximum contaminant level.
measured variable. A characteristic or component part that is
sensed and quantified (reduced to a reading of some kind) by a primary
element or sensor.
Mechanical joint A flexible device that joins pipes or fittings
together by the use of lugs and bolts.
medium-size water system. A water system that serves greater than
3,300 and less than or equal to 50,000 person.
meg. A procedure used for checking the insulation resistance on
motors, feeders, buss bar systems, grounds, and branch circuit wiring. Also
see megger.
megger (from megohm). An instrument used for checking the
insulation resistance on motors, feeders, buss bar systems, grounds, and
branch circuit wiring. Also see MEG.
megohm. Meg means one million, so 5 megohms means 5 million ohms.
A megger reads in millions of ohms.
meniscus (meh-NIS-cuss). The curved top of a column of liquid
(water, oil, mercury) in a small tube. When the liquid wets the sides of the
container (as with water), the curve forms a valley. When the confining
sides are not wetted (as with mercury), the curve forms a hill or upward
bulge.
mesh. One of the openings or spaces in a screen or woven fabric.
The value of the mesh is usually given as the number openings per inch. This
value does not consider the diameter of the wire or fabric; therefore, the
mesh number does not always have a definite relationship to the size of the
hole.
mesotrophic (MESS-o-TRO-rick). Reservoirs and lakes which contain
moderate quantities of nutrients and are moderately productive in terms of
aquatic animal and plant life.
metabolism (meh-TAB-uh-LIZ-um). The sum of the chemical reactions
occurring within a cell or a whole organism; includes the energy-releasing
breakdown of molecules (catabolism) and the synthesis of new molecules
(anabolism).
metabolite. Any product of metabolism, especially a transformed
chemical.
metalimnion (MET-uh-LIM-knee-on). The middle layer in a thermally
stratified lake or reservoir. In this layer there is a rapid decrease in
temperature with depth. Also called the THERMOCLINE.
metastatic. Pertaining to the transfer of disease from one organ
or part to another not directly connected with it.
methoxychlor (meth-OXY-klor). A pesticide which causes adverse
health effects in domestic water supplies and is also toxic to freshwater
and marine aquatic life. The chemical name for methoxychlor is 2,2-bis
(P-methoxyphenol)- 1, 1, I - trichloroethane.
methyl orange alkalinity. A measure of the total alkalinity in a
water sample. The alkalinity is measured by the amount of standard sulfuric
acid required to lower the pH of the water to a pH level of 4.5, as
indicated by the change in color of methyl orange from orange to pink.
Methyl orange alkalinity is expressed as milligrams per liter equivalent
calcium carbonate.
mg/L. See milligrams per liter.
microbial growth (my-KROW-bee-ul). The activity and growth of
microorganisms such as bacteria, algae, diatoms, plankton and fungi.
microgram (pg). One-millionth of a gram (3.5 x 10-8 oz.
0.000000035 oz.).
micrograms per liter (mg/L) One microgram of a substance dissolved
in each liter of water. This unit is equal to parts per billion (ppb) since
one liter of water is equal in weight to one billion micrograms.
micron (MY-kron). A unit of length. One millionth of a meter or
one thousandth of a millimeter. One micron equals 0.00004 of an inch.
microorganisms (MY-crow-OR-gan-IS-zums). Living organisms that can
be seen individually only with the aid of a microscope.
mil A unit of length equal to 0.001 of an inch. The diameter of
wires and tubing is measured in mils, as is the thickness of plastic
sheeting .
milligram (mg). One-thousandth of a grain (3.5 x 10-1 oz. 0.000035
oz.).
milligrams per liter (mg/L). A measure of concentration of a
dissolved substance. A concentration of one mg/L means that one milligram of
a substance is dissolved in each liter of water. For practical purposes,
this unit is equal to parts per million (ppm) since one liter of water is
equal in weight to one million milligrams. Thus a liter of water containing
10 milligrams of calcium has 10 parts of calcium per one million parts of
water, or 10 parts per million (10 ppm).
millimicron (MILL-uh-MY-kron). A unit of length equal to 10-3
microns (one thousandth of a micron), 10-6millimeters, or 10-9 meters;
correctly called a manometer, nm.
Million-gallons Per Day (MGD). A measure of water flow.
mineralization. The microbial conversion of an element from an
organic to an inorganic state.
modeling. Use of mathematical equations to simulate and predict
real events and processes.
molar or molarity. A molar solution consists of one gram molecular
weight of a compound dissolved in enough water to make one liter of
solution. A gram molecular weight is the molecular weight of a compound in
grains. For example, the molecular weight of sulfuric acid (H2SO4) is 98.
A one M solution of sulfuric acid would consist of 98 grains of H2SO4
dissolved in enough distilled water to make one liter of solution.
mole. The molecular weight of a substance, usually expressed in
grains.
molecular weight. The molecular weight of a compound in grams is
the sum of the atomic weights of the elements in the compound. The molecular
weight of sulfuric acid (H2SO4) in grams is 98. Element Atomic Weight Number
of Atoms Molecular Weight H 1 2 2 S 32 1 32 0 16 4 64
molecule (MOLL-uh-KULE). The smallest division of a compound that
still retains or exhibits all the properties of the substance.
monitoring. Measuring concentrations of substances in
environmental media or in human or other biological tissues.
monomer (MON-o-MER). A molecule of low molecular weight capable of
reacting with identical or different monomers to form Polymers.
monomictic (mo-no-MICK-tick). Lakes and reservoirs which are
relatively deep, do not freeze over during the winter months, and undergo a
single stratification and mixing cycle during the year. These lakes and
reservoirs usually become destratified during the mixing cycle, usually in
the fall of the year.
monovalent. Having a valence of one, such as the cuprous (copper)
ion, Cu+.
mortality. Death.
MOS. See margin of safety.
most probable number (MPN). MPN is the Most Probable Number of
coliform-group organisms per unit volume of sample water. Expressed as the
number of organisms per 100 mL off sample water.
motile (MO-till). Capable of self-propelled movement. A term that
is sometimes used to distinguish between certain types of organisms found in
water.
monitoring wells. Wells used to collect ground-water samples for
analysis to determine the amount, type, and spread of contaminants In ground
water.
motor efficiency. The ratio of energy delivered by a motor to the
energy supplied to it during a fixed period or cycle. Motor efficiency
ratings will vary depending upon motor manufacturer and usually will range
from 88.9 to 90.0 percent.
mudballs. Material that is approximately round in shape and varies
from pea-sized up to two or more inches in diameter. This material forms in
filters and gradually increases in size when not removed by the backwashing
process.
MPN See most probable number.
MTD. Maximum tolerated dose, the dose that an animal species can
tolerate for a major portion of its lifetime without significant impairment
or toxic effect other than carcinogenicity.
mulch. Any substance spread or allowed to remain on the soil
surface to conserve soil moisture and shield soil particles from the erosive
forces of raindrops and runoff.
multiple use. Use of land for more than one purpose; i.e., grazing
of livestock, wildlife production. recreation, watershed, and timber
production. Could also apply to use of bodies of water for recreational
purposes, fishing, and water supply.
multi-stage model Mathematical model based on the multi-stage
theory of the carcinogenic process, which yields risk estimates either equal
to or less than the one-hit model.
multi-stage pump. A pump that has more than one impeller A
single-stage pump has one impeller.
municipal sewage. Wastes (mostly liquid) originating from a
community; may be composed of domestic wastewaters and/or industrial
wastewaters.
mutagen. An agent that causes a permanent genetic change in a cell
other than that which occurs during normal genetic recombination.
mutagenicity. The capacity of a chemical or physical agent to
cause permanent alteration of the genetic material within living cells.
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N
N. See normal.
National Environmental Training Association (NETA). A professional
organization devoted to serving the environmental trainer and promoting
better operation of waterworks and pollution control facilities. For
information on NETA membership and publications, contact NETA, 8687 Via de
Ventura, Suite 214, Scottsdale, AZ 85258
National Institute of Occupational Safety and Health. See NIOSH.
National Interim Primary Drinking Water Regulations. Commonly
referred to as NIPDWRs.
National Pollutant Discharge. Elimination System permit is the
regulatory agency document issued by either a federal or state agency which
is designed to control all discharges of pollutants from point sources in
U.S. waterways. NPDES permits regulate discharges into navigable waters from
all point sources of pollution, including industries, municipal treatment
plants, large agricultural feed lots and return Irrigation flows.
National Secondary Drinking Water Regulations. Commonly referred
to as NSDWRs.
NCWS. See non-community water system.
near the first service connection. At one of the 20 percent of all
service connections in the entire system that are nearest the water supply
treatment facility, as measured by water transport time within the
distribution system.
necrosis. Death of cells or tissue.
nematodes. Roundworms, any of which are pathogenic for plants and
sometimes animals.
nephelometric (NEFF-el-o-MET-rick). A means of measuring turbidity
in a sample by using an instrument called a nephelometer. A nephelometer
passes light through a sample and the amount of light deflected (usually at
a 90-degree angle) is then measured.
neoplasm. An abnormal growth or tissue, as a tumor.
nephelometric turbidity unit (NTU). The unit of measure for
turbidity.
NETA. See National Environmental Training Association.
neurotoxicity. Exerting a destructive or poisonous effect on nerve
tissue.
newton. A force which, when applied to a body having a mass of one
kilogram, gives it an acceleration of one meter per second per second.
NIOSH The National Institute of Occupational Safety and Health is
an organization that tests and approves safety equipment for particular
applications. NIOSH is the primary Federal agency engaged in research in the
national effort to eliminate on-the-job hazards to the health and safety of
working people. The NIOSH Publications Catalog contains a listing of NIOSH
publications mainly on industrial hygiene and occupational health. To obtain
a copy of the catalog, write to National Technical Information Service
(NTIS), 5285 Port Royal Road, Springfield, VA 22161. NTIS Stock No.
PB-86-116-787, price $45.95.
NIPDWR. National Interim Primary Drinking Water Regulations.
nitrification. The biochemical transformation of ammonium nitrogen
to nitrate nitrogen.
nitrification inhibitor. A chemical that slows down the conversion
of ammonium to nitrate nitrogen.
nitrogen fixation. The biological or chemical process by which
elemental nitrogen, from the air, is converted to organic or available
nitrogen.
nitrogenous (nye-TRAH-jen-us). A term used to describe chemical
compounds (usually organic) containing nitrogen in combined forms. Proteins
and nitrates are nitrogenous compounds.
NOAEL No-observed-adverse-effect level; the highest dose in an
experiment which did not produce an observable adverse effect.
noble metal Chemically inactive metal (such as gold). A metal that
does not corrode easily and is much scarcer (and more valuable) than the
so-called useful or base metals. Also see base metal.
NOEL No-observed-effect level; dose level at which no effects are
noted.
nominal diameter. An approximate measurement of the diameter of a
pipe. Although the nominal diameter is used to describe the size or diameter
of a pipe, it is usually not the exact inside diameter of the pipe.
non-community water system (NCWS). A public water system that is
not a community water system. There are two types of NCWSs: transient and
non-transient.
non-conventional pollutant Any pollutant which is not a
statutorily listed or which is poorly understood by the scientific
community.
non-ionic polymer (NON-eye-ON-ick). A polymer that has no net
electrical charge.
non-point source. Pollution sources which are diffuse and do not
have a single point of origin or are not introduced into a receiving stream
from a specific outlet. The pollutants are generally carried off the land by
stormwater runoff. The commonly used categories for non-point sources are:
agriculture. forestry, urban, mining, construction, dams and channels, land
disposal, and saltwater intrusion.
non-potable (non-POE-tuh-bull). Water that may contain
objectionable pollution, contamination, minerals, or infective agents and is
considered unsafe and/or unpalatable for drinking.
non-transient non-community water system (NTNCWS). A public water
system that regularly serves at least 25 of the same nonresident persons per
day for more than six months per year.
normal. A normal solution contains one grain equivalent weight of
reactant (compound) per. liter of solution. The equivalent weight of an acid
is that weight which contains one gram atom of ionizable hydrogen or its
chemical equivalent. For example, the equivalent weight of sulfuric acid
(H2SO4 is 49 (98 divided by 2 because there are two replaceable hydrogen
ions). A one N solution of sulfuric acid would consist of 49 grains of H2SO4
dissolved in enough water to make one liter of solution.
NPL National Priorities List; a list of Superfund sites chosen for
immediate attention.
NSDWR. National Secondary Drinking Water Regulations.
NTNCWS. See non-transient non-community water system.
NTP. National Toxicology Program.
nutrient Any substance that is assimilated (taken in) by organisms
and promotes growth. Nitrogen and phosphorous are nutrients which promote
the growth of algae. There are other essential and trace elements which are
also considered nutrients.
nutrient pollution. Contamination of water resources by excessive
inputs of nutrients; insurface waters, excess algal production is a major
concern.
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O
Occupational Safety and Health Act of 1970. See OSHA.
odor threshold. The minimum odor of a water sample that can just
be detected after successive dilutions with odorless water. Also called
THRESHOLD ODOR.
offstream uses. Water withdrawn from surface or ground water
sources for use at another place.
offset (or DROOP). The difference between the actual value and the
desired value (or set point); characteristic of proportional controllers
that do not incorporate reset action.
OHM The unit of electrical resistance. The resistance of a
conductor in which one volt produces a current of one ampere.
olfactory fatigue (oh-FAK-tore-ee). A condition in which a
person's nose, after exposure to certain odors, is no longer able to detect
the odor.
oligotrophic (AH-lig-o-TRO-flck). Reservoirs and lakes which are
nutrient poor and contain little aquatic plant or animal life.
oncology. Study of cancer.
one-hit model Mathematical model based on the biological theory
that a single "hit" of some minimum critical amount of a carcinogen at a
cellular target -- namely, DNA -- can initiate an irreversible series of events,
eventually leading to a tumor.
optimal corrosion control treatment The corrosion control
treatment that minimizes the lead and copper concentrations at users' taps
while insuring that the treatment does not cause the water system to violate
any national primary drinking water regulations.
operation and maintenance costs. The ongoing, repetitive costs of
operating a water system; for example, employee wages and costs for
treatment chemicals and periodic equipment repairs.
oral. Of the mouth; through or by the mouth.
organic. Substances that come from animal or plant sources.
Organic substances always contain carbon. (Inorganic materials are chemical
substances of mineral origin.) Also see inorganic
organics. 1) A term used to refer to chemical compounds made from
carbon molecules. These compounds may be natural materials (such as animal
or plant sources) or man-made materials (such as synthetic organics). Also
see organic. 2) Any form of animal or plant life. Also see bacteria.
organism. Any form of animal or plant life. Also see bacteria..
orifice (OR-uh-fiss). An opening (hole) in a plate, wall or
partition An orifice flange or plate placed in a pipe consists of a slot or
a calibrated circular hole smaller than the pipe diameter. The difference in
pressure in the pipe above and at the orifice may be used to determine the
flow in the pipe.
ORP.
Oxidation-Reduction Potential. The electrical potential required
to transfer electrons from one compound or element (the oxidant) to another
compound or element (the reductant); used as a qualitative measure of the
state of oxidation in water treatment systems.
orthotolidine (or-tho-TOL-uh-dine). Orthotolidine is a
calorimetric indicator of chlorine residual. If chlorine is present, a
yellow-colored compound is produced. This reagent is no longer approved for
chemical analysis.
OSHA (0-shuh). The Williams-Steiger Occupational Safety and Health
Act of 1970 (OSHA) is a law designed to protect the health and safety of
industrial workers and also the operators of water supply systems and
treatment plants. OSHA also refers to the federal and state agencies which
administrator the OSHA regulations.
osmosis (oz-MOE-sis). The passage of a liquid from a weak solution
to a more concentrated solution across a semipermeable membrane. The
membrane allows the passage of the solvent (water) but not the dissolved
solids (solutes). This process tends to equalize the conditions on either
side of the membrane.
overall efficiency pump. The combined efficiency of a pump and
motor together. Also called the WIRE-TO-WATER EFFICIENCY.
overdraft The pumping of water from a groundwater basin or aquifer
in excess of the supply flowing into the basin. This pumping results in a
depletion or "mining" of the groundwater in the basin.
overflow rate. One of the guidelines for the design of settling
tanks and clarifiers in treatment plants. Used by operators to determine if
tanks and clarifiers are hydraulically (flow) over- or underloaded. Also
called SURFACE LOADING. Overflow Rate (GDP/sq ft) = Flow (GPD)/Surface Area
(sq ft)
overturn. The almost spontaneous mixing of all layers of water in
a reservoir or lake when the water temperature becomes similar from top to
bottom. This may occur in the fall/winter when the surface waters cool to
the same temperature as the bottom waters and also in the spring when the
surface waters warms after the ice melts.
oxidation (ox-uh-DAY-shun). Oxidation is the addition of oxygen,
removal of hydrogen, or the removal of electrons from an element or
compound. In the environment, organic matter is oxidized to more stable
substances. The opposite of reduction
oxidation-reduction potential. The electrical potential required
to transfer electrons from one compound or element (the oxidant) to another
compound or element (the reductant); used as a qualitative measure of the
state of oxidation in water treatment systems.
oxidizing agent Any substance, such as oxygen (O2) or chlorine
(Cl2), that will readily add (take on) electrons. The opposite is a reducing
agent.
ozonation (O-zoe-NAY-shun). The application of ozone to water for
disinfection or for taste and odor control.
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P
packed tower aeration. A method of treating water to remove
volatile organic chemical (VOCs) contaminants. As water is mixed with air,
VOCs move from water to air which then passes through carbon filters to trap
the contaminants.
palatable (PAL-a-ta-ble). Water at a desirable temperature that is
free from objectionable tastes, odors, colors, and turbidity. Pleasing to
the senses.
parshall flume. A device used to measure the flow in an open
channel. The flume narrows to a throat of fixed dimensions and then expands
again. The rate of flow can be calculated by measuring the difference in
head (pressure) before and at the throat of the flume.
particle count. The results of a microscopic examination of
treated water with a special "particle counter" which classifies suspended
particles by number and size.
particulate (par-TICK-you-let). A very small solid suspended in
water which can vary widely in size, shape, density, and electrical charge.
Colloidal and dispersed particulates are artificially gathered together by
the processes of coagulation and flocculation.
partition coefficient. A measure of the extent to which a
pesticide is divided between the soil and ater phases.
parts per million (PPM). Parts per million parts, a measurement
of concentration on a weight or volume basis. This term is equivalent to
milligrams per liter (mg/L) which is the preferred term.
Pascal. The pressure or stress of one newton per square meter.
(Abbreviated Pa) 1 psi = 6895 Pa = 6.895 kN/sq m = 0.0703 kg/sq cm
pathogenic organisms (path-o-JEN-ick). Organisms, including
bacteria, viruses or cysts, capable of causing diseases (typhoid, cholera,
dysentery) in a host (such as a person). There are many types of organisms
which do NOT cause disease. These organisms are called non-pathogenic.
pathogens. Microorganisms that can cause disease in other
organisms or in humans, animals and plants. They may be bacteria, viruses,
or parasites and are found in sewage in runoff from animal farms or rural
areas populated with domestic and/or wild animals, and in water used for
swimming. Fish and shellfish contaminated by pathogens, or the contaminated
water itself, can cause serious illnesses.
pathology. The study of disease.
percent saturation. The amount of a substance that is dissolved in
a solution compared with the amount that could be dissolved in the solution,
expressed as a percent. Amount of substance that is dissolved x 100% Amount
that could be dissolved in solution
percolating water (PURR-co-LAY-ting). Water that passes through
soil or rocks under the force of gravity.
percolation (PURR-ko-LAY-shun). 1) The slow seepage of water into
and through the ground. 2) The slow passage of water through a filter
medium.
performance evaluation sample. A reference sample provided to a
laboratory for the purpose of demonstrating that the laboratory can
successfully analyze the sample within limits of performance specified by
the Agency. The true value of the concentration of the reference material is
unknown to the laboratory at the time of the analysis.
periphyton (puh-RIF-uh-tawn). Microscopic plants and animals that
are firmly attached to solid surfaces under water such as rocks, logs,
pilings and other structures.
permeability. Generally used to refer to the ability of rock or
soil to transmit water.
permeate (PURR-me-ate). To penetrate and pass through, as water
penetrates and passes through soil and other porous materials.
permissible dose. The dose of a chemical that may be received by
an individual without the expectation of a significantly harmful result.
persistence. The resistance to degradation as measured by the
period of time required for complete decomposition of a material.
person. An individual, corporation, company, association,
partnership; municipality; or State, Federal, or tribal agency.
pesticide. Any substance or chemical designed or formulated to
kill or control weeds or animal pests. Also see algicide, herbicide,
insecticide and rodenticide.
petroleum derivatives. Chemicals formed when gasoline breaks down
in contact with ground water.
pH (pronounce as separate letters). pH is an expression of the
intensity of the basic or acid condition of a liquid. Mathematically, pH is
the logarithm (base 10) of the reciprocal of the hydrogen ion concentration,
[H+]. pH= Log (I/[H+]) The pH may range from 0 to 14, where 0 is most acid,
14 most basic, and 7 neutral. Natural waters usually have a pH between 6.5
and 8.5.
pharmacokinetics. The dynamic behavior of chemicals inside
biological systems; it includes the processes of uptake, distribution,
metabolism, and excretion.
phenolic compounds (FEE-noll-LICK). Organic compounds that are derivatives of
benzene.
phenolphthalein alkalinity (FEE-nol-THAY-leen). The alkalinity in
a water sample measured by the amount of standard acid required to lower the
pH to a level of 8.3, as indicated by the change in color of phenolphthalein
from pink to clear. Phenolphthalein alkalinity is expressed as milligrams
per liter equivalent calcium carbonate.
photosynthesis (foe-tow-SIN-thus-sis). A process in which
organisms, with the aid of chlorophyll (green plant enzyme), convert
carbon dioxide and inorganic substances into oxygen and additional plant
material, using sunlight for energy. All green plants grow by this process.
phytoplankton (Flo-tow-PANK-ton). Small, usually microscopic
plants (such as algae), found in lakes, reservoirs, and other bodies of
water.
pico. A prefix used in the metric system and other scientific
systems of measurement which means 10-12 or 0.000000000001
picocurie (pCi). A measure of radioactivity. One picocurie of
radioactivity is equivalent to 0.037 nuclear disintegrations per second.
plan view. A diagram or photo showing a facility as it would
appear when looking down on top of it.
plankton. 1) Small, usually microscopic, plants (phytoplankton)
and animals (zooplankton) in aquatic systems. 2) All of the smaller
floating, suspended or self-propelled organisms in a body of water.
plug flow. A type of flow that occurs in tanks, basins or reactors
when a slug of water moves through a tank without ever dispersing or mixing
with the rest of the water flowing through the tank.
plumes. The way polluted water extends downstream from the
pollution source (analogous to smoke from a smoke-stack as it drifts
downwind in the atmosphere).
point of disinfectant application. The point where disinfectant
is applied and water downstream of that point is not subject to
recontamination by surface water runoff.
point-of-entry treatment device. A treatment device applied to the
drinking water entering a house or building for the purpose of reducing
contaminants in the drinking water distributed throughout the house or
building .
point-of-use treatment device. A treatment device applied to a
single tap used for the purpose of reducing contaminants in drinking water
at that one tap.
point source. A stationery location or fixed facility from which
pollutants are discharged or emitted. Also, any single identifiable source
of pollution, e.g., a pipe, ditch, ship, ore pit, factory smokestack.
pole shader. A copper bar circling the laminated iron core inside
the coil of a magnetic starter.
pollutant. Generally, any substance introduced into the
environment that adversely affects the usefulness of a resource.
pollution. Generally, the presence of matter or energy whose
nature, location or quantity produces undesired environmental effects.
Under the Clean Water Act, for example, the term is defined as the man-made
or man-induced alteration of the physical, biological, and radiological
integrity of water.
polyelectrolyte (POLLY-ee-LECK-tro-lite). A high-molecular-weight
(relatively heavy) substance having points of positive or negative
electrical charges that is formed by either natural or man-made processes.
Natural polyelectrolytes may be of biological origin or derived from
starch products and cellulose derivatives. Man-made polyelectrolytes
consist of simple substances that have been made into complex substances of
high molecular weight. Used with other chemical coagulants to aid in binding
small suspended particles to larger chemical flocs for their removal from
water. Often called a polymer.
polymer. A chemical formed by the union of many monomers (a
molecule of low molecular weight). Polymers are used with other chemical
coagulants to aid in binding small suspended particles to larger chemical
flocs for their removal from water. All polyelectrolytes are polymers, but
not all polymers are polyelectrolytes.
population at risk. A population subgroup that is more likely to
be exposed to a chemical, or is more sensitive to a chemical, than is the
general population.
pore. A very small open space in a rock or granular material. Also
see interstice
porosity. the capacity of soil of rock to hold water.
positive displacement pump. A type of piston, diaphragm, gear or
screw pump that delivers a constant volume with each stroke. Positive
displacement pumps are used as chemical solution feeders.
postchlorination. The addition of chlorine to the plant effluent,
FOLLOWING plant treatment, for disinfection purposes.
potency. Amount of material necessary to produce a given level of
a deleterious effect.
potentiation. The effect of one chemical to increase the effect of
another chemical.
potentiometric surface. The level to which water will rise in
cased wells or other cased excavations into aquifers, measured as feet above
mean sea level.
potable water. Water that is safe and satisfactory for drinking
and cooking.
power factor. The ratio of the true power passing through an
electric circuit to the product of the voltage and amperage in the circuit.
This is a measure of the lag or load of the current with respect to the
voltage.
ppb. Parts per billion. Also pg/L or micrograms per liter.
ppm. Parts per million. Also mg/L or milligrams per liter.
prechlorination. The addition of chlorine at the headworks of the
plant PRIOR TO other treatment processes mainly for disinfection and control
of tastes, odors and aquatic growths. Also applied to aid in coagulation and
settling.
precipitate (pre-SIP-uh-TATE). 1) An insoluble, finely divided
substance which is a product of a chemical reaction within a liquid. 2) The
separation from solution of an insoluble substance.
precipitation (pre-SIP-uh-TAY-shun). 1) The process by which
atmospheric moisture falls onto a land or water surface as rain, snow, hail,
or other forms of moisture. 2) The chemical transformation of a substance in
solution into an insoluble form (precipitate).
Precision. The ability of an instrument to measure a process
variable and to repeatedly obtain the same result. The ability of an
instrument to reproduce the same results.
precursor, THM (pre-CURSE-or). Natural organic compounds found
in all surface and groundwaters. These compounds MAY react with halogens
(such as chlorine) to form trihalomethanes (try-HAL-o-METH-hanes) (THMs);
they MUST be present in order for THMs to form.
prescriptive (
pre-SKRIP-tive). Water rights which are acquired by diverting
water and putting it to use in accordance with specified procedures. These
procedures include filing a request to use unused water in a strewn, river
or lake with a state agency.
pressure control. A switch which operates on changes in pressure.
Usually this is a diaphragm pressing against a spring. When the force on the
diaphragm overcomes the spring pressure, the switch is actuated (activated).
pressure head. The vertical distance (in feet) equal to the
pressure (in psi) at a specific point. The pressure head is equal to the
pressure in psi times 2.31 ft/psi.
prevalence study. An epidemiological study which examines the
relationships between diseases and exposures as they exist in a defined
population at a particular point in time.
primacy. The responsibility for ensuring that a law is
implemented, and the authority to enforce a law and related regulations. A
primacy agency has the primary responsibility for administrating and
enforcing regulations.
primary element. An instrument which measures (senses) a physical
condition or variable of interest. Floats and thermocouples are examples of
primary elements. Also called a sensor.
prime. The action of filling a pump casing with water to remove
the air. Most pumps must be primed before startup or they will not pump any
water.
prior appropriation. A doctrine of water law that allocates the
right to use water on a first-come first-serve basis.
process variable. A physical or chemical quantity which is usually
measured and controlled in the operation of a water treatment plant or an
industrial plant.
product water. Water that has passed through a water treatment
plant. All the treatment processes are completed or finished. This water is
the product from the water treatment plant and is ready to be delivered to
the consumers. Also called finished water.
profile. A drawing showing elevation plotted against distance,
such as the vertical section or side view of a pipeline.
prospective study. An epidemiological study which examines the
development of disease in a group of persons determined to be presently free
of the disease.
prussian blue. A blue paste or liquid (often on a paper like
carbon paper) used to show a contact area. Used to determine if gate valve
seats fit properly.
PSIG. Pounds per Square Inch Gage pressure. The pressure within a
closed container or pipe measured with a gage in pounds per square inch. See
gage pressure.
public water system. A system for the provision to the public of
piped water for human consumption, If such system has at least fifteen
service connections or regularly serves an average of at least 25
individuals at least 60 days out of the year. Such term includes: 1) any
collection, treatment, storage, and distribution facilities under control of
the operator of such system and used primarily in connection with such
system, and 2) any collection or pretreatment storage facilities not under
such control which are used primarily in connection with such system. A
public water system is either a "community water system" or a "non-community
water system.'
pumping station. Mechanical devices installed in sewer or water
systems or other liquid-carrying pipelines that move the liquids to a higher
level.
pumping water level. The vertical distance in feet from the
centerline of the pump discharge to the level of the free pool while water
is being drawn from the pool.
purveyor, water (purr-VAY-or). An agency or person that supplies
water (usually potable water).
putrefaction (PEW-truh-FACK-shun). Biological decomposition of
organic matter, with the production of ill-smelling and tasting products,
associated with anaerobic (no oxygen present) conditions.
Q
qualitative. Descriptive of kind, type or direction, as opposed to
size, magnitude or degree.
quantitative. Descriptive of size, magnitude or degree.
quicklime. A material that is mostly calcium oxide (CaO) or
calcium oxide in natural association with a lesser amount of magnesium
oxide. Quicklime is capable of combining with water to form hydrated lime.
Also see hydrated lime.
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R
radial to impeller. Perpendicular to the impeller shaft. Material
being pumped flows at a right angle to the impeller.
radical. A group of atoms that is capable of remaining unchanged
during a series of chemical reactions. Such combinations (radicals) exist in
the molecules of many organic compounds; sulfate (SO42-) is an inorganic
radical.
radionuclide. Any man-made or natural element which emits
radiation in the form of alpha or beta particles, or as gamma rays.
range. The spread from minimum to maximum values that an
instrument is designed to measure. Also see span and effective range.
ranney collector. This water collector is constructed as a dug
well from 12 to 16 feet (3.5 to 5 m) in diameter that has been sunk as a
caisson near the bank of a river or lake. Screens are driven radially and
approximately horizontally from this well into the sand and the gravel
deposits underlying the river.
raw water. 1) Water in its natural state, prior to any treatment. 2) Usually the water entering the first treatment process of a water
treatment plant.
reaeration (RE-air-A-shun). The introduction of air through forced
air diffusers into the lower layers of the reservoir. As the air bubbles
form and rise through the water, oxygen from the air dissolves into the
water and replenishes the dissolved oxygen. The rising bubbles also cause
the lower waters to rise to the surface where oxygen from the atmosphere is
transferred to the water. This is sometimes called surface reaeration.
reagent (re-A-gent). A pure chemical substance that is used to
make new products or is used in chemical tests to measure, detect, or
examine other substances.
recarbonation (re-CAR-bun-NAY-shun). A process in which carbon
dioxide is bubbled into the water being treated to lower the pH. The pH may
also be lowered by the addition of acid. Recarbonation is the final stage in
the lime-soda ash softening process. This process converts carbonate ions to
bicarbonate ions and stabilizes the solution against the precipitation of
carbonate compounds.
receiver. A device which indicates the result of a measurement.
Most receivers in the water utility field use either a fixed scale and
movable indicator (pointer) such as pressure gage or a movable scale and
movable indicator like those used on a circular-flow recording chart. Also
called an indicator.
receiving waters. All distinct bodies of water that receive runoff
or wastewater discharges, such as streams, rivers, ponds, lakes, and
estuaries.
receptor. 1) In biochemistry: a specialized molecule in a cell
that binds a specific chemical with high specificity and high affinity. 2)
In exposure assessment: an organism that receives, may receive, or has
received environmental exposure to a chemical.
recharge. Process by which rain water (precipitation) seeps into
the ground-water system.
recharge area. Generally, an area that is connected with the
underground aquifer(s) by a highly porous soil or rock layer. Water entering
a recharge area may travel for miles underground.
recharge rate. The quantity of water per unit time that
replenishes or refills an aquifer.
recorder. A device that creates a permanent record, on a paper
chart or magnetic tape, of the changes of some measured variable.
reducing agent. Any substance, such as base metal (iron) or the
sulfide ion (S2-), that will readily donate (give up) electrons. The
opposite is an oxidizing agent.
reduction (re-DUCK-shun). Reduction is the addition of hydrogen,
removal of oxygen, or the addition of electrons to an element or compound.
Under anaerobic conditions (no dissolved oxygen present), sulfur compounds
are reduced to odor-producing hydrogen sulfide (H2S and other compounds.
The opposite of oxidation.
reference. A physical or chemical quantity whose value is known
exactly, and thus is used to calibrate or standardize instruments.
reliquifaction (re-LICK-we-FACK-shun).
rem. The unit of dose equivalent from ionizing radiation to the
total body or any internal organ or organ system. A millirem (mrem)" is
1/1000 of a rem.
renal Pertaining to the kidney.
repeat compliance period. Any subsequent compliance period after
the initial compliance period.
representative sample. A portion of material or water that is as
nearly identical in content and consistency as possible to that in the
larger body of material or water being sampled.
reservoir. Any natural or artificial holding area used to store;
regulate, or control water.
residual chlorine. The amount of free and/or available chlorine
remaining after a given contact time under specified conditions.
residual disinfectant concentration ("C" in CT calculations).
The concentration of disinfectant measured in mg/L in a representative
sample of water.
residue. The dry solids remaining after the evaporation of a
sample of water or sludge. Also see total dissolved solids
respiration. The process in which an organism uses oxygen for its
life processes and gives off carbon dioxide.
retrospective study. An epidemiological study which compares
diseased persons with non-diseased persons and works back in time to
determine exposures.
reverse osmosis (oz-MOE-sis). The application of pressure to a
concentrated solution which causes the passage of a liquid from the
concentrated solution to a weaker solution across a semipermeable membrane.
The membrane allows the passage of the solvent (water) but not the dissolved
solids (solutes). The liquid produced is a demineralized water. Also see
osmosis.
reversible effect. An effect which is not permanent, especially
adverse effects which diminish when exposure to a toxic chemical is ceased.
RfD (Reference dose). The daily exposure level which, during an
entire lifetime of a human, appears to be without appreciable risk on the
basis of all facts known at the time. Same as ADI.
rill. A small channel eroded into the soil surface by runoff,
rills easily can be smoothed out (obliterated) by normal tillage.
riparian rights. A doctrine of state water law under which a land
owner is entitled to use the water on or bordering his property, including
the right to prevent diversion or misuse of upstream waters. Riparian land
is land that borders on surface water.
risk. The potential for realization of unwanted adverse
consequences or events.
risk assessment. A qualitative or quantitative evaluation of the
environmental and/or health risk resulting from exposure to a chemical or
physical agent (pollutant); combines exposure assessment results with
toxicity assessment results to estimate risk.
risk characterization. Final component of risk assessment that
involves integration of the data and analysis involved in hazard evaluation,
dose-response evaluation, and human exposure evaluation to determine the
likelihood that humans will experience any of the various forms of toxicity
associated with a substance.
risk estimate. A description of the probability that organisms
exposed to a specified dose of chemical will develop an adverse response
(e.g., cancer).
risk factor. Characteristic (e.g., race, sex, age, obesity) or
variable (e.g., smoking, occupational exposure level) associated with
increased probability of a toxic effect.
risk management. Decisions about whether an assessed risk is
sufficiently high to present a public health concern and about the
appropriate means for control of a risk judged to be significant.
risk specific dose. The dose associated with a specified risk
level.
rodenticide (row-DENT-uh-SIDE). Any substance or chemical used to
kill or control rodents. rotameter (RODE-uh-ME-ter). A device
used to measure the flow rate of gases and liquids. The gas or liquid being
measured flows vertically up a tapered, calibrated tube. Inside the tube is
a small ball or bullet-shaped float (it may rotate) that rises or falls
depending on the flow rate. The flow rate may be read on a scale behind or
on the tube by looking at the middle of the ball or at the widest part or
top of the float.
rotor. The rotating part of a machine. The rotor is surrounded by
the stationary (non-moving) parts (stator) of the machine.
route of exposure. The avenue by which a chemical comes into
contact with an organism (e.g., inhalation, ingestion, dermal contact,
injection).
run-off. That part of precipitation, snow melt, or irrigation water
that runs off the land into streams or other surface water. It can carry
pollutants from the air and land into the receiving waters.
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sacrificial anode. An easily corroded material deliberately
installed in a pipe or tank. The intent of such an installation is to give
up (sacrifice) this anode to corrosion while the water supply facilities
remain relatively corrosion free.
safe. Condition of exposure under which there is a "practical
certainty" that no harm will result in exposed individuals.
Safe Drinking Water Act (SDWA). Commonly referred to as SDWA. An
Act passed by the U.S. Congress in 1974. The Act establishes a cooperative
program among local, state and federal agencies to insure safe drinking
water for consumers.
safe water. Water that does not contain harmful bacteria, or toxic
materials or chemicals. Water may have taste and odor problems, color and
certain mineral problems and still be considered safe for drinking.
safe yield . The annual quantity of water that can be taken from a
source of supply over a period of years without depleting the source beyond
its ability to be replenished naturally in "wet years".
salinity. 1)The relative concentration of dissolved salts, usually
sodium chloride, in a given water.. 2) A measure of the concentration of
dissolved mineral substances in water.
sand. Soil particles between 0.05 and 2 .0 mm in diameter.
sand filters. Devices that remove some suspended solids from
sewage. Air and bacteria decompose additional wastes filtering through the
sand so that cleaner water drains from the bed.
sanitary sewer. A sewer that transports only wastewaters (from
domestic residences and/or industries) to a wastewater treatment plant.
sanitary survey. An on-site review of the water source,
facilities, equipment, operation, and maintenance of a public water system
for the purpose of evaluating the adequacy of the facilities for producing
and distributing safe drinking water.
saprophytes (SAP-row-FIGHTS). Organisms living on dead or
decaying organic matter. They help natural decomposition of organic matter
in water.
saturated zone. The area below the water table where all open
spaces are filled with water.
saturator (SAT-you-RAY-tore). A device which produces a
fluoride solution for the fluoridation process. The device is usually a
cylindrical container with granular sodium fluoride on the bottom. Water
flows either upward or downward through the sodium fluoride to produce the
fluoride solution.
schedule, pipe. A sizing system of arbitrary numbers that specifies
the I.D. (inside diameter) and O.D. (outside diameter) for each diameter
pipe. This term is used for steel, wrought iron, and some types of plastic
pipe. Also used to describe the strength of some types of plastic pipe.
SCD (SWCD). Soil Conservation District (also called Soil
and Water Conservation District in some areas); a local government entity
with in a defined water or soil protection area tat provides assistance to
farmers and other local residents in conserving natural resources,
especially soil and water.
SCFM. Cubic Feet of air per Minute at Standard conditions of
temperature, pressure and humidity (O degrees C /14.7 psia /50% relative
humidity).
SCS. Soil Conservation Service. An agency of the United States
Department of Agriculture that provides technical assistance for resource
conservation to farmers, other Federal, state and local agencies, and to
local soil conservation districts.
SDWA. See Safe Drinking Water Act.
secchi disc (SECK-key). A flat, white disc lowered into the water
by a rope until it is just barely visible. At this point, the depth of the
disc from the water surface is the recorded Secchi disc transparency.
seepage. The percolation of water through the soil from unlined
channels, ditches, watercourses and water storage facilities.
sedimentation. A water treatment process in which solid particles
settle out of the water being treated in a large clarifier or sedimentation
basin .
sediment yield. The quantity of sediment arriving at a specific
location.
seize up. Seize up occurs when an engine overheats and a part
expands to the point where the engine will not run. Also called "freezing".
semi-confined aquifer. An aquifer that is partially confined by a
soil layer (or layers) of low permeability through which recharge and
discharge can occur.
sensor. An instrument that measure (senses) a physical condition
or variable of interest. Floats and thermocouples are examples of sensors.
Also called a primary element
septage. The liquid and semisolid contents removed by pumping from
a septic tank.
septic (SEP-tick). A condition produced by bacteria when all
oxygen supplies are depleted. If severe, bottom deposits and water turn
black, give off foul odors, and the water has a greatly increased chlorine
demand.
septic system. An onsite system designed to treat and dispose of
domestic sewage; a typical septic system consists of a tank that receives
wastes from a residence or business And a system of tile lines or a pit for
disposal of the liquid effluent that remains after decomposition of the
solids by bacteria in the tank.
sequestration (SEE-kwes-TRAY-shun). A chemical completing (forming
or joining together) of metallic cations (such as iron) with certain
inorganic compounds, such as phosphate. Sequestration prevents the
precipitation of the metals (iron). Also see chelation.
service line sample. A one-liter sample of water collected 'm
accordance with CFR Section 141.86(b)(6)of the code of Federal Regulations,
that has been standing for a least 6 hours in a service line.
service pipe. The pipeline extending from the water main to the
building served or to the consumers system.
set point. The position at which the control or controller is set.
This is the same as the desired value of the process variable.
sewage. The used water and solids that flow from homes through sewers
to a wastewater treatment plant. The preferred term is WASTEWATER.
sewage. Liquid and solid wastes carried in sewers.
sewer. An underground system of conduits (pipes and/or tunnels)
that collect and transport wastewaters and/or runoff; gravity sewers carry
free-flowing water and wastes; pressurized sewers carry pumped wastewaters
under pressure.
sewerage system. The network of sewers that carries sewage from
point of origin to point of treatment.
shock load. The arrival at a water treatment plant of raw water
containing unusual amounts of algae, colloidal matter, color, suspended
solids, turbidity, or other pollutants.
short-circuiting. A condition that occurs in tanks or basins when
some of the water travels faster than the rest of the flowing water. This is
usually undesirable since it may result in shorter contact, reaction, or
settling times in comparison with the theoretical (calculated) or presumed
detention times.
silt. Soil particles between 0.05 and 0.002 millimeter in
approximate diameter.
simulate. To reproduce the action of some process, usually on a
smaller scale.
single family structure. A building constructed as a single-family residence that is currently used as either a residence or a place of
business.
single-stage pump. A pump that has only one impeller. A
multi-stage pump has more than one impeller.
sink. A place in the environment where a compound or material
collects. See reservoir.
slake. To mix with water with a true chemical combination
(hydrolysis) taking place, such as in the slaking of lime.
slope. The slope or inclination of a trench bottom or a trench
side wall is the ratio of the vertical distance to the horizontal distance
or "rise over run." Also see grade (2).
slow sand filtration. A process involving passage of raw water
through a bed of sand at low velocity (generally less than 0.4 m/h)
resulting in substantial particulate removal by physical and biological
mechanisms.
sludge (sluj). The settleable solids separated from water during
processing.
slurry (SLUR-e). A watery mixture or suspension of insoluble (not
dissolved) matter; a thin watery mud or any substance resembling it (such as
a grit slurry or a lime slurry).
SMCLs. Secondary Maximum Contaminant Levels. Secondary MCLs for
various water quality indicators are established to protect public
welfare.
SNARL Suggested No Adverse Response Level. The concentration of a
chemical in water that is expected not to cause an adverse health effect.
soft water. Water having a low concentration of calcium and magnesium
ions. According to U.S. Geological Survey guidelines, soft water is water
having a hardness of 60 milligrams per liter or less.
software programs. Computer programs; the list of instructions that
tell a computer how to perform a given task or tasks.
soil erodibility. A measure of the soil's susceptibility to raindrop
impact, runoff and other erosional processes.
soil profile. A vertical section of the earth's highly weathered
upper surface often showing several distinct layers, or horizons.
soil structure. The arrangement of soil particles into aggregates.
soil texture. The proportions of soil particles (sand, silt, and
clay) in a soil profile.
solder. A metallic compound used to seal the joints between pipes.
Until recently, most solder contained 50 percent lead. The use of lead
solder containing more than 0.2% lead is now prohibited for pipes carrying
potable water.
sole source aquifer. An aquifer that supplies 50 percent or more
of the drinking water of an area.
solenoid (SO-luh-noid). A magnetically (electrical coil) operated
mechanical device. Solenoids can operate a small valve or a switch.
solution. A liquid mixture of dissolved substances. In a solution
it is impossible to see all the separate parts.
sorption. A surface phenomenon which may be either absorption or
adsorption, or a combination of the two; often used when the specific
mechanism is not known.
span. The scale or range of values an instrument is designed to
measure. Also see range.
specific conductance. A rapid method of estimating the
dissolved-solids content of a water supply. The measurement indicates the
capacity of a sample of water to carry an electrical current, which is
related to the concentration of ionized substances in the water. Also called
conductance.
specific gravity. Weight of a particle, substance, or chemical
solution in relation to the weight of water. Water has a specific gravity of
1.000 at 4 degrees C (39 degrees F). Particulates in raw water may have a
specific gravity of 1.005 to 2.5.
specific yield. The quantity of water that a unit volume of
saturated permeable rock or soil will yield when drained by gravity.
Specific yield may be expressed as a ratio or as a percentage by volume.
spoil Excavated material such as soil from the trench of a water
main.
spore. The reproductive body of an organism which is capable of
giving rise to a new organism either directly or indirectly. A viable (able
to live and grow) body regarded as the resting stage of an organism. A spore
is usually more resistant to disinfectants and heat than most organisms.
spring. Ground water seeping out of the earth where the water
table intersects the ground surface.
spring line. Theoretical center of a pipeline. Also, the guideline
for laying a course of bricks.
standard. A physical or chemical quantity whose value is known
exactly, and is used to calibrate or standardize instruments. Also see
reference.
Standard Method See Standard Methods for the Examination of
Water and Wastewater.
Standard Methods for the Examination of Water and Wastewater. A joint
publication of the American Public Health Association, American Water Works
Association, and the Water Pollution Control Federation which outlines the
procedures used to analyze the impurities in water and wastewater.
standard sample. The aliquot of finished drinking water that is
examined for the presence of coliform bacteria.
standard solution. A solution in which the exact concentration
of a chemical or compound is known.
standardize. To compare with a standard. 1) In wet chemistry, to
find out the exact strength of a solution by comparing it with a standard of
known strength. 2) To set up an instrument or device to read a standard.
This allows you to adjust the instrument so that it reads accurately, or
enables you to apply a correction factor to the readings.
starters. Devices used to start up large motors gradually to avoid
severe mechanical shock to a driven machine and to prevent disturbance to
the electrical lines (causing dimming and flickering of lights).
State. The agency of the State or Tribal government which has
jurisdiction over public water systems. During any period when a State or
Tribal government does not have primary enforcement responsibility pursuant
to Section 1413 of the Safe Drinking Water Act, the term "State" means the
Regional Administrator, U.S. Environmental Protection Agency.
static head. When water is not moving, the vertical distance (in
feet) from a specific point to the water surface is the static head. (The
static pressure in psi is the static head in feet times 0.433 psi/ft.) Also
see dynamic pressure and static pressure
static pressure. When water is not moving, the vertical distance
(in feet) from a specific point to the water surface is the static head. The
static pressure in psi is the static head in feet times 0.433 psi/ft. Also
see dynamic pressure and static head
static water depth. The vertical distance in feet from the
centerline of the pump discharge down to the surface level of the free pool
while no water is being drawn from the pool or water table.
static water level. 1) The elevation or level of the water table
in a well when the pump is not operating. 2) The level or elevation to which
water would rise in a tube connected to an artesian aquifer, or basin, or
conduit under pressure.
stator. That portion of a machine which contains the stationary
(non-moving) parts that surround the moving parts (rotor).
sterilization (STARE-uh-luh-ZAY-shun). The removal or
destruction of all microorganisms, including pathogenic and other bacteria,
vegetative forms and spores. Compare with disinfection.
stethoscope. An instrument used to magnify sounds and convey them
to the ear.
strip cropping. A crop production system that involves planting
alternating strips of row crops and close-growing forage crops; the forage
strips intercept and slow runoff from the less protected row crop strips.
stochastic. Based on the assumption that the actions of a chemical
substance results from probabilistic events.
storm sewer. A sewer that collects and transports surface runoff
to a discharge point (infiltration basin, receiving stream, treatment
plant).
stratification. The formation of separate layers (of temperature, plant, or animal life) in a lake or reservoir. Each layer has similar
characteristics such as all water in the layer has the same temperature.
Also see thermal stratification.
subchronic. Of intermediate duration, usually used to describe
studies or levels of exposure between 5 and 90 days.
submergence. The distance between the water surface and the media
surface in a filter.
submerged aquatic vegetation (SAV). Aquatic vegetation, such as
sea grasses, that cannot withstand excessive drying and therefore live with
their leaves at or below the water surface. SAVs provide an important
habitat for young fish and other aquatic organisms.
suction lift The NEGATIVE pressure [in feet (meters) of water or
inches (centimeters) of mercury vacuum] on the suction side of the pump. The
pressure can be measured from the centerline of the pump DOWN TO (lift) the
elevation of the hydraulic grade line on the suction side of the pump.
superchlorination (SUE-per-KLOR-uh-NAY-shun). Chlorination
with doses that are deliberately selected to produce free or combined
residuals so large as to require dechlorination.
Superfund. Federal law which authorizes EPA to manage the clean-up
of abandoned or uncontrolled hazardous waste sites.
supernatant (sue-per-NAY-tent). Liquid
removed from settled sludge. Supernatant commonly refers to the liquid
between the sludge on the bottom and the water surface of a basin or
container.
supersaturated. An unstable condition of a solution (water) in
which the solution contains a substance at a concentration greater than the
saturation concentration for the substance.
supplier of water. Any person who owns or operates a public water
system.
surface loading. One of the guidelines for the design of settling
tanks and clarifiers in treatment plants. Used by operators to determine if
tanks and clarifiers are hydraulically (flow) over- or underloaded. Also
called overflow rate.
surface pump. A mechanism for removing water or wastewater from
a sump or wet well.
surface runoff. Precipitation, snow melt, or irrigation in excess
of what can infiltrate the soil surface and be stored in small surface
depressions; runoff is a major transporter of non-point source pollutants.
surface water. All water naturally open to the atmosphere (rivers,
lakes. reservoirs, streams, impoundments, seas, estuaries, etc.) and all
springs. wells, or other collectors which are directly influenced by surface
water.
surfactant (sir-FAC-tent). Abbreviation for surface-active
agent. The active agent in detergents that possesses a high cleaning
ability.
surge chamber. A chamber or tank connected to a pipe and located
at or near a valve that may quickly open or close or a pump that may
suddenly start or stop. When the flow of water in a pipe starts or stops
quickly, the surge chamber allows water to flow into or out of the pipe and
minimize any sudden positive or negative pressure waves or surges in the
pipe.
suspended solids. I)Solids that either float on the surface or are
suspended in water or other liquids, and which are largely removable by
laboratory filtering. 2) The quantity of material removed from water in a
laboratory test, as prescribed in STANDARD METHODS FOR THE EXAMINATION OF
WATER AND WASTEWATER.
synergism. An interaction of two or more chemicals which results
in an effect that is greater than the sum of their effects taken
independently.
system with a single service connection. A system which supplies
drinking water to consumers via a single service line.
systemic. Relating to whole body, rather than its individual
parts.
systemic effects. Effects observed at sites distant from the entry
point of a chemical due to its absorption and distribution into the body.
sounding tube. A pipe or tube used for measuring the depths of
water.
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TCE. See trichloroethane
TDS. See total dissolved solids. telemetry (tel-LEM-uh-tree). The
electrical link between the transmitter and the receiver. Telephone lines
are commonly used to serve as the electrical line.
temperature sensor. A device that opens and closes a switch in
response to changes in the temperature. This device might be a metal
contact, or a thermocouple that generates minute electrical current
proportional to the difference in heat, or a variable resistor whose value
changes in response to changes in temperature. Also called a heat sensor
teratogenesis. The induction of nonhereditary congenital
malformations (birth defects) in a developing fetus by exogenous factors
acting in the womb; interference with normal embryonic development.
teratogenicity. The capacity of a physical or chemical agent to
cause teratogenesis in offspring.
terrace. A broad channel, bench, or embankment constructed
across the slope to intercept runoff and detain or channel it to protected
outlets, thereby reducing erosion from agricultural areas.
therapeutic index. The ratio of the dose required to produce toxic
or lethal effect to dose required to produce nonadverse or therapeutic
response.
thermal stratification (STRAT-uh-fuh-KAY-shun). The
formation of layers of different temperatures in a lake or reservoir. Also
see stratification
thermocline (THUR-moe-KLINE). The middle layer in a
thermally stratified lake or reservoir. In this layer there is a rapid
decrease in temperature with depth. Also called the METALIMNION.
thermocouple. A heat-sensing device made of two conductors of
different metals joined at their ends. An electric current is produced when
there is a difference in temperature between the ends.
THM See trihalomethanes
THM precursor. See precursor, THM.
threshold. The lowest dose of a chemical at which a specified
measurable effect is observed and below which it is not observed.
threshold odor. The minimum odor of a water sample that can just be
detected after successive dilutions with odorless water. Also called odor
threshold
threshold odor number. The greatest dilution of a sample with
odor-free water that still yields a just-detectable odor.
thrust block. A mass of concrete or similar material appropriately placed around a pipe to prevent movement when the pipe is carrying
water. Usually placed at bends and valve structures.
tillage. Plowing, seedbed preparation, and cultivation practices.
time lag. The time required for processes and control systems to
respond to a signal or to reach a desired level.
timer. A device for automatically starting or stopping a machine or
other device at a given time.
time-weighted average. The average value of a parameter (e.g.,
concentration of a chemical in air) that varies over time.
tissue. A group of similar cells.
titrate (TIE-trate). To TITRATE a sample, a chemical solution of
known strength is added on a drop-by-drop basis until a certain color
change, precipitate, or pH change in the sample is observed (end point).
Titration is the process of adding the chemical reagent in increments until
completion of the reaction, as signaled by the end point.
TNCWS. See transient non-community water system.
too numerous to count. The total number of bacterial colonies
exceeds 200 on a 47-nun diameter membrane filter used for coliform
detection.
topography. The arrangement of hills and valleys in a geographic
area.
total dissolved phosphorus. Total phosphorus content of material that
will pass through a filter of a specific size.
total dissolved solids (TDS). All of the dissolved solids
in a water. TDS is measured on a sample of water that has passed through a
very fine mesh filter to remove suspended solids. The water passing through
the filter is evaporated and the residue represents the dissolved solids.
Also see specific conductance
total dynamic head (TDH). When a pump is lifting or pumping
water, the vertical distance (in feet) from the elevation of the energy
grade line on the suction side of the pump to the elevation of the energy
grade line on the discharge side of the pump.
total nitrogen. The sum of all nitrogen forms.
total particulate phosphorus. Total phosphorus content of material
retained on a filter of a specific size.
total phosphorus. The sum of all phosphorus forms.
total residual chlorine. The amount of available chlorine
remaining after a given contact time. The sum of the combined available
residual chlorine and the free available residual chlorine. Also see
residual chlorine
total trihalomethanes (THMs). The sum of the concentration,
in milligrams per liter, of the several trihalomethane compounds,
rounded to two significant figures.
total trihalomethanes (TTHM). The sum of the concentration in
milligrams per liter of the trihalomethane compounds (trichloromethane
[chloroform], dibromochloromethane, bromodichloromethane and tribromomethane
[bromoform]), rounded to two significant figures.
totalizer. A device or meter that continuously measures and
calculates (adds) total flows in gallons, million gallons, cubic feet, or
some other unit of volume measurement. Also called an integrator.
toxaphene (TOX-uh-FEEN). A chemical that causes adverse
health effects in domestic water supplies and also is toxic to freshwater
and marine aquatic life.
toxic (TOX-ick). A substance which is poisonous to an organism.
toxic pollutants. Materials contaminating the environment that cause
death, disease. birth defects in organisms that ingest or absorb them. The
quantities and length of exposure necessary to cause these effects can
vary widely.
toxic substance. A chemical or mixture that may represent an
unreasonable risk of injury to health or the environment.
toxicant A harmful substance or agent that may injure an exposed
organism.
toxicity. The quality or degree of being poisonous or harmful to
plant, animal or human life.
toxicity assessment Characterization of the toxicological properties
and effects of a chemical, including all aspects of its absorption,
metabolism, excretion and mechanism of action, with special emphasis on
establishment of doseresponse characteristics.
toxicology. The science and study of poisons control.
transducer (trans-DUE-sir). A device which senses some
varying condition and converts it to an electrical signal for transmission
to some other device (a receiver) for processing or decision making.
transformation. Acquisition by a cell of the property of
uncontrolled growth.
TWS. See transient water system.
transient water system. A non-community water system that does not
serve 25 of the same nonresident persons per day for more than six months
per year. Also called a transient non-community water system (TNCWS).
transmission lines. Pipelines that transport raw water from its
source to a water treatment plant. After treatment, water is usually pumped
into pipelines (transmission lines) that are connected to a distribution
grid system.
transmissivity. The ability of an aquifer to transmit water.
transpiration (TRAN-spur-RAY-shun).The process by which water
vapor is released to the atmosphere by living plants.
treated wastewater. Wastewater that has been subjected to one or more
physical, chemical, and biological processes to reduce its pollution of
health hazard.
tremie (TREH-me). A device used to place concrete or grout
under water.
trichloroethane (TCE) (try-KLOR-o-ETH-hane). An organic chemical
used as a cleaning solvent that causes adverse health effects in domestic
water supplies.
trihalomethane . One of a family of organic compounds named as
derivatives of methane. THMs are generally the by-product from chlorination
of drinking water that contains organic material. The resulting compounds
(THMs) are suspected of causing cancer.
tube settler. A device that uses bundles of small bore (2 to 3
inches or 50 to 75 mm) tubes installed on an incline as an aid to
sedimentation. The tubes may come in a variety of shapes including circular
and rectangular. As water rises within the tubes, settling solids fall to
the tube surface. As the sludge (from the settled solids) in the tube gains
weight, it moves down the tubes and settles to the bottom of the basin for
removal by conventional sludge collection means. Tube settlers are sometimes
installed in sedimentation basins and clarifiers to improve particle
removal.
tubercle (TOO-burr-cull). A protective crust of corrosion
products (rust) which builds up over a pit caused by the loss of metal due
to corrosion.
tuberculation (too-BURR-que-LAY-shun). The development or
formation of small mounds of corrosion products (rust) on the inside of iron
pipe. These mounds (tubercules) increase the roughness of the inside of the
pipe thus increasing resistance to water flow.
turbid. Having a cloudy or muddy appearance.
turbidimeter. A device that measures the amount of suspended
solids in a liquid.
turbidity (ter-BID-it-tee). The cloudy appearance of water caused
by the presence of suspended and colloidal matter. In the waterworks field,
a turbidity measurement is used to indicate the clarity of water.
Technically, turbidity is an optical property of the water based on the
amount of light reflected by suspended particles. Turbidity cannot be
directly equated to suspended solids because white particles reflect more
light than dark-colored particles and many small particles will reflect more
light than an equivalent large particle.
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U
uncertainty factor. A number (equal to or greater than one) used
to divide NOAEL or LOAEL values derived from measurements in animals or
small groups of humans, in order to estimate a NOAEL value for the whole
human population.
unconfined aquifer. An aquifer containing water that is not under
pressure; the water level in a well is the same as the water table outside
the well.
unit cancer risk. Estimate of the lifetime risk caused by each
unit of exposure in the low exposure region.
unit hydrograph. The hydrograph of one inch of storm runoff
generated by a rainstorm of fairly uniform intensity within a specific
period of time.
unsaturated zone. The area between the land surface and water
table in which the pore spaces are only partially filled with water. Also
called "zone of aeration".
upper-bound estimate. Estimate not likely to be lower than the
true risk.
urban runoff. Stormwater from city streets and adjacent domestic
or commercial properties that may carry pollutants of various kinds into the
sewer systems and/or receiving waters.
user fee. A fee which is collected only from those persons who use
a particular service, as opposed to one collected from the public in
general. User fees generally vary in proportion to the degree of use of the
service.
UST'S. Underground storage tanks.
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V
variable costs. Input costs that change as the nature of the
production activity of its circumstances change; for example, as
production levels vary.
variance. A State with primacy may relieve a public water system
from a requirement respecting an MCL by granting a variance if certain
conditions exist. These are: 1) the system cannot meet the MCL in spite of
the application of best available treatment technology, treatment techniques
or other means (taking costs into consideration), due to the characteristics
of the raw water sources which are reasonably available to the system, and
2) the variance will not result in an unreasonable public health risk. A
system may also be granted a variance from a specified treatment technique
if it can show that, due to the nature of the system's raw water source,
such treatment is not necessary to public health. Also see exemption.
vegetative controls. Non-point source pollution control practices
that involve plants (vegetative cover) to reduce erosion and minimize the
loss of pollutants.
virus. The smallest form of microorganisms capable of causing
disease. Especially, a virus of fecal origin that is infectious to humans by
waterborne transmission.
volatile. Readily vaporizable at a relatively low temperature.
volatile acids. Acids produced during digestion. Fatty acids which
are soluble in water and can be steam-distilled at atmospheric pressure.
Also called "organic acids." Volatile acids are commonly reported as
equivalent to acetic acid.
volatile liquids. Liquids which easily vaporize or evaporate at
room temperatures.
volatile solids. Those solids in water or other liquids that are lost
on ignition of the dry solids at 550 degrees C.
volatilization. Loss of a substance through evaporation.
voltage. The electrical pressure available to cause a flow of
current (amperage) when an electrical circuit is closed. See electromotive
force (E.M.F.).
volumetric. A measurement based on the volume of some factor.
Volumetric titration is a means of measuring unknown concentrations of water
quality indicators in a sample by determining the volume of titrant or
liquid reagent needed to complete particular reactions.
vortex. A revolving mass of water which forms a whirlpool. This
whirlpool is caused by water flowing out of a small opening in the bottom of
a basin or reservoir. A funnel-shaped opening is created downward from the
water surface.
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W
wastewater. The used water and solids from a community (including
used water from industrial processes) that flow to a treatment plant. Storm
water, surface water, and groundwater infiltration also may be included in
the wastewater that enters a wastewater treatment plant. The term -sewage
usually refers to household wastes, but this word is being replaced by the
term -wastewater.
wastewater treatment plant. A facility that receives wastewaters (
and sometimes runoff) from domestic and/or industrial sources, and by a
combination of physical, chemical, and biological processes reduces (treats)
the wastewaters to less harmful byproducts; known by the acronyms , STP
(sewage treatment plant), and POTW (publicly owned treatment works).
waterborne disease outbreak. The significant occurrence of acute
infectious illness, epidemiologically associated with the ingestion of water
from a public water system that is deficient in treatment, as determined by
the appropriate local or state agency
water budget. A summation of inputs, outputs, and net changes to a
particular water resource system over a fixed period. (Also, water balance
model).
water hammer. The sound like someone hammering on a pipe that
occurs when a valve is opened or closed very rapidly. When a valve position
is changed quickly, the water pressure in a pipe will increase and decrease
back and forth very quickly. This rise and fall in pressures can do serious
damage to the system.
water purveyor (purr-VAY-or). An agency or person that supplies
water (usually potable water).
water solubility. The maximum concentration of a chemical compound
which can result when it is dissolved in water. If a substance is water
soluble, it can very readily disperse through the environment.
water storage pond. An impound for liquid wastes, so designated as
to accomplish some degree of biochemical treatment of the wastes.
water supplier. A person who owns or operates a public water
system.
water supply system. The collection, treatment, storage, and.
distribution of potable water from source to consumer.
water table. The level of ground water. The upper surface of the
zone of saturation of groundwater above an impermeable layer of soil or
rock (through which water cannot move) as in an unconfined aquifer. This
level can be very near the surface of the ground or far below it.
water treatment lagoon. An impound for liquid wastes, so designed
as to accomplish some degree of biochemical treatment of the wastes.
water well. An excavation where the intended use is for the
location, acquisition, development, or artificial recharge of groundwater
(excluding Sandpoint wells).
watershed. The land area that drains into a stream. An area of
land that contributes runoff to one specific delivery point; large
watersheds may be composed of several smaller "subsheds", each of which
contributes runoff to different locations that ultimately combine at a
common delivery point.
watt A unit of power equal to one joule per second. The power of a
current of one ampere flowing across a potential difference of one volt.
weir (weer). 1) A wall or plate placed in an open channel and used
to measure the flow of water. The depth of the flow over the weir can be
used to calculate the flow rate, or a chart or conversion table may be used.
2) A wall or obstruction used to control flow (from settling tanks and
clarifiers) to assure uniform flow rate and avoid short-circuiting.
weir diameter (weer). Many circular clarifiers have a circular
weir within the outside edge of the clarifier. All the water leaving the
clarifier flows over this weir. The diameter of the weir is the length of a
line from one edge of a weir to the opposite edge and passing through the
center of the circle formed by the weir
weir loading. A guideline used to determine the length of weir
needed on settling tanks and clarifiers in treatment plants. Used by
operators to determine if weirs are hydraulically (flow) overloaded.
Weir Loading (GPM/ft) = Flow (GPM)/ Length of Weir (ft)
well. A bored, drilled, or driven shaft, or a dug hole, whose
depth is greater than the largest surface dimension and whose purpose is to
reach underground water supplies or oil, or to store or bury fluids below
ground.
well field. Area containing one or more wells that produces usable
amount of water.
well monitoring. The measurement, by on-site instruments or
laboratory methods, of the quality of water in a well.
well plug. A watertight and gastight seal installed in a bore hole
or well to prevent movement of fluids.
wet chemistry. Laboratory procedures used to analyze a sample of
water using liquid chemical solutions (wet) instead of, or in addition to,
laboratory instruments.
wetlands. Any number of tidal and nontidal areas characterized
by saturated or nearly saturated soils most of the year that form an
interface between terrestrial (land-based) and aquatic environments; include
freshwater marshes around ponds and channels (rivers and streams), brackish
and salt marshes; other common names include swamps and bogs.
wire-to-water efficiency. The efficiency of a pump and motor
together. Also called the overall efficiency.
withdrawal The process of taking water from a source and conveying
it to a place for a particular type of use.
Y
yield. The quantity of water (expressed as a rate of flow -- GPM,
GPH, GPD, or total quantity per year) that can be collected for a given use
from surface or groundwater sources. The yield may vary with the use
proposed, with the plan of development, and also with economic considerations. Also see safe yield.
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Zzeta potential. In coagulation and flocculation
procedures, the difference in the electrical charge between the dense layer
of ions surrounding the particle and the charge of the bulk of the suspended
fluid surrounding this particle. The zeta potential is usually measured in
millivolts.
zone of aeration. The comparatively dry soil or rock located
between the ground surface and the top of the water table.
zone of saturation. The soil or rock located below the top of the
groundwater table. By definition, the zone of saturation is saturated with
water. Also see water table.
zooplankton (ZOE-PLANK-ton). Small, usually microscopic
animals(such as protozoans), found in lakes and reservoirs.
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References
Water Treatment Plant Operation. California State University,
Sacramento, School of Engineering, Applied Research and Design Center. 1988.
Surface Water Treatment: The New Rules. Harry von Huben. American Water
Works Association. 1991.
Safe Drinking Water Act Amendments, Regulations and Standards. Calabrese,
EJ; Gilbert, CE and Pastides, H. Eds. Lewis Publishers. Chelsea Michigan.
1988.
Water Resources Planning. Dzurik, AA. Rowman & Littlefield, Savage,
MD. 1990.
Code of Federal Regulations, Title 40, Chapter I, Section 141.2.July 1,
1991
Federal Register 56 FR 26547, June 7, 1991 (Lead and Copper) 56 FR 3578,
January 30, 1991 (Phase 11)
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