A B C D E F G H I J K L M N O P
Q R S
T U V W X Y Z
Note:
The terms contained within this glossary are general definitions and are accurate as they
relate to water analysis, water treatment, and Hach Company products. They are for
reference only and are not intended to be applied outside the scope of these areas.
All trademarks or product names mentioned are the property of their respective owners.
acid:
any substance capable of giving up a proton; a substance that ionizes in solution to give
the positive ion of the solvent; a solution with a pH measurement less than 7.
acidity: the
quantitative capacity of aqueous solutions to react with hydroxyl ions. It is measured by
titration with a standard solution of base to a specified end point.
acre-foot: the volume
of water, 43,560 cubic feet, that will cover an area of one acre to a depth of one foot; a
term used in sewage treatment in measuring the volume of material in a trickling filter.
activated sludge process:
removes organic matter from sewage by saturating it with air and microbial organisms.
activation: treatment
of a substance by heat, radiation, or activating reagent to produce a more complete or
rapid chemical or physical change.
advanced waste treatment:
any treatment method or process employed following biological treatment (1) to reduce
pollution load (2) to remove substances that may be harmful to receiving waters or the
environment (3) to produce a high-quality effluent suitable for reuse in any specific
manner or for discharge under critical conditions. The term tertiary treatment is
commonly used to denote advanced waste treatment methods.
adsorption: the
adhesion of an extremely thin layer solid, liquid, or vapor molecules to the surface of a
solid or liquid.
aerobic: living or
occurring only in the presence of oxygen.
aerobic biological
oxidation: any waste treatment process or other process utilizing aerobic organisms,
in the presence of air or oxygen, as the agent for reducing pollution load, oxygen demand,
or the amount of organic substance in waste. The term is used in reference to secondary
treatment of wastes.
alcohol: Any class of
organic compounds containing the hydroxyl group, OH. Specifically, the term is applied to
ethyl alcohol (C2H5OH).
algaecide: chemical
agent added to water to destroy algae.
alkalinity: the
capacity of water to neutralize acids, a property imparted by the water's content of
carbonate, bicarbonate, hydroxide, and on occasion borate, silicate, and phosphate. It is
expressed in milligrams per liter of equivalent calcium carbonate (mg/l CaCO3).
alternating current (ac):
current that reverses its direction at regular intervals, such as a common 115 volt
circuit.
alum: technically, a
double sulfate of ammonium or a univalent or trivalent metal but commonly used to denote
aluminum sulfate (Al2(SO4)3.
amines: a class of
organic compounds of nitrogen that may be considered as derived from ammonia (NH3)
by replacing one or more of the hydrogen atoms by organic radicals, such as CH3
or C6H5, as in methylamine and aniline. The former is a gas at
ordinary temperature and pressure, but other amines are liquids or solids. All amines are
basic in nature and usually combine readily with hydrochloric or other strong acids to
form salts.
anaerobic: living or
occurring only in the absence of free oxygen.
anaerobic biological
treatment: any waste treatment process utilizing anaerobic or facultative organisms in
the absence of air to reduce the organic matter in water.
anaerobic waste treatment:
(sludge processing) waste stabilization brought about through the action of microorganisms
in the absence of air or elemental oxygen.
anhydrous: a term
meaning without water.
angstrom: a unit of
length, used especially in expressing the length of light waves, equal to one
ten-thousandth of a micron, or one hundredth-millionth of a centimeter (1 x 10E-8 cm).
anion: ion having a
negative charge; an atom with extra electrons. Atoms of non-metals, in solution, become
anions.
aquifer: a subsurface
geological structure that contains water.
atom: the smallest
particle of an element which can exist alone or enter into a chemical combination.
atomic absorption:
quantitative chemical method used for the analysis of elemental constituents.
atomic mass: the mass
of an atom expressed in atomic mass units (amu); the total number of protons and neutrons
in the nucleus.
atomic mass unit (amu):
a unit of mass equal to 1/12 the mass of the carbon isotope with mass number 12,
approximately 1.6604 x 10E-24 gram.
atomic number: the
number of protons in the nucleus of an atom.
atomic weight: the
average weight of an atom of an element, usually expressed relative to one atom of the
carbon isotope taken to have a standard weight of 12.
autooxidation:
oxidation caused by the atmosphere; an oxidation reaction that is self-catalyzed and
spontaneous; an oxidation reaction begun only by an inductor.
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backflow prevention: a
system designed to protect potable water from wastewater contamination which could occur
if wastewater pressure exceeds potable water pressure over a cross-connection where one or
more check valves fail.
backsiphonage: the
backflow of contaminated or polluted water, from a plumbing fixture or cross-connection
into a water supply line, due to a lowering of the pressure in the line.
backwashing: the
process of cleaning a rapid sand or mechanical filter by reversing the flow of water.
bacteria: any of
numerous unicellular microorganisms of the class Schizomycetes, occurring in a wide
variety of forms, existing either as free-living organisms or parasites, and having a wide
range of biochemical, often pathogenic properties. Some bacteria are capable of causing
human, animal or plant diseases; others are essential in pollution control because they
break-down organic matter in air and water.
bacterial examination:
the examination of water and wastewater to determine the presence, number, and
identification of bacteria. Also called bacterial analysis.
banks, sludge:
accumulations of solid, sewage, or industrial waste deposits on the bed of a waterway.
base: any substance
which contains hydroxyl (OH) groups and furnishes hydroxide ions in solution; a molecular
or ionic substance capable of combining with a proton to form a new substance; a substance
that provides a pair of electrons for a covalent bond with an acid; a solution with a pH
of greater than 7.
bioassay: an assay
method using a change in biological activity as a qualitative or quantitative means of
analyzing a material response to industrial waste and other wastewater by using viable
organisms or live fish as test organisms.
biochemical oxygen demand
(BOD): the quantity of oxygen used in the biochemical oxidation of organic matter in a
specified time, at a specified temperature, and under specified conditions; standard test
used in assessing wastewater biological oxygen demand.
biocides: chemical
agents with the capacity to kill biological life forms. Bactericides, insecticides,
pesticides, etc. are examples.
biodegradability: the
susceptibility of a substance to decomposition by microorganisms; specifically, the rate
at which compounds may be chemically broken down by bacteria and/or natural environmental
factors.
biological wastewater
treatment: forms of wastewater treatment in which bacterial or biochemical action is
intensified to stabilize, oxidize, and nitrify the unstable organic matter present.
Intermittent sand filters, contact beds, trickling filters, and activated sludge processes
are examples.
biomonitoring: the use
of living organisms to test the suitability of effluent for discharge into receiving
waters and to test the quality of such waters downstream from a discharge.
blowdown: removal of
liquids and/or solids from a process vessel or storage vessel or line by the use of
pressure; often used to remove materials which, in high concentrations, could cause damage
to the vessel or line, or exceed limits established by best engineering practices.
blowoff: a controlled
outlet on a pipeline, tank, or conduit which is used to discharge water or accumulations
of material carried by the water.
breakdown: failure of
insulator or insulating medium to prevent discharge or current flow.
british thermal unit (btu):
the quantity of heat necessary to raise the temperature of 1 pound of water by 1 oF.
buffer: a solution
selected or prepared to minimize changes in hydrogen ion concentration which would
otherwise occur as a result of a chemical reaction..
bulking agent: a fine,
solid material which is sometimes added to a wastewater stream to produce clarification or
coagulation by adding bulk to the solids.
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cake, sludge:
the material resulting from air drying or dehydrating sludge.
calibration:
the checking, adjusting, or systematic standardizing of the graduations of a quantitative
measuring instrument.
calorie: the quantity
of heat necessary to raise the temperature of 1 gram of water 1 oC at 1
atmosphere pressure.
catalyst: a substance
that alters the velocity of a chemical reaction and may be recovered essentially unaltered
in form and amount at the end of the reaction.
cation: a positively
charged atom or group of atoms, or a radical which moves to the negative pole (cathode)
during electrolysis.
caustic: capable of
destroying or eating away by chemical action; a hydroxide of a light metal.
caustic soda: sodium
hydroxide, NaOH.
chemical analysis: the
use of a standard chemical analytical procedures to determine the concentration of a
specific analyte in a sample, or qualitatively or quantitatively measure a specific
parameter of a sample.
chemical coagulation:
the destabilization and initial aggregation of colloidal and finely divided suspended
matter by the addition of a floc-forming chemical.
chemical oxygen demand:
the amount of oxygen required for the chemical oxidation of organics in a liquid; a
chemical test that determines the oxygen equivalent of the amount of organic matter
oxidizable by potassium dichromate in a 50% sulfuric acid solution.
chemical precipitation:
(1) the process of utilizing chemicals to produce a separable solid phase within a liquid
medium; in analytical chemistry, precipitation is used to separate a solid phase in an
aqueous solution. (2) the process of softening water by the addition of lime and soda ash
as the precipitants.
chlorination: the
addition of chlorine to water or wastewater, generally for the purpose of disinfecting,
but frequently done to achieve other biological or chemical results.
chlorination break point:
the addition of chlorine to water, sewage, or industrial waste containing free ammonia to
the point where free residual chlorine is available.
chlorination, free
residual: the addition of chlorine to water, sewage or industrial wastes to produce,
directly or through the destruction of ammonia or certain organic nitrogenous compounds, a
free available chlorine residual.
chlorine, available:
the quantity of chlorine released by a bleaching powder when treated with acid.
chlorine, combined
available residual: that portion of the total residual chlorine remaining in water,
sewage or industrial waste at the end of a specified contact period, which will react
chemically and biologically as chloramines or organic chloramines.
chlorine demand: the
quantity of chlorine absorbed by wastewater (or water) in a given length of time.
chlorine, total residual:
free residual chlorine plus combined residual chlorine.
circuit: a path
through which an electrical current can flow when the path is complete.
clarification: the
composite wastewater treatment process consisting of flash mixing of coagulants, pH
adjusting chemicals, and/or polyelectrolytes, flocculation, and sedimentation.
clarifier: a unit
which provides for settling and removal of solids from wastewater.
coagulation: the
clumping of particles in order to settle out impurities; often induced by chemicals such
as lime or alum.
coliform organisms:
any of a number of organisms whose presence in wastewater is an indicator of pollution and
of potentially dangerous bacterial contamination.
complexing: the use of
chelating or sequestering agents to form relatively loose chemical bonding as a means of
treating certain pollutants such as nickel, copper, and cobalt.
compound: two of more
elements combined; a substance having different properties than of the elements used.
concentrated: being of
full strength, or undiluted.
concentration: in
solutions, the mass, volume, or number of moles of solute present in proportion to the
amount of solvent or total solution Common measures are: molarity, normality, percent,
molality, and by specific gravity scales.
condensate: water
obtained by evaporation or a product that has changed from a gaseous or vaporous form to a
liquid form.
conductance: a measure
of the conducting power of a solution equal to the reciprocal of the resistance. The
resistance is expressed in ohms.
conductivity: ability
of a material to carry current or heat.
contact coagulation: a
water clarification process which involves the addition of a coagulant with appropriate
mixing for the purpose of floc formation within a filter media, which will be periodically
back-flushed to permit the separation of the resulting solids from the main wastewater
stream.
contamination: a
general term signifying the introduction into water of microorganisms, chemicals, wastes
or sewage which renders the water unfit for its intended use.
cooling tower: a
device for cooling water through a combination of sensing and evaporative heat transfer.
Water passes over a number a wooden or plastic racks known as “fill”, that act
as a heat-transfer surface.
current: a movement of
electrons through a conductor. Measured in amperes.
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decant: to
remove the liquid portion of a settled mixture without disturbing the sediment.
dechlorination
process: a process by which excess chlorine is removed from water to a desired
level. Usually accomplished by chemical reduction, by passage through carbon beds or by
aeration at a suitable pH.
degradable:
that which can be reduced, broken down or chemically separated.
degreasing:
the process of removing greases and oils from sewage, waste, and sludge.
demineralization:
removal from water of mineral contaminants. Methods include ion exchange, flash
distillation, electrodialysis, or reverse osmosis.
detention time:
the time allowed for solids to collect in a settling tank. Theoretically detention time is
equal to the volume of the tank divided by the flow rate.
dew point:
the temperature at which the condensation of a vapor begins; the term is usually applied
to condensation of moisture from the water vapor in the atmosphere.
dialysis:
the separation of a colloid from a substance in solution by allowing the solution to
diffuse through a semipermeable membrane.
diatomaceous earth:
a filter medium used for filtration of effluents from secondary and tertiary treatments,
particularly when a very high grade of water for reuse in certain industrial purposes is
required; used as an absorbant for oils and oily emulsions in some wastewater treatment
designs; also used historically in preparing standard suspensions for turbidity
measurements.
digestion:
the biochemical decomposition of organic matter which results in the formation of mineral
compounds and simple organic compounds.
DI water:
deionized water, having had all the ions removed.
diluent: the
thinning agent used to dilute a fluid, usually water.
dilute: to
thin out, or having been thinned out; less than full strength.
diode: a
component that readily passes current in one direction but opposes current flow in the
opposite direction.
direct current (dc):
a non-oscillating current that flows continually in one direction through a circuit
disinfection:
effective killing by chemical or physical processes of all organisms capable of causing
infectious disease. Chlorination is the disinfection method commonly employed in
sewage-treatment processes.
dissolved oxygen (DO):
the oxygen dissolved in sewage, water, or other liquid, usually expressed in milligrams
per liter or percent of saturation. It is the test used in BOD determination.
dissolved solids: the total amount of dissolved material, organic and inorganic, contained
in water or wastewater. Excessive dissolved solids make water unpalatable for drinking and
unsuitable for industrial use. Measurements are expressed as ppm or mg/L.
distillation:
the process of heating a liquid to its boiling point, removing the vapors through a
cooling and condensing apparatus, and finally collecting the condensed liquid in a
separate receiver. It is commonly used for the separation of two or more liquids in a
mixture, or for the separation of the solvent from dissolved substances.
distilled water:
water that has been purified by distillation (boiling the water off as steam and
condensing it back to a liquid, leaving the impurities behind). Having been boiled, it is
also sterile.
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edta titration (edta): ethylenediaminetetraacetic
acid (or its salts). A standard method of measuring the hardness of a solution.
effluent: a liquid
that has passed through a processing operation.
effluent limitation:
any restriction (including schedules of compliance) established by a state or EPA on
quantities, rates, and concentrations of chemical, physical, biological, and other
constituents which are discharged from point sources into navigable water, the waters of
the contiguous zone, or the ocean.
electron: the
sub-atomic particle, with a negative charge, that orbits the nucleus of an atom.
element: a substance
that cannot be resolved into two or more other substances; a substance made up of atoms
with the same atomic number.
emulsion: a liquid
system in which one liquid is finely dispersed in another liquid in such a manner that the
two will not separate through the action of gravity alone.
end point: that stage
in the titration at which an effect, such as a color change, occurrs, indicating that a
diesired point in the titration has been reached.
enrichment: the
addition of nitrogen, phosphorous, and carbonaceous compounds, or other nutrients into a
lake or other waterway that greatly increases the growth potential for algae and other
aquatic plants. Most frequently, enrichment results from the inflow of sewage effluents or
from agricultural runoff.
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facultative: having
the power to live under different conditions either with or without oxygen.
fats (wastes):
triglyceride-esters of fatty acids. Erroneously used as synonymous with grease.
filtration: the
process of separating solids from a liquid by means of a porous substance through which
only the liquid can pass.
filter backwash: the
reversal of flow though a filter to wash clogged material out of the filter medium and
reduce conditions causing loss in flow through the filter.
floatation: the
process of removing finely divided particles from a liquid suspension by agitating
the liquid with gas bubbles thus increasing the buoyancy of the particles, and
concentrating them at the surface of the liquid medium.
floc: a very fine,
fluffy mass formed by the aggregation of fine suspended particles.
flocculation: the
process of separating suspended solids from wastewater by chemical creation of a
coagulated, or flocculent masses.
flowrate: usually
expressed as liters/minute (gallons/minute) or liters/day. Design flowrate is that used to
size the wastewater treatment process. Peak flowrate is 1.5 to 2.5 times design and
relates to the hydraulic flow limit and is specified for each plant.
fluid: a substance
which yields readily to any force which tends to alter its shape; fluids possess no
definite shape; the term includes both liquids and gases.
flux: a material used
to promote joining of metals in soldering.
formazin: a polymer
suspension used as the standard for turbidity.
formazin nephelometric
unit (FNU): an industry standard unit measurement used in the European Union,
equivalent to NTU.
formazin turbidity unit
(FTU): a measure of water turbidity equivalent, but not equal, to Jackson Turbidity
Units (JTU).
formula: an expression
of chemical composition, using symbols and figures.
FNU: see formazin
nephelometric unit.
FTU: see formazin
turbidity unit.
fuse: a protective
device containing a short piece of wire that melts and breaks when current through it
exceeds a rated value, thus de-energizing the circuit.
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gas: a fluid having
neither independent shape nor volume, but tending to expand indefinitely. The word is
often used to denote anesthetics, combustibles (gasoline), poisonous materials, etc.,
whether liquid or solids at ordinary temperatures.
grab sample: a single
sample of wastewater taken at neither set time nor flow.
group: a family of
elements with similar chemical properties, represented by a vertical column in the
periodic table.
ground wire: a
conductor leading from electrical equipment to a low resistance connection with the earth.
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hardness: a
characteristic of water, imparted by salts of calcium, magnesium, and iron, such as
bicarbonates, carbonates, sulfates, chlorides, and nitrates that cause curdling of soap,
deposition of scale in boilers, damage in some industrial process, and sometimes
objectionable taste. It may be determined by a standard laboratory procedure or computed
from the amounts of calcium and magnesium as well as iron, aluminum, manganese, barium,
strontium, and zinc; expressed as equivalent parts per million of calcium carbonate.
heavy metals: a
general term given to the ions of metallic elements such as copper, zinc, chromium, and
aluminum. They are removed from wastewater by forming an insoluble precipitate (usually a
metallic hydroxide).
hertz (Hz): in
electrical/electronic applications with alternating current, a unit of frequency where 1
Hz equals one cycle per second.
hot (circuit): connected,
alive, energized.
hydrocarbon: a
chemical compound containing only hydrogen and carbon; the largest source of hydrocarbons
comes from petroleum crude oil.
hydrogenation: the
infusing of unsaturated or impure hydrocarbons with hydrogen gas at controlled
temperatures and pressures for the purpose of obtaining saturated hydrocarbons and/or
removing various impurities such as sulfur and nitrogen.
hydrogen ion concentration:
the normality of a solution with respect to hydrogen ions, H+; it is related to
acidity measurements in most cases by the equation pH= log 1/2[1/(H+)] where H+
is the hydrogen ion concentration in gram equivalents per liter of solution.
hydroxyl radical: an
oxygen and hydrogen atom occurring as a group (OH-).
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impedance: total
opposition to flow of current, measured in ohms; combined effort of resistance,
inductance, and capacitance.
incineration: the
combustion of organic matter in wastewater sludge solids after water evaporation from the
solids.
indicator: a compound
that changes color at a particular pH, or over a particular narrow range of pH, used to
show titration end points.
influent: sewage,
water or other liquid, either raw or partly treated, flowing into a reservoir basin, or
treatment plant or any part thereof.
ion: an isolated
electron or positron; an atom or molecule which by loss or gain of one or more electrons
has acquired a net electric charge.
ion exchange: a
chemical reaction in which mobile hydrated ions of a solid are exchanged, equivalent for
equivalent, for ions of like charge in solution. The process can be used to remove ionic
pollutants from wastewater.
ionization: a process
by which a neutral atom or molecule loses or gains electrons, thereby acquiring a net
charge and becoming an ion; occurs as the result of the dissociation of the atoms of a
molecule in solution or of a gas in an electric field.
isomer: chemical
compound that has the same number, and kinds of atoms as another compound, but a different
structural arrangement of the atoms.
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jackson turbidity unit
(JTU): a measure of the turbidity of water, proportional to the ppm silica, where 100
ppm silica equals 21.5 JTU. This method was the standard for turbidity for many years; it
applied the use of a candle, measuring tube, and the human eye for determining the value.
This method has since been replaced by the use of a known turbidity standard, Formazin,
and the use of analytical instruments that will detect forward-scattered light and light
scattered at 90 degrees.
JTU: see jackson
turbidity unit.
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lagoon: in wastewater
treatment, a shallow pond where sunlight, bacterial action, and oxygen interact to restore
wastewater to a reasonable state of purity.
lime: any of a family
of chemicals consisting essentially of calcium hydroxide made from limestone (calcite)
which is composed mostly of calcium carbonate or a mixture of calcium carbonate and
magnesium carbonate.
limnology: the study
of the physical, chemical, meteorological and biological aspects of fresh water.
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manometer: an
instrument for measuring pressure liquids and gasses. It usually consists of a U-shaped
tube containing a liquid, the surface of which is in one end of the tube; moves
proportionally with changes in pressure on the liquid in the other end. Also, a tube type
differential pressure gauge.
mass: the quantity of
matter in a body as measured by its resistance to a change in acceleration; different but
proportional to weight.
mass number: the total
number of protons and neutrons in an atomic nucleus.
meniscus: the curved
upper surface of a non-turbulent liquid in a container; it is concave (curves upward) if
it wets the container walls, and convex (curves downward) if it does not. For accurate
measurements, readings should be taken at the flat center of the meniscus.
micro: a prefix
meaning one-millionth of a unit.
microorganism:
organisms (microbes) observable only through a microscope; larger, visible types are
called macroorganisms.
milligrams per liter
(mg/l): this is a weight per volume designation used in water and wastewater analysis.
1mg/L = 1ppm.
molal: a solution
concentration having a mole of solute per 1,000 grams of solvent, usually water.
molality: a measure of
solution concentration expressed in moles of solute per 1,000 grams of solvent.
molar: a solution
concentration having one mole of solute per liter of solution.
molarity: a measure of
solution concentration expressed in moles of solute per liter of solution.
mole: an amount of a
substance weighing the number of grams equal to the total atomic weight in one molecule
(or atom). Equivalent to gram-atomic, gram-molecular, and gram-formula weights.
molecular weight: the
sum of the atomic weights of all the atoms in a molecule.
molecule: the simplest
structural unit of a substance that retains the properties of the substance, and is
composed of one or more atoms.
most probable number (MPN):
that number of organisms per unit volume that, in accordance with statistical theory,
would be more likely than any other number to be yielded with the greatest frequency in a
specific test. Expressed as density of organisms per 100 ml. Results are computed from the
number of positive findings of coliform-group organisms resulting from multiple-portion
decimal-dilution plantings.
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nephelometer: an
instrument that measures scattered light in a liquid.
nephelometric turbidity
unit (NTU): a standard unit of turbidity measurement, equivalent to FNU.
neutralization:
chemical addition of either acid or base to a solution such that the pH is adjusted to 7.
neutron: an uncharged
sub-atomic particle, with a mass nearly equal to that of a proton. Present in the nucleus
of all atoms except hydrogen.
nitrification: the
conversion of nitrogenous matter or free nitrogen into nitrates and ammonia by bacteria.
non-ionic surfactants:
a general family of surfactants so called because in solution the entire molecule remains
associated. Non-ionic molecules orient themselves at surfaces not by an electrical charge,
but through separate grease-solublizing and water-soluble groups within the molecule.
nonsettleable matter:
the suspended matter which neither settles nor floats to the surface of water in a period
of one hour.
nonsettleable solids:
wastewater matter that will stay in suspension for an extended period of time. Such period
may be arbitrarily taken for testing purposes as one hour.
normal: a solution
concentration of one gram equivalent per liter of solution.
normality: a measure
of solution concentration expressed in equivalent weights of solute per liter of solution.
NTU: see nephelometric
turbidity unit.
nutrients:
materials which are considered essential to the support of biological life.
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ohm: a unit of
electrical resistance equal to that of a conductor in which a current of one ampere is
produced by a potential of one volt across its terminals.
organic matter:
chemical compounds based on carbon chains or rings, and also containing hydrogen with or
without oxygen, nitrogen, or other compounds.
organic nitrogen:
nitrogen combined in organic molecules such as protein, amines, and amino acids.
orthophosphate: an
acid or salt containing phosphorus as PO4, such as K3PO4
(potassium phosphate).
oxidant: a chemical
agent that oxidizes.
oxidation: in a broad
sense oxidation is the increase in positive valence of any element in a substance. On the
basis of the electron theory, oxidation is a process in which an element losses electrons.
In a narrow sense, oxidation means the chemical addition of oxygen to a substance.
ozone: oxygen in
molecular form with three atoms of oxygen forming each molecule (O3).
Atmospheric oxygen is molecular in form but each molecule contains only two atoms of
oxygen. Ozone is formed by passing high voltage electric charges through dry air. The
third atom of oxygen in each molecule of ozone is loosely bound and is easily released,
thus making it a powerful oxidant; used to purify water and treat industrial wastes.
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parts per million (ppm): the
unit commonly used to represent the degree of pollutant concentration where the
concentrations are small. Larger concentrations are given in percentages. 1ppm = 1mg/L. In
BOD analysis, the results are expressed in ppm, whereas in the suspended solids test, the
values are expressed in percents. In air, ppm is usually a volume/volume ratio; in water,
ppm represents a weight/volume ratio.
pathogenic bacteria:
bacteria which may cause disease in the organisms by their parasitic growth.
period: a series of
elements, arranged in order of atomic number represented by a horizontal row on the
Periodic Table.
periodic table: a
table in which the elements are commonly arranged in order of increasing atomic number.
Elements of similar properties are placed one under the other, yielding eight families or
groups of elements. Within each group there is a gradation of chemical and physical
properties, but in general a similarity of chemical behavior. From group to group,
however, there is a progressive shift of chemical behavior from one end of the table to
the other.
pH: the negative
logarithm of the hydrogen ion concentration (-log10[H+]) where H+ is
the hydrogen-ion concentration in moles per liter. Neutral water has a pH value of 7.
pH adjustment: a means
of maintaining the optimum pH through the use of chemical additives.
phenolphthalein alkalinity:
a measure of the hydroxides plus one-half of the normal carbonates in aqueous suspension.
Measured by the amount of sulfuric acid required to bring the water to a pH value of 8.3,
as indicated by a change in color of phenolphthalein. It is expressed in ppm of calcium
carbonate (CaCO3).
potable water: water
suitable for drinking or cooking purposes from both health and aesthetic considerations.
prechlorination:
chlorination of water prior to filtration, or chlorination of sewage prior to treatment.
precipitant: a
chemical or chemicals that cause a precipitate to form when added to a solution.
precipitate: the
discrete particles of material separate from the liquid solution.
precipitation, chemical:
to cause a solid substance to be separated (precipitate out) of a solution by the addition
of chemical additives; the process of softening water by the addition of lime and soda ash
as the precipitants.
pretreatment: any
wastewater treatment process used to partially reduce pollution load before the wastewater
is introduced into a main sewer system or delivered to a treatment plant; a substantial
reduction of the pollution load.
process, biological:
the process by which the life activities of bacteria, and other microorganisms in the
search for food, break down complex organic material into simple, more stable substances.
Self-purification of sewage, polluted streams, sludge digestion, and all so-called
secondary sewage treatments result from this process. Also called biochemical process.
process, oxidation:
any method of sewage treatment for the oxidation of the decomposable organic matter that
brings about the decomposition of such matter. The usual methods are biological
filtration, and activated sludge processes.
proton: a sub-atomic
particle, positively charged, in the nucleus of atoms.
putrefaction:
biological decomposition of organic matter accompanied by the production of a foul smell
associated with anaerobic condition.
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quantitative analysis:
chemical determination of the amounts or proportions of constituents in a substance.
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radical: an atom or
group of atoms with at least one unpaired electrons.
reagent: a chemical
substance used to cause a reaction for the purpose of chemical analysis.
recorder: a device
that makes a graph or other automatic record of the stage, pressure, depth, velocity, or
the movement or position of water controlling devices, usually as a function of time.
reduction: chemical
reaction in which an atom or molecule gains an electron; decrease in positive valence;
addition of hydrogen to a molecule.
reduction treatment:
the opposite of oxidation treatment wherein a reductant is used to lower the valence state
of a pollutant to a less toxic form; e.g. the use of SO2 to reduce Cr6+
to Cr3+ in an acidic solution.
residual chlorine:
chlorine remaining in water or wastewater at the end of specified contact period as
combined or free chlorine.
resistance: the
opposition which a device or material offers to the flow of current; measured in ohms.
resistor: a component
of an electrical circuit intended to offer resistance to electrical current flow.
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salinity: (1) the
relative concentration of salts, usually sodium chloride, in a given water. It is usually
expressed in terms of the number of ppm of chloride. (2) a measure of the concentration of
dissolved mineral substances in water.
salt: any compound
formed by combination of any negative ion (except hydroxide) with any positive ion (except
hydrogen or hydronium); the precipitate produced as the result of neutralization of an
acid with a base.
saturated: (1) in
organics, a chemical compound with all carbon bonds satisfied; it does not contain double
or triple bonds and thus cannot add elements or compounds. (2) in liquids, a solution that
contains enough of a dissolved solid, liquid, or gas so that no more will dissolve into
the solution at a given temperature and pressure.
scale: the precipitate
that forms on surfaces in contact with water as the results of a physical or chemical
change, often due to the presence of calcium carbonate (CaCO3) or magnesium
carbonate (MgCO3).
sedimentation: the
deposition of suspended matter carried by water, wastewater, or other liquids, by gravity.
It is usually accomplished by reducing the velocity of the liquid below the point at which
it can transport the suspended material. Also called settling.
settleable solids:
particles of debris and fine matter heavy enough to settle out of wastewater.
sewage: the total of
organic waste and wastewater generated by residential and commercial establishments.
sewage, combined: a
sewage containing both sanitary sewage and surface or storm water with or without
industrial wastes.
sewage, dilute: sewage
containing less than 150 ppm of suspended solids and BOD (weak sewage).
sewage, industrial:
sewage in which industrial wastes predominate.
sewage, raw: sewage
prior to receiving any treatment.
sewage, settled:
sewage from which most of the settleable solids have been removed by sedimentation.
sewage, storm: liquid
flowing in sewers during or following a period of heavy rainfall.
sludge: the solids
(and accompanying water and organic matter) which are separated from sewage or industrial
wastewater in treatment plant facilities. Sludge separation and disposal is one of the
major expenses in wastewater treatment operations.
sludge conditioning: a
process employed to prepare sludge for final disposal, e.g., thickening, digesting, heat
treatment or other procedures.
sludge digestion: the
process by which organic or volatile matter in sludge is gasified, liquefied, mineralized,
or converted into more stable organic matter through the activities of either anaerobic or
aerobic organisms.
sludge disposal: the
final disposal of solid wastes including the use of sewage sludge as fertilizers and soil
builders, and fill for low-lying lands.
sludge thickening: the
increase in solids concentrations of sludge in the sedimentation of digestion tank.
slurry: a watery
mixture or suspension of solids.
soda ash: a common
water treating chemical, sodium carbonate.
softening: the removal
of hardness—calcium and magnesium—from water.
solder: an alloy of
lead/tin used for making permanent electrical connections between parts and wire.
solute: the substance
that is dissolved to form a solution.
solution: a liquid
(solvent) that contains a dissolved substance (solute).
solvent: a liquid used
to dissolve another substance.
specific gravity: a
comparison by weight to an equal volume of pure water, at a standard temperature.
standard (or standardized
solution): a solution containing a known, precise concentration of an element or
chemical compound, often used to calibrate analytical chemistry measurement devices.
surface tension: the
property, due to molecular forces in the surface film, that tends to contract the liquid
into a form having the least surface/volume ratio.
surfactant: a
surface-active substance, such as a detergent or soap, that lowers the surface tension of
a solvent (usually water).
suspended matter: (1)
solids in suspension in water, wastewater or effluent. (2) solids in suspension that can
be removed readily by standard filtering procedures in a laboratory.
suspended solids: (1)
solids that either float on the surface of, or are in suspension in, water, wastewater, or
other liquids, and which are largely removable by laboratory filtering. (2) the quantity
of material removed from wastewater in a laboratory test, as prescribed in “Standard
Methods” and referred to as nonfilterable residue.
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tertiary treatment:
process utilized to remove practically all solids and organic matter from wastewater.
Granular activated carbon filtration is a tertiary treatment process. Phosphate removal by
chemical coagulation is also regarded as a step in tertiary treatment.
thermistor: a
semiconductor whose resistance will vary with temperature.
titration: a method of
analyzing the composition of a solution by adding known amounts of a standardized solution
until a given reaction (color change, precipitation, or conductivity change) is produced.
tracer: (1) a foreign
substance mixed with or attached to a given substance for the determination of the
location or distribution of the substance. (2) an element or compound that has been made
radioactive so that it can be easily followed (traced) in biological and industrial
processes. Radiation emitted by the radioisotope pinpoints its location.
treatment efficiency:
usually refers to the percentage reduction of a specific or group of pollutants by a
specific wastewater treatment step or treatment plant.
turbidimeter: an
instrument for measurement of turbidity in which a standard suspension is used for
reference.
turbidity: (1) a
condition in water or wastewater caused by the presence of suspended matter, resulting in
the scattering and absorption of light rays. (2) a measure of fine suspended matter in
liquids. (3) an analytical quantity usually reported in turbidity units (NTU/FNU, FTU,
JTU) determined by measurements of light diffraction.
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unsaturated: any
chemical compound with more than one bond between adjacent atoms, usually carbon, and thus
reactive toward the addition of other atoms at that point; for example: olefins,
diolefins, and unsaturated fatty acids.
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valence: the relative
ability of a biological substance to react or combine; a positive number that
characterizes the combining power of an element for other elements, as measured by the
number of bonds to other atoms which one atom of the given element forms upon chemical
combination – hydrogen is assigned valence 1, and the valence is the number of
hydrogen atoms, or their equivalent, with which an atom of the given element combines.
viscosity: the
resistance offered by a fluid (liquid or gas) to flow. The viscosity is a characteristic
property and is a measure of the combined effects of adhesion and cohesion.
volatile solids: the
quantity of solid in water, wastewater or other liquids, lost on ignition of the dry
solids at 600 oC.
voltage: the
electrical pressure (electromotive force) that makes current flow through a conductor.
volume: the space
occupied in three dimensions.
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washdown: water
resulting from cleaning of equipment, walls, floors, etc., within a plant.
watt: the practical
unit of electrical power.
wire gauge: wire size,
measured in diameter.
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zeolite process: an
ion-exchange process for softening water. The zeolite exchanges sodium ions for hardness
constituents (calcium, magnesium, etc.) in the water.
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