# Appendix A. List of Definitions

## A.1 List of Definitions

**accuracy.** How closely an instrument measures the true or actual
value of the process variable being measured or sensed.

**acidic.** The condition of water or soil which contains a sufficient
amount of acid substances to lower the pH below 7.0.

**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
organic materials from water.

**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.

**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.

**alkaline.** The condition of water or soil which contains a sufficient
amount of alkali substances to raise the pH above 7.0.

**alkalinity.** 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.

**analog.** The readout of an instrument by a pointer (or other
indicating means) against a dial or scale.

**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.

**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.

**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.

**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.** 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).

**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.

**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).

**calcium carbonate (CACO~3~) 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.

**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.** Any substance which tends to produce cancer in an
organism.

**clarifier.** 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.

**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.

**coagulant aid.** Any chemical or substance used to assist or modify
coagulation.

**coagulants.** 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.** 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.

**colloids.** 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.

**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 (CWS).** A public water system which serves at
least 15 service connections used by year round residents or regularly
serves at least 25 persons 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.

**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.

**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.

**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.

**degasification.** 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.

**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.

**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.

**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.** Water or some other liquid‑raw, partially or completely
treated‑flowing from a reservoir, basin, treatment process or treatment
plant.

**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.

**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.

**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.

**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.

**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.

**garnet.** 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.

**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.** Intestinal disease caused by an infestation of Giardia
flagellates.

**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.

**ground water under the direct influence (GWUDI) 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.

**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.

**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.

**humus.** Organic portion of the soil remaining after prolonged
microbial decomposition, hydrogeologic cycle. The natural process
recycling water from the atmosphere down to (and through) the earth and
back to the atmosphere again.

**influent.** Water or other liquid‑raw or partially flowing INTO a
reservoir, basin, treatment process or treatment plant.

**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.

**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.

**legionella.** A genus of bacteria, some species of which have caused a
type of pneumonia called Legionnaires Disease.

**linearity.** How closely an instrument measures actual values of a
variable through its effective range; a measure used to determine the
accuracy of an instrument.

**microbial growth.** The activity and growth of microorganisms such as
bacteria, algae, diatoms, plankton and fungi 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.** A unit of length. One millionth of a meter or one thousandth
of a millimeter. One micron equals 0.00004 of an inch.

**microorganisms.** Living organisms that can be seen individually only
with the aid of a microscope.

**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).

**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.

**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

**nephelometric.** 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.

**nephelometric turbidity unit (NTU).** The unit of measure for
turbidity.

**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.

**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.

**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.

**organic.** Substances that come from animal or plant sources. Organic
substances always contain carbon. (Inorganic materials are chemical
substances of mineral origin.)

**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). 2) Any form of animal or plant life.

**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.
Overflow Rate (GDP/sq ft) = Flow (GPD)/Surface Area (sq ft) 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.** 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.

**pathogenic organisms.** 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.

**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.

**pH.** 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
(1/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.

**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.

**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.

**pore.** A very small open space in a rock or granular material.

**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.

**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 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.\'

**range.** The spread from minimum to maximum values that an instrument
is designed to measure. Also see span and effective range.

**recarbonation.** 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.

**reservoir.** Any natural or artificial holding area used to store;
regulate, or control water.

**reverse osmosis.** 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.

**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.

**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.

**sedimentation.** A water treatment process in which solid particles
settle out of the water being treated in a large clarifier or
sedimentation basin.

**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.

**standard.** A physical or chemical quantity whose value is known
exactly, and is used to calibrate or standardize instruments.

**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.

**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.

**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.

**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.** Abbreviation for surface‑active agent. The active agent
in detergents that possesses a high cleaning ability.

**suspended solids.** 1)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.

**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).

**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.

**turbid.** Having a cloudy or muddy appearance.

**turbidimeter.** A device that measures the amount of suspended solids
in a liquid.

**turbidity.** 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.

**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.

**virus.** The smallest form of microorganisms capable of causing
disease. Especially, a virus of fecal origin that is infectious to
humans by waterborne transmission.

**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 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.

**zeta 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.

## 

## A.2 References

Calabrese, E.J., C.E. Gilbert, and H. Pastides, editors. 1988*. Safe
Drinking Water Act Amendments, Regulations and Standards*. Lewis
Publishers. Chelsea, MI.

California State University. 1988. *Water Treatment Plant Operation*.
School of Engineering, Applied Research and Design Center, Sacramento,
CA.

Dzurik, A.A., Rowman, and Littlefield. 1990. *Water Resources Planning*.
Savage, MD.

USEPA. 1991a. *Code of Federal Regulations*, Title 40, Chapter I,
Section 141.2. July 1.

USEPA. 1991b. "National Primary Drinking Water Regulations; Lead and
Copper Rule; Final Rule." 56 *FR* 26547, June 7, 1991. 56 *FR* 3578,
January 30 (Phase 11)

von Huben, H. 1991. Surface Water Treatment: The New Rules. AWWA.

THIS PAGE INTENTIONALLY LEFT BLANK