Glossary of Terms


The physical process occurring when liquids, gases, or suspended matter adhere to the surfaces of, or in the pores of, an absorbent material. Absorption occurs without chemical reaction.

activated carbon

Absorptive particles or granules of carbon that have a high capacity to selectively remove certain trace and soluble materials from water. The carbon is usually obtained by heating wood, bone or vegetable material to create charcoal.


Qualities that are attractive to the senses (e.g., the pleasing appearance, taste, and smell of potable water).



average daily consumption

The total demand for water during a period of time divided by the number of days in that time period. Also called the average daily demand.

AWWA – American Water Works Association

The American Water Works Association is an international, nonprofit, scientific and educational society dedicated to providing total water solutions assuring the effective management of water. Founded in 1881, the Association is the largest organization of water supply professionals in the world, with 50,000 members representing the full spectrum of the water community: public water and wastewater systems, environmental advocates, scientists, academicians, and others who hold a genuine interest in water.


Microscopic living organisms that usually consist of a single cell. Most bacteria use organic matter for their food and produce waste products as a result of their life processes.


Related to the study of bacteria.




Compounds formed by the reaction of hypochlorous acid (HClO or aqueous chlorine) and ammonia.




A metering device that is used to add chlorine to water.


Any process or combination of processes of which the main purpose is to reduce the concentration of suspended matter in a liquid.




A group of bacteria found in humans, plants, soil, air, and water. Fecal coliforms are a specific class of bacteria that only inhabit the intestines of warm-blooded animals. The presence of coliform bacteria is an indication that the water is polluted and may contain pathogenic (disease-causing) organisms.


The introduction into water of micro-organisms, chemicals, toxic substances, wastes, or wastewater in a concentration that makes the water unfit for its  intended use.

conventional filtration

centralized water treatment system, also known as conventional treatment, is a combined process of coagulation, flocculation, sedimentation (or clarification), filtration, and disinfection. It treats water in a central location and then distributes the treated water via dedicated distribution networks.

corporation stop

A type of shut off valve that is located at a street water main, is buried and non- accessible.


The gradual decomposition or destruction of a material due to chemical action, often an electrochemical reaction. Corrosion starts at the surface of a material and moves inward.


A connection between a drinking (potable) water system and an unapproved water supply that may lead to contamination of the water supply. For example, if you have a pump moving non-potable water and you use the drinking water system to supply water for the pump seal, a cross-connection or mixing between the two water systems can occur.



direct filtration

A method of treating water that 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.



distribution system

The equipment involved with the delivery of treated water from the treatment facility to the intended end-point user.

Escherichia coli

E. coli is the predominant coliform in feces and the only member of the coliform group exclusively associated with feces. Therefore, it is the most specific indicator of fecal pollution and the possible presence of pathogenic microorganisms.

filter media

Materials, such as sand or activated carbon, that purify water as it passes through the filter.

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.

fire flow

water for fire protection


Clumps of bacteria and particulate impurities that have come together and formed a cluster. Found in flocculation tanks and settling or sedimentation basins.



flush water main

A maintenance procedure whereby water is flushed down a pipe at high flow rate to discharge debris and contaminants.

free chlorine

Chlorine (Cl2) in a liquid or gaseous form. Free chlorine combines with water to form hypochlorous (HOCl) and hydrochloric (HCl) acids. Wastewater-free chlorine usually combines with an amine (ammonia or nitrogen) or other organic compounds to form combined chlorine compounds.

free chlorine residual



Ground Water that is at Risk of containing Pathogens

gate valve

A type of valve that uses a flow control element shaped like a sliding gate to block flow, often used as isolation valves.


A waterborne intestinal parasite that causes a disease called giardiasis (GEE-are-DIE-uh-sis) in infected humans. Symptoms of the disease include diarrhea, cramps, and weight loss. Giardia contamination is found in most surface waters and some ground waters.

ground water

The supply of fresh water found beneath the Earth's surface (usually in aquifers) that is often used for supplying wells and is a source of springs.


Ground Water Under the Direct Influence of surface water

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 objectionable tastes in drinking water.


An observed biological (e.g., pathogens), chemical (e.g., dissolved metals, nutrients) or physical agent (e.g., turbidity, debris) that could harm your water users or water system.

indicator bacteria

Bacteria in a water sample which indicates that fecal contamination is present.



isolation valves

A valve designed for isolation purposes when equipment needs to be worked on.




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 Units: a measure of clarity of water.

pathogenic organisms

Organisms, including bacteria, viruses, or cysts, capable of causing diseases (giardiasis, cryptosporidiosis, typhoid, cholera, dysentery) in a host (such as a person). There are many types of organisms that do NOT cause disease. These organisms are called non-pathogenic.

peak demand

The maximum momentary load placed on a water treatment plant, pumping station, or distribution system. This demand is usually the maximum average load in one hour or less but may be specified as the instantaneous load or the load during some other short time period.

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.

potable water

Water that does not contain objectionable pollution, contamination, minerals, or infective agents and is considered satisfactory for drinking.


Parts per million. The number of weight or volume units of a minor constituent present with each one million units of the major constituent of a solution or mixture. Used to express the results of most water and wastewater analyses, but presently milligrams per litre (mg/L) is the preferred term.


A force acting on a given area. The pressure is calculated by dividing the force by the area over which it is acting. The unit of pressure is the Pascal (metric system) or pound per square inch (psi).

pressure gauge

Instrument used to measure pressure.

pressure tank

A tank used in water systems to maintain pressure and provide storage.


Single-celled organisms with a more complex physiology than viruses and bacteria; average diameter of 1/100 mm.


Pound per Square Inch: An imperial unit of pressure. 1 psi = 1 pound per square inch.


A supplier or provider of water.

raw water

Water in its natural state, prior to any treatment. Usually the water entering the first treatment process of a water treatment plant.


A pond, lake, basin, or other structure (natural or artificial) that stores, regulates, or controls water.

residual chlorine

The amount of free and/or available chlorine remaining after a given contact time under specified conditions.


Risk, for the purposes of source assessments, is a factor generally defined as the probability (likelihood) that harm, injury or loss will occur to people or infrastructure, multiplied by the magnitude (consequence) of those hazards occuring


Solid material that settles to the bottom of a liquid.

small water systems

Water systems serving fewer than 500 people in a 24-hour period, as defined by the Government of BC

solenoid valve

A valve that uses the electromagnetic principle to cause mechanical movement to control flow. In this way, the valve can be operated remotely by an electrical signal.


A liquid containing a dissolved substance. The dissolved substance is called the solute. The liquid used to dissolve the solute is called the solvent.

source assessment

Source water assessments (SWAs) provide information about sources of drinking water used by public water systems.  SWAs are studies or reports developed by states to help local governments, water utilities, and others protect sources of drinking water. 

source protection

source water

Source water is the raw, untreated ground water and surface water that supplies your water intake or well.

surface water

All water naturally open to the atmosphere (rivers, lakes, reservoirs, streams, impoundments, seas, estuaries, etc.); also refers to springs, wells, or other collectors that are directly influenced by surface water.

swab or scour

A maintenance procedure where pipes are cleaned by physically scrubbing the inner surface of the piping.


Total Organic Carbon. TOC measures the amount of organic carbon in water.



turnover rate

The time between when water enters and leaves a storage structure such as a reservoir.


A membrane filter process used for the removal of some organic compounds in an aqueous (watery) solution.  Removes particles with pore sizes which range from 10-2 to 10-6 millimeters.


ultraviolet (UV)

In water treatment, a specific wavelength of light produced by a device used for disinfection.


A device which is used to control isolate or flow in a piping system.


A very simple life form that only multiplies inside the living cells of a host; average diameter of 1/10,000 mm.


Large distribution pipes that run along road major roadways.





A wall or obstruction used to control flow (from settling tanks and clarifiers) to ensure a uniform flow rate and to avoid short-circuiting.

well log

Records kept during well drilling that record the type of soil encountered, at what depths, and some characteristics of the aquifer.