This glossary is intended to serve as a general water supply systems usage guide. As
such, it contains some terms not used in the body of this document; however, these
terms are important for water treatment plant operators to know.
Absorption. The process of taking in or soaking up liquids; not to be confused with
Acid. A compound, usually having a sour taste, which is able to neutralize an alkali or
base; a substance that dissolves in water with a formation of hydrogen ions.
Acidity. A quantitative measurement of the total acid constituents of a water, both in
the ionized and unionized states expressed as pH.
Acre-Foot. A measurement used for reservoirs of water storage that is equivalent to
one acre (43,560 square feet) one foot deep, or 43,560 cubic feet or 325,830 gallons.
Adsorption. The adherence of dissolved, colloidal, and finely divided matter on the
surfaces of solid bodies with which they are brought in contact, not to be confused with
Aeration. The bringing about of intimate contact between air and a liquid by one of the
following methods: spraying the liquid in the air; bubbling air through the liquid; or by
agitation of the liquid to promote surface absorption of air.
Aerobic. Requiring the presence of free oxygen.
Agglomeration. The gathering together of dispersed suspended matter into larger flocs
of particles which settle rapidly.
Air Binding. The condition whereby entrained air clogs or otherwise interferes with
proper operation of a sand filter, pump, or pipe.
Algae. Tiny plant life, usually microscopic, existing in water. They are mostly green,
blue-green, or yellow-green, and are the cause of most tastes and odors in water.
Alkalinity. A term used to represent the content of carbonates, bicarbonates,
hydroxides, and occasionally borates, silicates, and phosphates in water.
Anaerobic. Requiring the absence of free oxygen.
Anion. A negatively charged ion in an electrolyte solution, attracted to the anode under
the influence of electric potential.
Appurtenances. Structures, devices and appliances, other than pipe and conduit,
which are used in connection with a water distribution system, for example, valves,
hydrants, corporation cocks, services, etc.