Technical Resources

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Symbols and Acronyms

gas chromatography   A method of separating a mixture of compounds into its constituents so they can be identified. The sample is vaporized into a gas-filled column, fractionated by being swept over a solid adsorbent, selectively eluted, and identified.

gas chromatography-mass spectrometry (GC-MS)  An analytical technique involving the use of both gas chromatography and mass spectrometry, the former to separate a complex mixture into its components and the latter to deduce the atomic and molecular weights of those components. It is particularly useful in identifying organic compounds.

gas dome  In sludge digestion tanks, usually a steel cover floating entirely or in part on the liquid sludge.

gasification  The transformation of soluble and suspended organic materials into gas during waste ­decomposition.

gas production  The creation of a gas by chemical or biological means.

gate valve  A valve in which the closing element consists of a disk that slides over the opening or cross-sectional area through which water passes.

gauge  (1) A device for indicating the magnitude or position of an element in specific units when such magnitude or position is subject to change; examples of such elements are the elevation of a water surface, the velocity of flowing water, the pressure of water, the amount or intensity of precipitation, and the depth of snowfall. (2) The act or operation of registering or measuring the magnitude or position of a thing when these characteristics are subject to change. (3) The operation of determining the discharge in a waterway by using both discharge measurements and a record of stage.

globe valve  A valve having a round, ball-like shell and horizontal disk.

gpcd  The rate of water, wastewater, or other flow measured in U.S. gallons (liters) per capita of served population per day.

gpd  The rate of water, wastewater, or other flow measured in U.S. gallons (liters) per day.

gpm  The rate of water, wastewater, or other flow measured in U.S. gallons (liters) per minute.

grab sample  A sample taken at a given place and time. It may be representative of the flow. See also composite sample.

gradient  The rate of change of any characteristic per unit of length or slope. The term is usually applied to such things as elevation, velocity, or pressure. See slope.

grease and oil  In wastewater, a group of substances including fats, waxes, free fatty acids, calcium and magnesium soaps, mineral oils, and certain other nonfatty materials; water-insoluble organic compounds of plant and animal origins or industrial wastes that can be removed by natural flotation skimming.

grease skimmer  A device for removing floating grease or scum from the surface of wastewater in a tank.

grit  The heavy suspended mineral matter present in water or wastewater, such as sand, gravel, or cinders. It is removed in a pretreatment unit called a grit chamber to avoid abrasion and wearing of subsequent treatment devices.

grit chamber  A detention chamber or an enlargement of a sewer designed to reduce the velocity of flow of the liquid to permit the separation of mineral (grit) from organic solids by differential sedimentation.

grit collector  A device placed in a grit chamber to convey deposited grit to a point of collection.

grit separator  Any process or device designed to separate grit from a water or wastewater stream.

grit washer  A device for washing organic matter out of grit.

ground  A conducting connection, whether intentional or accidental, between an electrical circuit or equipment and earth, or to some conducting body that serves in place of earth.

  Connected to earth or to some conducting body that serves in place of the earth.