G

G

GA Salt

A very coarse grainy salt of "Ground Alum" size, which was formerly used for regenerating zeolite water softeners, sometimes used coincidentally with alum as a coagulant.

Gallionella Ferruginea

One of several types of bacteria that use iron in their metabolism and are capable of depositing gelatinous ferric hydroxide.

Gallon

The common U.S. unit of measurement of liquid volume. (The international unit of volume measurement is the liter.)     One U.S. gallon has a volume of 231 cubic inches or 3.785 liters. The Imperial (British) gallon equals 277.418 cubic inches or 4.546 liters.

Galvanic Cell

A cell, consisting of dissimilar metals in contact with each other and with an electrolyte, which generates an electrical current.

Galvanic Corrosion

A form of corrosion which occurs in a galvanic cell in which one of the metals dissolves and goes into solution.     This form of corrosion is accelerated by high concentrations of dissolved minerals in water that increase electrical conductivity.     Galvanic corrosion may occur if two pipes of dissimilar metals are joined directly--without the use of a pipe fitting designed to insulate different metals from one another and prevent such corrosion of the pipes.

Galvanic Series

A list of metals and alloys presented in the order of their tendency to corrode (or go into solution).     Also called the electromotive series.     This is a practical application of the theoretical electrochemical series.

Galvanize

To coat a metal (especially iron or steel) with zinc.     Galvanization is the process of coating a metal with zinc.

Gamma decay

A type of radiation, gamma radiation, where gamma rays are emitted and that usually accompanies alpha or beta decay.  Gamma rays are photons, and are without rest mass or charge.  Alpha or beta decay may simply proceed directly to the ground (lowest energy) state of the daughter nucleus without gamma emission, but the decay may also proceed wholly or partly to higher energy states (excited states) of the daughter.  In the latter case, gamma emission may occur as the excited states transform to lower energy states of the same nucleus may transform to a lower energy state by ejecting an electron from the cloud surrounding the nucleus.  This orbital electron ejection is known as internal conversion and gives rise to an energetic electron and often an x-ray as the atomic cloud fills in the empty orbital of the ejected electron.  SEE ALSO <b>alpha decay; beta-minus decay; beta-plus decay; photon; radioactivity</b>.

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.

Gas Chromatograph (GC)

A chemical analytical instrument used to separate a sample into components during gas chromatography.

Gas Chromatography (GC)

Chromatography in which the sample mixture is vaporized and injected into a stream of carrier gas such as helium or nitrogen (mobile phase) which is moving through a column containing solid medium or medium coated with a relatively nonvolatile liquid (stationary phase).     The mobile phase sample is, thereby, separated into its component compounds according to the unique affinity of each compound for the stationary phase.     The components appear separately at the effluent end of the column where they can be detected and measured by density differences, thermal conductivity changes, or ionization detectors.     The detector gives a signal (in peak form) for each separated component compound; the intensity of the signal is proportional to the quantity of the compound injected, making it possible to provide a quantitative analysis by calibration.

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.

Gate Valve

A type of valve in which the closing element (the gate) is a disc that moves across the stream in a groove or slot for support against pressure.     A gate valve has relatively large full ports and a straight line flow pattern.     A gate valve creates very little pressure drop; this valve is, however, subject to leakage if the sealing surfaces are scored or marred or if debris becomes lodged in the groove.

Gauge Pipe

A number that defines the thickness of the sheet used to make steel pipe.     The larger the number, the thinner the pipe wall.

Gauge Pressure

The pressure within a closed container or pipe as measured with a gauge.     In contrast, absolute pressure is the sum of atmospheric pressure (14.7 lbs/sq in) PLUS pressure within a vessel (as measured by a gauge).     Most pressure gauges read in gauge pressure or psig (pounds per square inch gauge pressure).

Gavage

Type of exposure in which a substance is administered to an animal through a stomach tube.

Gel Resin

A "gellular resin" form of ion exchanger as opposed to macroporous exchangers.     Gel resin is typically cross-linked with eight percent divinylbenzene.

Gel Zeolite

A synthetic sodium alumina silicate cation exchange product that was very widely used in residential water softeners prior to the development of DVB/styrene cation resin.     Also called siliceous gel zeolite.

Geological Log

A detailed description of all underground features discovered during the drilling of a well (depth, thickness, and type of formations).

Geophysical Log

A record of the structure and composition of the earth encountered when drilling a well or similar type of test hole or boring.

Germicidal Ultraviolet

An ultraviolet light that peaks at a 2,537-angstrom wavelength and is in a wavelength that lies between 200 and 300 nanometers.     This is known as the germicidal or short-wave ultraviolet band.

Giardia

A common waterborne protozoan that forms cysts and is resistant to disinfectants such as chlorine and ultraviolet light.     Giardia can be removed by filters that capture all particles of four microns and greater in size.

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.

Glaubers Salt

An anhydrous sodium sulfate (Na2SO4 10H2O) salt compound.

Glauconite

A natural dull-green iron potassium silicate mineral occurring abundantly in greensand.     The approximate formula for glauconite is K15(Fe, Mg, Al)4-6(Si,Al)3O20(OH)4.

Globe Valve

A type of valve in which the closing element is a segment of a sphere or a flat or rounded gasket which is moved into or onto a round port.     The globe valve usually has small ports, an "S" flow pattern and relatively high pressure drop.     Globe valves provide tight dependable seals with minimum maintenance.

Glutaraldehyde

[OCH(CH<sub>2</sub>)<sub>3</sub>CHO] A general disinfectant for drinking water treatment equipment, including reverse osmosis membranes.  Available as sporicidin and cidex, for example; requires full strength use for disinfection.    A general disinfectant for drinking water treatment equipment, including reverse osmosis membranes. Available as sporicidin and cidex, for example; requires full strength use for disinfection.

Glycerin

A trihydroxy alcohol with sweet tast and syrup-like consistency; the "gylcerine" spelling has come into general use, but it is chemically incorrect.

Gooseneck

A portion of a service connection between the distribution system water main and a meter.     Sometimes called a pigtail.

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.

Grade

The elevation of the invert of the bottom of a pipeline, canal, culvert, or similar conduit.   The inclination or slope of a pipeline, conduit, stream channel, or natural ground surface usually expressed in terms of the ratio or percentage of number of units of vertical rise or fall per unit of horizontal distance. A 0.5 percent grade would be a drop of one-half foot per hundred feet of pipe.

Grain

A unit of weight equal to 0.0648 grams or 0.000143 pounds or 1/7000th of a pound.

Grains Per Gallon (gpg)

A common method of reporting water analysis results in the United States and Canada.     One grain per gallon equals 17.1 parts per million (ppm) or 17.1 milligrams per liter. Grains per Imperial gallon equals 14.3 mg/L (or ppm).

Gram

The basic unit of weight measurement in the metric system.     One gram equals 0.0022 pounds or 15.432 grains. The gram was originally devised as the weight of one cubic centimeter or one milliliter of water at 4 degrees Centigrade.

Gram-milliequivalent

The equivalent weight (in grams) divided by 1,000.

GRAS

Designation for materials listed by the U.S. Food and Drug Administration (FDA) as "generally regarded as safe."

Gravel Support Bed

Various layers of different sized gravel and coarse sand placed above the underdrain network to support filter or ion exchange media beds.     The gravel support bed contributes greatly to the distribution and collection of product water and the even dispersal of the backwash water flow.

Gravimetric

A means of measuring unknown concentrations of water quality indicators in a sample by weighing a precipitate or residue of the sample.

Gravimetric Measurement

Measurement on the basis of weight.

Gray (Gy)

The SI unit of absorbed dose of ionizing radiation.     One gray (Gy) equals 100 rads.

Greensand

A naturally-occurring mineral that consists largely of dark greenish grains of glauconite and which possesses ion exchange properties.     Greensand was the original product used in commercial and home cation exchange water softening units and was the base product for manufacturing manganese greensand zeolite products.

Grey Water

Waste water other than sewage, such as sink drainage or washing machine discharge.

Gross Alpha Particle Activity

The total radioactivity due to beta particle emission as inferred from measurements on a dry sample.

Gross Beta Particle Activity

The total radioactivity due to beta particle emission as inferred from measurements on a dry sample.

Groundwater

Water found beneath the surface of the ground.     Groundwater is primarily water which has seeped down from the surface by migrating through the interstitial spaces in soils and geologic formations.

Grouting

Cement-like fluid which is poured or injected into the bore hole during well drilling to seal crevices and to prevent contamination or loss of drilling mud.     Grouting provides protection around the metal well casing and helps prevent corrosion and infiltration into the well bore hole from surface water and shallow groundwater.     Grouting can sometimes improve the strength and elasticity of the rock formation itself.

Gulmite Screw

The screw which holds the swivel part of a yoke connector for a portable exchange tank in place.

Gypsum

(CaSO<sub>4</sub>   2H<sub>2</sub>O) A moderately insoluable calcium sulfate, containing 20.9 percent water, which is often used as a soil amendment to aid in building soil structure and permeability.     A moderately insoluble calcium sulfate, containing 20.9 percent water, which is often used as a soil amendment to aid in building soil structure and permeability.

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Updated on Mon, 22 Jun 2020 by Jonathan

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