coefficient is unity for any material whose grains are all the same size, and it increases
above unity with variation in the size of the grains.
Coliform Organisms. A group of bacteria, predominantly inhabitants of the intestine of
humans, but also found on vegetation, including all aerobic and facultative anaerobic
bacilli, that ferment lactose to produce a gas as one of the byproducts.
Colloids. Finely divided solids which will not settle, but may be removed by coagulation
or biochemical action.
Color, Apparent. Pigmentation due to the presence of suspended solids in a water
Color, True. Pigmentation due to the presence of finely divided particles or droplets
either dispersed, or in solution, in a water supply.
Community Water System. A public water system which serves at least 15 service
connections used by year-round residents or regularly serves at least 25 year-round
Compound. A substance containing molecules or two or more different elements which
have entered into chemical combination with each other to form another substance
unlike any of the constituent elements.
Concentration. A measure of the amount of dissolved substances contained per unit
volume of solution. May be expressed as grains per gallon, pounds per million gallons,
milligrams per liter.
Contaminant. As referred to in the Safe Drinking Water Act, means any physical
Contamination. A general term signifying the introduction into water of microorganisms,
chemicals, wastes, or sewage, which renders the water unfit for its intended use.
Usually considered to imply the presence, or possible presence, of disease-producing
Corrosion. The destruction of a substance; usually a metal, or its properties because
of a reaction with its (environment) surroundings.
Crenothrix. A genus of bacteria characterized by unbranched, attached filaments
having a gelatinous sheath in which iron is deposited. They precipitate metallic oxide
deposits in pipes, etc., which sometimes color the water. Also, after death, they cause
disagreeable taste and odors in water.