dependent on the degree of agitation and the size of particles. A colloid is a special
kind of suspension.
Temperature. (1) The thermal state of a substance with respect to its ability to
communicate heat to its environment. (2) The measure of the thermal state on the
arbitrarily chosen numerical scale, usually Centigrade or Fahrenheit.
Threshold Odor. The point at which, after successive dilutions with odorless water, the
odor of the water sample can just be detected. The threshold odor is expressed
quantitatively by the number of times the sample is diluted with equal quantities of
Threshold Treatment. The prevention of the deposition of calcium carbonate in water
after the softening treatment by the addition of a small quantity of sodium
Total Trihalomethanes (TTHM). The sum of the concentration in milligrams per liter of
the trihalomethane compounds (trichloromethane (chloroform)),
dibromochloromethane, bromodichloromethane, and tribromomethane (bromoform)),
rounded to two significant figures.
Transpiration. The process by which plants dissipate water into the atmosphere
through their leaves and other surfaces.
Treated Water. Water that has underground processing such as sedimentation,
filtration, softening, disinfection, etc., and is ready for consumption. Included is
purchased potable water which is retreated (chlorinated, fluoridated, etc.).
Tributary. A stream or other body of water, surface, or underground, which contributes
its water, even though intermittently and in small quantities, to another and larger
stream or body of water.
Trihalomethanes (THM). One of the family of organic compounds, named as
derivatives of methane, wherein three of the four hydrogen atoms in methane are each
substituted by a halogen atom in the molecular structure. Technically, THM belong to
the group of chemicals classified as volatile synthetic organic chemical (VOC)
compounds. The EPA, however, has addressed THMs and VOCs separately.
Tuberculation. Localized corrosion at scattered locations resulting in knoblike mounds.
Turbidity. (1) A condition in water caused by the presence of suspended matter,
resulting in the scattering and absorption of light rays. (2) A measure of fine
suspended matter in liquids. (3) An analytical quantity usually reported in arbitrary
turbidity units determined by measurements of light diffraction.