445TDS-TOTAL DISSOLVED SOLIDS: An expression for the combined content of all inorganic and
organic substances contained in a liquid which are present in a molecular, ionized or micro-
granular (colloidal sol) suspended form. Generally, the operational definition is that the solids
(often abbreviated TDS) must be small enough to survive filtration through a sieve size of two
micrometers. Total dissolved solids are normally only discussed for freshwater systems, since
salinity comprises some of the ions constituting the definition of TDS. The principal application of
TDS is in the study of water quality for streams, rivers and lakes, although TDS is generally
considered not as a primary pollutant (e.g. it is not deemed to be associated with health effects),
but it is rather used as an indication of aesthetic characteristics of drinking water and as an
aggregate indicator of presence of a broad array of chemical contaminants. Ion exchange is an
effective treatment process used to remove iron and manganese in a water supply. This process
is ideal as long as the water does not contain a large amount of TDS. When determining the total
dissolved solids, a sample should be filtered before being poured into an evaporating dish and
dried. Demineralization may be necessary in a treatment process if the water has a very high
value Total Dissolved Solids.
TEMPERATURE: The average energy of microscopic motions of particles.
TEMPERATURE SAMPLE: This test should be performed immediately in the field, this is a grab
sample.
THE RATE DECREASES: In general, when the temperature decreases, the chemical reaction
rate decreases also.
THEORY: A model describing the nature of a phenomenon.
THERMAL CONDUCTIVITY: A property of a material to conduct heat (often noted as ).
THERMOCHEMISTRY: The study of absorption/release of heat within a chemical reaction.
THERMODYNAMIC STABILITY: When a system is in its lowest energy state with its environment
(equilibrium).
THERMODYNAMICS: The study of the effects of changing temperature, volume or pressure (or
work, heat, and energy) on a macroscopic scale.
THERMOMETER: Device that measures the average energy of a system.
THICKENING, CONDITIONING AND DEWATERING: Common processes that are utilized to
reduce the volume of sludge.
TIME FOR TURBIDITY BREAKTHROUGH AND MAXIMUM HEADLOSS: Are the two factors
which determine whether or not a change in filter media size should be made.
TITRATION: The process of titrating one solution with another, also called volumetric analysis. A
method of testing by adding a reagent of known strength to a water sample until a specific color
change indicates the completion of the reaction.
TITRIMETRIC: Chemistry. Using or obtained by titration. Titrimetrically, adverb.
TOROID: A surface generated by the revolution of any closed plane curve or contour about an
axis lying in its plane. The solid enclosed by such a surface.
TORR: A unit to measure pressure (1 Torr is equivalent to 133.322 Pa or 1.3158×10−3 atm).
TOTAL ALKALINITY: A measure of the acid-neutralizing capacity of water which indicates its
buffering ability, i.e. measure of its resistance to a change in pH. Generally, the higher the total
alkalinity, the greater the resistance to pH change.
TOTAL COLIFORM: Total coliform, fecal coliform, and E. coli are all indicators of drinking water
quality. The total coliform group is a large collection of different kinds of bacteria. Fecal coliforms
are types of total coliform that mostly exist in feces. E. coli is a sub-group of fecal coliform. When
a water sample is sent to a lab, it is tested for total coliform. If total coliform is present, the sample
will also be tested for either fecal coliform or E. coli, depending on the lab testing method.
TOTAL DISSOLVED SOLIDS (TDS): The accumulated total of all solids that might be dissolved
in water.
TRANSIENT, NON-COMMUNITY WATER SYSTEM: TNCWS A water system which provides
water in a place such as a gas station or campground where people do not remain for long
periods of time. These systems do not have to test or treat their water for contaminants which
pose long-term health risks because fewer than 25 people drink the water over a long period.
They still must test their water for microbes and several chemicals. A Transient Non-community
Water System: Is not required to sample for VOC’s.