Glossary of Terms

Glossary of Terms - T


See Cross Flow Filtration.
See Tannin.
Any of a group of water soluble, natural organic phenolic compounds that are produced by metabolism in trees andplants, and are part of the degredation-resistant fulvic acid materials formed during the decomposition of vegetation.



See Also: Chelation Chelating Agent Organic Iron Trihalomethanes (THMs) Humic Acid Humic Substances Humin Fulvic Acid Chelation Chelating Agent Organic Iron Trihalomethanes (THMs) Humic Acid Humin Fulvic Acid Iron (Fe) Heme Dissolved Organic Carbon Total Organic Carbon (TOC) Crenothrix Polyspora Gallionella Ferruginea Organic Iron Iron (Fe) Heme

The minimum concentration of a chemical or biological substance which can just be tasted.
The abbreviation for "total dissolved solids".
The appearance of salt in RO product water which sometimes occurs as a result of the reduction of differential pressure across the membrane as can occur when the RO unit has been shut down for a period of time.

Water flow will cease to permeate through the membrane when there is insufficient differential water pressure across the membrane.

However TDS permeates through the membrane as a function of the TDS concentration difference across the membrane.

Trade name for a high temperature industrial plastic material used in cookware finishes, bearings, lubricating, plumbing sealants, and a practically inert coating on metal and glass surfaces.

Also called a heat sensor.

1. Electric potential or voltage. The term usually is used to mean high voltage, as in "high tension transformer" or "high tension lines."

2. Stretched to stiffness or tautness.

The introduction of nonhereditary congential malformations (birth defects) in a developing fetus by exogenous factors acting in the womb; interference with normal embryonic development.
The third stage of treatment that brings water to a high degree of refinement or conditioning following the reduction of substances in the primary and secondary stages of treatment.
Thin-film Composite.
Total Hardness.
The ability of a substance to conduct heat. Mathematically, the ratio of the rate of heat flow to the rate of temperature change in the particular substance.
A unit in an ozonation system that employs high temperature to destroy excess ozone.

See Also: Hydraulic Classification Stratification

The layer in a lake which divides the warm upper current-mixed zone (epilimnion) from the colder lower deep-water stagnant zone (hypolimnion).

During the warm summertime, the thermocline is the middle layer of the lake. Lying between the two layers, the thermocline loses heat rapidly.

Also called the metalimnion.

See Also: Turnover Hypolimnion Turnover Epilimnion

Materials such as certain synthetic resins and plastics that soften or fuse when heated and harden and become rigid when cooled, and that can usually be remelted and cooled time after time with no appreciable chemical change.
Certain plastics and synthetic resins that once solidified will not resoften or fuse when heated. Thermoset materials may decompose at high temperature, but will not soften or melt.
A class of reverse osmosis membranes made with polyamide-based polymer and fabricated with different materials in the separation and support layers.

See Also: Charged Polysulfone Membrane Polysulfone Reverse Osmosis

A genus of bacteria that obtain their energy from oxidation of sulfides, thiosulfates, or sulfur, forming sulfur, persulfates, sulfuric acid, and sulfates.

See Also: Desulfovibrio Sulfur (S) Crenothrix Polyspora Cyclospora Cyanobacteria-like Bodies (CLBs) Gallionella Ferruginea Organic Iron Organism Desulfovibrio

See Precursor.
See Trihalomethanes.
A very low concentration of a substance in water, the term is sometimes used to indicate the concentration which can just be detected.

Also called odor threshold.

See Trace Substance.
A mass of concrete of similar material appropriately placed around a pipe to prevent movement when the pipe is carrying water. Usually placed at bends and valve structures.
Plowing, seedbed preparation, and cultivation practices.
The time required for processes and control system to respond to a signal or to reach a desired level.
A group of similar cells.


An analytical process in which a standard solution in a calibrated vessel is added to a measure volume of sample until an endpoint, such as a color change, is reached. From the volume of the sample and the volume of standard solution used, the concentration of a specific material may be calculated.
See Transient Water System.
Total Organic Carbon.
The total number of bacterial colonies exceeds 200 on a 47mm diameter membrane filter used for coliform detection.
The arrangement of hills and valleys in a geographic area.
Water flow through channels which are constricted and marked by repeated twists, bends and winding turns. In an electrodialysis system, water flow in which spacers, turbulence promoters or cross traps are used to produce turbulence in the flow stream.
See Rated Capacity.
The total amount of chlorine residual present in a water sample, without regard to type.

See Also: Residual Chlorine Residual Chlorine Total Chlorine Total Residual Chlorine

When a pump is lifting or pumping water, the vertical distance (in feet) from the elevation of the energy grade line on the suction side of the pump to the elevation of the energy grade line on the discharge side of the pump.
The sum of all suspended and dissolved matter in a water sample.
The sum of all nitrogen forms.
The total amount of ozone gas which must be mixed with a liquid (water), solid, or gas in order to satisfy all the ozone oxidation requirements.
The sum of all phosphorus forms.

See Also: Residual Chlorine Total Chlorine Total Chlorine Residual

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.
A device that tallies and indicates the total quantity of flow through a measuring device.

Also called an integrator.

Having an adverse physiological effect on man.
Chemical elements and compounds, such as lead, radon, benzene, dioxin, and numerous others, that have toxic properties by either ingestion, inhalation, or absorption into the human body.

There is considerable variation in the degree of toxicity among the various toxic substances and in the exposure level that induces toxicity.

A harmful substance or agent that may injure an exposed organism.
The quality of being toxic.
Characterization of the toxicological properties and effects of a chemical, including all aspects of its absorption, metabolism, excretion, and mechanism of action, with special emphasis on establishment of dose-response characteristics.
The science and study of poisons control.
An element essential to plant and/or animal nutrition in trace concentration of one percent or less.

For example, iron, manganese, zinc, copper, potassium, sodium, etc. Such elements are also called micronutrients.

Acquisition by a cell of the property of uncontrolled growth.
A noncommunity water system that does not serve 25 of the same nonresident persons per day for more than six months per year. Also called a transient noncommunity water system (TNCWS).
The percentage of light wave length at 2537 angstrom units transmitted through water.
The ability of an aquifer to transmit water
The ability of water to trasmit or convey ultraviolet energy
The ability of water to transmit or convey ultraviolet energy.
The process by which water vapor is released to the atmosphere by living plants.
A device used to place concrete or grout under water.
A toxic volatile organic compound often used as a solvent.
A stage in a demand initiated regeneration (DIR) water softener or valve control cycle when the unit is ready for regeneration.
A group of organic chemicals, suspected of being carcinogenic, which are formed in water when chlorine being used as a disinfectant reacts with natural organic matter such as humic acids from decayed vegetation.

Humic acids are present in all natural water used as sources of drinking water supplies.

Chloroform is one of the most common THMs formed in this type of reaction.

See Also: Chelation Chelating Agent Organic Iron Humic Acid Humic Substances Humin Fulvic Acid Tannin Chelation Chelating Agent Organic Iron Humic Acid Humin Fulvic Acid Tannin

Having a valence of three.
The ability of a lake to support plant growth as measured by phosphorus content, algae abundance, and depth of light penetration.
Total solids
Total suspended solids


A protective crust of corrosion products (rust) which builds up over a pit caused by the loss of metal due to corrosion.
The process in which blister-like growths of metal oxides develop in pipes as a result of the corrosion of the pipe metal. Iron oxide tubercules often develop over pits in iron or steel pipe and can seriously restrict the flow of water.
Fraction of animals having a tumor of a certain type.
Having a cloudy or muddy appearance.
A device that measures the amount of light scattered by suspended solids in a liquid.
A type of flow characterized by crosscurrents and eddys as opposed to laminar flow. Turbulence may be caused by curves, bends, changes in channel size, obstructions, or excessive flow rates and will significantly increase pressure drop.
Devices which are inserted into the feedwater channel or the product water channel to increase the turbulence and improve the mixing characteristics of the fluid flow.

Typical turbulence promoters include baffles, spiral wires, balls, spacers, and static kinetic-type mixers.

See Turbulence.
The mixing of the lower and upper layers of a lake, generally occurring in the spring and the fall, caused by temperature change and density equalization.

Also called overturn.

See Also: Hypolimnion Thermocline Epilimnion Thermocline Hypolimnion Epilimnion

A pairing of cation and anion exchange tanks and typically operating in series. It is best used for the deionization of relatively high volumes of water and is capable of producing product water with resistivity of up to one megohm-centimeter.
A strong base polystyrene/divinylbenzene anion exchange resin in which the exchange site is a trimethylamine [-N(CH3)3].

Type 1 resins are inherently more stable both chemically and thermally than type 2 resins, especially in the hydroxide form. They, therefore, typically have a longer life potential and can be regenerated at higher temperatures (e.g., for low silica effluents).

However, type 1 resins have a lower affinity for hydroxide ion relative to other anions than does type 2 resin. It typically has lower operating capacity, lower regeneration efficiency, and lower organic fouling resistance than type 2 resin.

Type 1 resins sometimes emit a very fishy odor.

See Also: Type 2 Resin Slope Bead (Resin Bead) Type 2 Resin

A strong base polystyrene/divinylbenzene anion exchange resin in which the exchange site is a dimethylethanol amine [-N(CH3)2(CH2-CH2OH)], i.e., an alcohol takes the place of one of the methyl groups on the type 1 resin.

The alcohol can sometimes be cleaved off the amine group during operations leaving a weak base exchange site on the type 2 resin and imparting a characteristic alcohol-like odor.

Resins also typically require longer rinse times as they lose strong base capacity. The type 2 resin is not as stable as its type 1 counterpart, but because of its higher affinity for the hydroxide ion relative to other anions, it has a higher operating capacity, a higher regeneration efficiency, and is much more resistant to organic fouling.

See Also: Type 1 Resin Bead (Resin Bead) Type 1 Resin