Glossary of Terms

Glossary of Terms - U

A :B :C :D :E :F :G :H :I :J :K :L :M :N :O :P :Q :R :S :T :U :V :W :X :Y :Z :


The process of removing colloidal and dispersed particles from a liquid by passing the liquid through a membrane under high pressure. Separation or removal of particulates of more than 10A and less than 200 angstroms.
Highly-treated water that is deionized and mineral-free with high resistivity and no organics; it is usually used in the semiconductor and pharmaceutical industries.

Ultrapure water is NOT considered biologically pure (potable) or sterile.

There is no set numerical standard to determine exactly what "ultrapure" water is or should be.

Pertaining to ultraviolet light.
Radiation (light) having a wavelength shorter than 3900 angstroms, the wavelengths of visible light, and longer than 100 angstroms, the wavelengths of x-rays.

This wavelength puts ultraviolet light at the invisible violet end of the light spectrum.

Ultraviolet light is used as a disinfectant.

Substances which absorb ultraviolet radiation (light). Ultraviolet absorbers are added to plastic (such as used in plastic tanks and fittings) and rubber products to make them less likely to decay as the result of absorbing ultraviolet rays.
The area where the water is irradiated with ultraviolet rays.
The amount of ultraviolet rays required to inactivate certain microorganisms.
The amount of disinfectant ultraviolet rays delivered to the organisms in the water being disinfected. Dosage is a combination of UV intensity times the contact time and is measured in watt-seconds per square centimeter.
Light waves shorter than visible blue-violet waves of the spectrum having wave lengths of less than 3,900 D Angstroms.
Light rays beyond the violet of the spectrum invisible to humans.
A term used by public and municipal water systems to describe the difference between the amount of finished water produced and the amount registered on meters as sold.

Unaccounted-for water may range from 10 percent-35 percent of finished water produced by the utility and usually includes water lost from leaky water mains, water lost in firefighting or from fire hydrants, or other public or municipal uses.

A number (equal to or greater than one) used to divide the NOAEL or LOAEL value derived from measurements in animals or small groups of humans, in order to estimate a NOAEL value for the whole human population.
An aquifer containing water that is not under pressure; the water level in a well is the same as the water table outside the well.
A layer of gravel or grout used to fill the bottom curved base of a larger filter or softener tank, usually in a system with a header-lateral design.

Underbed is not necessarily the same as the media support bed.

A drain that carries away groundwater or the drainage from prepared beds to which water or wastewater has been applied.
A flow in which the velocities are the same in both magnitude and direction from point to point along the conduit.
The particle size distribution screen sizing for exchanger and filtration media as established by U.S. Mesh Standards.
The degree of variation in the size of the grains that constitute a granular material; the ratio of (a) the diameter of a grain of a size that is barely too large to pass through a sieve that allows 60% of the material (by weight) to pass through, to (b) the diameter of a grain of a size that is barely too large to pass through a sieve that allows 10% of the material (by weight) to pass through. The coefficient is unity for any material having grains all the same size, and it increases above unity with variation in size of grain.
Estimate of the lifetime risk caused by each unit of exposure in the low exposure region.
The hydrograph of one inch of storm runoff generated by a rainstorm of fairly uniform intensity within a specific period of time.
The official publication for drug product standards including six water quality standards for pharmaceutical uses. The USP was established by the U.S. Congress in 1884 to control makeup of drugs.

See Also: WFI Hydraulic Grade Line Energy Grade Line (EGL) WFI Slope Club Soda Community Water System Zone of Saturation Bottled Artesian Water Bottled Distilled Water Bottled Fluoridated Water Bottled Mineral Water Bottled Natural Water Lime Soap Bottled Spring Water Brackish Water Brine Internal Water Treatment Ion Exchange Aesthetic Contaminants Health Contaminant Drainage Basin Drinking Water Drinking Water Standards Municipal Water Permutit Process Phosphate Potable (Drinking) Water Etching External Water Treatment Water Softening WFI Sulfur (S) Safe Drinking Water Act (SDWA) Safe Water Sewage Silica Sodium Carbonate Softened Water Soft Water

Having a valence of one. Also called monovalent.
The area between the land surface and water table in which the pore spaces are only partially filled with water. Also called zone of aeration.
See Lime
A term used to indicate the direction (up) in which water or regenerant flows through an ion exchanger or filter media bed during any phase of the operating cycle. Also referred to as counter-current flow.
Is a means of forcing the brine solution upward through the cation exchanger for regenerating the resin. Where the softening flow is downward and the regenerating brine flow is upward, the mode is also called countercurrent flow.

Countercurrent flow means regeneration flows and service flows are in the opposite directions.

A pattern of water flow used in softeners in which the service water flows upward through the ion exchange bed; the media is restricted in movement, usually because of a packed bed. The regeneration brine usually flows downward in such systems.

Upflow softening is normally used to achieve higher operating efficiency.

Estimate not likely to be lower than the true risk.
The piping arrangement inside and at the top of softeners and filters to more uniformly distribute the incoming water over the resin or filter media bed.

In small domestic units, this distributor also distributes the brine for regeneration.

A radioactive metallic element found naturally only in combination with other substances. Uranium 238 (U-238) is the most common form, but about 0.7 percent of natural uranium is present as U-235, which is the important fissionable component in work with atomic energy.

Uranium in natural water exists as anionic complexes UO2(CO3)22- and UO2(CO3)34-.

Stormwater from city streets and adjacent domestic or commercial properties that may carry pollutants of various kinds into the sewer systems and/or receiving waters.
The abbreviation for "United States Environmental Protection Agency".
The product water consumer.
A fee which is collected only from those persons who use a particular service, as opposed to one collected from the public in general.

User fees generally vary in proportion to the degree of use of the service.

United States Pharmacopeia.
See Pharmaceutical Grade Water.
The abbreviation for "United States Public Health Service".
Underground Storage Tanks.