Glossary of Terms

Glossary of Terms - N

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A membrane treatment process which falls between reverse osmosis and ultrafiltration on the filtration/separation spectrum.

The nanofiltration process can pass more water at lower pressure operations than reverse osmosis, can remove particles in the 300 to 1,000 molecular weight range such as humic acid and organic color bodies present in water, and can reject selected (typically polyvalent) salts.

Nanofiltration may be used for selective removal of hardness ions in a process known as membrane softening.

One billionth (10-9) of a meter, and equal to one millimicron or 10 angstroms.
The NPDES permit is the regulatory agency document issued by either a federal or state agency which is designed to control all discharges of pollutants from point sources in U.S. waterways.

NPDES permits regulate discharges into navigable waters from all point sources of pollution, including industries, municipal treatment plants, large agricultural feed lots, and return irrigation flows.

The replacement of hardness-causing minerals by sodium and/or potassium as the result of the normal flow of water in the ground.
Carbonated water whose carbon dioxide content is from the same source as the water itself.
Ground, surface, or rain water sufficiently free of calcium and magnesium salts so that no curd will form when soap is used and no calcium- or magnesium-based scale will form when the water is heated.
Pertaining to public water system monitoring at one of the 20 percent of all service connections in the entire system that are nearest the water supply treatment facility, as measured by water transportation time within the distribution system.
Death of cells or tissue.
The electrical charge on an electrode or ion in solution due to the presence of an excess of electrons.
A condition of negative pressure or partial vacuum.
A pressure below that of the surrounding atmospheric pressure at a specific point; a partial vacuum.
Members of the phylum Nematoda, commonly called roundworms.

Nematodes have tiny cylindrical thread-like bodies that are pointed at both ends and covered with tough cuticle or skin-like membranes. Many are free-living dwellers in soil and water; others, like hookworms, Ascaris, pinworms, trichina worms, and filaria worms are parasites of man, animals, and plants.

An abnormal growth or tissue, as a tumor.
An instrument for measuring turbidity in water using a photometric analytical technique for measuring the light scattered by finely divided turbidity or colloidally dispersed particles suspended in water.

See Also: Turbidity Jackson Turbidity Unit (JTU) Turbidity Jackson Turbidity Unit (JTU) Community Water System Turbidity Jackson Turbidity Unit (JTU)

A means of measuring turbidity in a sample by using an instrument called a nephelometer.

A nephelometer passes light through a sample, and the amount of light deflected (usually at a 90-degree angle) is than measured.

See Also: Turbidity Nephelometric Turbidity Unit (NTU)

An arbitrary unit of measuring the turbidity in water by the light scattering effect of fine suspended particles in a light beam.
Exerting a destructive or poisonous effect on nerve tissue.
In electrical systems, the term used to indicate neither an excess nor a lack of electrons; a condition of balance between positive and negative charges. In chemistry, the term used to indicate a balance between acids and bases; the neutral point on the pH scale is 7.0, indicating the presence of equal numbers of free hydrogen (acidic) and hydroxide (basic) ions.
A trade name for a calcite mineral product (crushed southern limestone) which is used in loose media bed filters to modify the pH of low pH water sources.
In general, the addition of either an acid or a base to a solution as required to produce a neutral solution. The use of alkaline or basic materials to neutralize the acidity of some waters is a common practice in water conditioning.
A common designation for alkaline materials such as calcite (calcium carbonate) or magnesia (magnesium oxide) used in the neutralization of acid waters.
A fundamental particle found in the nucleus of an atom.

A neutron has a mass equal to that of a proton but carries no charge.

The force necessary to give acceleration of one meter per second to one kilogram of mass.
A natural nitrogen compound (NO3-) sometimes found in well or surface waters.

In high concentrations, nitrates can be harmful to young infants or young livestock.

See Also: Cyanosis

The biochemical transformation of ammonium nitrogen to nitrate nitrogen.
A chemical that slows down the conversion of ammonium to nitrate nitrogen.
The biological or chemical process by which elemental nitrogen, from the air, is converted to organic or available nitrogen.
A term used to describe chemical compounds (usually organic) containing nitrogen in combined forms.

Proteins and nitrates are nitrogenous compounds.

The highest dose in a toxicity experiment which did not produce an observable adverse effect.
Chemically unreactive, especially toward oxygen or resists chemical action such as corrosion caused by air, water, or (to a lesser degree) acids.

Gold, silver, platinum, palladium, and mercury are said to be "noble metals" because they don't rust and are resistant to acid damage.

Certain gases are called "noble gases" because they are inert (chemically inactive and stable.)

Chemically inactive metal (such as gold).

A metal that does not corrode easily and is much scarcer (and more valuable) than the so-called useful or base metals.

See Also: Alkali Free Base Form Weak Base Anion Exchangers Base Metal Lead (Pb) Inorganic Matter Base Metal

No-observed-effect level; dose level at which no effects are noted.
An approximate measurement of the diameter of a pipe.

Although the nominal diameter is used to describe the size or diameter of a pipe, it is usually not the exact inside diameter of the pipe.

Filter rating indicating the approximate size particle, the majority of which will not pass through the filter.

It is generally interpreted as meaning that 85 percent of the particles of the size equal to the nominal filter rating will be retained by the filter.

Water hardness due to the presence of compounds such as calcium and magnesium chlorides, sulfates, or nitrates; the excess of total hardness over total alkalinity.
A public water system that is not a community water system.

There are two types of NCWSs: transient and nontransient.

Any pollutant which is not statutorily listed or which is poorly understood by the scientific community.
Resistant to decomposition or decay by biological means such as bacterial action or from chemical or physical causes such as oxidation, heat, sunlight, or solvents.
Salt containing amounts of agents such as calcium or magnesium chloride which become soft or liquid by attracting and absorbing moisture from the air and preventing salt caking and bridging.
A polymer that has no net electrical charge.
Not disease-producing.
Pollution sources which are diffuse and do not have a single point of origin or are not introduced into a receiving stream from a specific outlet.

The pollutants are generally carried off the land by stormwater runoff. the commonly used categories for non-point sources are; agriculture, forestry, urban, mining, construction, dams and channels, land disposal, and saltwater intrusion.

Water that may contain objectionable pollution, contamination, minerals, or infective agents and is considered unsafe and/or unpalatable for drinking.
Very small, fine suspended solids, typically colloidal particles of less than 0.1 microns in diameter, which will not settle out of calm nonturbulent water, sewage, or other liquids in what is considered a reasonable time of about two hours.
A public water system that regularly serves at least 25 of the same nonresident persons per day for more than six months per year.
The flow of the entire feedwater stream in one direction directly through the filter media. The flow is usually "normal" or perpendicular to the media surface area.

See Also: Backflow XPLE or PEX Macroporous Resin Divinylbenzene (DVB) Polyethylene Cross-linked Polyethylene (XLPE or PEX) Back Siphonage Backwash Continous Flow Operation Cross Connection Intermittent Flow Venturi Cross flow filtration Conventional Filtration In-line Filtration Direct Filtration Cross flow filtration

A solution containing a gram equivalent weight of a substance in a liter of solution.
The standard statistical classification system, adopted in 1997 by the United States Office of Management and Budget (OMB), that assigns an industry number to businesses and business units by type of economic activity. The NAICS has been harmonized with and also adopted by Mexico and Canada. It replaces the Standard Industrial Classification (SIC) system used in the U.S. from 1938 until 1997. The NAICS is a standard industry classification system that facilitates the collection, tabulation, presentation, and analysis of data relating to establishments and ensures that data about the U.S. economy published by U.S. statistical agencies are uniform and comparable among the North American countries. The NAICS uses a six-digit numerical coding system to identify particular industries and their placement in the hierarchical structure of the classification system. The first two digits group establishments (or locations at which an economic activity occurs) into one of 20 sectors, such as for example, Agriculture, Mining, Construction, Manufacturing, Wholesale Trade, Retail Trade, and Administration and Support Services. The remaining digits designate one of the 1,170 industries identified in NAICS. When any employer applies for an Employer Identification Number (EIN), information about the type of activity in which that business is engaged is requested in order to assign a NAICS code. In addition, statistical agencies such as the Census Bureau and the Bureau of Labor Statistics assign NAICS codes based on information reported to them. Water treatment equipment manufacturing, for example, is in NAICS 333319, water softener and water conditioning direct selling and service providers are in NAICS 454390, water softening and conditioning equipment wholesaling is in 421720, water softening and conditioning compounds and materials wholesaling is in 422690, and water softening and conditioning support services are in 561990.
Acquired after admittance to a hospital.
A term used in reporting test results to mean that the substance being tested cannot be detected by the equipment or method being used for this particular test.

This term implies that it is possible that trace amounts may be present in quantities too small to be detected by the test equipment or method.

A list of Superfund sites chosen for immediate attention.
National Secondary Drinking Water Regulations.
See nontransient noncommunity water system.
National Toxicology Program
Nephelometric turbidity unit.
A term used in reporting test results to mean that the substance being tested cannot be detected by the equipment or method being used for this particular test.

This term implies that it is possible that trace amounts may be present in quantities too small to be detected by the test equipment or method.

Any substance that is assimilated (taken in) on organisms and promotes growth.

For example, carbon dioxide, nitrogen, phosphorous, potassium, and numerous mineral elements are essential nutrients which promote the growth of plants.

Water and oxygen are also included in this definition.

Contamination of water resources by excessive inputs of nutrients: in surface waters, excess algae production is a major concern.