Environmental Engineering Reference
In-Depth Information
Maximum contaminant level (MCL) —The maximum allowable concen-
tration of a contaminant in drinking water, as established by state
and federal regulations. Primary MCLs are health related and man-
datory. Secondary MCLs are related to the aesthetics of the water
and are highly recommended, but not required.
Membrane filter method —A laboratory method used for coliform test-
ing. The procedure uses an ultrathin filter with a uniform pore size
smaller than bacteria (less than 1  micron). After water is forced
through the filter, the filter is incubated in a special medium that
promotes the growth of coliform bacteria. Bacterial colonies with a
green-gold sheen indicate the presence of coliform bacteria.
Modes of transmission of disease —The ways in which diseases spread
from one person to another.
Multiple-tube fermentation method —A laboratory method used for coli-
form testing that uses a nutrient broth placed in a culture tube. Gas
production indicates the presence of coliform bacteria.
National Pollutant Discharge Elimination System (NPDES) —A require-
ment of the CWA that discharges meet certain requirements prior to
discharging waste to any water body. It sets the highest permissible
effluent limits, by permit, prior to making any discharge.
National Primary Drinking Water Regulations (NPDWRs) —Regulations
developed under the SDWA that establish maximum contaminant
levels, monitoring requirements, and reporting procedures for con-
taminants in drinking water that endanger human health.
Near Coastal Water Initiative —This initiative was developed in 1985 to
provide for the management of specific problems in waters near
coastlines that are not dealt with in other programs.
Nonbiodegradable —Substances that do not break down easily in the
environment.
Nonpolar covalently bonded —A molecule composed of atoms that share
their electrons equally, resulting in a molecule that does not have
p ol a r it y.
Organic chemical —A chemical substance of animal or vegetable origin
having carbon in its molecular structure.
Oxidation— Occurs when a substance either gains oxygen or loses
hydrogen or electrons in a chemical reaction; one of the chemical
treatment methods.
Oxidizer —A substance that oxidizes another substance.
Parts per million (PPM) —The number of weight or volume units of a
constituent present within each 1 million units of the solution or
mixture. PPM was formerly used to express the results of most water
and wastewater analyses, but it is being replaced by milligrams per
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