|A specified concentration of a contaminant in water.
If this concentration is reached or exceeded,
certain actions (e.g., further treatment and monitoring) must be taken
to comply with a drinking
|An underground bed or layer of earth, gravel, or
porous stone that yields water.
|A statement to the public advising that tap water must
be boiled before drinking it.
|Waterborne-disease outbreaks are classified according
to the strength of the epidemiologic and
water-quality data implicating water as the source of the outbreak
(see Table 2).
|All aerobic and facultative anaerobic, gram-negative,
nonspore-forming, rod-shaped bacteria
that ferment lactose with gas formation <48 hours at 95ºF
|community water system
|A public water system that serves year-round residents
of a community, subdivision, or mobile
home park that has >15 service connections or an average of
>25 residents for >60 days/year.
|Any actual or potential connection between a drinking
water supply and a possible source of
contamination or pollution (e.g., a wastewater line).
|Chemicals formed in water through reactions between
organic matter and disinfectants.
|Water pipes, storage reservoirs, tanks, and other
means used to deliver drinking water to consumers
or store it before delivery.
|A holding basin in which variations in flow and
composition of a liquid stream are averaged,
allowing storage and controlled release of wastewater to treatment
|Coliforms that grow and produce gas at 112.1ºF
(44.5ºC) in <24 hours.
|Water containing the material obtained by reversing
the flow of water through a filter to
dislodge the particles that have been retained on it.
|The process of removing suspended particles from water
by passing it through one or more
permeable membranes or media of limited diameter (e.g., sand,
anthracite, or diatomaceous earth).
|The water (e.g., drinking water) delivered to the
distribution system after treatment, if any.
|free, residual chlorine level
|The concentration of chlorine in water that is not
combined with other constituents, thus
serving as an effective disinfectant.
|A system that uses water extracted from the ground
(i.e., a well or spring).
|groundwater under the
influence of surface water
|Any water beneath the surface of the ground with
substantial occurrence of insects or direct
other macrooganisms, algae, or large-diameter pathogens (e.g.,
Giardia intestinalis or
Cryptosporidium) or substantial and relatively rapid shifts in
water characteristics (e.g., turbidity,
temperature, conductivity, or pH) that closely correlate with
climatologic or surface water
conditions. Direct influence must be determined for individual sources
in accordance with
criteria established by the state.
|The branch of geology that deals with the occurrence,
distribution, and effect of ground water.
|Individual (or private)
|A water system that is not owned or operated by a
water utility and that serves <15
residences or farms not having access to a public water system.
|A fountain intended for (or accessible to)
recreational use, often located at waterparks. In
contrast, noninteractive (ornamental) fountains are intended for
public display rather than
recreational use and are often located in front of buildings and
|maximum contaminant level
|The maximum permissible concentration (i.e., level) of
a contaminant in water supplied to any
user of a public water system.
|noncommunity water system
|A public water system that 1) serves an institution,
industry, camp, park, hotel, or business that
is used by the public for >60 days/year but not year-round; 2)
has >15 service connections or
serves an average of >25 persons; and 3) is not a community
|Public water system that serves >25 of the same
persons for >6 months/year (e.g., a factory or
school) but not year-round.
|A group of related, single-stranded RNA, nonenveloped
viruses (genus Norovirus, family
Caliciviridae) that cause acute gastroenteritis in humans.
Norovirus was recently approved as
the official genus name for the group of viruses provisionally
described as Norwalk-like viruses.
|public water system
|A system, classified as either a community water
system or a noncommunity water system, that
provides piped water to the public for human consumption and is
regulated under the Safe
Drinking Water Act.
|Surface water or groundwater that has not been treated
in any way.
|A filtration process that removes dissolved salts and
metallic ions from water by forcing it
through a semipermeable membrane. This process is also highly
effective in removing
microbes from water.
|Untreated water (i.e., raw water) used to produce
|The water in lakes, rivers, reservoirs, and oceans.
|Nonfecal and fecal coliforms that are detected by
using a standard test.
|Public water system that provides water to places
where persons do not remain for long periods
of time (e.g., restaurants, highway rest stations, or parks with their
own public water systems).
|The quality (e.g., of water) of having suspended
matter (e.g., clay, silt, or plankton) that results
in loss of clarity or transparency.
|Surface water or groundwater that has not been treated
in any way (also called raw water).
|A microbial, chemical, or physical parameter that
indicates the potential risk for infectious
diseases associated with using the water for drinking, bathing, or
recreational purposes. The
best indicator is one whose density or concentration correlates best
with health hazards associated
with a type of hazard or pollution.
|An area from which water drains to a single point; in
a natural basin, the area contributing flow
(i.e., water) to a place or point on a stream.
|A program to protect a watershed from contamination or