These definitions are not intended to be complete or to have legal force, but rather to help consumers understand drinking water-related terms in the context of their daily lives.
Also check out:
A Dictionary of Technical
and Legal Terms Related to Drinking Water.
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Action
Level: The level of lead or copper which, if
exceeded, triggers treatment or other requirements that a water
system must follow.
Acute Health Effect: An immediate (i.e.
within hours or days) effect that may result from exposure to
certain drinking water contaminants (e.g., pathogens).
Aquifer: A
natural underground layer, often of sand or gravel, that contains
water.
Best Available Technology: The water
treatment(s) that EPA certifies to be the most effective for
removing a contaminant.
Chronic Health
Effect: The possible result of exposure over many years
to a drinking water contaminant at levels above its MCL.
Coliform:
A group of related bacteria whose presence in drinking water
may indicate contamination by disease-causing microorganisms.
Community Water
System: A water system which supplies drinking water to
25 or more of the same people year-round in their residences.
Compliance: The act of meeting all state
and federal drinking water regulations.
Contaminant:
Anything found in water (including microorganisms, minerals,
chemicals, radionuclides, etc.) which may be harmful to human
health.
Cryptosporidium : A microorganism
commonly found in lakes and rivers which is highly resistant to
disinfection. Cryptosporidium has caused several large outbreaks of
gastrointestinal illness, with symptoms that include diarrhea,
nausea, and/or stomach cramps. People with severely weakened immune
systems (that is, severely immuno-compromised) are likely to have
more severe and more persistent symptoms than healthy individuals.
Disinfectant: A chemical (commonly
chlorine, chloramine, or ozone) or physical process (e.g.,
ultraviolet light) that kills microorganisms such as bacteria,
viruses, and protozoa.
Distribution System: A network of pipes
leading from a treatment plant to customers' plumbing systems.
Exemption: State or EPA permission for a water
system not to meet a certain drinking water standard. An exemption
allows a system additional time to obtain financial assistance or
make improvements in order to come into compliance with the
standard. The system must prove that: (1) there are compelling
reasons (including economic factors) why it cannot meet a MCL or
Treatment Technique; (2) it was in operation on the effective date
of the requirement, and (3) the exemption will not create an
unreasonable risk to public health. The state must set a schedule
under which the water system will comply with the standard for which
it received an exemption.
Finished Water: Water
that has been treated and is ready to be delivered to
customers.
Giardia lamblia : A microorganism frequently
found in rivers and lakes, which, if not treated properly, may cause
diarrhea, fatigue, and cramps after ingestion.
Ground Water: The
water that systems pump and treat from aquifers (natural reservoirs
below the earth's surface).
Health Advisory: An
EPA document that provides guidance and information on contaminants
that can affect human health and that may occur in drinking water,
but which EPA does not currently regulate in drinking water.
Inorganic Contaminants : Mineral-based
compounds such as metals, nitrates, and asbestos. These contaminants
are naturally-occurring in some water, but can also get into water
through farming, chemical manufacturing, and other human activities.
EPA has set legal limits on 15 inorganic contaminants.
Maximum
Contaminant Level (MCL): The highest level of a
contaminant that EPA allows in drinking water. MCLs ensure that
drinking water does not pose either a short-term or long-term health
risk. EPA sets MCLs at levels that are economically and
technologically feasible. Some states set MCLs which are more strict
than EPA's.
Maximum Contaminant Level Goal (MCLG): The
level of a contaminant at which there would be no risk to human
health. This goal is not always economically or technologically
feasible, and the goal is not legally enforceable.
Microorganisms:
Tiny living organisms that can be seen only with the aid of a
microscope. Some microorganisms can cause acute health problems when
consumed in drinking water. Also known as microbes.
Monitoring:
Testing that water systems must perform to detect and measure
contaminants. A water system that does not follow EPA's monitoring
methodology or schedule is in violation, and may be subject to legal
action.
Non-Transient, Non-Community Water
System: A water system which supplies water to 25 or more
of the same people at least six months per year in places other than
their residences. Some examples are schools, factories, office
buildings, and hospitals which have their own water systems.
Organic Contaminants: Carbon-based
chemicals, such as solvents and pesticides, which can get into water
through runoff from cropland or discharge from factories. EPA has
set legal limits on 56 organic contaminants.
Pathogen: A disease-causing organism.
Primacy
State: A State that has the responsibility and authority
to administer EPA's drinking water regulations within its borders.
The State must have rules at least as stringent as EPA's.
Public
Notification: An advisory that EPA requires a water
system to distribute to affected consumers when the system has
violated MCLs or other regulations. The notice advises consumers
what precautions, if any, they should take to protect their health.
Public Water System
(PWS): Any water system which provides water to at least
25 people for at least 60 days annually. There are more than 170,000
PWSs providing water from wells, rivers and other sources to about
250 million Americans. The others drink water from private wells.
There are differing standards for PWSs of different sizes and types.
Radionuclides: Any man-made or natural
element that emits radiation and that may cause cancer after many
years of exposure through drinking water.
Raw Water: Water in its
natural state, prior to any treatment for drinking.
Sample: The water that is analyzed for the
presence of EPA-regulated drinking water contaminants. Depending on
the regulation, EPA requires water systems and states to take
samples from source water, from water leaving the treatment
facility, or from the taps of selected consumers.
Sanitary Survey: An
on-site review of the water sources, facilities, equipment,
operation, and maintenance of a public water systems for the purpose
of evaluating the adequacy of the facilities for producing and
distributing safe drinking water.
Secondary Drinking Water
Standards: Non-enforceable federal guidelines regarding
cosmetic effects (such as tooth or skin discoloration) or aesthetic
effects (such as taste, odor, or color) of drinking water.
Sole Source
Aquifer: An aquifer that supplies 50 percent or more of
the drinking water of an area.
Source Water: Water in its natural state,
prior to any treatment for drinking.
Surface Water: The
water that systems pump and treat from sources open to the
atmosphere, such as rivers, lakes, and reservoirs.
Transient, Non-Community Water System: A
water system which provides water in a place such as a gas station
or campground where people do not remain for long periods of time.
These systems do not have to test or treat their water for
contaminants which pose long-term health risks because fewer than 25
people drink the water over a long period. They still must test
their water for microbes and several chemicals.
Treatment
Technique: A required process intended to reduce the
level of a contaminant in drinking water.
Turbidity : The
cloudy appearance of water caused by the presence of tiny particles.
High levels of turbidity may interfere with proper water treatment
and monitoring.
Variance : State or
EPA permission not to meet a certain drinking water standard. The
water system must prove that: (1) it cannot meet a MCL, even while
using the best available treatment method, because of the
characteristics of the raw water, and (2) the variance will not
create an unreasonable risk to public health. The State or EPA must
review, and allow public comment on, a variance every three years.
States can also grant variances to water systems that serve small
populations and which prove that they are unable to afford the
required treatment, an alternative water source, or otherwise comply
with the standard.
Violation: A failure to meet any state or
federal drinking water regulation.
Vulnerability
Assessment: An evaluation of drinking water source
quality and its vulnerability to contamination by pathogens and
toxic chemicals.
Watershed: The land
area from which water drains into a stream, river, or
reservoir.
Wellhead Protection Area: The area
surrounding a drinking water well or well field which is protected
to prevent contamination of the
well(s).
