Eductor (E-duck-ter): A hydraulic
device used to create a negative pressure (suction) by forcing liquid
through a restriction, such as a Venturi. An eductor or aspirator (the
hydraulic device) may be used in the laboratory instead of a vacuum pump.
As an injector, it is used to produce vacuum for chlorinators.
Effluent: The outflow of water from a process.
Element: A substance which cannot
be separated into its constituent parts and still retain its chemical
identity. For example, sodium (Na) is an element.
End point: Samples are titrated
to the end point. This means that a chemical is added, drop by drop,
to a sample until a certain colour change (blue to clear, for example)
occurs. This is called the End Point of the titration. In addition to
a colour change, an end point may be reached by the formation of a precipitate
or the reaching of a specified pH. An end point may be detected by the
use of an electronic device such as a pH meter.
Enteric: Of intestinal origin,
especially applied to wastes or bacteria.
Enteric pathogen: A disease causing organism of intestinal origin.
Environmental hazards: A hazard
that can present a problem for the environment.
Escherichia coli: Bacterium found
in the gut, used as an indicator of faecal contamination of water. (E.
coli)
Eutrophication: (1) The increase
in nutrient levels in a body of water (river, lake, sea) due to pollution
from sewage, effluent or storm water.
(2) Degradation of water quality due to enrichment by nutrients such
as nitrogen and phosphorus, resulting in excessive algal growth and decay
and often low dissolved oxygen in the water.
Explosive: To violently expand or burst, often with great noise.
Exposure: Contact of a chemical,
physical or biological agent with the outer boundary of an organism (e.g.
through inhalation, ingestion or dermal contact).