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E. Coli |
The common abbreviation of
Escherichia Coli. |
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Eductor |
A device utilizing a nozzle
and throat, installed in a stream of water to create a partial vacuum to
draw air or liquid into the stream; commonly used to draw regeneration
chemicals into an ion exchange water treatment system, such a softener or
deionizer. |
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Effective Size |
A measure of the size of
particles of ion exchanger or filter medium; defined as the diameter of a
specific particle in a bed, batch or lot which has 10 percent smaller and
90 percent larger particles. |
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Efficiency |
The ratio of output per
unit input or the effectiveness of performance of a system; in an ion
exchange system, often expressed as the amount of regenerant required to
produce a unit of capacity, such as the pounds of salt per kilograin of
hardness removal. |
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Effluent |
The stream emerging from a
unit, system or process, such as the softened water from an ion exchange
softener. |
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Ejector |
A device which used a high
velocity jet to entrain a gas or liquid in a stream of air or liquid. (See
eductor.) |
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Electrodialysis |
A process in which a direct
current is applied to a cell to draw charged ions through ion selective
semipermeable membranes, thus removing the ions from the solution. |
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Electrolysis |
In general, the chemical
change caused by the passage of an electric current, often a decomposition
of a material; the decomposition of water into oxygen and hydrogen by the
application of a direct current; the action in which one metal goes into
solution in a galvanic cell at the junction between dissimilar metals in a
water system. (See galvanic corrosion.) |
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Electrolyte |
A nonmetallic substance
that carries an electric current, or a substance which, when dissolved in
water, separates into ions which can carry an electric current. (See
conductance, ionization.) |
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Electron |
A fundamental particle
found in the atom which carries a single negative charge. |
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Elution |
The stripping of ions from
an ion exchange material by other ions, either because of greater affinity
or because of much higher concentration. |
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Endpoint |
The point at which a
process is stopped because a predetermined value of a measurable variable
is reached. |
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Equilibrium |
The state in which the
action of multiple forces produce a stead balance. |
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Equilibrium Reaction |
A chemical reaction which
proceeds primarily in one direction until the concentrations of reactants
and products reach an equilibrium. |
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Equivalent Weight |
The weight in grams of an
element, compound or ion which would react with or replace 1 gram of
hydrogen; the molecular weight in grams divided by the valence. |
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Erosion |
The process in which
material is worn away by a stream of air or liquid, often due to the
presence of abrasive particles in the stream; a physical or mechanical
wearing process rather than a chemical solution process. |
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Escherichia Coli |
One of the members of the
coliform groups of bacteria indicating fecal contamination. (See fecal,
coliform.) |
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Exchange Velocity |
The rate with which one ion
is displaced from an ion exchange material in exchange for another ion. |
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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. |
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Exhaustion |
The state of an ion
exchange material that is no longer capable of effective function due to
the depletion of the initial supply of exchangeable ions. (See ion
exchange, endpoint.) |
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Exposure |
Contact between a person
and a chemical. Exposures are calculated as the amount of chemical
available for absorption by a person. |
