Glossary Of Water Treatment Industry Terms . . ."E"

E. Coli - The common abbreviation of Escherichia Coli.

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.

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.

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.

effluent - The stream emerging from a unit, system or process, such as the softened water from an ion exchange softener.

ejector - A device which used a high velocity jet to entrain a gas or liquid in a stream of air or liquid. (See eductor.)

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.

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.)

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.)

electron - A fundamental particle found in the atom which carries a single negative charge.

elution - The stripping of ions from an ion exchange material by other ions, either because of greater affinity or because of much higher concentration.

endpoint - The point at which a process is stopped because a predetermined value of a measurable variable is reached.

equilibrium - The state in which the action of multiple forces produce a stead balance.

equilibrium reaction - A chemical reaction which proceeds primarily in one direction until the concentrations of reactants and products reach an equilibrium.

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.

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.

Escherichia Coli - One of the members of the coliform groups of bacteria indicating fecal contamination. (See fecal, coliform.)

exchange velocity - The rate with which one ion is displaced from an ion exchange material in exchange for another ion.

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.)