Technical Resources

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Symbols and Acronyms


washout   Condition whereby excessive influent flows (typically at peak flow conditions) cause the solids in the aeration basins and/or clarifiers to be carried over into downstream processes or discharged to the receiving stream.

waste activated sludge (WAS)  Solids removed from the activated-sludge process to prevent an excessive buildup in the system.

wastewater  The spent or used water of a community or industry containing dissolved and suspended matter.

water column  (1) The water above the valve in a set of pumps. (2) A measure of head or pressure in a closed pipe or conduit.

water vapor  The gaseous form of water; molecules of water present as a gas in an atmosphere of other gases. Movement takes place from higher to lower vapor pressure regions to maintain vapor pressure equilibrium. Also called aqueous vapor.

watt  The electrical unit of power. Power is the measure of the rate of doing work. A watt is the rate of energy transfer from one ampere flowing under a pressure of one volt at a unity power factor. It is analogous to horsepower or foot-pounds per minute of mechanical power. One horsepower is equivalent to approximately 746 W.

weir  A device that has a crest and some side containment of known geometric shape, such as a V, trapezoid, or rectangle, and is used to measure flow of liquid. The liquid surface is exposed to the atmosphere. Flow is related to the upstream height of water above the crest, position of crest with respect to downstream water surface, and geometry of the weir opening.

weir overflow rate  The amount of flow applied to a treatment process (typically a clarifier) per linear measure of weir (gpd/lin ft).

wet-air oxidation  A method of sludge disposal that involves the oxidation of sludge solids in water suspension under high pressure and temperature. Also called the wet oxidation process.
wire-to-water efficiency  The ratio of mechanical output of a pump to the electrical input at the meter.

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