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Definition of wastewater
The spent water of a community. From the standpoint of source, it may be a combination of the liquid and water carried wastes from residences, commercial buildings, industrial plants, and institutions, together with any groundwater, surface water, and storm water that may be present. In recent years, the word wastewater has taken presence over the word sewage.
Definition of absorption
The taking up of one substance into the body of another.
Definition of acidity
The quantitative capacity of aqueous solutions to react with hydroxl ions. It is measured by titration with a standard solution of a base to a specific end point. Usually expressed as milligrams per liter of calcium carbonate.
Definition of an Acre-foot
(1) A volume of water 1 ft. deep and 1 acre in area, or 43,560 cu. ft. (2) A 43,560 cu. ft. volume of trickling filter medium.
Definition of activated carbon
Carbon particles usually obtained by carbonization of cellulosic material in the absence of air and possessing a high obsorptive capacity.
Defintion of activated sludge
A biological wastewater treatment plant process in which a mixture of wastewater and activated sludge is agitated and aerated. The activated sludge subsequently separated from the treated wastewater (mixed liquor) by sedimentation and wasted or returned to the process as needed.
Definition of adsorption
(1) the adherence of a gas, liquid, or dissolved material on the surface of a solid. (2) A change in concentration of gas or solute at the interface of a two-phase system. Should not be confused with absorption.
Definition of Aeration
(1) The bringing about of intimate contact between air and a liquid by one or more of the following methods: (a) spraying the liquid in the air, (b) bubbling air through the liquid to promote surface absorption of air. (2) The supplying of air to confined spaces under nappes, downstream from gates and conduits, etc..., to relieve low pressure and to replenish air entrainment and removed from such confined spaces by flowing water. (3) Relief of the effects of cavitation by admitting air to the section affected.
Definition of aerator
A device that promotes aeration.
Definition of aerobic
Requiring, or not destroyed by, the presence of free elemental oxygen.
Definition of aerobic bacteria
Bacteria that require free elemental oxygen for their growth.
Definition of agglomeration
The coalesence of dispersed suspended matter into larger flocs or particles which settle rapidly.
Definition of agitator
Mechanical apparatus for mixing and/or aerating; a device for creating turbulence.
Definition of algae
Primitive plants, one-or many celled, usually aquatic, and capable of elaborating their foodstuffs by photosynthesis.
Definition of algicide
Any substance or chemical applied to kill or control algal growths.
Definition of alkaline
The condition of wastewater, or soil which contains a sufficient amount of alkali substances to raise the pH above 7.0.
Definition of alkalinity
The capacity of water to neutralize acids, a property imparted by the water\'s content of carbonates, bicarbonates, hydroxides, and occasionally borates, silicates, and phosphates. It is expressed in milligrams per liter of equivalent calcium carbonate.
Definition of ammonia
A chemical combination of hydrogen (H) and nitrogen (N) occuring extensively in nature. The combination used in wastewater engineering is expressed as NH3.
Definition of amperometric
Pertaining to measurement by electric current flowing or generated, rather than by voltage.
Definition of anaerobic
Requiring, or not destroyed by, the absence of air or free (elemental) oxygen.
Definition of anaerobic bacteria
Bacteria that grow only in the absence of free elemental oxygen.
Definition of bacteria
A group of universally distributed, rigid, essentially unicellular microscopic organisms lacking chlorophyll. Bacteria usually appear as spheroid, rod-like, or curved entities, but occasionally appear as sheets, chains, or branched filimanents. Bacteria are usually regarded as plants, but are not.
Definition of baffles
Deflector vanes, guides, grids, gratings, or similar devices constructed or placed in flowing water, wastewatet, or slurry systems to check or effect a more uniform distribution of velocities; absorb energy; divert, guide, or agitate the liquids; and check eddies.
Defintion of biochemical oxidation
The process by which the life activities of bacteria and other microorganisms, in the search for food, break down complex organic materials into simple, more stable substances.
Defintion of biochemical process
The process by which the life activities of bacteria and other microorganisms, in search for food, break down complex organic materials into simple, more stable substances.
Definition of biological oxidation
The process whereby living organisms in the presence of oxygen convert the organic matter contained in wastewater into a more stable or a mineral form.
Defintion of biota
Animal and plant life, or fauna and flora, of a stream or other water body.
Definition of BOD
(1) Abbreviation for biochemical oxygen demand. The quantity of oxygen used in the biochemical oxidation of organic matter in a specific time, at a specific temperature, and under specified conditions. (2) A standard test used in assessing wastewater strength.
Definition of BOD load
The BOD content, usually expressed in pounds per unit of time, of wastewater passing into a waste treatment system or to a body of water.
Definition of breakpoint chlorination
Addition of chlorine to water or wastewater until the chlorine demand has been satisfied and further additions result in residual that is directly proportional to the amount added beyond the breakpoint.
Definition of buffer
Any of certain combinations of chemicals used to stabilize the pH values or alkalinities of solutions.
Definition of calibration
(1) The determination, checking, or rectifying of the graduation of any instrument giving quantitative measurements. (2) The process of taking measurements or of making observations to establish the relationship between two quantities.
Definition of catch basin
A chamber or well, usually built at the curbline of a street, which admits surface water for discharge into a stormwater drain.
Definition of centrifuge
A mechanical device in which centrifugal force is used to seperate solids from liquids and/or to seperate liquids of different densities.
Definition of chloramines
Compunds of organic or inorganic nitrogen and chlorine.
Definition of chlorine
An element ordinarily existing as a greenish-yellow gas about 2.5 times as heavy as air. At atmospheric pressure and a temperature of -30.1°F, the gas becomes an amber liquid about 1.5 times as heavy as water. The chemical symbol of chlorine is Cl, its atomic weight is 35.457, and its molecular weight is 70.914.
Definition of chlorination
The application of chlorine to water or wastewater, generally for the purpose of disinfection, but frequently for accomplishing other biological or chemical results.
Definition of chlorine contact chamber
A detention basin provided primarily to secure the diffusion of chlorine through the liquid. Also called chlorination chamber.
Definition of clarification
Any process or combination of processes the primary purpose of which is to reduce the concentration of suspended matter in a liquid.
Definition of clarifier
A unit of which the primary purpose is to secure clarification. Usually applied to sedimentation tanks or basins.
Definition of coliform-group bacteria
A group of bacteria predominately inhabiting the intesines of man or animal, but also occasionally found elsewhere. It includes all aerobic and all facultative anerobic, Gram-negative, non-spore-forming bacilli that ferment lactose with production of gas. Also included are all bacteria that produce a dark, purplish-green colony with metallic sheen by the membrane filter technique used for coliform identification. The two groups are not always identical, but they are generally of equal sanitary significance.
Definition of colloids
(1) Finely divided solids which will not settle but may be removed by coagulation or biochemical action or membrane filtration; they are intermediate between true solutions and suspensions. (2) In general, particles of colloidal dimensions are approximately 10 A to 1 ohm in size. Colloidal particles are distinguished from ordinary molecules by their inability to diffuse through membranes that allow ordinary molecules and ions to pass freely.
Definition of combined residual chlorination
The application of chlorine to water or wastewater to produce, with the natural or added ammonia or with certain organic nitrogen compounds, a combined chlorine residual.
Definition of comminution
The process of cutting and screening solids contained in wastewater flow before it enters the flow pumps or other units in the treatment plant.
Definition of composite sample
A combination of individual samples of water or wastewater taken at selected intervals, generally hourly for some specified period, to minimize the effect of the variability of the individual sample. Individual samples may have equal volume or may be roughly proportioned to the flow at the time of sampling.
Definition of cross connection
(1) A physical connection through which a supply of potable water could be contaminated or polluted (2) A connection between a supervised potable water supply and an unsupervised supply of unknown potability.
Definition of culture
Any organic growth that has been developed intentionally by provision of suitable nutrients and environment.
Definition of decantation
Separation of a liquid from solids, or from a liquid of higher density, by drawing off the upper layer after the heavier material has settled.
Definition of dechlorination
The partial or complete reduction of residual chlorine in a liquid by any chemical or physical process.
Definition of the decomposition of wastewater
(1) The breakdown of organic matter in wastewater by bacterial action, either aerobic or anaerobic. (2) Transformation of organic or inorganic materials contained in wastewater through the action of chemical or biological processess.
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