Colloids. Microscopic suspended particles which do not settle in a standing liquid and can only be
Demineralization. The process of removing dissolved minerals from water by ion exchange, reverse
osmosis, electrodialysis, distillation or other processes.
Denitrification. The biological process which converts nitrates in the wastes to molecular nitrogen.
Desalinization. The process of removing dissolved salts from water.
Detention (Retention). The dwell or residence of wastewater, usually expressed in hours, in a treatment
Disinfection. The process of killing the major portion of microorganisms in a waste stream with the
probability that all pathogenic organisms are killed. This is not necessarily true for viruses.
Dissolved Oxygen. Elemental oxygen dissolved or molecularly dispersed in wastewater. Does not include
any oxygen present in the combined form even though a compound may be an oxidizing agent.
Expressed in mg/L.
Dissolved Solids. The solids remaining in a waste after filtering by specific test procedures. Expressed in
Dragout. The liquid which is removed from a process step such as plating by the film retained on the
work or part passing through the process.
Effluent. Wastewater leaving a particular system, treatment process or treatment plant.
Environmental Impact. The effects of a proposed facility or action on the environment, including changes
to the air, streams, wildlife habitat, aesthetics, recreation and other similar factors.
Equalization. The holding or storing of wastes having differing qualities and rates of discharge for finite
periods to facilitate blending and achievement of relatively uniform characteristics.
Explosive. A material which by the influence of thermal or mechanical shock decomposes rapidly with
the evolution of much heat and gas. In the military context, it is the material used to propel a projectile
or to produce fragmentation of the projectile at its terminal point. Such explosives are classified into two
divisions, termed high and low explosives in accordance. with behavior or use. Detonating or high
explosives include primary explosives such as detonators (lead azide, mercury fulminate, etc.) and
secondary explosives such as RDX and TNT. Low explosives exert a powerful push with a low burning
rate and are used primarily as propellants and are often referred to by that name. Propellants include
materials such as nitrocellulose, nitroglycerine and nitroguanidine.
Filtration. A unit operation in which solid or colloidal material is separated from a liquid by movement
through a granular or porous sheet type material such as cloth or paper.
Fixed Solids. The non-volatile component of the total solids, either suspended or dissolved, consisting or
inorganic materials. The ash residue remaining after igniting dried residue from the total solids test at
550C. Expressed in mg/L.
Floe. Gelatinous mass formed in liquids by the addition of coagulant, by microbiological processes or by
Flocculation. The process of floe formation normally achieved by direct or induced slow mixing.
Flume. An open, inclined channel or conduit for conveying water.
Fume Scrubber. Equipment used to remove objectionable fumes from a gas or air stream. Normally
achieved by contact of the gas stream with a counter-current liquid stream in "which objectionable
constituents are collected.
Grease. A group of substances including fats, waxes, free fatty acids, calcium and magnesium soaps,
mineral oils and certain other non-fatty materials. The grease analysis will measure both free and
emulsified oils and greases. Generally expressed in mg/L.
Grit. Heavy suspended mineral matter such as sand, gravel and cinders which is present in wastewater.
Hardness. A characteristics of water imparted principally by the presence of calcium and magnesium
compounds. Hardness is undesirable from the standpoint that it reacts with soap resulting in increased
consumption. Also it is the prime cause of boiler scale and can adversely affect some industrial
processes. Normally expressed in mg/L as CaCO3.
Heavy Metals. Metals that can be precipitated by hydrogen sulfide in an acid solution, for example lead,
silver, mercury, copper, chromium, zinc and nickel.