atmospheric deposition
	Sedimentation of solids, liquids, or gaseous materials from the air. Snow, rain, and dust are the most familiar examples, but acids, metals, and toxic organic chemicals also can be transported by winds and deposited far from the source of origin.
best available, economically achievable technology (BAT)
	The best pollution control available; the Clean Water Act effectively negates this category by stipulating that equipment must be economically feasible.
best practical control technology (BPT)
	The best technology for pollution control available at reasonable cost and operable under normal conditions.
biochemical oxygen demand (BOD)
	A standard test for measuring the amount of dissolved oxygen utilized by aquatic microorganisms.
coliform bacteria
	Bacteria that live in the intestines (including the colon) of humans and other animals; used as a measure of the presence of feces in water or soil.
cultural eutrophication
	An increase in biological productivity and ecosystem succession caused by human activities.
dissolved oxygen (DO) content
	Amount of oxygen dissolved in a given volume of water at a given temperature and atmospheric pressure; usually expressed in parts per million (ppm).
effluent sewerage
	A low-cost alternative sewage treatment for cities in poor countries that combines some features of septic systems and centralized municipal treatment systems. A septic tank near each residence collects and processes solid wastes--and must be pumped periodically just like a septic tank--while liquid effluent is collected and piped to a central treatment plant. This avoids drainfields in urban areas and yet allows sewer pipes and treatment plants to be downsized, saving money.
eutrophic
	Rivers and lakes rich in organisms and organic material (eu = truly; trophic = nutritious).
nonpoint sources
	Scattered, diffuse sources of pollutants, such as runoff from farm fields, golf courses, construction sites, etc.
oligotrophic
	Condition of rivers and lakes that have clear water and low biological productivity (oligo = little; trophic = nutrition); are usually clear, cold, infertile headwater lakes and streams.
oxygen sag
	Oxygen decline downstream from a pollution source that introduces materials with high biological oxygen demands.
point sources
	Specific locations of highly concentrated pollution discharge, such as factories, power plants, sewage treatment plants, underground coal mines, and oil wells.
primary treatment
	A process that removes solids from sewage before it is discharged or treated further.
red tide
	A population explosion or bloom of minute, single-celled marine organisms called dinoflagellates. Billions of these cells can accumulate in protected bays where the toxins they contain can poison other marine life.
secondary treatment
	Bacterial decomposition of suspended particulates and dissolved organic compounds that remain after primary sewage treatment.
tertiary treatment
	The removal of inorganic minerals and plant nutrients after primary and secondary treatment of sewage.
thermal plume
	A plume of hot water discharged into a stream or lake by a heat source, such as a power plant.

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