advanced sewage treatment
Third level of sewage cleanup, which uses a series of specialized chemical and physical processes to remove specific pollutants left in the water after primary and secondary treatment. See primary sewage treatment and secondary sewage treatment.
Composed of material that can be broken down by decomposers.
Material that can be broken down into simpler substances (elements and compounds) by bacteria or other decomposers. Paper and most organic wastes such as animal manure are biodegradable but can take decades to biodegrade in modern landfills. Compare degradable pollutant, nondegradable-pollutant, slowly degradable pollutant.
Organic compound made up of atoms of carbon, hydrogen, and chlorine. Examples include DDT and PCBs.
Overnourishment of aquatic ecosystems with plant nutrients (mostly nitrates and phosphates) resulting from human activities such as agriculture, urbanization, and discharges from industrial plants and sewage treatment plants. See eutrophication.
Structure built across a river to control the river's flow or to create a reservoir. See reservoir.
Potentially polluting chemical that is broken down completely or reduced to acceptable levels by natural physical, chemical, and biological processes.
Purification of saltwater or brackish (slightly salty) water by removal of dissolved salts.
Condition in which an area does not get enough water because of lower-than-normal precipitation or higher-than-normal temperatures that increase evaporation.
Exhaustion of 80% of the estimated supply of a nonrenewable resource. Finding, extracting, and processing the remaining 20% usually costs more than it is worth. May also apply to the depletion of a renewable resource, such as a fish or tree species.
Distance above sea level.