APES Module 8: Aquatic Pollution Terms & Definitions

tertiary sewage treatment

Specialized chemical and physical processes that reduce the amount of specific pollutants left in wastewater after primary and secondary sewage treatment. This type of treatment usually is expensive

cultural eutrophication

Overnourishment of aquatic ecosystems with plant nutrients (mostly nitrates and phosphates) because of human activities such as agriculture, urbanization, and discharges from industrial plants and sewage treatment plants.

biological oxygen demand (BOD)

Amount of dissolved oxygen needed by aerobic decomposers to break down the organic materials in a given volume of water at a certain temperature over a specified time period.

dissolved oxygen (DO) content

Amount of oxygen gas (O2) dissolved in a given volume of water at a particular temperature and pressure, often expressed as a concentration in parts of oxygen per million parts of water.

eutrophication

Physical, chemical, and biological changes that take place after a lake, estuary, or slow-flowing stream receives inputs of plant nutrients - mostly nitrates and phosphates from natural erosion and runoff from the surrounding land basin.

nonpoint source

Large or dispersed land areas such as crop fields, streets, and lawns that discharge pollutants into the environment over a large area.

oxygen-demanding wastes

Organic materials that are usually biodegraded by aerobic (oxygen-consuming) bacteria if there is enough dissolved oxygen in the water

point source

Single identifiable source that discharges pollutants into the environment. Examples are the smokestack of a power plant or an industrial plant, drainpipe of a meatpacking plant, chimney of a house, or exhaust pipe of an automobile.

primary sewage treatment

Mechanical sewage treatment in which large solids are filtered out by screens and suspended solids settle out as sludge in a sedimentation tank.

secondary sewage treatment

Second step in most waste treatment systems in which aerobic bacteria decompose up to 90% of degradable, oxygen-demanding organic wastes in wastewater. This usually involves bringing sewage and bacteria together in trickling filters or in the activated sludge process

septic tank

Underground tank for treating wastewater from a home in rural and suburban areas. Bacteria in the tank decompose organic wastes, and the sludge settles to the bottom of the tank. The effluent flows out of the tank into the ground through a field of drainpipes.

sludge

Gooey mixture of toxic chemicals, infectious agents, and settled solids removed from wastewater at a sewage treatment plant.

bioaccumulation

An increase in the concentration of a chemical in specific organs or tissues at a level higher than would normally be expected.

biomagnification

Increase in concentration of DDT, PCBs, and other slowly degradable, fat-soluble chemicals in organisms at successively higher trophic levels of a food chain or web

DDT

Dichlorodiphenyltrichloroethane, a chlorinated hydrocarbon that has been widely used as an insecticide but is now banned in some countries.

dioxins

Family of 75 different chlorinated hydrocarbon compounds formed as unwanted by-products in chemical reactions involving chlorine and hydrocarbons, usually at high temperatures.

hazardous waste

Any solid, liquid, or containerized gas that can catch fire easily, is corrosive to skin tissue or metals, is unstable and can explode or release toxic fumes, or has harmful concentrations of one or more toxic materials that can leach out.

industrial solid waste

Solid waste produced indirectly by mines, factories, refineries, food growers, and businesses that supply people with goods and services.

integrated waste management

Variety of strategies for both waste reduction and waste management to deal with solid wastes.

municipal solid waste

Solid materials discarded by homes and businesses in or near urban areas. See solid waste.

open dumps

Fields or holes in the ground where garbage is placed and sometimes covered with soil. They are rare in developed countries, but widely used in many developing countries.

polychlorinated biphenyls (PCBs)

Group of 209 different toxic, oily, synthetic chlorinated hydrocarbon compounds that can be biologically amplified in food chains and webs.

precautionary principle

When there is scientific uncertainty about potentially serious harm from chemicals or technologies, decision makers should act to prevent harm to humans and the environment.

recycling

Collecting and reprocessing a resource so that it can be made into new products. An example is collecting aluminum cans, melting them down, and using the aluminum to make new cans or other aluminum products.

reuse

Using a product over and over again in the same form. An example is collecting, washing, and refilling glass beverage bottles.

sanitary landfill

Waste disposal site on land in which waste is spread in thin layers, compacted, and covered with a fresh layer of clay or plastic foam each day.

solid waste

Any unwanted or discarded material that is not a liquid or a gas.

toxic waste

Form of hazardous waste that causes death or serious injury (such as burns, respiratory diseases, cancers, or genetic mutations).

carcinogen

Chemicals, ionizing radiation, and viruses that cause or promote the development of cancer.

dose

The amount of a potentially harmful substance an individual ingests, inhales, or absorbs through the skin.

dose-response curve

Plot of data showing effects of various doses of a toxic agent on a group of test organisms.

epidemology

Study of the patterns of disease or other harmful effects from toxic exposure within defined groups of people to find out why some people get sick and some do not.

hazardous chemical

Chemical that can cause harm because it is flammable or explosive, can irritate or damage the skin or lungs (such as strong acidic or alkaline substances), or can cause allergic reactions of the immune system (allergens).

median lethal dose (LD50)

Amount of a toxic material per unit of body weight of test animals that kills half the test population in a certain time.

mutagen

Chemical or form of radiation that causes inheritable changes (mutations) in the DNA molecules in the genes found in chromosomes.

neurotoxins

Chemicals that can harm the human nervous system (brain, spinal cord, peripheral nerves).

pathogen

Organism that produces disease.

risk

The probability that something undesirable will result from deliberate or accidental exposure to a hazard.

risk assessment

Process of gathering data and making assumptions to estimate short- and long-term harmful effects on human health or the environment from exposure to hazards associated with the use of a particular product or technology.

teratogen

Chemical, ionizing agent, or virus that causes birth defects.

toxicity

Measure of how harmful a substance is.