biochemical oxygen demand (bod) is the amount of dissolved oxygen needed by aerobic biological organisms in a body of water to break down organic material present in a given water sample at certain temperature over a specific time period. the term also refers to a chemical procedure for determining this amount. this is not a precise quantitative test, although it is widely used as an indication of the organic quality of water. the bod value is most commonly expressed in milligrams of oxygen consumed per litre of sample during 5 days of incubation at 20&nbsp;Â°c and is often used as a robust surrogate of the degree of organic pollution of water. bod can be used as a gauge of the effectiveness of wastewater treatment plants. it is listed as a conventional pollutant in the u.s. clean water act. bod is similar in function to chemical oxygen demand (cod), in that both measure the amount of organic compounds in water. however, cod is less specific, since it measures everything that can be chemically oxidized, rather than just levels of biologically active organic matter. ==background== most natural waters contain small quantities of organic compounds. aquatic microorganisms have evolved to use some of these compounds as food. microorganisms living in oxygenated waters use dissolved oxygen to oxidatively degrade the organic compounds, releasing energy which is used for growth and reproduction. populations of these microorganisms tend to increase in proportion to the amount of food available. this microbial metabolism creates an oxygen demand proportional to the amount of organic compounds useful as food. under some circumstances, microbial metabolism can consume dissolved oxygen faster than atmospheric oxygen can dissolve into the water or the autotrophic community (algae, cyanobacteria and macrophytes) can produce. fish and aquatic insects may die when oxygen is depleted by microbial metabolism.goldman, charles r. & horne, alexander j. limnology (1983) mcgraw-hill isbn 0-07-023651-8 pp.88&267 biochemical oxygen demand is the amount of oxygen required for microbial metabolism of organic compounds in water. this demand occurs over some variable period of time depending on temperature, nutrient concentrations, and the enzymes available to indigenous microbial populations. the amount of oxygen required to completely oxidize the organic compounds to carbon dioxide and water through generations of microbial growth, death, decay, and cannibalism is total biochemical oxygen demand (total bod). total bod is of more significance to food webs than to water quality. diss
Anaerobic_digestion Environmental_science Water_quality_indicators