Biological Oxygen Demand of Water
Biochemical oxygen demand (BOD) is defined as the amount of oxygen required by bacteria while stabilizing decomposable organic matter under aerobic conditions. The results are commonly expressed in terms of weight of oxygen required per unit volume of the initial sample.
BOD determinations are made by measuring residual dissolved oxygen in a water sample or a diluted aliquot after an incubation period (usually 5 days at 20° C). The BOD test has little geochemical significance, but it is widely used to determine the strength of domestic and industrial wastes in terms of the oxygen that they will require if discharged into a natural water course.
It is generally considered to be the most useful way of expressing stream pollution loads and for comparing one set of conditions with another.