BOD stands for Biological Oxygen Demand. It is the amount of dissolved oxygen required for biological oxidation of organic matter by aerobic microorganisms in a unit volume of water. BOD values are generally closer to the amount of oxidizable organic matter present in water and therefore, BOD is used as a measure of the degree of water pollution and waste level. The BOD value is expressed in milligrams of oxygen consumed per liter of water sample at 20°C temperature. The incubation time in the BOD test is a minimum of 5 days.