When a body of wastewater contains too much biological material, the bacteria and other microorganisms in it cannot successfully decompose all the organic matter for food, growth and energy. This breaking down of the biological material requires oxygen; therefore, by measuring the amount of oxygen that is depleted from the sample as a result of such bacterial action, the balance within the aquatic environment can be measured. The BOD is a standard test, which takes five days to run, and is performed by introducing a population of bacteria and microorganisms to attempt to duplicate what would happen in a natural stream. The most commonly used method to estimate the total quantity of biodegradable organic material in wastewater. Compare to Chemical Oxygen Demand (COD).
Source: ACT Glossary
Category: Green