Biochemical oxygen demand (BOD)

A measure of the amount of food available to the microorganisms in a particular waste. It is measured by the amount of dissolved oxygen used up during a specific time period (usually 5 d, expressed as BOD5).

Widely used parameter of organic pollution applied to both wastewater and surface water … involving the measurement of the dissolved oxygen used by microorganisms in the biochemical oxidation of organic matter.

Source: Handbook of water and wastewater treatment plant operations