The oxygen used in meeting the metabolic needs of aerobic organisms in water containing organic compounds. Numerically, it is expressed in terms of the oxygen consumed in water at a temperature of 68°F (20°C) during a five-day period. The BOD is used as an indication of the degree of water pollution.
The amount of oxygen required for a biological reaction, especially the oxygen required to oxidize materials in natural water supplies (e.g., rivers or lakes).