The amount of oxygen required by aerobic microorganisms to decompose the organic matter in a sample of water, such as that polluted by sewage. It is used as a measure of the degree of water pollution. Also called biological oxygen demand生化需氧量：需氧微生物在水样品中分解有机物质所需氧气的量，如在被垃圾污染的水中。用于测量水的污染程度 也作 biological oxygen demand