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biochemical oxygen demand (BOD)

A chemical test for determining the level of pollution of water by organic matter. Two equal samples of water are taken, and the first is treated chemically to "mop up" any dissolved oxygen. Both samples are then incubated in the dark for some days, after which the second sample is given a similar chemical treatment. The allows the amount of "mopped-up" oxygen to be estimated. The difference between the two estimations, represents the amount of oxygen that has been used up by living and dead organic matter in the water during the period of storage.

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