Biological Oxygen Demand

BOD

 The biological oxygen demand is defined as the ‘measure of dissolved oxygen required to decompose the organic matter in water biologically’

 Normally, it is measured over 5 days

What’s it for then?

 Since most aquatic organisms need oxygen to carry out anaerobic respiration/ photosynthesis…

 Water with High BOD, but can’t replenish oxygen fast enough, won’t be able to meet the needs of the aquatic community…

 …Hence they will eventually suffocate

Some Comparations

 Rapid waters can rapidly replenish Oxygen supply due to its fast flow

 Lakes are less efficient at doing this

 Pure water BOD = 1 ppm

 Polluted water BOD = 5 ppm or above

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