Define the terms C O D and B O D?

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Biochemical Oxygen Demand (BOD) :The measure of the total contamination caused by compounds which can be oxidised in the presence of microorganisms. The BOD is taken as a realistic measure of water quality – clean water would have a BOD value of less than 5 ppm whereas highly polluted river water could have a BOD value of 17 ppm or more.

Chemical Oxygen Demand (COD)is the amount of oxygen required to oxidise and stabilize the organic and inorganic matter present in a certain volume of water sample.It is measured by using a chemical oxidising agent.