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Chemical Oxygen Demand - Chemical oxygen demand or COD is the amount of oxygen required for the chemical oxidation of organic matter with the help of strong chemical oxidants.
COD has certain advantages over BOD. COD measures the amount of oxygen required to oxidize both biologically oxidisable and biologically non-oxidisable materials.
Thus, COD value for a given sample will be greater than the BOD value.
Results of COD can be obtained within 5 hours as compared to 5 days requirement for BOD.
Moreover COD procedure is relatively easy and can give reproducible results