The key difference ...
Published by Muna Hindiyeh, Associated Professor at German Jordanian University. Senior Water Quality Expert
The key difference between BOD and COD is that the BOD is the oxygen demand of microorganisms to oxidize organic matter in the water under aerobic conditions while the COD is the oxygen demand to oxidize all the pollutants organic and inorganic in the water chemically .
High BOD can be a result due to domestic sewage, petroleum residues and wastes of animals and crops.
COD always high in comparison to BOD since COD is a measurement of a complete breakdown of pollutants, unlike BOD in which biochemical breakdown is often not complete as a chemical breakdown.
COD test utilizes a strong oxidizing reagent to oxidize materials in water while BOD test does not use a chemical reagent instead it allows microorganisms to act on the organic matter.