Difference Between BOD and COD l BOD vs COD

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 in the water chemically.

Quality of a given water sample depends on some variable factors. Also, it can be categorized in several ways such as biological, physical and chemical. They are namely pH, turbidity, microorganisms, dissolved-oxygen content, and dissolved-nutrients. The main parameter, which can affect the water quality, is the composition of water. Normally water contains gases, inorganic ions, organic compounds, living organisms and some of the other trace chemical compounds. The composition varies depending on the different factors such as temperature, source and level of pollution, etc. Oxygen demand is one of the most common ways of measuring the quality of water. Both biological oxygen demand (BOD) and chemical oxygen demand (COD) are coming under that phenomenon. The main intention of this article is to give a clear idea about both of the concepts, similarities, differences, and practical usage of them.


1. Overview and Key Difference
2. What is BOD
3. What is COD
4. Similarities Between BOD and COD
5. Side by Side Comparison – BOD vs COD in Tabular Form
6. Summary

What is BOD?

BOD is the abbreviation of biological oxygen demand in water. It is also called as biochemical oxygen demand. There is a significant relationship among organic matter, microbial population and dissolved oxygen content in water. Aerobic microorganisms need oxygen for their metabolism. Hence, they use dissolved oxygen and convert organic matter into energy. Moreover, they utilize the provided energy from organic food, for their further metabolic reactions and especially for their reproduction. Thus, the population density is increasing concerning the gained energy, but it depends on the available food content. The metabolic requirement for the newly created population again creates a demand for the dissolved oxygen, which is proportional to the available food.