Question

What do you understand about BOD and COD? How are these determined? Which one is preferred?

Answer 1

Hint :We know that the chemical measures of water quality include dissolved oxygen (DO), chemical oxygen demand (COD), biochemical oxygen demand (BOD), total dissolved solids (TDS), pH, nutrients (nitrates and phosphorus), heavy metals, soil chemicals (including copper, zinc, cadmium, lead and mercury) and pesticides.

Complete Step By Step Answer:
COD (Chemical oxygen demand) refers to the amount of oxygen being required to breakdown the pollutants using chemicals whereas BOD on the other hand is the amount of oxygen required to breakdown the organic pollutants biologically i.e. through micro-organisms. COD is generally higher than BOD as more organic compounds can easily be chemically oxidized compared to being biologically oxidised. BOD refers to the amount of dissolved oxygen required by the aerobic (in the presence of oxygen) biological organisms in order to break down the organic material that is present in a given sample of water at a certain temperature over a specific period of time.
COD or Chemical Oxygen Demand is the total measurement of all chemicals (organics & in-organics) in the water / waste water; BOD is a measure of the amount of oxygen that is required for the bacteria to degrade the organic components present in water/waste water.

Note :
Remember to never get confused between COD and BOD. The term biological oxygen demand (BOD) we generally hear whenever there is something related to water pollution so it simply means that there are some organisms in water which demand oxygen. Chemical oxygen demand (COD) test is commonly used to indirectly measure the amount of organic compounds in water. In environmental chemistry, the chemical oxygen demand (COD) is an indicative measure of the amount of oxygen that can be consumed by reactions in a measured solution. It is commonly expressed in mass of oxygen consumed over volume of solution.