Misconception about Wastewater BOD and COD Parameters ??

There is generally misconception about wastewater BOD and COD parameters that:

1. These represent toxicity of wastewater
2. BOD represents the organic compounds in wastewater
3. COD represents inorganic compounds in wastewater
4. These can be removed by simple gravitational settling of wastewater
5. These can be detected through taste, smell and color
6. Increase use of inorganic chemicals such as caustic soda in the process increases COD of wastewater

?BOD and COD parameters represent the presence and indirect quantification of organic compounds in the wastewater. These don’t have any relation with the inorganic chemical compounds. BOD represents the presence and indirect quantification of biodegradable organic compounds (which microorganisms, present naturally in the wastewater, can oxidize/biodegrade), whereas COD represents the presence and indirect quantification of all the organic compounds i.e. biodegradable and non-biodegradable. Microorganisms (mos) can’t oxidize non-biodegradable organic compounds.

Therefore, the COD values are generally higher than the BOD values. If these values are equal (which is generally not) then it means that all the organic compounds present in wastewater are biodegradable and there is no non-biodegradable fraction. The ratio of BOD to COD (BOD: COD) values gives us the information about the ease or difficulty of wastewater to be treated biologically.

The more the ratio is closer to one, the more easily the wastewater will be treated biologically (means there is less quantity of non-biodegradable compounds).

Biological treatment is where most biodegrade organic compounds of wastewater by utilizing dissolved oxygen (DO) i.e. oxygen/air is artificially supplied in the treatment plant.??

Must Read: Difference between BOD and COD

Impact: When wastewater of higher BOD and COD values is discharged into rivers/water streams, the naturally present mos in the water streams, start biodegrading the organic compounds.

These mos also consume DO of the rivers/water steams during biodegradation resulting in DO depletion in the rivers, which is the lifeline of the aquatic life (fish, plants etc.) and as a result this life starts dying and water becomes polluted.??#netsolwater

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