What Is BOD and COD in Wastewater?

When it comes to wastewater treatment, two of the most commonly used terms are BOD and COD. Both of these terms refer to the amount of organic matter present in the wastewater.

Understanding what BOD and COD mean is crucial when it comes to designing and operating a wastewater treatment plant. In this article, we will explore what BOD and COD are and how they differ.

What is BOD?

BOD stands for Biological Oxygen Demand. It is a measure of the amount of oxygen that microorganisms need to break down organic matter in the water.

When wastewater enters a treatment plant, bacteria and other microorganisms begin to consume the organic matter present in the water. As they do so, they require oxygen to carry out their metabolic processes.

The BOD of wastewater is measured by determining how much oxygen is consumed by these microorganisms during a specific period of time. The more organic matter present in the water, the higher its BOD will be.

What is COD?

COD stands for Chemical Oxygen Demand. It is also a measure of the amount of organic matter present in water, but it differs from BOD in that it measures both biodegradable and non-biodegradable organic matter.

COD measures how much oxygen would be required to completely oxidize all of the organic matter present in water using chemical oxidizing agents such as potassium permanganate or dichromate.

Differences between BOD and COD

While both BOD and COD are measures of organic matter present in wastewater, there are several key differences between them:

  • BOD only measures biodegradable organic matter while COD measures both biodegradable and non-biodegradable organic matter.
  • BOD takes longer to measure than COD.
  • COD results can be affected by certain chemicals that may interfere with oxidation reactions.
  • BOD is a more accurate measure of the amount of organic matter that can be biologically degraded in wastewater.

Why are BOD and COD important?

Both BOD and COD are important measures when it comes to designing and operating wastewater treatment plants. They provide information about the amount of organic matter present in the water, which affects the amount of oxygen required to treat the wastewater.

If there is too much organic matter present in the water, it can deplete oxygen levels in waterways, leading to fish kills and other environmental problems. Additionally, high levels of organic matter can interfere with disinfection processes used to treat wastewater.

Conclusion

In conclusion, BOD and COD are both measures of organic matter present in wastewater. While they differ in how they measure organic matter, both are important when it comes to designing and operating wastewater treatment plants. By monitoring BOD and COD levels, treatment plant operators can ensure that they are effectively treating wastewater while minimizing their impact on the environment.

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Daniel Bennet