What Is BOD and COD in Water Treatment?

Water treatment plants play a vital role in ensuring that the water we drink is safe and free from harmful pollutants. Two important parameters that are used to assess the quality of water are BOD (Biochemical Oxygen Demand) and COD (Chemical Oxygen Demand).

These parameters help determine the level of organic matter and pollutants present in water. Let’s take a closer look at what BOD and COD mean and how they are measured.

BOD (Biochemical Oxygen Demand)

BOD measures the amount of oxygen that is required by microorganisms to decompose organic matter in water. It serves as an indicator of the level of organic pollution in water bodies. The higher the BOD, the greater the pollution levels.

Why is BOD important?

A high BOD indicates that there is a significant amount of organic matter present in the water, which can deplete oxygen levels when discharged into natural water bodies. This depletion can harm aquatic life, leading to fish kills and other adverse effects on ecosystems.

How is BOD measured?

BOD is typically measured by collecting a water sample and incubating it for a specific period under controlled conditions. During this incubation period, bacteria consume oxygen as they decompose organic matter present in the sample. The difference in dissolved oxygen levels before and after incubation determines the BOD value.

COD (Chemical Oxygen Demand)

COD measures the amount of oxygen required to chemically oxidize both biodegradable and non-biodegradable organic compounds present in water. It provides an estimate of the total amount of organic substances that can be oxidized.

Why is COD important?

COD testing helps wastewater treatment plants assess their treatment processes’ efficiency. It also provides insights into the presence of toxic substances in water, as certain chemicals can contribute significantly to the COD value.

How is COD measured?

COD is determined by adding a strong oxidizing agent, such as potassium dichromate, to a water sample and then measuring the amount of oxygen consumed during the oxidation process. The more oxygen consumed, the higher the COD value.

Differences between BOD and COD

While both BOD and COD provide information about organic pollution levels in water, there are some key differences between them:

  • Measurement time: BOD requires several days for incubation, while COD can be measured relatively quickly.
  • Substances detected: BOD mainly measures biodegradable organic matter, whereas COD measures both biodegradable and non-biodegradable substances.
  • Oxidizing agents used: BOD relies on natural microbial activity for decomposition, while COD uses chemical oxidants.

In conclusion

BOD and COD are essential parameters used in water treatment to assess the level of organic pollution. By monitoring these values, treatment plants can take appropriate measures to ensure clean and safe drinking water.

Understanding the differences between BOD and COD helps in determining which test is more suitable for specific applications. It is crucial to regularly monitor these parameters to protect our precious water resources and maintain a healthy environment.

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Emma Gibson