# Biochemical Oxygen Demand (BOD) vs Chemical Oxygen Demand (COD) – Key Differences

> What is BOD? BOD is the biochemical oxygen demand, which quantifies the amount of dissolved oxygen (DO) required by aerobic organisms to decompose organic...

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## What is BOD?

- BOD is the biochemical oxygen demand, which quantifies the amount of dissolved oxygen (DO) required by aerobic organisms to decompose organic material in a given water sample at a certain temperature and time.

- As BOD is a biological process, it is not a quantitatively precise test. However, BOD is a commonly employed test method that indicates the organic quality of water.

- The BOD is calculated by incubating a sealed sample of water for five days and measuring the oxygen loss since the commencement of the test.

- Two measurements are required for the BOD calculation of a sample. The initial DO is followed by the final DO five days later.

- BOD is measured in milligrammes of oxygen used per litre of sample during five days of incubation at 20 degrees Celsius (BOD5). The BOD has a direct impact on the DO of rivers and streams.

- Leaves, woody debris, topsoil, animal dung, food processing plants, sewage treatment plants, feedlots, malfunctioning septic systems, urban stormwater runoff, and effluents from pulp and paper mills are the sources of BOD.

- The rate of oxygen consumption relies on the water's temperature, pH, the type of bacteria present, and the type of organic matter present.

- The larger the BOD in a given body of water, the less oxygen is available to aquatic organisms in that body of water.

- Due to increased BOD, aquatic organisms would experience stress, suffocate, and finally perish.

## What is COD?

- The chemical oxygen demand (COD) estimates the quantity of DO necessary for the breakdown of organic materials and the oxidation of inorganic compounds such as ammonia and nitrite.

- Commonly, COD tests are performed on sewage or natural water samples that are contaminated with domestic and industrial pollutants.

- A closed water sample is incubated with a strong oxidant, such as potassium dichromate (K2Cr2O7), in conjunction with boiling sulfuric acid (H2SO4) at a certain temperature and for a specific time.

- COD is associated with BOD. COD, however, is the only method for measuring industrial pollutants in water, which cannot be quantified using BOD.

- COD is the only method for measuring cellulose in water. COD is measured by plants that treat wastewater from commercial activity.

## Difference between Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) - BOD vs COD

![Difference between Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD)
](https://biologynotesonline.com/wp-content/uploads/2024/05/image-385.png)Difference between Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD)

## Similarities Between BOD and COD

- COD and BOD values can be expressed in mg/L or ppm (parts per million).

- Both values quantify the oxygen required to oxidise contaminants in water.

- Additionally, these readings show the degree of water pollution.

- In addition, both BOD and COD are essential in calculating the amount of trash in wastewater.

Difference between Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) pdf Download

## References

- https://theconstructor.org/environmental-engg/difference-chemical-oxygen-demand-cod-biological-oxygen-demand-bod/34792/

- [https://www.researchgate.net/profile/Lakna-Panawala/publication/318305894_Difference_Between_BOD_and_COD/links/5b08d33c4585157f87167337/Difference-Between-BOD-and-COD.pdf](https://www.researchgate.net/profile/Lakna-Panawala/publication/318305894_Difference_Between_BOD_and_COD/links/5b08d33c4585157f87167337/Difference-Between-BOD-and-COD.pdf)

- https://www.researchgate.net/profile/Lakna-Panawala/publication/318305894_Difference_Between_BOD_and_COD/links/5b08d33c4585157f87167337/Difference-Between-BOD-and-COD.pdf

- https://www.netsolwater.com/biological-oxygen-demand-vs-chemical-oxygen-demand.php?blog=1276

- https://www.differencebetween.com/difference-between-bod-and-vs-cod/

- https://camblab.info/what-are-the-differences-between-chemical-oxygen-demand-cod-and-biological-oxygen-demand-bod/

- https://butlerms.com/faq-items/what-is-the-difference-between-cod-and-bod/