Biochemical Oxygen Demand

Table of Contents

Don’t you often think, how do fishes and other aquatic animals breathe underwater?

Yes, water bodies do contain a small amount of dissolved oxygen, which is essential for both fishes and other aquatic organisms to undergo aerobic respiration.

That dissolved oxygen is used by the aquatic organisms for respiration. The heterotrophic microorganisms present in the water also uses the dissolved oxygen. These microorganisms uses the organic matter as their food source. The number of microorganisms becomes high when there is high concentration of organic matter which in turn requires more oxygen for respiration.

Biochemical oxygen demand (BOD) generally describes how much oxygen is required to break down organic matter in water.

What is BOD?

BOD – Biochemical Oxygen Demand is applied to determine the aerobic destructibility of organic substances.

BOD is the biological method used for the measurement of the total amount of dissolved oxygen (DO) used by microbes in the biological process of metabolizing organic molecules present in water.

The total amount of oxygen gas present in the water is called dissolved oxygen (DO). The non-compound oxygen present in water may either be a by-product of the photosynthesis of the aquatic plants or the dissolved atmospheric oxygen gas.

Also Read: Photosynthesis in Plants

In some water bodies, organic matter is a great source of BOD. These organic matters include sewage and other pollutants present in the water bodies. The greater the BOD, the lower is the dissolved oxygen available for aerobic animals such as fishes and other aquatic organisms.

The BOD is accordingly a reliable measure of the organic pollution of water bodies. The main reason for treating wastewater prior to its discharge into a water resource is to reduce its BOD level (the demand for oxygen).

Importance of BOD

  1. BOD measures the amount of oxygen consumed by microorganisms for the process of decomposition of the organic matters in the water bodies.
  2. It indicates the amount of organic pollution present in an aquatic ecosystem.
  3. BOD is calculated in sewage treatment or wastewater treatment to find the destruction of organic wastes by aerobic microbes
  4. It determines the amount of organic matter present in soils, sewages, sediment, garbage, sludge, etc.
  5. The biochemical oxygen demand also determines the rate of respiration in living beings.
  6. BOD is also used in the medicinal & pharmaceutical industries to test the oxygen consumption of cell cultures.

Also Read: Sewage Treatment

This article concludes the introduction to biochemical oxygen demand (BOD) and its importance.

To know more about biochemical oxygen demand (BOD), different BOD levels, BOD levels in drinking water, other related topics and important questions, keep visiting our website at BYJU’S Biology.

Frequently Asked Questions on Biochemical Oxygen Demand


What is biochemical oxygen demand in simple words?

In simple words, biochemical oxygen demand is the amount of oxygen required by microorganisms to break down the organic matter present in the waterbody.


What is the role of biochemical oxygen demand?

Biochemical oxygen demand indicates the amount of organic pollution present in an aquatic ecosystem.


What happens when BOD is low?

When BOD is low, the dissolved oxygen present in the water body is high. This indicates that the water is less polluted by organic matter.


What causes high BOD levels?

High BOD levels are caused by high consumption of dissolved oxygen by microorganisms. It indicates that the water is highly polluted with organic matter.

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