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Last updated date: 30th Nov 2023
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MVSAT Dec 2023

Measuring ‘Biochemical Oxygen Demand’ (BOD) is a method used for?

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Hint: Biochemical oxygen demand is the amount of oxygen taken up by microorganisms that decompose organic waste matter in water (BOD). It represents the sum of organic waste in an aquatic environment. Certain environmental stresses (hot summer temperatures) and other human-induced factors (the addition of excess fertilisers to a water body) can reduce the amount of dissolved oxygen in a water body, putting local aquatic life at risk.

Complete answer:
It is the amount of dissolved oxygen needed by aerobic biological organisms in a given water sample to degrade organic matter. It is usually measured in milligrams of oxygen absorbed per litre of sample. As a result, it is used to calculate the volume of organic pollutants in water. Bacteria in water live and multiply when organic matter and oxygen are sufficient for oxidation. Approximately one-third of the food bacteria eaten becomes the organisms' solid organic cell content. The remaining two-thirds were oxidised to carbon dioxide and water by the bacteria's oxidative activity on the oxygen dissolved in the water. The biodegradation of organic matter by microorganisms in the water body receiving the organisms consumes a high amount of oxygen, causing a sharp reduction in the dissolved oxygen from the waste discharge point downstream.

Biological oxygen demand is basically a measure of how much oxygen is needed to extract waste organic matter from water during the decomposition process by aerobic bacteria.
Leaf’s debris, dead plants and animals, animal manure, wastewater treatment plants, and urban storm water runoff are all sources of biological oxygen demand.
BOD reduction is used to assess the efficacy of wastewater treatment plants. The biological oxygen demand (BOD) of wastewater effluents is used to predict the short-term effect on the oxygen levels of the receiving water.