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Doctors Medicines MCQs Q&A

Increased biological oxygen demand is an indication of 1. Low microbial contamination. 2. Absence of microbial pollution. 3. High level of microbial contamination. Which of the above statements is/are correct?

Increased biological oxygen demand is an indication of 1. Low microbial contamination. 2. Absence of microbial pollution. 3. High level of microbial contamination. Which of the above statements is/are correct? Correct Answer 3 only

Biological Oxygen Demand (BOD):

  • If too much of organic matter is added to water, all the available oxygen will be used up
  • This causes oxygen-dependent aquatic life to die
  • Thus, anaerobic bacteria (which do not require oxygen) begin to break down the organic waste and produce chemicals that have a foul smell and are harmful to human health
  • Aerobic (oxygen requiring) bacteria will use more oxygen and degrade these organic wastes and make the water more depleted in dissolved oxygen
  • Thus, the amount of oxygen required by bacteria to break down the organic matter present in a certain volume of a sample of water is called Biochemical Oxygen Demand (BOD)
  • The amount of BOD in the water is a measure of the amount of organic material in the water, in terms of how much oxygen will be required to break it down biologically
  • Thus, BOD in river water increases when sewage gets mixed with river water

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