Question

BOD (biological oxygen demand) is

• A. Amount of oxygen consumed by microorganisms for decaying organic matter per unit volume of water
• B. Amount of $CO$ consumed by microorganisms per unit of sewage water
• C. Amount of oxygen required by aquatic plants for survival
• D. None of the above

Answer 1

The correct option is A Amount of oxygen consumed by microorganisms for decaying organic matter per unit volume of water

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.
Clean water would have a BOD value less than or equal to 5 ppm whereas highly polluted water could have a BOD value of 17 ppm or more. Therefore, pure water has less BOD values and contaminated water has high BOD value.