BOD of waste water is estimated by measuring the amount of which of the following option ?

Oxygen consumption.

The Biochemical Oxygen Demand (BOD) test is a measure of the amount of dissolved oxygen consumed by microorganisms in a water sample over a specific period. It is used as an indicator of organic pollution in water bodies. Organic pollutants, such as sewage, agricultural runoff, or industrial waste, introduce high levels of organic matter into the water. When these organic substances are decomposed by bacteria and other microorganisms, they consume oxygen from the water.

If the BOD of a water sample is high, it means that there is a significant amount of organic pollution present, requiring a higher rate of oxygen uptake by microorganisms to decompose the organic matter. The higher the BOD value, the greater the oxygen demand, indicating a higher level of pollution in the water.