Biochemical oxygen demand (BOD) is defined as the amount of oxygen required by the bacteria to decompose the organic.

matter present in the certain volume of sample water.

Higher the BOD of water highly polluted is the water. Lesser the BOD of water less polluted is the water.

Drinking water have BOD of the range of less than 5ppm and highly polluted water have BOD of the value of 17ppm or more.