BOD: Biochemical oxygen demand (BOD) in water refers to the amount of dissolved oxygen required by microorganisms to decompose organic matter present in water. This is a measure of the severity of pollution. BOD measures the amount of organic matter present in water. The lower the BOD in the water, the cleaner it will be. BOD in safe drinking water should be zero. If BOD is high, the need for treatment will also be high. BOD is often used in wastewater treatment plants as an index of the degree of organic pollution in water. The BOD value of moderately polluted rivers can be in the range of 2 to 8 mg/L. When the BOD value exceeds 8 mg/L, rivers can be considered seriously polluted (A B .