Biochemical Oxygen Demand (BOD) measures the amount of oxygen required by

• A. The amount of oxygen needed by aerobic organisms
• B. The amount of oxygen used by chemical oxidation
• C. The amount of carbon dioxide produced
• D. The amount of solids in water

Answer: (A)

Biochemical Oxygen Demand measures the amount of oxygen needed by aerobic microorganisms to biologically oxidize organic matter in water. This reflects how much oxygen will be consumed as these microbes break down waste, indicating the potential for oxygen depletion in streams or effluent-receiving waters. The standard test estimates this demand over a fixed period, usually five days at 20°C, to compare pollution levels and treatment effectiveness. Higher BOD means more biodegradable organic material and a greater risk of lowering dissolved oxygen for aquatic life. This concept differs from chemical oxidation (which is COD), carbon dioxide production, or solids content, which do not quantify the biological oxygen requirement of microorganisms.