Which parameter measures the oxygen required to break down the organic material in a given volume of water through aerobic biological activity?

• A. Chlorination
• B. Bulking
• C. CBOD
• D. BOD

Answer: (D)

Biochemical Oxygen Demand measures the amount of dissolved oxygen that aerobic microorganisms need to break down organic material in a given volume of water. It’s typically assessed as BOD5, the oxygen consumed over five days at 20°C, and it reflects how much organic pollution is present and how much oxygen will be used if the water is discharged into a natural body of water. A higher BOD means more organic matter and a greater potential for oxygen depletion, while a lower BOD indicates cleaner water. CBOD is a related measure focusing specifically on the carbonaceous portion of the demand, often with inhibitors to isolate that factor. Chlorination is a disinfection process, and bulking is a sludge problem, neither of which measure oxygen demand.