What is the typical range of biochemical oxygen demand (BOD) in wastewater?

• A. 160-280 mg/L
• B. 50-100 mg/L
• C. 400-600 mg/L
• D. 5-15 mg/L

Answer: (A)

Biochemical oxygen demand tells you how much oxygen the organic material in wastewater will consume as microbes break it down—measured as BOD over a set period (usually 5 days). It’s a measure of the wastewater’s strength: higher BOD means more available organic matter and a greater oxygen demand for treatment.

Typical municipal wastewater before treatment has a BOD in the hundreds of mg/L range, commonly around 150–300 mg/L. The range 160–280 mg/L fits that common strength of influent wastewater, making it the best representation among the options.

The other ranges don’t match what’s usually found in untreated municipal wastewater: 5–15 mg/L would be a highly treated effluent value, not influent; 50–100 mg/L is on the low side for typical influent; 400–600 mg/L would be unusually strong for standard municipal wastewater.