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

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.

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.