What is the maximum CBOD concentration allowed in a Type B dispersal bed leachate?

• A. 5 mg/L
• B. 10 mg/L
• C. 15 mg/L
• D. 20 mg/L

Answer: (B)

CBOD measures how much oxygen will be consumed by biodegradable carbon in the leachate as it degrades in the soil. In a Type B dispersal bed, the design sets a maximum CBOD concentration to protect the soil treatment zone and nearby groundwater from excessive oxygen demand. Keeping CBOD at or below 10 mg/L ensures the soil can adequately treat the leachate without tipping into oxygen-starved, anaerobic conditions that could reduce treatment effectiveness, cause odors, or impact groundwater quality. Higher values (like 15 or 20 mg/L) would impose a greater oxygen demand than the soil can reliably handle, while a value as low as 5 mg/L would be more protective than the standard requires. So, 10 mg/L is the appropriate limit.