BOD of Abattoir Effluent

Average biochemical oxygen demand (BOD) of effluent of an abattoir is:

Correct Answer: 1500–2000 mg/litre

The average Biochemical Oxygen Demand (BOD) of abattoir effluent is 1500–2000 mg/litre, which is significantly higher than domestic sewage.

Why BOD is High in Abattoir Effluent?

• Abattoir wastewater contains blood, gut contents, fat, manure, and tissue fragments — all highly organic.
• High organic load = high BOD = more oxygen consumed by microbes to decompose organic matter.

BOD Reduction by Treatment

• Primary treatment (sedimentation): reduces BOD by 75–80%.
• Biological filters (secondary treatment): reduces BOD by 95%.

Comparison

• Domestic sewage BOD: ~300 mg/litre.
• Abattoir effluent BOD: 1500–2000 mg/litre — 5–7x higher.
• This is why abattoirs require dedicated, multi-stage effluent treatment plants before discharge.