ADLib Glossary (B)

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Biochemical Oxygen Demand - Definition

This is a parameter used to quantify the risk of causing pollution from organic wastes. BOD is a measure, in mg/l, of the amount of oxygen needed by micro-organisms to break down the organic matter. It is defined as the amount of oxygen used by micro-organisms per unit volume of water at a given temperature, for a given time. The table below shows typical BOD levels for common agricultural substances with polluting potential.

WASTE TYPE

Typical BOD LEVEL Mg/l

Treated Domestic Sewage

40

Raw Domestic Sewage

350

Vegetable Washings

2000

Dirty Water

1500

Liquid Waste from Slurry Stores

3500

Liquid Sewage Sludge

15000

Cattle Slurry

15000

Pig Slurry

25000

Brewer's Grain Effluent

40000

Silage Effluent

55000

Milk

140000

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