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Biochemical Oxygen Demand - Industrial Waste Water Management

A lot has been written and said about the subject of BOD. But very few know that BOD5 is calculated using simple concentration formulas from laboratory tests. However, before going into the calculation part let us start from the fundamentals of BOD.

Wikipedia defines BOD as follows:

Biochemical oxygen demand or B.O.D. is the amount of disssolved oxygen needed by aerobic biological organisms in a body of water to break down organic material present in a given water sample at certain temperature over a specific time period. The term also refers to a chemical procedure for determining this amount. This is not a precise quantitative test, although it is widely used as an indication of the organic quality of water. The BOD value is most commonly expressed in milligrams of oxygen consumed per litre of sample during 5 days of incubation at 20 °C and is often used as a robust surrogate of the degree of organic pollution of water.

For further reading on the Wikipedia article refer the following link:


The 5-day BOD test determines the oxygen demand of a waste exposed to biological organisms (controlled seed) for an incubation period of five days. Usually this demand is caused by degradation of organics according to the following simplified equation, but reduced inorganics in some industries may also cause demand (Fe2+, S2-, SO32-)

Organic Waste + O2 (D.O.) --------------> CO2 + H2O

A brilliant explanation related to BOD and COD has also been provided in an old thread on "Cheresources" by Milton Beychok one of the administrators of this forum at the following link:


Now coming to the calculation part, the BOD is a calculated value in mg/L based on initial and final concentrations of Dissolved oxygen in the seeded and unseeded water sample. A simple calculation spreadsheet is attached for the purpose of arriving at the BOD5 value based on a known reference.

Would appreciate comments on this blog entry from the readers of "Cheresources"


See attachments in Download section: http://www.cheresour...ter-management/

Qalander (Chem)
Sep 09 2011 01:39 AM
Nice info intiation,usually such abbreviated terms are 'mistaken' and 'less understood' all across the process engineers domain and your effort is commendable indeed.

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