Dear Nabeel,

The BOD5 test is more than 100 years old. It was derived in the UK to determine the effects of degradable organic matter on the dissolved oxygen of a river (68°F summer water temperature and 5 days the longest time to reach the sea). A “clean” river had a BOD of 2 mg/L and polluted river a BOD >4mg/L. A sewage effluent with a BOD of 20mg/L was acceptable for discharge into a clean river provided that the dilution was greater than eight fold.

Today the BOD test can be used to calculate the designed oxygen requirement for an activated sludge plant. In addition, plotting a BOD/time curves can be used in conjunction with re-aeration and self-purification equations for times series modelling of the likely impacts of discharges on a receiving waterway.

Kind Regards

Michael Lever

In genral, BOD test is used as one the standard in measuring organic pollution, the higher the BOD the higher the pollution,

Regrads

 The engineering community tends to favour COD in their modelling of treatment facilities designed to remove organics. BOD5  (a semi-quantitative test) carried out on raw wastewater serves as an indicator of the biodegradability of the that wastewater. Also, if serial dilutions of the raw wastewater, carried out during the testing procedure yields significantly different results, this may indicate the presence of toxic material in the raw wastewater which should prompt the designer to conduct additional, more sophisticated toxicity tests.

Thank you dear friends, professors and colleagues. But the question is directed towards design purposes not the BOD5 test itself nor about its competence over COD or not. Thank you in advance dear friends. 

Hello Dr. Nabeel

Knowing the BOD5 is also important to evaluate the biodegradability of the wastewater by measuring the BOD/COD ratio, whereby BOD/COD ratio > 0.5 indicates higher biodegradability.

Thanks a lot dear Dr. Haider . I hope to cooperate with you in the future. As we are near and belong to the same governorate (Babylon).