Maybe this questions already answered in others forum. But I would like to know
How is it possible that BOD value higher than COD?
For COD we used dichromate reagent, and for BOD measurement we used respirometer-manometric method. We always pay the details about each measurement (like for COD, exact sample volume, digest, and measure; and for BOD using nitrification inhibitor to prevent nitrifying bacteria, incubate 5 days at 20±1°C). But from 5 samples in the batch, always 1-2 samples that got BOD value higher than COD.
Others forum stated that it is possible because the nitrogen/sulfur substances in the sample too high so that the dichromate will not oxidized in COD and BOD value will be higher, but in BOD we already used nitrification inhibitor. Also,
Is there any research/paper that stated the possibility of BOD value higher than COD?
Typically, COD is always higher than BOD because
COD= the amount of organic + inorganic materials in the sample while;
BOD = the amount of organic material only in a sample.
However, In some cases, it is possible for the BOD value to be higher than the COD value. This situation may arise due to the nature of the organic matter present in the water sample.
A higher BOD value than COD may indicate that the organic matter in the water is more biodegradable, and microorganisms are actively breaking it down.
In special cases ammonia/organic matter is higher and BOD is used to oxidize the natural organic matter and organic waste in the water. these bacteria use oxygen to convert ammonia into nitrate. If the wastewater contains high levels of ammonia, the nitrifying bacteria consume a significant amount of oxygen, which can lead to an increase in BOD relative to COD
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