Why the COD is within norms and BOD out of norms ? 2

[RuwanR]

The norm for COD is 250 mg/l and the actual value is 45 mg/l.The norm for BOD is 30 mg/l ,actual is 40 mg/l per day and 90 mg/l for 5 days. What is the reason for this relative to a waste water treatment plant ?

 

[moltenmetal]

Incorrect testing. There is no way that the BOD can be greater than the COD, ever. It is very possible for the BOD to be lower than the COD- in fact the BOD can be zero and the COD very high if all the species in the water are toxic to organisms!

 

[bimr]

Probably an error of some sort. The BOD procedure is more difficult than the procedure to determine the COD.

Some compounds are not biodegradable, but will chemically oxidized. These compounds will show a high COD and zero BOD.