WEF Discussion Forums
Biological Nutrient Removal
Nirtification effect on BOD analysis
I wish to find about about the nitrification effect on BOD analysis.
iN the test method used in our department it is stated that the BOD
value calculated is a total sum of carbonaceous dan nitrogenaceous.
My concern is is this value calculated true according to defination of BOD?
How mandatory in nitrification inhibator? If i use nitrification
inhibitor does that mean i should use the term CBOD instead of BOD?
Please enlighten me on the matter
BOD is usually considered to be the oxygen utilized for biochemical degradation of organic (carbonaceous) material. However, inorganic material including reduced nitrogen compounds also exert demand (nitrogenous) causing interferences. When a nitrification inhibitor is used in the 5-day BOD test to eliminate interference caused by nitrification, the results should be reported as CBOD5. In practice, CBOD5 and BOD5 may not be different. However, if reporting of CBOD5 is required, then use of the inhibitor should be considered mandatory.
Gunalan, I'm not sure where you're located. Your regulatory authority likely has specified you to run BOD, and you'd have to get your permit modified to analyze and report CBOD.
Since BOD measures DO depletion, it is a report of the amount of organic material consumed, along with nitrification. For most monitoring, the amount of nitrification is negligible.
The quickest way you can measure the impact of nitrification in your case, would be to run BODs and CBOD's using Hach's powder pillows. To run CBOD, you just add an additional powder pilllow for the inhibitor.
We used to operate a wastewater lagoon with a long HRT-~30 days. With that long a hold up time, nitrification had a significant impact on the BOD, and we changed our permit to report CBOD.
Key point for us, with the excessive HRT, our fecal coliforms died off naturally and we were able to meet our fecal coliform limit without disinfection. Because we didn't disinfect the effluent, our BOD samples contained a high proportion of nitrifying bacteria which skewed our BOD results high.
If you are disinfecting your effluent, and then seeding your samples with a raw sewage sample, I would not expect nitrification to be a significant factor in your results.