[MoiraKarin]

Hi everyone  ,
We ar doing experiments on efluents analysis, decreasing the cod of samples using electrolisis. My concern is the interference of ammonia. When we determine COD (Chemical Oxygen Demand), we used Potassium Dichromate  (with  the Hanna set) as oxidizing agent and ammonia will react to dichromate and it cause serious error. i looked up the Standard method for the examination of water and wastewater, but doesnt say to much about how to remove the interference. We ar sure the ammonia is the cause of interference because we did the same  process with water adding the same quantity of savery and let it the same time in eletrolisis and the result shown cod of 2000 ppm in average.
Could any of you recomend me any advice, document or website that I will able to read the correct cod of the samples

[MoiraKarin]

Hi everyone  ,
We ar doing experiments on efluents analysis, decreasing the cod of samples using electrolisis. My concern is the interference of ammonia. When we determine COD (Chemical Oxygen Demand), we used Potassium Dichromate  (with  the Hanna set) as oxidizing agent and ammonia will react to dichromate and it cause serious error. i looked up the Standard method for the examination of water and wastewater, but doesnt say to much about how to remove the interference. We ar not sure the ammonia is the cause of interference because we did the same  process with water adding the same quantity of savery and let it the same time in eletrolisis and the result shown cod of 2000 ppm in average.
Could any of you recomend me any advice, document or website that I will able to read the correct cod of the samples

[eugenedakin]

Hello MoiraKarin,

Good question.

The reason for running a Chemical Oxygen Demand (COD) test is to determine an approximate oxygen requirement to degrade a water/waste stream. This is only an estimate, and the test will definitely be different that the Biological Oxygen Demand (BOD) test that requires much more time to complete. One possible method to determine the interference is to perform a series of ammonia spikes with BOD tests and compare the results to COD tests.

Since each water stream is different, you will need to make your own correction curve.

I hope this helps,

Eugene