The initial COD of my sample sewage water is around 170-200 ppm only but the COD of my supposedly treated water goes up to 300 ppm? I've used iron plate electrodes in a bipolar configuration and a constant current supply of 3.3 A.
Some compounds from your WW start to be soluble or they are converted to other compounds that are oxidized during the COD measurement.
regards
G
What are the other chemical characteristics before and after treatment?
What chemical(s) is(are) added before electro-coagulation?
After knowing about such information, someone can answer your question.
Difficult to knwo with so little information. I could imagine that the treatment add either Fe2+ or H2O2 to the water. Both are easy to test for.
Hi, Jefferson,
The most probable possibility is that you added, made or measured something wrong.
Verify your parameters and give us more details.
Good luck.
What method do you use for COD determination? What is the unceratinity of determination?
Best regards
Vit
If you are using an iron electrode you probably have residual ferrous ions in solution . That iron will show up as COD on the test.
To be absolutely sure if your COD test you should use a standard addition method.
That is add a known quantity of COD to your sample from before and and after electrocoagulation and retest. If you do not get the expected results you should question the test method and identify the interference.
Hi guys! I've tried to remove the residual ferrous ions first and tried the COD analysis again. It now resulted to the expected lower COD value. Thank you all for your answers.
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