I want to check the chemical oxygen demand of a sample in which inoculum was added previously. I am wondering if the presence of bacteria would cause any issue with COD? I assume that bacterial biomass upon digestion may release organic chemicals that could contribute to COD.
Also, I doubt if I centrifuge, it may affect the COD itself because some chemicals could become part of the bacterial pellet.
Thanks
No effect and BOD test needs the presence of bacteria seed in order to consume the organic materials and oxygen available in the sample.
The presence of inoculum can indeed interfere with the result of the sample COD. For this interference check, you can add the same amount of inoculum to a sample with the known COD. I suggest performing the total COD (with inoculum), COD of the centrifuged sample and COD of the filtered sample (3 micrometers) to evaluate which of these results best represent the data.
Absolutely no effect.
COD is always measured in the présence of bacteria.
In fact, COD measures the oxygen being consumed during the oxidation of oxidizable organic matter in presence of a strong oxidizing agent.
COD is also generally used to indirectly determine the amount of organic compounds in aquatic systems. High COD indicates the presence of all forms of organic matter, both biodegradable and nonbiodegradable and hence the degree of pollution in waters. This makes COD useful as an indicator of organic pollution in surface waters. In other words, COD can also be used as an alternative to BOD.
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