YES, it is possible.

REASON: the COD is not formed by organic carbon only.

Best regards

Vit

Since your question is made in a project on wet air oxidation I assume the treatment you have done is oxidation. Then another reason is that oxidation of organic matter can occur without mineralisation. Thus oxidation initially decreases COD but makes no difference for DOC as organic matter is just changed to contain more oxidised functinal groups (adding hydroxy, keto and carboxyl groups). 

Dear All,

I appreciate your efforts in explaining. My experimental results are in agreement with the explanation you people have given. Although I am very confused about the terms degradation, oxidation, reduction and mineralisation. Can anyone explain about these? 

Thanks & Regards,

Arun

Both COD and TOC are based on the same reaction, the oxidation of organic matter to CO2 . The former measures the amount of O2 needed and the latter the amount of CO2 - C produced. Although the concentration values are not equal, the removal efficiencies should be the same for full mineralisation. Take for example 1 mM of hexose (180 mg/L) demands 192 mg COD/L (1.066 g O/g hx), and 72 mg TOC/L (0.4 gC/ghx). A 50% oxidation to CO2 (mineralisation) will leave in solution 90 mg hx/L (96 mgCOD/L and 36 mg TOC/L) all at 50% of initial value. COD does not measure NH4 oxidation to NOx. so it is not included in this balance. But if oxidation does not end up in mineralisation, then the removal efficiencies are different as Henrik Andersen commented.

Thank you very much Prof. Oscar Monroy. Your answer to this question is well explained . I appreciate the example .

Regards,

Arun