Why Does COD Increase After Wastewater Ozone Treatment?

The main reasons for the increase in COD after ozone treatment include:

First, the mechanism of ozone's action: Ozone can decompose large molecular groups, making some previously undetectable substances visible. Therefore, in the initial stage, ozone primarily acts by opening rings and breaking chains, which leads to a temporary increase in COD.

Second, the oxidation of recalcitrant substances: Ozone treatment can partially oxidize some recalcitrant organic compounds, making them more readily oxidized by potassium dichromate, thus increasing COD.