Dissolved oxygen in the anoxic tank
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The dissolved oxygen level in the anoxic tank is 0, while it is 4 at the inlet of the aerobic tank and 4.8 at its outlet. It seems that the values for the anoxic tank are incorrect. Are there any substances that could affect the dissolved oxygen levels in the anoxic tank?
What method did you use for the test? Could you explain in detail your testing process?
Measurement errors can be ruled out; if the dissolved oxygen meter itself is accurate, it will not affect the readings.
Iodometry is used; I’m not entirely sure about the specific steps, but this has always been the way it’s done, and it has been tested before, so there shouldn’t be any issues with the procedures.
If the testing method is correct, there should be a high amount of reducing substances in the influent water; I’m not sure whether there is any backflow.
The key lies in the instruments and the testing points. However, DO is not measured using a dedicated DO instrument; other measurement methods have to be employed.
Does the anoxic tank have an odor? If there is dissolved oxygen, then it’s fine.
It’s also possible to measure the pH; check whether the oxygen levels at the inlet and outlet are lower, as this would indicate low dissolved oxygen levels as well.
Check the color of the sludge; if it is dark or even black, it indicates low dissolved oxygen levels； If it is close to the sludge in the aerobic tank, it indicates that the dissolved oxygen measurement is inaccurate.