What are the control issues of dissolved oxygen in the sewage treatment process?

Summary of dissolved oxygen control issues in sewage treatment process

There is a close relationship between dissolved oxygen and sludge concentration, with high activated sludge concentration having a significantly higher demand for dissolved oxygen than low activated sludge concentration; The dissolved oxygen is related to the amount of organic matter in the raw water. Specifically, the more organic matter there is in the raw water, the more dissolved oxygen microorganisms need to consume to metabolize and decompose these organic matter, and vice versa; Dissolved oxygen is also related to some special components in the raw water, such as the presence of detergents in the water, which creates a barrier layer at the liquid level of the aeration tank to isolate the atmosphere and affect the improvement of aeration efficiency.
Question 1:
The sewage plant I operate is a comprehensive industrial wastewater treatment plant. At present, there are a lot of foam in the biochemical zone. The conductivity has increased from the original 3ms/cm to 8ms/cm, and the SVI value is 200. The dissolved oxygen has not been able to go up, only 0.6mg/l, and toxic substances are suspected to enter. What should I do in the current situation?
Reply:
1. I don't know what the color of foam is: if it is viscous white and the stacking height is obvious, it is necessary to consider that the influent load is too high (for example, the COD influent is too high), so it is necessary to investigate the organic content of the influent before making a judgment.
2. What you said is that the inability to increase dissolved oxygen is inversely related to the suspected entry of toxic substances. In other words, if toxic substances enter, dissolved oxygen can actually increase.
Question 2:
Why does DO decrease when the influent BODCOD increases while the MLSS aeration air volume remains constant? MLSS is controlled by sludge discharge to keep it constant.
Reply:
1. The increase in organic matter concentration enhances the removal ability of microorganisms while maintaining the same removal rate, and naturally requires more DO consumption when dealing with newly added organic matter.
2. There is a concept to be mentioned here, which is the same MLLSS, but the activity of activated sludge varies at different stages. For example, there is a difference in workload between 10 elderly people and 10 young people. Naturally, 10 young people have more food to eat than 10 elderly people, which means that DO will be consumed more.