Fenton reaction tank and related reagent dosing

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Hello everyone. I am currently carrying out adjustments related to the Fenton process for treating chemical industry wastewater. The current flow rate is 20 m³/h, with a COD level of 10,500; the COD level in the treated water is 8,700. I have some questions: 1. Regarding the order in which ferrous sulfate and hydrogen peroxide should be added – some say they should be added simultaneously, while others suggest adding ferrous sulfate first and then hydrogen peroxide after about ten minutes. What is the difference between these approaches? During our testing, we first added hydrogen peroxide to the wastewater, with no obvious reaction occurring; then we gradually added ferrous sulfate, and the water sample immediately reacted – it turned light red first, and as more ferrous sulfate was added, the red color became increasingly intense, likely due to a more vigorous reaction. Continuous aeration for stirring was necessary, and it’s unclear how long stirring should continue. In other words, how long does it take for the Fenton reaction to complete? How long does it take for the hydrogen peroxide to be depleted so as not to affect subsequent COD measurements? (The current color of the water is dark red.) 2. The Fenton tank has dimensions of 4mX2mX3m, with a total of 4 compartments; after adding the chemical, should the color of the water be the same in all 4 compartments, or should the color be darker in the front compartments and lighter in the rear compartments for better results? 3. The most important factors are the amounts of hydrogen peroxide and ferrous sulfate to be added. Given an current flow rate of 20 m³/h and a COD level of 10,500, how should the amounts of these two chemicals be calculated? If a pilot test is conducted, should the dosage of chemicals be determined based on the COD removal rate or some other indicator? 4. In the Fenton reaction, the pH level needs to be maintained between 3 and 5. What can be used to adjust this pH value? Currently, there is no equipment in this project for adjusting pH; so how can the pH of the incoming water be adjusted? Could ferrous sulfate be used for that purpose? (I’m highly skeptical about this; moreover, there are many drawbacks to using more of these two medications.) There are quite a few issues, so I hope an expert can provide a detailed explanation. Thank you in advance! !