I would like some advice on the sequence of coagulation, air flotation, and oxidation
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What is the typical order of air flotation, coagulation, and oxidation (such as chemical dosing or ozone application)? As for specific water samples, it’s dyeing wastewater, with a COD of around 1000 and SS of 500. An experienced professional with over a decade of experience told me that the sequence should be flotation + oxidation + coagulation, but in that case, pH adjustment becomes quite complicated. Of course, the effect is the main criterion; once the effect is satisfactory, then we can consider the order of processes. I think a combination of coagulation, air flotation, and oxidation is a good option – less chemicals are needed, but I’m not sure about the effectiveness in that case.
The recommended methods are air flotation, coagulation, and oxidation. Flotation can remove some of the oils, resulting in a partial reduction of COD. Coagulation eliminates SS and COD, while oxidation removes the remaining COD (usually less than 150).
If there is little oil in the water and oil removal is not necessary, it is recommended to use coagulation + ozone + air flotation. Typical dyeing wastewater contains relatively little oil, so there is no need for special oil removal procedures. The SS level in such water is high, and coagulation can help remove a significant amount of suspended solids; as a result, the SS level in the water after coagulation can be reduced to below 10 PPM, and the color intensity is also significantly reduced ； This can reduce the load on the ozone stage, and the effective removal of SS and coloration lays a good foundation for improving the quality of water treated with ozone ； Finally, air flotation treatment is carried out to remove the SS generated in the ozone stage on a selective basis. Generally, the COD removal rate in the coagulation stage is between 25–50%, while it is between 10–60% in the ozone stage (the removal efficiency varies depending on the quality of water). The removal rate in the flotation stage is between 10–20% (flotation can be omitted if the ozone treatment is effective enough). Specific removal effects are recommended to be tested experimentally in order to obtain more accurate data.