Treatment of printing and dyeing wastewater

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The color of the raw water used in our company’s printing and dyeing processes is grayish-black, with a pH level of around 9.5. Ferrous sulfate solution is added to the regulation tank at a concentration of 2.2 parts per thousand, in order to adjust the pH level and carry out basic pre-treatment. Ferric chloride solution is added to the secondary sedimentation tank at a concentration of 1.6 parts per thousand; calcium hypochlorite is then added at a concentration of 4 parts per thousand. These three chemicals are primarily used in the treatment process, and all parameters of the treated water meet the required standards. However, the chloride ion concentration in the raw water is 1,000, while it rises to 4,000 in the treated water, which is significantly above the allowable levels. I’m not sure what the cause of this is. Could you tell me where the problem lies? Can I replace the chemicals mentioned above with polyferric sulfate?