Case Study on Decolorization Treatment of Dyeing and Printing Wastewater

       1. The Problem

　　Textile dyeing wastewater is widely recognized in the industry as one of the most challenging types of industrial effluent due to its high organic content, complex composition, intense coloration, and significant variations in water quality. The application of novel dyes and auxiliary chemicals has further increased treatment difficulty. Dyes in the wastewater exist in dissolved, colloidal, and suspended forms. Among them, neutral and reactive dyes exhibit high solubility and remain in the aqueous phase, making them extremely difficult to remove by conventional coagulation methods. Even after biological treatment, the effluent often retains noticeable coloration—typically yellow—and the treatment of high-concentration, recalcitrant organic pollutants remains a significant challenge.

　　2.Client Requirements

　　The client aims to effectively treat high-concentration, recalcitrant organic wastewater, address the issue of colored effluent, ensure compliance with discharge standards, and keep treatment costs within an acceptable range for the facility.

　　3.Treatment Challenges

　　Complex Composition: Textile dyeing wastewater contains a large amount of organic dyes with chromophoric groups, as well as various auxiliaries such as neutral electrolytes, pH adjusters, and surfactants, resulting in highly complex water quality and significant challenges for biodegradation.

　　Difficulty in Dye Removal: Different types of dyes exist in varying states in water, and those with high solubility are particularly difficult to remove using conventional treatment methods.

　　Difficulty in Cost Control: Achieving effective treatment while keeping costs within a reasonable range places high demands on the selection of treatment processes and chemical reagents.

　　4.Treatment Performance

　　With appropriate treatment processes and chemical reagents, excellent decolorization and pollutant removal efficiencies can be achieved. For example, after applying a specific decolorization treatment process, color removal efficiency can exceed 90%, and chemical oxygen demand (COD) removal efficiency can also reach over 90%, enabling the treated wastewater to meet discharge standards.

　　5.Treatment Processes and Water Treatment Chemicals

　　Treatment Process

　　Bar Screen → Equalization Tank → Dissolved Air Flotation (DAF) Tank → Pump → Aerobic Tank → Coagulation/Flocculation Reactor → Sedimentation Tank → Dewatering Area → Standard Effluent Outlet

　　Water Treatment Chemicals

　　     Textile Dyeing Wastewater Decolorizing Agent:This product employs an innovative process that simultaneously achieves decolorization and removal of COD, BOD, ammonia nitrogen, total phosphorus, and other pollutants. Its application is straightforward—simply add the agent during the pretreatment stage, mix thoroughly, and adjust the pH to effectively separate dyes from water, reduce other contaminants, and enhance the biodegradability of the wastewater. Specifically formulated for organic dye-containing wastewater, this chemical delivers rapid and noticeable treatment results, requires low dosage, exhibits strong adaptability, and effectively addresses decolorization while reducing overall treatment costs.

　　Other coagulants, such as ferrous sulfate, aluminum sulfate, and polyaluminum chloride (PAC), can be dosed under specific pH conditions to remove certain pollutants and assist in decolorization. However, the decolorization efficiency of different coagulants varies depending on the type of dye.

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