The printing and dyeing industry consumes a large amount of water, usually 100-200 tons per ton of textile processed, of which 80% -90% is discharged as printing and dyeing wastewater. Common governance methods include recycling and harmless treatment.

Recycling and reuse: (1) Wastewater can be recycled and reused according to its water quality characteristics, such as the separation of bleaching and refining wastewater and dyeing and printing wastewater. The former can be washed by convection and reused as one water to reduce emissions.

Harmless treatment can be divided into: (1) physical treatment methods such as precipitation and adsorption. The sedimentation method is mainly used to remove suspended solids in wastewater; The adsorption method is mainly used to remove dissolved pollutants and decolorize wastewater. (2) Chemical treatment methods include neutralization, coagulation, and oxidation. The neutralization method is used to regulate the acidity and alkalinity of wastewater, and can also reduce the chromaticity of wastewater; The coagulation method is used to remove dispersed dyes and colloidal substances from wastewater; The oxidation method involves oxidizing reducing substances in wastewater to precipitate sulfide dyes and reducing dyes. (3) Biological treatment methods include activated sludge, biological turntable, biological drum, and biological contact oxidation method. In order to improve the effluent quality, meet discharge standards or recycling requirements, it is often necessary to adopt several methods for joint treatment.