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

(2) Alkali recovery and utilization usually use the evaporation method. If the amount of alkali is large, it can be recovered by three effect evaporation. If the amount of alkali is small, it can be recovered by thin film evaporation;

(3) Dye recycling. Like Shilin dyes, they can be acidified to form cryptic acid, which forms colloidal particles. Suspended in residual liquid, recovered and reused after sedimentation and filtration.

The harmless treatment of printing and dyeing industry wastewater can be divided into:

(1) There are physical treatment methods such as precipitation and adsorption. The sedimentation method mainly removes suspended solids from wastewater; The adsorption method is mainly used to remove dissolved pollutants and decolorize printing and dyeing wastewater.

(2) Chemical treatment methods include neutralization, coagulation, and oxidation. The neutralization method is 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 and reducing dyes.

(3) Biological treatment methods include activated sludge, biological rotary table, biological rotary drum, and biological contact oxidation. In order to improve the effluent quality, meet discharge standards or recovery requirements. Multiple methods are often required for joint processing.