How to deal with printing and dyeing industrial wastewater

The printing and dyeing industry uses a large amount of water, usually 100 to 200 tons of water per 1 t of textile processing. 80% to 90% of them are discharged by printing and dyeing wastewater. Commonly used treatment methods are recycling and harmless treatment.

Recycling: (1) Waste water can be recycled according to the characteristics of water quality, such as bleaching and scouring wastewater and dyeing printing wastewater, the former can be convective washing. Use more water to reduce emissions; (2) lye recycling, usually by evaporation method, such as large amount of lye, can be recovered by three-effect evaporation, small amount of lye, can be recovered by thin film evaporation; (3) dye recovery. If the Shilin dye can be acidified into cryptic acid, it is a colloidal particle. It is suspended in the residual liquid, filtered through a precipitate, and recycled. The harmless treatment can be divided into: (1) physical treatment methods include precipitation method and adsorption method. The precipitation method mainly removes suspended matter in the wastewater; the adsorption method mainly removes dissolved pollutants and decolorization in the wastewater. (2) The chemical treatment method includes a neutralization method, a coagulation method, and an oxidation method. The neutralization method is to adjust the pH in the wastewater, and also to reduce the color of the wastewater; the coagulation method is to remove the disperse dye and the colloidal substance in the waste water; the oxidation method is to oxidize the reducing substance in the waste water to precipitate the sulfur dye and the vat dye. (3) Biological treatment methods include activated sludge, biological turntables, biological drums, and biological contact oxidation methods. In order to improve the quality of the effluent, meet emission standards or recycling requirements. It is often necessary to combine them in several ways.