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 recycled and decontaminated by backwashing filters to meet the corresponding standards.
The backwashing filter can recycle the wastewater of the printing and dyeing industry according to the water quality characteristics, such as the separation of bleaching and smelting wastewater and dyeing printing wastewater. The former can be convectively washed, used more than one water to reduce emissions; usually it is recovered by evaporation method, such as alkali. The liquid volume is large, and it can be recovered by three-effect evaporation. The amount of alkali liquid is small, and it can be recovered by evaporation of the film; 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 of the backwashing filter can be divided into a physical method and a chemical method, and the physical treatment method includes a precipitation method and an adsorption method. The precipitation method mainly removes suspended matter in the wastewater; the adsorption method mainly removes dissolved pollutants and discoloration in the wastewater. The chemical treatment methods include 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 dyes and colloidal substances in the wastewater; the oxidation method is to oxidize the reducing substances in the wastewater to precipitate the sulfur dyes and the vat dyes. 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.www.inocofiltration.com