Printing and dyeing industry uses a large amount of water.Usually,the water consumption of 1 ton of textile for each printing and dyeing process is 100 ~ 200 tons, of which 80% of the dyeing wastewater discharged. Commonly used printing and dyeing wastewater treatment methods are recycling and harmless treatment.

Recycling is divided into three aspects:

1. The wastewater can be recycled according to the characteristics of water quality, such as bleaching and cooking wastewater and dyeing printing wastewater can be recycled separately, the former can be used for convection washing.

2. The recovery and utilization of alkali liquor is usually recovered by evaporation method. If the amount of alkali liquor is large, it can be recovered by evaporation. The amount of alkali liquor is small and can be recovered by evaporation of film.

3. The recovery and utilization of dyestuffs, such as the acidizing of the sulphide acid, colloidal particles, suspended in the residual solution, and recovery and utilization after precipitation and filtration.

 

There are three different methods for the innocuous treatment of printing and dyeing wastewater:

1. Physical treatment including precipitation and adsorption, and so on. The precipitation method is mainly used to remove the suspended matter in the wastewater, and the adsorption method is mainly used to remove the dissolved pollutants and decolorization.

2. Chemical treatment including neutralization, coagulation and oxidation, etc. The neutralization method can adjust the PH of wastewater and reduce the chroma of wastewater。The coagulation method is to remove disperse dyes and colloids from wastewater.The oxidation method is to oxidize the reducing substances in waste water and precipitate vulcanized dyes and vat dyes.

3. Biological treatment including activated sludge, biological turntable, biological drum and biological contact oxidation, etc. In order to improve the effluent quality and meet the discharge standards or recovery requirements, it is often necessary to adopt several methods of combined treatment.

Related reading:High Quality Wastewater Treatment