How to treat printing and dyeing wastewater by chemical method

Chemical processes commonly used in printing and dyeing wastewater treatment are as follows:

Neutralization: In printing and dyeing wastewater, this method can only adjust the PH value of wastewater, but can't remove pollutants in wastewater. When biological treatment is adopted, the PH value should be controlled between 6 and 9 before entering the biological treatment equipment.

Coagulation method: a large number of fine particles such as dyes and detergents in wastewater are combined into large particles and removed by chemical agents. Coagulants used in printing and dyeing wastewater treatment include basic aluminum chloride, polyacrylamide, aluminum sulfate, alum and ferric chloride.

Air flotation: printing and dyeing wastewater contains a large number of organic colloidal particles in the form of various oils and fats. These impurities agglomerate to form flocs with small particles, light weight and poor sedimentation performance, which can be separated by air flotation. At present, in the treatment of printing and dyeing wastewater, air flotation tends to replace sedimentation, which is the main treatment method of printing and dyeing wastewater. Pressurized dissolved air flotation is mainly used for air flotation treatment of printing and dyeing wastewater.

Electrolysis: this method has good decoloration effect. For direct dyes, mordant dyes, sulfur dyes, disperse dyes and other printing and dyeing wastewater, the decoloration rate is above nine layers, and for acid dye wastewater, the decoloration rate is above 70%. Disadvantages of this method: large power consumption, large electrode material consumption, DC power supply, suitable for treating a small amount of wastewater.