What are the technological methods for treating printing and dyeing wastewater with polyaluminium chloride?

In recent years, with the rapid development of the dye industry and the continuous use of various dyes, the number and types of dyes entering the environment have increased day by day. It is reported that for every 1t of dye produced, 2% of the product will be lost with wastewater, and the loss in the printing and dyeing process is even greater, about 10% of the dye used, which seriously pollutes the environment. At present, a typical treatment process has been formed for the treatment of printing and dyeing wastewater, which can be summarized as three-level treatment:

(1) Primary treatment, mainly to remove larger fibers and particles and other easily precipitated impurities, in preparation for subsequent treatment, the treatment equipment is screens, regulating tanks, etc.;

(2) Secondary treatment, to remove most of the pollutants in printing and dyeing wastewater, the typical process is physicochemical method-biological method (anaerobic biological treatment-aerobic biological treatment);

(3) Tertiary treatment (treatment), the main treatment objects are difficult to biodegrade organic matter, microorganisms and other dissolved substances. Sometimes, tertiary treatment is not for discharge, but for direct reuse, with physicochemical method as the main treatment method. In order to better treat printing and dyeing wastewater, the research status of physicochemical method and biological method used for secondary and tertiary treatment is introduced and reviewed respectively.

From the perspective of physical and chemical methods and biological methods, this paper summarizes the research status and new progress of printing and dyeing wastewater treatment methods, introduces examples of various methods for treating printing and dyeing wastewater, and points out the advantages and disadvantages of each method and technical key points. Finally, it looks forward to the development direction of printing and dyeing wastewater treatment technology, strives to adjust the industrial structure of the printing and dyeing industry, strengthens the transformation of printing and dyeing equipment and the development and application of new printing and dyeing processes and technologies, actively promotes clean production, carries out comprehensive resource utilization, adopts low-waste and no-waste processes, equipment and perfect management, reduces the generation of wastewater and pollutants from the source, and completely solves the problem of printing and dyeing wastewater pollution.