January 28, 2022

Printing and dyeing wastewater

The printing and dyeing industry is a major emitter of industrial wastewater. According to incomplete statistics, the daily discharge of printing and dyeing wastewater in China is 3×10 6 to 4×10 6 m 3 . Printing and dyeing wastewater has the characteristics of large amount of water, high content of organic pollutants, deep color, large alkali, and large variation in water quality, and it is a difficult-to-treat industrial wastewater. In recent years, due to the development of chemical fiber fabrics, the rise of artificial silk, and advances in printing and dyeing finishing technologies, PVA slurries, rayon-based hydrolysates (mainly phthalates) and new types of additives are difficult to biodegrade organic materials. A large amount of wastewater has entered the printing and dyeing wastewater, its COD concentration has also increased from the original hundreds of mg/L to 2000 ~ 3000mg/L, so that the original biological treatment system COD removal rate dropped from 70% to 50% or even lower. The traditional biological treatment process has been seriously challenged; the COD removal rate of such printing and dyeing wastewater by traditional chemical precipitation and air flotation is only about 30%. Therefore, the development of economical and effective printing and dyeing wastewater treatment technology has increasingly become a topic of concern for the environmental protection industry today. ?

All the four processes of printing and dyeing must discharge the waste water. The pretreatment stage (including singeing, desizing, scouring, bleaching, mercerizing, etc.) must be used to discharge desizing, scouring, bleaching, and mercerizing wastewater, and the dyeing process should be discharged. Dyeing wastewater, printing process discharge printing waste water and soap liquid waste, finishing process discharges waste water. Printing and dyeing wastewater is the mixed wastewater of the above types of wastewater, or the integrated wastewater other than bleached wastewater. ?

The quality of printing and dyeing wastewater varies depending on the type of fiber used and the processing technology, and the composition of pollutants varies greatly. The general printing and dyeing wastewater pH is 6-10, CODCr is 400-10001000mg/L, BOD5 is 100-400 mg/L, SS is 100-200 mg/L, color is 100-400 times. However, when the printing and dyeing process and the type of fiber used and the processing technology are changed, the quality of the wastewater will be greatly changed.

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