Brief Introduction
Waste water discharged from printing and dyeing, woolen dyeing and finishing, and silk mills that process cotton, hemp, chemical fibers and their blended products, silk. The fiber type and processing technology are different, and the water volume and water quality of printing and dyeing wastewater are also different. Among them, the amount of wastewater in printing and dyeing plants is relatively large, and each printing and dyeing process 1 ton of textiles consumes 100 to 200 tons of water, of which 80% to 90% is discharged as wastewater. Printing and dyeing wastewater has the characteristics of large water volume, high content of organic pollutants, large alkalinity, and large changes in water quality. It is one of the difficult-to-treat industrial wastewaters. The wastewater contains dyes, slurries, additives, oils, acid and alkali, and fiber impurities. , Sand materials, inorganic salts, etc
source
The four processes of the printing and dyeing process must discharge wastewater. The pretreatment stage (including singeing, desizing, smelting, bleaching, mercerizing, etc.) must discharge desizing wastewater, smelting wastewater, bleaching wastewater and mercerizing wastewater, and discharge from the dyeing process. Dyeing wastewater, the printing process discharges printing wastewater and soap liquid wastewater, and the finishing process discharges the finishing wastewater. Printing and dyeing wastewater is a mixed wastewater of the above types of wastewater, or a comprehensive wastewater other than bleaching wastewater.
classification
7、Finishing process wastewater. It mainly contains fiber scraps, resin, formaldehyde, oil and slurry, with little water. The concentration of wastewater in the wool textile dyeing and finishing plant is high. For every 454kg of washed wool produced, there is about 318t of wastewater. The water quality is brown and colloidal. The organic pollutants in BOD amount to 91-114kg.
Features
The discharge of printing and dyeing wastewater is very large. According to European statistics, the weight ratio of fabric to discharged wastewater is 1:150 to 1:200, while in my country it is about 1:200 to 1:400. my country's textile industry wastewater ranks sixth in the country's industrial wastewater discharge, 80% of which is printing and dyeing wastewater.
The printing and dyeing wastewater contains unreacted dyes, pigments (paints), with a strong color, and unreacted auxiliary agents, as well as the products after the reaction and the fall off on the fabric. More serious are carcinogenic and teratogenic organic compounds, toxic heavy metals and so on.
The combination and properties of various components in wastewater show irregular changes with market changes, seasonal changes, and supply changes.
Printing and dyeing wastewater is one of the more difficult to treat in industrial wastewater. Due to technical and economic reasons, most of the bio-physical treatment methods used can only meet the basic emission requirements. Although there is a slight decrease in chromaticity, organic substances are only decomposed into smaller substances. It is difficult to control and grasp the nature of these decomposition products, and there is no guarantee that they will not cause harm to the environment.
The current treatment method occupies a large area, has a large investment, and the treatment cost is high, so that the production cost remains high. It is estimated that after wastewater treatment reaches the secondary discharge standard, the treatment cost is basically equivalent to the price of urban tap water. If the wastewater reuse requirements are to be met, the treatment cost will be higher, so the actual operation is quite difficult
