Printing and dyeing wastewater is the wastewater discharged from printing and dyeing factories that mainly process cotton, linen, chemical fibers and their blended products. The amount of printing and dyeing wastewater is large, and the water consumption of 1 ton of textile is 100~200 tons per printing and dyeing processing, of which 80~90% becomes wastewater. Wastewater contains dyes, slurries, additives, oils, acids and alkalis, fiber impurities, sand substances, inorganic salts, etc., and nitro and amine compounds and heavy metal elements such as copper, chromium, zinc, arsenic and other heavy metal elements in the dye structure have greater biological toxicity and seriously pollute the environment. Textile printing and dyeing wastewater has the characteristics of large water volume, high organic pollutant content, large alkalinity, and large changes in water quality, and is one of the industrial wastewater that is difficult to treat.

1. Overview of printing and dyeing wastewater:

Printing and dyeing wastewater is the wastewater discharged from printing and dyeing factories that mainly process cotton, linen, chemical fibers and their blended products. The amount of printing and dyeing wastewater is large, and the water consumption of 1 ton of textile is 100~200 tons per printing and dyeing processing, of which 80~90% becomes wastewater. Wastewater contains dyes, slurries, additives, oils, acids and alkalis, fiber impurities, sand substances, inorganic salts, etc., and nitro and amine compounds and heavy metal elements such as copper, chromium, zinc, arsenic and other heavy metal elements in the dye structure have greater biological toxicity and seriously pollute the environment. Textile printing and dyeing wastewater has the characteristics of large water volume, high organic pollutant content, large alkalinity, and large changes in water quality, and is one of the industrial wastewater that is difficult to treat.

2. the treatment method:

At present, the main methods of printing and dyeing wastewater treatment include physicochemical method, biochemical method, chemical method and the treatment method of several process combinations, and the pretreatment in wastewater treatment is mainly to improve the water quality of wastewater, remove suspended solids and impurities that can be directly settled, adjust the quality and quantity of wastewater, reduce the temperature of wastewater, etc., improve the overall effect of wastewater treatment, and ensure the stability of the whole treatment system, so pretreatment has an extremely important position in the treatment of printing and dyeing wastewater. Biochemical adopts hydrolysis acidification combined with biological contact oxidation technology, and enters the quartz sand filter tank and oxidation pond after passing through the secondary sedimentation tank, and discharges up to the standard.

3. Examples of process combinations:

Hydrolysis acidification + aerobic biochemistry + MBR+RO process for reuse

4. the process characteristics:

（1）The effluent quality is better, and the COD, color, and salt are significantly reduced
（2）The effluent quality is stable and the amount of sludge discharge is small
（3） After MBR effluent, more than 35% of reclaimed water can be reused into the RO system
（4） The reclaimed water is of excellent quality and can be used in any process in printing and dyeing, which reduces the operating cost of the enterprise