Printing and dyeing wastewater is the wastewater from the printing and dyeing plants which mainly process cotton, hemp, chemical fiber and their blended products. The amount of printing and dyeing wastewater is large, and every 1 ton of textile waste water is 100 ~ 200 tons, of which 80 ~ 90% becomes wastewater.
Characteristics of wastewater
Printing and dyeing printing wastewater is one of the more difficult to treat industrial wastewater, it has the characteristics of high COD concentration, high color, high salt content, difficult biodegradation of organic matter and large variation of water quality and quantity with time (intermittent discharge of sewage) , the treatment of printing and dyeing wastewater is outstanding chroma and the removal of refractory organic matter.
Method
The treatment of printing and dyeing wastewater usually adopts hydrolytic acidification-biological contact oxidation-biological carbon-based treatment process, in recent years, this treatment process is used in printing and dyeing wastewater treatment, more mature process. The aim of hydrolytic acidification is to improve the biodegradability and b/C value of some macromolecular substances and insoluble substances in printing and dyeing wastewater by hydrolytic acidification, which can be degraded into small molecular substances and soluble substances, to create conditions for subsequent aerobic biochemical treatment. At the same time, all the excess sludge from aerobic biochemical treatment is returned to anaerobic biochemical stage by sedimentation tank, and then anaerobic digestion is carried out to reduce the discharge of excess sludge in the whole system. Both anaerobic hydrolysis acidification tank and biological contact oxidation tank are equipped with fillers, which belong to biofilm process, and biological carbon tank is equipped with activated carbon and oxygen, which has the characteristics of suspension growth and attachment growth, the function of pulse influent is to agitate the anaerobic hydrolysis acidification tank.