Printing and dyeing wastewater is characterized by large discharged water volume, high organic matter content, deep chromaticity, high alkalinity and high salinity. Therefore, the development of high-efficiency regeneration technology for printing and dyeing wastewater and the improvement of the reuse rate of printing and dyeing wastewater is the trend of the development of the printing and dyeing industry, which is the key to realizing the green transformation of the industry, and it is also an important means of accomplishing the goal of clean production of printing and dyeing industry in terms of water conservation and emission reduction.

printing and dyeing wastewater treatment and reuse methods

1. Printing and dyeing wastewater treatment methods

Printing and dyeing wastewater treatment technology mainly includes chemical method, physical method, physical-chemical method, biochemical method and so on. Physical method in the membrane separation technology is currently the fastest growing water treatment technology, printing and dyeing wastewater treatment water quality is better, can be directly reused in production, there are problems is mainly a high investment cost, membrane parts of the life is shorter and post-processing difficulties and other issues. The commonly used oxidizing agent in chemical method contains Fenton reagent and ozone, Fenton reagent has the advantages of simple operation, rapid reaction, easy to produce flocculation, the disadvantages of high treatment cost, poor oxidation efficiency, low utilization of oxidizing agent and other problems. The commonly used adsorbent in the physicochemical method is activated carbon, which has the advantages of good adsorption and decolorization effect, strong hydrophilicity, etc. It is mainly used in the treatment of low concentration of wastewater or deep treatment process. In biochemical method, aerobic biological treatment has better removal effect rate for BOD, but worse removal efficiency for chromaticity and COD; anaerobic biological treatment has the advantage of easy hydrolysis of difficult biodegradation of organic matter, but it can't completely degrade organic pollutants. Therefore, most of the domestic and foreign printing and dyeing wastewater treatment using anaerobic and aerobic joint process.

2. Printing and dyeing wastewater reuse methods

Printing and dyeing textile wastewater composition is complex and difficult, it is difficult to form a specific treatment and reuse process, so the domestic printing and dyeing textile enterprises to choose the wastewater treatment and reuse process is mainly based on their own wastewater composition characteristics and reuse of water quality requirements, commonly used treatment and reuse process is as follows:

(1) Printing and dyeing mixed wastewater + air flotation + anaerobic biological treatment + coagulation and sedimentation (coagulant + flocculant + activated carbon) + membrane biological treatment + water reuse. Membrane biological reaction treatment method is a combination of membrane separation and biochemical method of water treatment technology, the advantages of this treatment method can maintain a high concentration of activated sludge, by reducing the sludge load to achieve the purpose of reducing the amount of sludge generated.

(2) Printing and dyeing mixed wastewater + secondary biochemical treatment + ozone oxidation + filtration / adsorption + water reuse. Oxidation method + activated sludge biological treatment of printing and dyeing wastewater and reuse, the treatment cost is lower than the membrane separation treatment technology and the effluent water quality reaches the reuse standard, can be used for production and equipment cleaning process.

(3) Printing and dyeing wastewater + secondary biochemical treatment method + ozone oxidation method + membrane separation treatment + water reuse. Membrane separation treatment technology commonly used processes for ultrafiltration (NF) and reverse osmosis (RO), applied to printing and dyeing wastewater reuse project, the main advantage of effective treatment of wastewater organic matter, desalination effect is obvious.