Advanced Treatment And Reuse Technology Of Printing And Dyeing Wastewater And Its Technology

There are many researches on the reuse of printing and dyeing wastewater in China.

(1) most of the reused technologies are in the experimental stage, mostly for small and pilot tests. The actual engineering applications are few, and the water reuse rate is low, generally not more than 50%. Preceding process There is no promotion and application of high efficient technology which is conducive to improving the quality and reuse rate of reclaimed water.

(2) reuse treatment is mainly based on the treatment of printing and dyeing wastewater on the basis of standard treatment, so as to achieve the quality standard of reclaimed water. Coagulation, adsorption, filtration and oxidation are used in the treatment process, and the key technologies for removing salinity and hardness are few.

(3) due to the limitation of the existing technology level, the reuse of printing and dyeing wastewater will bring a series of problems to the production and wastewater treatment system, including the accumulation of organic pollutants and inorganic salts. At present, there are few studies on the long-term reuse of wastewater and the impact on the water treatment system, especially the accumulation of inorganic salts.

The advanced treatment of printing and dyeing wastewater mainly deals with the effluent from the conventional two stage treatment system. The pollutants are mainly chroma, COD, and salinity (electrical conductivity), so that the effluent water quality can meet the requirements of the production process. The quality requirements of printing and dyeing process and products are different, and the requirements for the quality of recycled water are also different. Therefore, there is no uniform water quality standard for reuse of printing and dyeing wastewater in China. According to the industry experience, water quality indicators must be controlled within the water consumption index. Therefore, the textile printing and dyeing industry requires much more water quality than the miscellaneous water used in the city.

The waste water is composed of adsorbent. Filter bed Contaminants are adsorbed on the surface of porous materials or removed by filtration. Activated carbon is the most commonly used sorbent for advanced treatment of printing and dyeing wastewater. It has many micropores and a specific surface area of up to 500~600 m2/g. It has strong adsorption and decolorization properties and is especially suitable for decolorization and adsorption of water-soluble dyes whose molecular weight is less than 400. However, activated carbon has poor adsorption effect on hydrophobic dyes, and its regeneration is more complex and expensive, which limits the application of adsorption in advanced treatment of printing and dyeing wastewater. Natural minerals such as kaolin, diatomite, activated clay and pulverized coal also have high adsorption properties, and are also used in advanced treatment of printing and dyeing wastewater. In addition, Li Mengying, et al. [2] studied the use of Penicillium for the treatment of dyeing wastewater. The results showed that it had better treatment effect on the chromaticity of black and red dye bath wastewater, and the removal rate reached 98% and 74.5%, providing a new choice for the development of adsorption method. Although the adsorption method is effective, the regeneration of adsorbents after use is rather difficult. If it is not recycled, it will cause two pollution. Therefore, the development of new and highly efficient and easily regenerated adsorbent is the research direction of the current adsorption method.

Membrane has different permeability to different substances. Membrane separation technology is based on the characteristics of membrane, and the separation of mixtures under certain mass transfer force. The membrane separation technologies for advanced treatment of dyeing wastewater mainly include microfiltration (MF), ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO). MF and UF are often used as pretreatment of NF and RO; UF can separate macromolecular organic matter, colloid and suspended solid; NF can achieve simultaneous desalination and concentration; RO can remove soluble metal salts, organic matter, colloidal particles and retain all ions. Ruan Huimin, et al. [3] UF+RO process was used to treat effluent from biochemical treatment of a printing and dyeing factory in Zhejiang. The membrane system was influent COD 100~350 mg/L, chroma was 180 times, and conductivity 350 800~1 S/cm. After treatment, the effluent COD<10 mg/L, chroma 1~2 times, conductivity <30 mu S/cm. Xujie Lu et al. [4] using biofilter combined with membrane separation method, when the influent COD was 150~450 mg/L, the effluent COD dropped to 50 mg/L below, the removal rate was as high as 91%, and the color, turbidity, and so on. Iron and manganese concentration The removal effect is very good.

The advantages of membrane separation technology are: it can not only remove the residual organic matter in the water, reduce the chromaticity, but also remove inorganic salts and prevent the accumulation of inorganic salts in the system, which is a promising technology in the advanced treatment of printing and dyeing wastewater. However, the cost of membrane process is high, and the membrane module is easy to be polluted to shorten its service life. Only by controlling and reducing membrane fouling to prolong membrane life and reduce costs, membrane separation technology will be more widely applied in advanced treatment of printing and dyeing wastewater.