Study On Reuse Of Dyeing And Printing Of Textile Wastewater And The Reuse Water Quality Standard For The Dyeing Industry

Deficient water resources and serious pollution make it necessary to reuse wastewater. Textile industry is one of the industries that consume a large amount of water and generate tremendous pollutants. It is reported that usually the renewal percentage of polluted water is only less than 10%. The dyeing wastewater is the main pollution resource from textile industry, which not only takes a high volume but also contains large amount of contaminations. The water demand in textile and dyeing industry keeps growing year by year, however, along with the decreasing water supply, the rising water price and the appearance of more strict pollution control standards, it becomes an important and urgent task in the textile and dyeing industry to raise the water renewal percentage and furthermore save the water resource.The geological distribution of dyeing wastewater, the quality and volume, the wastewater treatment processes and the current wastewater renewal state have been analyzed in this study, based on the investigation results from some major textile and dyeing companies in China. It will work as an useful reference for the establishment of the reuse water quality standard for the dyeing industry, the future research work on the advanced pollution treatment technologies and the application assessment of the dyeing wastewater reuse.A pilot-scale (300t/d) study was set up for advanced treatment of dyeing wastewater by hydrolysis acidification-biological contact oxidation-biological aerated filter-sub-filter technology. The retention time for hydrolysis acidification, the biological contact oxidation and the biological aerated filter were 20h, 12.5h and 2.6, respectively. The experimental data indicated that after 6 months the effluent quality kept stable, with the COD of less than 50mg/L, the color of lower than 2, the turbidity of 1NTU, the hardness of less than 140mg/L, the pH of 6.7-7.5 and the effluent concentration for Fe and Mn both less than 0.1mg/L. The effluent quality met well the reuse of urban recycling water-water quality standard for industrial process GB/T 19923-2005.This study has developed a wastewater treatment system and then reused the effluent into the dyeing process for lab, pilot and field scale test step by step. According to the quality analysis results of the final products which were dyed with the reused water, it was showed that the purified wastewater was adequate to reuse directly into the dyeing process and had no negative effect on the dyeing quality, which proved the feasibility of dyeing wastewater reuse process.In this study, the related regulations and standards on wastewater reuse in China and other countries were investigated as well. With reference to water standards on textile and dyeing industry and on the basis of field investigations and laboratory tests, one water quality standard of reused water in textile and dyeing industry (suggested) was established, including the monitoring methods for relevant water quality index and suggestions on the wastewater reuse range, reuse processes and treatment system design. For further promotion for the dyeing wastewater reuse, the study also analyzes the dyeing industry policies, national water-saving plan and cleaner production requirements, and further elaborates on the importance and necessity of wastewater reuse in textile and dyeing industry.The economic profit assessment is established in this study for one 300m~3/d dyeing wastewater pilot-scale project and a new 5000m~3/d dyeing wastewater field-scale project. Fro the field-scale project, the investment capital will be decreased by 1.86 RMB/ton, which generated a profit of RMB 340,000 per year for the production factory. Treatment and reuse of wastewater can save water resource effectively, as well as reduce total discharge of wastes, which has great effect of environment, economy and society.