Recycling Of Wastewater In Dacron Printing And Dyeing With Disperse Dyes

Great discharge of waste water from dacron printing and dyeing industry brings about increasingly severe burden on the environmental protection in the town of Meili in Changshu city, Jiangsu province. Taking this fact into consideration, this paper attempted to test the feasibility of the recycling of the dacron waste water for disperse dyes so as to solve the contradiction between the stricter environmental quantity control and the large amount of waste water discharge.Based on the physical and chemical properties of disperse dyes, the mechanism of dyeing dacron, and the unique features of dyeing at high temperature and under high pressure, this study analyzed the current processes widely applied to the treatment of printing and dyeing wastewater. And the chromaticity was selected as the indicator representing the quality of reused water. Furthermore, from the perspective of processes and operating costs, a comparison between biochemical-based and materialized treatment methods was conducted, which showed the biochemical treatment was a more suitable and applicable water reuse process. As a case study, the biochemical process was adaptively used in HuaDa sewage treatment station in the Town. A frequent monitor on chromaticity, COD and salt accumulation of the discharged water was guaranteed, and the operating section using reused water was also kept in track, in order to confirm whether the reused water affects the wastewater treatment efficiency or quality of the products.The results showed, during the reuse of water in dacron printing and dyeing, the controlled chromaticity proved to be a qualified and representative indicator. If the controlled chromaticity was lower than40times, dyeing and washing water from products with would not affect the dark color and light-colored ones, that is to say, the color as well as the sheen will be guaranteed. In addition, the operating costs of biochemical treatment could save1.65RMB per tones of treated wastewater, which was much lower than other processes. The complete biochemical treatment system could reduced0.792million tones of wastewater and0.4752million tones of COD, and an annual profit of1.3068million RMB could also be foreseen. Therefore, with better economic and environmental effects, the biochemical treatment method was of great vaiue for widely application in the dacron printing and dyeing industry with disperse dyes.