Reuse Processes of Cotton Knitted Fabric Printing and Dyeing Wastewater Based on Water Network Optimization

The printing and dyeing industry contributes significantly to water pollution in China and produces a large amount of wastewater with a low reuse rate. The characteristics of wastewater from typical cotton knitted fabric manufacturers in China were studied. Based on the pilot experiment results, water pinch technology and water network optimization methods were employed to determine the water quality and flow of both slightly and highly polluted wastewater. The methods were based on the principles of cleaner production and wastewater source separation to maximize the reuse rate of wastewater and minimize the discharge quantity. The slightly polluted wastewater was directly reused to the production processes while the highly polluted wastewater was treated by ultrafiltration combined with nanofiltration before reuse. An economical analysis indicated that this reuse process was cost-effective.