| The company being studied in this paper is a collectivized enterprise engaged in dyeing and finishing synthetic fabrics business in Tongxiang economic development zone, Zhejiang Province. As the company is increasing its production capacity and profits, the demands of protecting ecological environment and lowing production costs shall also be satisfied. Subjected to the more stringent wastewater discharge/emission standard and the raising of percentage of reusing water, the company urgently needs to improve reusing percentage of its dyeing wastewater to minimizing the water resource input and wastewater output. Based on the wastewater features of this company, this paper designed a reuse system for the effluent from the secondary treatment process which helping to mitigate regional water pollution situation and facilitate the company’s sustainable development.The capacity of bio-chemical wastewater treatment station is 4000 m3/d. According to the requirement of reusing percentage of dyeing wastewater made by provincial environmental protection bureau and the requirement of processing water quality by Standard Reusing Water for Textile Dyeing and Finishing Industry, the capacity of the reusing system is 2310 m3/d The reusing water will supply to the dyeing workshop of the company.The main processes adopted by the reusing system are Ozone-flotation and sand filtration. Ozone-flotation process is an integrated water treatment method which combining ozone oxidation and efficient air flotation process and be able to complete demulsification/flocculation, solid-liquid separation, elimination of color, odor and disinfection in one operating unit. This process not only meet the reuse requirement ofdyeing wastewater after deep treatment, but also has the advantages as easy to operate,short process, low investment, less energy consumption and etc. In addition, to insure the quality of effluent meet reuse standard, a by-pass membrane treatment equipment with a 500 m3/d capacity has been installed in the end of the process to prevent ion enrichment and eliminate inorganic salt of reuse water.The total investment of this wastewater reuse project is 8,951,500 RMB. When the project start commissioning, it will reduce the expense 2,550,000 RMB per year(annual running day 300) with its daily running cost 1.64 RMB/m3 and lay a foundation of sustainable development of the company. |
