Characteristics And Application Of Dissolved Ozone Flotation Treatment Of Printing And Dyeing Wastewater Secondary Biochemical Effluent

In view of the increasing discharge standards of printing and dyeing wastewater and the issues of treatment quality and efficiency enhancement,the paper systematically studied the treatment characteristics of the ozone flotation process on the secondary treatment water of printing and dyeing wastewater,and analyzed the effects of different organic pollution loads on the ozone flotation system.Combining with the needs of upgrading and reforming the wastewater treatment system of a printing and dyeing enterprise in Shaanxi,a technical process plan with ozone flotation as the core was proposed and verified by the laboratory,which provided theoretical and technical support for the application of this technology in the advanced treatment of printing and dyeing wastewater.In the experiment,the secondary treatment water of a printing and dyeing plant was used as raw water,and polyaluminum chloride was used as the coagulant.Under the conditions of inlet water flow of 20 m³/h,residence time of 30 min,reflux ratio of 50%,and solution pressure of 0.4 MPa,the study The effect of different ozone dosage and coagulant dosage on the treatment effect is discussed.The research results show that the key parameter that affects the stable operation of the ozone floatation process is the influent load.Under low load conditions（influent COD is 80-100 mg/L）,the optimal dosage of coagulant and O₃ is 60 mg/L and 25 mg/L respectively,and the removal rates of COD,UV₂₉₀ and color are 49.36%,47.1%and 84.5%.Under the condition of high load（the influent COD is 100-180 mg/L）,the optimal dosage of coagulant and O₃ are 60 mg/L and 48 mg/L,respectively,and the removal rates of COD,UV₂₉₀ and color are 32.4%,44.2%and 88.4%.Three-dimensional fluorescence analysis shows that ozone has a good effect on removing proteinaceous organic matter and fulvic acid-like substances,and the fluorescence peak intensity is reduced by 70.2%and 67.8%,respectively.The ozone air floatation process has high-efficiency sterilization ability,and the inactivation rate of total bacteria and coliform bacteria reaches 99.92%and99.95%,respectively.Aiming at the problems that the COD and antimony in the secondary effluent of the total discharge are difficult to reach the standard,and the reuse rate of the reclaimed water is low,the existing wastewater treatment system of a printing and dyeing plant in Shaanxi is transformed by using a process with ozone flotation as the core.The retrofit plan collects the desalination and bleaching wastewater and alkali-reducing wastewater after treatment by the combined process of“UASB/contact oxidation/ozone air floatation”,and then discharges it to the sewage treatment plant in the park.Dyeing,water washing and domestic sewage are collected in a unified manner,and then recycled to production after two-stage hydrolytic acidification/contact oxidation/dissolved ozone floatation/RO membrane combined process.The operation results show that the application of ozone air floatation technology to the reconstruction project has improved the stability of the discharge of the wastewater,and the quality of the discharged wastewater meets the indirect discharge standards in Table 3 of the"Water Discharge Standards for Textile Dyeing and Finishing Industry"（GB4287-2012）and"The limit requirements of the Comprehensive Wastewater Discharge Standard of the Yellow River Basin（Shaanxi Section）（DB61-224-2011）.The quality of the reused water meets the requirements of the Standard for Recycled Water Quality in Textile Dyeing and Finishing Industry（FZ/T01107-2011）,and the reuse rate of enterprise water is increased to more than 40%.