Research On Enhanced Pollutants Removal Efficiency In Wastewater Treatment Plant Located In Chemical Industrial Park

Along with the rapid growth of economy in China, the demand for construction materials in daily life is also undergoing great changes, more and more chemical synthetic products come into our life. These products have brought great convenience to our life, however, at the same time, they also produces a large number of environmental problems. Most of these products are biological toxic and hard to be biodegraded, which causes severe challenges to th e comprehensive environmental governance in end treating processes in industries.The study in this paper was carried out in a wastewater treatment plant(WWTP) located in Yixing, Jiangsu province. Based on the present situation of the WWTP operation and problem analysis diagnostics, a combined process of Cyclic Combined Hydrolytic Acidification-Cyclic Activated Sludge System(CASS) –Flocculation Sedimentation-Sand Filtration-Catalytic Ozonation was designed and developed. Pollutants removal of the process and the practical feasibility of the operating strategy were investigated. The operating parameters of each unit were optimized through small scale experiments and the most appropriate operating strategy were: HRT in the hydrolysis acidification reactor was 8h, CASS process was operated with each cycle of 6h, including continuous water inlet and aeration 4h, precipitation 1h and discharge 1h, MLSS 3200mg/L, DO 3.0 mg/L, SRT 28.8d, a reflux ratio of 200%, and drainage ratio of 0.25. Meanwhile, the dosage o f olymeric aluminum ferric in the flocculation sedimentation tank was 3.6mg/L(measured by iron). Under these conditions, the average removal rate of COD, NH3-N, TN and TP were as high as 83.29%, 95.34%, 61.29%, 82./7%, respectively, which means the effluent can met the A level of class one standard of discharge standard of pollutants for municipal wastewater treatmentplant.Treatment performance and effects of important operating parameters of heterogeneou catalytic ozonation of biologically treated efflue nt were investigated under the condition that high proportion of chemical industry waste water were presented. Considered the practical feasibility, the most suitable reaction conditions have been determined, which were: catalyst filling capacity of 500g/L, ozone dosage of 0.96g/h, and the reaction time of 30 min under the condition of real water temperature and p H(without regulation). Under this condition, the catalyst were repeated being used for 8 days, a relatively stable COD removal efficiency of 63% was invesitgated. This showed the repeated use of the catalyst is possible, and the catalyst was suitable for industrial applications.Through the additional of hydroxyl radical scavenger to the influent of the continuous catalytic ozonation, the expression of catalytic activity was seriously inhibited, which preliminary explored the ozone catalyzed reaction mechanism. The oxidation process of the catalytic ozonation could be a mainly indirect oxidation of ?OH reaction as well as a variety of oxidation as synergistic effects. Meanwhile, based on the qualitative analysis of the pollutants in the influent and effluent in catalytic ozonation process through GC-MC, the chemical structure, molecular weight distribution and their transformation were explored, which provided a theoretical and technical support for chemical wastewater treatment.The research has a high practical engineering significance and value, and the research results will not only help the operation of the WWTP A for upgrading and reconstructing, but also have a good reference value for WWTP with similar influent in chemical industry parks. Further more, it also helps to improve the water environment quality in Taihu watershed.