Pilot-scale Experiment On Advanced Treatment Of Petrochemical Secondary Effluent By Micro Flocculation Sand Filtration And Catalytic Ozonation

The petrochemical secondary effluent still contains lots of refractory organic matters. By 2015, the Ministry of Environmental Protection issued Emission standard of pollutants for petroleum chemistry industry(GB 31571-2015),which substantially improved the water quality of petrochemical secondary effluent. Thus, it is very important to find an efficient process for advanced treatment of petrochemical secondary effluent, which could meet the new emission standard, minimize the discharges of organic compounds and protect environment. In this paper, the advanced treatment of petrochemical secondary effluent by combined micro flocculation sand filtration and catalytic ozonation process was put forward, optimizing the unit technology and evaluating the effect of the combined process. Main conclusions are as follows:The results of micro flocculation sand filtration unit experiment showed that, in the optimal dosage of 10 mg/L, the efficiency of using PAFC is better than that of PAC, the COD removal rate was 13.8%, TOC removal rate was 1.7%, ammonia nitrogen removal rate was 26.5%, TP removal rate was 50.6% and SS removal rate was 50.6%.Three-dimensional fluorescence spectrum analysis showed that there were aromatic proteins and soluble microbial metabolites detected in the petrochemical secondary effluent,while these organic matters cannot be effectively removed by micro flocculation sand filtration.GC-MS results showed that there were about 7 kinds of organic matters detected in the petrochemical secondary effluent,while these organic matters cannot be effectively removed by micro flocculation sand filtration.In ozone catalytic oxidation unit, the catalysts, using commercially available activated alumina as carrier, was supported transition metal oxides. The optimal performance of eliminating organic matters was attained when the dosage of ozone was 36 mg/L and the recycle ratio was 100%. On this condition, the influent and effluent average COD were 78.8 mg/L and 46 mg/L, respectively, the average removal rate of COD was 41.6%.The least dosage of ozone was required for eliminating 1g COD,which is 1.10 g O3/g COD. The removal rate of TOC was 71.4% and the colority was 26.3 degrees with its removal rate of 52%. Three-dimensional fluorescence spectrum analysis showed that aromatic proteins and soluble microbial metabolites could be effectively removed by ozone catalytic oxidation. GC-MS results showed that only 1 dominant organic matter was detected in the effluent,indicating that targeted organic matters could be effectively removed by ozone catalytic oxidation.The results of combined operation experiment showed that the average removal rate of COD, ammonia nitrogen,TP were 50.3%, 25.4%, 58.5%, respectively; with effluent COD of 45.8 mg/L, ammonia nitrogen of 1.4 mg/L, TP of 0.14 mg/L. The effluent quality can meet the Emission standard of pollutants for petroleum chemistry industry(GB 31571-2015). Technical and economic analysis showed that the operation cost is 0.64 Yuan/t in the pilot experiment.