Evaluation On The Removal Of Organics From Reclaimed Water By Heterogeneous Catalysts And Hydrogen Peroxide Catalytic Ozonation Processes

Reclaimed water has been widely used in landscape environment of urban rivers and lakes,municipal utilities,groundwater supply,agricultural irrigation,industrial and residential daily water,due to its advantages of stable water quality and low production cost.The reuse of reclaimed water realized the reduction of pollutant emission,improvement of water ecological environment and the virtuous cycle of water ecological system,effectively alleviating the water crisis in water shortage areas.Recently,it has been becoming a hot topic to improve the quality of reclaimed water to increase the way of reuse reclaimed water and reduce the possible safety risks in the recycling process.This study selected secondary biological effluent from a sewage treatment plant in Beijing as the research object,and the catalytic ozonation method was used to remove the organics in the effluent,improve the quality of reclaimed water,and expand the scenarios and ways of its reuse.The removal efficiency of organic matters in reclaimed water by single ozone treatment,ozone combined with H₂O₂（H₂O₂/O₃）,and heterogeneous catalytic ozone oxidation were studied,respectively.To this end,the variations of SCOD,DOC,UV₂₅₄,organic three-dimensional fluorescence and molecular weight distribution of organic matter from different processes were compared.The results showed that the comprehensive removal rate of SCOD,DOC and UV₂₅₄by heterogeneous catalytic ozone oxidation was the highest when the ozone dosage was 20 mg/L,with 30 min removal rates of62.96%,55.61%and 79.26%,respectively.Analysis of three-dimensional fluorescence showed that the dimension of fluorescence response region of aromatic protein,humic acid,soluble organic matter,fulvic acid and humic acid organic matter in reclaimed water decreased significantly.The results of molecular weight distribution analysis showed that the molecular weight of organic compounds in the effluent was mainly distributed in fraction of<1 k,1～3 k and>100 k,but after heterogeneous catalytic oxidation,the organic compounds in the effluent were mainly distributed in the range of molecular weight<1 k,indicating that heterogeneous catalytic oxidation exhibited a good removal efficiency for the organic compounds with molecular weight of>1 k.According to the ozone utilization ratio test results,when the ozone dosage is 20 mg/L,the comprehensive ozone utilization ratio of the 30 min reactor treated by ozone alone is 76.52%.Finally,the comprehensive ozone utilization rate of H₂O₂/O₃combined process in 30 min was 85.35%,and the comprehensive ozone utilization rate of heterogeneous catalytic oxidation process in 30 min was 87.79%.Therefore,the 0.71m³catalytic oxidation of heterogeneous catalyst A（Al-Si compound）with 20mg/L of ozone dosage,127 L/h inlet flow rate and 30 min ozone reaction contact time was selected as the optical process of pilot treatment,then the design of field pilot test process was carried out and the stability of pilot test was continuously monitored.The 14-days average removal rates of SCOD,DOC and UV₂₅₄were 53.6%,55.15%and 81.19%respectively,with good treatment results.