Advanced Treatment Efficiencies Of Coking Wastewater By Catalytic Ozonation And Pilot Study Design

Xuan Gang coking wastewater treatment plant has used a biological treatment process based on anoxic-aerobic(A/O process).The COD concentration of effluent was still as high as 653 mg/L,the TN concentration was 250 mg/L,and the chroma was 280 times.It was far from meeting the emission standards required by the Coking Chemical Industry Pollutant Emission Standard(GB16171-2012),and further advanced treatment is required.In this paper,the effluent of A/O biological treatment process was taken as the research object.The advanced treatment efficiencies of homogeneous ozone catalytic oxidation(O3/H2O2)and heterogeneous ozone catalytic oxidation were investigated through laboratory experiments.The transformation of the refractory organic matter in coking wastewater was studied in ozonation and different catalytic ozonation processes to determine suitable advanced treatment methods and operation parameters.Based on the results of the laboratory pilot study and combined with the preliminary research work,the coking wastewater plant of zhongluangroup in chengde,hebei province was selected as the field pilot test site,and the renovation plan for the coking wastewater treatment of zhongluangroup was proposed,and the design of the on-site pilot plant was carried out.The experimental results showed that in alone ozonation process,under the conditions of 30 min reaction time,inlet gas flow of 500 ml/min,and ozone input concentration of 27.5 mg/min(in gas),the COD removal rate was 40.5%,the TOC removal rate was 10.6%,the chroma removal rate was 79.0%,and the ozone utilization rate was 37.5%.In O3/H2O2 process,the optimal dosage of H2O2 was determined to be 100 mg/L by comparing the treatment effects under different dosages of H2O2.Under the optimal dosage,the COD removal rate,TOC removal rate and chrominance removal rate were 54.7%,16.6%and 82.0%,respectively,significantly higher than that in alone ozonation.The ratio of BOD5 to COD(B/C)was 0.16.The number of organic compounds measured during GC-MS scan decreased from 232 to 184.In addition,the addition of H2O2 promoted the decomposition of ozone,accelerated the transfer of gaseous ozone to liquid ozone,resulted in the increase the ozone utilization rate to 44.5%.In heterogeneous catalytic ozonation process,catalysts with two different supports such as Mn supported Al2O3(Mn/Al2O3)and Mn supported activated carbon(Mn/AC),were prepared.By comparing the degradation effects of two different catalysts on coking wastewater,it was concluded that Mn/Al2O3 has the best catalytic efficiency,and its removal efficiency on COD was 53.6%.The removal efficiency of TOC was 16.7%.The removal efficiency of color was 84%.Ozone utilization was 44.5%and B/C was 0.145.In 3d fluorescence detection,soluble microorganisms,fulvic acid series,humic acids and aromatic proteins were effectively removed.After treatment,all substances with molecular weight of more than 10k in wastewater were removed.GC-MS scanning analysis showed that the number of substances in water decreased from 232 to 192.By comparing homogeneous catalytic ozonation and heterogeneous catalytic ozonation process,the most suitable catalyst for Chengde Zhongluan Group coking wastewater plant was Mn/Al2O3 catalyst.In order to make the final effluent water quality index meet the national steel industry emission standards,combined withour previous research work,the combination processes of "coagulation sedimentation+ozone pre-oxidation+EGSB+two-stage A2/O+catalytic ozonation+MBR" were selected to upgrade the current wastewater treatment plant.According to the above conclusions,the design of the on-site pilot process was carried out,where dimensional parameters for each process were calculated and process drawing was given.The design inlet flow rate was 0.05 m3/h,the residence time of the coagulation sedimentation tank was calculated to be 2 h,the residence time of the adjustment tank was 24 h,the ozone pre-oxidation contactor was 0.5 h,the EGSB residence time was 24 h,the two-stage A/O residence time was 60 h,the catalytic ozonation contactor residence time was 0.5 h,and the MBR residence time was 6 h.