Abstract: The COD of the effluent from the secondary biological treatment process of coking wastewater couldn't meet the standard.In order to resolve the problem,the effects of advanced treatment of coking wastewater by single ozonation,O_3/H_2O_2oxidation and UV-Fenton processes respectively,were investigated through laboratory test,which were carried out in semi-continuous mode.The quality of effluent from the different processes were analyzed,where UV_(254),BOD_5/COD,the luminescent bacteria toxicity,three-dimensional fluorescence spectrum were evaluated.The influence of different advanced oxidation processes on effluent quality was explored.The results show that the increase of ozone dosage and addition of H_2O_2can significantly enhance the removal of organic compounds in the secondary biochemical effluent from coking wastewater.When the COD of the influent is(200±10)mg/L,the average COD removal rate for 120 min reaction in single ozonation process is 36%with the ozone dosage of 30 mg/L.When the COD of the influent is(200±10)mg/L,the average COD remov-al rate for 120 min reaction in UV-Fenton process is 50%with the H_2O_2dosage of 2 g/L and the molar ratio of Fe~(2+)and H_2O_2of 1∶10.When the COD of the influent is(200±10)mg/L,the average COD removal rate for 120 min reaction in O_3/H_2O_2oxidation process is63%with the ozone dosage of 30 mg/L and H_2O_2dosage of 2 g/L,which meets the Emission Standard of Pollutants for Coking Chemical Industry,China(GB 16171—2012).Among the three processes,the O_3/H_2O_2oxidation process is the most effective for organic compounds removal.This is mainly attributed to the synergistic production of strong oxidizing radicals by O_3and H_2O_2.However,when the concentration of H_2O_2is too high,·OH produced in the system reacts with H_2O_2instead,resulting in the decline of oxidation capacity of O_3/H_2O_2system.All the three processes can reduce its toxicity.The results of acute toxicity test of with luminescent bacteria shows that the relative luminosity of effluent after single ozonation and O_3/H_2O_2oxidation for 15 min increaseto 90%and 87%,respectively.After UV-Fenton oxidation for 30 min,the relative luminescence of effluent increases to 71.57%.Compared with single ozonation and O_3/H_2O_2oxidation process,the effluent of UV-Fenton treatment has relatively higher acute toxicity,which may be related to the disinfection effect of ozone.The three processes can hardly improve its biodegradability,while BOD_5/COD only increases from 0.02 to about 0.1.The comparative analysis of UV_(254)and EEM(Excitation-emission Matrix)show that the three processes have obvious decomposition effect on aromatic compounds and fluorescent substances in the secondary biochemical effluent.The conjugated double-bond substances of humic acid-like substances in wastewater can be preferentially degraded in single ozonation process,while O_3/H_2O_2oxidation process has more significant oxidation effect on cyclic conjugated pollutants.In the UV-Fenton process,humic acid-like substances and UV-fulvic acid-like in coking wastewater are oxidized preferentially,and eventually converted into visible fulvic acid-like and protein-like,which still have relatively high concentration in the effluent.Among the three oxidation processes,the removal of fluorescent substances by UV-Fenton oxidation process is the worst.