Study On Advanced Treatment Of Leachate From Municipal Waste Incineration Plant By Advanced Oxidation Processes Based On UV

Incineration leachate contains high amounts of organic pollutants.Combined biological processes are utilized to degrade this wastewater in China.However,the effluent still contains hundreds mg/L of chemical oxygen demand(COD)and the biodegradability is very poor.And the refractory organic substances with large molecular weight,such as humic acid and fulvic acid,remian in the effluent Therefore,biological treated incineration leachate from municipal solid waste(MSW)incineration in north China as the research object in this thesis.Advanced oxidation processes based on UV were chosen to degrade this wastewater.The effect of treatment and influence factors were investigated.The degradation mechanisms and acute toxity of refractory organic matters were detected as well.First of all,UV/PMS was adopted to advanced degrade the incineration leachate in this thesis.The results showed that incineration leachate was treated efficiently by UV/PMS,and there was a synergy effect between UV and PMS.The optimized conditions were PMS dosage of 25 g/gCOD and pH of?9,COD removal of wastewater reached 70.60%within 60 minutes.The results of EPR spectra showed that the addition UV facilitated the generation of ·OH and SO4·-.·OH,SO4·-and·Cl were indentified as main free radicals.However,SO4·-and·C1 were likely scavenged by the HCO3-in the wastewater,which decreased the degradation of the refractory organics by UV/PMS.The results of FTIR,Uv-vis,3D-EEM and HPLC showed that nearly all of the refractory organics were transformed into intermediates with low molecular weight.The degree of aromatization and humification of the wastewater are greatly decrased.The toxicity of wastewater is greatly decreased.However,UV/PMS generated SO42-,which will cause secondary pollutionVUV/03 was adopted to advance degrade incineration leachate.The experimental results showed that the synergistic effect between the VUV and the O3 processes on BOD5/COD improvement.The reaction conditions were optimized as follows:22.40 mg/(L·min)of O3 dosage and initial pH of-9.BOD5/COD was increased from 0.16 to 0.73 under the optimal conditions.the results of measuring 03 concentration in gas phase and aqueous phase showed that VUV sharply accelerated the O3 utilization,which increased from 10%to 30%.The results of EPR spectra showed that ·H,·OOH and ·OH were indentified as main free radicals.The results of OH concentration by tert butyl alcohol method indicated that the accumulated ·OH concentration increased from?1 mg/L to?68 mg/L.The results of FTIR,Uv-vis,3D-EEM and HPLC showed the refractory organic matters,e.g.,the humic-like acid and fulvic-like acid substances,were partly degraded into the aliphatic intermediates with micro-molecular weight.And the degree of aromatization and humification of the wastewater were decreased.Moreover,the acute toxicity of the wastewater decreased after being treated by VUV/O3Finally,in order to further improve the degradation rate and shorten the reaction time of incineration leachate by VUV/O3 process,the ZnCo2O4 catalyst was successfully prepared by hydrothermal synthesis.And VUV/O3/ZnCo2O4 was ultilized to advanced treat incineration leachate.The expermental results showed that,when the O3 dosage was 22.40 mg/(L·min),the pH was?9,and the ZnCo2O4 dosage was 0.2 g/L,the BOD5/COD of wastewater increased from 0.16 to 0.72 in 30 minutes.The degradation rate of organic matter increased effectively.The results of EPR spectra showed that ZnCo2O4 catalyzed the generation of more ·OH in VUV/O3,and accumulated ·OH concentration increased from?68 mg/L to?82 mg/L.Meanwhile,compared with sole O3 and VUV/O3,VUV/O3/ZnCo2O4 improved the degradation rate of fulvic acid and humic acid in wastewater,and more macromolecular organic matters degraded into small organic intermediates in wastewater.Moreover,the toxicity of wastewater was effectively decreased by VUV/O3/ZnCo2O4 process within 30 minutes.