The Mechanism Of Catalytic Ozonation Of DEHP And Humic Substance Of High Concentration In Landfill Leachate

How to dispose the landfill leachate which was consisting of a lot of refractory and toxic materials is one of most difficult issues. Di(2-ethylhexyl) phthalate (DEHP) was an endocrine disrupting pollutant in the landfill leachate, even at low concentration. And humic substance was the main organic matter in landfill leachate, which was refractory organic. This thesis focused on the oxidation of DEHP and humic substance in landfill leachate.Liquid-phase extraction method and GC-FID were used to analyse phthalic acid esters (PAEs) in landfill leachate from two municipal solid wastes (MSW) landfill sites in Tianjin. DEHP and di-n-butyl phthalate (DBP) were found in all the leachates. DEHP was the most abundant of the PAEs, which concentration was 65.3~1212.0μg/L. The concentration of DBP was 3.8~9.3μg/L. Other PAEs were not detected. Natural organic matter in landfill leachate was fractionated into hydrophobic compouds and other hydrophilic organics by XAD resin. Results showed that dissoluble humic substance was the main organic matter in landfill leachate treated by biological process.The efficiency of ozonation on removing DEHP and humic substance was studied. The effects of ozone concentration, DEHP concentration, pH, temperature, quenching agent on the removal rate of DEHP were evaluated. Results showed that DEHP was effectively degraded by ozonation. The optimum condition was the concentration of O3 with 16.8mg/L, temperature under 35.5℃, and pH under 10. The mechanism of removing DEHP and humic substance by ozonation were proved that radical reaction took the main role. In addition, UV-Vis, GC-MS were utilized to analyze the oxidation intermediates in ozonation process of DEHP, and the detailed degradation path was illuminated.Homogeneous catalysed ozonation of high concentration humic substance was investigated with the existence of Fe(II), Mn(II) and Cu(II). The results showed that both ozonation and catalytic ozonation achieved chroma and UV254 removal well. All catalytic ozonation processes resulted in a significant increase on the removal of TOC and CODCr. The removal efficiency of TOC increased from 28.6% to 57.9% by Fe(II), 68.9% by Mn(II) and 74.5% by Cu(II) at 60min. Cu(II) was found to be the most effective among the three catalysts. All the optimum dose of the three catalysts was 0.6mg/L. Initial pH, temperature, quenching agent influenced humic substance removal also. Ozonation efficiency was improved by ?OH induced by Fe(II) and Cu(II) catalysed ozonation, but the catalytic effect was shown by MnO2-OH? created in Mn(II) catalysed process.A bench-scale study had been undertaken on the catalytic ozonation of landfill leachate treated by biological process from a MSW landfill site in Tianjin. It was proved that organic materials in leachate could be successfully removed by catalytic ozonation on the presence of Cu(II) with 0.6 mg/L. And the concentration of Cu in the effluent was lower than that in the Integrated Wastewater Discharge Standard.