Study On Deep Treatment Of Incineration Landfill Leachate By Ozone Combined Process

Three ozone combination processes, namely single stage ozone-biological activated carbon（O₃-BAC）, two stage O₃-BAC and O₃- Na₂COO₃ coagulation- BAC were applied for advanced treatment of the biologically treated effluent of incineration leachate. The results showed that the two stage O₃-BAC process could remove 75.9% ± 2.1% of COD, 78.8% ± 2.9% of UV254 and 96.8% ± 0.9% of chroma at ozone dosage of 200mg/L. The treated effluent was with COD of below 100mg/L and chroma of below 40 times, meeting the emission requirements. At the same ozone dosage, however, the single stage O₃-BAC process removed 68.2% ± 1.3% of COD, 69.7% ± 0.5% of UV254 and 92.5% ± 1.1% of chroma. The treated effluent was with COD of around 150mg/L and chroma of about 60 times, failing to meet the emission requirements. Namely, ozone dosage of 290mg/L is required by single stage O₃-BAC in order to achieve similar pollutant removals as those in two stage O₃-BAC at O₃ dosage of 200mg/L. In two stage O₃-BAC process at ozone dosage of 200mg/L, the removal of total nitrogen was poor, but the removal of total phosphorus was as high as 63.5%±4.4%. The phosphorus concentration in the effluent was stabilized at 1mg/L or less, directly meeting the emission requirement of GB16889-2008. The p H of water was decreased after ozone oxidation, while increased after BAC treatment. The two stage O₃-BAC could effectively reduce the accumulation of carboxylic acid substances in the ozone oxidation tower, avoiding the decrease in p H and thereby inhibiting the generation of hydroxyl radical in the ozone oxidation reaction.It was found that calcium phosphate, calcium carbonate and etc were generated in the ozone oxidation, which lead to clogging in the BAC and thus affected the operation. Coagulating the ozone oxidized effluent with Na₂CO₃ could efficiently relieve the fouling and blockage in the BAC. The process of O₃-Na₂CO₃ coagulation-BAC efficiently removed COD, TOC and chroma, with effluent meeting the standard of pollution control for MSW landfill（GB 16889-2008）. BAC performed better for pollutant removal in anaerobic condition than in aerobic condition. However, the system was poor for TN removal, althrough addition of carbon source could be of some benefitial. With ozonation and BAC, the species and concentration of organic pollutants, especially aromatic compounds, were greatly decreased based on GC-MS analysis. Concenrations of calcium, zinc, manganese and copper were greatly decreased, but iron was little changed. The whole toxicity were greatly reduced with ozonation and BAC, however, SOS/umu genetic toxicity and zebrafish early developmental toxicity in the treated effluent were still strong, which should be paid much attention.