| As the final disposal of municipal solid waste, sanitary landfill has been widely applied for its simple process, low investment, large handling capacity and low operating cost. However, with the progress of urbanization and the residents' demands for a higher living environment quality, the odor emission from landfill sites has become a severe pollution problem. In this research, the odor pollution and its control has been studied at Tianziling Landfill site. The odor pollution source, odor pollutants and dynamic variation characteristics were investigated. The landfill odor control technology of novel daily cover material was developed as well as the demonstration research. Main conclusions were:1. Chemical characterization of odorous gases at Tianziling landfill site was studied. It was found that the dumping area and leachate treatment plant were the main odor emission sources. Sixty-eight odorous compounds were quantified by Gas chromatography-mass spectrometry (GC/MS). The result showed that H2S and NH3 were the principal compounds of odor emissions, followed by halogenated compounds, aromatic compounds, sulfur compounds, volatile fatty acids, oxygenated organics and other hydrocarbon.The seasonal variations of main odor emissions (H2S and NH3) affected by the amount of landfill solid waste, fresh clay, the value of air pressure, temperature, moisture and wind direction were investigated. It was found that the value of air pressure, temperature and moisture took the most important part in influencing concentration variation of H2S and NH3 concentrations; the dispersal direction of the main odorants from dumping area to factory boundary was mainly affected by the east wind, southeast wind and northeast wind; there were no significant differences in reducing emission of H2S and NH3 by simply adding the amount of landfill cover materials or deodorant.2. Charcoal sludge compst, the novel daily cover material for odor control, was developed., The result of simulation experiment was shown that the removal efficiencies of H2S and NH3 by charcoal sludge compost (>85%) was much higher than that by covered soil, aged refuse and fresh clay. Meanwhile, the charcoal sludge compost also performed high removal efficiencies in removing volatile fatty acids (88%), aromatic compounds (95%), and halogenated compounds (86%).The sulfoxidation and nitrification in charcoal sludge compost was higher than that in other three landfill cover materials. H2S and NH3 produced by biodegradation of MSW could be removed and converted to SO42--S and NO3--N.3. Temporal shifts of bacterial community compositions in four kinds of landfill cover materials were different, which were assessed by using scanning electron microscope (SEM) and polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE). The principal components analysis based on DGGE patterns indicated that there were statistically significant differences between charcoal sludge compst and the other three kinds of cover materials (P<0.01). These results suggested the larger amount and higher abundance of dominant microflora in charcoal sludge compost was probably in relation with the best performance of odor removal efficiency.4. The simple landfill units (400 m3) was designed and established in Tianziling landfill site at Hangzhou to investigate the variations of main odor emissions (H2S and NH3) and odor intensity of MSW during the first fifty-five days. It was found that emission concentrations of H2S and NH3 were stable (0.2 mg/m3 and 5 mg/m3 , respectively). There was a siginificant downtrend of odor intensity with time, so it was important for odor control at initial landfill stage. Odor removal efficiencies by five landfill cover materials: fresh clay, covered soil, charcoal sludge compst, aged refuse and the aged refuse - fresh clay mixture were compared. Results showed that the removal efficiencies of H2S and NH3 by charcoal sludge compost were most excellent (>85%). The removal efficiencies of H2S and NH3 by charcoal sludge compost were 30% and 28%, respectively, more than that by fresh clay. Moreover, on the first day of experiment, the removal efficiencies of H2S and NH3 by charcoal sludge compost were above 34% and 30%, respectively, compared with fresh clay. Its outlet concentrations of H2S and NH3 were less than the concentration limits given by the secondary emission standard for odor pollutants (GB14554-93). In conclusion, charcoal sludge compost was the most suitable daily cover material, which could control the odor pollutions effectively. |
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