| Summary: | 碩士 === 國立成功大學 === 環境工程學系碩博士班 === 90 === This research investigated the process performance of three-stage bioreactors treating PAN wastewater with high-strength nitrogenous compounds. By the water quality analysis of the PAN manufacturing wastewater, high concentration of organic nitrogen were found and the TKN/COD ratios were achieved 0.15-0.26 that indicated the complicated characteristics in biodegradation for the PAN wastewater. In order to enhanced biodegradation of nitrogenous compounds in PAN wastewater, a combined three-stage process of thermophilic anaerobic / anoxic denitrification / aerobic nitrification fluidized beds was employed. In the three-stage process, nitrogenous compounds were effectively degraded in thermophilic anaerobic fluidized bed, and organic carbon was removed in the denitrification fluidized bed. In the other way, nitrifiers could oxide the residual organic nitrogen and ammonia to nitrate completely in the final stage of aerobic nitrification fluidized bed.
In the beginning, a series of batch study in PAN wastewater degraded by three individual process, which were thermophilic anaerobic, anoxic denitrification, and aerobic nitrification process. The biodegradation study clearly showed that high concentration of PAN wastewater would inhibit the thermophilic anaerobes, and the biokinetic in PAN wastewater obeyed to Haldane inhibition model. On the other hand, denitrifers could utilized limited organic carbon in PAN wastewater for denitrification, and according to nitrogen production profiles, in the total COD of PAN wastewater, 27% were easily degraded, 19% were degradable, and 54% were hard to be degraded. For nitrification, the result of biokinetic study showed that high strength organic compounds would inhibit the bioactivity of nitrifiers.
In order to effectively convert organic nitrogen into ammonia in thermophilic anaerobic situation, the pre-removed strategy of sulfate and sucrose-adding would increase the activity of thermophilic anaerobes.
By the process control for treating PAN wastewater, the operation was not stable in the first period due to the variation of wastewater, including concentration and components of wastewater. In the second period, the operation performance got better in three stage process for adding sucrose as co-substrates. PAN wastewater was treated by only two stage process (anoxic denitrification / aerobic nitrification) in the third period, PAN wastewater could not be effectively degraded. In the fourth period, the three-stage process was operated again. Because the thermophilic anaerobe were enhanced in degrading nitrogenous compounds, the operation became stable and better in treating PAN wastewater. The concentration of effluent in three-stage process of COD and organic nitrogen were 175 mg/L and 13 mg/L, respectively. By the way, the bioactivity test showed the better activities for denitrifiers and nitrifiers in the fourth period.
Finally, the microbial biology technology was applied to the microbial population in the thermophilic anaerobic reactor. From the result of DGGE, the diversity of PAN-degrading bacteria would change in different volume loading. The bacteria communities in the thermophilic anaerobic fluidized bed were studied by fluorescent in situ hybridization (FISH) and confocal laser scanning microscopy(CLSM). Alpha and delta－Proteobacteria dominated the bacteria population, and some high G+C content bacteria and Clostridium could be characterized in this system.
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