| Summary: | 碩士 === 國立中興大學 === 環境工程學系所 === 97 === The advantages of thermophilic aerobic biological system include smaller area requirement, destruction of most pathogenics, high biodegradation rates, low sludge yields, excellent process stability, and higher substrate utilization rate. But the theoretical knowledge, such as kinetic paramters of biodegradation and microbial community, is still unclear for the application of the system in practice. Farther research on relevant design parameters, operation requirements, and microbial community are needed.
In this research, cultures with the degradation ability of high concentration organic, oil-content, and pulp wastewater were added to a thermophilic continuous flow bioreactor of 32 L. The artificial wastewater consists of glutamic acid and sucrose for the influent substrate of 10,000 mg-COD/L. The bioreactor was operated at 55℃. When the system reached to the state, the treatment efficiency of high concentration organic wastewater was evaluated, and the kinetic parameters for the thermophilic biodegradation parameters were determined. Besides, PCR-DGGE was employed to determine the microbial community of mixed culture in this bioreactor.
The result showed that the highest removal efficiency of sCOD is up to 90% in the system. It confirms that the thermophilic aerobic biological treatment process has exhibited considerable advantages for the treatment of high-strength wastewaters. The removal rate of TKN from the influent with TKN mass of 2190 mg daily calculated by mass balance is up to 90%. It shows that the system could eliminate ammonia nitrogen by stripping.
The results of batch test for different substrate concentrations showed that the specific growth rate almost tended to increase with an increase in substrate concentrations because of operating at higher temperature. Comparing with low substrate concentration conditions, the high substrate concentration got higher specific substrate utilization rate over 3 times.
The result of batch test for microbial decay to inference the growth coefficient of microbial in the system showed that Ki is 0.13 mg-cell/mg-cell¬-d, and from which the Yobs of 0.21 mg-cell/mg-COD is obtained. Comparing with mesophilic microbial, thermophilic microbial has higher decay coefficient and lower growth coefficient. The result suggested that the thermophilic microbial can be used in decreasing sludge production. Additionally, a nonlinear regression technique was employed to determine the kinetic parameters of the thermophilic aerobic biodegradation process, and it suggested that Haldane, Aiba, and Teissier models can be successfully used for this study.
The molecular approach of PCR-DGGE was used to assess microbial diversity in the thermophilic aerobic biological treatment bioreactor. PCR amplifications were carried out by 968f-gc and 1392r primer sets which target with the 16S rDNA universal region of eubacteria. The linear denaturing gradient of DGGE ranging from 30% to 70% was for the analysis of mixed thermophilic microbial populations. DGGE banding patterns were evaluated, and bacterial populations were identified by sequencing individual bands. As a result, the species of Bacillus sp., Tepidiphilus sp., and Caldilinea aerophila genewere were certainly the dominant microorganisms in the bioreactor.
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