| Summary: | 碩士 === 國立中興大學 === 環境工程學系所 === 98 === A thermophilic aerobic system has many advantages, such as high organic loading, higher substrate utilization rate, high biodegradation rate, low sludge yield, smaller area requirement, excellent process stability, and destruction of most pathogenics, over a traditional aerobic one. However, it also has disadvantages, such as low settlability that results in the problem of low quality effluent. Therefore, a thermophilic aerobic membrane system was set up to improve effluent quality in this study.
In this research, the thermophilic aerobic membrane bioreactor of 25 L was operated at 55℃. The thermophilic aerobic membrane system consisted of mixed culture with Bacillus sp., Tepidiphilus sp., and Caldilinea aerophila sp.. The high concentration organic wastewater consisted of glutamic acid and sucrose to make the influent substrate of 10,000 mg-COD/L for the system. When the system reached steady state, the treatment efficiency of high concentration organic wastewater was evaluated. Furthermore, kinetic models were employed to fit to the batch experimental kinetic parameters of the thermophilic aerobic membrane system. In addition, PCR-DGGE was employed to determine the microbial community of mixed culture in the bioreactor. Besides, SEM-EDS was employed to determine the causes of membrane fouling in this bioreactor.
The result showed that the highest removal efficiency of sCOD, TKN, Org-N were up to 97, 87, and 99.5% , respectively, in the thermophilic aerobic membrane system. The maximum specific substrate utilization rate was found to be 111.84 mg-sub/mg-cell-day in the research, and it was achieved at the initial substrate concentration of 20,000 mg/L. That confirms that the thermophilic aerobic membrane system has exhibited considerable advantages for the treatment of high-strength wastewaters. Additionally, a nonlinear regression technique was employed to determine the kinetic parameters of the thermophilic aerobic biodegradation process, and it suggested that Webb model could be successfully used because of its high correlation coefficient of 0.92. Moreover, the kinetic parameters of μmax, Ks, and Ki evaluated by Webb model were 8.59 mg-cell/mg-cell-day, 1,320 mg-COD/L, and 1.80×1012 mg-COD/L, respectively.
The molecular approach of PCR-DGGE was used to assess microbial diversity in the thermophilic aerobic membrane system. 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 gradients of DGGE ranging from 30% to 70% were used 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 Thermus sp. was certainly the dominant microorganisms in the bioreactor. Furthermore, the approach of SEM-EDS was used to assess membrane fouling in the thermophilic aerobic membrane system. As a result, biological slime formation and scale formation caused membrane fouling.
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