Isolation and Application of Sulfolane-Degrading Bacteria to Treat Sulfolane in Real Wastewater by Combining Biological New Environmental Technology (BioNET®)
| Autor: | LIU, YI-HONG, 劉奕宏 |
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| Rok vydání: | 2017 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 105 Petrochemical industry is foundation of national development and has great contribution to social and economic growth. As improvement of economic environment, people pay attention to environment quality so that numerous pollution control facilities and technologies are established. Sulfolane is extensively used as extractive solvent in sour-gas processing plant to remove hydrogen sulfide and in petrochemical industry to recover valuble products. However, as repeated use of sulfolane, deteriorated sulfolane becomes corrosive and may leak into environment to threaten aquatic and terrestrial organisms. Toxic sulfolane may also flow into the activated sludge system to cause shock loading and make effluent water quality fail to meet discharge standard. Thus, it is important to remove sulfolane from environment and maintain stable wastewater treatment efficiency. To deal with sulfolane, biological strategy is superior to physical and chemical strategies because of environmental friendly and cost consideration. Among several biological technologies, bioaugmentation is the addition specific microorganisms into soil, groundwater or wastewater treatment system to speed up the rate of degradation of a contaminant. Therefore, isolation of microbes capable of degrading target contaminant is an important issue. Moreover, maintenance of added microbes in the polluted area and system promises successful bioaugmentation. Biological New Environmental Technology (BioNET®) is the core of the biological treatment system with "porous biological carrier". The carrier contains high surface area to facilitate massive microbial attachment so that sludge age is prolonged and bacterial diversity is maintained. BioNET® has the advantages of easy operation, high processing load and high efficiency. In order to solve the wastewater treatment system of petrochemical plant suffered by sulfolane shock loading, in this study, sulfolane degrading bacteria from the activated sludge system of petrochemical plant were enriched and isolated. After confirming thier sulfolane degrading ability, target sulfolane degrading bacterium used for bioaugmentation was further selected by comparing their utilization of various diluted real wastewater with and without 1000 mg/L sulfolane. Sulfolane biodegradation of target sulfolane degrading bacterium was then investigated under various pHs, sulfolane and sulfate concentrations. After establishing the optimal sulfolane-degrading contidition, bioaugmentation effect was evaluated by sulfolane removal efficiency when BioNET® reaction tank was operated in the presence and absence of sulfolane degrading bacterium. Enrichment could enhance sulfolane degrading rate of mixed culture from 3.9 to 7.1 times. There were 18 strains isolated from the enriched activated sludge. Among these isolates, 3 strains (strain Y-a, Y-d and Y-f) were capable of degrading sulfolane and all identified as Cupriavidus metallidurans using 16S rDNA sequencing. Strain C. metallidurans Y-a, C. metallidurans Y-d and C. metallidurans Y-f could utilize real wastewater and degrade 1000 mg/L sulfolane in real wastewater. Among these 3 strains, strain C. metallidurans Y-d had the highest sulfolane and sCOD removal efficiencies so was chosen for the following experiments. The specific growth rate and specific substrate utilization rate of strain C. metallidurans Y-d at pH of 7-9 were obviously higher than those at pH of 6. 1000 mg/L sulfolane was almost completely degraded at pH of 7-9. The optimal pH of strain C. metallidurans Y-d to degrade sulfolane was 8. When increasing sulfolane concentration from 500 mg/L to 2000 mg/L, the specific growth rate increased from 0.194 to 0.479 and the specific substrate utilization rate increased from 0.480 to 0.593. Therefore, strain C. metallidurans Y-d was capable of degrading 2000 mg/L sulfolane. High sulfate concentration causing high osmotic pressure had a negative effect on sulfolane degradation. The results of BioNET® reaction tank experiments indicated that average sulfolane and sCOD concentrations in the effluent in the presence of strain C. metallidurans Y-d were significantly lower than those in the absence of strain C. metallidurans Y-d. The sCOD average concentration in the effluent with bioaugmentation could meet the petrochemical plant effluent standard. Bioaugmentation could substantially enhance sulfolane removal efficiency of BioNET® reaction tank. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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