A Study on Bubble Respirometer to Monitor Microbial Activity in Passive Bioventing System
| Autor: | Kuan-Hsine Li, 李冠賢 |
|---|---|
| Rok vydání: | 2015 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 103 At a site of oil contamination, the concentration of contaminants is usually high in soil when leak is found, it is because oil tanks and pipelines are often buried underground for a long period of time. Bioventing is a proper technology to remove contaminants such as diesel of low volatility, as oxygen and nutrients are provided to sustain the mass growth of aerobic microorganisms that degrade oil contaminants in the polluted area, thus achieving pollutant removal. The effectiveness of bioventing depends on microorganisms in soil to degrade the target contaminants. By constantly monitoring the changes in the activity of these microorganisms, it assists to evaluate the practical performance of biological remediation. A wind-driven bioventing pilot containing diesel contaminated soil at high concentration (approximately 20,000 mg/kg) was built for this study. A bubble respirometer was introduced in combination with the bioslurry method to monitor the activity of microorganisms in soil as the experiment setup to investigate the relationship between the degradation of diesel concentration and the activity of microorganisms in soil during the biovetning process. In the microorganism growth experiment using the bioventing pilot, the diesel-degraded microorganisms were domesticate for 4 weeks, while the relative diesel concentration (C/C0) reached 0.8. The results of accumulated oxygen uptake curve and 24-hour average oxygen uptake curve indicated that the activity of diesel-degraded microorganisms increased after 3 weeks, and the diesel degradation continued. In the microorganism growth experiment using the bioventing pilot with the addition or nutrients, the relative diesel concentration reached the highest at 0.65 in week one for Bacillus cereus, Pseudomonas putida and the mixture of three microorganism, and 0.8 for Achromobacter xylosoxidans, however in week 4, the relative diesel concentration reached 0.3 for the mixture. The activity monitoring with bubble respirometer suggested that the activity of Bacillus cereus and Pseudomonas putida continued to increase for 2 weeks, 3 weeks for Achromobacter xylosoxidans and 4 weeks for the mixture before it started to decline. The 24-hour average oxygen uptake curve showed clearly the changes in the period of microorganism oxygen uptake before and after addition of nutrients, and was related to the changes in the relative diesel concentration for 4 weeks or more. Therefore, if the microorganism activity monitoring is combined with elemental analysis to understand nutrient consumption, and the environmental conditions are maintained in favor of the microorganism degradation, the remediation performance of bioventing will be enhanced effectively. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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