Title page for etd-0720114-180927


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URN etd-0720114-180927
Author Wei-ting Cheng
Author's Email Address No Public.
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Department Biological Sciences
Year 2013
Semester 2
Degree Master
Type of Document
Language zh-TW.Big5 Chinese
Title Use of quantitative real-time PCR to evaluate the effectiveness of enhanced biodegradation on chlorinated organic contaminants
Date of Defense 2014-07-28
Page Count 143
Keyword
  • reductive dechlorination
  • quantitative real-time PCR
  • denaturing gradient gel electrophoresis
  • bioremediation
  • trichlorethylene
  • Abstract The goal of this study is using molecular biology techniques to assess the effectiveness of anaerobic in situ bioremediation of chlorinated organic contaminants. In this study, a chlorinated organic contaminated site was injected with emulsified carbon-releasing substrate (ECS) to promote in situ microbial growth, as well as to release hydrogen generated by anaerobic decomposition of the ECS to enhance dechlorination of chlorinated organic compounds. DNAs were extracted from groundwater samples to analyze the microbial communities by using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE). In order to understand the role of Dehalococcoides species in the dechlorination process, quantitative real-time PCR was used to detect the presence and shift of these bacteria and associated dehalogenase genes. The results showed all temperatures of the monitoring wells were generally maintained at 25-30℃ during this study. After ECS was injected, the total organic carbon (TOC) raised and its concentration was much higher than the background. The TOC was consumed gradually by microorganisms, indicated that ECS was a sustained-release matrix and could provide a source of nutrients for microbial growth. At the beginning of ECS injection, oxidation-reduction potential and dissolved oxygen of all injection wells slowly decreased to reduced state that could enhance the following anaerobic bioremediation. The trichloroethylene decreased below the detection limit (<1 μg/L). The trichlorethylene-degradation byproducts, dichloroethenes and vinyl chloride, were found in groundwater samples. The expression of reductive dehalogenase genes (TceA, VcrA and BvcA) were consistent with the concentration of chlorinated organic contaminants indicated that reductive dechlorination process was developed in this anaerobic environment. In quantitative analysis, the amount of Dehalococcoides species was affected by pH, but still maintained a constant number during the remediation processes, demonstrated that Dehalococcoides species played an important role in anaerobic dechlorination. Fifty-one dechlorination bacterial species were identified from the groundwater, including Acidovorax spp., Alcaligenes spp., Clostridium spp., Dehalobacter spp., Dehalococcoides spp., Desulfuromonas spp., Enterobacter spp., Hydrogenophaga spp., Methylosinus spp., Pseudomonas spp., Ralstonia spp., Rhodococcus spp., Stenotrophomonas spp., Variovorax spp., Wautersia spp. and so on. Other anaerobic bioremediation related bacteria species found including: (1) 54 denitrifying associated species; (2) 12 manganese(IV) reduction and iron(III) reduction species; (3) 9 sulfate-reducing species; (4) Clostridium spp. and Ruminococcus spp. that could generate hydrogen. All these bacteria could create an anaerobic environment and promote the reductive dechlorination. Due to the diversity of groundwater environment, the ECS injection area still possesses both aerobic and anoxic regions. Thirteen bacterial methanotrophs were recognized from the groundwater. These methanotrophic bacteria consumed methane as their carbon source and cut down the release of methane into the atmosphere. In conclusion, the injection of ECS is an effective and feasible bioremediation way to treat chlorinated organic contaminated sites.
    Advisory Committee
  • Chih-Ming Kao - chair
  • Chien-Cheng Chen - co-chair
  • Jong-Kang Liu - advisor
  • Files
  • etd-0720114-180927.pdf
  • Indicate in-campus at 99 year and off-campus access at 99 year.
    Date of Submission 2014-08-21

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