Title page for etd-0718115-165840


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URN etd-0718115-165840
Author Dai-Wei Chiu
Author's Email Address No Public.
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Department Environmental Engineering
Year 2014
Semester 2
Degree Master
Type of Document
Language zh-TW.Big5 Chinese
Title Using poly-glutamic acid to enhance the anaerobic dechlorination of trichoroethylene
Date of Defense 2015-07-24
Page Count 88
Keyword
  • γ-PGA
  • denaturing gradient gel electrophoresis (DGGE)
  • real-time PCR
  • trichloroethylene
  • reductive dechlorination
  • Abstract Groundwater at many existing and former industrial areas and disposal sites are contaminated by halogenated organic compounds that were released into the environment. Trichloroethylene (TCE) is one of the most commonly found halogenated organic compounds in groundwater. Application of in situ anaerobic bioremediation is a feasible technology to remediate TCE-contaminated site. However, enhanced in situ bioremediation requires the injection of primary substrates. The poly-(γ-glutamic acid) (γ-PGA) is a biopolymer synthesized by biochemical processes. Due to its characteristics of moisture resistance, high viscosity, no toxicity, and chelating ability with metals, it has been widely applied by the industry. In this study, microcosm study was performed to evaluate the feasibility of using γ-PGA as a primary substrate to enhance the dechlorinating process of TCE under anaerobic conditions. Molecular biological techniques [e.g., PCR-DGGE (polymerase chain reaction-denatured gradient gel electrophoresis), real-time PCR] were used to evaluate the microbial diversity and variations in dominant bacterial species during the microcosm study. Results indicate that the γ-PGA could be used as the substrate and resulted in the TCE dechlorinating TCE effectively. Results show that TCE concentrations dropped from 4.23 to 0.26 mg/L within 42 days of operation. Up to 99% of TCE could be removed after 84 days of operation. In microcosms with emulsified oil addition, pH dropped to 5.7 after 84 days of operation. Results show that the pH remained neutral (pH = 7.32) in microcosms with γ-PGA addition after 84 days of incubation. This indicates that γ-PGA had good buffering capacity during the anaerobic processes. The total organic carbon (TOC) concentrations in microcosms dropped from 1,978 to 646 mg/L after 84 days of operation. The significant decrease in TOC concentrations indicate that the γ-PGA was consumed by microbial consortia in microcosms causing the shifting of oxidation-reduction potential from aerobic to anaerobic conditions, which favored the occurrence of reductive dechlorination. The population of Dehalococcoides spp. increased from 1×104 to 1.5×106 after 84 days of operation in PGA addition microcosms. This indicates that the addition of γ-PGA enhanced the growth of Dehalococcoides spp., which could significantly activate the TCE dechlorination. The addition of γ-PGA created anaerobic conditions and leaded to a more complete TCE removal via biodegradation mechanisms. Results show that the enhanced anaerobic bioremediation is an effective and applicable technology to remediate TCE-contaminated groundwater.
    Advisory Committee
  • Jong-Kang Liu - chair
  • Shu-Hao Liang - co-chair
  • Lei Yang - co-chair
  • Jimmy C. M. Kao - advisor
  • Files
  • etd-0718115-165840.pdf
  • Indicate in-campus at 99 year and off-campus access at 99 year.
    Date of Submission 2015-08-18

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