Chlorinated aliphatic hydrocarbons (CAHs) include tetrachloroethene (PCE), trichloroethene (TCE), and others. The industrial solvent TCE is among the most ubiquitous chlorinated compounds found in groundwater pollution. TCE in environment can be removed by physical, chemical and biological procedures.
Dehalorespiration is a biological pathway from which bacteria can derive energy from the reductive dechlorination of chlorinated ethenes using hydrogen or organic acids as electron donors and yielding chloride and ethene as degradation products. Dehalorespiration can be used to remediate chlorinated ethene contaminated aquifers if an appropriate aquifer ecosystem exists including populations of dechlorinating bacteria and companion organisms that contribute to the biogeochemical environment conducive to dehalorespiration activity. Enhanced in-situ aerobic or anaerobic bioremediation of chlorinated solvents is a cost-effective, expanding technology for the clean-up of chlorinated solvent-contaminated sites. The objective of this pilot-scale study was to apply an enhanced in situ bioremediation technology to remediate TCE-contaminated groundwater. Both aerobic and anaerobic remedial systems were evaluated at a TCE-spill site located in southern Taiwan. In the aerobic bioremediation zone, the effectiveness of air, nutrient, and sugarcane molasses injection to enhance the aerobic cometabolism on TCE degradation was evaluated. Results show that the decreases in TCE concentration were observed over 204 days operating period. Up to 73¢H-99¢H of TCE removal efficiency was obtained in this treatment system. In the anaerobic test zone, the effectiveness of nutrient and sugarcane molasses injection to enhance the anaerobic dechlorination on TCE degradation was also evaluated. Results show that the decreases in TCE concentration were observed over a 193-day operating period. Up to 53¢H-91¢H of TCE removal efficiency was obtained in this treatment system. Polymerase chain reaction was applied to analyze the gene variation in TCE-microbial degraders during the treatment process. Results from this study indicate that the aerobic TCE-degraders (type¢¹methanotrophs and type ¢º methanotrophs) and the gene of degradation enzymes (toluene monooxygenase, toluene dioxygenase, particulate methane monooxygenase) were detected after the treatment process in the aerobic test zone. In the anaerobic treatment zone, Dehalococcoides (anaerobic TCE-degrader) and the gene of degradation enzyme (vcrA and tceA) were detected and a significant drop of TCE concentration was also observed. Based on 16S rDNA sequence analysis, samples of groundwater from aerobic/anaerobic bioremediation zone are close related to the genera of Dehalococcoides sp. MB, Dehalococcoides ethenogenes 195, Dehalococcoides sp. VS, Acidovorax sp., Alicycliphilus sp., Burkholderiales, Caulobacter sp., Caulobacter tuntrae, Caulobacter vibrioides, Comamonadaceae, Hydrogenophaga sp., Iron-reducing bacterium, Mitsuaria chitosanitabida, Rhodocyclacea, Pseudomonas sp., Rhodoferax ferrireducens, Acinetobater sp., actinomycete, Pseudomonas aeruginosa and Variovorax sp. Results reveal that both the aerobic cometabolism and anaerobic dechlorination are feasible and applicable technologies to clean up TCE contaminated aquifers. Thus, the in situ bioremediation technology has the potential to be developed into an environmentally, economically and naturally acceptable remediation technology.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0207110-212744 |
| Date | 07 February 2010 |
| Creators | Chien, Hua-yi |
| Contributors | Huang Wen-Yen, Chen Ku-Fan, Yu Kuang-Chung, Lai Chin-Hsing, Kao Chih-Ming, Tsai Li-Jyur |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | Cholon |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0207110-212744 |
| Rights | campus_withheld, Copyright information available at source archive |
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