Removal of TCE and VC in Groundwater by a Biobarrier
| Autor: | Chao-Wen Liu, 劉詔文 |
|---|---|
| Rok vydání: | 2004 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 92 The biodegradation and removal of trichloroethylene (TCE) and vinyl chloride (VC) in groundwater under aerobic condition by indigenous soil cells and toluene-degrading cell (Pseudomonas putida F1) were investigated in this study. A series of batch experiments using toluene as co-substrate to induce toluene dioxygenase (TDO) for co-metabolizing of TCE and VC were carried out. In addition, bioremediation of TCE and VC in contaminated saturated aquifer were studied by laboratory scale column tests, which were designed to simulate the bio-barriers under the conditions of enhancing activity of in-situ soil cells by bio-stimulation. Batch experimental results showed that the indigenous soil cells and P. putida F1 could effectively co-metabolize TCE with 100 mg/L toluene added and the removal efficiency of TCE was 87% and 94%, respectively. However, when P. putida F1 seeded to soil, the TCE removal efficiency decreased from 94% to 89% due to the competition for toluene between P. putida F1 and indigenous soil cells. Additionally, indigenous soil cells could utilize VC as a sole carbon source and the removal efficiency of VC was around 60%. It also found that the supplement of exogenous primary substrate, e.g. toluene, did not increase the degradation of VC in this study. Thus, further studies are needed to figure out if any other compatible co-substrate could enhance the co-metabolize degradation of VC by indigenous cells. Soil column tests included (1) indigenous soil column for aerobic oxidation of VC, (2) indigenous soil column for aerobic co-metabolism of TCE and (3) indigenous soil column with adding P. putida F1 for TCE co-metabolism. The test results indicated that TCE and VC would breakthrough along the columns during the initial start up period due to the lack of induced toluene dioxygenase or the low activity of microorganisms. Moreover, the dominant biodegradation occurred in the front end of the column after 20 days of operation. It observed that the concentrations of TCE and VC in the column effluent decreased with the increase of the operation time. The removal efficiencies of TCE and VC were greater than 99% after 30 days of operation. As a result, the soil columns could effectively biodegrade the contaminants when the growth of microorganisms approached to steady phase. In addition, no other chlorinated byproducts were detected while TCE and VC were biodegraded. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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