| dc.contributor.advisor |
Reible , Danny D . |
|
| dc.contributor.committeeMember |
Bennett , Philip |
|
| dc.contributor.committeeMember |
Charbeneau , Randall |
|
| dc.contributor.committeeMember |
Gilbert , Robert |
|
| dc.contributor.committeeMember |
Liljestrand , Howard |
|
| dc.creator |
Yan , Fei , Ph . D . |
|
| dc.date.accessioned |
2012 -10 -03T20 :16 :06Z |
|
| dc.date.accessioned |
2012 -11 -29T20 :54 :22Z |
|
| dc.date.available |
2012 -10 -03T20 :16 :06Z |
|
| dc.date.available |
2012 -11 -29T20 :54 :22Z |
|
| dc.date.created |
2012 -08 |
|
| dc.date.issued |
2012 -10 -03 |
|
| dc.date.submitted |
August 2012 |
|
| dc.identifier.uri |
http : / /hdl .handle .net /2152 /ETD -UT -2012 -08 -6260 |
|
| dc.description.abstract |
Capping is typically used to control contaminant release from the underlying sediments . However , the presence of conventional caps often eliminates or slows natural degradation that might otherwise occur at the surface sediment . This is primarily due to the development of reducing conditions within the sediment that discourage hydrocarbon degradation . The objective of this study was to develop a novel active capping method , an electrode enhanced cap , to manipulate the redox potential to produce conditions more favorable for hydrocarbon degradation and evaluate the approach for the remediation of PAH contaminated sediment .
A preliminary study of electrode enhanced biodegradation of PAH in sediment slurries showed that naphthalene and phenanthrene concentration decreased significantly within 4 days , and PAH degrading genes increased by almost 2 orders of magnitude .
In a sediment microcosm more representative of expected field conditions , graphite cloth was used to form an anode at the sediment -cap interface and a similar cathode was placed a few centimeters above within a thin sand layer . With the application of 2V voltage , ORP increased and pH dropped around the anode reflecting water electrolysis . Various cap amendments (buffers ) were employed to moderate pH changes . Bicarbonate was found to be the most effective in laboratory experiments but a slower dissolving buffer , e .g . siderite , may be more effective under field conditions . Phenanthrene concentration was found to decrease slowly with time in the vicinity of the anode . In the sediment at 0 -1 cm below the anode , phenanthrene concentrations decreased to ~70 % of initial concentration with no bicarbonate , and to ~50 % with bicarbonate over ~70 days , whereas those in the control remained relatively constant . PAH degrading gene increased compared with control , providing microbial evidence of PAH biodegradation .
A voltage -current relationship , which incorporated separation distance and the area of the electrodes , was established to predict current . A coupled reactive transport model was developed to simulate pH profiles and model results showed that pH is neutralized at the anode with upflowing groundwater seepage .
This study demonstrated that electrode enhanced capping can be used to control redox potential in a sediment cap , provide microbial electron acceptors , and stimulate PAH degradation . |
|
| dc.format.mimetype |
application /pdf |
|
| dc.language.iso |
eng |
|
| dc.subject |
Polycyclic aromatic hydrocarbon (PAH ) |
|
| dc.subject |
Biodegradation |
|
| dc.subject |
Sediment capping |
|
| dc.subject |
Redox |
|
| dc.subject |
Electrode |
|
| dc.subject |
Electrochemical |
|
| dc.title |
PAH degradation and redox control in an electrode enhanced sediment cap |
|
| dc.description.department |
Civil , Architectural , and Environmental Engineering |
|
| dc.type.genre |
thesis |
* |
| dc.type.material |
text |
* |
| thesis.degree.name |
Doctor of Philosophy |
|
| thesis.degree.level |
Doctoral |
|
| thesis.degree.discipline |
Civil Engineering |
|
| thesis.degree.grantor |
University of Texas at Austin |
|
| thesis.degree.department |
Civil , Architectural , and Environmental Engineering |
|
| dc.date.updated |
2012 -10 -03T20 :16 :17Z |
|
| dc.identifier.slug |
2152 /ETD -UT -2012 -08 -6260 |
|