Title page for ETD etd-10092000-15360015


Type of Document Master's Thesis
Author Rectanus, Heather Veith
URN etd-10092000-15360015
Title Assessment of Intrinsic Bioremediation at a PCE Contaminated Site
Degree Master of Science
Department Civil Engineering
Advisory Committee
Advisor Name Title
Novak, John T. Committee Co-Chair
Widdowson, Mark A. Committee Co-Chair
Berry, Duane F. Committee Member
Keywords
  • Microcosms
  • SEAM3D
  • Bioremediation
  • Natural Attenuation
  • PCE
Date of Defense 2000-08-18
Availability unrestricted
Abstract
Groundwater parameter analysis, microcosm experiments, and microcosms

modeling were undertaken to assess the potential of Monitored Natural

Attenuation as a remediation strategy at Site 12 at the Naval Amphibious

Base (NAB) Little Creek. Site 12 was contaminated with PCE waste disposed

by a former dry cleaning facility. In the groundwater analysis, contaminant

characteristics and redox indicators were evaluated to assess the

reductive dechlorination potential of Site 12. The results of the

groundwater analysis indicated that Site 12 exhibited sulfate-reducing

and methanogenic conditions which provide the required environment

for reductive dechlorination. However, Site 12 only demonstrated partial

reductive dechlorination to cis-1,2-DCE and possible anaerobic oxidation

of cis-1,2-DCE and VC to CO_{2}. Microcosms were designed to further

evaluate the extent of microbial degradation of the chlorinated ethenes

at Site 12 and to provide concentration versus time data for the estimation

of chlorinated ethenes' biodegradation rates. The extent of degradation

in the microcosms was consistent with the groundwater data. However,

ethene production was not observed and the quantity of TCE measured

for two of the microcosms differed substantially when compared to

the groundwater data. The microcosm model used SEAM3D to simulate

the results of the microcosm experiments (concentration versus time

data) to estimate the biodegradation rates of PCE and its daughter

products. The SEAM3D reductive dechlorination package, based on Monod

kinetics, predicted for the MLS12-Shallow microcosm maximum specific

utilization rates for PCE, TCE, cis-1,2-DCE and VC at 0.4, 0.42, 0.05,

and 0.25 day^{-1}, respectively and half saturation coefficients for

PCE, TCE, cis-1,2-DCE and VC at 0.41, 0.01, 0.07, and 0.02 mg/L, respectively.

The results of this study suggest that while the groundwater environment

provides the necessary conditions for reductive dechlorination, Site

12 is not an efficient system for reductive dechlorination. This lack

of efficiency may stem from sparse microbial populations capable of

reducing cis-1,2-DCE or the system may contain levels of PCE which

inhibit the further reduction of cis-1,2-DCE. Based on the observed

inhibitory relationship between PCE and cis-1,2-DCE and VC production,

source removal would reduce the PCE levels and encourage further reductive

dechlorination at Site 12. Therefore, the recommended first step for

a monitered natural attenuation-based remediation strategy at Site

12 should be source removal.

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