Enhancement of anaerobic biodegradation of petroleum hydrocarbons in contaminated groundwater: laboratory mesocosm studies

• Author / Creator

  Fan, Xiaoying

• This project was a part of a study to evaluate natural attenuation (NA) as a viable remedial option for petroleum hydrocarbon (PHC) contamination at upstream oil- and gas-contaminated sites in Alberta, Canada. Laboratory mesocosms were set up using groundwater and sediment materials collected from two PHC contaminated sites (Site 1 and Site 3) in Alberta to investigate the enhancement of anaerobic PHC biodegradation by amendment of terminal electraon acceptors (TEAs, nitrate or sulfate) and/or nutrients (ammonium and phosphate).

  Multiple lines of evidence, including the removal of benzene, toluene, ethylbenzene and xylenes (BTEX) and CCME F1 fraction hydrocarbons (C6 to C10), rapid depletion of TEAs, the production of biogenic gases, and detection of the metabolites verified that anaerobic PHC biodegradation was occurring in both laboratory mesocosm studies. Selective biodegradation of PHCs under different reducing conditions was observed. However, there was no conclusive evidence that one reducing condition will universally favor the biodegradation of specific PHCs. In both studies, nutrient amendment showed no enhancement effects.

  The calculated first-order biodegradation rates in Site 1 mesocosm study ranged from 0.0032 to 0.033 d-1 for benzene, 0 to 0.028 d-1 for ethylbenzene, 0.0021 to 0.036 d-1 for m-, p-xylenes, and 0.0006 to 0.0045 d-1 for F1-BEX (F1 hydrocarbons exclduding BEX) under the tested conditions. The laboratory first-order biodegradation rates of BEX were higher than the estimated field rates, indicating the potential of enhanced anaerobic biodegradation in situ. However, when comparing the TEA amended mesocosms with the unamended controls (in which iron reduction might be the predominant process), the enhancement effects were less apparent and inconsistent.

  The calculated first-order biodegradation rates in Site 3 mesocosm study ranged from 0 to 0.0009 d-1 for benzene, 0 to 0.011 d-1 for ethylbenzene, 0 to 0.0016 d-1 for m- and p-xylenes, and 0 to 0.15 d-1 for o-xylene. Sulfate amendment significantly stimulated biodegradation of all xylenes and CCME F1 hydrocarbons. However, there was no definitive evidence that nitrate or sulfate amendment could enhance benzene or ethylbenzene biodegradation.

• Subjects / Keywords

  • Anaerobic biodegradation
  • Enhanced attenuation
  • Laboratory mesocosm
  • Petroleum hydrocarbons
  • Contaminated groundwater

• Graduation date

  Spring 2010

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3GD8C

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.