Evaluation of in Situ Bioremediation Approaches in Meeting International Standards for Organic and Residual Metals Toxicity in Soils
Drilling fluids and muds are an essential component of the rotary drilling process used to drill for oil and gas on land and in offshore environments. However, the bioaccumulation of petroleum contaminated soils/drilling mud due to oil and natural gas exploration has posed a major environmental concern due to its prolonged environmental persistence and its leachability below the rhizosphere. The main objectives of this research were: (i) To assess initial toxicity of drilling mud and related contaminated soils from an agricultural setting in Galliano, Sicily (Phase one) and (ii) To develop a low intervention bioremediation approach using bioplug technology to ensure that the soil/drilling mud has met U.S. and international soil/ground water quality standards by performing a microcosm study (Phase two). Total petroleum hydrocarbon content of the drilling mud reduced to 617.0±176.0, 446.0±195.0, and 533.0±138.0 mg/kg from 5000.0±530.0 mg/kg after treatment via mixing (84.2-95% reduction). The PAH and phenol concentration of the drilling mud resulted in a 97-99.5% reduction via mixing (5d study) and 69.4-77.9% reduction via in situ treatment (40d study). The metals of concern for the drilling mud are cadmium and selenium. Both metals had exceeded Italian and La DEQ soil leachability standards, which were established at 0.005 mg/L for cadmium and 0.010 and 0.050 mg/L for selenium, respectively. In situ bioremediation was performed on a cross-section of Italian soil/mud to test the effectiveness of bioplug technology. Total petroleum hydrocarbons had reduced from 217.12±43.38 and 149.68±45.51 mg/kg to 15.16±3.35 and 34.27±15.86 mg/kg for the control drilling mud test beds, and from 89.20±67.42, 141.71±64.80, and 197.87±77.38 mg/kg to 5.24±6.15, 15.02±10.20, and 9.65±9.37 mg/kg for the experimental drilling mud test beds, respectively. The efficiency of degradation for control and experimental setups were 85.1±11.2% and 92.9±3.0%, respectively. Overall, the microcosm experiment indicated that a significant reduction in total petroleum hydrocarbons had taken place for the drilling mud using bioplug technology and will be installed at the Italian site.
Advisor:Ralph J. Portier; Vince Wilson; Ed Overton
School:Louisiana State University in Shreveport
School Location:USA - Louisiana
Source Type:Master's Thesis
Date of Publication:08/06/2002