• Anaerobic Biodegradation Of Benzene Under Environmental Conditions Of Sub -Arctic Groundwaters

      Raad, Nada Itani; Kane, Douglas (2001)
      This research was conducted to detect and understand the potential for anaerobic degradation of benzene in a sub-arctic aquifer environment. The major hypothesis tested in this dissertation is that indigenous microorganisms from anaerobic groundwater wells contaminated with BTEX (benzene, toluene, ethylbenzene, xylenes) can use benzene as a carbon or energy source under conditions favoring iron- and sulfate-reduction and methanogenesis. To test this hypothesis microcosms were prepared and incubated under anaerobic conditions, with either hematite (Fe2O3) or sodium sulfate (Na2SO4) added to permit growth of iron and sulfate reducing bacteria. Several concentrations of benzene were used as a substrate, and the microcosms were incubated at temperatures of 21�C and 4�C. Cell counts were done and some characteristics of the bacteria, such as shape, gram staining, and spore formation were determined. The aromatic hydrocarbon benzene, was anaerobically transformed under both psychrophilic (4�C) and mesophilic (21�C) conditions. The temperature and substrate concentration played a role in determining the rate at which benzene was biodegraded under conditions favorable to iron-reducing, sulfate-reducing, or methanogenic bacteria. The rate of degradation under conditions favoring methanogenesis was faster than that under iron and sulfate-reducing conditions at 4�C, but not at 21�C. In general, at 21�C the biodegradation of benzene was faster in the presence of an exogenous electron acceptor. Benzene degraded completely under iron and sulfate-reducing conditions but did not degrade completely in most of the microcosms under methanogenic conditions. Phenol and was detected as intermediates for this transformation under all conditions. Benzene degradation rates were independent of the electron acceptor. This suggests that removal of benzene was initiated via fermentation reactions occurring under all conditions. Addition of a small concentration of sulfate or ferric as electron acceptors made degradation more complete. The in vitro research conducted on the anaerobic biodegradation of benzene provided new insight into the anaerobic degradation processes that occur at cold temperatures associated with sub-arctic environments. It also provided insights of the roles different types of microorganisms may play in the natural attenuation of contaminants.
    • Analysis and comparison of cyanide detoxification methods from spent heaps

      Kroeger, Edwin Bane; Huang, Scott L.; Nelson, Michael G.; Bandopadhyay, Sukumar; Braddock, Joan F.; Chen, Gang; White, Daniel H. (1997)
      This work entailed the testing of cyanide degradation of microorganisms isolated by the U.S. Bureau of Mine's Salt Lake Research Center (SLRC) and native strains isolated from an Alaskan mine, development of conceptual designs for in situ biological detoxification of leached heaps, and comparison of common in situ and ex situ heap detoxification processes using a cost comparison, sensitivity analysis, and Monte Carlo simulation. Microorganisms from an Alaskan mine site and SLRC were tested for cyanide degradation. Testing of samples from the Ryan Lode site indicated that several bacterial colonies could tolerate cyanide, but no degradation was found. Once degradation was confirmed in the SLRC sample, a winter survival rate test and an in situ heap detoxification test were performed. Winter survival experiments indicated approximately 5-20% of the bacterial population in heap agglomerate samples were viable after a winter and subsequent coldroom wait. In addition, bacteria colonized the agglomerate where nutrients were available. During August 1993, a 250 ton test heap was constructed on a heap that was undergoing detoxification using the INCO air-SO$\sb2$ process. The test heap was inoculated with bacteria in October 1993 and September 1994. Unfortunately, the test was terminated at an early stage, limiting the conclusions. The detoxification processes chosen for comparison were in situ biological, peroxide, and chlorination, and ex situ biological, INCO air-SO$\sb2,$ peroxide, and chlorination. To compare the costs, a hypothetical heap of 1 million tons was used. In situ biological detoxification had a cost of $0.41 per ton of ore treated, followed by ex situ biological detoxification, with a cost of \$0.92 per ton. The remaining methods ranged from $1.05 to \$1.35 per ton. The biological detoxification methods were most sensitive to the rinsing rate, labor costs, and capital costs. The chemical detoxification methods were most sensitive to oxidant cost, oxidant to cyanide ratio, and starting cyanide concentration. For the Monte Carlo simulation, in situ biological detoxification had a cost of $0.63 per ton treated, followed by in situ peroxide with a cost of \$1.09 per ton. The remaining methods ranged from $1.11 to \$1.45 per ton.
    • Micro Scale Analysis Of Fluid Flow And Diffusion In Coarse Grained Porous Media

      Fourie, Walter Johannes; Barnes, David L. (2011)
      X-ray computed tomography and finite element analysis were used to visualize the internal geometry of porous media and calculate the hydraulic conductivity and the diffusion of a dissolved species through the media. The results were compared to laboratory generated results. The calculated hydraulic conductivity showed good agreement with the laboratory results, over-predicting the laboratory results with only 12.5%. Comparison of the calculated results with the Kozeny-Carman equation showed that the Kozeny-Carman equation over-predicted the laboratory results between 62% and 740% depending on the formulation used. The tortuosity and specific surface area showed the highest correlation in predicting the difference between the Kozeny-Carman equation and the modeling results, while the porosity showed the greatest influence in determining the magnitude of the hydraulic conductivity as calculated by the Kozeny-Carman equation. The calculation of the diffusion of potassium iodide through ceramic disks and sandstone showed accurate prediction of the concentration in the receiving cell for the length of the experiment (35 days) for one of the ceramic disks and the sandstone. The other ceramic disk showed accurate prediction up to 20 days, after which it deviated. The results from the study indicate that the diffusional tortuosity and the hydrodynamic tortuosity differ in magnitude, and that they can not be used interchangeably, since (1) the ceramic disks showed the closest prediction to the laboratory results when the diffusional tortuosity is used, rather than the hydrodynamic tortuosity, and when it enters the equation to the first power; and (2) the sandstone showed the closest prediction to the laboratory results when the diffusional tortuosity is used, and when it enters the equation to the second power. Broadly speaking, the results from this study show that the micro scale analysis of porous media allows the accurate calculation of macro scale parameters.
    • Thermally enhanced bioventing of petroleum hydrocarbons in cold regions

      Filler, Dennis M.; Carlson, Robert F. (1997)
      Petroleum-based contamination of the environment has and will likely continue to be a problem as long as oil and natural gas supply much of the world energy demands. In cold regions, where vast quantities of these fuels are extracted and used, climate and frozen soils limit remedial efforts to a few technologies. Bioventing has shown promise as a viable method for the remediation of spilled petroleum-based fuels in cold regions. An in situ study of bioventing with soil warming was conducted at a Fairbanks, Alaska site. The main purpose of this research effort was to compare the effectiveness of thermal enhancement techniques applied to bioventing. Objectives included (1) developing a suitable thermal insulation system(s) that would provide year-round bioventing of petroleum contaminated soils, (2) modeling of the thermal regime below three treatment areas, (3) relating monitoring and testing data to thermally enhanced biodegradation, and (4) presenting the information in a way that is useful to engineers, biologists and environmental scientists. Active soil warming with electrical heat tape beneath polystyrene insulation and sand and gravel overburden raised subsurface soil temperatures from the ground surface to the water table by as much as 15$\sp\circ$F. The actively warmed test plot was successfully heated year-round, preventing soil freezing and enhancing microbial activity. Soil gas, microbiological, and geochemical sampling data evidenced correlation between increased bioactivity and soil warming. Passively treated soils evidenced some winter increase in temperatures, although some periodic soil freezing did occur. Overall, biodegradation within both passively treated and untreated contaminated test plots was noticeably slower than within the actively warmed plot. Thermally enhanced bioventing successfully remediated hydrocarbon contamination in vadose zone soils at a subarctic site within two years. After oxygen, temperature appears to be the most important factor affecting microbial activity and biodegradation. Variable and low moisture contents did not seem detrimental to bioactivity.