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Attachment A <br />bacteriological analysis of the shale. In general, successful bioremediation of <br />hydrocazbons requires oxygen and the control of other parameters. The cost of an <br />extensive testing program and problematic control of physical and chemical properties <br />coupled with great uncertainty for success, negated further consideration of this <br />alternative. However, OOSI conducted other tests at the mine related to bioremediation <br />treatment. <br />Bacteriological Sampling <br />The retort process was expected to sterilize any natural bacteria present in the ambient <br />groundwater near the retorts. Samples of sediment collected from the Upper Manhole in <br />2005 showed a reasonable amount of bacteria were present with moderate diversity. <br />However, it is not known if bacteria from these samples are representative of bacteria <br />present inside the retorts. It is generally thought that, after over 20 years of retort <br />drainage, if indigenous bacteria were present and able to actively bioremediate the <br />hydrocarbons in the retort, increased water quality should be evident through analytical <br />data from water samples. In addition, the presence of high concentrations of sulfate and <br />other inorganics are not easily treated through bioremediation techniques. Discussions <br />with other experts in the field of bioremediation also indicated the potential success of <br />injection of inoculants may be short-lived. The lack of available oxygen to the retorts <br />was also an issue. <br />Passive Biologic Treatment Studies <br />In an effort to investigate ex-situ bioremediation, OOSI investigated passive treatment <br />technologies that focused on the potential removal of sulfate, a very conservative and <br />highly concentrated solute in the retort mine water. <br />Most constructed wetlands treatment projects aze designed to address nutrient loading, <br />acid mine drainage, and metal removal. While a few laboratory studies have been <br />conducted to evaluate the removal of sulfate in fluidized bed reactors and up-flow <br />anaerobic sludge-bed reactors, sulfate removal under alkaline conditions has not been <br />shown to be effective in constructed wetlands. <br />In the sulfate-reducing process, sulfate-reducing bacteria use sulfate as an electron <br />acceptor and hydrogen or organic compounds are oxidized to reduce sulfate to sulfide <br />and the sulfide reacts with some metals to form sulfide compounds with a low solubility. <br />The process requires an abundance of organic carbon as an energy source, and the <br />reactions are inhibited by the presence of calcium and sodium in the water (Sivulaa <br />2006). Biological treatment of sulfate in water also produces hydrogen sulfide gas which <br />causes corrosion, odor, increased chemical oxygen demand, and can result in increased <br />toxicity that may lead to process failure (Hulshoff 1998). Low temperatures also reduce <br />the effectiveness of this type of treatment (Gammon 1999). <br />Constructed wetlands may not be suitable for treating sulfate in groundwater because <br />sulfate is a conservative contaminant that can only be passively removed by bacterial <br />tt <br />