Towards improved bioreactor design for remote field scale hydrocarbon bioaugmentation

Hydrocarbon contamination has a negative impact on the environment and can persist in the environment for long periods of time without some form of treatment. Microbial bioremediation utilizing bacteria is an increasingly applied method for treating hydrocarbon contamination. It is a more environmentally friendly option, generally cheaper, and provides a complete breakdown of the contamination into water and carbon dioxide. With its growing popularity, research on the topic has also increased. However, there is limited research on producing the bacteria in the field in a cost-effective manner. To address this, a series of experiments meant to evaluate media types and growth conditions for maximum growth in field bioreactors were evaluated. Investigation of various sources of field-related contamination were also evaluated to determine which source or sources of contamination have a detrimental effect on the target bacterial consortium so that these contamination sources can be addressed. The first chapter provided a background on the subject and the issues faced with bacterial bioremediation. The second chapter investigated the type of nutrients and growth conditions that provide optimal growth while factoring in cost. It was found that Bushnell Haas media supplemented with dextrose yielded high bacterial numbers while still being cost-effective. Chapter 3 investigated the bacterial community in two separate environments. The first was conducted in sterile laboratory conditions, where standard laboratory procedures were used to culture the consortium. The second environment was more representative of the field bioreactor, utilizing an air pump for aeration, larger vessels and the same media types evaluated in Chapter 2. From the results in Chapter 3, we were able to build on the findings from Chapter 2 and determine that Bushnell Haas not only produced sufficient cell density but also yielded a bacterial community of the target genera Bacillus spp. and Pseudomonas spp. Chapter 4 evaluated three main sources of contamination in the field bioreactors, including air for aeration, water, and exposure to the environment. From these experiments, it was evident that unsterilized water had the most significant impact on the community. Chapter 5 then evaluated the bacterial community in a field bioreactor used for treating contaminated soil. The results of this chapter revealed that the community consisted of a majority of contaminating bacteria. Based on the findings of Chapter 4, suggestions are made on which sources of contamination should be addressed to increase the proportion of target genera. Each of these chapters contains a conclusion on the findings of each respective chapter. The final chapter then provided a conclusion to all the chapters, bringing together the findings from the four previous chapters. In addition to bringing the chapters together, future directions of this research are suggested.