| Summary: | There is a need for sustainable approaches in the remediation of hydrocarbon (HC)-impacted environments. Bioremediation has gained prominence but to be effective this requires consideration of the physical, chemical and biological processes in an environmental matrix. In the first part of this study, physical constraints to effective bioremediation of drill cutting (DC) were quantified using slurry-phase treatments. The DC:water ratio and aeration of the DC slurries were optimised. Results indicated that physical parameters, unless effectively managed, could greatly influence the performance of bioremediation campaign, both in terms of end-point and duration. Once physical aspects have been addressed, it is important to understand both chemical and biological processes. There has been a great deal of work considering the significance of chemical processes such as bioavailability, pH performance range and nutrient optimisation. These were not investigated in this programme of research. Bioaugmentation (microbial seeding of contaminated soils) has been proposed as a significant method for bioremediating HC-contaminated matrices. However, the value of bioaugmentation has been the subject of considerable controversy. The performance of bioaugmentation was studied in this project both directly and indirectly. Compounds capable of encouraging the activity of HC degraders were added to media. This "conditioning" process was investigated and quantified in three major experiments. Firstly, the conditioning of a HC-degrading bacterial consortium using selective enrichment substrates was studied. Here, INT reduction was monitored over time using 96-well microplates containing mineral media supplemented with diesel, toluene, hexadecane and phenanthrene. The colour development resulting from conditioning on different substrates varied significantly (P≤ 0.05). Secondly, the performance of HC degraders (Pseudomonas putida F1 and it's bioluminescent derivative, P. putida TVA8) after conditioning on a range of catabolic inducer substrates was studied. The development of an optimised experimental procedure to study carbon transformation of toluene as a consequence of conditioning was reported. Cultures conditioned on toluene had significantly (P≤ 0.05) higher activity, biomass and toluene degradation rates than the other treatments. Finally, the effect of conditioning three HC-degrading bacteria (Pseudomonas putida NCIMB 9816, Pseudomonas sp. and Klebsiella sp.), individually and in combination, on degradative performance and relative species abundance was assessed. DGGE profiles indicated significant (P≤ 0.05) changes in relative species abundance but, generally, there were no significant differences in HC degradation or cumulative respiration. The results reported in this thesis, at the genotypic, phenotypic and functional levels reveal the complexity of HC remediation and the need to combine detailed analytical chemistry with focussed microbial measurements.
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