Master of Science in Chemical Engineering (MSChE)


Chemical Engineering

Document Type



The influence of the oligochaete Ilyodrilus templetoni on the degradation of phenanthrene and benzo(a)pyrene present in a field-contaminated sediment was studied in microcosm experiments. Results indicate an enhanced degradation of phenanthrene and benzo(a)pyrene in microcosms inhabited by I. templetoni. Total phenanthrene reduction was observed at an average of 9.78 % in worm microcosms, while no reduction was observed in the control microcosms. Benzo(a)pyrene reduction, on the other hand, was determined at 78.60 % and 30.04 % in worm and control microcosms, respectively. The lowest concentrations of these PAHs at the end of 97-day study were observed well below the surface of the sediment in worm microcosms. Mass balance analysis was done based on the possible transport routes of the sediment PAHs to possibly explain the major fate pathway for phenanthrene and benzo(a)pyrene in this study. Further, the influence of the oligochaetes on the physico-chemical characteristics (specifically, redox and porewater dissolved oxygen) and the microbial characteristics of the sediment were also assessed. Dissolved oxygen (DO) measurements indicated a limited penetration of oxygen within the 3 mm of sediment depth. Comparisons of the two sets of measurements (two months apart) indicate an increase in DO of both the worm and control microcosms. The DO increase in control microcosm was primarily due to photosynthesis on the relatively stable sediment surface. On the other hand, a larger shift in redox profile was observed in worm microcosms, at depths way beyond the penetration depth of DO. In control microcosms, although redox potential also increased, the larger increase occurred only in the upper layers, probably due to active photosynthesis on the surface. Molecular technique of microbiological analysis by DGGE analysis of sediment samples obtained at different depths of the microcosms suggests that the presence of the oligochaetes had influenced the microbial profile of the sediment in this study. High microbial diversity was also observed, which seem to have varied with depth in the microcosms.



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Committee Chair

Danny D. Reible