Browsing by Author "Detlef R. Knappe, Committee Member"

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    Initial Investigations of Aerobic Granulation in an Annular Gap Bioreactor
    (2005-04-19) Williams, Jon Christopher; Morton A. Barlaz, Committee Member; Joel J. Ducoste, Committee Member; Detlef R. Knappe, Committee Member; Francis L. de los Reyes III, Committee Chair
    This research describes the design, construction, and characterization of a novel annular gap bioreactor. The bioreactor was conceived as a tool for the shear-based control of activated sludge floc particle size in batch and continuous-run experiments. Initial experiments on the feasibility of cultivating aerobic granular sludge in the bioreactor are described. The bioreactor was found to experience turbulent Taylor vortex flow, rather than laminar Couette flow, at all rotational speeds tested. This flow regime is the result of inner cylinder rotation. Despite turbulent flow conditions, the bioreactor was found to behave approximately as a plug-flow device when not aerated, and as a complete-mix reactor when aerated. Floc size control was found to depend on bioreactor rotational speed for two sludges tested, with higher rotational speed leading to smaller particle size. Three experimental attempts at aerobic granular sludge cultivation in the annular gap bioreactor are described in this study. Although none of the three attempts was successful at producing aerobic granules, the experiments allowed critical control issues related to bioreactor operation and influent composition to be identified and addressed. The Bacterial and Eukaryal population dynamics during each run were tracked with denaturing gradient gel electrophoresis and rDNA sequence analysis, using methods developed or streamlined in the course of this research. The foundational work described in this study culminated in the development of a series of protocols and recommendations for the next phase of aerobic granular sludge investigation with this novel annular gap bioreactor.
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    Quantifying Activated Sludge Bulking-Causative Filamentous Bacteria Using Molecular Methods
    (2003-04-22) Liao, Jiangying; Francis de los Reyes III, Committee Chair; Morton A. Barlaz, Committee Member; Detlef R. Knappe, Committee Member
    Filamentous bulking is a widespread problem in activated sludge wastewater treatment plants. In North Carolina, 63% of wastewater treatment plants (WWTPs) surveyed have experienced bulking. Determining the dominant bulking-causative bacteria and their level of proliferation is a necessary step in bulking control. This study used molecular techniques, i.e. quantitative Fluorescent in situ Hybridization (FISH) and membrane hybridization to identify and quantify the specific filamentous microorganisms and their threshold values for causing bulking in both lab scale reactors and full scale treatment plants. Filament length of a specific filamentous organism, Eikelboom Type 1851, correlated strongly with the sludge volume index (SVI) and was identified to be the major bulking-causative microorganism in lab scale reactors and a full scale activated sludge plant. The full scale plant is a biological nutrient removal (BNR) plant, a common operational mode in North Carolina, suggesting that this organism may be prevalent in North Carolina WWTPs. The threshold value for Eikelboom Type 1851-caused-bulking was determined. This threshold value will allow the monitoring of incremental improvements in control methods and the delineation of the niche of Eikelboom Type 1851 in activated sludge. Furthermore, the lab scale experiments verified the kinetic selection theory and the filamentous backbone theory for Type 1851.