Title page for ETD etd-10132005-152536


Type of Document Dissertation
Author Kavanaugh, Rathi G.
URN etd-10132005-152536
Title Investigation of bacterial populations in a biological nutrient removal system
Degree PhD
Department Environmental Sciences and Engineering
Advisory Committee
Advisor Name Title
Randall, Clifford W. Committee Chair
Benoit, Robert E. Committee Member
Boardman, Gregory D. Committee Member
Hoehn, Robert C. Committee Member
Yousten, Allan A. Committee Member
Keywords
  • Bacteriology Cultures and culture media
  • Bacteria
Date of Defense 1991-01-05
Availability restricted
Abstract
Bacterial populations proliferating in a pilot scale biological nutrient removal system (BNR) were studied. The objective of the research was to develop media and methods to identify bacterial populations in BNR systems. Samples were obtained from the last aerobic zone of a University of Cape Town (UCT)-type system. The most probable numbers (MPN) of bacteria in the samples were analyzed in liquid media containing volatile fatty acids as sole sources of carbon. Samples were also transferred to denitrification medium, and MPN's of denitrifiers were recorded. The growth in liquid medium was plated on solid medium. Gram-negative cultures were isolated and identified. The phosphorus-removal capacity of five isolates also was studied.

The results indicated that several different genera of bacteria are involved in the removal of phosphorus in an operating BNR system. Four major groups of phosphorus storing bacteria, Aeromonas/Vibrio, coliforms, Pseudomonas spp and Acinetobacter spp, were recovered. The identification of cultures on denitrification medium also recovered Pseudomonas, Aeromonas, coliforms and Acinetobacter, indicating the overlap in the function of these genera. The phosphorus accumulations in three of the tested cultures showed accumulations in excess of 10 percent.

The MPN's of bacteria in acetate and propionate media obtained using samples from the pilot scale BNR system and a full scale activated sludge system were statistically analyzed. The analyses showed significant differences between MPN in acetate and propionate medium using samples from the BNR system, whereas there were no significant differences in samples from the conventional activated sludge plant. The possibility of the application of these data in process control and modeling is proposed.

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