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UBC Theses and Dissertations

A microbiological study of the enhanced biological phosphate removal process Chu, Angus


The research objective in this thesis is to define and clarify specific functional properties of sewage treatment process biomass. The specific objective is to determine whether the bacteria recovered from sludge correspond to the organisms with the real functional capability to sequester phosphate within the sewage ecosystem. This objective has been broken down into three categories. The first category deals with these organisms in terms of their recovery and viability. The second deals with their identification. The third deals with the phosphate accumulating ability of the isolated organisms. To address the question of recovery, the microscopic numbers of bacteria isolated from sludge were compared to the organisms recovered from plating. The results from this comparison was similar to previously published data (1-10% recovery). The 8 um fractionation assay allowed the fractionation of sewage into two separate components (filtrate and filter) and the ability to look at the fractions in terms of recovery and phosphate accumulating capacity. From this assay it was shown that the floes were responsible for the majority of the phosphate accumulation. Microscopic autoradiography also confirmed this observation. The cross plating technique was an attempt to improve recovery from solid media and to look at whether different organisms were selected under different nutrient conditions. Identification of two of the populations isolated from different media suggested that the type of media played a central role in recovery. Microplating was attempted in order to look at colony development at the microscopic level to answer some fundamental questions regarding recovery from floes and free bacteria. To answer the question of which bacteria are responsible for the phenomenon of phosphate accumulation, a pure culture autoradiographic assay was developed to screen organisms isolated from sludge for their potential to accumulate excessive amounts of phosphates. Autoradiography of pure cultures after growth in plate conditions mimicking the nutritional parameters of the Bio-P process allowed the correlation of the potential to accumulate phosphate to individual isolated bacteria. From these results it was shown that, contrary to what many investigators believe, Acinetobacter may not be the only genus in tertiary sewage treatment that is responsible for phosphate accumulation. The results indicate that there are specific groups within the genus Acinetobacter and other genera that have the potential to accumulate phosphate under these conditions.

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