Thesis (M.S.)--University of Wisconsin--Madison, 1959. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 62-68).

Thesis (M.S.)--Oregon State University, 2006. / Printout. Includes bibliographical references. Also available online.

Thesis (M. Sc.)--University of Hong Kong, 2005.

Thesis (M. Sc.)--University of Hong Kong, 2006.

Thesis (MScIng)--University of Stellenbosch, 2005. / Bibliography. Also available via the Internet.

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 234-240). Also available via the Internet.

It has previously been shown that low p0₂ stimulated the respiration of facultative bacteria suggesting that precise control of dissolved oxygen in waste treatment systems might be an effective method of increasing carbon dioxide production at the expense of cell yield. In continuous cultures of glucose limited Escherichia coli B, controlled at less than 8mmHg, we have demonstrated a 57% increase in carbon dioxide production at the expense of both cell yield and supernatant carbon. Batch cultures of Pseudomonas aeruginosa 9027 showed an even greater loss of efficiency at low oxygen tensions. Studies with mixed populations (batch culture) showed some evidence of yield reduction (in spite of inherent difficulties with floculation and natural selection). However, the reduction was considered to be too small to warrant the practical application of dissolved oxygen control in waste treatment systems. While completely anaerobic E. coli B cells appear to be uncoupled by aeration, alternating a continuous culture between anaerobic and aerobic growth did not similarily affect the cells - evidently E. coli B requires a substantial amount of time (over 4 hours) to fully adapt to anaerobic conditions. In any case, unlike E. coli B, the growth of stable anaerobic mixed populations did not become "uncoupled" when aerated - indicating that this technique would not be suitable in waste systems. Studies with an ultra-violet irradiated continuous culture of E. coli B showed considerable increases in carbon dioxide production at the expense of cell yield. In addition, the process of floculation was greatly enhanced. The practical possibilities of implementation in waste treatment systems, warrent further investigation of the effects of u.v. irradiation on bacterial growth. / Science, Faculty of / Microbiology and Immunology, Department of / Graduate

When secondary sewage effluent is converted to snow, the nutrients and residual organics become concentrated in the early meltwater discharge through melt-freeze processes within the snow-pack. The early season melt comes off relatively slowly. Providing the soil can absorb the early melt, the bulk of the nutrients will be removed even if later season melt rates exceeds the soil's infil-trability. This could provide an inexpensive method for nutrient removal from secondary sewage effluents. Laboratory experiments showed that the degree of impurity concentration was largely independent of the number of diurnal melt-freeze cycles, snow depth, snow temperature and initial concentration of impurity in the snow. As a result, the removal of impurities from a snowpack can be expressed in terms of the cumulative melt discharge. A simple exponential decay process was found to describe the impurity removal well for most cases. The first 20% of the melt removed, on the average, 65% of the phosphorus and 86% of the nitrogen from snow made from sewage effluent; and 92% of the potassium chloride from snow made from potassium chloride solution. Stripping of ammonia during snow production and melting increased the overall nitrogen removal to about 90%. A field investigation of salt movement through a natural snowpack confirmed the laboratory results. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

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