UBC Theses and Dissertations

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UBC Theses and Dissertations

Treatment and disposal of secondary sewage effluent through snowmaking Zapf-Gilje, Reidar


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.

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