Portland State University. Department of Civil Engineering
Term of Graduation
Date of Publication
Master of Science in Civil Engineering (MSCE)
Sewage tanks, Sewage -- Purification, Density currents
1 online resource (3, xiv, 165 pages)
Deviations from ideal flow and settling occur in circular wastewater treatment tanks because of tank geometry, flow conditions, and density currents caused by variations in suspended solids concentration and temperature distributions. Thermally induced density currents were investigated in this study. Under winter, low flow conditions, measurements were made of vertical and radial temperature distributions in the circular chlorination tank at Lake Oswego, Or., and in the circular primary and secondary clarifiers at Bend, Or. Thermistor arrays were used to collect the data which exhibited both vertically well-mixed and a two-layer flow regime. Inlet geometry and suspended solids in the secondary clarifiers caused a warm bottom inflow and apparent thermal instability. Meteorological measurements were also made. The calculated winter heat loss values indicated that convective mixing may have inhibited particle sedimentation in the clarifiers.
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LaLiberte, David M., "Density Currents in Circular Wastewater Treatment Tanks" (1990). Dissertations and Theses. Paper 4085.