Document Type
Thesis - Open Access
Award Date
2008
Degree Name
Master of Science (MS)
Department / School
Civil and Environmental Engineering
Abstract
The feasibility of utilizing the existing anaerobic digester feeding pumps to effectively mix the three primary anaerobic digesters at the Sioux Falls Water Reclamation Plant (SFWRP) was investigated. The digesters were originally designed to be mixed by the recirculation of sludge and the recirculation of biogas through gas compressors. The gas compressors are currently at the end of their useful life and are scheduled to be replaced in the next 3-4 years. The effectiveness of mixing the primary digesters strictly through hydraulic recirculation was measured by computing the active volume of the anaerobic digesters with various mixing schemes. The analysis of the digesters was also based on measuring initial dispersion, effluent quality, velocity gradient, mixing energy, and hydraulic retention time (HRT). The biogas production and volatile solids (VS) reduction in the digesters was monitored throughout the testing period and compared with historical trends to determine any impact on their reduction with the current mixing schemes. The results showed that the digesters being fed (recirculated) through the top resulted in a higher active volume than those digesters being fed into the side. The digesters fed(recirculated) into the top experienced a 93-98% active volume while the digesters fed(recirculated) into the side experienced a 60-68% active volume. The study also found that the velocity gradient was 3.65 sec-1 in the digesters being fed in the top and side. In addition, the mixing energy was found to be 0.06 hp/1000 ft3 in the digesters being fed in both the top and side. The digesters that were side fed experienced a lower average volatile solids reduction and average biogas production, 51.3% and 7.3 ft3/lb VS added compared to 53.0% and 8.2 ft3/lb VS added, which was determined for the digesters fed in the top. The digesters that were mixed into the top were found to be significantly different than the digesters mixed into the side. Mixing into the top of the anaerobic digester provided sufficient mixing for the anaerobic digesters compared to historical data and proved to be the most effective scheme.
Library of Congress Subject Headings
Sewage -- Purification -- Anaerobic treatment -- South Dakota -- Sioux Falls
Sewage sludge digestion -- South Dakota -- Sioux Falls
Format
application/pdf
Number of Pages
149
Publisher
South Dakota State University
Recommended Citation
Knadle, Brian R., "City of Sioux Falls Anaerobic Digester Mixing Study" (2008). Electronic Theses and Dissertations. 1451.
https://openprairie.sdstate.edu/etd2/1451
