Type of Document Dissertation Author Kim, Jong Min URN etd-07222010-070756 Title A study of multi-stage sludge digestion systems Degree PhD Department Civil Engineering Advisory Committee
Advisor Name Title Novak, John T. Committee Chair Boardman, Gregory D. Committee Member Chen, Jiann-shin Committee Member Higgins, Matthew J. Committee Member Keywords
- Nutrient removal
- biopolymer composition
- dewatered biosolids odor
- indicator organism reduction
- Multi-stage digestion system
- solids reduction
Date of Defense 2010-07-14 Availability restricted AbstractVarious combinations of multi-stage thermophilic and/or mesophilic anaerobic sludge digestion systems were studied to evaluate their solids reduction, odor generation after centrifugal dewatering and indicator organism reduction in comparison to single-stage thermophilic and/or mesophilic anaerobic digestion systems. Pre-aeration of sludge in a thermophilic temperature was also tested followed by single or multi-stage anaerobic digestion systems. It was found that multi stage systems were capable of greater solids removal and placing thermophilic system in multi stage system enhanced indicator organism destruction below EPA Class A biosolids requirement. However, all the digestion systems in the study showed less than 3 log reduction of indicator organism DNA/g solids, which was much smaller than indicator organism reduction measured by standard culturing method. It was also found that the thermophilic anaerobic digestion system could increase organic sulfur-based odors from dewatered biosolids while placing a mesophilic digester reduced odors. It was exclusively observed from sludges containing high sulfate such as ones in this study.
A combined anaerobic and aerobic sludge digestion system was also studied to evaluate their solids and nitrogen reduction efficiencies. The aerobic digester was continuously aerated to maintain dissolved oxygen level below 1 ppm and intermittently aerated. It was found that 90 % or more nitrogen removal was possible at the aerobic SRT greater than 3 days and the optimum aeration ratio could be determined.
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