Master of Science in Civil Engineering (MSCE)


Civil and Environmental Engineering

Document Type



In the field of municipal wastewater treatment, anaerobic digestion is a well-established, effective process for stabilization of organic sludge with the attractive features of low operating costs and production of methane as a useful by-product. Application of anaerobic digestion for the treatment of saline industrial wastewater sludge, however, has not been well established. The studies described in this thesis were conducted with the overall goal of assessing the feasibility of mesophilic anaerobic digestion processes for treatment of waste activated sludge (WAS) containing moderate salinity (approximately 3% m/v). Experiments employed two 30-gallon conical-bottom HDPE reactors. In the first phase of testing, intended to produce acclimated microbial populations, both reactors were operated in batch mode without mixing for a period lasting 48 days. In the second phase of testing, two different reactor operating strategies were evaluated. One reactor was unmixed with operation at a 60-day target hydraulic residence time, while the second was a mixed system with a 30-day target hydraulic residence time. Temperature, pH, alkalinity, solids concentrations, organic acid concentrations, biogas evolution rates, and biogas methane content were measured over a period lasting more than 180 days. Results demonstrate that elevated salinity of 3% m/v does not preclude effective anaerobic digestion. Both reactors exhibited stable pH, alkalinity, and gas composition with >60% methane. The high VSS destruction efficiency, 41.3% (HR reactor) and 49% (LR reactor), showed the reactor well functioned. Both reactors exhibited a methane content of approximately 65% after 70 days (July 9, 2008) operation, which indicates that the lipid degradation was not inhibited under this digestion condition.



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Committee Chair

William M. Moe