Electronic Thesis and Dissertation Repository


Master of Engineering Science


Civil and Environmental Engineering


George Nakhla

2nd Supervisor

Jesse Zhu

Joint Supervisor


This research investigated the efficacy of the anaerobic fluidized bed bioreactor (AnFBR) technology in treating municipal wastewater sludges. Primary sludge (PS) and thickened waste activated sludge (TWAS) were studied in two lab-scale AnFBRs using High-density polyethylene (HDPE) as carrier media. PS was investigated at various organic loading rates (OLRs) ranging from 9 to 18 kg chemical oxygen demand (COD)/m3-d corresponding to hydraulic retention times (HRTs) of 2 to 4 days, with maximum COD and volatile suspended solid (VSS) removal efficiency of 70% and 72%, respectively. For TWAS, VSS destruction efficiency varied from 53% at an HRT of 4 days and OLR of 12 kg COD/m3-d to 61% at an HRT of 8 days and an OLR of 6 kg COD/m3-d. The results showed that mesophilic anaerobic fluidized bed bioreactor is highly effective for COD removal and VSS reduction of municipal biosolids compared with conventional anaerobic digestion. Furthermore, the specific bacterial community activity tests showed a significant difference between solid retention times (SRT) based on general VSS and retention times based on the activity of methanogenic, acidogenic, and acetogenic microbes. While SRTs based on VSS measurements in the PS AnFBR were 3.3 days, the activity-based retention times varied from 12.2 to 14.6 days. Similarly, in the TWAS AnFBR, the SRTs based on VSS measurements were 5.0 days, and the activity-based retention times ranged from 8.0 to 9.4 days. These specific microbial activities tests can provide a better understanding of the performance of full-scale digesters, help to determine the rate-limiting process and optimize the operation conditions.