(727f) Review and Modeling of Organic Removal in Anaerobic Sludge Blanket Bioreactors for Methane Production and Energy Recovery from Domestic Wastewater

The current domestic wastewater treatment paradigm centers on aerobic wastewater treatment technologies such as activated sludge. While effective in meeting U.S. EPA regulated discharge standards for organics and suspended solids, providing oxygen to aerobic microorganisms is energy-intensive, typically accounting for ~50% of wastewater treatment facility costs. In total, wastewater conveyance and treatment accounts for ~3% of our nation’s electrical energy usage. Direct anaerobic treatment of dilute wastewater is a viable methane-generating alternative to aerobic wastewater treatment. Anaerobic microorganisms convert wastewater organics (fats, carbohydrates, proteins, etc.) to methane-rich biogas, which can be harnessed to create energy via technologies such as combined heat & power. If more energy is generated from the methane produced than is used to run the process itself, then the process can be considered “energy-positive” (or a net energy producer). Anaerobic sludge blanket bioreactors, most notably upflow anaerobic sludge blanket (UASB) bioreactors and anaerobic baffled reactors (ABRs), have been studied at bench- and pilot-scale for several decades. UASBs are also currently operated at full-scale in several locations worldwide, mostly in warmer climates. Despite the number of completed studies, no current review critically examines performance data from different sized sludge blanket bioreactors collected under varying conditions (e.g., varying wastewater temperatures and hydraulic residence times). Further, no current review study conducts predictive modeling (i.e., Monte Carlo Simulation) on aggregated sludge blanket bioreactor data to better understand the operation of such bioreactors under varying conditions. This study aggregates and examines data from 145 UASBs studies and 56 ABRs studies to understand bioreactor performance (e.g., chemical oxygen demand and total suspended solids removal) and methane generation. This study also employs Monte Carlo Simulation using @Risk to better predict bioreactor performance under varying conditions. Additionally, this study identifies critical gaps in literature (e.g., a lack of consistently reported methane generation) that may impact full-scale implementation in certain climates (e.g., cold weather climates). Last, results from this study can help inform decision makers to better understand of anaerobic sludge blanket bioreactors can meet regulatory standards or generate methane for renewable energy at their wastewater treatment facilities.