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LCA and Cost Analysis of Membrane Bioreactor Systems: Influence of Scale, Population Density, Climate, and Methane Recovery
Mosley, J., S. Cashman, Cissy Ma, J. Garland, AND X. Xue. LCA and Cost Analysis of Membrane Bioreactor Systems: Influence of Scale, Population Density, Climate, and Methane Recovery. LCA XVI Conference, Charleston, SC, September 27 - 29, 2016.
This study demonstrates the holistic analyses of one of the transformative technologies in resource recovery: both transitional aerobic membrane bioreactors (AeMBR) and transitional anaerobic MBRs (AnMBR) used in municipal wastewater treatment and their performances under different scenarios. The study explored the environmental and economic impacts of aerobic and anaerobic systems coupled with other system components such as sewer collection, water reuse, water delivery system, etc. to shed light on the appropriate scale of operation.
Future changes in drinking and waste water infrastructure need to incorporate a holistic view of the water service sustainability tradeoffs and potential benefits when considering shifts towards new treatment technology, decentralized systems, energy recovery and reuse of treated wastewater. This study calculates the life cycle environmental and cost profiles of both transitional aerobic membrane bioreactors (AeMBR) and transitional anaerobic MBRs (AnMBR), which produce recycled water that can displace potable water. MBRs represent an intriguing technology to provide decentralized wastewater treatment services and energy recovery potentials. A number of scenarios for these technologies were investigated for different scale systems (0.05 to 10 million gallon per day (MGD)) serving various population density (2,000 to 100,000 #ppl/sqm) and land area combinations. For the psychrophilic AnMBR, scenario analyses were conducted to determine the influence of climate conditions, with permutations run for multiple methane recovery options. Net energy benefits, considering the displaced drinking water by the delivered recycled water, started at the 1 MGD scale for the AeMBR and at the 5 MGD scale for the mesophilic AnMBR. For all scales investigated, the psychrophilic AnMBR reactor resulted in net energy benefits. When examining the energy demand results normalized to a cubic meter of water treated, all energy demand impacts decrease as the scale increased. The study also found that all impacts decrease comparatively as the population density increases, with the highest energy and greenhouse gas burdens realized for the semi-rural single family land use and the lowest overall burdens seen for the high-density urban land use. Ambient temperature played a key role, with the most benefits and least impacts from psychrophilic AnMBR operated in warm climate conditions and with combined heat and power generation from methane recovered from both the headspace and the permeate. While AeMBRs are largely commercialized at the scales investigated, the data behind the AnMBR model is based on bench-scale and pilot scale systems. As more full scale AnMBRs are commissioned, and operational data is better understood, the LCA model framework presented in this work can be continually improved upon.