Life cycle assessment and economic analysis of anaerobic membrane bioreactor whole-plant configurations for resource recovery from domestic wastewater.

ABSTRACT

The use of the anaerobic membrane bioreactor (AnMBR) process for domestic wastewater treatment presents an opportunity to mitigate environmental, social, and economic impacts currently incurred from energy-intensive conventional aerobic activated sludge processes. Previous studies have performed detailed evaluations on improving AnMBR process subcomponents to maximize energy recovery and dissolved methane recovery. Few studies have broadly evaluated the role of chemical use, membrane fouling management, and dissolved methane removal technologies. A life cycle assessment was conducted to holistically compare multiple AnMBR-based domestic wastewater treatment trains to conventional activated sludge (CAS) treatment. These treatment trains included different scouring methods to mitigate membrane fouling (gas-sparging and granular activated carbon-fluidizing) with consideration of upstream treatment (primary sedimentation vs. screening only), downstream treatment (dissolved methane removal and nutrient removal) and sludge management (anaerobic digestion and lime stabilization). This study determined two process subcomponents (sulfide and phosphorus removal and sludge management) that drove chemical use and residuals generation, and in turn the environmental and cost impacts. Furthermore, integrating primary sedimentation and a vacuum degassing tank for dissolved methane removal maximized net energy recovery. Sustainability impacts were further mitigated by operating at a higher flux and temperature, as well as by substituting biological sulfide removal for chemical coagulation.