Energy-efficient wastewater reuse is an important water management objective for water-scarce regions. Mainstream anaerobic wastewater treatment offers the potential for energy-positive secondary treatment with low biosolids production. But anaerobic effluent requires further treatment to remove and recover dissolved methane. Also, the fate and removal of trace effluent contaminants and biogas impurities are largely unknown. The staged anaerobic fluidized membrane bioreactor (SAF-MBR), with pilot units in South Korea and California, is one promising example of an energy-positive replacement for conventional aerobic activated sludge processes. Pilot experiments at Stanford University’s Codiga Resource Recovery Center achieved greater than 96% removal of dissolved methane from the SAF-MBR process effluent via counter current air stripping with random packed media. The low air:water ratio employed for this separation required less than 10% of the recoverable energy in the dissolved methane, making the removal theoretically energy positive. Trace organic contaminant removal in the column was not observed at significant levels; however, the effluent gas stream contained significant levels of siloxanes relative to the primary reactor biogas. Further study of the fate of contaminants of emerging concern and the benefit of carbon sorption-treatment are underway for to inform utilization of the SAF-MBR process in non-potable reuse and surface spreading applications in compliance with California water reuse regulations.

Effluent polishing for non-potable wastewater reuse from anaerobic membrane bioreactors

ACS Fall 2021

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