A bench-scale anaerobic membrane bioreactor (AnMBR) equipped with submerged flatsheet
microfiltration membranes was operated at psychrophilic temperature (15 C)
treating simulated and actual domestic wastewater (DWW). Chemical oxygen demand
(COD) removal during simulated DWW operation averaged 92 5% corresponding to an
average permeate COD of 36 21 mg/L. Dissolved methane in the permeate stream represented
a substantial fraction (40e50%) of the total methane generated by the system due
to methane solubility at psychrophilic temperatures and oversaturation relative to Henry’s
law. During actual DWW operation, COD removal averaged 69 10%. The permeate COD
and 5-day biochemical oxygen demand (BOD5) averaged 76 10 mg/L and 24 3 mg/L,
respectively, indicating compliance with the U.S. EPA’s standard for secondary effluent
(30 mg/L BOD5). Membrane fouling was managed using biogas sparging and permeate
backflushing and a flux greater than 7 LMH was maintained for 30 days. Comparative
fouling experiments suggested that the combination of the two fouling control measures
was more effective than either fouling prevention method alone. A UniFrac based
comparison of bacterial and archaeal microbial communities in the AnMBR and three
different inocula using pyrosequencing targeting 16S rRNA genes suggested that mesophilic
inocula are suitable for seeding psychrophilic AnMBRs treating low strength
wastewater. Overall, the research described relatively stable COD removal, acceptable flux,
and the ability to seed a psychrophilic AnMBR with mesophilic inocula, indicating future
potential for the technology in practice, particularly in cold and temperate climates where
DWW temperatures are low during part of the year.