Membrane fouling, methane production and microbial community under fluidization of biocarrier with conductive surface in anaerobic fluidized bed membrane bioreactor for greywater treatment

A comparative study of organic removal efficiency, fouling control, and methane production from synthetic greywater was performed operating three anaerobic fluidized bed membrane bioreactors (AFMBRs). Granular activated carbon (GAC) particles, polyaniline-coated polyethylene terephthalate (PET) beads, and uncoated PET beads were added as scouring agent to control fouling through each AFMBR. The use of PET spherical beads coated with polyaniline as a fluidized medium improved both fouling reduction and methane production kinetics. Although the GAC particles showed the highest organic removal efficiency in AFMBR due to adsorption capability, their progressive fragmentation reduced the methanogenic population and accelerated fouling rate. Microbial activity was adversely affected when the bulk biomass was exposed to the surfactant in the synthetic greywater. Microbiome analysis showed that the methanogenic archaeal population in the GAC bulk biomass reduced significantly from 10 to 0.5%, which corroborates the decrease in methane production rate. The methanogens on the PET beads shifted gradually from acetoclastic Methanosaeta to hydrogenotrophic Methanospirillum presumably because of the detachment of the biofilm that suppressed the slow-growing Methanosaeta. In addition, the key exoelectrogenic microbes were related to Desulfovibrio and Geobacter, which may be associated with direct interspecies electron transfer with the methanogens.