| description |
This study examines the distribution of biomass within submerged membrane bioreactor (MBR) systems, and how, from an engineering and ecological perspective, this may be important to the function, design and operation of submerged MBRs for wastewater treatment. The microbial-membrane interface, particularly with respect to biofouling, can be a defining feature of the MBR process in biological wastewater treatment. Submerged aerobic MBRs are revealed to be a series of compartments: mixed liquor suspended biomass (MLSB); extra-membrane loosely bound biofilm (EMLB); extra-membrane tightly bound biofilm (EMTB); and intra-membrane core biofilm (IMCB; formed in voids 20 - 100 µm in diameter) with both flat sheet and hollow-fibre membranes. Microscopy and 16S rRNA gene sequencing were used to characterize the biomass from these compartments within a laboratory scale aerobic MBR feed with synthetic wastewater. Although there were similarities distinct differences in the predominant populations between compartments were observed, Dysgonomonas, a facultative anaerobe, Acetobacterium, a gram-positive anaerobe, and Blastobacter, capable of nitrogen-fixation, were predominant in the IMCB. Xanthobacter, a denitrifier , and Subtercola, a floc-forming bacteria were present in the MLSB. Rhodocista, known to be a phototroph or aerobic chemoheterotroph was found in the MLSB as well as the EMTB and EMLB. Mycoplana and Caldimonas, aerobic chemoorganoheterotrophs, were unique to EMLB and EMTB, respectively. Changes in substrate availability, including dissolved oxygen concentration, and microenviornmental conditions across the compartments, are likely important factors shaping these communities within these compartments. |