This paper provides an improved understanding of the effect of sidestrearn (SS) and submerged (Sub) MBR configurations on hydraulic and biological system performance for a tubular membrane geometry. Effects of key flow parameters, these being aeration rate (U-G) in the Sub MBR and cross flow velocity (CFV) in the SS MBR, on fouling behaviour have been assessed during short-term flux-step experiments. Both synthetic and real sewage feeds have been used. Series of tests carried out with both feeds indicate the similar fouling behaviour observed for Sub and SS MBRs operated at U-G of 0.07-0.11 m s(-1) and CFV of 0.25-0.55 in s(-1) respectively. Analysis of the TMP-based parameters determined from the flux-step experiments show the effect of U-G in Sub configuration to be greater than those of CFV in SS MBR, and to be more efficient at higher fluxes (up to 97 % decrease in fouling rate for U-G increased from 0.02 to 0.2 in s(-1), at 291 m(-2) h(-1)). The influence of MBR configuration on biomass characteristics was also assessed by acclimatising the biomass at three MLSS concentrations for both configurations and revealed the carbohydrate contained in the biomass supernatant to be a possible indicator of fouling for MBR operation.