Membrane Fouling Characterisation in Aerobic Submerged Membrane Bioreactors

Abstract

Fouling characteristics of aerobic submerged membrane bioreactors (MBRs) were analysed under different operating flux, solids retention time (SRT) and membrane material. Micro-structural analyses of the foulants on the membrane surfaces showed that dominant foulants were different under different flux conditions. Membrane fouling occurred through a biofilm dominated process under lower flux conditions, but the mechanism shifted towards a non-biofilm, bio-organic fouling process as the flux increased, or SRT decreased. The use of confocal laser scanning microscopy to image organic foulants directly on the membrane surface, coupled with image analyses showed that physico-chemical characterisation was unable to explain the differences in membrane fouling of the contrasting membrane materials indicating the limitations of current conventional methods in describing the fouling process. Microbial community structure of the activated sludges and in the fouling layers were analysed by terminal restriction fragment length polymorphism, and supported conclusions based on imaging techniques.