Characterization of biofoulants illustrates different membrane fouling mechanisms for aerobic and anaerobic membrane bioreactors. Membrane fouling mechanisms for aerobic and anaerobic membrane bioreactors

In this study, membrane performance and foulants characteristics were compared for both Aerobic Membrane Bioreactor (AeMBR) and Anaerobic Membrane Bioreactor (AnMBR). Both employed a similar reactor configuration and were operated at the same condition. Similar COD removal efficiencies were seen in both systems while fouling rates were higher in the AeMBR. The size distribution of Soluble Microbial Products (SMP) and Extracellular Polymeric Substances (EPS) in the AnMBR showed that a majority of the EPS fragments could be derived from the retained SMP fractions, suggesting that the major contributor to AnMBR membrane fouling was the physical retention of SMP components. Although more EPS was present on the AeMBR membranes than the AnMBR, SMP was not a main contributor to membrane fouling as all foulant fractions in AeMBR-SMP were totally permeated through the membrane. However, a larger amount of ATP was present in the AeMBR as compared to the AnMBR suggesting that the derivation of AeMBR-EPS may be from microbial activity of certain bacterial populations attached on the membrane, such as Comamonas and unclassified Chitinophagaceae. This study underlines the different fouling mechanisms associated with AeMBR and AnMBR and facilitates developing different strategies for fouling control in AeMBR and AnMBR.