Dead-end filtration of jet loop bioreactor and activated sludge suspensions

Abstract

Fouling is the main disadvantage of membrane processes which causes decrease in flux with time. Although there are various mathematical models representing fouling with time, a simplified approach is still needed for predicting flux decline behavior over the course of filtration. Furthermore, a comparative study to determine the effects of floc size and extracellular polymeric substance (EPS)/soluble microbial product (SMP) content for different biological suspension is important in understanding of membrane fouling. The objective of this study was to analyze filtration of two different biological suspensions and to use a simplified model to identify the effects of SMP, EPS, and floc size on fouling. The experimental data were successfully represented by a simplified model with a single fitting parameter. The fouling was independent from membrane material and pore size; however, it depended on either floc size or the EPSp content depending on the properties of biological suspension. When the floc size of the biological suspension was small (e.g. jet loop membrane bioreactor), neither EPS nor SMP contributed fouling significantly. The fouling was mainly dominated by the small floc size. However, for biological suspension with larger floc sizes (e.g. activated sludge system), the fouling was independent from floc size. For such sludge samples, the fouling was well correlated with EPSp.