Polarity-Molecular Weight Profile of Extracellular Polymeric Substances in a Membrane Bioreactor: Comparison between Bulk Sludge and Cake Layers

Abstract

Extracellular polymeric substances (EPS) are reported to be the major foulant in membrane bioreactor (MBR) processes. It is important to understand the EPS fractions which cause irreversible fouling to reduce operation cost and energy consumption in MBR. In this study, we developed polarity-molecular weight profiling, in which EPS components were plotted on two-dimensional matrix of its polarity and molecular weight, and applied it to investigate EPS of bulk sludge and cake layers from a labscale MBR. The EPS components were also characterized via three-dimensional excitation-emission matrix (3D-EEM) spectroscopy. The result showed that hydrophilic substances as large as 100 − 670 kDa was found only in loosely-bound EPS (LB-EPS) of bulk sludge but not in that of cake layers nor in permeate. Hydrophobic substances smaller than 20 kDa were mainly found in soluble microbial products (SMP) in bulk sludge. Hydrophilic substances larger than 670 kDa was mainly found in tightly-bound EPS (TB-EPS) of bulk sludge and in LB-and TB-EPS of cake layers. These findings suggest that, after conditioning of micropores of virgin membrane by hydrophobic substances smaller than 20 kDa in SMP, hydrophilic biopolymers as large as 100 − 670 kDa in bulk sludge clog the narrowed micropores inside membrane, causing irreversible fouling.

Effect of high temperature toward microalgal organic matter and its impact toward membrane distillation application

“…It is known that loosely bound EPS has strong affinity toward membrane fouling, especially substances larger than 100 kDa such as polysaccharides which will accumulate on the membrane surfaces to form cake layer (Hong et al, 2018). In MD process, the LMW polysaccharide could cause immediate and irreversible plugging and narrowing of membrane.…”

“…HMW sEPS that was deposited onto the virgin membranes would also have the chance to be further degraded into smaller molecules due to consistent high temperature imposed in the MD application. These broken-down fractions can be pulled into the conditioned micropores to plug the flow channels, eventually leading to mass production of 450 kDa to 1100 kDa smaller chain polysaccharides from either living or dead cells (Hong et al, 2018). Thus, in MD process, monosaccharides and LMW components that are majorly contained in the sEPS would cause immediate and irreversible plugging and narrowing of membrane.…”

A methodological review on the characterization of microalgal biofilm and its extracellular polymeric substances

“…Meanwhile, their study postulated that the characteristics of AOM should not be overlooked though the dissolved organic carbon is always considered as a decisive factor of biofouling potential in addition to operating conditions and membrane properties (Henderson et al, 2008). Moreover, hydrophobic substances from the sEPS could be adsorbed by the substrate via pore conditioning, facilitating the accumulation of hydrophilic loosely bEPS on these type of conditioned ‘pockets’ and promoting biofilm formation (Hong et al, 2018). It was always reported that algal culture was highly hydrophilic with the presence of polysaccharides and hydroxyl acids (Rafiee et al, 2020).…”

Freshwater Suspended Particulate Matter – Key Components and Processes in Floc Formation and Dynamics.

“…methyl-, ethyl-), hydrophobic amine and benzyl-groups. (Flemming and Wingender, 2010;Hong et al, 2018;Neu, 1996;Sutherland, 2001) Some EPS exhibit hydrophilic and hydrophobic regions (e.g. emulsan, a highly acetylated polysaccharide, allowing detachment from hydrophobic surfaces) or hydrophobic moieties (e.g.…”