Membrane fouling potentials and cellular properties of bacteria isolated from fouled membranes in a MBR treating municipal wastewater

Abstract

Membrane fouling remains a major challenge for wider application of membrane bioreactors (MBRs) to wastewater treatment. Membrane fouling is mainly caused by microorganisms and their excreted microbial products. For development of more effective control strategies, it is important to identify and characterize the microorganisms that are responsible for membrane fouling. In this study, 41 bacterial strains were isolated from fouled microfiltration membranes in a pilot-scale MBR treating real municipal wastewater, and their membrane fouling potentials were directly measured using bench-scale cross-flow membrane filtration systems (CFMFSs) and related to their cellular properties. It was found that the fouling potential was highly strain dependent, suggesting that bacterial identification at the strain level is essential to identify key fouling-causing bacteria (FCB). The FCB showed some common cellular properties. The most prominent feature of FCB was that they formed convex colonies having swollen podgy shape and smooth lustrous surfaces with high water, hydrophilic organic matter and carbohydrate content. However, general and rigid biofilm formation potential as determined by microtiter plates and cell surface properties (i.e., hydrophobicity and surface charge) did not correlate with the fouling potential in this study. These results suggest that the fouling potential should be directly evaluated under filtration conditions, and the colony water content could be a useful indicator to identify the FCB.

Functional Determinants of Extracellular Polymeric Substances in Membrane Biofouling: Experimental Evidence from Pure-Cultured Sludge Bacteria

“…JSB10; UMFI, 0.404) UMFI values within the same genus of Bacillus offered overwhelming evidence of the strain-dependent nature of fouling behavior. Similar findings are presented in the literature (35). Specifically, 5 strains of Bacillaceae isolated from fouled membrane exhibited significantly different fouling behaviors.…”

Membrane fouling induced by AHL-mediated soluble microbial product (SMP) formation by fouling-causing bacteria co-cultured with fouling-enhancing bacteria

“…Representative strains were selected from 17 operational taxonomic units (OTUs) composed of 41 bacterial strains isolated in our previous study 8 (Table 1 ). However, since 4 strains could not be cultured on M9 medium, only 13 strains were used for the following studies.…”

“…However, since 4 strains could not be cultured on M9 medium, only 13 strains were used for the following studies. The degree of fouling potential of the isolated strains was categorized in three groups (high, I; moderate, II; low: III) 8 (Table 1 ). All the strains were cultivated with M9 medium containing 48 mM Na 2 HPO 4 , 22 mM KH 2 PO 4 , 8.5 mM NaCl, 19 mM NH 4 Cl, 2 mM MgSO 4 , 100 μM CaCl 2 , 20 mM glucose, and trace element.…”

“… a Fouling potential: The degrees of fouling potential of the isolated strains were determined with cross-flow membrane filtration system (CFMFS) when cultivated as single-culture and categorized as follow: high, I; moderate, II; low: III 8 . …”

“…Extensive studies have been conducted to isolate and characterize key bacteria responsible for membrane fouling 6 – 9 . In our previous study, forty-one bacterial strains were isolated from a pilot-scale MBR treating municipal wastewater, tested for their fouling potential using a cross-flow filtration unit, and related to their cellular properties 8 . Thirteen out of 41 isolated strains displayed significant fouling potentials when they were cultivated as single-cultures, and thus were considered as fouling-causing bacteria (FCB).…”