Physico-chemical characterisation versus in situ micro-structural characterisation of membrane fouling in membrane bioreactors

2011 ◽  
Vol 63 (8) ◽  
pp. 1781-1787 ◽  
Author(s):  
T. C. A Ng ◽  
H. Y. Ng
Keyword(s):  
Membrane Fouling ◽  
Laser Scanning ◽  
Extracellular Polymeric Substances ◽  
Membrane Bioreactors ◽  
Operating Conditions ◽  
Laser Scanning Microscopy ◽  
Confocal Laser ◽  
Critical Flux ◽  
Membrane Materials ◽  
Physico Chemical

Fouling characteristics of aerobic submerged membrane bioreactors were analysed under two different membrane materials. Polyethersulfone (PES) membranes were found to foul faster at sub-critical flux than polyolefin (PO) membranes. Physico-chemical characterisation, by means of comparison of extracellular polymeric substances (EPS) and soluble microbial products (SMP) concentrations, as well as the mixed liquor suspended solids (MLSS) concentration were unable to explain the differences in membrane fouling of the contrasting membrane materials. The use of confocal laser scanning microscopy (CLSM) to image organic foulants directly on the membrane surface, coupled with image analyses showed that membrane fouling mechanism shifted from a biofilm initiated process on PO membranes to a bio-organic dominated process on PES membranes under sub-critical flux conditions. These results show that physico-chemical characterisation of an MBR process may not effectively distinguish the effectiveness of different membrane materials, so long as operating conditions are identical, and that characterisation of foulants on the membrane surfaces was necessary to elucidate the differences in membrane fouling.

scholarly journals Characterization of microbial aggregates in relation to membrane biofouling in submerged membrane bioreactors

2021 ◽  
Author(s):  
Heather Elizabeth Kraemer
Keyword(s):  
Laser Scanning ◽  
Extracellular Polymeric Substances ◽  
Municipal Wastewater ◽  
Pilot Scale ◽  
Membrane Bioreactors ◽  
Laser Scanning Microscopy ◽  
The Other ◽  
Major Constituent ◽  
Confocal Laser ◽  
Microbial Flocs

The purpose of this study was to characterize microbial aggregates and extracellular polymeric substances (EPS) that contribute to biofouling of submerged polymeric microfiltration membranes. Two issues were addressed in this study, (1) the influence operational and recovery cleanings of membranes have on biofouling amelioration and (2) the influence physicochemical properties of microbial flocs have on biofouling. The experiments in this study employed two pilot scale Zee Weed™ membrane bioreactors (MBRs). In one MBR, a ZW-I0 module was installed to treat secondary municipal wastewater at a sludge retention time (SRT) of30 days and operated under permeate/relaxation conditions. In the other MBR, two ZW -10 modules were installed to treat secondary municipal wastewater at an SRT of 12 days. One module operated under permeate/relaxation conditions, while the other operated under permeate/backwash conditions. Sludge samples from the MBRs were characterized by measuring the surface charge, hydrophobicity, and EPS composition of the microbial flocs. Membrane fibre samples were collected from each ZW -10 module during permeation and after recovery cleanings. The biofoulant on the membrane was analyzed using confocal laser scanning microscopy (CLSM) after simultaneous staining with the lectins concanavalin A (ConA), wheat germ agglutinin (WGA), and soybean agglutinin (SBA). The CLSM analysis of the membrane fibres sampled showed that the biofoulant on the membrane was composed of a heterogeneous colonization of microbes and EPS known to contain glucose, mannose, N -acetylglucosamine, and galactose. The dominant carbohydrate in the biofoulant was shown to be N -acetylglucosamine, which is part of both the cell wall of bacteria and the extracellular matrix. The reversible biofoulant was composed of individual cells, aggregates of cells, and EPS. The major constituent of the irreversible biofoulant was inferred to be EPS, which was observed as a fibrous network of material that remained adhered to the membrane after recovery cleaning the modules with a 2000 ppm hypochlorite solution. By using a permeate backwash rather than relaxation as an operational cleaning method, the rate of biofouling may be reduced. The rate of biofoulant accumulation on hydrophilic membranes may be reduced at higher SR Ts because the biomass at higher SR Ts has a higher hydrophobicity when compared to the biomass at lower SRTs.

Evaluation of the extracellular polymeric substances by confocal laser scanning microscopy in conventional activated sludge and advanced membrane bioreactors treating hospital wastewater

2014 ◽  
Vol 69 (11) ◽  
pp. 2287-2294 ◽  
Author(s):  
Mousaab Alrhmoun ◽  
Claire Carrion ◽  
Magali Casellas ◽  
Christophe Dagot
Keyword(s):  
Activated Sludge ◽  
Confocal Laser Scanning Microscopy ◽  
Laser Scanning ◽  
Extracellular Polymeric Substances ◽  
Membrane Bioreactors ◽  
Laser Scanning Microscopy ◽  
Confocal Laser Scanning ◽  
Scanning Microscopy ◽  
Confocal Laser ◽  
Conventional Activated Sludge

Confocal laser scanning microscopy (CLSM) combined with fluorescent viability indicators, was used in this study to investigate the impact of hospital wastewaters on floc structure and composition. In this work, three pilot-scale projects, two membrane bioreactors (MBRs) with a submerged or external membrane bioreactor and a conventional activated sludge, were installed and operated for 65 days. They were fed with an influent sampled directly from the hospital drainage system, which contained micropollutant concentrations ranging from ng/L to mg/L. Samples of flocs were observed using CLSM to characterize the extracellular polymeric substances (EPS) stained with concanavalin A–tetra methylrhodamine and fluorescein isothiocyanate solution and combined with a fluorescent viability indicator (Baclight® Bacterial Viability Kit, Molecular Probes), allowing visualization of isolated stained cells in the three-dimensional structure of flocs (damaged or not). The results of CLSM of the sludge composition were compared with classical biochemical analysis of EPS made through a thermal extraction method. The results showed a good relation between these analyses and the statistical treatment of microscopic pictures.

scholarly journals Characterization of microbial aggregates in relation to membrane biofouling in submerged membrane bioreactors

2021 ◽  
Author(s):  
Heather Elizabeth Kraemer
Keyword(s):  
Laser Scanning ◽  
Extracellular Polymeric Substances ◽  
Municipal Wastewater ◽  
Pilot Scale ◽  
Membrane Bioreactors ◽  
Laser Scanning Microscopy ◽  
The Other ◽  
Major Constituent ◽  
Confocal Laser ◽  
Microbial Flocs

The purpose of this study was to characterize microbial aggregates and extracellular polymeric substances (EPS) that contribute to biofouling of submerged polymeric microfiltration membranes. Two issues were addressed in this study, (1) the influence operational and recovery cleanings of membranes have on biofouling amelioration and (2) the influence physicochemical properties of microbial flocs have on biofouling. The experiments in this study employed two pilot scale Zee Weed™ membrane bioreactors (MBRs). In one MBR, a ZW-I0 module was installed to treat secondary municipal wastewater at a sludge retention time (SRT) of30 days and operated under permeate/relaxation conditions. In the other MBR, two ZW -10 modules were installed to treat secondary municipal wastewater at an SRT of 12 days. One module operated under permeate/relaxation conditions, while the other operated under permeate/backwash conditions. Sludge samples from the MBRs were characterized by measuring the surface charge, hydrophobicity, and EPS composition of the microbial flocs. Membrane fibre samples were collected from each ZW -10 module during permeation and after recovery cleanings. The biofoulant on the membrane was analyzed using confocal laser scanning microscopy (CLSM) after simultaneous staining with the lectins concanavalin A (ConA), wheat germ agglutinin (WGA), and soybean agglutinin (SBA). The CLSM analysis of the membrane fibres sampled showed that the biofoulant on the membrane was composed of a heterogeneous colonization of microbes and EPS known to contain glucose, mannose, N -acetylglucosamine, and galactose. The dominant carbohydrate in the biofoulant was shown to be N -acetylglucosamine, which is part of both the cell wall of bacteria and the extracellular matrix. The reversible biofoulant was composed of individual cells, aggregates of cells, and EPS. The major constituent of the irreversible biofoulant was inferred to be EPS, which was observed as a fibrous network of material that remained adhered to the membrane after recovery cleaning the modules with a 2000 ppm hypochlorite solution. By using a permeate backwash rather than relaxation as an operational cleaning method, the rate of biofouling may be reduced. The rate of biofoulant accumulation on hydrophilic membranes may be reduced at higher SR Ts because the biomass at higher SR Ts has a higher hydrophobicity when compared to the biomass at lower SRTs.

scholarly journals Bactericidal compounds controlling growth of the plant pathogen pseudomonas syringae pv. actinidiae, which forms biofilms composed of a novel exopolysaccharide

2020 ◽  
Author(s):  
S Ghods ◽  
Ian Sims ◽  
MF Moradali ◽  
BHA Rehma
Keyword(s):  
Pseudomonas Syringae ◽  
Chlorine Dioxide ◽  
Laser Scanning ◽  
Extracellular Polymeric Substances ◽  
Virulent Strain ◽  
Bactericidal Effect ◽  
Cell System ◽  
Laser Scanning Microscopy ◽  
Base Layer ◽  
Confocal Laser

© 2015, American Society for Microbiology. Pseudomonas syringae pv. actinidiae is the major cause of bacterial canker and is a severe threat to kiwifruit production worldwide. Many aspects of the disease caused by P. syringae pv. actinidiae, such as the pathogenicity-relevant formation of a biofilm composed of extracellular polymeric substances (EPSs), are still unknown. Here, a highly virulent strain of P. syringae pv. actinidiae, NZ V-13, was studied with respect to biofilm formation and architecture using a flow cell system combined with confocal laser scanning microscopy. The biofilm formed by P. syringae pv. actinidiae NZ V-13 was heterogeneous, consisting of a thin cellular base layer 5 μm thick and microcolonies with irregular structures. The major component of the EPSs produced by P. syringae pv. actinidiae NZ V-13 bacteria was isolated and identified to be an exopolysaccharide. Extensive compositional and structural analysis showed that rhamnose, fucose, and glucose were the major constituents, present at a ratio of 5:1.5:2. Experimental evidence that P. syringae pv. actinidiae NZ V-13 produces two polysaccharides, a branched α-D-rhamnan with side chains of terminal α-D-Fucf and an α-D-1,4-linked glucan, was obtained. The susceptibility of the cells in biofilms to kasugamycin and chlorine dioxide was assessed. About 64 and 73% of P. syringae pv. actinidiae NZ V-13 cells in biofilms were killed when kasugamycin and chlorine dioxide were used at 5 and 10 ppm, respectively. Kasugamycin inhibited the attachment of P. syringae pv. actinidiae NZ V-13 to solid surfaces at concentrations of 80 and 100 ppm. Kasugamycin was bacteriostatic against P. syringae pv. actinidiae NZ V-13 growth in the planktonic mode, with the MIC being 40 to 60 ppm and a bactericidal effect being found at 100 ppm. Here we studied the formation, architecture, and composition of P. syringae pv. actinidiae biofilms as well as used the biofilm as a model to assess the efficacies of bactericidal compounds.

scholarly journals Calcite Biomineralization by Bacterial Isolates from the Recently Discovered Pristine Karstic Herrenberg Cave

2011 ◽  
Vol 78 (4) ◽  
pp. 1157-1167 ◽  
Author(s):  
Anna Rusznyák ◽  
Denise M. Akob ◽  
Sándor Nietzsche ◽  
Karin Eusterhues ◽  
Kai Uwe Totsche ◽  
...  
Keyword(s):  
Laser Scanning ◽  
Extracellular Polymeric Substances ◽  
Large Fraction ◽  
Laser Scanning Microscopy ◽  
Confocal Laser ◽  
Rrna Gene ◽  
Seepage Water ◽  
Bacterial Cells ◽  
Content Type ◽  
Rich Media

ABSTRACTKarstic caves represent one of the most important subterranean carbon storages on Earth and provide windows into the subsurface. The recent discovery of the Herrenberg Cave, Germany, gave us the opportunity to investigate the diversity and potential role of bacteria in carbonate mineral formation. Calcite was the only mineral observed by Raman spectroscopy to precipitate as stalactites from seepage water. Bacterial cells were found on the surface and interior of stalactites by confocal laser scanning microscopy. Proteobacteria dominated the microbial communities inhabiting stalactites, representing more than 70% of total 16S rRNA gene clones. Proteobacteria formed 22 to 34% of the detected communities in fluvial sediments, and a large fraction of these bacteria were also metabolically active. A total of 9 isolates, belonging to the generaArthrobacter,Flavobacterium,Pseudomonas,Rhodococcus,Serratia, andStenotrophomonas, grew on alkaline carbonate-precipitating medium. Two cultures with the most intense precipitate formation,Arthrobacter sulfonivoransandRhodococcus globerulus, grew as aggregates, produced extracellular polymeric substances (EPS), and formed mixtures of calcite, vaterite, and monohydrocalcite.R. globerulusformed idiomorphous crystals with rhombohedral morphology, whereasA. sulfonivoransformed xenomorphous globular crystals, evidence for taxon-specific crystal morphologies. The results of this study highlighted the importance of combining various techniques in order to understand the geomicrobiology of karstic caves, but further studies are needed to determine whether the mineralogical biosignatures found in nutrient-rich media can also be found in oligotrophic caves.

scholarly journals Powdered Activated Carbon Exacerbates Fouling in MBR Treating Olive Mill Wastewater

Water ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 2498 ◽  
Author(s):  
Noya Ran ◽  
Jack Gilron ◽  
Revital Sharon-Gojman ◽  
Moshe Herzberg
Keyword(s):  
Activated Carbon ◽  
Membrane Permeability ◽  
Membrane Fouling ◽  
Biofilm Formation ◽  
Laser Scanning ◽  
Powdered Activated Carbon ◽  
Laser Scanning Microscopy ◽  
Confocal Laser ◽  
Permeate Flux ◽  
Wastewater Treatment Process

Membrane fouling is a major obstacle in membrane bioreactors (MBRs) that treat wastewater. The addition of powdered activated carbon (PAC) is commonly suggested as a way to improve the MBR wastewater treatment process with respect to membrane fouling and effluent quality. Integrating the PAC addition into the MBR may also improve the stability of the acclimated microbial community for biodegrading the recalcitrant organic compounds that can also enhance membrane fouling. In this study, the ability of the MBR-PAC system to decrease membrane fouling was evaluated. Two pilot-scale reactors were operated: one reactor was supplemented with suspended PAC, and one was operated under similar conditions, without PAC. The feed to the reactors comprised domestic and olive oil mill wastewater. Surprisingly, the permeate flux and the membrane permeability decreased faster in the MBR supplemented with PAC compared to the control reactor. Corroborating these MBR fouling results, soluble microbial products (SMPs), originating from the PAC-supplemented reactor, were found to be more adhesive to an ultrafiltration membrane mimetic surface (polyether sulfone) as analyzed in a quartz crystal microbalance with dissipation monitoring (QCM-D). While the PAC had almost no effect on the dissolved organic carbon in the MBR, it altered the molecular weight distribution of the organic molecules in the SMP as observed with gel permeation chromatography: The fractions of 577–789 kDa and the one bigger than 4 × 103 kDa, were elevated and reduced, respectively, by the addition of PAC. A biofilm formation analysis using a confocal laser scanning microscopy showed a higher amount of biofilm on the membrane taken from the PAC reactor, but this membrane showed no traces of PAC particles when analyzed with a scanning electron microscope (SEM). Taken together, altering the composition of the dissolved organic matter in the MBR by PAC addition promoted its adhesion to the membrane, induced biofilm formation, and more prominently, decreased membrane permeability.

scholarly journals Raman Spectroscopic Characterization of Endodontic Biofilm Matrices

2019 ◽  
Vol 2019 ◽  
pp. 1-7 ◽  
Author(s):  
Tatiana Ramirez-Mora ◽  
Claudia Dávila-Pérez ◽  
Fernando Torres-Méndez ◽  
Grettel Valle-Bourrouet
Keyword(s):  
Raman Spectroscopy ◽  
Laser Scanning ◽  
Extracellular Polymeric Substances ◽  
Principal Component ◽  
Spectroscopic Characterization ◽  
Laser Scanning Microscopy ◽  
Confocal Scanning Laser Microscopy ◽  
Confocal Laser ◽  
Total Biomass ◽  
Endodontic Infections

Endodontic persistent infections are often mediated by bacterial biofilms. This mode of bacterial growth is characterized by the presence of a matrix mainly composed of extracellular polymeric substances (EPSs) that protect the encased microorganisms. To establish better control and disinfection protocols, elucidation of the main components of biofilm matrices present in endodontic infections is required. The aim of the present study was to characterize the principal components ofE. faecalis,A. naeslundii, and dual-species biofilm matrices by means of Raman spectroscopy and confocal scanning laser microscopy (CSLM) techniques. The total biomass of biofilms was quantified via crystal violet assays, and the monospecies biofilms showed higher biomass than the dual-species biofilms. Raman spectroscopy and confocal laser scanning microscopy were used to identify the biochemical composition and structure of the biofilm matrices. Spectra originating from the biofilms of two endodontic pathogens show the presence of carbohydrates, proteins, fatty acids, and nucleic acids in all samples; however, variation in the levels of expression of these biomolecules allows spectroscopic differentiation of the biofilms using principal component analysis. This study is the first attempt to identify the composition of monospecies and dual-species biofilms of endodontic origin. Our data provides an important approach to the understanding of molecular dynamics of endodontic infections.

scholarly journals Effects of Operational Parameters on Biofilm Formation of Mixed Bacteria for Hydrogen Fermentation

2020 ◽  
Vol 12 (21) ◽  
pp. 8863
Author(s):  
Jie Mei ◽  
Huize Chen ◽  
Qiang Liao ◽  
Abdul-Sattar Nizami ◽  
Ao Xia ◽  
...  
Keyword(s):  
Formation Process ◽  
Biofilm Formation ◽  
Laser Scanning ◽  
Extracellular Polymeric Substances ◽  
Packed Bed ◽  
Dark Fermentation ◽  
Laser Scanning Microscopy ◽  
Packed Bed Reactor ◽  
Confocal Laser ◽  
Operational Parameters

Dark fermentation of organic wastes, such as food waste and algae, via mixed hydrogen-producing bacteria (HPB) is considered a sustainable approach for hydrogen production. The biofilm system protects microorganisms from the harmful environment and avoids the excessive loss of bacteria caused by washout, which ensures that the dark fermentation process remains stable. In this study, a downflow anaerobic packed-bed reactor was commissioned to investigate the biofilm formation process of mixed HPB under various operational parameters. Scanning electron microscopy indicated changes in surface morphology during the biofilm formation period. Proteins and polysaccharides in extracellular polymeric substances were identified by confocal laser scanning microscopy to reveal their distribution characteristics. A hydraulic retention time of 0.5 d, a substrate concentration of 15 g/L and an HPB inoculum ratio of 35% were identified as the optimal operational parameters for biofilm formation. The diversity of bacteria between suspension and biofilm showed significantly different distributions; Clostridiales and Lactobacillales were identified as the dominant orders in the biofilm formation process. The abundances of Clostridiales and Lactobacillales were 15.1% and 56.2% in the biofilm, respectively.

scholarly journals Microbial Composition and Structure of Aerobic Granular Sewage Biofilms

2007 ◽  
Vol 73 (19) ◽  
pp. 6233-6240 ◽  
Author(s):  
S. D. Weber ◽  
W. Ludwig ◽  
K.-H. Schleifer ◽  
J. Fried
Keyword(s):  
Activated Sludge ◽  
Laser Scanning ◽  
Extracellular Polymeric Substances ◽  
Phase 1 ◽  
Simultaneous Detection ◽  
Laser Scanning Microscopy ◽  
Confocal Laser ◽  
Microbial Composition ◽  
Granule Formation ◽  
Biofilm Development

ABSTRACT Aerobic activated sludge granules are dense, spherical biofilms which can strongly improve purification efficiency and sludge settling in wastewater treatment processes. In this study, the structure and development of different granule types were analyzed. Biofilm samples originated from lab-scale sequencing batch reactors which were operated with malthouse, brewery, and artificial wastewater. Scanning electron microscopy, light microscopy, and confocal laser scanning microscopy together with fluorescence in situ hybridization (FISH) allowed insights into the structure of these biofilms. Microscopic observation revealed that granules consist of bacteria, extracellular polymeric substances (EPS), protozoa and, in some cases, fungi. The biofilm development, starting from an activated sludge floc up to a mature granule, follows three phases. During phase 1, stalked ciliated protozoa of the subclass Peritrichia, e.g., Epistylis spp., settle on activated sludge flocs and build tree-like colonies. The stalks are subsequently colonized by bacteria. During phase 2, the ciliates become completely overgrown by bacteria and die. Thereby, the cellular remnants of ciliates act like a backbone for granule formation. During phase 3, smooth, compact granules are formed which serve as a new substratum for unstalked ciliate swarmers settling on granule surfaces. These mature granules comprise a dense core zone containing bacterial cells and EPS and a loosely structured fringe zone consisting of either ciliates and bacteria or fungi and bacteria. Since granules can grow to a size of up to several millimeters in diameter, we developed and applied a modified FISH protocol for the study of cryosectioned biofilms. This protocol allows the simultaneous detection of bacteria, ciliates, and fungi in and on granules.

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