Extracellular Polymeric Substances Extraction Research Articles

Bioremediation of chromium contaminated water by diatoms with concomitant lipid accumulation for biofuel production

Hexavalent chromium compounds such as chromate and dichromate, commonly designated as Cr (VI) compounds, are widely used heavy metals in different industries and are considered highly toxic to most life forms. Unfortunately, they have become a major pollutant of groundwater and rivers around dichromate using industries. Bioremediation is widely used to decrease the amount of dichromate in wastewater but requires large amounts of precious fresh water. Here we tested two marine micro-algal species, Phaeodactylum tricornutum strain CCY0033 and Navicula pelliculosa strain CCMP543, for their ability of dichromate bioremediation and concomitantly producing lipids that can serve as biofuel. Dichromate tolerance of the strains was investigated under different growth conditions in order to obtain high biomass yields, high lipid accumulation and high dichromate removal from the medium. Both algal strains grew well and produced high biomass in media containing up to 1 mg of dichromate per liter. Variations in growth conditions revealed that dichromate removal from the medium correlated positively with biomass yield. Dichromate removal using living cells was in the same order of magnitude as with autoclaved dead cells or when using extracted extracellular polymeric substances (EPS). This suggests biosorption of dichromate to cell-associated polymeric substances as the major mechanism of the bioremediation process. For both strains, optimal dichromate removal and lipid production were achieved at a light intensity of 55 μmol m−2s−1 and at a sodium nitrate concentration of 3 mM. The optimal temperature for dichromate removal and lipid production was 23 °C for P. tricornutum and 27 °C for N. pelliculosa. Compared to P. tricornutum strain CCY0033, N. pelliculosa strain CCMP543 produced an overall higher lipid yield under these conditions.

Influence of extracellular polymeric substances on cell-NPs heteroaggregation process and toxicity of cerium dioxide NPs to Microcystis aeruginosa

The presence of abundant extracellular polymeric substances (EPS) play a vital role in affecting heteroaggregation process and toxicity of nanoparticles (NPs) to Microcystis aeruginosa. Interactions between n-CeO2 and cyanobacteria with/without EPS and the toxicity of n-CeO2 to M. aeruginosa were investigated in this study. Aggregation kinetics of n-CeO2 under both soluble EPS (SEPS) and bound EPS (BEPS) indicated the presence of EPS could induced the formation of EPS-NPs aggregates. Heteroaggregation between cells and n-CeO2 was confirmed through co-settling experiment and SEM-EDS observation. SEPS contributed to the observable heteroaggregation using spectral measurement. Heteroaggregation between cells and n-CeO2 under no BEPS was hardly obtained through spectral measurement, but SEM-EDS observation convinced this process. And the DLVO theory explained this heteroaggregation process under various EPS conditions, where the energy barrier decreased with gradual EPS extraction. In addition, the order for 96 h half growth inhibition concentration (IC50) was Raw M9 > M9-SEPS > M9+BEPS > M9-BEPS. These results revealed that not all heteroaggregation between cell-NPs can lead to the NPs toxicity to cells. BEPS act more important role in buffering against the toxicity of NPs from ambient adverse factors, but SEPS increase the stability of NPs which could aggravate the adverse effects of NPs in the environment.

Comparison of Extraction Methods of Extracellular Polymeric Substances from Activated Sludge

Extracellular polymeric substances (EPSs) are biosynthetic polymers of microbial origin in the sludge activation process and crucially affect the properties of sludge in biological wastewater treatment reactors, such as the formation of sludge flocs, stabilization of sludge structure, and protection of microbes against noxious environmental conditions. However, the EPS extraction efficiency differs significantly according to the extraction method used. In this study, soluble EPSs and loosely bound EPSs can be extracted by centrifugation first and tightly bound EPSs in activated sludge require additional eight treatments for extraction, respectively. Three physical methods (centrifugation, sonication, and heating) and five chemical methods (cation exchange resin, NaOH, formaldehyde+NaOH, EDTA, and formaldehyde+EDTA) were tested, and the content and composition of TB-EPS were analyzed. Meanwhile, the functional groups and elements in TB-EPS were investigated. Results showed that the heating method did not introduce exogenous substances during the EPS extraction process and that the destruction of cells from this method was relatively slight. Heating was shown to be a gentle and efficient method in this study. The three-dimensional excitation and emission matrix (EEM) fluorescence spectroscopy showed that the cation exchange resin method had good extraction effect on humic-like and protein-like substances. As to fulvic-acid-like substances, NaOH was better than the other seven methods. Infrared spectroscopy showed that no notable difference appeared in the functional groups of the TB-EPS extracted by physical methods, whereas chemical methods induced big differences and showed particular bands that did not appear in the TB-EPS extracted by physical methods. Overall, the amounts of TB-EPS elements extracted using chemical methods were greater than those extracted using physical methods. In conclusion, a method must be selected and established for each case, taking into consideration the experimental purpose, and the most appropriate method should be chosen carefully.

Inhibition of Nitzschia ovalis biofilm settlement by a bacterial bioactive compound through alteration of EPS and epiphytic bacteria

Marine ecosystems contain benthic microalgae and bacterial species that are capable of secreting extracellular polymeric substances (EPS), suggesting that settlement of these microorganisms can occur on submerged surfaces, a key part of the first stage of biofouling. Currently, anti-fouling treatments that help control this phenomenon involve the use of biocides or antifouling paints that contain heavy metals, which over a long period of exposure can spread to the environment. The bacterium Alteromonas sp. Ni1-LEM has an inhibitory effect on the adhesion of Nitzschia ovalis, an abundant diatom found on submerged surfaces. We evaluated the effect of the bioactive compound secreted by this bacterium on the EPS of biofilms and associated epiphytic bacteria. Three methods of EPS extraction were evaluated to determine the most appropriate and efficient methodology based on the presence of soluble EPS and the total protein and carbohydrate concentrations. Microalgae were cultured with the bacterial compound to evaluate its effect on EPS secretion and variations in its protein and carbohydrate concentrations. An effect of the bacterial supernatant on EPS was observed by assessing biofilm formation and changes in the concentration of proteins and carbohydrates present in the biofilm. These results indicate that a possible mechanism for regulating biofouling could be through alteration of biofilm EPS and alteration of the epiphytic bacterial community associated with the microalga. How to cite: Infante, C.D., Castillo, F., Pérez, V., et al. Inhibition of Nitzschia ovalis biofilm settlement by a bacterial bioactive compound through alteration of EPS and epiphytic bacteria. Electron J Biotechnol 2018;33 https://doi.org/10.1016/j.ejbt.2018.03.002.

Nano‐layered TiO2 for effective bacterial disintegration of waste activated sludge and biogas production

AbstractBACKGROUNDProper management of the huge amount of waste activated sludge generated during the conventional treatment of wastewater is nowadays a major environmental issue. Proper treatment of sludge needs huge investment and proper handling. To address this issue, the immobilized photocatalyst (TiO2) mediated exocellular fractionation of bacterial pretreatment for anaerobic digestion was utilized as a sludge treatment technique.RESULTTi was deposited on glass substrate by a DC spluttering technique, and a TiO2 layer was formed by annealing in oxygen atmosphere. This immobilized TiO2 efficiently extricated the extracellular components after 45 min by removing 99% of the total extractable extracellular polymeric substances. The exocellular fractionated bacterial pretreatment induced 20% of COD solubilization with methane generation of about 0.0217 g COD g‐1 COD d‐1, which was higher than the sludge without any treatment and sludge with bacterial pretreatment only.CONCLUSIONAn 8% increase in COD solubilization was achieved, which generated high quantities of methane. With the advantage of methane generation, the maximum profitable sludge reduction was obtained. Thin film deposition of TiO2 enables easy recovery of TiO2. The cost, energy, and solid balance analysis confirmed that this treatment method is field applicable. © 2018 Society of Chemical Industry

Quantifying biostabilisation effects of biofilm-secreted and extracted extracellular polymeric substances (EPSs) on sandy substrate

Abstract. Microbial assemblages (“biofilms”) preferentially develop at water–sediment interfaces and are known to have a considerable influence on sediment stability and erodibility. There is potential for significant impacts on sediment transport and morphodynamics, and hence on the longer-term evolution of coastal and fluvial environments. However, the biostabilisation effects remain poorly understood and quantified due to the inherent complexity of biofilms and the large spatial and temporal (i.e. seasonality) variations involved. Here, we use controlled laboratory tests to systematically quantify the effects of natural biofilm colonisation as well as extracted extracellular polymeric substances (EPSs) on sediment stability. Extracted EPSs may be useful to simulate biofilm-mediated biostabilisation and potentially provide a method of speeding up timescales of physical modelling experiments investigating biostabilisation effects. We find a mean biostabilisation effect due to natural biofilm colonisation and development of almost 4 times that of the uncolonised sand. The presented cumulative probability distribution of measured critical threshold for erosion of colonised sand reflects the large spatial and temporal variations generally seen in natural biostabilised environments. For identical sand, engineered sediment stability from the addition of extracted EPSs compares well across the measured range of the critical threshold for erosion and behaves in a linear and predictable fashion. Yet, the effectiveness of extracted EPSs to stabilise sediment is sensitive to the preparation procedure, time after application and environmental conditions such as salinity, pH and temperature. These findings are expected to improve biophysical experimental models in fluvial and coastal environments and provide much-needed quantification of biostabilisation to improve predictions of sediment dynamics in aquatic ecosystems.

Alteration of the characteristics of extracellular polymeric substances (EPS) extracted from the fungus Phanerochaete chrysosporium when exposed to sub-toxic concentrations of nickel (II)

The fungus Phanerochaete chrysosporium was incubated at five sub-toxic concentrations of Ni2+ (0.5, 1, 5, 10 and 25 mg/L, respectively), and its metal immobilization ability as well as the alteration of some characteristics regarding the extracellular polymeric substances (EPS) were investigated. With the increased Ni2+ concentrations in the broth, higher Ni2+ amounts were measured in both intact fungal cells (biomass before EPS extraction) and EPS-free biomass (biomass after EPS extraction). The Ni2+ immobilization ability of the extracted EPS displayed a similar level at Ni2+ concentrations higher than 1 mg/L. The presence of Ni2+ in the broth decreased the zeta-potential of the intact biomass and increased cell surface hydrophobicity (CSH). Fourier transform infrared spectroscopy (FT-IR) analyses identified the presence of some functional groups, such as carboxyl, phosphoryl and hydroxyl groups, in the extracted EPS. The high hydrophobicity (>60%) of the extracted EPS was decreased by the increased Ni2+ concentration. The protein (PN) and polysaccharide (PS) content in the EPS was also affected by the increased Ni2+ concentration, and the abundance of PN-like molecules ranging from 0.5 kDa to 14 kDa was enriched. However, the fluorescence characteristics and apparent molecular weight (aMW) of the extracted EPS were not affected by the Ni2+ concentration. Therefore, one possible defense mechanism developed by the fungus towards Ni2+ stress is the adjustment of its EPS composition.

Extracellular polymeric substances, a key element in understanding biofilm phenotype.

One of the key elements in the establishment and maintenance of the biofilm structure and properties is the extracellular matrix. The extracellular matrix is composed of water and extracellular polymeric substances (EPS): primarily polysaccharides, proteins and DNA. Characterization of the matrix requires component identification, as well as determination of the relative concentration of EPS constituents, including their physicochemical properties and descriptions of their interactions. Several types of experimental approaches with varying degrees of destructiveness can be utilized for this characterization. The analysis of biofilm by infrared spectroscopy gives information about the chemical content of the matrix and the proportions of different EPS. The sensitivity of a biofilm to hydrolytic enzymes targeting different EPS gives insight into the composition of the matrix and the involvement of matrix components in the integrity of the structure. Using both chemical and physical treatments, extraction and purification of EPS from the biofilm also provides a means of determining matrix composition. Purified and/or artificial EPS can be used to obtain artificial matrices and to study their properties. Using examples from the literature, this review will illustrate selected technologies useful in the study of EPS that provide a better understanding of the structure-function relationships in extracellular matrix, and thus the structure-function relationships of the biofilm phenotype.

Microbial characteristics of landfill leachate disposed by aerobic moving bed biofilm reactor.

An aerobic moving bed biofilm reactor (MBBR) was applied to treat landfill leachate generated from a domestic waste incineration plant. Pollutant removal efficiency of this reactor under stable operating condition was studied. The biomass, bacteria species, and microbial metabolism in this reactor were investigated. These results showed that the average removal efficiency of chemical oxygen demand (COD) and ammonia nitrogen in the aerobic MBBR achieved 64% and 97% in the optimum conditions, respectively. The three-dimensional fluorescence spectrum revealed that the content of soluble microbial byproducts from extracellular polymeric substances extraction in suspended sludge was much higher than that on biofilm, and the types of pollutants were various in different regions of the reactor. It also indicated that the MBBR system had a stable, rich and regular microorganism community, including large amounts of nitrifying bacteria and denitrifying bacteria. Scanning electron microscopy suggested that biofilm attached to the packing provided a good anoxic-aerobic micro environment system to achieve a high metabolic activity, which favored COD and ammonia removal.

An improved protocol for extracting extracellular polymeric substances from granular filter media

Extracellular polymeric substances (EPS) are an important parameter in drinking-water biofilters, and, to date, this is the first study to compare protocols from the literature for extracting EPS from granular filter media. Five extraction protocols were compared, and one was improved by varying the type of initial physical treatment and the shaking intensity, temperature, and time of incubation. Extracting EPS from granular filter media in triplicate by combining 2 g (wet weight) of filter media with 10 mL of extraction buffer (10 mM Tris, 10 mM EDTA, 2.5% NaCl, pH 8), vortexing for 1 min, and incubating for 4 h at 35 °C with shaking at 200 rpm yielded significantly higher EPS polysaccharide and/or protein concentrations than did protocols from the literature. This improved protocol extracted a significant fraction of the biofilm attached to sand but was less effective on biofilm attached to anthracite or granular activated carbon (GAC). A survey of 11 full-scale biofilters from the U.S. and Canada revealed that EPS polysaccharide and protein concentrations can vary over one order of magnitude, from 0.02 to 0.60 mg glucose/g total solids (TS) and 0.27 to 3.38 mg bovine serum albumin/g TS, respectively. Backwashing significantly lowered the biomass and EPS polysaccharide concentrations, but the majority of the biofilm remained attached to the filter media after backwashing, as expected. The fraction of EPS polysaccharides and proteins removed during backwashing did not differ between anthracite and GAC biofilters. The improved EPS extraction protocol can be utilized to investigate the role of EPS in biofilter performance.

Quantitative and qualitative characterization of extracellular polymeric substances from Anammox enrichment

Abstract Extracellular polymeric substances (EPS) from different Anammox biomass were extracted and characterized by quantitative and qualitative analysis to investigate the link between their characteristics and the enrichment process in lab scale bioreactors. Quantitatively, a decrease of protein to polysaccharide ratio and an increase in total EPS extraction yield were observed during the enrichment process. In the three dimensional excitation emission matrixes, the spectra showed similar location of the fluorescence peaks for all of the samples. Whereas, samples extracted from sludge containing enriched Anammox bacteria possessed two distinct peaks in the low excitation wavelength range (220–230 nm). Multi-excitation peaks might occur as evidenced by the identical fluorescence chromatograms after size exclusion chromatography (SEC) separation at excitation/emission wavelength of 221/350 nm and 280/330 nm. With the process of Anammox enrichment, UV chromatogram at 210 nm after SEC, which is an indicator of polysaccharides, showed increase in both intensity and number of peaks. However, all fluorescence chromatograms, which reflect proteins and soluble microbial by-products, showed similar peak patterns with increased intensity. An increase of EPS hydrophobicity was observed during the enrichment process for both reactors.

Biological hydrolysis pretreatment on secondary sludge: Enhancement of anaerobic digestion and mechanism study

The performance of biological hydrolysis (BH) pretreatment on municipal secondary sludge was evaluated in this study. During 6-day BH at 42°C (BH42), soluble chemical oxygen demand (sCOD) increased from 175.2±38.2mg/L to 3314.5±683.4mg/L; the dominant volatile fatty acid (VFA) was acetic acid, and its concentration increased from 41.5±2.1mg/L to 786.0±133.2mg/L. The extracted extracellular polymeric substances (EPS) from untreated secondary sludge contained three main fractions, and Fraction I gradually decreased from 133.9kDa to 24.9kDa during 6-day BH42. The BH pre-treatment at 42°C and 55°C both achieved more than 4-log reduction of total coliforms and 3-log reduction of E. coli. The BH pretreated secondary sludge at 15-day biochemical methane potential (BMP) test was comparable with the untreated secondary sludge after 30-day BMP, showing a significant enhancement on the acceleration of biogas production by BH pretreatment.

Optimum selection of extraction methods of extracellular polymeric substances in activated sludge for effective extraction of the target components

Effects of extraction methods of extracellular polymeric substances (EPS) from activated sludge on extraction efficiency and extract composition were investigated. EPS extract was characterized based on protein and polysaccharide composition, excitation-emission matrix (EEM) and molecular weight (MW) profile. Four methods were applied to extract EPS from activated sludge: combination of formaldehyde and sodium hydroxide, combination of sodium hydroxide and heating, cation exchange resin (CER) for tightly-bound EPS, and sonication for loosely-bound EPS. Extraction methods affected not only extraction efficiency but also composition of proteins and polysaccharides, EEM spectra and MW profile of extracted EPS. Combination of formaldehyde and alkaline is preferable to acquire high extraction efficiency with less cell lysis. Upon EEM analysis, the CER method was appropriate to detect a wide range of fluorescent organic substances, while alkaline extraction was less efficient for detection of humic acid-like substances. Alkaline extraction is more appropriate for extraction of large EPS molecules with a variety of MWs. However, it should be noted that changes in MW distribution may occur during alkaline extraction. Consequently, selection of extraction methods is crucial to achieving effective extraction of the target components of EPS.

Proteomic analysis of rat peripheral nerves

Biodiversity forms the basis for a large pool of potential products and productive organisms offered by terrestrial cyanobacteria. They are stuck together by EPS (extracellular polymeric substances) that can obtain antiviral, antibacterial or anti-inflammatory substances. Most stress conditions, e.g. drought, induce the production of protective EPS or biotechnological-products for pharmaceutical application. However, the growth of a phototrophic biofilm is limited under submerged conditions. Therefore, a semi-continuous process to produce EPS by cyanobacteria was developed in an aerosol-based ePBR (emerse photobioreactor) that imitates the natural habitat of terrestrial cyanobacteria.The process consists of a growth-phase (biomass production), followed by a dry-phase (EPS-production) and a consecutive extraction. The EPS-productivities of Trichocoleus sociatus (ranging from 0.03 to 0.04 g L−1 d−1) were 32 times higher than described in topic-related literature. In comparison to submerge cultivations in shaking flasks, the EPS-productivities were sevenfold higher. To ensure that the extraction solvent has no influence on cell viability, a cell-vitality-test was performed. However, no statistically significant difference between the amount of living and dead cells before and after the extraction was detected. A bioactivity assay was then performed to identify antimicrobial activity within EPS extracts from emerse and submerge cultivations. The EPS revealed an antibacterial effect against gram-negative bacteria (E. coli) which was two times higher than EPS from a submerged cultivation.

Enhancement of extracellular polymeric substances (EPS) production in Spirulina (Arthrospira sp.) by two-step cultivation process and partial characterization of their polysaccharidic moiety

The interactive effects of light intensity and NaCl concentration were investigated for Spirulina two-step cultivation process using Full Factorial Design. In the experiment interval, light intensity had no effect while the NaCl concentration had significant effect on the enhancement of extracellular polymeric substances (EPS) production. Interestingly, results revealed a significant negative interaction between light and NaCl concentration indicating that high NaCl concentration (40gL−1) and low light intensity (10μmol photons m−2s−1) enhanced the EPS production. Under these conditions, EPS production reached a maximum of 1.02gg−1 of biomass (dry weight), which is 1.67-folds greater than EPS content under optimal growth conditions (10μmol photons m−2s−1, 1gL−1, 30°C). Desalting and deproteinezation steps of EPS were efficient to obtain polysaccharides (PS) with high carbohydrate (67.3±1.1%), low soluble proteins (5.14±0.32%), ash (5.85±0.71%) and sulfate (2.42±0.12%) contents. Rheological studies of PS at different concentrations (1%, 2.5% and 5%) revealed that the viscosity of the solution increased with the increase of PS concentration. In addition, PS exhibited a non Newtonian shear-thinning nature, a predominant gel-like behavior and a good resistance to consecutive heating-cooling cycles. The adopted process could be, then, a promising and economic strategy to enhance EPS production and extract polysaccharides with interesting rheological properties.

A semi-continuous process based on an ePBR for the production of EPS using Trichocoleus sociatus

Biodiversity forms the basis for a large pool of potential products and productive organisms offered by terrestrial cyanobacteria. They are stuck together by EPS (extracellular polymeric substances) that can obtain antiviral, antibacterial or anti-inflammatory substances. Most stress conditions, e.g. drought, induce the production of protective EPS or biotechnological-products for pharmaceutical application. However, the growth of a phototrophic biofilm is limited under submerged conditions. Therefore, a semi-continuous process to produce EPS by cyanobacteria was developed in an aerosol-based ePBR (emerse photobioreactor) that imitates the natural habitat of terrestrial cyanobacteria.The process consists of a growth-phase (biomass production), followed by a dry-phase (EPS-production) and a consecutive extraction. The EPS-productivities of Trichocoleus sociatus (ranging from 0.03 to 0.04gL−1d−1) were 32 times higher than described in topic-related literature. In comparison to submerge cultivations in shaking flasks, the EPS-productivities were sevenfold higher. To ensure that the extraction solvent has no influence on cell viability, a cell-vitality-test was performed. However, no statistically significant difference between the amount of living and dead cells before and after the extraction was detected. A bioactivity assay was then performed to identify antimicrobial activity within EPS extracts from emerse and submerge cultivations. The EPS revealed an antibacterial effect against gram-negative bacteria (E. coli) which was two times higher than EPS from a submerged cultivation.

Comparison of two chemical extraction methods for proteins and polysaccharides of Spirogyra fluviatilis in extracellular polymeric substances

Under natural circumstances, Spirogyra fluviatilis excretes large amounts of extracellular polymeric substances (EPS) and forms a mucilage layer. This study used two algal EPS extraction methods such as NH4OH and formaldehyde-NaOH to compare the extraction yields of EPS and the levels of its primary components of polysaccharides and proteins. The results indicated that the extraction yields of EPS using formaldehyde-NaOH and NH4OH are 8.05 mg EPS/g-fresh algae and 5.26 mg EPS/g-fresh algae, respectively. The ratio of proteins to polysaccharides in EPS is around 0.24 to 0.34, which is not a significant difference between the two extraction methods. In other words, the level of polysaccharides is always higher than the level of proteins in EPS extraction with both two methods

Determination of quorum-sensing signal substances in water and solid phases of activated sludge systems using liquid chromatography–mass spectrometry

The detection of acyl homoserine lactones (AHLs) in activated sludge is essential for clarifying their function in wastewater treatment processes. An LC–MS/MS method was developed for the detection of AHLs in both the aqueous and solid phases of activated sludge. In addition, the effects of proteases and extracellular polymeric substances (EPS) on the detection of AHLs were evaluated by adding protease inhibitors and extracting EPS, respectively. Recoveries of each AHL were improved by adding 50μL of protease inhibitor, and recoveries were also improved from 0 to 56.9% to 24.2%–105.8% by EPS extraction. Applying the developed method to determine the type and concentration of AHLs showed that C4-HSL, C6-HSL, C8-HSL and 3-oxo-C8-HSL were widely detected in a suspended activated sludge system. The dominant AHL was C8-HSL, with a highest concentration of 304.3ng/L. C4-HSL was mainly distributed in the aqueous phase, whereas C6-HSL, C8-HSL and 3-oxo-C8-HSL were preferentially distributed in the sludge phase.

Double-win effects of in-situ ozonation on improved filterability of mixed liquor and ceramic UF membrane fouling mitigation in wastewater treatment?

The effects of in-situ ozonation on mixed liquor filterability and ceramic membrane fouling in wastewater treatment were systematically studied by evaluating the mixed liquor filterability with a factor analysis method, modeling the membrane fouling process with nine fouling models, and analyzing the mechanism of membrane fouling mitigation with a redundancy analysis method. In-situ ozonation had trade-off effects on the filterability of mixed liquor. On one hand, the filterability of mixed liquor was improved as a result of the remarkable reduction of mixed liquid suspended solids (MLSS), sludge volume after 30min sedimentation (SV30) and extractable extra-cellular polymeric substances (EPS). On the other hand, the filterability of mixed liquor deteriorated as a result of the obvious increase of dissolved organic carbon (DOC) and soluble microbial products (SMP). The contribution of sludge properties (MLSS, SV30, EPS) to the filterability of mixed liquor was nearly doubled compared with that of the supernatant properties (DOC, SMP). The filterability of mixed liquor was effectively improved with increase of ozone dosage (≤5mg/L). Meanwhile, membrane fouling was effectively mitigated by in-situ ozonation with the maximum normalized TMP (ΔTMP) reduction of 55.6% achieved at ozone dosage of 5mg/L (1.3mg-ozone/g-MLSS). The combined intermediate-standard model excellently fitted the experimental data at different ozone dosages and the alleviation of intermediate blocking mainly contributed to the fouling mitigation by in-situ ozonation (≤5mg/L). The cake layer resistance was maximally reduced by 61.5% at ozone dosage of 5mg/L mainly as a result of the significantly improved filterability of mixed liquor. The gel layer resistance was maximally reduced by 32.3% at ozone dosage of 5mg/L mainly as a result of the direct oxidation of organic foulants deposited on membrane surface.

Hydrophobic features of EPS extracted from anaerobic granular sludge: an investigation based on DAX-8 resin fractionation and size exclusion chromatography.

The hydrophobic fractionation of extracellular polymeric substances (EPS) extracted from anaerobic granular sludge was performed on the DAX-8 resin (two elution pH conditions, i.e., pH2 and pH5 were tested). The impact of seven different EPS extraction methods on EPS hydrophobicity features was assessed. The results showed that the extraction methods and bulk solution pH influenced dramatically the biochemical composition of the EPS, and in turn, the hydrophobicity determined. Besides, EPS extracting reagents i.e., formaldehyde, ethanol, sodium dodecyl sulfate (SDS), and Tween 20 not only introduced extra carbon content in the total organic carbon (TOC) measurement but also interacted with the DAX-8 resin. By comparing the apparent molecular weight (aMW) distribution of untreated and pH-adjusted EPS samples, more complete EPS aMW information was preserved at pH5. Thus, elution at pH5 was preferred in this study for the qualitative analysis of EPS hydrophobic features. The hydrophobic fraction of EPS retained by the resin at pH5 was ascribed to a wide aMW range, ranging from >440 to 0.3kDa. Within this range, EPS molecules ranging from 175 to 31kDa were mostly retained by the DAX-8 resin, which indicates that these EPS molecules are highly hydrophobic.