Properties Of Extracellular Polymeric Substances Research Articles

Effects and mechanisms of oxytetracycline and norfloxacin on microbial extracellular polymeric substances (EPS) in biological denitrification of aquaculture wastewater

The direct equalizing ray method was employed to design three groups of mixtures of oxytetracycline(OTC) and norfloxacin(NOR) with varying proportions(Group R1 had a higher proportion of OTC, while R2 had similar concentrations of both antibiotics, and R3 had a higher proportion of NOR).The effects of these mixtures on the content and properties of extracellular polymeric substances (EPS) in the biological denitrification process were investigated using an sequencing batch reactor activated sludge reactor (SBR). The results revealed that the removal rates of ammonia nitrogen(NH3-N) decreased in all three groups with the addition of antibiotics. As the antibiotic concentration increased, the EPS content decreased by 68.46%, 55.53%, and 65.03% in R1, R2, and R3, respectively. To understand the interaction mechanism of mixed antibiotics on EPS in activated sludge, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) techniques were employed. The findings demonstrated significant effects of mixed antibiotics on functional groups such as C-O, CO, and C-O-C. Specifically, hydrogen bonding was found to be the primary influencing factor in the R1 ratio, while Π-Π conjugation played a major role in the R3 ratio.

Sustained oxidation of Tea-Fe(III)/H2O2 simultaneously achieves sludge reduction and carbamazepine removal: The crucial role of EPS regulation

Establishing an economic and sustained Fenton oxidation system to enhance sludge dewaterability and carbamazepine (CBZ) removal rate is a crucial path to simultaneously achieve sludge reduction and harmless. Leveraging the principles akin to "tea making", we harnessed tea waste to continually release tea polyphenols (TP), thus effectively maintaining high level of oxidation efficiency through the sustained Fenton reaction. The results illustrated that the incorporation of tea waste yielded more favorable outcomes in terms of water content reduction and CBZ removal compared to direct TP addition within the Fe(III)/hydrogen peroxide (H2O2) system. Concomitantly, this process mainly generated hydroxyl radical (•OH) via three oxidation pathways, effectively altering the properties of extracellular polymeric substances (EPS) and promoting the degradation of CBZ from the sludge mixture. The interval addition of Fe(III) and H2O2 heightened extracellular oxidation efficacy, promoting the desorption and removal of CBZ. The degradation of EPS prompted the transformation of bound water to free water, while the formation of larger channels drove the discharge of water. This work achieved the concept of treating waste with waste through using tea waste to treat sludge, meanwhile, can provide ideas for subsequent sludge harmless disposal.

Impacts of electric field coupled membrane bioreactor on phenol wastewater with high salinity: Performance, membrane fouling and eco-friendly strategy

Electric field coupled membrane bioreactor (EMBR) enhanced the treatment performance of phenol wastewater with high salinity, improved sludge settleability, and alleviated membrane fouling. The sludge volume index (SVI) and fouling rate were positively correlated with the extracellular polymeric substance (EPS) content, indicating that the electric field improved sludge settleability by improving the properties of EPS, successfully reducing the fouling rate by 42.86 %. The phenol-degrading and salt-tolerant genera were enriched, and the EPS secretion genera were reduced in EMBR. Moreover, EMBR effectively resisted salt stress by increasing the relative abundance of betaine synthesis (betA) and transport genes (proV and proW), glutamate synthesis genes (gltB and gltD), salt stress response gene (rpoS), and F-type H+/Na+-transport ATPase genes (atpA and atpD), as well as reducing the relative abundance of genes related to cell membrane permeability. Meanwhile, EMBR decreased the production of intracellular reactive oxygen species (ROS), activated the antioxidant system and inhibited the ROS-mediated Save our Soul (SOS) response, which further improved salt tolerance of microorganisms. Furthermore, the inhibition of the SOS response reduced the dissemination of antibiotic resistance genes (ARGs). The co-occurrence patterns of ARGs and genera indicated that EMBR could also suppress the dissemination of ARGs by reducing the relative abundance of ARGs hosts.

Glycine betaine modulates extracellular polymeric substances to enhance microbial salinity tolerance

High salinity inhibits microbial activity in the bioremediation of saline wastewater. To alleviate osmotic stress, glycine betaine (GB), an osmoprotectant, is added to enhance the secretion of extracellular polymeric substances (EPS). These EPS are pivotal in withstanding environmental stressors, yet the intricate interplay between GB supplementation and microbial responses through EPS modifications—encompassing composition, molecular architecture, and electrochemical features—remains elusive in hypersaline conditions. Here we show microbial strategies for salinity endurance by investigating the impact of GB on the dynamic alterations of EPS properties. Our findings reveal that GB supplementation at 3.5% salinity elevates the total EPS (T-EPS) content from 12.50 ± 0.05 to 24.58 ± 0.96 mg per g dry cell weight. The observed shift in zeta potential from −28.95 to −6.25 mV at 0% and 3.5% salinity, respectively, with GB treatment, indicates a reduction in electrostatic repulsion and compaction. Notably, the EPS protein secondary structure transition from β-sheet to α-helix, with GB addition, signifies a more compact protein configuration, less susceptible to salinity fluctuations. Electrochemical analyses, including cyclic voltammetry (CV) and differential pulse voltammetry (DPV), reveal GB's role in promoting the release of exogenous electron shuttles, such as flavins and c-type cytochromes (c-Cyts). The enhancement in DPV peak areas (QDPV) with GB addition implies an increase in available extracellular electron transfer sites. This investigation advances our comprehension of microbial adaptation mechanisms to salinity through EPS modifications facilitated by GB in saline habitats.

Revealing the roles of biochar derived from iron-rich fermented sludge residue in anaerobic digestion

Anaerobic biological treatment of waste activated sludge (WAS) is proven as a low-carbon footprint technology with dual advantages of bio-fuel recovery and sludge stabilization. However, sludge residue after anaerobic biological treatment has been a serious obstacle to build waste-free cities. In this study, sludge residue, iron-rich sludge residue, and iron-rich fermented sludge residue were selected as the raw materials of biochar and the roles of prepared biochar in anaerobic digestion of WAS were investigated. Results indicated that the prepared biochar improved methane production and biochar derived from iron-rich fermented sludge residue (PFF-BC) obtained the best performance, with an increment of 23.4%. Mechanism analysis illustrated that the structural characteristics of PFF-BC were updated, including iron species, defect levels, and specific surface area, which played positive roles in the conversion of intermediate metabolites. Meanwhile, the compositions and electro-activity properties of extracellular polymeric substances were both stimulated by PFF-BC. Correspondingly, the activities of electron transport system and cytochrome c increased by 23.4% and 36.7%, respectively. For microbial communities, the abundances of electroactive microorganisms (such as Anaerolineaceae, Syntrophomonas and Methanosaeta) increased and direct interspecies electron transfer might be established, improving CO2-reduction and acetoclastic methanogenesis pathways. These findings will provide important references for stepwise resource recovery and final disposal of WAS.

Potential role of AgNPs within wastewater in deteriorating sludge floc structure and settleability during activated sludge process: Filamentous bacteria and quorum sensing

Excellent sludge floc structure and settleability are essential to maintain the process stability and excellent effluent quality during the activated sludge process. The underlying effect of silver nanoparticles (AgNPs) within wastewater on sludge floc structure and settleability is still unclear. The potential role of AgNPs in promoting filamentous bacterial proliferation and deteriorating sludge floc structure and settleability based on quorum sensing (QS) were investigated in this study. The results indicated that N-acyl homoserine lactose (AHL) concentration sharply increased from 23.56 to 108.41 ng/g VSS in the sequencing batch reactor with 1 mg/L AgNPs. AgNPs strengthened communication between filamentous bacteria, which triggered the filamentous bacterial QS system involving the synthetic gene hdtS and sensing genes traR and lasR. Filamentous bacterial proliferation was promoted by the triggered QS via positively regulating its cell cycle progression including chromosomal replication and divisome formation. In addition, extracellular protein production was obviously increased from 43.56 to 97.91 mg/g VSS through QS by regulating arginine and tyrosine secretion during filamentous bacterial proliferation under 1 mg/L AgNPs condition, which led to an increase in the negative charge and hydrophily at the cell surface. AgNPs resulted in an obvious increase in the surface energy barrier (WT) between bacteria. The change in the physicochemical properties of extracellular polymeric substance (EPS) induced by QS among filamentous bacteria obviously inhibited bacterial aggregation between filamentous bacteria and floc-forming bacteria under AgNPs condition, thus resulting in serious deterioration of the sludge floc structure and settleability. This study provided new insights into the microcosmic mechanism for the effect of AgNPs on sludge floc structure and settleability.

Exploring nutrient removal mechanisms in column-type SBR with simultaneous nitrification and denitrification

A comprehensive investigation utilized a column-type sequencing batch reactor (SBR) to efficiently remove nutrients throughout various phases of its operational cycle by forming granules. This study assessed the influence and mechanisms of a simultaneous nitrification and denitrification (SND) system employing a column-type sequential batch reactor (SBR). The primary focus was on elucidating the functional groups involved in nitrogen transformation and removal within the extracellular polymeric substances (EPS). The research findings demonstrate the superior performance of the SBR process compared to the control group. It achieved an impressive SND efficiency of 69%, resulting in a remarkable 66% total nitrogen removal. Furthermore, a detailed analysis unveiled that the SBR process had a beneficial impact on the composition and properties of EPS. This impact was observed through increased EPS content and enhanced capacity to transport, convert, and retain nitrogen effectively. Additionally, after initial acclimatization, the SBR process showed its effectiveness in removing nutrients (88–98%) and COD (93%) from the generated wastewater within a hydraulic retention time (HRT) of 6 h. A statistically significant difference between the treatments for the investigated mixing ratios was found by univariate analysis of variance (ANOVA). Machine learning (CatBoost model) was employed to understand each parameter’s relationship and predict the outcomes in measurable quantity. The findings of the SBR trials showed that the concentration of generated wastewater and the HRT impacted the treatment efficiency. However, the effluent may still need other physicochemical processes, such as membrane filtering, coagulation, electrocoagulation, etc., as post-treatment options, even though COD, nutrients, and turbidity have been entirely or significantly effectively removed. Overall, this work offers insightful information on the critical function of the SBR bacterial community in promoting SND.

DBP-FP change of biofilm in drinking water distribution system induced by sequential UV and chlorine disinfection: Effect of UV dose and influencing mechanism

The issue of biofilm-related disinfection byproducts (DBPs) in drinking water distribution system (DWDS) has garnered significant attention. This study sought to examine the changes in biofilm-originated halogenated DBP formation potential (biofilm DBP-FP) in simulated continuous-flow DWDSs subjected to sequential UV and chlorine disinfection (UV–Cl2) treatments with varying UV doses and to propose the underlying mechanism. The formation potential of trihalomethanes (THMs), haloacetic acids (HAAs), and the total organic halogen (TOX, X = Cl and Br) produced by biofilm were measured. Results showed that the biofilm TOCl-FP was at a minimum with a UV dose of 80 mJ/cm2, corresponding to the lowest amounts of protein and polysaccharides in the extracellular polymeric substances (EPS). Sphingobium, Methylobacterium, and Sphingomonas played a crucial role in protein and polysaccharide biosynthesis. Bacterial community composition characterization together with metabolic function analysis indicated that dominant bacteria varied and metabolic function shifted due to UV-Cl2 disinfection, with Alphaproteobacteria increasing in relative abundance and Bacteroidia showing the opposite trend with increasing UV doses. Correlation analysis suggested that the UV-Cl2 disinfection process led to changes in the water matrix, including organics, inorganics, bacteria, and components that provide environmental pressure for the biofilm. These changes ultimately influenced the properties of the biofilm EPS, which had a direct impact on biofilm DBP-FP.

Determining the mechanism for biomass segregation between granules and flocs in anammox granular system from the prospective of EPS

Granules and flocs have been widely found co-existing in anammox granular systems, but the segregation mechanism of granules and flocs is still largely unknown. Here, the chemical composition, physical properties, spectral characteristics, and adherence properties of extracellular polymeric substances (EPS) extracted from anammox granules (Granule-EPS) and flocs (Floc-EPS), which were closely related to sludge aggregation, were tested and compared. Granule-EPS exhibited more complex texture with larger biomolecule size and higher molecular weight than Floc-EPS. Moreover, Floc-EPS showed weaker co-aggregation ability, which might be due to its lower proteins/polysaccharides ratio, more compact protein secondary structure, stronger hydrophilicity, and lower intermolecular hydrogen bond proportion, than Granule-EPS. Besides, due to the looser connection between Floc-EPS biomolecules compared to Granule-EPS biomolecules, the structure of adhered Floc-EPS layer was looser than that of the adhered Granule-EPS, which was in accordance with the lower sludge intensity of anammox flocs compared to granules (595.2 ± 36.8 Pa vs. 315.3 ± 13.8 Pa; p = 0.001). More importantly, during the process of anammox flocs aggregation, a portion of EPS formed structure EPS that was difficult to extract, to maintain a tight structure of the granules. We therefore assumed that biomass segregation between anammox granules and flocs was due to the difference in the tightness of the adhered layer structure they formed. Overall, the results improve our understanding of anammox granular system, especially for the segregation phenomenon between granules and flocs.

Plant growth‐promoting rhizobacteria mediate soil hydro‐physical properties: An investigation with Bacillus subtilis and its mutants

AbstractPlant growth‐promoting rhizobacteria and other soil bacteria have the potential to improve soil hydro‐physical properties and processes through the production of extracellular polymeric substances (EPS). However, the mechanisms by which EPS mediates changes in soil properties and processes remain incompletely understood, partly due to variations in EPS composition produced under different environmental conditions. In this study, we investigated the influence of different bacterial traits on intrinsic soil properties and processes of evaporation and infiltration using sand treated with the wild‐type Bacillus subtilis variant (UD1022) and its two mutant variants, – and srf. The – mutant suppresses EPS production through alterations in the eps and tasA genes, while the srf mutant lacks the gene for surfactin production. Experimental results confirmed that the solution viscosity of the – mutant was the lowest and the solution surface tension of the srf mutant was the highest among the three tested bacteria strains. The distinct intrinsic properties of EPS produced by these bacterial strains resulted in varied hydro‐physical responses in the treated sand. Key influences included modifications in wettability, hydraulic decoupling (or mixed wettability), and aggregation, which collectively led to reduced evaporation rates and heterogeneous water distribution during infiltration in the bacteria‐treated sands. Our findings advance the understanding of the role bacterial EPS play in vadose zone hydrology and offer insights for the development of sustainable strategies for increasing water retention, supporting crop production in arid regions, and facilitating land restoration.

Potential role of quorum quenching activity of silver nanoparticles in controlling non-filamentous bulking within activated sludge process

The effective prevention and control of non-filamentous bulking is a significant challenge. In this study, the underlying effect of quorum sensing (QS) on inducing non-filamentous bulking and the maintenance effect of silver nanoparticles (AgNPs) on sludge floc stability, aggregation and settleability based on the quorum quenching (QQ) activity during non-filamentous bulking were investigated. The results showed that the concentration of N-acyl homoserine lactone (AHL) increased significantly in the activated sludge system at a high organic load rate (OLR), triggering the AHL-mediated QS. Additionally, the triggered QS promoted exopolysaccharide secretion, reducing the surface charge and hydrophobicity of the sludge aggregates, and further deteriorating the settleability of the sludge aggregates. AgNPs, a quorum sensing inhibitor (QSI), inhibited the AHL-QS based on QQ activity under high OLR, which maintained the physicochemical properties of extracellular polymeric substances (EPS). AgNPs-QQ maintained the surface energy barrier and electrostatic barrier of sludge aggregates and the gel properties of exopolysaccharides, which is favorable for microbial aggregation. The appropriate concentrations of AgNPs (≤10 mg/L) had no negative effect on biological nutrient removal in the sequencing batch reactors (SBRs) at the high organic loading. Therefore, AgNPs effectively prevent and control non-filamentous bulking by their QQ activity in the activated sludge process. Thus, the present study provided new insights into controlling non-filamentous bulking during the activated sludge process.

Charge transfer interactions exist in extracellular polymeric substances: Comparison with natural organic matter

Extracellular polymeric substances (EPS) and natural organic matter (NOM) are widely present in the environment. While the molecular basis of NOM's optical properties and reactivity after treatment with sodium borohydride (NaBH4) has been successfully explained by the charge transfer (CT) model, the corresponding structure basis and properties of EPS remain poorly understood. In this work, we investigated the reactivity and optical properties of EPS after NaBH4 treatment, comparing them to the corresponding changes in NOM. After reduction, EPS exhibited optical properties and a reactivity with Au3+ similar to NOM, manifesting an irreversible loss of visible absorption (≥70%) associated with blue-shifted fluorescence emission (8–11 nm) and a lower rate of gold nanoparticles formation (decreasing by ≥ 32%), which can be readily explained by the CT model as well. Furthermore, the absorbance and fluorescence spectra of EPS were solvent polarity dependent, contrary to the superposition model. These findings contribute to an original understanding of the reactivity and optical properties of EPS and facilitate further cross-disciplinary studies.

Bacterial extracellular polymeric substances: Biosynthesis and interaction with environmental pollutants

Extracellular polymeric substances (EPS) are highly hydrated matrices produced by bacteria, containing various polymers such as polysaccharides, proteins, lipids, and DNA. Extracellular polymer concentrations, ions, and functional groups provide physical stability to the EPS. Constituents of EPS form the three-dimensional architecture and help acquire nutrition for the bacteria. Structural and functional diversity of the extracellular polymer depends on the specific glycosyltransferases, polymerase and transporter proteins. These enzymes are encoded by specific genes present in operons such as crd, alg, wca, and gum reported in Agrobacterium, Pseudomonas, Enterobacteriaceae, and Xanthomonas. The operons regulate the biosynthesis of extracellular polymers such as curdlan, alginate, colonic acid, and xanthan, respectively. Various functional groups in the EPS, such as carbonyl, hydroxyl, phosphoryl, and amide, provide the sorption site for interaction with environmental pollutants. Hydrophobic interactions and coordinate bonds mainly dominate the binding of EPS with environmental pollutants. EPS binds, emulsifies, and solubilizes the organic compounds, enhancing the degradation process. EPS binds with heavy metals through complexation, surface adsorption, precipitation, and ion exchange mechanisms. The biodegradability efficiency and nontoxicity properties of EPS make it an excellent biopolymer for decontaminating environmental pollutants. This review summarizes an overview of the biosynthetic mechanisms and interaction of the bacterial extracellular polymer with environmental pollutants. Interaction mechanisms of pollutants with EPS and EPS-mediated bioremediation will help develop removal applications. Moreover, understanding the genes responsible for EPS production, and implementation of new genetic methodology can be helpful for the enhanced biosynthesis of EPS to control pollution by sequestrating more environmental pollutants.

Insight into the roles of microalgae on simultaneous nitrification and denitrification in microalgal-bacterial sequencing batch reactors: Nitrogen removal, extracellular polymeric substances, and microbial communities

This study explored the influence and mechanism of microalgae on simultaneous nitrification and denitrification (SND) in microalgal-bacterial sequencing batch reactors (MB-SBR). It particularly focused on nitrogen transformation in extracellular polymeric substances (EPS) and functional groups associated with nitrogen removal. The results showed that MB-SBR achieved more optimal performance than control, with an SND efficiency of 68.01% and total nitrogen removal efficiency of 66.74%. Further analyses revealed that microalgae changed compositions and properties of EPS by increasing EPS contents and improving transfer, conversion, and storage capacity of nitrogen in EPS. Microbial community analysis demonstrated that microalgae promoted the enrichment of functional groups and genes related to SND and introduced diverse nitrogen removal pathways. Moreover, co-occurrence network analysis elucidated the interactions between communities of bacteria and microalgae and the promotion of SND by microalgae as keystone connectors in the MB-SBR. This study provides insights into the roles of microalgae for enhanced SND.

Spectroscopic fingerprints profiling the polysaccharide/protein/humic architecture of stratified extracellular polymeric substances (EPS) in activated sludge

Extracellular polymeric substances (EPS), with a stratified structure including tightly-bound EPS (TB-EPS), loosely-bound EPS (LB-EPS), and soluble EPS (S-EPS) surrounding the microbial cells, are known to vitally affect the physicochemical and biological functions of activated sludge in wastewater treatment. Polysaccharides (PS), proteins (PN), and humic acids (HA) are key components of EPS but their roles in constructing the multi-layer architecture are still unclear. This study explored the EPS characteristics in relation to the components using spectroscopic fingerprinting techniques. Ultraviolet-visible (UV-vis) spectra demonstrated stark difference between TB-EPS and other EPS. Fluorescence excitation-emission matrix (FEEM) and apparent quantum yield revealed further detailed differences. Fluorescence quotient analysis highlighted the dominance of TB-EPS, LB-EPS, and S-EPS in the excitation/emission wavelength (Ex/Em) region of Em = 350–400 nm, Em > 400 nm, and low-Stokes shift band (Em − Ex < 25 nm), respectively. Wavelength-wise prediction of the FEEM intensity was achieved through multiple linear regression against the chemical composition and variance partitioning analysis witnessed binary interactions of PS×HA and PS×PN in S-EPS, PN×HA and PS×PN in LB-EPS, and ternary interaction of PS×PN×HA in TB-EPS as well as the wavelength-specific fluorescence responses of these interactions. Further, X-ray photoelectron spectroscopy, infrared spectra, and circular dichroism spectra corroborated the differences in primary, secondary, and tertiary structures across the EPS layers. Ultrahigh-performance liquid chromatography-mass spectrometry detected molecular fragments confirming the multi-component hybridization among PS, PN, and HA. This study demonstrates a spectroscopic approach to sensitively fingerprint the fine structure of EPS, which has the potential for rapid monitoring of EPS and related sludge properties in wastewater treatment systems.

Aggregation and construction mechanisms of microbial extracellular polymeric substances with the presence of different multivalent cations: Molecular dynamic simulation and experimental verification

Interactions between cations and extracellular polymeric substances (EPS) play an important role in the formation of microbial aggregates and have key effects on the physical properties of activated sludge across wastewater and sludge treatment process. Here, a molecular model of EPS cluster in activated sludge was constructed and simulated by molecular dynamics (MD) to probe the structural properties of EPS and the interaction between EPS and prevalent multivalent cations (Ca2+, Mg2+, Al3+). Then the predicted changes in physical properties were validated against the dynamic light scattering, XAD resin fractionation and rheology test. The binding dynamics and interactions mechanisms between multivalent cations and EPS functional groups were further investigated using MD in combination with spectroscopic analysis. Results suggest that biopolymers are originally aggregated by electrostatic and intermolecular interactions forming dynamic clusters with negatively charged surface functional groups, which induced electrostatic repulsion preventing further agglomeration of biopolymer clusters. In the presence of multivalent cations, surface polar functional groups in biopolymers are connected, causing the rearrangement of EPS molecular conformation that forms larger and denser agglomerates. Reduced solvent accessible surface area, enhanced hydrophobicity, and increased binding free energy lead to a strong gel-like network of EPS. Ca2+ and Al3+ predominantly interact with functional groups in polysaccharides, promoting agglomeration of macromolecules. In contrast, Mg2+ and Al3+ disrupted the secondary structure of proteins, exposing hydrophobic interaction sites. Al3+ can better agglomerate biopolymers with its higher positive charge and shorter coordination distance as compared to Ca2+ and Mg2+, but compromised by the effect of hydration. This work offers a novel approach to explore the construction and molecular aggregation of EPS, enriching the theoretical basis for optimization of wastewater and sludge treatment.

Characterising soil extracellular polymeric substances (EPS) by application of spectral-chemometrics and deconstruction of the extraction process

Extracellular polymeric substances (EPS) exuded by microbes are found in diverse habitats, including soil. The quantification and characterization of EPS are essential prerequisites for understanding the ecological functions of extracellular products in soil. However, few studies have conducted in-depth profiling of soil EPS extraction steps and chemical characteristics. Here we examine the C and N contents, biopolymer contents, and optical properties of EPS involving three soil pre-treatment methods (moist soil, moist soil pre-incubated, and air-dried soil pre-incubated) and simultaneously track the compositional changes during the two-step extraction process (extract with CaCl2 in Step 1 and phosphate buffer solution (PBS) with cation exchange resin (CER) in Step 2). The optical properties of soil EPS are investigated using ultraviolet-visible adsorption (UV–Vis), excitation-emission-matrix fluorescence (EEM), and fourier transform infrared (FTIR) spectroscopy coupled with multivariate analytical methods such as parallel factor analysis (PARAFAC), principal component analysis (PCA), and correlation analysis. Results show that Step 2 releases significantly more dissolved organic carbon and biopolymers (polysaccharides, proteins, and uronic acids) from soils. UV–Vis and EEM spectroscopy suggest that the fractions extracted in Step 2 exhibit higher mean aromaticity, molecular weight, and humification degree than those extracted in Step 1. When using the standard method to extract EPS from moist aggregates (Step 2), EPS has a distinct fluorescence profile, rich in tryptophan- and tyrosine-like signals. Reassuringly, the fluorescence-profiles found in pre-extracts (Step 1) are very different - except where i) aggregates have an experimental drying step added, and ii) pure water is used as a pre-extractant. Drying of aggregates is thus problematic, and the use of pure water as an alternative pre-extractant is not advisable. Soil treatments have significant effects on the qualities of the various extracts which are detected by both the FTIR-PCA and EEM-PCA analyses. EEM fluorescence profiles of EPS suggest that both tryptophan-like and tyrosine-like substances are key components of the EPS extracted from all soils regardless of pretreatment. Our findings indicate that chemical characterization of soil EPS combined with spectral-chemometric approaches can be applied to identify and characterise the extracellular responses of soil microbes and thus help reveal the ecological functions of extracellular products in soils.

Enhanced Sludge Dewaterability by Efficient Oxidation of α-Mn2O3/Peroxymonosulfate: Analysis of the Mechanism and Evaluation of Engineering Application

Sludge dewatering reduces huge volumes of sludge, which can help save costs of subsequent sludge treatment and disposal. Extracellular polymeric substances (EPS) in sludge hinder the efficient removal of sludge water due to their strong hydrophilicity and water-holding capacity. In this study, we prepared a new type of α-Mn2O3 by the hydrothermal method and explored the effects of α-Mn2O3/peroxymonosulfate (PMS) on the properties of EPS and sludge dewaterability. Results confirmed that centrifuged weight reduction (CWR) increased from 87.5 to 94.7%, while water content (WC) decreased from 78.1 to 70.4%, under optimized additions of α-Mn2O3 and PMS, which were 0.12 mmol/g VSS and 0.18 mmol/g VSS, respectively. The mechanism investigations indicated that α-Mn2O3/PMS clearly degraded the EPS, destroyed their structure, and weakened their hydrophilicity and water-holding capacity, leading to much reduced intermolecular forces of EPS and the transformation of bound water to free water. Furthermore, we also ascertained the oxidized mechanism of α-Mn2O3/PMS on the degradation of EPS, and the pathway for generating reactive oxygen species (ROS) was also uncovered. Remarkably, SO4•– and •OH were the leading ROS on the degradation of EPS during oxidation with beyond 70% rate of contribution. Importantly, prepared α-Mn2O3 was compared with the standard Mn2O3 to verify the feasibility of applying it in practical engineering applications. This research has great significance for applying persulfate to enhance sludge dewaterability, which is expected to promote the wide application of manganese oxides (MnOx)/PMS in sludge reduction and dewatering.

Enhanced sludge dewaterability by ferrate/ferric chloride: The key role of Fe(IV) on the changes of EPS properties

The complex characteristics of extracellular polymeric substances (EPS) seriously affect the improvement of sludge dewaterability. Ferrate (Fe(VI))/ferric chloride (Fe(III)) was applied through its strong oxidability to effectively enhance sludge dewaterablity by changing the properties of EPS in this study. Results confirmed that water content (WC), specific resistance to filtration (SRF) and capillary suction time (CST) fell from 82.8 %, 9.3 × 1010 s2/g and 35.1 s to 76.1 %, 2.6 × 1010 s2/g and 16.2 s, respectively, when adding 12 mg Fe(VI)/g VSS and 12 mg Fe(III)/g VSS with the dosing interval of 5 min. Investigations of the mechanism strongly suggested that Fe(VI) was successfully catalyzed by Fe(III), promoting the generation of methyl phenyl sulfone (PMSO2) and facilitating the electron transfer, with Fe(IV) having the major role in the oxidation process. Furthermore, sludge water-holding capacity and hydrophilicity waned after oxidation due to the destruction of EPS structure, which promoted the decrement of bound water to enhance the discharge of sludge water, so as to improve the efficiency of dewatering.

Extraction, characterization, and biosurfactant properties of extracellular polymeric substance from textile wastewater activated sludge

Textile wastewater treatment generates sludge that needs to be disposed of safely. The cost of sludge management is 50% of the total treatment cost of the wastewater. To reduce the expense, the sludge can be repurposed as a valuable resource by extracting extracellular polymeric substance (EPS). EPS contains polysaccharides, proteins, and humic substances, which are surface-active substances that act as potential biosurfactants. In this study, we investigated sludges (sludge 1 and sludge 2) from two different textile industries for EPS production. The results showed a maximum EPS yield of 179mg/g-activated sludge from the wastewater from sludge 2. The EPS from textile wastewater activated sludge had a protein/carbohydrate ratio of 0.27-0.56, lower than that of municipal activated sludge. This difference is due to variations in nitrogen/carbon ratio in these wastewaters. Based on the biosurfactant activity test, EPS from both textile wastewaters could lower the water surface tension to around 60mN/m and emulsify olive oil better than Tween 20 and 80. However, only EPS from sludge 2 showed better xylene emulsification than EPS from sludge 1 due to the difference in humic acid content.