Extracellular Polymeric Substances Research Articles

Enhanced activity of mixed-culture electroactive biofilms and sulfamethoxazole removal efficiency by adding N-acyl-homoserine lactones in bio-electrochemical system

ABSTRACT The addition of exogenous quorum sensing signaling molecules significantly enhanced the degradation efficiency of antibiotics, such as chloramphenicol in bio-electrochemical systems (BESs). However, the effects and mechanisms by which AHLs addition in BES facilitated the removal of sulfamethoxazole (SMX) remained inadequately explored. This study systematically compared the electrochemical performance and SMX removal efficiency in BES under two conditions: with and without the addition of N-acyl-homoserine lactones (AHLs) signaling molecules. In comparison to the control group, the AHL-treated group exhibited an increase in maximum output voltage from 340 to 489.67 mV, alongside a notable enhancement in SMX removal efficiency over 120 h ranging from 14.65% to 15.76%. Analyses of the live and dead cells and extracellular polymeric substances (EPS) composition revealed that following AHLs addition, both the ratio of live to dead cells and protein content within EPS increased by 12.66% and 74.37%, respectively. Furthermore, microbial community structure analysis indicated that after AHLs supplementation, there was a marked increase in the abundance of electroactive microorganisms as well as antibiotic-degrading and nitrogen-removing bacteria. Notably, Klebsiella – characterised by its electroactivity along with antibiotic degradation and nitrogen removal capabilities – exhibited a relative abundance reaching 56.84% in AHL, reflecting an increase of 28.31% compared to Blank; additionally, electroactive bacteria Dysgonomonas showed a relative abundance rise of 2.49%. Collectively, these findings suggested that enhancements in SMX removal efficiency upon AHLs addition were primarily driven by improvements in electrochemical performance coupled with alterations in microbial community structure.

Chromium(VI) and Nitrate Removal from Groundwater Using Biochar-Assisted Zero Valent Iron Autotrophic Bioreduction: Enhancing Electron Transfer Efficiency and Reducing EPS Accumulation.

Current strategies primarily utilize heterotrophic or mixotrophic bioreduction for the simultaneous removal of Cr(VI) and NO3- from groundwater. However, given the oligotrophic nature of groundwater, autotrophic bioreduction could be more appropriate, though it remains notably underdeveloped. Here, an autotrophic bioreduction technology utilizing biochar (BC)-assisted zero valent iron (ZVI) is proposed. The pyrolysis temperature of BC was optimized to enhance electron transfer efficiency and reduce extracellular polymeric substances (EPS) accumulation. BC500, with the superior electron transfer capabilities, was the most effective. After an 11-week period, the ZVI+BC500 biotic column still achieved 100% removal efficiency for Cr(VI) and 93.37±0.33% for NO3-, with initial concentrations of 26 mg/L and 50 mg/L, respectively. Its performance significantly surpasses that of ZVI alone, effectively reducing the interference of Cr(VI) on denitrification. The presence of quinone and phenolic compounds in BC500, serving as electron-accepting and electron-donating groups, improves the efficiency of electron transfer between ZVI and microbes. Metagenomic analysis showed an increase in the growth of autotrophic bacteria such as Hydrogenophaga spp. and Rhodanobacter denitrificans, and heterotrophic bacteria including Arenimonas daejeonensis and Chryseobacterium shandongense. The promotion facilitates the expression of genes associated with Cr(VI) reduction (chrR, nemA) and denitrification (narG, nirS). BC500 also enhanced EPS production, which facilitates the adsorption and reduction of Cr(VI), mitigating its inhibitory effects on denitrification. Notably, in the ZVI+BC500 biotic column, the accumulated EPS primarily consists of loosely bound EPS rather than tightly bound EPS, potentially reducing the risk of pore clogging during in-situ groundwater treatment.

Sulfamethoxazole removal in nitrifying membrane aerated biofilms: Physiological responses and antibiotic resistance genes.

Efficient removal of ammonia nitrogen and sulfamethoxazole (SMX) from wastewater has become increasingly critical due to their detrimental effects on aquatic ecosystems and public health. This study aimed to investigate the nitrogen transformation and SMX removal in a membrane aerated biofilm reactor (MABR) under different SMX concentrations (0 ∼ 200 μg·L-1) with a nitrifying membrane bioreactor (MBR) as a control. Results suggested that SMX removal in MABR was better than that of MBR with SMX addition (50 ∼ 200 μg·L-1). Membrane aerated biofilms tended to secrete more extracellular polymeric substances (EPS) and generate less antioxidant enzymes in response to SMX stress when compared with nitrifying sludge in MBR. Metagenomic analysis indicated that distinct succession of microbial community was observed in both systems after SMX addition, and the relative abundance of nitrifying bacteria (Nitrosomonas, Nitrospira, and Nitrobacter) evidently decreased under SMX concentration of 200 μg·L-1. The proliferation of predominant antibiotic resistance gene (ARG) sul2 was suppressed more obviously in MABR than that in MBR. Thus, this study provided extensive insights into the advantages of nitrifying MABR in simultaneous removal of ammonium and antibiotics with less risk of associated ARGs spread.

Application of Central Composite Design for Commercial Laundry Wastewater Treatment by Packed bed Electrocoagulation using sacrificial iron electrodes.

This research paper deals with a novel method utilizing packed bed electrocoagulation (PBEC) comprising of sacrificial iron electrodes and coupled with extracellular polymeric substances (EPS) used as flocculent agents for the treatment of commercial laundry wastewater (LWW). The study employs stainless steel cathodes, graphite anodes, and scrap iron pieces as sacrificial electrodes, ensuring efficient treatment in dynamic batch mode operation with enhanced contact time facilitated by serpentine flow. The initial characteristics of LWW were COD 579 ± 30 mg/L, TSS of 60 ± 10 mg/L, TS of 622 ± 20 mg/L, turbidity of 110 ± 5 NTU, pH of 9 ± 0.5, NPEOs of 570 ±150 μg/L and conductivity of 494 ± 20 mS/cm. The results demonstrate effective removal of turbidity (98 ± 2%), TS (95 ± 3%), COD (89 ± 5%), and NPEOs (53 ± 2%) under optimized current intensity: 2.99A, treatment time: 58.8 minutes and enhanced EPS dose from 5.8 mg/L to 8.0 mg/L. The economic feasibility analysis reveals energy consumption as the primary expenditure, with a treatment cost of 1.20$CAN/m3. This research introduces sustainable treatment for commercial LWW, meeting Quebec's reuse standards, implying reuse potential and responsible wastewater management.

Microbial Life in Playa-Lake Sediments: Adapted Structure, Plastic Function to Extreme Water Activity Variations

Saline shallow lakes in arid and semi-arid regions frequently undergo drying episodes, leading to significant variations in salinity and water availability. Research on the impacts of salinity and drought on the structure and function of biofilms in hypersaline shallow lakes is limited. This study aimed to understand the potential changes of biofilms in playa-lake sediments during the drying process. Sediments were sampled at different depths (surface, subsurface) and hydrological periods (wet, retraction, and dry), which included a decrease in water activity (aw, the availability of water for microbial use) from 0.99 to 0.72. aw reduction caused a greater effect on functional variables compared to structural variables, indicating the high resistance of the studied biofilms to changes in salinity and water availability. Respiration and hydrolytic extracellular enzyme activities exhibited higher values under high aw, while phenol oxidase activity and prokaryote biomass increased at lower aw. This shift occurred at both depths but was more pronounced at the surface, possibly due to the more extreme conditions (up to 0.7 aw). The increased levels of extracellular polymeric substances and carotenoids developed at low aw may help protect microorganisms in high salinity and drought environments. However, these harsh conditions may interfere with the activity of hydrolytic enzymes and their producers, while promoting the growth of resistant prokaryotes and their capacity to obtain C and N sources from recalcitrant compounds. The resilience of biofilms in hypersaline lakes under extreme conditions is given by their resistant biochemichal structure and the adaptability of their microbial functioning.

Linked variations of bioleaching performance, extracellular polymeric substances (EPS) and passivation layer in the uranium bacterial-leaching system

Linked variations of bioleaching performance, extracellular polymeric substances (EPS) and passivation layer in the uranium bacterial-leaching system

Double effects of mitigating cyanobacterial blooms using modified clay technology: regulation and optimization of the microbial community structure

Harmful algal blooms (HABs) are global hazards under global climate change and eutrophication conditions. Modified clay (MC) method is widely used to control HABs in Asian and American coastal waters. However, little research has been conducted on the underlying mechanisms by which MC controls blooms in freshwater environments. Herein, experiments and bioinformatics analyses were conducted for MC-based control of freshwater blooms in a closed water body with an area of approximately 240 m2 in the Fuchun River, China. Results revealed that the dominant bloom species were Microcystis, and an 87.68–97.01% removal efficiency of whole algal biomass was achieved after 3 h of MC treatment. The weaker zeta potentials of Microcystis species and hydrophilic groups such as O-H and P-O-P in the extracellular polymeric substances (EPS) surrounding Microcystis cells made them easier to be flocculated and removed by MC particles, and the relative abundance of Microcystis decreased to 29.12% and that of Cyanobium increased to 40.97%. Therefore, MC changes the cyanobacterial community structure, which is accompanied by the elimination of Microcystis sp. apical dominance and enhanced competition between Cyanobium and Microcystis in the phytoplankton community, increasing cyanobacterial community diversity. Under MC treatment, residual microorganisms, including cyanobacteria, had a high potential for DNA damage repair and were more likely to survive after being subjected to oxidative stress. In the meanwhile, the abundance of genes involved in genetic information processing, signal transduction, and photosynthesis was decreased indicating that the residual microbiome was week in proliferation and light energy harvesting. Therefore, accompanied with the destruction of Microcystis colonies, MC changes the function of cyanobacteria and phycosphere microbiome, further hindering bloom development. These findings illustrate that MC can regulate and optimize the microbial community structure through which MC controls cyanobacterial blooms in ecosystems.

Modulation of irrigation-induced microbial nitrogen‑iron redox to per- and polyfluoroalkyl substances' water-soil interface release in paddy fields: Activation or immobilization?

Understanding the modulation of paddy field irrigation to the migration of per- and polyfluoroalkyl substances (PFAS) at the water-soil interface is pivotal for the management of PFAS pollution in paddy soil and surrounding surface water environments. In flooded soils, soil organic matter was transformed into aromatic protein-like dissolved organic matter (DOM). Meanwhile, Na+, K+, and Mg2+ were translocated into extracellular polymeric substances (EPS) under the catalysis of cation channel enzymes (p < 0.05), provided ion bridging for the binding of DOM and PFAS, and accelerated the accumulation of C4–C9 PFAS in overlying water (41.79–99.14 %). Short-chain PFAS's accumulation in soil solution of drought soils was stimulated by microorganisms secreting soluble microbial by-product-like DOM (53.15–97.96 %). Furthermore, PFAS's distribution in flood soils was dominated by bacterial denitrification and iron-reduction, whereas iron-oxidation and ammoxidation controlled that in drought soils. The transformation of organic carbon including CO and COC caused by irrigation-induced redox modulated PFAS cross-media translocation. Iron‑nitrogen redox in flooded paddy soils immobilized the PFAS's migration into overlying water (p < 0.05). Our findings have profound implications for PFAS's pollution control, surface water environmental protection, and rice production security in paddy fields.

In vitro antibacterial activity of photoactivated flavonoid glycosides against Acinetobacter baumannii

Acinetobacter baumannii’s extensive antibiotic resistance makes its infections difficult to treat, so effective strategies to fight this bacterium are urgently needed. This study aims to evaluate the effectiveness of antimicrobial photodynamic therapy (aPDT) mediated by Rutin-Gal(III) complex and Quercetin against A. baumannii. Absorbance spectra, fluorescence spectra, and minimum inhibitory concentration (MIC) of Rutin-Gal(III) complex and Quercetin were determined. The intracellular reactive oxygen species (ROS), extracellular polymeric substances (EPS), cell membrane permeability, expression of ompA and blaOXA−23, anti-biofilm activity, and anti-metabolic activity of Rutin-Gal(III) complex- and Quercetin-mediated aPDT were measured. Rutin-Gal(III) complex and Quercetin revealed absorption peaks in the visible spectra. Quercetin and Rutin-Gal(III) complex displayed fluorescence peaks at 524 nm and 540 nm, respectively. MIC values for the Rutin-Gal(III) complex and Quercetin were 64 µg/mL and 256 µg/mL, respectively. Quercetin- and Rutin-Gal(III) complex-mediated aPDT significantly reduced the colony forming units/mL (58.4% and 67.5%), EPS synthesis (47.4% and 56.5%), metabolic activity (30.5% and 36.3%), ompA (5.5- and 10.5-fold), and blaOXA−23 (4.1-fold and 7.8-fold) genes expression (respectively; all P < 0.05). Quercetin- and Rutin-Gal(III) complex-mediated aPDT enhanced notable biofilm degradation (36.2% and 40.6%), ROS production (2.55- and 2.90-folds), and membrane permeability (10.8– and 9.6-folds) (respectively; all P < 0.05). The findings indicate that Rutin-Gal(III) complex- and Quercetin-mediated aPDT exhibits antibacterial properties and could serve as a valuable adjunctive strategy to conventional antibiotic treatments for A. baumannii infections. One limitation of this study is that it was conducted solely on the standard strain; testing on clinical isolates would allow for more reliable interpretation of the results.

Different nitrogen conditions regulating extracellular polymeric substances and erosion resistance of sewer sediment: Mechanism of microbial metabolism and molecular response

Nitrogen biotransformation plays a vital role in the metabolism of microbial communities in sewers. Extracellular polymeric substances (EPS) secreted by microbial communities can form gel-like sewer sediments, causing clogging of the sewer. However, knowledge on the effects of varying nitrogen conditions on the erosion resistance of sewer sediments and EPS produced by sewer microorganisms is limited. In this study, two typical organic/inorganic nitrogen ratios of sewage were reproduced in simulated sewer reactors, i.e., 3/7 (R1 group) and 7/3 (R2 group). Higher organic nitrogen (ON) concentrations were found to increase the critical erosion shear stress by 26.43%; this was ascribed to increased particle diameter, weakened electrostatic repulsion of sediments and stimulated EPS secretion in the R2 group. The protein and polysaccharide contents of the R2 group were 48.84% and 34.25% higher than those of the R1 group, respectively, which was supported by increased gene abundances for aromatic amino acid synthesis, general secretory pathways of protein, and synthesis of precursors and polysaccharides. Tightly-bound EPS in R2 group exhibited increased contents of hydrophobic protein secondary structures and intermolecular hydrogen bonds, thereby promoting the formation of gel-like sediment structures with enhanced erosion resistance. However, the microbial diversity and the abundance of key genes involved in EPS generation and secretion (e.g., tyrB, yajC, secB, gumF, and gumH) obviously decreased in the R1 group. Moreover, high ON concentrations increased microbial diversity and enhanced microbial glycolysis, tricarboxylic acid cycle and ammonium assimilation. This study reveals the formation mechanisms of EPS in sewer sediments under different nitrogen conditions and their effects on sediment erosion resistance, which contributed to improved sewer system operation and sewer sediment control.

Asymmetric Flow Field-Flow Fractionation for Comprehensive Characterization of Hetero-aggregates made of nano-Silver and Extracellular Polymeric Substances

The present study explores the capability of asymmetrical flow field-flow fractionation (AF4) coupled online with diode array (DAD), fluorescence detectors (FLD), multi-angle light scattering (MALS) and dynamic light scattering (DLS) to characterize silver nanoparticles (nAg) hetero-aggregates formed with diatoms derived extracellular polymeric substances (EPS). The content of EPS varied from 10.5 to 105 mgC L-1 and nAg were dispersed at 4 mg L-1 in a freshwater medium. Good recoveries (∼ 76.9 ± 8.4%) of nAg-EPS were obtained from AF4-DAD signals, but an anomalous elution was observed as EPS concentration increased: AF4 retention times decreased despite average gyration radii measured by MALS for nAg-EPS increased (from 16 nm to 24 nm), which suggests a change in the aggregation state, as evaluated by UV-Vis scans obtained from DAD. A regular Brownian relaxation of nAg-EPS was proven for each EPS concentration using these 2 detectors. The comparison of on-line and batch DLS measurements validated in addition, that no (dis)aggregation occurs upon injections. After a thorough comparison with classical AF4 using standards, the frit-inlet-AF4 was used. Slightly higher recovery (79.6±4.6 %) was obtained but similar deviation of nAg-EPS elution occurred, excluding the implication of membrane differential fouling of nAg-EPS /conditioning effects of EPS. The investigation of physico-chemical parameters controlling the Brownian relaxation of nAg-EPS suggests the influence of nAg-EPS structure and EPS loading. This study demonstrates the suitable use of AF4 coupled to multiple detectors to probe-out eco-corona formation and characterize polydisperse systems containing NPs, EPS and their hetero-aggregates in freshwaters, even under a non-ideal size-fractionation scenario.

Molecular mechanisms of iron nanominerals formation in fungal extracellular polymeric substances (EPS) layers during fungus-mineral interactions

Extracellular polymeric substances (EPS), which envelop on fungal hyphae surface, interact strongly with minerals and play a crucial role in the formation of nanoscale minerals during biomineralization in nature environments. However, it remains poorly understood about the molecular mechanisms of nanominerals (i.e., iron nanominerals) formation in fungal EPS halos during fungus-mineral interactions. This process is vital because fungi typically grow attached to various mineral surfaces in nature. According to the changes of thickness of the fungal cell and EPS layers during the Trichoderma guizhouense NJAU 4742 and hematite cultivation experiments, we found that fungal biomineralization could trigger the formation of EPS layers. Fe-dominated nanominerals, aromatic C (283-286.1 eV), alkyl C (287.6-288.3 eV), and carboxylic C (288.4-289.1 eV) were the dominant chemical groups on the EPS layers, as determined by nanoscale secondary ion mass spectrometry (NanoSIMS), high-resolution transmission electron microscope (HRTEM), and carbon 1s near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. Further, evidence from Fe K-edge X-ray absorption near-edge structure (XANES) and X-ray photoelectron spectroscopy (XPS) spectra indicated that oxygen vacancy (OV) was formed on the Fe-dominated nanomineral surface during fungus-mineral interactions, which played an important role in catalyzing H2O2 decomposition and HO∗ production. Taken together, the intrinsic peroxidase-like activity by reactive oxygen species (ROS) could modulate the Fe-dominated nanominerals formation in EPS layers to newly form a physical barrier between the cell and the external environments around hyphae, providing novel insights into the effects of ROS-mediated fungal-mineral interactions on fungal nutrient recycling, attenuation of contaminants, and biological control in nature environments.

Mechanistic insight of fungal–microalgal pellets in photobioreactor for heavy-metal wastewater bioremediation

The high cost of harvesting microalgae limits their industrial application. Fungal–microalgal pellets can efficiently harvest microalgae and enhance heavy-metal adsorption. However, the molecular response mechanism of fungal–microalgal pellets under heavy-metal stress remains unclear. Fungal–microalgal pellets in a photobioreactor were used as a research object, and a 98 % harvesting efficiency could be achieved with adding exogenous carbon and nitrogen at pH 5.0–6.0 for 12 h of co-culture. Humic acid- and tryptophan-rich proteins in extracellular polymeric substances (EPS) participate in Cd(II) complexation. The Cd(II) response in fungal-microalgal pellets involves amino acids, glucose, lipids, energy metabolism, and antioxidant systems. The turning point was at 48 h. Proline, histidine, and glutamine synthesis and the adenosine-triphosphate (ATP) binding cassette (ABC) transport pathway play important roles in resistance to Cd(II) biotoxicity. This study provides a reference for the large-scale cultivation of fungal-microalgal symbiotic pellets and the practical application for industrial heavy-metal wastewater.

Fe (II)/Fe (III) regulated adaptive biofilm responses and microbial metabolic mechanisms for enhanced cycloalkane biodegradation

Oxidation of organic contaminants by iron-cycling microorganisms is an effective remediation strategy for contaminated environments. However, studies on the removal of cycloalkane using this method have been limited, and little is known about how microbes adapt to iron concentrations and how the latter stimulates contaminant degradation. Here, we investigated the biodegradation of cyclohexane (CyH) in three sequencing batch bioreactors (SBRs) with different iron concentrations (SBRs are named: Low 2.5 μM, Suit 7.5 μM, High 75 μM). The Suit reactor showed a more efficient CyH removal performance (average 98.61 ± 0.62 %) than the Low reactor (average 55.75 ± 3.38 %), which was associated with more extracellular polymeric substances (EPS) release and improved biofilm structure. The High reactor exhibited a gradual adaptation process due to the apparent accumulation of reactive oxygen species (ROS) under iron stress, with an average removal efficiency of (86.83 ± 18.81 %). However, the High reactor had a higher microbial activity (1.08-fold increase in ATPase activity) and electron transport system activity (1.18-fold increase) to facilitate direct electron transfer in the presence of insoluble iron compared to the Suit one, largely due to the dominant genus Novosphingobium. Metagenomics and metatranscriptomics analyses revealed lactone (a key intermediate) formation as a potential degradation pathway across three SBRs in our study under iron regulation. Notably, there were differences in the key functional genes expressed under different iron concentrations: genes related to anti-oxidative stress and iron-driven pathways, biofilm regulation-related pathways, and encoding protein complexes III and IV were found in the High, Suit, and Low reactors, respectively. This study enhances understanding of microbiota adaptation mechanisms to iron-disturbed conditions and provides a new insight into iron-cycling mediated biofilm formation and inhibition.

Methylisothiazolinone modulates community assembly and improves syntrophic cooperation via adaptive evolution during sludge anaerobic digestion

Various antimicrobials could pose multifaced threats to anaerobic digestion (AD) of waste-activated sludge (WAS), yet it is still unclear how antimicrobials would affect the metabolic activity and assembly process of anaerobic microbiome. In this study, a typical antimicrobial, methylisothiazolinone (MIT), was introduced in AD and induced an initial lag effect on methane production that was eventually recovered. Although MIT disintegrated WAS to promote the release of bioavailable substrates from extracellular polymeric substances (EPS), it also caused adverse stress to the microbiome. The initial microbial metabolic activities and syntrophic relationships associated with methane generation were distinctly inhibited. Because the self-adaptive systems of two-component systems (e.g., ddpF, and ddpD) and quorum sensing (e.g., cheR, and cydB) were activated to restore the syntrophic interaction among functional anaerobes, metabolic activities were gradually recovered for methane generation. Ultimately, the methane-generation species (e.g., Methanobacterium, and Methanomassiliicoccus) were driven as core species by deterministic processes, while non-functional species (e.g., Nitrospirota) were marginalized by stochastic processes under MIT stress. Overall, this finding indicated the intrinsic drive of evolutionary adaptation, unraveled the community assembly process at phylogenetic level under antimicrobial stress, and gave direction on the assessment and mitigation of external contaminant-related ecological risks in WAS treatment.

The waste recycling approach for enhancing wastewater sludge dewaterability by using iron-mud (IM)/sawdust derived carbon composite

The dewaterability of wastewater sludge by the solid waste of iron-mud (IM)/carbon (IMS) composite prepared via the in-situ carbothermal reduction method was systematically studied in this paper. It investigated the effects of different IMS materials, IM dosages and stirring speeds on sludge dewaterability, including water content (WC), capillary suction time (CST), extracellular polymeric substances (EPS) contents and particle size. The results of dewatering tests demonstrated that IMS materials significantly enhanced sludge dewaterability, resulting in a reduction of 39.85% in CST and 13.26% reduction in WC in the dewatered sludge under optimum condition (IMS-3 dosage of 8% dry solids; stirring speed of 250 r/min for 30 minutes). Electron paramagnetic resonancec (EPR) and scavenging experiments were conducted to better understand the dewatering process mechanism. This results indicated that both hydroxyl radicals (•OH) and superoxide radicals (•O2−) collaborate during the dewatering process. Furthermore, analysis were performed on the particle size of sludge flocs and scanning electron microscopy (SEM) imaging of sludge morphology to reveal the synergistic effects of IMS treatment. A two-step mechanism involving oxidation and Fe(III)-based re-flocculation maybe explain the synergistic effect of IMS treatment. This novel recycle-based IMS composite approach offers a new management strategy for industrial solid wastes while enhancing the sludge dewatering efficiency.

Mechanistic insights into melanoidins-induced hydrophilicity of thermal hydrolyzed sludge and its impact on dewaterability

Although thermal hydrolysis pretreatment enhances disposal efficiency of sludge, it inevitably leads to melanoidins formation, which will negatively impact the subsequent wastewater treatment processes. However, their effect on the dewaterability of thermal hydrolyzed sludge (THS) remains poorly understood. This study aimed to uncover the underlying mechanisms of how melanoidins affecting dewaterability of THS. Using resin-adsorption method to reduce melanoidins content by 50% led to 21% and 6% decreases in capillary suction time and specific resistance to filtration, respectively, and a 14% increase in sludge cake solid content. Conversely, accumulating melanoidins to 200% worsened THS dewaterability, altering surface morphology and reducing floc stability, which increased the content of bound water by 9%. Additionally, a higher melanoidins level increased the hydrophilic components in extracellular polymeric substances while reducing hydrophobic sites and structures. These findings indicate that melanoidins impair THS dewaterability by altering flocs spatial properties and increasing hydrophilic structures and components.

A three-stage oxidation method improves sludge dewaterability by achieving sustained oxidation and phased enhanced coagulation: Ingeniously using H2O2 as a “converter”

Sludge reduction is essential for mitigating the environmental hazards associated with sludge. The use of ferric chloride (Fe(III)) catalyzed ferrate (Fe(VI)) can significantly enhance sludge dewaterability by increasing the Fe(VI) oxidation rate and maintaining in-situ enhanced coagulation. However, its weak oxidation ability at the sludge’s original pH limits its practical application. To address this, hydrogen peroxide (H2O2) strengthened Fe(VI)/Fe(III) was employed to efficiently improve sludge dewaterability without pH adjustment, thereby enhancing the environmental utilization capacity of sludge. Compared to raw sludge, the treatment of Fe(VI)/Fe(III)–H2O2 resulted in approximately the 95% reduction in specific resistance to filtration (SRF) and increased the bioavailable phosphorus (P) content in dewatered sludge. During the oxidation process, highly reactive species such as tetravalent iron (Fe(IV)) and hydroxyl radicals (OH) were generated, facilitating the release of tightly bound water in extracellular polymeric substances (EPS). Importantly, the oxidation process was divided into three stages (persistent moderate oxidation — fast strong oxidation — sustained weak oxidation) based on the predominant reactive species (Fe(IV) or OH). This division promoted more robust and more durable oxidation processes. Phased enhanced coagulation occurred during the oxidation process. The gradual increase in Fe(III) content led to the re-flocculation of damaged EPS, enlarging the size of sludge drainage pores/channels and improving water discharge efficiency. Additionally, the costs and carbon emissions of chemicals for the Fe(VI)/Fe(III)–H2O2 process were 18% and 52% lower than those of the traditional Fenton method. This study not only achieves the goals of sludge reduction and resource collection but also provides insights into selecting sludge conditioning methods that meet pollution reduction and carbon emission reduction requirements.

Cation exchange resin coupled with bacterial pretreatment to promote waste activated sludge reduction: Performance and mechanism

Due to the rapid advancement of industrialization and urbanization, there has been a significant rise in the generation of industrial wastewater and domestic wastewater, which results in the rapid increase of waste activated sludge (WAS). However, the complex structure and slow hydrolysis of sludge limit aerobic digestion of WAS. This study evaluated the effect of lysozyme-secreting strain Proteus mirabilis sp. SJ25 and the new isolation of surfactant-secreting strain Enterobacter cloacae sp. WH11 on the promotion of sludge hydrolysis, and introduced cation exchange resin (CER) to enhance the promotion effect. The reduction efficiencies of suspended solids (SS) and volatile suspended solids (VSS) enhanced by 25.0 and 24.9 %, respectively, and the soluble chemical oxygen demand (SCOD) release was increased by 2370.27 mg/L when the inoculum of strain SJ25 and strain WH11 were 3 % and 6 %, and the dosage of CER was 2.0 g/g SS against the control. The fluorescence region integral (FRI) results showed a significant quantity of dissolved organic matter (DOM) was let out, and the biodegradability of the sludge was improved. The alterations in several physicochemical characteristics of the sludge also suggested that the extracellular polymeric substances (EPS) were disrupted and an enormous quantity of sludge cells were lysed. In addition, functional gene prediction from the Kyoto Encyclopedia of Genes and Genomes (KEGG) database indicated that CER coupled with bacterial pretreatment enhanced microbial metabolic capacity. This work suggests a novel pathway for the development of novel pretreatment methods to promote sludge hydrolysis.

Biomimetic surface design enables a resilient solid electrolyte interphase for high-performance anodes

Surface coating presents an effective methodology for mitigating the detrimental effects of large volume changes inherent to high-capacity anode materials (e.g. Si, SiOx). However, designs often prioritize the protection of internal active particles, inadvertently neglecting the intricate interplay between the coating layer and the external electrolyte which exhibits profound influences on the solid electrolyte interphases (SEIs). Inspired by the extracellular polymeric substance (EPS) protecting biological cells (e.g. yeast) from predation and chemical damages, we prepare a conducting polymer-based EPS system (CP-EPS) on a surface bilayer comprising soft carbon membranes and compact graphene walls, constructing the biomimetic cellular structure. The CP-EPS chemically interacts with electrolyte catalyzing the symbiosis of integrated LiF-enriched SEIs and physically provide sufficient resilience for SEIs. This resilient SEIs offer excellent reaction kinetics and roughness which protects the structural integrity of the particle and itself from pulverization and excessive SEI thickening. The prepared SiOx anode delivers a superior average coulombic efficiency of 99.4% over 200 cycles at 0.5C and a high reversible capacity of 730 mAh g-1 after 300 cycles at 2C.