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1.
Huan Jing Ke Xue ; 42(4): 1946-1955, 2021 Apr 08.
Artículo en Chino | MEDLINE | ID: mdl-33742830

RESUMEN

The effects of polyether sulfone (PES) microplastics and 2,4-dichlorophenol (2,4-DCP) on the loosely-bound extracellular polymeric substances (LB-EPS) and tightly-bound EPS (TB-EPS) of anaerobic granular sludge were investigated. In addition, high-throughput sequencing technology was used to analyze the changes in the microbial community and gene functions in the anaerobic granular sludge. The results revealed that the chemical oxygen demand (COD) removal rates of the 2,4-DCP and PES+2,4-DCP experimental groups were 35% and 37%, which were 57% and 55% lower than that of the blank control group, while the COD removal rates of the PES experimental group remained around 90%. After the addition of the PES microplastics and 2,4-DCP, the protein and polysaccharide contents in the LB-EPS decreased compared with the control group, and the polysaccharide content in TB-EPS increased the least. In presence of the PES microplastics and 2,4-DCP, the activity of coenzyme F420 was inhibited. Through high-throughput sequencing, the microbial richness and diversity of the anaerobic granular sludge in the experimental group were reduced with the addition of the PES microplastics or 2,4-DCP. In the control group and the experimental group, the dominant bacteria at the phylum level were Proteobacteria (13.45%-44.47%), Firmicutes (6.86%-21.67%), and Actinobacteria (3.16%-18.11%). The abundance of ß-Proteobacteria in the PES+2,4-DCP experimental group was reduced by 15.28%, while the abundance of γ-Proteobacteria increased by 28.44% compared with the control group. Based on the phylogenetic investigation of the communities using the reconstruction of unobserved states (PICRUSt) analysis, it was found that in the experimental group with the PES microplastics or 2,4-DCP, the genes related to the sludge energy metabolism function were 0.25%-0.72% more than the control group; therefore, the abundance of genes related to the transport function group decreased significantly.


Asunto(s)
Microbiota , Aguas del Alcantarillado , Anaerobiosis , Reactores Biológicos , Matriz Extracelular de Sustancias Poliméricas , Filogenia , Plásticos , Polímeros , Sulfonas , Eliminación de Residuos Líquidos
2.
Bioresour Technol ; 329: 124920, 2021 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-33677423

RESUMEN

Hydroxylamine (NH2OH), one of the most important intermediates of anammox was employed to test the recovery performance because of its stimulation to anammox bacteria. Batch test indicated simultaneous addition of 1.83 ~ 9.17 mg N /L NH2OH relieved Cr(VI) inhibition because of extracellular reduction to Cr(III). The recovery efficiency (RE) was over 166%, with the effluent Cr(VI) and Cr(III) below 0.25 and 0.12 mg/L, respectively. Anammox activity after Cr(VI) inhibition was effectively recovered by 8 mg N/L NH2OH with RE at 218%. The long-term operation showed 1 ~ 2 mg N/L NH2OH accelerated the recover speed of nitrogen removal rate with 2.84 folds, as well as improving NH4+ conversion ratio and reducing NO3- production. After 55 days recovery, extracellular polymeric substance concentration, anammox activity and heme content recovered better with NH2OH addition. This study will provide the theoretical basis for rapid recovery of anammox activity by NH2OH when suffering Cr(VI) inhibition.


Asunto(s)
Matriz Extracelular de Sustancias Poliméricas , Nitrógeno , Reactores Biológicos , Cromo , Hidroxilamina , Hidroxilaminas , Oxidación-Reducción
3.
Water Res ; 195: 116959, 2021 May 01.
Artículo en Inglés | MEDLINE | ID: mdl-33676179

RESUMEN

The properties of biofilm EPS are determined by the multiple interactions between its constituents and the surrounding environment. Because of the high complexity of biofilm EPS, its constituents' characterisation is still far from thorough, and identification of these interactions cannot be done yet. Therefore, we use gels of bacterial alginate-like exopolysaccharides (ALEs) as a model component for biofilm EPS in this work. These gels have been examined for their cohesive properties as a function of CaCl2 and KCl concentration. Hereto, ALE gel layers were formed on membranes by dead-end filtration of ALE solutions. Accumulation of the cations Ca2+ and K+ in the gels could be well predicted from a Donnan equilibrium model based on the fixed negative charges in the ALE. This suggests that there is no specific binding of Ca2+ to the ALE and that on the time scale of the experiments, the Ca2+ ions can distribute freely over the gel and the surrounding solution. The concentration of fixed negative charges in the ALE was estimated around 1 mmol/g VSS (volatile suspended solids, organic mass) from the Donnan equilibrium. Moreover, an accumulation of H+ was predicted. Gels with more CaCl2 in the supernatant were more compact and bore a higher osmotic pressure than those with less CaCl2, revealing the role of Ca2+ ions in the network crosslinking. It is hypothesised that this mechanism later transitions into a rearrangement of the ALE molecules, which eventually leads to a fibrous network structure with large voids.


Asunto(s)
Alginatos , Matriz Extracelular de Sustancias Poliméricas , Biopelículas , Geles , Iones
4.
Bioresour Technol ; 330: 125000, 2021 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-33773266

RESUMEN

Anaerobic digestion (AD) of waste activated sludge (WAS) is widely used for stabilisation, mass reduction and resource recovery. However, AD performance is often hampered by the poor digestibility and slow degradation rate for WAS. A series of bench-scale tests was conducted using innovative electrochemical pretreatment (EPT) method to enhance the destruction of the extracellular polymeric substances (EPS) matrix and anaerobic digestibility. The results showed that the EPS matrix destruction was enhanced by 15-30% after EPT for 0.5 h at voltages of 8-15 V. The highest improvement in hydrolysis rate and overall digestibility was achieved at EPT of 15 V for 1.5 h, which was determined as 59% (from 0.27 to 0.43 d-1) and 28% (from 105 to 134 mL CH4/g VSSadded) respectively, compared with the WAS treatment without EPT. The economic analysis showed 1 h, 12 V EPT was more economically feasible.


Asunto(s)
Matriz Extracelular de Sustancias Poliméricas , Aguas del Alcantarillado , Anaerobiosis , Hidrólisis , Eliminación de Residuos Líquidos
5.
Chemosphere ; 271: 129879, 2021 May.
Artículo en Inglés | MEDLINE | ID: mdl-33736214

RESUMEN

Membrane bioreactors (MBRs) are considered a promising tool for resource recovery in wastewater treatment. Nevertheless, membrane fouling is an inevitable phenomenon that deteriorates the MBR performance. Although many studies have attempted to elucidate the effect of sludge characteristics on MBR fouling, they posed certain limitations. Most of the previous studies focused on the initial sludge or employ the results of short-term batch tests without long-term transmembrane pressure (TMP) profiles in the interpretation of fouling behaviors. This study was conducted considering these limitations to determine the sludge characteristics most closely related to long-term TMP profiles and to identify their role in fouling behaviors. In long-term TMP profiles, critical time (tc; time to TMP jump) and fouling rates (the increase in the TMP slope) were used as fouling indexes, which were used to correlate with average values of sludge characteristics before and after experiments. According to the results, the concentration of the total soluble microbial product (SMP) and extracted extracellular polymeric substance (eEPS) in sludge significantly increased by 1.9 times and up to 28 times after experiment. The increase in the SMP and eEPS caused early TMP jumps and resulted in low-fouling rates by increasing particle size. Owing to the increase in the SMP and eEPS concentration, the origin of fouling potential was shifted from suspended solids to colloids and soluble materials. Fouling resistance caused by soluble material increased by up to 11.38 times.


Asunto(s)
Aguas del Alcantarillado , Purificación del Agua , Reactores Biológicos , Matriz Extracelular de Sustancias Poliméricas , Membranas Artificiales
6.
Int J Nanomedicine ; 16: 1929-1942, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-33727807

RESUMEN

Background: Staphylococcus aureus biofilms pose a unique challenge in healthcare due to their tolerance to a wide range of antimicrobial agents. The high cost and lengthy timeline to develop novel therapeutic agents have pushed researchers to investigate the use of nanomaterials to deliver antibiofilm agents and target biofilm infections more efficiently. Previous studies have concentrated on improving the efficacy of antibiotics by deploying nanoparticles as nanocarriers. However, the dispersal of the extracellular polymeric substance (EPS) matrix in biofilm-associated infections is also critical to the development of novel nanoparticle-based therapies. Methods: This study evaluated the efficacy of enzyme-functionalized mesoporous silica nanoparticles (MSNs) against methicillin-resistant S. aureus (MRSA) and methicillin-sensitive S. aureus (MSSA) biofilms. MSNs were functionalized with the enzyme lysostaphin, which causes cell lysis of S. aureus bacteria. This was combined with two other enzyme functionalized MSNs, serrapeptase and DNase I which will degrade protein and eDNA in the EPS matrix, to enhance eradication of the biofilm. Cell viability after treatment with enzyme-functionalized MSNs was assessed using a MTT assay and CLSM, while crystal violet staining was used to assess EPS removal. Results: The efficacy of all three enzymes against S. aureus cells and biofilms was significantly improved when they were immobilized onto MSNs. Treatment efficacy was further enhanced when the three enzymes were used in combination against both MRSA and MSSA. Regardless of biofilm maturity (24 or 48 h), near-complete dispersal and killing of MRSA biofilms were observed after treatment with the enzyme-functionalized MSNs. Disruption of mature MSSA biofilms with a polysaccharide EPS was less efficient, but cell viability was significantly reduced. Conclusion: The combination of these three enzymes and their functionalization onto nanoparticles might extend the therapeutic options for the treatment of S. aureus infections, particularly those with a biofilm component.


Asunto(s)
Biopelículas/crecimiento & desarrollo , Enzimas/metabolismo , Nanopartículas/química , Dióxido de Silicio/química , Staphylococcus aureus/fisiología , Biomasa , Supervivencia Celular , Matriz Extracelular de Sustancias Poliméricas/metabolismo , Humanos , Staphylococcus aureus Resistente a Meticilina/fisiología , Pruebas de Sensibilidad Microbiana , Nanopartículas/ultraestructura , Porosidad
7.
Sci Total Environ ; 771: 145372, 2021 Jun 01.
Artículo en Inglés | MEDLINE | ID: mdl-33548719

RESUMEN

Biological predation has a significant effect on biofouling layers in gravity-driven membrane (GDM) filtration systems. However, the detailed process of predatory activities is still not well known. This study explored the effects of predator movement patterns on the biofouling layer at different temperatures and the factors affecting the stable flux level. The results indicated that Demospongiae, Spirotrichea and Saccharomycetes were the main species, with the body contracting or rotating in one position at 5 °C, and Litostomatea accounted for 55.1% at 10 °C. The weak agility of these species resulted in a less porous biofouling layer with a high extracellular polymeric substance (EPS) concentration, which was responsible for the low permeate flux and the time to reach flux stability. Bdelloidea was dominant at 20 and 30 °C, and the more heterogeneous biofouling layer with a lower EPS concentration was related to their intense creeping and swimming movements and their ability to create current in the water. The grazing of spongy flocs by predators affected the GDM system performance, and a high stable flux was obtained with large and loose flocs. In addition, the diversity of the eukaryotic community decreased after the flux stabilized due to the particular predominance of Bdelloidea at high temperatures, corresponding to a high stable flux. Pollutant removal was less affected by eukaryotes, and decreased ammonia nitrogen removal rates were related to the lower activity of nitrifying bacteria. Moreover, the reliable linear correlation between the temperature and the stable flux implied that the stable flux could be well predicted in the GDM system. The findings are beneficial for developing new strategies for regulating flocs and the biofouling layer to improve the performance of GDM systems.


Asunto(s)
Incrustaciones Biológicas , Purificación del Agua , Matriz Extracelular de Sustancias Poliméricas , Filtración , Membranas Artificiales , Agua
8.
Chemosphere ; 271: 129813, 2021 May.
Artículo en Inglés | MEDLINE | ID: mdl-33556632

RESUMEN

Dynamic membrane bioreactors mainly rely on the in-situ formed biofilms on support materials to reject fine particles in water. The development of irremovable biofilms on support materials can decrease the cleaning efficiency when removing the unwanted biofilms with low permeability by water flushing. In the present study, the initial formed biofilms on support materials at 5-day solids retention time (SRT) were removable by water flushing. After repeated cleaning with off-line water flushing during operation, however, irremovable biofilms were developed gradually inside the mesh pores and thus, rapid rising in transmembrane pressure occurred in every one to three days. At 20-day SRT, the biofilms formed on support materials with the same operation time were still removable. Therefore, both low SRT and repeated water flushing promoted the formation of irremovable biofilms on support materials. Further study found that the composition and microbial community between the irremovable and removable biofilms were significantly different, which differentiated the biofilm adhesion and removability. The irremovable biofilms had a greater faction of proteins (49.0%) and ß-d-glucopyranose polysaccharides (17.8%) in extracellular polymeric substance (EPS), while the removable biofilms had a greater fraction of α-d-glucopyranose polysaccharides. After repeated cleaning with off-line water flushing during operation, Nitrospiraceae was selectively enriched in the irremovable biofilms at a relative abundance of 39.1%, which could have resulted in the particular EPS matrix that strengthened the biofilm adhesion.


Asunto(s)
Microbiota , Agua , Biopelículas , Reactores Biológicos , Matriz Extracelular de Sustancias Poliméricas , Membranas Artificiales
9.
J Environ Manage ; 284: 112103, 2021 Apr 15.
Artículo en Inglés | MEDLINE | ID: mdl-33567355

RESUMEN

Extracellular polymeric substances (EPS) were extracted from aerobic granule sludge (AGS) using 8 M aqueous urea solution. It seems that the knowledge of these multi-component systems properties and the ability to predict their phase behavior is necessary for the extraction units design as well as process optimization. In this regard, water activity using the Dynamic Vapor Sorption (DVS) method, viscosity and shear stress, pH, and conductivity were measured at 283.15-343.15 K and 0.0108 to 0.0375 wt fraction of EPS. The salting effects in ternary systems assessed and the results were interpreted in terms of solute-water and solute-solute interactions. It was found these systems were not semi-ideal and except at 283.15 K, had a positive deviation from ideal solution behavior and only at this temperature as the optimum extraction temperature, the salting-in effect was observed for each concentration of EPS. The ternary solutions behave like pseudo-plastic fluids while aqueous urea solution is a Newtonian fluid. Increasing the temperature causes a decrease and increase in pH and conductivity of ternary solutions, respectively and the presence of EPS increases those of 8 M urea solution significantly.


Asunto(s)
Matriz Extracelular de Sustancias Poliméricas , Urea , Aguas del Alcantarillado , Temperatura , Agua
10.
Water Res ; 193: 116861, 2021 Apr 01.
Artículo en Inglés | MEDLINE | ID: mdl-33548693

RESUMEN

The potential of the formation of anammox-hydroxyapatite (HAP) granule composites as a cost-effective approach to removing nitrogen and phosphorus in the treatment of wastewater has been recently reported. Before these annamox granules, which consist of an anammox biofilm layer and an HAP crystallizing layer, can be used in applications, the formation mechanism of hydroxyapatite (HAP) encapsulation in the granules needs to be further studied. In this work, the role of extracellular polymeric substance (EPS) secreted by microorganisms and HAP core in Ca and P removal in anammox-HAP coupled granular sludge was investigated. According to the Lamer model, it is possible that the nucleation time of the granules becomes shorter as the crystal seeds. The enhanced buffering capacity of the granules was 0.08 mmol-H+ SS-g-1 with the pH kept above 6.5 for a comfortable environment for anammox. The results of this study show that ion competition and exchange, mainly between cations of Ca2+ and Mg2+ and between anions of PO43- and CO32-, affects the precipitation process. The results of this study indicate that the addition of granule crystal seeds can be used as a strategy to hasten the anammox process, and therefore accelerate the overall process.


Asunto(s)
Reactores Biológicos , Aguas del Alcantarillado , Durapatita , Matriz Extracelular de Sustancias Poliméricas , Nitrógeno , Oxidación-Reducción
11.
Environ Pollut ; 275: 116035, 2021 Apr 15.
Artículo en Inglés | MEDLINE | ID: mdl-33581631

RESUMEN

Extracellular Polymeric Substances (EPS) influenced Poly Cyclic Aromatic Hydrocarbons (PAHs) degrading Klebsiella pneumoniae was isolated from the marine environment. To increase the EPS production by Klebsiella pneumoniae, several physicochemical parameters were tweaked such as different carbon sources (arabinose, glucose, glycerol, lactose, lactic acid, mannitol, sodium acetate, starch, and sucrose at 20 g/L), nitrogen sources (ammonium chloride, ammonium sulphate, glycine, potassium nitrate, protease peptone and urea at 2 g/L), different pH, carbon/nitrogen ratio, temperature, and salt concentration were examined. Maximum EPS growth and biodegradation of Anthracene (74.31%), Acenaphthene (67.28%), Fluorene (62.48%), Naphthalene (57.84%), and mixed PAHs (55.85%) were obtained using optimized conditions such as glucose (10 g/L) as carbon source, potassium nitrate (2 g/L) as the nitrogen source at pH 8, growth temperature of 37 °C, 3% NaCl concentration and 72 h incubation period. The Klebsiella pneumoniae biofilm architecture was studied by confocal laser scanning microscopy (CLSM) and scanning electron microscope (SEM). The present study demonstrates the EPS influenced PAHs degradation of Klebsiella pneumoniae.


Asunto(s)
Hidrocarburos Aromáticos , Hidrocarburos Policíclicos Aromáticos , Biodegradación Ambiental , Matriz Extracelular de Sustancias Poliméricas , Nitrógeno
12.
Bioresour Technol ; 326: 124764, 2021 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-33524884

RESUMEN

The role of EPS in removal of carbonaceous organic matters and NH4+-N in simulated mariculture wastewater was examined at salinity of 0-3.5% in a multi-soil-layering bioreactor. Results showed that at 3.5% of salinity, the total activity of dehydrogenases (which were used to decompose carbonaceous organic matters) could be promoted by 13.2%-33.8% by EPS, increasing the removal rates of COD and NH4+-N by 13.2%-33.8% and 27.8%-42.1%, respectively. Besides, the activity of amylase in EPS was enhanced by 79.8%. However, reactions of some key enzymes such as acetate kinase and Na+K+-ATPase would not be accelerated by EPS, resulting in an inhibition of 44.3%-57.7% on energy gaining from ATP, and further inducing cytotoxicity. It was found that the glycolysis efficiency was promoted by 4.12%-59.3% in the presence of EPS, and glycolysis could also occur in EPS. Additionally, tyrosine was the main component in EPS to balance osmotic pressure.


Asunto(s)
Matriz Extracelular de Sustancias Poliméricas , Aguas Residuales , Amoníaco , Reactores Biológicos , Nutrientes , Salinidad , Aguas del Alcantarillado
13.
Bioresour Technol ; 326: 124744, 2021 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-33540212

RESUMEN

Cell immobilization was used to enrich and retain functional bacteria within partial denitrification-Anammox (PD/A) process to achieve its fast start-up for the first time. To do so, residue sludge and Anammox sludge were immobilized in poly (vinyl alcohol)/sodium alginate (PVA/SA) gel for PD cultivation and Anammox bacteria inoculation, respectively. Stable PD with NO3--N to NO2--N transformation ratio (NTR) of 72.0% was achieved within 13 days at 25 °C and successfully combined with Anammox on 14th day. The hydrous porous PVA/SA gel matrix played the role of extracellular polymeric substance (EPS) and thus protected the microbes against low temperature. Satisfactory nitrogen removal rate (NRR) (301.6 ± 6.1 g N/(m3·d)) was achieved even when temperature decreased to 13 °C. The contribution of nitrogen removal via Anammox was as high as 77.10%. Abundance of Thauera and Candidatus Kuenenia increased from 0.9% and 1.1% to 30.6% and 2.1%, respectively.


Asunto(s)
Reactores Biológicos , Desnitrificación , Bacterias , Matriz Extracelular de Sustancias Poliméricas , Nitrógeno , Oxidación-Reducción , Aguas del Alcantarillado
14.
Bioresour Technol ; 326: 124778, 2021 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-33545627

RESUMEN

The newly developed carrier granular sludge (CGS) with polyvinyl alcohol/chitosan (PVA/CS) and PVA/CS/Fe gel beads assistance showed higher intensity and anammox activity than the natural granular sludge (NGS). Through comprehensive investigation, it was found: (1) the gel beads provided a stable framework of cells entangle with extracellular polymeric substances (EPS) to enhance the sludge intensity. In this framework, ß-polysaccharides are distributed at the edge of CGS as a protection layer, α-polysaccharides and proteins are spread in the whole cross-section as backbones, and Fe2+/Fe3+ in CGS-PVA/CS/Fe act as bridges to link with the negatively charged groups on bacterial surfaces and proteins. (2) The porous gel beads satisfied a relatively unimpeded mass transfer. Thus, the sludge activity, microbe's metabolism, membrane transportation and environmental adaption in CGS were apparently improved. The results improved the understanding about the advantages of the CGS and indicated their possible application in full-scale anammox processes.


Asunto(s)
Quitosano , Aguas del Alcantarillado , Matriz Extracelular de Sustancias Poliméricas , Hierro , Alcohol Polivinílico
15.
Environ Pollut ; 274: 116605, 2021 Apr 01.
Artículo en Inglés | MEDLINE | ID: mdl-33545521

RESUMEN

Estuarine ecosystems near mega-cities are sinks of anthropogenic endocrine disrupting chemicals (EDCs). As the most important primary producer, indigenous microalgae and their secreted extracellular polymeric substances (EPSs) might interact with EDCs and contribute to their fate and risk. Tetraselmis sp. is a representative model of estuarine microalga, for which EDC toxicity and its effects on EPS synthesis have rarely been studied. Through microalgal isolation, algal cell growth tests, EDC removal and the characterization of related EPS profiles, the present work intends to clarify the comparative responses of Tetraselmis sp. to nonylphenol (NP), bisphenol A (BPA) and 17α-ethinylestradiol (EE2). The results showed that the half inhibitory concentration on cell growth was 0.190-0.313 mg/dm3 for NP, which was one order of magnitude lower than the comparable values for BPA and EE2 at 2.072-3.254 mg/dm3. Regarding chlorophyll, NP induced its degradation, EE2 led to its decreased production, and BPA had no obvious effect. Under EDC stress, only the concentrations of colloidal polysaccharides and proteins responded dose-dependently to EE2. Except for the colloidal fraction in the EE2 treatment group, the increase in neutral monosaccharides, especially glucose and galactose, was a common response to EDCs. Compared to the recalcitrant BPA, NP underwent abiotic degradation in alga-free water, and EE2 could be biodegraded in water containing this microalga. The chemical-specific responses of cell growth, chlorophyll and related EPS profiles were driven by the different fates of EDCs, and the underlying mechanism was further discussed. The results obtained in the present work are of critical importance for understanding the fate and effects of different EDCs mediated by microalgae and their related EPSs.


Asunto(s)
Disruptores Endocrinos , Contaminantes Químicos del Agua , Compuestos de Bencidrilo/toxicidad , Ecosistema , Disruptores Endocrinos/análisis , Disruptores Endocrinos/toxicidad , Etinilestradiol/análisis , Etinilestradiol/toxicidad , Matriz Extracelular de Sustancias Poliméricas/química , Fenoles , Contaminantes Químicos del Agua/análisis , Contaminantes Químicos del Agua/toxicidad
16.
Sci Total Environ ; 772: 144961, 2021 Jun 10.
Artículo en Inglés | MEDLINE | ID: mdl-33581531

RESUMEN

In order to deeply investigate the influences of side-stream phosphorus (P) recovery operation on mainstream biological P removal system, an improved activated sludge model no. 2 (ASM2d) was established to illuminate the metabolic processes of P in a side-stream P recovery reactor. The improved ASM2d (named D-EPS-ASM2d) was established by extending of the P metabolic processes of double-layer extracellular polymeric substances (EPS) into conventional ASM2d model. The predicted effluent concentrations of COD, NH4, and TP by the D-EPS-ASM2d had good fits with measured values in the side-stream P recovery process. Comparing with conventional ASM2d, the likelihood values of D-EPS-ASM2d related to COD, NH4, and TP effluents were increased from 0.694, 0.837 and 0.762 to 0.868, 0.904 and 0.920, respectively, implying the simulation performances of D-EPS-ASM2d on nutrient removal processes were significantly improved. Besides, the calibrated values of fPP,TEPS was 0.09, 0.102 and 0.123 as side-stream volume (SSV) increasing from 0.3 to 0.9, implying the fraction of P removal by tightly-bound EPS was enhanced with the increase of SSV.


Asunto(s)
Matriz Extracelular de Sustancias Poliméricas , Fósforo , Reactores Biológicos , Simulación por Computador , Ríos , Aguas del Alcantarillado
17.
Ecotoxicol Environ Saf ; 210: 111874, 2021 Mar 01.
Artículo en Inglés | MEDLINE | ID: mdl-33421723

RESUMEN

Given the high content of Ca2+ in waste paper recycling wastewater, the anaerobic granular sludge (AnGS) undergoes calcification during wastewater treatment and affects the treatment efficiency. To restore the activity of calcified AnGS and improve the performance of AnGS, four types of N-acyl-homoserine lactones (AHLs) were added to the AnGS system while papermaking wastewater treatment. The addition of N-butyryl-DL-homoserine lactone(C4-HSL) and N-octanoyl-DL-homoserine lactone (C8-HSL) had an inhibitory affect the COD removal efficiency and SMA of sludge at the inception. The addition of N-hexanoyl-L-homoserine lactone (C6-HSL) has no obvious effect on the COD removal efficiency, but can improve the SMA of sludge more obviously. The addition of N-(ß-ketocaproyl)-DL-homoserine lactone (3O-C6-HSL) can increased COD removal efficiency and promoted SMA together obviously. The addition of C6-HSL and 3O-C6-HSL can increase volatile suspended solid (VSS)/total suspended solid (TSS), and regulate extracellular polymeric substance (EPS) secretion in AnGS. Analysis of microbial sequencing revealed changes in the microbial community structure following AHL addition, which enhanced the methane metabolism pathway in sludge. The addition of C6-HSL, C8-HSL, and 3O-C6-HSL increased Methanosaeta population, thus increasing the aceticlastic pathway in sludge. Thus, exogenous AHLs can play an important role in regulating microbial community structure, and in improving the performance of AnGS.


Asunto(s)
Lactonas/administración & dosificación , Microbiota/efectos de los fármacos , Aguas del Alcantarillado , Anaerobiosis , Matriz Extracelular de Sustancias Poliméricas/metabolismo , Metano/metabolismo , Papel , Aguas Residuales
18.
Bioresour Technol ; 323: 124638, 2021 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-33418351

RESUMEN

To develop a more green and effective method for tetracycline (TC) removal, a hybrid material (conversion phosphors-TiO2, UCPs-TiO2) was coupled with a biofilm to achieve enhanced removal of TC. The removal of TC by biofilm coupled with UCPs-TiO2 under visible light reached 82%, which was 35% higher than that in treatment using only the biofilm. Extracellular polymeric substance (EPS) promoted the production of hydroxyl radicals by UCPs-TiO2, as the EPS acted as an electron transfer medium and accelerated the TC mineralization. Biofilm in the coupled system tolerated TC stress by regulating its antibiotic resistance genes (ARG) and superoxidedismutase (SOD), and allowed it to maintain stable and efficient removal of TC. This study documents a method to couple a hybrid material with microbial aggregates, creating a promising system for removing refractory organics, such as TC, from water. The study also offers insight into the mechanisms underlying TC removal by microbial aggregates combined with new functional materials.


Asunto(s)
Matriz Extracelular de Sustancias Poliméricas , Tetraciclina , Biopelículas , Luz , Titanio
19.
Monogr Oral Sci ; 29: 155-194, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-33427213

RESUMEN

Biofilm formation depends on many factors, one of them being the surface (substrate) on which the biofilm is formed, and dental restorative materials are such substrates. Biofilms play a crucial role for caries formation and inflammation of gingival, periodontal, or mucosal tissues next to restorations. Even general health problems such as systemic infections in immunocompromised patients may result from biofilms on dental materials (e.g., on dentures). Furthermore, biofilms may change material or surface properties. Biofilms on restorative materials have been investigated by several in vitro, in situ, and in vivo methods measuring a large number of different endpoints. Basically, datasets obtained from different methodological approaches are most suitable for final assessments. While surface properties like wettability or surface free energy (SFE) influence biofilm formation to a certain extent, the most relevant surface properties are material roughness followed by surface chemistry. The pellicle, which is formed rapidly on restorations after in vivo exposure, masks or levels off the influence of surface properties like wettability or SFE on biofilm formation. The prevention of biofilm formation is mainly based on general oral hygiene regimens. Furthermore, optimal polishing of restorative materials is instrumental. Several antimicrobial substances have been incorporated into restorative materials, which act by being released or as surface repellents. However, the optimal biofilm-preventive restorative material has not been found so far. New approaches in this context should aim at: (1) better understanding the role of the biofilm matrix (extracellular polymeric substance), and (2) implementing ecology-based approaches for the modification of dysbiotic disease-associated biofilms.


Asunto(s)
Adhesión Bacteriana , Matriz Extracelular de Sustancias Poliméricas , Biopelículas , Materiales Dentales , Película Dental , Humanos
20.
J Environ Manage ; 281: 111919, 2021 Mar 01.
Artículo en Inglés | MEDLINE | ID: mdl-33418384

RESUMEN

While cleaning wastewater, biological wastewater treatment processes such as membrane bioreactors (MBR) produce a significant amount of sludge that requires costly management. In the oxic-settling-anoxic (OSA) process, sludge is retained for a temporary period in side-stream reactors with low oxygen and substrate, and then it is recirculated to the main reactor. In this way, excess sludge production is reduced. We studied the influence of the rate of sludge exchange between MBR and side-stream anoxic reactors on sludge yield reduction within MBR. Two MBRs, namely, MBROSA and MBRcontrol, each coupled with separate external anoxic side-stream reactors, were run in parallel for 350 days. Unlike MBRcontrol, MBROSA had sludge exchange with the external reactors connected to it. During the investigation over a sludge interchange rate (SIR) range of 0-22%, an SIR of 11% achieved the highest sludge reduction (58%). Greater volatile solids destruction i.e., bacterial cell lysis and extracellular polymeric substance (EPS) destruction occurred at the SIR of 11%, which helped to achieve the highest sludge reduction. The enhanced volatile solids destruction was evident by the release of nutrients in the external anoxic reactors. It was confirmed that the sludge yield reduction was achieved without compromising the wastewater treatment quality, sludge settleability and hydraulic performance of the membrane in MBR.


Asunto(s)
Matriz Extracelular de Sustancias Poliméricas , Aguas del Alcantarillado , Reactores Biológicos , Eliminación de Residuos Líquidos , Aguas Residuales
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