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1.
Bioresour Technol ; 302: 122865, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32004814

RESUMO

Fermentative caproate production from wastewater is attractive but is currently limited by the low product purity and concentration. In this work, continuous, selective production of caproate from acetate and ethanol, the common products of wastewater anaerobic fermentation, was achieved in an anaerobic membrane bioreactor (AnMBR). The reactor was continuously operated for over 522 days without need for chemical cleaning. With an ethanol-to-acetate ratio of 3.0, the effluent caproate concentration was 2.62 g/L on average and the caproate ratio in liquid products reached 74%. Further raising the influent ethanol content slightly increased the effluent caproate level but lowered the product selectivity and resulted in microbial inhibition. The Clostridia (the major caproate-producing bacteria) and Methanobacterium species (which consume hydrogen to alleviate microbial inhibition) was significantly enriched in the acclimated sludge. Our results imply a great potential of utilizing AnMBR to recover caproate from the effluent of wastewater acidogenic fermentation process.


Assuntos
Reatores Biológicos , Caproatos , Anaerobiose , Bactérias Anaeróbias , Fermentação
2.
Environ Sci Technol ; 54(6): 3599-3608, 2020 03 17.
Artigo em Inglês | MEDLINE | ID: mdl-32062962

RESUMO

Pursuing efficient approaches to promote the extracellular electron transfer (EET) of extracellular respiratory bacteria is essential to their application in environmental remediation and waste treatment. Here, we report a new strategy of tuning electron flux by clustered regularly interspaced short palindromic repeat (CRISPR)-ddAsCpf1-based rediverting (namely STAR) to enhance the EET capacity of Shewanella oneidensis MR-1, a model extracellular respiratory bacterium widely present in the environment. The developed CRISPR-ddAsCpf1 system enabled approximately 100% gene repression with the green fluorescent protein (GFP) as a reporter. Using a WO3 probe, 10 representative genes encoding for putative competitive electron transfer proteins were screened, among which 7 genes were identified as valid targets for EET enhancement. Repressing the valid genes not only increased the transcription level of the l-lactate metabolism genes but also affected the genes involved in direct and indirect EET. Increased riboflavin production was also observed. The feasibility of this strategy to enhance the bioreduction of methyl orange, an organic pollutant, and chromium, a typical heavy metal, was demonstrated. This work implies a great potential of the STAR strategy with the CIRPSR-ddAsCpf1 system for enhancing bacterial EET to favor more efficient environmental remediation applications.


Assuntos
Poluentes Ambientais , Shewanella , Repetições Palindrômicas Curtas Agrupadas e Regularmente Espaçadas , Transporte de Elétrons , Elétrons
3.
Environ Sci Technol ; 54(6): 3306-3315, 2020 03 17.
Artigo em Inglês | MEDLINE | ID: mdl-32109355

RESUMO

Aeromonas species are indigenous in diverse aquatic environments and play important roles in environmental remediation. However, the pollutant transformation mechanisms of these bacteria remain elusive, and their potential in pollution control is largely unexploited so far. In this work, we report an efficient and simple genome regulation tool to edit Aeromonas hydrophila and identify its biomolecular pathways for pollutant transformation. The genome regulation system, which is based on the type II clustered regularly interspaced short palindromic repeat interference (CRISPRi) system from Streptococcus pyogenes, can serve as a reversible and multiplexible platform for gene knockdown in A. hydrophila. A single-plasmid CRISPRi system harboring both dCas9 and the sgRNA was constructed in A. hydrophila and used to silence diverse genes with varied sizes and expression levels. With this system, up to 467-fold repression of gfp expression was achieved, and the function of the essential gene-ftsZ was identified quickly and accurately. Furthermore, simultaneous transcriptional repression of multiple targeted genes was realized. We discovered that the ars operon played an essential role in arsenic detoxification, and the extracellular electron transfer (EET) pathway was involved in methyl orange reduction, but not in vanadium reduction by A. hydrophila. Our method allows better insights and effective genetic manipulation of the pollutant transformation processes in Aeromonas, which might facilitate more efficient utilization of the Aeromonas species and other microbial species for environmental remediation applications.


Assuntos
Repetições Palindrômicas Curtas Agrupadas e Regularmente Espaçadas , Poluentes Ambientais , Aeromonas hydrophila , Proteínas de Bactérias , Expressão Gênica , Técnicas de Silenciamento de Genes
4.
Anal Chem ; 92(5): 3990-3997, 2020 Mar 03.
Artigo em Inglês | MEDLINE | ID: mdl-32020800

RESUMO

Mercury (Hg), as a highly harmful environmental pollutant, poses severe ecological and health risks even at low concentrations. Accurate and sensitive methods for detecting Hg2+ ions in aquatic environments are highly needed. In this work, we developed a highly sensitive fluorescence sensor for Hg2+ detection with an integrated use of biosynthetic CdSe/CdS quantum dots (QDs) and liposome carrier signal amplification. To construct such a sensor, three single-stranded DNA probes were rationally designed based on the thymine-Hg2+-thymine (T-Hg2+-T) coordination chemical principles and by taking advantage of the biocompatibility and facile-modification properties of the biosynthetic QDs. Hg2+ could be determined in a range from 0.25 to 100 nM with a detection limit of 0.01 nM, which met the requirements of environmental sample detection. The sensor also exhibited a high selectivity for Hg2+ detection in the presence of other high-level metal ions. A satisfactory capacity of the sensor for detecting environmental samples including tap water, river water, and landfill leachate was also demonstrated. This work opens up a new application scenario for biosynthetic QDs and holds a great potential for environmental monitoring applications.

5.
Biotechnol Bioeng ; 2020 Feb 12.
Artigo em Inglês | MEDLINE | ID: mdl-32048726

RESUMO

The bioreduction capacity of Cr(VI) by Shewanella is mainly governed by its bidirectional extracellular electron transfer (EET). However, the low bidirectional EET efficiency restricts its wider applications in remediation of the environments contaminated by Cr(VI). Cyclic adenosine 3',5'-monophosphate (cAMP) commonly exists in Shewanella strains and cAMP-cyclic adenosine 3',5'-monophosphate receptor protein (CRP) system regulates multiple bidirectional EET-related pathways. This inspires us to strengthen the bidirectional EET through elevating the intracellular cAMP level in Shewanella strains. In this study, an exogenous gene encoding adenylate cyclase from the soil bacterium Beggiatoa sp. PS is functionally expressed in Shewanella oneidensis MR-1 (the strain MR-1/pbPAC) and a MR-1 mutant lacking all endogenous adenylate cyclase encoding genes (the strain Δca/pbPAC). The engineered strains exhibit the enhanced bidirectional EET capacities in microbial electrochemical systems compared with their counterparts. Meanwhile, a three times more rapid reduction rate of Cr(VI) is achieved by the strain MR-1/pbPAC than the control in batch experiments. Furthermore, a higher Cr(VI) reduction efficiency is also achieved by the strain MR-1/pbPAC in the Cr(VI)-reducing biocathode experiments. Such a bidirectional enhancement is attributed to the improved production of cAMP-CRP complex, which upregulates the expression levels of the genes encoding the c-type cytochromes and flavins synthetic pathways. Specially, this strategy could be used as a broad-spectrum approach for the other Shewanella strains. Our results demonstrate that elevating the intracellular cAMP levels could be an efficient strategy to enhance the bidirectional EET of Shewanella strains and improve their pollutant transformation capacity.

6.
Bioresour Technol ; 297: 122448, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31771810

RESUMO

In this work, a single microbial electrochemical system was developed for multiple goals simultaneously - CO2 reduction, biogas purification, upgrading and sulfur recovery. This system consists of a methanogen-inoculated biocathode for CO2 reduction and a ferrous ion (Fe2+)-mediated abiotic anode for hydrogen sulfide (H2S) oxidation. In the cathodic chamber, methane production rate of 20.6 ± 1.0 µmol·h-1 and high upgrading level (up to 98.3% methane content) were achieved. In the anodic chamber, H2S was completely removed and selectively converted into elemental sulfur particles. The system showed stable performance during continuous operation for treating both pure CO2 and mixed gases, with a cathodic coulombic efficiency of up to 85.2%. This simple system holds a great potential for practical application for biogas upgrading and sulfur recovery from waste water/gases.


Assuntos
Biocombustíveis , Dióxido de Carbono , Metano , Enxofre , Águas Residuárias
7.
ACS Appl Mater Interfaces ; 12(1): 443-450, 2020 Jan 08.
Artigo em Inglês | MEDLINE | ID: mdl-31814385

RESUMO

Nickel hydroxide (Ni(OH)2)-based electrocatalysts are promising for the oxygen evolution reaction (OER) due to their low cost, but their activity and durability still need substantial improvement to meet practical application. Here, we report a sulfate-functionalized Ni(OH)2 nanobelt (S-Ni(OH)2) electrocatalyst, which exhibited self-enhanced OER activity due to its self-renewed surface during anodic oxidation. The S-Ni(OH)2 was in situ grown on the nickel foam (NF) surface in potassium peroxydisulfate solution through one-step hydrothermal treatment. This material outperformed all the existing electrocatalysts in the intensity and duration of the OER activity enhancement. An overpotential drop of 70 mV is shown by the S-Ni(OH)2/NF electrode during 110 h reaction at a current density of 100 mA cm-2, and the overpotential remains as low as 358 mV at a current density of 200 mA cm-2. Such activity enhancement during OER is mainly ascribed to the formation of a highly active NiOOH/Ni(SO4)0.3(OH)1.4 composite on the S-Ni(OH)2 surface as a result of gradual sulfate release. Given the facile and environmentally benign fabrication process (without external addition of a Ni source and surfactant) and good electrochemical properties (high activity and long lifetime), the S-Ni(OH)2 holds great potential for practical OER application. The surface self-renewal strategy developed here might also be expanded to other electrocatalysts and electrochemical processes.

8.
ChemSusChem ; 2019 Oct 31.
Artigo em Inglês | MEDLINE | ID: mdl-31674132

RESUMO

Nickel hydroxide is promising for use in supercapacitor applications because of its low cost and tunable electrochemical properties, but its performance is usually restricted by insufficient conductivity and surface reactivity. In this work, sulfate-functionalized Ni(OH)2 (SNO) nanoplates were grown in situ on nickel foam (NF) by a green and facile one-step hydrothermal treatment of NF without the need for an external Ni source or surfactant addition. The resulting material showed a 9.3 times higher areal capacity and 1.8 times higher rate capability than the sulfate-free control and retained 81.3 % capacity after 5000 cycles. If used as the positive electrode in a hybrid supercapacitor, the SNO/NF//activated carbon system achieved >95 % Coulombic efficiency, a maximum energy density of 3.59 Wh m-2 , and a maximum power density of 44.63 Wm-2 , which surpass those achievable by most known Ni-based supercapacitors. Detailed material characterization and DFT calculations revealed that the introduction of sulfate expanded the layer spacing of Ni(OH)2 and improved the electrical conductivity and wettability to favor more efficient electrolyte diffusion, charge transfer, and reactant adsorption. The high loading of reactive components and inherited porous structure also contributed to the superior capacitive performance of the SNO/NF electrodes. Therefore, SNO/NF holds great potential for commercialized supercapacitor applications.

9.
Environ Sci Technol ; 53(24): 14604-14611, 2019 Dec 17.
Artigo em Inglês | MEDLINE | ID: mdl-31747260

RESUMO

Although arsenic at a high concentration imposes strong selective pressure on microbes, various microbes have been found to grow in As-rich environments. So far, little is known about how microbes can sense and move toward arsenate in the environment, and the underlying molecular mechanisms have not been revealed. Here, we report the chemotaxis response toward arsenate (As(V)) by Shewanella putrefaciens CN-32, a model dissimilatory metal-reducing bacterium (DMRB), and elucidate the mechanisms. We find that S. putrefaciens CN-32 exhibits a chemotactic behavior toward As(V) and diverse electron acceptors. To sense As(V), S. putrefaciens CN-32 requires functional arsenate respiratory reductase but does not depend on its metal-reducing-like respiratory pathway. We observe that such a sense is governed by an energy taxis mechanism and mediated by several methyl-accepting chemotaxis proteins (MCPs), rather than a specific MCP. Moreover, we reveal that the chemotactic signal transduction pathway is conserved in Shewanella, and histidine kinase and flagella-mediated motility are essential for taxis toward As(V). This work reverses the conventional view about arsenic as a chemotactic inhibitor to microbes by revealing the positive chemotaxis of Shewanella to As(V).

10.
Environ Int ; 129: 86-94, 2019 08.
Artigo em Inglês | MEDLINE | ID: mdl-31121519

RESUMO

Chromium is a common heavy metal widely present in aquatic environments. Cost-effective remediation of chromium-contaminated environment can be realized by microbial reduction of Cr(VI) to Cr(III). The genus Aeromonas species is one of such Cr(VI) reducers, whose reduction mechanism remains unrevealed and the main factors governing the Cr(VI) reduction pathways are unknown yet. In this work, the performances and mechanisms of Cr(VI) anaerobic reduction by Aeromonas hydrophila ATCC 7966 were investigated. This strain exhibited excellent Cr(VI) resistance and could utilize a suite of electron donors to support Cr(VI) bioreduction. The Cr(VI) bioreduction processes involved both extracellular (the metal-reducing and respiratory pathway) and intracellular reaction pathways. Adding anthraquinone-2,6-disulfonate or humic acid as a mediator substantially enhanced the Cr(VI) bioreduction. The forms and distribution of the Cr(VI) bioreduction products were affected by the medium composition. Soluble organo-Cr(III) complexes were identified as the main Cr(VI) reduction products when basal salts medium was adopted. Given the environmental ubiquity of the genus Aeromonas, the findings in this work may facilitate a better understanding about the transformation behaviors and fates of Cr(VI) in environments and provide useful clues to tune the bioremediation of chromium-contaminated environments.


Assuntos
Aeromonas hydrophila/metabolismo , Compostos de Cromo/metabolismo , Biodegradação Ambiental , Oxirredução
11.
Environ Int ; 129: 273-278, 2019 08.
Artigo em Inglês | MEDLINE | ID: mdl-31146161

RESUMO

China's national development strategy now prioritizes environmental protection over economic growth, which has driven a rapid development of China's wastewater sector. In particular, the treatment capacity of municipal wastewater treatment plants (WWTPs) has been substantially strengthened and stricter effluent quality control enforced. However, the operating performance of most WWTPs is still poor and does not meet the sustainable development demands. In this study, the current status of WWTPs operation in China was comprehensively analyzed, the key barriers to improving the plants operating efficiency were identified by taking into account the different plant scales, geographic distribution, discrepancy between cities and counties, and the influence of environmental policies and supplementary facilities. The underdeveloped sewer network was mainly responsible for the low operating ratios (i.e., utilization degree of the designed treatment capacity) of the plants (76% in counties and 85% in cities) especially for those in north China, although the situation is plant specific because a considerable fraction of plants (19%) are still running under overload condition. Other challenges include the high energy consumption of the plants (0.313 kWh/m3), and severely lagged implementation of sludge disposal (up to 40% sludge was still improperly disposed), arising mainly from the poor management on the sewer and sludge. Lastly, several possible directions of improvement to overcome these barriers were discussed. This work may provide valuable implications for optimizing municipal wastewater management in China towards higher efficiency and sustainability.


Assuntos
Eliminação de Resíduos Líquidos , Águas Residuárias/análise , China , Esgotos , Eliminação de Resíduos Líquidos/instrumentação
12.
ACS Nano ; 13(5): 5841-5851, 2019 May 28.
Artigo em Inglês | MEDLINE | ID: mdl-30969107

RESUMO

Biosynthesis offers opportunities for cost-effective and sustainable production of semiconductor quantum dots (QDs), but is currently restricted by poor controllability on the synthesis process, resulting from limited knowledge on the assembly mechanisms and the lack of effective control strategies. In this work, we provide molecular-level insights into the formation mechanism of biogenic QDs (Bio-QDs) and its connection with the cellular substrate metabolism in Escherichia coli. Strengthening the substrate metabolism for producing more reducing power was found to stimulate the production of several reduced thiol-containing proteins (including glutaredoxin and thioredoxin) that play key roles in Bio-QDs assembly. This effectively diverted the transformation route of the selenium (Se) and cadmium (Cd) metabolic from Cd3(PO4)2 formation to CdS xSe1- x QDs assembly, yielding fine-sized (2.0 ± 0.4 nm), high-quality Bio-QDs with quantum yield (5.2%) and fluorescence lifetime (99.19 ns) far exceeding the existing counterparts. The underlying mechanisms of Bio-QDs crystallization and development were elucidated by density functional theory calculations and molecular dynamics simulation. The resulting Bio-QDs were successfully used for bioimaging of cancer cells and tumor tissue of mice without extra modification. Our work provides fundamental knowledge on the Bio-QDs assembly mechanisms and proposes an effective, facile regulation strategy, which may inspire advances in controlled synthesis and practical applications of Bio-QDs as well as other bionanomaterials.

13.
Environ Int ; 126: 560-567, 2019 05.
Artigo em Inglês | MEDLINE | ID: mdl-30852443

RESUMO

Photocatalytic catalysis is widely used for pollutant degradation. Since some pollutants with oxidative nature are readily reduced rather than oxidized and reductive reaction caused by photogenerated electrons is limited in the presence of oxygen, photocatalytic reduction process is more applicable for the degradation of pollutants with oxidative nature than oxidation. In this work, a novel bio-photoelectric reductive degradation system (BPRDS), composed of an electrochemically active bacterium Shewanella oneidensis MR-1 and a visible-light photocatalyst Ag3PO4, was established under anaerobic conditions and its photodegradation performance was evaluated through degrading rhodamine B (RhB), a typical organic pollutant. The as-synthesized Ag3PO4 nanoparticles exhibited absorption in the entire visible spectral range of 400-800 nm. RhB could be degraded in BPRDS with visible light irradiation under anaerobic conditions, but not be decomposed in the absence of Shewanella cells. Block of Mtr respiratory pathway, a transmembrane electron transport chain, resulted in a reduction in degradation rate of RHB in BPRDS. Dose of riboflavin also substantially decreased the RhB degradation. These results suggest that the electrons released by Shewanella were involved in the RhB photodegradation, which was achieved via a stepwise N-deethylation process. In BPRDS, RhB was degraded by photoreduction, rather than photooxidation. This work is useful to develop integrated physico-chemical-microbial systems for pollutant degradation, facilitate better understanding about the biophotoelectric reductive degradation mechanisms and beneficial to their applications for environmental remediation.


Assuntos
Fosfatos/química , Rodaminas/metabolismo , Shewanella/metabolismo , Compostos de Prata/química , Catálise , Luz , Oxirredução , Fosfatos/efeitos da radiação , Fotólise , Compostos de Prata/efeitos da radiação
14.
Sci Total Environ ; 664: 133-139, 2019 May 10.
Artigo em Inglês | MEDLINE | ID: mdl-30739848

RESUMO

A non-radical reaction between peroxysulfates and phenolic compounds, as important structural moieties of natural organic matters, has been reported recently, implying new opportunities for environmental remediation without need for catalyst or energy input. However, this approach seems to be ineffective for halogenated aromatic compounds, an important disinfection by-products (DBPs). Here, we shed light on the interactions between peroxymonosulfate (PMS) and chlorophenols and the influential factors. The results show that the chlorophenols transformation kinetics were highly dependent on the solution pH and chlorophenol species: raising the pH significantly accelerated the chlorophenols degradation, and at alkaline pH the removal rates of different chlorophenols were in the order of trichlorophenol > dichlorophenol > chlorophenol > tetrachlorophenol. The faster degradation of pollutants with more chlorine groups was mainly due to their relatively higher dissociation degree, which favors a direct pollutant-PMS interaction to generate radicals for their degradation. The chlorophenol degradation intermediate (i.e. benzoquinone) further mediated the generation of singlet oxygen at alkaline pH, thereby contributing to accelerated pollutant removal. The slower degradation of tetrachlorophenol than other chlorophenols was likely due to its strong electrostatic epulsion to PMS which restricted the reaction. Our work unveils the chlorophenols degradation mechanisms in PMS reaction system, which may facilitate a better understanding and optimization of advanced oxidation processes for pollution control to reduce potential DBPs accumulation.

15.
Environ Sci Technol ; 53(5): 2344-2352, 2019 03 05.
Artigo em Inglês | MEDLINE | ID: mdl-30735361

RESUMO

Antagonism between heavy metal and selenium (Se) could significantly affect their biotoxicity, but little is known about the mechanisms underlying such microbial-mediated antagonistic processes as well as the formed products. In this work, we examined the cadmium (Cd)-Se interactions and their fates in Caenorhabditis elegans through in vivo and in vitro analysis and elucidated the machinery of Se-stimulated Cd detoxification. Although the Se introduction induced up to 3-fold higher bioaccumulation of Cd in C. elegans than the Cd-only group, the nematode viability remained at a similar level to the Cd-only group. The relatively lower level of reactive oxygen species in the Se & Cd group confirms a significantly enhanced Cd detoxification by Se. The Cd-Se interaction, mediated by multiple thiols, including glutathione and phytochelatin, resulted in the formation of less toxic cadmium selenide (CdSe)/cadmium sulfide (CdS) nanoparticles. The CdSe/CdS nanoparticles were mainly distributed in the pharynx and intestine of the nematodes, and continuously excreted from the body, which also benefitted the C. elegans survival. Our findings shed new light on the microbial-mediated Cd-Se interactions and may facilitate an improved understanding and control of Cd biotoxicity in complicated coexposure environments.


Assuntos
Nanopartículas , Selênio , Animais , Cádmio , Caenorhabditis elegans , Compostos de Sulfidrila
16.
Biotechnol Bioeng ; 116(5): 961-971, 2019 05.
Artigo em Inglês | MEDLINE | ID: mdl-30659584

RESUMO

Dissimilatory metal reducer Geobacter sulfurreducens can mediate redox processes through extracellular electron transfer and exhibit potential-dependent electrochemical activity in biofilm. Understanding the microbial acclimation to potential is of critical importance for developing robust electrochemically active biofilms and facilitating their environmental, geochemical, and energy applications. In this study, the metabolism and redox conduction behaviors of G. sulfurreducens biofilms developed at different potentials were explored. We found that electrochemical acclimation occurred at the initial hours of polarizing G. sulfurreducens cells to the potentials. Two mechanisms of acclimation were found, depending on the polarizing potential. In the mature biofilms, a low level of biosynthesis and a high level of catabolism were maintained at +0.2 V versus standard hydrogen electrode (SHE). The opposite results were observed at potentials higher than or equal to +0.4 V versus SHE. The potential also regulated the constitution of the electron transfer network by synthesizing more extracellular cytochrome c such as OmcS at 0.0 and +0.2 V and exhibited a better conductivity. These findings provide reasonable explanations for the mechanism governing the electrochemical respiration and activity in G. sulfurreducens biofilms.

17.
ACS Appl Mater Interfaces ; 10(41): 35090-35098, 2018 Oct 17.
Artigo em Inglês | MEDLINE | ID: mdl-30247017

RESUMO

A bioelectrochemical system (BES) allows direct electricity production from wastes, but its low-power density, which is mainly associated with its poor anodic performance, limits its practical applications. Here, the anodic performance of a BES can be significantly improved by electrodepositing vitamin B2 (VB2) onto a graphene [reduced graphene oxide (rGO)]-modified glassy carbon electrode (VB2/rGO/GC) with Geobacter sulfurreducens as the model microorganisms. The VB2/rGO/GC electrode results in 200% higher electrochemical activity than a bare GC anode. Additionally, in microbial electrolysis cells, the current density of this composite electrode peaks at ∼210 µA cm-2 after 118 h and is maintained for 113 h. An electrochemical analysis coupled with molecular simulations reveals that using VB2 as a linker between the electrochemically active protein of this model strain and the rGO surface accelerates the electron transfer, which further improves the bioelectricity generation and favors the long-term stability of the BES. The VB2 bound with a flexible ribityl group as the organic molecular bridge efficiently mediates energy conversion in microbial metabolism and artificial electronics. This work provides a straightforward and effective route to significantly enhance the bioenergy generation in a BES.


Assuntos
Fontes de Energia Bioelétrica , Citocromos/química , Técnicas Eletroquímicas , Geobacter/metabolismo , Grafite/química , Riboflavina/química
18.
Chemosphere ; 193: 840-846, 2018 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-29874757

RESUMO

The presence of antibiotics in wastewater has been widely confirmed. Membrane bioreactor (MBR), as an efficient wastewater treatment technology, has attracted increasing interest in its ability to remove antibiotics in recent years. However, its long-term operation stability and the underlying mechanisms for antibiotics removal are still poorly understood. In this study, a hollow fiber MBR was used to treat low concentration sulfamethazine (SMZ) contained wastewater. The long-term effects of various SMZ concentrations on nutrients removal, SMZ degradation, and sludge characteristics were investigated. During the 244 days operation, the overall SMZ removal efficiency could reach 95.4 ± 4.5% under various SMZ concentrations and hydraulic retention times. The reactor exhibited high chemical oxygen demand and NH4+-N removal efficiencies, which reached 93.0% and 96.2%, respectively. A sludge concentration of 4.1 ± 0.3 g/L was maintained in the system without excess sludge discharge. The dosage of SMZ had obvious effect on sludge characteristics. The contents of extracellular polymeric substances (EPS) in MBR decreased after a long-term operation of the reactor under SMZ pressure. The low sludge concentration and the reduced EPS content were also beneficial for mitigating membrane fouling. Thus, this study provides a low-cost, efficient and simple approach to treat SMZ-contained wastewater.


Assuntos
Reatores Biológicos/normas , Sulfametazina/química , Águas Residuárias/química , Purificação da Água/métodos
19.
Environ Sci Pollut Res Int ; 25(23): 22810-22817, 2018 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-29855881

RESUMO

Reversed A2O process (anoxic-anaerobic-aerobic) and conventional A2O process (anaerobic-anoxic-aerobic) are widely used in many wastewater treatment plants (WWTPs) in Asia. However, at present, there are still no consistent results to figure out which process has better total phosphorous (TP) removal performance and the mechanism for this difference was not clear yet. In this study, the treatment performances of both processes were compared in the same full-scale WWTP and the TP removal dynamics was analyzed by a modeling method. The treatment performance of full-scale WWTP showed the TP removal efficiency of the reversed A2O process was more efficient than in the conventional A2O process. The modeling results further reveal that the TP removal depends highly on the concentration and composition of influent COD. It had more efficient TP removal than the conventional A2O process only under conditions of sufficient influent COD and high fermentation products content. This study may lay a foundation for appropriate selection and optimization of treatment processes to suit practical wastewater properties.


Assuntos
Modelos Teóricos , Fósforo/isolamento & purificação , Eliminação de Resíduos Líquidos/métodos , Anaerobiose , Análise da Demanda Biológica de Oxigênio , Reatores Biológicos , Fermentação , Fósforo/análise , Eliminação de Resíduos Líquidos/instrumentação , Águas Residuárias/química
20.
J Integr Med ; 16(4): 290-296, 2018 07.
Artigo em Inglês | MEDLINE | ID: mdl-29866613

RESUMO

OBJECTIVE: The main objective of this study was to preliminarily determine the optimum formulation of a Chinese herbal formula that may have neuroprotective effects against rotenone-induced Parkinson's disease (PD). METHODS: Seven recipes were made from Dihuang (DH, Rehmannia glutinosa Libosch), Roucongrong (RCR, Cistanche deserticola Y.C.Ma), Niuxi (NX, Achyranthes bidentata Bl.) and Shanzhuyu (SZY, Cornus officinalis Sieb. et Zucc) in different proportions, according to the principles of uniform design (4 factors 7 levels). Tyrosine hydroxylase (TH)-positive neurons in substantia nigra pars compacta (SNpc) were detected by immunohistochemistry and rotenone-exposure days necessary to induce PD symptoms were recorded. To probe one likely mechanism of the formulas, echinacoside (ECH) concentrations of all seven recipes were determined by high-performance liquid chromatography and related to number of TH-positive neurons. RESULTS: The data showed that recipe 4 (DH:RCR:SZY:NX = 1:1:1:1) and recipe 7 (DH:RCR:SZY:NX = 7:5:3:1) partially reversed rotenone-induced death of TH-positive neurons in the SNpc and significantly increased rotenone-exposed days compared with model group. Pharmacologically, there was not a strong correlation between ECH concentration and TH-positive neurons. CONCLUSION: The investigated formulations of Chinese herbs had neuroprotective effects against PD models, and the neuroprotective effects were weakly related to the proportion of key herbs. However the neuroprotective effects of the formula may not result from a single active constituent.


Assuntos
Medicamentos de Ervas Chinesas/administração & dosagem , Fármacos Neuroprotetores/administração & dosagem , Doença de Parkinson/tratamento farmacológico , Rotenona/efeitos adversos , Animais , Modelos Animais de Doenças , Medicamentos de Ervas Chinesas/química , Humanos , Masculino , Fármacos Neuroprotetores/química , Doença de Parkinson/etiologia , Plantas Medicinais/química , Ratos , Ratos Wistar
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