RESUMO
Escherichia coli (E. coli) is an opportunistic pathogen that can cause clinical mastitis in dairy cows worldwide. Mastitis produces severe symptoms in dairy cows, such as udder inflammation, the production of harmful substances, reduced milk production, and altered milk quality. Intramammary injections of rifaximin have a beneficial effect on dairy cow mastitis, especially for mastitis caused by E. coli. However, we do not know whether the currently accepted clinical administration scheme is reasonable. Therefore, the purpose of this experiment was to evaluate the clinical dosing regimen for curing mastitis induced by E. coli. In this study, the pharmacokinetics of four single dose groups (50, 100, 200, and 400 µg/gland) were studied in CD-1 lactating mice, and the main pharmacokinetic parameters were obtained by non-compartment and two-compartment model of Phoenix 8.1 software. A total of 5,000 colony-forming units (CFU) of E. coli ATCC25922 were injected into the mammary glands of mice under anatomic microscope guidance. After 12 h of growth in vivo, the mouse mastitis model was successfully developed. In pharmacodynamics experiment, 12 different dosing regimens (doses ranged from 25 to 800 µg/gland and two dosing intervals of 12 and 24 h) were used to study the therapeutic potential of rifaximin for mastitis. The PK/PD model was established by integrating pharmacokinetics and pharmacodynamics using the inhibitory sigmoid Emax model. The optimal antibacterial effect was 2log10CFU/gland reduction of bacterial colony counts in vivo, when the magnitude of AUC24/MIC exceeded 57.80 h. A total of 57.80 h of AUC24/MIC was defined as a target value in the Monte Carlo simulation. The clinically recommended dosage regimen of 100 mg/gland every 12 h in a day achieved a 91.08% cure rate for the treatment of bovine mastitis caused by E. coli infection.
Assuntos
Doenças dos Bovinos , Infecções por Escherichia coli , Mastite Bovina , Feminino , Bovinos , Animais , Camundongos , Escherichia coli , Rifaximina/uso terapêutico , Lactação , Infecções por Escherichia coli/tratamento farmacológico , Infecções por Escherichia coli/veterinária , Leite/microbiologia , Mastite Bovina/tratamento farmacológico , Mastite Bovina/microbiologia , Glândulas Mamárias AnimaisRESUMO
To reduce the harm caused to the environment by fuel combustion and meet the increasingly stringent emission standards, the sulfur content of fuels should be reduced. Dibenzothiophene, benzothiophene, and their derivatives are sulfur-containing components of fuels that are difficult to desulfurize and can therefore cause great environmental damage. Biodesulfurization is a desulfurization method that has the advantage of being able to remove dibenzothiophene and its derivatives removed easily under conditions that are relatively mild when compared with hydrodesulfurization. This paper introduces the advantages of thermophilic biodesulfurization compared with mesophilic biodesulfurization; analyzes the desulfurization mechanism, including the desulfurization pathways and enzymic systems of desulfurization bacteria; and discusses the application of biodesulfurization in oil desulfurization. The main problems existing in biodesulfurization and possible solutions are also analyzed in this paper. Biological desulfurization is a promising method for desulfurization; accordingly, more studies investigating biodesulfurization of actual oil are needed to enable the industrialized application of biodesulfurization.
Assuntos
Óleos/metabolismo , Enxofre/metabolismo , Tiofenos/metabolismo , Animais , Biodegradação Ambiental , Gasolina/microbiologia , HumanosRESUMO
Biological removal of sulfide, nitrate, and phenol at loading rates of 600 g S/(m(3) day), 900 g N/(m(3) day), and 450 g C/(m(3) day), respectively, from synthetic wastewaters was achieved in an expanded granular sludge bed (EGSB) reactor, whose rates are much higher than literature works and are considered feasible for handling high-strength petrochemical wastewaters without dilution. Effects of C/S ratio (2-2.5:1) on EGSB performance were noted insignificantly. The strains Bacillus sp., Thauera sp., and Pseudomonas sp. were the heterotrophic denitrifiers and the strains Thiobacillus sp., Azoarcus sp., and Sulfurovum sp. were the autotrophic denitrifiers in the EGSB granules. The EGSB reactor experienced biological breakdown at loadings higher than 1200 g S/(m(3) day), 1800 g N/(m(3) day), and 900 g C/(m(3) day) by the following mechanism: high sulfide first inhibits heterotrophic denitrifies (Bacillus sp. and Pseudomonas sp.), thereby accumulating nitrite in the system; then, the accumulated nitrite inhibits autotrophic denitrifiers (Thiobacillus sp., Azoarcus sp., and Sulfurovum sp.) to complete breakdown of the system.
Assuntos
Consórcios Microbianos , Nitratos/metabolismo , Fenol/metabolismo , Esgotos/microbiologia , Sulfetos/metabolismo , Purificação da Água/métodos , Reatores Biológicos/microbiologiaRESUMO
Biological conversion of sulfide, acetate, and nitrate to, respectively, elemental sulfur (S(0)), carbon dioxide, and nitrogen-containing gas (such as N2) at NaCl concentration of 35-70 g/L was achieved in an expanded granular sludge bed (EGSB) reactor. A C/N ratio of 1:1 was noted to achieve high sulfide removal and S(0) conversion rate at high salinity. The extracellular polymeric substance (EPS) quantities were increased with NaCl concentration, being 11.4-mg/g volatile-suspended solids at 70 mg/L NaCl. The denitrifying sulfide removal (DSR) consortium incorporated Thauera sp. and Halomonas sp. as the heterotrophs and Azoarcus sp. being the autotrophs at high salinity condition. Halomonas sp. correlates with the enhanced DSR performance at high salinity.
Assuntos
Halomonas/metabolismo , Sulfetos/metabolismo , Águas Residuárias/microbiologia , Purificação da Água/métodos , Biodegradação Ambiental , Desnitrificação , Halomonas/crescimento & desenvolvimento , Cloreto de Sódio/análise , Cloreto de Sódio/metabolismo , Sulfetos/química , Águas Residuárias/química , Purificação da Água/instrumentaçãoRESUMO
Denitrifying sulfide removal (DSR) process comprising both heterotrophic and autotrophic denitrifiers can simultaneously convert nitrate, sulfide, and acetate into nitrogen gas, elemental sulfur (S(0)), and carbon dioxide, respectively. Sulfide- and nitrate-laden wastewaters at 2-35 g/L NaCl were treated by DSR process. A C/N ratio of 3:1 was proposed to maintain high S(0) conversion rate. The granular sludge with a compact structure and smooth outer surface was formed. The microbial communities of DSR consortium via high-throughput sequencing method suggested that salinity shifts the predominating heterotrophic denitrifiers at <10 g/L NaCl to autotrophic denitrifiers at >10 g/L NaCl.
Assuntos
Desnitrificação , Consórcios Microbianos , Salinidade , Sulfetos/metabolismo , Águas Residuárias/química , Águas Residuárias/microbiologia , Acetatos/metabolismo , Dióxido de Carbono/metabolismo , Nitratos/metabolismo , Nitrogênio/metabolismo , Esgotos/química , Esgotos/microbiologia , Enxofre/metabolismoRESUMO
In this study, two intramammary infusions of cefquinome sulfate were investigated for pharmacokinetics and bioavailability. Twelve lactating cows for each group were administered an effective dose of 75 mg/gland for cefquinome, with milk samples collected at various time intervals. The concentrations of cefquinome in milk at different times were determined by the UPLC-MS/MS method. Analyses of noncompartmental pharmacokinetics were conducted on the concentration of cefquinome in milk. Mean pharmacokinetic parameters of group A and group B following intramammary administration were as follows: AUClast 300558.57 ± 25052.78 ng/mL and 266551.3 ± 50654.85 ng/mL, Cmax 51786.35 ± 11948.4 ng/mL and 59763.7 ± 8403.2 ng/mL, T1/2 5.69 ± 0.62 h and 5.25 ± 1.62 h, MRT 7.43 ± 0.79 h and 4.8 ± 0.78 h, respectively. Pharmacokinetic experiments showed that the relative bioavailability of group B was 88.69% that of group A. From our findings, group B (3 g: 75 mg) shows a quicker drug elimination process than group A (8 g: 75 mg), which suggests that the withdrawal period for the new formulation may be shorter.
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The strong physiological toxicity of Cr(VI) makes it widely concerned in wastewater treatment. At present, the simplest and harmless method for treating Cr(VI) is known to be biologically reducing it to Cr(III), making it precipitate as Cr(OH)3(s), and then removing Cr(III) by solid separation technology. Studies have shown that Cr(VI) reduction bacteria can use CH4 and H2 as electron donors to reduce Cr(VI). Based on this, in this study, C3H8 was used as the only electron donor to investigate the potential of C3H8 matrix membrane bioreactor in the Cr(VI) wastewater treatment. The experiment was divided into three stages, each of which run stably for at least 30 days, and the whole process run for 120 days in total. The experiment is divided into three stages, each stage runs stably for at least 30 days, for a total of 120 days. With the increase of the Cr(VI) load, the removal rate gradually decreased. In stage 3, when Cr(VI) concentration was 2.0 mg·L-1, the removal rate was reduced from 90% in the first stage to 75%. According to X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis, it is known that Cr(III) is the main product during this process and it is adsorbed on the biofilm as Cr(OH)3 precipitate. During the experiment, the amount of extracellular polymeric substance (EPS) produced by microorganisms increased initially and then decreased, and the amount of polysaccharides (PS) was always more than protein (PN). By analyzing the microbial community structure after inoculating sludge and adding Cr(VI), Nocardia and Rhodococcus dominate the biofilm samples. Chromate reductase, cytochrome c, nitrate reductase, and other functional genes related to chromate reductase increased gradually during the experiment.
Assuntos
Matriz Extracelular de Substâncias Poliméricas , Propano , Matriz Extracelular de Substâncias Poliméricas/metabolismo , Oxirredução , Cromo/metabolismo , BiofilmesRESUMO
As set in the maximum residue limit regulations of the European Commission, this study aimed to obtain the residual parameters in milk with optimized UPLC-MS/MS conditions and to determine the conclusive drug withdrawal period to ensure food safety. In this research, an ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed to study cefquinome sulfate's residue elimination in milk and to calculate cefquinome's withdrawal period. Twelve healthy cows free of endometritis were selected for the experiment. Before using the drug, the vaginal orifice and perineum of each cow was disinfected. One dose of intrauterine perfusion was used for each cow, followed by an additional dose after 72 h. Before administration and 12 h, 18 h, 24 h, 36 h, 42 h, 48 h, 60 h, 66 h, 72 h, 84 h, 90 h, and 96 h after the last dose, milk (10 mL) was gathered from each cow's teat and pooled. For the measurement of cefquinome concentrations in milk, UPLC-MS/MS was performed. A calibration curve was generated using linear regression as follows: Y = 250.86X - 102.29, with a correlation coefficient of 0.9996; the limits of detection and the limits of quantitation were 0.1 µg·kg-1 and 0.2 µg·kg-1, respectively. The average recovery of cefquinome was 88.60 ± 16.33% at 0.2 µg·kg-1, 100.95 ± 2.54% at 10 µg·kg-1, and 97.29 ± 1.77% at 50 µg·kg-1. For 5 consecutive days at the three spiking levels, the intra and inter-day relative standard deviations (RSD) were 1.28%-13.73% and 1.81%-18.44%, respectively; the residual amount of cefquinome was less than the maximum residue limit of 20 µg·kg-1, 36 h after administration; and the residual amount was less than the limit of detection (0.1 µg·kg-1) 48 h after administration. The withdrawal time of cefquinome in cow's milk was 39.8 h, as calculated using WTM1.4 software. In terms of clinical practical use, the withdrawal period of milk was temporarily set at 48 h after the administration of the cefquinome sulfate uterus injection to cows, in accordance with the recommended dose and course.
RESUMO
Biodegradable candelilla wax (CW) was creatively used for hydrophobic modification of coal fly ash cenospheres (FACs), a waste product from thermal power plants, and a new spherical hollow particulate adsorbent with fast oil adsorption rate and easy agglomeration was prepared. CW was confirmed to physically coat FACs and the optimum mass of wax added to 3 g of FACs was 0.05 g. From a series of batch scale experiments, CW-FACs were found to adsorb oil, reaching adsorption efficiency of 80.6% within 10 s, and aggregate into floating clumps which were easily removed from the water's surface. The oil adsorption efficiency was highly dependent on hydrophobicity of the used adsorbent, the adsorption of Venezuela oil onto CW-FACs was found to be a homogenous monolayer, and the capacity and intensity of the adsorption decreased as temperature increased from 10 to 40 °C. The Langmuir isotherm model was the best fit, with the maximum adsorption capacity achieved at 649.38 mg/g. CW-FACs were also found to be highly stable in concentrated acid, alkaline and salt solutions, as well as for spills of different oil products. Furthermore, the retention rate of the oil adsorption capacity of the CW-FACs after 6 cycles of adsorption-extraction was as high as 93.2%. Therefore, CW-FACs can be widely used, easily recycled, and reused for marine oil spill remediation, which is also a good alternative disposal solution for FACs.
Assuntos
Poluição por Petróleo , Poluentes Químicos da Água , Cinza de Carvão/química , Carvão Mineral , Poluentes Químicos da Água/análise , Compostos Orgânicos , AdsorçãoRESUMO
Deltamethrin, an important pyrethroid insecticide, is frequently detected in human samples. This study aims to assess the potential effects of deltamethrin on human health and investigate the patterns of residue enrichment and elimination in 112 healthy laying hens. These hens were administered 20 mg·kg-1 deltamethrin based on their body weight. Gas chromatography-mass spectrometry (GC-MS) was used to investigate the residue enrichment pattern and elimination pattern of deltamethrin in the hens. The results indicated a significant increase in the concentration of deltamethrin in chicken manure during the treatment period. By the 14th day of administration, the concentration of deltamethrin in the stool reached 13,510.9 ± 172.24 µg·kg-1, with a fecal excretion rate of 67.56%. The pulmonary deltamethrin concentration was the second highest at 3844.98 ± 297.14 µg·kg-1. These findings suggest that chicken feces contain substantial amounts of deltamethrin after 14 days of continuous administration, and that it can easily transfer to the lungs. After 21 days of drug withdrawal, the residual concentration of deltamethrin in the fat of laying hens was 904.25 ± 295.32 µg·kg-1, with a half-life of 17 days and a slow elimination rate. In contrast, the lungs showed relatively low elimination half-lives of 0.2083 days, indicating faster elimination of deltamethrin in this tissue. These results highlight differences in the rate of deltamethrin elimination in different tissues during drug withdrawal. The fat of laying hens exhibited the highest residue of deltamethrin and the slowest elimination rate, while the lungs showed the fastest elimination rate. Moreover, deltamethrin was found to accumulate in the edible tissues of eggs and laying hens, suggesting that humans may be exposed to deltamethrin through food.
RESUMO
In order to improve the visible light response, N-doping ZnS (N-ZnS) nanospheres with Zn vacancy and porous surface were prepared by a simple one-pot hydrothermal method. Characterizations and density functional theory simulations showed excellent visible light response of N-ZnS. N-doping introduced impurity energy levels, which led to orbital hybridization and changed the original dipole moment. The presence of ortho Zn vacancy (O-Znv) can effectively reduce e--h+ recombination and photocorrosion. Furthermore, O-Znv caused lattice distortion (twisted the -S-Zn-N-(O-Znv)-S-Zn-S- chemical bond chain), resulting in "vacancy effect" to accelerate e- flow. Under visible light, the photocatalytic degradation efficiency of tetracycline (TC) and 2,4-dichlorophenol (2,4-DCP) was 90.31% and 60.84%, respectively. TOC degradation efficiency was 31.4% and 25.6%, respectively. Combined with Fukui index and LC-MS methods, it was found that TC and 2,4-DCP were degraded under the constant attack of active substances such as ·OH. This work can provide a reference for the application of catalytic materials in the field of visible light photocatalysis.
Assuntos
Poluentes Ambientais , Catálise , Elétrons , Luz , Fotoquímica , Sulfetos , Tetraciclina , Água , Zinco , Compostos de ZincoRESUMO
Sulfide partial denitrification (SPD) is an alternative pathway for nitrite production accompanied with elemental sulfur (S0) production for nitrate removal from wastewater with anammox. In this study, the SPD granular sludge was cultivated for the first time in an upflow anaerobic sludge bed (UASB) reactor to reach the efficacy of maximum nitrate-to-nitrite transformation ratio of 92% and an in-situ maximum NO3--N reduction rate of 2.46 kg-N/m3-d, both much higher than literature results. Mature granules had an average particle size of 2.52 mm and hold smooth surface with excess rod bacteria. The elements Ca and S, and proteins in extracellular polymeric substances contributed to granule structure's stability. Enriched Thiobacillus genus was proposed to accumulate nitrite at moderate HRT (2-6 h). The immobilized functional strains assist efficient partial nitrification reactions to be realized with formed S0 as byproduct.
Assuntos
Nitritos , Águas Residuárias , Reatores Biológicos , Desnitrificação , Nitratos , Nitritos/análise , Nitrogênio , Oxirredução , Esgotos , Sulfetos , Águas Residuárias/análiseRESUMO
This study for the first time bioreduced Te(IV) using elemental sulfur (S0) as electron donor, achieving 91.17%±0.8% conversion with reaction rate of 0.77 ± 0.01 mg/L/h in a 60-day cultivation. Characterization using X-ray photoelectron spectroscopy and X-ray power diffraction analyses confirmed that most removed Te(IV) was reduced to elemental Te(0) deposits, while ion chromatogram analysis showed that most S(0) was oxidized to sulfite and sulfate. High-throughput 16S rRNA gene sequencing indicated that the Te(IV) reduction coupled to S(0) oxidation was mediated synergistically by a microbial consortia with S(0)-oxidizing bacteria (Thiobacillus) to generate volatile fatty acids as metabolites and Te(IV)-reducing bacteria (Rhodobacter) to consume formed volatile fatty acids to yield Te(0). The synergy between these two strains presents a novel bioremediation consortium to efficiently treat Te(IV) wastewaters.
Assuntos
Elétrons , Enxofre , Oxirredução , RNA Ribossômico 16S/genética , SulfatosRESUMO
Pyridine and its derivatives are widely consumed and detected in the environment persistently, which can cause potential adverse impacts on environment and human health. Considering the fact that pyridine could absorb UV light at 254 nm to generate excited one, which could react with reductive radicals, promoting its structural changes, we proposed that one typical efficient advanced reduction process (ARP) which combines UV irradiation with sulfite could be used to eliminate pyridine quickly. Sulfite/UV process showed a higher pyridine removal rate with a pseudo-first-order reaction rate constant of 0.1439 min-1, which was 3 times of that in UV irradiation and 1.3 times in UV/H2O2 process. This was primarily due to reductive radicals (eaq-, H⢠and SO3â¢-) produced by UV irradiation. The removal rate of pyridine was highest in slightly alkaline environment. And the presence of oxygen, as well as certain concentration of humid acid just showed slight inhibition, indicating the possibility of application in practical environment. A positive impact was observed with increasing sulfite dosage, but it was gradually inhabited when the dosage was over 5 mM. The present study may provide an alternative efficient technology for the degradation of pyridine ring-containing substances.
Assuntos
Poluentes Químicos da Água , Purificação da Água , Humanos , Peróxido de Hidrogênio , Oxirredução , Piridinas , Raios Ultravioleta , Poluentes Químicos da Água/análiseRESUMO
Denitrification and dissimilatory nitrate reduction to ammonium (DNRA) are two competing pathways in nitrate-reducing process. In this study, a series of C/S ratios from 8:1 to 2:4 were investigated in a sequencing biofilm batch reactor (SBBR) to determine the role of reducers (sulfide and acetate) on their competition. The results showed that the proportion of DNRA increased in high electron system, either in organic-rich system or in sulfide-rich system. The highest DNRA ratio increased to 16.4% at the C/S ratio of 2:3. Excess electron donors, particularly sulfide, were favorable for DNRA in a limited nitrate environment. Moreover, a higher reductive environment could facilitate DNRA, especially, when ORP was lower than - 400 mV in this system. 16S rRNA gene sequencing analysis demonstrated that Geobacter might be the important participant involved in DNRA process in organic-rich system, while Desulfomicrobium might be the dominant DNRA bacteria in sulfide-rich system. DNRA cultivation could enrich nitrogen conversion pathways in conventional denitrification systems and deepen the insight into nitrogen removal at low C/N.
Assuntos
Compostos de Amônio , Nitratos , Compostos de Amônio/metabolismo , Biofilmes , Desnitrificação , Humanos , Nitratos/metabolismo , Nitrogênio , Oxirredução , RNA Ribossômico 16S/metabolismo , SulfetosRESUMO
Pyrethroid pesticides, with low toxicity to birds and mammals and short persistence in the environment, are widely used now. With the development of intensive poultry farming, pesticide application leads to residues in poultry products and pollution in ecological environment. The aim of the present study was to examine deltamethrin subchronic toxicity in laying chickens. One hundred and twelve laying chickens were randomly assigned to 14 groups including 13 groups medicated with deltamethrin (n = 8) and one unmedicated group used as control (n = 8). Tissue samples were collected during and after administration for weighing and histopathological analysis. A single dose of deltamethrin (20 mg·kg-1·BW·d) was administered orally to laying chickens for 14 days. The results showed that deltamethrin has no significant effect on the relative organ weight of laying chickens (p > 0.05). The activities of aspartate aminotransferase and cholinesterase in the plasma gradually decreased over time in the medicated group (p < 0.05). Plasma concentrations of urea nitrogen, uric acid, cholesterol, triglycerides, and creatinine significantly increased during treatment (p < 0.05), and significant liver damage and loss of intestinal villous epithelium were observed. The intestinal wall thickness, villus height, and crypt depth of laying chickens were altered by deltamethrin treatment. During treatment was withdrawn, the intestinal repair was more extensive than the liver repair.
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In this study, an ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed for the residue depletion of imidocarb (IMD) in bovine tissues, and the drug withdrawal time of IMD was determined. Twenty-five clinically healthy cattle (body weight 300 kg ± 15 kg) were randomly divided into five groups of five cattle each. The cattle were treated subcutaneously injecting a single dose of a generic IMD formulation, at the recommended dosage of 3.0 mg/kg. The five groups of cattle were slaughtered respectively at 96, 160, 198, 213, and 228 days after IMD administration. Samples from the liver, kidney, muscle, fat, and injection site were collected from each animal. After subtilis proteinase was used to digest the tissue, the content of IMD in the samples was analyzed by UPLC-MS/MS method. In conclusion, the method validation results showed that the method meets the criteria, and the longest withdrawal time of 224 days for the liver can be selected as the conclusive withdrawal time to guarantee consumer safety.
RESUMO
Imidocarb (IMD) is commonly used for treatment of eperythrozoon, babesia, piroplasma and trypanosoma in animals, but there are few studies on its pharmacokinetics in cattle. The purpose of this study was to obtain pharmacokinetic parameters and assess the bioequivalence of subcutaneous injections of two IMD formulations in cattle. Forty-eight healthy cattle, 24 males and 24 females, were randomLy divided into two groups (test group and reference group) with 12 males and 12 females per group. The generic IMD was injected subcutaneously with a single dose of 3.0 mg/kg in the test group. Reference group animals were given one injection of the marketed IMD at the same dosage. The limit of detection (LOD) and limit of quantification (LOQ) for IMD in cattle plasma were 0.05 ng/mL and 0.1 ng/mL, respectively. The recoveries ranged from 88.50% to 92.42%, and the equation of this calibration curve was Y = 13672.1X+187.43. The pharmacokinetics parameters of the test group showed that the maximum concentration of 2257.5±273.62 ng/mL was obtained at 2.14±0.67 h, AUC0-t 14553.95±1946.85 ng·h/mL, AUC∞ 15077.88±1952.19 ng·h/mL, T1/2 31.77±25.75 h, CL/F 0.14±0.02 mL/h/g, and Vz/F 6.53±5.34 mL/g. There was no significant difference in AUC0-t, AUC∞ and Cmax between the test group and the reference group (P>0.05). The 90% confidence interval of AUC0-t, AUC0-∞ and Cmax in the test group was included in 80%-125% AUC0-t, AUC0-∞ and 70%-143% Cmax in the reference group, respectively. Based on these results, the two preparations were found to be bioequivalent.
Assuntos
Imidocarbo , Animais , Bovinos , Feminino , Masculino , Área Sob a Curva , Estudos Cross-Over , Injeções Subcutâneas , Comprimidos , Equivalência TerapêuticaRESUMO
Waste sludge lysate was produced by dehydration after pyrolysis of waste activated sludge. In addition to dominant components such as protein, polysaccharide, and volatile fatty acids (VFAs), it also contained melanoidins, which produced from Maillard reaction. The inclusion of melanoidins will lead to poor biological degradation in conventional anaerobic digestion (AD). While microbial electrolysis cell (MEC) was proved an enhanced degradation of complex organic matter for hydrogen production. The results showed that under high concentration conditions, conventional AD caused the accumulation of propionic acid and slowed down the use of acetic acid, but MEC overcame the defects and increased the chemical oxygen demand (COD) removal efficiency by 40.33%, and achieved average hydrogen production rate (0.15 ± 0.05 L L-1 day-1), which was 79 times that of AD system (0.0019 ± 0.0009 L L-1 day-1). Therefore, MEC can enhanced biodegradation of the waste sludge lysate for high hydrogen production.
Assuntos
Reatores Biológicos , Esgotos , Anaerobiose , Eletrólise , Ácidos Graxos Voláteis , Hidrogênio , MetanoRESUMO
The growth of bacteria will lead to water quality deterioration and equipment damage. Therefore, it is necessary to control the growth and reproduction of microorganisms in water treatment. A new type of magnetic recoverable CuZnO@Fe3O4@GO composites was prepared by ultrasonic method, and the composites were characterized and analyzed by SEM, TEM, XPS, and other methods. The optimum mass ratio of composites was determined by orthogonal experiment, and the antibacterial properties and mechanism of the composite were investigated by gram-positive bacteria Staphylococcus aureus and gram-negative bacteria Escherichia coli. Finally, the antibacterial properties of the composites in the effluent of the secondary sedimentation tank were researched. It was shown that the optimum mass ratio of the composites was GO:Fe3O4:CuZnO =1:2:3. When the dosage of composites was 180 mg L-1 and the action time was 100 min, the antibacterial rate against S. aureus and E. coli reached more than 99.5%. The composites could destroy the cell structure of two kinds of bacteria, increase the content of active oxygen in bacteria cells, and enhance the leakage rate of protein by more than 9 times in 150 min, thereby causing the death of the bacteria. And the antibacterial rate of the composites in effluent of the secondary sedimentation tank could reach 99%, and the magnetic recovery rate could reach more than 98%. After 5 cycles of use, the antibacterial rate could still exceed 90%.