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Resultados 1541-1550 de 3,243
Isolation and Characterization of an Erythromycin-Degrading Strain and Application for Bioaugmentation in a Biological Aerated Filter
2015
Gao, Pin | Wei, Xin | Gu, Chaochao | Wu, Xiaoqian | Xue, Gang | Shi, Weimin | Sun, Weimin
An erythromycin-degrading bacterium was isolated from the activated sludge of a sewage treatment plant (STP). Based on the morphological and physiological characteristics, the isolated strain was identified and named as Pseudomonas sp. ERY-E. In an inorganic salt medium inoculated at 1 % (v/v) of ERY-E strain containing 50 mg/L of erythromycin (ERY), the removal efficiency of ERY as high as 83.7 % was obtained under the optimum conditions with temperature of 30 °C, pH of 7.0, and 10 mg/L of yeast as the external carbon source. Subsequently, the ERY-E strain was used for bioaugmenting a biological aerated filter (BAF) to treat surface water containing low-concentration ERY. The influence of hydraulic retention time (HRT) and air-liquid ratio (A/L) on the performance of BAF was investigated. The average removal efficiencies of ERY and permanganate index (CODMₙ) were about 60.6 and 26.1 % in bioaugmented system (BAF₂) and 26.9 and 26.0 % in unbioaugmented system (BAF₁), respectively, under the optimum conditions with HRT of 4.0 h and A/L of 4:1 at steady state. Due to the stable removal of CODMₙ in BAF₂ as compared with BAF₁, it can be concluded that the introduction of ERY-E strain could collaborate with the indigenous microorganisms to attain a better ERY removal efficiency. As a result, the bioaugmented BAF method can be considered as an alternative technology for the treatment of surface water containing low-concentration emerging pollutants.
Mostrar más [+] Menos [-]Can Simple Soil Parameters Explain Field-Scale Variations in Glyphosate-, Bromoxyniloctanoate-, Diflufenican-, and Bentazone Mineralization?
2015
Norgaard, Trine | de Jonge, Lis W. | Moldrup, Per | Olsen, Preben | Johnsen, Anders R.
The large spatial heterogeneity in soil physico-chemical and microbial parameters challenges our ability to predict and model pesticide leaching from agricultural land. Microbial mineralization of pesticides is an important process with respect to pesticide leaching since mineralization is the major process for the complete degradation of pesticides without generation of metabolites. The aim of our study was to determine field-scale variation in the potential for mineralization of the herbicides glyphosate, bromoxyniloctanoate, diflufenican, and bentazone and to investigate whether this variation can be predicted by variations in basic soil parameters. Sixty-five soil samples were sampled from an agricultural, loamy field in Silstrup, Denmark, from a 60 × 165 m rectangular grid. The mineralization potential of the four pesticides was determined using a 96-well microplate ¹⁴C-radiorespirometric method. Initial mineralization rates were determined using first-order kinetics for glyphosate and bromoxyniloctanoate and zero-order kinetics for diflufenican and bentazone. The mineralization rates of the four pesticides varied between the different pesticides and the different soil samples, but we could not establish correlations between the pesticide mineralization rates and the measured soil parameters. Only the glyphosate mineralization rates showed slightly increasing mineralization potentials towards the northern area of the field, with increasing clay and decreasing OC contents. The mineralization potentials for glyphosate and bentazone were compared with 9-years leaching data from two horizontal wells 3.5 m below the field. The field-scale leaching patterns, however, could not be explained by the pesticide mineralization data. Instead, field-scale pesticide leaching may have been governed by soil structure and preferential flow events.
Mostrar más [+] Menos [-]Nitrogen-Regulated Interactions Between Microcystis aeruginosa and Spiramycin Contaminant
2015
Liu, Ying | Chen, Shi | Zhang, Jian | Gao, Baoyu
Nitrogen significantly regulated (p < 0.05) the effects of spiramycin on the growth and antioxidant responses of Microcystis aeruginosa as well as the biodegradation of spiramycin by M. aeruginosa during a 7-day exposure test. At a nitrogen level of 0.5 mg L⁻¹, the activities of superoxide dismutase and catalase were stimulated by 100–400 ng L⁻¹of spiramycin to protect algal cells from oxidative damage, resulting in alleviated toxicity of spiramycin and low malondialdehyde content in M. aeruginosa. The catalase activity was inhibited by 400 ng L⁻¹of spiramycin at higher nitrogen levels of 5–50 mg L⁻¹, leading to significant growth inhibition (p < 0.05) and higher malondialdehyde content through accumulation of hydrogen peroxide. Stimulated glutathione content and glutathione S-transferase activity were coupled to the biodegradation of spiramycin in M. aeruginosa. The 7-day biodegradation percentage of spiramycin varied from 8.9 to 29.6 %, which was enhanced by increased nitrogen concentration and decreased spiramycin concentration. Due to the regulation of algal growth, the toxicity of M. aeruginosa were significantly enhanced (p < 0.05) by 100 ng L⁻¹of spiramycin at a nitrogen concentration of 0.5 mg L⁻¹while significantly reduced (p < 0.05) by 400 ng L⁻¹of spiramycin at nitrogen levels of 5–50 mg L⁻¹, according to the luminescent bacteria test. Low concentration of coexisting spiramycin contaminant should be considered during the control of M. aeruginosa bloom, especially under nitrogen deficient condition.
Mostrar más [+] Menos [-]Displacement of Br− and P22 in a Wetland Environment
2015
Vidales-Contreras, Juan A. | Rodríguez Fuentes, Humberto | Luna-Maldonado, Alejandro I. | Hernandez-Escareño, Jesus J.
Relative displacement of bromide (Br⁻) and coliphage P22 was analyzed in surface water and vadose zone solution from a 3-ha surface flow constructed wetland. In the vadose zone, water samples at 0.3-, 0.76-, 1.5-, and 3-m depth were collected to quantify Br⁻ and P22 simultaneously added into the wetland influent for a transport study. When P22 was detected, Br⁻ arrived earlier to the monitoring depths than the phage suggesting that preferential flow facilitated P22 displacement in the vadose zone. Concentrations for both tracers indicated that bacteriophage removal through the vadose zone profile was exceeding 99.21 % of the peak concentration observed in surface water samples. For transport parameter estimation, the temporal moment method (MOM) was used to calculate convective velocity (v) and longitudinal dispersion coefficient (D) from the outlet Br⁻ breakthrough curve. The transport parameters were estimated to be 55.7 m day⁻¹ and 1652 m² day⁻¹ for v and D, respectively. For P22 simulation, a first-order removal coefficient of 0.3 day⁻¹ (R ² = 0.943) was assessed. The observed results suggest that this method can be applied for solute transport simulation in constructed wetlands.
Mostrar más [+] Menos [-]Ectomycorrhizal Community Structure of Salix and Betula spp. at a Saline Site in Central Poland in Relation to the Seasons and Soil Parameters
2015
Hrynkiewicz, Katarzyna | Szymańska, Sonia | Piernik, Agnieszka | Thiem, Dominika
Saline stress is one of the most important abiotic factors limiting the growth and development of plants and associated microorganisms. While the impact of salinity on associations of arbuscular fungi is relatively well understood, knowledge of the ectomycorrhizal (EM) fungi of trees growing on saline land is limited. The main objective of this study was to determine the density and diversity of EM fungi associated with three tree species, Salix alba, Salix caprea and Betula pendula, growing in saline soil during two seasons, autumn and spring. The site was located in central Poland, and the increased salinity of the soil was of anthropogenic origin from soda production. The degree of EM colonisation of fine root tips varied between 9 and 34 % and depended on the tree species of interest (S. caprea < S. alba < B. pendula) and season (spring < autumn). Moreover, the ectomycorrhizal colonisation of B. pendula was positively correlated with pH and CaCO₃, while for S. caprea and S. alba, colonisation was associated with most of the other soil parameters investigated; e.g. salinity, Cₒᵣgand N. Analysis of EM fungi revealed four to five different morphotypes per each season: Tomentella sp. Sa-A, Hebeloma collariatum Sc-A, Geopora sp. Sc-A, Helotiales sp. Bp-A in the autumn and Tomentella sp. Sa-S, Tomentella sp. Sc-S and three morphotypes from the families Thelephoraceae and Pyronemataceae in the spring. In conclusion, the density of EM is related to the level of salinity (ECₑ), season and tree species. Tomentella spp., Hebeloma sp., Geopora sp. and Helotiales sp. are groups of species highly adapted to saline conditions.
Mostrar más [+] Menos [-]Gene Expression of Secale cereale (Fall Rye) Grown in Petroleum Hydrocarbon (PHC) Impacted Soil With and Without Plant Growth-Promoting Rhizobacteria (PGPR), Pseudomonas putida
2015
Gurska, Jolanta | Glick, Bernard R. | Greenberg, Bruce M.
Phytoremediation employs plants to sequester, degrade, and transform contaminants. This remediation technology depends on sufficient plant growth, often not achievable with high contaminant concentrations. One way to improve plant growth on impacted soils is by using plant growth-promoting rhizobacteria (PGPR). PGPR are naturally occurring soil microbes that stimulate plant growth through variety of means. We examined what changes in gene expression occurred in a grass species Secale cereale treated with PGPR, Pseudomonas putida PGPR (UW4), grown in petroleum hydrocarbon (PHC) impacted soil. UW4 promoted plant growth on the PHC impacted soil. Using differential display polymerase chain reaction (ddPCR), six genes were identified based on their altered expression as an effect of PHC exposure and plant PGPR treatment. The changes in levels of expression of selected genes were measured using quantitative PCR (qPCR). There was upregulation of all six genes examined, two of which were statistically significant. In roots, two genes were upregulated significantly and one gene appeared to be downregulated.
Mostrar más [+] Menos [-]CO2 Capture on Metallic Oxide Powders Prepared Through Chemical Combustion and Calcination Methods
2015
Granados-Correa, F. | Bonifacio-Martínez, J. | Hernández-Mendoza, H. | Bulbulian, S.
Mg, Zn, Mn, and Al oxide powders have been synthesized through chemical combustion and calcination methods to compare their CO₂ capture performances. The characteristic properties of the adsorbents were evaluated by X-ray diffraction analysis, scanning electron microscopy, and N₂ physisorption measurements. The porous γ-Al₂O₃ prepared through combustion with a BET-specific surface area of 192.1 m²/g, achieving a maximum gas adsorption capacity of 1.71 mmol/g at 60 °C and 1.5 MPa. The MgO adsorbent performed poorly during CO₂ capture, while that Zn and Mn oxides showed no CO₂ adsorption. The results showed theoretical contribution to the field of separation science.
Mostrar más [+] Menos [-]Pilot-Scale Investigation of Micropollutant Removal with Granular and Powdered Activated Carbon
2015
Meinel, F. | Ruhl, A. S. | Sperlich, A. | Zietzschmann, F. | Jekel, M.
Activated carbon is investigated as adsorptive barrier for organic micropollutants (OMP) within the Berlin water cycle. In a pilot plant using granular activated carbon (GAC) as upper layer in dual-media filtration, OMP concentrations in treated wastewater could be reduced without any negative impact on filtration efficiency. OMP breakthroughs occurred after shorter runtimes than estimated according to isotherm experiments with powdered activated carbon (PAC). Batch adsorption tests comparing the used GAC to new GAC showed that the capacity of the used GAC was not exhausted, indicating that besides direct site competition, pore blocking is also responsible for the poor GAC performance. A pilot plant application of PAC of the same type as GAC showed significantly higher OMP removals at lower dosages, taking advantage of immobilization of PAC particles in the filters. Both PAC and GAC applications can be integrated into tertiary wastewater treatment without significant constructional changes.
Mostrar más [+] Menos [-]Experimental Design and Process Optimization for Uranium Polluted Soils Decontamination by Acid Washing
2015
Radu, Aura Daniela | Panturu, Eugenia | Woinaroschy, Alexandru | Isopescu, Raluca
Uranium soil depollution is of great concern as, like any other radionuclide, it may accumulate in time and generate a negative impact on human health. There are several decontamination technologies, among these the acid washing still in use for its simplicity and low cost. Though a classical method, it still can be improved by using the best operating conditions to increase the decontamination degree. The present study aims to propose an optimization approach based on experimental design. The investigation takes into account the main operating parameters (duration, temperature, and pH) and the soil characteristics (texture and organic matter content). This work presents an “ex situ” uranium-contaminated soil treatment using a 0.1 M H₂SO₄solution with pulp density of 0.5. The experiments followed a 2³factorial design for the evaluation of factors and interaction effects. The factors’ influence differed from one type of soil to another. The 2³experiment was augmented using a non-central composite design that allowed the formulation of a second degree model for the response surface. The best values for the operating parameters were identified using optimization procedures. Statistical modelling and optimization were performed in Matlab® v7.7. The results obtained proved that the soil type is very important for selecting better operating conditions. These improvements determined an increased decontamination degree of up to 10–13 % compared with standard operating conditions that were considered as central point in the experimental plan.
Mostrar más [+] Menos [-]Efficient Adsorptive Removal of Humic Acid from Water Using Zeolitic Imidazole Framework-8 (ZIF-8)
2015
Lin, Kun-Yi Andrew | Chang, Hsuan-Ang
To develop an efficient adsorbent for humic acid, the present study represents the first attempt to investigate the capability of zeolitic imidazole frameworks to remove humic acid from water. Zeolitic imidazole framework-8 (ZIF-8) is particularly selected as a prototype ZIF to adsorb humic acid owing to its high stability in aqueous solutions. ZIF-8 was synthesized and characterized using scanning electronic microscopy (SEM), powder X-ray diffraction pattern (PXRD), Fourier transform infrared spectroscopy (FT-IR), and thermogravimetric analyzer (TGA) and then used to adsorb humic acid under various conditions. The structure of ZIF-8 was found to remain intact after the exposure to humic acid in water. Factors affecting the adsorption were examined, including solid-to-liquid ratio, mixing time, temperature, pH, presence of salt, and surfactants. The adsorption capacity of ZIF-8 was found to be much higher than that of activated carbon, fly ash, zeolites, graphite, etc., showing its promising potential for removal of humic acid. The adsorption mechanism could be attributed to the electrostatic interaction between the positive surface of ZIF-8 and the acidic sites of humic acid, as well as the π–π stacking interaction between imidazole of ZIF-8 and benzene rings of humic acid. The humic acid adsorption to ZIF-8 could be enhanced in the acidic conditions, and the adsorption process remained highly stable in the solutions of a wide range of NaCl concentrations. ZIF-8 can be also regenerated by simple ethanol-washing process and reused for humic acid adsorption. These features enable ZIF-8 to be an efficient and stable adsorbent to remove humic acid from water.
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