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1.
● Simultaneous NH4+/NO3– removal was achieved in the FeS denitrification system ● Anammox coupled FeS denitrification was responsible for NH4+/NO3– removal ● Sulfammox, Feammox and Anammox occurred for NH4+ removal ● Thiobacillus, Nitrospira , and Ca. Kuenenia were key functional microorganisms An autotrophic denitrifying bioreactor with iron sulfide (FeS) as the electron donor was operated to remove ammonium (NH 4+) and nitrate (NO 3−) synergistically from wastewater for more than 298 d. The concentration of FeS greatly affected the removal of NH 4+/NO 3−. Additionally, a low hydraulic retention time worsened the removal efficiency of NH 4+/NO 3−. When the hydraulic retention time was 12 h, the optimal removal was achieved with NH 4+ and NO 3− removal percentages both above 88%, and the corresponding nitrogen removal loading rates of NH 4+ and NO 3− were 49.1 and 44.0 mg/(L·d), respectively. The removal of NH 4+ mainly occurred in the bottom section of the bioreactor through sulfate/ferric reducing anaerobic ammonium oxidation (Sulfammox/Feammox), nitrification, and anaerobic ammonium oxidation (Anammox) by functional microbes such as Nitrospira, Nitrosomonas, and Candidatus Kuenenia. Meanwhile, NO 3− was mainly removed in the middle and upper sections of the bioreactor through autotrophic denitrification by Ferritrophicum, Thiobacillus, Rhodanobacter, and Pseudomonas, which possessed complete denitrification-related genes with high relative abundances. 相似文献
2.
Managers of small populations often need to estimate the expected time to extinction T e of their charges. Useful models for extinction times must be ecologically realistic and depend on measurable parameters. Many populations become extinct due to environmental stochasticity, even when the carrying capacity K is stable and the expected growth rate is positive. A model is proposed that gives T e by diffusion analysis of the log population size n t (= log e N t). The model population grows according to the equation N t+1 = R tN t, with K as a ceiling. Application of the model requires estimation of the parameters k = logK, r d = the expected change in n, v r = Variance(log R), and ϱ the autocorrelation of the r t. These are readily calculable from annual census data (r d is trickiest to estimate). General formulas for T e are derived. As a special case, when environmental fluctuations overwhelm expected growth (that is r d 0), T e = 2n o(k - n o/2)/v r. If the r t are autocorrelated, then the effective variance is v re v r (1 + ϱ)/(1 - ϱ). The theory is applied to populations of checkerspot butterfly, grizzly bear, wolf, and mountain lion. 相似文献
3.
The mean and variance of lifetime reproductive success, E LRS and V LRS, influence the ratio of effective to census population size, N e/N c. Because the complete data needed to calculate E LRS and V LRS are seldom available, we provide alternatives for estimating N e/N c from incomplete data. These estimates should be useful to conservation biologists trying to compute the effective size of a censused population. An analytical approach makes assumptions regarding the process influencing offspring survival. We provide a method for examining the validity of those assumptions and show that particular violations can result in either over- or underestimates. When the assumptions are violated or when more data are available, we suggest estimating N e/N c using computer simulations of models based on individuals. We examine how such simulations can be used to estimate N e/N c using an individual-based model for Lesser Snow Geese ( Anser caerulescens ). We demonstrate that such estimates can be biased unless the simulations are based on complete cohorts and samples of known age. We show that because the estimate of N e/N c depends on the stage of the reproductive cycle used as a point of reference in the model, the census population size N c must be based on the same stage to provide unbiased estimates of N e. 相似文献
4.
• CeO2 doping significantly improved low-temperature NH3-SCR activity on FeTiOx. • The crystallinity of FeTiOx was decreased dramatically after CeO2 doping. • Unique Ce-O-Fe structure in FeCe0.2TiOx accounted for its superior redox property. • Facile activation of NH3 to-NH2 on FeCe0.2TiOx promoted the DeNOx efficiency. FeTiO x has been recognized as an environmental-friendly and cost-effective catalyst for selective catalytic reduction (SCR) of NO x with NH 3. Aimed at further improving the low-temperature DeNO x efficiency of FeTiO x catalyst, a simple strategy of CeO 2 doping was proposed. The low-temperature (<250℃) NH 3-SCR activity of FeTiO x catalyst could be dramatically enhanced by CeO 2 doping, and the optimal composition of the catalyst was confirmed as FeCe 0.2TiO x, which performed a NO x conversion of 90% at ca. 200℃. According to X-ray diffraction (XRD), Raman spectra and X-ray absorption fine structure spectroscopy (XAFS) analysis, FeCe 0.2TiO x showed low crystallinity, with Fe and Ce species well mixed with each other. Based on the fitting results of extended X-ray absorption fine structure (EXAFS), a unique Ce-O-Fe structure was formed in FeCe 0.2TiO x catalyst. The well improved specific surface area and the newly formed Ce-O-Fe structure dramatically contributed to the improvement of the redox property of FeCe 0.2TiO x catalyst, which was well confirmed by H 2-temperature-programmed reduction (H 2-TPR) and in situ XAFS experiments. Such enhanced redox capability could benefit the activation of NO and NH 3 at low temperatures for NO x removal. The detailed reaction mechanism study further suggested that the facile oxidative dehydrogenation of NH 3 to highly reactive-NH 2 played a key role in enhancing the low-temperature NH 3-SCR performance of FeCe 0.2TiO x catalyst. 相似文献
5.
MC-LR removal performances under different AOPs were compared systematically. Higher removal efficiency and synergistic effects were obtained by combined process. The acute biotoxicity raised in different degrees after oxidation. ![]() Microcystin-LR attracts attention due to its high toxicity, high concentration and high frequency. The removal characteristics of UV/H 2O 2 and O 3/H 2O 2 advanced oxidation processes and their individual process for MC-LR were investigated and compared in this study. Both the removal efficiencies and rates of MC-LR as well as the biotoxicity of degradation products was analyzed. Results showed that the UV/H 2O 2 process and O 3/H 2O 2 were effective methods to remove MC-LR from water, and they two performed better than UV-, O 3-, H 2O 2-alone processes under the same conditions. The effects of UV intensity, H 2O 2 concentration and O 3 concentration on the removal performance were explored. The synergistic effects between UV and H 2O 2, O 3 and H 2O 2 were observed. UV dosage of 1800 mJ·cm −2 was required to remove 90% of 100 mg·L −1 MC-LR, which amount significantly decreased to 500 mJ·cm −2 when 1.7 mg·L −1 H 2O 2 was added. 0.25 mg·L −1 O 3, or 0.125 mg·L −1 O 3 with 1.7 mg·L −1 H 2O 2 was needed to reach 90% removal efficiency. Furthermore, the biotoxicity results about these UV/H 2O 2, O 3/H 2O 2 and O 3-alone processes all present rising trends with oxidation degree of MC-LR. Biotoxicity of solution, equivalent to 0.01 mg·L −1 Zn 2+, raised to 0.05 mg·L −1 Zn 2+ after UV/H 2O 2 or O 3/H 2O 2 reaction. This phenomenon may be attributed to the aldehydes and ketones with small molecular weight generated during reaction. Advice about the selection of MC-LR removal methods in real cases was provided. 相似文献
9.
为研究乌鲁木齐市米东区大气降水中的化学组分特征及来源,对2017-2019年降水中主要离子浓度及来源进行了分析.研究结果显示,米东区2017-2019年降水的雨量加权pH年均值为7.95,雨量加权平均电导率年均值为16.15 mS·m-1,雨量加权平均总离子浓度为72.75-95.89 μeq·L-1,年均浓度为81.... 相似文献
10.
•CeOx/GF-EP process had the better degradation efficiency than GF-EP process. •CeOx/GF-EP process had the flexible application in the pH range from 5.0 to 9.0. •CeOx could enhance surface hydrophilicity and reduce the charge-transfer resistance. •The interfacial electron transfer process was revealed. E-peroxone (EP) was one of the most attractive AOPs for removing refractory organic compounds from water, but the high energy consumption for in situ generating H 2O 2 and its low reaction efficiency for activating O 3 under acidic conditions made the obstacles for its practical application. In this study, cerium oxide was loaded on the surface of graphite felt (GF) by the hydrothermal method to construct the efficient electrode (CeO x/GF) for mineralizing carbamazepine (CBZ) via EP process. CeO x/GF was an efficient cathode, which led to 69.4% TOC removal in CeO x/GF-EP process with current intensity of 10 mA in 60 min. Moreover, CeO x/GF had the flexible application in the pH range from 5.0 to 9.0, TOC removal had no obvious decline with decrease of pH. Comparative characterizations showed that CeO x could enhance surface hydrophilicity and reduce the charge-transfer resistance of GF. About 5.4 mg/L H 2O 2 generated in CeO x/GF-EP process, which was 2.1 times as that in GF-EP process. The greater ozone utility was also found in CeO x/GF-EP process. More O 3 was activated into hydroxyl radicals, which accounted for the mineralization of CBZ. An interfacial electron transfer process was revealed, which involved the function of oxygen vacancies and Ce 3+/Ce 4+ redox cycle. CeO x/GF had the good recycling property in fifth times’ use. 相似文献
13.
• CW-Fe allowed a high-performance of NO3‒-N removal at the COD/N ratio of 0. • Higher COD/N resulted in lower chem-denitrification and higher bio-denitrification. • The application of s-Fe0 contributed to TIN removal in wetland mesocosm. • s-Fe0 changed the main denitrifiers in wetland mesocosm. ![]() Sponge iron (s-Fe 0) is a porous metal with the potential to be an electron donor for denitrification. This study aims to evaluate the feasibility of using s-Fe 0 as the substrate of wetland mesocosms. Here, wetland mesocosms with the addition of s-Fe 0 particles (CW-Fe) and a blank control group (CW-CK) were established. The NO 3‒-N reduction property and water quality parameters (pH, DO, and ORP) were examined at three COD/N ratios (0, 5, and 10). Results showed that the NO 3‒-N removal efficiencies were significantly increased by 6.6 to 58.9% in the presence of s-Fe 0. NH 4+-N was mainly produced by chemical denitrification, and approximately 50% of the NO 3‒-N was reduced to NH 4+-N, at the COD/ratio of 0. An increase of the influent COD/N ratio resulted in lower chemical denitrification and higher bio-denitrification. Although chemical denitrification mediated by s-Fe 0 led to an accumulation of NH 4+-N at COD/N ratios of 0 and 5, the TIN removal efficiencies increased by 4.5%‒12.4%. Moreover, the effluent pH, DO, and ORP values showed a significant negative correlation with total Fe and Fe (II) ( P<0.01). High-throughput sequencing analysis indicated that Trichococcus (77.2%) was the most abundant microorganism in the CW-Fe mesocosm, while Thauera, Zoogloea, and Herbaspirillum were the primary denitrifying bacteria. The denitrifiers, Simplicispira, Dechloromonas, and Denitratisoma, were the dominant bacteria for CW-CK. This study provides a valuable method and an improved understanding of NO 3‒-N reduction characteristics of s-Fe 0 in a wetland mesocosm. 相似文献
14.
● Systematic information of recent progress in photocatalytic NO x removal is provided. ● The photocatalysts with special morphologies are reviewed and discussed. ● The morphology and photocatalytic NO x removal performance is related. The significant increase of NO x concentration causes severe damages to environment and human health. Light-driven photocatalytic technique affords an ideal solution for the removal of NO x at ambient conditions. To enhance the performance of NO x removal, 1D, 2D and 3D photocatalysts have been constructed as the light absorption and the separation of charge carriers can be manipulated through controlling the morphology of the photocatalyst. Related works mainly focused on the construction and modification of special morphologic photocatalyst, including element doping, heterostructure constructing, crystal facet exposing, defect sites introducing and so on. Moreover, the excellent performance of the photocatalytic NO x removal creates great awareness of the application, which has promising practical applications in NO x removal by paint (removing NO x indoor and outdoor) and pavement (degrading vehicle exhausts). For these considerations, recent advances in special morphologic photocatalysts for NO x removal was summarized and commented in this review. The purpose is to provide insights into understanding the relationship between morphology and photocatalytic performance, meanwhile, to promote the application of photocatalytic technology in NO x degradation. 相似文献
16.
Membrane bioreactor achieved mercury removal using nitrate as an electron acceptor. The biological mercury oxidation increased with the increase of oxygen concentration. Ferrous sulfide could make both Hg2+ and MeHg transform into HgS-like substances. Nitrate drives mercury oxidation through katE, katG, nar, nir, nor, and nos. Mercury (Hg 0) is a hazardous air pollutant for its toxicity, and bioaccumulation. This study reported that membrane biofilm reactor achieved mercury removal from flue gas using nitrate as the electron acceptor. Hg 0 removal efficiency was up to 88.7% in 280 days of operation. Oxygen content in flue gas affected mercury redox reactions, mercury biooxidation and microbial methylation. The biological mercury oxidation increased with the increase of oxygen concentration (2%‒17%), methylation of mercury reduced with the increase of oxygen concentration. The dominant bacteria at oxygen concentration of 2%, 6%, 17%, 21% were Halomonas, Anaerobacillus, Halomonas and Pseudomonas, respectively. The addition of ferrous sulfide could immobilize Hg 2+ effectively, and make both Hg 2+ and MeHg transform into HgS-like substances, which could achieve the inhibition effect of methylation, and promote conversion of mercury. The dominant bacteria changed from Halomonas to Planctopirus after FeS addition. Nitrate drives mercury oxidation through katE, katG, nar, nir, nor, and nos for Hg 0 removal in flue gas. 相似文献
17.
• UV/VUV/I– induces substantial H2O2 and IO3– formation, but UV/I– does not. • Increasing DO level in water enhances H2O2 and iodate productions. • Increasing pH decreases H2O2 and iodate formation and also photo-oxidation. • The redox potentials of UV/VUV/I– and UV/VUV changes with pH changes. • The treatability of the UV/VUV/I– process was stronger than UV/VUV at pH 11.0. Recently, a photochemical process induced by ultraviolet (UV), vacuum UV (VUV), and iodide (I –) has gained attention for its robust potential for contaminant degradation. However, the mechanisms behind this process remain unclear because both oxidizing and reducing reactants are likely generated. To better understand this process, this study examined the evolutions of hydrogen peroxide (H 2O 2) and iodine species (i.e., iodide, iodate, and triiodide) during the UV/VUV/I – process under varying pH and dissolved oxygen (DO) conditions. Results show that increasing DO in water enhanced H 2O 2 and iodate production, suggesting that high DO favors the formation of oxidizing species. In contrast, increasing pH (from 6.0 to 11.0) resulted in lower H 2O 2 and iodate formation, indicating that there was a decrease of oxidative capacity for the UV/VUV/I – process. In addition, difluoroacetic acid (DFAA) was used as an exemplar contaminant to verify above observations. Although its degradation kinetics did not follow a constant trend as pH increases, the relative importance of mineralization appeared declining, suggesting that there was a redox transition from an oxidizing environment to a reducing environment as pH rises. The treatability of the UV/VUV/I – process was stronger than UV/VUV under pH of 11.0, while UV/VUV process presented a better performance at pH lower than 11.0. 相似文献
18.
● 548 representative nor genes were collected to create complete phylogenetic trees. ● The distribution of nor and nod genes were detected in 18 different phyla. ● The most conserved amino acids in NOR were located adjacent to the active site. ● nor-universal and Clade-specific primers were designed, suggested, and tested. Nitric oxide reductases (NORs) have a central role in denitrification, detoxification of nitric oxide (NO) in host-pathogen interactions, and NO-mediated cell-cell signaling. In this study, we focus on the phylogeny and detection of qNOR and cNOR genes because of their nucleotide sequence similarity and evolutionary relatedness to cytochrome oxidases, their key role in denitrification, and their abundance in natural, agricultural, and wastewater ecosystems. We also include nitric oxide dismutase (NOD) due to its similarity to qNOR. Using 548 nor sequences from publicly accessible databases and sequenced isolates from N 2O-producing bioreactors, we constructed phylogenetic trees for 289 qnor/ nod genes and 259 cnorB genes. These trees contain evidence of horizontal gene transfer and gene duplication, with 13.4% of the sequenced strains containing two or more nor genes. By aligning amino acid sequences for q nor + cnor, qnor, and cnor, we identified four highly conserved regions for NOR and NOD, including two highly conserved histidine residues at the active site for qNOR and cNOR. Extending this approach, we identified conserved sequences for: 1) all nor ( nor-universal); 2) all qnor ( qnor-universal) and all cnor ( cnor-universal); 3) qnor of Comamonadaceae; 4) Clade-specific sequences; and 5) nod of Candidatus Methylomirabilis oxyfera. Examples of primer performance were confirmed experimentally. 相似文献
19.
• Cu and Cr can be mostly incorporated into CuFexAlyCr2−x−yO4 with a spinel structure. • Spinel phase is the most crucial structure for Cu and Cr co-stabilization. • Compared to Al, Fe and Cr are easier to be incorporated into the spinel structure. • ‘Waste-to-resource’ by thermal process at attainable temperatures can be achieved. Chromium slag usually contains various heavy metals, making its safe treatment difficult. Glass-ceramic sintering has been applied to resolve this issue and emerged as an effective method for metal immobilization by incorporating heavy metals into stable crystal structures. Currently, there is limited knowledge about the reaction pathways adopted by multiple heavy metals and the co-stabilization functions of the crystal structure. To study the Cu/Cr co-stabilization mechanisms during thermal treatment, a simulated system was prepared using a mixture with a molar ratio of Al 2O 3:Fe 2O 3:Cr 2O 3:CuO= 1:1:1:3. The samples were sintered at temperatures 600–1300°C followed by intensive analysis of phase constitutions and microstructure development. A spinel phase (CuFe xAl yCr 2−x−yO 4) started to generate at 700°C and the incorporation of Cu/Cr into the spinel largely complete at 900°C, although the spinel peak intensity continued increasing slightly at temperatures above 900°C. Fe 2O 3/Cr 2O 3 was more easily incorporated into the spinel at lower temperatures, while more Al 2O 3 was gradually incorporated into the spinel at higher temperatures. Additionally, sintered sample microstructures became more condensed and smoother with increased sintering temperature. Cu / Cr leachability substantially decreased after Cu/Cr incorporation into the spinel phase at elevated temperatures. At 600°C, the leached ratios for Cu and Cr were 6.28% and 0.65%, respectively. When sintering temperature was increased to 1300°C, the leached ratios for all metal components in the system were below 0.2%. This study proposes a sustainable method for managing Cu/Cr co-exist slag at reasonable temperatures. 相似文献
20.
● Synergistic removal of carbamazepine (CBZ) was obtained in the FeS-S2O82– process. ● SO4•− and •OH were identified as the main radicals in the FeS-S2O82– process. ● Heterogeneous oxidation would be dominant first, followed by homogeneous reaction. ● Degradation pathway of CBZ was well elucidated by experiments and DFT calculations. As persulfate (S 2O 82–) is being increasingly used as an alternative oxidizing agent, developing low-cost and eco-friendly catalysts for efficient S 2O 82– activation is potentially useful for the treatment of wastewater containing refractory organic pollutant. In this study, the degradative features and mechanisms of carbamazepine (CBZ) were systematically investigated in a novel FeS- S 2O 82– process under near-neutral conditions. The results exhibited that CBZ can be effectively eliminated by the FeS-S 2O 82– process and the optimal conditions were: 250 mg/L FeS, 0.5 mmol/L S 2O 82–, and pH = 6.0. The existence of Cl − (1 and 50 mmol/L) has little influence on the CBZ elimination, while both HCO 3− and HPO 42− (1 and 50 mmol/L) significantly suppressed the CBZ removal in the FeS-S 2O 82– process. CBZ could be degraded via a radical mechanism in the FeS-S 2O 82– process, the working radical species (i.e., SO 4•− and •OH) were efficiently formed via the promoted decomposition of S 2O 82– by the surface Fe 2+ on the FeS and the dissolved ferrous ions in solution. Based on the identified oxidized products and Fukui index calculations, a possible degradation pathway of CBZ was speculated. More importantly, a two-stage oxidation mechanism of CBZ elimination was speculated in the FeS-S 2O 82– process, the activation of S 2O 82– by the surface-active Fe (II) of FeS dominated in the initial 5 min, while homogeneous oxidation reactions played more essential parts than others in the following reaction stage (5–60 min). Overall, this study demonstrated that the FeS-S 2O 82– process is capable of removing CBZ from water efficiently. 相似文献
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