Frontiers of Environmental Science & Engineering

ISSN 2095-2201

ISSN 2095-221X(Online)

CN 10-1013/X

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A review of atmospheric mercury emissions, pollution and control in China
Shuxiao WANG,Lei ZHANG,Long WANG,Qingru WU,Fengyang WANG,Jiming HAO
Front.Environ.Sci.Eng.. 2014, 8 (5): 631-649.

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Mercury, as a global pollutant, has significant impacts on the environment and human health. The current state of atmospheric mercury emissions, pollution and control in China is comprehensively reviewed in this paper. With about 500–800 t of anthropogenic mercury emissions, China contributes 25%–40% to the global mercury emissions. The dominant mercury emission sources in China are coal combustion, non-ferrous metal smelting, cement production and iron and steel production. The mercury emissions from natural sources in China are equivalent to the anthropogenic mercury emissions. The atmospheric mercury concentration in China is about 2–10 times the background level of North Hemisphere. The mercury deposition fluxes in remote areas in China are usually in the range of 10–50 μg∙m-2∙yr-1. To reduce mercury emissions, legislations have been enacted for power plants, non-ferrous metal smelters and waste incinerators. Currently mercury contented in the flue gas is mainly removed through existing air pollution control devices for sulfur dioxide, nitrogen oxides, and particles. Dedicated mercury control technologies are required in the future to further mitigate the mercury emissions in China.

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Charge and separation characteristics of nanofiltration membrane embracing dissociated functional groups
Zhun MA,Meng WANG,Xueli GAO,Congjie GAO
Front.Environ.Sci.Eng.. 2014, 8 (5): 650-658.

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The current work focused on the investigation of charge and separation characteristics of nanofiltration (NF) membrane embracing dissociated functional groups under different electrolyte solutions. The electro-kinetic method was carried out to assess the membrane volume charge density (X) with different salt concentrations ranging from 0.1 to 10 mol·m-3 and different electrolyte species, such as type 1–1, type 2–1 and type 3–1. The Donnan steric pore model-dielectric exclusion (DSPM-DE) model was employed to evaluate the separation characteristics of the NF membrane for wide range of electrolyte concentration (from 25.7 to 598.9 mol·m-3). The results indicated that the dissociation of the hydrophilic functional groups and the specific adsorption contributed to charge formation on membrane surface. The former played a dominant role in type 1–1 and type 2–1 electrolytes at dilute aqueous solutions (0.1–0.5 mol·m-3). However, for type 3–1 electrolyte, specific adsorption should contribute to the charge effect to a large extent. Moreover, the correlation between the volume charge density and feed concentration was in accordance with Freundlich isotherm. Furthermore, it was found that the separation characteristic of NF membrane could be evaluated well by DSPM-DE model coupling with electro-kinetic method in a whole concentration range.

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Promoting effect of Zr on the catalytic combustion of methane over Pd/γ-Al2O3 catalyst
Hongbo NA,Tianle ZHU,Zhiming LIU,Yifei SUN
Front.Environ.Sci.Eng.. 2014, 8 (5): 659-665.

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The effect of Zr on the catalytic performance of Pd/γ-Al2O3 for the methane combustion was investigated. The results show that the addition of Zr can improve the activity and stability of Pd/γ-Al2O3 catalyst, which, based on the catalyst characterization (N2 adsorption, XRD, CO-Chemisorption, XPS, CH4-TPR and O2-TPO), is ascribed to the interaction between Pd and Zr. The active phase of methane combustion over supported palladium catalyst is the Pd0/Pd2+ mixture. Zr addition inhibits Pd aggregation and enhances the redox properties of active phase Pd0/ Pd2+. H2 reduction could effectively reduce the oxidation degree of Pd species and regenerate the active sites (Pd0/ Pd2+).

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Quantitative characterization of Cu binding potential of dissolved organic matter (DOM) in sediment from Taihu Lake using multiple techniques
Front.Environ.Sci.Eng.. 2014, 8 (5): 666-674.

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Dissolved organic matter (DOM) plays an important role in heavy metal speciation and distribution in the aquatic environment especially for eutrophic lakes which have higher DOM concentration. Taihu Lake is the third largest freshwater and a high eutrophic lake in the downstream of the Yangtze River, China. In the lake, frequent breakout of algae blooms greatly increased the concentration of different organic matters in the lake sediment. In this study, sediment samples were collected from various part of Taihu Lake to explore the spatial difference in the binding potential of DOM with Cu. The titration experiment was adopted to quantitatively characterize the interaction between Cu(II) and DOM extracted from Taihu Lake sediments using ion selective electrode (ISE) and fluorescence quenching technology. The ISE results showed that the exogenous DOM had higher binding ability than endogenous DOM, and DOM derived from aquatic macrophytes had a higher binding ability than that derived from algae. The fluorescence quenching results indicated that humic substances played a key role in the complexation between DOM and Cu(II) in the lake. However, because of the frequent breakout of algae blooms, protein-like matters are also main component like humic matters in Taihu Lake. Therefore, the metals bound by protein-like substances should be caused concern as protein-like substances in DOM were unstable and they will release bound metal when decomposed.

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Removal of clofibric acid from aqueous solution by polyethylenimine-modified chitosan beads
Front.Environ.Sci.Eng.. 2014, 8 (5): 675-682.

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Polyethylenimine (PEI)-modified chitosan was prepared and used to remove clofibric acid (CA) from aqueous solution. PEI was chemically grafted on the porous chitosan through a crosslinking reaction, and the effects of PEI concentration and reaction time in the preparation on the adsorption of clofibric acid were optimized. Scanning electron microscopy (SEM) showed that PEI macromolecules were uniformly grafted on the porous chitosan, and the analysis of pore size distribution indicated that more mesopores were formed due to the crosslinking of PEI molecules in the macropores of chitosan. The PEI-modified chitosan had fast adsorption for CA within the initial 5 h, while this adsorbent exhibited an adsorption capacity of 349 mg·g-1 for CA at pH 5.0 according to the Langmuir fitting, higher than 213 mg·g-1 on the porous chitosan. The CA adsorption on the PEI-modified chitosan was pH-dependent, and the maximum adsorption was achieved at pH 4.0. Based on the surface charge analysis and comparison of different pharmaceuticals adsorption, electrostatic interaction dominated the sorption of CA on the PEI-modified chitosan. The PEI-modified chitosan has a potential application for the removal of some anionic micropollutants from water or wastewater.

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Estimation of photolysis half-lives of dyes in a continuous-flow system with the aid of quantitative structure-property relationship
Davoud BEIKNEJAD,Mohammad Javad CHAICHI
Front.Environ.Sci.Eng.. 2014, 8 (5): 683-692.

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In this paper the photolysis half-lives of the model dyes in water solutions and under ultraviolet (UV) radiation were determined by using a continuous-flow spectrophotometric method. A quantitative structure-property relationship (QSPR) study was carried out using 21 descriptors based on different chemometric tools including stepwise multiple linear regression (MLR) and partial least squares (PLS) for the prediction of the photolysis half-life (t1/2) of dyes. For the selection of test set compounds, a K-means clustering technique was used to classify the entire data set, so that all clusters were properly represented in both training and test sets. The QSPR results obtained with these models show that in MLR-derived model, photolysis half-lives of dyes depended strongly on energy of the highest occupied molecular orbital (EHOMO), largest electron density of an atom in the molecule (ED+) and lipophilicity (logP). While in the model derived from PLS, besides aforementioned EHOMO and ED+ descriptors, the molecular surface area (Sm), molecular weight (MW), electronegativity (χ), energy of the second highest occupied molecular orbital (EHOMO-1) and dipole moment (μ) had dominant effects on logt1/2 values of dyes. These were applicable for all classes of studied dyes (including monoazo, disazo, oxazine, sulfonephthaleins and derivatives of fluorescein). The results were also assessed for their consistency with findings from other similar studies.

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Abundance and distribution of ammonia-oxidizing archaea in Tibetan and Yunnan plateau agricultural soils of China
Kun DING,Xianghua WEN,Liang CHEN,Daishi HUANG,Fan FEI,Yuyang LI
Front.Environ.Sci.Eng.. 2014, 8 (5): 693-702.

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As low oxygen and high ultraviolet (UV) exposure might significantly affect the microbial existence in plateau, it could lead to a specialized microbial community. To determine the abundance and distribution of ammonia-oxidizing archaea (AOA) in agricultural soil of plateau, seven soil samples were collected respectively from farmlands in Tibet and Yunnan cultivating the wheat, highland-barley, and colza, which are located at altitudes of 3200–3800 m above sea level. Quantitative PCR (q-PCR) and clone library targeting on amoA gene were used to quantify the abundances of AOA and ammonia-oxidizing bacteria (AOB), and characterize the community structures of AOA in the samples. The number of AOA cells (9.34 × 107–2.32 × 108 g-1 soil) was 3.86–21.84 times greater than that of AOB cells (6.91 × 106–1.24 × 108 g-1 soil) in most of the samples, except a soil sample cultivating highland-barley with an AOA/AOB ratio of 0.90. Based Kendall’s correlation coefficient, no remarkable correlation between AOA abundance and the environmental factor was observed. Additionally, the diversities of AOA community were affected by total nitrogen and organic matter concentration in soils, suggesting that AOA was probably sensitive to several environmental factors, and could adjust its community structure to adapt to the environmental variation while maintaining its abundance.

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Comparison of growth and lipid accumulation properties of two oleaginous microalgae under different nutrient conditions
Front.Environ.Sci.Eng.. 2014, 8 (5): 703-709.

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This study compared the growth and lipid accumulation properties of two oleaginous microalgae, namely, Scenedesmus sp. LX1 and Chlorella sp. HQ, under different nutrient conditions. Both algal species obtained the highest biomass, lipid content and lipid yield under low-nutrient conditions (mBG11 medium). The biomass, lipid content and lipid yield of Scenedesmus sp. LX1 were 0.42 g·L–1, 22.5% and 93.8 mg·L–1, respectively. These values were relatively higher than those of Chlorella sp. HQ (0.30 g·L–1, 17.1% and 51.3 mg·L–1, respectively). These algae were then cultivated in an SE medium that contained more nutrients; as a result, the biomass and lipid yield of Scenedesmus sp. LX1 reduced more significantly than those of Chlorella sp. HQ. Opposite results were observed in lipid and triacylglycerols (TAGs) contents. The cell sizes of both algal species under low-nutrient conditions were larger than those under high-nutrient conditions. Chlorella sp. HQ cells did not aggregate, but Scenedesmus sp. LX1 cells flocculated easily, particularly under low-nutrient conditions. In summary, low-nutrient conditions favour the growth and lipid production of both algae, but Scenedesmus sp. LX1 outperforms Chlorella sp. HQ.

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Assessment of metals in dry-toilet collected matters from suburban areas of Ulaanbaatar, Mongolia, using biosolids quality guidelines and potential ecological risk index
Xuan LIU,Zifu LI,Eric BOSC,Heinz-Peter MANG
Front.Environ.Sci.Eng.. 2014, 8 (5): 710-718.

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Dry-toilet collected matter (DCM) from traditional dry-toilet pits are a potential health and ecological risk in suburban areas. In this study, the characteristics of metals in DCMs from suburban areas of Ulaanbaatar were surveyed. The results indicate that DCMs contain a high percentage of organic matter and nutrients, while heavy metals are at low levels, which shows good agricultural potential. The concentration ranges of Cr, Cu, Hg, Ni, Pb, and Zn were 11±5, 46±9, 0.08±0.05, 9±3, 17±9, and 338±86 mg·kg-1, respectively. The concentration of Cd was below 0.5 mg·kg-1, and a high positive relation was shown between chromium and nickel concentrations. The heavy metals in DCMs were safe for land application but Zn in DCMs was close to the effects range median (ERM), which is toxic in some cases, such as amphipod bioassays. Because it is mandatory to treat DCMs to reduce pathogens, in the case of heavy metal enrichment and agricultural reuse, composting or pyrolysis are better choices than incineration. Compared with global soil background values, the heavy metals in DCMs showed a low level of ecological risk, but a medium level when compared with Mongolian soil background values. The ecological risk of six heavy metals was in the descending order Hg>Cu>Zn>Pb>Ni>Cr and the contribution rate of Hg exceeded 60%.

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Current status and developing trends of the contents of heavy metals in sewage sludges in China
Jun YANG,Mei LEI,Tongbin CHEN,Ding GAO,Guodi ZHENG,Guanghui GUO,Duujong LEE
Front.Environ.Sci.Eng.. 2014, 8 (5): 719-728.

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It is essential to determine the heavy metal concentrations in sewage sludge to select appropriate disposal methods. We conducted a national survey of heavy metal concentrations of sewage sludge samples from 107 municipal sewage treatment plants located in 48 cities covering the 31 provinces and autonomous regions, as well as Hong Kong, Macao and Taiwan by Xinjiang Production and Construction Corps in 2006, and identified the temporal trends of heavy metal contents in sewage sludge by comparison with surveys conducted in 1994–2001. In 2006, the average concentrations of As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn in sewage sludge were 20.2, 1.97, 93.1, 218.8, 2.13, 48.7, 72.3, and 1058 mg·kg-1, respectively. Because of the decreased discharge of heavy metals into industrial wastewater in China and the increasingly stringent regulations governing the content of industrial wastes entering sewers, the average concentrations of Cd, Cr, Cu, Hg, Ni, Pb, and Zn have decreased by 32.3%, 49.7%, 54.9%, 25.0%, 37.2%, 44.8%, and 27.0%, respectively, during the past 12 years. The concentrations of Cd, Cr, Cu, Ni, and Zn in the samples exceeded the heavy metal limits of the Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant in China (GB 18918-2002) by 6.5%, 3.7%, 6.5%, 6.5%, and 11.2%, respectively. From these results, 85 of the 107 municipal sludges analyzed would be considered suitable for land application.

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High specificity detection of Pb2+ ions by p-SCN-Bz-DTPA immunogen and p-NH2-Bn-DTPA coating antigen
Ruozhen YU,Zheng FANG,Wei MENG,Zhenguang YAN,Lina DU,Hong WANG,Zhengtao LIU
Front.Environ.Sci.Eng.. 2014, 8 (5): 729-736.

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Only one bifunctional metal-chelator was used to prepare immunogen and coating antigen in all of the previous researches. However, the antibody-specific recognition to the spacer arm of the bifunctional metal-chelator might lower the specificity of heavy metal ions immunoassay. Two different bifunctional metal-chelators were adopted to prepare the immunogen and coating antigen respectively in our study to avoid this problem. The conjugates of keyhole limpet hemocyanin (KLH) and p-SCN-Bz-DTPA-Pb were used as immunogen, whereas the conjugates of bovine serum albumin (BSA) and p-NH2-Bn-DTPA-Pb were used as coating antigen. Polyclonal antibodies specific to DTPA-Pb chelates were obtained from rabbits. Indirect competitive enzyme-linked immunosorbent assay (ELISA) was adopted to detect Pb2+ ion solutions prepared by Pb2+ standard solution and ultrapure water. In the mixing microplate, DTPA and Pb2+ ions formed chelates and combined with specific antibodies. After incubation, the DTPA-Pb and the antibodies complex were added into the wells of the reaction microplate. The reaction microplate was coated by the conjugates of BSA and p-NH2-DTPA-Pb, which competed for the specific antibodies. The result signals presented a good sigmoid curve when the Pb2+ concentration ranges from 0.01 to 100 mg·L-1. The IC50 of the indirect competitive ELISA is 0.23±0.04 mg·L-1 Pb2+ ion. The cross-reaction with Cd2+, Cu2+, Fe2+, Mn2+, Zn2+, and other divalent ions were less than 5%.

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Evaluation of the ecological status with benthic indices in the coastal system: the case of Bohai Bay (China)
Wenqian CAI,Wei MENG,Lusan LIU,Kuixuan LIN
Front.Environ.Sci.Eng.. 2014, 8 (5): 737-746.

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Based on biologic and environmental materials collected from coastal areas of Bohai Bay (China) in April, 2008, three biotic indices (AZTI’s Marine Biotic Index (AMBI), Shannon–Wiener Index and W-statistic) were applied together to evaluate the ecological status of the sampling area. The results showed a clear spatial gradient from a worse ecological status in the near-shore areas (especially around Haihe and Jiyun River Estuaries) to a better status in the offshore areas. While all the three indices could assist decision makers in visualizing spatial changes of organic pollutants in Bohai Bay, two indices, i.e., AMBI and Shannon-Wiener index, were effective in distinguishing sites from Haihe River Estuary, Jiyun River Estuary and other area. However, W-statistic can’t tell the differences between estuaries and other area. It would be explained that organic pollutants and/or other environmental stresses in Bohai Bay were not strong enough to reduce the size of macrozoobenthos, which may cause both of the abundance and biomass curves crossed. To our knowledge, this is the first time that several benthic indices were used to assess the benthic ecological status in Bohai Bay, which gave the similar results. Furthermore, there is indication that the ecological status is related to excess input of wastewater along main rivers and outlets. In a word, AMBI, Shannon–Wiener Index and W-statistic could be able to assess the benthic ecological status of Bohai Bay under the organic pollutants pressure.

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Impacts of de-icing salt pollution on urban road greenspace: a case study of Beijing
Zhouyuan LI,Yingmei LIANG,Junhui ZHOU,Xiao SUN
Front.Environ.Sci.Eng.. 2014, 8 (5): 747-756.

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De-icing salt contamination of urban soil and greenspace has been a common issue of concern in many countries for years. In the 2009/2010 winter, Beijing experienced a contamination accident resulting from the overuse of de-icing salt, reported as almost 30000 tons, which severely damaged urban vegetation alongside roadways. The methods of sampling and rating for both soil contamination and response of the plant populations were developed to rapidly assess this emergency environmental event. Results showed that the shrubs were more severely damaged than the arbors in terms of both degree and extent, as almost all of the surveyed shrubs were severely damaged from the salt contamination, while only about 1/4 of the recorded arbors were rated as “severely injured” according to the integral plant injury index. The rating of the injury level showed that the trees like Pinus bungeana, Sophora japonica, and the shrubs like Euonymus japonicus, Sabina vulgaris showed less tolerance to de-icing salt pollution. The patterns of vegetation damage demonstrated that the ever-green shrubs alongside roads and the deciduous arbors in the center of roads were most vulnerable to the salt damage.

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Cleaning the energy sources for water heating among Nanjing households: barriers and opportunities for solar and natural gas
Lingyun ZHU,Beibei LIU,Jun BI
Front.Environ.Sci.Eng.. 2014, 8 (5): 757-766.

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Energy for water heating accounts for an increasing part in residential energy demand in China. An extensive survey was conducted to analyze the determinants of household energy choices for water heaters among residents in Nanjing, China. Two sets of variables were examined as potential influences: building features and household socio-economic characteristics. Results suggest that building features such as gas availability and building structures, and household characteristics such as household head’s education degree and energy-conserving sense are crucial determinants in choosing natural gas as water heater energy. Installation permission for solar water heater, building stories, and residential location serve as determining factors in choosing solar water heaters. Based on these, barriers and opportunities are discussed for transitions toward cleaner water heating energies, and suggestions are given for local governments to promote cleaner energy replacement in China.

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Seismic vulnerability assessment of water supply network in Tianjin, China
Yanxi CHEN,Zhiguang NIU,Jiaqi BAI,Yufei WANG
Front.Environ.Sci.Eng.. 2014, 8 (5): 767-775.

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The water supply network (WSN) system is a critical element of civil infrastructure systems. Its complexity of operation and high number of components mean that all parts of the system cannot be simply assessed. Earthquakes are the most serious natural hazard to a WSN, and seismic risk assessment is essential to identify its vulnerability to different stages of damage and ensure the system safety. In this paper, using a WSN located in the airport area of Tianjin in northern China as a case study, a quantitative vulnerability assessment method was used to assess the damage that the water supply pipelines would suffer in an earthquake, and the finite element software ABAQUS and fuzzy mathematic theory were adopted to construct the assessment method. ABAQUS was applied to simulate the seismic damage to pipe segments and components of the WSN. Membership functions based on fuzzy theory were established to calculate the membership of the components in the system. However, to consider the vulnerability of the whole system, fuzzy cluster analysis was used to distinguish the importance of pipe segments and components. Finally, the vulnerability was quantified by these functions. The proposed methodology aims to assess the performance of WSNs based on pipe vulnerabilities that are simulated and calculated by the model and the mathematical method based on data of damage. In this study, a whole seismic vulnerability assessment method for a WSN was built, and these analyses are expected to provide necessary information for a mitigation plan in an earthquake disaster.

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N2O emission from a sequencing batch reactor for biological N and P removal from wastewater
Lei SHEN,Yuntao GUAN,Guangxue WU,Xinmin ZHAN
Front.Environ.Sci.Eng.. 2014, 8 (5): 776-783.

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Nitrous oxide (N2O) is a greenhouse gas that can be released during biological nitrogen removal from wastewater. N2O emission from a sequencing batch reactor (SBR) for biological nitrogen and phosphorus removal from wastewater was investigated, and the aims were to examine which process, nitrification or denitrification, would contribute more to N2O emission and to study the effects of heterotrophic activities on N2O emission during nitrification. The results showed that N2O emission was mainly attributed to nitrification rather than to denitrification. N2O emission during denitrification mainly occurred with stored organic carbon as the electron donor. During nitrification, N2O emission was increased with increasing initial ammonium or nitrite concentrations. The ratio of N2O emission to the removed ammonium nitrogen (N2O-N/NH4-N) was 2.5% in the SBR system with high heterotrophic activities, while this ratio was in the range from 0.14% to 1.06% in batch nitrification experiments with limited heterotrophic activities.

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Microalgae Scenedesmus obliquus as renewable biomass feedstock for electricity generation in microbial fuel cells (MFCs)
Sanath KONDAVEETI,Kwang Soon CHOI,Ramesh KAKARLA,Booki MIN
Front.Environ.Sci.Eng.. 2014, 8 (5): 784-791.

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Renewable algae biomass, Scenedesmus obliquus, was used as substrate for generating electricity in two chamber microbial fuel cells (MFCs). From polarization test, maximum power density with pretreated algal biomass was 102 mW·m-2 (951 mW·m-3) at current generation of 276 mA·m-2. The individual electrode potential as a function of current generation suggested that anodic oxidation process of algae substrate had limitation for high current generation in MFC. Total chemical oxygen demand (TCOD) reduction of 74% was obtained when initial TCOD concentration was 534 mg·L-1 for 150 h of operation. The main organic compounds of algae oriented biomass were lactate and acetate, which were mainly used for electricity generation. Other by-products such as propionate and butyrate were formed at a negligible amount. Electrochemical Impedance Spectroscopy (EIS) analysis pinpointed the charge transfer resistance (112 ?) of anode electrode, and the exchange current density of anode electrode was 1214 nA·cm-2.

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Spent rechargeable lithium batteries in e-waste: composition and its implications
Xianlai ZENG,Jinhui LI
Front.Environ.Sci.Eng.. 2014, 8 (5): 792-796.

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The amount of spent rechargeable lithium batteries (RLBs) is growing rapidly owing to wide application of these batteries in portable electronic devices and electric vehicles, which obliges that spent RLBs should be handled properly. Identification of spent RLBs can supply fundamental information for spent RLBs recycling. This study aimed to determine the differences of physical components and chemical compositions among various spent RLBs. All the samplings of RLBs were rigorously dismantled and measured by an inductive coupled plasma atomic emission spectrometer. The results indicate that the average of total weight of the separator, the anode and the cathode accounted for over 60% of all the RLBs. The weight ratio of valuable metals ranged from 26% to 76%, and approximately 20% of total weight was Cu and Al. Moreover, no significant differences were found among different manufacturers, applications, and electrolyte types. And regarding portable electronic devices, there is also no significant difference in the Co-Li concentration ratios in the leaching liquid of RLBs.

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Concept and application of anaerobic suspended granular sludge bed (SGSB) reactor for wastewater treatment
Mingxia ZHENG,Zhong YAN,Jiane ZUO,Kaijun WANG
Front.Environ.Sci.Eng.. 2014, 8 (5): 797-804.

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Bed expansion serves an important function in the design and operation of an upflow anaerobic reactor. An analysis of the flow pattern of expanded granular sludge bed (EGSB) reactors shows that most EGSB reactors do not behave as expanded bed reactors, as is widely perceived. Rather, these reactors behave as fluidized bed reactors based on the classic chemical reactor theory. In this paper, four bed expansion modes, divided as static bed, expanded bed, suspended bed, and fluidized bed, for bioreactors are proposed. A high-rate anaerobic suspended granular sludge bed (SGSB) reactor was then developed. The SGSB reactor is an upflow anaerobic reactor, and its expansion degree can be easily controlled within a range to maintain the suspended status of the sludge bed by controlling upflow velocity. The results of the full-scale reactor confirmed that the use of SGSB reactors is advantageous. The full-scale SGSB reactor runs stably and achieves high COD removal efficiency (about 90%) at high loading rates (average 40 kg-COD·m-3·d-1, maximum to 52 kg-COD·m-3·d-1) based on the SGSB theory, and its expansion degree is between 22% and 37%.

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19 articles