Frontiers of Environmental Science & Engineering

ISSN 2095-2201

ISSN 2095-221X(Online)

CN 10-1013/X

Postal Subscription Code 80-973

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Review of challenges and strategies for balanced urban–rural environmental protection in China
Beidou XI,Xiaoguang LI,Jixi GAO,Ying ZHAO,Hongliang LIU,Xunfeng XIA,Tianxue YANG,Lieyu ZHANG,Xuan JIA
Front. Environ. Sci. Eng.. 2015, 9 (3): 371-384.

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With the rise of environmentalism in China, great efforts have been devoted to environmental protection over the past several decades. Compared with urban environmental protection, rural environmental protection has not been attached enough importance in China due to the dual-track structure of socio-economic development. As a result, rural China is shouldering disproportionally heavy environmental burdens partly because of the differences and biases between urban and rural environmental protection seen in environmental policies, environmental rights and interests, environmental protection investment, and the environmental protection awareness of people. To eliminate the gap between rural and urban environmental protection, and achieve the goal of “balanced urban–rural environmental protection” (BUREP), government should consider mapping out proper policies and strategies. In this paper we put forward an innovative strategy of BUREP against the background of China’s urban-rural environmental protection. First, we review the current status of rural environmental protection status and its challenges compared with urban environmental protection in China. Secondly, we analyzed the main driving factors and reasons deeply, and then we put forward the BUREP strategy base on the unequal status between urban and rural environment. Finally, we proposed the framework of BUREP. This study may serve as a scientific reference regarding decision-making in coordinating urban and rural environmental protection and in constructing the new countryside of China.

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Comparing the adsorption behaviors of Cd, Cu and Pb from water onto Fe-Mn binary oxide, MnO2 and FeOOH
Wei XU,Huachun LAN,Hongjie WANG,Hongming LIU,Jiuhui QU
Front. Environ. Sci. Eng.. 2015, 9 (3): 385-393.

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The adsorption potential of FMBO, FeOOH, MnO2 for the removal of Cd2+, Cu2+ and Pb2+ in aqueous systems was investigated in this study. Comparing to FMBO and FeOOH, MnO2 offered a much higher removal capacity towards the three metal ions. The maximal adsorption capacity of MnO2 for Cd2+, Cu2+ and Pb2+ were 1.23, 2.25 and 2.60 mmol·g-1, respectively. And that for FMBO were 0.37, 1.13, and 1.18 mmol·g-1 and for FeOOH were 0.11, 0.86 and 0.48 mmol·g-1, respectively. The adsorption behaviors of the three metal ions on the three adsorbents were all significantly affected by pH values and heavy metal removal efficiency increased with pH increased. The Langmuir and Freundlich adsorption models were used to describe the adsorption equilibrium of the three metal ions onto the three adsorbents. Results showed that the adsorption equilibrium data fitted well to Langmuir isotherm and this indicated that adsorption of metal ions occurred on the three metal oxides adsorbents limited to the formation of a monolayer. More negative charged of MnO2 surface than that of FMBO and FeOOH could be ascribed by lower pHiep of MnO2 than that of FMBO and FeOOH and this could contribute to more binding sites on MnO2 surface than that of FMBO and FeOOH. The higher metal ions uptake by MnO2 than FMBO and FeOOH could be well explained by the surface charge mechanism.

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Pharmaceutical compounds in aquatic environment in China: locally screening and environmental risk assessment
Yongshan CHEN,Xiuping XI,Gang YU,Qiming CAO,Bin WANG,François VINCE,Youwei HONG
Front. Environ. Sci. Eng.. 2015, 9 (3): 394-401.

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An environmental risk assessment was performed for pharmaceutical compounds present in the aquatic environment of China. Predicted environmental concentration (PEC) of the compounds were calculated according to European Medicines Evaluation Agency (EMEA) guidelines. Available ecotoxicological data compromised by applying a very conservative assessment factor (AF) were employed to calculate the predicted no-effect concentration (PNEC). The screening principle and the risk assessment were based on risk quotient (RQ), which derived from the PEC and related PNEC values. PEC results indicated that all the compounds except sulfadimethoxine and levocarnitine, should carry out phase II risk assessment in EMEA guideline. RQ values suggested that more than 36 pharmaceuticals may be imposed health threats to the aquatic environment; especially the antibiotic therapeutic class including amoxicillin, sulfasalazine, trimethoprim, oxytetracycline and erythromycin showed high RQ values. These substances with high RQ value (RQ≥1) were regarded as top-priority pharmaceuticals for control in the aquatic environment of China. However, the antibiotic substances which had low risk quotient (RQ <1), should be reassessed by its potentially induced resistance under low concentration in future.

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Application of Fe0/C/Clay ceramics for decoloration of synthetic Acid Red 73 and Reactive Blue 4 wastewater by micro-electrolysis
Xiaowei ZHANG,Qinyan YUE,Dongting YUE,Baoyu GAO,Xiaojuan WANG
Front. Environ. Sci. Eng.. 2015, 9 (3): 402-410.

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Dyes are common pollutants in textile wastewaters, and the treatment of the wastewater has now attracted much attention due to its wide application and low biodegradability. In this study, Fe0/C/Clay ceramics, a kind of novel micro-electrolysis filler, were sintered and employed in a dynamic micro-electrolysis reactor for synthetic Acid Red 73 (AR73) and Reactive Blue 4 (RB4) wastewater treatment. The effects of influent pH, hydraulic retention time (HRT), and aeration on the decoloration efficiencies of AR73 and RB4 were studied. The optimum conditions for wastewater treatment were: AR73, influent pH of 4, HRT of 2 h and aeration; RB4, influent pH of 5, HRT of 6 h and aeration. Under the optimum conditions, decoloration efficiency of AR73 and RB4 wastewater was 96% and 83%, respectively. Results of UV-vis spectrum scanning demonstrated that the chromophores were broken. Continuous running tests showed that improvement of micro-electrolysis system with Fe0/C/Clay ceramics for AR73 and RB4 synthetic wastewater treatment could avoid failure of micro-electrolysis reactor, which indicated great potential for the practical application of the ceramics in the field of actual industrial wastewater treatment.

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Ferrihydrite preparation and its application for removal of anionic dyes
Yongjuan WU,Wentao ZHANG,Wenxiao YU,Hui LIU,Rufen CHEN,Yu WEI
Front. Environ. Sci. Eng.. 2015, 9 (3): 411-418.

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Anionic dyes are hazardous and toxic to living organisms. For this study, ferrihydrite was prepared to test its removal capabilities on anionic dyes. A ferrihydrite particle prepared in neutral environmental conditions is sphere-like with a diameter of 2–4 nm and its total surface area is approximately 229 m2·g-1. In this paper, the effects of solution pH, competitive anions, and temperature on the adsorption of acid fuchsine onto ferrihydrite and the regeneration-reutilization of ferrihydrite were investigated in detail. The results indicate that ferrihydrite is an efficient sorbent for the removal of acid fuchsine at pH 4.0. The inhibitory effect of various competing anions on the present adsorption follows the precedence relationship: NO3-<Cl-<SO42-<H2PO4-. Adsorption isotherms of acid fuchsine on ferrihydrite fit the Langmuir equation well. The Gibbs free energy, enthalpy, and entropy data of adsorption indicate that this adsorption is a spontaneous, exothermic, and physical process. A ferrihydrite was regenerated and reused five times, still retaining its original adsorption capacity.

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Effects of rape straw and red mud on extractability and bioavailability of cadmium in a calcareous soil
Junxing YANG,Liqun WANG,Jumei LI,Dongpu WEI,Shibao CHEN,Qingjun GUO,Yibing MA
Front. Environ. Sci. Eng.. 2015, 9 (3): 419-428.

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Screening of cost-effective soil amendments is important to develop “in situ” remediation techniques for cadmium (Cd) contaminated soils. In this study, different soil amendments, including red mud, a by-product of the alumina industry, and acid-treated, nano-treated by nano-particle milling, nano and acid-treated red muds, zeolite, corn straw, and rape straw, were evaluated to immobilize Cd in two added levels (2 and 5 mg Cd·kg-1 soil) in a calcareous soil by single and sequential extractions and by cucumber (Cucumis sativus L.) pot experiments. Results indicated that cruciferous rape straw significantly decreased the concentrations of water soluble, extractable Cd in soils, and Cd in cucumber plants, and it was more effective than gramineous corn straw. Also, red mud generally decreased the extractability and bioavailability of Cd added to calcareous soils more effectively than zeolite. Furthermore, the efficiency of red mud could be increased by the treatment of nano-particle milling due to the increase in specific surface area of red mud. It is potential to use rape straw and red mud as soil amendments to develop a cost-effective and efficient “in situ” remediation technology for Cd mildly contaminated calcareous soils.

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Decomposition of aqueous chlorinated contaminants by UV irradiation with H2O2
Eunsung KAN,Chang-Il KOH,Kyunghyuk LEE,Joonwun KANG
Front. Environ. Sci. Eng.. 2015, 9 (3): 429-435.

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In the present study, the decomposition rates of carbon tetrachloride (CCl4) and 2,4-dichlorophenol (2,4-DCP) in water by the ultraviolet (UV) light irradiation alone and H2O2/UV were experimentally investigated. The detailed experimental studies have been conducted for examining treatment capacities of the two different ultraviolet light sources (low and medium pressure Hg arc) in H2O2/UV processes. The low or medium UV lamp alone resulted in a 60%–90% decomposition of 2,4-DCP while a slight addition of H2O2 resulted in a drastic enhancement of the 2,4-DCP decomposition rate. The decomposition rate of 2,4-DCP with the medium pressure UV lamp alone was about 3–6 times greater than the low pressure UV lamp alone. In the direct photolysis of aqueous CCl4, the medium pressure UV lamp had advantage over the low pressure UV lamp because the molar extinction coefficient of CCl4 at shorter wavelength (210–220 nm) is about 20 to 50 times higher than that at 254 nm. However, adding H2O2 to the medium pressure UV lamp system rendered a negative oxidation rate because H2O2 acted as a UV absorber being competitive with CCl4 due to negligible reaction between CCl4 and OH radicals. The results from the present study indicated significant influence of the photochemical properties of the target contaminants on the photochemical treatment characteristics for designing cost-effective UV-based degradation of toxic contaminants.

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Catalytic wet air oxidation of phenol, nitrobenzene and aniline over the multi-walled carbon nanotubes (MWCNTs) as catalysts
Shaoxia YANG,Yu SUN,Hongwei YANG,Jiafeng WAN
Front. Environ. Sci. Eng.. 2015, 9 (3): 436-443.

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Wet air oxidation (WAO) is one of effective technologies to eliminate hazardous, toxic and highly concentrated organic compounds in the wastewater. In the paper, multi-walled carbon nanotubes (MWCNTs), functionalized by O3, were used as catalysts in the absence of any metals to investigate the catalytic activity in the catalytic wet air oxidation (CWAO) of phenol, nitrobenzene (NB) and aniline at the mild operating conditions (reaction temperature of 155°C and total pressure of 2.5 MPa) in a batch reactor. The MWCNTs were characterized with scanning electron microscopy (SEM), transmission electron microscopy (TEM), gas adsorption measurements (BET), fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). The functionalized MWCNTs showed good catalytic performance. In the CWAO of phenol over the functionalized MWCNTs, total phenol removal was obtained after 90 min run, and the reaction apparent activation energy was ca. 40 kJ·mol-1. The NB was not removed in the CWAO of single NB, while ca. 97% NB removal was obtained and 40% NB removal was attributed to the catalytic activity after 180 min run in the presence of phenol. Ca. 49% aniline conversion was achieved after 120 min run in the CWAO of aniline.

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Modified pretreatment method for total microbial DNA extraction from contaminated river sediment
Yun FANG,Meiying XU,Xingjuan CHEN,Guoping SUN,Jun GUO,Weimin WU,Xueduan LIU
Front. Environ. Sci. Eng.. 2015, 9 (3): 444-452.

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Extraction of high-quality microbial DNA from contaminated environmental samples is an essential step in microbial ecological study. Based on previously published methods for soil and sediment samples, a modified pretreatment method was developed for extracting microbial DNA from heavily contaminated river sediment samples via selection of optimal pretreatment parameters (i.e., reagent solution, reaction duration, and temperature). The pretreatment procedure involves washing the river sediment sample for three times with a solution containing 0.1 mol·L-1 ethylene diamine tetraacetic acid (EDTA), 0.1 mol·L-1 Tris (pH 8.0), 1.5 mol·L-1 NaCl, 0.1 mol·L-1 NaH2PO4, and Na2HPO4 at 65°C with 180 r·min-1 for 15 min to remove humic materials and heavy metals prior to the employment of standard DNA extraction procedures. We compared the results of standard procedure DNA extraction following pretreatment, without pretreatment, and with using a commercial PowerSoilTM DNA Isolation Kit. The results indicated that the pretreatment significantly improved the DNA quality based on DNA yield, DNA fragment length, and determination of prokaryotic diversity. Prokaryotic diversity exhibited in the DNA with the pretreatment was also considerably higher than that extracted with the PowerSoilTM DNA Isolation Kit only. The pretreatment method worked well even with a small amount of sediment sample (0.25 g or even lower). The method provides a novel, simple, cost-effective tool for DNA extraction for microbial community analysis in environmental monitoring and remediation processes.

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Microbial communities biostimulated by ethanol during uranium (VI) bioremediation in contaminated sediment as shown by stable isotope probing
Mary Beth LEIGH,Wei-Min WU,Erick CARDENAS,Ondrej UHLIK,Sue CARROLL,Terry GENTRY,Terence L. MARSH,Jizhong ZHOU,Philip JARDINE,Craig S. CRIDDLE,James M. TIEDJE
Front. Environ. Sci. Eng.. 2015, 9 (3): 453-464.

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Stable isotope probing (SIP) was used to identify microbes stimulated by ethanol addition in microcosms containing two sediments collected from the bioremediation test zone at the US Department of Energy Oak Ridge site, TN, USA. One sample was highly bioreduced with ethanol while another was less reduced. Microcosms with the respective sediments were amended with 13C labeled ethanol and incubated for 7 days for SIP. Ethanol was rapidly converted to acetate within 24 h accompanied with the reduction of nitrate and sulfate. The accumulation of acetate persisted beyond the 7 d period. Aqueous U did not decline in the microcosm with the reduced sediment due to desorption of U but continuously declined in the less reduced sample. Microbial growth and concomitant 13C-DNA production was detected when ethanol was exhausted and abundant acetate had accumulated in both microcosms. This coincided with U(VI) reduction in the less reduced sample. 13C originating from ethanol was ultimately utilized for growth, either directly or indirectly, by the dominant microbial community members within 7 days of incubation. The microbial community was comprised predominantly of known denitrifiers, sulfate-reducing bacteria and iron (III) reducing bacteria including Desulfovibrio, Sphingomonas, Ferribacterium, Rhodanobacter, Geothrix, Thiobacillus and others, including the known U(VI)-reducing bacteria Acidovorax, Anaeromyxobacter, Desulfovibrio, Geobacter and Desulfosporosinus. The findings suggest that ethanol biostimulates the U(VI)-reducing microbial community by first serving as an electron donor for nitrate, sulfate, iron (III) and U(VI) reduction, and acetate which then functions as electron donor for U(VI) reduction and carbon source for microbial growth.

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Probability distributions of arsenic in soil from brownfield sites in Beijing (China): statistical characterization of the background populations and implications for site assessment studies
Front. Environ. Sci. Eng.. 2015, 9 (3): 465-474.

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A probabilistic analysis was performed on soil arsenic concentration data from 4 brownfield sites at Beijing (Chaoyang and Haidian Districts), involved in environmental assessment studies. The available data sets were processed to provide a statistical characterization of the background populations and differentiate “anomalous data” from the natural range of variation of arsenic concentrations in soil. The site-specific background distributions and the existing wide-scale background values defined for the Beijing area were compared, discussing related implications for the definition of metal contamination soil screening levels (SSLs) in site assessment studies. The statistical analysis of As data sets discriminated site-specific background populations, encompassing 88% to 94% of the sample data, from outliers values, associated with either subsoil natural enrichments or possible anthropogenic releases. Upper Baseline Concentration (UBC) limits (+ 2σ level), including most of the site-specific metal background variability, were derived based on the statistical characterization of the background populations. Sites in the Chaoyang South District area had UBC values in the range 10.4–12.6 mg·kg-1. These ranges provide meaningful SSL values to be adopted for As in local site assessment studies. Using the wide-scale background value for the Beijing area would have erroneously classified most of the areas in the subject sites as potentially contaminated.

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Determination and occurrence of endocrine disrupting compounds, pharmaceuticals and personal care products in fish (Morone saxatilis)
Yong YU,Laosheng WU
Front. Environ. Sci. Eng.. 2015, 9 (3): 475-481.

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Endocrine disrupting compounds (EDCs), pharmaceuticals and personal care products (PPCPs) have attracted much attention due to widespread contamination in aquatic environment. In this study, we determined 13 EDCs and PPCPs in fish blood, bile and muscle by using gas chromatography-mass spectrometry (GC-MS). The limits of quantitation (LOQ) were in the ranges of 0.23–2.54, 0.22–2.36 ng·mL-1, and 0.24–2.57 ng·g-1 dry weight (dw) for fish blood, bile and muscle, respectively. Recoveries of target compounds spiked into sample matrices and passed through the entire analytical procedure ranged from 65% to 95%, from 60% to 92% and from 62% to 91% for blood, bile and muscle, respectively. The methods were applied to the analysis of fish from a lake in California. Target compounds were relatively low in bile, and only bisphenol A (BPA) and diclofenac were measurable near the LOQ. Seven of 13 compounds were detected in blood, with total concentrations up to 39 ng·mL-1. Only BPA was frequently found in muscle, with mean concentration of 7.26 ng·g-1 dw. The estimated daily intake of BPA through fish consumption for U.S. resident was significantly lower than the tolerable daily intake recommended by the European Food Safety Authority. This study showed that the exposure to the bisphenol A from fish diet is unlikely to pose a health risk.

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Occurrence and health risk assessment of trace heavy metals via groundwater in Shizhuyuan Polymetallic Mine in Chenzhou City, China
Bingbing XU,Qiujin XU,Cunzhen LIANG,Li LI,Lijia JIANG
Front. Environ. Sci. Eng.. 2015, 9 (3): 482-493.

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The Shizhuyuan Polymetallic Mine in Chen-zhou City is an important multi-metal deposit in China. After a dam accident in 1985, there are still a number of mining plants, smelters and tailing ponds in this area. These had the potential to pollute the surrounding groundwater. In this study, groundwater samples were collected from 20 residents’ wells in this area during both dry and wet seasons. In particular, this study focused on the exposure and the health risk assessment of trace heavy metal in groundwater. Multiple statistical analysis and fuzzy comprehensive method were employed to reveal the distribution characteristics of heavy metal and to assess the groundwater quality. Results indicated that Cr, Fe, Ni, Cu, Zn, As, Cd, Ba, Hg and Pb were widespread with low exposure levels. There were 19 wells with low level exposure and one well with a moderate level exposure in the dry season. All of the wells were in low level exposure during the wet season. As and Mn exhibited potential non-carcinogenic concern, because their maximum hazard quotient (HQ) was higher than 1.0. This may cause adverse health effect on adults in dry season or on children in both seasons. Only As, showed that the maximum carcinogenic risk was more than 10-4, suggesting a high cancer risk for children in both dry and wet seasons. Therefore, analysis and reduction the concentrations of As and Mn in groundwater are needed in order to protect the health of residents and especially children in the area.

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An enhanced environmental multimedia modeling system based on fuzzy-set approach: I. Theoretical framework and model development
Chesheng ZHAN,Rongrong ZHANG,Xiaomeng SONG,Baolin LIU
Front. Environ. Sci. Eng.. 2015, 9 (3): 494-505.

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Multimedia environmental modeling is extremely complex due to the intricacy of the systems with the consideration of many related factors. Traditional environmental multimedia models (EMMs) are usually based on one-dimensional and first-order assumptions, which may cause numerical errors in the simulation results. In this study, a new user-friendly fuzzy-set enhanced environmental multimedia modeling system (FEEMMS) is developed, and includes four key modules: an air dispersion module, a polluting source module, an unsaturated zone module, and a groundwater module. Many improvements over previous EMMs have been achieved through dynamically quantifying the intermedia mass flux; incorporating fuzzy-set approach into environmental multimedia modeling system (EMMS); and designing a user-friendly graphic user interface (GUI). The developed FEEMMS can be a useful tool in estimating the time-varying and spatial-varying chemical concentrations in air, soil, and groundwater; characterizing the potential risk to human health presented by contaminants released from a contaminated site; and quantifying the uncertainties associated with modeling systems and subsequently providing robustness and flexibility for the remediation-related decision making.

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Regional characteristics of industrial energy efficiency in China: application of stochastic frontier analysis method
Front. Environ. Sci. Eng.. 2015, 9 (3): 506-521.

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This paper analyzed regional industrial energy efficiency in China with Total-Factor Energy Efficiency (TFEE). The East region has the best energy efficiency and the Central and the West regions stand as the second and the third respectively. However, it is found that industrial energy efficiency of all regions increased from 1998 to 2006. This result is consistent with level of economic development of every region. The industries of all provinces in China are not yet at the frontier efficiency position, therefore, to the frontier as target, their technology levels and production processes should be adjusted accordingly. Compared with the conventional energy efficiency, the inverse of energy intensity, which is defined as the ratio of actual output to energy input, is regarded as Single-Factor Energy Efficiency (SFEE) index. Although TFEE ranks are not changed for each region, they are different for each province. The comparative result also shows that the substitution among inputs (labor, capital stock, and energy) to produce the output is significant. The SFEE scores could be over-estimated if energy is taken as the single input in the production. Finally, we identified determining factors affecting industrial energy efficiency using Tobit model. The results indicate that an increase of per capita Gross Domestic Product (GDP), the percentage of output value of industry invested by Hong Kong, Macao, Taiwan and abroad, energy price and investment of scientific and technological activities for industry could be possible contributors and drivers to the industrial energy efficiency. However, increasing of heavy industry will lead to worse industrial energy efficiency.

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Selective recovery of Cu2+ and Ni2+ from wastewater using bioelectrochemical system
Haiping LUO,Bangyu QIN,Guangli LIU,Renduo ZHANG,Yabo TANG,Yanping HOU
Front. Environ. Sci. Eng.. 2015, 9 (3): 522-527.

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As the bioelectrochemical system, the microbial fuel cell (MFC) and the microbial electrolysis cell (MEC) were developed to selectively recover Cu2+ and Ni2+ ions from wastewater. The wastewater was treated in the cathode chambers of the system, in which Cu2+ and Ni2+ ions were removed by using the MFC and the MEC, respectively. At an initial Cu2+ concentration of 500 mg·L-1, removal efficiencies of Cu2+ increased from 97.0%±1.8% to 99.0%±0.3% with the initial Ni2+ concentrations from 250 to 1000 mg·L-1, and maximum power densities increased from 3.1±0.5 to 5.4±0.6 W·m-3. The Ni2+ removal mass in the MEC increased from 6.8±0.2 to 20.5±1.5 mg with the increase of Ni2+ concentrations. At an initial Ni2+ concentration of 500 mg·L-1, Cu2+ removal efficiencies decreased from 99.1%±0.3% to 74.2%±3.8% with the initial Cu2+ concentrations from 250 to 1000 mg·L-1, and maximum power densities increased from 3.0±0.1 to 6.3±1.2 W·m-3. Subsequently, the Ni2+ removal efficiencies decreased from 96.9%±3.1% to 73.3%±5.4%. The results clearly demonstrated the feasibility of selective recovery of Cu2+ and Ni2+ from the wastewater using the bioelectrochemical system.

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Achievement of high rate nitritation with aerobic granular sludge reactors enhanced by sludge recirculation events
Zulkifly JEMAAT,Josep Anton TORA,Albert BARTROLI,Julián CARRERA,Julio PEREZ
Front. Environ. Sci. Eng.. 2015, 9 (3): 528-533.

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A ratio control strategy has been used to demonstrate the feasibility of this automatic control procedure for the achievement of stable full and partial nitritation. The control strategy assured constant ratio between the dissolved oxygen (DO) and the total ammonia nitrogen (TAN) concentrations in the bulk liquid of aerobic granular sludge reactors operating in continuous mode. Three different set-ups with different reactor capacities were used (3, 110, and 150 L). High strength synthetic wastewaters and reject water were tested with similar performance. Achieved nitrogen loading rates ranged between 0.4 and 6.1 kgN·m-3·d-1, at temperatures between 20°C and 30°C. Granular sludge and nitritation were stable in the long term continuous operation of the reactors. Suitable stable effluent for Anammox has been obtained using the desired TAN setpoint (i.e. 50% of influent ammonium oxidation). An existing biofilm model developed incorporating the implemented control loops and validated in a previous publication was used to investigate the effects of the ammonium concentration of the influent and the biofilm density on the achievement of full nitritation. The model demonstrated how sludge recirculation events led to a stable and significant increase of the biomass concentration in the reactor, which in turn resulted in the achievement of high nitrogen loading rates, due to the action of the control strategy. The model predicted an enhancement of stable full nitritation at higher ammonium concentrations in the influent. Poor influence of the biofilm density in the achievement of full nitritation was predicted with the model.

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Simulation of long-term nutrient removal in a full-scale closed-loop bioreactor for sewage treatment: an example of Bayesian inference
Zheng LI,Rong QI,Wei AN,Takashi MINO,Tadashi SHOJI,Willy VERSTRAETE,Jian GU,Shengtao LI,Shiwei XU,Min YANG
Front. Environ. Sci. Eng.. 2015, 9 (3): 534-544.

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In this study, the performance of nitrogen and phosphorus removal in a full-scale closed-loop bioreactor (oxidation ditch) system was simulated using the ASM2d model. Routine data describing the process for two years were compiled for calibration and validation. To overcome the identifiability problem, the classic Bayesian inference approach was utilized for parameter estimation. The calibrated model could describe the long-term trend of nutrient removal and short-term variations of the process performance, showing that the Bayesian method was a reliable and useful tool for the parameter estimation of the activated sludge models. The anoxic phosphate uptake by polyphosphate accumulating organisms (PAO) contributed 71.2% of the total Poly-P storage, which reveals the dominance of denitrifying phosphorus removal process under the oxygen limiting conditions. It was found that 58.7% of the anoxic Poly-P storage and denitrification by PAO in the reactor was achieved in the aerated compartment, implying that the PAO’s anoxic activity was significantly stimulated by the low dissolved oxygen (DO) level in this compartment due to the oxygen gradient caused by brush aerator.

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Preparation and application of a phosphorous free and non-nitrogen scale inhibitor in industrial cooling water systems
Guangqing LIU,Mengwei XUE,Jingyi HUANG,Huchuan WANG,Yuming ZHOU,Qingzhao YAO,Lei LING,Ke CAO,Yahui LIU,Yunyun BU,Yiyi CHEN,Wendao WU,Wei SUN
Front. Environ. Sci. Eng.. 2015, 9 (3): 545-553.

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A novel environmentally friendly type of calcium carbonate, zinc (II) and iron (III) scale inhibitor Acrylic acid- allylpolyethoxy carboxylate copolymer (AA-APEL) was synthesized. The anti-scale property of the AA-APEL toward CaCO3, zinc (II) and iron (III) in the artificial cooling water was studied through static scale inhibition tests. The observation shows that both calcium carbonate, zinc (II) and iron (III) inhibition increase with increasing the dosage of AA-APEL. The effect on formation of CaCO3 was investigated with combination of scanning electronic microscopy (SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD) analysis and fourier transform infrared spectrometer, respectively. The results showed that the AA-APEL copolymer not only influenced calcium carbonate crystal morphology and crystal size but also the crystallinity. The crystallization of CaCO3 in the absence of inhibitor was rhombohedral calcite crystal, whereas a mixture of calcite with vaterite crystals was found in the presence of the AA-APEL copolymer. Inhibition mechanism is proposed that the interactions between calcium or iron ions and polyethylene glycol (PEG) are the fundamental impetus to restrain the formation of the scale in cooling water systems.

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A biofilter model for simultaneous simulation of toluene removal and bed pressure drop under varied inlet loadings
Jinying XI,Insun KANG,Hongying HU,Xian ZHANG
Front. Environ. Sci. Eng.. 2015, 9 (3): 554-562.

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In this study, a biofiltration model including the effect of biomass accumulation and inert biomass growth is developed to simultaneously predict the Volatile Organic Compounds (VOCs) removal and filter bed pressure drop under varied inlet loadings. A laboratory-scale experimental biofilter for gaseous toluene removal was set up and operated for 100 days with inlet toluene concentration ranging from 250 to 2500 mg?m-3. According to sensitivity analysis based on the model, the VOCs removal efficiency of the biofilter is more sensitive to Henry’s constant, the specific surface area of the filter bed and the thickness of water layer, while the filter bed pressure drop is more sensitive to biomass yield coefficient and original void fraction. The calculated toluene removal efficiency and bed pressure drop satisfactorily fit the experimental data under varied inlet toluene loadings, which indicates the model in this study can be used to predict VOCs removal and bed pressure drop simultaneously. Based on the model, the effect of mass-transfer parameters on VOCs removal and the stable-run time of a biofilter are analyzed. The results demonstrate that the model can function as a good tool to evaluate the effect of biomass accumulation and optimize the design and operation of biofilters.

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FESE′s Best Papes of 2014
Front. Environ. Sci. Eng.. 2015, 9 (3): 563-563.

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