Frontiers of Environmental Science & Engineering

ISSN 2095-2201

ISSN 2095-221X(Online)

CN 10-1013/X

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A comprehensive overview of rural solid waste management in China
Chao ZENG,Dongjie NIU,Youcai ZHAO
Front. Environ. Sci. Eng.. 2015, 9 (6): 949-961.

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This paper aims to conduct a comprehensive review of rural solid waste (RSW) in terms of characteristics, management and legislation. Survey results show that RSW generation rates range from 0.25 to 2.1 kg·(capita·d)−1 in different rural villages across regions of China. Total RSW generation has been increasing, which is far higher than official data in 2014. RSW are dominated by food residue and coal ash/cinder/dust (at approximately 70%). Most of RSW are still discarded randomly without any treatment in China. Scattered RSW generation sources, imperfect legislation system, poor infrastructure on treatment and disposal are identified as the biggest challenge for RSW management currently in China. To improve RSW management, increasing financial resources, establishing sorting collection and transportation network, promoting sorting collection and recycling, improving treatment technology are proposed as the possible solution.

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Effect of effluent organic matter on ozonation of bezafibrate
Huan HE,Qian SUI,Shuguang LU,Wentao ZHAO,Zhaofu QIU,Gang YU
Front. Environ. Sci. Eng.. 2015, 9 (6): 962-969.

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The influence of three effluent organic matter (EfOM) model compounds, humic acid (HA), bovine serum albumin (BSA), and sodium alginate (AGS), on the ozonation of bezafibrate (BF), a typical pharmaceutical and personal care product (PPCP), was investigated. The results show that ozonation efficiently removed BF from aqueous solution with removal efficiencies>95% within 8 min for all conditions. The reaction rate of BF decreased with increasing model compounds concentrations and the influence was more pronounced for HA and BSA, while less pronounced for AGS. Although BF concentration was significantly reduced, the degree of mineralization achieved was only approximately 11%. The addition of HA and BSA improved the mineralization of the solution, while the influence of AGS was minor. The acute toxicity of BF solution during ozonation was determined using the Luminescent bacteria test, and the toxicity exhibited an initial increase and a successive reduction. An overall decreased acute toxicity was observed with an increase of HA. The presence of BSA increased the formation rate of toxicity intermediates and resulted in inhibition peak forward.

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Comparison of masking agents for antimony speciation analysis using hydride generation atomic fluorescence spectrometry
Jianhong XI,Mengchang HE,Kunpeng WANG,Guizhi ZHANG
Front. Environ. Sci. Eng.. 2015, 9 (6): 970-978.

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A sensitive atomic spectrometric method for the redox speciation analysis of Sb in water is described. The proposed method is based on the selective generation of stibine from Sb(III) in a continuous flow system using non-dispersive atomic fluorescence spectrometry for detection. The effects of the HCl concentration on the fluorescence intensities of Sb(III) and Sb(V) were investigated. The results indicated that atomic fluorescence emission due to Sb(V) can constructively interfere with the determination of Sb(III). For the determination of Sb(III), four compounds were tested as masking agents to inhibit the generation of stibine from Sb(V). The effects of the concentrations of the masking agents and of HCl on the fluorescence signals from Sb(III) and Sb(V) were studied. The results indicated that citric acid and NaF can successfully suppress hydride generation from Sb(V). To evaluate the developed methodology and the influence of the matrix, the recovery of Sb(III) from natural water that was spiked with different Sb(III) and Sb(V) concentrations was tested.

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Development of highly active coated monolith SCR catalyst with strong abrasion resistance for low-temperature application
Lina GAN,Shan LEI,Jian YU,Hongtao MA,Yo YAMAMOTO,Yoshizo SUZUKI,Guangwen XU,Zhanguo ZHANG
Front. Environ. Sci. Eng.. 2015, 9 (6): 979-987.

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Monolith SCR catalysts coated with V2O5-WO3/TiO2 were prepared by varying binder and coating thickness. Comparing with a monolith extruded with 100% V2O5-WO3/TiO2 powder, a coated monolith with a catalyst-coating layer of 260 μm in thickness exhibited the similar initial NOx reduction activity at 250°C. After 4 h abrasion (attrition) in an air stream containing 300 g·m−3 fine sands (50–100 μm) at a superficial gas velocity of 10 m·s−1, the catalyst still has the activity as a 100% molded monolith does in a 24-h activity test and it retains about 92% of its initial activity at 250°C. Estimation of the equivalent durable hours at a fly ash concentration of 1.0 g·m−3 in flue gas and a gas velocity of 5 m·s−1 demonstrated that this coated monolith catalyst is capable of resisting abrasion for 13 months without losing more than 8% of its initial activity. The result suggests the great potential of the coated monolith for application to de-NOx of flue gases with low fly ash concentrations from, such as glass and ceramics manufacturing processes.

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Applicability of the Arrhenius model for Ammonia Oxidizing Bacteria subjected to temperature time gradients
Front. Environ. Sci. Eng.. 2015, 9 (6): 988-994.

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The aim of this work is to identify the range of applicability of Arrhenius type temperature dependence for Ammonia Oxidizing Bacteria (AOB) subjected to temperature time gradients through continuous titrimetric tests. An innovative online differential titrimetric technique was used to continuously monitor the maximum biologic ammonia oxidation rate of the biomass selected in a pilot scale membrane bioreactor, as a function of temperature time gradients. The monitoring technique is based on the measurement of alkalinity and hydrogen peroxide consumption rates in two parallel reactors operated in non-limiting substrate conditions for AOB; both reactors were continuously fed with mixed liquor and in one of them AOB were inhibited with allylthiourea. The effects of temperature decrease rates in the range 1 to 4°C·h−1 were evaluated by controlling the titrimetric reactor in the temperature range 10°C–20°C. The dependence of growth kinetics on temperature time gradients and the range of applicability of Arrhenius model for temperature dependency of AOB growth kinetics were assessed. The Arrhenius model was found to be accurate only with temperature gradients lower than 2°C·h−1. The estimated Arrhenius coefficients (θ) were shown to increase from 1.07 to 1.6 when the temperature decrease rate reached 4°C·h−1.

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Concentration levels of disinfection by-products in 14 swimming pools of China
Xiaolu ZHANG,Hongwei YANG,Xiaofeng WANG,Yu ZHAO,Xiaomao WANG,Yuefeng XIE
Front. Environ. Sci. Eng.. 2015, 9 (6): 995-1003.

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Swimming has become a popular exercising and recreational activity in China but little is known about the disinfection by-products (DBPs) concentration levels in the pools. This study was conducted as a survey of the DBPs in China swimming pools, and to establish the correlations between the DBP concentrations and the pool water quality parameters. A total of 14 public indoor and outdoor pools in Beijing were included in the survey. Results showed that the median concentrations for total trihalomethanes (TTHM), nine haloacetic acids (HAA9), chloral hydrate (CH), four haloacetonitriles (HAN4), 1,1-dichloropropanone, 1,1,1-trichloropropanone and trichloronitromethane were 33.8, 109.1, 30.1, 3.2, 0.3, 0.6 µg?L−1 and below detection limit, respectively. The TTHM and HAA9 levels were in the same magnitude of that in many regions of the world. The levels of CH and nitrogenous DBPs were greatly higher than and were comparable to that in typical drinking water, respectively. Disinfection by chlorine dioxide or trichloroisocyanuric acid could substantially lower the DBP levels. The outdoor pools had higher TTHM and HAA9 levels, but lower trihaloacetic acids (THAA) levels than the indoor pools. The TTHM and HAA9 concentrations could be moderately correlated with the free chlorine and total chlorine residuals but not with the total organic carbon (TOC) contents. When the DBP concentration levels from other survey studies were also included for statistical analysis, a good correlation could be established between the TTHM levels and the TOC concentration. The influence of chlorine residual on DBP levels could also be significant.

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Organic nitrogen in PM2.5 in Beijing
Qian ZHANG,Fengkui DUAN,Kebin HE,Yongliang MA,Haiyan LI,Takashi KIMOTO,Aihua ZHENG
Front. Environ. Sci. Eng.. 2015, 9 (6): 1004-1014.

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Nitrogenous species, as important chemical components in PM2.5, include organic nitrogen (ON) and inorganic nitrogen (IN), both of which have potential effects on human health, climate change and visibility degradation. In this study, we analyzed total nitrogen (TN) by CHN Elemental analyzer and inorganic nitrogen by ion chromatography (IC) respectively to obtain ON by calculating the difference between TN and IN. The results show that the mean ON concentrations in winter and summer are both 2.86 μg·m−3, ten times higher than other places reported on average. ON contributes about 20%–30% to TN on average in both seasons, presenting higher contribution in summer. N:C ratios are much higher in summer than winter. ON sources or formation were strengthened by heavy PM2.5 pollution loads, especially sensitive to sulfate. ON concentrations are higher at night in the both seasons, however with distinguished day and night difference patterns influenced by relative humidity (RH) conditions. In winter, ON concentrations increase with RH on average through low RH values to high RH values. The variations are far larger than the ones caused by day and night difference. However in summer, day and night difference dominates the variations of ON concentrations at low RH values, and RH conditions promote ON concentrations increase significantly only at high RH values. Dust related source and anthropogenic emission related secondary source are identified as important sources for ON. At heavy pollution loads, ON sources are more of secondary formation, possibly strengthened by combination influence of RH and acidity increase.

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The calculation of equivalence factor for ecological footprints in China: a methodological note
Moucheng LIU,Wenhua LI,Dan ZAHNG,Ning SU
Front. Environ. Sci. Eng.. 2015, 9 (6): 1015-1024.

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The Ecological Footprint (EF), a physical indicator to measure the extent of humanity’s use of natural resources, has gained much attention since it was first used by Wackernagel and Rees in 1996. In order to appraise land area types with different levels of productivity, they introduced the concept of an equivalence factor. This relates to the average primary biomass productivities of different types of land (i.e. arable land, pasture, forest, water/fishery, built-up land and fossil energy land) to the regional average primary biomass productivity of all land types in a given year. Hence, the equivalence factor is an important parameter in the EF model and it directly affects the reliability of all results. Thus, this article calculates equivalence factors on the national and provincial levels in China based on Net Primary Production (NPP) from MODIS 1 km data in 2008. Firstly, based on the Light Utility Efficiency and CASA model, the NPP of different biologically productive lands of China and of different provinces was calculated. Secondly, China’s equivalence factor for 6 land area types was calculated based on NPP: arable land and built-up land has an equivalence factor of 1.71, forest and fossil energy land has a factor of 1.41, pasture has a factor of 0.44 and water/fishery 0.35; Finally, the equivalence factor of 6 land area types in different provinces was also calculated. The NPP of each ecosystem type varies along with the equivalence factor in different provinces. However, the ranking of the equivalence factors in different provinces remain the same, with that of arable land being the largest, and the water/fishery being the smallest.

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An enhanced environmental multimedia modeling system based on fuzzy-set approach: II. Model validation and application
Rongrong ZHANG,Chesheng ZHAN,Xiaomeng SONG,Baolin LIU
Front. Environ. Sci. Eng.. 2015, 9 (6): 1025-1035.

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Part I of this study develops an enhanced environmental multimedia modeling system (EMMS) based on fuzzy-set approach. Once the model development is complete, the composite module and the entire modeling system need to be tested and validated to ensure that the model can simulate natural phenomena with reasonable and reliable accuracy. The developed EMMS is first tested in a complete case study. And then verification results are conducted to compare with extensively researched literature data. In the third step, the data from an experimental landfill site is used for a pilot-scale validation. The comparisons between EMMS outputs and the literature data indicate that the EMMS can perform accurate modeling simulation. The modules of EMMS could support the entire environmental multimedia modeling system. Further field-scale validation is finished. The results are satisfactory. Most of the modeling yields closely match the monitoring data collected from sites. In addition, with the aid of fuzzy-set approach, EMMS can be a reliable and powerful tool to address the complex environmental multimedia pollution problems and provide an extensive support for decision makers in managing the contaminated environmental systems.

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An integrated model for structure optimization and technology screening of urban wastewater systems
Front. Environ. Sci. Eng.. 2015, 9 (6): 1036-1048.

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The conventional approach to wastewater system design and planning considers each component separately and does not provide the optimum performance of the entire system. However, the growing concern for environmental protection, economic efficiency, and sustainability of urban wastewater systems requires an integrated modeling of subsystems and a synthetic evaluation of multiple objectives. In this study, a multi-objective optimization model of an integrated urban wastewater system was developed. The model encompasses subsystems, such as a sewer system, stormwater management, municipal wastewater treatment, and a wastewater reclamation system. The non-dominated sorting genetic algorithm (NSGA-II) was used to generate a range of system design possibilities to optimize conflicting environmental and economic objectives. Information from a knowledge base, which included rules for generating treatment trains as well as the performance characteristics of commonly used water pollution control measures, was utilized. The trade-off relationships between the objectives, total water pollution loads to the environment, and life cycle costs (which consist of investment as well as operation and maintenance costs), can be illustrated using Pareto charts. The developed model can be used to assist decision makers in the preliminary planning of system structure. A benchmark city was constructed to illustrate the methods of multi-objective controls, highlight cost-effective water pollution control measures, and identify the main pressures on urban water environment.

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API-based assessment on urban air environment bearing capability in China
Jinnan WANG,Jing ZHANG,Hongqiang JIANG,Yaling LU
Front. Environ. Sci. Eng.. 2015, 9 (6): 1049-1055.

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Given the complexity and time-consuming of the conventional environmental capacity based assessment on air environment carrying capacity; a new method for assessing urban air environment carrying capacity based on air pollution index (API) is presented. By using this new method, the air environmental bearing capability of 333 cities at the prefecture level and above is assessed. The results show that of the 333 cities 9.6% is of high bearing capability, 34.5% relatively high bearing capability, 52.6% medium bearing capability, 2.7% low capability, and 0.6% is of weak bearing capability; in terms of regional distribution, the western region is of relatively high air environment bearing capability, followed by north-eastern and eastern regions, and the ambient air quality in the middle region is quite poor; among the 12 urban agglomerations in key regions, Pearl River delta, west side of Taiwan Strait and Chengdu-Chongqing agglomerations are of relatively high carrying capacity while other agglomerations are of medium bearing capability. The assessment results imply that the existing air quality standard (GB3095-1996) is quite unsound.

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Development of an integrated policy making tool for assessing air quality and human health benefits of air pollution control
Xuezhen QIU,Yun ZHU,Carey JANG,Che-Jen LIN,Shuxiao WANG,Joshua FU,Junping XIE,Jiandong WANG,Dian DING,Shicheng LONG
Front. Environ. Sci. Eng.. 2015, 9 (6): 1056-1065.

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Efficient air quality management is critical to protect public health from the adverse impacts of air pollution. To evaluate the effectiveness of air pollution control strategies, the US Environmental Protection Agency (US EPA) has developed the Software for Model Attainment Test-Community Edition (SMAT-CE) to assess the air quality attainment of emission reductions, and the Environmental Benefits Mapping and Analysis Program-Community Edition (BenMAP-CE) to evaluate the health and economic benefits of air quality improvement respectively. Since scientific decision-making requires timely and coherent information, developing the linkage between SMAT-CE and BenMAP-CE into an integrated assessment platform is desirable. To address this need, a new module linking SMAT-CE to BenMAP-CE has been developed and tested. The new module streamlines the assessment of air quality and human health benefits for a proposed air pollution control strategy. It also implements an optimized data gridding algorithm which significantly enhances the computational efficiency without compromising accuracy. The performance of the integrated software package is demonstrated through a case study that evaluates the air quality and associated economic benefits of a national-level control strategy of PM2.5. The results of the case study show that the proposed emission reduction reduces the number of nonattainment sites from 379 to 25 based on the US National Ambient Air Quality Standards, leading to more than US$334 billion of economic benefits annually from improved public health. The integration of the science-based software tools in this study enhances the efficiency of developing effective and optimized emission control strategies for policy makers.

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Removing phosphorus from aqueous solutions by using iron-modified corn straw biochar
Fenglin LIU,Jiane ZUO,Tong CHI,Pei WANG,Bo YANG
Front. Environ. Sci. Eng.. 2015, 9 (6): 1066-1075.

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Iron-modified corn straw biochar was used as an adsorbent to remove phosphorus from agricultural runoff. When agricultural runoffs with a total phosphorus (TP) concentration of 1.86 mg·L−1 to 2.47 mg·L−1 were filtered at a hydraulic retention time of 2 h through a filtration column packed with the modified biochar, a TP removal efficiency of over 99% and an effluent TP concentration of less than 0.02 mg·L−1 were achieved. The isotherms of the phosphorus adsorption by the modified biochar fitted the Freundlich equation better than the Langmuir equation. The mechanism of the phosphorus adsorbed by the modified biochar was analyzed by using various technologies, i.e. scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis, X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR). The results indicated that the surface of the modified biochar was covered by small iron granules, which were identified as Fe3O4. The results also showed that new iron oxides were formed on the surface of the modified biochar after the adsorption of phosphorus. Moreover, new bonds of Fe-O-P and P-C were found, which suggested that the new iron oxides tend to be Fe5(PO4)4(OH)3. Aside from removing phosphorus, adding the modified biochar into soil also improved soil productivity. When the modified biochar-to-soil rate was 5%, the stem, root, and bean of broad bean plants demonstrated increased growth rates of 91%, 64%, and 165%, respectively.

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Combined process of biofiltration and ozone oxidation as an advanced treatment process for wastewater reuse
Xinwei LI,Hanchang SHI,Kuixiao LI,Liang ZHANG
Front. Environ. Sci. Eng.. 2015, 9 (6): 1076-1083.

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The effluent of a wastewater treatment plant was treated in a pilot plant for reclaimed water production through the denitrification biofilter (DNBF) process, ozonation (O3), and biologic aerated filtration (BAF). The combined process demonstrated good removal performance of conventional pollutants, including concentrations of chemical oxygen demand (27.8 mg·L−1) and total nitrogen (9.9 mg·L−1) in the final effluent, which met the local discharge standards and water reuse purposes. Micropollutants (e.g., antibiotics and endocrine-disrupting chemicals) were also significantly removed during the proposed process. Ozonation exhibited high antibiotic removal efficiencies, especially for tetracycline (94%). However, micropollutant removal efficiency was negatively affected by the nitrite produced by DNBF. Acute toxicity variations of the combined process were estimated by utilizing luminescent bacteria. Inhibition rate increased from 9% to 15% during ozonation. Carbonyl compound concentrations (e.g., aldehydes and ketones) also increased by 58% as by-products, which consequently increased toxicity. However, toxicity eventually became as low as that of the influent because the by-products were effectively removed by BAF. The combined DNBF/O3/BAF process is suitable for the advanced treatment of reclaimed water because it can thoroughly remove pollutants and toxicity.

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Microbial electrolysis cells with biocathodes and driven by microbial fuel cells for simultaneous enhanced Co(II) and Cu(II) removal
Jingya SHEN,Yuliang SUN,Liping HUANG,Jinhui YANG
Front. Environ. Sci. Eng.. 2015, 9 (6): 1084-1095.

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Cobalt and copper recovery from aqueous Co(II) and Cu(II) is one critical step for cobalt and copper wastewaters treatment. Previous tests have primarily examined Cu(II) and Co(II) removal in microbial electrolysis cells (MECs) with abiotic cathodes and driven by microbial fuel cell (MFCs). However, Cu(II) and Co(II) removal rates were still slow. Here we report MECs with biocathodes and driven by MFCs where enhanced removal rates of 6.0±0.2 mg?L−1?h−1 for Cu(II) at an initial concentration of 50 mg?L−1 and 5.3±0.4 mg?L−1 h−1 for Co(II) at an initial 40 mg?L−1 were achieved, 1.7 times and 3.3 times as high as those in MECs with abiotic cathodes and driven by MFCs. Species of Cu(II) was reduced to pure copper on the cathodes of MFCs whereas Co(II) was removed associated with microorganisms on the cathodes of the connected MECs. Higher Cu(II) concentrations and smaller working volumes in the cathode chambers of MFCs further improved removal rates of Cu(II) (115.7 mg?L−1?h−1) and Co(II) (6.4 mg?L−1?h−1) with concomitantly achieving hydrogen generation (0.05±0.00 mol?mol−1 COD). Phylogenetic analysis on the biocathodes indicates Proteobacteria dominantly accounted for 67.9% of the total reads, followed by Firmicutes (14.0%), Bacteroidetes (6.1%), Tenericutes (2.5%), Lentisphaerae (1.4%), and Synergistetes (1.0%). This study provides a beneficial attempt to achieve simultaneous enhanced Cu(II) and Co(II) removal, and efficient Cu(II) and Co(II) wastewaters treatment without any external energy consumption.

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Combination of the direct electro-Fenton process and bioremediation for the treatment of pyrene-contaminated soil in a slurry reactor
Wendi XU,Shuhai GUO,Gang LI,Fengmei LI,Bo WU,Xinhong GAN
Front. Environ. Sci. Eng.. 2015, 9 (6): 1096-1107.

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A combined treatment technology (DEF-BIO) using the direct electro-Fenton (DEF) process and bioremediation (BIO) was established in this study. The performance of the DEF-BIO process on the remediation of a pyrene (PYR)-contaminated soil was evaluated in a slurry reactor. The appropriate order of application was to conduct the DEF process followed by BIO, evaluated through analysis of the degradation characteristics of each process individually. In addition, the application time of the DEF process affected the efficiency of the combined process. The optimum time to apply the DEF process was determined through an analysis of the induced changes in PYR intermediates, pH, soil organic matter (SOM) and bacteria. The optimum application time of the DEF process was 6 h. All the induced changes were beneficial for the BIO phase. The removal of PYR was 91.02% for DEF–BIO after 72 h, and the efficiency was almost 50% increased, compared with the individual DEF and BIO treatments. Therefore, the combined process of DEF–BIO process may be an efficient and promising method for the remediation.

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Influencing mechanism of high solid concentration on anaerobic mono-digestion of sewage sludge without agitation
Yuyao ZHANG,Huan LI,Can LIU,Yingchao CHENG
Front. Environ. Sci. Eng.. 2015, 9 (6): 1108-1116.

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High-solids anaerobic digestion of sewage sludge was a promising process, but high solid concentration negatively influenced methane production. The influencing mechanism was systematically analyzed in this study through a series of static anaerobic digestion experiments at total solids (TS) contents of 3%–15%. The results showed that TS 6% was the boundary between low-solids and high-solids anaerobic digestion, and the accumulative methane yield decreased exponentially when TS increased from 6% to 15%. The performance of anaerobic digestion was directly determined by the efficiency of mass transfer, and the relation between methane yield and sludge diffusive coefficients was well described by a power function. Thus, the increasing TS resulted in an exponential increase in sludge viscosity but an exponential decrease in diffusive coefficient. The blocked mass transfer led to the accumulation of volatile fatty acids (VFAs) and free ammonia. Acetic metabolism was the main process, whereas butyric and propionic metabolisms occurred at the initial stage of high-solids anaerobic digestion. The concentration of VFAs reached the maximum at the initial stage, which were still lower than the threshold influencing methanogens. The concentration of free ammonia increased gradually, and the methanogenesis was inhibited when free ammonia nitrogen exceeded 50 mg·L−1. Consequently, the deterioration of high-solids anaerobic digestion was related to the blocked mass transfer and the resulting ammonia accumulation.

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Simultaneous CO2 capture and H2 generation using Fe2O3/Al2O3 and Fe2O3/CuO/Al2O3 as oxygen carriers in single packed bed reactor via chemical looping process
Jie ZHU,Wei WANG,Xiuning HUA,Zhou XIA,Zhou DENG
Front. Environ. Sci. Eng.. 2015, 9 (6): 1117-1129.

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The chemical looping concept provided a novel way to achieve carbon separation during the production of energy or substances. In this work, hydrogen generation with inherent CO2 capture in single packed bed reactor via this concept was discussed. Two oxygen carriers, Fe2O3 60 wt.% and Fe2O3 55 wt.%/CuO 5 wt.% supported by Al2O3, were made by ball milling method. First, according to the characteristics of the reduction breakthrough curve, a strict fuel supply strategy was selected to achieve simultaneous CO2 capture and H2 production. Then, in the long term tests using CO as fuel, it was proved that CuO addition improved hydrogen generation with the maximum intensity of 3700 μmol H2·g−1 Fe2O3 compared with Fe-Al of 2300 μmol H2·g−1 Fe2O3. The overall CO2 capture efficiency remained 98%–98.8% over 100 cycles. Moreover, the reactivity of deactivated materials was recovered nearly like that of fresh ones by sintering treatment. Finally, two kinds of complex gases consist of CO, H2, CH4 and CO2 were utilized as fuels to test the feasibility. The results showed all components could be completely converted by Fe-Cu-Al in the reduction stage. The intensity of hydrogen production and the overall CO2 capture efficiency were in the range of 2000–2400 μmol H2·g−1 Fe2O3 and 89%–95%, respectively.

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Performance and kinetics of iron-based oxygen carriers reduced by carbon monoxide for chemical looping combustion
Xiuning HUA,Wei WANG,Feng WANG
Front. Environ. Sci. Eng.. 2015, 9 (6): 1130-1138.

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Chemical looping combustion is a promising technology for energy conversion due to its low-carbon, high-efficiency, and environmental-friendly feature. A vital issue for CLC process is the development of oxygen carrier, since it must have sufficient reactivity. The mechanism and kinetics of CO reduction on iron-based oxygen carriers namely pure Fe2O3 and Fe2O3 supported by alumina (Fe2O3/Al2O3) were investigated using thermo-gravimetric analysis. Fe2O3/Al2O3 showed better reactivity over bare Fe2O3 toward CO reduction. This was well supported by the observed higher rate constant for Fe2O3/Al2O3 over pure Fe2O3 with respective activation energy of 41.1±2.0 and 33.3±0.8 kJ·mol−1. The proposed models were compared via statistical approach comprising Akaike information criterion with correction coupled with F-test. The phase-boundary reaction and diffusion control models approximated to 95% confidence level along with scanning electron microscopy results; revealed the promising reduction reactions of pure Fe2O3 and Fe2O3/Al2O3. The boosting recital of iron-based oxygen carrier support toward efficient chemical looping combustion could be explained accurately through the present study.

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Treatment of swine wastewater in aerobic granular reactors: comparison of different seed granules as factors
Lin LIU,Qiyu YOU,Valerie GIBSON,Xu HUANG,Shaohua CHEN,Zhilong YE,Chaoxiang LIU
Front. Environ. Sci. Eng.. 2015, 9 (6): 1139-1148.

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The granulation process, physic-chemical properties, pollution removal ability and bacterial communities of aerobic granules with different feed-wastewater (synthetic wastewater, R1; swine wastewater, R2), and the change trend of some parameters of two types of granules in long-term operated reactors treating swine wastewater were investigated in this experiment. The result indicated that aerobic granulation with the synthetic wastewater had a faster rate compared with swine wastewater and that full granulation in R1 and R2 was reached on the 30th day and 39th day, respectively. However, although the feed wastewater also had an obvious effect on the biomass fraction and extracellular polymeric substances of the aerobic granules during the granulation process, these properties remained at a similar level after long-term operation. Moreover, a similar increasing trend could also be observed in terms of the nitrogen removal efficiencies of the aerobic granules in both reactors, and the average specific removal rates of the organics and ammonia nitrogen at the steady-state stage were 35.33 mg·g−1 VSS and 51.46 mg·g−1 VSS for R1, and 35.47 mg·g−1 VSS and 51.72 mg·g−1 VSS for R2, respectively. In addition, a shift in the bacterial diversity occurred in the granulation process, whereas bacterial communities in the aerobic granular reactor were not affected by the seed granules after long-term operation.

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