Search

Abstract: In the previous studies, a method was developed to assess soil erosion based on land use information. In this paper, we present another approach that uses environmental data to assess soil erosion. A soil erosion characteristic index EI is proposed, and its value is derived using the Analytic Hierarchy Process (AHP) technique based on standardized environmental information stored in minimum polygons that tile the erodible area under consideration. The approach is applied to a case study of the Yellow River basin, north China, where serious erosion is occurring. To represent different grades of soil erosion, the range of EI is divided into six levels according to standard grades of soil erosion intensity. The application indicates that the method deals properly with data scarcity, with the results giving a satisfactory representation of the characteristics of soil erosion in the Yellow River basin. The spatial–temporal distribution of EI in the Yellow River basin is predicted, and the results interpreted to give the long-term trend and state of soil depletion. Comparisons are given between EI and surveyed soil erosion zoning maps for the Yellow River basin at the end of the 1980s and 1990s. The output reliability and the approach applicability in smaller spatial scales are investigated in a case study of Zhifanggou basin. [Copyright &y& Elsevier]

Abstract: This study presents a special problem on vertical distribution for sediment and copper in hyper-concentrated turbulent solid-liquid system that is essentially different from the ordinary low-concentrated turbulent system. A resonance type turbulent simulation equipment is used for the experimental study in which a vertically uniform turbulent field of the mixture of loess and water is produced in a testing cylinder with a grille stirrer that moves up and down harmoniously with varying vibration frequencies. In order to compare the variations of the vertical profiles of sediment and copper in low- and hyper-concentrated solid-liquid system, different scenarios for input sediment content ranging from 5 to 800 kg/m3 was considered in the experimental studies. It was found that solids copper content increases with input sediment content, S0, and reaches its peak as S0 goes to 10 kg/m3 and then decreases rapidly with increasing input sediment content. Such a behavior is possibly resulted from the joint effect of the specific adsorption of copper on loess, precipitation of carbonate and hydroxide of copper due to high carbonate content in the loess and the so-called “particulate concentration effect” due to the present of the sediment variation in water. The vertical sediment concentration distribution resulted from the uniform turbulence is generally uniform, but slight non-uniformity does occur as sediment concentration exceeds certain value. However, the vertical concentration distributions of soluble copper seem not to be affected much by the variation of sediment concentrations. [Copyright &y& Elsevier]

Abstract: The electrochemical behavior of marmatite–carbon paste electrode in the presence and absence of Acidithiobacillus ferrooxidans was investigated by electrochemical impedance spectroscopy (EIS) measurement. The effects of the concentration of Fe3+ ions, bacterial strain and temperature on the EIS spectra of the marmatite electrode were examined. The experimental data indicated that the impedance diagrams of the marmatite electrode in the different electrolytes had the similar features with two semicircles in the higher frequency range and a line in the lower frequency range. An equivalent circuit has been considered for the analysis of the EIS spectra of the marmatite electrode in the solution of 10g/L Fe2+ ions without and with microorganisms. The fitting of experimental data along with a preliminary estimation for the characteristic parameters of the impedance model could validate the proposed mechanism, which suggested that the dissolution of marmatite proceeded by the similar kinetic processes occurring in the marmatite–solution interface in the different systems during the leaching process. [Copyright &y& Elsevier]

Abstract: Bioleaching of a marmatite flotation concentrate with a moderately thermoacidophilic iron-oxidizing bacterial strain (MLY) was investigated in batch experiments. Experimental results showed that the dissolution rate of marmatite was influenced markedly by pH, temperature, pulp density and particle size of ore. The bioleaching of the concentrate by the moderate thermophile was more effective when carried out under the higher acidity and temperature compared with Acidithiobacillus ferrooxidans. The adapted strain of the moderate thermophile could provide more rapid and complete oxidation of marmatite than its original strain and in the sterile control. [Copyright &y& Elsevier]

Abstract: A membrane-free baffled microbial fuel cell (MFC) was developed to treat synthetic Cu(II) sulfate containing wastewater in cathode chamber and synthetic glucose-containing wastewater fed to anode chamber. Maximum power density of 314mW/m3 with columbic efficiency of 5.3% was obtained using initial Cu2+ concentration of 6400mg/L. Higher current density favored the cathodic reduction of Cu2+, and removal of Cu2+ by 70% was observed within 144h using initial concentration of 500mg/L. Powder X-ray diffraction (XRD) analysis indicated that the Cu2+ was reduced to Cu2O or Cu2O plus Cu which deposited on the cathode, and the deficient cathodic reducibility resulted in the formation of Cu4(OH)6SO4 at high initial Cu2+ concentration (500–6400mg/L). This study suggested a novel low-cost approach to remove and recover Cu(II) from Cu2+-containing wastewater using MFC-type reactor. [Copyright &y& Elsevier]

Abstract: This work studied an alkalophilic Gram-positive bacterium, Corynebacterium sp. strain MFC03, for its ability to produce electricity in the absence of an exogenous mediator under alkaline pH in microbial fuel cells (MFCs). The experimental results demonstrated that the strain MFC03 was capable of utilizing organic acids, sugars and alcohols as electron donors to generate electricity under above desired conditions. At an optimal pH of 9.0, the glucose-fed MFC achieved a maximum power density of 7.3mW/m2 and a Coulombic efficiency (CE) of 5.9%. In the presence of 0.1mM anthroquinone-2,6-disulfonate (AQDS), the maximum power density was enhanced to 41.8mW/m2 and CE was increased to 18.4%. The cyclic voltammetry measurements revealed that the electron transfer mechanism in the strain MFC03-based MFC was mainly via the excreted redox compounds in the medium solution. [Copyright &y& Elsevier]

Abstract: The removal of Acid Orange 7 (AO7) in simulated wastewater was experimentally investigated using a three-dimensional electrode reactor with granular activated carbon as the particle electrode, ACF (activated carbon fiber)/Fe as the anode, and ACF/Ti as the cathode. Particular attention was paid to the reaction mechanisms and the dye degradation pathway in the system. The removal of AO7 in the system was mainly dependent on the oxidation by the produced active substances ( OH, etc.) and the coagulation by Fe(II) or Fe(III) dissolved from the anode. The former mechanism was predominant. A possible pathway for AO7 degradation was proposed by monitoring the temporal evolution of intermediates in the solution, with the use of some techniques including GC/MS, FTIR and HPLC. The AO7 molecule was observed to be firstly decomposed to aromatic intermediates, further degraded to ring opening products and finally mineralized to CO2, H2O and inorganic salts. The intermediates increased the biodegradability of the wastewater, which was proved by the increase of the BOD/COD value after electrolysis treatment. The three-dimensional electrode method can be considered an effective alternative to dye wastewater pretreatment prior to the biological process. [Copyright &y& Elsevier]

Aerobic granules were utilized as an effective biosorbent to remove Cr3+ from aqueous solution. The results showed that the initial pH, contact time, and Cr3+ concentration affected the biosorption process significantly. Both Freundlich and Langmuir isotherms were able to describe the equilibrium data reasonably with high correlation coefficients (R 2 >0.95) and pseudo-second-order model best fitted the biosorption process at experimental conditions. Moreover, Environmental Scanning Electronic microscope (ESEM), X-ray energy dispersion (EDX), and Fourier transform infrared (FTIR) analyses revealed that metal complexation, chemical precipitation, and ion exchange were involved in the removal of Cr3+ with aerobic granules. Further analysis by a metal ion fraction test demonstrated that metal complexation could be the dominant mechanism of biosorption, whereas chemical precipitation and ion exchange appeared only to have minor role in the overall Cr3+ biosorption process. [Copyright &y& Elsevier]

Experiments were conducted to investigate the behavior of the integrated system with biofilm reactors and zero-valent iron (ZVI) process for coking wastewater treatment. Particular attention was paid to the performance of the integrated system for removal of organic and inorganic nitrogen compounds. Maximal removal efficiencies of chemical oxygen demand (COD), ammonia nitrogen (NH3-N) and total inorganic nitrogen (TIN) were up to 96.1, 99.2 and 92.3%, respectively. Moreover, it was found that some phenolic compounds were effectively removed. The refractory organic compounds were primarily removed in ZVI process of the integrated system. These compounds, with molecular weights either ranged 10,000–30,000Da or 0–2000Da, were mainly the humic acid (HA) and hydrophilic (HyI) compounds. Oxidation–reduction and coagulation were the main removal mechanisms in ZVI process, which could enhance the biodegradability of the system effluent. Furthermore, the integrated system showed a rapid recovery performance against the sudden loading shock and remained high efficiencies for pollutants removal. Overall, the integrated system was proved feasible for coking wastewater treatment in practical applications. [Copyright &y& Elsevier]

The defluoridation efficiency (ε F) of electrocoagulation (EC) is closely related to the pH level of the F−-containing solution. The pH level usually needs to be adjusted by adding acid in order to obtain the highest ε F for the F−-containing groundwater. The use of combined EC (CEC), which is the combination of chemical coagulation with EC, was proposed to remove fluoride from drinking water for the first time in this study. The optimal scheme for the design and operation of CEC were obtained through experiments on the treatment of F−-containing groundwater. It was found, with OH− being the only alkalinity of the raw water, that the highest efficiency would be obtained when the molar ratio of alkalinity and fluoride to Al(III) (γ Alkalinity+F) was controlled at 3.0. However, when the raw water contained alkalinity, a correction coefficient was needed to correct the concentration of to obtain the optimal defluoridation condition of γ Alkalinity+F =3.0 for CEC. The correction coefficient of concentration was concluded as 0.60 from the experiment. For the practical F−-containing groundwater treatment, CEC can achieve similar ε F as an acid-adding EC process. The consumption of aluminum electrode was decreased in CEC. The energy consumption also declined greatly in CEC, which is less than one third of that in the acid-adding EC process. [Copyright &y& Elsevier]

Abstract: A novel aerobic gram-positive bacterial strain capable of utilizing quinoline as sole source of carbon, nitrogen and energy was isolated from activated sludge of a coke plant wastewater treatment process. The isolate was identified as Rhodococcus sp. QL2 based on its morphology, physiochemical properties in addition to the results from 16S rDNA sequence analysis. The optimum temperature and the pH for its growth were 35–40°C and 8.0, respectively. Extra nitrogen sources stimulated the bacterial growth on quinoline. Strain QL2 had strong quinoline degradability, and its degradation kinetics could be described with Haldane''s model. Strain QL2 also had a broad range of substrate utilization. Identification of intermediates by GC/MS showed Rhodococcus sp. QL2 degraded quinoline via two pathways simultaneously. [Copyright &y& Elsevier]

Abstract: With a hybrid wastewater treatment process consisting of neutralization, precipitation, modified two-phase anaerobic digestion, and biological aerated filter (BAF) being developed, the yellow ginger processing wastewater with high COD and high sulphate was treated successfully in the laboratory. With an inserted stripping unit, the modified two-phase anaerobic digestion process eliminated the inhibition of methanogens to the greatest extent, which results in a high-efficiency COD removal. Subsequently, the effluent from the anaerobic units was treated with excellent results in the novel BAF which was equipped with special carriers. This was due to the simultaneous nitrification and denitrification (SND) that occurred there. When the raw water with COD of 18,000–20,000mg/L, SO4 2− of 8,500–11,000mg/L, and NH4 +-N of 220–300mg/L was treated by the hybrid process, the concentrations of COD, NH4 +-N, and total nitrogen (TN) in the effluent were lower than 100, 10 and 15mg/L, respectively. [Copyright &y& Elsevier]

Abstract: Bottom ash, a power plant waste, was used to remove the organic pollutants in coking wastewater and papermaking wastewater. Particular attention was paid on the effect of bottom ash particle size and dosage on the removal of chemical oxygen demand (COD). UV–vis spectra, fluorescence excitation-emission matrix (FEEM) spectra, Fourier transform infrared (FTIR) spectra, and scanning electron microscopic (SEM) photographs were investigated to characterize the wastewaters and bottom ash. The results show that the COD removal efficiencies increase with decreasing particle sizes of bottom ash, and the COD removal efficiency for coking wastewater is much higher than that for papermaking wastewater due to its high percentage of particle organic carbon (POC). Different trends of COD removal efficiency with bottom ash dosage are also observed for coking and papermaking wastewaters because of their various POC concentrations. Significant variations are observed in the FEEM spectra of wastewaters after treatment by bottom ash. New excitation-emission peaks are found in FEEM spectra, and the fluorescence intensities of the peaks decrease. A new transmittance band in the region of 1400–1420cm−1 is observed in FTIR spectra of bottom ash after adsorption. The SEM photographs reveal that the surface of bottom ash particles varies evidently after adsorption. [Copyright &y& Elsevier]

Abstract: Ti/Sb-SnO2 anodes were prepared by thermal decomposition to examine the influence of the amount of Sb dopant on the structure and electrocatalytic capability of the electrodes in the oxidation of 4-chlorophenol. The physicochemical properties of the Sb-SnO2 coating were markedly influenced by different amounts of Sb dopant. The electrodes, which contained 5% Sb dopant in the coating, presented a much more homogenous surface and much smaller mud-cracks, compared with Ti/Sb-SnO2 electrodes containing 10% or 15% Sb dopant, which exibited larger mud cracks and pores on the surface. However, the main microstructure remained unchanged with the addition of the Sb dopant. No new crystal phase was observed by X-ray diffraction (XRD). The electrochemical oxidation of 4-chlorophenol on the Ti/SnO2 electrode with 5% Sb dopant was inclined to electrochemical combustion; while for those containing more Sb dopant, intermediate species were accumulated. The electrodes with 5% Sb dopant showed the highest efficiency in the bulk electrolysis of 4-chlorophenol at a current density of 20 mA/cm2 for 180 min; and the removal rates of 4-chlorophenol and COD were 51.0% and 48.9%, respectively. [Copyright &y& Elsevier]

Advanced treatment of coking wastewater was investigated experimentally with coagulation and zero-valent iron (ZVI) processes. Particular attention was paid to the effect of dosage and pH on the removal of chemical oxygen demand (COD) in the two processes. The results showed that ZVI was more effective than coagulation for advanced treatment of coking wastewater. The jar tests revealed that maximal COD removal efficiency of 27.5–31.8% could be achieved under the optimal condition of coagulation, i.e. 400mg/L of Fe2(SO4)3 as coagulant at pH 3.0–5.0. On the other hand, the COD removal efficiency could be up to 43.6% under the idealized condition of ZVI upon 10g/L active carbon and 30g/L iron being dosed at pH 4.0. The mechanisms for COD removal in ZVI were dominated by coagulation, precipitation and oxidation–reduction. ZVI would also enhance the biodegradability of effluent by increasing BOD5/COD from 0.07 to 0.53. Moreover, some ester compounds could be produced in the reaction. Although ZVI was found more efficient than coagulation in eliminating low molecular weight (<2000Da) compounds in the wastewater, there were still a few residual contaminants which could hardly be eliminated by either of the process. [Copyright &y& Elsevier]