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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]

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]

Dissolved organic matter(DOM)is an important element of natural aquatic systems. Due to differences in their hydrophobic/hydrophilic properties and various functional groups, chemical appearances of DOM fractions also vary. In this study, seven natural waters, extending from Xiaheyan to Toudaoguai along the Ning-Meng section of the Yellow river, were sampled in April 2015. Four DOM fractions were obtained by pumping through XAD-4 and XAD-8 resins, i.e., hydrophobic acid (HOA), hydrophobic base (HOB), weak hydrophobic acid (WHOA), and hydrophilic matter (HYI). Based on detection by three-dimensional excitation-emission matrix fluorescence (EEM) and correlation analysis, relationships with five metal ions (Pb, Zn, Cu, Cr, As) were analyzed. Results show that DOC gradually increased along an upstream to downstream continuum in the Ning-Meng section. HYI (small molecular proteins) was the main DOM fraction present, followed by HOA, suggesting enhanced microbial-sourced impact from industrial sewage discharges. The significant peaks of humic-like (A, C) and protein-like compounds (T 1 ) in the EEM chart further highlight the effect of endogenous pollution caused by wastewater. Furthermore, SPSS fitting results indicate that DOM is correlated with all five metal ions, especially with Cu. In terms of the four DOM fractions, HYI showed the strongest correlation with Cu, illustrating the significant relationship between HYI and Cu during the migration and transformation process. Moreover, the fluorescence intensity of protein-like compounds decreased with increasing Cu concentration, possibly due to fluorescence quenching caused by complexation between Cu and proteins in HYI.

Electrochemical oxidation by boron-doped diamond (BDD) electrode is an effective method of degrading refractory organics. Compared with TOC detection, the amount of gas escape can more effectively and intuitively reflect the mineralization and the removal extent. In this study, indole is chosen as a typical pollutant and the detection of its removal rate was compared at current densities of 10, 20, and 30 mA·cm -2 . Meanwhile, the degradation mechanism was analyzed based on the changes in the carbon and nitrogen forms and conservation status. As a result, BDD electrodes displayed a higher removal efficiency to indole, which can completely be removed after 8 h, 5 h, and 4 h with current densities of 10, 20 and 30 mA·cm -2 , respectively. Changes in TOC removal and CO 2 generation were both increased with increasing the current densities, suggesting that the mineralization extent was in accordance with current densities. Furthermore, the escaped CO 2 , combined with TOC and TIC constituted a conservative carbon system. The byproduct isatin was stable and accumulated at 4-5 h, as TOC, TON, and CO 2 generation was unchanged at this stage. Finally, the XPS analysis suggested the adsorption by-products such as isatin and benzoquinone on the BDD surface, which can further be removed by increasing the electrolysis time. This study demonstrated the mineralization process of indole based on the escaped gas detection and the changes in the carbon and nitrogen forms, which will increase the understanding of the electrolysis process.

Electrochemical systems were built to investigate the degradation of benzotriazole (BTA) on boron-doped diamond (BUU) and PbO2 anodes and give an insight into the mineralization ability of two electrodes in terms of the amount and activity of hydroxyl radicals. Results of bulk electrolysis showed that both BDD and PbO2 displayed perfect BTA degradation performance after 12 hours' electrolysis, with the removal percentages of 99. 48% and 98. 36%, respectively, while the mineralization ability of BDD was much stronger than that of PbO2, with the efficiency of 87. 69% for BDD and 35. 96% for PbO2. Less hydroxyl radical and hydrogen production in BDD system suggested the less amount of active sites on BDD surface, thus further verified that the generated hydroxyl radical amount was not the primary factor determining the mineralization ability of anodes. However, BDD displayed larger binding energy of adsorbed oxygen and thinner adsorption layer than those of PbO2, indicating that the BDD electrode surface was of greater catalytic activity, thus the generated hydroxyl radicals were more free, which was the key to its better mineralization ability.

The electricity generation performance of a microbial fuel cell (MFC) utilizing Dioscorea zingiberensis wastewater was studied with an H-shape reactor. Indexes including pH, conductivity, oxidation peak potential and chemical oxygen demand (COD) of the anolyte were monitored to investigate the contaminants degradation performance of the MFC during the electricity generation process, besides, contaminant ingredients in anodic influent and effluent were analyzed by GC-MS and IR spectra as well. The maximum power density of the MFC could achieve 118.1 mW/m2 and the internal resistance was about 480 omega. Connected with a 1 000 omega external resistance, the output potential was about 0.4 V. Fed with 5 mL Dioscorea zingiberensis wastewater, the electricity generation lasted about 133 h and the coulombic efficiency was about 3.93%. At the end of electricity generation cycle, COD decreased by 90.1% while NH4(+) -N decreased by 66.8%. Furfural compounds, phenols and some other complicated organics could be decomposed and utilized in the electricity generation process, and the residual contaminants in effluent included some long-chain fatty acids, esters, ethers, and esters with benzene ring, cycloalkanes, cycloolefins, etc. The results indicate that MFC, which can degrade and utilize the organic contaminants in Dioscorea zingiberensis wastewater simultaneously, provides a new approach for resource recovery treatment of Dioscorea zingiberensis wastewater.

The two-chamber microbial fuel cells (MFCs) were constructed with excess sludge as the anodic substrate and CuSO4 solution as the catholyte. The start up method, degradation of the anodic sludge, removal of the Cu2+ and products on cathode were investigated in the study. The results of batch experiments showed that Cu2+ can be used as cathodic electron acceptors, e. g. a stable voltage output of 0.478 V and a maximum power density of 536 mW/m3 were obtained at external resistance of 1 000 omega and Cu2+ concentration of 6 400 mg/L. The Cu2+ contained in wastewater could be removed effectively by the MFC process, e. g. 97.8% of Cu2+ was removed in a MFC reactor at the end of 288 h with initial Cu2+ concentration of 1 000 mg/L and external resistance of 0 omega. The cathodic products depended on cathodic reducibility, most of Cu2+ was deposited as Cu2O and a small part as Cu4 (OH), 6SO4 with lower cathodic reducibility, metal copper deposited on the cathode with higher cathodic reducibility. Using excess sludge as anodic substrate could support the MFCs for long-term operation. The acclimation stage of the exoelectrogenic bacteria on the anode had an impact on MFC performance and cathodic reduction of Cu2+, and the stability of exoelectrogenic biofilm on anode could be determined by monitoring the anode potential. The MFC with excess sludge as anodic substrate can degrade organic matter in sludge and accomplish Cu(2+) -containing wastewater treatment and copper recovery simultaneously.

Based on the data of surface phytoplankton investigated by Hong Kong Environmental Protection Department in Shenzhen Bay in 2006, variation characteristics of phytoplankton communities and the relationship between the phytoplankton diversity indices and environmental factors were analyzed in the present paper. Results showed that a total of 27 genera and 34 species of phytoplankton were identified. Of these, 18 were diatoms (52.94%), 10 were dinoflagellates (29.41%), 6 were from other minor groups (17.65%). The cell abundance was estimated to be from 2.13 x 10(6) to 4.15 x 10(6) cells/L, with an average of 2.92 x 10(6) cells/L. The maximum cell abundance appeared in the autumn (October), followed in spring (May). The cell abundance showed double abundance peaks annually. The cell abundance of phytoplankton decreased from the middle bay to the bay mouth. In the marine area, the diversity index of the phytoplankton ranged from 0.76 to 2.52; the evenness of phytoplankton ranged from 0.29 to 0.74; the diversity and evenness of phytoplankton community were rather low, which indicated that the relative abundances of the species diverged from evenness, phytoplankton community were not steady, and only few dominant species increased rapidly. The species richness index ranged from 0.57 to 2.17, the high eutrophic water body caused the species richness index declined. Better relationship was found between phytoplankton diversity indices and nutrient, salinity, dissolved oxygen.

The possibility of electricity generation in a single chamber microbial fuel cell fed with Dioscorea zingiberensis C. H. Wright wastewater was demonstrated, and the effects of COD and SO4(2-) concentration on MFC performance were investigated. Under the same conductivity and COD concentration, the power density generated from wastewater equaled to 80.3% of that from glucose. At low COD concentration, the electricity generation increased with increasing COD loading rates, and the maximum power density was 322 mW/m2; while the COD concentration was enhanced over 2766 mg/L, the stable times for electricity generation was reduced and the MFC could not recover to previous performance as refueling. That indicates high COD loading rates would inhibit microbial activity. The COD removal rates varied from 68.2% to 84.8%, and it decreased when COD concentration climbed up. The power density was enhanced with SO4(2-) concentration increasing up to 7716 mg/L (Conductivity > 8.19 mS/cm) after which no further improvements in power density were observed. The maximum power density of the wastewater containing SO4(2-) was lower by 14.5% on average than that of the wastewater which removed SO4(2-). And its coulombic efficiencies declined substantially as SO4(2-) concentration increasing, which imply that the SO4(2-) is deoxidized as the electron acceptor, which takes the MFC efficiency down.

Based on the field data of Shenzhen coastal water quality in 2002-2007, variation characteristics of nutrients including NH4+ -N, NO3- -N, NO2- -N, PO4(3-) -P and DIN were presented. And the correlationships between nutrients and pH, salinity were also investigated. Furthermore, eutrophication index (E), organic pollution index (A) and potential eutrophication were employed to assess the eutrophication degree of Shenzhen coastal waters. Results show that the nutrient levels of east coast are higher than that of west coast. And the peak year of nutrients are 2002 and 2006. The average concentrations of PO4(3-) -P and DIN are 0.007 mg/L and 0.078 mg/L for Shenzhen east coast while 0.090 mg/L and 1.544 mg/L for west coast. Nutrients in Shenzhen coastal waters have negative correlations with pH and salinity. The N/P ratios are all far more than 16 indicating that Shenzhen coast belongs to seriously P-limiting water. Eutrophication degree of Shenzhen east coast is far lower than that of west coast, and the average eutrophication index of east coast is 0.11 while 42.15 for west coast. Furthermore, west coast is classified as P-limiting moderate level potential eutrophication area and even as P-limiting potential eutrophication level.