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Tan Y.,The Key Laboratory of Water and Sediment science | Ji G.,The Key Laboratory of Water and Sediment science
Bioresource Technology | Year: 2010

Status of, and changes in, the bacterial communities at two acclimation stages (with- and without-ultrasound) in a small 70 °C ultrasound-enhanced anaerobic reactor for treating carbazole-containing wastewater reactor were analyzed by PCR-DGGE and real-time PCR techniques. PCR-DGGE results indicated that a large number of bands occurred in the whole sludge samples. Pseudomonas sp., Comamonas sp., and Diaphorobacter sp. were identified as being able to utilize carbazole as a carbon source, survive in an anaerobic and ultra-high-temperature environment and become dominant bacterial taxa during the with-ultrasound stage in the reactor. Total bacterial density in the with-ultrasonic stages was 10 × higher than in the without-ultrasonic treatment. The proportion of Pseudomonas was relatively stable at 0.13%-0.15% in both acclimation stages, which indicates that Pseudomonas can flourish and promote carbazole degradation either with or without-ultrasound. These studies provide information on carbazole degradation under ultra-high-temperature conditions in an anaerobic environment. © 2009 Elsevier Ltd. All rights reserved. Source

Wang Y.,Beijing Normal University | Wang Y.,The Key Laboratory of Water and Sediment science | Shen Z.,Beijing Normal University | Shen Z.,The Key Laboratory of Water and Sediment science | And 2 more authors.
Chemosphere | Year: 2010

The erbium (Er)-chitosan-fluorine (F) modified PbO2 electrode was prepared by electrodeposition method, and its use for adsorption and electrochemical degradation of 2,4-dichlorophenol (2,4-DCP) in aqueous solution was compared with F-PbO2 and Er-F-PbO2 electrodes in a batch experiment. The electrodes were characterized by scanning electron microscopy, X-ray diffraction and cyclic voltammetry. Degradation of 2,4-DCP depending on Er and chitosan contents was discussed. The results showed that Er2O3 and chitosan were scattered between the prevailing crystal structure of β-PbO2 and thus decreased the internal stress of PbO2 film. Prior to each electrolysis, the modified PbO2 anode was first pre-saturated with 2,4-DCP solution for 360 min to preclude the 2,4-DCP decrease due to adsorption. Among the electrodes examined in our study, the highest adsorption and electrochemical degradation for 2,4-DCP and TOC removals that are due to oxidation and adsorption of the organic products onto the chitosan was observed on Er-chitosan-F-PbO2 electrode. At an applied current density of 5 mA cm-2, the removal percentages of 2,4-DCP and TOC (solution volume: 180 mL, initial 2,4-DCP concentration: 90 mg L-1) were 95% after 120 min and 53% after 360 min, respectively. At Er amount of 10 mM in the precursor coating solution, the degradation and mineralization removal for 2,4-DCP on the Er-F-PbO2 electrode reached a maximum. At chitosan amount of 5 g L-1, the highest TOC removal on the Er-chitosan-F-PbO2 electrode was observed. Intermediates mainly including aliphatic carboxylic acids were examined and a possible degradation pathway for 2,4-DCP in aqueous solution involving dechlorination and hydroxylation reactions was proposed. © 2010 Elsevier Ltd. All rights reserved. Source

Miao C.,Peking University | Miao C.,The Key Laboratory of Water and Sediment science | Ni J.,Peking University | Ni J.,The Key Laboratory of Water and Sediment science | Borthwick A.G.L.,University of Oxford
Progress in Physical Geography | Year: 2010

The Yellow River basin contributes approximately 6% of the sediment load from all river systems globally, and the annual runoff directly supports 12% of the Chinese population. As a result, describing and understanding recent variations of water discharge and sediment load under global change scenarios are of considerable importance. The present study considers the annual hydrologic series of the water discharge and sediment load of the Yellow River basin obtained from 15 gauging stations (10 mainstream, 5 tributaries). The Mann-Kendall test method was adopted to detect both gradual and abrupt change of hydrological series since the 1950s. With the exception of the area draining to the Upper Tangnaihai station, results indicate that both water discharge and sediment load have decreased significantly (p<0.05). The declining trend is greater with distance downstream, and drainage area has a significant positive effect on the rate of decline. It is suggested that the abrupt change of the water discharge from the late 1980s to the early 1990s arose from human extraction, and that the abrupt change in sediment load was linked to disturbance from reservoir construction. © The Author(s) 2010. Source

Zhu Y.,The Key Laboratory of Water and Sediment science | Zhu Y.,Peking University | Huang W.,CAS Chengdu Institute of Biology | Ni J.,The Key Laboratory of Water and Sediment science | Ni J.,Peking University
Journal of Cleaner Production | Year: 2010

This study proposes a new approach for diosgenin production from Dioscorea zingiberensis C. H. Wright tubers with respect to resources utilization and clean production. This process consisted of two successive parts, i.e., recovery of starch from raw material, and microbial hydrolysis of the residue to produce diosgenin by Trichoderma reesei. In the first step, about 75.4% of hemicellulose and 98.0% of starch were removed from the tubers. In the second step, about 90.2% of diosgenin was released from saponins by T. reesei at 30 °C, at an aeration of 0.80 vvm and agitation rate of 300 rpm in a 5.0 L bioreactor. Significant reduction of pollutant production was detected by replacing the traditional approach with the proposed new method. About 99.2% of reducing sugar, 99.4% of chemical oxygen demand, 99.2% of total organic carbon, 100% of SO42-, and 100% of acid was reduced in the new processing wastewater. © 2009 Elsevier Ltd. All rights reserved. Source

Zhao H.-Z.,Peking University | Zhao H.-Z.,The Key Laboratory of Water and Sediment science | Sun J.-J.,Peking University | Sun J.-J.,The Key Laboratory of Water and Sediment science | And 2 more authors.
Carbon | Year: 2010

To gain insights into the direct electron transfer (DET) mechanism of multi-walled carbon nanotubes (MWCNTs), we investigated the conformational changes that occur in proteins when they interact with MWCNTs. We used glucose oxidase (GOD) as an example. Using cyclic voltammetry measurements, the GOD that was immobilized on the MWCNT-modified carbon paper electrode exhibited apparent direct electrochemistry compared to that on the bare electrode without MWCNTs. The structural transformation of GOD upon adsorption on the MWCNTs was characterized spectrally. GOD was not denatured, and only small shifts of the wavenumber of the β-sheet structure were observed. There was a consistent tendency for the amount of α-helix to decrease and the β-sheet to increase. The α-helix content dropped from 21.2% to 19.6% as measured using Fourier transform infrared spectroscopy and from 27.1% to 25.9% as measured using circular dichroism. The reduction in the amount of α-helix led to a less shielded GOD active site and weakened the resistance of the electron transfer. These MWCNT-induced conformational changes could account for the DET between GOD and the MWCNT-modified electrode surface. © 2009 Elsevier Ltd. All rights reserved. Source

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