The nitrite accumulation in the denitrification process is investigated with sequencing batch reactor （SBR） treating pre-treated landfill leachate in anoxic/anaerobic up-flow anaerobic sludge bed I（UASB）. Nitrite ...The nitrite accumulation in the denitrification process is investigated with sequencing batch reactor （SBR） treating pre-treated landfill leachate in anoxic/anaerobic up-flow anaerobic sludge bed I（UASB）. Nitrite accumulates obviously at different initial nitrate concentrations （64.9,54.8,49.3 and 29.5 mg·L^-1 ） and low temperatures, and the two break points on the oxidation-reduction potential （ORP） profile indicate the completion of nitrate and nitrite reduction. Usually, the nitrate reduction rate is used as the sole parameter to characterize the denitrification rate, and nitrite is not even measured. For accuracy, the total oxidized nitrogen （nitrate ＋ nitrite） is used as a measure, though details characterizing the process may be overlooked. Additionally, batch tests are conducted to investigate the effects of C/N ratios and types of carbon sources on the nitrite accumulation during the denitrification. It is observed that carbon source is sufficient for the reduction of nitrate to nitrite, but for further reduction of nitrite to nitrogen gas, is deficient when C/N is below the theoretical critical level of 3.75 based on the stoichiometry of denitrification. Five carbon sources used in this work, except for glucose, may cause the nitrite accumulation. From experimental results and cited literature, it is concluded that Alcaligene species may be contained in the SBR activated-sludge system.展开更多
In the suspended sludge system, when pH and temperature were suitable and carbon source was not limited, the denitrification and C-uptake rate followed a zero-order reaction. Mixed VFA C-source had higher denitrificat...In the suspended sludge system, when pH and temperature were suitable and carbon source was not limited, the denitrification and C-uptake rate followed a zero-order reaction. Mixed VFA C-source had higher denitrification rate than single VFA C-source consisting of them. When VFA were used as carbon source, consumed carbon quantity for denitrification was closed to 1. 07 mg VFA-C/mg NO-N. About 20% of the applied C/N was used for assimilative purposes. As rising up influent C/N by increasing the C load ,the sludge yield YN increased. The part of carbon consumption increased and the effluent oxidized nitrogen decreased. At pH 7. 5, 25℃ and sludge yield 0.72 mg VSS/mg NO-N, the calculated influent VFA-C /NO critical value was 1. 43 for complete denitrification.展开更多
[ Objective] The research aimed to study influence of different C/N ratios on aerobic denitdfication characteristics of the strain. [ Method] 5 aerobic denitdfying bacteria were isolated from activated sludge at low t...[ Objective] The research aimed to study influence of different C/N ratios on aerobic denitdfication characteristics of the strain. [ Method] 5 aerobic denitdfying bacteria were isolated from activated sludge at low temperature and low C/N ratio, and their denitdfication capabilities were verified. Influence of different C/N ratios on denitdfication capability of the strain was determined. [ Result] In the five isolated aerobic denitdf- ying bacteria, except HFX08 was G-, HFX00, HFX01, HFX12 and HFX13 were G ＋. HFX08 belonged to Pseudomonas, and other strains be- longed to Acinetobacter. As C/N ratio increased, denitdfication velocity increased, and the highest removal rate of nitrogen for the five strains could reach over 92%. [ Conclusion] The research could provide reference for design and operation of the sewage treatment process with low C/N ratio in winter in the north.展开更多
In this paper, Ti-C-N nanocomposite films are deposited under different nitrogen flow rates by pulsed bias arc ion plating using Ti and graphite targets in the Ar/N2 mixture gas. The surface morphologies, compositions...In this paper, Ti-C-N nanocomposite films are deposited under different nitrogen flow rates by pulsed bias arc ion plating using Ti and graphite targets in the Ar/N2 mixture gas. The surface morphologies, compositions, microstructures, and mechanical properties of the Ti-C-N films are investigated systematically by field emission scanning electron mi- croscopy （FE-SEM）, x-ray photoelectron spectroscopy （XPS）, grazing incident x-ray diffraction （GIXRD）, Raman spectra, and nano-indentation. The results show that the nanocrystalline Ti（C,N） phase precipitates in the film from GIXRD and XPS analysis, and Raman spectra prove the presence of diamond-like carbon, indicating the formation of nanocomposite film with microstructures comprising nanocrystalline Ti（C,N） phase embedded into a diamond-like matrix. The nitrogen flow rate has a significant effect on the composition, structure, and properties of the film. The nano-hardness and elastic modulus first increase and then decrease as nitrogen flow rate increases, reaching a maximum of 34.3 GPa and 383.2 GPa, at a nitrogen flow rate of 90 sccm, respectively.展开更多
Soil organic carbon （SOC） and soil inorganic carbon （SIC） are important C pools in the Loess Plateau of Northwest China, however, variations of SOC and SIC stocks under different cultivation practices and nitrogen...Soil organic carbon （SOC） and soil inorganic carbon （SIC） are important C pools in the Loess Plateau of Northwest China, however, variations of SOC and SIC stocks under different cultivation practices and nitrogen （N） fertilization rates are not clear in this area. A long-term field experiment started in June 2003 was conducted to investigate the SOC and SIC stocks in a calcareous soil of the Chinese Loess Plateau under four cultivation practices, i.e., fallow （FA）, conventional cultivation （CC）, straw mulch （SM）, and plastic film-mulched ridge and straw-mulched furrow （RF）, in combination with three N fertilization rates, i.e., 0 （NO）, 120 （N120）, and 240 （N240） kg N/hm2. Results indicate that the crop straw addition treatments （SM and RF） increased the contents of soil microbial biomass C （SMBC） and SOC, and the SOC stock increased by 10.1%-13.3% at the upper 20 cm soil depth in comparison to the 8-year fallow （FA） treatment. Meanwhile, SIC stock significantly increased by 19% at the entire tested soil depth range （0-100 cm） under all crop cultivation practices in comparison to that of soil exposed to the long-term fallow treatment, particularly at the upper 60 cm soil depth. Furthermore, moderate N fertilizer application （120 kg N/hm2） increased SOC stock at the upper 40 cm soil depth, whereas SIC stock decreased as the N fertilization rate increased. We conclude that the combined application of crop organic residues and moderate N fertilization rate could facilitate the sequestrations of SOC and SIC in the calcareous soil.展开更多
The oilseed cake, vetch, rapeseed straw, wheat straw and corn straw were buried in tobacco-planted soil. The decomposition rates, the variation of active organic C and N contents in the residues and the relationship b...The oilseed cake, vetch, rapeseed straw, wheat straw and corn straw were buried in tobacco-planted soil. The decomposition rates, the variation of active organic C and N contents in the residues and the relationship between active organic C and N contents and decomposition rate were investigated. The results showed the decomposition rates of different organic materials were all high in the early period and then low in the late period. Among the organic materials, the decomposition rates ranked as oilseed cake 〉 vetch 〉 wheat straw and rapeseed straw 〉 corn straw. The decomposition rate was positively related to total N content （P〈0.01）, but was negatively related to the active organic C/N ratio （P〈0.01）. However, there was no significant relationship between decomposition ratio and active organic C content. With the proceeding of decomposition, the active organic C content and the total N content in rapeseed straw, vetch, wheat straw and corn straw all trended to increase, but the active organic C/N ratio trended to decrease. However, the variation of active organic C content, total N content and active organic C/N ratio in oilseed cake was on the contrary.展开更多
基金Supported by the National Natural Science Foundation of China （50978003）, the Natural Science Foundation of Beijing （8091001）, the Funding Project for Academic Human Resources Development in Institutions of Higher Learning Under the Jurisdiction of Beijing Municipality （PHR 20090502）, and the State Key Laboratory of Urban Water Resource and Environment （HIT） （QAK200802）.
文摘The nitrite accumulation in the denitrification process is investigated with sequencing batch reactor （SBR） treating pre-treated landfill leachate in anoxic/anaerobic up-flow anaerobic sludge bed I（UASB）. Nitrite accumulates obviously at different initial nitrate concentrations （64.9,54.8,49.3 and 29.5 mg·L^-1 ） and low temperatures, and the two break points on the oxidation-reduction potential （ORP） profile indicate the completion of nitrate and nitrite reduction. Usually, the nitrate reduction rate is used as the sole parameter to characterize the denitrification rate, and nitrite is not even measured. For accuracy, the total oxidized nitrogen （nitrate ＋ nitrite） is used as a measure, though details characterizing the process may be overlooked. Additionally, batch tests are conducted to investigate the effects of C/N ratios and types of carbon sources on the nitrite accumulation during the denitrification. It is observed that carbon source is sufficient for the reduction of nitrate to nitrite, but for further reduction of nitrite to nitrogen gas, is deficient when C/N is below the theoretical critical level of 3.75 based on the stoichiometry of denitrification. Five carbon sources used in this work, except for glucose, may cause the nitrite accumulation. From experimental results and cited literature, it is concluded that Alcaligene species may be contained in the SBR activated-sludge system.
文摘In the suspended sludge system, when pH and temperature were suitable and carbon source was not limited, the denitrification and C-uptake rate followed a zero-order reaction. Mixed VFA C-source had higher denitrification rate than single VFA C-source consisting of them. When VFA were used as carbon source, consumed carbon quantity for denitrification was closed to 1. 07 mg VFA-C/mg NO-N. About 20% of the applied C/N was used for assimilative purposes. As rising up influent C/N by increasing the C load ,the sludge yield YN increased. The part of carbon consumption increased and the effluent oxidized nitrogen decreased. At pH 7. 5, 25℃ and sludge yield 0.72 mg VSS/mg NO-N, the calculated influent VFA-C /NO critical value was 1. 43 for complete denitrification.
基金Special Funds for Environmental Protection of the Governmental Public Industry Research,China(200909043)
文摘[ Objective] The research aimed to study influence of different C/N ratios on aerobic denitdfication characteristics of the strain. [ Method] 5 aerobic denitdfying bacteria were isolated from activated sludge at low temperature and low C/N ratio, and their denitdfication capabilities were verified. Influence of different C/N ratios on denitdfication capability of the strain was determined. [ Result] In the five isolated aerobic denitdf- ying bacteria, except HFX08 was G-, HFX00, HFX01, HFX12 and HFX13 were G ＋. HFX08 belonged to Pseudomonas, and other strains be- longed to Acinetobacter. As C/N ratio increased, denitdfication velocity increased, and the highest removal rate of nitrogen for the five strains could reach over 92%. [ Conclusion] The research could provide reference for design and operation of the sewage treatment process with low C/N ratio in winter in the north.
基金Project supported by the National Natural Science Foundation of China(Grant No.51271047)
文摘In this paper, Ti-C-N nanocomposite films are deposited under different nitrogen flow rates by pulsed bias arc ion plating using Ti and graphite targets in the Ar/N2 mixture gas. The surface morphologies, compositions, microstructures, and mechanical properties of the Ti-C-N films are investigated systematically by field emission scanning electron mi- croscopy （FE-SEM）, x-ray photoelectron spectroscopy （XPS）, grazing incident x-ray diffraction （GIXRD）, Raman spectra, and nano-indentation. The results show that the nanocrystalline Ti（C,N） phase precipitates in the film from GIXRD and XPS analysis, and Raman spectra prove the presence of diamond-like carbon, indicating the formation of nanocomposite film with microstructures comprising nanocrystalline Ti（C,N） phase embedded into a diamond-like matrix. The nitrogen flow rate has a significant effect on the composition, structure, and properties of the film. The nano-hardness and elastic modulus first increase and then decrease as nitrogen flow rate increases, reaching a maximum of 34.3 GPa and 383.2 GPa, at a nitrogen flow rate of 90 sccm, respectively.
基金supported by the National Natural Science Foundation of China (41671295)the National Technology R&D Pillar Program in the 12th Five Year Plan of China (2012BAD15B04)
文摘Soil organic carbon （SOC） and soil inorganic carbon （SIC） are important C pools in the Loess Plateau of Northwest China, however, variations of SOC and SIC stocks under different cultivation practices and nitrogen （N） fertilization rates are not clear in this area. A long-term field experiment started in June 2003 was conducted to investigate the SOC and SIC stocks in a calcareous soil of the Chinese Loess Plateau under four cultivation practices, i.e., fallow （FA）, conventional cultivation （CC）, straw mulch （SM）, and plastic film-mulched ridge and straw-mulched furrow （RF）, in combination with three N fertilization rates, i.e., 0 （NO）, 120 （N120）, and 240 （N240） kg N/hm2. Results indicate that the crop straw addition treatments （SM and RF） increased the contents of soil microbial biomass C （SMBC） and SOC, and the SOC stock increased by 10.1%-13.3% at the upper 20 cm soil depth in comparison to the 8-year fallow （FA） treatment. Meanwhile, SIC stock significantly increased by 19% at the entire tested soil depth range （0-100 cm） under all crop cultivation practices in comparison to that of soil exposed to the long-term fallow treatment, particularly at the upper 60 cm soil depth. Furthermore, moderate N fertilizer application （120 kg N/hm2） increased SOC stock at the upper 40 cm soil depth, whereas SIC stock decreased as the N fertilization rate increased. We conclude that the combined application of crop organic residues and moderate N fertilization rate could facilitate the sequestrations of SOC and SIC in the calcareous soil.
基金Supported by National Key Technology Research and Development Program(2012BAD40B02Yunnan Provincial Tobacco Company Plan Project(2012YN48)~~
文摘The oilseed cake, vetch, rapeseed straw, wheat straw and corn straw were buried in tobacco-planted soil. The decomposition rates, the variation of active organic C and N contents in the residues and the relationship between active organic C and N contents and decomposition rate were investigated. The results showed the decomposition rates of different organic materials were all high in the early period and then low in the late period. Among the organic materials, the decomposition rates ranked as oilseed cake 〉 vetch 〉 wheat straw and rapeseed straw 〉 corn straw. The decomposition rate was positively related to total N content （P〈0.01）, but was negatively related to the active organic C/N ratio （P〈0.01）. However, there was no significant relationship between decomposition ratio and active organic C content. With the proceeding of decomposition, the active organic C content and the total N content in rapeseed straw, vetch, wheat straw and corn straw all trended to increase, but the active organic C/N ratio trended to decrease. However, the variation of active organic C content, total N content and active organic C/N ratio in oilseed cake was on the contrary.
