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Microbial activity related to N cycling in the rhizosphere of maize stressed by heavy metals

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Journal of Environmental Sciences 2005年第3期17卷 448-451页

作者： YANGYe CHENYing-xu TIANGuang-ming ZHANGZi-jian departmentofenvironmentalengineering ZhejiangUniversityHangzhou310029China departmentofenvironmentalengineering ZhejiangUniversityHangzhou310029China

A greenhouse experiment was carried out to compare differences in potential activities of ammonification, nitrification and denitrification in rhizosphere and bulk soil in a heavy-metal-stressed system. Exchangeable fractions of Cd, Cu and Cr were all higher in the rhizosphere of maize than in bulk soil. Results showed that the mineralization of N in soil was stimulated by low concentration of Cd. Addition of Cd at low levels stimulated the ammonifying and nitrifying activity in soil, while inhibitory influences were shown at high levels. Nitrifying bacteria was proved to be the most sensitive one, whilst the effect on denitrifying bacteria was very limited. Comparing Cd, Cu and Cr(VI) at 20 mg/kg soil, Cd was the most effective inhibitor of ammonification and denitrification, while Cr(VI) had the strongest inhibitory influence on nitrifying activity. Root exudates played important roles on the different exchangeable metal fractions and bacterial activities between rhizosphere and non-rhizosphere. Nitrate was the main form of mineral N in soil, as well as the main form of N absorbed by plants, but the formation and relative absorption of ammonium were promoted in response to high Cd exposure.

关键词： heavy metal nitrogen cycle rhizosphere root exudates

Biological removal of air loaded with a hydrogen sulfide and ammonia mixture

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Journal of Environmental Sciences 2004年第4期16卷 656-661页

作者： CHENYing-xu YINJun FANGShi departmentofenvironmentalengineering ZhejiangUniversityHangzhou310029China

The nuisance impact of air pollutant emissions from wastewater pumping stations is a major issue of concern to China. Hydrogen sulfide and ammonia are commonly the primary odor and are important targets for removal. An alternative control technology, biofiltration, was studied. The aim of this study is to investigate the potential of unit systems packed with compost in terms of ammonia and hydrogen sulfide emissions treatment, and to establish optimal operating conditions for a full-scale conceptual design. The laboratory scale biofilter packed with compost was continuously supplied with hydrogen sulfide and ammonia gas mixtures. A volumetric load of less than 150 gH 2S/(m3·d) and 230 gNH 3/(m3·d) was applied for about fifteen weeks. Hydrogen sulfide and ammonia elimination occurred in the biofilter simultaneously. The removal efficiency, removal capacity and removal kinetics in the biofilter were studied. The hydrogen sulfide removal efficiency reached was very high above 99%, and ammonia removal efficiency was about 80%. Hydrogen sulfide was oxidized into sulphate. The ammonia oxidation products were nitrite and nitrate. Ammonia in the biofilter was mainly removed by adsorption onto the carrier material and by absorption into the water fraction of the carrier material. High percentages of hydrogen sulfide or ammonia were oxidized in the first section of the column. Through kinetics analysis, the presence of ammonia did not hinder the hydrogen sulfide removal. According to the relationship between pressure drop and gas velocity for the biofilter and Reynolds number, non-Darcy flow can be assumed to represent the flow in the medium.

关键词： biological removal hydrogen sulfide ammonia mixture

Electrokinetic characteristic and coagulation behavior of flocculant polyaluminum silicate chloride (PASiC)

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Journal of Environmental Sciences 2003年第1期15卷 69-74页

作者： YUEQin－yan GAOBao－yu 等 departmentofenvironmentalengineering SchoolofEnvironmentalShangdongUniversityJina250100China

The electrokinetic characteristics and coagulation behaviors of polyaluminum silicate chloride (PASiC) and polyaluminum chloride (PAC) were studied and compared by streaming current (SC) measurement and jar test method. The experimental results showed that the interaction between polysilicic acid characterized negative charge and hydrolyzed aluminum species result in a decrease of the charge neutralizing ability of PASiC, compared to PAC. The decrease has a close relationship with the basicity ( B ) and Al/Si molar ratio in PASiC. The less the B value and the Al/Si molar ratio, the lower the charge neutralizing ability of PASiC is. In contrast, the preparation technique for PASiC affects the charge-neutralization of PASiC to a smaller extent. In addition, compared with PAC, PASiC may enhance aggregating efficiency and give better coagulating effects.

关键词： flocculant polyaluminum chloride (PASiC) streaming current (SC) electrokinetic characteristics coagulation effect

Stability of expanded granular sludge bed process for terylene artificial silk printing and dyeing wastewater treatment

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Journal of Environmental Sciences 2005年第3期17卷 419-424页

作者： GUANBao-hong departmentofenvironmentalengineering ZhejiangUniversityHangzhou310027China

Terylene artificial silk printing and dyeing wastewater(TPD wastewater), containing averaged 710 mg/L terephthalic acid(TA) as the main carbon source and the character pollutant, was subjected to expanded granular sludge bed(EGSB) process. The stability of the EGSB process was firstly conducted by laboratory experiment. TA ionization was the predominated factor influencing the acid-base balance of the system. High concentration of TA in wastewater resulted in sufficient buffering capacity to neutralize the volatile fatty acids(VFA) generated from substrate degradation and provided strong base for anaerobic system to resist the pH decrease below 6.5. VFA and UFA caused almost no inhibition on the anaerobic process and biogas production except that pH was below 6.35 and VFA was at its maximum value. Along with the granulating of the activated sludge, the efficiency of organic removal and production rate of biogas increased gradually and became more stable. After start-up, the efficiency of COD removal increased to 57%—64%, pH stabilized in a range of 7.99—8.04, and production rate of biogas was relatively high and stable. Sludge granulating, suitable influent of pH and loading were responsible for the EGSB stability. The variation of VFA concentration only resulted in neglectable rebound of pH, and the inhibition from VFA could be ignored in EGSB. The EGSB reactor was stable for TPD wastewater treatment.

关键词： expanded granular sludge bed stability anaerobic treatment dyeing and printing wastewater

Catalytic dechlorination of o-chlorophenol by nanoscale Pd/Fe

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Journal of Environmental Sciences 2004年第4期16卷 621-623页

作者： WEIJian-jun XUXin-hua WANGDa-hui departmentofenvironmentalengineering ZhejiangUniversityHangzhou310027China

Transformation of chlorophenols by nanoscale bimetallic particles represents one of the latest innovative technologies for environmental remediation. Nanoscale Pd/Fe bimetallic particles were synthesized in the laboratory for treatment of o-chlorophenol. Most of the nanoscale particles are in the size range of 20—100 nm. BET specific surface area of the nanoscale Pd/Fe particles is 12.4 m2/g. In comparison, a commercially available Fe powder(<100 mesh) has a specific surface area of just 0\^49 m2/g. Batch experiments demonstrated that the nanoscale Pd/Fe bimetallic particles can effectively dechlorinate o-chlorophenol. Dechlorination efficiency is affected by the mass fraction of Pd in the bimetal, nanoscale Pd/Fe mass concentration and mixing intensity.

关键词： nanoscale particles Pd/Fe dechlorination o-chlorophenol

Modeling of mass transfer characteristics of bubble column reactor with surfactant present

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Journal of Zhejiang University Science 2004年第6期5卷 714-720页

作者：赵伟荣史惠祥汪大翚 departmentofenvironmentalengineering ZhejiangUniversityHangzhou310027China

Danckwert's method was used to determine the specific interfacial area, a, and the individual mass transfer coefficient, κL, during absorption of CO2 in a bubble column with an anionic surfactant in the carbonate-bicarbonate buffer solution and NaAsO2 as catalyst, the presence of which decreases the specific interracial area and the individual mass transfer coefficient. The specific interfacial area and the individual mass transfer coefficient increase with increasing superficial gas velocity. The specific interfacial area decreases whereas the individual mass transfer coefficient increases with increasing temperature. The results of experiments were used to determine the dependence of a, κL, and κLa on the surface tension, the temperature of the absorption phase, and the superficial velocity of the gas. The calculated results from the correlation were found to be within 10% deviation from the actual experimental results.

关键词：表面活性剂气体吸附物质转换效率气泡队列反应器化学工业液相

Kinetics of photoelectrocatalytic degradation of humic acid using B_2O_3·TiO_2/Ti photoelectrode

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Journal of Environmental Sciences 2005年第2期17卷 208-211页

作者： JIANGYan-li LIUHui-ling LUChun-mei departmentofenvironmentalengineering HarbinInstituteofTechnologyHarbin150001China／／SchoolofLifeScienceandChemistryHarbinCollegeHarbin150001China departmentofenvironmentalengineering HarbinInstituteofTechnologyHarbin150001China

An innovative photoelectrode, B 2O 3·TiO 2/Ti electrode, was prepared by galvanostaticanodisation. The morphology and crystalline texture of the B 2O 3·TiO 2 film on electrode were examined by atomic force microscopy(AFM) and X-ray diffraction respectively. The examination results indicated that the anatase was the dominant component. The kinetics of photoelectrocatalytic(PEC) degradation of humic acid(HA) was investigated; the results demonstrated that effects from strongness to weakness on the photoelectrocatalytic degraded rate of humic acid: power of UV-lamp, area of TiO 2 film, bias, original concentration of humic acid solution. The optimum conditions were power of UV-lamp 125 W, area of TiO 2 film 42.0 cm 2, bias 1.4 V, original concentration of humic acid solution 5 mg/L in this PEC reaction system.

关键词： TiO 2 photoelectrocatalytic degradation humic acid kinetics

Effect of substrate concentration on the bioleaching of heavy metals from sewage sludge

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Journal of Environmental Sciences 2004年第5期16卷 788-792页

作者： CHENYing-xu HUAYu-mei ZHANGShao-hui departmentofenvironmentalengineering ZhejiangUniversityHangzhou310029China

The effect of elemental sulfur concentration on bioleaching of Cu, Zn and Pb and loss of fertilizer value from sewage sludge was investigated in flasks by batch experiments. The results showed that the ultimate pH of sludges with 3—5 g/L of sulfur added was about 1.3 and the production of SO 2- 4 had good correlation with the elemental sulfur concentration. The sensitivity of removal efficiency of metals to sulfur concentration was: Pb>Cu>Zn. The sulfur concentration except for 3—5 g/L had significant effect on the solubilization of Cu, Pb and Zn. The highest solubilization efficiency for sludge with 3 g/L of sulfur was 87.86% for Cu, 32.72% for Pb and 92.14% for Zn, which could make the treated sludge easily meet the metal limitations for land application. The sulfur concentration of 3 g/L was enough for the solubilization of all three heavy metals. The influence of sulfur concentration on solubilization of total nitrogen and potassium from sludge was negligible, but that on solublization of total phosphorus was of great importance. The loss of nitrogen, phosphorus and potassium of sludge with 3 g/L of sulfur by bioleaching was 38.2%, 52.1% and 42.8% respectively, and the sludge still remained satisfactory fertilizer value after bioleaching.

关键词： sewage sludge heavy metals bioleaching substrate fertilizer value

Degradation of chlorophenol by in－situ electrochemically generated oxidant

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Journal of Zhejiang University Science 2004年第2期5卷 180-185页

作者：丛燕青吴祖成叶倩谭天恩 departmentofenvironmentalengineering ZhejiangUniversityHangzhou310027China

A novel in-situ electrochemical oxidation method was applied to the degradation of wastewater containing chlorophenol. Under oxygen sparging, the strong oxidant, hydrogen dioxide, could be in-situ generated through the reduction of oxygen on the surface of the cathode. The removal rate ofchlorophenol could be increased 149% when oxygen was induced in the electrochemical cell. The promotion factor was estimated to be about 82.63% according to the pseudo-first-order reaction rate constant (min^-1). Important operating parameters such as current density, sparged oxygen rate were investigated. Higher sparged oxygen rate could improve the degradation of chlorophenol. To make full use of oxygen, however, sparged oxygen rate of 0.05 m3/h was adopted in this work. Oxidation-reduction potential could remarkably affect the generation of hydrogen peroxide. It was found that the removal rate of chlorophenol was not in direct proportion to the applied current density. The optimum current density was 3.5 mA/cm^2 when initial chlorophenol concentration was 100 mg/L and sparged oxygen rate was 0.05 m^3/h.

关键词：氯酚氧化剂废水处理环境保护环境污染