Characterization of Methylocystis strain JTA1 isolated from aged refuse and its tolerance to chloroform

To accelerate the efficiency of methane biodegradation in landfills,a Gram-negative,rod-shaped,non-motile,non-spore-forming bacterium,JTA1,which can utilize methane as well as acetate,was isolated from the Laogang MSW landfills,Shanghai,China.Strain JTA1 was a member of genus Methylocystis on the basis of 16S rRNA and pmoA gene sequence similarity.The maximum specific cell growth rates(μmax=0.042 hr-1,R2=0.995) was derived through Boltzmann simulation,and the apparent half-saturation constants(Km(app)=7.08mmol/L,R2=0.982) was calculated according to Michaelis-Menton hyperbolic model,indicating that Methylocystis strain JTA1 had higher-affinity potential for methane oxidation than other reported methanotrophs.By way of adding the strain JTA1 culture,the methane consumption of aged refuse reached 115mL,almost two times of control experiment.In addition,high tolerance of Methylocystis strain JTA1 to chloroform could facilitate the methane oxidation of aged refuse bio-covers.At the chloroform concentration of 50mg/L,the methane-oxidation rate of bio-cover reached 0.114mL/(day·g),much higher than the highest rate,0.0135mL/(day·g),of reported bio-covers.In conclusion,strain JTA1 opens up a new possibility for environmental biotechnology,such as soil or landfills bioremediation and wastewater decontamination.     

Electrochemical dechlorination of chloroform in neutral aqueous solution on palladium/foam-nickel and palladium/polymeric pyrrole film/foam-nickel electrodes

Electrochemical dechlorination of chloroform in neutral aqueous solution was investigated using palladium-loaded electrodes at ambient temperature. Palladium/foam-nickel （Pd/foam-Ni） and palladium/polymeric pyrrole film/foam-nickel （Pd/PPy/foam-Ni） composite electrodes which provided catalytic surface for reductive dechlorination of chloroform in aqueous solution were prepared using an electrodepositing method. Scanning electron microscope （SEM） micrographs showed that polymeric pyrrole film modified the electrode-surface characteristics and resulted in the uniform dispersion of needle-shaped palladium particles on foam-Ni supporting electrode. The experimental results of dechlorination indicated that the removal efficiency of chloroform and current efficiency in neutral aqueous solution on Pd/PPy/foam-Ni electrode could be up to 36.8% and 33.0% at dechlorination current of 0.1 mA and dechlorination time of 180 min, which is much higher than that of Pd/foam-Ni electrode.     

顶空气相色谱法测定水中三氯甲烷四氯化碳的参数优化及测定影响因素探讨

本文探讨了如何提高顶空气相色谱法测定三氯甲烷及四氯化碳的灵敏度、精密度与准确度。重点讨论了平衡条件的优化以及带顶空自动进器的气相色谱仪的各个关键参数的优化。     

实验室中三氯甲烷废液的回收利用

通过对三氯甲烷废液的回收及用于环境样品阴离子洗涤剂的测定中作为萃取液对比实验,得出回收的三氯甲烷与纯三氯甲烷实验结果一致,经检验,二者无显著性差异。回收后的三氯甲烷不仅能取得良好的实验结果,而且具有一定的经济效益和环境效益。     

松花江饮用水氯消毒中氯仿形成的优化控制

通过对松花江水进行大量实验 ,找出TOC的含量、投氯量、温度和 pH值等对氯仿形成的定量关系 ,确定了饮用水氯化的优化条件 ,使饮用水氯化过程中形成的氯仿含量不超过国家饮用水的标准     

Formation of organochlorine compounds in kraft pulp bleaching processes

The most abundant volatile organochlorine compounds (VOCCs), trichloroacetic and dichloroacetic acids and AOX, were determined in bleaching effluent and waste water from three kraft pulp mills during ClO₂ bleaching. 0.6–7.7 g of VOCCs per ton bleached pulp were formed, the most abundant being chloroform and dichloroacetic acid methyl ester. Most of the VOCCs were removed during treatment, and it was estimated that 2–30 t of VOCCs would be removed annually from activated sludge treatment plants in Finnish kraft pulp mills using elemental chlorine free bleaching, most likely by volatilization. Dichloroacetic acid was formed in considerably higher amounts than trichloroacetic acid, and both compounds were removed effectively during treatment. The formation of all organochlorine compounds decreased considerably when non-chlorinated bleaching was employed.     

Fenton process for degradation of selected chlorinated aliphatic hydrocarbons exemplified by trichloroethylene, 1,1-dichloroethylene and chloroform

The degradation of selected chlorinated aliphatic hydrocarbons (CAHs) exemplified by trichloroethylene (TCE), 1,1-dichloroethylene (DCE), and chloroform (CF) was investigated with Fenton oxidation process. The results indicate that the degradation rate was primarily affected by the chemical structures of organic contaminants. Hydroxyl radicals (·OH) preferred to attack the organic contaminants with an electron-rich structure such as chlorinated alkenes (i.e., TCE and DCE). The dosing mode of Fenton’s reagent, particularly of Fe²⁺, significantly affected the degradation efficiency of studied organic compound. A new “time-squared” kinetic model, C = C _o exp(−k _obs t ²), was developed to express the degradation kinetics of selected CAHs. This model was applicable to TCE and DCE, but inapplicable to CF due to their varied reaction rate constants towards ?OH. Chloride release was monitored to examine the degree of dechlorination during the oxidation of selected CAHs. TCE was more easily dechlorinated thanDCE and CF.Dichloroacetic acid (DCAA) was identified as the major reaction intermediate in the oxidation of TCE, which could be completely removed as the reaction proceeded. No reaction intermediates or byproducts were identified in the oxidation of DCE and CF. Based on the identified intermediate, the reaction mechanism of TCE with Fenton’s reagent was proposed.     

零价铁对水中四氯化碳还原脱氯研究

文章研究了Fe0的纯度、粒径和投加量以及酸洗预处理对水溶液中四氯化碳的还原性脱氯作用的影响,并对其脱氯的主要产物——氯仿进行了讨论。结果表明:(1)Fe0纯度越高,粒径越小,四氯化碳的去除效果越好;(2)在实验范围内,Fe0投加量越大,四氯化碳的去除效率越高;(3)酸洗后,四氯化碳的去除效果明显的提高;(4)Fe0纯度、粒径和投加量以及酸洗处理对四氯化碳的还原产物氯仿亦具有一定的影响,四氯化碳的去除与氯仿的产生之间存在着一定的对应关系。     

真空采血管顶空气相色谱法检测水中三氯甲烷、四氯化碳

采用真空采血管顶空填充柱气相色谱法测定水中三氯甲烷和四氯化碳,结果表明,三氯甲烷在10.0～50.0μg/L,四氯化碳在0.5～4.0μg/L浓度范围内呈良好线性关系,其r值分别为0.9994和0.9998;三氯甲烷和四氯化碳RSD分别在1.64%~2.27%和1.45%~2.40%之间;加标回收率分别在97.0%~103.5%和94.0%~103.2%之间。该方法操作简单,具有较好的灵敏度和准确度,适用于水中三氯甲烷和四氯化碳的检测。     

土层中石油烃类污染物索氏抽提流程改进及回收氯仿资源化研究

通过对土层中石油烃类污染物索氏抽提流程的改进 ,实现蒸馏氯仿的回收与再利用。实验结果表明 ,用改进索氏抽提流程测的有机物含量与传统的流程相比 ,所减少的石油烃类物质损耗占总石油物质含量的 1 0 % ;同时 ,蒸馏回收的氯仿的 70 %可以重新用于索氏抽提 ,由此产生的误差小于 1 % ,不会影响残油微生物降解试验的分析精度 ,具有资源回收与保护环境的双重效应