A review:Advances in microbial remediation of trichloroethylene (TCE)

Research works in the recent past have revealed three major biodegradation processes leading to the degradation of trichloroethylene. Reductive dechlorination is an anaerobic process in which chlorinated ethenes are used as electron acceptors. On the other hand, cometabolism requires oxygen for enzymatic degradation of chlorinated ethenes, which however yields no benefit for the bacteria involved. The third process is direct oxidation under aerobic conditions whereby chlorinated ethenes are directly used as electron donors by microorganisms. This review presented the current research trend in understanding biodegradation mechanisms with regard to their field applications. All the techniques used are evaluated, with the focus being on various factors that influence the process and the outcome.

电性矿物强化脱氯菌对水中TCE的降解

针对地下水环境中脱氯菌污染修复周期长、电子供给难度大、易带来二次污染等问题,设计以天然矿物电气石的电场刺激、水解供氢和水体调节性能强化含脱卤拟球菌(Dehalococcoides spp.)的混合脱氯菌功能,通过将电气石和脱氯菌共同固定化,开发适用于地下水环境的生物强化原位修复技术.研究了共同包埋的电气石和脱氯菌对地下水典型有机污染物三氯乙烯(TCE)的降解性能.结果表明,在包埋材料海藻酸钠含量6%、凝固剂氯化钙含量6%、电气石含量1.0%、交联时间24 h条件下制得的固定化微球弹性好,机械强度高,粒径均匀分布在3~5 mm,具有多孔洞内结构和较为致密的外表面,既可提供电气石和细菌附着的场所,又能有效地防止微球内部菌体的流失.同时,包埋后的电气石仍能快速调节水体的pH和ORP,为厌氧脱氯菌提供适宜的生长代谢环境.无论是固定化还是分离体系,电气石的加入均增强了脱氯菌对TCE的还原脱氯效果,而电气石-脱氯菌共同固定化体系不仅能加快TCE的降解,在无外加电子供体的情况下仅180 h即可将16 mg/L的TCE完全去除,还显著促进了中间产物的进一步脱氯,反应800 h时终产物乙烯的转化率达到64%,比菌体系提升了1倍.电气石对共同包埋的脱氯菌更有效地起到了电场刺激和电子供体的作用,使其快速稳定的增殖.该复合固定化的应用方式促进了脱氯菌的富集及与电气石的接触,更加充分地发挥了电气石表面电场的直接和间接强化作用,可解决实际地下水修复过程中微生物和强化剂易分离失效的问题,促进地下水有机污染原位生物修复技术的发展.

基于移动互联网的混合式TCE教学模式效果探索

以卫生统计学课程为例,采用TCE教学模式改革传统教学方式,探索基于在线学习平台的混合式TCE教学模式的教学效果,以期提升学生学习的主观能动性,增强教学效果。

ORC-GAC-Fe^0 system for the remediation of trichloroethylene and monochlorobenzene contaminated aquifer:1. Adsorption and degradation

Activities at a former Chemistry Triangle in Bitterfeld, Germany, resulted in contamination of groundwater with a mixture of trichloroethylene(TCE) and monochlorobenzene(MCB). The objective of this study was to develop a barrier system, which includes an ORC(oxygen release compounds) and GAC(granular activated carbon) layer for adsorption of MCB and bioregeneration of GAC, a Fe 0 layer for chemical reductive dechlorination of TCE and other chlorinated hydrocarbon in situ . A laboratory-scale column experiment was conducted to evaluate the feasibility of this proposed system. This experiment was performed using a series of continuous flow Teflon columns including an ORC column, a GAC column, and a Fe 0 column. Simulated MCB and TCE contaminated groundwater was pumped upflow into this system at a flow rate of 1.1 ml/min. Results showed that 17%—50% of TCE and 28%—50% of MCB were dissipated in ORC column. Chloride ion, however, was not released, which suggest the dechlorination do not happen in ORC column. In GAC column, the adsorption of contaminants on activated carbon and their induced degradation by adapted microorganisms attached to the carbon surface were observed. Due to competitive exchange processes, TCE can be desorbed by MCB in GAC column and further degraded in iron column. The completely dechlorination rate of TCE was 0.16—0.18 cm -1 , 1—4 magnitudes more than the formation rate of three dichloroethene isomers. Cis-DCE is the main chlorinated product, which can be cumulated in the system, not only depending on the formation rate and its decaying rate, but also the initial concentration of TCE.

Guinea Pig Maximization Test for Trichloroethylene and Its Metabolites

Objectives To study the contact allergenic activities of trichloroethylene (TCE) and its three metabolites trichloroacetic acid, trichloroethanol and chloral hydrate. Methods A modified guinea pig maximization test (GPMT) was adopted. The skin sensitization (edema and erythema) was observed in trichloroethylene, trichloroacetic acid, trichloroethanol, chloral hydrate and 2,4-dinitrochlorobenzene. Results The allergenic rate of TCE, trichloroacetic acid and 2,4-dinitrochlorobenzene was 71.4%, 58.3% and 100.0% respectively, and that of trichloroethanol and chloral hydrate was 0%. The mean response score of TCE, trichloroacetic acid and 2,4-dinitrochlorobenzene was 2.3, 1.1, 6.0 respectively. The histopathological analysis also showed an induction of allergenic transfomation in guinea pig skin by both TCE and trichloroacetic acid. Conclusion TCE appears to be a strong allergen while trichloroacetic acid a moderate one. On the other hand, both trichloroethanol and chloral hydrate are weak sensitization potentials. Immunologic reaction induced by TCE might be postulated as the pathological process of this illness. Consequently, it is suggested that in the mechanism of Occupational Dermatitis Medicamentose-Like (ODML) induced by TCE, the chemical itself might be the main cause of allergy. As one of its metabolic products, trichloroacetic acid might be a subordinate factor.

ADSORPTION OF CHLOROFORM AND TRICHLOROETHYLENE IN WATER WITH A NEW KIND OF HYPERCROSSLINKED RESINS

In this paper two newly developed hypercrosslinked resins were used to treat micropolluted drinking water and their static and kinetic adsorption were investigated at 293 K. The results show that these two adsorbents are superior to Amberlite XAD-4 for removing chloroform and trichloroethylene in aqueous solutions. The breakthrough capacity and the total capacities from mini-column adsorption studies for chloroform and trichloroethylene on XAD-4, ZH-01 and ZH-00 are calculated respectively under experimental conditions

Cometabolic microbial degradation of trichloroethylene in the presence of toluene

Trichloroethylene(TCE), a common groundwater pollutant, was cometabolized by microorganisms in the presence of toluene as a growth substrate. The effect of concentrations of toluene and TCE and temperature on biodegradation was discussed. Acclimated microorganisms degraded TCE after a lag period of 5 to 22 h depending on toluene concentrations. Approximately 60%, 90% and 64% of TCE were degraded at toluene to TCE concentration ratios of 23∶1, 115∶1 and 230∶1, respectively. At a TCE concentration of 1 46 μg/ml, 80% of TCE and 98 4% of toluene were removed. But less degradation of TCE and toluene was observed when TCE concentration was above 48 8 μg/ml. The lag time of TCE decreased and the TCE biodegradation rates increased with the increase of temperature.

Bio-removal of mixture of benzene,toluene,ethylbenzene,and xylenes/total petroleum hydrocarbons/trichloroethylene from contaminated water

Four pure cultures were isolated from soil samples potentially contaminated with gasoline compounds either at a construction site near a gas station in Fai Chi Kei,Macao SAR or in the northern parts of China（Beijing,and Hebei and Shandong）.The effects of different concentrations of benzene,toluene,ethylbenzene,and three isomers（ortho-,meta-,and para-） of xylene（BTEX）,total petroleum hydrocarbons（TPH）,and trichloroethylene（TCE）,when they were present in mixtures,on the bio-removal effciencies of microbial isolates were investigated,together with their interactions during the bio-removal process.When the isolates were tested for the BTEX（50-350 mg/L）/TPH（2000 mg/L） mixture,BTEoX in BTEoX/TPH mixture was shown with higher bio-removal effciencies,while BTEmX in BTEmX/TPH mixture was shown with the lowest,regardless of isolates.The TPH in BTEmX/TPH mixture,on the other hand,were generally shown with higher bio-removal effciencies compared to when TPH mixed with BTEoX and BTEpX.When these BTEX mixtures（at 350 mg/L） were present with TCE（5-50 mg/L）,the stimulatory effect of TCE toward BTEoX bio-removal was observed for BTEoX/TCE mixture,while the inhibitory effect of TCE toward BTEmX for BTEmX/TCE mixture.The bio-removal effciency for TPH was shown lower in TPH（2000 mg/L）/TCE（5-50 mg/L） mixtures compared to TPH present alone,implying the inhibitory effect of TCE toward TPH bio-removal.For the mixture of BTEX（417 mg/L）,TPH（2000 mg/L） along with TCE（5- 50 mg/L）,TCE was shown co-metabolically removed more effciently at 15 mg/L,probably utilizing BTEX and/or TPH as primary substrates.

Study on the active sites of Cu-ZSM-5 in trichloroethylene catalytic combustion with air

The catalytic activity of Cu-ZSM-5 in trichloroethylene （TCE） combustion increases with the increasing skeletal Cu amount and however decreases with the increase of surface amorphous CuO, which is detected by infrared spectroscopy （IR） and diffuse reflectance ultraviolet-visible spectroscopy （DRS-UV-vis）, therefore the skeletal Cu species are concluded to be the active sites for the TCE combustion.

Dechlorination of Trichloroethylene in Groundwater by Nanoscale Bimetallic Fe/Pd Particles

Palladium/iron bimetallic nanoparticles were synthesized using microemulsion method in the water-in-oil (W/O) microemulsion system, which was made up of iso-octane, cetyltrimethyl-ammonium bromide (CTAB), butanol and water and characterized by measuring the conductivity of the solution. Transmission electron microscope (TEM) and energy dispersive X-ray microanalysis (EDX) analysis showed that the av-erage diameter of synthesized palladium/iron bimetallic nanoparticles was less than 80 nm, which was much smaller than the particles produced by the solution method. The palladium/iron bimetallic nanoscale particles produced in the laboratory showed better performance on dechlorinating TCE than the other materials. The nanoscale Fe/Pd particles exhibited high reactivity. When Pd content is 0.5%, the best TCE dechlorination efficiency is achieved within 30min. And Fe/Pd nanoparticles show persistent reaction activity in some sense.

HLA-DM Polymorphism and Risk of Trichloroethylene Induced Medicamentosa-like Dermatitis

Objective To establish the association between genetic polymorphisms of HLA-DMA and HLA-DMB and risk of developing trichloroethylene-induced medicamentosa-like dermatitis （TIMLD）. Methods Sixty-one cases were medically confirmed to have been affected with TIMLD and 60 controls were selected from exposed workers who were free from TIMLD The TIMLD cases and controls were similar in terms of age, sex, and duration of exposure. DNA was extracted both from the TIMLD cases and controls, HLA-DMA and HLA-DMB loci were amplified by using Touchdown PCR, and the alleles and genotypes were confirmed by restriction fragment length polymorphism （RFLP） and direct sequencing. Finally, the frequencies of HLA-DMA and HLA-DMB variants were compared between the two groups. Results The results showed that the frequency of HLA-DMA＊0101 and HLA-DMB＊0103 alleles was significantly increased in TIMLD patients than in controls （71.3% wv. 55.0% for HLA-DMA＊0101; P〈0.05） （11.5% vs. 3.3% for HLA-DMB＊0103; P〈0.05）. In addition, the frequency of HLA-DMA＊0102-＊0102 homozygous genotype was also significantly higher in the controls than in the patients （25.0% wv. 8.2%, P〈0.05）, whereas the frequency of heterozygous HLA-DMB ＊0101-＊0102 genotype was lower in the patients in comparison with the controls. Conclusion The polymorphisms of HLA-DM may be associated with the susceptibility to TIMLD.

Identification and Characterisation of a Bacterial Isolate Capable of Growth on Trichloroethylene as the Sole Carbon Source

The aim of this research work was to isolate microbes from soil, to investigate their potential use as effective bioremediation tools for trichloroethylene—a potent environmental pollutant. The isolate showing good growth in presence of TCE was named PM102. Microbiological characterisation of the PM102 isolate showed that it was a gram negative rod. Detailed structure was revealed by scanning electron microscopy. pH and temperature optima, salt tolerance and optimum TCE concentration for growth of PM102 were determined. The ability of this bacterium to degrade TCE was studied in acidic and neutral pH by biochemical test and chloride release. Five TCE inducible bands were detected in the protein profile of the isolate as studied by SDS PAGE. A major TCE inducible band of 51.61 kDa was excised from the gel and injected into rabbit to raise specific antibody. The bacterium was identified as Stenotrophomonas maltophilia PM102 by 16S rDNA amplification and sequencing. The 16S rRNA gene sequence has been deposited in the NCBI GenBank with accession number JQ797560. This genus has not been described previously as being capable of TCE degradation. We report for the first time a Stenotrophomonas sp. that grows on TCE as the sole carbon source.

Reaction Kinetics of Ozonation of Trichloroethylene and Benzene in Gas and Liquid Phases

The kinetics of ozonation reactions of trichloroethylene (TCE) and benzene in gas and liquid phases at 101.3 kPa and 298 K was investigated in this paper. The ozonation of TCE is first order with respect to the ozone concentration and one and half order to TCE in the gas phase with the average rate constant 57.30 (mol·L^-1 )^-l.5·s^-1,and the TCE ozonation in aqueous medium is first order with respect to both ozone and trichloroethylene with the average rate constant 6.30 (mol·L^-1)-l·s^-1. The ozonation of benzene in the gas phase is first order in ozone but independent of the benzene concentration with the average reaction rate constant 0.0011s^-1. The overall kinetics of reaction between ozone and benzene in aqueous solution is found to be first order with one-half order in both ozone and bezene, with the average reaction rate constant 2.67s^-1. It is found that the ozonation rate of pallutants is much quicker than that of self-decomposition of ozone in both gas and aqueous phase.

Trichloroethylene Induces Biphasic Concentration-dependent Changes in Cell Proliferation and the Expression of SET-Associated Proteins in Human Hepatic L-02 Cells

Trichloroethylene （TCE） is a major pollutant that affects both occupational and general environments. The liver is an important target organ of TCEE. Substantial efforts and remarkable progress into understanding TCE cytotoxicity have been made in cultured liver cells. However, the molecular mechanisms by which TCE induces hepatotoxicity are not well understood. SET （also known as protein phosphatase 2A inhibitor, 12PP2A, or template-activating factor-I, TAF-D is a nuclear protein that regulates histone modification, gene transcription, DNA replication, nucleosome assembly,

Behaviour of Trichloroethylene Decomposition in a Plasma-Catalytic Combined Process

A nonthermal plasma processing combined with Cr2O3/TiO2 catalyst was applied to the decomposition of trichloroethylene （TCE）. A dielectric barrier discharge reactor was used as the nonthermal plasma reactor. The effects of the reaction temperature and input power on the decomposition of TCE and the formation of byproducts including HCl, Cl2, CO, NO, NO2 and O3 were examined. With an identical input power, the increase in the reactor temperature lowered the decomposition of TCE. The presence of the catalyst downstream the plasma reactor not only enhanced the decomposition of TCE but also affected the distribution of byproducts significantly. However any synergetic effect as a result of the combination of the nonthermal plasma with the catalyst was not observed, i.e., the TCE decomposition ei^ciency in the plasma- catalyst combined system was almost similar to the sum of those obtained with each process. To improve the decomposition of TCE argon as a plasma-assisting gas was added to the feeding gas and a large enhancement in the TCE decomposition was achieved.

Remediation of Trichloroethylene and Monochlorobenzene-Contaminated Aquifers Using the ORC-GAC-Fe^0-CaCO_3 System: Volatilization, Precipitation, and Porosity Losses

The objectives of this study were to illustrate the reaction processes, to identify and quantify the precipitates formed, and to estimate the porosity losses in order to eliminate drawbacks during remediating monochlorobenzene (MCB) and trichloroethylene (TCE)-contaminated aquifers using the ORC-GAC-Fe0-CaCO3 system. The system consisted of four columns (112 cm long and 10 cm in diameter) with oxygen-releasing compound (ORC), granular activated carbon (GAC), zero-valent iron (Fen), and calcite used sequentially as the reactive media. The concentrations of MCB in the GAC column effluent and TCE in the Fe0 column effluent were below the detection limit. However, the concentrations of MCB and TCE in the final calcite column exceeded the maximum contaminant level (MCL) under the Safe Drinking Water Act of the US Environmental Protection Agency (US EPA) that protects human health and environment. These results suggested that partitioning of MCB and TCE into the gas phase could occur, and also that transportation of volatile organic pollutants in the gas phase was important. Three main precipitates formed in the ORC-GAC-Fe0-CaCO3 system: CaCO3 in the ORC column along with Fe(OH)2 and FeCO3 in the Fe0 column. The total porosity losses caused by mineral precipitation corresponded to about 0.24% porosity in the ORC column, and 1% in the Fe0 column. The most important cause of porosity losses was anaerobic corrosion of iron. The porosity losses caused by gas because of the production and entrapment of oxygen in the ORC column and hydrogen in the Fe0 column should not be ignored. Volatilization, precipitation and porosity losses were considered to be the main drawbacks of the ORC-GAC-Fe0-CaCO3 system in remediating the MCB and TCE-contaminated aquifers. Thus, measurements such as using a suitable oxygen-releasing compound, weakening the increase in pH using a buffer material such as soil, stimulating biodegradation rates and minimizing the plugging caused by the relatively high dissolved oxygen levels should be taken to eliminate the drawbacks and to improve the efficiency of the ORC-GAC-Fe0-CaCO3 system.

A Proposed Mechanism of Photocatalytic Oxidation of Trichloroethylene in Gas Phase

GC/MS has been used to identify gas phase products and intermediates formed during the gas phase photocatalytic oxidation of trichloroethylene (TCE) on TiO(2) with low BET surface area. A new byproduct, oxalyl choloride (ClCOCOCl) was detected together with other byproducts such as COCl(2), CHCl(3), DCAC and C(2)HCl(5). Firstly the method of perturbation on the reaction system was conducted. Very little amount of water was carried into the feed gas and subsequent changes were observed. The discussion based on the product distribution changes led to a postulated mechanism consisting of two stages.

Incorporation of lanthanum into SBA-15 and its catalytic activity in trichloroethylene combustion

The direct synthesis of La-SBA-15 mesoporous material by two-step synthesis method was reported. The effect of pH value during the process on the incorporation of La into the framework of SBA-15 was investigated, and XRD, UV-vis, FT-/R, and ICP were used to characterize the obtained La-SBA-15. The experimental results showed that a large amount of La could enter SBA-15 framework under suitable pH value while a highly ordered mesostructure of samples containing La was retained. In addition, the obtained La-SBA-15 exhibited good catalytic performance in the combustion of trichloroethylene.