Field-scale modeling of acidity production and remediation efficiency during in situ reductive dechlorination

Science.gov (United States)

Brovelli, A.; Robinson, C. E.; Barry, D. A.; Gerhard, J.

2009-12-01

Enhanced reductive dechlorination is a viable technology for in situ remediation of chlorinated solvent DNAPL source areas. Although in recent years increased understanding of this technology has led to more rapid dechlorination rates, complete dechlorination can be hindered by unfavorable conditions. Hydrochloric acid produced from dechlorination and organic acids generated from electron donor fermentation can lead to significant groundwater acidification. Adverse pH conditions can inhibit the activity of dehalogenating microorganisms and thus slow or stall the remediation process. The extent of acidification likely to occur at a contaminated site depends on a number of factors including (1) the extent of dechlorination, (2) the pH-sensitivity of dechlorinating bacteria, and (3) the geochemical composition of the soil and water, in particular the soil’s natural buffering capacity. The substantial mass of solvents available for dechlorination when treating DNAPL source zones means that these applications are particularly susceptible to acidification. In this study a reactive transport biogeochemical model was developed to investigate the chemical and physical parameters that control the build-up of acidity and subsequent remediation efficiency. The model accounts for the site water chemistry, mineral precipitation and dissolution kinetics, electron donor fermentation, gas phase formation, competing electron-accepting processes (e.g., sulfate and iron reduction) and the sensitivity of microbial processes to pH. Confidence in the model was achieved by simulating a well-documented field study, for which the 2-D field scale model was able to reproduce long-term variations of pH, and the concurrent build up of reaction products. Sensitivity analyses indicated the groundwater flow velocity is able to reduce acidity build-up when the rate of advection is comparable or larger than the rate of dechlorination. The extent of pH change is highly dependent on the presence of

The impact of bioaugmentation on dechlorination kinetics and on microbial dechlorinating communities in subsurface clay till

DEFF Research Database (Denmark)

Bælum, Jacob; Scheutz, Charlotte; Chambon, Julie Claire Claudia

2014-01-01

A molecular study on how the abundance of the dechlorinating culture KB-1 affects dechlorination rates in clay till is presented. DNA extracts showed changes in abundance of specific dechlorinators as well as their functional genes. Independently of the KB-1 added, the microbial dechlorinator abu......, highlights the ecological behavior of KB-1 in clay till, and reinforces the importance of using multiple functional genes as biomarkers for reductive dechlorination. © 2013 Elsevier Ltd. All rights reserved....

Enhanced reductive dechlorination of DDT in an anaerobic system of dissimilatory iron-reducing bacteria and iron oxide

International Nuclear Information System (INIS)

Li, F.B.; Li, X.M.; Zhou, S.G.; Zhuang, L.; Cao, F.; Huang, D.Y.; Xu, W.; Liu, T.X.; Feng, C.H.

2010-01-01

The transformation of DDT was studied in an anaerobic system of dissimilatory iron-reducing bacteria (Shewanella decolorationis S12) and iron oxide (α-FeOOH). The results showed that S. decolorationis could reduce DDT into DDD, and DDT transformation rate was accelerated by the presence of α-FeOOH. DDD was observed as the primary transformation product, which was demonstrated to be transformed in the abiotic system of Fe 2+ + α-FeOOH and the system of DIRB + α-FeOOH. The intermediates of DDMS and DBP were detected after 9 months, likely suggesting that reductive dechlorination was the main dechlorination pathway of DDT in the iron-reducing system. The enhanced reductive dechlorination of DDT was mainly due to biogenic Fe(II) sorbed on the surface of α-FeOOH, which can serve as a mediator for the transformation of DDT. This study demonstrated the important role of DIRB and iron oxide on DDT and DDD transformation under anaerobic iron-reducing environments. - This is the first case reporting the reductive dechlorination of DDT in an anaerobic system of dissimilatory iron-reducing bacteria and iron oxide.

Enhanced reductive dechlorination of DDT in an anaerobic system of dissimilatory iron-reducing bacteria and iron oxide

Energy Technology Data Exchange (ETDEWEB)

Li, F.B., E-mail: cefbli@soil.gd.c [Guangdong Key Laboratory of Agricultural Environment Pollution Integrated Control, Guangdong Institute of Eco-Environmental and Soil Sciences, Guangzhou 510650 (China); Li, X.M. [Guangdong Key Laboratory of Agricultural Environment Pollution Integrated Control, Guangdong Institute of Eco-Environmental and Soil Sciences, Guangzhou 510650 (China); Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640 (China); Graduate School of Chinese Academy of Sciences, Beijing 100039 (China); Zhou, S.G.; Zhuang, L. [Guangdong Key Laboratory of Agricultural Environment Pollution Integrated Control, Guangdong Institute of Eco-Environmental and Soil Sciences, Guangzhou 510650 (China); Cao, F. [Guangdong Key Laboratory of Agricultural Environment Pollution Integrated Control, Guangdong Institute of Eco-Environmental and Soil Sciences, Guangzhou 510650 (China); Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640 (China); Graduate School of Chinese Academy of Sciences, Beijing 100039 (China); Huang, D.Y.; Xu, W.; Liu, T.X. [Guangdong Key Laboratory of Agricultural Environment Pollution Integrated Control, Guangdong Institute of Eco-Environmental and Soil Sciences, Guangzhou 510650 (China); Feng, C.H. [School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510641 (China)

2010-05-15

The transformation of DDT was studied in an anaerobic system of dissimilatory iron-reducing bacteria (Shewanella decolorationis S12) and iron oxide (alpha-FeOOH). The results showed that S. decolorationis could reduce DDT into DDD, and DDT transformation rate was accelerated by the presence of alpha-FeOOH. DDD was observed as the primary transformation product, which was demonstrated to be transformed in the abiotic system of Fe{sup 2+} + alpha-FeOOH and the system of DIRB + alpha-FeOOH. The intermediates of DDMS and DBP were detected after 9 months, likely suggesting that reductive dechlorination was the main dechlorination pathway of DDT in the iron-reducing system. The enhanced reductive dechlorination of DDT was mainly due to biogenic Fe(II) sorbed on the surface of alpha-FeOOH, which can serve as a mediator for the transformation of DDT. This study demonstrated the important role of DIRB and iron oxide on DDT and DDD transformation under anaerobic iron-reducing environments. - This is the first case reporting the reductive dechlorination of DDT in an anaerobic system of dissimilatory iron-reducing bacteria and iron oxide.

Preliminary Results of Reductive Dechlorination Conducted at the X-749/X-120 Area of the DOE Portsmouth Gaseous Diffusion Plant, Piketon, Ohio

International Nuclear Information System (INIS)

Rieske, D. E.; Baird, D. R.; Lawson, N. E.

2006-01-01

Reductive dechlorination is being implemented at the X-749/X-120 trichloroethene (TCE) plume South Barrier Wall containment site at the Department of Energy (DOE) Portsmouth Gaseous Diffusion Plant (PORTS). The purpose of this paper is to present the effectiveness of the reductive dechlorination at PORTS. Reductive dechlorination is an in situ remediation technology that utilizes existing subsurface microbes to biologically degrade volatile organic compounds in groundwater. Monitoring in the barrier wall area reveals the presence of Hydrogen Release Compound (HRC) injected in the spring of 2004 in two groundwater monitoring wells closest to the injection points. Oxidation/reduction potential in these two wells has decreased steadily since injection, but has not yet reached optimal reducing levels for TCE degradation. Monitoring the effectiveness of the injection is hampered by near-stagnant groundwater flow due in part to the South Barrier Wall. The X-749/X-120 TCE groundwater plume lies beneath approximately 91 acres in the southern portion of PORTS, and extends southward threatening to cross the DOE property boundary. A 1,077-foot long subsurface bentonite barrier wall was installed in 1993 at the southern DOE property boundary to restrict movement of contaminated groundwater from traveling off-site until other remedial technologies could be implemented. In 2003, TCE was detected on the south side of the barrier wall (but still within DOE property) above drinking water standards of 5 micrograms per liter. Monitoring has also detected TCE in groundwater beyond the western edge of the barrier wall. In the spring of 2004, DOE initiated the injection of a reductive dechlorination compound known as Hydrogen Release Compound-extended release formula (HRC-X) into the subsurface using direct push technology (DPT). The HRC-X was injected within the saturated zone from the top of bedrock to 10 feet above bedrock as the probe was withdrawn from the push. A total of 180 DPT

Bacteria of an anaerobic 1,2-dichloropropane-dechlorinating mixed culture are phylogenetically related to those of other anaerobic dechlorinating consortia.

Science.gov (United States)

Schlötelburg, C; von Wintzingerode, F; Hauck, R; Hegemann, W; Göbel, U B

2000-07-01

A 16S-rDNA-based molecular study was performed to determine the bacterial diversity of an anaerobic, 1,2-dichloropropane-dechlorinating bioreactor consortium derived from sediment of the River Saale, Germany. Total community DNA was extracted and bacterial 16S rRNA genes were subsequently amplified using conserved primers. A clone library was constructed and analysed by sequencing the 16S rDNA inserts of randomly chosen clones followed by dot blot hybridization with labelled polynucleotide probes. The phylogenetic analysis revealed significant sequence similarities of several as yet uncultured bacterial species in the bioreactor to those found in other reductively dechlorinating freshwater consortia. In contrast, no close relationship was obtained with as yet uncultured bacteria found in reductively dechlorinating consortia derived from marine habitats. One rDNA clone showed >97% sequence similarity to Dehalobacter species, known for reductive dechlorination of tri- and tetrachloroethene. These results suggest that reductive dechlorination in microbial freshwater habitats depends upon a specific bacterial community structure.

Development and sensitivity analysis of a fullykinetic model of sequential reductive dechlorination in subsurface

DEFF Research Database (Denmark)

Malaguerra, Flavio; Chambon, Julie Claire Claudia; Albrechtsen, Hans-Jørgen

2010-01-01

and natural degradation of chlorinated solvents frequently occurs in the subsurface through sequential reductive dechlorination. However, the occurrence and the performance of natural sequential reductive dechlorination strongly depends on environmental factor such as redox conditions, presence of fermenting...... organic matter / electron donors, presence of specific biomass, etc. Here we develop a new fully-kinetic biogeochemical reactive model able to simulate chlorinated solvents degradation as well as production and consumption of molecular hydrogen. The model is validated using batch experiment data......Chlorinated hydrocarbons originating from point sources are amongst the most prevalent contaminants of ground water and often represent a serious threat to groundwater-based drinking water resources. Natural attenuation of contaminant plumes can play a major role in contaminated site management...

Reductive dechlorination of tetrachlorobisphenol A by Pd/Fe bimetallic catalysts

International Nuclear Information System (INIS)

Huang, Qiang; Liu, Wen; Peng, Ping’an; Huang, Weilin

2013-01-01

Highlights: • TCBPA can be rapidly and completely dechlorinated by Pd/Fe bimetallic catalysts. • The observed rate constants are functions of dosages, initial concentration, Pd coverage and solution pH. • Pd dosage is the major factor in the observed rates of the reaction. • This is the first report investigating the dechlorination of TCBPA by Pd/Fe catalysts. -- Abstract: The Pd/Fe bimetallic catalysts of micron sizes were synthesized and the rates of tetrachlorobisphenol A (TCBPA) degradation were measured under various conditions using a batch reactor system. The results showed that TCBPA was rapidly dechlorinated to tri-, di- and mono-chlorobisphenol A and to bisphenol A (BPA). The observed rate constants (k obs ) were found to increase as functions of the Pd coverage on the Fe particles and the dosages of the catalysts within the reactors. The k obs value decreased as the initial TCBPA concentration increased, suggesting that the TCBPA dechlorination may follow a surface-site limiting Langmuir–Hinshelwood rate model. The weakly acidic solution, especially at or near pH 6.0, also favored the dechlorination of TCBPA. At pH 6.0, Pd coverage of 0.044 wt% and catalyst dosage of 5 g L −1 , TCBPA with an initial concentration of 20 μM was completely transformed within 60 min, and BPA was detected as the major product through the reaction time. Meanwhile, the k obs values measured at constant solution pH correlated linearly with the mass of particle-bound Pd introduced to the reactors, regardless of Pd/Fe catalyst dosage or Pd surface coverage. This study suggested that Pd/Fe catalysts could be potentially employed to rapidly degrade TCBPA in the contaminated environment

A conceptual model linking functional gene expression and reductive dechlorination rates of chlorinated ethenes in clay rich groundwater sediment

DEFF Research Database (Denmark)

Bælum, Jacob; Chambon, Julie Claire Claudia; Scheutz, Charlotte

2013-01-01

We used current knowledge of cellular processes involved in reductive dechlorination to develop a conceptual model to describe the regulatory system of dechlorination at the cell level; the model links bacterial growth and substrate consumption to the abundance of messenger RNA of functional gene...

Reductive dechlorination of {gamma}-hexachlorocyclohexane using Fe-Pd bimetallic nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Nagpal, Varima; Bokare, Alok D. [Center for Nanobioscience, Agharkar Research Institute, G.G. Agarkar Road, Pune 411004, Maharashtra (India); Chikate, Rajeev C. [Department of Chemistry, MES Abasaheb Garware College, Karve Road, Pune 411004 (India); Rode, Chandrashekhar V. [Chemical Engineering and Process Development Division, National Chemical Laboratory, Pune 411008 (India); Paknikar, Kishore M., E-mail: paknikar@vsnl.com [Center for Nanobioscience, Agharkar Research Institute, G.G. Agarkar Road, Pune 411004, Maharashtra (India)

2010-03-15

Nanoscale Fe-Pd bimetallic particles were synthesized and used for degradation of lindane ({gamma}-hexachlorocyclohexane) in aqueous solution. Batch studies showed that 5 mg/L of lindane was completely dechlorinated within 5 min at a catalyst loading of 0.5 g/L and the degradation process followed first-order kinetics. GC-MS analysis in corroboration with GC-ECD results showed the presence of cyclohexane as the final degradation product. The proposed mechanism for the reductive dechlorination of lindane involves Fe corrosion-induced hydrogen atom transfer from the Pd surface. The enhanced degradation efficiency of Fe-Pd nanoparticles is attributed to: (1) high specific surface area of the nanoscale metal particles (60 m{sup 2}/g), manyfold greater that of commercial grade micro- or milli-scale iron particles ({approx}1.6 m{sup 2}/g); and, (2) increased catalytic reactivity due to the presence of Pd on the surface. Recycling and column studies showed that these nanoparticles exhibit efficient and sustained catalytic activity.

Comparison of an assay for Dehalococcoides DNA and a microcosm study in predicting reductive dechlorination of chlorinated ethenes in the field

International Nuclear Information System (INIS)

Lu Xiaoxia; Wilson, John T.; Kampbell, Donald H.

2009-01-01

The study aims to compare the detection of 16S rRNA gene of Dehalococcoides species and the microcosm study for biotransformation in predicting reductive dechlorination of chlorinated ethenes in ground water at hazardous waste sites. A total of 72 ground water samples were collected from 12 PCE or TCE contaminated sites in the United States. The samples were analyzed and used to construct microcosms in the laboratory. The results showed that the presence of Dehalococcoides DNA was well associated with dechlorination to ethene in the field. Nearly half of the wells where Dehalococcoides DNA was detected had ethene as a dechlorination end product. In comparison, for ground water samples of 16 wells where ethene was detected, ethene was produced in 11 of the corresponding microcosms. For most microcosms, during two years of incubation, dechlorination was less extensive than that observed in the field. - Positive results of the assay for Dehalococcoides DNA and the microcosm study may suggest that reductive dechlorination is occurring in the field

Impact of estuarine gradients on reductive dechlorination of 1,2,3,4-tetrachlorodibenzo-p-dioxin in river sediment enrichment cultures.

Science.gov (United States)

Dam, Hang T; Häggblom, Max M

2017-02-01

Polychlorinated dibenzo-p-dioxins (PCDDs) are among the most persistent organic pollutants. Although the total input of PCDDs into the environment has decreased substantially over the past four decades, their input via non-point sources is still increasing, especially in estuarine metropolitan areas. Here we report on the microbially mediated reductive dechlorination of PCDDs in anaerobic enrichment cultures established from sediments collected from five locations along the Hackensack River, NJ and investigate the impacts of sediment physicochemical characteristics on dechlorination activity. Dechlorination of 1,2,3,4-tetrachlorodibenzo-p-dioxin (1,2,3,4-TeCDD) and abundance of Dehalococcoides spp. negatively correlated with salinity and sulfate concentration in sediments used to establish the cultures. 1,2,3,4-TeCDD was dechlorinated to a lesser extent in cultures established from sediments from the tidally influenced estuarine mouth of the river. In cultures established from low salinity sediments, 1,2,3,4-TeCDD was reductively dechlorinated with the accumulation of 2-monochlorodibenzo-p-dioxin as the major product. Sulfate concentrations above 2 mM inhibited 1,2,3,4-TecDD dechlorination activity. Consecutive lateral- and peri- dechlorination took place in enrichment cultures with a minimal accumulation of 2,3-dichlorodibenzo-p-dioxin in active cultures. A Dehalococcoides spp. community was enriched and accounted for up to 64% of Chloroflexi detected in these sediment cultures. Copyright © 2016 Elsevier Ltd. All rights reserved.

The role of humic substances in the anaerobic reductive dechlorination of 2,4-dichlorophenoxyacetic acid by Comamonas koreensis strain CY01

Energy Technology Data Exchange (ETDEWEB)

Wang Yibo [College of Life Sciences, South China Normal University, Guangdong Key Lab of Biotechnology for Plant Development, Guangzhou, 510631 (China)] [Guangdong Institute of Eco-environment and Soil Sciences, Guangzhou, 510650 (China)] [College of Life Science and Chemistry, Tianshui Normal University, Tianshui, 741000 (China); Wu Chunyuan [Guangdong Institute of Eco-environment and Soil Sciences, Guangzhou, 510650 (China); Wang Xiaojing, E-mail: wangyb02@163.com [College of Life Sciences, South China Normal University, Guangdong Key Lab of Biotechnology for Plant Development, Guangzhou, 510631 (China); Zhou Shungui, E-mail: sgzhou@soil.gd.cn [Guangdong Institute of Eco-environment and Soil Sciences, Guangzhou, 510650 (China)

2009-05-30

The role of the humic model compound, anthraquinone-2,6-disulfonate (AQDS), in the anaerobic reductive dechlorination of 2,4-dichlorophenoxyacetic acid (2,4-D) by the Fe(III)- and humic substances (HS)-reducing bacterium, Comamonas koreensis strain CY01 was investigated. The results taken as a whole indicated that (i) strain CY01 could couple glucose oxidation to 2,4-D reductive dechlorination; (ii) reductive dechlorination of 2,4-D by strain CY01 was greatly stimulated by the addition of AQDS; (iii) the transfer of electrons from biogenic AH{sub 2}QDS to 2,4-D was an abiotic process which can take place in the absence of microorganisms; and (iv) AH{sub 2}QDS was reoxidized during the chemical reaction, AQDS can serve again as electron acceptor for microorganisms, thus acting as electron shuttles. All the results suggested that 2,4-D reductive dechlorination by CY01 strain was a biochemical process that oxidizes the electron donors and transfers the electron to the acceptors through redox mediator, AQDS. We proposed the possible mechanism for the HS dependent reduction of 2,4-D. Our results suggested that microbial reduction of HS and subsequent chemical reduction of organic pollutants represent an important path of electron flow in anoxic natural environments. This work is a necessary preliminary step for better understanding the biodegradation of 2,4-D in subsurface soil.

Dechlorination of PCBs in the rhizosphere of switchgrass and poplar

International Nuclear Information System (INIS)

Meggo, Richard E.; Schnoor, Jerald L.; Hu, Dingfei

2013-01-01

Polychlorinated biphenyl (PCB) congeners (PCB 52, 77, and 153) singly and in mixture were spiked and aged in soil microcosms and subsequently planted with switchgrass (Panicum virgatum) or poplar (Populus deltoids x nigra DN34). The planted reactors showed significantly greater reductions in PCB parent compounds when compared to unplanted systems after 32 weeks. There was evidence of reductive dechlorination in both planted and unplanted systems, but the planted microcosms with fully developed roots and rhizospheres showed greater biotransformation than the unplanted reactors. These dechlorination products accounted for approximately all of the molar mass of parent compound lost. Based on the transformation products, reductive dechlorination pathways are proposed for rhizospheric biotransformation of PCB 52, 77, and 153. This is the first report of rhizosphere biotransformation pathways for reductive dechlorination in marginally aerobic, intermittently flooded soil as evidenced by a mass balance on transformation products. -- Highlights: •Soil was spiked and aged and then planted with poplar and switchgrass. •Planted microcosms showed significant reductive dechlorination and greater biotransformation than unplanted reactor. •Rhizospheric reductive dechlorination pathways are proposed. -- This study provides insight into rhizospheric transformation of PCBs

A remediation performance model for enhanced metabolic reductive dechlorination of chloroethenes in fractured clay till

Science.gov (United States)

Manoli, Gabriele; Chambon, Julie C.; Bjerg, Poul L.; Scheutz, Charlotte; Binning, Philip J.; Broholm, Mette M.

2012-04-01

A numerical model of metabolic reductive dechlorination is used to describe the performance of enhanced bioremediation in fractured clay till. The model is developed to simulate field observations of a full scale bioremediation scheme in a fractured clay till and thereby to assess remediation efficiency and timeframe. A relatively simple approach is used to link the fermentation of the electron donor soybean oil to the sequential dechlorination of trichloroethene (TCE) while considering redox conditions and the heterogeneous clay till system (clay till matrix, fractures and sand stringers). The model is tested on lab batch experiments and applied to describe sediment core samples from a TCE-contaminated site. Model simulations compare favorably to field observations and demonstrate that dechlorination may be limited to narrow bioactive zones in the clay matrix around fractures and sand stringers. Field scale simulations show that the injected donor is expected to be depleted after 5 years, and that without donor re-injection contaminant rebound will occur in the high permeability zones and the mass removal will stall at 18%. Long remediation timeframes, if dechlorination is limited to narrow bioactive zones, and the need for additional donor injections to maintain dechlorination activity may limit the efficiency of ERD in low-permeability media. Future work should address the dynamics of the bioactive zones, which is essential to understand for predictions of long term mass removal.

Geochemical and microbial community determinants of reductive dechlorination at a site biostimulated with glycerol

NARCIS (Netherlands)

Atashgahi, Siavash; Lu, Yue; Zheng, Ying; Saccenti, Edoardo; Suarez-Diez, Maria; Ramiro-Garcia, Javier; Eisenmann, Heinrich; Elsner, Martin; J.M. Stams, Alfons; Springael, Dirk; Dejonghe, Winnie; Smidt, Hauke

2017-01-01

Biostimulation is widely used to enhance reductive dechlorination of chlorinated ethenes in contaminated aquifers. However, the knowledge on corresponding biogeochemical responses is limited. In this study, glycerol was injected in an aquifer contaminated with cis-dichloroethene (cDCE), and

Effects of activated carbon on reductive dechlorination of PCBs by organohalide respiring bacteria indigenous to sediments.

Science.gov (United States)

Kjellerup, B V; Naff, C; Edwards, S J; Ghosh, U; Baker, J E; Sowers, K R

2014-04-01

Polychlorinated biphenyls (PCBs) have accumulated in aquatic sediments due to their inherent chemical stability and their presence poses a risk due to their potential toxicity in humans and animals. Granular activated carbon (GAC) has been applied to PCB contaminated sediment sites to reduce the aqueous concentration by sequestration thus reducing the PCB exposure and toxicity to both benthic and aquatic organisms. However, it is not known how the reduction of PCB bioavailability by adsorption to GAC affects bacterial transformation of PCBs by indigenous organohalide respiring bacteria. In this study, the impact of GAC on anaerobic dechlorination by putative organohalide respiring bacteria indigenous to sediment from Baltimore Harbor was examined. It was shown that the average Cl/biphenyl after dehalogenation of Aroclor 1260 was similar between treatments with and without GAC amendment. However, GAC caused a substantial shift in the congener distribution whereby a smaller fraction of highly chlorinated congeners was more extensively dechlorinated to mono- through tri-chlorinated congeners compared to the formation of tri- through penta-chlorinated congeners in unamended sediment. The results combined with comparative sequence analysis of 16S rRNA gene sequences suggest that GAC caused a community shift to putative organohalide respiring phylotypes that coincided with more extensive dechlorination of ortho and unflanked chlorines. This shift in activity by GAC shown here for the first time has the potential to promote greater degradation in situ by promoting accumulation of less chlorinated congeners that are generally more susceptible to complete mineralization by aerobic PCB degrading bacteria. Copyright © 2013 Elsevier Ltd. All rights reserved.

Comparison of Bimetallic and Trimetallic Catalyst in Reductive Dechlorination; Influence of Copper Addition

Czech Academy of Sciences Publication Activity Database

Kaštánek, František; Kaštánek, Petr; Maléterová, Ywetta; Kallistová, A.; Šolcová, Olga

2015-01-01

Roč. 2, č. 7 (2015), s. 1954-1958 E-ISSN 3159-0040 R&D Projects: GA TA ČR TA04020700 Institutional support: RVO:67985858 ; RVO:67985831 Keywords : PCB * reductive dechlorination * bimetallic and trimetallic catalysts Subject RIV: CI - Industrial Chemistry, Chemical Engineering http://www.jmest.org/wp-content/uploads/JMESTN42350950.pdf

Dechlorination of Hexachloroethane in Water Using Iron Shavings and Amended Iron Shavings: Kinetics and Pathways

Directory of Open Access Journals (Sweden)

D. L. Wu

2014-01-01

Full Text Available In contrast to previous studies which employed zero-valent iron powder, this paper investigated reductive dechlorination of hexachloroethane (HCA using iron shavings and bimetallic iron shavings modified with Cu, Ag, or Pd. Results clearly show that iron shavings offer superior reductive dechlorination of HCA. In addition, surface-normalized pseudo first-order dechlorination rates of 0.0073 L·m−2·h−1, 0.0136 L·m−2·h−1, 0.0189 L·m−2·h−1, and 0.0084 L·m−2·h−1 were observed in the presence of iron shavings (Fe0 and the bimetallic iron shavings Cu/Fe, Ag/Fe, and Pd/Fe, respectively. Bimetallic iron shavings consisting of Cu/Fe and Ag/Fe could greatly enhance the reductive reaction rate; Pd/Fe was used to achieve complete dechlorination of HCA within 5 hours. The additives of Ag and Pd shifted product distributions, and the reductive dechlorination of HCA occurred via β reductive elimination and sequential hydrogenolysis in the presence of all iron shavings. This study consequently designed a reaction pathway diagram which reflected the reaction pathway and most prevalent dechlorination products. Iron shavings are a common byproduct of mechanical processing plants. While the purity of such Fe metals may be low, these shavings are readily available at low costs and could potentially be used in engineering applications such as contamination control technologies.

Microbially enhanced dissolution and reductive dechlorination of PCE by a mixed culture: Model validation and sensitivity analysis

Science.gov (United States)

Chen, Mingjie; Abriola, Linda M.; Amos, Benjamin K.; Suchomel, Eric J.; Pennell, Kurt D.; Löffler, Frank E.; Christ, John A.

2013-08-01

Reductive dechlorination catalyzed by organohalide-respiring bacteria is often considered for remediation of non-aqueous phase liquid (NAPL) source zones due to cost savings, ease of implementation, regulatory acceptance, and sustainability. Despite knowledge of the key dechlorinators, an understanding of the processes and factors that control NAPL dissolution rates and detoxification (i.e., ethene formation) is lacking. A recent column study demonstrated a 5-fold cumulative enhancement in tetrachloroethene (PCE) dissolution and ethene formation (Amos et al., 2009). Spatial and temporal monitoring of key geochemical and microbial (i.e., Geobacter lovleyi and Dehalococcoides mccartyi strains) parameters in the column generated a data set used herein as the basis for refinement and testing of a multiphase, compositional transport model. The refined model is capable of simulating the reactive transport of multiple chemical constituents produced and consumed by organohalide-respiring bacteria and accounts for substrate limitations and competitive inhibition. Parameter estimation techniques were used to optimize the values of sensitive microbial kinetic parameters, including maximum utilization rates, biomass yield coefficients, and endogenous decay rates. Comparison and calibration of model simulations with the experimental data demonstrate that the model is able to accurately reproduce measured effluent concentrations, while delineating trends in dechlorinator growth and reductive dechlorination kinetics along the column. Sensitivity analyses performed on the optimized model parameters indicate that the rates of PCE and cis-1,2-dichloroethene (cis-DCE) transformation and Dehalococcoides growth govern bioenhanced dissolution, as long as electron donor (i.e., hydrogen flux) is not limiting. Dissolution enhancements were shown to be independent of cis-DCE accumulation; however, accumulation of cis-DCE, as well as column length and flow rate (i.e., column residence time

Evaluation of biodegradable plastics as solid hydrogen donors for the reductive dechlorination of fthalide by Dehalobacter species.

Science.gov (United States)

Yoshida, Naoko; Ye, Lizhen; Liu, Fengmao; Li, Zhiling; Katayama, Arata

2013-02-01

Biodegradable plastics (BPs) were evaluated for their applicability as sustainable and solid H(2) donors for microbial reductive dechlorination of 4,5,6,7-tetrachlorophthalide (fthalide). After a screening test of several BPs, the starch-based plastic (SP) that produced the highest levels of H(2) was selected for its use as the sole H(2) donor in this reaction. Fthalide dechlorination was successfully accomplished by combining an H(2)-producing SP culture and a KFL culture containing Dehalobacter species, supplemented with 0.13% and 0.5% SP, respectively. The efficiency of H(2) use in dechlorination was evaluated in a combined culture containing the KFL culture and strain Clostridium sp. Ma13, a new isolate that produces H(2) from SP. Results obtained with this culture indicated increased H(2)-fraction for fthalide dechlorination much more in this culture than in compared with a KFL culture supplemented with 20mM lactate, which are 0.75 H(2)·glucose(-1) and 0.015 H(2)·lactate(-1) in mol ratio, respectively. Copyright © 2012 Elsevier Ltd. All rights reserved.

Biological reductive dechlorination of tetrachloroethylene and trichloroethylene to ethylene under methanogenic conditions

International Nuclear Information System (INIS)

Freedman, D.L.; Gossett, J.M.

1989-01-01

A biological process for remediation of groundwater contaminated with tetrachloroethylene (PCE) and trichloroethylene (TCE) can only be applied if the transformation products are environmentally acceptable. Studies with enrichment cultures of PCE- and TCE-degrading microorganisms provide evidence that, under methanogenic conditions, mixed cultures are able to completely dechlorinate PCE and TCE to ethylene, a product which is environmentally acceptable. Radiotracer studies with [ 14 C]PCE indicated that [ 14 C]ethylene was the terminal product; significant conversion to 14 CO 2 or 14 CH 4 was not observed. The rate-limiting step in the pathway appeared to be conversion of vinyl chloride to ethylene. To sustain reductive dechlorination of PCE and TCE, it was necessary to supply an electron donor; methanol was the most effective, although hydrogen, formate, acetate, and glucose also served. Studies with the inhibitor 2-bromoethanesulfonate suggested that methanogens played a key role in the observed biotransformations of PCE and TCE

A remediation performance model for enhanced metabolic reductive dechlorination of chloroethenes in fractured clay till

DEFF Research Database (Denmark)

Manoli, Gabriele; Chambon, Julie C.; Bjerg, Poul L.

2012-01-01

A numerical model of metabolic reductive dechlorination is used to describe the performance of enhanced bioremediation in fractured clay till. The model is developed to simulate field observations of a full scale bioremediation scheme in a fractured clay till and thereby to assess remediation...

Investigations in the microbial degradation of polychlorinated dibenzo-p-dioxins and means of reductive dechlorination and aerobic mineralization

International Nuclear Information System (INIS)

Rosenbrock, P.

1997-12-01

The work had the objective to develop a biological method for cleaning up PCDD/PCDF contaminated upper soil layers (PCDDs/PCDFs: polychlorinated dibenzo-p-dioxins and dibenzofurans). Since highly chlorinated aromatic compounds persist in soil under aerobic conditions, reductive dechlorination of the compounds under anaerobic conditions was aimed at in a first phase of the project. A second, topped phase was destined for aerobic mineralization of the dechlorinated matrices. The tests were carried out on three farmland soils following long-term contamination with PCDDs/PCDFs. (orig./MG)

Use Of Statistical Tools To Evaluate The Reductive Dechlorination Of High Levels Of TCE In Microcosm Studies

Science.gov (United States)

A large, multi-laboratory microcosm study was performed to select amendments for supporting reductive dechlorination of high levels of trichloroethylene (TCE) found at an industrial site in the United Kingdom (UK) containing dense non-aqueous phase liquid (DNAPL) TCE. The study ...

Effects of ferrous ions on the reductive dechlorination of trichloroethylene by zero-valent iron

International Nuclear Information System (INIS)

Liu, C.-C.; Tseng, D.-H.; Wang, C.-Y.

2006-01-01

The surface characteristics of zero-valent iron (ZVI) and the efficiency of reductive dechlorination of trichloroethylene (TCE) in the presence of ferrous ions were studied. The experimental results indicated that the acid-washing of a metallic iron sample enhanced the efficiency of TCE degradation by ZVI. This occurred because acid-washing changed the conformation of oxides on the surface of iron from maghemite (γ-Fe 2 O 3 ) to the more hydrated goethite (α-FeOOH), as was confirmed by XPS analysis. However, when ferrous ions were simultaneous with TCE in water, the TCE degradation rate decreased as the concentration of ferrous ion increased. This was due to the formation of passive precipitates of ferrous hydroxide, including maghemite and magnetite (Fe 3 O 4 ), that coated on the surface of acid-washed ZVI, which as a result inhibited the electron transfer and catalytic hydrogenation mechanisms. On the other hand, in an Fe 0 -TCE system without the acid-washing pretreatment of ZVI, ferrous ions were adsorbed into the maghemite lattice which was then converted to semiconductive magnetite. Thus, the electrons were transferred from the iron surface and passed through the precipitates, allowing for the reductive dechlorination of TCE

Reductive dechlorination of chlorinated hydrocarbons as non-aqueous phase liquid (NAPL): Preliminary investigation on effects of cement doses

Energy Technology Data Exchange (ETDEWEB)

Do, Si-Hyun, E-mail: sihyun2@hanyang.ac.kr [Department of Chemical Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Batchelor, Bill [Zachry Department of Civil Engineering, Texas A and M University, College Station, TX 77843 (United States)

2012-07-15

The reactivities of various types of iron mixtures to degrade chlorinated hydrocarbons (PCE, TCE and 1,1,1-TCA) in the form of non-aqueous phase liquids were investigated. The iron mixtures included a mixture of Fe(II) and Portland cement (Fe(II)-C), a mixture of Fe(II), Fe(III) and Ca(OH){sub 2} (Fe(II/III)-L), and a mixture of Fe(II), Fe(III), Ca(OH){sub 2}, and Portland cement (Fe(II/III)-C). When the same amount of Fe(II) was used, Fe(II)-C was more reactive with chlorinated ethylenes (i.e. PCE and TCE) than Fe(II/III)-L. The reductive pathway for high concentrations of total PCE (i.e. above solubility) with Fe(II)-C was determined to be a combination of two-electron transfer, {beta}-elimination and hydrogenolysis. Increasing the cement dose from 5% to 10% in Fe(II)-C did not affect PCE dechlorination rates, but it did favor the {beta}-elimination pathway. In addition, when Fe(II/III)-C with 5%C was used, PCE dechlorination was similar to that by Fe(II)-C, but this mixture did not effectively degrade TCE. A modified second-order kinetic model was developed and shown to appropriately describe degradation of TCE at high concentrations. Fe(II/III)-L effectively degraded high concentrations of 1,1,1-TCA at rates that were similar to those obtained with Fe(II)-C using 10% C. Moreover, both increasing cement doses and the presence of Fe(III) increased dechlorination rates of 1,1,1-TCA, which was mainly through the hydrogenolysis pathway. The reactivity of Fe(II/III)-L was strongly dependent on the target compound (i.e. less reactivity with TCE, more with 1,1,1-TCA). Therefore, Fe(II/III)-L could be a potential mixture for degrading 1,1,1-TCA, but it should be modified to degrade TCE more effectively. - Highlights: Black-Right-Pointing-Pointer TCE yield indicated that PCE dechlorination was through hydrogenolysis and {beta}-elimination. Black-Right-Pointing-Pointer {beta}-elimination, especially PCE to dichloroacetylene, was favored with the higher cement doses. Black

Dechlorination of short chain chlorinated paraffins by nanoscale zero-valent iron.

Science.gov (United States)

Zhang, Zhi-Yong; Lu, Mang; Zhang, Zhong-Zhi; Xiao, Meng; Zhang, Min

2012-12-01

In this study, nanoscale zero-valent iron (NZVI) particles were synthesized and used for the reductive dehalogenation of short chain chlorinated paraffins (SCCPs) in the laboratory. The results show that the dechlorination rate of chlorinated n-decane (CP(10)) by NZVI increased with decreased solution pH. Increasing the loading of NZVI enhanced the dechlorination rate of CP(10). With an increase in temperature, the degradation rate increased. The reduction of CP(10) by NZVI was accelerated with increasing the concentration of humic acid up to 15 mg/L but then was inhibited. The dechlorination of CP(10) within the initial 18 h followed pseudo-first order rate model. The formation of intermediate products indicates a stepwise dechlorination pathway of SCCPs by NZVI. The carbon chain length and chlorination degree of SCCPs have a polynominal impact on dechlorination reactions. Copyright © 2012 Elsevier B.V. All rights reserved.

Effects of different electron donor feeding patterns on TCE reductive dechlorination performance.

Science.gov (United States)

Panagiotakis, I; Antoniou, K; Mamais, D; Pantazidou, M

2015-03-01

This study investigates how the feeding pattern of e(-) donors might affect the efficiency of enhanced in situ bioremediation in TCE-contaminated aquifers. A series of lab-scale batch experiments were conducted using butyrate or hydrogen gas (H2) as e(-) donor and a TCE-dechlorinating microbial consortium dominated by Dehalococcoides spp. The results of these experiments demonstrate that butyrate is similarly efficient for TCE dechlorination whether it is injected once or in doses. Moreover, the present work indicates that the addition of butyrate in great excess cannot be avoided, since it most likely provide, even indirectly, significant part of the H2 required. Furthermore, methanogenesis appears to be the major ultimate e(-) accepting process in all experiments, regardless the e(-) donor used and the feeding pattern. Finally, the timing of injection of H2 seems to significantly affect dechlorination performance, since the injection during the early stages improves VC-to-ETH dechlorination and reduce methanogenic activity.

Effect of heterogeneity on enhanced reductive dechlorination: Analysis of remediation efficiency and groundwater acidification

Science.gov (United States)

Brovelli, A.; Lacroix, E.; Robinson, C. E.; Gerhard, J.; Holliger, C.; Barry, D. A.

2011-12-01

Enhanced reductive dehalogenation is an attractive in situ treatment technology for chlorinated contaminants. The process includes two acid-forming microbial reactions: fermentation of an organic substrate resulting in short-chain fatty acids, and dehalogenation resulting in hydrochloric acid. The accumulation of acids and the resulting drop of groundwater pH are controlled by the mass and distribution of chlorinated solvents in the source zone, type of electron donor, alternative terminal electron acceptors available and presence of soil mineral phases able to buffer the pH (such as carbonates). Groundwater acidification may reduce or halt microbial activity, and thus dehalogenation, significantly increasing the time and costs required to remediate the aquifer. In previous work a detailed geochemical and groundwater flow simulator able to model the fermentation-dechlorination reactions and associated pH change was developed. The model accounts for the main processes influencing microbial activity and groundwater pH, including the groundwater composition, the electron donor used and soil mineral phase interactions. In this study, the model was applied to investigate how spatial variability occurring at the field scale affects dechlorination rates, groundwater pH and ultimately the remediation efficiency. Numerical simulations were conducted to examine the influence of heterogeneous hydraulic conductivity on the distribution of the injected, fermentable substrate and on the accumulation/dilution of the acidic products of reductive dehalogenation. The influence of the geometry of the DNAPL source zone was studied, as well as the spatial distribution of soil minerals. The results of this study showed that the heterogeneous distribution of the soil properties have a potentially large effect on the remediation efficiency. For examples, zones of high hydraulic conductivity can prevent the accumulation of acids and alleviate the problem of groundwater acidification. The

Heterogeneous hyporheic zone dechlorination of a TCE groundwater plume discharging to an urban river reach.

Science.gov (United States)

Freitas, Juliana G; Rivett, Michael O; Roche, Rachel S; Durrant Neé Cleverly, Megan; Walker, Caroline; Tellam, John H

2015-02-01

The typically elevated natural attenuation capacity of riverbed-hyporheic zones is expected to decrease chlorinated hydrocarbon (CHC) groundwater plume discharges to river receptors through dechlorination reactions. The aim of this study was to assess physico-chemical processes controlling field-scale variation in riverbed-hyporheic zone dechlorination of a TCE groundwater plume discharge to an urban river reach. The 50-m long pool-riffle-glide reach of the River Tame in Birmingham (UK) studied is a heterogeneous high energy river environment. The shallow riverbed was instrumented with a detailed network of multilevel samplers. Freeze coring revealed a geologically heterogeneous and poorly sorted riverbed. A chlorine number reduction approach provided a quantitative indicator of CHC dechlorination. Three sub-reaches of contrasting behaviour were identified. Greatest dechlorination occurred in the riffle sub-reach that was characterised by hyporheic zone flows, moderate sulphate concentrations and pH, anaerobic conditions, low iron, but elevated manganese concentrations with evidence of sulphate reduction. Transient hyporheic zone flows allowing input to varying riverbed depths of organic matter are anticipated to be a key control. The glide sub-reach displayed negligible dechlorination attributed to the predominant groundwater baseflow discharge condition, absence of hyporheic zone, transition to more oxic conditions and elevated sulphate concentrations expected to locally inhibit dechlorination. The tail-of-pool-riffle sub-reach exhibited patchy dechlorination that was attributed to sub-reach complexities including significant flow bypass of a low permeability, high organic matter, silty unit of high dechlorination potential. A process-based conceptual model of reach-scale dechlorination variability was developed. Key findings of practitioner relevance were: riverbed-hyporheic zone CHC dechlorination may provide only a partial, somewhat patchy barrier to CHC

A stereospecific pathway for the introduction of deuterium on the brassinosteroid skeleton by reductive dechlorination of chlorocarbonates

Czech Academy of Sciences Publication Activity Database

Marek, Aleš; Patil, Mahadeo Rajshekhar; Klepetářová, Blanka; Kohout, Ladislav; Elbert, Tomáš

2012-01-01

Roč. 53, č. 16 (2012), s. 2048-2050 ISSN 0040-4039 R&D Projects: GA AV ČR IAA400550801 Institutional research plan: CEZ:AV0Z40550506 Keywords : brassinosteroids * reductive dechlorination * stereospecific reactions Subject RIV: CC - Organic Chemistry Impact factor: 2.397, year: 2012

Effects of ferrous ions on the reductive dechlorination of trichloroethylene by zero-valent iron

Energy Technology Data Exchange (ETDEWEB)

Liu, C.-C. [Graduate Institute of Environmental Engineering, National Central University, Chungli, Taiwan 32001 (China); Tseng, D.-H. [Graduate Institute of Environmental Engineering, National Central University, Chungli, Taiwan 32001 (China)]. E-mail: dhtseng@ncuen.ncu.edu.tw; Wang, C.-Y. [Graduate Institute of Environmental Engineering, National Central University, Chungli, Taiwan 32001 (China)

2006-08-25

The surface characteristics of zero-valent iron (ZVI) and the efficiency of reductive dechlorination of trichloroethylene (TCE) in the presence of ferrous ions were studied. The experimental results indicated that the acid-washing of a metallic iron sample enhanced the efficiency of TCE degradation by ZVI. This occurred because acid-washing changed the conformation of oxides on the surface of iron from maghemite ({gamma}-Fe{sub 2}O{sub 3}) to the more hydrated goethite ({alpha}-FeOOH), as was confirmed by XPS analysis. However, when ferrous ions were simultaneous with TCE in water, the TCE degradation rate decreased as the concentration of ferrous ion increased. This was due to the formation of passive precipitates of ferrous hydroxide, including maghemite and magnetite (Fe{sub 3}O{sub 4}), that coated on the surface of acid-washed ZVI, which as a result inhibited the electron transfer and catalytic hydrogenation mechanisms. On the other hand, in an Fe{sup 0}-TCE system without the acid-washing pretreatment of ZVI, ferrous ions were adsorbed into the maghemite lattice which was then converted to semiconductive magnetite. Thus, the electrons were transferred from the iron surface and passed through the precipitates, allowing for the reductive dechlorination of TCE.

Exploring the Genome and Proteome of Desulfitobacterium hafniense DCB2 for its Protein Complexes Involved in Metal Reduction and Dechlorination

Energy Technology Data Exchange (ETDEWEB)

Sang-Hoon, Kim; Hardzman, Christina; Davis, John k.; Hutcheson, Rachel; Broderick, Joan B.; Marsh, Terence L.; Tiedje, James M.

2012-09-27

Desulfitobacteria are of interest to DOE mission because of their ability to reduce many electron acceptors including Fe(III), U(VI), Cr(VI), As(V), Mn(IV), Se(VI), NO₃- and well as CO₂, sulfite, fumarate and humates, their ability to colonize more stressful environments because they form spores, fix nitrogen and they have the more protective Gram positive cell walls. Furthermore at least some of them reductively dechlorinate aromatic and aliphatic pollutants. Importantly, most of the metals and the organochlorine reductions are coupled to ATP production and support growth providing for the organism's natural selection at DOE's contaminant sites. This work was undertaken to gain insight into the genetic and metabolic pathways involved in dissimilatory metal reduction and reductive dechlorination, (ii) to discern the commonalities among these electron-accepting processes, (iii) to identify multi-protein complexes catalyzing these functions and (iv) to elucidate the coordination in expression of these pathways and processes.

Nitrate reductase gene involvement in hexachlorobiphenyl dechlorination by Phanerochaete chrysosporium

International Nuclear Information System (INIS)

De, Supriyo; Perkins, Michael; Dutta, Sisir K.

2006-01-01

Polychlorobiphenyl (PCB) degradation usually occurs through reductive dechlorination under anaerobic conditions and phenolic ring cleavage under aerobic conditions. In this paper, we provide evidence of nitrate reductase (NaR) mediated dechlorination of hexachlorobiphenyl (PCB-153) in Phanerochaete chrysosporium under non-ligninolytic condition and the gene involved. The NaR enzyme and its cofactor, molybdenum (Mo), were found to mediate reductive dechlorination of PCBs even in aerobic condition. Tungsten (W), a competitive inhibitor of this enzyme, was found to suppress this dechlorination. Chlorine release assay provided further evidence of this nitrate reductase mediated dechlorination. Commercially available pure NaR enzyme from Aspergillus was used to confirm these results. Through homology search using TBLASTN program, NaR gene was identified, primers were designed and the RT-PCR product was sequenced. The NaR gene was then annotated in the P. chrysosporium genome (GenBank accession no. AY700576). This is the first report regarding the presence of nitrate reductase gene in this fungus with the explanation why this fungus can dechlorinate PCBs even in aerobic condition. These fungal inoculums are used commercially as pellets in sawdust for enhanced bioremediation of PCBs at the risk of depleting soil nitrates. Hence, the addition of nitrates to the pellets will reduce this risk as well as enhance its activity

Hexachlorobenzene dechlorination as affected by organic fertilizer and urea applications in two rice planted paddy soils in a pot experiment

International Nuclear Information System (INIS)

Liu, C.Y.; Jiang, X.; Yang, X.L.; Song, Y.

2010-01-01

Reductive dechlorination is a crucial pathway for HCB degradation, the applications of organic materials and nitrogen can alter microbial activity and redox potential of soils, thus probably influence HCB dechlorination. To evaluate hexachlorobenzene (HCB) dechlorination as affected by organic fertilizer (OF) and urea applications in planted paddy soils, a pot experiment was conducted in two types of soils, Hydragric Acrisols (Ac) and Gleyi-Stagnic Anthrosols (An). After 18 weeks of experiment, HCB residues decreased by 28.2-37.5% of the initial amounts in Ac, and 42.1-70.9% in An. The amounts of HCB metabolites showed that dechlorination rates in An were higher than in Ac, which was mainly attributed to the higher pH and dissolved organic carbon (DOC) content of An. Both in Ac and An, the additions of 1% and 2% OF had negative effect on HCB dechlorination, which was probably because excessive nitrogen in OF decreased degraders' activity and the degradation of organic carbon in OF accepted electrons. The application of 0.03% urea could enhance HCB dechlorination rates slightly, while 0.06% urea accelerated HCB dechlorination significantly both in Ac and An. It could be assumed that urea served as an electron donor and stimulated degraders to dechlorinate HCB. In addition, the methanogenic bacteria were involved in dechlorination process, and reductive dechlorination in planted paddy soil might be impeded for the aerenchyma and O 2 supply into the rhizosphere. Results indicated that soil types, rice root system, methanogenic bacteria, OF and urea applications all had great effects on dechlorination process.

Phylogenetically distinct bacteria involve extensive dechlorination of aroclor 1260 in sediment-free cultures.

Directory of Open Access Journals (Sweden)

Shanquan Wang

Full Text Available Microbial reductive dechlorination of the persistent polychlorinated biphenyls (PCBs is attracting much attention in cleanup of the contaminated environment. Nevertheless, most PCB dechlorinating cultures require presence of sediment or sediment substitutes to maintain their dechlorination activities which hinders subsequent bacterial enrichment and isolation processes. The information on enriching sediment-free PCB dechlorinating cultures is still limited. In this study, 18 microcosms established with soils and sediments were screened for their dechlorination activities on a PCB mixture - Aroclor 1260. After one year of incubation, 10 out of 18 microcosms showed significant PCB dechlorination with distinct dechlorination patterns (e.g., Process H, N and T classified based on profiles of PCB congeners loss and new congeners formation. Through serial transfers in defined medium, six sediment-free PCB dechlorinating cultures (i.e., CW-4, CG-1, CG-3, CG-4, CG-5 and SG-1 were obtained without amending any sediment or sediment-substitutes. PCB dechlorination Process H was the most frequently observed dechlorination pattern, which was found in four sediment-free cultures (CW-4, CG-3, CG-4 and SG-1. Sediment-free culture CG-5 showed the most extensive PCB dechlorination among the six cultures, which was mediated by Process N, resulting in the accumulation of penta- (e.g., 236-24-CB and tetra-chlorobiphenyls (tetra-CBs (e.g., 24-24-CB, 24-25-CB, 24-26-CB and 25-26-CB via dechlorinating 30.44% hepta-CBs and 59.12% hexa-CBs after three months of incubation. For culture CG-1, dechlorinators mainly attacked double flanked meta-chlorines and partially ortho-chlorines, which might represent a novel dechlorination pattern. Phylogenetic analysis showed distinct affiliation of PCB dechlorinators in the microcosms, including Dehalogenimonas and Dehalococcoides species. This study broadens our knowledge in microbial reductive dechlorination of PCBs, and provides

Humin as an electron donor for enhancement of multiple microbial reduction reactions with different redox potentials in a consortium.

Science.gov (United States)

Zhang, Dongdong; Zhang, Chunfang; Xiao, Zhixing; Suzuki, Daisuke; Katayama, Arata

2015-02-01

A solid-phase humin, acting as an electron donor, was able to enhance multiple reductive biotransformations, including dechlorination of pentachlorophenol (PCP), dissimilatory reduction of amorphous Fe (III) oxide (FeOOH), and reduction of nitrate, in a consortium. Humin that was chemically reduced by NaBH4 served as an electron donor for these microbial reducing reactions, with electron donating capacities of 0.013 mmol e(-)/g for PCP dechlorination, 0.15 mmol e(-)/g for iron reduction, and 0.30 mmol e(-)/g for nitrate reduction. Two pairs of oxidation and reduction peaks within the humin were detected by cyclic voltammetry analysis. 16S rRNA gene sequencing-based microbial community analysis of the consortium incubated with different terminal electron acceptors, suggested that Dehalobacter sp., Bacteroides sp., and Sulfurospirillum sp. were involved in the PCP dechlorination, dissimilatory iron reduction, and nitrate reduction, respectively. These findings suggested that humin functioned as a versatile redox mediator, donating electrons for multiple respiration reactions with different redox potentials. Copyright © 2014 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

Efficient photocatalytic reductive dechlorination of 4-chlorophenol to phenol on {0 0 1}/{1 0 1} facets co-exposed TiO_2 nanocrystals

International Nuclear Information System (INIS)

Jiang, Guodong; Wei, Meng; Yuan, Songdong; Chang, Qing

2016-01-01

Graphical abstract: - Highlights: • 4-Chlorophenol is dechlorinated over {0 0 1}/{1 0 1} co-exposed TiO_2 nanocrystals. • Photo-electrons are accumulated on {1 0 1} facets due to surface heterojunction. • Fluorine will trap photoelectrons to depress the dechlorination performance. • Sufficient isopropanol promotes the dechlorination activity and selectivity. - Abstract: 4-chlorophenol could be efficiently photoreductively dechlorinated over anatase TiO_2 nanocrystals with co-exposed {0 0 1} and {1 0 1} facets, which were synthesized and further characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Although fluorine could adsorb on {0 0 1} facets to decrease their surface energy, enabling TiO_2 to expose high energy {0 0 1} facets, the surface bonded fluorine might depress the photoreductive dechlorination efficiency of 4-chlorophenol, attributed to the electron trapping role of surface ≡Ti−F groups. Due to the formation of a surface heterojunction between {1 0 1} and {0 0 1} facets in a single TiO_2 nanocrystal, electrons and holes were spontaneously self-separated and selectively migrate to {1 0 1} and {0 0 1} facets, respectively. Electron trapping experiments demonstrated that photogenerated electrons are the responsible for the reductive dechlorinaton of 4-chlorophenol to phenol. To avoid the oxidative degradation of 4-chlorophenol by holes and ensure sufficient electrons to reductively dechlorinate the substrate, moderate scavengers were required in the reaction system and dissolved oxygen, which might deplete electron on TiO_2, also should be removed. With the optimal scavengers, the conversion efficiency of 4-chlorophenol (4-CP) achieved 97.5% and the selectivity for phenol was 92.5%, which were much higher than that of commercial TiO_2 P25.

Reductive dechlorination of 3,3',4,4'-tetrachlorobiphenyl (PCB77) using palladium or palladium/iron nanoparticles and assessment of the reduction in toxic potency in vascular endothelial cells

International Nuclear Information System (INIS)

Venkatachalam, Karthik; Arzuaga, Xabier; Chopra, Nitin; Gavalas, Vasilis G.; Xu, Jian; Bhattacharyya, Dibakar; Hennig, Bernhard; Bachas, Leonidas G.

2008-01-01

Palladium-based nanoparticles immobilized in polymeric matrices were applied to the reductive dechlorination of 3,3',4,4'-tetrachlorobiphenyl (PCB77) at room temperature. Two different dechlorination platforms were evaluated using (1) Pd nanoparticles within conductive polypyrrole films; or (2) immobilized Fe/Pd nanoparticles within polyvinylidene fluoride microfiltration membranes. For the first approach, the polypyrrole film was electrochemically formed in the presence of perchlorate ions that were incorporated into the film to counter-balance the positive charges of the polypyrrole chain. The film was then incubated in a solution containing tetrachloropalladate ions, which were exchanged with the perchlorate ions within the film. During this exchange, reduction of tetrachloropalladate by polypyrrole occurred, which led to the formation of palladium nanoparticles within the film. For the second approach, the membrane-supported Fe/Pd nanoparticles were prepared in three steps: polymerization of acrylic acid in polyvinylidene fluoride microfiltration membrane pores was followed by ion exchange of Fe 2+ , and then chemical reduction of the ferrous ions bound to the carboxylate groups. The membrane-supported iron nanoparticles were then soaked in a solution of tetrachloropalladate resulting in the deposition of Pd on the Fe surface. The nanoparticles prepared by both approaches were employed in the dechlorination of PCB77. The presence of hydrogen was required when the monometallic Pd nanoparticles were employed. The results indicate the removal of chlorine atoms from PCB77, which led to the formation of lower chlorinated intermediates and ultimately biphenyl. Toxicity associated with vascular dysfunction by PCB77 and biphenyl was compared using cultured endothelial cells. The data strongly suggest that the dechlorination system used in this study markedly reduced the proinflammatory activity of PCB77, a persistent organic pollutant

Synergistic effect of nano-sized mackinawite with cyano-cobalamin in cement slurries for reductive dechlorination of tetrachloroethylene

International Nuclear Information System (INIS)

Kyung, Daeseung; Sihn, Youngho; Kim, Sangwoo; Bae, Sungjun; Amin, Muhammad Tahir; Alazba, Abdulrahman Ali; Lee, Woojin

2016-01-01

Highlights: • Complete degradation of PCE was observed in nFeS-Cbl(III)-cement at pH 12. • PCE was completely degraded to non-chlorinated organic compounds by this system. • Co redox couple and Ca species in cement played a pivotal role for PCE reduction. • Increases in Cbl(III) concentration, cement ratio, and pH enhanced PCE degradation. • Efficiency of the system for PCE reduction was good even at high concentration of PCE. - Abstract: Experiments were conducted to investigate the reductive dechlorination of tetrachloroethylene (PCE) by nano-Mackinawite (nFeS) with cyano-cobalamin (Cbl(III)) in cement slurries. Almost complete degradation of PCE by nFeS-Cbl(III) was observed in cement slurries in 5 h and its degradation kinetics (k_o_b_s_-_P_C_E = 0.57 h"−"1) was 6-times faster than that of nFeS-Cbl(III) without the cement slurries. PCE was finally transformed to non-chlorinated organic compounds such as ethylene, acetylene, and C3-C4 hydrocarbons by nFeS-Cbl(III) in cement slurries. X-ray photoelectron spectroscopy and PCE degradation by cement components (SiO_2, Al_2O_3, and CaO) revealed that both the reduced Co species in Cbl(III) and the presence of Ca in cement played an important role for the enhanced reductive dechlorination of PCE. The increase in the concentration of Cbl(III) (0.005–0.1 mM), cement ratio (0.05–0.2), and suspension pH (11.5–13.5) accelerated the PCE degradation kinetics by providing more favorable environments for the production of reactive Ca species and reduction of Co species. We also observed that the degradation efficiency of PCE by nFeS-Cbl(III)-cement lasted even at high concentration of PCE. The experimental results obtained from this study could provide fundamental knowledge of redox interactions among nFeS, Cbl(III), and cement, which could significantly enhance reductive dechlorination of chlorinated organics in contaminated natural and engineered environments.

Synergistic effect of nano-sized mackinawite with cyano-cobalamin in cement slurries for reductive dechlorination of tetrachloroethylene

Energy Technology Data Exchange (ETDEWEB)

Kyung, Daeseung [Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 34141 (Korea, Republic of); Sihn, Youngho [Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 34141 (Korea, Republic of); Kim, Sangwoo [Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 34141 (Korea, Republic of); Bae, Sungjun [Department of Environmental Engineering, Konkuk University, 120 Neungdong-ro, Gwangjin-gu, Seoul 05029 (Korea, Republic of); Amin, Muhammad Tahir; Alazba, Abdulrahman Ali [Alamoudi Water Chair, King Saud University, Riyadh 11451 (Saudi Arabia); Lee, Woojin, E-mail: woojin_lee@kaist.ac.kr [Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 34141 (Korea, Republic of)

2016-07-05

Highlights: • Complete degradation of PCE was observed in nFeS-Cbl(III)-cement at pH 12. • PCE was completely degraded to non-chlorinated organic compounds by this system. • Co redox couple and Ca species in cement played a pivotal role for PCE reduction. • Increases in Cbl(III) concentration, cement ratio, and pH enhanced PCE degradation. • Efficiency of the system for PCE reduction was good even at high concentration of PCE. - Abstract: Experiments were conducted to investigate the reductive dechlorination of tetrachloroethylene (PCE) by nano-Mackinawite (nFeS) with cyano-cobalamin (Cbl(III)) in cement slurries. Almost complete degradation of PCE by nFeS-Cbl(III) was observed in cement slurries in 5 h and its degradation kinetics (k{sub obs-PCE} = 0.57 h{sup −1}) was 6-times faster than that of nFeS-Cbl(III) without the cement slurries. PCE was finally transformed to non-chlorinated organic compounds such as ethylene, acetylene, and C3-C4 hydrocarbons by nFeS-Cbl(III) in cement slurries. X-ray photoelectron spectroscopy and PCE degradation by cement components (SiO{sub 2}, Al{sub 2}O{sub 3}, and CaO) revealed that both the reduced Co species in Cbl(III) and the presence of Ca in cement played an important role for the enhanced reductive dechlorination of PCE. The increase in the concentration of Cbl(III) (0.005–0.1 mM), cement ratio (0.05–0.2), and suspension pH (11.5–13.5) accelerated the PCE degradation kinetics by providing more favorable environments for the production of reactive Ca species and reduction of Co species. We also observed that the degradation efficiency of PCE by nFeS-Cbl(III)-cement lasted even at high concentration of PCE. The experimental results obtained from this study could provide fundamental knowledge of redox interactions among nFeS, Cbl(III), and cement, which could significantly enhance reductive dechlorination of chlorinated organics in contaminated natural and engineered environments.

Efficient photocatalytic reductive dechlorination of 4-chlorophenol to phenol on {0 0 1}/{1 0 1} facets co-exposed TiO{sub 2} nanocrystals

Energy Technology Data Exchange (ETDEWEB)

Jiang, Guodong; Wei, Meng; Yuan, Songdong [College of Chemistry and chemical engineering, Hubei Collaborative Innovation Center for High Efficient Utilization of Solar Energy, Hubei University of Technology, Wuhan 430068 (China); Chang, Qing, E-mail: changqinghust@163.com [Key Laboratory of Catalysis and Materials Science of the State Ethnic Affairs Commission and Ministry of Education, College of Resources and Environmental Science, South-Central University for Nationalities, Wuhan 430074 (China)

2016-01-30

Graphical abstract: - Highlights: • 4-Chlorophenol is dechlorinated over {0 0 1}/{1 0 1} co-exposed TiO{sub 2} nanocrystals. • Photo-electrons are accumulated on {1 0 1} facets due to surface heterojunction. • Fluorine will trap photoelectrons to depress the dechlorination performance. • Sufficient isopropanol promotes the dechlorination activity and selectivity. - Abstract: 4-chlorophenol could be efficiently photoreductively dechlorinated over anatase TiO{sub 2} nanocrystals with co-exposed {0 0 1} and {1 0 1} facets, which were synthesized and further characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Although fluorine could adsorb on {0 0 1} facets to decrease their surface energy, enabling TiO{sub 2} to expose high energy {0 0 1} facets, the surface bonded fluorine might depress the photoreductive dechlorination efficiency of 4-chlorophenol, attributed to the electron trapping role of surface ≡Ti−F groups. Due to the formation of a surface heterojunction between {1 0 1} and {0 0 1} facets in a single TiO{sub 2} nanocrystal, electrons and holes were spontaneously self-separated and selectively migrate to {1 0 1} and {0 0 1} facets, respectively. Electron trapping experiments demonstrated that photogenerated electrons are the responsible for the reductive dechlorinaton of 4-chlorophenol to phenol. To avoid the oxidative degradation of 4-chlorophenol by holes and ensure sufficient electrons to reductively dechlorinate the substrate, moderate scavengers were required in the reaction system and dissolved oxygen, which might deplete electron on TiO{sub 2}, also should be removed. With the optimal scavengers, the conversion efficiency of 4-chlorophenol (4-CP) achieved 97.5% and the selectivity for phenol was 92.5%, which were much higher than that of commercial TiO{sub 2} P25.

Green remediation: enhanced reductive dechlorination using recycled rinse water as bioremediation substrate

International Nuclear Information System (INIS)

Dawson, Gaynor; McKeon, Tom

2007-01-01

Enhanced reductive dechlorination (ERD) has rapidly become a remedy of choice for use on chlorinated solvent contamination when site conditions allow. With this approach, solutions of an organic substrate are injected into the affected aquifer to stimulate biological growth and the resultant production of reducing conditions in the target zone. Under the reducing conditions, hydrogen is produced and ultimately replaces chlorine atoms on the contaminant molecule causing sequential dechlorination. Under suitable conditions the process continues until the parent hydrocarbon precursor is produced, such as the complete dechlorination of trichloroethylene (TCE) to ethene. The process is optimized by use of a substrate that maximizes hydrogen production per unit cost. When natural biota are not present to promote the desired degradation, inoculates can be added with the substrate. The in-situ method both reduces cost and accelerates cleanup. Successful applications have been extended from the most common chlorinated compounds perchloroethylene (PCE) and TCE and related products of degradation, to perchlorate, and even explosives such as RDX and trinitrotoluene on which nitrates are attacked in lieu of chloride. In recent work, the process has been further improved through use of beverage industry wastewaters that are available at little or no cost. With material cost removed from the equation, applications can maximize the substrate loading without significantly increasing total cost. The extra substrate loading both accelerates reaction rates and extends the period of time over which reducing conditions are maintained. In some cases, the presence of other organic matter in addition to simple sugars provides for longer performance times of individual injections, thereby working in a fashion similar to emulsified vegetable oil. The paper discusses results of applications at three different sites contaminated with chlorinated ethylenes. The applications have included

Reductive dechlorination of trichloroethene DNAPL source zones: source zone architecture versus electron donor availability

Science.gov (United States)

Krol, M.; Kokkinaki, A.; Sleep, B.

2014-12-01

The persistence of dense-non-aqueous-phase liquids (DNAPLs) in the subsurface has led practitioners and regulatory agencies to turn towards low-maintenance, low-cost remediation methods. Biological degradation has been suggested as a possible solution, based on the well-proven ability of certain microbial species to break down dissolved chlorinated ethenes under favorable conditions. However, the biodegradation of pure phase chlorinated ethenes is subject to additional constraints: the continuous release of electron acceptor at a rate governed by mass transfer kinetics, and the temporal and spatial heterogeneity of DNAPL source zones which leads to spatially and temporally variable availability of the reactants for reductive dechlorination. In this work, we investigate the relationship between various DNAPL source zone characteristics and reaction kinetics using COMPSIM, a multiphase groundwater model that considers non-equilibrium mass transfer and Monod-type kinetics for reductive dechlorination. Numerical simulations are performed for simple, homogeneous trichloroethene DNAPL source zones to demonstrate the effect of single source zone characteristics, as well as for larger, more realistic heterogeneous source zones. It is shown that source zone size, and mass transfer kinetics may have a decisive effect on the predicted bio-enhancement. Finally, we evaluate the performance of DNAPL bioremediation for realistic, thermodynamically constrained, concentrations of electron donor. Our results indicate that the latter may be the most important limitation for the success of DNAPL bioremediation, leading to reduced bio-enhancement and, in many cases, comparable performance with water flooding.

Effects of bioaugmentation on enhanced reductive dechlorination of 1,1,1-trichloroethane in groundwater - a comparison of three sites

DEFF Research Database (Denmark)

Scheutz, Charlotte; Durant, Neal D.; Broholm, Mette Martina

2014-01-01

, microcosms were amended with various concentrations of chloroethanes (TCA or monochloroethane [CA]) and/or chloroethenes (tetrachloroethene [PCE], trichloroethene [TCE], or 1,1-dichloroethene [1,1-DCE]). Results showed that combined electron donor addition and bioaugmentation stimulated dechlorination of TCA...... and 1,1-dichloroethane (1,1-DCA) to CA, and dechlorination of PCE, TCE, 1,1-DCE and cDCE to ethane. Dechlorination of CA was not observed. Bioaugmentation improved the rate and extent of TCA and 1,1-DCA dechlorination at two sites, but did not accelerate dechlorination at a third site where geochemical...... conditions were reducing and Dhc and Dhb were indigenous. TCA at initial concentrations of 5 mg/L inhibited (i.e., slowed the rate of) TCA dechlorination, TCE dechlorination, donor fermentation, and methanogenesis. 1 mg/L TCA did not inhibit dechlorination of TCA, TCE or cDCE. Moreover, complete...

Potential of isotope analysis (C, Cl) to identify dechlorination mechanisms

Science.gov (United States)

Cretnik, Stefan; Thoreson, Kristen; Bernstein, Anat; Ebert, Karin; Buchner, Daniel; Laskov, Christine; Haderlein, Stefan; Shouakar-Stash, Orfan; Kliegman, Sarah; McNeill, Kristopher; Elsner, Martin

2013-04-01

Chloroethenes are commonly used in industrial applications, and detected as carcinogenic contaminants in the environment. Their dehalogenation is of environmental importance in remediation processes. However, a detailed understanding frequently accounted problem is the accumulation of toxic degradation products such as cis-dichloroethylene (cis-DCE) at contaminated sites. Several studies have addressed the reductive dehalogenation reactions using biotic and abiotic model systems, but a crucial question in this context has remained open: Do environmental transformations occur by the same mechanism as in their corresponding in vitro model systems? The presented study shows the potential to close this research gap using the latest developments in compound specific chlorine isotope analysis, which make it possible to routinely measure chlorine isotope fractionation of chloroethenes in environmental samples and complex reaction mixtures.1,2 In particular, such chlorine isotope analysis enables the measurement of isotope fractionation for two elements (i.e., C and Cl) in chloroethenes. When isotope values of both elements are plotted against each other, different slopes reflect different underlying mechanisms and are remarkably insensitive towards masking. Our results suggest that different microbial strains (G. lovleyi strain SZ, D. hafniense Y51) and the isolated cofactor cobalamin employ similar mechanisms of reductive dechlorination of TCE. In contrast, evidence for a different mechanism was obtained with cobaloxime cautioning its use as a model for biodegradation. The study shows the potential of the dual isotope approach as a tool to directly compare transformation mechanisms of environmental scenarios, biotic transformations, and their putative chemical lab scale systems. Furthermore, it serves as an essential reference when using the dual isotope approach to assess the fate of chlorinated compounds in the environment.

Population dynamics of dechlorinators and factors affecting the level and products of PCB dechlorination in sediments

Energy Technology Data Exchange (ETDEWEB)

Kim, J.S.; Sokol, R.C.; Liu, X.; Bethoney, C.M.; Rhee, G.Y. [State Univ. of New York and New York State Department of Health, Albany, NY (United States)

1996-12-31

Microbial dechlorination of polychlorinated biphenyls (PCBs) often stops although a significant number of removable chlorines remain. To determine the reason for the cessation, we investigated the limitation of organic carbon, PCB bioavailability, and inhibition by metabolic products. Enrichment with carbon sources did not induce additional chlorination, indicating the plateau was not due to depletion of organic carbon. The bioavailability was not limiting, since a subcritical micelle concentration of the surfactant, which enhanced desorption without inhibiting dechlorinating microorganisms, failed to lower the plateau. Neither was it due to accumulation of metabolites, since no additional dechlorination was detected when plateau sediments were incubated with fresh medium. Similarly, dechlorination was not inhibited in freshly spiked sediment slurries. Dechlorination ended up at the same level with nearly identical congener profiles, regardless of treatment. These results indicate that cessation of dechlorination was due to the accumulation of daughter congeners, which cannot be used as electron acceptors by microbes. To determine whether the decreasing availability affected the microorganisms, we determined the population dynamics of dechlorinators using the most probable number technique. The growth dynamics of the dechlorinators mirrored the time course of dechlorination. It started when the population increased by two orders of magnitude. Once dechlorination stopped the dechlorinating population also began to decrease. When dechlorinators were inoculated into PCB-free sediments, the population decreased over time. The decrease of the population as dechlorination ceased confirms that the diminishing availability of congeners was the reason for the incomplete dechlorination. Recent findings have shown that a second phase of dechlorination of certain congeners can occur after a long lag. 45 refs., 8 figs.

Anaerobic bacteria that dechlorinate perchloroethene.

Science.gov (United States)

Fathepure, B Z; Nengu, J P; Boyd, S A

1987-01-01

In this study, we identified specific cultures of anaerobic bacteria that dechlorinate perchlorethene (PCE). The bacteria that significantly dechlorinated PCE were strain DCB-1, an obligate anaerobe previously shown to dechlorinate chlorobenzoate, and two strains of Methanosarcina. The rate of PCE dechlorination by DCB-1 compared favorably with reported rates of trichloroethene bio-oxidation by methanotrophs. Even higher PCE dechlorination rates were achieved when DCB-1 was grown in a methanogenic consortium. PMID:3426224

Isolation of novel bacteria within the Chloroflexi capable of reductive dechlorination of 1,2,3-trichloropropane.

Science.gov (United States)

Yan, J; Rash, B A; Rainey, F A; Moe, W M

2009-04-01

Two strictly anaerobic bacterial strains were isolated from contaminated groundwater at a Superfund site located near Baton Rouge, LA, USA. These strains represent the first isolates reported to reductively dehalogenate 1,2,3-trichloropropane. Allyl chloride (3-chloro-1-propene), which is chemically unstable, was produced from 1,2,3-trichloropropane, and it was hydrolysed abiotically to allyl alcohol and also reacted with the sulfide- and cysteine-reducing agents in the medium to form various allyl sulfides. Both isolates also dehalogenated a variety of other vicinally chlorinated alkanes (1,2-dichloropropane, 1,2-dichloroethane, 1,1,2-trichloroethane, 1,1,2,2- tetrachloroethane) via dichloroelimination reactions. A quantitative real-time PCR (qPCR) approach targeting 16S rRNA genes indicated that both strains couple reductive dechlorination to cell growth. Growth was not observed in the absence of hydrogen (H2) as an electron donor and a polychlorinated alkane as an electron acceptor. Alkanes containing only a single chlorine substituent (1-chloropropane, 2-chloropropane), chlorinated alkenes (tetrachlorothene, trichlorothene, cisdichloroethene, trans-dichloroethene, vinyl chloride) and chlorinated benzenes (1-chlorobenzene and 1,2- dichlorobenzene) were not dechlorinated. Phylogenetic analysis based on 16S rRNA gene sequence data showed these isolates to represent a new lineage within the Chloroflexi. Their closest previously cultured relatives are 'Dehalococcoides' strains, with 16S rRNA gene sequence similarities of only 90%.

Contributions of Fe Minerals to Abiotic Dechlorination

Science.gov (United States)

Most applications of enhanced in situ bioremediation are based on biological reductive dechlorination. Anaerobic metabolism can also produce reactive minerals that allow for in situ biogeochemical transformation of chlorinated organic contaminants such as PCE, TCE, and cis-DCE. ...

Performance and Mechanism of Piezo-Catalytic Degradation of 4-Chlorophenol: Finding of Effective Piezo-Dechlorination.

Science.gov (United States)

Lan, Shenyu; Feng, Jinxi; Xiong, Ya; Tian, Shuanghong; Liu, Shengwei; Kong, Lingjun

2017-06-06

Piezo-catalysis was first used to degrade a nondye pollutant, 4-chlorophenol (4-CP). In this process, hydrothermally synthesized tetragonal BaTiO 3 nano/micrometer-sized particles were used as the piezo-catalyst, and the ultrasonic irradiation with low frequency was selected as the vibration energy to cause the deformation of tetragonal BaTiO 3 . It was found that the piezoelectric potential from the deformation could not only successfully degrade 4-chlorophenol but also effectively dechlorinate it at the same time, and five kinds of dechlorinated intermediates, hydroquinone, benzoquinone, phenol, cyclohexanone, and cyclohexanol, were determined. This is the first sample of piezo-dechlorination. Although various active species, including h + , e - , •H, •OH, •O 2 - , 1 O 2 , and H 2 O 2 , were generated in the piezoelectric process, it was confirmed by ESR, scavenger studies, and LC-MS that the degradation and dechlorination were mainly attributed to •OH radicals. These •OH radicals were chiefly derived from the electron reduction of O 2 , partly from the hole oxidation of H 2 O. These results indicated that the piezo-catalysis was an emerging and effective advanced oxidation technology for degradation and dechlorination of organic pollutants.

Reductive dechlorination of trichloroacetic acid (TCAA) by electrochemical process over Pd-In/Al_2O_3 catalyst

International Nuclear Information System (INIS)

Liu, Yanzhen; Mao, Ran; Tong, Yating; Lan, Huachun; Zhang, Gong; Liu, Huijuan; Qu, Jiuhui

2017-01-01

Highlights: • TCAA was efficiently removed by Pd-In/Al_2O_3 based electro-reductive process. • The active species for TCAA electroreduction involved electron (e"−) and atomic H*. • The atomic H* played a major contribution to TCAA removal. - Abstract: Electrochemical reduction treatment was found to be a promising method for dechlorination of Trichloroacetic acid (TCAA), and acceleration of electron transfer or enhancement of the concentration of atomic H* significantly improve the electrochemical dechlorination process. Bimetallic Pd-based catalysts have the unique property of simultaneously catalyzing the production of atomic H* and reducing target pollutants. Herein, a bimetallic Pd–In electrocatalyst with atomic ratio of 1:1 was evenly deposited on an Al_2O_3 substrate, and the bimetallic Pd-In structure was confirmed via X-ray photoelectron spectroscopy (XPS). Electrochemical removal of trichloroacetic acid (TCAA) by the Pd-In/Al_2O_3 catalyst was performed in a three-dimensional reactor. 94% of TCAA with the initial concentration of 500 μg L"−"1 could be degraded within 30 min under a relatively low current density (0.9 mA cm"−"2). In contrast to the presence of refractory intermediates (dichloroacetic acid (DCAA)) found in the Pd/Al_2O_3 system, TCAA could be thoroughly reduced to monochloroacetic acid (MCAA) using Pd-In/Al_2O_3 catalysts. According to scavenger experiments, an electron transfer process and atomic H* formation function both existed in the TCAA reduction process, and the enhanced indirect atomic H* reduction process (confirmed by ESR signals) played a chief role in the TCAA removal. Moreover, the synergistic effects of Pd and In were proven to be able to enhance both direct electron transfer and indirect atomic H* formation, indicating a promising prospect for bimetallic electrochemical reduction treatment.

Diverse Reductive Dehalogenases Are Associated with Clostridiales-Enriched Microcosms Dechlorinating 1,2-Dichloroethane

KAUST Repository

Merlino, Giuseppe; Balloi, Annalisa; Marzorati, Massimo; Mapelli, Francesca; Rizzi, Aurora; Lavazza, Davide; de Ferra, Francesca; Carpani, Giovanna; Daffonchio, Daniele

2015-01-01

The achievement of successful biostimulation of active microbiomes for the cleanup of a polluted site is strictly dependent on the knowledge of the key microorganisms equipped with the relevant catabolic genes responsible for the degradation process. In this work, we present the characterization of the bacterial community developed in anaerobic microcosms after biostimulation with the electron donor lactate of groundwater polluted with 1,2-dichloroethane (1,2-DCA). Through a multilevel analysis, we have assessed (i) the structural analysis of the bacterial community; (ii) the identification of putative dehalorespiring bacteria; (iii) the characterization of functional genes encoding for putative 1,2-DCA reductive dehalogenases (RDs). Following the biostimulation treatment, the structure of the bacterial community underwent a notable change of the main phylotypes, with the enrichment of representatives of the order Clostridiales . Through PCR targeting conserved regions within known RD genes, four novel variants of RDs previously associated with the reductive dechlorination of 1,2-DCA were identified in the metagenome of the Clostridiales-dominated bacterial community.

Diverse Reductive Dehalogenases Are Associated with Clostridiales-Enriched Microcosms Dechlorinating 1,2-Dichloroethane

KAUST Repository

Merlino, Giuseppe

2015-03-06

The achievement of successful biostimulation of active microbiomes for the cleanup of a polluted site is strictly dependent on the knowledge of the key microorganisms equipped with the relevant catabolic genes responsible for the degradation process. In this work, we present the characterization of the bacterial community developed in anaerobic microcosms after biostimulation with the electron donor lactate of groundwater polluted with 1,2-dichloroethane (1,2-DCA). Through a multilevel analysis, we have assessed (i) the structural analysis of the bacterial community; (ii) the identification of putative dehalorespiring bacteria; (iii) the characterization of functional genes encoding for putative 1,2-DCA reductive dehalogenases (RDs). Following the biostimulation treatment, the structure of the bacterial community underwent a notable change of the main phylotypes, with the enrichment of representatives of the order Clostridiales . Through PCR targeting conserved regions within known RD genes, four novel variants of RDs previously associated with the reductive dechlorination of 1,2-DCA were identified in the metagenome of the Clostridiales-dominated bacterial community.

Reductive dechlorination of trichloroethylene (TCE) in competition with Fe and Mn oxides – observed dynamics in H2-dependent terminal electron accepting processes

DEFF Research Database (Denmark)

Paul, Laiby; Jakobsen, Rasmus; Smolders, Erik

2016-01-01

The determination of hydrogen (H2) concentration together with the products of microbial reduction reactions in a trichloroethylene dechlorinating system is conducted to delineate the ongoing predominant terminal electron accepting processes (TEAP). Formate was used as electron donor and synthetic...

Graphene oxide-mediated rapid dechlorination of carbon tetrachloride by green rust

DEFF Research Database (Denmark)

Huang, Li-Zhi; Hansen, Hans Christian B.; Daasbjerg, Kim

2017-01-01

Graphene-based nanomaterials can mediate environmentally relevant abiotic redox reactions of chlorinated aliphatic hydrocarbons. In this study as low amounts as ∼0.007 % of graphene oxide (GO) was found to catalyze the reduction of carbon tetrachloride by layered Fe(II)-Fe(III) hydroxide (Green R....... This study indicates that traces of graphene oxide can affect reaction pathways as well as kinetics for dechlorination processes in anoxic sediments by facilitating a partial dechlorination....

Enhanced anaerobic dechlorination of polychlorinated biphenyl in sediments by bioanode stimulation

International Nuclear Information System (INIS)

Yu, Hui; Feng, Chunhua; Liu, Xiaoping; Yi, Xiaoyun; Ren, Yuan; Wei, Chaohai

2016-01-01

The application of a low-voltage electric field as an electron donor or acceptor to promote the bioremediation of chlorinated organic compounds represents a promising technology meeting the demand of developing an efficient and cost-effective strategy for in situ treatment of PCB-contaminated sediments. Here, we reported that bioanode stimulation with an anodic potential markedly enhanced dechlorination of 2,3,4,5-tetrachlorobiphenyl (PCB 61) contained in the sediment at an electronic waste recycling site of Qingyuan, Guangdong, China. The 110-day incubation of the bioanode with a potential poised at 0.2 V relative to saturated calomel electrode enabled 58% transformation of the total PCB 61 at the initial concentration of 100 μmol kg"−"1, while only 23% was reduced in the open-circuit reference experiment. The introduction of acetate to the bioelectrochemical reactor (BER) further improved PCB 61 transformation to 82%. Analysis of the bacterial composition showed significant community shifts in response to variations in treatment. At phylum level, the bioanode stimulation resulted in substantially increased abundance of Actinobacteria, Bacteroidetes, and Chloroflexi either capable of PCB dechlorination, or detected in the PCB-contaminated environment. At genus level, the BER contained two types of microorganisms: electrochemically active bacteria (EAB) represented by Geobacter, Ignavibacterium, and Dysgonomonas, and dechlorinating bacteria including Hydrogenophaga, Alcanivorax, Sedimentibacter, Dehalogenimonas, Comamonas and Vibrio. These results suggest that the presence of EAB can promote the population of dechlorinating bacteria which are responsible for PCB 61 transformation. - Highlights: • A bioelectrochemical reactor (BER) was constructed for anaerobic PCB dechlorination. • Bioanode stimulation substantially enhanced dechlorination of PCB 61. • Electrochemically active bacteria and dechlorinating bacteria coexisted in the BER. - Bioanode

Forensic Analysis of Polychlorinated Dibenzo-p-Dioxin and Furan Fingerprints to Elucidate Dechlorination Pathways.

Science.gov (United States)

Rodenburg, Lisa A; Dewani, Yashika; Häggblom, Max M; Kerkhof, Lee J; Fennell, Donna E

2017-09-19

Polychlorinated dibenzo-p-dioxins and -furans (PCDD/Fs) are persistent organic pollutants whose main removal process in the environment is due to biodegradation, and particularly anaerobic reductive dechlorination. Since PCDD/F congeners that are substituted in the lateral 2, 3, 7, and 8 positions are the most toxic, removal of these chlorines is advantageous, but previous studies have only demonstrated their removal under laboratory conditions. We evaluated a concentration data set of PCDD/F congeners with four or more chlorines along with all 209 polychlorinated biphenyl (PCB) congeners in surface water, treated and untreated wastewater, landfill leachate, and biosolids (NY CARP data set) to determine whether peri and peri/lateral dechlorination of PCDD/Fs occurs in these environments. Positive Matrix Factorization (PMF) applied to the data set revealed a factor indicative of the microbial dechlorination of PCBs, and this factor also contained a variety of non-2,3,7,8 substituted PCDD/F congeners. These results suggest that dechlorination of PCDD/Fs at the lateral positions is facile if not preferred in these environments. The relative lack of tetra- and penta-chlorinated PCDD/Fs suggested that dechlorination proceeds to PCDD/F congeners with less than four chlorines. The PMF results were confirmed by examining three samples that contained >90% PCB dechlorination products from the Fresh Kills Landfill and the Hudson River. Even without factor analysis, these samples demonstrated almost identical PCDD/F congener patterns. This study suggests that PCDD/Fs are reductively dechlorinated to nontoxic non-2,3,7,8 PCDD/F congeners in sewers and landfills as well as in the sediment of the Upper Hudson River.

Identification of Multiple Dehalogenase Genes Involved in Tetrachloroethene-to-Ethene Dechlorination in a Dehalococcoides-Dominated Enrichment Culture

Directory of Open Access Journals (Sweden)

Mohamed Ismaeil

2017-01-01

Full Text Available Chloroethenes (CEs are widespread groundwater toxicants that are reductively dechlorinated to nontoxic ethene (ETH by members of Dehalococcoides. This study established a Dehalococcoides-dominated enrichment culture (designated “YN3” that dechlorinates tetrachloroethene (PCE to ETH with high dechlorination activity, that is, complete dechlorination of 800 μM PCE to ETH within 14 days in the presence of Dehalococcoides species at 5.7±1.9×107 copies of 16S rRNA gene/mL. The metagenome of YN3 harbored 18 rdhA genes (designated YN3rdhA1–18 encoding the catalytic subunit of reductive dehalogenase (RdhA, four of which were suggested to be involved in PCE-to-ETH dechlorination based on significant increases in their transcription in response to CE addition. The predicted proteins for two of these four genes, YN3RdhA8 and YN3RdhA16, showed 94% and 97% of amino acid similarity with PceA and VcrA, which are well known to dechlorinate PCE to trichloroethene (TCE and TCE to ETH, respectively. The other two rdhAs, YN3rdhA6 and YN3rdhA12, which were never proved as rdhA for CEs, showed particularly high transcription upon addition of vinyl chloride (VC, with 75±38 and 16±8.6 mRNA copies per gene, respectively, suggesting their possible functions as novel VC-reductive dehalogenases. Moreover, metagenome data indicated the presence of three coexisting bacterial species, including novel species of the genus Bacteroides, which might promote CE dechlorination by Dehalococcoides.

Effects of biochar on dechlorination of hexachlorobenzene and the bacterial community in paddy soil.

Science.gov (United States)

Song, Yang; Bian, Yongrong; Wang, Fang; Herzberger, Anna; Yang, Xinglun; Gu, Chenggang; Jiang, Xin

2017-11-01

Anaerobic reductive dechlorination is an important degradation pathway for chlorinated organic contaminants in paddy soil. This study investigated the effects of amending paddy soil with wheat straw biochar on both the dechlorination of hexachlorobenzene (HCB), a typical highly chlorinated contaminant, and on the structure of soil bacteria communities. Soil amendment of 0.1% biochar did not significantly affect the dechlorination of HCB in the soil. However, biochar amendment at higher application levels (5%) stimulated the dechlorination of HCB in the first month of anaerobic incubation and inhibited the dechlorination of HCB after that period. The stimulation effect may be ascribed to the graphite carbon and carbon-centered persistent radicals, which are redox active, in biochar. The inhibiting effect could be partly ascribed to the reduced bioavailability of HCB in biochar-amended soils. High-throughput sequencing revealed that the amendment of biochar changed the soil bacterial community structure but not the bacterial abundances and diversities. The relative abundance of Dehalococcoidaceae in the tested soils showed a significant relationship with the dechlorination percentages of HCB, indicating that Dehalococcoidaceae may be the main HCB-dechlorinating bacteria in the studied paddy soil. The results indicated that low application levels of biochar did not affect the dechlorination of HCB in the paddy soil, while high application levels of biochar mainly inhibited the dechlorination of HCB due to the reduced bioavailability of HCB and the reduced abundances of certain dechlorinating bacteria in the biochar-amended paddy soil. Copyright © 2017 Elsevier Ltd. All rights reserved.

PCB dechlorination in anaerobic soil slurry reactors

International Nuclear Information System (INIS)

Klasson, K.T.; Evans, B.S.

1993-01-01

Many industrial locations, including the US Department of Energy's, have identified needs for treatment of polychlorinated biphenyl (PCB) wastes and remediation of PCB-contaminated sites. Biodegradation of PCBs is a potentially effective technology for the treatment of PCB-contaminated soils and sludges, including mixed wastes; however, a practical remediation technology has not yet been demonstrated. In laboratory experiments, soil slurry bioreactors inoculated with microorganisms extracted from PCB-contaminated sediments from the Hudson River have been used to obtain anaerobic dechlorination of PCBS. The onset of dechlorination activity can be accelerated by addition of nutritional amendments and inducers. After 15 weeks of incubation with PCB-contaminated soil and nutrient solution, dechlorination has been observed under several working conditions. The best results show that the average chlorine content steadily dropped from 4.3 to 3.5 chlorines per biphenyl over a 15-week period

Time-dependent bacterial community and electrochemical characterizations of cathodic biofilms in the surfactant-amended sediment-based bioelectrochemical reactor with enhanced 2,3,4,5-tetrachlorobiphenyl dechlorination.

Science.gov (United States)

Wan, Hui; Yi, Xiaoyun; Liu, Xiaoping; Feng, Chunhua; Dang, Zhi; Wei, Chaohai

2018-05-01

Applying an electric field to stimulate the microbial reductive dechlorination of polychlorinated biphenyls (PCBs) represents a promising approach for bioremediation of PCB-contaminated sites. This study aimed to demonstrate the biocathodic film-facilitated reduction of PCB 61 in a sediment-based bioelectrochemical reactor (BER) and, more importantly, the characterizations of electrode-microbe interaction from microbial and electrochemical perspectives particularly in a time-dependent manner. The application of a cathodic potential (-0.45 V vs. SHE) significantly improved the rate and extent of PCB 61 dechlorination compared to the open-circuit scenario (without electrical stimulation), and the addition of an external surfactant further increased the dechlorination, with Tween 80 exerting more pronounced effects than rhamnolipid. The bacterial composition of the biofilms and the bioelectrochemical kinetics of the BERs were found to be time-dependent and to vary considerably with the incubation time and slightly with the coexistence of an external surfactant. Excellent correlations were observed between the dechlorination rate and the relative abundance of Dehalogenimonas, Dechloromonas, and Geobacter, the dechlorination rate and the cathodic current density recorded from the chronoamperometry tests, and the dechlorination rate and the charge transfer resistance derived from the electrochemical impedance tests, with respect to the 120 day-operation. After day 120, PCB 61 was resistant to further appreciable reduction, but substantial hydrogen production was detected, and the bacterial community and electrochemical parameters observed on day 180 were not distinctly different from those on day 120. Copyright © 2018 Elsevier Ltd. All rights reserved.

Microbial dechlorination activity during and after chemical oxidant treatment

Energy Technology Data Exchange (ETDEWEB)

Doğan-Subaşı, Eylem [Flemish Institute for Technological Research (VITO), Separation and Conversion Technology, Boeretang 200, 2400 Mol (Belgium); Laboratory of Microbial Ecology and Technology (LabMET), Ghent University, Coupure Links 653, 9000 Gent (Belgium); Bastiaens, Leen, E-mail: leen.bastiaens@vito.be [Flemish Institute for Technological Research (VITO), Separation and Conversion Technology, Boeretang 200, 2400 Mol (Belgium); Boon, Nico [Laboratory of Microbial Ecology and Technology (LabMET), Ghent University, Coupure Links 653, 9000 Gent (Belgium); Dejonghe, Winnie [Flemish Institute for Technological Research (VITO), Separation and Conversion Technology, Boeretang 200, 2400 Mol (Belgium)

2013-11-15

Highlights: • Combined treatment was possible below 0.5 g/L of KMnO{sub 4} and 1 g/L of Na{sub 2}S{sub 2}O{sub 8}. • By-products SO{sub 4}{sup 2−} and MnO{sub 2(s)} had inhibitory effects on dehalogenating bacteria. • Oxidation reduction potential (ORP) was identified as a crucial parameter for recovery of oxidant exposed cells. • Bioaugmentation is a necessity at 0.5 g/L of KMnO{sub 4} and 1 g/L of Na{sub 2}S{sub 2}O{sub 8} and above. -- Abstract: Potassium permanganate (PM) and sodium persulfate (PS) are used in soil remediation, however, their compatibility with a coinciding or subsequent biotreatment is poorly understood. In this study, different concentrations of PM (0.005–2 g/L) and PS (0.01–4.52 g/L) were applied and their effects on the abundance, activity, and reactivation potential of a dechlorinating enrichment culture were investigated. Expression of the tceA, vcrA and 16S rRNA genes of Dehalococcoides spp. were detected at 0.005–0.01 g/L PM and 0.01–0.02 g/L PS. However, with 0.5–2 g/L PM and 1.13–4.52 g/L PS no gene expression was recorded, neither were indicator molecules for total cell activity (Adenosine triphosphate, ATP) detected. Dilution did not promote the reactivation of the microbial cells when the redox potential was above −100 mV. Similarly, inoculated cells did not dechlorinate trichloroethene (TCE) above −100 mV. When the redox potential was decreased to −300 mV and the reactors were bioaugmented for a second time, dechlorination activity recovered, but only in the reactors with 1.13 and 2.26 g/L PS. In conclusion, our results show that chemical oxidants can be combined with a biotreatment at concentrations below 0.5 g/L PM and 1 g/L PS.

Accelerated anaerobic dechlorination of DDT in slurry with Hydragric Acrisols using citric acid and anthraquinone-2,6-disulfonate (AQDS).

Science.gov (United States)

Liu, Cuiying; Xu, Xianghua; Fan, Jianling

2015-12-01

The application of electron donor and electron shuttle substances has a vital influence on electron transfer, thus may affect the reductive dechlorination of 1,1,1-trichoro-2,2-bis(p-chlorophenyl)ethane (DDT) in anaerobic reaction systems. To evaluate the roles of citric acid and anthraquinone-2,6-disulfonate (AQDS) in accelerating the reductive dechlorination of DDT in Hydragric Acrisols that contain abundant iron oxide, a batch anaerobic incubation experiment was conducted in a slurry system with four treatments of (1) control, (2) citric acid, (3) AQDS, and (4) citric acid+AQDS. Results showed that DDT residues decreased by 78.93%-92.11% of the initial quantities after 20days of incubation, and 1,1-dichloro-2,2-bis(4-chlorophenyl)-ethane (DDD) was the dominant metabolite. The application of citric acid accelerated DDT dechlorination slightly in the first 8days, while the methanogenesis rate increased quickly, and then the acceleration effect improved after the 8th day while the methanogenesis rate decreased. The amendment by AQDS decreased the Eh value of the reaction system and accelerated microbial reduction of Fe(III) oxides to generate Fe(II), which was an efficient electron donor, thus enhancing the reductive dechlorination rate of DDT. The addition of citric acid+AQDS was most efficient in stimulating DDT dechlorination, but no significant interaction between citric acid and AQDS on DDT dechlorination was observed. The results will be of great significance for developing an efficient in situ remediation strategy for DDT-contaminated sites. Copyright © 2015. Published by Elsevier B.V.

Complete dechlorination of 2,4-dichlorophenol in aqueous solution on palladium/polymeric pyrrole-cetyl trimethyl ammonium bromide/foam-nickel composite electrode

Energy Technology Data Exchange (ETDEWEB)

Sun, Zhirong, E-mail: zrsun@bjut.edu.cn [College of Environmental and Energy Engineering, Beijing University of Technology, Beijing 100124 (China); Wei, Xuefeng; Han, Yanbo; Tong, Shan [College of Environmental and Energy Engineering, Beijing University of Technology, Beijing 100124 (China); Hu, Xiang, E-mail: huxiang99@163.com [College of Chemical Engineering, Beijing University of Chemical Technology, Beijing 100029 (China)

2013-01-15

Highlights: ► Pd/PPy-CTAB/foam-Ni electrode with high surface area and low Pd content was prepared. ► The composite electrode was applied to dechlorination of 2,4-DCP in aqueous solution. ► Complete dechlorination of 2,4-DCP was achieved with higher current efficiency. ► Removal efficiency kept 100% after 10 times dechlorination on the stable electrode. ► The electrochemically reductive activation energy was 25.8 kJ mol{sup −1} in this system. -- Abstract: The electrochemically reductive dechlorination of 2,4-dichlorophenol (2,4-DCP) in aqueous solution on palladium/polymeric pyrrole-cetyl trimethyl ammonium bromide/foam-nickel electrode (Pd/PPy-CTAB/foam-Ni electrode) was investigated in this paper. Pd/PPy-CTAB/foam-Ni electrode was prepared and characterized by cyclic voltammetry (CV), scanning electron microscope (SEM), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) adsorption and inductively coupled plasma-atomic emission spectroscopy (ICP-AES). The influences of some experimental factors such as the dechlorination current, dechlorination time and the initial pH on the removal efficiency and the current efficiency of 2,4-DCP dechlorination on Pd/PPy-CTAB/foam-Ni electrode were studied. Complete removal of 2,4-DCP was achieved and the current efficiency of 47.4% could be obtained under the conditions of the initial pH of 2.2, the dechlorination current of 5 mA and the dechlorination time of 50 min when the initial 2,4-DCP concentration was 100 mg L{sup −1}. The analysis of high performance liquid chromatography (HPLC) identified that the intermediate products were 2-chlorophenol (2-CP) and 4-chlorophenol (4-CP). The final products were mainly phenol. Its further reduction product cyclohexanone was also detected. The electrocatalytic dechlorination pathways of 2,4-DCP on Pd/PPy-CTAB/foam-Ni electrode were discussed. The stability of the electrode was favorable that it could keep dechlorination efficiency at 100% after having been reused

[Effect of composting organic fertilizer supplies on hexachlorobenzene dechlorination in paddy soils].

Science.gov (United States)

Liu, Cui-Ying; Jiang, Xin

2013-04-01

A rice pot experiment was conducted in two soils, Hydragric Acrisols (Ac) and Gleyi-Stagnic Anthrosols (An). Three treatments including control and additions of 1% or 2% composting organic fertilizer were designed for each soil. The objective of this research was to evaluate the reductive dechlorination of hexachlorobenzene (HCB) as affected by organic fertilizer supplies in planted paddy soils, and to analyze the relationship between methane production and HCB dechlorination. The results showed that the HCB residues were decreased by 28.6%-30.1% of the initial amounts in Ac, and 47.3% -61.0% in An after 18 weeks of experiment. The amount of HCB and its metabolite uptake by rice plants was only a few thousandths of the initial HCB amount in soils. The main product of HCB dechlorination was pentachlorobenzene (PeCB). The rates of HCB dechlorination in An were higher than those in Ac, which was mainly attributed to the higher pH and dissolved organic carbon (DOC) content of An. The applications of both 1% and 2% composting organic fertilizer showed significant inhibition on PeCB production after the 6th and 10th week in Ac and An, respectively. In both tested soils, no significant difference of PeCB production rates was observed between the applications of 1% and 2% composting organic fertilizer. The role of methanogenic bacteria in HCB dechlorination was condition-dependent.

Effects of Aqueous Film-Forming Foams (AFFFs) on Trichloroethene (TCE) Dechlorination by a Dehalococcoides mccartyi-Containing Microbial Community.

Science.gov (United States)

Harding-Marjanovic, Katie C; Yi, Shan; Weathers, Tess S; Sharp, Jonathan O; Sedlak, David L; Alvarez-Cohen, Lisa

2016-04-05

The application of aqueous film-forming foams (AFFFs) to extinguish chlorinated solvent-fueled fires has led to the co-contamination of poly- and perfluoroalkyl substances (PFASs) and trichloroethene (TCE) in groundwater and soil. Although reductive dechlorination of TCE by Dehalococcoides mccartyi is a frequently used remediation strategy, the effects of AFFF and PFASs on TCE dechlorination are not well-understood. Various AFFF formulations, PFASs, and ethylene glycols were amended to the growth medium of a D. mccartyi-containing enrichment culture to determine the impact on dechlorination, fermentation, and methanogenesis. The community was capable of fermenting organics (e.g., diethylene glycol butyl ether) in all AFFF formulations to hydrogen and acetate, but the product concentrations varied significantly according to formulation. TCE was dechlorinated in the presence of an AFFF formulation manufactured by 3M but was not dechlorinated in the presence of formulations from two other manufacturers. Experiments amended with AFFF-derived PFASs and perfluoroalkyl acids (PFAAs) indicated that dechlorination could be inhibited by PFASs but that the inhibition depends on surfactant concentration and structure. This study revealed that the fermentable components of AFFF can stimulate TCE dechlorination, while some of the fluorinated compounds in certain AFFF formulations can inhibit dechlorination.

Photocatalytic reductive dechlorination of 2-chlorodibenzo-p-dioxin by Pd modified g-C3N4 photocatalysts under UV-vis irradiation: Efficacy, kinetics and mechanism.

Science.gov (United States)

Ding, Jiafeng; Long, Gaoyuan; Luo, Yang; Sun, Runze; Chen, Mengxia; Li, Yajun; Zhou, Yanfang; Xu, Xinhua; Zhao, Weirong

2018-05-09

Polychlorinated dibenzo-p-dioxins (PCDDs), as a group of notorious anthropogenic environmental toxicants, are arguably ubiquitous in nature. In this study, we investigated the photocatalytic reductive dechlorination of 2-chlorodibenzo-p-dioxin (2-CDD) over Pd/g-C 3 N 4 catalysts under UV-vis irradiation. The g-C 3 N 4 and a series of Pd/g-C 3 N 4 catalysts were prepared by thermal polymerization and mechanical mixing-illumination method and characterized by XRD, TEM, BET, SEM and UV-vis DRS analyses. Among all the samples, the Pd/g-C 3 N 4 (5 wt%) yielded the optimal dechlorination activity with a total 2-CDD conversion of 54% within 4 h, and 76% of those converted 2-CDD were evolved to dibenzo-p-dioxin (DD). The kinetics of dechlorination could be described as pseudo-first-order decay model (R 2  > 0.84). Corresponding rate constants (k) increased from 0.052 to 0.17 h -1 with Pd contents up to 5 wt% and decreased to 0.13 h -1 with a 10 wt% of Pd. The enhanced activities originated from the surface plasmonic resonance (SPR) effect of Pd nanoparticles and the formation of Schottky barrier between Pd and g-C 3 N 4 , which extend the spectrum responsive range and suppress the charge recombination of g-C 3 N 4 . This is the first report on the photocatalytic reductive removal of PCDDs and may provide a new approach for PCDDs pollution control. Copyright © 2018 Elsevier B.V. All rights reserved.

Factors Influencing TCE Anaerobic Dechlorination Investigated via Simulations of Microcosm Experiments

Science.gov (United States)

Mao, X.; Harkness, M.; Lee, M. D.; Mack, E. E.; Dworatzek, S.; Acheson, C.; McCarty, P.; Barry, D. A.; Gerhard, J. I.

2006-12-01

SABRE (Source Area BioREmediation) is a public-private consortium whose charter is to determine if enhanced anaerobic bioremediation can result in effective and quantifiable treatment of chlorinated solvent DNAPL source areas. The focus of this 4-year, $5.7 million research project is a field site in the United Kingdom containing a TCE DNAPL source area. In preparation, a microcosm study was performed to determine the optimal combination of factors to support reductive dechlorination of TCE in site soil and groundwater. The study consisted of 168 bottles distributed between four laboratories (Dupont, GE, SiREM, and Terra Systems) and tested the impact of six carbon substrates (lactate, acetate, methanol, SRS (soybean oil), hexanol, butyl acetate), bioaugmentation with KB-1 bacterial culture, three TCE levels (100 mg/L, 400 mg/L, and 800 mg/L) and two sulphate levels (200 mg/L, >500 mg/L) on TCE dechlorination. This research presents a numerical model designed to simulate the main processes occurring in the microcosms, including substrate fermentation, sequential dechlorination, toxic inhibition, and the influence of sulphate concentration. In calibrating the model to over 60 of the microcosm experiments, lumped parameters were employed to quantify the effect of key factors on the conversion rate of each chlorinated ethene in the TCE degradation sequence. Results quantify the benefit (i.e., increased stepwise dechlorination rate) due to both bioaugmentation and the presence of higher sulphate concentrations. Competitive inhibition is found to increase in significance as TCE concentrations increase; however, inclusion of Haldane inhibition is not supported. Over a wide range of experimental conditions and dechlorination steps, SRS appears to induce relatively little hydrogen limitation, thereby facilitating relatively quick conversion of TCE to ethene. In general, hydrogen limitation is found to increase with increasing TCE concentration and with bioaugmentation, and

Phylogenetic analysis of TCE-dechlorinating consortia enriched on a variety of electron donors.

Science.gov (United States)

Freeborn, Ryan A; West, Kimberlee A; Bhupathiraju, Vishvesh K; Chauhan, Sadhana; Rahm, Brian G; Richardson, Ruth E; Alvarez-Cohen, Lisa

2005-11-01

Two rapidly fermented electron donors, lactate and methanol, and two slowly fermented electron donors, propionate and butyrate, were selected for enrichment studies to evaluate the characteristics of anaerobic microbial consortia that reductively dechlorinate TCE to ethene. Each electron donor enrichment subculture demonstrated the ability to dechlorinate TCE to ethene through several serial transfers. Microbial community analyses based upon 16S rDNA, including terminal restriction fragment length polymorphism (T-RFLP) and clone library/sequencing, were performed to assess major changes in microbial community structure associated with electron donors capable of stimulating reductive dechlorination. Results demonstrated that five phylogenic subgroups or genera of bacteria were present in all consortia, including Dehalococcoides sp., low G+C Gram-positives (mostly Clostridium and Eubacterium sp.), Bacteroides sp., Citrobacter sp., and delta Proteobacteria (mostly Desulfovibrio sp.). Phylogenetic association indicates that only minor shifts in the microbial community structure occurred between the four alternate electron donor enrichments and the parent consortium. Inconsistent detection of Dehalococcoides spp. in clone libraries and T-RFLP of enrichment subcultures was resolved using quantitative polymerase chain reaction (Q-PCR). Q-PCR with primers specific to Dehalococcoides 16S rDNA resulted in positive detection of this species in all enrichments. Our results suggest that TCE-dechlorinating consortia can be stably maintained on a variety of electron donors and that quantities of Dehalococcoides cells detected with Dehalococcoides specific 16S rDNA primer/probe sets do not necessarily correlate well with solvent degradation rates.

Dechlorination of TCE with palladized iron

Science.gov (United States)

Fernando, Quintus; Muftikian, Rosy; Korte, Nic

1997-01-01

The present invention relates to various methods, such as an above-ground method and an in-ground method, of using a palladized iron bimetallic system for the dechlorination of chlorinated organic compounds from effluents containing the same. The use of palladized iron bimetallic system results in the dechlorination of the chlorinated organic compound into environmentally safe reaction products. The present invention also provides kits, devices, and other instruments that use the above-mentioned palladized iron bimetallic system for the dechlorination of chlorinated organic compounds.

Influence of physical factors and geochemical conditions on groundwater acidification during enhanced reductive dechlorination

Science.gov (United States)

Brovelli, A.; Barry, D. A.; Robinson, C.; Gerhard, J.

2010-12-01

Enhanced reductive dehalogenation is an attractive in situ treatment technology for chlorinated contaminants. The process includes two acid-forming microbial reactions: fermentation of an organic substrate resulting in short-chain fatty acids, and dehalogenation resulting in hydrochloric acid. The accumulation of acids and the resulting drop of groundwater pH are controlled by the mass and distribution of chlorinated solvents in the source zone, type of electron donor, availability of alternative terminal electron acceptors and presence of soil mineral phases able to buffer the pH (such as carbonates). Groundwater acidification may reduce or halt microbial activity, and thus dehalogenation, significantly increasing the time and costs required to remediate the aquifer. For this reason, research in this area is gaining increasing attention. In previous work (Robinson et al., 2009 407:4560, Sci. Tot. Environ, Robinson and Barry, 2009 24:1332, Environ. Model. & Software, Brovelli et al., 2010, submitted), a detailed geochemical and groundwater flow model able to predict the pH change occurring during reductive dehalogenation was developed. The model accounts for the main processes influencing groundwater pH, including the groundwater composition, the electron donor used and soil mineral phase interactions. In this study, the model was applied to investigate how spatial variability occurring at the field scale affects groundwater pH and dechlorination rates. Numerical simulations were conducted to examine the influence of heterogeneous hydraulic conductivity on the distribution of the injected, fermentable substrate and on the accumulation/dilution of the acidic products of reductive dehalogenation. The influence of the geometry of the DNAPL source zone was studied, as well as the spatial distribution of soil minerals. The results of this study showed that the heterogeneous distribution of the soil properties have a potentially large effect on the remediation efficiency

Comparison of dechlorination rates for field DNAPL vs synthetic samples: effect of sample matrix

Science.gov (United States)

O'Carroll, D. M.; Sakulchaicharoen, N.; Herrera, J. E.

2015-12-01

Nanometals have received significant attention in recent years due to their ability to rapidly destroy numerous priority source zone contaminants in controlled laboratory studies. This has led to great optimism surrounding nanometal particle injection for insitu remediation. Reported dechlorination rates vary widely among different investigators. These differences have been ascribed to differences in the iron types (granular, micro, or nano-sized iron), matrix solution chemistry and the morphology of the nZVI surface. Among these, the effects of solution chemistry on rates of reductive dechlorination of various chlorinated compounds have been investigated in several short-term laboratory studies. Variables investigated include the effect of anions or groundwater solutes such as SO4-2, Cl-, NO3-, pH, natural organic matters (NOM), surfactant, and humic acid on dechlorination reaction of various chlorinated compounds such as TCE, carbon tetrachloride (CT), and chloroform (CF). These studies have normally centered on the assessment of nZVI reactivity toward dechlorination of an isolated individual contaminant spiked into a ground water sample under ideal conditions, with limited work conducted using real field samples. In this work, the DNAPL used for the dechlorination study was obtained from a contaminatied site. This approach was selected to adequately simulate a condition where the nZVI suspension was in direct contact with DNAPL and to isolate the dechlorination activity shown by the nZVI from the groundwater matrix effects. An ideal system "synthetic DNAPL" composed of a mixture of chlorinated compounds mimicking the composition of the actual DNAPL was also dechlorinated to evaluate the DNAPL "matrix effect" on NZVI dechlorination activity. This approach allowed us to evaluate the effect of the presence of different types of organic compounds (volatile fatty acids and humic acids) found in the actual DNAPL on nZVI dechlorination activity. This presentation will

Stable carbon isotope fractionation of chlorinated ethenes by a microbial consortium containing multiple dechlorinating genes.

Science.gov (United States)

Liu, Na; Ding, Longzhen; Li, Haijun; Zhang, Pengpeng; Zheng, Jixing; Weng, Chih-Huang

2018-08-01

The study aimed to determine the possible contribution of specific growth conditions and community structures to variable carbon enrichment factors (Ɛ- carbon ) values for the degradation of chlorinated ethenes (CEs) by a bacterial consortium with multiple dechlorinating genes. Ɛ- carbon values for trichloroethylene, cis-1,2-dichloroethylene, and vinyl chloride were -7.24% ± 0.59%, -14.6% ± 1.71%, and -21.1% ± 1.14%, respectively, during their degradation by a microbial consortium containing multiple dechlorinating genes including tceA and vcrA. The Ɛ- carbon values of all CEs were not greatly affected by changes in growth conditions and community structures, which directly or indirectly affected reductive dechlorination of CEs by this consortium. Stability analysis provided evidence that the presence of multiple dechlorinating genes within a microbial consortium had little effect on carbon isotope fractionation, as long as the genes have definite, non-overlapping functions. Copyright © 2018 Elsevier Ltd. All rights reserved.

16S rRNA gene-based detection of tetrachloroethene-dechlorinating Desulfuromonas and Dehalococcoides species

Energy Technology Data Exchange (ETDEWEB)

Loeffler, F.E.; Sun, Q.; Li, J.; Tiedje, J.M.

2000-03-01

Members of the genera Desulfuromonas and Dehalococcoides reductively dechlorinate tetrachloroethene (PCE) and trichloroethene. Two primer pairs specific to hypervariable regions of the 16S rRNA genes of the Dehalococcoides group (comprising Dehalococcoides ethenogenes and Dehalococcoides sp. strain FL2) and the acetate-oxidizing, PCE-dechlorinating Desulfuromonas group (comprising Desulfuromonas sp. strain BB1 and Desulfuromonas chloroethenica) were designed. The detection threshold of a nested PCR approach using universal bacterial primers followed by a second PCR with the Desulfuromonas dechlorinator-targeted primer pair was 1 x 10{sup 3} BB1 cells added per gram (wet weight) of sandy aquifer material. Total community DNA isolated from sediments of three Michigan rivers and six different chloroethene-contaminated aquifer samples was used as template in nested PCR. All river sediment samples yielded positive signals with the BB1- and the Dehalococcoides-targeted primers. One chloroethene-contaminated aquifer tested positive with the Dehalococcoides-targeted primers, and another contaminated aquifer tested positive with the Desulfuromonas dechlorinator-targeted primer pair. Restriction fragment analysis of the amplicons could discriminate strain BB1 from other known Desulfuromonas species. Microcosm studies confirmed the presence of PCE-dechlorinating, acetate-oxidizing Desulfuromonas and hydrogenotrophic Dehalococcoides species in samples yielding positive PCR signals with the specific primers.

Effect of TCE concentration and dissolved groundwater solutes on NZVI-promoted TCE dechlorination and H2 evolution.

Science.gov (United States)

Liu, Yueqiang; Phenrat, Tanapon; Lowry, Gregory V

2007-11-15

Nanoscale zero-valent iron (NZVI) is used to remediate contaminated groundwater plumes and contaminant source zones. The target contaminant concentration and groundwater solutes (NO3-, Cl-, HCO3-, SO4(2-), and HPO4(2-)) should affect the NZVI longevity and reactivity with target contaminants, but these effects are not well understood. This study evaluates the effect of trichloroethylene (TCE) concentration and common dissolved groundwater solutes on the rates of NZVI-promoted TCE dechlorination and H2 evolution in batch reactors. Both model systems and real groundwater are evaluated. The TCE reaction rate constant was unaffected by TCE concentration for [TCE] TCE concentration up to water saturation (8.4 mM). For [TCE] > or = 0.46 mM, acetylene formation increased, and the total amount of H2 evolved at the end of the particle reactive lifetime decreased with increasing [TCE], indicating a higher Fe0 utilization efficiency for TCE dechlorination. Common groundwater anions (5mN) had a minor effect on H2 evolution but inhibited TCE reduction up to 7-fold in increasing order of Cl- TCE reduction but increased acetylene production and decreased H2 evolution. NO3- present at > 3 mM slowed TCE dechlorination due to surface passivation. NO3- present at 5 mM stopped TCE dechlorination and H2 evolution after 3 days. Dissolved solutes accounted for the observed decrease of NZVI reactivity for TCE dechlorination in natural groundwater when the total organic content was small (< 1 mg/L).

Dechlorination of hexachlorobenzene using ultrafine Ca-Fe composite oxides

International Nuclear Information System (INIS)

Ma Xiaodong; Zheng Minghui; Liu Wenbin; Qian Yong; Zhang Bing; Liu Wenxia

2005-01-01

Ca-Fe composite oxides with different Ca/Fe atomic ratios were synthesized by co-precipitation method and characterized by X-ray diffraction (XRD), scanning electron microscopy with elemental X-ray analysis (SEM-EDX) and inductively coupled plasma optical emission spectrometer (ICP-OES). Their dechlorination activities were evaluated using hexachlorobenzene (HCB) as a model compound. The results indicate that the dechlorination activity is related to the composition of metal oxides. Different compositions lead to the formation of different phases of Ca-Fe composite oxides. When Ca/Fe atomic ratio was 3.4, the dechlorination activity reached 97%, which was the highest in the dechlorination of HCB at 300 deg. C for 0.5 h. This may be related to the formation of Ca 2 Fe 2 O 5 phase and small agglomerate size of oxide crystal of about 1 μm. The effect of reaction time on HCB dechlorination and the pathway of dechlorination were investigated using the Ca-Fe composite oxide with the highest activity. It was found that hydrodechlorination took place in the destruction of HCB, the dechlorination efficiency is almost 100% after 2 h reaction. After reaction, quantitative measurement of chloride ion and qualitative analysis of CaCO 3 indicate besides hydrodechlorination, other degradation routes may be present. The mechanism of synergic dechlorination using Ca-Fe composite oxides was discussed

Modeling 3D-CSIA data: Carbon, chlorine, and hydrogen isotope fractionation during reductive dechlorination of TCE to ethene.

Science.gov (United States)

Van Breukelen, Boris M; Thouement, Héloïse A A; Stack, Philip E; Vanderford, Mindy; Philp, Paul; Kuder, Tomasz

2017-09-01

Reactive transport modeling of multi-element, compound-specific isotope analysis (CSIA) data has great potential to quantify sequential microbial reductive dechlorination (SRD) and alternative pathways such as oxidation, in support of remediation of chlorinated solvents in groundwater. As a key step towards this goal, a model was developed that simulates simultaneous carbon, chlorine, and hydrogen isotope fractionation during SRD of trichloroethene, via cis-1,2-dichloroethene (and trans-DCE as minor pathway), and vinyl chloride to ethene, following Monod kinetics. A simple correction term for individual isotope/isotopologue rates avoided multi-element isotopologue modeling. The model was successfully validated with data from a mixed culture Dehalococcoides microcosm. Simulation of Cl-CSIA required incorporation of secondary kinetic isotope effects (SKIEs). Assuming a limited degree of intramolecular heterogeneity of δ 37 Cl in TCE decreased the magnitudes of SKIEs required at the non-reacting Cl positions, without compromising the goodness of model fit, whereas a good fit of a model involving intramolecular CCl bond competition required an unlikely degree of intramolecular heterogeneity. Simulation of H-CSIA required SKIEs in H atoms originally present in the reacting compounds, especially for TCE, together with imprints of strongly depleted δ 2 H during protonation in the products. Scenario modeling illustrates the potential of H-CSIA for source apportionment. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

Reductive dehalogenation activity of indigenous microorganism in sediments of the Hackensack River, New Jersey.

Science.gov (United States)

Sohn, Seo Yean; Häggblom, Max M

2016-07-01

Organohalogen pollutants are of concern in many river and estuarine environments, such as the New York-New Jersey Harbor estuary and its tributaries. The Hackensack River is contaminated with various metals, hydrocarbons and halogenated organics, including polychlorinated biphenyls (PCBs) and polychlorinated dibenzo-p-dioxins. In order to examine the potential for microbial reductive dechlorination by indigenous microorganisms, sediment samples were collected from five different estuarine locations along the Hackensack River. Hexachlorobenzene (HCB), hexabromobenzene (HBB), and pentachloroaniline (PCA) were selected as model organohalogen pollutants to assess anaerobic dehalogenating potential. Dechlorinating activity of HCB and PCA was observed in sediment microcosms for all sampling sites. HCB was dechlorinated via pentachlorobenzene (PeCB) and trichlorobenzene (TriCB) to dichlorobenzene (DCB). PCA was dechlorinated via tetrachloroaniline (TeCA), trichloroanilines (TriCA), and dichloroanilines (DCA) to monochloroaniline (MCA). No HBB debromination was observed over 12 months of incubation. However, with HCB as a co-substrate slow HBB debromination was observed with production of tetrabromobenzene (TeBB) and tribromobenzene (TriBB). Chloroflexi specific 16S rRNA gene PCR-DGGE followed by sequence analysis detected Dehalococcoides species in sediments of the freshwater location, but not in the estuarine site. Analysis targeting 12 putative reductive dehalogenase (rdh) genes showed that these were enriched concomitant with HCB or PCA dechlorination in freshwater sediment microcosms. Copyright © 2016 Elsevier Ltd. All rights reserved.

Efficient dechlorination of carbon tetrachloride by hydrophobic green rust intercalated with dodecanoate anions

DEFF Research Database (Denmark)

Ayala Luis, Karina Barbara; Ginette Anneliese Cooper, Nicola; Bender Koch, Christian

2012-01-01

similar to those found in heavily contaminated groundwater close to polluted industrial sites (14 988 mu M) was reduced mainly to the fully dechlorinated products carbon monoxide (CO, yields >54 and formic acid (HCOOH, yields >6. Minor formation of chloroform (CF), the only chlorinated degradation product......The reductive dechlorination of carbon tetrachloride (CT) by Fe-II-Fe-III hydroxide (green rust) intercalated with dodecanoate, (Fe4Fe2III)-Fe-II (OH)(12)(C12H23O2)(2)center dot gamma H2O (designated GR(C12)), at pH similar to 8 and at room temperature was investigated. CT at concentration levels...

Humic acid and metal ions accelerating the dechlorination of 4-chlorobiphenyl by nanoscale zero-valent iron

Institute of Scientific and Technical Information of China (English)

Yu Wang; Dongmei Zhou; Yujun Wang; Xiangdong Zhu; Shengyang Jin

2011-01-01

Transformation of polychlorinated biphenyls (PCBs) by zero-valent iron represents one of the latest innovative technologies for environmental remediation.The dechlorination of 4-chlorobiphenyl (4-C1BP) by nanoscale zero-valent iron (NZVI) in the presence of humic acid or metal ions was investigated.The results showed that the de chlorination of 4-CIBP by NZVI increased with decreased solution pH.When the initial pH value was 4.0,5.5,6.8,and 9.0,the de chlorination efliciencies of 4-C1BP after 48 hr were 53.8%,47.8%,35.7%,and 35.6%,respectively.The presence of humic acid inhibited the reduction of 4-ClBP in the first 4 hr,and then significantly accelerated the dechlorination by reaching 86.3% in 48 hr.Divalent metal ions,Co2+,Cu2+,and Ni2+,were reduced and formed bimetals with NZVI,thereby enhanced the dechlorination of 4-CIBP.The dechlorination percentages of 4-CIBP in the presence of 0.1 mmol/L Co2+,Cu2+ and Ni2+ were 66.1%,66.0% and 64.6% in 48 hr,and then increased to 67.9%,71.3% and 73.5%,after 96 hr respectively.The dechlorination kinetics of 4-CIBP by the NZVI in all cases followed pseudo-first order model.The results provide a basis for better understanding of the dechlorination mechanisms of PCBs in real environment.

Dechlorination of chlorinated phenols by subnanoscale Pd 0 /Fe 0 intercalated in smectite: pathway, reactivity, and selectivity.

Science.gov (United States)

Jia, Hanzhong; Wang, Chuanyi

2015-12-30

Smectite clay was employed as templated matrix to prepare subnanoscale Pd(0)/Fe(0) particles, and their components as well as intercalated architectures were well characterized by X-ray energy dispersive spectroscopy (X-EDS) and X-ray diffraction (XRD). Furthermore, as-prepared Pd(0)/Fe(0) subnanoscale nanoparticles were evaluated for their dechlorination effect using chlorinated phenols as model molecules. As a result, pentachlorophenol (PCP) is selectively transformed to phenol in a stepwise dechlorination pathway within 6h, and the dechlorination rate constants show linearly relationship with contents of Pd as its loadings <0.065%. Comparing with PCP, other chlorinated phenols display similar degradation pattern but within much shorter time frame. The dechlorination rate of chlorinated phenols increases with decreasing in number of -Cl attached to aromatic ring, which can be predicted by the total charge of the aromatic ring, exhibiting an inversely linear relationship with the dechlorination rates. While the selectivity of dechlorination depends on the charges associated with the individual aromatic carbon. Chloro-functional groups at the ortho-position are easier to be dechlorinated than that at meta- and para- positions yielding primarily 3,4,5-TCP as intermediate from PCP, further to phenol. The effective dechlorination warrants their potential utilizations in development of in-situ remediation technologies for organic pollutants in contaminated water. Copyright © 2015 Elsevier B.V. All rights reserved.

Simulation Of Enhanced Reductive Dechlorination For Remediation Of Tce In A Fractured Clay System: A New Model Approach And Application To Field Site

DEFF Research Database (Denmark)

Manoli, Gabriele; Chambon, Julie Claire Claudia; Christiansen, Camilla Maymann

2010-01-01

with interspersed sand lenses and stringers. The transport model couples diffusion dominated transport in the clay matrix, with advective‐dispersive transport in the fractures and higher permeability sand lenses. The reactive model calculates sequential reductive dechlorination of TCE (trichloroethylene) to its...... a contamination of trichloroethylene located in a fractured clay till. The site is simulated using the model developed. Fracture geometry, site parameters and degradation rates are based on observations from the site and lab studies. The risk for drinking water is assessed and cleanup times are simulated using...

Dechlorination of PCB by radiation

International Nuclear Information System (INIS)

Shinozaki, Yoshiharu

1978-01-01

On the PCB poisoning accident in Japan occurred in 1968, Tokyo Metropolitan Isotope Research Center started to investigate the decomposition of PCB (polychlorinated biphenyl) on the request of Metropolitan government. The research center has found that if PCB is dissolved or extracted in alkaline 2-propanol solution and then irradiated with γ-ray, PCB is dechlorinated in chain-reactive manner, and biphenyl and salts (KCl or NaCl) are formed. Afterwards, it has been found that photolysis has also similar effect on PCB. Then, the basic design of a disposal pilot plant using ultraviolet ray and its economic evaluation have been performed, which is composed of photolysis reaction process, refining process and waste disposal process. However, its disposal cost only has reached the value three times as high as that of incineration process. If this is conducted by radiolysis, its disposal cost can be reduced to about 1/12 of that of ultraviolet ray system when an electron accelerator is employed. Cs-137 source gives better results than Co-60. Dechlorination process of PCB has been thus established. Further reduction of total cost will be the keypoint of radiolysis system to be adopted. If the application of electron accelerators to sludge treatment in the future, the effective use of recovered products, and the possibility of using Cs-137 large sources are considered, it is expected that the disposal cost of radiolysis process system becomes comparable with the incineration process. (Wakatsuki, Y.)

Chasing halorespirers: High throughput multiplex detection of dechlorinating bacteria using Pri-Lock probes

Energy Technology Data Exchange (ETDEWEB)

Maphosa, F.; Doorn, R. van; Vos, W. de; Cor Schoen, C.; Smidt, H.

2009-07-01

Bioremediation management strategies for sites contaminated with chlorinated compounds require monitoring technologies that enable simultaneous detection and quantification of a wide range of microorganisms involved in reductive dechlorination. Many multiplex, quantitative detection methods available suffer from compromises between the level of multiplexing, throughput and accuracy of quantification. (Author)

Dechlorination of chlorinated phenols by subnanoscale Pd{sup 0}/Fe{sup 0} intercalated in smectite: pathway, reactivity, and selectivity

Energy Technology Data Exchange (ETDEWEB)

Jia, Hanzhong; Wang, Chuanyi, E-mail: jiahz0143@aliyun.com

2015-12-30

Graphical abstract: Dechlorination process of pentachlorophenol (PCP) by smectite-templated Pd{sup 0}/Fe{sup 0}. - Highlights: • Smectite was employed as templated matrix to prepare subnanoscale Pd{sup 0}/Fe{sup 0} particles. • Dechlorination rate depends linearly on the Pd content as its loadings <0.065 wt.%. • Dechlorination rates correlate with the total charge of C on chlorinated phenols. • The dechlorination selectivity relies on charges of individual C in aromatic ring. - Abstract: Smectite clay was employed as templated matrix to prepare subnanoscale Pd{sup 0}/Fe{sup 0} particles, and their components as well as intercalated architectures were well characterized by X-ray energy dispersive spectroscopy (X-EDS) and X-ray diffraction (XRD). Furthermore, as-prepared Pd{sup 0}/Fe{sup 0} subnanoscale nanoparticles were evaluated for their dechlorination effect using chlorinated phenols as model molecules. As a result, pentachlorophenol (PCP) is selectively transformed to phenol in a stepwise dechlorination pathway within 6 h, and the dechlorination rate constants show linearly relationship with contents of Pd as its loadings <0.065%. Comparing with PCP, other chlorinated phenols display similar degradation pattern but within much shorter time frame. The dechlorination rate of chlorinated phenols increases with decreasing in number of -Cl attached to aromatic ring, which can be predicted by the total charge of the aromatic ring, exhibiting an inversely linear relationship with the dechlorination rates. While the selectivity of dechlorination depends on the charges associated with the individual aromatic carbon. Chloro-functional groups at the ortho-position are easier to be dechlorinated than that at meta- and para- positions yielding primarily 3,4,5-TCP as intermediate from PCP, further to phenol. The effective dechlorination warrants their potential utilizations in development of in-situ remediation technologies for organic pollutants in contaminated

Dechlorination of Hexachlorobenzene in Contaminated Soils Using a Nanometallic Al/CaO Dispersion Mixture: Optimization through Response Surface Methodology

Science.gov (United States)

Jiang, Yuhui; Shang, Yixuan; Yu, Shuyao; Liu, Jianguo

2018-01-01

Hexachlorobenzene (HCB) contamination of soils remains a significant environmental challenge all over the world. Reductive stabilization is a developing technology that can decompose the HCB with a dechlorination process. A nanometallic Al/CaO (n-Al/CaO) dispersion mixture was developed utilizing ball-milling technology in this study. The dechlorination efficiency of HCB in contaminated soils by the n-Al/CaO grinding treatment was evaluated. Response surface methodology (RSM) was employed to investigate the effects of three variables (soil moisture content, n-Al/CaO dosage and grinding time) and the interactions between these variables under the Box-Behnken Design (BBD). A high regression coefficient value (R2 = 0.9807) and low p value (soil moisture content, n-Al/CaO dosage, and grinding time were found to be 7% (m/m), 17.7% (m/m), and 24 h, respectively, in the experimental ranges and levels. Under optimal conditions, the dechlorination efficiency was 80%. The intermediate product analysis indicated that dechlorination was the process by stepwise loss of chloride atoms. The main pathway observed within 24 h was HCB → pentachlorobenzene (PeCB) → 1,2,3,4-tetrachlorobenzene (TeCB) and 1,2,4,5-TeCB. The results indicated that the moderate soil moisture content was crucial for the hydrodechlorination of HCB. A probable mechanism was proposed wherein water acted like a hydrogen donor and promoted the hydrodechlorination process. The potential application of n-Al/CaO is an environmentally-friendly and cost-effective option for decontamination of HCB-contaminated soils. PMID:29702570

Pentachlorophenol dechlorination with zero valent iron: a Raman and GCMS study of the complex role of surficial iron oxides.

Science.gov (United States)

Gunawardana, Buddhika; Swedlund, Peter J; Singhal, Naresh; Nieuwoudt, Michel K

2018-04-20

The dechlorination of chlorinated organic pollutants by zero valent iron (ZVI) is an important water treatment process with a complex dependence on many variables. This complexity means that there are reported inconsistencies in terms of dechlorination with ZVI and the effect of ZVI acid treatment, which are significant and are as yet unexplained. This study aims to decipher some of this complexity by combining Raman spectroscopy with gas chromatography-mass spectrometry (GC-MS) to investigate the influence of the mineralogy of the iron oxide phases on the surface of ZVI on the reductive dechlorination of pentachlorophenol (PCP). Two electrolytic iron samples (ZVI-T and ZVI-H) were found to have quite different PCP dechlorination reactivity in batch reactors under anoxic conditions. Raman analysis of the "as-received" ZVI-T indicated the iron was mainly covered with the ferrous oxide (FeO) wustite, which is non-conducting and led to a low rate of PCP dechlorination. In contrast, the dominant oxide on the "as-received" ZVI-H was magnetite which is conducting and, compared to ZVI-T, the ZVI-H rate of PCP dechlorination was four times faster. Treating the ZVI-H sample with 1 N H 2 SO 4 made small change to the composition of the oxide layers and also minute change to the rate of PCP dechlorination. However, treating the ZVI-T sample with H 2 SO 4 led to the loss of wustite so that magnetite became the dominant oxide and the rate of PCP dechlorination increased to that of the ZVI-H material. In conclusion, this study clearly shows that iron oxide mineralogy can be a contributing factor to apparent inconsistencies in the literature related to ZVI performance towards dechlorination and the effect of acid treatment on ZVI reactivity.

Validation of an Integrative Methodology to Assess and Monitor Reductive Dechlorination of Chlorinated Ethenes in Contaminated Aquifers

Czech Academy of Sciences Publication Activity Database

Tarnawski, S.E.; Rossi, P.; Brennerová, Mária; Stavělová, M.; Holliger, Ch.

2016-01-01

Roč. 4, February (2016), s. 7 E-ISSN 2296-665X R&D Projects: GA TA ČR TA02020534 Institutional support: RVO:61388971 Keywords : dechlorination * integrative methodology * chlorinated ethenes Subject RIV: EE - Microbiology, Virology

Identification of abiotic and biotic reductive dechlorination in a chlorinated ethene plume after thermal source remediation by means of isotopic and molecular biology tools

DEFF Research Database (Denmark)

Badin, Alice; Broholm, Mette Martina; Jacobsen, Carsten S.

2016-01-01

-Cl isotope analysis together with the almost absent VC 13C depletion in comparison to cDCE 13C depletion suggested that cDCE was subject to abiotic degradation due to the presence of pyrite, possible surface-bound iron (II) or reduced iron sulphides in the downgradient part of the plume. This interpretation...... reduced redox conditions which favor active reductive dechlorination and/or may lead to a series of redox reactions which may consecutively trigger biotically induced abiotic degradation. Finally, this study illustrates the valuable complementary application of compound-specific isotopic analysis combined...

Polyphasic characterization of a PCP-to-phenol dechlorinating microbial community enriched from paddy soil

Energy Technology Data Exchange (ETDEWEB)

Yoshida, Naoko [EcoTopia Science Institute, Nagoya University Nagoya 464-8603 (Japan)]. E-mail: ysd75@esi.nagoya-u.ac.jp; Yoshida, Yukina [Graduate School of Engineering, Nagoya University, Nagoya 464-8603 (Japan); Handa, Yuko [Graduate School of Engineering, Nagoya University, Nagoya 464-8603 (Japan); Kim, Hyo-Keun [Korea Ginseng and Tobacco Research Institute, Taejon 305-345 (Korea, Republic of); Ichihara, Shigeyuki [Faculty of Agriculture, Meijo University, Nagoya 468-8502 (Japan); Katayama, Arata [EcoTopia Science Institute, Nagoya University Nagoya 464-8603 (Japan); Graduate School of Engineering, Nagoya University, Nagoya 464-8603 (Japan)

2007-08-01

Dechlorination of PCP has been observed previously under anaerobic condition in paddy soil. However, there is poor information about the dechlorination pathway of PCP and the microbial community associated with the PCP dechlorination in paddy soil. In this study, an anaerobic microbial community dechlorinating PCP was enriched by serial transfers from a paddy soil using a medium containing PCP, lactate and the steam-sterilized paddy soil. The enriched microbial community dechlorinated PCP completely to phenol under the anaerobic condition by a dechlorinating pathway as follows; PCP {sup {yields}} 2,3,4,5-tetrachlorophenol {sup {yields}} 3,4,5-trichlorophenol {sup {yields}} 3,5-dichlorophenol {sup {yields}} 3-chlorophenol {sup {yields}} phenol. Intermediate products such as 3-chlorophenol were not accumulated, which were immediately dechlorinated to phenol. The enriched microbial community was characterized physiologically by testing the effects of electron donors and electron acceptors on the dechlorinating activity. The dechlorinating activity was promoted with lactate, pyruvate, and hydrogen as electron donors but not with acetate. Electron acceptors, nitrate and sulphate, inhibited the dechlorinating activity competitively but not iron (III). The microbial group associated with the anaerobic dechlorination was characterized by the effect of specific inhibitors on the PCP dechlorination. Effects of specific metabolic inhibitors and antibiotics indicated the involvement of Gram-positive spore-forming bacteria with the PCP dechlorinating activity, which was represented as bacteria of phylum Firmicutes. The structure of the microbial community was characterized by fluorescence in situ hybridization, quinone profiling, and PCR-DGGE (denaturing gel gradient electrophoresis). The combined results indicated the predominance of Clostridium species of phylum Firmicutes in the microbial community. Desulfitobacterium spp. known as anaerobic Gram-positive spore

Polyphasic characterization of a PCP-to-phenol dechlorinating microbial community enriched from paddy soil

International Nuclear Information System (INIS)

Yoshida, Naoko; Yoshida, Yukina; Handa, Yuko; Kim, Hyo-Keun; Ichihara, Shigeyuki; Katayama, Arata

2007-01-01

Dechlorination of PCP has been observed previously under anaerobic condition in paddy soil. However, there is poor information about the dechlorination pathway of PCP and the microbial community associated with the PCP dechlorination in paddy soil. In this study, an anaerobic microbial community dechlorinating PCP was enriched by serial transfers from a paddy soil using a medium containing PCP, lactate and the steam-sterilized paddy soil. The enriched microbial community dechlorinated PCP completely to phenol under the anaerobic condition by a dechlorinating pathway as follows; PCP → 2,3,4,5-tetrachlorophenol → 3,4,5-trichlorophenol → 3,5-dichlorophenol → 3-chlorophenol → phenol. Intermediate products such as 3-chlorophenol were not accumulated, which were immediately dechlorinated to phenol. The enriched microbial community was characterized physiologically by testing the effects of electron donors and electron acceptors on the dechlorinating activity. The dechlorinating activity was promoted with lactate, pyruvate, and hydrogen as electron donors but not with acetate. Electron acceptors, nitrate and sulphate, inhibited the dechlorinating activity competitively but not iron (III). The microbial group associated with the anaerobic dechlorination was characterized by the effect of specific inhibitors on the PCP dechlorination. Effects of specific metabolic inhibitors and antibiotics indicated the involvement of Gram-positive spore-forming bacteria with the PCP dechlorinating activity, which was represented as bacteria of phylum Firmicutes. The structure of the microbial community was characterized by fluorescence in situ hybridization, quinone profiling, and PCR-DGGE (denaturing gel gradient electrophoresis). The combined results indicated the predominance of Clostridium species of phylum Firmicutes in the microbial community. Desulfitobacterium spp. known as anaerobic Gram-positive spore-forming bacteria dechlorinating PCP were not detected by PCR using a

ELECTROCHEMICAL DECHLORINATION OF TRICHLOROETHYLENE USING GRANULAR-GRAPHITE ELECTRODES

Science.gov (United States)

Electrochemical dechlorination of TCE was conducted in a glass column using granular graphite as electrodes. A constant voltage of 15 volt was applied resulting in 60-62 mA of current. Approximately 4-6% of the TCE was dechlorinated. Among the reduced TCE, more than 95% was compl...

MODELING THE ELECTROLYTIC DECHLORINATION OF TRICHLOROETHYLENE IN A GRANULAR GRAPHITE-PACKED REACTOR

Science.gov (United States)

A comprehensive reactor model was developed for the electrolytic dechlorination of trichloroethylene (TCE) at a granular-graphite cathode. The reactor model describes the dynamic processes of TCE dechlorination and adsorption, and the formation and dechlorination of all the major...

Complete biological reductive transformation of tetrachloroethene to ethane.

Science.gov (United States)

de Bruin, W P; Kotterman, M J; Posthumus, M A; Schraa, G; Zehnder, A J

1992-01-01

Reductive dechlorination of tetrachloroethene (perchloroethylene; PCE) was observed at 20 degrees C in a fixed-bed column, filled with a mixture (3:1) of anaerobic sediment from the Rhine river and anaerobic granular sludge. In the presence of lactate (1 mM) as an electron donor, 9 microM PCE was dechlorinated to ethene. Ethene was further reduced to ethane. Mass balances demonstrated an almost complete conversion (95 to 98%), with no chlorinated compounds remaining (less than 0.5 micrograms/liter). When the temperature was lowered to 10 degrees C, an adaptation of 2 weeks was necessary to obtain the same performance as at 20 degrees C. Dechlorination by column material to ethene, followed by a slow ethane production, could also be achieved in batch cultures. Ethane was not formed in the presence of bromoethanesulfonic acid, an inhibitor of methanogenesis. The high dechlorination rate (3.7 mumol.l-1.h-1), even at low temperatures and considerable PCE concentrations, together with the absence of chlorinated end products, makes reductive dechlorination an attractive method for removal of PCE in bioremediation processes. PMID:1622277

Dechlorination of Hexachlorobenzene in Contaminated Soils Using a Nanometallic Al/CaO Dispersion Mixture: Optimization through Response Surface Methodology

Directory of Open Access Journals (Sweden)

Yuhui Jiang

2018-04-01

Full Text Available Hexachlorobenzene (HCB contamination of soils remains a significant environmental challenge all over the world. Reductive stabilization is a developing technology that can decompose the HCB with a dechlorination process. A nanometallic Al/CaO (n-Al/CaO dispersion mixture was developed utilizing ball-milling technology in this study. The dechlorination efficiency of HCB in contaminated soils by the n-Al/CaO grinding treatment was evaluated. Response surface methodology (RSM was employed to investigate the effects of three variables (soil moisture content, n-Al/CaO dosage and grinding time and the interactions between these variables under the Box-Behnken Design (BBD. A high regression coefficient value (R2 = 0.9807 and low p value (<0.0001 of the quadratic model indicated that the model was accurate in predicting the experimental results. The optimal soil moisture content, n-Al/CaO dosage, and grinding time were found to be 7% (m/m, 17.7% (m/m, and 24 h, respectively, in the experimental ranges and levels. Under optimal conditions, the dechlorination efficiency was 80%. The intermediate product analysis indicated that dechlorination was the process by stepwise loss of chloride atoms. The main pathway observed within 24 h was HCB → pentachlorobenzene (PeCB → 1,2,3,4-tetrachlorobenzene (TeCB and 1,2,4,5-TeCB. The results indicated that the moderate soil moisture content was crucial for the hydrodechlorination of HCB. A probable mechanism was proposed wherein water acted like a hydrogen donor and promoted the hydrodechlorination process. The potential application of n-Al/CaO is an environmentally-friendly and cost-effective option for decontamination of HCB-contaminated soils.

The kinetics of the radiation-induced chain dechlorination of hexachloroethane in alcohols

International Nuclear Information System (INIS)

Sawai, Takeshi; Ohara, Naoki; Shimokawa, Toshinari

1978-01-01

The kinetics of the radiation-induced dechlorination of hexachloroethane was investigated in deoxygenated alcohol solutions. The major products were hydrogen chloride, pentachloroethane, 1,1,2,2-tetrachloroethane, tetrachloroethylene, and aldehydes or acetone. No 1,1,1,2-tetrachloroethane was observed. The radiation-chemical yields of these products and the disappearance of hexachloroethane were quite high; these facts indicate that a chain reaction is involved in these processes. After the hexachloroethane had effectively dechlorinated down to tetrachloro compounds, there were no marked changes in the lower chlorinated compound upon continuous irradiation. Tetrachloroethane was formed via pentachloroethane, but tetrachloroethylene was produced by means of C 2 Cl 5 →C 2 Cl 4 + cl reaction and the yield was particularly high in methanol compared with the other alcohols. The chain length of the dechlorination from hexachloroethane to pentachloroethane and from pentachloroethane to tetrachloroethane increased in the order of 2-propanol>ethanol>methanol. The G(-C 2 Cl 6 ) and G(products) were proportional to (dose rate)sup(-1/2), and the ratio of G(C 2 HCl 5 ) to G(C 2 Cl 4 ) was a constant in each alcohol solution, regardless of the dose rate. The α-hydroxy alkyl radical is the chain carrier for the dechlorination reaction of hexachloroethane in alcohol solutions. The relative rates of the dechlorination were found to be 1, 3, and 14 for C*H 2 OH (*: radical), CH 3 C*HOH (*: radical), and (CH 3 ) 2 C*OH (*: radical), respectively. The order in the rate is in agreement with that of the redox potential of these radicals. The effect of the irradiation temperature on the products yields was also examined. (auth.)

Characterization of an H2-utilizing enrichment culture that reductively dechlorinates tetrachloroethene to vinyl chloride and ethene in the absence of methanogenesis and acetogenesis.

OpenAIRE

Maymó-Gatell, X; Tandoi, V; Gossett, J M; Zinder, S H

1995-01-01

We have been studying an anaerobic enrichment culture which, by using methanol as an electron donor, dechlorinates tetrachloroethene (PCE) to vinyl chloride and ethene. Our previous results indicated that H2 was the direct electron donor for rductive dechlorination of PCE by the methanol-PCE culture. Most-probable-number counts performed on this culture indicated low numbers ( or equal to 10(6)/ml...

Enhanced reductive de-chlorination of a solvent contaminated aquifer through addition and apparent fermentation of cyclodextrin

Science.gov (United States)

Blanford, William James; Pecoraro, Michael Philip; Heinrichs, Rebecca; Boving, Thomas Bernhard

2018-01-01

In a field study, aqueous cyclodextrin (CD) was investigated for its ability to extract chlorinated volatile organic compounds (cVOC), such as trichloroethylene (TCE), 1,1,1-trichloroethane (TCA), and dichloroethene (DCE) through in-situ flushing of a sandy aquifer. After cessation of aquifer flushing, a plume of CD was left. Changes in CD, cVOC, and inorganic terminal electron acceptors (TEAs) (DO, nitrate, sulfate, iron) were monitored in four rounds of wellwater sampling (20, 210, 342, and 425 days after cessation of active pumping). Post-CD flushing VOC levels rebounded (850% for TCE, 190% for TCA, and 53% for DCE) between the first two sampling rounds, apparently due to rate-limited desorption from aquifer media and dissolution from remaining NAPL. However, substantial reduction in the mass of TCE (6.3 to 0.11 mol: 98%) and TCA (2.8 to 0.73 mol: 74%) in groundwater was observed between 210 and 425 days. DCE should primarily be produced from the degradation of TCE and is expected to subsequently degrade to chloroethene. Since DCE levels decreased only slightly (0.23 to 0.17 mol: 26%), its degradation rate should be similar to that produced from the decaying TCE. Cyclodextrin was monitored starting from day 210. The mass of residual CD (as measured by Total Organic Carbon) decreased from 150 mol (day 210) to 66 (day 425) (56% decrease). The naturally anaerobic zone within the aquifer where residual CD mass decreased coincided with a loss of other major potential TEAs: nitrate (97% loss), sulfate (31%) and iron (31%). In other studies, TCE and 1,1,1-TCA have been found to be more energetically favorable TEAs than sulfate and iron and their degradation via reductive dechlorination has been found to be enhanced by the fermentation of carbohydrates. Such processes can explain these observations, but more investigation is needed to evaluate whether residual levels of CD can facilitate the anaerobic degradation of chlorinated VOCs.

Electrocatalytic Reduction-oxidation of Chlorinated Phenols using a Nanostructured Pd-Fe Modified Graphene Catalyst

International Nuclear Information System (INIS)

Shi, Qin; Wang, Hui; Liu, Shaolei; Pang, Lei; Bian, Zhaoyong

2015-01-01

A Pd-Fe modified graphene (Pd-Fe/G) catalyst was prepared by the Hummers oxidation method and bimetallic co-deposition method. The catalyst was then characterized by various characterization techniques and its electrochemical property toward the electrocatalytic reduction-oxidation of chlorinated phenols was investigated by using cyclic voltammetry and differential pulse voltammetry. The results of the characterization show that the Pd-Fe/G catalyst in which the weight proportion of Pd and Fe is 1:1 has an optimal surface performance. The diameter of the Pd-Fe particles is approximately 5.2 ± 0.3 nm, with a uniform distribution on the supporting graphene. This is smaller than the Pd particles of a Pd-modified graphene (Pd/G) catalyst. The Pd-Fe/G catalyst shows a higher electrocatalytic activity than the Pd/G catalyst for reductive dechlorination when feeding with hydrogen gas. The reductive peak potentials of −0.188 V, −0.836 V and −0.956 V in the DPV curves are attributed to the dechlorination of ortho-Cl, meta-Cl, and para-Cl in 2-chlorophenol, 3-chlorophenol and 4-chlorophenol, respectively. In accordance with an analysis of the frontier orbital theory, the order of ease of dechlorination with Pd-Fe/G catalyst is 2-chlorophenol > 3-chlorophenol > 4-chlorophenol. The Pd-Fe/G catalyst has a greater activity than the Pd/G catalyst in accelerating the two-electron reduction of O_2 to H_2O_2, which is attributed to the higher current of the reduction peak at approximately −0.40 V when feeding with oxygen gas. Therefore, the Pd-Fe/G catalyst exhibits a higher electrocatalytic activity than the Pd/G catalyst for the reductive dechlorination and acceleration of the two-electron reduction of O_2 to H_2O_2.

EFFECTS OF REACTOR CONDITIONS ON ELECTROCHEMICAL DECHLORINATION OF TRICHLOROETHYLENE USING GRANULAR-GRAPHITE ELECTRODE.

Science.gov (United States)

Trichloroethylene (TCE) was electrochemically dechlorinated in aqueous environments using granular graphite cathode in a mixed reactor. Effects of pH, current, electrolyte type, and flow rate on TCE dechlorination rate were evaluated. TCE dechlorination rate constant and gas pr...

Dechlorination kinetics of TCE at toxic TCE concentrations: Assessment of different models.

Science.gov (United States)

Haest, P J; Springael, D; Smolders, E

2010-01-01

The reductive dechlorination of trichloroethene (TCE) in a TCE source zone can be self-inhibited by TCE toxicity. A study was set up to examine the toxicity of TCE in terms of species specific degradation kinetics and microbial growth and to evaluate models that describe this self-inhibition. A batch experiment was performed using the TCE dechlorinating KB-1 culture at initial TCE concentrations ranging from 0.04mM to saturation (8.4mM). Biodegradation activity was highest at 0.3mM TCE and no activity was found at concentrations from 4 to 8mM. Species specific TCE and cis-DCE (cis-dichloroethene) degradation rates and Dehalococcoides numbers were modeled with Monod kinetics combined with either Haldane inhibition or a log-logistic dose-response inhibition on these rates. The log-logistic toxicity model appeared the most appropriate model and predicts that the species specific degradation activities are reduced by a factor 2 at about 1mM TCE, respectively cis-DCE. However, the model showed that the inhibitive effects on the time for TCE to ethene degradation are a complex function of degradation kinetics and the initial cell densities of the dechlorinating species. Our analysis suggests that the self-inhibition on biodegradation cannot be predicted by a single concentration threshold without information on the cell densities.

Dechlorination of Aromatic Xenobiotic Compounds by Anaerobic Microorganisms

Science.gov (United States)

1988-07-01

dechlorination of 3 6C1- 2,3,7,8-TCDD have been initiated but are incomplete at this time. The sources of anaerobic dechlorinating bacteria were the...SETHUNATHAN, 1983). Active anaerobic habitatsa DDT Soil, rumen fluid, sewage sludge, sediments, microbial cultures Lindane Soil, sediments, microbial... anaerobic bacteria (Reference 24). Sediments containing relatively high levels of PCBs (> 50 ppm) all showed losses of up to one-third of the chlorine

Dechlorination of Environmental Contaminants Using a Hybrid Nanocatalyst: Palladium Nanoparticles Supported on Hierarchical Carbon Nanostructures

Directory of Open Access Journals (Sweden)

Hema Vijwani

2012-01-01

Full Text Available This paper demonstrates the effectiveness of a new type of hybrid nanocatalyst material that combines the high surface area of nanoparticles and nanotubes with the structural robustness and ease of handling larger supports. The hybrid material is made by fabricating palladium nanoparticles on two types of carbon supports: as-received microcellular foam (Foam and foam with carbon nanotubes anchored on the pore walls (CNT/Foam. Catalytic reductive dechlorination of carbon tetrachloride with these materials has been investigated using gas chromatography. It is seen that while both palladium-functionalized carbon supports are highly effective in the degradation of carbon tetrachloride, the rate of degradation is significantly increased with palladium on CNT/Foam. However, there is scope to increase this rate further if the wettability of these structures can be enhanced in the future. Microstructural and spectroscopic analyses of the fresh and used catalysts have been compared which indicates that there is no change in density or surface chemical states of the catalyst after prolonged use in dechlorination test. This implies that these materials can be used repeatedly and hence provide a simple, powerful, and cost-effective approach for dechlorination of water.

Microbial community analysis of switchgrass planted and unplanted soil microcosms displaying PCB dechlorination.

Science.gov (United States)

Liang, Yi; Meggo, Richard; Hu, Dingfei; Schnoor, Jerald L; Mattes, Timothy E

2015-08-01

Polychlorinated biphenyls (PCBs) pose potential risks to human and environmental health because they are carcinogenic, persistent, and bioaccumulative. In this study, we investigated bacterial communities in soil microcosms spiked with PCB 52, 77, and 153. Switchgrass (Panicum virgatum) was employed to improve overall PCB removal, and redox cycling (i.e., sequential periods of flooding followed by periods of no flooding) was performed in an effort to promote PCB dechlorination. Lesser chlorinated PCB transformation products were detected in all microcosms, indicating the occurrence of PCB dechlorination. Terminal restriction fragment length polymorphism (T-RFLP) and clone library analysis showed that PCB spiking, switchgrass planting, and redox cycling affected the microbial community structure. Putative organohalide-respiring Chloroflexi populations, which were not found in unflooded microcosms, were enriched after 2 weeks of flooding in the redox-cycled microcosms. Sequences classified as Geobacter sp. were detected in all microcosms and were most abundant in the switchgrass-planted microcosm spiked with PCB congeners. The presence of possible organohalide-respiring bacteria in these soil microcosms suggests that they play a role in PCB dechlorination therein.

Impact of dechlorination processes on the sediment-water exchange of PCDD/F in Passaic river cores

Energy Technology Data Exchange (ETDEWEB)

Adriaens, P.; Khijniak, A. [Civil and Environmental Engineering, Univ. of Michigan, Ann Arbor (United States); Jones, K.; Green, N. [Environmental Science, Lancaster Univ. (United Kingdom); Gruden, C. [Univ. of Toledo, OH (United States)

2004-09-15

The potential for natural dechlorination processes in sediments to impact the biogeochemical cycling of dioxins and furans has been proposed as a possible mechanism to explain the prevalence of lesser halogenated dioxins and furans at the air-water interface. The hypothesis was supported by multiple lines of evidence, but has not been directly demonstrated. Field evidence indicated dynamic air-water exchange of PCDD/Fs in the Raritan Bay/Hudson River Estuary, whereby lesser chlorinated (predominantly diCDD/F) were present in the particle and apparent dissolved phase. Fugacity calculations indicated that the water column served as the source of these homologue groups. Laboratory evidence from Passaic River sediment cores and microbiallymediated dechlorination demonstrated that historic dioxins can undergo extensive dechlorination reactions, culminating in the formation of mono-and diCDD homologues. Similar pathways have been observed with PCDF, resulting in the accumulation of triCDF. The current paper reports on an investigation addressing the hypothesis of whether the lesser chlorinated PCDD/F observed at the air-water interface could be the result of selective dissolution of these congeners or homologues from sediments as they are produced during microbial dechlorination.

Role of bicarbonate as a pH buffer and electron sink in microbial dechlorination of chloroethenes

Directory of Open Access Journals (Sweden)

Delgado Anca G

2012-09-01

Full Text Available Abstract Background Buffering to achieve pH control is crucial for successful trichloroethene (TCE anaerobic bioremediation. Bicarbonate (HCO3− is the natural buffer in groundwater and the buffer of choice in the laboratory and at contaminated sites undergoing biological treatment with organohalide respiring microorganisms. However, HCO3− also serves as the electron acceptor for hydrogenotrophic methanogens and hydrogenotrophic homoacetogens, two microbial groups competing with organohalide respirers for hydrogen (H2. We studied the effect of HCO3− as a buffering agent and the effect of HCO3−-consuming reactions in a range of concentrations (2.5-30 mM with an initial pH of 7.5 in H2-fed TCE reductively dechlorinating communities containing Dehalococcoides, hydrogenotrophic methanogens, and hydrogenotrophic homoacetogens. Results Rate differences in TCE dechlorination were observed as a result of added varying HCO3− concentrations due to H2-fed electrons channeled towards methanogenesis and homoacetogenesis and pH increases (up to 8.7 from biological HCO3− consumption. Significantly faster dechlorination rates were noted at all HCO3− concentrations tested when the pH buffering was improved by providing 4-(2-hydroxyethyl-1-piperazineethanesulfonic acid (HEPES as an additional buffer. Electron balances and quantitative PCR revealed that methanogenesis was the main electron sink when the initial HCO3− concentrations were 2.5 and 5 mM, while homoacetogenesis was the dominant process and sink when 10 and 30 mM HCO3− were provided initially. Conclusions Our study reveals that HCO3− is an important variable for bioremediation of chloroethenes as it has a prominent role as an electron acceptor for methanogenesis and homoacetogenesis. It also illustrates the changes in rates and extent of reductive dechlorination resulting from the combined effect of electron donor competition stimulated by HCO3− and the changes in pH exerted by

Radiation dechlorination of PCE and PCB in the quarter operation flow apparatus

International Nuclear Information System (INIS)

Mucka, V.; Silber, R.; Pospisil, M.; Camra, M.; Bartonicek, B.

1999-01-01

The aim of this work was to verify practical possibilities of radiation dechlorination of liquid chlorinated substrates [perchloroethylene (PCE) and polychlorinated biphenyls (PCB)] in the quarter operation flow apparatus. In this apparatus may be disposable work over 50 dm 3 of media. Radiation dechlorination of PCE proceeds more effectively as dechlorination of PCB in flow regimes, too. Radiation chemical yield of G(-OH - ) decrease with increasing applied radiation dose and at the dose 5 kGy for PCE it is 200 · 10 -2 eV -1 and for PCB this value is 55 · 10 -2 eV -1 . At increasing original concentration of PCE or PCB the G-values decreases. The radical chain mechanism of dechlorination of PCE and PCB was proposed

Chloroethene Biodegradation Potential, ADOT/PF Peger Road Maintenance Facility, Fairbanks, Alaska

Science.gov (United States)

Bradley, Paul M.; Chapelle, Frances H.

2004-01-01

A series of 14C-radiotracer-based microcosm experiments were conducted to assess: 1) the extent, rate and products of microbial dechlorination of trichloroethene (TCE), cis-dichloroethene (cis-DCE) and vinyl chloride (VC) in sediments at the Peger Road site; 2) the effect of three electron donor amendments (molasses, shrimp and crab chitin, and 'Hydrogen Release Compound' (HRC)) on microbial degradation of TCE in three Peger Road sediments; and 3) the potential significance at the site of chloroethene biodegradation processes other than reductive dechlorination. In these experiments, TCE biodegradation yielded the reduced products, DCE and VC, and the oxidation product CO 2. Biodegradation of DCE and VC involved stoichiometric oxidation to CO 2. Both laboratory microcosm study and field redox assessment results indicated that the predominant terminal electron accepting process in Peger Road plume sediments under anoxic conditions was Mn/Fe-reduction. The rates of chloroethene biodegradation observed in Peger Road sediment microcosms under low temperature conditions (4?C) were within the range of those observed in sediments from temperate (20?C) aquifer systems. This result confirmed that biodegradation can be a significant mechanism for in situ contaminant remediation even in cold temperature aquifers. The fact that CO2 was the sole product of cis-DCE and VC biodegradation detected in Peger Road sediments indicated that a natural attenuation assessment based on reduced daughter product accumulation may significantly underestimate the potential for DCE and VC biodegradation at the Peger Road. Neither HRC nor molasses addition stimulated TCE reductive dechlorination. The fact that molasses and HRC amendment did stimulate Mn/Fe-reduction suggests that addition of these electron donors favored microbial Mn/Fe-reduction to the detriment of microbial TCE dechlorinating activity. In contrast, amendment of sediment microcosms with shrimp and crab chitin resulted in the

Studies on dechlorination of DDT (1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane) using magnesium/palladium bimetallic system

International Nuclear Information System (INIS)

Gautam, Sumit Kumar; Suresh, Sumathi

2007-01-01

The aim of our investigation was to compare the rates of dechlorination of DDT using Mg 0 /Pd 4+ system in two different reaction phases, namely, water-acetone and 0.05% biosurfactant in water. Since palladium is expensive and its toxicity effects are not well known we also examined the reuse efficiency of Pd 0 immobilized on alumina for dechlorinating DDT. Studies on the dechlorination of DDT in water-acetone (1:1, v/v) and 0.05% biosurfactant phases revealed that the reaction followed second order kinetics and rate of reaction is dependent upon both initial concentrations of the target compound and Mg 0 /Pd 4+ . The presence of acid enhanced the rate of reaction by providing protons and preventing passivation of metal that occurs due to deposition of magnesium hydroxide. GC-MS analyses revealed the formation of completely dechlorinated hydrocarbon skeleton of DDT namely, diphenylethane (DPE), as the end product in both reaction phases (water-acetone and 0.05% biosurfactant in water) thereby implying the removal of all five chlorine atoms (three alkyl and two aryl) of DDT. The optimum ratio of water and acetone to facilitate successful dechlorination reaction was found to be 9:1. Results suggested that salt form (K 2 PdCl 6 ) of palladium had higher potential to dechlorinate DDT as compared to pellet (Pd 0 -alumina) form (efficiencies of 95 and 36%, respectively, for 100 ppm initial concentration of DDT). We noted that Pd 0 -alumina pellets could be reused at least four times for successful dechlorination of DDT provided Mg 0 granules are present in sufficient quantity. Technical grade DDT (50 ppm) containing significant amounts of DDD was dechlorinated almost completely by the Mg 0 /Pd 4+ (10 mg/0.2 mg/ml) within 1 h in water-biosurfactant phase. Our studies reveal that Mg/Pd system is a promising option due to its high reactivity and its ability to achieve complete dechlorination of DDT. This bimetallic system may be useful for designing indigenous permeable

Abiotic dechlorination in rock matrices impacted by long-term exposure to TCE.

Science.gov (United States)

Schaefer, Charles E; Towne, Rachael M; Lippincott, David R; Lacombe, Pierre J; Bishop, Michael E; Dong, Hailiang

2015-01-01

Field and laboratory tests were performed to evaluate the abiotic reaction of trichloroethene (TCE) in sedimentary rock matrices. Hydraulically conductive fractures, and the rock directly adjacent to the hydraulically conductive fractures, within a historically contaminated TCE bedrock aquifer were used as the basis for this study. These results were compared to previous work using rock that had not been exposed to TCE (Schaefer et al., 2013) to assess the impact of long-term TCE exposure on the abiotic dechlorination reaction, as the longevity of these reactions after long-term exposure to TCE was hitherto unknown. Results showed that potential abiotic TCE degradation products, including ethane, ethene, and acetylene, were present in the conductive fractures. Using minimally disturbed slices of rock core at and near the fracture faces, laboratory testing on the rocks confirmed that abiotic dechlorination reactions between the rock matrix and TCE were occurring. Abiotic daughter products measured in the laboratory under controlled conditions were consistent with those measured in the conductive fractures, except that propane also was observed as a daughter product. TCE degradation measured in the laboratory was well described by a first order rate constant through the 118-d study. Observed bulk first-order TCE degradation rate constants within the rock matrix were 1.3×10(-8) s(-1). These results clearly show that abiotic dechlorination of TCE is occurring within the rock matrix, despite decades of exposure to TCE. Furthermore, these observed rates of TCE dechlorination are expected to have a substantial impact on TCE migration and uptake/release from rock matrices. Copyright © 2014 Elsevier Ltd. All rights reserved.

Chemical dechlorination of pesticides at a superfund site in Region II

International Nuclear Information System (INIS)

Pendergrass, S.; Prince, J.

1991-01-01

Selecting technologies for cleaning up hazardous waste sites is a complex task, due in part to the rapidly changing nature of the state-of-the-art in technology. There is strong support for use of innovative technologies as specified in Section 121(b) of CERCLA. However, use of an innovative technology requires overcoming a variety of challenges. These challenges include: Screening potentially appropriate technologies, including innovative technologies, and selecting one or more potential innovative technologies for which preliminary results are promising; however, site-specific data are needed prior to technology evaluation. Evaluating the effectiveness of the proposed technology for the site through the use of treatability studies. Gaining acceptance for the innovative technology, which may employ new or unfamiliar concepts. Determining optimal design and operating parameters for full-scale remediation. This paper discusses the technology evaluation process and how that process supported the selection of an innovative technology for the Myers Property site, a Superfund site in Region II. A case study is presented showing how technology screening and laboratory treatability studies were used to evaluate an innovative technology (chemical dechlorination), which was selected as the technology for remediation of soils and sediments contaminated with pesticides at this environmentally sensitive site in New Jersey. The remedy selected by the U.S. EPA for this site designates chemical dechlorination as the selected technology, but does not specify any particular vendor or process. Rather, the remedy sets forth technology performance standards and recommends certain design tasks which may be used to select a particular chemical process. This paper discusses he of these design tasks as they might apply to innovative technologies, using chemical dechlorination as a model

Effects of 1,1,1-Trichloroethane and Triclocarban on Reductive Dechlorination of Trichloroethene in a TCE-Reducing Culture.

Science.gov (United States)

Wen, Li-Lian; Chen, Jia-Xian; Fang, Jia-Yi; Li, Ang; Zhao, He-Ping

2017-01-01

Chlorinated compounds were generally present in the environment due to widespread use in the industry. A short-term study was performed to evaluate the effects of 1,1,1- trichloroethane (TCA) and triclocarban (TCC) on trichloroethene (TCE) removal in a reactor fed with lactate as the sole electron donor. Both TCA and TCC inhibited TCE reduction, but the TCC had a more pronounced effect compared to TCA. The TCE-reducing culture, which had never been exposed to TCA before, reductively dechlorinated TCA to 1,1-dichloroethane (DCA). Below 15 μM, TCA had little effect on the transformation of TCE to cis -dichloroethene (DCE); however, the reduction of cis -DCE and vinyl chloride (VC) were more sensitive to TCA, and ethene production was completely inhibited when the concentration of TCA was above 15 μM. In cultures amended with TCC, the reduction of TCE was severely affected, even at concentrations as low as 0.3 μM; all the cultures stalled at VC, and no ethene was detected. The cultures that fully transformed TCE to ethene contained 5.2-8.1% Dehalococcoides . Geobacter and Desulfovibrio , the bacteria capable of partially reducing TCE to DCE, were detected in all cultures, but both represented a larger proportion of the community in TCC-amended cultures. All cultures were dominated by Clostridium _sensu_stricto_7, a genus that belongs to Firmicutes with proportions ranging from 40.9% (in a high TCC (15 μM) culture) to 88.2%. Methanobacteria was detected at levels of 1.1-12.7%, except in cultures added with 15 and 30 μM TCA, in which they only accounted for ∼0.4%. This study implies further environmental factors needed to be considered in the successful bioremediation of TCE in contaminated sites.

Effects of 1,1,1-Trichloroethane and Triclocarban on Reductive Dechlorination of Trichloroethene in a TCE-Reducing Culture

Directory of Open Access Journals (Sweden)

Li-Lian Wen

2017-08-01

Full Text Available Chlorinated compounds were generally present in the environment due to widespread use in the industry. A short-term study was performed to evaluate the effects of 1,1,1- trichloroethane (TCA and triclocarban (TCC on trichloroethene (TCE removal in a reactor fed with lactate as the sole electron donor. Both TCA and TCC inhibited TCE reduction, but the TCC had a more pronounced effect compared to TCA. The TCE-reducing culture, which had never been exposed to TCA before, reductively dechlorinated TCA to 1,1-dichloroethane (DCA. Below 15 μM, TCA had little effect on the transformation of TCE to cis-dichloroethene (DCE; however, the reduction of cis-DCE and vinyl chloride (VC were more sensitive to TCA, and ethene production was completely inhibited when the concentration of TCA was above 15 μM. In cultures amended with TCC, the reduction of TCE was severely affected, even at concentrations as low as 0.3 μM; all the cultures stalled at VC, and no ethene was detected. The cultures that fully transformed TCE to ethene contained 5.2–8.1% Dehalococcoides. Geobacter and Desulfovibrio, the bacteria capable of partially reducing TCE to DCE, were detected in all cultures, but both represented a larger proportion of the community in TCC-amended cultures. All cultures were dominated by Clostridium_sensu_stricto_7, a genus that belongs to Firmicutes with proportions ranging from 40.9% (in a high TCC (15 μM culture to 88.2%. Methanobacteria was detected at levels of 1.1–12.7%, except in cultures added with 15 and 30 μM TCA, in which they only accounted for ∼0.4%. This study implies further environmental factors needed to be considered in the successful bioremediation of TCE in contaminated sites.

PALLADIUM-FACILITATED ELECTROLYTIC DECHLORINATION OF 2-CHLOROBIPHENYL USING A GRANULAR-GRAPHITE ELECTRODE.

Science.gov (United States)

Palladium-assisted electrocatalytic dechlorination of 2-chlorobiphenyl (2-Cl BP) in aqueous solutions was conducted in a membrane-separated electrochemical reactor with granular-graphite packed electrodes. The dechlorination took place at a granular-graphite cathode while Pd was ...

Chlorination and dechlorination rates in a forest soil — A combined modelling and experimental approach

Energy Technology Data Exchange (ETDEWEB)

Montelius, Malin, E-mail: malin.montelius@liu.se [Department of Thematic Studies — Environmental Change, Linköping University, 581 83 Linköping (Sweden); Svensson, Teresia [Department of Thematic Studies — Environmental Change, Linköping University, 581 83 Linköping (Sweden); Lourino-Cabana, Beatriz [EDF, Laboratoire National d' Hydraulique et Environnement, 78401 Chatou (France); Thiry, Yves [Andra, Research and Development Division, Parc de la Croix Blanche, 1/7 rue Jean Monnet, 92298 Châtenay-Malabry Cedex (France); Bastviken, David [Department of Thematic Studies — Environmental Change, Linköping University, 581 83 Linköping (Sweden)

2016-06-01

Much of the total pool of chlorine (Cl) in soil consists of naturally produced organic chlorine (Cl{sub org}). The chlorination of bulk organic matter at substantial rates has been experimentally confirmed in various soil types. The subsequent fates of Cl{sub org} are important for ecosystem Cl cycling and residence times. As most previous research into dechlorination in soils has examined either single substances or specific groups of compounds, we lack information about overall bulk dechlorination rates. Here we assessed bulk organic matter chlorination and dechlorination rates in coniferous forest soil based on a radiotracer experiment conducted under various environmental conditions (additional water, labile organic matter, and ammonium nitrate). Experiment results were used to develop a model to estimate specific chlorination (i.e., fraction of Cl{sup −} transformed to Cl{sub org} per time unit) and specific dechlorination (i.e., fraction of Cl{sub org} transformed to Cl{sup −} per time unit) rates. The results indicate that chlorination and dechlorination occurred simultaneously under all tested environmental conditions. Specific chlorination rates ranged from 0.0005 to 0.01 d{sup −1} and were hampered by nitrogen fertilization but were otherwise similar among the treatments. Specific dechlorination rates were 0.01–0.03 d{sup −1} and were similar among all treatments. This study finds that soil Cl{sub org} levels result from a dynamic equilibrium between the chlorination and rapid dechlorination of some Cl{sub org} compounds, while another Cl{sub org} pool is dechlorinated more slowly. Altogether, this study demonstrates a highly active Cl cycling in soils. - Highlights: • Chlorination and dechlorination rates in soil were revealed by a radiotracer method. • Chlorination was hampered by nitrogen addition. • Both Cl{sup −} and many Cl{sub org} compounds are highly reactive in soils. • Some formed Cl{sub org} seem to be refractory.

IDENTIFICATION OF CHLOROMETHANE FORMATION PATHS DURING ELECTROCHEMICAL DECHLORINATION OF TCE USING GRAPHITE ELECTRODES

Science.gov (United States)

The purpose of this research is to investigate the formation of chloromethane during TCE dechlorination in a mixed electrochemical reactor using graphite electrodes. Chloromethane was the major chlorinated organic compound detected in previous dechlorination experiments. In order...

IDENTIFICATION OF CHLOROMETHANE FROMATION PATHS DURING ELECTROCHEMICAL DECHLORINATION OF TCE USING GRAPHITE ELECTRODES

Science.gov (United States)

The purpose of this research is to investigate the formation of chloromethane during TCE dechlorination in a mixed electrochemical reactor using graphite electrodes. Chloromethane was the major chlorinated organic compound detected in previous dechlorination experiments. In order...

Introduction of a De Novo Bioremediation Ability, Aryl Reductive Dechlorination, into Anaerobic Granular Sludge by Inoculation of Sludge with Desulfomonile tiedjei

DEFF Research Database (Denmark)

Ahring, Birgitte Kiær; Christiansen, Nina; Mathrani, Indra Madan

1992-01-01

Methanogenic upflow anaerobic granular-sludge blanket (UASB) reactors treat wastewaters at a high rate while simultaneously producing a useful product, methane; however, recalcitrant environmental pollutants may not be degraded. To impart 3-chlorobenzoate (3-CB)-dechlorinating ability to UASB rea...

Dechlorinating ability of TCE-fed microcosms with different electron donors

International Nuclear Information System (INIS)

Panagiotakis, Iraklis; Mamais, Daniel; Pantazidou, Marina; Marneri, Matina; Parapouli, Maria; Hatziloukas, Efstathios; Tandoi, Valter

2007-01-01

The main objective of the work presented herein is to assess the effect of different electron donors (butyric acid and methanol) on the dechlorinating activity of two microbial cultures where active methanogenic populations are present, in an effort to evaluate the importance of the electron donor selection process. The ability of each anaerobic culture to dechlorinate TCE, when enriched with either butyric acid or methanol, was verified based on the results of gas chromatography. In addition, the fluorescent in situ hybridization (FISH) and the polymerase chain reaction (PCR) methods gave positive results for the presence of Dehalococcoides spp. According to results of the batch tests conducted in this study, it appears that the selection of the electron donor for stimulating TCE dechlorination depends on microbial culture composition; therefore, the decision on the appropriate electron donor should be based on site-specific microcosm studies

Sustainable remediation: electrochemically assisted microbial dechlorination of tetrachloroethene-contaminated groundwater.

Science.gov (United States)

Patil, Sayali S; Adetutu, Eric M; Rochow, Jacqueline; Mitchell, James G; Ball, Andrew S

2014-01-01

Microbial electric systems (MESs) hold significant promise for the sustainable remediation of chlorinated solvents such as tetrachlorethene (perchloroethylene, PCE). Although the bio-electrochemical potential of some specific bacterial species such as Dehalcoccoides and Geobacteraceae have been exploited, this ability in other undefined microorganisms has not been extensively assessed. Hence, the focus of this study was to investigate indigenous and potentially bio-electrochemically active microorganisms in PCE-contaminated groundwater. Lab-scale MESs were fed with acetate and carbon electrode/PCE as electron donors and acceptors, respectively, under biostimulation (BS) and BS-bioaugmentation (BS-BA) regimes. Molecular analysis of the indigenous groundwater community identified mainly Spirochaetes, Firmicutes, Bacteroidetes, and γ and δ-Proteobacteria. Environmental scanning electron photomicrographs of the anode surfaces showed extensive indigenous microbial colonization under both regimes. This colonization and BS resulted in 100% dechlorination in both treatments with complete dechlorination occurring 4 weeks earlier in BS-BA samples and up to 11.5 μA of current being generated. The indigenous non-Dehalococcoides community was found to contribute significantly to electron transfer with ∼61% of the current generated due to their activities. This study therefore shows the potential of the indigenous non-Dehalococcoides bacterial community in bio-electrochemically reducing PCE that could prove to be a cost-effective and sustainable bioremediation practice. © 2013 The Authors. Microbial Biotechnology published by John Wiley & Sons Ltd and Society for Applied Microbiology.

Radiation dechlorination of PCE in aqueous solutions under various conditions

International Nuclear Information System (INIS)

Mucka, V.; Lizalova, B.; Pospisil, M.; Silber, R.; Polakova, D.

2002-01-01

Complete text of publication follows. Radiation technology of water purification from chlorinated compounds seems to be one of the promising method (Getoff, 1996), analogously as it was shown (Mueka et al., 2000) with radiation degradation of polychlorinated biphenyls (PCBs). A systematic study of dechlorination of tetrachloroethylene (PCE) in aqueous solutions (initial concentrations ranging from 9.2 x 10 -6 to 2.5 x 10 -4 mol dm -3 ), initiated by γ-rays of 60 Co or by accelerated electrons (EB, 4.5 MeV) in presence of various modifiers (atmospheric oxygen, N 2 O-oxide, HCO 3 - - and NO 3 - - ions as well as various pH-values), was the aim of this paper. The studies showed that both actual concentration c of PCE and radiation yield G(Cl - ) decreased rapidly with increasing dose up to the dose of 2 kGy and the degree of dechlorination raised sharply in this dose-interval. The dechlorination was slightly promoted by atmospheric oxygen. Similarly, a promotion effect was detected in the case of the PCE-solutions saturated, prior to their irradiation, with the N 2 O-oxide. On the other hand, a presence of NO 3 - - or HCO 3 - -ions in irradiated samples led to an inhibiting effect. The inhibiting effect increased markedly with increasing concentration of both at above-mentioned ions up to the concentration of about 100 mg dm -3 . A pronounced inhibition of γ-radiation dechlorination of PCE was observed in alkaline aqueous solutions. The results obtained in this paper support the idea that the radiation dechlorination of PCE in aqueous solutions proceeds via an oxidative mechanism in which the γ-irradiation was found to be more effective than the EB-irradiation

Two dechlorinated chlordecone derivatives formed by in situ chemical reduction are devoid of genotoxicity and mutagenicity and have lower proangiogenic properties compared to the parent compound.

Science.gov (United States)

Legeay, Samuel; Billat, Pierre-André; Clere, Nicolas; Nesslany, Fabrice; Bristeau, Sébastien; Faure, Sébastien; Mouvet, Christophe

2018-05-01

Chlordecone (CLD) is a chlorinated hydrocarbon insecticide, now classified as a persistent organic pollutant. Several studies have previously reported that chronic exposure to CLD leads to hepatotoxicity, neurotoxicity, raises early child development and pregnancy complications, and increases the risk of liver and prostate cancer. In situ chemical reduction (ISCR) has been identified as a possible way for the remediation of soils contaminated by CLD. In the present study, the objectives were (i) to evaluate the genotoxicity and the mutagenicity of two CLD metabolites formed by ISCR, CLD-5a-hydro, or CLD-5-hydro (5a- or 5- according to CAS nomenclature; CLD-1Cl) and tri-hydroCLD (CLD-3Cl), and (ii) to explore the angiogenic properties of these molecules. Mutagenicity and genotoxicity were investigated using the Ames's technique on Salmonella typhimurium and the in vitro micronucleus micromethod with TK6 human lymphoblastoid cells. The proangiogenic properties were evaluated on the in vitro capillary network formation of human primary endothelial cells. Like CLD, the dechlorinated derivatives of CLD studied were devoid of genotoxic and mutagenic activity. In the assay targeting angiogenic properties, significantly lower microvessel lengths formed by endothelial cells were observed for the CLD-3Cl-treated cells compared to the CLD-treated cells for two of the three tested concentrations. These results suggest that dechlorinated CLD derivatives are devoid of mutagenicity and genotoxicity and have lower proangiogenic properties than CLD.

Use of carbon stable isotope to investigate chloromethane formation in the electrolytic dechlorination of trichloroethylene

International Nuclear Information System (INIS)

Fang Yuanxiang; Al-Abed, Souhail R.

2007-01-01

Carbon stable isotope trichloroethylene ( 13 C TCE) was used to investigate the formation of chloromethane (CM) during the electrolytic dechlorination of trichloroethylene (TCE) at a granular-graphite packed cathode. A method was developed to use a conventional GC/MS to analyze and quantify regular and 13 C TCE and their dechlorination products. The concentration of a 13 C compound can be calculated, based on the concentration of its regular counterpart, from the response ratio of two fragments of different mass per charge values from the compounds in a sample and two characteristic MS spectrum ratios: one is the response ratio of the two fragments of the regular compound, and the other is the response ratio of the corresponding fragments of the regular and 13 C compounds at the same concentrations. The method was used to analyze the regular and 13 C compounds observed in an experiment of dechlorination in an ammonium acetate solution that contained both regular TCE and 13 C TCE. Results of analysis confirmed that CM was not a direct product of TCE dechlorination at the granular graphite cathode that cis-DCE was an intermediate product of TCE dechlorination, and that 1,1-DCE was not a dechlorination product

Use of carbon stable isotope to investigate chloromethane formation in the electrolytic dechlorination of trichloroethylene

Energy Technology Data Exchange (ETDEWEB)

Fang Yuanxiang [National Risk Management Research Laboratory, USEPA 26 W. Martin Luther King Dr. Cincinnati, OH 45268 (United States); Al-Abed, Souhail R. [National Risk Management Research Laboratory, USEPA 26 W. Martin Luther King Dr. Cincinnati, OH 45268 (United States)]. E-mail: Al-Abed.Souhail@epa.gov

2007-03-22

Carbon stable isotope trichloroethylene ({sup 13}C TCE) was used to investigate the formation of chloromethane (CM) during the electrolytic dechlorination of trichloroethylene (TCE) at a granular-graphite packed cathode. A method was developed to use a conventional GC/MS to analyze and quantify regular and {sup 13}C TCE and their dechlorination products. The concentration of a {sup 13}C compound can be calculated, based on the concentration of its regular counterpart, from the response ratio of two fragments of different mass per charge values from the compounds in a sample and two characteristic MS spectrum ratios: one is the response ratio of the two fragments of the regular compound, and the other is the response ratio of the corresponding fragments of the regular and {sup 13}C compounds at the same concentrations. The method was used to analyze the regular and {sup 13}C compounds observed in an experiment of dechlorination in an ammonium acetate solution that contained both regular TCE and {sup 13}C TCE. Results of analysis confirmed that CM was not a direct product of TCE dechlorination at the granular graphite cathode that cis-DCE was an intermediate product of TCE dechlorination, and that 1,1-DCE was not a dechlorination product.

Identification of abiotic and biotic reductive dechlorination in a chlorinated ethene plume after thermal source remediation by means of isotopic and molecular biology tools

DEFF Research Database (Denmark)

Badin, Alice; Broholm, Mette Martina; Jacobsen, Carsten S.

2016-01-01

Thermal tetrachloroethene (PCE) remediation by steam injection in a sandy aquifer led to the release of dissolved organic carbon (DOC) from aquifer sediments resulting in more reduced redox conditions, accelerated PCE biodegradation, and changes in microbial populations. These changes were...... documented by comparing data collected prior to the remediation event and eight years later. Based on the premise that dual C-Cl isotope slopes reflect ongoing degradation pathways, the slopes associated with PCE and TCE suggest the predominance of biotic reductive dechlorination near the source area. PCE...... is supported by the relative lack of Dhc in the downgradient part of the plume. The results of this study show that thermal remediation can enhance the biodegradation of chlorinated ethenes, and that this effect can be traced to the mobilisation of DOC due to steam injection. This, in turn, results in more...

Chain dechlorination of organic chlorinated compounds in alcohol solutions by 60Co gamma-rays, (1)

International Nuclear Information System (INIS)

Sawai, Takeshi; Shimokawa, Toshinari; Sawai, Teruko; Hosoda, Ieji; Kondo, Masaharu.

1975-01-01

A study was made on radiolytic dechlorination of pentachlorobenzene in alkaline alcohol solutions. The dechlorination yield (G(Cl - )) was found to depend on the alcohols used as solvent and the concentrations of the chlorinated benzene and hydroxide ion. The high yields obtained in alkaline 2-propanol, sec-butanol and ethanol indicate a chain process in the dechlorination reaction. The value of G(Cl - ) was highest in 2-propanol, and the principal products generated were potassium chloride, acetone and the lower chlorinated benzenes, while a decrease was seen in the hydroxide ion concentration. The concentrations produced of potassium chloride and acetone, as well as the decrease in hydroxide ion concentration, are all roughly equal at all doses. With increasing irradiation dose, pentachlorobenzene was dechlorinated to tetra, tri, di and monochlorobenzene. 1,2,4,5-tetrachlorobenzene, 1,2,4-trichlorobenzene and 1,4-dichlorobenzene were main products. A discussion is given of the detailed mechanism of the dechlorination in alkaline alcohols and the effect of alcohols on G(Cl - ). (auth.)

Improved Dechlorinating Performance of Upflow Anaerobic Sludge Blanket Reactors by Incorporation of Dehalospirillum multivorans into Granular Sludge

Science.gov (United States)

Hörber, Christine; Christiansen, Nina; Arvin, Erik; Ahring, Birgitte K.

1998-01-01

Dechlorination of tetrachloroethene, also known as perchloroethylene (PCE), was investigated in an upflow anaerobic sludge blanket (UASB) reactor after incorporation of the strictly anaerobic, reductively dechlorinating bacterium Dehalospirillum multivorans into granular sludge. This reactor was compared to the reference 1 (R1) reactor, where the granules were autoclaved to remove all dechlorinating abilities before inoculation, and to the reference 2 (R2) reactor, containing only living granular sludge. All three reactors were fed mineral medium containing 3 to 57 μM PCE, 2 mM formate, and 0.5 mM acetate and were operated under sterile conditions. In the test reactor, an average of 93% (mole/mole) of the effluent chloroethenes was dichloroethene (DCE), compared to 99% (mole/mole) in the R1 reactor. The R2 reactor, with no inoculation, produced only trichloroethene (TCE), averaging 43% (mole/mole) of the effluent chloroethenes. No dechlorination of PCE was observed in an abiotic control consisting of sterile granules without inoculum. During continuous operation with stepwise-reduced hydraulic retention times (HRTs), both the test reactor and the R1 reactor showed conversion of PCE to DCE, even at HRTs much lower than the reciprocal maximum specific growth rate of D. multivorans, indicating that this bacterium was immobilized in the living and autoclaved granular sludge. In contrast, the R2 reactor, with no inoculation of D. multivorans, only converted PCE to TCE under the same conditions. Immobilization could be confirmed by using fluorescein-labeled antibody probes raised against D. multivorans. In granules obtained from the R1 reactor, D. multivorans grew mainly in microcolonies located in the centers of the granules, while in the test reactor, the bacterium mainly covered the surfaces of granules. PMID:9572963

Desorption, partitioning, and dechlorination characteristics of PCBs in sediments in interaction with reactive activated carbon.

Science.gov (United States)

Choi, Hyeok; Lawal, Wasiu; Al-Abed, Souhail R

2015-04-28

Sediment (WHS) in Waukegan Harbor, Illinois, heavily contaminated and aged with polychlorinated biphenyls (PCBs), was treated with reactive activated carbon (RAC) impregnated with palladized iron nanoparticles. Lab test proceeded in a direct mixing configuration of RAC and WHS. A compartment configuration, where RAC was physically separated from WHS, was also designed to trace the sequential transport and fate of PCBs, including desorption, adsorption, dechlorination, and re-partitioning. PCBs, once desorbed from WHS, were immediately sequestrated to RAC and subject to dechlorination. Direct mixing of WHS with RAC was one-order of magnitude more effective for dechlorination than compartment configuration. Compared to their desorption-followed by-adsorption route, direct physical contact of RAC with PCBs bound to WHS exhibited negligible contribution to the availability of PCBs for dechlorination reaction. Addition of RAC even in compartment configuration facilitated PCBs desorption from WHS. However, slow desorption of PCBs limited overall performance, resulting in a five-order of magnitude lower dechlorination yield when compared with treatment of purely aqueous PCBs. The low dechlorination yield reflected real world complexities in treating 3.19% organic carbon-containing WHS aged with PCBs for 40 years. These observations were further supported when compared with results on clean Cesar Creek sediment spiked with 2-chlorinated biphenyls. Copyright © 2015 Elsevier B.V. All rights reserved.

Destruction of TCE Using Oxidative and Reductive Pathways as Potential In-Situ Treatments for the Contaminated Paducah Groundwater

Energy Technology Data Exchange (ETDEWEB)

Lewis, S; Li, Y; Xu, J; Tee, Y; Lynch, Andrew

2007-05-01

When considering reductive technologies for ground water remediation, it is important to understand the underlying principles that govern kinetics of zero-valent metal dechlorination. Studies involving the use of nanoscale metals (characteristic length <100nm) for chloro-organic degradation have increased reaction rates by 1-2 orders of magnitude with minimal intermediate formation. Typically, these metals are synthesized using modifications of the aqueous phase reduction of metal ions using sodium borohydride presented by Glavee and coworkers. The use of a bimetallic system increases the reactivity of the particle surface by incorporating a second metal that can typically act as a hydrogenation promotor.

Enhancement of Degradation and Dechlorination of Trichloroethylene via Supporting Palladium/Iron Bimetallic Nanoparticles onto Mesoporous Silica

Directory of Open Access Journals (Sweden)

Jianjun Wei

2016-07-01

Full Text Available This study is aimed to prevent the agglomeration of Pd/Fe bimetallic nanoparticles and thus improve the efficiency toward degradation and dechlorination of chlorinated organic contaminants. A mesoporous silica with a primary pore diameter of 8.3 nm and a specific surface area of 688 m2/g was prepared and used as the host of Pd/Fe nanoparticles. The Pd/Fe nanoparticles were deposited onto or into the mesoporous silica by reduction of ferrous ion and hexachloropalladate ion in aqueous phase. Batch degradation and dechlorination reactions of trichloroethylene were conducted with initial trichloroethylene concentration of 23.7 mg/L, iron loading of 203 or 1.91 × 103 mg/L and silica loading of 8.10 g/L at 25 °C. Concentration of trichloroethylene occurs on the supported Pd/Fe nanoparticles, with trichloroethylene degrading to 56% and 59% in 30 min on the supported Pd/Fe nanoparticles with weight percentage of palladium to iron at 0.075% and 0.10% respectively. The supported Pd/Fe nanoparticles exhibit better dechlorination activity. When the supported Pd/Fe nanoparticles with a weight percentage of palladium to iron of 0.10% were loaded much less than the bare counterpart, the yield of ethylene plus ethane in 10 h on them was comparable, i.e., 19% vs. 21%. This study offers a future approach to efficiently combine the reactivity of supported Pd/Fe nanoparticles and the adsorption ability of mesoporous silica.

Dechlorination and decomposition of chloroform induced by glow discharge plasma in an aqueous solution

Energy Technology Data Exchange (ETDEWEB)

Liu, Yongjun, E-mail: lyjglow@sohu.com [College of Environmental Science & Engineering, Dalian Maritime University, Dalian 116026 (China); Brook Byers Institute for Sustainable Systems, Georgia Institute of Technology, Atlanta 30332 (United States); Crittenden, John C. [Brook Byers Institute for Sustainable Systems, Georgia Institute of Technology, Atlanta 30332 (United States); Wang, Lei [College of Environmental Science & Engineering, Xiamen University of Technology, Xiamen 361024 (China); Liu, Panliang [Brook Byers Institute for Sustainable Systems, Georgia Institute of Technology, Atlanta 30332 (United States)

2016-05-05

Highlights: • Hydrated electrons played an important role for chloroform decomposition. • Oxygen enhanced hydrolyses are critical for the chloroform mineralization. • Energy efficiency of GDP is higher than those of the typical competitive processes. - Abstract: In this study, efficient dechlorination and decomposition of chloroform (CF) induced by glow discharge plasma (GDP) in contact with a sodium sulfate solution was investigated. Intermediate byproducts were determined by ionic chromatography and headspace gas chromatography, respectively. Results showed that CF can be effectively dechlorinated and decomposed under the action of GDP. Both removal and dechlorination of CF increased with increasing pH and with addition of hydroxyl radical scavengers to the solution. Addition of H{sub 2}O{sub 2} to the solution slightly decreased the CF removal. Formic acid, oxalic acid and dichloromethane were determined as the major intermediate byproducts. Final products were carbon dioxide and hydrochloric acid. Hydrated electrons were the most likely active species responsible for initiation of the dechlorination, and hydroxyl radicals may be the ones for the oxidation of the organic intermediate byproducts. Hydrolyses of the chloromethyl radicals contributed much in the mineralization of the organic chlorine. Reaction mechanism was proposed based on the dechlorination kinetics and the distribution of intermediate byproducts.

Dechlorination and decomposition of chloroform induced by glow discharge plasma in an aqueous solution

International Nuclear Information System (INIS)

Liu, Yongjun; Crittenden, John C.; Wang, Lei; Liu, Panliang

2016-01-01

Highlights: • Hydrated electrons played an important role for chloroform decomposition. • Oxygen enhanced hydrolyses are critical for the chloroform mineralization. • Energy efficiency of GDP is higher than those of the typical competitive processes. - Abstract: In this study, efficient dechlorination and decomposition of chloroform (CF) induced by glow discharge plasma (GDP) in contact with a sodium sulfate solution was investigated. Intermediate byproducts were determined by ionic chromatography and headspace gas chromatography, respectively. Results showed that CF can be effectively dechlorinated and decomposed under the action of GDP. Both removal and dechlorination of CF increased with increasing pH and with addition of hydroxyl radical scavengers to the solution. Addition of H_2O_2 to the solution slightly decreased the CF removal. Formic acid, oxalic acid and dichloromethane were determined as the major intermediate byproducts. Final products were carbon dioxide and hydrochloric acid. Hydrated electrons were the most likely active species responsible for initiation of the dechlorination, and hydroxyl radicals may be the ones for the oxidation of the organic intermediate byproducts. Hydrolyses of the chloromethyl radicals contributed much in the mineralization of the organic chlorine. Reaction mechanism was proposed based on the dechlorination kinetics and the distribution of intermediate byproducts.

Effect of a base-catalyzed dechlorination process on the genotoxicity of PCB-contaminated soil

Energy Technology Data Exchange (ETDEWEB)

DeMarini, D.M.; Houk, V.S.; Kornel, A.; Rogers, C.J.

1992-01-01

We evaluated the genotoxicity of dichloromethane (DCM) extracts of PCB-contaminated soil before and after the soil had been treated by a base-catalyzed dechlorination process, which involved heating a mixture of the soil, polyethylene glycol, and sodium hydroxide to 250-350 C. This dechlorination process reduced by over 99% the PCB concentration in the soil, which was initially 2,200 ppm. The DCM extracts of both control and treated soils were not mutagenic in strain TA100 of Salmonella, but they were mutagenic in strain TA98. The base-catalyzed dechlorination process reduced the mutagenic potency of the soil by approximately one-half. The DCM extracts of the soils before and after treatment were equally genotoxic in a prophage-induction assay in E. coli, which detects some chlorinated organic carcinogens that were not detected by the Salmonella mutagenicity assay. These results show that treatment of PCB-contaminated soil by this base-catalyzed dechlorination process did not increase the genotoxicity of the soil.

INFLUENCES OF PH AND CURRENT ON ELECTROLYTIC DECHLORINATION OF TRICHLOROETHYLENE AT A GRANULAR-GRAPHITE PACKED ELECTRODE

Science.gov (United States)

Electrolytic dechlorination using a granular-graphite packed cathode is an alternative method for the remediation of chlorinated organic compounds. Its effectiveness under various conditions needs experimental investigation. Dechlorination of trichloroethylene (TCE) was conducted...

Microbial transformation and degradation of polychlorinated biphenyls

Energy Technology Data Exchange (ETDEWEB)

Field, Jim A. [Department of Chemical and Environmental Engineering, University of Arizona, PO Box 210011, Tucson, AZ 85721 (United States)], E-mail: jimfield@email.arizona.edu; Sierra-Alvarez, Reyes [Department of Chemical and Environmental Engineering, University of Arizona, PO Box 210011, Tucson, AZ 85721 (United States)

2008-09-15

This paper reviews the potential of microorganisms to transform polychlorinated biphenyls (PCBs). In anaerobic environments, higher chlorinated biphenyls can undergo reductive dehalogenation. Meta- and para-chlorines in PCB congeners are more susceptible to dechlorination than ortho-chlorines. Anaerobes catalyzing PCB dechlorination have not been isolated in pure culture but there is strong evidence from enrichment cultures that some Dehalococcoides spp. and other microorganisms within the Chloroflexi phylum can grow by linking the oxidation of H{sub 2} to the reductive dechlorination of PCBs. Lower chlorinated biphenyls can be co-metabolized aerobically. Some aerobes can also grow by utilizing PCB congeners containing only one or two chlorines as sole carbon/energy source. An example is the growth of Burkholderia cepacia by transformation of 4-chlorobiphenyl to chlorobenzoates. The latter compounds are susceptible to aerobic mineralization. Higher chlorinated biphenyls therefore are potentially fully biodegradable in a sequence of reductive dechlorination followed by aerobic mineralization of the lower chlorinated products. - Higher chlorinated biphenyls are potentially fully biodegradable in a sequence of anaerobic reductive dechlorination followed by aerobic mineralization of the lower chlorinated products.

Microbial transformation and degradation of polychlorinated biphenyls

International Nuclear Information System (INIS)

Field, Jim A.; Sierra-Alvarez, Reyes

2008-01-01

This paper reviews the potential of microorganisms to transform polychlorinated biphenyls (PCBs). In anaerobic environments, higher chlorinated biphenyls can undergo reductive dehalogenation. Meta- and para-chlorines in PCB congeners are more susceptible to dechlorination than ortho-chlorines. Anaerobes catalyzing PCB dechlorination have not been isolated in pure culture but there is strong evidence from enrichment cultures that some Dehalococcoides spp. and other microorganisms within the Chloroflexi phylum can grow by linking the oxidation of H 2 to the reductive dechlorination of PCBs. Lower chlorinated biphenyls can be co-metabolized aerobically. Some aerobes can also grow by utilizing PCB congeners containing only one or two chlorines as sole carbon/energy source. An example is the growth of Burkholderia cepacia by transformation of 4-chlorobiphenyl to chlorobenzoates. The latter compounds are susceptible to aerobic mineralization. Higher chlorinated biphenyls therefore are potentially fully biodegradable in a sequence of reductive dechlorination followed by aerobic mineralization of the lower chlorinated products. - Higher chlorinated biphenyls are potentially fully biodegradable in a sequence of anaerobic reductive dechlorination followed by aerobic mineralization of the lower chlorinated products

Modeling multi-component transport and enhanced anaerobic dechlorination processes in a single fracture-clay matrix system

DEFF Research Database (Denmark)

Chambon, Julie Claire Claudia; Broholm, Mette Martina; Binning, Philip John

2010-01-01

Clayey tills contaminated with chlorinated solvents are a threat to groundwater and are difficult to remediate. A numerical model is developed for assessing leaching processes and for simulating the remediation via enhanced anaerobic dechlorination. The model simulates the transport...... to the physical processes, mainly diffusion in the matrix, than to the biogeochemical processes, when dechlorination is assumed to take place in a limited reaction zone only. The inclusion of sequential dechlorination in clay fracture transport models is crucial, as the contaminant flux to the aquifer...

Reductive Anaerobic Biological In Situ Treatment Technology Treatability Testing

National Research Council Canada - National Science Library

Alleman, Bruce

2002-01-01

Enhanced biological reductive dechlorination (EBRD) shows a great deal of promise for efficiently treating groundwater contaminated with chlorinated solvents, but demonstration sites around the country were reporting mixed results...

Parameter Sensitivity and Laboratory Benchmarking of a Biogeochemical Process Model for Enhanced Anaerobic Dechlorination

Science.gov (United States)

Kouznetsova, I.; Gerhard, J. I.; Mao, X.; Barry, D. A.; Robinson, C.; Brovelli, A.; Harkness, M.; Fisher, A.; Mack, E. E.; Payne, J. A.; Dworatzek, S.; Roberts, J.

2008-12-01

A detailed model to simulate trichloroethene (TCE) dechlorination in anaerobic groundwater systems has been developed and implemented through PHAST, a robust and flexible geochemical modeling platform. The approach is comprehensive but retains flexibility such that models of varying complexity can be used to simulate TCE biodegradation in the vicinity of nonaqueous phase liquid (NAPL) source zones. The complete model considers a full suite of biological (e.g., dechlorination, fermentation, sulfate and iron reduction, electron donor competition, toxic inhibition, pH inhibition), physical (e.g., flow and mass transfer) and geochemical processes (e.g., pH modulation, gas formation, mineral interactions). Example simulations with the model demonstrated that the feedback between biological, physical, and geochemical processes is critical. Successful simulation of a thirty-two-month column experiment with site soil, complex groundwater chemistry, and exhibiting both anaerobic dechlorination and endogenous respiration, provided confidence in the modeling approach. A comprehensive suite of batch simulations was then conducted to estimate the sensitivity of predicted TCE degradation to the 36 model input parameters. A local sensitivity analysis was first employed to rank the importance of parameters, revealing that 5 parameters consistently dominated model predictions across a range of performance metrics. A global sensitivity analysis was then performed to evaluate the influence of a variety of full parameter data sets available in the literature. The modeling study was performed as part of the SABRE (Source Area BioREmediation) project, a public/private consortium whose charter is to determine if enhanced anaerobic bioremediation can result in effective and quantifiable treatment of chlorinated solvent DNAPL source areas. The modelling conducted has provided valuable insight into the complex interactions between processes in the evolving biogeochemical systems

Desorption, partitioning, and dechlorination characteristics of PCBs in sediments in interaction with reactive activated carbon

International Nuclear Information System (INIS)

Choi, Hyeok; Lawal, Wasiu; Al-Abed, Souhail R.

2015-01-01

Highlights: • Problematic aged real PCBs-contaminated sediment (WHS) was examined. • Performance of reactive activated carbon (RAC) impregnated with Pd–ZVI was tested. • Fate and transport of PCBs bound to WHS in the presence of RAC was fully traced. • Direct mixing configuration was compared with compartment configuration. • Results reflected real world complexities associated with slow desorption of PCBs. - Abstract: Sediment (WHS) in Waukegan Harbor, Illinois, heavily contaminated and aged with polychlorinated biphenyls (PCBs), was treated with reactive activated carbon (RAC) impregnated with palladized iron nanoparticles. Lab test proceeded in a direct mixing configuration of RAC and WHS. A compartment configuration, where RAC was physically separated from WHS, was also designed to trace the sequential transport and fate of PCBs, including desorption, adsorption, dechlorination, and re-partitioning. PCBs, once desorbed from WHS, were immediately sequestrated to RAC and subject to dechlorination. Direct mixing of WHS with RAC was one-order of magnitude more effective for dechlorination than compartment configuration. Compared to their desorption-followed by-adsorption route, direct physical contact of RAC with PCBs bound to WHS exhibited negligible contribution to the availability of PCBs for dechlorination reaction. Addition of RAC even in compartment configuration facilitated PCBs desorption from WHS. However, slow desorption of PCBs limited overall performance, resulting in a five-order of magnitude lower dechlorination yield when compared with treatment of purely aqueous PCBs. The low dechlorination yield reflected real world complexities in treating 3.19% organic carbon-containing WHS aged with PCBs for 40 years. These observations were further supported when compared with results on clean Cesar Creek sediment spiked with 2-chlorinated biphenyls

Desorption, partitioning, and dechlorination characteristics of PCBs in sediments in interaction with reactive activated carbon

Energy Technology Data Exchange (ETDEWEB)

Choi, Hyeok, E-mail: hchoi@uta.edu [Department of Civil Engineering, The University of Texas at Arlington, 416 Yates Street, Arlington, TX 76019-0308 (United States); Environmental and Earth Sciences Program, The University of Texas at Arlington, 500 Yates Street, Arlington, TX 76019-0049 (United States); Lawal, Wasiu [Environmental and Earth Sciences Program, The University of Texas at Arlington, 500 Yates Street, Arlington, TX 76019-0049 (United States); Al-Abed, Souhail R. [National Risk Management Research Laboratory, U.S. Environmental Protection Agency, 26 W. Martin Luther King Dr., Cincinnati, OH 45268 (United States)

2015-04-28

Highlights: • Problematic aged real PCBs-contaminated sediment (WHS) was examined. • Performance of reactive activated carbon (RAC) impregnated with Pd–ZVI was tested. • Fate and transport of PCBs bound to WHS in the presence of RAC was fully traced. • Direct mixing configuration was compared with compartment configuration. • Results reflected real world complexities associated with slow desorption of PCBs. - Abstract: Sediment (WHS) in Waukegan Harbor, Illinois, heavily contaminated and aged with polychlorinated biphenyls (PCBs), was treated with reactive activated carbon (RAC) impregnated with palladized iron nanoparticles. Lab test proceeded in a direct mixing configuration of RAC and WHS. A compartment configuration, where RAC was physically separated from WHS, was also designed to trace the sequential transport and fate of PCBs, including desorption, adsorption, dechlorination, and re-partitioning. PCBs, once desorbed from WHS, were immediately sequestrated to RAC and subject to dechlorination. Direct mixing of WHS with RAC was one-order of magnitude more effective for dechlorination than compartment configuration. Compared to their desorption-followed by-adsorption route, direct physical contact of RAC with PCBs bound to WHS exhibited negligible contribution to the availability of PCBs for dechlorination reaction. Addition of RAC even in compartment configuration facilitated PCBs desorption from WHS. However, slow desorption of PCBs limited overall performance, resulting in a five-order of magnitude lower dechlorination yield when compared with treatment of purely aqueous PCBs. The low dechlorination yield reflected real world complexities in treating 3.19% organic carbon-containing WHS aged with PCBs for 40 years. These observations were further supported when compared with results on clean Cesar Creek sediment spiked with 2-chlorinated biphenyls.

Dechlorination of PCBs in Aqueous Extracts from Soils Contaminated by PCBs by Application of Zero-valent Nano-iron in Statu Nascendi. Influence of Microwaves on the Rate of Reaction

Czech Academy of Sciences Publication Activity Database

Kaštánek, František; Maléterová, Ywetta; Šolcová, Olga; Kaštánek, P.

2010-01-01

Roč. 1, č. 1 (2010), s. 50-56 R&D Projects: GA AV ČR KAN400720701; GA ČR GA104/09/0694 Keywords : nano-Fe * PCB * reductive dechlorination Subject RIV: CI - Industrial Chemistry, Chemical Engineering

Biological reduction of chlorinated solvents: Batch-scale geochemical modeling

Science.gov (United States)

Kouznetsova, Irina; Mao, Xiaomin; Robinson, Clare; Barry, D. A.; Gerhard, Jason I.; McCarty, Perry L.

2010-09-01

Simulation of biodegradation of chlorinated solvents in dense non-aqueous phase liquid (DNAPL) source zones requires a model that accounts for the complexity of processes involved and that is consistent with available laboratory studies. This paper describes such a comprehensive modeling framework that includes microbially mediated degradation processes, microbial population growth and decay, geochemical reactions, as well as interphase mass transfer processes such as DNAPL dissolution, gas formation and mineral precipitation/dissolution. All these processes can be in equilibrium or kinetically controlled. A batch modeling example was presented where the degradation of trichloroethene (TCE) and its byproducts and concomitant reactions (e.g., electron donor fermentation, sulfate reduction, pH buffering by calcite dissolution) were simulated. Local and global sensitivity analysis techniques were applied to delineate the dominant model parameters and processes. Sensitivity analysis indicated that accurate values for parameters related to dichloroethene (DCE) and vinyl chloride (VC) degradation (i.e., DCE and VC maximum utilization rates, yield due to DCE utilization, decay rate for DCE/VC dechlorinators) are important for prediction of the overall dechlorination time. These parameters influence the maximum growth rate of the DCE and VC dechlorinating microorganisms and, thus, the time required for a small initial population to reach a sufficient concentration to significantly affect the overall rate of dechlorination. Self-inhibition of chlorinated ethenes at high concentrations and natural buffering provided by the sediment were also shown to significantly influence the dechlorination time. Furthermore, the analysis indicated that the rates of the competing, nonchlorinated electron-accepting processes relative to the dechlorination kinetics also affect the overall dechlorination time. Results demonstrated that the model developed is a flexible research tool that is

PCE dechlorination by non-Dehalococcoides in a microbial electrochemical system.

Science.gov (United States)

Yu, Jaecheul; Park, Younghyun; Nguyen, Van Khanh; Lee, Taeho

2016-08-01

The bioremediation of tetrachloroethene (perchloroethene; PCE) contaminated sites generally requires a supply of some fermentable organic substrates as an electron donor. On the other hand, organic substrates can induce the massive growth of microorganisms around the injection wells, which can foul the contaminated subsurface environment. In this study, PCE dechlorination to ethene was performed in a microbial electrochemical system (MES) using the electrode (a cathode polarized at -500 mV vs. standard hydrogen electrode) as the electron donor. Denaturing gel gradient electrophoresis and pyrosequencing revealed a variety of non-Dehalococcoides bacteria dominant in MES, such as Acinetobacter sp. (25.7 % for AS1 in suspension of M3), Rhodopseudomonas sp. (10.5 % for AE1 and 10.1 % for AE2 in anodic biofilm of M3), Pseudomonas aeruginosa (22.4 % for BS1 in suspension of M4), and Enterobacter sp. (21.7 % for BE1 in anodic biofilm of M4) which are capable of electron transfer, hydrogen production and dechlorination. The Dehalococcoides group, however, was not detected in this system. Therefore, these results suggest that a range of bacterial species outside the Dehalococcoides can play an important role in the microbial electrochemical dechlorination process, which may lead to innovative bioremediation technology.

On the mechanism of dechlorination of polychlorinated biphenyls (PCBs) induced by electron beam irradiation in aqueous and aqueous micellar solutions, transformer oil, and sediment

International Nuclear Information System (INIS)

Chaychian, M.; Silverman, J.; Al-Sheirkhly, M.

2011-01-01

Complete text of publication follows. The widespread release of PCBs into the environment presents a serious problem due to their persistence and toxicity. Ionizing radiation, such as gamma rays and high-energy electron beam, is remarkably effective in dechlorinating PCBs into biphenyls. The kinetics of the reductive dechlorination of PCBs in aqueous and aqueous micellar solutions and in transformer oil is being studied by pulse radiolysis and steady-state radiolysis. In aqueous micellar solutions, dichlori-, tetrachloro-, and decachlorobiphenyl congeners were solubilized in water using a commercially available non-ionic surfactant, Triton X-100, and subsequently pulse irradiated by electron accelerator using optical detection method. The reaction rate constant between decachlorobiphenyl and aqueous electrons e aq ·- , and Triton with e aq ·- in the 2% Triton solution, were measured as 2.6 x 10 9 Lmol -1 s -1 and 1.2 x 10 7 Lmol -1 s -1 , respectively. We have also measured in aqueous solutions, the reaction rate constant of e aq ·- with dichlorobiphenyl as 3.8 x 10 9 Lmol -1 s -1 . In aqueous-propanol, the reaction rate constants of e aq ·- with dichlorobiphenyl, tetrachlorobiphenyl, and dechachlorobiphenyl are 2 x 10 9 Lmol -1 s -1 , 3 x 10 9 Lmol -1 s -1 , and 7 x 10 9 Lmol -1 s -1 , respectively. In addition to the presence of PCBs as high-dielectric component, transformer oil contains many aromatic hydrocarbons; the most abundant being biphenyl, fluorine, and phenanthrene. Solvated electrons formed by irradiation of the oil react either with PCB to lead to dechlorination or with the aromatic hydrocarbons present in the oil to form radical anions. These species are shown to transfer an electron to chlorinated biphenyls relative rapidly, leading to dechlorination. The rate constants for several such reactions, determined in 2-propanol solutions, are in the range of 10 7 - 10 8 Lmol -1 s -1 . These rapid reactions explain why PCB can be dechlorinated in oil

Dechlorinating reaction of organic chlorides

Energy Technology Data Exchange (ETDEWEB)

Yahata, Taneaki; Kihara, Shinji [Japan Atomic Energy Research Inst., Oarai, Ibaraki (Japan). Oarai Research Establishment; Ohuchi, Misao

1996-06-01

Dechlorination has been examined by the reaction between iron, aluminum powder or CaO and organic chlorides such as C{sub 2}HCl{sub 3} and CH{sub 2}Cl{sub 2}. Progress of the reaction was analyzed with mass spectrometer. The reaction between iron and organic chloride was rapidly occurred at the temperature between 350 and 440degC in an atmosphere of argon. Above 380degC, more than 99.5% of C{sub 2}HCl{sub 3} was decomposed within approximately 100 minutes. At 440degC, approximately 60% of C{sub 2}HCl{sub 3} was decomposed by the reaction with aluminium powder within approximately 100 minutes. At 440degC, reaction between C{sub 2}HCl{sub 3} and CaO powder were occurred rapidly in an atmosphere of argon to form CaCl{sub 2} and free carbon. Also in an atmosphere of air, nearly the same result was obtained. In this reaction, CaCl{sub 2}, CO and CO{sub 2} were formed. CH{sub 2}Cl{sub 2} was also decomposed by the reaction with iron at the temperature between 380 and 440degC. In the reaction, FeCl{sub 2}, carbon and hydrogen were formed. CH{sub 3}{sup +} and CH{sub 4} were observed during the dechlorinating reaction of CH{sub 2}Cl{sub 2}. Variation in particle size of iron powder such as 100, 150 and 250 mesh did not affect the reaction rate. (author)

Effects Of Aging And Oxidation Of Palladized Iron Embedded In Activated Carbon On The Dechlorination Of 2-Chlorobiphenyl

Science.gov (United States)

Reactive activated carbon (RAC) impregnated with palladized iron has been developed to effectively treat polychlorinated biphenyls (PCBs) in the environment by coupling adsorption and dechlorination of PCBs. In this study, we addressed the dechlorination reactivity and capacity ...

DDT, DDD, AND DDE DECHLORINATION BY ZERO-VALENT IRON

Science.gov (United States)

Traditionally, destruction of DDT [1,1,1-trichIoro-2,2-bis(p-chlorophenyl)ethane] for environmental remediation required high-energy processes such as incineration. Here, the capability of powdered zero-valent iron to dechlorinate DDT and related compounds at room tempera...

Enhanced CAH dechlorination in a low permeability, variably-saturated medium

Science.gov (United States)

Martin, J.P.; Sorenson, K.S.; Peterson, L.N.; Brennan, R.A.; Werth, C.J.; Sanford, R.A.; Bures, G.H.; Taylor, C.J.; ,

2002-01-01

An innovative pilot-scale field test was performed to enhance the anaerobic reductive dechlorination (ARD) of chlorinated aliphatic hydrocarbons (CAHs) in a low permeability, variably-saturated formation. The selected technology combines the use of a hydraulic fracturing (fracking) technique with enhanced bioremediation through the creation of highly-permeable sand- and electron donor-filled fractures in the low permeability matrix. Chitin was selected as the electron donor because of its unique properties as a polymeric organic material and based on the results of lab studies that indicated its ability to support ARD. The distribution and impact of chitin- and sand-filled fractures to the system was evaluated using hydrologic, geophysical, and geochemical parameters. The results indicate that, where distributed, chitin favorably impacted redox conditions and supported enhanced ARD of CAHs. These results indicate that this technology may be a viable and cost-effective approach for remediation of low-permeability, variably saturated systems.

Anaerobic reductive dehalogenation of polychlorinated dioxins

Energy Technology Data Exchange (ETDEWEB)

Bunge, Michael [Aarhus Univ. (DK). Dept. of Biological Sciences, Microbiology, and Interdisciplinary Nanoscience Centre (iNANO); Lechner, Ute [Halle-Wittenberg Univ., Halle (Germany). Inst. of Biology/Microbiology

2009-09-15

Polychlorinated dibenzo-p-dioxins and -furans (PCDD/Fs) are among the most harmful environmental contaminants. Their widespread distribution due to unintentional or unknown release coincides with environmental persistence, acute and chronic toxicity to living organisms, and long-term effects due to the compounds' tendency for bioaccumulation and biomagnification. While microbial aerobic degradation of PCDD/Fs is mainly reported for the turnover of low chlorinated congeners, this review focuses on anaerobic reductive dehalogenation, which may constitute a potential remediation strategy for polychlorinated compounds in soils and sediments. Microorganisms in sediments and in microcosms or enrichment cultures have been shown to be involved in the reductive dechlorination of dioxins. Bacteria related to the genus Dehalococcoides are capable of the reductive transformation of dioxins leading to lower chlorinated dioxins including di- and monochlorinated congeners. Thus, reductive dehalogenation might be one of the very few mechanisms able to mediate the turnover of polychlorinated dioxins by reducing their toxicity and paving the way for a subsequent breakdown of the carbon skeleton. (orig.)

Reductive Dehalogenation of Trichloroacetic Acid by Trichlorobacter thiogenes gen. nov., sp. nov.

Science.gov (United States)

De Wever, Helene; Cole, James R.; Fettig, Michael R.; Hogan, Deborah A.; Tiedje, James M.

2000-01-01

A bacterium able to grow via reductive dechlorination of trichloroacetate was isolated from anaerobic soil enrichments. The isolate, designated strain K1, is a member of the δ proteobacteria and is related to other known sulfur and ferric iron reducers. In anaerobic mineral media supplemented with acetate and trichloroacetate, its doubling time was 6 h. Alternative electron donor and acceptors were acetoin and sulfur or fumarate, respectively. Trichloroacetate dehalogenation activity was constitutively present, and the dechlorination product was dichloroacetate and chloride. Trichloroacetate conversion seemed to be coupled to a novel sulfur-sulfide redox cycle, which shuttled electrons from acetate oxidation to trichloroacetate reduction. In view of its unique physiological characteristics, the name Trichlorobacter thiogenes is suggested for strain K1. PMID:10831402

Reductive dehalogenation of chlorophenols by Desulfomonile tiedjei DCB-1.

Science.gov (United States)

Mohn, W W; Kennedy, K J

1992-01-01

Reductive dehalogenation of chlorophenols has been reported in undefined anaerobic cultures but never before in an anaerobic pure culture. We found that the sulfate-reducing bacterium Desulfomonile tiedjei DCB-1 reductively dehalogenates pentachlorophenol (PCP) and other chlorophenols. The maximum rate of PCP dechlorination observed was 54 mu mol of Cl- h-1 g of protein-1. 3-Chlorobenzoate appeared to serve as a required inducer for PCP dehalogenation; however, neither PCP nor 3-chlorophenol induced dehalogenation. Dehalogenation was catalyzed by living cells, and formate served as a required electron donor. D. tiedjei dehalogenated meta-chlorine substituents of chlorophenols (i.e., PCP was degraded to 2,4,6-trichlorophenol). Generally, more highly chlorinated phenol congeners were more readily dechlorinated, and 3-chlorophenol was not dehalogenated. Growing cultures dehalogenated PCP, but greater than 10 microM PCP (approximately 1.7 mmol g of protein-1) reversibly inhibited growth. PMID:1599254

Oxidation-reduction processes in ground water at Naval Weapons Industrial Reserve Plant, Dallas, Texas

Science.gov (United States)

Jones, S.A.; Braun, Christopher L.; Lee, Roger W.

2003-01-01

Concentrations of trichloroethene in ground water at the Naval Weapons Industrial Reserve Plant in Dallas, Texas, indicate three source areas of chlorinated solvents?building 1, building 6, and an off-site source west of the facility. The presence of daughter products of reductive dechlorination of trichloroethene, which were not used at the facility, south and southwest of the source areas are evidence that reductive dechlorination is occurring. In places south of the source areas, dissolved oxygen concentrations indicated that reduction of oxygen could be the dominant process, particularly south of building 6; but elevated dissolved oxygen concentrations south of building 6 might be caused by a leaking water or sewer pipe. The nitrite data indicate that denitrification is occurring in places; however, dissolved hydrogen concentrations indicate that iron reduction is the dominant process south of building 6. The distributions of ferrous iron indicate that iron reduction is occurring in places south-southwest of buildings 6 and 1; dissolved hydrogen concentrations generally support the interpretation that iron reduction is the dominant process in those places. The generally low concentrations of sulfide indicate that sulfate reduction is not a key process in most sampled areas, an interpretation that is supported by dissolved hydrogen concentrations. Ferrous iron and dissolved hydrogen concentrations indicate that ferric iron reduction is the primary oxidation-reduction process. Application of mean first-order decay rates in iron-reducing conditions for trichloroethene, dichloroethene, and vinyl chloride yielded half-lives for those solvents of 231, 347, and 2.67 days, respectively. Decay rates, and thus half-lives, at the facility are expected to be similar to those computed. A weighted scoring method to indicate sites where reductive dechlorination might be likely to occur indicated strong evidence for anaerobic biodegradation of chlorinated solvents at six sites

Potential for waste reduction

International Nuclear Information System (INIS)

Warren, J.L.

1990-01-01

The author focuses on wastes considered hazardous under the Resource Conservation and Recovery Act. This chapter discusses wastes that are of interest as well as the factors affecting the quantity of waste considered available for waste reduction. Estimates are provided of the quantities of wastes generated. Estimates of the potential for waste reduction are meaningful only to the extent that one can understand the amount of waste actually being generated. Estimates of waste reduction potential are summarized from a variety of government and nongovernment sources

Dechlorination of 1,2– dichloroethane by Pseudomonas aeruginosa ...

African Journals Online (AJOL)

As part of our attempt at isolating and stocking some indigenous microbial species, we isolated a bacterium from a waste dumpsite with appreciable dechlorination activity. 16S rDNA profiling revealed the isolate to be a strain of Pseudomonas aeruginosa and the sequence has been deposited in the NCBI nucleotide ...

Session 6: Synergistic effects in selective hydro dechlorination on bimetallic catalysts

Energy Technology Data Exchange (ETDEWEB)

Srebowata, A.; Legawiec-Jarzyna, M.; Juszczyk, W.; Karpinski, Z. [Institute of Physical Chemistry of PAS, Warszawa (Poland)

2004-07-01

Catalytic removal of chlorine from organic compounds has recently attracted increasing interest. A special case of this important environmental issue is the hydro-dechlorination (HDC). HDC of three compounds was investigated: dichloro-difluoro-methane, carbon tetrachloride and 1,2-dichloroethane. Since the most desired products of the mentioned reactions are: CH{sub 2}F{sub 2}, chloroform and ethene (highlighted below), our attention was focused at the rates of formation of these products: CCl{sub 2}F{sub 2} {yields} CH{sub 2}F{sub 2} {yields} CH{sub 4}; CCl{sub 4} {yields} CHCl{sub 3} {yields} CH{sub 4}; ClCH{sub 2}-CH{sub 2}Cl {yields} CH{sub 2}=CH{sub 2} {yields} CH{sub 3}CH{sub 3}. In fact, Selection of the most suitable HDC catalyst depends on the C-Cl bond strength in a molecule subjected to reaction. A relatively weak C-Cl bond in CCl{sub 4} (306 kJ/mol) does not require a high dechlorination potential, which can be directly correlated with the strength of a metal-chlorine bond. Thus Pt is a better catalyst than Pd in CCl{sub 4} reaction. In addition, an improvement of Pt-based catalysts can be achieved by alloying with metals which bind chlorine even less strongly than Pt (i.e. with Au). In contrast, Pd is a better catalyst than Pt for hydro-dechlorination of a stronger C-Cl bond (about 350 kJ/mol), present in CCl{sub 2}F{sub 2} and ClCH{sub 2}-CH{sub 2}Cl. However, a good performance of Pd can still be improved by alloying it with much less active Pt (or Au), as a result of weakening of the metal-chlorine bond. This effect leads to a higher selectivity toward partial dehalogenation, i.e. to formation of a desired CH{sub 2}F{sub 2} (at the expense of CH{sub 4}). In a similar way, combination of Pd with Co and Cu is rationalized. For HDC of ClCH{sub 2}-CH{sub 2}Cl, addition of a metal characterized by a poor hydrogenation strength (like Cu or Ag) to Pd (or Pt) reduces undesired formation of ethane, giving higher yields of ethene. (authors)

Solidification of metal chloride waste from pyrochemical process via dechlorination-chlorination reaction system

Energy Technology Data Exchange (ETDEWEB)

Park, H.S.; Cho, I.H.; Lee, K.R.; Choi, J.H.; Eun, H.C.; Kim, I.T.; Park, G.I. [Korea Atomic Energy Research Inst., Deajeon (Korea, Republic of)

2014-07-01

The metal chloride wastes generated from the pyro-chemical process to recover uranium and TRUs has been considered as a problematic waste due to the high volatility and low compatibility with conventional silicate glass. Our research group has suggested the dechlorination approach for the solidification of this kind of waste by using a synthetic composite, SAP (SiO{sub 2}-Al{sub 2}O{sub 3}-P{sub 2}O{sub 5}). During the dechlorination, metal elements are chemically interacted with the inorganic composite, SAP, while chlorine is vaporized as gaseous chlorine. Metal elements in the salt were immobilized into phosphate and silicate glass which are uniformly distributed in tens of nm scale. During the dechlorination, gaseous chlorine is captured by Li{sub 2}O-Li{sub 2}O{sub 2} composite that can be converted into metal chloride (LiCl). About 98wt% of oxide composite was converted into LiCl that can be used as an electrolyte in the electrochemical process. The method suggested in this study can provide a chance to minimize the waste volume for the final disposal of salt wastes from a pyro-chemical process. (author)

Cost and Performance Report for Reductive Anaerobic Biological in Situ Treatment Technology (RABITT) Treatability Testing

National Research Council Canada - National Science Library

Alleman, Bruce

2003-01-01

Enhanced biological reductive dechlorination (EBRD) shows a great deal of promise for efficiently treating groundwater contaminated with chlorinated solvents, but demonstration sites around the country were reporting mixed results...

Borohydride, micellar, and exciplex-enhanced dechlorination of chlorobiphenyls

Energy Technology Data Exchange (ETDEWEB)

Epling, G.A.; Florio, E.M.; Bourque, A.J.; Qian, H.H.; Stuart, J.D.

1988-08-01

The photodechlorination of polychlorinated biphenyls (PCB's) has been studied in the presence of sodium borohydride, detergents, and exciplex-forming additives. In a family of 13 representative PCB's these variations generally led to a dramatically increased rate of photodegradation. Further, the products of photoreaction in the presence of sodium borohydride are more cleanly the simple dechlorinated aromatics, with fewer side reactions than observed with ordinary photolysis.

Changing redox potential by controlling soil moisture and addition of inorganic oxidants to dissipate pentachlorophenol in different soils

International Nuclear Information System (INIS)

Lin Jiajiang; He Yan; Xu Jianming

2012-01-01

The potential for dissipation of pentachlorophenol (PCP) was investigated in soils from four different sites in China. These were an umbraqualf (Soil 1), a Plinthudult (Soil 2), a Haplustalf (Soil 3) and an Argiustoll (Soil 4) which were either flooded, to produce anaerobic conditions, or incubated aerobically at 60% water-holding capacity (WHC). The dissipation of PCP in Soil 1 at 60% WHC was higher than under flooded condition, while the opposite occurred in the other three soils. Under flooded conditions, the redox potential decreased significantly in Soil 1 and Soil 4, where sulphate reduction was occurred and the dissipation of PCP was statistically significant (about 96% and 98%, respectively) at the end of incubation. After addition of inorganic oxidants, dissipation of PCP was significantly inhibited by FeCl 3 , while Na 2 SO 4 and NaNO 3 had different effects, depending upon the soil type. - Highlights: ► The extent of the aerobic/anaerobic interface depends upon the soil properties. ► The dissipation of PCP was accelerated in some soils due to the soil-water interface. ► The addition of oxidants inhibited the decrease in soil redox potential. ► Most external oxidants added under flooded condition inhibited PCP dechlorination. - The addition of inorganic oxidants limited the decrease in redox potential and inhibited the reductive dechlorination of pentachlorophenol.

Understanding Hydrothermal Dechlorination of PVC by Focusing on the Operating Conditions and Hydrochar Characteristics

Directory of Open Access Journals (Sweden)

Tian Li

2017-03-01

Full Text Available To remove chlorine from chlorinated wastes efficiently, the hydrothermal treatment (HT of PVC was investigated with a lower alkaline dosage in this work. Some typical operating conditions were investigated to find out the most important factor affecting the dechlorination efficiency (DE. The FTIR technique was employed to detect the functional groups in PVC and hydrochars generated to reveal the possible pathways for chlorine removal. The results show that the HT temperature was a key parameter to control the dechlorination reaction rate. At a HT temperature of 240 °C, about 94.3% of chlorine could be removed from the PVC with 1% NaOH. The usage of NaOH was helpful for chlorine removal, while a higher dosage might also hinder this process because of the surface poisoning and coverage of free sites. To some extent, the DE was increased with the residence time. At a residence time of 30 min, the DE reached a maximum of 76.74%. A longer residence time could promote the generation of pores in hydrochar which is responsible for the reduction in DE because of the re-absorption of water-soluble chlorine. According to the FTIR results, the peak intensities of both C=CH and C=C stretching vibrations in hydrochar were increased, while the peak at around 3300 cm−1 representing the –OH group was not obvious, indicating that the dehydrochlorination (elimination reaction was a main route for chlorine removal under these conditions studied in this work.

Effect of emplaced nZVI mass and groundwater velocity on PCE dechlorination and hydrogen evolution in water-saturated sand

International Nuclear Information System (INIS)

Kim, Hye-Jin; Leitch, Megan; Naknakorn, Bhanuphong; Tilton, Robert D.; Lowry, Gregory V.

2017-01-01

Highlights: • Reactivity of nZVI increased linearly with nZVI concentration above 10 g/L, but was non-linear below 10 g/L. • nZVI reactivity with PCE is more sensitive to solution redox potential than solution pH. • Mass transfer limits the reactivity of emplaced nZVI under typical groundwater flow velocity. • Lowering pH increases H_2 evolution from nZVI more than reactivity with PCE. • Design of nZVI remediation strategies should consider mass loading and flow velocity on performance and lifetime. - Abstract: The effect of nZVI mass loading and groundwater velocity on the tetrachloroethylene (PCE) dechlorination rate and the hydrogen evolution rate for poly(maleic acid-co-olefin) (MW = 12 K) coated nZVI was examined. In batch reactors, the PCE reaction rate constant (3.7 × 10"−"4 L hr"−"1 m"−"2) and hydrogen evolution rate constant (1.4 nanomol L hr"−"1 m"−"2) were independent of nZVI concentration above 10 g/L, but the PCE dechlorination rate decreased and the hydrogen evolution rate increased for nZVI concentration below 10 g/L. The nonlinearity between nZVI mass loading and PCE dechlorination and H_2 evolution was explained by differences in pH and E_h at each nZVI mass loading; PCE reactivity increased when solution E_h decreased, and the H_2 evolution rate increased with decreasing pH. Thus, nZVI mass loading of <5 g/L yields lower reactivity with PCE and lower efficiency of Fe° utilization than for higher nZVI mass loading. The PCE dechlorination rate increased with increasing pore-water velocity, suggesting that mass transfer limits the reaction at low porewater velocity. Overall, this work suggests that design of nZVI-based reactive barriers for groundwater treatment should consider the non-linear effects of both mass loading and flow velocity on performance and expected reactive lifetime.

Effect of emplaced nZVI mass and groundwater velocity on PCE dechlorination and hydrogen evolution in water-saturated sand

Energy Technology Data Exchange (ETDEWEB)

Kim, Hye-Jin [Civil & Environmental Engineering, Carnegie Mellon University, Pittsburgh, PA 15213-3890 (United States); Chemical Research Division, Environmental Health Research Department, National Institute of Environmental Research, Incheon 404-708 (Korea, Republic of); Leitch, Megan [Civil & Environmental Engineering, Carnegie Mellon University, Pittsburgh, PA 15213-3890 (United States); Center for Environmental Implications of Nanotechnology, Carnegie Mellon University, Pittsburgh, PA 15213-3890 (United States); Naknakorn, Bhanuphong [Civil & Environmental Engineering, Carnegie Mellon University, Pittsburgh, PA 15213-3890 (United States); Tilton, Robert D. [Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213-3890 (United States); Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213-3890 (United States); Center for Environmental Implications of Nanotechnology, Carnegie Mellon University, Pittsburgh, PA 15213-3890 (United States); Lowry, Gregory V., E-mail: glowry@cmu.edu [Civil & Environmental Engineering, Carnegie Mellon University, Pittsburgh, PA 15213-3890 (United States); Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213-3890 (United States); Center for Environmental Implications of Nanotechnology, Carnegie Mellon University, Pittsburgh, PA 15213-3890 (United States)

2017-01-15

Highlights: • Reactivity of nZVI increased linearly with nZVI concentration above 10 g/L, but was non-linear below 10 g/L. • nZVI reactivity with PCE is more sensitive to solution redox potential than solution pH. • Mass transfer limits the reactivity of emplaced nZVI under typical groundwater flow velocity. • Lowering pH increases H{sub 2} evolution from nZVI more than reactivity with PCE. • Design of nZVI remediation strategies should consider mass loading and flow velocity on performance and lifetime. - Abstract: The effect of nZVI mass loading and groundwater velocity on the tetrachloroethylene (PCE) dechlorination rate and the hydrogen evolution rate for poly(maleic acid-co-olefin) (MW = 12 K) coated nZVI was examined. In batch reactors, the PCE reaction rate constant (3.7 × 10{sup −4} L hr{sup −1} m{sup −2}) and hydrogen evolution rate constant (1.4 nanomol L hr{sup −1} m{sup −2}) were independent of nZVI concentration above 10 g/L, but the PCE dechlorination rate decreased and the hydrogen evolution rate increased for nZVI concentration below 10 g/L. The nonlinearity between nZVI mass loading and PCE dechlorination and H{sub 2} evolution was explained by differences in pH and E{sub h} at each nZVI mass loading; PCE reactivity increased when solution E{sub h} decreased, and the H{sub 2} evolution rate increased with decreasing pH. Thus, nZVI mass loading of <5 g/L yields lower reactivity with PCE and lower efficiency of Fe° utilization than for higher nZVI mass loading. The PCE dechlorination rate increased with increasing pore-water velocity, suggesting that mass transfer limits the reaction at low porewater velocity. Overall, this work suggests that design of nZVI-based reactive barriers for groundwater treatment should consider the non-linear effects of both mass loading and flow velocity on performance and expected reactive lifetime.

Dechlorination of 2,4-dichlorophenoxyacetic acid by sodium carboxymethyl cellulose-stabilized Pd/Fe nanoparticles

International Nuclear Information System (INIS)

Zhou, Hongyi; Han, Jian; Baig, Shams Ali; Xu, Xinhua

2011-01-01

Highlights: ► CMC-stabilized Pd/Fe nanoparticles were synthesized and used for 2,4-D removal. ► Particle stability, ζ-potential and IEP of non- and stabilized Pd/Fe were compared. ► Dechlorination of 2,4-D by different Pd/Fe systems was investigated. ► The reaction mechanism has been discussed and presented in the article. ► Effects of CMC/Fe mass ratio and pH were also investigated. - Abstract: This paper describes the synthesis of sodium carboxymethyl cellulose (CMC)-stabilized Pd/Fe nanoparticles and their applications to the dechlorination of 2,4-dichlorophenoxyacetic acid (2,4-D) under controlled laboratorial conditions. For this purpose batch mode experiments were conducted to understand the effects of CMC on the surface characteristics of Pd/Fe nanoparticles, optimum removal of 2,4-D and other surface interactions mechanism. Our experimental results demonstrated considerable enhancements in particle stability and chemical reactivity with the addition of CMC to Pd/Fe nanoparticles. Transmission electron microscopy (TEM) analysis indicated that CMC-stabilized Pd/Fe nanoparticles were well dispersed, and nanoparticles remained in suspension for days compared to non-stabilized Pd/Fe nanoparticles precipitated within minutes. The isoelectric point (IEP) of the nanoparticles shifted from pH 6.5 to 2.5, suggesting that CMC-stabilized Pd/Fe nanoparticles were negatively charged over a wider pH range. Our batch experiments demonstrated that CMC-stabilized Pd/Fe nanoparticles (0.6 g Fe L −1 ) were able to remove much higher levels of 2,4-D with only one intermediate 2-chlorophenoxyacetic acid (2-CPA) and the final organic product phenoxyacetic acid (PA), than non-stabilized Pd/Fe nanoparticles or microsized Pd/Fe particles. The removal percentage of 2,4-D increased from 10% to nearly 100% as the reaction pH decreased from 11.5 to 2.5. The optimal CMC/Fe mass ratio for the dechlorination of 2,4-D was determined to be 5/1, and the removal of 2,4-D was

Bioelectrocatalytic dechlorination of trichloroacetic acid at gel-immobilized hemoglobin on multiwalled carbon nanotubes modified graphite electrode: Kinetic modeling and reaction pathways

International Nuclear Information System (INIS)

Liu, Qi; Yu, Jianming; Xu, Yinghua; Wang, Jiade; Ying, Le; Song, Xinxin; Zhou, Gendi; Chen, Jianmeng

2013-01-01

Highlights: ► The electrons transfer from enzyme in the electrode to COCs was the key step. ► The average current efficiency was influenced by pH and temperature of the systems. ► The most favourable degradation conditions for TCA were found to be pH 3 and 310 K. ► The activation energy of 26.2 kJ mol −1 was also calculated by the Arrhenius equation. ► Bioelectrocatalytic mechanism of TCA was verified by kinetic expressions. -- Abstract: In bioelectrochemically reductive dechlorination of chlorinated organic compounds (COCs), the electrons transfer from enzyme in the electrode to COCs was the key step, which determined the average current efficiency (CE) and was influenced by the pH and temperature of the systems. In this work, the effect of temperature (288–318 K) and pH (2–11) of the electrolyte on decholrination of trichloroacetic acid (TCA) was investigated in the sodium alginate/hemoglobin-multiwalled carbon nanotubes-graphite composite electrode (Hb/SA–MWCNT–GE). The results showed that the most favourable degradation conditions for TCA by Hb/SA–MWCNT–GE were found to be pH 3 and 310 K. By varying the pH of the systems, it was found that a proton accompanied with an electron transfer between the electrode and heme Fe(III)/Fe(II) of Hb during the reaction. Additionally, the activation energy of 26.2 kJ mol −1 was also calculated by the Arrhenius equation for the reaction. The total mass balance of the reactant and the products was in the range of 97–105% during the bioelectrochemically reductive reaction. The CE only decreased from 87% to 83% when the Hb/SA–MWCNT–GE was used 5 times. Based on the intermediates detected, a pathway was proposed for TCA degradation in which it underwent dechlorination process. The main degradation mechanism described by a parallel reaction rather than by a sequential reaction for dechlorination of TCA in Hb/SA–MWCNT–GE system was proposed. These data provided relevant information about the

Characterization of natural anaerobic dechlorination of TCE and 1,1,1-TCA in clay till including isotope fractionation and molecular biological tools

DEFF Research Database (Denmark)

Damgaard, Ida; Bælum, J.; Hunkeler, D.

2010-01-01

One of the major challenges when using enhanced reductive dechlorination (ERD) as a remediation technology at clay till sites is to obtain good contact between added agents such as donor, bacteria and the contamination. It is unclear whether degradation only takes place in fractures and/or sand l...... including the location of degradation in the fracture matrix geology. An extensive field collection of cores and discrete soil sampling has been conducted and samples have been analysed using state of the art microbial and chemical tools including isotope fractionation....

Kinetic analysis of dechlorination and oxidation of PrOCl by using a non-isothermal TG method

International Nuclear Information System (INIS)

Yang, H.C.; Eun, H.C.; Cho, Y.Z.; Lee, H.S.; Kim, I.T.

2009-01-01

Thermal dechlorination and oxidation process of praseodymium oxychloride, PrOCl, was studied from the view point of reaction kinetics. On the basis of data of thermogravimetry under different oxygen partial pressures at various heating rates, a kinetic analysis was performed using an isoconversional method and a master plot method. The results of the isoconversional method of TG data suggested that the dechlorination and oxidation of PrOCl followed a single step with activation energy of 112.6 ± 3.4 kJ mol -1 , and from master plot methods, the reaction was described by a linear-contracting phase boundary reaction

Thermal dechlorination of PCB-209 over Ca species-doped Fe₂O₃.

Science.gov (United States)

Su, Guijin; Huang, Linyan; Shi, Ruifang; Liu, Yexuan; Lu, Huijie; Zhao, Yuyang; Yang, Fan; Gao, Lirong; Zheng, Minghui

2016-02-01

Degradation reaction of decachlorobiphenyl (PCB-209) was investigated over the synthesized Ca species-doped Fe2O3 at 300 °C. The 1%Ca-Fe2O3 exhibited the highest activity among the four catalysts prepared with the pseudo-first order reaction at k(obs) = 0.103 min(-1). PCB-207, PCB-197, PCB-176, PCB-184, PCB-150, PCB-136, PCB-148, PCB-104, PCB-96, PCB-54, PCB-19, PCB-4 and PCB-1 were identified as the dominant isomers in their respective nonachlorobiphenyl (NonaCB) to monochlorobiphenyl (MonoCB) homologue groups. Analysis of the hydrodechlorination products indicated that dechlorination was much more favored on meta- and para-than on ortho-positions. The formation of significantly predominant NonaCB and octachlorobiphenyl (OctaCB) isomers was attributed to lower energy principles and to the 90° dihedral angles of two aromatic rings which prevented the hydrodechlorination at ortho-positions. When the number of chlorine atoms is not more than 7, the steric effect supports the formation of predominant PCB isomers having chlorines at four ortho-positions. During the dechlorination of tetrachlorobiphenyl (TetraCB) formed to generate monochlorobiphenyl (MonoCB) isomers, the chlorine atoms fully substituted at the ortho-positions have to be successively removed, with the first two dechlorinations preferentially occurring at the two different benzene rings. This is dissimilar to that of octachloronaphthalene (PCN-75) in which the hydrodechlorination reaction happened preferentially at ortho-position due to the existence of steric effects. The opposite roles of the steric effect in ortho-position between PCB-209 and PCN-75 might be due to the difference of the π-conjugated plane caused by the dihedral angle of 90° and 0° of the two aromatic rings. Copyright © 2015 Elsevier Ltd. All rights reserved.

The oxidative p-dichlorobenzene dechlorinating in the presence of copper (ΙΙ complexes and nitrogen (ΙΙ, ΙV oxides

Directory of Open Access Journals (Sweden)

Valentina Yemelyanova

2012-12-01

Full Text Available The results of dechlorination in the solution CuCl2–TBP–NaNO2–О2–Н2О kinetics research are presented in the article. All system components influence to the dechlorination process is studied and quantitatively described. The composition of copper intermediate complexes participating in reaction is studied by the instrumentality of UV-spectroscopy. Established part of binuclear copper complexes in the catalytic intermediate complex constants of formation were estimated and compared with the kinetic and spectrophotometric methods. The composition of the intermediate complexes responsible for process is defined, the mechanism scheme is offered, the p-dichlorobenzene dechlorination limiting stage including redox-disintegration of the intermediate complex consisting of dimeric complex of copper (II, I chloride, nitrogen oxide and p-dichlorobenzene is defined.

Evidence of rock matrix back-diffusion and abiotic dechlorination using a field testing approach

Science.gov (United States)

Schaefer, Charles E.; Lippincott, David R.; Klammler, Harald; Hatfield, Kirk

2018-02-01

An in situ field demonstration was performed in fractured rock impacted with trichloroethene (TCE) and cis-1,2-dichloroethene (DCE) to assess the impacts of contaminant rebound after removing dissolved contaminants within hydraulically conductive fractures. Using a bedrock well pair spaced 2.4 m apart, TCE and DCE were first flushed with water to create a decrease in dissolved contaminant concentrations. While hydraulically isolating the well pair from upgradient contaminant impacts, contaminant rebound then was observed between the well pair over 151 days. The magnitude, but not trend, of TCE rebound was reasonably described by a matrix back-diffusion screening model that employed an effective diffusion coefficient and first-order abiotic TCE dechlorination rate constant that was based on bench-scale testing. Furthermore, a shift in the TCE:DCE ratio and carbon isotopic enrichment was observed during the rebound, suggesting that both biotic and abiotic dechlorination were occurring within the rock matrix. The isotopic data and back-diffusion model together served as a convincing argument that matrix back-diffusion was the mechanism responsible for the observed contaminant rebound. Results of this field demonstration highlight the importance and applicability of rock matrix parameters determined at the bench-scale, and suggest that carbon isotopic enrichment can be used as a line of evidence for abiotic dechlorination within rock matrices.

Photocatalytic dechlorination of PCB 138 using leuco-methylene blue and visible light; reaction conditions and mechanisms

International Nuclear Information System (INIS)

Izadifard, Maryam; Langford, Cooper H.; Achari, Gopal

2010-01-01

A study of dechlorination of PCB 138, under visible light employing methylene blue (MB) and triethylamine (TEA) in acetonitrile/water has been conducted to investigate the details of the mechanism of dechlorination and to determine the efficiency of the process for this representative congener. Two other amines, N-methyldiethanolamine (MEDA) and (triethanolamine) TEOA also replaced TEA and two other solvents, methanol and ethanol replacing acetonitrile were examined for effects on reaction rates. The results show that PCB 138 can be dechlorinated efficiently in this photocatalytic reaction. Clarifying ambiguities in several previous reports, the reduced form of MB, leuco-methylene blue (LMB) was identified as responsible for the photoreaction with its excited state transferring an electron to PCBs; oxidized LMB (i.e. MB) is reduced back to LMB by the excess amine present. The reaction depends on a cycle driven by the amine as a sacrificial electron donor. MEDA proved to be the most efficient electron donor; apparently in consequence of the most favourable steady state concentration of LMB. Methanol and ethanol may be used to replace acetonitrile with little change in the efficiency of the reaction.

Dechlorination of 2,4-dichlorophenoxyacetic acid by sodium carboxymethyl cellulose-stabilized Pd/Fe nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Zhou, Hongyi, E-mail: zhouhy@zjut.edu.cn [College of Biological and Environmental Engineering, Zhejiang University of Technology, Hangzhou 310032 (China); Han, Jian [College of Biological and Environmental Engineering, Zhejiang University of Technology, Hangzhou 310032 (China); Baig, Shams Ali; Xu, Xinhua [Department of Environmental Engineering, Zhejiang University, Hangzhou 310027 (China)

2011-12-30

Highlights: Black-Right-Pointing-Pointer CMC-stabilized Pd/Fe nanoparticles were synthesized and used for 2,4-D removal. Black-Right-Pointing-Pointer Particle stability, {zeta}-potential and IEP of non- and stabilized Pd/Fe were compared. Black-Right-Pointing-Pointer Dechlorination of 2,4-D by different Pd/Fe systems was investigated. Black-Right-Pointing-Pointer The reaction mechanism has been discussed and presented in the article. Black-Right-Pointing-Pointer Effects of CMC/Fe mass ratio and pH were also investigated. - Abstract: This paper describes the synthesis of sodium carboxymethyl cellulose (CMC)-stabilized Pd/Fe nanoparticles and their applications to the dechlorination of 2,4-dichlorophenoxyacetic acid (2,4-D) under controlled laboratorial conditions. For this purpose batch mode experiments were conducted to understand the effects of CMC on the surface characteristics of Pd/Fe nanoparticles, optimum removal of 2,4-D and other surface interactions mechanism. Our experimental results demonstrated considerable enhancements in particle stability and chemical reactivity with the addition of CMC to Pd/Fe nanoparticles. Transmission electron microscopy (TEM) analysis indicated that CMC-stabilized Pd/Fe nanoparticles were well dispersed, and nanoparticles remained in suspension for days compared to non-stabilized Pd/Fe nanoparticles precipitated within minutes. The isoelectric point (IEP) of the nanoparticles shifted from pH 6.5 to 2.5, suggesting that CMC-stabilized Pd/Fe nanoparticles were negatively charged over a wider pH range. Our batch experiments demonstrated that CMC-stabilized Pd/Fe nanoparticles (0.6 g Fe L{sup -1}) were able to remove much higher levels of 2,4-D with only one intermediate 2-chlorophenoxyacetic acid (2-CPA) and the final organic product phenoxyacetic acid (PA), than non-stabilized Pd/Fe nanoparticles or microsized Pd/Fe particles. The removal percentage of 2,4-D increased from 10% to nearly 100% as the reaction pH decreased from 11

Influence of iron-bearing phyllosilicates on the dechlorination kinetics of 1,1,1-trichloroethane in Fe(II)/cement slurries.

Science.gov (United States)

Jung, Bahngmi; Batchelor, Bill

2007-07-01

This study examines the effect of iron-bearing phyllosilicates on dechlorination rates of chlorinated aliphatic hydrocarbons (CAHs) in iron-based degradative solidification/stabilization (DS/S-Fe(II)). Laboratory batch experiments were conducted to evaluate dechlorination rates of 1,1,1-trichloroethane (1,1,1-TCA) in a mixture solution of Fe(II), cement and three different iron-bearing phyllosilicates (biotite, vermiculite, and montmorillonite). A first-order rate model was generally used to describe the dechlorination kinetics and the rate constants were dependent on soil mineral type (biotite, vermiculite, and montmorillonite), Fe(II) dose, and the mass ratio of cement to soil mineral. The pseudo-first-order rate constant for montmorillonite was lower than that for biotite and vermiculite by factors of 11-27 when the mass ratio of cement to phyllosilicates was fixed at one. The presence of biotite and vermiculite increase and the presence of montmorillonite decrease the degradation rate that would be observed in their absence. The effect of cement/mineral ratio on rate constants with three different soil minerals indicates that biotite was more reactive than the other two phyllosilicates. This may be due to high accessible natural Fe(II) content in biotite. Montmorillonite appears to inhibit dechlorination by either inactivating Fe(II) by ion exchange or by physically blocking active sites on cement hydration products.

The interactive biotic and abiotic processes of DDT transformation under dissimilatory iron-reducing conditions.

Science.gov (United States)

Jin, Xin; Wang, Fang; Gu, Chenggang; Yang, Xinglun; Kengara, Fredrick O; Bian, Yongrong; Song, Yang; Jiang, Xin

2015-11-01

The objective of the study was to elucidate the biotic and abiotic processes under dissimilatory iron reducing conditions involved in reductive dechlorination and iron reduction. DDT transformation was investigated in cultures of Shewanella putrefaciens 200 with/without α-FeOOH. A modified first-order kinetics model was developed and described DDT transformation well. Both the α-FeOOH reduction rate and the dechlorination rate of DDT were positively correlated to the biomass. Addition of α-FeOOH enhanced reductive dechlorination of DDT by favoring the cell survival and generating Fe(II) which was absorbed on the surface of bacteria and iron oxide. 92% of the absorbed Fe(II) was Na-acetate (1M) extractable. However, α-FeOOH also played a negative role of competing for electrons as reflected by the dechlorination rate of DDT was inhibited when increasing the α-FeOOH from 1 g L(-1) to 5 g L(-1). DDT was measured to be toxic to S. putrefaciens 200. The metabolites DDD, DDE and DDMU were recalcitrant to S. putrefaciens 200. The results suggested that iron oxide was not the key factor to promote the dissipation of DDX (DDT and the metabolites), whereas the one-electron reduction potential (E1) of certain organochlorines is the main factor and that the E1 higher than the threshold of the reductive driving forces of DIRB probably ensures the occur of reductive dechlorination. Copyright © 2015 Elsevier Ltd. All rights reserved.

Dechlorination of PCBs, CAHs, herbicides and pesticides neat and in soils at 25 degrees C using Na/NH3.

Science.gov (United States)

Pittman, Charles U; He, Jinbao

2002-05-03

Na/NH3 reductions have been used to dehalogenate polychlorinated biphenyls (PCBs), chlorinated aliphatic hydrocarbons (CAHs) and pesticides at diffusion controlled rates at room temperature in model compound studies in both dry NH3 and when water was added. The rate ratio of dechlorination (aliphatic and aromatic compounds) versus reaction of the solvated electron with water is very large, allowing wet soils or sludges to be remediated without an unreasonable consumption of sodium. Several soils, purposely contaminated with 1,1,1-trichloroethane, 1-chlorooctane and tetrachloroethylene, were remediated by slurring the soils in NH3 followed by addition of sodium. The consumption of sodium per mole of chlorine removed was examined as a function of both the hazardous substrate's concentration in the soil and the amount of water present. The Na consumption per Cl removed increases as the amount of water increases and as the substrate concentration in soil decreases. However, remediation was still readily accomplished from 5000 to 3000ppm to sub ppm levels of RCl in the presence of substantial amounts of water. PCB- and dioxin-contaminated oils were remediated with Na/NH3 as were PCB-contaminated soils and sludges from contaminated sites. Ca/NH3 treatments also successfully remediated PCB-contaminated clay, sandy and organic soils but laboratory studies demonstrated that Ca was less efficient than Na when substantial amounts of water were present. The advantages of solvated electron reductions using Na/NH3 include: (1) very rapid dehalogenation rates at ambient temperature, (2) soils (even clay soils) break down into particles and slurry nicely in NH3, (3) liquid ammonia handling technology is well known and (4) removal from soils, recovery and recycle of ammonia is easy due to its low boiling point. Finally, dechlorination is extremely fast even for the 'corner' chlorines in the substrate Mirex (structure in Eq. (5)).

Radiation-induced destruction of organic compounds in aqueous solutions by dual oxidation/reduction mechanism

Energy Technology Data Exchange (ETDEWEB)

Chaychiana, M.; Silverman, J.; Al-Sheikhly, M. [Department of Materials Science and Engineering, University of Maryland (United States); Poster, D.; Neta, P.; Huie, R. [Chemical Science and Technology Laboratory, National Institute of Standard and Technology (United States)

2011-07-01

This research presents the feasibility and mechanisms of using high energy electrons for the dechlorination of polychlorinated biphenyls (PCBs) in marine sediment, and hazardous organic compounds in waste water. The remediation of the organic contaminants by ionizing radiation is achieved by means of both reduction and oxidation processes. PCBs in marine sediment can be effectively dechlorinated by reduction, while toxic organic compounds in water are removed mainly by oxidation. Radiolytic degradation of aqueous suspensions of PCBs in marine sediments in the presence of isopropanol was also studied. Addition of isopropanol was necessary to enhance the radiolytic yield and the dechlorination of PCBs. Also presented are results from an examination of the oxidative and reductive effects of electron-beam irradiation on the concentrations of six organic solvents in water. The organic solvents in water were prepared to mimic a pharmaceutical waste stream. Radiation-induced destruction of benzene was also investigated using pulse radiolysis technique. Pulse radiolysis with spectrophotometric and conductometric detection was utilized to study the formation and reactions of radicals from benzene and dienes in aqueous solutions. The benzene OH adduct, {sup ●}C{sub 6}H{sub 6}OH, reacts with O{sub 2} (k = 3x10{sup 8} L mol{sup -1} s{sup -1}) in a reversible reaction. The peroxyl radical, HOC{sub 6}H{sub 6}O{sub 2}{sup ●}, undergoes O{sub 2}●- elimination, bimolecular decay, and reaction with benzene to initiate a chain reaction, depending on the dose rate, benzene concentration, and pH. The occurrence of the chain reaction is demonstrated in low-dose-rate gamma radiolysis experiments where the consumption of O{sub 2} was monitored. (author)

Organometallic copper I, II or III species in an intramolecular dechlorination reaction

KAUST Repository

Poater, Albert

2013-03-15

The present paper gives insight into an intramolecular dechlorination reaction involving Copper (I) and an ArCH2Cl moiety. The discussion of the presence of a CuIII organometallic intermediate becomes a challenge, and because of the lack of clear experimental detection of this proposed intermediate, and due to the computational evidence that it is less stable than other isomeric species, it can be ruled out for the complex studied here. Our calculations are completely consistent with the key hypothesis of Karlin et al. that TMPA-CuI is the substrate of intramolecular dechlorination reactions as well as the source to generate organometallic species. However the organometallic character of some intermediates has been refused because computationally these species are less stable than other isomers. Thus this study constitutes an additional piece towards the full understanding of a class of reaction of biological relevance. Further, the lack of high energy barriers and deep energy wells along the reaction pathway explains the experimental difficulties to trap other intermediates. © Springer-Verlag Berlin Heidelberg 2013.

Biosupported Bimetallic Pd Au Nanocatalysts for Dechlorination of Environmental Contaminants

Energy Technology Data Exchange (ETDEWEB)

De Corte, S.; Fitts, J.; Hennebel, T.; Sabbe, T.; Bliznuk, V.; Verschuere, S.; van der Lelie, D.; Verstraete, W.; Boon, N.

2011-08-30

Biologically produced monometallic palladium nanoparticles (bio-Pd) have been shown to catalyze the dehalogenation of environmental contaminants, but fail to efficiently catalyze the degradation of other important recalcitrant halogenated compounds. This study represents the first report of biologically produced bimetallic Pd/Au nanoparticle catalysts. The obtained catalysts were tested for the dechlorination of diclofenac and trichloroethylene. When aqueous bivalent Pd(II) and trivalent Au(III) ions were both added to concentrations of 50 mg L{sup -1} and reduced simultaneously by Shewanella oneidensis in the presence of H{sub 2}, the resulting cell-associated bimetallic nanoparticles (bio-Pd/Au) were able to dehalogenate 78% of the initially added diclofenac after 24 h; in comparison, no dehalogenation was observed using monometallic bio-Pd or bio-Au. Other catalyst-synthesis strategies did not show improved dehalogenation of TCE and diclofenac compared with bio-Pd. Synchrotron-based X-ray diffraction, (scanning) transmission electron microscopy and energy dispersive X-ray spectroscopy indicated that the simultaneous reduction of Pd and Au supported on cells of S. oneidensis resulted in the formation of a unique bimetallic crystalline structure. This study demonstrates that the catalytic activity and functionality of possibly environmentally more benign biosupported Pd-catalysts can be improved by coprecipitation with Au.

Dechlorination/Solidification of LiCl waste by using a synthetic inorganic composite with different compositions

Energy Technology Data Exchange (ETDEWEB)

Kim, Na Young; Cho, In Hak; Park, Hwan Seo; Ahn, Do Hee [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2016-09-15

Waste salt generated from a pyro-processing for the recovery of uranium and transuranic elements has high volatility at vitrification temperature and low compatibility in conventional waste glasses. For this reason, KAERI (Korea Atomic Energy Research Institute) suggested a new method to de-chlorinate waste salt by using an inorganic composite named SAP (SiO{sub 2}-Al{sub 2}O{sub 3}-P{sub 2}O{sub 5}). In this study, the de-chlorination behavior of waste salt and the microstructure of consolidated form were examined by adding B{sub 2}O{sub 3} and Fe{sub 2}O{sub 3} to the original SAP composition. De-chlorination behavior of metal chloride waste was slightly changed with given compositions, compared with that of original SAP. In the consolidated forms, the phase separation between Si-rich phase and P-rich phase decreases with the amount of Al{sub 2}O{sub 3} or B{sub 2}O{sub 3} as a connecting agent between Si and P-rich phase. The results of PCT (Product Consistency Test) indicated that the leach-resistance of consolidated forms out of reference composition was lowered, even though the leach-resistance was higher than that of EA (Environmental Assessment) glass. From these results, it could be inferred that the change in the content of Al or B in U-SAP affected the microstructure and leach-resistance of consolidated form. Further studies related with correlation between composition and characteristics of wasteform are required for a better understanding.

Radiation induced dechlorination of some chlorinated hydrocarbons in aqueous suspensions of various solid particles

Czech Academy of Sciences Publication Activity Database

Múčka, V.; Buňata, M.; Čuba, V.; Silber, R.; Juha, Libor

2015-01-01

Roč. 112, Jul (2015), s. 108-116 ISSN 0969-806X R&D Projects: GA ČR GA13-28721S Institutional support: RVO:68378271 Keywords : chlorinated hydrocarbons * TCE * PCE * PCBs * dechlorination * gamma irradiation * modifiers * cell membrane permeability Subject RIV: CH - Nuclear ; Quantum Chemistry Impact factor: 1.207, year: 2015

Catabolic thiosulfate disproportionation and carbon dioxide reduction in strain DCB-1, a reductively dechlorinating anaerobe

Energy Technology Data Exchange (ETDEWEB)

Mohn, W.W.; Tiedje, J.M. (Michigan State Univ., East Lansing (USA))

1990-04-01

Strain DCB-1 is a strict anaerobe capable of reductive dehalogenation. We elucidated metabolic processes in DCB-1 which may be related to dehalogenation and which further characterize the organism physiologically. Sulfoxy anions and CO2 were used by DCB-1 as catabolic electron acceptors. With suitable electron donors, sulfate and thiosulfate were reduced to sulfide. Sulfate and thiosulfate supported growth with formate or hydrogen as the electron donor and thus are probably respiratory electron acceptors. Other electron donors supporting growth with sulfate were CO, lactate, pyruvate, butyrate, and 3-methoxybenzoate. Thiosulfate also supported growth without an additional electron donor, being disproportionated to sulfide and sulfate. In the absence of other electron acceptors, CO2 reduction to acetate plus cell material was coupled to pyruvate oxidation to acetate plus CO2. Pyruvate could not be fermented without an electron acceptor. Carbon monoxide dehydrogenase activity was found in whole cells, indicating that CO2 reduction probably occurred via the acetyl coenzyme A pathway. Autotrophic growth occurred on H2 plus thiosulfate or sulfate. Diazotrophic growth occurred, and whole cells had nitrogenase activity. On the basis of these physiological characteristics, DCB-1 is a thiosulfate-disproportionating bacterium unlike those previously described.

Dechlorination Reaction of Metal Chloride Wastes with Inorganic Composite (SiO{sub 2}-Al{sub 2}O{sub 3}- P{sub 2}O{sub 5}) at 650 .deg. C

Energy Technology Data Exchange (ETDEWEB)

Ahn, Soo Na; Park, Hwan Seo; Cho, In Hak; Kim, In Tae; Cho, Yong Zun [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2011-05-15

Pyrochemical process to recover uranium and transuranic elements from the spent nuclear fuel indispensably generates radioactive metal chlorides waste containing fission products. These wastes are difficult to solidify and stabilize by conventional method due to their volatility and low comparability with silicate glass. Our research group is under development of dechlorination method to remove Clinduced problems. For dechlorination of metal chloride waste, an inorganic composite, SiO{sub 2}-Al{sub 2}O{sub 3}-P{sub 2}O{sub 5} (SAP), has been investigated as dechlorination agent. The composite reacts with metal chloride to produce aluminosilicates, alumino phosphate and orthophosphate. The products are thermally stable up to 1200 .deg. C and compatible with silicate glass. In this study, modified SAP containing Fe{sub 2}O{sub 3} as another component was investigated to enhance the dechlorination reaction and characterize the reaction behavior of LiCl

Sequential reductive and oxidative biodegradation of chloroethenes stimulated in a coupled bioelectro-process.

Science.gov (United States)

Lohner, Svenja T; Becker, Dirk; Mangold, Klaus-Michael; Tiehm, Andreas

2011-08-01

This article for the first time demonstrates successful application of electrochemical processes to stimulate sequential reductive/oxidative microbial degradation of perchloroethene (PCE) in mineral medium and in contaminated groundwater. In a flow-through column system, hydrogen generation at the cathode supported reductive dechlorination of PCE to cis-dichloroethene (cDCE), vinyl chloride (VC), and ethene (ETH). Electrolytically generated oxygen at the anode allowed subsequent oxidative degradation of the lower chlorinated metabolites. Aerobic cometabolic degradation of cDCE proved to be the bottleneck for complete metabolite elimination. Total removal of chloroethenes was demonstrated for a PCE load of approximately 1.5 μmol/d. In mineral medium, long-term operation with stainless steel electrodes was demonstrated for more than 300 days. In contaminated groundwater, corrosion of the stainless steel anode occurred, whereas DSA (dimensionally stable anodes) proved to be stable. Precipitation of calcareous deposits was observed at the cathode, resulting in a higher voltage demand and reduced dechlorination activity. With DSA and groundwater from a contaminated site, complete degradation of chloroethenes in groundwater was obtained for two months thus demonstrating the feasibility of the sequential bioelectro-approach for field application.

Copper-mediated reductive dechlorination by green rust intercalated with dodecanoate

DEFF Research Database (Denmark)

Huang, Lizhi; Yin, Zhou; Cooper, Nicola G.A.

2018-01-01

A layered FeII-FeIII hydroxide (green rust, GR) was intercalated with dodecanoate (known as GRC12) and then amended with CuII (GRC12(Cu)) before reaction with chloroform (CF), carbon tetrachloride (CT), trichloroethylene (TCE) or tetrachloroethylene (PCE). Reduction of CT by GRC12(Cu) was 37 times...

Microbial reductive dehalogenation of trihalomethanes by a Dehalobacter-containing co-culture.

Science.gov (United States)

Zhao, Siyan; Rogers, Matthew J; He, Jianzhong

2017-07-01

Trihalomethanes such as chloroform and bromoform, although well-known as a prominent class of disinfection by-products, are ubiquitously distributed in the environment due to widespread industrial usage in the past decades. Chloroform and bromoform are particularly concerning, of high concentrations detected and with long half-lives up to several hundred days in soils and groundwater. In this study, we report a Dehalobacter- and Desulfovibrio-containing co-culture that exhibits dehalogenation of chloroform (~0.61 mM) to dichloromethane and bromoform (~0.67 mM) to dibromomethane within 10-15 days. This co-culture was further found to dechlorinate 1,1,1-trichloroethane (1,1,1-TCA) (~0.65 mM) to 1,1-dichloroethane within 12 days. The Dehalobacter species present in this co-culture, designated Dehalobacter sp. THM1, was found to couple growth with dehalogenation of chloroform, bromoform, and 1,1,1-TCA. Strain THM1 harbors a newly identified reductive dehalogenase (RDase), ThmA, which catalyzes chloroform, bromoform, and 1,1,1-TCA dehalogenation. Additionally, based on the sequences of thmA and other identified chloroform RDase genes, ctrA, cfrA, and tmrA, a pair of chloroform RDase gene-specific primers were designed and successfully applied to investigate the chloroform dechlorinating potential of microbial communities. The comparative analysis of chloroform RDases with tetrachloroethene RDases suggests a possible approach in predicting the substrate specificity of uncharacterized RDases in the future.

ENVIROMETAL TECHNOLOGIES, INC., METAL-ENHANCED DECHLORINATION OF VOLATILE ORGANIC COMPOUNDS USING AN IN-SITU REACTIVE IRON WALL

Science.gov (United States)

This report summarizes the results of a field demonstration conducted under the SITE program. The technology that was demonstrated was a metal-enhanced dechlorination process developed by EnviroMetal Technologies, Inc. to treat groundwater contaminated with chlorinated volatile ...

Hydroxyl-radical induced dechlorination of pentachlorophenol in water

International Nuclear Information System (INIS)

He Yongke; Wu Jilan; Fang Xingwang; Sonntag, C. von

1998-01-01

The hydroxyl-radical induced dechlorination of pentachlorophenol (PCP) in water has been investigated pulse radiolytically. Hydroxyl radicals react with PCP by both electron transfer and addition. The former process results in pentachlorophenoxyl radicals (PCP-O), the latter process followed by rapid HCl elimination gives birth to deprotonated hydroxytetrachlorophenoxyl radicals ( - O-TCP-O). These phenoxyl radicals exhibit maximum absorption around 452 nm, which hinders the proper estimation of the ratio of the two processes. However, these two processes cause different changes in conductivity. In basic solution, the electron transfer causes a conductivity increase due to the formation of OH - whereas an addition followed by HCl elimination results in a conductivity decrease. The concurrence of these two processes reduces the relative variation in conductivity, from which about 53% electron transfer is deduced

Estimation of rate constants of PCB dechlorination reactions using an anaerobic dehalogenation model.

Science.gov (United States)

Karakas, Filiz; Imamoglu, Ipek

2017-02-15

This study aims to estimate anaerobic dechlorination rate constants (k m ) of reactions of individual PCB congeners using data from four laboratory microcosms set up using sediment from Baltimore Harbor. Pathway k m values are estimated by modifying a previously developed model as Anaerobic Dehalogenation Model (ADM) which can be applied to any halogenated hydrophobic organic (HOC). Improvements such as handling multiple dechlorination activities (DAs) and co-elution of congeners, incorporating constraints, using new goodness of fit evaluation led to an increase in accuracy, speed and flexibility of ADM. DAs published in the literature in terms of chlorine substitutions as well as specific microorganisms and their combinations are used for identification of pathways. The best fit explaining the congener pattern changes was found for pathways of Phylotype DEH10, which has the ability to remove doubly flanked chlorines in meta and para positions, para flanked chlorines in meta position. The range of estimated k m values is between 0.0001-0.133d -1 , the median of which is found to be comparable to the few available published biologically confirmed rate constants. Compound specific modelling studies such as that performed by ADM can enable monitoring and prediction of concentration changes as well as toxicity during bioremediation. Copyright © 2016 Elsevier B.V. All rights reserved.

Stabilization/Solidification of Radioactive LiCl-KCl Waste Salt by Using SiO2-Al2O3-P2O5(SAP) Inorganic Composite: Part 1. Dechlorination Behavior of LiCl-KCl and Characteristics of Consolidation

International Nuclear Information System (INIS)

Cho, In Hak; Park, Hwan Seo; Ahn, Soo Na; Kim, In Tae; Cho, Yong Zun

2012-01-01

The metal chloride wastes from a pyrochemical process to recover uranium and transuranic elements has been considered as a problematic waste difficult to apply to a conventional solidification method due to the high volatility and low compatibility with silicate glass. In this study, a dechlorination approach to treat LiCl-KCl waste for final disposal was adapted. In this study, a SiO 2 -Al 2 O 3 -P 2 O 5 (SAP) inorganic composite as a dechlorination agent was prepared by a conventional sol-gel process. By using a series of SAPs, the dechlorination behavior and consolidation of reaction products were investigated. Different from LiCl waste, the dechlorination reaction occurred mainly at two temperature ranges. The thermogravimetric test indicated that the first reaction range was about 400 degree C for LiCl and the second was about 700 degree C for KCl. The SAP 1071 (Si/Al/P=1/0.75/1 in molar) was found to be the most favorable SAP as a dechlorination agent under given conditions. The consolidation test revealed that the bulk shape and the densification of consolidated forms depended on the SAP/Salt ratios. The leaching test by PCT-A method was performed to evaluate the durability of consolidated forms. This study provided the basic information on the dechlorination approach. Based on the experimental results, the dechlorination method using a SiO 2 -Al 2 O 3 -P 2 O 5 (SAP) could be considered as one of alternatives for the immobilization of waste salt.

Dechlorination of chloropicrin and 1,3-dichloropropene by hydrogen sulfide species: redox and nucleophilic substitution reactions.

Science.gov (United States)

Zheng, Wei; Yates, Scott R; Papiernik, Sharon K; Guo, Mingxin; Gan, Jianying

2006-03-22

The chlorinated fumigants chloropicrin (trichloronitromethane) and 1,3-dichloropropene (1,3-D) are extensively used in agricultural production for the control of soilborne pests. The reaction of these two fumigants with hydrogen sulfide species (H2S and HS-) was examined in well-defined anoxic aqueous solutions. Chloropicrin underwent an extremely rapid redox reaction in the hydrogen sulfide solution. Transformation products indicated reductive dechlorination of chloropicrin by hydrogen sulfide species to produce dichloro- and chloronitromethane. The transformation of chloropicrin in hydrogen sulfide solution significantly increased with increasing pH, indicating that H2S is less reactive toward chloropicrin than HS- is. For both 1,3-D isomers, kinetics and transformation products analysis revealed that the reaction between 1,3-D and hydrogen sulfide species is an S(N)2 nucleophilic substitution process, in which the chlorine at C3 of 1,3-D is substituted by the sulfur nucleophile to form corresponding mercaptans. The 50% disappearance time (DT50) of 1,3-D decreased with increasing hydrogen sulfide species concentration at a constant pH. Transformation of 1,3-D was more rapid at high pH, suggesting that the reactivity of hydrogen sulfide species in the experimental system stems primarily from HS-. Because of the relatively low smell threshold values and potential environmental persistence of organic sulfur products yielded by the reaction of 1,3-D and HS-, the effects of reduced sulfide species should be considered in the development of alternative fumigation practices, especially in the integrated application of sulfur-containing fertilizers.

Continuous-flow column study of reductive dehalogenation of PCE upon bioaugmentation with the Evanite enrichment culture

Science.gov (United States)

Azizian, Mohammad F.; Behrens, Sebastian; Sabalowsky, Andrew; Dolan, Mark E.; Spormann, Alfred M.; Semprini, Lewis

2008-08-01

A continuous-flow anaerobic column experiment was conducted to evaluate the reductive dechlorination of tetrachloroethene (PCE) in Hanford aquifer material after bioaugmentation with the Evanite (EV) culture. An influent PCE concentration of 0.09 mM was transformed to vinyl chloride (VC) and ethene (ETH) within a hydraulic residence time of 1.3 days. The experimental breakthrough curves were described by the one-dimensional two-site-nonequilibrium transport model. PCE dechlorination was observed after bioaugmentation and after the lactate concentration was increased from 0.35 to 0.67 mM. At the onset of reductive dehalogenation, cis-dichloroethene (c-DCE) concentrations in the column effluent exceeded the influent PCE concentration indicating enhanced PCE desorption and transformation. When the lactate concentration was increased to 1.34 mM, c-DCE reduction to vinyl chloride (VC) and ethene (ETH) occurred. Spatial rates of PCE and VC transformation were determined in batch-incubated microcosms constructed with aquifer samples obtained from the column. PCE transformation rates were highest in the first 5 cm from the column inlet and decreased towards the column effluent. Dehalococcoides cell numbers dropped from ˜ 73.5% of the total Bacterial population in the original inocula, to about 0.5% to 4% throughout the column. The results were consistent with estimates of electron donor utilization, with 4% going towards dehalogenation reactions.

Landscape planning for agricultural nonpoint source pollution reduction III: Assessing phosphorus and sediment reduction potential

Science.gov (United States)

Diebel, M.W.; Maxted, J.T.; Robertson, Dale M.; Han, S.; Vander Zanden, M. J.

2009-01-01

Riparian buffers have the potential to improve stream water quality in agricultural landscapes. This potential may vary in response to landscape characteristics such as soils, topography, land use, and human activities, including legacies of historical land management. We built a predictive model to estimate the sediment and phosphorus load reduction that should be achievable following the implementation of riparian buffers; then we estimated load reduction potential for a set of 1598 watersheds (average 54 km2) in Wisconsin. Our results indicate that land cover is generally the most important driver of constituent loads in Wisconsin streams, but its influence varies among pollutants and according to the scale at which it is measured. Physiographic (drainage density) variation also influenced sediment and phosphorus loads. The effect of historical land use on present-day channel erosion and variation in soil texture are the most important sources of phosphorus and sediment that riparian buffers cannot attenuate. However, in most watersheds, a large proportion (approximately 70%) of these pollutants can be eliminated from streams with buffers. Cumulative frequency distributions of load reduction potential indicate that targeting pollution reduction in the highest 10% of Wisconsin watersheds would reduce total phosphorus and sediment loads in the entire state by approximately 20%. These results support our approach of geographically targeting nonpoint source pollution reduction at multiple scales, including the watershed scale. ?? 2008 Springer Science+Business Media, LLC.

Purification and characterization of the 3-chloro-4-hydroxy-phenylacetate reductive dehalogenase of Desulfitobacterium hafniense

DEFF Research Database (Denmark)

Christensen, Nina; Ahring, Birgitte Kiær; Wohlfarth, Gert

1998-01-01

The membrane-bound 3-chloro-4-hydroxyphenylacetate (Cl-OHPA) reductive dehalogenase from the chlorophenol- educing anaerobe Desulfitobacterium hafniense was purified 11.3-fold to apparent homogeneity in the presence of the detergent CHAPS. The purified dehalogenase catalyzed the reductive...... dechlorination of Cl-OHPA to 4-hydroxyphenylacetate with reduced methyl viologen as the electron donor at a specific activity of 103.2 nkat/mg protein. SDS-PAGErevealed a single protein band with an apparent molecular mass of 46.5 kDa. The enzyme contained 0.68±0.2 mol corrinoid, 12.0±0.7 mol iron, and 13...

The potential for reductive dechlorination after thermal treatment of TCE-contaminated aquifers

DEFF Research Database (Denmark)

Friis, Anne Kirketerp

Klorerede opløsningsmidler som fx triklorethen (TCE) er en alvorlig kilde til jord- og grundvandsforurening. Der er kun ganske få afværgeteknikker, der er effektive i området tæt på kilden til forureningen, og en af de mest anvendelige er termisk oprensning, hvor undergrunden opvarmes, så...... elektrisk opvarmning (ERH) i felten, var der bakterier som overlevede i eller blev transporteret til det opvarmede område med grundvandet. Disse bakterier kunne delvist nedbryde TCE (til cDCE) og bibeholdt redoxforhold efter opvarmningen, der kun var lidt mindre favorable for dechlorering i forhold til...... bioaugmenteret ved tilførsel af organisk stof og en mikrobiel blandingskultur med deklorerende bakterier. Bioaugmentationen førte til deklorering af TCE til ethen både i laboratorieopvarmede samt in-situ-opvarmede sedimenter. Dette faktum har påvist et potentiale og behov for bioaugmentation efter ERH...

EFFECT OF CONTAMINANT AND ORGANIC MATTER BIOAVAILABILITY ON THE MICROBIAL DEHALOGENATION OF SEDIMENT-BOUND CHLOROBENZENES. (R825513C007)

Science.gov (United States)

The extent of reductive dechlorination occurring in contaminated, estuarine sediments was investigated. Contaminant and organic matter bioavailability and their effect on the reductive dechlorination of sediment-bound chlorobenzenes was the main focus of the work presented her...

Chlorinated Electron Acceptor Abundance Drives Selection of Dehalococcoides mccartyi (D. mccartyi Strains in Dechlorinating Enrichment Cultures and Groundwater Environments

Directory of Open Access Journals (Sweden)

Alfredo Pérez-de-Mora

2018-05-01

Full Text Available Dehalococcoides mccartyi (D. mccartyi strains differ primarily from one another by the number and identity of the reductive dehalogenase homologous catalytic subunit A (rdhA genes within their respective genomes. While multiple rdhA genes have been sequenced, the activity of the corresponding proteins has been identified in only a few cases. Examples include the enzymes whose substrates are groundwater contaminants such as trichloroethene (TCE, cis-dichloroethene (cDCE and vinyl chloride (VC. The associated rdhA genes, namely tceA, bvcA, and vcrA, along with the D. mccartyi 16S rRNA gene are often used as biomarkers of growth in field samples. In this study, we monitored an additional 12 uncharacterized rdhA sequences identified in the metagenome in the mixed D. mccartyi-containing culture KB-1 to monitor population shifts in more detail. Quantitative PCR (qPCR assays were developed for 15 D. mccartyi rdhA genes and used to measure population diversity in 11 different sub-cultures of KB-1, each enriched on different chlorinated ethenes and ethanes. The proportion of rdhA gene copies relative to D. mccartyi 16S rRNA gene copies revealed the presence of multiple distinct D. mccartyi strains in each culture, many more than the two strains inferred from 16S rRNA analysis. The specific electron acceptor amended to each culture had a major influence on the distribution of D. mccartyi strains and their associated rdhA genes. We also surveyed the abundance of rdhA genes in samples from two bioaugmented field sites (Canada and United Kingdom. Growth of the dominant D. mccartyi strain in KB-1 was detected at the United Kingdom site. At both field sites, the measurement of relative rdhA abundances revealed D. mccartyi population shifts over time as dechlorination progressed from TCE through cDCE to VC and ethene. These shifts indicate a selective pressure of the most abundant chlorinated electron acceptor, as was also observed in lab cultures. These

Stabilization/Solidification of Radioactive LiCl-KCl Waste Salt by Using SiO{sub 2}-Al{sub 2}O{sub 3}-P{sub 2}O{sub 5}(SAP) Inorganic Composite: Part 1. Dechlorination Behavior of LiCl-KCl and Characteristics of Consolidation

Energy Technology Data Exchange (ETDEWEB)

Cho, In Hak; Park, Hwan Seo; Ahn, Soo Na; Kim, In Tae; Cho, Yong Zun [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2012-03-15

The metal chloride wastes from a pyrochemical process to recover uranium and transuranic elements has been considered as a problematic waste difficult to apply to a conventional solidification method due to the high volatility and low compatibility with silicate glass. In this study, a dechlorination approach to treat LiCl-KCl waste for final disposal was adapted. In this study, a SiO{sub 2}-Al{sub 2}O{sub 3}-P{sub 2}O{sub 5} (SAP) inorganic composite as a dechlorination agent was prepared by a conventional sol-gel process. By using a series of SAPs, the dechlorination behavior and consolidation of reaction products were investigated. Different from LiCl waste, the dechlorination reaction occurred mainly at two temperature ranges. The thermogravimetric test indicated that the first reaction range was about 400 degree C for LiCl and the second was about 700 degree C for KCl. The SAP 1071 (Si/Al/P=1/0.75/1 in molar) was found to be the most favorable SAP as a dechlorination agent under given conditions. The consolidation test revealed that the bulk shape and the densification of consolidated forms depended on the SAP/Salt ratios. The leaching test by PCT-A method was performed to evaluate the durability of consolidated forms. This study provided the basic information on the dechlorination approach. Based on the experimental results, the dechlorination method using a SiO{sub 2}-Al{sub 2}O{sub 3}-P{sub 2}O{sub 5}(SAP) could be considered as one of alternatives for the immobilization of waste salt.

Carbon, Chlorine, and Hydrogen Isotope Fractionation in Transformation of TCE to Ethene by a Dehalococcoides Culture

NARCIS (Netherlands)

Kuder, T.; van Breukelen, B.M.; Vanderford, M.; Philip, P.

2013-01-01

Carbon (C), chlorine (Cl), and hydrogen (H) isotope effects were determined during dechlorination of TCE to ethene by a mixed Dehalococcoides (Dhc) culture. The C isotope effects for the dechlorination steps were consistent with data published in the past for reductive dechlorination (RD) by Dhc.

Annual Reporting of Monitoring at Morrill, Kansas in 2015

Energy Technology Data Exchange (ETDEWEB)

LaFreniere, Lorraine M. [Argonne National Lab. (ANL), Argonne, IL (United States)

2016-06-01

In September 2005, the CCC/USDA initiated periodic sampling of groundwater, in accord with a program (Argonne 2005b) approved by the KDHE (2005), to monitor carbon tetrachloride concentrations in the groundwater. Under the KDHE-approved monitoring plan (Argonne 2005b), groundwater was sampled twice yearly for VOCs analyses through 2011. During the initial two years of monitoring, analysis for selected geochemical parameters was also conducted to aid in the evaluation of possible natural contaminant degradation (reductive dechlorination) processes in the subsurface environment. Consistently low levels of dissolved oxygen (DO) and oxidation-reduction potential (ORP) at monitoring well MW1D (in the deepest portion of the contaminated aquifer) and the presence of chloroform (the primary degradation product of carbon tetrachloride) suggested that some degree of reductive dechlorination was occurring.

Low and high acetate amendments are equally as effective at promoting complete dechlorination of trichloroethylene (TCE).

Science.gov (United States)

Wei, Na; Finneran, Kevin T

2013-06-01

Experiments with trichloroethylene-contaminated aquifer material demonstrated that TCE, cis-DCE, and VC were completely degraded with concurrent Fe(III) or Fe(III) and sulfate reduction when acetate was amended at stoichiometric concentration; competing TEAPs did not inhibit ethene production. Adding 10× more acetate did not increase the rate or extent of TCE reduction, but only increased methane production. Enrichment cultures demonstrated that ~90 μM TCE or ~22 μM VC was degraded primarily to ethene within 20 days with concurrent Fe(III) or Fe(III) + sulfate reduction. The dechlorination rates were comparable between the low and high acetate concentrations (0.36 vs 0.34 day(-1), respectively), with a slightly slower rate in the 10× acetate amended incubations. Methane accumulated to 13.5 (±0.5) μmol/tube in the TCE-degrading incubations with 10× acetate, and only 1.4 (±0.1) μmol/tube with low acetate concentration. Methane accumulated to 16 (±1.5) μmol/tube in VC-degrading enrichment with 10× acetate and 2 (±0.1) μmol/tube with stoichiometric acetate. The estimated fraction of electrons distributed to methanogenesis increased substantially when excessive acetate was added. Quantitative PCR analysis indicated that 10× acetate did not enhance Dehalococcoides biomass but rather increased the methanogen abundance by nearly one order of magnitude compared to that with stoichiometric acetate. The data suggest that adding low levels of substrate may be equally if not more effective as high concentrations, without producing excessive methane. This has implications for field remediation efforts, in that adding excess electron donor may not benefit the reactions of interest, which in turn will increase treatment costs without direct benefit to the stakeholders.

Metagenomic and Metatranscriptomic Analyses Reveal the Structure and Dynamics of a Dechlorinating Community Containing Dehalococcoides mccartyi and Corrinoid-Providing Microorganisms under Cobalamin-Limited Conditions

Energy Technology Data Exchange (ETDEWEB)

Men, Yujie; Yu, Ke; Bælum, Jacob; Gao, Ying; Tremblay, Julien; Prestat, Emmanuel; Stenuit, Ben; Tringe, Susannah G.; Jansson, Janet; Zhang, Tong; Alvarez-Cohen, Lisa; Liu, Shuang-Jiang

2017-02-10

The aim of this study is to obtain a systems-level understanding of the interactions betweenDehalococcoidesand corrinoid-supplying microorganisms by analyzing community structures and functional compositions, activities, and dynamics in trichloroethene (TCE)-dechlorinating enrichments. Metagenomes and metatranscriptomes of the dechlorinating enrichments with and without exogenous cobalamin were compared. Seven putative draft genomes were binned from the metagenomes. At an early stage (2 days), more transcripts of genes in theVeillonellaceaebin-genome were detected in the metatranscriptome of the enrichment without exogenous cobalamin than in the one with the addition of cobalamin. Among these genes, sporulation-related genes exhibited the highest differential expression when cobalamin was not added, suggesting a possible release route of corrinoids from corrinoid producers. Other differentially expressed genes include those involved in energy conservation and nutrient transport (including cobalt transport). The most highly expressed corrinoidde novobiosynthesis pathway was also assigned to theVeillonellaceaebin-genome. Targeted quantitative PCR (qPCR) analyses confirmed higher transcript abundances of those corrinoid biosynthesis genes in the enrichment without exogenous cobalamin than in the enrichment with cobalamin. Furthermore, the corrinoid salvaging and modification pathway ofDehalococcoideswas upregulated in response to the cobalamin stress. This study provides important insights into the microbial interactions and roles played by members of dechlorinating communities under cobalamin-limited conditions.

IMPORTANCEThe key

Deposition of Fe-Ni nanoparticles on Al2O3 for dechlorination of chloroform and trichloroethylene

International Nuclear Information System (INIS)

Hsieh, S.-H.; Horng, J.-J.

2006-01-01

This research proposes an efficient method for depositing Fe-Ni nanoparticles on Al 2 O 3 microparticles to decompose containments in ground water, such as chloroform and trichloroethylene. The Fe-Ni nanoparticles can be deposited onto the surface of Al 2 O 3 microparticles by electroless plating technique. The reasons why the Fe-Ni nanoparticles would be deposited on the surface of Al 2 O 3 microparticles is to avoid the agglomeration of Fe-Ni nanoparticles due to their surface effect and magnetic property. The results show that the sizes of Fe-Ni particles on Al 2 O 3 particles are between several and several hundreds of nanometers, the contents of Fe and Ni in Fe-Ni nanoparticles can be adjusted from 8 to 60 at.% for Fe and 40 to 92 at.% for Ni, the specific surface area of Fe-Ni nanoparticles can reach to 117 m 2 /g, and the reaction mechanism of dechlorination of chloroform of 2 mg/L by Fe-Ni/Al 2 O 3 particles of 5 g/L appears to be pseudo first order with a half life of 0.7 h and the half life is 0.25 h for the dechlorination of trichloroethylene of 2 mg/L

Consequence assessment for Airborne Releases of SO2 from the Y-12 Pilot Dechlorination Facility

International Nuclear Information System (INIS)

Pendergrass, W.R.

1992-06-01

The Atmospheric Turbulence and Diffusion Division was requested by the Department of Energy's Oak Ridge Operations Office to conduct a consequence assessment for potential atmospheric releases of SO 2 from the Y-12 Pilot Dechlorination Facility. The focus of the assessment was to identify ''worst'' case meteorology which posed the highest concentration exposure potential for both on-site as well as off-site populations. A series of plausible SO 2 release scenarios were provided by Y-12 for the consequence assessment. Each scenario was evaluated for predictions of downwind concentration, estimates of a five-minute time weighted average, and estimate of the dimension of the puff. The highest hazard potential was associated with Scenario 1, in which a total of eight SO 2 cylinders are released internally to the Pilot Facility and exhausted through the emergency venting system. A companion effort was also conducted to evaluate the potential for impact of releases of SO 2 from the Pilot Facility on the population of Oak Ridge. While specific transport trajectory data is not available for the Pilot Facility, extrapolations based on the Oak Ridge Site Survey and climatological records from the Y-12 meteorological program does not indicate the potential for impact on the city of Oak Ridge. Steering by the local topographical features severely limits the potential impact ares. Due to the lack of specific observational data, both tracer and meteorological, only inferences can be made concerning impact zones. It is recommended tat the Department of Energy Oak Ridge Operations examine the potential for off-site impact and develop the background data to prepare impact zones for releases of hazardous materials from the Y-12 facility

INFLUENCE OF HYDRAULIC RETENTION TIME ON EXTENT OF PCE DECHLORINATION AND PRELIMINARY CHARACTERIZATION OF THE ENRICHMENT CULTURE. (R826694C703)

Science.gov (United States)

The extent of tetrachloroethene (PCE) dechlorination in two chemostats was evaluated as a function of hydraulic retention time (HRT). The inoculum of these chemostats was from an upflow anaerobic sludge blanket (UASB) reactor that rapidly converts PCE to vinyl chloride (VC) an...

Innovative leaching of cobalt and lithium from spent lithium-ion batteries and simultaneous dechlorination of polyvinyl chloride in subcritical water

Energy Technology Data Exchange (ETDEWEB)

Liu, Kang; Zhang, Fu-Shen, E-mail: fszhang@rcees.ac.cn

2016-10-05

Highlights: • A co-treatment process for recovery of Co and Li and simultaneous detoxification of PVC in subcritical water was proposed. • PVC was used as a hydrochloric acid source. • More than 95% Co and nearly 98% Li were leached under the optimum conditions. • Neither corrosive acid nor reducing agent was used. • The co-treatment process has technical, economic and environmental benefits over the traditional recovery processes. - Abstract: In this work, an effective and environmentally friendly process for the recovery of cobalt (Co) and lithium (Li) from spent lithium-ion batteries (LIBs) and simultaneously detoxification of polyvinyl chloride (PVC) in subcritical water was developed. Lithium cobalt oxide (LiCoO{sub 2}) power from spent LIBs and PVC were co-treated by subcritical water oxidation, in which PVC served as a hydrochloric acid source to promote metal leaching. The dechlorination of PVC and metal leaching was achieved simultaneously under subcritical water oxidation. More than 95% Co and nearly 98% Li were recovered under the optimum conditions: temperature 350 °C, PVC/LiCoO{sub 2} ratio 3:1, time 30 min, and a solid/liquid ratio 16:1 (g/L), respectively. Moreover, PVC was completely dechlorinated at temperatures above 350 °C without any release of toxic chlorinated organic compounds. Assessment on economical and environmental impacts revealed that the PVC and LiCoO{sub 2} subcritical co-treatment process had significant technical, economic and environmental benefits over the traditional hydrometallurgy and pyrometallurgy processes. This innovative co-treatment process is efficient, environmentally friendly and adequate for Co and Li recovery from spent LIBs and simultaneous dechlorination of PVC in subcritical water.

The reduction of 4-chloronitrobenzene by Fe(II)-Fe(III) oxide systems - correlations with reduction potential and inhibition by silicate

Energy Technology Data Exchange (ETDEWEB)

Jones, Adele M., E-mail: adele.jones1@unsw.edu.au; Kinsela, Andrew S.; Collins, Richard N.; Waite, T. David, E-mail: d.waite@unsw.edu.au

2016-12-15

Recent studies have demonstrated that the rate at which Fe(II)-Fe(III) oxyhydroxide systems catalyze the reduction of reducible contaminants, such as 4-chloronitrobenzene, is well correlated to their thermodynamic reduction potential. Here we confirm this effect in the presence of Fe(III) oxyhydroxide phases not previously assessed, namely ferrihydrite and nano-goethite, as well as Fe(III) oxyhydroxide phases previously examined. In addition, silicate is found to decrease the extent of Fe(II) sorption to the Fe(III) oxyhydroxide surface, increasing the reduction potential of the Fe(II)-Fe(III) oxyhydroxide suspension and, accordingly, decreasing the rate of 4-chloronitrobenzene reduction. A linear relationship between the reduction potential of the Fe(II)-Fe(III) oxyhydroxide suspensions and the reduction rate of 4-chloronitrobenzene (normalized to surface area and concentration of sorbed Fe(II)) was obtained in the presence and absence of silicate. However, when ferrihydrite was doped with Si (through co-precipitation) the reduction of 4-chloronitrobenzene was much slower than predicted from its reduction potential. The results obtained have significant implications to the likely effectiveness of naturally occurring contaminant degradation processes involving Fe(II) and Fe(III) oxyhydroxides in groundwater environments containing high concentrations of silicate, or other species which compete with Fe(II) for sorption sites.

Reductive tetrachloroethene dehalogenation in the presence of oxygen by Sulfurospirillum multivorans: physiological studies and proteome analysis.

Science.gov (United States)

Gadkari, Jennifer; Goris, Tobias; Schiffmann, Christian L; Rubick, Raffael; Adrian, Lorenz; Schubert, Torsten; Diekert, Gabriele

2018-01-01

Reductive dehalogenation of organohalides is carried out by organohalide-respiring bacteria (OHRB) in anoxic environments. The tetrachloroethene (PCE)-respiring Epsilonproteobacterium Sulfurospirillum multivorans is one of few OHRB able to respire oxygen. Therefore, we investigated the organism's capacity to dehalogenate PCE in the presence of oxygen, which would broaden the applicability to use S. multivorans, unlike other commonly oxygen-sensitive OHRB, for bioremediation, e.g. at oxic/anoxic interphases. Additionally, this has an impact on our understanding of the global halogen cycle. Sulfurospirillum multivorans performs dehalogenation of PCE to cis-1,2-dichloroethene at oxygen concentrations below 0.19 mg/L. The redox potential of the medium electrochemically adjusted up to +400 mV had no influence on reductive dehalogenation by S. multivorans in our experiments, suggesting that higher levels of oxygen impair PCE dechlorination by inhibiting or inactivating involved enzymes. The PCE reductive dehalogenase remained active in cell extracts of S. multivorans exposed to 0.37 mg/L oxygen for more than 96 h. Analysis of the proteome revealed that superoxide reductase and cytochrome peroxidase amounts increased with 5% oxygen in the gas phase, while the response to atmospheric oxygen concentrations involved catalase and hydrogen peroxide reductase. Taken together, our results demonstrate that reductive dehalogenation by OHRB is not limited to anoxic conditions. © FEMS 2017. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Fabrication and evaluation of Au-Pd core-shell nanocomposites for dechlorination of diclofenac in water.

Science.gov (United States)

Wang, Xu; Li, Jian-Rong; Fu, Ming-Lai; Yuan, Baoling; Cui, Hao-Jie; Wang, Ya-Fen

2015-01-01

Nanocomposites with core-shell structure usually exhibit excellent catalytic properties due to unique interfaces and synergistic effect among composites. In this study, Au-Pd bimetallic nanoparticles (NPs) with core-shell structure (Au-Pd cs) by using Au NPs as core and Pd as shell were successfully fabricated and, for the first time, were used to investigate the dechlorination of diclofenac (DCF) at H2 atmosphere in water at room temperature. The degradation products were studied as well by using HPLC/Q-ToF MS/MS. The operational factors such as pH and composition of the Au-Pd cs were also studied. The results showed that nearly 100% of DCF (30 mg L(-1), 50 mL, pH=7) was dechlorinated in 4.5 h by 10 mL of 56 mg L(-1) of Au-Pd cs. Ninety per cent of DCF was degraded in 6.5 h by the mixture of Au and Pd NPs. However, the individual Au NPs had no obvious effect in degrading DCF and the monometallic Pd NPs with comparable concentration only degraded less than 20% of DCF. Furthermore, the reaction mechanism of this catalytic process was studied in detail. It was found that the degradation was a second-order exponential reaction. The two main degradation products were obtained by cleaving the carbon-halogen bond of DCF and this made the degradation products more environmentally friendly.

Enhanced dechlorination of trichloroethylene using electrospun polymer nanofibrous mats immobilized with iron/palladium bimetallic nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Ma, Hui [State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, Donghua University, Shanghai 201620 (China); College of Chemistry, Chemical Engineering and Biotechnology, Donghua University, Shanghai 201620 (China); Huang, Yunpeng; Shen, Mingwu; Guo, Rui; Cao, Xueyan [College of Chemistry, Chemical Engineering and Biotechnology, Donghua University, Shanghai 201620 (China); Shi, Xiangyang, E-mail: xshi@dhu.edu.cn [State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, Donghua University, Shanghai 201620 (China); College of Chemistry, Chemical Engineering and Biotechnology, Donghua University, Shanghai 201620 (China); CQM - Centro de Quimica da Madeira, Universidade da Madeira, Campus da Penteada, 9000-390 Funchal (Portugal)

2012-04-15

Fe/Pd bimetallic nanoparticles (NPs) have held great promise for treating trichloroethylene (TCE)-contaminated groundwater, without the accumulation of chlorinated intermediates. However, the conventionally used colloidal Fe/Pd NPs usually aggregate rapidly, resulting in a reduced reactivity. To reduce the particle aggregation, we employed electrospun polyacrylic acid (PAA)/polyvinyl alcohol (PVA) polymer nanofibers as a nanoreactor to immobilize Fe/Pd bimetallic NPs. In the study, the water-stable PAA/PVA nanofibrous mats were complexed with Fe (III) ions via the binding with the free carboxyl groups of PAA for subsequent formation and immobilization of zero-valent iron (ZVI) NPs. Fe/Pd bimetallic NPs were then formed by the partial reduction of Pd(II) ions with ZVI NPs. The formed electrospun nanofibrous mats containing Fe/Pd bimetallic NPs with a diameter of 2.8 nm were characterized by scanning electron microscopy, energy-dispersive spectroscopy, transmission electron microscopy, thermogravimetric analysis, and inductively coupled plasma-atomic emission spectroscopy. The Fe/Pd NP-containing electrospun PAA/PVA nanofibrous mats exhibited higher reactivity than that of the ZVI NP-containing mats or colloidal Fe/Pd NPs in the dechlorination of trichloroethylene (TCE), which was used as a model contaminant. With the high surface area to volume ratio, high porosity, and great reusability of the fibrous mats immobilized with the bimetallic NPs, the composite nanofibrous mats should be amenable for applications in remediation of various environmental contaminants.

Enhanced dechlorination of trichloroethylene using electrospun polymer nanofibrous mats immobilized with iron/palladium bimetallic nanoparticles

International Nuclear Information System (INIS)

Ma, Hui; Huang, Yunpeng; Shen, Mingwu; Guo, Rui; Cao, Xueyan; Shi, Xiangyang

2012-01-01

Fe/Pd bimetallic nanoparticles (NPs) have held great promise for treating trichloroethylene (TCE)-contaminated groundwater, without the accumulation of chlorinated intermediates. However, the conventionally used colloidal Fe/Pd NPs usually aggregate rapidly, resulting in a reduced reactivity. To reduce the particle aggregation, we employed electrospun polyacrylic acid (PAA)/polyvinyl alcohol (PVA) polymer nanofibers as a nanoreactor to immobilize Fe/Pd bimetallic NPs. In the study, the water-stable PAA/PVA nanofibrous mats were complexed with Fe (III) ions via the binding with the free carboxyl groups of PAA for subsequent formation and immobilization of zero-valent iron (ZVI) NPs. Fe/Pd bimetallic NPs were then formed by the partial reduction of Pd(II) ions with ZVI NPs. The formed electrospun nanofibrous mats containing Fe/Pd bimetallic NPs with a diameter of 2.8 nm were characterized by scanning electron microscopy, energy-dispersive spectroscopy, transmission electron microscopy, thermogravimetric analysis, and inductively coupled plasma-atomic emission spectroscopy. The Fe/Pd NP-containing electrospun PAA/PVA nanofibrous mats exhibited higher reactivity than that of the ZVI NP-containing mats or colloidal Fe/Pd NPs in the dechlorination of trichloroethylene (TCE), which was used as a model contaminant. With the high surface area to volume ratio, high porosity, and great reusability of the fibrous mats immobilized with the bimetallic NPs, the composite nanofibrous mats should be amenable for applications in remediation of various environmental contaminants.

Prediction of Reduction Potentials of Copper Proteins with Continuum Electrostatics and Density Functional Theory.

Science.gov (United States)

Fowler, Nicholas J; Blanford, Christopher F; Warwicker, Jim; de Visser, Sam P

2017-11-02

Blue copper proteins, such as azurin, show dramatic changes in Cu 2+ /Cu + reduction potential upon mutation over the full physiological range. Hence, they have important functions in electron transfer and oxidation chemistry and have applications in industrial biotechnology. The details of what determines these reduction potential changes upon mutation are still unclear. Moreover, it has been difficult to model and predict the reduction potential of azurin mutants and currently no unique procedure or workflow pattern exists. Furthermore, high-level computational methods can be accurate but are too time consuming for practical use. In this work, a novel approach for calculating reduction potentials of azurin mutants is shown, based on a combination of continuum electrostatics, density functional theory and empirical hydrophobicity factors. Our method accurately reproduces experimental reduction potential changes of 30 mutants with respect to wildtype within experimental error and highlights the factors contributing to the reduction potential change. Finally, reduction potentials are predicted for a series of 124 new mutants that have not yet been investigated experimentally. Several mutants are identified that are located well over 10 Å from the copper center that change the reduction potential by more than 85 mV. The work shows that secondary coordination sphere mutations mostly lead to long-range electrostatic changes and hence can be modeled accurately with continuum electrostatics. © 2017 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

Fenton-like oxidation of 2,4-DCP in aqueous solution using iron-based nanoparticles as the heterogeneous catalyst.

Science.gov (United States)

Li, Renchao; Gao, Ying; Jin, Xiaoying; Chen, Zuliang; Megharaj, Mallavarapu; Naidu, Ravendra

2015-01-15

In this report, various iron-based nanoparticles (nZVI, n-Ni/Fe, n-Pd/Fe) were used for both heterogeneous Fenton oxidation of 2,4-dichlorophenol (2,4-DCP) and reductive dechlorination of 2,4-DCP in order to understand their roles in the Fenton oxidation and the reductive degradation of 2,4-DCP. The dechlorination efficiency of 2,4-DCP using nZVI, n-Ni/Fe, n-Fe/Pd and Fe(2)(+) was 6.48%, 6.80%, 15.95%, 5.02%, while Fenton oxidation efficiency of 2,4-DCP was 57.87%, 34.23%, 27.94%, 19.61% after 180 min, respectively. The new findings included a higher dechlorination using n-Fe/Pd due to Pd effective catalysis and the effective heterogeneous Fenton oxidation using nZVI depending on reductive dechlorination and heterogeneous Fenton oxidation occurs simultaneously. However, nZVI as the potential catalyst for heterogeneous Fenton was observed, and SEM, EDS and XRD demonstrate that change on the nZVI surface occurred due to the Fe(2+) leaching, and Total Organic Carbon (TOC) (30.71%) shows that 2,4-DCP was degraded. Furthermore, the experiment indicates that the pH values and concentration of 2,4-DCP significantly impacted on the heterogeneous Fenton oxidation of 2,4-DCP and the data fits well with the pseudo first-order kinetic model, which was a diffusion-controlled reaction. Finally, a possible mechanism for degradation of 2,4-DCP was proposed. Copyright © 2014 Elsevier Inc. All rights reserved.

Bioremediation of 1,2-dichloroethane contaminated groundwater: Microcosm and microbial diversity studies

International Nuclear Information System (INIS)

Wang, S.Y.; Kuo, Y.C.; Huang, Y.Z.; Huang, C.W.; Kao, C.M.

2015-01-01

In this study, the effectiveness of bioremediating 1,2-dichloroethane (DCA)-contaminated groundwater under different oxidation–reduction processes was evaluated. Microcosms were constructed using indigenous bacteria and activated sludge as the inocula and cane molasses and a slow polycolloid-releasing substrate (SPRS) as the primary substrates. Complete DCA removal was obtained within 30 days under aerobic and reductive dechlorinating conditions. In anaerobic microcosms with sludge and substrate addition, chloroethane, vinyl chloride, and ethene were produced. The microbial communities and DCA-degrading bacteria in microcosms were characterized by 16S rRNA-based denatured-gradient-gel electrophoresis profiling and nucleotide sequence analyses. Real-time polymerase chain reaction was applied to evaluate the variations in Dehalococcoides spp. and Desulfitobacterium spp. Increase in Desulfitobacterium spp. indicates that the growth of Desulfitobacterium might be induced by DCA. Results indicate that DCA could be used as the primary substrate under aerobic conditions. The increased ethene concentrations imply that dihaloelimination was the dominate mechanism for DCA biodegradation. - Highlights: • DCA can be used as the primary substrate and degraded by the indigenous microbial consortia. • Reductive dechlorination of DCA can be enhanced by the supplement of substrates and sludge. • Dihaloelimination is the dominant mechanism for DCA dechlorination and ethene is the end product. • SPRS can serve as the primary substrate and creates anaerobic conditions for DCA dechlorination. • Reductive dechlorination is a feasible option for DCA-contaminated groundwater remediation. - DCA can serve as the primary substrate and degraded by indigenous bacteria aerobically. Dihaloelimination is the dominant mechanism and ethene is the end product via dechlorination

The potential of household solid waste reduction in Sukomanunggal District, Surabaya

Science.gov (United States)

Warmadewanthi, I. D. A. A.; Kurniawati, S.

2018-01-01

The rapid population growth affects the amount of waste generated. Sukomanunggal Subdistrict is the densest area in West Surabaya which has a population of 100,602 inhabitants with a total area of 11.2 km2. The population growth significantly affects the problem of limited land for landfill facilities (final processing sites). According to the prevailing regulations, solid waste management solutions include the solid waste reduction and management. This study aims to determine the potential reduction of household solid waste at the sources. Household solid waste samplings were performed for eight consecutive days. The samples were then analyzed to obtain the generation rate, density, and composition so that the household solid waste reduction potential for the next 20 years could be devised. Results of the analysis showed that the value of waste is 0.27 kg/person/day, while the total household solid waste generation amounted to 27,162.58 kg/day or 187.70 m3/day. Concerning the technical aspects, the current solid waste reduction in Sukomanunggal Subdistrict has reached 2.1% through the application of waste bank, composting, and scavenging activities at the dumping sites by the garbage collectors. In the year of 2036, the potential reduction of household solid waste in Sukomanunggal Subdistrict has been estimated to reach 28.0%.

De-chlorination and solidification of radioactive LiCl waste salt by using SiO_2-Al_2O_3-P_2O_5 (SAP) inorganic composite including B_2O_3 component

International Nuclear Information System (INIS)

Lee, Ki Rak; Park, Hwan-Seo; Cho, In-Hak; Choi, Jung-Hoon; Eun, Hee-Chul; Lee, Tae-Kyo; Han, Seung Youb; Ahn, Do-Hee

2017-01-01

SAP (SiO_2-Al_2O_3-P_2O_5) composite has been recently studied in KAERI to deal with the immobilization of radioactive salt waste, one of the most problematic wastes in the pyro-chemical process. Highly unstable salt waste was successfully converted into stable compounds by the dechlorination process with SAPs, and then a durable waste form with a high waste loading was produced when adding glassy materials to dechlorination product. In the present study, U-SAP composite which is SAP bearing glassy component (Boron) was synthesized to remove the adding and mixing steps of glassy materials for a monolithic wasteform. With U-SAPs prepared by a sol-gel process, a series of wasteforms were fabricated to identify a proper reaction condition. Physical and chemical properties of dechlorination products and U-SAP wasteforms were characterized by XRD, DSC, SEM, TGA and PCT-A. A U-SAP wasteform showed suitable properties as a radioactive wasteform such as dense surface morphology, high waste loading, and high durability at the optimized U-SAP/salt ratio 2.

Comment on 'evaluation of dechlorination mechanisms during anaerobic fermentation of blached kraft mill effluent by W.J. Parker, E.R. Hall and G.J. Farquhar'

Digital Repository Service at National Institute of Oceanography (India)

Sarkar, A.

Comment on "Evaluation of dechlorination mechanisms during anaerobic fermentation of bleached kraft mill effluent", is put forth. The data reproduced in Table 1 does not seem to be authentic as the method of preprationo of the chlorinated organic...

Diversity of reductive dehalogenase genes from environmental samples and enrichment cultures identified with degenerate primer PCR screens.

Directory of Open Access Journals (Sweden)

Laura Audrey Hug

2013-11-01

Full Text Available Reductive dehalogenases are the critical enzymes for anaerobic organohalide respiration, a microbial metabolic process that has been harnessed for bioremediation efforts to resolve chlorinated solvent contamination in groundwater and is implicated in the global halogen cycle. Reductive dehalogenase sequence diversity is informative for the dechlorination potential of the site or enrichment culture. A suite of degenerate PCR primers targeting a comprehensive curated set of reductive dehalogenase genes was designed and applied to twelve DNA samples extracted from contaminated and pristine sites, as well as six enrichment cultures capable of reducing chlorinated compounds to non-toxic end-products. The amplified gene products from four environmental sites and two enrichment cultures were sequenced using Illumina HiSeq, and the reductive dehalogenase complement of each sample determined. The results indicate that the diversity of the reductive dehalogenase gene family is much deeper than is currently accounted for: one-third of the translated proteins have less than 70% pairwise amino acid identity to database sequences. Approximately 60% of the sequenced reductive dehalogenase genes were broadly distributed, being identified in four or more samples, and often in previously sequenced genomes as well. In contrast, 17% of the sequenced reductive dehalogenases were unique, present in only a single sample and bearing less than 90% pairwise amino acid identity to any previously identified proteins. Many of the broadly distributed reductive dehalogenases are uncharacterized in terms of their substrate specificity, making these intriguing targets for further biochemical experimentation. Finally, comparison of samples from a contaminated site and an enrichment culture derived from the same site eight years prior allowed examination of the effect of the enrichment process.

Noise and Fuel Burn Reduction Potential of an Innovative Subsonic Transport Configuration

Science.gov (United States)

Guo, Yueping; Nickol, Craig L.; Thomas, Russell H.

2014-01-01

A study is presented for the noise and fuel burn reduction potential of an innovative double deck concept aircraft with two three-shaft direct-drive turbofan engines. The engines are mounted from the fuselage so that the engine inlet is over the main wing. It is shown that such an aircraft can achieve a cumulative Effective Perceived Noise Level (EPNL) about 28 dB below the current aircraft noise regulations of Stage 4. The combination of high bypass ratio engines and advanced wing design with laminar flow control technologies provide fuel burn reduction and low noise levels simultaneously. For example, the fuselage mounted engine position provides more than 4 EPNLdB of noise reduction by shielding the inlet radiated noise. To identify the potential effect of noise reduction technologies on this concept, parametric studies are presented to reveal the system level benefits of various emerging noise reduction concepts, for both engine and airframe noise reduction. These concepts are discussed both individually to show their respective incremental noise reduction potential and collectively to assess their aggregate effects on the total noise. Through these concepts approximately about 8 dB of additional noise reduction is possible, bringing the cumulative noise level of this aircraft to 36 EPNLdB below Stage 4, if the entire suite of noise reduction technologies would mature to practical application. In a final step, an estimate is made for this same aircraft concept but with higher bypass ratio, geared, turbofan engines. With this geared turbofan propulsion system, the noise is estimated to reach as low as 40-42 dB below Stage 4 with a fuel burn reduction of 43-47% below the 2005 best-in-class aircraft baseline. While just short of the NASA N+2 goals of 42 dB and 50% fuel burn reduction, for a 2025 in service timeframe, this assessment shows that this innovative concept warrants refined study. Furthermore, this design appears to be a viable potential future passenger

In situ redox manipulation of subsurface sediments from Fort Lewis, Washington: Iron reduction and TCE dechlorination mechanisms

Energy Technology Data Exchange (ETDEWEB)

JE Szecsody; JS Fruchter; DS Sklarew; JC Evans

2000-03-21

Pacific Northwest National Laboratory (PNNL) conducted a bench-scale study to determine how effective chemically treated Ft. Lewis sediments can degrade trichloroethylene (TCE). The objectives of this experimental study were to quantify: (1) sediment reduction and oxidation reactions, (2) TCE degradation reactions, and (3) other significant geochemical changes that occurred. Sediment reduction and oxidation were investigated to determine the mass of reducible iron in the Ft. Lewis sediments and the rate of this reduction and subsequent oxidation at different temperatures. The temperature dependence was needed to be able to predict field-scale reduction in the relatively cold ({approximately}11 C) Ft. Lewis aquifer. Results of these experiments were used in conjunction with other geochemical and hydraulic characterization to design the field-scale injection experiment and predict barrier longevity. For example, the sediment reduction rate controls the amount of time required for the dithionite solution to fully react with sediments. Sediment oxidation experiments were additionally conducted to determine the oxidation rate and provide a separate measure of the mass of reduced iron. Laboratory experiments that were used to meet these objectives included: (1) sediment reduction in batch (static) systems, (2) sediment reduction in 1-D columns, and (3) sediment oxidation in 1-D columns. Multiple reaction modeling was conducted to quantify the reactant masses and reaction rates.

The effect of ammonium chloride and urea application on soil bacterial communities closely related to the reductive transformation of pentachlorophenol.

Science.gov (United States)

Yu, Huan-Yun; Wang, Yong-kui; Chen, Peng-cheng; Li, Fang-bai; Chen, Man-jia; Hu, Min

2014-05-15

Pentachlorophenol (PCP) is widely distributed in the soil, and nitrogen fertilizer is extensively used in agricultural production. However, studies on the fate of organic contaminants as affected by nitrogen fertilizer application have been rare and superficial. The present study aimed to examine the effect of ammonium chloride (NH4Cl) and urea (CO(NH2)2) application on the reductive transformation of PCP in a paddy soil. The study showed that the addition of low concentrations of NH4Cl/CO(NH2)2 enhanced the transformation of PCP, while the addition of high concentrations of NH4Cl/CO(NH2)2 had the opposite effect. The variations in the abundance of soil microbes in response to NH4Cl/CO(NH2)2 addition showed that both NH4Cl and CO(NH2)2 had inhibitory effects on the growth of dissimilatory iron-reducing bacteria (DIRB) of the genus Comamonas. In contrast, for the genus Shewanella, low concentrations of NH4Cl inhibited growth, and high concentrations of NH4Cl enhanced growth, whereas all concentrations of CO(NH2)2 showed enhancement effects. In addition, consistent patterns of variation were found between the abundances of dechlorinating bacteria in the genus Dehalobacter and PCP transformation rates under NH4Cl/CO(NH2)2 addition. In conclusion, nitrogen application produced variations in the structure of the soil microbial community, especially in the abundance of dissimilatory iron-reducing bacteria and dechlorinating bacteria, which, in turn, affected PCP dechlorination. Copyright © 2014 Elsevier B.V. All rights reserved.

Biotransformation of chlorinated aliphatic solvents in the presence of aromatic compounds under methanogenic conditions

International Nuclear Information System (INIS)

Liang, L.N.; Grbic-Galic, D.

1993-01-01

Transformation of carbon tetrachloride (CT) and tetrachloroethylene (PCE) was studied under methanogenic conditions, in the presence or absence of toluene, ethylbenzene, phenol, and benzoate. Microbial inoculate for the experiments were derived from three groundwater aquifers contaminated by jet fuel or creosote. CT and PCE were reductively dechlorinated in all the examined castes (CT to chloroform [CF]; PCE to trichloroethylene [TCE], trans-1,2-dichloroethylene [DCE], and vinyl chloride [VC]). In the aquifer microcosms, the electron donors used for the reductive transformations were most likely the unidentified organic compounds present on aquifer solids, or storage materials in microorganisms. Alternatively, molecular hydrogen from the anaerobic incubator atmosphere could have been used. The addition of benzoate caused a decrease in rates of dechlorination if benzoate was transformed. Phenol and ethylbenzene were not degraded and did not influence the transformation of CT or PCE. Toluene, in most of the studied cases, had no influence on reductive dechlorination of either CT or PCE. Only in microcosms derived from a JP-4 jet fuel-contaminated aquifer did the anaerobic degradation of toluene occur simultaneously with reductive dechlorination of PCE, suggesting that toluene might possibly have been used as an electron donor for reductive transformation of chlorinated solvents

Stockholm CHP potential - An opportunity for CO2 reductions?

International Nuclear Information System (INIS)

Danestig, Maria; Gebremehdin, Alemayehu; Karlsson, Bjoern

2007-01-01

The potential for combined heat and power (CHP) generation in Stockholm is large and a total heat demand of about 10 TWh/year can be met in a renewed large district heating system. This model of the Stockholm district heating system shows that CHP generation can increase from 8% in 2004 to 15.5% of the total electricity generation in Sweden. Increased electricity costs in recent years have awakened an interest to invest in new electricity generation. Since renewable alternatives are favoured by green certificates, bio-fuelled CHP is most profitable at low electricity prices. Since heat demand in the district heating network sets the limit for possible electricity generation, a CHP alternative with a high electricity to heat ratio will be more profitable at when electricity prices are high. The efficient energy use in CHP has the potential to contribute to reductions in carbon dioxide emissions in Europe, when they are required and the European electricity market is working perfectly. The potential in Stockholm exceeds Sweden's undertakings under the Kyoto protocol and national reduction goals. (author)

Deposition of Fe-Ni nanoparticles on Al{sub 2}O{sub 3} for dechlorination of chloroform and trichloroethylene

Energy Technology Data Exchange (ETDEWEB)

Hsieh, S.-H. [Graduate School of Engineering Science and Technology, National Yunlin University of Science and Technology, Taiwan (China) and Department of Materials Science and Engineering, National Formosa University, Taiwan (China)]. E-mail: shhsieh@sunws.nfu.edu.tw; Horng, J.-J. [Department of Safety, Health, and Environmental Engineering, National Yunlin University of Science and Technology, Douliou, Yunlin 640, Taiwan (China)

2006-11-30

This research proposes an efficient method for depositing Fe-Ni nanoparticles on Al{sub 2}O{sub 3} microparticles to decompose containments in ground water, such as chloroform and trichloroethylene. The Fe-Ni nanoparticles can be deposited onto the surface of Al{sub 2}O{sub 3} microparticles by electroless plating technique. The reasons why the Fe-Ni nanoparticles would be deposited on the surface of Al{sub 2}O{sub 3} microparticles is to avoid the agglomeration of Fe-Ni nanoparticles due to their surface effect and magnetic property. The results show that the sizes of Fe-Ni particles on Al{sub 2}O{sub 3} particles are between several and several hundreds of nanometers, the contents of Fe and Ni in Fe-Ni nanoparticles can be adjusted from 8 to 60 at.% for Fe and 40 to 92 at.% for Ni, the specific surface area of Fe-Ni nanoparticles can reach to 117 m{sup 2}/g, and the reaction mechanism of dechlorination of chloroform of 2 mg/L by Fe-Ni/Al{sub 2}O{sub 3} particles of 5 g/L appears to be pseudo first order with a half life of 0.7 h and the half life is 0.25 h for the dechlorination of trichloroethylene of 2 mg/L.

GHG REDUCTION POTENTIAL OF BIOGAS RESOURCE UTILZATION IN HOLBÆK’S HEATING AND ELECTRICITY SECTOR

OpenAIRE

DAO, THI THU HUONG DIU

2013-01-01

This project is set out to identify the GHG reduction potentials of the 3 identified biogas plants in the Holbæk municipality. The GHG reduction of the 3 plants will be calculated in association with 2 biogas applications, which are CHP and upgrading biogas for individual heating purposes. The GHG reduction potentials of the 3 plants will be reflected to Holbæk’s specific GHG reduction target to see how these potentials contribute to the set goal. Departure from that, future version of biogas...

One-electron standard reduction potentials of nitroaromatic and cyclic nitramine explosives

International Nuclear Information System (INIS)

Uchimiya, Minori; Gorb, Leonid; Isayev, Olexandr; Qasim, Mohammad M.; Leszczynski, Jerzy

2010-01-01

Extensive studies have been conducted in the past decades to predict the environmental abiotic and biotic redox fate of nitroaromatic and nitramine explosives. However, surprisingly little information is available on one-electron standard reduction potentials (E o (R-NO 2 /R-NO 2 - )). The E o (R-NO 2 /R-NO 2 - ) is an essential thermodynamic parameter for predicting the rate and extent of reductive transformation for energetic residues. In this study, experimental (linear free energy relationships) and theoretical (ab initio calculation) approaches were employed to determine E o (R-NO 2 /R-NO 2 - ) for nitroaromatic, (caged) cyclic nitramine, and nitroimino explosives that are found in military installations or are emerging contaminants. The results indicate a close agreement between experimental and theoretical E o (R-NO 2 /R-NO 2 - ) and suggest a key trend: E o (R-NO 2 /R-NO 2 - ) value decreases from di- and tri-nitroaromatic (e.g., 2,4-dinitroanisole) to nitramine (e.g., RDX) to nitroimino compound (e.g., nitroguanidine). The observed trend in E o (R-NO 2 /R-NO 2 - ) agrees with reported rate trends for reductive degradation, suggesting a thermodynamic control on the reduction rate under anoxic/suboxic conditions. - Reduction of explosives becomes less thermodynamically favorable as the one-electron standard reduction potential decreases from di- and tri-nitroaromatic, nitramine, to nitroimino compounds.

Growing Pereskia aculeata under intermittent irrigation according to levels of matric potential reduction

Directory of Open Access Journals (Sweden)

Carla Regina Amorim dos Anjos Queiroz

2015-03-01

Full Text Available Pereskia aculeata Mill., popularly known in Brazil as “Ora-pro-nobis”, is an unconventional edible vegetable. Taking into account its potential for agronomic cultivation, this study aimed to evaluate the growth response of this plant under intermittent drought through controlled reductions in the substrate matric potential, in a greenhouse. Treatments consisted of adding to the pots a volume of water to raise the matric potential to -5 kPa, according to the water retention curve in the substrate, whenever the mean substrate matric potential reached values between -10 kPa and -70 kPa, depending on the treatment. At 140 days after transplanting, leaf area and dry mass of leaves, stems and roots were determined. The intermittent reduction of the matric potential in the root zone of “Ora-pro-nobis” affected less the dry mass accumulation in leaves (reduction of 21.4% than in stems (reduction of 48.1% and roots (reduction of 63.7%, and that is interesting because leaves are the main commercial product of this plant. The treatment also modified the proportionality of dry mass allocation among plant parts and reduced the photosynthetic efficiency of leaves, fact evidenced by the linear increase of the specific leaf area (0.63 cm2 g-1kPa-1 and leaf area ratio (0.39 cm-2 g-1kPa-1, although not affecting directly the leaf area.

One-electron standard reduction potentials of nitroaromatic and cyclic nitramine explosives

Energy Technology Data Exchange (ETDEWEB)

Uchimiya, Minori, E-mail: sophie.uchimiya@ars.usda.go [Environmental Laboratory, U.S. Army Engineer Research and Development Center, Vicksburg, MS 39180 (United States); Gorb, Leonid [SpecPro Inc, 3909 Halls Ferry Road, Vicksburg, MS 39180 (United States); Isayev, Olexandr [Department of Chemistry, Case Western Reserve University, Cleveland, OH 44106 (United States); Qasim, Mohammad M. [Environmental Laboratory, U.S. Army Engineer Research and Development Center, Vicksburg, MS 39180 (United States); Leszczynski, Jerzy [Environmental Laboratory, U.S. Army Engineer Research and Development Center, Vicksburg, MS 39180 (United States); Interdisciplinary Center for Nanotoxicity, Jackson State University, Jackson, MS 39217 (United States)

2010-10-15

Extensive studies have been conducted in the past decades to predict the environmental abiotic and biotic redox fate of nitroaromatic and nitramine explosives. However, surprisingly little information is available on one-electron standard reduction potentials (E{sup o}(R-NO{sub 2}/R-NO{sub 2}{sup -})). The E{sup o}(R-NO{sub 2}/R-NO{sub 2}{sup -}) is an essential thermodynamic parameter for predicting the rate and extent of reductive transformation for energetic residues. In this study, experimental (linear free energy relationships) and theoretical (ab initio calculation) approaches were employed to determine E{sup o}(R-NO{sub 2}/R-NO{sub 2}{sup -}) for nitroaromatic, (caged) cyclic nitramine, and nitroimino explosives that are found in military installations or are emerging contaminants. The results indicate a close agreement between experimental and theoretical E{sup o}(R-NO{sub 2}/R-NO{sub 2}{sup -}) and suggest a key trend: E{sup o}(R-NO{sub 2}/R-NO{sub 2}{sup -}) value decreases from di- and tri-nitroaromatic (e.g., 2,4-dinitroanisole) to nitramine (e.g., RDX) to nitroimino compound (e.g., nitroguanidine). The observed trend in E{sup o}(R-NO{sub 2}/R-NO{sub 2}{sup -}) agrees with reported rate trends for reductive degradation, suggesting a thermodynamic control on the reduction rate under anoxic/suboxic conditions. - Reduction of explosives becomes less thermodynamically favorable as the one-electron standard reduction potential decreases from di- and tri-nitroaromatic, nitramine, to nitroimino compounds.

Determination of one-electron reduction potentials of some radiosensitive compounds by pulse radiolysis

International Nuclear Information System (INIS)

Zuo Zhihua; Yao Side; Li Hucheng; Lin Nianyun; Jin Yizun

1994-01-01

One-electron reduction potential (E 7 1 ) is one of the important parameters of radiosensitive compound with high electron affinity. In this work one-electron reduction potentials of some radiosensitizers, such as Miso, 911, CMNa, SMU-1, SMU-2, SMD, SNN, S 3 and BSO, were determined pulse radiolytically by using anthraquinone-2-sulfate (AQS), duroquinone (DQ) and methyl viologen (MV 2+ ) as references

Uncovering the intrinsic relationship of electrocatalysis and molecular electrochemistry for dissociative electron transfer to polychloroethanes at silver cathode

International Nuclear Information System (INIS)

Huang, Binbin; Zhu, Yuanyuan; Li, Jing; Zeng, Guangming; Lei, Chao

2017-01-01

Highlights: • Thermodynamics of dissociative electron transfer to C–Cl bonds at Ag are studied. • The catalyzed dissociative electron transfer theory was proposed for the first time. • The adsorption of organic chlorides onto Ag plays a key role for dechlorination. • The catalytic property of Ag is ascribed to the lower of intrinsic barrier energy. • The relationship of electrocatalysis and molecular electrochemistry is indicated. - Abstract: The relationship between electrocatalysis and molecular electrochemistry for the reductive dechlorination of organic chlorides has been a central topic for decades. Herein, we try to reveal the catalytic property of silver electrode by investigating the thermodynamics of dissociative electron transfer (DET) to C–Cl bonds of polychloroethanes (PCAs) on both inert (GC) and catalytic (Ag) electrodes. By extending the “sticky” DET model reported by Savéant, we show that the catalyzed DET model can well describe the activation-driving force relationships for the electrocatalytic dechlorination on Ag, where in addition to the possible ion-dipole interations, the adsorption of chlorinated species onto Ag surface, which is found to play a fundamental role in the electrocatalysis process in this study, is introduced in the new developed DET model. In this work, we firstly report that the catalytic property of Ag electrode characterizing with drastically postive shift of reduction potential is ascribed to the lower of intrinsic barrier free energy, rather than the activation free energy, for the reductive dechlorination. Moreover, the intrinsic relationship of electrocatalysis and molecular electrochemistry is clearly indicated and quantitatively developed. These results may provide new insights in uncovering both the nature of catalytic property of Ag and the relationship of electrocatalysis and molecular electrochemistry for PCAs and other halocarbons.

The little bacteria that can – diversity, genomics and ecophysiology of ‘Dehalococcoides’ spp. in contaminated environments

Science.gov (United States)

Taş, Neslihan; Van Eekert, Miriam H. A.; De Vos, Willem M.; Smidt, Hauke

2010-01-01

Summary The fate and persistence of chlorinated organics in the environment have been a concern for the past 50 years. Industrialization and extensive agricultural activities have led to the accumulation of these pollutants in the environment, while their adverse impact on various ecosystems and human health also became evident. This review provides an update on the current knowledge of specialized anaerobic bacteria, namely ‘Dehalococcoides’ spp., which are dedicated to the transformation of various chlorinated organic compounds via reductive dechlorination. Advances in microbiology and molecular techniques shed light into the diversity and functioning of Dehalococcoides spp. in several different locations. Recent genome sequencing projects revealed a large number of genes that are potentially involved in reductive dechlorination. Molecular approaches towards analysis of diversity and expression especially of reductive dehalogenase‐encoding genes are providing a growing body of knowledge on biodegradative pathways active in defined pure and mixed cultures as well as directly in the environment. Moreover, several successful field cases of bioremediation strengthen the notion of dedicated degraders such as Dehalococcoides spp. as key players in the restoration of contaminated environments. PMID:21255338

Emerging economies. Potentials, pledges and fair shares of greenhouse gas reduction

Energy Technology Data Exchange (ETDEWEB)

Fekete, Hanna; Hoehne, Niklas; Hagemann, Markus [Ecofys Germany GmbH, Koeln (Germany); Wehnert, Timon; Mersmann, Florian [Wuppertal Institute for Climate, Environment, Energy GmbH (Germany); Vieweg, Marion; Rocha, Marcia; Schaeffer, Michiel; Hare, William [Climate Analytics gGmbH, Berlin (Germany)

2013-04-15

Greenhouse gas emissions need to decrease substantially to limit global average temperature to a maximum of 2 C warming above the preindustrial level in 2100. Emerging economies are of increasing importance in this global effort. In this report we assess how ambitious emission reduction pledges of emerging economies are compared to business as usual emissions, the countries' mitigation potential and respective efforts based on different equity principles. We also compare the pledges and the identified mitigation potential of emerging economies to a global emissions pathway needed to limit global temperature increase to 2 C. Our assessment includes Brazil, China, India, Mexico, South Africa and South Korea. We find that emerging economies have a substantial impact on future global emission levels. This is due to high current levels and high projected growth rates. Also, in most of the countries a large emission reduction potential is available. Action needs to be taken soon to enable the full use of the potential until 2020 and most emerging economies will need significant support from developed countries to implement those.

Potential reduction of non-residential solid waste in Sukomanunggal district West Surabaya

Science.gov (United States)

Warmadewanthi, I. D. A. A.; Reswari, S. A.

2018-01-01

Sukomanunggal district a development unit 8 with the designation as a regional trade and services, industrial, education, healthcare, offices, and shopping center. The development of this region will make an increasing solid waste generation, especially waste from non-residential facilities. The aims of this research to know the potential reduction of waste source. The method used is the Likert scale questionnaire to determine the knowledge, attitude, and behavior of non-residential facilities manager. Results from this research are the existing reduction of non-residential solid waste is 5.34%, potential reduction of the waste source is optimization of plastic and paper waste with the reduction rate up to 19,52%. The level of public participation existing amounted to 46.79% with a willingness to increase recycling efforts amounted to 72.87%. Efforts that can be developed to increase public awareness of 3R are providing three types of bins, modification of solid waste collection schedule according to a type of waste that has been sorted, the provision of the communal bin.

Polyhydroxyalkanoate as a slow-release carbon source for in situ bioremediation of contaminated aquifers: From laboratory investigation to pilot-scale testing in the field.

Science.gov (United States)

Pierro, Lucia; Matturro, Bruna; Rossetti, Simona; Sagliaschi, Marco; Sucato, Salvatore; Alesi, Eduard; Bartsch, Ernst; Arjmand, Firoozeh; Papini, Marco Petrangeli

2017-07-25

A pilot-scale study aiming to evaluate the potential use of poly-3-hydroxy-butyrate (PHB) as an electron donor source for in situ bioremediation of chlorinated hydrocarbons in groundwater was conducted. Compared with commercially available electron donors, PHB offers a restricted fermentation pathway (i.e., through acetic acid and molecular hydrogen) by avoiding the formation of any residual carbon that could potentially spoil groundwater quality. The pilot study was carried out at an industrial site in Italy, heavily contaminated by different chlorinated aliphatic hydrocarbons (CAHs). Prior to field testing, PHB was experimentally verified as a suitable electron donor for biological reductive dechlorination processes at the investigated site by microcosm studies carried out on site aquifer material and measuring the quantitative transformation of detected CAHs to ethene. Owing to the complex geological characteristics of the aquifer, the use of a groundwater circulation well (GCW) was identified as a potential strategy to enable effective delivery and distribution of electron donors in less permeable layers and to mobilise contaminants. A 3-screened, 30-m-deep GCW coupled with an external treatment unit was installed at the site. The effect of PHB fermentation products on the in situ reductive dechlorination processes were evaluated by quantitative real-time polymerase chain reaction (qPCR). The results from the first 4 months of operation clearly demonstrated that the PHB fermentation products were effectively delivered to the aquifer and positively influenced the biological dechlorination activity. Indeed, an increased abundance of Dehalococcoides mccartyi (up to 6.6 fold) and reduced CAH concentrations at the installed monitoring wells were observed. Copyright © 2016 Elsevier B.V. All rights reserved.

Potentially bioavailable natural organic carbon and hydrolyzable amino acids in aquifer sediments

Science.gov (United States)

Thomas, Lashun K.; Widdowson, Mark A.; Novak, John T.; Chapelle, Francis H.; Benner, Ronald; Kaiser, Karl

2012-01-01

This study evaluated the relationship between concentrations of operationally defined potentially bioavailable organic -carbon (PBOC) and hydrolyzable amino acids (HAAs) in sediments collected from a diverse range of chloroethene--contaminated sites. Concentrations of PBOC and HAA were measured using aquifer sediment samples collected at six selected study sites. Average concentrations of total HAA and PBOC ranged from 1.96 ± 1.53 to 20.1 ± 25.6 mg/kg and 4.72 ± 0.72 to 443 ± 65.4 mg/kg, respectively. Results demonstrated a statistically significant positive relationship between concentrations of PBOC and total HAA present in the aquifer sediment (p amino acids are known to be readily biodegradable carbon compounds, this relationship suggests that the sequential chemical extraction procedure used to measure PBOC is a useful indicator of bioavailable carbon in aquifer sediments. This, in turn, is consistent with the interpretation that PBOC measurements can be used for estimating the amount of natural organic carbon available for driving the reductive dechlorination of chloroethenes in groundwater systems.

De-chlorination and solidification of radioactive LiCl waste salt by using SiO{sub 2}-Al{sub 2}O{sub 3}-P{sub 2}O{sub 5} (SAP) inorganic composite including B{sub 2}O{sub 3} component

Energy Technology Data Exchange (ETDEWEB)

Lee, Ki Rak; Park, Hwan-Seo; Cho, In-Hak; Choi, Jung-Hoon; Eun, Hee-Chul; Lee, Tae-Kyo; Han, Seung Youb; Ahn, Do-Hee [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2017-09-15

SAP (SiO{sub 2}-Al{sub 2}O{sub 3}-P{sub 2}O{sub 5}) composite has been recently studied in KAERI to deal with the immobilization of radioactive salt waste, one of the most problematic wastes in the pyro-chemical process. Highly unstable salt waste was successfully converted into stable compounds by the dechlorination process with SAPs, and then a durable waste form with a high waste loading was produced when adding glassy materials to dechlorination product. In the present study, U-SAP composite which is SAP bearing glassy component (Boron) was synthesized to remove the adding and mixing steps of glassy materials for a monolithic wasteform. With U-SAPs prepared by a sol-gel process, a series of wasteforms were fabricated to identify a proper reaction condition. Physical and chemical properties of dechlorination products and U-SAP wasteforms were characterized by XRD, DSC, SEM, TGA and PCT-A. A U-SAP wasteform showed suitable properties as a radioactive wasteform such as dense surface morphology, high waste loading, and high durability at the optimized U-SAP/salt ratio 2.

Potential for the reduction of greenhouse gas emissions through the use of mobility services

DEFF Research Database (Denmark)

Grischkat, Sylvie; Hunecke, Marcel; Böhler, Susanne

2014-01-01

gas emissions per person and year was found to be 78 kg in an optimistic scenario and 25 kg in a pessimistic scenario. Extrapolated to the German metropolitan population, behaviour-related measures alone could result in a 1.8 million ton (optimistic scenario) or 0.6 million ton (pessimistic scenario......This study evaluates potential for the reduction of greenhouse gas emissions in the passenger transport sector achievable through the use of mobility services. Beside car-sharing and -pooling, six services targeted at improving and encouraging the use of urban public transportation were considered......) reduction of greenhouse gas emissions, respectively. In order to exploit this potential fully, however, target group specific information should be obtained and communication strategies developed, as addressed in this paper. This study further presents the limitation of reduction potential quantification...

Use of γ-hexachlorocyclohexane as a terminal electron acceptor by an anaerobic enrichment culture

International Nuclear Information System (INIS)

Elango, Vijai; Kurtz, Harry D.; Anderson, Christina; Freedman, David L.

2011-01-01

Highlights: ► Use of γ-hexachlorocyclohexane as a terminal electron acceptor was demonstrated. ► H 2 served as the electron donor for an enrichment culture that dechlorinated γ-HCH. ► H 2 consumption for acetogenesis and methanogenesis stopped in HEPES media. ► Addition of vancomycin significantly slowed the rate of γ-HCH dechlorination. ► Previously identified chlororespiring microbes were not detected in the enrichment. - Abstract: The use of γ-hexachlorocyclohexane (HCH) as a terminal electron acceptor via organohalide respiration was demonstrated for the first time with an enrichment culture grown in a sulfate-free HEPES-buffered anaerobic mineral salts medium. The enrichment culture was initially developed with soil and groundwater from an industrial site contaminated with HCH isomers, chlorinated benzenes, and chlorinated ethenes. When hydrogen served as the electron donor, 79–90% of the electron equivalents from hydrogen were used by the enrichment culture for reductive dechlorination of the γ-HCH, which was provided at a saturation concentration of approximately 10 mg/L. Benzene and chlorobenzene were the only volatile transformation products detected, accounting for 25% and 75% of the γ-HCH consumed (on a molar basis), respectively. The enrichment culture remained active with only hydrogen as the electron donor and γ-HCH as the electron acceptor through several transfers to fresh mineral salts medium for more than one year. Addition of vancomycin to the culture significantly slowed the rate of γ-HCH dechlorination, suggesting that a Gram-positive organism is responsible for the reduction of γ-HCH. Analysis of the γ-HCH dechlorinating enrichment culture did not detect any known chlororespiring genera, including Dehalobacter. In bicarbonate-buffered medium, reductive dechlorination of γ-HCH was accompanied by significant levels of acetogenesis as well as methanogenesis.

Cost reduction potentials of offshore wind power in Germany

International Nuclear Information System (INIS)

Hobohm, Jens; Krampe, Leonard; Peter, Frank

2014-01-01

Offshore wind power is a major hope for the German energy turnaround. However, it will only be possible to tap its cost reduction potentials if industry, the political leadership and the administrative authorities join forces to create the necessary preconditions. An important requirement for this capital-intensive technology are stable legal and political framework conditions. A recent study on the future shows what needs to be done.

Reactive transport modeling of chemical and isotope data to identify degradation processes of chlorinated ethenes in a diffusion-dominated media

DEFF Research Database (Denmark)

Chambon, Julie Claire Claudia; Damgaard, Ida; Jeannottat, Simon

. Degradation and transport processes of chlorinated ethenes are not well understood in such geological settings, therefore risk assessment and remediation at these sites are particularly challenging. In this work, a combined approach of chemical and isotope analysis on core samples, and reactive transport...... the source zone (between 6 and 12 mbs). Concentrations and stable isotope ratios of the mother compounds and their daughter products, as well as redox parameters, fatty acids and microbial data, were analyzed with discrete sub-sampling along the cores. More samples (each 5 mm) were collected around...... of dechlorination and degradation pathways (biotic reductive dechlorination or abiotic β-elimination with iron minerals) in three core profiles. The model includes diffusion in the matrix, sequential reductive dechlorination, abiotic degradation, isotope fractionation due to degradation and due to diffusion...

Photodegradation of the azole fungicide climbazole by ultraviolet irradiation under different conditions: Kinetics, mechanism and toxicity evaluation

Energy Technology Data Exchange (ETDEWEB)

Liu, Wang-Rong; Ying, Guang-Guo, E-mail: guang-guo.ying@gig.ac.cn; Zhao, Jian-Liang; Liu, You-Sheng; Hu, Li-Xin; Yao, Li; Liang, Yan-Qiu; Tian, Fei

2016-11-15

Highlights: • Climbazole (CZ) could be effectively degraded under UV-254 irradiation. • CZ underwent direct and self-sensitized photolysis involving ROS. • The main photodegradation by-products of CZ were identified and semi-quantitated. • Pathway includes hydroxylative dechlorination, dechlorination, and de-pinacolone. • The toxicity of the photodegradation system reduced after UV-254 irradiation. - Abstract: Climbazole (CZ) has been known to persist in various environmental media, and may cause potential risks to aquatic organisms. This study investigated the photodegradation of CZ by ultraviolet (UV, 254 nm) under different conditions. The results revealed that CZ could be effectively degraded in aqueous solutions under UV-254 irradiation with a half-life of 9.78 min (pH = 7.5), and the photodegradation followed pseudo-first-order kinetics. pH had almost no effect on its rate constants and quantum yields; but the water quality of natural waters could affect the photolysis of CZ, and the coexisting constituents such as Fe{sup 3+}, NO{sub 3}{sup −}, and HA obviously inhibited its photolysis. The addition of different radical scavengers also inhibited the photodegradation of CZ due to the reduction of reactive oxygen species (ROS). CZ underwent direct and self-sensitized photolysis involving ROS. Based on the identified photodegradation by-products, the proposed pathways included hydroxylative dechlorination, dechlorination and de-pinacolone. Moreover, toxicity evaluation using duckweed found significant toxicity reduction in the photodegradation system of CZ after the irradiation of UV-254, and the remaining by-products did not pose extra toxicity compared with CZ itself. These findings from present study suggest that CZ in effluent could be further reduced by applying UV photolysis treatment.

Greenhouse gas emission reduction by means of fuel switching in electricity generation: Addressing the potentials

International Nuclear Information System (INIS)

Delarue, Erik; D'haeseleer, William

2008-01-01

Many countries committed themselves in the Kyoto protocol to reduce greenhouse gas (GHG) emissions. Some of these targeted emission reductions could result from a switch from coal-fired to gas-fired electricity generation. The focus in this work lies on Western Europe, with the presence of the European Union Emission Trading Scheme (EU ETS). For the switching to occur, several conditions have to be fulfilled. First, an economical incentive must be present, i.e. a sufficiently high European Union Allowance (EUA) price together with a sufficiently low natural gas price. Second, the physical potential for switching must exist, i.e. at a given load, there must remain enough power plants not running to make switching possible. This paper investigates what possibilities exist for switching coal-fired plants for gas-fired plants, dependent on the load level (the latter condition above). A fixed allowance cost and a variable natural gas price are assumed. The method to address GHG emission reduction potentials is first illustrated in a methodological case. Next, the GHG emission reduction potentials are addressed for several Western European countries together with a relative positioning of their electricity generation. GHG emission reduction potentials are also compared with simulation results. GHG emission reduction potentials tend to be significant. The Netherlands have a very widespread switching zone, so GHG emission reduction is practically independent of electricity generation. Other counties, like Germany, Spain and Italy could reduce GHG emissions significantly by switching. With an allowance cost following the switch level of a 50% efficient gas-fired plant and a 40% efficient coal-fired plant in the summer season (like in 2005), the global GHG emission reduction (in the electricity generating sector) for the eight modeled zones could amount to 19%

Emission Reduction Potential with the Renewal of the Vehicle Fleet in Croatia

International Nuclear Information System (INIS)

Zidov, B.; Brlek, G.; Brajkovic, J.; Karan, M.

2015-01-01

The European Union has identified the typical areas of application of measures to tackle the problem of pollutants emissions into the air. Road transport is recognized as the largest polluter of the environment and an increase in CO2 emissions is most difficult to suppress in this type of transport. Looking at the projected trend of emission reductions in Croatia, it is clear that for achieving the minimum targets by 2050, as proposed by the European Union, implementation of the very strong measures in the coming period will be inevitable. The main aim of the paper refers to the analysis of potential emission reduction of pollutants generated by passenger vehicles registered in Croatia, assuming the implementation of measures that will result in technological renewal of the fleet at the national level. Generally considering, passenger cars before the Euro 1 standard, Euro 1 and Euro 2 standards together emit nearly 40 percent of all CO2 emissions generated by passenger cars registered in Croatia. Assuming replacement of all cars up to and including Euro 2, with Euro 6 vehicles, and taking into account certain assumptions, the potential reductions in emissions of NOx, CO, CH4 and particles were quantified. The potential reduction in NOx emissions is approximately 3,061 tons, in CO emissions approximately 14482 tons, in CH4 approximately 114 tons and in particulate matter approximately 257 tons. Depending on the engine size, with the replacement of the typical gasoline 20 years old passenger vehicle with the new one, without changing the driving mode, annual savings of up to 209 liters of gasoline fuel and reduction of CO2 emissions by 475 kg could be achieved (according to the assumptions described in the paper). With the replacement of diesel vehicles under the same conditions, the savings of up to 311 liters of diesel fuel annually and reduction of CO2 emissions by 815 kg could be achieved. (author).

Potential energy savings and CO2 emissions reduction of China's cement industry

International Nuclear Information System (INIS)

Ke, Jing; Zheng, Nina; Fridley, David; Price, Lynn; Zhou, Nan

2012-01-01

This study analyzes current energy and carbon dioxide (CO 2 ) emission trends in China's cement industry as the basis for modeling different levels of cement production and rates of efficiency improvement and carbon reduction in 2011–2030. Three cement output projections are developed based on analyses of historical production and physical and macroeconomic drivers. For each of these three production projections, energy savings and CO 2 emission reduction potentials are estimated in a best practice scenario and two continuous improvement scenarios relative to a frozen scenario. The results reveal the potential for cumulative final energy savings of 27.1 to 37.5 exajoules and energy-related direct emission reductions of 3.2 to 4.4 gigatonnes in 2011–2030 under the best practice scenarios. The continuous improvement scenarios produce cumulative final energy savings of 6.0 to 18.9 exajoules and reduce CO 2 emissions by 1.0 to 2.4 gigatonnes. This analysis highlights that increasing energy efficiency is the most important policy measure for reducing the cement industry's energy and emissions intensity, given the current state of the industry and the unlikelihood of significant carbon capture and storage before 2030. In addition, policies to reduce total cement production offer the most direct way of reducing total energy consumption and CO 2 emissions. - Highlights: ► This study models output and efficiency improvements in Chinese cement industry from 2011–2030. ► Energy savings and CO 2 emission reductions estimated for 3 scenarios relative to frozen scenario. ► Results reveal cumulative final energy savings potential of 27.1–37.5 EJ and 3.2–4.4 Gt CO 2 reductions. ► Increasing efficiency is the most important policy for reducing cement energy and emissions intensity.

The Effectiveness of Positive Coping Program on Reduction of Addiction Potential in Students

Directory of Open Access Journals (Sweden)

Fatemeh Nematollahi

2010-02-01

Full Text Available Objective: This study aimed to study the effectiveness of positive coping program on reduction of addiction potential in dormitory girl students. Method: The research method was semi experimental method namely: pre test-post test with witness group. In selection of sample, first addiction potential scale administered among 160 dormitory girl students, and 20 of them who were scored higher than cutoff score on addiction potential scale selected and divided to two experimental and witness groups. Experimental group received 10 sessions training which each session was 90 minutes. Positive coping program was based on three components of Bob Murray’s theory namely: social relationships, goal setting and spirituality. After finishing of training Post test were administered in both experimental and witness groups. Results: The results showed positive coping training was significantly reduced students’ addiction potential. Conclusion: The training of positive coping can be affect on reduction of girl students’ addiction potential.

Calibration of redox potential in sperm wash media and evaluation of oxidation-reduction potential values in various assisted reproductive technology culture media using MiOXSYS system.

Science.gov (United States)

Panner Selvam, M K; Henkel, R; Sharma, R; Agarwal, A

2018-03-01

Oxidation-reduction potential describes the balance between the oxidants and antioxidants in fluids including semen. Various artificial culture media are used in andrology and IVF laboratories for sperm preparation and to support the development of fertilized oocytes under in vitro conditions. The composition and conditions of these media are vital for optimal functioning of the gametes. Currently, there are no data on the status of redox potential of sperm processing and assisted reproduction media. The purpose of this study was to compare the oxidation-reduction potential values of the different media and to calibrate the oxidation-reduction potential values of the sperm wash medium using oxidative stress inducer cumene hydroperoxide and antioxidant ascorbic acid. Redox potential was measured in 10 different media ranging from sperm wash media, freezing media and assisted reproductive technology one-step medium to sequential media. Oxidation-reduction potential values of the sequential culture medium and one-step culture medium were lower and significantly different (p value to identify the physiological range of oxidation-reduction potential that does not have any adverse effect on normal physiological sperm function. © 2017 American Society of Andrology and European Academy of Andrology.

Reduction of emissions from Brazilian cattle raising and the generation of energy: Intensification and confinement potentials

International Nuclear Information System (INIS)

Palermo, Giuseppe Cernicchiaro; D'Avignon, Alexandre Louis de Almeida; Freitas, Marcos Aurélio Vasconcelos

2014-01-01

The identification of the main sources of anthropic greenhouse gas emissions (GHG) associated with the mitigation and removal of these emissions has become an important instrument in the attenuation of the climatic changes predicted by the IPCC. The largest emission source in Brazil is forest conversion. This land use change has always had a strong relationship with the expansion of agriculture, an activity of great importance in the country, which has the largest commercial cattle herd in the planet. Following the considerable reduction in emissions from deforestation, agriculture has been since 2010 the most important source (MCTI (Ministério da Ciência, Tecnologia e Inovação), 2013. Brasília: Ministério daCiência, Tecnologia e Inovação, Brasil). Seeking to discover the possibilities of altering the emissions profile in the agricultural sector, four scenarios were developed related to how this is dealt with in the beef cattle sector, calculating the potential removal of carbon from the atmosphere through natural regeneration of biomes. The results suggest that picketing and rotation scenario has the greatest potential, with a carbon reduction of 17.7 Gt CO 2 eq, while the shared raising with grain legumes scenario has the lowest calculated reduction potential of 7.1 Gt CO 2 eq was calculated. The animal confinement scenario had an intermediary reduction potential of 8.3 Gt CO 2 eq. The mosaic of methods scenario, in which it is attempted to simulate the parallel adoption of the measures proposed in all other scenarios, had a reduction potential of 13.1 Gt CO 2 eq. In the scenarios where animal confinement occurs, the treatment of waste with biodigestion allows the generation of biogas and biofertilizers, contributing to an increase in the potential carbon reduction. - Highlights: • We identify one main source of anthropic GHG in Brazil after forest conversion (deforestation), the beef cattle raising. • Four scenarios to mitigate emissions from cattle

Anaerobic transformation of DDT related to iron(III) reduction and microbial community structure in paddy soils.

Science.gov (United States)

Chen, Manjia; Cao, Fang; Li, Fangbai; Liu, Chengshuai; Tong, Hui; Wu, Weijian; Hu, Min

2013-03-06

We studied the mechanisms of microbial transformation in functional bacteria on 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) in two different field soils, Haiyan (HY) and Chenghai (CH). The results showed that microbial activities had a steady dechlorination effect on DDT and its metabolites (DDx). Adding lactate or glucose as carbon sources increased the amount of Desulfuromonas, Sedimentibacter, and Clostridium bacteria, which led to an increase in adsorbed Fe(II) and resulted in increased DDT transformation rates. The electron shuttle of anthraquinone-2,6-disulfonic disodium salt resulted in an increase in the negative potential of soil by mediating the electron transfer from the bacteria to the DDT. Moreover, the DDT-degrading bacteria in the CH soil were more abundant than those in the HY soil, which led to higher DDT transformation rates in the CH soil. The most stable compound of DDx was 1,1-dichloro-2,2-bis(p-chloro-phenyl)ethane, which also was the major dechlorination metabolite of DDT, and 1-chloro-2,2-bis-(p-chlorophenyl)ethane and 4,4'-dichlorobenzo-phenone were found to be the terminal metabolites in the anaerobic soils.

Use of emulsified vegetable oil to support bioremediation of TCE DNAPL in soil columns.

Science.gov (United States)

Harkness, Mark; Fisher, Angela

2013-08-01

The interaction between emulsified vegetable oil (EVO) and trichloroethylene (TCE) dense non-aqueous phase liquid (DNAPL) was observed using two soil columns and subsequent reductive dechlorination of TCE was monitored over a three year period. Dyed TCE DNAPL (~75 g) was emplaced in one column (DNAPL column), while the second was DNAPL-free (plume column). EVO was added to both columns and partitioning of the EVO into the TCE DNAPL was measured and quantified. TCE (1.9 mM) was added to the influent of the plume column to simulate conditions down gradient of a DNAPL source area and the columns were operated independently for more than one year, after which they were connected in series. Initially limited dechlorination of TCE to cDCE was observed in the DNAPL column, while the plume column supported complete reductive dechlorination of TCE to ethene. Upon connection and reamendment of the plume column with EVO, near saturation levels of TCE from the effluent of the DNAPL column were rapidly dechlorinated to c-DCE and VC in the plume column; however, this high rate dechlorination produced hydrochloric acid which overwhelmed the buffering capacity of the system and caused the pH to drop below 6.0. Dechlorination efficiency in the columns subsequently deteriorated, as measured by the chloride production and Dehalococcoides counts, but was restored by adding sodium bicarbonate buffer to the influent groundwater. Robust dechlorination was eventually observed in the DNAPL column, such that the TCE DNAPL was largely removed by the end of the study. Partitioning of the EVO into the DNAPL provided significant operational benefits to the remediation system both in terms of electron donor placement and longevity. Copyright © 2013 Elsevier B.V. All rights reserved.

Potential for Landing Gear Noise Reduction on Advanced Aircraft Configurations

Science.gov (United States)

Thomas, Russell H.; Nickol, Craig L.; Burley, Casey L.; Guo, Yueping

2016-01-01

The potential of significantly reducing aircraft landing gear noise is explored for aircraft configurations with engines installed above the wings or the fuselage. An innovative concept is studied that does not alter the main gear assembly itself but does shorten the main strut and integrates the gear in pods whose interior surfaces are treated with acoustic liner. The concept is meant to achieve maximum noise reduction so that main landing gears can be eliminated as a major source of airframe noise. By applying this concept to an aircraft configuration with 2025 entry-into-service technology levels, it is shown that compared to noise levels of current technology, the main gear noise can be reduced by 10 EPNL dB, bringing the main gear noise close to a floor established by other components such as the nose gear. The assessment of the noise reduction potential accounts for design features for the advanced aircraft configuration and includes the effects of local flow velocity in and around the pods, gear noise reflection from the airframe, and reflection and attenuation from acoustic liner treatment on pod surfaces and doors. A technical roadmap for maturing this concept is discussed, and the possible drag increase at cruise due to the addition of the pods is identified as a challenge, which needs to be quantified and minimized possibly with the combination of detailed design and application of drag reduction technologies.

Magnetite nanoparticles enhance the performance of a combined bioelectrode-UASB reactor for reductive transformation of 2,4-dichloronitrobenzene.

Science.gov (United States)

Wang, Caiqin; Ye, Lu; Jin, Jie; Chen, Hui; Xu, Xiangyang; Zhu, Liang

2017-09-04

Direct interspecies electron transfer (DIET) among the cometabolism microbes plays a key role in the anaerobic degradation of persistent organic pollutants and stability of anaerobic bioreactor. In this study, the COD removal efficiency increased to 99.0% during the start-up stage in the combined bioelectrode-UASB system (R1) with magnetite nanoparticles addition, which was higher than those in the coupled bioelectrode-UASB (R2; 83.2%) and regular UASB (R3; 71.0%). During the stable stage, the increase of 2,4-dichloronitrobenzene (2,4-DClNB) concentration from 25 mg L -1 to 200 mg L -1 did not affect the COD removal efficiencies in R1 and R2, whereas the performance of R3 was deteriorated obviously. Further intermediates analysis indicated that magnetite nanoparticles enhanced the reductive dechlorination of 2,4-DClNB. High-throughput sequencing results showed that the functional microbes like Syntrophobacter and Syntrophomonas which have been reported to favor the DIET, were predominant on the cathode surface of R1 reactor. It is speculated that the addition of magnetite nanoparticles favors the cooperative metabolism of dechlorinating microbes and electricigens during 2,4-DClNB degradation process in the combined bioelectrode-UASB reactor. This study may provide a new strategy to improve the performance of microbial electrolysis cells and enhance the pollutant removal efficiency.

Cathodic Potential Dependence of Electrochemical Reduction of SiO2 Granules in Molten CaCl2

Science.gov (United States)

Yang, Xiao; Yasuda, Kouji; Nohira, Toshiyuki; Hagiwara, Rika; Homma, Takayuki

2016-09-01

As part of an ongoing fundamental study to develop a new process for producing solar-grade silicon, this paper examines the effects of cathodic potential on reduction kinetics, current efficiency, morphology, and purity of Si product during electrolysis of SiO2 granules in molten CaCl2 at 1123 K (850 °C). SiO2 granules were electrolyzed potentiostatically at different cathodic potentials (0.6, 0.8, 1.0, and 1.2 V vs Ca2+/Ca). The reduction kinetics was evaluated based on the growth of the reduced Si layer and the current behavior during electrolysis. The results suggest that a more negative cathodic potential is favorable for faster reduction. Current efficiencies in 60 minutes are greater than 65 pct at all the potentials examined. Si wires with sub-micron diameters are formed, and their morphologies show little dependence on the cathodic potential. The impurities in the Si product can be controlled at low level. The rate-determining step for the electrochemical reduction of SiO2 granules in molten CaCl2 changes with time. At the initial stage of electrolysis, the electron transfer is the rate-determining step. At the later stage, the diffusion of O2- ions is the rate-determining step. The major cause of the decrease in reduction rate with increasing electrolysis time is the potential drop from the current collector to the reaction front due to the increased contact resistance among the reduced Si particles.

Assessing the Feasibility of DNAPL Source Zone Remediation: Review of Case Studies

Science.gov (United States)

2004-05-01

such as sugars, alcohols, fatty acids that are fermented to hydrogen and used for reductive dechlorination) are more soluble than the chlorinated...addition because a greater percentage of the hydrogen produced during the fermentation of added electron donors is consumed by dechlorinating...Battelle, 2002; Stegemeier and Vinegar , 2001; Roote, 2003; USEPA, 1999): i) increasing vapor pressure and volatilization rates of low boiling point

Exploring the Poverty Reduction Potential of Social Marketing in Tourism Development

Directory of Open Access Journals (Sweden)

Dao V. Truong

2015-12-01

Full Text Available Although social marketing has been demonstrated to be an effective tool of behavior change in a variety of contexts, its poverty reduction potential in tourism development has captured limited research attention. This paper explores the potential contribution of social marketing to tourism-related poverty alleviation in Sapa, Vietnam. It does so by creating an understanding of how local residents perceive poverty, then exploring whether social marketing could be a potential solution in the case of Sapa. Through participant observations and semi-structured interviews, this study reveals that local people perceive poverty as a lack of rice and/or income and ascribe it to both internal and external factors. Local women often follow tourists to sell handicrafts, causing discomfort for tourists and driving them away from certain destinations. Insufficient capital and farming land are also identified as a critical barrier to poverty reduction. This study argues that by understanding the poor people’s perspectives on poverty, we can identify meaningful approaches to poverty alleviation. Thereby, social marketing can be one of the tools to bring the marginalized voice of poor people to the attention of decision-makers.

Reductive dechlorination of trichloroethylene and tetrachloroethylene under aerobic conditions in a sediment column

International Nuclear Information System (INIS)

Enzien, M.V.; Picardal, F.; Hazen, T.

1994-01-01

This study investigated the bioremediation of chlorinated solvents in a sediment column. Biodegradation potentials of trichloroethylene and tetrachloroethylene during aerobic methanotrophic biostimulation were studied at the Savannah River Site. 30 refs., 3 figs., 3 tabs

REDOX AND REDUCTION POTENTIALS AS PARAMETERS TO PREDICT THE DEGRADATION PATHWAY OF CHLORINATED BENZENES IN ANAEROBIC ENVIRONMENTS

NARCIS (Netherlands)

DOLFING, J; HARRISON, BK

1993-01-01

The anaerobic degradation pathway of hexachlorobenzene starts with a series of reductive dehalogenation steps. In the present paper it was evaluated whether the dehalogenation pathway observed in microbial ecosystems could be predicted by the redox potential and/or the reduction potential (the

The impact of electrochemical reduction potentials on the electrocatalytic activity of graphene oxide toward the oxygen reduction reaction in an alkaline medium

International Nuclear Information System (INIS)

Toh, Shaw Yong; Loh, Kee Shyuan; Kamarudin, Siti Kartom; Daud, Wan Ramli Wan

2016-01-01

We report the synthesis of graphene via the electrochemical reduction of graphene oxide (GO). In this study, GO nanosheets from aqueous dispersion were pre-assembled on a glassy carbon (GC) electrode and then electrochemically reduced in 1 M KOH under various constant reduction potentials in the range of −0.6 V to −1.5 V (vs. Ag/AgCl). X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy analyses revealed that the graphitic structure was substantially restored in the resulting electrochemically reduced graphene oxide (ERGO). The ERGO electrodes exhibited significantly enhanced catalytic activity toward the oxygen reduction reaction (ORR) in an alkaline medium compared with the initial GO electrode. Of the ERGO electrodes produced at various cathodic potentials, the ERGO-1.2 V electrode, which was produced at a reduction potential of −1.2 V, demonstrated the best catalytic activity toward the ORR in an alkaline medium. The ORR on GO and ERGO electrodes was shown to proceed via a two-electron mechanism at low overpotentials. The agreement between the spectroscopy results and electrochemical measurements provide strong evidence that the enhanced ORR catalytic activity is mainly attributed to the restoration of GO’s graphitic structure. Furthermore, the ERGO-1.2 V electrode showed excellent tolerance to the methanol poisoning effect compared with a Pt/C catalyst electrode.

Anaerobic Transformation of Chlorinated Aliphatic Hydrocarbons in a Sand Aquifer Based on Spatial Chemical Distributions

Science.gov (United States)

Semprini, Lewis; Kitanidis, Peter K.; Kampbell, Don H.; Wilson, John T.

1995-04-01

We estimated the distribution of chlorinated aliphatic hydrocarbons (CAHs) from groundwater samples collected along three transects in a sand aquifer. Trichloroethylene (TCE) leaked and contaminated the aquifer probably more than a decade before we collected the measurements. The data show significant concentrations of TCE, cis-l,2-dichloroethylene (c-DCE), vinyl chloride (VC), and ethene. We attributed DCE, VC, and ethene to the reductive dehalogenation of TCE. The CAH concentrations varied significantly with depth and correlate with sulfate and methane concentrations. Anoxic aquifer conditions exist with methane present at relatively high concentrations at depth. High concentrations of TCE correspond with the absence of methane or low methane concentrations, whereas products of TCE dehalogenation are associated with higher methane concentrations and low sulfate concentrations. Indications are that the dechlorination of TCE and DCE to VC and ethene is associated with sulfate reduction and active methanogenesis. TCE dechlorination to DCE is likely occurring under the less reducing conditions of sulfate reduction, with further reductions to VC and ethene occurring under methanogenic conditions. We estimated that about 20% of TCE has dechlorinated to ethene. The analysis of the data enhanced our knowledge of natural in situ transformation and transport processes of CAHs.

Reductive Dechlorination of Trichloroethylene and Tetrachloroethylene under Aerobic Conditions in a Sediment Column

OpenAIRE

1994-01-01

Biodegradation of trichloroethylene and tetrachloroethylene under aerobic conditions was studied in a sediment column. Cumulative mass balances indicated 87 and 90% removal for trichloroethylene and tetrachloroethylene, respectively. These studies suggest the potential for simultaneous aerobic and anaerobic biotransformation processes under bulk aerobic conditions.

Nanoscale zerovalent iron alters soil bacterial community structure and inhibits chloroaromatic biodegradation potential in Aroclor 1242-contaminated soil

International Nuclear Information System (INIS)

Tilston, Emma L.; Collins, Chris D.; Mitchell, Geoffrey R.; Princivalle, Jessica; Shaw, Liz J.

2013-01-01

Nanoscale zerovalent iron (nZVI) has potential for the remediation of organochlorine-contaminated environments. Environmental safety concerns associated with in situ deployment of nZVI include potential negative impacts on indigenous microbes whose biodegradative functions could contribute to contaminant remediation. With respect to a two-step polychlorinated biphenyl remediation scenario comprising nZVI dechlorination followed by aerobic biodegradation, we examined the effect of polyacrylic acid (PAA)-coated nZVI (mean diameter = 12.5 nm) applied at 10 g nZVI kg −1 to Aroclor-1242 contaminated and uncontaminated soil over 28 days. nZVI had a limited effect on Aroclor congener profiles, but, either directly or indirectly via changes to soil physico-chemical conditions (pH, Eh), nZVI addition caused perturbation to soil bacterial community composition, and reduced the activity of chloroaromatic mineralizing microorganisms. We conclude that nZVI addition has the potential to inhibit microbial functions that could be important for PCB remediation strategies combining nZVI treatment and biodegradation. Highlights: ► Impact of nano-sized zerovalent iron on microbes was investigated in soil microcosms. ► Zerovalent iron had short-lived effects on redox potential and Aroclor dechlorination. ► Microbial populations also showed short-lived perturbations in their size. ► The activity of chloroaromatic degrading microbes did not recover within 28 days. ► Zerovalent iron application inhibits ensuing PCB bioremediative microbial functions. - nZVI inhibits microbial functions of potential importance for remediation strategies combining nZVI treatment and biodegradation.

Study on Greenhouse Gas Reduction Potential in Residential, Commercial and Transportation Sectors of Korea

International Nuclear Information System (INIS)

Kim, H. G.; Jeong, Y. J.

2011-11-01

The establishment of the sectoral model was made. The sectors cover residential, commercial and transportation sectors. The establishment of the model includes designing Reference Energy System, Development of the reference scenario, setting up various scenarios in which GHG reductions were taken into account by evaluating the reduction potential in the cost effective way

Characteristics of dechlorination for LiCl salt by the surface temperature-controlled reactor

Energy Technology Data Exchange (ETDEWEB)

Cho, In Hak [Chungnam National University, Daejeon (Korea, Republic of); Park, Hwan Seo; Ahn, Soo Na; Eun, Hee Chul; Kim, In Tae; Cho, Yong Jun [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2011-05-15

Molten salt waste is generated from a pyrochemical process to separate reusable U and TRU elements from a spent nuclear fuel. The spent lithium chloride waste is highly soluble in water and contains volatile radioactive elements such as Cs. However, these wastes are difficult to directly immobilize into durable matrix such as glass or ceramic wasteform for final disposal. ANL(Argonne National Laboratory) suggested the conversion of metal chloride into a sodalite for the immobilization of a chloride waste, glass-bonded sodalite, which was fabricated at about 915 .deg. C after mixing the salt-loaded zeolite and borosilicate glass powder. Although this wasteform shows high leach-resistance, the waste volume greatly increases. The previous study was to treat metal chloride wastes by using SAP(SiO{sub 2}-Al{sub 2}O{sub 3}-P{sub 2}O{sub 5}) materials. By using this method, the final waste volume reduced and leach-resistance was good. In this study, characteristics of dechlorination reaction of LiCl with an inorganic composite, SAP, was investigated by using a specific surface temperature-controlled reactor

Impacts of Residual Surfactant on Tetrachloroethene (PCE) Degradation Following Pilot-Scale SEAR Treatment at a Chloroethene-Impacted Site

Science.gov (United States)

Ramsburg, C. A.; Abriola, L. M.; Pennell, K. D.; Löffler, F. E.; Gamache, M.; Petrovskis, E. A.

2003-04-01

A pilot-scale surfactant-enhanced aquifer remediation (SEAR) demonstration was completed during the summer of 2000 at the Bachman Road site (Oscoda, MI USA). For this test, an aqueous solution of 60 g/L Tween 80 (polyoxyethylene (20) sorbitan monooleate) was used to recover tetrachloroethene (PCE) from a suspected source zone, located underneath a former dry-cleaning facility. Tween 80 was selected for use based upon its demonstrated capacity to solubilize PCE, “food-grade” status, and biodegradative potential. Hydraulic control was maintained throughout the test, with 95% of the injected surfactant mass recovered by a single extraction well. Source-zone monitoring conducted 15 months after SEAR treatment revealed the presence of previously undetected volatile fatty acids (acetate and formate) and PCE degradation products (trichloroethene, cis-1,2-dichloroethene, trans-1,2-dichlorethene, and vinyl chloride), in conjunction with PCE concentration reductions of approximately two orders-of-magnitude. The detection of volatile fatty acids is relevant, as they are likely fermentation products of residual Tween 80. Microbial reductive dechlorination is limited by available electron donors, and microcosm studies demonstrated that both acetate and formate support reductively dechlorinating populations present at the oligotrophic Bachman Road site aquifer. Surfactant transport simulations, using a regional flow model developed for the site, were employed to determine appropriate down-gradient monitoring locations. Drive point samples taken 15 months post-treatment in the vicinity of the simulated residual surfactant plume, contained elevated concentrations of acetate and PCE daughter products. Ongoing efforts include continued site-monitoring, and microcosm studies to corroborate a causal relationship between Tween 80 fermentation and PCE dechlorination.

Microwave – assisted reduction of racemic intermediates potential immunosuppressant

Directory of Open Access Journals (Sweden)

Wender A. Silva

2012-06-01

Full Text Available Immunosuppressant are drugs that reduce the immune response, as important in the treatment of autoimmune diseases and rejection attenuators in organ transplants, the structural point of view generally have a high complexity. Within this context it is indispensable structural simplifications, new molecules are proposed with potential action on a stage is a necessary, reduction system α,β-unsaturated specifically, chalcone, to their respective alcohol saturated. Therefore, a new method was developed for microwave assisted subsequently coupling to other fragments to the total synthesis of the novel compounds.

To what extent can isotopes help substantiate natural attenuation of chlorinated ethenes?

DEFF Research Database (Denmark)

Badin, A.; Broholm, Mette Martina; Hunkeler, D.

to which isotopes could help substantiate natural attenuation of chlorinated ethenes at the field scale. Our work hence aims at exploring the latter based on data acquired in 2006 in a site located in Denmark which is contaminated with PCE and its end-products TCE, cDCE, and VC. Previous work on this site...... has enabled to demonstrate that PCE and TCE were undergoing reductive dechlorination while cDCE would be at least partially degraded through reductive dechlorination1. However, the magnitude of the contaminants attenuation by biodegradation was not evaluated. Based on simple modeling including...

Potential for greenhouse gas emission reductions using surplus electricity in hydrogen, methane and methanol production via electrolysis

International Nuclear Information System (INIS)

Uusitalo, Ville; Väisänen, Sanni; Inkeri, Eero; Soukka, Risto

2017-01-01

Highlights: • Greenhouse gas emission reductions using power-to-x processes are studied using life cycle assessment. • Surplus electricity use led to greenhouse gas emission reductions in all studied cases. • Highest reductions can be achieved by using hydrogen to replace fossil based hydrogen. • High reductions are also achieved when fossil transportation fuels are replaced. - Abstract: Using a life cycle perspective, potentials for greenhouse gas emission reductions using various power-to-x processes via electrolysis have been compared. Because of increasing renewable electricity production, occasionally surplus renewable electricity is produced, which leads to situations where the price of electricity approach zero. This surplus electricity can be used in hydrogen, methane and methanol production via electrolysis and other additional processes. Life cycle assessments have been utilized to compare these options in terms of greenhouse gas emission reductions. All of the power-to-x options studied lead to greenhouse gas emission reductions as compared to conventional production processes based on fossil fuels. The highest greenhouse gas emission reductions can be gained when hydrogen from steam reforming is replaced by hydrogen from the power-to-x process. High greenhouse gas emission reductions can also be achieved when power-to-x products are utilized as an energy source for transportation, replacing fossil transportation fuels. A third option with high greenhouse gas emission reduction potential is methane production, storing and electricity conversion in gas engines during peak consumption hours. It is concluded that the power-to-x processes provide a good potential solution for reducing greenhouse gas emissions in various sectors.

Microbial mineralization of cis-dichloroethene and vinyl chloride as a component of natural attenuation of chloroethene contaminants under conditions identified in the field as anoxic

Science.gov (United States)

Bradley, Paul M.

2012-01-01

Chlororespiration is a key component of remediation at many chloroethene-contaminated sites. In some instances, limited accumulation of reductive dechlorination daughter products may suggest that natural attenuation is not adequate for site remediation. This conclusion is justified when evidence for parent compound (tetrachloroethene, PCE, or trichloroethene, TCE) degradation is lacking. For many chloroethene-contaminated shallow aquifer systems, however, non-conservative losses of the parent compounds are clear but the mass balance between parent compound attenuation and accumulation of reductive dechlorination daughter products is incomplete. Incomplete mass balance indicates a failure to account for important contaminant attenuation mechanisms, and is consistent with contaminant degradation to non-diagnostic mineralization products. An ongoing technical debate over the potential for mineralization of dichloroethene (DCE) and vinyl chloride (VC) to CO2 in the complete absence of diatomic oxygen has largely obscured the importance of microbial DCE/VC mineralization at dissolved oxygen (DO) concentrations below the current field standard (DO conditions. This study demonstrates that oxygen-based microbial mineralization of DCE and VC can be substantial under field conditions that are frequently characterized as "anoxic." Because mischaracterization of operant contaminant biodegradation processes can lead to expensive and ineffective remedial actions, a modified framework for assessing the potential importance of oxygen during chloroethene biodegradation was developed.

CO2 emissions and reduction potential in China's chemical industry

International Nuclear Information System (INIS)

Zhu, Bing; Zhou, Wenji; Hu, Shanying; Li, Qiang; Griffy-Brown, Charla; Jin, Yong

2010-01-01

GHG (Increasing greenhouse gas) emissions in China imposes enormous pressure on China's government and society. The increasing GHG trend is primarily driven by the fast expansion of high energy-intensive sectors including the chemical industry. This study investigates energy consumption and CO 2 emissions in the processes of chemical production in China through calculating the amounts of CO 2 emissions and estimating the reduction potential in the near future. The research is based on a two-level perspective which treats the entire industry as Level one and six key sub-sectors as Level two, including coal-based ammonia, calcium carbide, caustic soda, coal-based methanol, sodium carbonate, and yellow phosphorus. These two levels are used in order to address the complexity caused by the fact that there are more than 40 thousand chemical products in this industry and the performance levels of the technologies employed are extremely uneven. Three scenarios with different technological improvements are defined to estimate the emissions of the six sub-sectors and analyze the implied reduction potential in the near future. The results highlight the pivotal role that regulation and policy administration could play in controlling the CO 2 emissions by promoting average technology performances in this industry.

In the field of energy cost reduction, what is the potential?; En matiere de reduction des depenses d`energie: quel est le gisement?

Energy Technology Data Exchange (ETDEWEB)

Millet, B. [Departement Industrie, CEREN (France)

1996-12-31

Through a segmentation of the fuel and electric power consumptions in the various industrial sectors and energy consumption process types in France in 1990, the energy conservation potential in the French metalworking and mechanical industry is analyzed and its evolution up to 2005 is assessed. It is shown that the reduction potential amounts to 450 kTep or 20 percent of the metalworking and metallic construction industry energy consumption, with an important part for the out-of-process sector (space heating, compressed air production, lighting). In the process sector, important reductions could be realized in thermal treatments and metal heating prior forming

Standard test method for measurement of oxidation-reduction potential (ORP) of soil

CERN Document Server

American Society for Testing and Materials. Philadelphia

2009-01-01

1.1 This test method covers a procedure and related test equipment for measuring oxidation-reduction potential (ORP) of soil samples removed from the ground. 1.2 The procedure in Section 9 is appropriate for field and laboratory measurements. 1.3 Accurate measurement of oxidation-reduction potential aids in the analysis of soil corrosivity and its impact on buried metallic structure corrosion rates. 1.4 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard. 1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

Application of a long-lasting colloidal substrate with pH and hydrogen sulfide control capabilities to remediate TCE-contaminated groundwater.

Science.gov (United States)

Sheu, Y T; Chen, S C; Chien, C C; Chen, C C; Kao, C M

2015-03-02

A long-lasting emulsified colloidal substrate (LECS) was developed for continuous carbon and nanoscale zero-valent iron (nZVI) release to remediate trichloroethylene (TCE)-contaminated groundwater under reductive dechlorinating conditions. The developed LECS contained nZVI, vegetable oil, surfactants (Simple Green™ and lecithin), molasses, lactate, and minerals. An emulsification study was performed to evaluate the globule droplet size and stability of LECS. The results show that a stable oil-in-water emulsion with uniformly small droplets (0.7 μm) was produced, which could continuously release the primary substrates. The emulsified solution could serve as the dispensing agent, and nZVI particles (with diameter 100-200 nm) were distributed in the emulsion evenly without aggregation. Microcosm results showed that the LECS caused a rapid increase in the total organic carbon concentration (up to 488 mg/L), and reductive dechlorination of TCE was significantly enhanced. Up to 99% of TCE (with initial concentration of 7.4 mg/L) was removed after 130 days of operation. Acidification was prevented by the production of hydroxide ion by the oxidation of nZVI. The formation of iron sulfide reduced the odor from produced hydrogen sulfide. Microbial analyses reveal that dechlorinating bacteria existed in soils, which might contribute to TCE dechlorination. Copyright © 2014 Elsevier B.V. All rights reserved.

Effect of groundwater geochemistry on pentachlorophenol remediation by smectite-templated nanosized Pd0/Fe0.

Science.gov (United States)

Jia, Hanzhong; Gu, Cheng; Li, Hui; Fan, Xiaoyun; Li, Shouzhu; Wang, Chuanyi

2012-09-01

Zero-valent iron holds great promise in treating groundwater, and its reactivity and efficacy depend on many surrounding factors. In the present work, the effects of solution chemistry such as pH, humic acid (HA), and inorganic ions on pentachlorophenol (PCP) dechlorination by smectite-templated Pd(0)/Fe(0) were systematically studied. Smectite-templated Pd(0)/Fe(0) was prepared by saturating the negatively charged sites of smectite clay with Fe(III) and a small amount of Pd(II), followed by borohydride reduction to convert Fe(III) and Pd(II) into zero-valent metal clusters. Batch experiments were conducted to investigate the effects of water chemistry on PCP remediation. The PCP dechlorination rate critically depends on the reaction pH over the range 6.0~10.0; the rate constant (k (obs)) increases with decreasing the reaction pH value. Also, the PCP remediation is inhibited by HA, which can be attributed to the electron competition of HA with H(+). In addition, the reduction of PCP can be accelerated by various anions, following the order: Cl(-) > HCO (3) (-) > SO (4) (2-) ~no anion. In the case of cations, Ca(2+) and Mg(2+) (10 mM) decrease the dechlorination rate to 0.7959 and 0.7798 from 1.315 h(-1), respectively. After introducing HA into the reaction systems with cations or/and anions, the dechlorination rates are similar to that containing HA alone. This study reveals that low pH and the presence of some anions such as Cl(-) facilitate the PCP dechlorination and induce the rapid consumption of nanosized zero-valent iron simultaneously. However, the dechlorination rate is no longer correlated to the inhibitory or accelerating effects by cations and anions in the presence of 10 mg/L HA.

The hydrogen concentration as parameter to identify natural attenuation processes of volatile chlorinated hydrocarbons in ground water; Die Wasserstoffkonzentration als Parameter zur Identifizierung des natuerlichen Abbaus von leichtfluechtigen Chlorkohlenwasserstoffen (LCKW) im Grundwasser

Energy Technology Data Exchange (ETDEWEB)

Alter, M.D.

2006-06-15

In this study, the hydrogen concentration as parameter to identify natural attenuation processes of volatile chlorinated hydrocarbons was investigated. The currently accepted and recommended bubble strip method for hydrogen sampling was optimized, and a storage method for hydrogen samples was developed. Furthermore batch experiments with a dechlorinating mixed culture and pure cultures were carried out to study H{sub 2}-concentrations of competing redox processes. The extraction of hydrogen from ground water was optimized by a reduced inlet diameter of the usually applied gas sampling bulbs, allowing a maximal turbulent ow and gas transfer. With a gas volume of 10 ml and flow rates of 50 to 140 ml/min, the course of extraction almost followed the theoretical course of equilibration. At flow rates > 100 ml/min a equilibrium of 98% was achieved within 20 min. Until recently it was generally accepted that hydrogen samples can be stored only for 2 hours and therefore have to be analyzed immediately in the eld. Here, it was shown that eld samples can be stored for 1-3 days until analysis. For the dechlorination of tetrachloroethene (PCE), a hydrogen threshold concentration of 1-2 nM was found with the dechlorinating mixed culture as well as with a pure culture of Sulfurospirillum multivorans in combination with another pure culture Methanosarcina mazei. No dechlorination was detectable below this concentration. With the dechlorinating mixed culture, this finding is valid for all successive dechlorination steps until ethene. The hydrogen threshold concentration for denitrification were below the detection limit of 0,2 nM with the dechlorinating mixed culture. A threshold concentration of 3,1-3,5 nM was found for sulphate reduction and a threshold of 7-9 nM H{sub 2} for hydrogenotrophic methanogenesis. This implies that the natural dechlorination at contaminated sites is preferred to competing processes like sulphate reduction and methanogenesis. The threshold

Galvanic interpretation of self-potential signals associated withmicrobial sulfate-reduction

Energy Technology Data Exchange (ETDEWEB)

Williams, Kenneth H.; Hubbard, Susan S.; Banfield, Jillian F.

2007-05-02

We have evaluated the usefulness of the self-potential (SP)geophysical method to track the onset and location of microbialsulfate-reduction in saturated sediments during organic carbon amendment.Following stimulation of sulfate-reducing bacteria (SRB) by addition oflactate, anomalous voltages exceeding 600 mV correlated in space and timewith the accumulation of dissolved sulfide. Abiotic experiments in whichthe sulfide concentration at the measurement electrode was systematicallyvaried showed a positive correlation between the magnitude of the SPanomaly and differences in the half-cell potential associated with themeasurement and reference electrodes. Thus, we infer that the SPanomaliesresulted from electrochemical differences that developedbetween sulfide-rich regions and areas having higher oxidation potential.In neither experiment did generation of an SP anomaly require thepresence of an in situ electronic conductor, as is required by othermodels. These findings emphasize the importance of incorporation ofelectrochemical effects at electrode surfaces in interpretation of SPdata from geophysical studies. We conclude that SP measurements provide aminimally invasive means for monitoring stimulated sulfate-reductionwithin saturated sediments.

CO2 substitution potential and CO2 reduction costs of an energetic exploitation of solid biomasses in Germany

International Nuclear Information System (INIS)

Becher, S.

1995-01-01

For the reduction of the anthropogenic greenhouse effect, the CO 2 , emissions are clearly to be reduced in future, according to the resolution made by the Federal Republic. Against the background of this objective, possible contributions of the biogenous solid fuels for the reduction of the CO 2 release of fossil origin are presented and discussed. For that, first the existing potentials of biomass in Germany and their present use are shown. Based on this, the CO 2 emissions by the present use already avoided, as well as the existing unexploited potentials of the CO 2 reduction potentials still to be exploited are determined. In accordance with an 'integral' starting point, thereby all pre- and post-positioned processes are considered. Finally, the specific CO 2 reduction costs are analysed and compared with other options. (orig.) [de

In situ remediation of chlorinated solvent-contaminated groundwater using ZVI/organic carbon amendment in China: field pilot test and full-scale application.

Science.gov (United States)

Yang, Jie; Meng, Liang; Guo, Lin

2018-02-01

Chlorinated solvents in groundwater pose threats to human health and the environment due to their carcinogenesis and bioaccumulation. These problems are often more severe in developing countries such as China. Thus, methods for chlorinated solvent-contaminated groundwater remediation are urgently needed. This study presents a technique of in situ remediation via the direct-push amendment injection that enhances the reductive dechlorination of chlorinated solvents in groundwater in the low-permeability aquifer. A field-based pilot test and a following real-world, full-scale application were conducted at an active manufacturing facility in Shanghai, China. The chlorinated solvents found at the clay till site included 1,1,1-trichloroethane (1,1,1-TCA), 1,1-dichloroethane (1,1-DCA), 1,1-dichloroethylene (1,1-DCE), vinyl chloride (VC), and chloroethane (CA). A commercially available amendment (EHC ® , Peroxychem, Philadelphia, PA) combining zero-valent iron and organic carbon was used to treat the above pollutants. Pilot test results showed that direct-push EHC injection efficiently facilitated the in situ reductive remediation of groundwater contaminated with chlorinated solvents. The mean removal rates of 1,1,1-TCA, 1,1-DCA, and 1,1-DCE at 270 days post-injection were 99.6, 99.3, and 73.3%, respectively, which were obviously higher than those of VC and CA (42.3 and 37.1%, respectively). Clear decreases in oxidation-reduction potential and dissolved oxygen concentration, and increases in Fe 2+ and total organic carbon concentration, were also observed during the monitoring period. These indicate that EHC promotes the anaerobic degradation of chlorinated hydrocarbons primarily via long-term biological reductive dechlorination, with instant chemical reductive dechlorination acting as a secondary pathway. The optimal effective time of EHC injection was 0-90 days, and its radius of influence was 1.5 m. In full-scale application, the maximum concentrations of 1,1,1-TCA

Effect of Set Potential on Hexavalent Chromium Reduction and Electricity Generation from Biocathode Microbial Fuel Cells

KAUST Repository

Huang, Liping

2011-06-01

Setting a biocathode potential at ?300 mV improved the subsequent performance of an MFC for Cr(VI) reduction compared to a control (no set potential). With this set potential, the startup time was reduced to 19 days, the reduction of Cr(VI) was improved to 19.7 mg/L d, and the maximum power density was increased to 6.4 W/m3 compared to the control (26 days, 14.0 mg/L d and 4.1 W/m3). Set potentials of ?150 mV and ?300 mV also improved system performance and led to similarly higher utilization of metabolic energy gained (PMEG) than set potentials of +200 mV and ?450 mV. We observed putative pili at ?150 and ?300 mV potentials, and aggregated precipitates on bacterial surfaces in both poised and nonpoised controls. These tests show that there are optimal potentials that can be set for developing a Cr(VI) biocathode. © 2011 American Chemical Society.

Effect of Set Potential on Hexavalent Chromium Reduction and Electricity Generation from Biocathode Microbial Fuel Cells

KAUST Repository

Huang, Liping; Chai, Xiaolei; Chen, Guohua; Logan, Bruce E

2011-01-01

Setting a biocathode potential at ?300 mV improved the subsequent performance of an MFC for Cr(VI) reduction compared to a control (no set potential). With this set potential, the startup time was reduced to 19 days, the reduction of Cr(VI) was improved to 19.7 mg/L d, and the maximum power density was increased to 6.4 W/m3 compared to the control (26 days, 14.0 mg/L d and 4.1 W/m3). Set potentials of ?150 mV and ?300 mV also improved system performance and led to similarly higher utilization of metabolic energy gained (PMEG) than set potentials of +200 mV and ?450 mV. We observed putative pili at ?150 and ?300 mV potentials, and aggregated precipitates on bacterial surfaces in both poised and nonpoised controls. These tests show that there are optimal potentials that can be set for developing a Cr(VI) biocathode. © 2011 American Chemical Society.

ANAEROBIC DDT BIOTRANSFORMATION: ENHANCEMENT BY APPLICATION OF SURFACTANTS AND LOW OXIDATION REDUCTION POTENTIAL

Science.gov (United States)

Enhancement of anaerobic DDT (1,1,1-trichloro-2,2-bis(p-chlorophenyl) ethane) biotransformation by mixed cultures was studied with application of surfactants and oxidation reduction potential reducing agents. Without amendments, DDT transformation resulted mainly in the pr...

Reduction potentials of energy demand and GHG emissions in China's road transport sector

International Nuclear Information System (INIS)

Yan Xiaoyu; Crookes, Roy J.

2009-01-01

Rapid growth of road vehicles, private vehicles in particular, has resulted in continuing growth in China's oil demand and imports, which has been widely accepted as a major factor effecting future oil availability and prices, and a major contributor to China's GHG emission increase. This paper is intended to analyze the future trends of energy demand and GHG emissions in China's road transport sector and to assess the effectiveness of possible reduction measures. A detailed model has been developed to derive a reliable historical trend of energy demand and GHG emissions in China's road transport sector between 2000 and 2005 and to project future trends. Two scenarios have been designed to describe the future strategies relating to the development of China's road transport sector. The 'Business as Usual' scenario is used as a baseline reference scenario, in which the government is assumed to do nothing to influence the long-term trends of road transport energy demand. The 'Best Case' scenario is considered to be the most optimized case where a series of available reduction measures such as private vehicle control, fuel economy regulation, promoting diesel and gas vehicles, fuel tax and biofuel promotion, are assumed to be implemented. Energy demand and GHG emissions in China's road transport sector up to 2030 are estimated in these two scenarios. The total reduction potentials in the 'Best Case' scenario and the relative reduction potentials of each measure have been estimated

Biological versus mineralogical chromium reduction: potential for reoxidation by manganese oxide.

Science.gov (United States)

Butler, Elizabeth C; Chen, Lixia; Hansel, Colleen M; Krumholz, Lee R; Elwood Madden, Andrew S; Lan, Ying

2015-11-01

Hexavalent chromium (Cr(vi), present predominantly as CrO4(2-) in water at neutral pH) is a common ground water pollutant, and reductive immobilization is a frequent remediation alternative. The Cr(iii) that forms upon microbial or abiotic reduction often co-precipitates with naturally present or added iron (Fe), and the stability of the resulting Fe-Cr precipitate is a function of its mineral properties. In this study, Fe-Cr solids were formed by microbial Cr(vi) reduction using Desulfovibrio vulgaris strain RCH1 in the presence of the Fe-bearing minerals hematite, aluminum substituted goethite (Al-goethite), and nontronite (NAu-2, Clay Minerals Society), or by abiotic Cr(vi) reduction by dithionite reduced NAu-2 or iron sulfide (FeS). The properties of the resulting Fe-Cr solids and their behavior upon exposure to the oxidant manganese (Mn) oxide (birnessite) differed significantly. In microcosms containing strain RCH1 and hematite or Al-goethite, there was significant initial loss of Cr(vi) in a pattern consistent with adsorption, and significant Cr(vi) was found in the resulting solids. The solid formed when Cr(vi) was reduced by FeS contained a high proportion of Cr(iii) and was poorly crystalline. In microcosms with strain RCH1 and hematite, Cr precipitates appeared to be concentrated in organic biofilms. Reaction between birnessite and the abiotically formed Cr(iii) solids led to production of significant dissolved Cr(vi) compared to the no-birnessite controls. This pattern was not observed in the solids generated by microbial Cr(vi) reduction, possibly due to re-reduction of any Cr(vi) generated upon oxidation by birnessite by active bacteria or microbial enzymes. The results of this study suggest that Fe-Cr precipitates formed in groundwater remediation may remain stable only in the presence of active anaerobic microbial reduction. If exposed to environmentally common Mn oxides such as birnessite in the absence of microbial activity, there is the potential

Successful operation of continuous reactors at short retention times results in high-density, fast-rate Dehalococcoides dechlorinating cultures.

Science.gov (United States)

Delgado, Anca G; Fajardo-Williams, Devyn; Popat, Sudeep C; Torres, César I; Krajmalnik-Brown, Rosa

2014-03-01

The discovery of Dehalococcoides mccartyi reducing perchloroethene and trichloroethene (TCE) to ethene was a key landmark for bioremediation applications at contaminated sites. D. mccartyi-containing cultures are typically grown in batch-fed reactors. On the other hand, continuous cultivation of these microorganisms has been described only at long hydraulic retention times (HRTs). We report the cultivation of a representative D. mccartyi-containing culture in continuous stirred-tank reactors (CSTRs) at a short, 3-d HRT, using TCE as the electron acceptor. We successfully operated 3-d HRT CSTRs for up to 120 days and observed sustained dechlorination of TCE at influent concentrations of 1 and 2 mM TCE to ≥ 97 % ethene, coupled to the production of 10(12) D. mccartyi cells Lculture (-1). These outcomes were possible in part by using a medium with low bicarbonate concentrations (5 mM) to minimize the excessive proliferation of microorganisms that use bicarbonate as an electron acceptor and compete with D. mccartyi for H2. The maximum conversion rates for the CSTR-produced culture were 0.13 ± 0.016, 0.06 ± 0.018, and 0.02 ± 0.007 mmol Cl(-) Lculture (-1) h(-1), respectively, for TCE, cis-dichloroethene, and vinyl chloride. The CSTR operation described here provides the fastest laboratory cultivation rate of high-cell density Dehalococcoides cultures reported in the literature to date. This cultivation method provides a fundamental scientific platform for potential future operations of such a system at larger scales.

Interaction of 2,4,6-trichlorophenol with high carbon iron filings: Reaction and sorption mechanisms

Energy Technology Data Exchange (ETDEWEB)

Sinha, Alok [Environmental Engineering and Management Programme, Department of Civil Engineering, Indian Institute of Technology Kanpur, Kanpur 208016 (India); Bose, Purnendu [Environmental Engineering and Management Programme, Department of Civil Engineering, Indian Institute of Technology Kanpur, Kanpur 208016 (India)], E-mail: pbose@iitk.ac.in

2009-05-15

Reductive dehalogenation of 2,4,6-trichlorophenol (2,4,6-TCP) by two types of high carbon iron filings (HCIF), HCIF-1 and HCIF-2 was studied in batch reactors. While the iron, copper, manganese and carbon content of the two types of HCIF was similar, the specific surface area of HCIF-1 and HCIF-2 were 1.944 and 3.418 m{sup 2} g{sup -1}, respectively. During interaction with HCIF-1, 2,4,6-TCP adsorbed on HCIF-1 surface resulting in rapid reduction of aqueous phase 2,4,6-TCP concentration. However, reductive dehalogenation of 2,4,6-TCP was negligible. During interaction between 2,4,6-TCP and HCIF-2, both 2,4,6-TCP adsorption on HCIF-2, and 2,4,6,-TCP dechlorination was observed. 2,4,6-TCP partitioning between solid and aqueous phase could be described by a Freundlich isotherm, while 2,4,6-TCP dechlorination could be described by an appropriate rate expression. A mathematical model was developed for describing the overall interaction of 2,4,6-TCP with HCIF-2, incorporating simultaneous adsorption/desorption and dechlorination reactions of 2,4,6-TCP with the HCIF surface. 2,4-Dichlorophenol (2,4-DCP), 2-chlorophenol (2-CP) and minor amounts of 4-chlorophenol (4-CP) evolved as 2,4,6-TCP dechlorination by-products. The evolved 2,4-DCP partitioned strongly to the HCIF surface. 4-CP and 2-CP accumulated in the aqueous phase. No transformation of 2-CP or 4-CP to phenol was observed.

Mercury methylation and reduction potentials in marine water: An improved methodology using {sup 197}Hg radiotracer

Energy Technology Data Exchange (ETDEWEB)

Koron, Neza [National Institute of Biology, Marine Biology Station, Fornace 41, 6330 Piran (Slovenia); Bratkic, Arne [Department of Environmental Sciences, ' Jozef Stefan' Institute, Jamova 39, 1000 Ljubljana (Slovenia); Ribeiro Guevara, Sergio, E-mail: ribeiro@cab.cnea.gov.ar [Laboratorio de Analisis por Activacion Neutronica, Centro Atomico Bariloche, Av. Bustillo km 9.5, 8400 Bariloche (Argentina); Vahcic, Mitja; Horvat, Milena [Department of Environmental Sciences, ' Jozef Stefan' Institute, Jamova 39, 1000 Ljubljana (Slovenia)

2012-01-15

A highly sensitive laboratory methodology for simultaneous determination of methylation and reduction of spiked inorganic mercury (Hg{sup 2+}) in marine water labelled with high specific activity radiotracer ({sup 197}Hg prepared from enriched {sup 196}Hg stable isotope) was developed. A conventional extraction protocol for methylmercury (CH{sub 3}Hg{sup +}) was modified in order to significantly reduce the partitioning of interfering labelled Hg{sup 2+} into the final extract, thus allowing the detection of as little as 0.1% of the Hg{sup 2+} spike transformed to labelled CH{sub 3}Hg{sup +}. The efficiency of the modified CH{sub 3}Hg{sup +} extraction procedure was assessed by radiolabelled CH{sub 3}Hg{sup +} spikes corresponding to concentrations of methylmercury between 0.05 and 4 ng L{sup -1}. The recoveries were 73.0{+-}6.0% and 77.5{+-}3.9% for marine and MilliQ water, respectively. The reduction potential was assessed by purging and trapping the radiolabelled elemental Hg in a permanganate solution. The method allows detection of the reduction of as little as 0.001% of labelled Hg{sup 2+} spiked to natural waters. To our knowledge, the optimised methodology is among the most sensitive available to study the Hg methylation and reduction potential, therefore allowing experiments to be done at spikes close to natural levels (1-10 ng L{sup -1}). - Highlights: Black-Right-Pointing-Pointer Inorganic mercury methylation and reduction in marine water were studied. Black-Right-Pointing-Pointer High specific activity {sup 197}Hg was used to label Hg{sup 2+} spikes at natural levels. Black-Right-Pointing-Pointer Methylmercury extraction had 73% efficiency for 0.05-4 ng L{sup -1} levels. Black-Right-Pointing-Pointer High sensibility to assess methylation potentials, below 0.1% of the spike. Black-Right-Pointing-Pointer High sensibility also for reduction potentials, as low as 0.001% of the spike.

Reinterpreting the importance of oxygen-based biodegradation in chloroethene-contaminated groundwater

Science.gov (United States)

Bradley, Paul M.

2011-01-01

Chlororespiration is common in shallow aquifer systems under conditions nominally identified as anoxic. Consequently, chlororespiration is a key component of remediation at many chloroethene-contaminated sites. In some instances, limited accumulation of reductive dechlorination daughter products is interpreted as evidence that natural attenuation is not adequate for site remediation. This conclusion is justified when evidence for parent compound (tetrachloroethene, PCE, or trichloroethene, TCE) degradation is lacking. For many chloroethene-contaminated shallow aquifer systems, however, nonconservative losses of the parent compounds are clear but the mass balance between parent compound attenuation and accumulation of reductive dechlorination daughter products is incomplete. Incomplete mass balance indicates a failure to account for important contaminant attenuation mechanisms and is consistent with contaminant degradation to nondiagnostic mineralization products like CO2. While anoxic mineralization of chloroethene compounds has been proposed previously, recent results suggest that oxygen-based mineralization of chloroethenes also can be significant at dissolved oxygen concentrations below the currently accepted field standard for nominally anoxic conditions. Thus, reassessment of the role and potential importance of low concentrations of oxygen in chloroethene biodegradation are needed, because mischaracterization of operant biodegradation processes can lead to expensive and ineffective remedial actions. A modified interpretive framework is provided for assessing the potential for chloroethene biodegradation under different redox conditions and the probable role of oxygen in chloroethene biodegradation.

Urban passenger transport energy saving and emission reduction potential: A case study for Tianjin, China

International Nuclear Information System (INIS)

Peng, Binbin; Du, Huibin; Ma, Shoufeng; Fan, Ying; Broadstock, David C.

2015-01-01

Highlights: • Potential to reduce urban passenger transport is projected between 2010 and 2040. • Four scenarios reflecting different policy mixes are considered. • The potential for energy conservation and emission reductions are obtained. • Vehicle population regulation is most effective in energy saving and reducing overall GHG. • Emission standards are the most effective measure to reduce pollutant emissions. - Abstract: With rapid growth of the vehicle population, urban passenger transport in China is largely responsible for increases in energy consumption, greenhouse gas (GHG) emissions, and also atmospheric pollutants (NO x , CO, HC, PM). In this paper, we first develop an urban passenger transport energy saving and emission reduction potential evaluation model using the “Long Range Energy Alternatives Planning (LEAP)” tool; and then take Tianjin city as an empirical case to evaluate the reduction potential of final energy consumption, GHG emissions and pollutants emissions of Tianjin’s urban passenger transport sector between 2010 and 2040 under four scenarios, i.e. BAU (business as usual) scenario, PP (the 12th five-year plan policy) scenario, CP (comprehensive policy) scenario and HP (hybrid policy of PP and CP) scenario. The results show that due to the public transport promotion, energy consumption and CO 2 emissions in 2040 can be reduced by 22% and 22.6% in the PP scenario, compared to BAU. The largest reductions in energy consumption, CO 2 and atmospheric pollutants emissions can be achieved under CP scenario, in which vehicle population regulation is the most effective to be implemented. Emissions standard regulation is the most effective measure to reduce atmospheric pollutant emissions in all the scenarios and green energy promotion is especially effective to reduce NO x and PM

[Research on carbon reduction potential of electric vehicles for low-carbon transportation and its influencing factors].

Science.gov (United States)

Shi, Xiao-Qing; Li, Xiao-Nuo; Yang, Jian-Xin

2013-01-01

Transportation is the key industry of urban energy consumption and carbon emissions. The transformation of conventional gasoline vehicles to new energy vehicles is an important initiative to realize the goal of developing low-carbon city through energy saving and emissions reduction, while electric vehicles (EV) will play an important role in this transition due to their advantage in energy saving and lower carbon emissions. After reviewing the existing researches on energy saving and emissions reduction of electric vehicles, this paper analyzed the factors affecting carbon emissions reduction. Combining with electric vehicles promotion program in Beijing, the paper analyzed carbon emissions and reduction potential of electric vehicles in six scenarios using the optimized energy consumption related carbon emissions model from the perspective of fuel life cycle. The scenarios included power energy structure, fuel type (energy consumption per 100 km), car type (CO2 emission factor of fuel), urban traffic conditions (speed), coal-power technologies and battery type (weight, energy efficiency). The results showed that the optimized model was able to estimate carbon emissions caused by fuel consumption more reasonably; electric vehicles had an obvious restrictive carbon reduction potential with the fluctuation of 57%-81.2% in the analysis of six influencing factors, while power energy structure and coal-power technologies play decisive roles in life-cycle carbon emissions of electric vehicles with the reduction potential of 78.1% and 81.2%, respectively. Finally, some optimized measures were proposed to reduce transport energy consumption and carbon emissions during electric vehicles promotion including improving energy structure and coal technology, popularizing energy saving technologies and electric vehicles, accelerating the battery R&D and so on. The research provides scientific basis and methods for the policy development for the transition of new energy vehicles

Scenario analysis on CO2 emissions reduction potential in China's iron and steel industry

International Nuclear Information System (INIS)

Wang Ke; Wang Can; Lu Xuedu; Chen Jining

2007-01-01

The international climate community has begun to assess a range of possible options for strengthening the international climate change effort after 2012. Analysis of the potential for sector-based emissions reduction and relevant mitigation options will provide the necessary background information for the debate. In order to assess the CO 2 abatement potential of China's steel industry, a model was developed using LEAP software to generate 3 different CO 2 emission scenarios for the industry from 2000 to 2030. The abatement potentials of different scenarios were compared, and their respective feasibilities were assessed according to the cost information. High priority abatement measures were then identified. The results show that the average CO 2 abatement per year in the Recent Policy scenario and in the New Policy scenario, compared with the reference scenario, are 51 and 107 million tons, respectively. The corresponding total incremental costs are 9.34 and 80.95 billion dollars. It is concluded that there is great potential for CO 2 abatement in China's steel industry. Adjusting the structure of the industry and technological advancement will play an important role in emissions reduction. Successful implementation of current sustainable development policies and measures will result in CO 2 abatement at a low cost. However, to achieve higher levels of abatement, the cost will increase dramatically. In the near future, specific energy conservation technologies such as dry coke quenching, exhaust gas and heat recovery equipment will be of great significance. However, taking a long term perspective, emissions reduction will rely more on the adjustment of production processes and the application of more modern large scale plants. Advanced blast furnace technology will inevitably play an important role

Transformation of tetrachloroethene in an upflow anaerobic sludgeblanket reactor

DEFF Research Database (Denmark)

Christiansen, N.; Christensen, S.R.; Arvin, E.

1997-01-01

Reductive dechlorination of tetrachloroethene was studied in a mesophilic upflow anaerobic sludge blanket reactor. Operating the reactor in batch mode the dynamic transformation of tetrachloroethene, trichloroethene and dichloroethene (DCE) was monitored. Tetrachloroethene was reductively...... methane-producing bacteria were inhibited by the chlorinated ethenes....

Performance and emission reduction potential of micro-gasifier improved through better design

Directory of Open Access Journals (Sweden)

Kamil Dino Adem

2017-01-01

Full Text Available Biomass gasification is getting popular for household cooking application in most developing countries including Ethiopia. The preference for biomass gasification is due to the generation of less CO (Carbon Monoxide and PM (Particulate Matter in comparison with other biomass cookstoves. Our study showed the improvement in thermal efficiency and emission reduction potential of micro-gasifier. A prototype micro-gasifier was built and tested using the water boiling test protocol. The test results gave a thermal efficiency of 39.6% and a specific fuel consumption of 57 g of fuel/ liter of water. With regard to indoor air pollution, the maximum CO & PM registered were 12.5 ppm and 1.85 mg/m3, respectively. Using clean development mechanism (CDM methodology, the estimated emission reduction potential of the micro-gasifier is 1.30 tCO2 per micro-gasifier per year. Generally, the micro-gasifier has better performance compared to the previous designs proposed by other researchers. Thus, disseminating our micro-gasifier at a larger scale in developing countries such as Ethiopia will be beneficial in reducing deforestation and emission that will be brought about by using open-fire stoves and thus, helps to obtain carbon credit.

Reductive destruction and decontamination of aqueous solutions of chlorinated antimicrobial agent using bimetallic systems

Energy Technology Data Exchange (ETDEWEB)

Ghauch, Antoine, E-mail: antoine.ghauch@aub.edu.lb [American University of Beirut, Faculty of Arts and Sciences, Department of Chemistry, P.O. Box 11-0236 Riad El Solh, 1107-2020 Beirut (Lebanon); Tuqan, Almuthanna [American University of Beirut, Faculty of Arts and Sciences, Department of Chemistry, P.O. Box 11-0236 Riad El Solh, 1107-2020 Beirut (Lebanon)

2009-05-30

Palladium, ruthenium and silver were investigated as catalysts for the dechlorination of dichlorophen (DCP, 2,2'-methylenebis(4-chlorophenol)), an antimicrobial and anthelmintic agent largely used as algicide, fungicide and bactericide. Experiments were undertaken under oxic and anoxic conditions for experimental durations up to 180 min (3 h). The anoxic conditions were achieved by purging the solutions with nitrogen gas. Reactions were performed in a 12 {+-} 0.5 mg L{sup -1} DCP solution (V = 20 mL) using 0.8 g of Fe{sup 0} (40 g L{sup -1}). Along with micrometric Fe{sup 0}, five Fe{sup 0}-plated systems were investigated: Pd (1%), Ru (0.01%), Ru (0.1%), Ru (1%) and Ag (1%). Metal plating was controlled by atomic absorption spectroscopy. DCP degradation was monitored using: (i) two HPLC devices, (ii) ion chromatography, (iii) UV and fluorescence spectrophotometry. Results indicated: (i) total dechlorination with Fe/Pd, (ii) partial dechlorination (40%) with Fe/Ru, and no reaction with Fe/Ag. DCP is vanished completely after 90 min of contact with Fe/Pd following a first order kinetic. The observed degradation rate k{sub obs} was about (3.98 {+-} 0.10) x 10{sup -2} min{sup -1}, the calculated half-life t{sub 1/2} about 17.4 {+-} 0.9 min and a t{sub 50} about 10.1 {+-} 0.5 min. A DCP degradation pathway map was also proposed.

Greenhouse gases reduction potential through consumer’s behavioral changes in terms of food-related product selection

International Nuclear Information System (INIS)

Yoshikawa, Naoki; Fujiwara, Natsumi; Nagata, Junko; Amano, Koji

2016-01-01

Highlights: • Greenhouse gases (GHG) reduction potential by shopping behavior change is analyzed. • Four scenarios related to food consumption is evaluated using life cycle assessment. • Total GHG reduction potential by four scenarios in Japan is 1367 kt-CO_2/year. • Potential reduces to 45% when considering feasible ratio of taking behavior change. • Contribution of seasonal production/consumption scenario is highest among scenarios. - Abstract: Sustainable consumption plays an important role in the mitigation of global warming and the conservation of energy. Promoting more environmentally responsible consumer behavior, especially through open communication between stakeholders, is one way to achieve low-carbon consumption. This study evaluates the potential for reducing greenhouse gas (GHG) emissions through behavioral transformation of consumers in terms of their daily shopping habits. In this context, the behavioral transformative actions pertain to certain foods and daily necessities, and are analyzed from a life cycle assessment perspective. We developed multiple product-selection scenarios to evaluate GHG emissions related to the daily purchase of commodities. Based on the life cycle assessment, we estimated the GHG emissions that result from the production and distribution of these commodities, pertaining to both the current product selection and to a possibly improved selection. The results of our study show that because of seasonal consumption patterns and energy conversion, there is a substantial potential to reduce GHG emissions resulting from out-of-season produce cultivation. The GHG reduction potential is not high for each individual commodity because diverse commodities are needed on a daily basis. However, various actions in combination could have substantial potential for reducing emissions.

Energy saving and CO2-reduction potential of micro-cogeneration in the Netherlands (2010-2030). Update 2008

International Nuclear Information System (INIS)

Van Gastel, M.; De Jong, A.; Schlatmann, S.; Bakker, E.J.; Jeeninga, H.; Boerakker, Y.; Seebregts, A.; Menkveld, M.; Van Wolferen, H.; Turkstra, J.W.; Dam, J.; Harmsen, R.; Rooijers, F.; Koot, M.

2008-05-01

Various parties have been asked to come to a joint point of view with regard to establishing the potential of micro CHP for energy saving and CO2 emission reduction in the Netherlands from 2010 to 2030, assuming that micro CHP will have a successful market introduction. The result of this memo is a method for determining the technical potential of micro CHP for the reduction of energy use and CO2 emissions. This report is an update of the 2006 report [mk] [nl

Sodium intake in US ethnic subgroups and potential impact of a new sodium reduction technology: NHANES Dietary Modeling.

Science.gov (United States)

Fulgoni, Victor L; Agarwal, Sanjiv; Spence, Lisa; Samuel, Priscilla

2014-12-18

Because excessive dietary sodium intake is a major contributor to hypertension, a reduction in dietary sodium has been recommended for the US population. Using the National Health and Nutrition Examination Survey (NHANES) 2007-2010 data, we estimated current sodium intake in US population ethnic subgroups and modeled the potential impact of a new sodium reduction technology on sodium intake. NHANES 2007-2010 data were analyzed using The National Cancer Institute method to estimate usual intake in population subgroups. Potential impact of SODA-LO® Salt Microspheres sodium reduction technology on sodium intake was modeled using suggested sodium reductions of 20-30% in 953 foods and assuming various market penetrations. SAS 9.2, SUDAAN 11, and NHANES survey weights were used in all calculations with assessment across age, gender and ethnic groups. Current sodium intake across all population subgroups exceeds the Dietary Guidelines 2010 recommendations and has not changed during the last decade. However, sodium intake measured as a function of food intake has decreased significantly during the last decade for all ethnicities. "Grain Products" and "Meat, Poultry, Fish, & Mixtures" contribute about 2/3rd of total sodium intake. Sodium reduction, using SODA-LO® Salt Microspheres sodium reduction technology (with 100% market penetration) was estimated to be 185-323 mg/day or 6.3-8.4% of intake depending upon age, gender and ethnic group. Current sodium intake in US ethnic subgroups exceeds the recommendations and sodium reduction technologies could potentially help reduce dietary sodium intake among those groups.

Socio-economic and Engineering Assessments of Renewable Energy Cost Reduction Potential

Science.gov (United States)

Seel, Joachim

This dissertation combines three perspectives on the potential of cost reductions of renewable energy--a relevant topic, as high energy costs have traditionally been cited as major reason to vindicate developments of fossil fuel and nuclear power plants, and to justify financial support mechanisms and special incentives for renewable energy generators. First, I highlight the role of market and policy drivers in an international comparison of upfront capital expenses of residential photovoltaic systems in Germany and the United States that result in price differences of a factor of two and suggest cost reduction opportunities. In a second article I examine engineering approaches and siting considerations of large-scale photovoltaic projects in the United States that enable substantial system performance increases and allow thus for lower energy costs on a levelized basis. Finally, I investigate future cost reduction options of wind energy, ranging from capital expenses, operating expenses, and performance over a project's lifetime to financing costs. The assessment shows both substantial further cost decline potential for mature technologies like land-based turbines, nascent technologies like fixed-bottom offshore turbines, and experimental technologies like floating offshore turbines. The following paragraphs summarize each analysis: International upfront capital cost comparison of residential solar systems: Residential photovoltaic (PV) systems were twice as expensive in the United States as in Germany in 2012. This price discrepancy stems primarily from differences in non-hardware or "soft" costs between the two countries, of which only 35% be explained by differences in cumulative market size and associated learning. A survey of German PV installers was deployed to collect granular data on PV soft costs in Germany, and the results are compared to those of a similar survey of U.S. PV installers. Non-module hardware costs and all analyzed soft costs are lower in

The power sector in China and India: greenhouse gas emissions reduction potential and scenarios for 1990-2020

International Nuclear Information System (INIS)

Kroeze, Carolien; Vlasblom, Jaklien; Gupta, Joyeeta; Boudri, Christiaan; Blok, Kornelis

2004-01-01

Emissions of greenhouse gases from China and India are expected to increase in the coming two decades. The objectives of this study are two-fold: (1) to quantify the technical potential of various options to reduce emissions of greenhouse gases from the electricity sector in China and India in the year 2020, and (2) to evaluate a business-as-usual (BAU) scenario plus a number of best practice technology (BPT) scenarios for emission reduction of greenhouse gases from electricity production in China and India up to the year 2020. Options to reduce emissions include end use efficiency improvement, fuel switches, and efficiency improvement of existing and new power plants. For China, we calculated that the individual options analysed have technical potentials to reduce 2020 emissions ranging from 1% to 43% (relative to 2020 unabated emissions) and for India from 4% to 45%. Relatively large reduction potentials are calculated for end use efficiency improvement (43% for China and 45% for India), replacement of coal by renewable energy (23% for China and 14% for India) and natural gas (11% for China and 14% for India). Reducing electricity losses during transmission and distribution would reduce emissions by 7% (China) and 6% (India) and electrical efficiency improvement of power plants by 9% in both countries. The reduction options differ with respect to their feasibility. In the BAU scenario, emissions increase considerably between 1990 and 2020. Next, we present results for three BPT scenarios, which reflect the combined technical potential of selected options to reduce emissions. Our calculations indicate that all three scenarios have a potential to reduce emissions to about half the 2020 BAU level. The three scenarios are very different in their assumptions on reduction options, indicating that there are different strategies possible for realising relatively large emission reductions in China and India. We conclude that end use efficiency improvement may be one of

Dechlorination and chlorine rearrangement of 1,2,5,5,6,9,10-heptachlorodecane mediated by the whole pumpkin seedlings.

Science.gov (United States)

Li, Yanlin; Hou, Xingwang; Yu, Miao; Zhou, Qunfang; Liu, Jiyan; Schnoor, Jerald L; Jiang, Guibin

2017-05-01

Short chain chlorinated paraffins (SCCPs) are ubiquitously present as persistent organic pollutants in the environment. However, little information on the interaction of SCCPs with plants is currently available. In this work, young pumpkin plants (Cucurbita maxima × C. Moschata) were hydroponically exposed to the congener of chlorinated decane, 1,2,5,5,6,9,10-heptachlorodecane (1,2,5,5,6,9,10-HepCD), to investigate the uptake, translocation and transformation of chlorinated decanes in the intact plants. It was found that parent HepCD was taken up by the pumpkin roots, translocated from root to shoots, and phytovolatilized from pumpkin plants to air via the plant transpiration flux. Our data suggested that dechlorination of 1,2,5,5,6,9,10-HepCD to lower chlorinated decanes and rearrangement of chlorine atoms in the molecule were all mediated by the whole pumpkin seedlings. Chlorinated decanes were found in the shoots and roots of blank controls, indicating that chlorinated decanes in the air could be absorbed by leaves and translocated from shoots to roots. Lower chlorinated congeners (C 10 H 17 Cl 5 ) tended to detain in air compared to higher chlorinated congeners (C 10 H 16 Cl 6 and other C 10 H 15 Cl 7 ). Potential transformation pathway and behavior of 1,2,5,5,6,9,10-HepCD in pumpkin were proposed based on these experiments. Copyright © 2017 Elsevier Ltd. All rights reserved.

Interaction of perchlorate and trichloroethene bioreductions in mixed anaerobic culture

Energy Technology Data Exchange (ETDEWEB)

Wen, Li-Lian [Department of Environmental Engineering, College of Environmental and Resource Science, Zhejiang University, Hangzhou (China); Zhejiang Prov Key Lab Water Pollut Control & Envi, Zhejiang University, Hangzhou, Zhejiang (China); Yang, Qiang [Hangzhou Institute of Environmental Protection Science, Hangzhou (China); Zhang, Zhao-Xin; Yi, Yang-Yi [Department of Environmental Engineering, College of Environmental and Resource Science, Zhejiang University, Hangzhou (China); Tang, Youneng [Department of Civil and Environmental Engineering, FAMU-FSU College of Engineering, Florida State University, Tallahassee, FL 32310-6046 (United States); Zhao, He-Ping, E-mail: zhaohp@zju.edu.cn [Department of Environmental Engineering, College of Environmental and Resource Science, Zhejiang University, Hangzhou (China); Zhejiang Prov Key Lab Water Pollut Control & Envi, Zhejiang University, Hangzhou, Zhejiang (China); Hangzhou Institute of Environmental Protection Science, Hangzhou (China)

2016-11-15

This work evaluated the interaction of perchlorate and trichloroethene (TCE), two common co-contaminants in groundwater, during bioreduction in serum bottles containing synthetic mineral salts media and microbial consortia. TCE at concentrations up to 0.3 mM did not significantly affect perchlorate reduction; however, perchlorate concentrations higher than 0.1 mM made the reduction of TCE significantly slower. Perchlorate primarily inhibited the reduction of vinyl chloride (VC, a daughter product of TCE) to ethene. Mechanistic analysis showed that the inhibition was mainly because perchlorate reduction is thermodynamically more favorable than reduction of TCE and its daughter products and not because of toxicity due to accumulation of dissolved oxygen produced during perchlorate reduction. As the initial perchlorate concentration increased from 0 to 600 mg/L in a set of serum bottles, the relative abundance of Rhodocyclaceae (a putatively perchlorate-reducing genus) increased from 6.3 to 80.6%, while the relative abundance of Dehalococcoides, the only known genus that is able to reduce TCE all the way to ethene, significantly decreased. Similarly, the relative abundance of Proteobacteria (a phylum to which most known perchlorate-reducing bacteria belong) increased from 22% to almost 80%. - Graphical abstract: Fig. A plots the interaction of TCE and perchlorate bio-reduction under different concentrations of perchlorate and suggests that initial ethene wasn't formed until the perchlorate was completely reduced. B shows the electron donor utilization and oxygen generated during the experiment and indicates that it is perchlorate reduction over-competed for electron donor rather than oxygen generated that inhibits TCE reductive dechlorination. - Highlight: • Perchlorate slowed but did not inhibit the complete dechlorination of TCE. • The inhibition was mainly due to the thermodynamic preference of perchlorate to TCE. • The generated oxygen was consumed and

Cost reduction potentials in the German market for balancing power

International Nuclear Information System (INIS)

Flinkerbusch, Kai; Heuterkes, Michael

2010-01-01

This article examines potential cost reductions in the market for balancing power by pooling all four German control areas. In a united control area both the procurement and the production of balancing power may be more efficient than in four separated control areas. Our data contain bids on energy procurement as well as balancing power flows in the period from December 2007 to November 2008. A reference scenario simulates the market results for secondary and tertiary balancing power. Subsequently, we simulate a united control area. We show that in the period under review the total costs of balancing power are reduced by 17%. (author)

Applications of surface analysis in the environmental sciences: dehalogenation of chlorocarbons with zero-valent iron and iron-containing mineral surfaces

Energy Technology Data Exchange (ETDEWEB)

McGuire, Molly M.; Carlson, Daniel L.; Vikesland, Peter J.; Kohn, Tamar; Grenier, Adam C.; Langley, Laura A.; Roberts, A. Lynn; Fairbrother, D. Howard

2003-10-31

Halogenated organic compounds are common pollutants in groundwater. Consequently, there is widespread interest in understanding the reactions of these compounds in the environment and developing remediation strategies. One area of ongoing research involves the reductive dechlorination of organohalides with zero-valent metals or metal sulfide minerals. These processes have been studied almost exclusively from the perspective of the aqueous phase. In this paper we illustrate the utility of surface analysis techniques, including electron spectroscopies, vibrational spectroscopies, and atomic force microscopy in elucidating the roles played by the surface. A dual analysis approach to the study of reductive dechlorination, combining traditional solution phase analysis with surface analytical techniques, also is demonstrated using a liquid cell coupled to an ultrahigh vacuum surface analysis chamber.

Dechlorination of polychlorinated biphenyls by iron and its oxides.

Science.gov (United States)

Sun, Yifei; Liu, Xiaoyuan; Kainuma, Masashi; Wang, Wei; Takaoka, Masaki; Takeda, Nobuo

2015-10-01

The decomposition efficiency of polychlorinated biphenyls (PCBs) was determined using elemental iron (Fe) and three iron (hydr)oxides, i.e., α-Fe2O3, Fe3O4, and α-FeOOH, as catalysts. The experiments were performed using four distinct PCB congeners (PCB-209, PCB-153, and the coplanar PCB-167 and PCB-77) at temperatures ranging from 180 °C to 380 °C and under an inert, oxidizing or reducing atmosphere composed of N2, N2+O2, or N2+H2. From these three options N2 showed to provide the best reaction atmosphere. Among the iron compounds tested, Fe3O4 showed the highest activity for decomposing PCBs. The decomposition efficiencies of PCB-209, PCB-167, PCB-153, and PCB-77 by Fe3O4 in an N2 atmosphere at 230 °C were 88.5%, 82.5%, 69.9%, and 66.4%, respectively. Other inorganic chlorine (Cl) products which were measured by the amount of inorganic Cl ions represented 82.5% and 76.1% of the reaction products, showing that ring cleavage of PCBs was the main elimination process. Moreover, the dechlorination did not require a particular hydrogen donor. We used X-ray photoelectron spectroscopy to analyze the elemental distribution at the catalyst's surface. The O/Fe ratio influenced upon the decomposition efficiency of PCBs: the lower this ratio, the higher the decomposition efficiency. X-ray absorption near edge structure spectra showed that α-Fe2O3 effectively worked as a catalyst, while Fe3O4 and α-FeOOH were consumed as reactants, as their final state is different from their initial state. Finally, a decomposition pathway was postulated in which the Cl atoms in ortho-positions were more difficult to eliminate than those in the para- or meta-positions. Copyright © 2015 Elsevier Ltd. All rights reserved.

A Comparison of Modeling Approaches in Simulating Chlorinated Ethene Removal in a Constructed Wetland by a Microbial Consortia

National Research Council Canada - National Science Library

Campbell, Jason

2002-01-01

The purpose of this study is to compare different approaches to modeling the reductive dechlorination of chlorinated ethenes in the anaerobic region of an upward flow constructed wetland by microbial consortia...

Decomposition of PCBs in oils using gamma radiolysis

International Nuclear Information System (INIS)

Mincher, B.J.; Arbon, R.E.; Schwendiman, G.L.

1996-01-01

This paper investigates the radiolysis of the polychlorinated biphenyls (PCBs) in several oil matrices. The results of mechanism and kinetic studies in isooctane are presented. The decomposition of PCBs in isooctane is shown to occur by reductive dechlorination due to electron capture and to proceed with pseudo-first-order kinetics. The rate is dependent on the initial PCB concentration. Electron capture detection gas chromatograms confirm that dechlorination also occurs with commercial Aroclor PCBs in irradiated transformer and hydraulic oils. The results of a demonstration experiment involving PCB contaminated waste hydraulic oils are presented

Potential Cost Savings From Reduction of Regional Variation in Medicare Spending

Directory of Open Access Journals (Sweden)

Yunjie Song

2016-04-01

Full Text Available Potential cost savings estimated from reduction of regional variation in Medicare spending are considerable but questioned. This article evaluates the validity of the principal methods that have been used in the estimations of the potential savings. Three estimation approaches were identified. The first approach uses adjusted expenditures to calculate avoidable costs, but adjusted expenditures can be independent of avoidable costs, and measurement errors are not controlled. The second approach uses an outcome variable to replace its causal factors, and is not acceptable because the association between the outcomes and the causes is untestable. The final approach uses surveys to directly measure physician beliefs and patient preferences, but the sole study using this approach is weakened by sample selection biases and incomplete controls. A development of reliable measures and a switch of observation from clinic settings to geographic contexts could make the estimations more convincing.

Design features and cost reduction potential of JSFR

International Nuclear Information System (INIS)

Katoh, Atsushi; Hayafune, Hiroki; Kotake, Shoji

2014-01-01

Highlights: • Japan Sodium Cooled Fast Reactor (JSFR) is designed to reduce plant commodity. • Cost reduction effectiveness by innovative designs is estimated by bottom up method. • JSFR achieves 76% construction cost reduction compared with Monju by design effort. • Commercial JSFR construction cost could be less than that of conventional LWR. - Abstract: To improve the economic competitiveness of the Japan Sodium-cooled Fast Reactor (JSFR), several innovative designs have been introduced, e.g. reduction of number of main cooling loop, shorter pipe arrangement by adopting thermally durable material, in fact high chromium ferrite steel, a compact reactor vessel (RV), integration of a primary pump and an intermediate heat exchanger (IHX). Since they had not been introduced in the past and existing reactors, a new approach for construction cost estimation has been introduced to handle innovative technologies, for example, concerning different kinds of material, fabrication processes of equipment etc. As results of JSFR construction cost estimations based on the new method and the latest conceptual JSFR design, economic goals of Generation IV nuclear energy systems can be achieved by expecting the following cost reduction effects: commodity reduction by adopting innovative design, an economy of scale by power generation increase, learning effect etc. It is well analyzed quantitatively that feasibility of innovative designs is essential for economic competitiveness of JSFR

Design features and cost reduction potential of JSFR

Energy Technology Data Exchange (ETDEWEB)

Katoh, Atsushi, E-mail: kato.atsushi@jaea.go.jp [Japan Atomic Energy Agency, 4002 Narita, Oarai-machi, Higashi-ibaraki-gun, Ibaraki-ken 311-1393 (Japan); Hayafune, Hiroki [Japan Atomic Energy Agency, 4002 Narita, Oarai-machi, Higashi-ibaraki-gun, Ibaraki-ken 311-1393 (Japan); Kotake, Shoji [The Japan Atomic Power Company, 1-1 Kanda-midoricyo, Chiyoda-ku, Tokyo-to 101-0053 (Japan)

2014-12-15

Highlights: • Japan Sodium Cooled Fast Reactor (JSFR) is designed to reduce plant commodity. • Cost reduction effectiveness by innovative designs is estimated by bottom up method. • JSFR achieves 76% construction cost reduction compared with Monju by design effort. • Commercial JSFR construction cost could be less than that of conventional LWR. - Abstract: To improve the economic competitiveness of the Japan Sodium-cooled Fast Reactor (JSFR), several innovative designs have been introduced, e.g. reduction of number of main cooling loop, shorter pipe arrangement by adopting thermally durable material, in fact high chromium ferrite steel, a compact reactor vessel (RV), integration of a primary pump and an intermediate heat exchanger (IHX). Since they had not been introduced in the past and existing reactors, a new approach for construction cost estimation has been introduced to handle innovative technologies, for example, concerning different kinds of material, fabrication processes of equipment etc. As results of JSFR construction cost estimations based on the new method and the latest conceptual JSFR design, economic goals of Generation IV nuclear energy systems can be achieved by expecting the following cost reduction effects: commodity reduction by adopting innovative design, an economy of scale by power generation increase, learning effect etc. It is well analyzed quantitatively that feasibility of innovative designs is essential for economic competitiveness of JSFR.

Field Evidence for Co-Metabolism of Trichloroethene Stimulated by Addition of Electron Donor to Groundwater

Energy Technology Data Exchange (ETDEWEB)

Conrad, Mark E.; Brodie, Eoin L.; Radtke, Corey W.; Bill, Markus; Delwiche, Mark E.; Lee, M. Hope; Swift, Dana L.; Colwell, Frederick S.

2010-05-17

For more than 10 years, electron donor has been injected into the Snake River aquifer beneath the Test Area North site of the Idaho National Laboratory for the purpose of stimulating microbial reductive dechlorination of trichloroethene (TCE) in groundwater. This has resulted in significant TCE removal from the source area of the contaminant plume and elevated dissolved CH4 in the groundwater extending 250 m from the injection well. The delta13C of the CH4 increases from 56o/oo in the source area to -13 o/oo with distance from the injection well, whereas the delta13C of dissolved inorganic carbon decreases from 8 o/oo to -13 o/oo, indicating a shift from methanogenesis to methane oxidation. This change in microbial activity along the plume axis is confirmed by PhyloChip microarray analyses of 16S rRNA genes obtained from groundwater microbial communities, which indicate decreasing abundances of reductive dechlorinating microorganisms (e.g., Dehalococcoides ethenogenes) and increasing CH4-oxidizing microorganisms capable of aerobic co-metabolism of TCE (e.g., Methylosinus trichosporium). Incubation experiments with 13C-labeled TCE introduced into microcosms containing basalt and groundwater from the aquifer confirm that TCE co-metabolism is possible. The results of these studies indicate that electron donor amendment designed to stimulate reductive dechlorination of TCE may also stimulate co-metabolism of TCE.

Potential for greenhouse gas reduction in industry through increased heat recovery and/or integration of combined heat and power

International Nuclear Information System (INIS)

Axelsson, H.; Harvey, S.; Aasblad, A.; Berntsson, T.

2003-01-01

The potential for greenhouse gas (GHG) reduction in industry through process integration measures depends to a great extent on prevailing technical and economic conditions. A step-wise methodology developed at the author's department based on pinch technology was used to analyse how various parameters influence the cost-optimal configuration for the plant's energy system, and the opportunities for cost-effective GHG emissions reduction compared to this solution. The potential for reduction of GHG emissions from a given plant depends primarily on the design of the industrial process and its energy system (internal factors) and on the electricity-to-fuel price ratio and the specific GHG emissions from the national power generation system (external factors)

Potential energy consumption reduction of automotive climate control systems

International Nuclear Information System (INIS)

Nielsen, Filip; Uddheim, Åsa; Dalenbäck, Jan-Olof

2016-01-01

Highlights: • Twenty-on energy saving measures for vehicle interior climate were evaluated. • Few single energy saving measures could reduce the energy use significantly. • The operation of the system in intermediate conditions determines the energy use. • Required heating/cooling of passenger compartment had small effect on energy use. - Abstract: In recent years fuel consumption of passenger vehicles has received increased attention by customers, the automotive industry, regulatory agencies and academia. One area which affect the fuel consumption is climate control systems. Twenty-one energy saving measures were evaluated regarding the total energy use for vehicle interior climate using simulation. Evaluated properties were heat flow into the passenger compartment, electrical and mechanical work. The simulation model included sub models of the passenger compartment, air-handling unit, Air Conditioning (AC) system, engine and engine cooling system. A real-world representative test cycle, which included tests in cold, intermediate and warm conditions, was used for evaluation. In general, few single energy saving measures could reduce the energy use significantly. The measures with most potential were increased blower efficiency with a reduction of 46% of the electrical work and increased AC-system disengage temperature with a reduction of 27% of the mechanical work. These results show that the operation of the climate control system had a large effect on the energy use, especially compared to the required heating and cooling of the passenger compartment. As a result energy saving measures need to address how heating and cooling is generated before reducing the heat flow into the passenger compartment.

Inventory and Policy Reduction Potential of Greenhouse Gas and Pollutant Emissions of Road Transportation Industry in China

Directory of Open Access Journals (Sweden)

Ye Li

2016-11-01

Full Text Available In recent years, emissions from the road transportation industry in China have been increasing rapidly. To evaluate the reduction potential of greenhouse gas and pollutant emissions of the industry in China, its emission inventory was calculated and scenario analysis was created for the period between 2012 and 2030 in this paper. Based on the Long-range Energy Alternatives Planning System (LEAP model, the development of China’s road transportation industry in two scenarios (the business-as-usual (BAU scenario and the comprehensive-mitigation (CM scenario was simulated. In the Comprehensive Mitigation scenario, there are nine various measures which include Fuel Economy Standards, Auto Emission Standards, Energy-saving Technology, Tax Policy, Eco-driving, Logistics Informatization, Vehicle Liquidation, Electric Vehicles, and Alternative Fuels. The cumulative energy and emission reductions of these specific measures were evaluated. Our results demonstrate that China’s road transportation produced 881 million metric tons of CO2 and emitted 1420 thousand tons of CO, 2150 thousand tons of NOx, 148 thousand tons of PM10, and 745 thousand tons of HC in 2012. The reduction potential is quite large, and road freight transportation is the key mitigation subsector, accounting for 85%–92% of the total emission. For energy conservation and carbon emission mitigation, logistics informatization is the most effective method, potentially reducing 1.80 billion tons of coal equivalent and 3.83 billion tons of CO2 from 2012 to 2030. In terms of air pollutant emission mitigation, the auto emission standards measure performs best with respect to NOx, PM10, and HC emission mitigation, and logistic informatization measure is the best in CO emission reduction. In order to maximize the mitigation potential of China’s road transportation industry, the government needs to implement various measures in a timely and strict fashion.

Indirect Evidence Link PCB Dehalogenation with Geobacteraceae in Anaerobic Sediment-Free Microcosms

Czech Academy of Sciences Publication Activity Database

Pravečková, Martina; Brennerová, Mária; Holliger, Ch.; De Alencastro, F.; Rossi, P.

2016-01-01

Roč. 7, June (2016), s. 933 ISSN 1664-302X Institutional support: RVO:61388971 Keywords : polychlorinated biphenyl congeners * Delor 103 * reductive dechlorination Subject RIV: EE - Microbiology, Virology Impact factor: 4.076, year: 2016

Selected constants oxydo-reduction potentials tables of constants and numerical data affiliated to the International Union of Pure and Applied Chemistry, v.8

CERN Document Server

Charlot, G

1958-01-01

Selected Constants: Oxydo-Reduction Potentials contains Tables of the most probable value of the normal oxidation-reduction potential, or of the formal or apparent potential, of a given oxidation-reduction system. This book is prepared under the sponsorship of the Commission on Electrochemical Data of the Section of Analytical Chemistry of the International Union of Pure and Applied Chemistry. It is included in a general program of the Section of Analytical Chemistry. Entry items are classified in alphabetical order. This book will be of value to specialized and non-specialized chemists, teach

Wheat straw biochar-supported nanoscale zerovalent iron for removal of trichloroethylene from groundwater.

Directory of Open Access Journals (Sweden)

Hui Li

Full Text Available This study synthesized the wheat straw biochar-supported nanoscale zerovalent iron (BC-nZVI via in-situ reduction with NaBH4 and biochar pyrolyzed at 600°C. Wheat straw biochar, as a carrier, significantly enhanced the removal of trichloroethylene (TCE by nZVI. The pseudo-first-order rate constant of TCE removal by BC-nZVI (1.079 h-1 within 260 min was 1.4 times higher and 539.5 times higher than that of biochar and nZVI, respectively. TCE was 79% dechlorinated by BC-nZVI within 15 h, but only 11% dechlorinated by unsupported nZVI, and no TCE dechlorination occurred with unmodified biochar. Weakly acidic solution (pH 5.7-6.8 significantly enhanced the dechlorination of TCE. Chloride enhanced the removal of TCE, while SO42-, HCO3- and NO3- all inhibited it. Humic acid (HA inhibited BC-nZVI reactivity, but the inhibition decreased slightly as the concentration of HA increased from 40 mg∙L-1 to 80 mg∙L-1, which was due to the electron shutting by HA aggregates. Results suggest that BC-nZVI was promising for remediation of TCE contaminated groundwater.

Sodium intake status in United States and potential reduction modeling: an NHANES 2007-2010 analysis.

Science.gov (United States)

Agarwal, Sanjiv; Fulgoni, Victor L; Spence, Lisa; Samuel, Priscilla

2015-11-01

Limiting dietary sodium intake has been a consistent dietary recommendation. Using NHANES 2007-2010 data, we estimated current sodium intake and modeled the potential impact of a new sodium reduction technology on sodium intake. NHANES 2007-2010 data were used to assess current sodium intake. The National Cancer Institute method was used for usual intake determination. Suggested sodium reductions using SODA-LO (®) Salt Microspheres ranged from 20% to 30% in 953 foods and usual intakes were modeled by using various reduction factors and levels of market penetration. SAS 9.2, SUDAAN 11, and NHANES survey weights were used in all calculations with assessment across gender and age groups. Current (2007-2010) sodium intake (mg/day) exceeds recommendations across all age gender groups and has not changed during the last decade. However, sodium intake measured as a function of food intake (mg/g food) has decreased significantly during the last decade. Two food categories contribute about 2/3rd of total sodium intake: "Grain Products" and "Meat, Poultry, Fish & Mixtures". Sodium reduction, with 100% market penetration of the new technology, was estimated to be 230-300 mg/day or 7-9% of intake depending upon age and gender group. Sodium reduction innovations like SODA-LO (®) Salt Microspheres could contribute to meaningful reductions in sodium intake.

Effects of oxidation reduction potential in the bypass micro-aerobic sludge zone on sludge reduction for a modified oxic-settling-anaerobic process.

Science.gov (United States)

Li, Kexun; Wang, Yi; Zhang, Zhongpin; Liu, Dongfang

2014-01-01

Batch experiments were conducted to determine the effect of oxidation reduction potential (ORP) on sludge reduction in a bypass micro-aerobic sludge reduction system. The system was composed of a modified oxic-settling-anaerobic process with a sludge holding tank in the sludge recycle loop. The ORPs in the micro-aerobic tanks were set at approximately +350, -90, -150, -200 and -250 mV, by varying the length of aeration time for the tanks. The results show that lower ORP result in greater sludge volume reduction, and the sludge production was reduced by 60% at the lowest ORP. In addition, low ORP caused extracellular polymer substances dissociation and slightly reduced sludge activity. Comparing the sludge backflow characteristics of the micro-aerobic tank's ORP controlled at -250 mV with that of +350 mV, the average soluble chemical oxygen (SCOD), TN and TP increased by 7, 0.4 and 2 times, median particle diameter decreased by 8.5 μm and the specific oxygen uptake rate (SOUR) decreased by 0.0043 milligram O2 per gram suspended solids per minute. For the effluent, SCOD and TN and TP fluctuated around 30, 8.7 and 0.66 mg/L, respectively. Therefore, the effective assignment of ORP in the micro-aerobic tank can remarkably reduce sludge volume and does not affect final effluent quality.

Stable carbon isotope analysis to distinguish biotic and abiotic degradation of 1,1,1-trichloroethane in groundwater sediments

DEFF Research Database (Denmark)

Broholm, Mette Martina; Hunkeler, Daniel; Tuxen, Nina

2014-01-01

not appear to be reductive dechlorination via 1,1-DCA. In the biotic microcosms, the degradation of 1,1,1-TCA occurred under iron and sulfate reducing conditions. Biotic reduction of iron and sulfate likely resulted in formation of FeS, which can abiotically degrade 1,1,1-TCA. Hence, abiotic degradation of 1...

Reduction potential, shadow prices, and pollution costs of agricultural pollutants in China.

Science.gov (United States)

Tang, Kai; Gong, Chengzhu; Wang, Dong

2016-01-15

This paper analyses the reduction potential, shadow prices, and pollution costs of agricultural pollutants in China based on provincial panel data for 2001-2010. Using a parameterized quadratic form for the directional output distance function, we find that if agricultural sectors in all provinces were to produce on the production frontier, China could potentially reduce agricultural emissions of chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP) by 16.0%, 16.2%, and 20.4%, respectively. Additionally, our results show that the shadow price of TN increased rapidly and continuously, while that of COD and TP fluctuated for the whole period. For the whole country, the average shadow price of COD, TN, and TP are 8266 Yuan/tonne, 25,560 Yuan/tonne, and 10,160 Yuan/tonne, respectively. The regional shadow prices of agricultural pollutants are unbalanced. Furthermore, we show that the pollution costs from emissions of COD, TN, and TP are 6.09% of the annual gross output value of the agricultural sector and are highest in the Western and lowest in the Eastern provinces. Our estimates suggest that there is scope for further pollution abatement and simultaneous output expansion for China's agriculture if farmers promote greater efficiency in their production process. Policymakers are required to dynamically adjust the pollution tax rates and ascertain the initial permit price in an emission trading system. Policymakers should also consider the different pollution costs for each province when making the reduction allocations within the agricultural sector. Copyright © 2015 Elsevier B.V. All rights reserved.

Assessment of Energy Efficiency Improvement and CO2 Emission Reduction Potentials in India's Cement Industry

Energy Technology Data Exchange (ETDEWEB)

Morrow, III, William R. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Hasanbeigi, Ali [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Xu, Tengfang [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

2012-12-03

India’s cement industry is the second largest in the world behind China with annual cement production of 168 Mt in 2010 which accounted for slightly greater than six percent of the world’s annual cement production in the same year. To produce that amount of cement, the industry consumed roughly 700 PJ of fuel and 14.7 TWh of electricity. We identified and analyzed 22 energy efficiency technologies and measures applicable to the processes in the Indian cement industry. The Conservation Supply Curve (CSC) used in this study is an analytical tool that captures both the engineering and the economic perspectives of energy conservation. Using a bottom-up electricity CSC model and compared to an electricity price forecast the cumulative cost-effective plant-level electricity savings potential for the Indian cement industry for 2010- 2030 is estimated to be 83 TWh, and the cumulative plant-level technical electricity saving potential is 89 TWh during the same period. The grid-level CO2 emissions reduction associated with cost-effective electricity savings is 82 Mt CO2 and the electric grid-level CO2 emission reduction associated with technical electricity saving potential is 88 Mt CO2. Compared to a fuel price forecast, an estimated cumulative cost-effective fuel savings potential of 1,029 PJ with associated CO2 emission reduction of 97 Mt CO2 during 2010-2030 is possible. In addition, a sensitivity analysis with respect to the discount rate used is conducted to assess the effect of changes in this parameter on the results. The result of this study gives a comprehensive and easy to understand perspective to the Indian cement industry and policy makers about the energy efficiency potential and its associated cost over the next twenty years.

Potential reduction of carbon emissions from Crude Palm Oil production based on energy and carbon balances

International Nuclear Information System (INIS)

Patthanaissaranukool, Withida; Polprasert, Chongchin; Englande, Andrew J.

2013-01-01

Highlights: ► We evaluate energy and carbon equivalence from CPO production based on a CBM. ► Energy spent and produced via carbon movement from palm oil mill was determined. ► Scenarios were formulated to evaluate the potential reduction of carbon emission. ► Utilization of biomass from palm oil mill shows the high potential of C-reduction. -- Abstract: This study aimed to evaluate energy and carbon equivalences (CE) associated with palm oil milling and to evaluate sustainability alternatives for energy consumption. Appropriate ways to reduce carbon emissions were also evaluated. A field survey was carried out to quantify the input and output of energy and materials following the conceptual framework of a carbon-balanced model (CBM), which exclude other non-CO 2 greenhouse gases. Survey results indicate that the electrical energy consumption for daily mill start-up averaged 18.7 ± 5.4 kWh/ton Fresh Fruit Bunches (FFBs). This energy is equivalent to 114.4 ± 33.2 kWh/ton Crude Palm Oil (CPO) which was found to be offset by that generated in the mills using palm fiber as a solid fuel. Currently, organic residues contained in the wastewater are anaerobically converted to methane. The methane is used as fuel to generate electricity and sold to an outside grid network at a generation rate of 8.1 ± 2.1 kWh/ton FFB. Based on the CBM approach, carbon emissions observed from the use of fossil energy in palm oil milling were very small; however, total carbon emission from oil palm plantation and palm oil milling were found to be 12.3 kg CE/ton FFB, resulting in the net carbon reduction in CPO production of 2.8 kg CE/ton FFB or 53.7 kg CE/ha-y. Overall, the sum of C-reduction was found 1.2 times greater than that of C-emission. This figure can be increased up to 5.5, if all biomass by-products are used as fuel to generate electricity only. The full potential for carbon reduction from palm oil milling is estimated at 0.94 kW of electric power for every hectare of

An Examination of Drag Reduction Mechanisms in Marine Animals, with Potential Applications to Uninhabited Aerial Vehicles

Science.gov (United States)

Musick, John A.; Patterson, Mark R.; Dowd, Wesley W.

2002-01-01

Previous engineering research and development has documented the plausibility of applying biomimetic approaches to aerospace engineering. Past cooperation between the Virginia Institute of Marine Science (VIMS) and NASA focused on the drag reduction qualities of the microscale dermal denticles of shark skin. This technology has subsequently been applied to submarines and aircraft. The present study aims to identify and document the three-dimensional geometry of additional macroscale morphologies that potentially confer drag reducing hydrodynamic qualities upon marine animals and which could be applied to enhance the range and endurance of Uninhabited Aerial Vehicles (UAVs). Such morphologies have evolved over eons to maximize organismal energetic efficiency by reducing the energetic input required to maintain cruising speeds in the viscous marine environment. These drag reduction qualities are manifested in several groups of active marine animals commonly encountered by ongoing VIMS research programs: namely sharks, bony fishes such as tunas, and sea turtles. Through spatial data acquired by molding and digital imagery analysis of marine specimens provided by VIMS, NASA aims to construct scale models of these features and to test these potential drag reduction morphologies for application to aircraft design. This report addresses the efforts of VIMS and NASA personnel on this project between January and November 2001.

Assessing the potential of spectral induced polarization to detect in situ changes in iron reduction

Science.gov (United States)

Rosier, C. L.; Price, A.; Sharma, S.; Atekwana, E. A.

2016-12-01

The near surface geophysical technique Spectral Induced Polarization (SIP), provides promise as an effective method measuring in situ biofilm formation/development. Yet, potential mechanisms responsible for observed shifts in SIP response due to biofilm are not clearly understood. In order to address possible mechanisms we assessed the influence of Shewanella oneidensis (MR1) cell density (colony forming units; CFU), biofilm production (Bradford assay) and iron reduction metabolism (colorimetric assay) on SIP response. Laboratory measurements were collected over three months on columns packed with either iron-coated or iron-free sands and amended with artificial ground water and acetate in order to stimulate biofilm production and microbial iron reduction. Additionally, scanning electron microscopy (SEM) was used to confirm the presence of S. oneidensis cells and biofilm. Our results suggest that during early/initial stage (75 days) of column incubation, SIP measurements revealed that phase and imaginary conductivity responses decreased as the concentration of reduced iron decreased below 2.0 mM. In contrast, we observed only a moderate increase in phase and imaginary conductivity ( 30%) within iron-free columns as a result of increases in S. oneidensis cells (CFU 1.5 x 1011) and biofilm production (7.0 mg ml-1). SEM analysis confirmed the presence of biofilm and cells within both iron-coated and iron-free columns. We hypothesize that the production of microbial metabolic byproducts is a potential mechanism explaining large phase shits observed in previous studies ( 50 mrads) rather than the conductivity of cells or biofilm. Our findings provide support for the following: i) ratio of cells to biofilm production only moderately influences both phase and imaginary conductivity response and ii) largest phase and imaginary conductivity response resulted from microbial metabolism (i.e. iron reduction) and potentially biofilm trapping of conductive materials (i

The Role of Nicotine Dependence in E-Cigarettes' Potential for Smoking Reduction.

Science.gov (United States)

Selya, Arielle S; Dierker, Lisa; Rose, Jennifer S; Hedeker, Donald; Mermelstein, Robin J

2017-07-07

E-cigarettes (Electronic Nicotine Delivery Systems, or ENDS) are an increasingly popular tobacco product among youth. Some evidence suggests that e-cigarettes may be effective for harm reduction and smoking cessation, although these claims remain controversial. Little is known about how nicotine dependence may contribute to e-cigarettes' effectiveness in reducing or quitting conventional smoking. A cohort of young adults were surveyed over 4 years (approximately ages 19-23). Varying-coefficient models (VCMs) were used to examine the relationship between e-cigarette use and conventional smoking frequency, and how this relationship varies across users with different nicotine dependence levels. Lifetime, but not recent, e-cigarette use was associated with less frequent concurrent smoking of conventional cigarettes among those with high levels of nicotine dependence. However, nondependent e-cigarette users smoked conventional cigarettes slightly more frequently than those who had never used e-cigarettes. Nearly half of ever e-cigarette users reported using them to quit smoking at the last measurement wave. For those who used e-cigarettes in a cessation attempt, the frequency of e-cigarette use was not associated with reductions in future conventional smoking frequency. These findings offer possible support that e-cigarettes may act as a smoking reduction method among highly nicotine-dependent young adult cigarette smokers. However, the opposite was found in non-dependent smokers, suggesting that e-cigarette use should be discouraged among novice tobacco users. Additionally, although a substantial proportion of young adults used e-cigarettes to help them quit smoking, these self-initiated quit attempts with e-cigarettes were not associated with future smoking reduction or cessation. This study offers potential support for e-cigarettes as a smoking reduction tool among highly nicotine-dependent young adult conventional smokers, although the extent and nature of this

Integrated characterization of natural attenuation of a PCE plume after thermal remediation of the source zone - incl. dual isotope and microbial techniques

DEFF Research Database (Denmark)

Broholm, Mette Martina

dechlorination 1-1.5 km downstream the source area, where the plume descends into more reduced groundwater. The objective of the new (2014) study is to evaluate how the source remediation has impacted the plume and in particular the natural attenuation within the plume. A large monitoring campaign including...... down-gradient which co-inside with the reduction in redox conditions. The findings document a significant increase in cDCE degradation without accumulation of VC. This reduces the risk posed by the contaminant plume to the drinking water resource. This project is unique in the integrated...... area, resulted in the release of dissolved organic matter and some geochemical changes. This has had an effect on redox conditions and biodegradation by reductive dechlorination particularly in the near source area. However, also in the further downstream area of the plume redox and contaminant levels...

Comparison of different chlorophenols degradation in aqueous solutions by gamma irradiation under reducing conditions

International Nuclear Information System (INIS)

Peng, Yunxia; He, Shijun; Wang, Jianlong; Gong, Wenqi

2012-01-01

The reductive degradation of chlorophenols (CPs), including 2-CP, 4-CP and 2,4-DCP by gamma irradiation was investigated and compared. The results showed that the most efficient degradation took place with 2,4-DCP, followed by 2-CP and then 4-CP. This confirmed that the number and position of chlorine atoms existing in the benzene ring have significant impact on dechlorination and decomposition of CPs. The G-values of decomposition of CPs, the formation of intermediate products and chloride ion, and the degradation rate (K CPs and K Cl −1 ) were also determined. - Highlights: ► Reductive degradation of 2-CP, 4-CP and 2,4-DCP by γ radiation was compared. ► Number and position of chlorine affect their dechlorination and decomposition. ► G-values of CPs decomposition, intermediate formation and chloride release were determined.

Biodegradation of Polychlorinated Biphenyls and Volatile Chlorinated Hydrocarbons in Contaminated Soils and Ground Water in Field Condition

Czech Academy of Sciences Publication Activity Database

Kaštánek, František; Demnerová, K.; Pazlarová, J.; Burkhard, J.; Maléterová, Ywetta

1999-01-01

Roč. 44, č. 1 (1999), s. 39-47 ISSN 0964-8305 Institutional research plan: CEZ:AV0Z4072921 Keywords : reductive dechlorination * river sediments * enrichment Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 0.568, year: 1999

Hydrogeologic characterization and assessment of bioremediation of chlorinated benzenes and benzene in wetland areas, Standard Chlorine of Delaware, Inc. Superfund Site, New Castle County, Delaware, 2009-12

Science.gov (United States)

Lorah, Michelle M.; Walker, Charles W.; Baker, Anna C.; Teunis, Jessica A.; Emily Majcher,; Brayton, Michael J.; Raffensperger, Jeff P.; Cozzarelli, Isabelle M.

2015-01-01

desorption from the sediments.When highly reducing, methanogenic, or sulfate-reducing conditions existed in the wetland groundwater, molar composition of the volatile organic compounds (VOCs) showed that chlorobenzene and benzene were predominant, indicating biodegradation of the chlorinated benzenes through reductive dechlorination pathways. Temporal changes in redox conditions between 2009 and 2011–12 have shifted the locations in the wetland study area where reductive dechlorination is evident. Microbial community analyses of sediment showed relatively high cell numbers and diversity of populations (Dehalococcoides, Dehalobacter, Desulfitobacterium, and Geobacter) that are known to contain species capable of reductive dechlorination, confirming groundwater geochemistry evidence of the occurrence of reductive dechlorination. Natural attenuation was not sufficient, however, to reduce total VOC concentrations along upward groundwater flowpaths in the wetland sediments, most likely due to the additional source of contaminants in the upper sediments. In situ microcosms that were unamended except for the addition of 13C-labeled contaminants in some treatments, confirmed that the native microbial community was able to biodegrade the higher chlorinated benzenes through reductive dechlorination and that 1,2-dichlorobenzene, chlorobenzene, and benzene could be degraded to carbon dioxide through oxidation pathways. Microcosms that were bioaugmented with the anaerobic dechlorinating consortium WBC-2 and deployed in the wetland sediments showed reductive dechlorination of tri-, di-, and monochlorobenzene, and 13C-chlorobenzene treatments showed complete degradation of chlorobenzene to carbon dioxide under anaerobic conditions.Experiments with a continuous flow, fixed-film bioreactor seeded with native microorganisms in groundwater from the wetland area showed both aerobic and anaerobic biodegradation of dichlorobenzenes, monochlorobenzene, and benzene, although

Benzoate-driven dehalogenation of chlorinated ethenes in microbial cultures from a contaminated aquifer

Energy Technology Data Exchange (ETDEWEB)

Bunge, M.; Kleikemper, J.; Miniaci, C.; Duc, L.; Muusse, M.G.; Zeyer, J. [Swiss Federal Institute of Technology (ETH), Zurich (Switzerland). Inst. of Biogeochemistry and Pollutant Dynamics, Soil Biology; Hause, G. [Halle-Wittenberg Univ., Halle (Germany). Biocenter

2007-10-15

Microbial dehalogenation of tetrachloroethene (PCE) and cis-dichloroethene (cis-DCE) was studied in cultures from a continuous stirred tank reactor initially inoculated with aquifer material from a PCE-contaminated site. Cultures amended with hydrogen and acetate readily dechlorinated PCE and cis-DCE; however, this transformation was incomplete and resulted in the accumulation of chlorinated intermediates and only small amounts of ethene within 60 days of incubation. Conversely, microbial PCE and cis-DCE dechlorination in cultures with benzoate and acetate resulted in the complete transformation to ethene within 30 days. Community fingerprinting by denaturing gradient gel electrophoresis (DGGE) revealed the predominance of phylotypes closely affiliated with Desulfitobacterium, Dehalococcoides, and Syntrophus species. The Dehalococcoides culture VZ, obtained from small whitish colonies in cis-DCE dechlorinating agarose cultures, revealed an irregular cell diameter between 200 and 500 nm, and a spherical or biconcave disk-shaped morphology. These organisms were identified as responsible for the dechlorination of cis-DCE to ethene in the PCE-dechlorinating consortia, operating together with the Desulfitobacterium as PCE-to-cis-DCE dehalogenating bacterium and with a Syntrophus species as potential hydrogen-producing partner in cultures with benzoate. (orig.)

Design requirements for ERD and ISCO: How close and how fast to achieve an effective remediation?

DEFF Research Database (Denmark)

Chambon, Julie Claire Claudia; Lemming, Gitte; Manoli, Gabriele

2011-01-01

Clayey tills contaminated with chlorinated solvents are a threat to groundwater and are difficult to remediate. Full scale Enhanced Reductive Dechlorination (ERD) and In-Situ Chemical Oxidation (ISCO) are promising remediation technologies for such sites, but the delivery of reactants...

Potential Impact of the REDD+ Program on Poverty Reduction in Nghe An Province, Vietnam

Directory of Open Access Journals (Sweden)

Nguyen Dinh Tien

2017-10-01

Full Text Available The REDD+ program provides a mechanism for providing financial rewards to forest owners and users who contribute to the reduction of carbon emissions from deforestation and forest degradation. This paper determines the potential impact of the REDD+ program on poverty reduction by comparing income and poverty rate between two household groups that were willing to participate in this study, but that will not participate in the REDD+. The results showed that carbon payment from forests is a significant contributor to the increase in household income of poor people. The average income of households participating in the program is VND 20.68 million in contrast to those not participating whose average income is VND 14.72 million. Results showed that the REDD+ program intervention helped reduce the poverty rate in the two communes by 6.40% (from 39.4% to 33%. The paper recommends that the REDD+ program should facilitate the distribution of land titles to provide security of tenure for individual households that are participating in the program. While the program can contribute to poverty reduction, the program payments can increase income inequality and conflicts between those involved and those not involved in the program and legal ownership of the lands. In addition, a comprehensive research study on the impact of the program on forest conservation and poverty reduction is necessary. Stakeholders of the program should recognize and acknowledge the trade-offs between conservation and economic development or poverty reduction. A comprehensive trade-off analysis of program implementation and a business-as-usual option of commodity production is needed, which could reveal the indirect economic, political, and social costs and benefits of the program.

Reduction Potentials and Acidity Constants of Mn Superoxide Dismutase Calculated by QM/MM Free-Energy Methods

Czech Academy of Sciences Publication Activity Database

Heimdal, J.; Kaukonen, M.; Srnec, Martin; Rulíšek, Lubomír; Ryde, U.

2011-01-01

Roč. 12, č. 17 (2011), s. 3337-3347 ISSN 1439-4235 R&D Projects: GA MŠk LC512 Institutional research plan: CEZ:AV0Z40550506 Keywords : acidity constants * enzymes * free-energy * perturbation * molecular modelling * reduction potentials Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.412, year: 2011

Development of Sulfidogenic Sludge from Marine Sediments and Trichloroethylene Reduction in an Upflow Anaerobic Sludge Blanket Reactor.

Science.gov (United States)

Guerrero-Barajas, Claudia; Ordaz, Alberto; García-Solares, Selene Montserrat; Garibay-Orijel, Claudio; Bastida-González, Fernando; Zárate-Segura, Paola Berenice

2015-10-15

The importance of microbial sulfate reduction relies on the various applications that it offers in environmental biotechnology. Engineered sulfate reduction is used in industrial wastewater treatment to remove large concentrations of sulfate along with the chemical oxygen demand (COD) and heavy metals. The most common approach to the process is with anaerobic bioreactors in which sulfidogenic sludge is obtained through adaptation of predominantly methanogenic granular sludge to sulfidogenesis. This process may take a long time and does not always eliminate the competition for substrate due to the presence of methanogens in the sludge. In this work, we propose a novel approach to obtain sulfidogenic sludge in which hydrothermal vents sediments are the original source of microorganisms. The microbial community developed in the presence of sulfate and volatile fatty acids is wide enough to sustain sulfate reduction over a long period of time without exhibiting inhibition due to sulfide. This protocol describes the procedure to generate the sludge from the sediments in an upflow anaerobic sludge blanket (UASB) type of reactor. Furthermore, the protocol presents the procedure to demonstrate the capability of the sludge to remove by reductive dechlorination a model of a highly toxic organic pollutant such as trichloroethylene (TCE). The protocol is divided in three stages: (1) the formation of the sludge and the determination of its sulfate reducing activity in the UASB, (2) the experiment to remove the TCE by the sludge, and (3) the identification of microorganisms in the sludge after the TCE reduction. Although in this case the sediments were taken from a site located in Mexico, the generation of a sulfidogenic sludge by using this procedure may work if a different source of sediments is taken since marine sediments are a natural pool of microorganisms that may be enriched in sulfate reducing bacteria.

Development of Sulfidogenic Sludge from Marine Sediments and Trichloroethylene Reduction in an Upflow Anaerobic Sludge Blanket Reactor

Science.gov (United States)

Guerrero-Barajas, Claudia; Ordaz, Alberto; García-Solares, Selene Montserrat; Garibay-Orijel, Claudio; Bastida-González, Fernando; Zárate-Segura, Paola Berenice

2015-01-01

The importance of microbial sulfate reduction relies on the various applications that it offers in environmental biotechnology. Engineered sulfate reduction is used in industrial wastewater treatment to remove large concentrations of sulfate along with the chemical oxygen demand (COD) and heavy metals. The most common approach to the process is with anaerobic bioreactors in which sulfidogenic sludge is obtained through adaptation of predominantly methanogenic granular sludge to sulfidogenesis. This process may take a long time and does not always eliminate the competition for substrate due to the presence of methanogens in the sludge. In this work, we propose a novel approach to obtain sulfidogenic sludge in which hydrothermal vents sediments are the original source of microorganisms. The microbial community developed in the presence of sulfate and volatile fatty acids is wide enough to sustain sulfate reduction over a long period of time without exhibiting inhibition due to sulfide. This protocol describes the procedure to generate the sludge from the sediments in an upflow anaerobic sludge blanket (UASB) type of reactor. Furthermore, the protocol presents the procedure to demonstrate the capability of the sludge to remove by reductive dechlorination a model of a highly toxic organic pollutant such as trichloroethylene (TCE). The protocol is divided in three stages: (1) the formation of the sludge and the determination of its sulfate reducing activity in the UASB, (2) the experiment to remove the TCE by the sludge, and (3) the identification of microorganisms in the sludge after the TCE reduction. Although in this case the sediments were taken from a site located in Mexico, the generation of a sulfidogenic sludge by using this procedure may work if a different source of sediments is taken since marine sediments are a natural pool of microorganisms that may be enriched in sulfate reducing bacteria. PMID:26555802

Potential for Methanosarcina to contribute to uranium reduction during acetate-promoted groundwater bioremediation

DEFF Research Database (Denmark)

Holmes, Dawn E; Orellana, Roberto; Giloteaux, Ludovic

2017-01-01

Previous studies of in situ bioremediation of uranium-contaminated groundwater with acetate injections have focused on the role of Geobacter species in U(VI) reduction because of a lack of other abundant known U(VI)-reducing microorganisms. Monitoring the levels of methyl CoM reductase subunit...... an important role in the long-term bioremediation of uranium-contaminated aquifers after depletion of Fe(III) oxides limits the growth of Geobacter species. The results also suggest that Methanosarcina have the potential to influence uranium geochemistry in a diversity of anaerobic sedimentary environments....

SGLT2 inhibitors: their potential reduction in blood pressure.

Science.gov (United States)

Maliha, George; Townsend, Raymond R

2015-01-01

The sodium glucose co-transporter 2 (SGLT2) inhibitors represent a promising treatment option for diabetes and its common comorbidity, hypertension. Emerging data suggests that the SGLT2 inhibitors provide a meaningful reduction in blood pressure, although the precise mechanism of the blood pressure drop remains incompletely elucidated. Based on current data, the blood pressure reduction is partially due to a combination of diuresis, nephron remodeling, reduction in arterial stiffness, and weight loss. While current trials are underway focusing on cardiovascular endpoints, the SGLT2 inhibitors present a novel treatment modality for diabetes and its associated hypertension as well as an opportunity to elucidate the pathophysiology of hypertension in diabetes. Copyright © 2015 American Society of Hypertension. Published by Elsevier Inc. All rights reserved.

Salt in bread in Europe: potential benefits of reduction.

Science.gov (United States)

Quilez, Joan; Salas-Salvado, Jordi

2012-11-01

Bread is widely considered to be the foodstuff that provides the most dietary salt to the diet. As such, it is one of the key public health targets for a salt reduction policy. In this respect, it has been shown that a reduction in the salt content of bread is possible, and an alternative approach involves partial replacement with other, mainly potassium-based salts, which also counteract the effects of sodium. This replacement should be undertaken on the basis of criteria that maintain the product's sensory profile, and it tends to be more successful in breads with more naturally flavorful taste. The present review was conducted to examine salt intake in Europe and the health problems associated with its excessive consumption; particular focus is placed on the salt content of bread and the effects of its possible reduction and/or correction. The beneficial effects of such changes are highlighted by way of a theoretical calculation in baguette-type wheat bread. European legislation in the field of nutrition and health claims allows the positive aspects of such salt reduction and replacement methods to be stated. © 2012 International Life Sciences Institute.

Dehalogenation Potential of Municipal Waste Incineration Fly Ash. I. General Principles

Czech Academy of Sciences Publication Activity Database

Pekárek, Vladimír; Karban, Jindřich; Fišerová, Eva; Bureš, M.; Pacáková, V.; Večerníková, Eva

2003-01-01

Roč. 10, č. 1 (2003), s. 39-43 ISSN 0944-1344 R&D Projects: GA AV ČR IAA4072206 Institutional research plan: CEZ:AV0Z4032918; CEZ:AV0Z4072921 Keywords : dechlorination * fly ash * hexachlorobenzene Subject RIV: CC - Organic Chemistry Impact factor: 1.216, year: 2003

Cost reduction potentials of offshore wind power in Germany; Kostensenkungspotenziale der Offshore-Windenergie in Deutschland

Energy Technology Data Exchange (ETDEWEB)

Hobohm, Jens; Krampe, Leonard; Peter, Frank [Prognos AG, Berlin (Germany). Bereich Energiewirtschaft

2014-01-15

Offshore wind power is a major hope for the German energy turnaround. However, it will only be possible to tap its cost reduction potentials if industry, the political leadership and the administrative authorities join forces to create the necessary preconditions. An important requirement for this capital-intensive technology are stable legal and political framework conditions. A recent study on the future shows what needs to be done.

Oxygen Reduction on Gas-Diffusion Electrodes for Phosphoric Acid Fuel Cells by a Potential Decay Method

DEFF Research Database (Denmark)

Li, Qingfeng; Gang, Xiao; Hjuler, Hans Aage

1995-01-01

The reduction of gaseous oxygen on carbon supported platinum electrodes has been studied at 150 degrees C with polarization and potential decay measurements. The electrolyte was either 100 weight percent phosphoric acid or that acid with a fluorinated additive, potassium perfluorohexanesulfonate ......6F13SO3K). The pseudo-Tafel curves of the overpotential vs. log (ii(L)/(i(L) - i)) show a two-slope behavior, probably due to different adsorption mechanisms. The potential relaxations as functions of log (t + tau) and log (-d eta/dt) have been plotted. The variations of these slopes...

Carbon reduction potentials of China's industrial parks: A case study of Suzhou Industry Park

International Nuclear Information System (INIS)

Wang, Hongsheng; Lei, Yue; Wang, Haikun; Liu, Miaomiao; Yang, Jie; Bi, Jun

2013-01-01

Industrial parks are the economic engines for many China regions, but they also consume a great deal of energy and emit greenhouse gases. However, few empirical studies have examined these special communities. We selected SIP (Suzhou Industrial Park) as a case study. Carbon emissions from SIP were accounted from the consumption perspective to analyze their characteristics. Results showed total carbon emissions grew 85.2% from 2005 to 2010, and carbon intensity (carbon emissions per unit of GDP (gross domestic product)) decreased by 9%. Scenario analysis was then used to depict emissions trajectories under three different pathways. The total carbon emissions and per capita carbon emissions for SIP will undoubtedly increase in the near future under a business-as-usual scenario, improved-policy scenario, and low-carbon scenario; the carbon intensity will decrease by 38% under low-carbon scenario, but it will still be difficult to reach the national mitigation target. In addition, geographic-boundary-based accounting methodology was applied for comparison analysis, carbon emissions show a large gap of 42.4–65.1% from 2005 to 2010, due to failure to account for cross-boundary emissions from imported electricity. Therefore, comprehensive analysis from a consumption perspective is necessary to provide a fair and comprehensive tool for China's local decision-makers to evaluate carbon mitigation potentials. - Highlights: ► Carbon reduction potentials of industrial parks, which are important communities in China, were analyzed. ► Comprehensive carbon emission inventories were developed for a China's industrial park. ► Policies were recommended for industrial parks to achieve low-carbon development target. ► Consumption-based emission inventory is necessary for local government to evaluate carbon reduction potentials

Investigation of mechanisms of dechlorination of archaeological ferrous objects corroded in marine environment. Case of processing in aerated and deaerated alkaline solutions

International Nuclear Information System (INIS)

Kergourlay, Florian

2012-01-01

After a bibliographic study on the present knowledge on dechlorination mechanisms within corrosion layers of archaeological objects of submarine origin, this research thesis presents an analytical methodology which comprises characterization experimental techniques (from optical microscopy to Raman spectroscopy) and in situ investigation of the evolution of the corrosion layer during a processing under synchrotron radiation. The obtained results are then presented and discussed: morphological, elemental and structural characteristics. The author also compares the corrosion system between an object recently taken out of water and an object which has been air dried. He also comments and discusses the in situ observation by X ray diffraction under micro-beam of the evolution of the corrosion system during the processing. The ex situ characterization of corrosion systems after the rinsing and drying steps (after processing) is reported. Results are discussed in terms of thermodynamics. A kinetic approach is proposed

Potential reduction of carbon dioxide emissions from the use of electric energy storage on a power generation unit/organic Rankine system

International Nuclear Information System (INIS)

Mago, Pedro J.; Luck, Rogelio

2017-01-01

Highlights: • A power generation organic Rankine cycle with electric energy storage is evaluated. • The potential carbon dioxide emissions reduction of the system is evaluated. • The system performance is evaluated for a building in different climate zones. • The system emissions and cost are compared with those of conventional systems. • Use of carbon emissions cap and trade programs on the system is evaluated. - Abstract: This paper evaluates the potential carbon dioxide emissions reduction from the implementation of electric energy storage to a combined power generation unit and an organic Rankine cycle relative to a conventional system that uses utility gas for heating and utility electricity for electricity needs. Results indicate that carbon dioxide emission reductions from the operation of the proposed system are directly correlated to the ratio of the carbon dioxide emission conversion factor for electricity to that of the fuel. The location where the system is installed also has a strong influence on the potential of the proposed system to save carbon dioxide emissions. Finally, it is shown that by using carbon emissions cap and trade programs, it is possible to establish a frame of reference to compare/exchange operational cost gains with carbon dioxide emission reductions/gains.

Assessment of Energy Efficiency Improvement and CO₂ Emission Reduction Potentials in the Cement Industry in China

Energy Technology Data Exchange (ETDEWEB)

Hasanbeigi, Ali [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Morrow, William [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Masanet, Eric [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Sathaye, Jayant [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Xu, Tengfang [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

2012-06-15

China’s annual cement production (i.e., 1,868 Mt) in 2010 accounted for nearly half of the world’s annual cement production in the same year. We identified and analyzed 23 energy efficiency technologies and measures applicable to the processes in the cement industry. The Conservation Supply Curve (CSC) used in this study is an analytical tool that captures both the engineering and the economic perspectives of energy conservation. Using a bottom-up electricity CSC model, the cumulative cost-effective electricity savings potential for the Chinese cement industry for 2010-2030 is estimated to be 251 TWh, and the total technical electricity saving potential is 279 TWh. The CO₂ emissions reduction associated with cost-effective electricity savings is 144 Mt CO₂ and the CO₂ emission reduction associated with technical electricity saving potential is 161 Mt CO₂. The fuel CSC model for the cement industry suggests cumulative cost-effective fuel savings potential of 4,326 PJ which is equivalent to the total technical potential with associated CO₂ emission reductions of 406 Mt CO₂. In addition, a sensitivity analysis with respect to the discount rate used is conducted to assess the effect of changes in this parameter on the results. We also developed a scenario in which instead of only implementing the international technologies in 2010-2030, we implement both international and Chinese domestic technologies during the analysis period and calculate the saving and cost of conserved energy accordingly. The result of this study gives a comprehensive and easy to understand perspective to the Chinese cement industry and policy makers about the energy efficiency potential and its associated cost.

Defining the sources of airborne polychlorinated biphenyls: evidence for the influence of microbially dechlorinated congeners from river sediment?

Energy Technology Data Exchange (ETDEWEB)

Chiarenzelli, J. [SUNYat Oswego, NY (United States); Bush, B.; Casey, A.; O' Keefe, P. [SUNY at Albany, School of Public Health, Rensselaer, NY (United States); Barnard, E.; Smith, B. [New York State Dept. of Health, Wadsworth Center for Laboratories and Research, Albany, NY (United States); Gilligan, E. [Syracuse Univ., Dept. of Civil an Environmental Engineering, NY (United States); Johnson, G. [Energy and Geoscience Institute, Dept, of Civil and Environmental Engineering, Salt Lake City, UT (United States)

2000-07-01

During sampling in 1993, elevated levels of polychlorinated biphenyls were discovered near three industrial facilities on the Akwesasne Mohawk Nation Reserve along the St. Lawrence River, straddling the Canadian-US. border. Volatilization of Aroclor 1248, which was used extensively at all three sites, was identified as the dominant source, augmented in a minor way by a dechlorinated source, presumably from river sediment and waters. These two sources were found to account for 80 per cent of the contamination. Further, it was established that at a small cove adjacent to an industrial landfill, summer concentrations of PCBs exceeded winter concentrations by a factor of 27. Observation showed the presence of similar congener-specific PCB patterns at all sample sites and an increase in the concentrations of chlorine to biphenyl ratios during the summer months. During the colder months PCB concentrations at all sites declined, nevertheless, PCB levels were still higher than those measured elsewhere in the Great Lakes region during the same time period. Results of this investigation suggest that atmospheric deposition from local contaminant sources can elevate concentrations in produce and vegetative matter, complicating exposure routes and bioaccumulation via modeling of food chain. 22 refs., 4 tabs. 1 fig.

Are phantoms useful for predicting the potential of dose reduction in full-field digital mammography?

International Nuclear Information System (INIS)

Gennaro, Gisella; Katz, Luc; Souchay, Henri; Alberelli, Claudio; Maggio, Cosimo di

2005-01-01

A phantom study was performed in full-field digital mammography to investigate the opportunity and the magnitude of a possible dose reduction that would leave the image quality above the accepted thresholds associated with some classical phantoms. This preliminary work is intended to lay the groundwork for a future clinical study on the impact of dose reduction on clinical results. Three different mammography phantoms (ACR RMI 156, CIRS 11A and CDMAM 3.4) were imaged by a full-field digital mammography unit (GE Senographe 2000D) at different dose levels. Images were rated by three observers with softcopy reading and scoring methods specific to each phantom. Different types of data analysis were applied to the ACR (American College of Radiology) and the other two phantoms, respectively. With reference to the minimum acceptance score in screen/film accreditation programmes, the ACR phantom showed that about 45% dose reduction could be applied, while keeping the phantom scores above that threshold. A relative comparison was done for CIRS and CDMAM, for which no threshold is defined. CIRS scoring remained close to the reference level down to 40% dose reduction, the inter- and intra-observer variability being the main source of uncertainty. Contrast-detail curves provided by CDMAM overlapped down to 50% dose reduction, at least for object contrast values ranging between 30% and 3%. This multi-phantom study shows the potential of further reducing the dose in full-field digital mammography beyond the current values. A common dose reduction factor around 50% seems acceptable for all phantoms. However, caution is required before extrapolating the results for clinical use, given the limitations of these widely used phantoms, mainly related to their limited dynamic range and uniform background

Effect of long-term fertilization on humic redox mediators in multiple microbial redox reactions.

Science.gov (United States)

Guo, Peng; Zhang, Chunfang; Wang, Yi; Yu, Xinwei; Zhang, Zhichao; Zhang, Dongdong

2018-03-01

This study investigated the effects of different long-term fertilizations on humic substances (HSs), humic acids (HAs) and humins, functioning as redox mediators for various microbial redox biotransformations, including 2,2',4,4',5,5'- hexachlorobiphenyl (PCB 153 ) dechlorination, dissimilatory iron reduction, and nitrate reduction, and their electron-mediating natures. The redox activity of HSs for various microbial redox metabolisms was substantially enhanced by long-term application of organic fertilizer (pig manure). As a redox mediator, only humin extracted from soils with organic fertilizer amendment (OF-HM) maintained microbial PCB 153 dechlorination activity (1.03 μM PCB 153 removal), and corresponding HA (OF-HA) most effectively enhanced iron reduction and nitrate reduction by Shewanella putrefaciens. Electrochemical analysis confirmed the enhancement of their electron transfer capacity and redox properties. Fourier transform infrared analysis showed that C=C and C=O bonds, and carboxylic or phenolic groups in HSs might be the redox functional groups affected by fertilization. This research enhances our understanding of the influence of anthropogenic fertility on the biogeochemical cycling of elements and in situ remediation ability in agroecosystems through microorganisms' metabolisms. Copyright © 2017 Elsevier Ltd. All rights reserved.

Assessment of 1-chloro-4-[2,2-dichloro-1-(4-chlorophenyl)ethenyl]benzene (DDE) Transformation Rates on the Palos Verdes Shelf, CA

Science.gov (United States)

Eganhouse, Robert P.; Pontolillo, James

2008-01-01

In 1953, the world's largest producer of DDT, Montrose Chemical Corporation, began to discharge process wastes into sewers of the Los Angeles County Sanitation Districts (LACSD), California. By 1971, when the sewer connection was terminated, approximately 1,500-2,000 metric tons of DDT had been introduced to the LACSD treatment plant in Carson, CA. After treatment, effluent from this plant was released to the ocean through a submarine outfall system on the Palos Verdes Shelf (PVS) near Los Angeles, resulting in the accumulation of highly contaminated marine sediments. Numerous investigations of the PVS have been undertaken since the late 1960s, but few have focused on the biogeochemical fate of DDT and its transformation products. In the early 1990s, it was shown that DDE, the major DDT compound in the sediments, was being reductively dechlorinated by microorganisms resident in sediments on the PVS. The U.S. Geological Survey undertook a study in cooperation with the U.S. Environmental Protection Agency to provide a better understanding of the range of reductive dechlorination rates on the PVS and the environmental factors that control them. Existing data show that rates of reductive dechlorination are variable spatially. A comparison of data from two cores collected approximately 7 kilometers downcurrent from the outfall systems in 1992 and 2003 yielded an average first-order transformation rate of approximately 0.05 yr-1. A multistep reaction model suggests that inventories of DDE in PVS sediments at the study site will continue to decline, whereas the inventory of the metabolite DDNU will reach a maximum around 2014.

Enhanced reductive dechlorination in clay till contaminated with chlorinated solvents

DEFF Research Database (Denmark)

Damgaard, Ida

Chlorinated solvents are among the most frequently found contaminants in groundwater. In fractured media, chlorinated ethenes and ethanes are transported downwards through preferential pathways with subsequent diffusion into the sediment matrix. Due to slow back diffusion it can serve as a long...... (direct push delivery, Gl. Kongevej). Degradation of chlorinated ethenes (and ethanes) in the clay till matrix and in embedded high permeability features was investigated by high resolution sampling of intact cores combined with groundwater sampling. An integrated approach using chemical analysis...... (hydraulic fracturing with gravitational injection and direct push delivery) were therefore tested in clay till by injection of amendment-comparable tracers to investigate the possibility to overcome diffusion limitations in the low permeability matrix. The study of hydraulic fracturing demonstrated...

DDE in sediments of the Palos Verdes shelf, California: In situ transformation rates and geochemical fate

Science.gov (United States)

Eganhouse, R.P.; Pontolillo, J.

2008-01-01

From 1947 to 1971 the world's largest manufacturer of DDT discharged process wastes into the sewers of Los Angeles County. Roughly 870-1450 t of DDT were released to the ocean off Palos Verdes, CA, a portion of which (???100 t) resides in sediments on the continental shelf and slope. The most abundant DDT compound in the sediments, p,p???-DDE, is degrading by reductive dechlorination, butthe rate of transformation and factors controlling it are not well understood. In order to estimate in situ transformation rates and predict the long-term fate of p,p???-DDE, box cores were collected in 1992 and 2003 from a single location on the Palos Verdes Shelf and analyzed for 8 DDT compounds and 84 polychlorinated biphenyl (PCB) congeners. The PCBs show no evidence of dechlorination, and inventories did not change between 1992 and 2003. By contrast, the inventory of p,p???-DDE decreased by 43%, whereas that of p,p???-DDMU, the putative reductive dechlorination product increased by 34%. The first-order transformation rate for p,p???-DDE at the study site is 0.051 ?? 0.006 yr-1. A multistep reaction model suggests that inventories of p,p???-DDE and p,p???-DDMU will continue to decline, whereas that of p,p???-DDNU will reach a maximum around 2014.

Chromium tolerance and reduction potential of Staphylococci ...

African Journals Online (AJOL)

In order to study the microbiology of chromium tolerance and reduction at a fly ash dumping site in South Africa, 15 core samples were investigated. It was shown that the 30 year old dumping site exhibited high concentrations of Cr (VI) ranging from 1.6 to 9.6 mg/g. From this contaminated fly ash dumping site, 67 chromium ...

Technology learning for fuel cells. An assessment of past and potential cost reductions

International Nuclear Information System (INIS)

Schoots, K.; Van der Zwaan, B.C.C.; Kramer, G.J.

2010-01-01

Fuel cells have gained considerable interest as a means to efficiently convert the energy stored in gases like hydrogen and methane into electricity. Further developing fuel cells in order to reach cost, safety and reliability levels at which their widespread use becomes feasible is an essential prerequisite for the potential establishment of a 'hydrogen economy'. A major factor currently obviating the extensive use of fuel cells is their relatively high costs. At present we estimate these at about 1100 EUR(2005)W for an 80 kW fuel cell system but notice that specific costs vary markedly with fuel cell system power capacity. We analyze past fuel cell cost reductions for both individual manufacturers and the global market. We determine learning curves, with fairly high uncertainty ranges, for three different types of fuel cell technology - AFC, PAFC and PEMFC - each manufactured by a different producer. For PEMFC technology we also calculate a global learning curve, characterised by a learning rate of 21% with an error margin of 4%. Given their respective uncertainties, this global learning rate value is in agreement with those we find for different manufacturers. In contrast to some other new energy technologies, R and D still plays a major role in today's fuel cell improvement process and hence probably explains a substantial part of our observed cost reductions. The remaining share of these cost reductions derives from learning-by-doing proper. Since learning-by-doing usually involves a learning rate of typically 20%, the residual value for pure learning we find for fuel cells is relatively low. In an ideal scenario for fuel cell technology we estimate a bottom-line for specific (80 kW system) manufacturing costs of 95 EUR(2005)W. Although learning curves observed in the past constitute no guarantee for sustained cost reductions in the future, when we assume global total learning at the pace calculated here as the only cost reduction mechanism, this ultimate cost

High potential oxidation-reduction titration of absorbance changes induced by pulsed laser and continuous light in chromatophores of photosynthesizing bacteria Rhodospirillum rubrum and Ectothiorhodospira shaposhnikovii

International Nuclear Information System (INIS)

Remennikov, S.M.; Chamorovsky, S.K.; Kononenko, A.A.; Venediktov, P.S.; Rubin, A.B.

1975-01-01

The photoreactions, activated both by pulsed laser and continuous light were studied in the membranes of isolated bacterial chromatophores poised at different oxidation-reduction potentials over a range of +200 mV to +500 mV. In Rhodospirillum rubrum a midpoint potential of oxidation-reduction curves for the laser-induced positive absorbance changes centred around 430 nm and carotenoid red shifts coincides with that for continuous light-induced absorbance changes, bleaching at 865 nm and blue shift at 800 nm, of the photosynthetic reaction centre bacteriochlorophyll. In Ectothiorhodospira shaposhnikovii the photosynthetic reaction centre bacteriochlorophyll, its photooxidation can be seen as light-induced absorbance changes, bleaching at 890 nm, blue shift at 800 nm and broad band appearance near 440 nm, has a midpoint oxidation-reduction potential of +390 mV at pH 7.4. The analysis of the oxidation-reduction titration curves for the high-potential c-type cytochrome absorbance changes induced both by pulsed laser and continuous light allowed to show that at least two haems of this cytochrome with a midpoint potential of +290 mV (pH 7.4), associated with each reaction centre bacteriochlorophyll, can donate electrons to the oxidized pigment directly

Investigation of potential extreme load reduction for a two-bladed upwind turbine with partial pitch

DEFF Research Database (Denmark)

Kim, Taeseong; Larsen, Torben J.; Yde, Anders

2015-01-01

This paper presents a wind turbine concept with an innovative design combining partial pitch with a two-bladed (PP-2B) turbine configuration. Special emphasis is on extreme load reduction during storm situations at standstill, but operational loads are also investigated. In order to compare...... loads are reduced by approximately 20% for the PP-2B and 18% for the PP-3B compared with the 3B turbine for the parked condition in a storm situation. Moreover, a huge potential of 60% is observed for the reduction of the extreme tower bottom bending moment for the PP-2B turbine, when the wind direction...... is from ±90° to the turbine, but this also requires that the turbine is parked in a T-configuration. © 2014 The Authors. Wind Energy published by John Wiley & Sons, Ltd....

Global Transcriptomic and Proteomic Responses of Dehalococcoides ethenogenes Strain 195 to Fixed Nitrogen Limitation

Energy Technology Data Exchange (ETDEWEB)

Lee, Patrick K. H. [University of California, Berkeley; Dill, Brian [ORNL; Louie, Tiffany S. [University of California, Berkeley; Shah, Manesh B [ORNL; Verberkmoes, Nathan C [ORNL; Andersen, Gary L. [Lawrence Berkeley National Laboratory (LBNL); Zinder, Stephen H. [Cornell University; Alvarez-Cohen, Lisa [Lawrence Berkeley National Laboratory (LBNL)

2012-01-01

Bacteria of the genus Dehalococcoides play an important role in the reductive dechlorination of chlorinated ethenes. A systems level approach was taken in this study to examine the global transcriptomic and proteomic responses of exponentially growing D. ethenogenes strain 195 to fixed nitrogen limitation (FNL) as dechlorination activity and cell yield both decrease during FNL. As expected, the nitrogen-fixing (nif) genes were differentially up-regulated in the transcriptome and proteome of strain 195 during FNL. Aside from the nif operon, a putative methylglyoxal synthase-encoding gene (DET1576), the product of which is predicted to catalyze the formation of the toxic electrophile methylglyoxal and implicated in the uncoupling of anabolism from catabolism in bacteria, was strongly up-regulated in the transcriptome and could potentially play a role in the observed growth inhibition during FNL. Carbon catabolism genes were generally down regulated in response to FNL and a number of transporters were differentially regulated in response to nitrogen limitation, with some playing apparent roles in nitrogen acquisition while others were associated with general stress responses. A number of genes related to the functions of nucleotide synthesis, replication, transcription, translation, and post-translational modifications were also differentially expressed. One gene coding for a putative reductive dehalogenase (DET1545) and a number coding for oxidoreductases, which have implications in energy generation and redox reactions, were also differentially regulated. Interestingly, most of the genes within the multiple integrated elements were not differentially expressed. Overall, this study elucidates the molecular responses of strain 195 to FNL and identifies differentially expressed genes that are potential biomarkers to evaluate environmental cellular nitrogen status.

Potential reduction of energy consumption in public university library

Science.gov (United States)

Noranai, Z.; Azman, ADF

2017-09-01

Efficient electrical energy usage has been recognized as one of the important factor to reduce cost of electrical energy consumption. Various parties have been emphasized about the importance of using electrical energy efficiently. Inefficient usage of electrical energy usage lead to biggest factor increasing of administration cost in Universiti Tun Hussein Onn Malaysia. With this in view, a project the investigate potential reduction electrical energy consumption in Universiti Tun Hussein Onn Malaysia was carried out. In this project, a case study involving electrical energy consumption of Perpustakaan Tunku Tun Aminah was conducted. The scopes of this project are to identify energy consumption in selected building and to find the factors that contributing to wastage of electrical energy. The MS1525:2001, Malaysian Standard - Code of practice on energy efficiency and use of renewable energy for non-residential buildings was used as reference. From the result, 4 saving measure had been proposed which is change type of the lamp, install sensor, decrease the number of lamp and improve shading coefficient on glass. This saving measure is suggested to improve the efficiency of electrical energy consumption. Improve of human behaviour toward saving energy measure can reduce 10% from the total of saving cost while on building technical measure can reduce 90% from total saving cost.

Permeable Reactive Barrier: Technology Update

Science.gov (United States)

2011-06-01

Vukovic 1998; Taylor et al. 2002; Waybrant, Blowes, and Ptacek 1998; Robertson, Vogan, and Lombardo 2008; Hulshof et al. 2003). Solid substrates used...Reductive Dechlorination of Tetrachloroethene to Growth,” Applied Environmental Microbiology 59: 2991–97. Hulshof , A. M. H., D. W. Blowes, C. J

Selected Natural Attenuation Monitoring Data, Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington, 2007 and 2008

Science.gov (United States)

Dinicola, R.S.; Huffman, R.L.

2009-01-01

Previous investigations indicate that natural attenuation and biodegradation of chlorinated volatile organic compounds (VOCs) are substantial in groundwater beneath the 9-acre former landfill at Operable Unit 1 (OU 1), Naval Undersea Warfare Center, Division Keyport, Washington. Phytoremediation combined with on-going natural attenuation processes was the preferred remedy selected by the Navy, as specified in the Record of Decision for the site. The Navy planted two hybrid poplar plantations on the landfill in spring 1999 to remove and to control the migration of chlorinated VOCs in shallow groundwater. The U.S. Geological Survey (USGS) has continued to monitor groundwater geochemistry to ensure that conditions remain favorable for contaminant biodegradation as specified in the Record of Decision. In this report are groundwater geochemical and selected VOC data collected at OU 1 by the USGS during June 18-21, 2007, and June 16-18, 2008, in support of long-term monitoring for natural attenuation. For 2007 and 2008, strongly reducing conditions (sulfate reduction and methanogenesis) most favorable for reductive dechlorination of VOCs were inferred for 9 of 16 upper-aquifer wells and piezometers in the northern and southern phytoremediation plantations. Predominant redox conditions in groundwater from the intermediate aquifer just downgradient from the landfill remained mildly reducing and somewhat favorable for reductive dechlorination of VOCs. Dissolved hydrogen (H2) concentrations measured in the upper aquifer during 2007 and 2008 generally have been lower than H2 concentrations measured before 2002. However, widespread and relatively high methane and sulfide concentrations indicate that the lower H2 concentrations measured do not support a trend from strongly to mildly reducing redox conditions because no widespread changes in groundwater redox conditions were identified that should result in less favorable conditions for the reductive dechlorination of the

NASA's Vision for Potential Energy Reduction from Future Generations of Propulsion Technology

Science.gov (United States)

Haller, Bill

2015-01-01

Through a robust partnership with the aviation industry, over the past 50 years NASA programs have helped foster advances in propulsion technology that enabled substantial reductions in fuel consumption for commercial transports. Emerging global trends and continuing environmental concerns are creating challenges that will very likely transform the face of aviation over the next 20-40 years. In recognition of this development, NASA Aeronautics has established a set of Research Thrusts that will help define the future direction of the agency's research technology efforts. Two of these thrusts, Ultra-Efficient Commercial Vehicles and Transition to Low-Carbon Propulsion, serve as cornerstones for the Advanced Air Transport Technology (AATT) project. The AATT project is exploring and developing high-payoff technologies and concepts that are key to continued improvement in energy efficiency and environmental compatibility for future generations of fixed-wing, subsonic transports. The AATT project is primarily focused on the N+3 timeframe, or 3 generations from current technology levels. As should be expected, many of the propulsion system architectures technologies envisioned for N+3 vary significantly from todays engines. The use of batteries in a hybrid-electric configuration or deploying multiple fans distributed across the airframe to enable higher bypass ratios are just two examples of potential advances that could enable substantial energy reductions over current propulsion systems.

Biomarkers’ Responses to Reductive Dechlorination Rates and Oxygen Stress in Bioaugmentation Culture KB-1TM

Directory of Open Access Journals (Sweden)

Gretchen L. W. Heavner

2018-02-01

Full Text Available Using mRNA transcript levels for key functional enzymes as proxies for the organohalide respiration (OHR rate, is a promising approach for monitoring bioremediation populations in situ at chlorinated solvent-contaminated field sites. However, to date, no correlations have been empirically derived for chlorinated solvent respiring, Dehalococcoides mccartyi (DMC containing, bioaugmentation cultures. In the current study, genome-wide transcriptome and proteome data were first used to confirm the most highly expressed OHR-related enzymes in the bioaugmentation culture, KB-1TM, including several reductive dehalogenases (RDases and a Ni-Fe hydrogenase, Hup. Different KB-1™ DMC strains could be resolved at the RNA and protein level through differences in the sequence of a common RDase (DET1545-like homologs and differences in expression of their vinyl chloride-respiring RDases. The dominant strain expresses VcrA, whereas the minor strain utilizes BvcA. We then used quantitative reverse-transcriptase PCR (qRT-PCR as a targeted approach for quantifying transcript copies in the KB-1TM consortium operated under a range of TCE respiration rates in continuously-fed, pseudo-steady-state reactors. These candidate biomarkers from KB-1TM demonstrated a variety of trends in terms of transcript abundance as a function of respiration rate over the range: 7.7 × 10−12 to 5.9 × 10−10 microelectron equivalents per cell per hour (μeeq/cell∙h. Power law trends were observed between the respiration rate and transcript abundance for the main DMC RDase (VcrA and the hydrogenase HupL (R2 = 0.83 and 0.88, respectively, but not transcripts for 16S rRNA or three other RDases examined: TceA, BvcA or the RDase DET1545 homologs in KB1TM. Overall, HupL transcripts appear to be the most robust activity biomarker across multiple DMC strains and in mixed communities including DMC co-cultures such as KB1TM. The addition of oxygen induced cell stress that caused respiration

Biomarkers' Responses to Reductive Dechlorination Rates and Oxygen Stress in Bioaugmentation Culture KB-1TM.

Science.gov (United States)

Heavner, Gretchen L W; Mansfeldt, Cresten B; Debs, Garrett E; Hellerstedt, Sage T; Rowe, Annette R; Richardson, Ruth E

2018-02-08

Using mRNA transcript levels for key functional enzymes as proxies for the organohalide respiration (OHR) rate, is a promising approach for monitoring bioremediation populations in situ at chlorinated solvent-contaminated field sites. However, to date, no correlations have been empirically derived for chlorinated solvent respiring, Dehalococcoides mccartyi (DMC) containing, bioaugmentation cultures. In the current study, genome-wide transcriptome and proteome data were first used to confirm the most highly expressed OHR-related enzymes in the bioaugmentation culture, KB-1 TM , including several reductive dehalogenases (RDases) and a Ni-Fe hydrogenase, Hup. Different KB-1™ DMC strains could be resolved at the RNA and protein level through differences in the sequence of a common RDase (DET1545-like homologs) and differences in expression of their vinyl chloride-respiring RDases. The dominant strain expresses VcrA, whereas the minor strain utilizes BvcA. We then used quantitative reverse-transcriptase PCR (qRT-PCR) as a targeted approach for quantifying transcript copies in the KB-1 TM consortium operated under a range of TCE respiration rates in continuously-fed, pseudo-steady-state reactors. These candidate biomarkers from KB-1 TM demonstrated a variety of trends in terms of transcript abundance as a function of respiration rate over the range: 7.7 × 10 -12 to 5.9 × 10 -10 microelectron equivalents per cell per hour (μeeq/cell∙h). Power law trends were observed between the respiration rate and transcript abundance for the main DMC RDase (VcrA) and the hydrogenase HupL (R² = 0.83 and 0.88, respectively), but not transcripts for 16S rRNA or three other RDases examined: TceA, BvcA or the RDase DET1545 homologs in KB1 TM . Overall, HupL transcripts appear to be the most robust activity biomarker across multiple DMC strains and in mixed communities including DMC co-cultures such as KB1 TM . The addition of oxygen induced cell stress that caused respiration rates

Potential Applicability of Persuasive Communication to Light-Glow Reduction Efforts: A Case Study of Marine Turtle Conservation

Science.gov (United States)

Kamrowski, Ruth L.; Sutton, Stephen G.; Tobin, Renae C.; Hamann, Mark

2014-09-01

Artificial lighting along coastlines poses a significant threat to marine turtles due to the importance of light for their natural orientation at the nesting beach. Effective lighting management requires widespread support and participation, yet engaging the public with light reduction initiatives is difficult because benefits associated with artificial lighting are deeply entrenched within modern society. We present a case study from Queensland, Australia, where an active light-glow reduction campaign has been in place since 2008 to protect nesting turtles. Semi-structured questionnaires explored community beliefs about reducing light and evaluated the potential for using persuasive communication techniques based on the theory of planned behavior (TPB) to increase engagement with light reduction. Respondents ( n = 352) had moderate to strong intentions to reduce light. TPB variables explained a significant proportion of variance in intention (multiple regression: R 2 = 0.54-0.69, P benefits to the local economy" ( P Selective legislation and commitment strategies may be further useful strategies to increase community light reduction. As artificial light continues to gain attention as a pollutant, our methods and findings will be of interest to anyone needing to manage public artificial lighting.

Web-based computational chemistry education with CHARMMing III: Reduction potentials of electron transfer proteins.

Directory of Open Access Journals (Sweden)

B Scott Perrin

2014-07-01

Full Text Available A module for fast determination of reduction potentials, E°, of redox-active proteins has been implemented in the CHARMM INterface and Graphics (CHARMMing web portal (www.charmming.org. The free energy of reduction, which is proportional to E°, is composed of an intrinsic contribution due to the redox site and an environmental contribution due to the protein and solvent. Here, the intrinsic contribution is selected from a library of pre-calculated density functional theory values for each type of redox site and redox couple, while the environmental contribution is calculated from a crystal structure of the protein using Poisson-Boltzmann continuum electrostatics. An accompanying lesson demonstrates a calculation of E°. In this lesson, an ionizable residue in a [4Fe-4S]-protein that causes a pH-dependent E° is identified, and the E° of a mutant that would test the identification is predicted. This demonstration is valuable to both computational chemistry students and researchers interested in predicting sequence determinants of E° for mutagenesis.

Reductive detoxification of acrolein as a potential role for aldehyde reductase (AKR1A) in mammals.

Science.gov (United States)

Kurahashi, Toshihiro; Kwon, Myoungsu; Homma, Takujiro; Saito, Yuka; Lee, Jaeyong; Takahashi, Motoko; Yamada, Ken-Ichi; Miyata, Satoshi; Fujii, Junichi

2014-09-12

Aldehyde reductase (AKR1A), a member of the aldo-keto reductase superfamily, suppresses diabetic complications via a reduction in metabolic intermediates; it also plays a role in ascorbic acid biosynthesis in mice. Because primates cannot synthesize ascorbic acid, a principle role of AKR1A appears to be the reductive detoxification of aldehydes. In this study, we isolated and immortalized mouse embryonic fibroblasts (MEFs) from wild-type (WT) and human Akr1a-transgenic (Tg) mice and used them to investigate the potential roles of AKR1A under culture conditions. Tg MEFs showed higher methylglyoxal- and acrolein-reducing activities than WT MEFs and also were more resistant to cytotoxicity. Enzymatic analyses of purified rat AKR1A showed that the efficiency of the acrolein reduction was about 20% that of glyceraldehyde. Ascorbic acid levels were quite low in the MEFs, and while the administration of ascorbic acid to the cells increased the intracellular levels of ascorbic acid, it had no affect on the resistance to acrolein. Endoplasmic reticulum stress and protein carbonylation induced by acrolein treatment were less evident in Tg MEFs than in WT MEFs. These data collectively indicate that one of the principle roles of AKR1A in primates is the reductive detoxification of aldehydes, notably acrolein, and protection from its detrimental effects. Copyright © 2014 Elsevier Inc. All rights reserved.

Integrating Stable Isotope - Reactive Transport Model Approach for Assessment of Chlorinated Solvent Degradation

Science.gov (United States)

2016-06-01

aerobic cometabolism, reductive dechlorination evidence was reported from the toe of the plume, where TCE enters the Lower Lithologic Unit. The CSM of the...modeling in reactive transport: 50 years of artificial recharge in the Amsterdam Water Supply Dunes . J. Hydrology 454: 7-25. Khan, F. I., et al

Reduction - competitive tomorrow

International Nuclear Information System (INIS)

Worley, L.; Bargerstock, S.

1995-01-01

Inventory reduction is one of the few initiatives that represent significant cost-reduction potential that does not result in personnel reduction. Centerior Energy's Perry nuclear power plant has embarked on an aggressive program to reduce inventory while maintaining plant material availability. Material availability to the plant was above 98%, but at an unacceptable 1994 inventory book value of $47 million with inventory carrying costs calculated at 30% annually

Reactive Minerals and Dechlorinating Communities: Mechanisms Governing the Degradation of Chlorinated Ethenes during Back Diffusion from Low Permeability Zones in Aerobic and Anaerobic Environments

Science.gov (United States)

Berns, E. C.; Zeng, R.; Singh, H.; Valocchi, A. J.; Sanford, R. A.; Strathmann, T. J.; Schaefer, C. E.; Werth, C. J.

2017-12-01

Low permeability zones (LPZs) comprised of silts and clays, and contaminated with chlorinated ethenes, can act as a long term source of contaminated groundwater by diffusion into adjacent high permeability zones (HPZs). Following initial remediation efforts, chlorinated ethenes that have diffused into LPZs will back diffuse and recontaminate HPZs. Because chlorinated ethenes are known to cause cancer and damage the liver, kidneys, and central nervous system, it is important to understand how they degrade in natural systems and how to model their fate and transport. Previous work has shown that anaerobic hydrogenolysis reactions are facilitated by both dechlorinating microorganisms and reactive minerals. Abiotic dichloro-elimination reactions with reactive minerals can also degrade chlorinated ethenes to acetylene, albeit at slower rates than biotic processes. More recently, studies have explored aerobic abiotic degradation of chlorinated ethenes to formate, glycolate, and carbon dioxide. This study focuses on these biotic and abiotic reactions and their contributions to chlorinated ethene degradation under aerobic and anaerobic conditions at the LPZ/HPZ interface. A two-dimensional flow cell was constructed to model this interface using clay and sand from Pease Air Force Base. The clay was inoculated with a dechlorinating enrichment culture. Tenax adsorbent beads equilibrated with trichloroethylene (TCE) were used as a chlorinated ethene source zone at the base of the clay. TCE and its degradation products diffused from the clay into the sand, where they were removed from the flow cell by groundwater at a rate of 50 mL/day. Volatile compounds were trapped in a sample loop and removed every 48 hours for analysis by GC-FID. Organic and inorganic ions in the effluent were analyzed on the HPLC and IC. The experiment was terminated by freezing the flow cell, and chemical profiles through the flow cell material were created to show the spatial distribution of degradation

LCOE reduction potential of parabolic trough and solar tower CSP technology until 2025

Science.gov (United States)

Dieckmann, Simon; Dersch, Jürgen; Giuliano, Stefano; Puppe, Michael; Lüpfert, Eckhard; Hennecke, Klaus; Pitz-Paal, Robert; Taylor, Michael; Ralon, Pablo

2017-06-01

Concentrating Solar Power (CSP), with an installed capacity of 4.9 GW by 2015, is a young technology compared to other renewable power generation technologies. A limited number of plants and installed capacity in a small challenging market environment make reliable and transparent cost data for CSP difficult to obtain. The International Renewable Energy Agency (IRENA) and the DLR German Aerospace Center gathered and evaluated available cost data from various sources for this publication in order to yield transparent, reliable and up-to-date cost data for a set of reference parabolic trough and solar tower plants in the year 2015 [1]. Each component of the power plant is analyzed for future technical innovations and cost reduction potential based on current R&D activities, ongoing commercial developments and growth in market scale. The derived levelized cost of electricity (LCOE) for 2015 and 2025 are finally contrasted with published power purchase agreements (PPA) of the NOOR II+III power plants in Morocco. At 7.5% weighted average cost of capital (WACC) and 25 years economic life time, the levelized costs of electricity for plants with 7.5 (trough) respectively 9 (tower) full-load hours thermal storage capacity decrease from 14-15 -ct/kWh today to 9-10 -ct/kWh by 2025 for both technologies at direct normal irradiation of 2500 kWh/(m².a). The capacity factor increases from 41.1% to 44.6% for troughs and from 45.5% to 49.0% for towers. Financing conditions are a major cost driver and offer potential for further cost reduction with the maturity of the technology and low interest rates (6-7 - ct/kWh for 2% WACC at 2500 kWh/(m2.a) in 2025).

Potential repair of free radical adducts of dGMP and dG by a series of reductants. A pulse radiolytic study

International Nuclear Information System (INIS)

O'Neill, P.; Chapman, P.W.

1985-01-01

Using the technique of pulse radiolysis, it has been demonstrated that the interaction of hydroxyl-radical adducts of dG and dGMP with a series of reductants with different oxidation potentials at pH 7.0-7.4 proceeds via an electron transfer process (k approx. 1.4-34 x 10 8 dm 3 mol -1 s -1 ). The one-electron oxidation of dGMP (dG) by Br2-anion radicals was shown to result in the formation of a species, the properties of which are similar to those of the OH-radical adduct of dGMP with oxidizing properties based upon both spectral and kinetic information. The nature of the dGMP species produced on interaction with Br2-anion radicals to produce specific base damage. The implications of these findings are presented in terms of potential free radical repair of hydroxyl radical damage and of synergistic effects whereby one reductant may be regenerated at the expense of another reductant. (author)

Chlorinated volatile organic compounds (Cl-VOCs) in environment - sources, potential human health impacts, and current remediation technologies.

Science.gov (United States)

Huang, Binbin; Lei, Chao; Wei, Chaohai; Zeng, Guangming

2014-10-01

Chlorinated volatile organic compounds (Cl-VOCs), including polychloromethanes, polychloroethanes and polychloroethylenes, are widely used as solvents, degreasing agents and a variety of commercial products. These compounds belong to a group of ubiquitous contaminants that can be found in contaminated soil, air and any kind of fluvial mediums such as groundwater, rivers and lakes. This review presents a summary of the research concerning the production levels and sources of Cl-VOCs, their potential impacts on human health as well as state-of-the-art remediation technologies. Important sources of Cl-VOCs principally include the emissions from industrial processes, the consumption of Cl-VOC-containing products, the disinfection process, as well as improper storage and disposal methods. Human exposure to Cl-VOCs can occur through different routes, including ingestion, inhalation and dermal contact. The toxicological impacts of these compounds have been carefully assessed, and the results demonstrate the potential associations of cancer incidence with exposure to Cl-VOCs. Most Cl-VOCs thus have been listed as priority pollutants by the Ministry of Environmental Protection (MEP) of China, Environmental Protection Agency of the U.S. (U.S. EPA) and European Commission (EC), and are under close monitor and strict control. Yet, more efforts will be put into the epidemiological studies for the risk of human exposure to Cl-VOCs and the exposure level measurements in contaminated sites in the future. State-of-the-art remediation technologies for Cl-VOCs employ non-destructive methods and destructive methods (e.g. thermal incineration, phytoremediation, biodegradation, advanced oxidation processes (AOPs) and reductive dechlorination), whose advantages, drawbacks and future developments are thoroughly discussed in the later sections. Copyright © 2014 Elsevier Ltd. All rights reserved.

Low-Carbon Watershed Management: Potential of Greenhouse Gas Reductions from Wastewater Treatment in Rural Vietnam

Science.gov (United States)

Mohan, Geetha; Jian, Pu; Takemoto, Kazuhiko; Fukushi, Kensuke

2016-01-01

Currently in many cities and rural areas of Vietnam, wastewater is discharged to the environment without any treatment, which emits considerable amount of greenhouse gas (GHG), particularly methane. In this study, four GHG emission scenarios were examined, as well as the baseline scenario, in order to verify the potential of GHG reduction from domestic wastewater with adequate treatment facilities. The ArcGIS and ArcHydro tools were employed to visualize and analyze GHG emissions resulting from discharge of untreated wastewater, in rural areas of Vu Gia Thu Bon river basin, Vietnam. By applying the current IPCC guidelines for GHG emissions, we found that a reduction of GHG emissions can be achieved through treatment of domestic wastewater in the studied area. Compared with baseline scenario, a maximum 16% of total GHG emissions can be reduced, in which 30% of households existing latrines are substituted by Japanese Johkasou technology and other 20% of domestic wastewater is treated by conventional activated sludge. PMID:27699202

Potentials for energy saving and CO2 reduction in Baden-Wuerttemberg. Status report

International Nuclear Information System (INIS)

Weimer, W.; Luenstroth, U.

1993-01-01

In order to protect the climate the Administration of the state of Baden-Wuerttemberg aims at cutting energy-related CO 2 -emissions by 30% by the year 2005. This study analyses the potentials of energy consumption and CO 2 -reduction in the state of Baden-Wuerttemberg in the framework of an evaluation of literature. As special emphasis is put on technical steps such as an increase in efficiency with respect to the generation and consumption of energy as well as on the substitution of fossil energy sources by regenerative techniques of energy generation. In order to obtain considerable potentials of energy-saving a moderate increase in energy prices as well as several actions to reduce impediments are required . However, an achievement of those goals by the year 2005 is only partly possible, because of the time required. The evaluation of literature serves as a preparation of the comprehensive project Klimavertraegliche Energieversorgung in Baden-Wuerttemberg (greenhouse-gas-reduced energy supply in Baden-Wuerttemberg) of the Center of Technology Assessment in Baden-Wuerttemberg. (orig.) [de

A Third-Generation Adaptive Statistical Iterative Reconstruction Technique: Phantom Study of Image Noise, Spatial Resolution, Lesion Detectability, and Dose Reduction Potential.

Science.gov (United States)

Euler, André; Solomon, Justin; Marin, Daniele; Nelson, Rendon C; Samei, Ehsan

2018-06-01

The purpose of this study was to assess image noise, spatial resolution, lesion detectability, and the dose reduction potential of a proprietary third-generation adaptive statistical iterative reconstruction (ASIR-V) technique. A phantom representing five different body sizes (12-37 cm) and a contrast-detail phantom containing lesions of five low-contrast levels (5-20 HU) and three sizes (2-6 mm) were deployed. Both phantoms were scanned on a 256-MDCT scanner at six different radiation doses (1.25-10 mGy). Images were reconstructed with filtered back projection (FBP), ASIR-V with 50% blending with FBP (ASIR-V 50%), and ASIR-V without blending (ASIR-V 100%). In the first phantom, noise properties were assessed by noise power spectrum analysis. Spatial resolution properties were measured by use of task transfer functions for objects of different contrasts. Noise magnitude, noise texture, and resolution were compared between the three groups. In the second phantom, low-contrast detectability was assessed by nine human readers independently for each condition. The dose reduction potential of ASIR-V was estimated on the basis of a generalized linear statistical regression model. On average, image noise was reduced 37.3% with ASIR-V 50% and 71.5% with ASIR-V 100% compared with FBP. ASIR-V shifted the noise power spectrum toward lower frequencies compared with FBP. The spatial resolution of ASIR-V was equivalent or slightly superior to that of FBP, except for the low-contrast object, which had lower resolution. Lesion detection significantly increased with both ASIR-V levels (p = 0.001), with an estimated radiation dose reduction potential of 15% ± 5% (SD) for ASIR-V 50% and 31% ± 9% for ASIR-V 100%. ASIR-V reduced image noise and improved lesion detection compared with FBP and had potential for radiation dose reduction while preserving low-contrast detectability.

Action Potential Broadening in Capsaicin-Sensitive DRG Neurons from Frequency-Dependent Reduction of Kv3 Current.

Science.gov (United States)

Liu, Pin W; Blair, Nathaniel T; Bean, Bruce P

2017-10-04

Action potential (AP) shape is a key determinant of cellular electrophysiological behavior. We found that in small-diameter, capsaicin-sensitive dorsal root ganglia neurons corresponding to nociceptors (from rats of either sex), stimulation at frequencies as low as 1 Hz produced progressive broadening of the APs. Stimulation at 10 Hz for 3 s resulted in an increase in AP width by an average of 76 ± 7% at 22°C and by 38 ± 3% at 35°C. AP clamp experiments showed that spike broadening results from frequency-dependent reduction of potassium current during spike repolarization. The major current responsible for frequency-dependent reduction of overall spike-repolarizing potassium current was identified as Kv3 current by its sensitivity to low concentrations of 4-aminopyridine (IC 50 action potentials of small-diameter rat DRG neurons showed spike broadening at frequencies as low as 1 Hz and that spike broadening resulted predominantly from frequency-dependent inactivation of Kv3 channels. Spike width helps to control transmitter release, conduction velocity, and firing patterns and understanding the role of particular potassium channels can help to guide new pharmacological strategies for targeting pain-sensing neurons selectively. Copyright © 2017 the authors 0270-6474/17/379705-10$15.00/0.

The cooperative electrochemical oxidation of chlorophenols in anode-cathode compartments

International Nuclear Information System (INIS)

Wang Hui; Wang Jianlong

2008-01-01

By using a self-made carbon/polytetrafluoroethylene (C/PTFE) O 2 -fed as the cathode and Ti/IrO 2 /RuO 2 as the anode, the degradation of three organic compounds (phenol, 4-chlorophenol, and 2,4-dichlorophenol) was investigated in the diaphragm (with terylene as diaphragm material) electrolysis device by electrochemical oxidation process. The result indicated that the concentration of hydrogen peroxide (H 2 O 2 ) was 8.3 mg/L, and hydroxyl radical (HO·) was determined in the cathodic compartment by electron spin resonance spectrum (ESR). The removal efficiency for organic compounds reached about 90% after 120 min, conforming to the sequence of phenol, 4-chlorophenol, and 2,4-dichlorophenol. And the dechlorination degree of 4-chlorophenol exceeded 90% after 80 min. For H 2 O 2 , HO· existed in the catholyte and reduction dechlorination at the cathode, the mineralization of organics in the cathodic compartment was better than that in the anodic compartment. The degradation of organics was supposed to be cooperative oxidation by direct or indirect electrochemical oxidation at the anode and H 2 O 2 , HO· produced by oxygen reduction at the cathode. High-performance liquid chromatography (HPLC) allowed identifying phenol as the dechlorination product of 4-chlorophenol in the cathodic compartment, and hydroquinone, 4-chlorocatechol, benzoquinone, maleic, fumaric, oxalic, and formic acids as the main oxidation intermediates in the cathodic and anodic compartments. A reaction scheme involving all these intermediates was proposed

Accurate Computation of Reduction Potentials of 4Fe−4S Clusters Indicates a Carboxylate Shift in Pyrococcus furiosus Ferredoxin

DEFF Research Database (Denmark)

Kepp, Kasper Planeta; Ooi, Bee Lean; Christensen, Hans Erik Mølager

2007-01-01

This work describes the computation and accurate reproduction of subtle shifts in reduction potentials for two mutants of the iron-sulfur protein Pyrococcus furiosus ferredoxin. The computational models involved only first-sphere ligands and differed with respect to one ligand, either acetate (as...

A Potential Reduction Method for Canonical Duality, with an Application to the Sensor Network Localization Problem

OpenAIRE

Latorre, Vittorio

2014-01-01

We propose to solve large instances of the non-convex optimization problems reformulated with canonical duality theory. To this aim we propose an interior point potential reduction algorithm based on the solution of the primal-dual total complementarity (Lagrange) function. We establish the global convergence result for the algorithm under mild assumptions and demonstrate the method on instances of the Sensor Network Localization problem. Our numerical results are promising and show the possi...

Degradation of chlorinated compounds in an anaerobic-aerobic process

Energy Technology Data Exchange (ETDEWEB)

Alfan-Guzman, R.; Guerrero-Barajas, C.; Garcia-Pena, I.

2009-07-01

Remediation technologies that involves gas transport (e.g., soil vapor extraction and air sparging of groundwater) cause the emission of gases contaminated with chlorinated solvents. Under anaerobic conditions, reductive dechlorination of trichloroethylene (TCE) proceeds via the formation of cis and trans dichloroethene (DCEs) and vinyl chloride (VC) as intermediates. (Author)

Principal Components as a Data Reduction and Noise Reduction Technique

Science.gov (United States)

Imhoff, M. L.; Campbell, W. J.

1982-01-01

The potential of principal components as a pipeline data reduction technique for thematic mapper data was assessed and principal components analysis and its transformation as a noise reduction technique was examined. Two primary factors were considered: (1) how might data reduction and noise reduction using the principal components transformation affect the extraction of accurate spectral classifications; and (2) what are the real savings in terms of computer processing and storage costs of using reduced data over the full 7-band TM complement. An area in central Pennsylvania was chosen for a study area. The image data for the project were collected using the Earth Resources Laboratory's thematic mapper simulator (TMS) instrument.

Experimental design for assessment of electrokinetically enhanced delivery of lactate and bacteria in 1,2-cis-dichloroethylene contaminated limestone

DEFF Research Database (Denmark)

Hyldegaard, Bente Højlund; Nedergaard, L. W.; Ottosen, Lisbeth

2015-01-01

Bacterial dechlorination of chlorinated solvents often causes accumulation of the intermediate cis-DCE. Back diffusion of e.g. cis-DCE, due to the dual porosity of limestone, often limits the remediation efficiency. A remediation scheme capable of establishing contact between contaminant, degrading...... bacteria and electron donor within the low permeable limestone matrix is required. The technology EK-BIO, which combines enhanced reductive dechlorination and electrokinetics (EK), was assessed. This novel technology has not previously been tested in limestone. An experimental set-up was designed to meet...... that fermentative bacteria were distributed by electrophoresis. This study suggests that EK application can establish the essential contact and overcome back diffusion. Thereby, EK-BIO may be superior to advection-based technologies for bioremediation of chlorinated solvent contaminated limestone matrices....

Hexavalent chromium reduction potential of Cellulosimicrobium sp. isolated from common effluent treatment plant of tannery industries.

Science.gov (United States)

Bharagava, Ram Naresh; Mishra, Sandhya

2018-01-01

Present study deals with the isolation and characterization of a bacterium capable for the effective reduction of Cr(VI) from tannery wastewater. Based on the 16S rRNA gene sequence analysis, this bacterium was identified as Cellulosimicrobium sp. (KX710177). During the Cr(VI) reduction experiment performed at 50, 100, 200,and 300mg/L of Cr(VI) concentrations, the bacterium showed 99.33% and 96.98% reduction at 50 and 100mg/L at 24 and 96h, respectively. However, at 200 and 300mg/L concentration of Cr(VI), only 84.62% and 62.28% reduction was achieved after 96h, respectively. The SEM analysis revealed that bacterial cells exposed to Cr(VI) showed increased cell size in comparison to unexposed cells, which might be due to either the precipitation or adsorption of reduced Cr(III) on bacterial cells. Further, the Energy Dispersive X-ray (EDX) analysis showed some chromium peaks for cells exposed to Cr(VI), which might be either due to the presence of precipitated reduced Cr(III) on cells or complexation of Cr(III) with cell surface molecules. The bacterium also showed resistance and sensitivity against the tested antibiotics with a wide range of MIC values ranging from 250 to 800mg/L for different heavy metals. Thus, this multi-drug and multi-metal resistant bacterium can be used as a potential agent for the effective bioremediation of metal contaminated sites. Copyright © 2017 Elsevier Inc. All rights reserved.

GAMMA RADIATION INTERACTS WITH MELANIN TO ALTER ITS OXIDATION-REDUCTION POTENTIAL AND RESULTS IN ELECTRIC CURRENT PRODUCTION

Energy Technology Data Exchange (ETDEWEB)

Turick, C.; Ekechukwu, A.; Milliken, C.

2011-05-17

The presence of melanin pigments in organisms is implicated in radioprotection and in some cases, enhanced growth in the presence of high levels of ionizing radiation. An understanding of this phenomenon will be useful in the design of radioprotective materials. However, the protective mechanism of microbial melanin in ionizing radiation fields has not yet been elucidated. Here we demonstrate through the electrochemical techniques of chronoamperometry, chronopotentiometry and cyclic voltammetry that microbial melanin is continuously oxidized in the presence of gamma radiation. Our findings establish that ionizing radiation interacts with melanin to alter its oxidation-reduction potential. Sustained oxidation resulted in electric current production and was most pronounced in the presence of a reductant, which extended the redox cycling capacity of melanin. This work is the first to establish that gamma radiation alters the oxidation-reduction behavior of melanin, resulting in electric current production. The significance of the work is that it provides the first step in understanding the initial interactions between melanin and ionizing radiation taking place and offers some insight for production of biomimetic radioprotective materials.

Effects of Muscle-Specific Oxidative Stress on Cytochrome c Release and Oxidation-Reduction Potential Properties.

Science.gov (United States)

Ke, Yiling; Mitacek, Rachel M; Abraham, Anupam; Mafi, Gretchen G; VanOverbeke, Deborah L; DeSilva, Udaya; Ramanathan, Ranjith

2017-09-06

Mitochondria play a significant role in beef color. However, the role of oxidative stress in cytochrome c release and mitochondrial degradation is not clear. The objective was to determine the effects of display time on cytochrome c content and oxidation-reduction potential (ORP) of beef longissimus lumborum (LL) and psoas major (PM) muscles. PM discolored by day 3 compared with LL. On day 0, mitochondrial content and mitochondrial oxygen consumption were greater in PM than LL. However, mitochondrial content and oxygen consumption were lower (P stress can affect cytochrome c release and ORP changes.

Evaluation of the odour reduction potential of alternative cover materials at a commercial landfill.

Science.gov (United States)

Solan, P J; Dodd, V A; Curran, T P

2010-02-01

The availability of virgin soils and traditional landfill covers are not only costly and increasingly becoming scarce, but they also reduce the storage capacity of landfill. The problem can be overcome by the utilisation of certain suitable waste streams as alternative landfill covers. The objective of this study was to assess the suitability of Construction & Demolition fines (C&D), Commercial & Industrial fines (C&I) and woodchip (WC) as potential landfill cover materials in terms of odour control. Background odour analysis was conducted to determine if any residual odour was emitted from the cover types. It was deemed negligible for the three materials. The odour reduction performance of each of the materials was also examined on an area of an active landfill site. A range of intermediate cover compositions were also studied to assess their performance. Odour emissions were sampled using a Jiang hood and analysed. Results indicate that the 200 mm deep combination layer of C&D and wood chip used on-site is adequate for odour abatement. The application of daily cover was found to result in effective reduction allowing for the background odour of woodchip.

Quinone 1 e ^– and 2 e ^– /2 H ⁺ Reduction Potentials: Identification and Analysis of Deviations from Systematic Scaling Relationships

Energy Technology Data Exchange (ETDEWEB)

Huynh, Mioy T.; Anson, Colin W.; Cavell, Andrew C.; Stahl, Shannon S.; Hammes-Schiffer, Sharon

2016-11-10

Quinones participate in diverse electron transfer and proton-coupled electron transfer processes in chemistry and biology. An experimental study of common quinones reveals a non-linear correlation between the 1 e^– and 2 e^–/2 H⁺ reduction potentials. This unexpected observation prompted a computational study of 128 different quinones, probing their 1 e^– reduction potentials, pKa values, and 2 e^–/2 H⁺ reduction potentials. The density functional theory calculations reveal an approximately linear correlation between these three properties and an effective Hammett constant associated with the quinone substituent(s). However, deviations from this linear scaling relationship are evident for quinones that feature halogen substituents, charged substituents, intramolecular hydrogen bonding in the hydroquinone, and/or sterically bulky substituents. These results, particularly the different substituent effects on the 1 e^– versus 2 e^– /2 H⁺ reduction potentials, have important implications for designing quinones with tailored redox properties.

Current status and future potential for advanced volume reduction technologies

International Nuclear Information System (INIS)

Rutland, L.; Naughton, M.D.; Papaiya, N.C.

1984-01-01

With escalating costs for disposal of low-level radioactive waste (LLW) from nuclear power plants, and the possibility of unavailability of disposal space, some nuclear power utilities responded by commiting to implementing advanced volume reduction (VR) systems. This paper presents recent experience to implement advanced volume reduction technologies; their performance and typical operating and capital costs. This experience in the light of current economic conditions may enable us to predict the direction that future advanced VR technology commitments is taking

Assessment of GHG Emission Reduction Potential from Source-separated Organic Waste (SOW) Management: Case Study in a Higher Educational Institution in Malaysia

International Nuclear Information System (INIS)

Ng, C.G.; Sumiani Yusoff

2015-01-01

In Malaysia, the greenhouse gases (GHGs) emissions reduction via composting of source-separated organic waste (SOW) in municipal solid waste (MSW) has not been assessed. Assessment of GHG emissions reduction via composting of SOW is important as environmental impacts from waste management are waste-specific and local-specific. The study presents the case study for potential carbon reduction via composting of SOW in University of Malaya (UM). In this study, a series of calculations were used to evaluate the GHG emission of different SOW management scenarios. The calculations based on IPCC calculation methods (AM0025) include GHGs emissions from land filling, fuel consumption in transportation and SOW composting activity. The methods were applied to assess the GHG emissions from five alternative SOW management scenarios in UM. From the baseline scenario (S0), a total of 1,636.18 tCO2e was generated. In conjunction with target of 22 % recycling rate, as shown in S1, 14 % reduction in potential GHG emission can be achieved. The carbon reduction can be further enhanced by increasing the SOW composting capacity. The net GHG emission for S1, S2, S3 and S4 were 1,399.52, 1,161.29, 857.70 and 1,060.48 tCO2e, respectively. In general, waste diversion for composting proved a significant net GHG emission reduction as shown in S3 (47 %), S4 (35 %) and S2 (29 %). Despite the emission due to direct on-site activity, the significant reduction in methane generation at landfill has reduced the net GHG emission. The emission source of each scenario was studied and analysed. (author)

Potential Occupant Injury Reduction in Pre-Crash System Equipped Vehicles in the Striking Vehicle of Rear-end Crashes.

Science.gov (United States)

Kusano, Kristofer D; Gabler, Hampton C

2010-01-01

To mitigate the severity of rear-end and other collisions, Pre-Crash Systems (PCS) are being developed. These active safety systems utilize radar and/or video cameras to determine when a frontal crash, such as a front-to-back rear-end collisions, is imminent and can brake autonomously, even with no driver input. Of these PCS features, the effects of autonomous pre-crash braking are estimated. To estimate the maximum potential for injury reduction due to autonomous pre-crash braking in the striking vehicle of rear-end crashes, a methodology is presented for determining 1) the reduction in vehicle crash change in velocity (ΔV) due to PCS braking and 2) the number of injuries that could be prevented due to the reduction in collision severity. Injury reduction was only performed for belted drivers, as unbelted drivers have an unknown risk of being thrown out of position. The study was based on 1,406 rear-end striking vehicles from NASS / CDS years 1993 to 2008. PCS parameters were selected from realistic values and varied to examine the effect on system performance. PCS braking authority was varied from 0.5 G's to 0.8 G's while time to collision (TTC) was held at 0.45 seconds. TTC was then varied from 0.3 second to 0.6 seconds while braking authority was held constant at 0.6 G's. A constant braking pulse (step function) and ramp-up braking pulse were used. The study found that automated PCS braking could reduce the crash ΔV in rear-end striking vehicles by an average of 12% - 50% and avoid 0% - 14% of collisions, depending on PCS parameters. Autonomous PCS braking could potentially reduce the number of injured drivers who are belted by 19% to 57%.

A fault tree analysis (FTA) of hydrogen explosion potentiality on reduction furnace ME-11 in nuclear power fuel element fabrication process

International Nuclear Information System (INIS)

Achmad Suntoro

2012-01-01

Fault Tree Analysis (FTA) diagrams for the potentiality of hydrogen gas explosion in reduction furnace of ME-11 has been created after modification of its logic control. These FTA diagrams can be used as additional information in designing preventive maintenance program and operational steps of the furnace. The encountering of two conditions, i.e. explosion ignition and the potentially explosive of hydrogen gas, is the search focus of the FTA, and it may be done by breaking and tracing down to any possibility of initial causes for these two conditions to occur coincidently. Two locations of the potentially explosive area were identified: furnace chamber and combustion chamber of the exhaust gas. The possible explosion ignitions for the furnace are only from spark, fire and hot material because the operation of the furnace does not use high-pressure hydrogen. However, these explosion ignitions are part of the on going reduction process, therefore it is important that the hydrogen gas volume composition during the process always be supervised. (author)

Preventing preterm births: trends and potential reductions with current interventionsin 39 very high human development index countries

Science.gov (United States)

Chang, Hannah H.; Larson, Jim; Blencowe, Hannah; Spong, Catherine Y.; Howson, Christopher P.; Cairns-Smith, Sarah; Lackritz, Eve M.; Lee, Shoo K.; Mason, Elizabeth; Serazin, Andrew C.; Walani, Salimah; Simpson, Joe Leigh; Lawn, Joy E.

2013-01-01

Summary Background Each year,1.1 million babies die from prematurity, andmany survivors are disabled. Worldwide, 15 million babies are preterm(10,000 births, country-by-country analyses were performed based on target population, incremental coverage increase,and intervention efficacy. Cost savings were estimated based on reported costs for preterm care in the USAadjusted usingWorld Bank purchasing power parity. Findings From 2010, even if all VHHDI countries achieved annual preterm birth rate reductions of the best performers, (Sweden and Netherlands), 2000-2010 or 2005-2010(Lithuania, Estonia)), rates would experience a relative reduction of<5% by 2015 on average across the 39 countries.Our analysis of preterm birth rise 1998-2004 in USA suggests half the change is unexplained, but important drivers includeinductions/cesareandelivery and ART.For all 39 VHHDI countries, five interventionsmodeling at high coveragepredicted 5%preterm birth rate relative reduction from 9.59 to 9.07% of live births:smoking cessation (0.01 rate reduction), decreasing multiple embryo transfers during assisted reproductive technologies (0.06), cervical cerclage (0.15), progesterone supplementation (0.01), and reduction of non-medically indicated labour induction or caesarean delivery (0.29).These translate to 58,000 preterm births averted and total annual economic cost savings of ~US$ 3 billion. Interpretation Even with optimal coverage of current interventions, many being complex to implement, the estimated potential reduction in preterm birth is tiny. Hence we recommenda conservative target of 5% preterm birth rate relative reductionby 2015. Our findings highlight the urgent need for discovery research into underlying mechanisms of preterm birth, and developmentof innovative interventions. Furthermore, the highest preterm birth rates occur in low-income settings where the causes of prematurity may differand have simpler solutions, such as birth spacing and treatment of infections in

Photodegradation of Dechlorane Plus in n-nonane under the irradiation of xenon lamp

Energy Technology Data Exchange (ETDEWEB)

Wang, Siwen; Huang, Jun; Yang, Yang; Yu, Gang, E-mail: yg-den@tsinghua.edu.cn; Deng, Shubo; Wang, Bin

2013-09-15

Highlights: • Photodegradation of isomers of Dechlorane Plus (DP) as a potential persistent organic pollutant were studied. • UV-C was found to be the main contributor to DP photodegradation. • DP degradation followed the pseudo first-order kinetics. • Sequential dechlorination was found as the degradation mechanism. -- Abstract: Photodegradation has been regarded as the main mechanism for the removal of many halogenated organic pollutants in the environment. The photodegradation of Dechlorane Plus (DP), an emerging contaminant taken worldwide concerns in recent years, was investigated under the irradiation of a xenon lamp. Rapid photodegradation was found under the irradiation of 200–750 nm light, while the degradation became much slower when the range of light wavelength changed to 280–750 nm. DP degradation followed the pseudo first-order kinetics. The quantum yields of 200–280 nm (UV-C) were about 2–3 orders of magnitude higher than 280–320 nm, and no yields can be detected in 320–750 nm range, in an agreement with the changing photodegradation rates with wavelength. The photodegradation products were identified as lower chlorinated DPs, implicating a mechanism of reductive dechlorination. No photoisomerization or solvent adducts were observed, and the difference of photodegradation rate between syn- and anti-DP isomers was negligible.

Substrate interactions in dehalogenation of 1,2-dichloroethane, 1,2-dichloropropane, and 1,1,2-trichloroethane mixtures by Dehalogenimonas spp.

Science.gov (United States)

Dillehay, Jacob L; Bowman, Kimberly S; Yan, Jun; Rainey, Fred A; Moe, William M

2014-04-01

When chlorinated alkanes are present as soil or groundwater pollutants, they often occur in mixtures. This study evaluated substrate interactions during the anaerobic reductive dehalogenation of chlorinated alkanes by the type strains of two Dehalogenimonas species, D. lykanthroporepellens and D. alkenigignens. Four contaminant mixtures comprised of combinations of the chlorinated solvents 1,2-dichloroethane (1,2-DCA), 1,2-dichloropropane (1,2-DCP), and 1,1,2-trichloroethane (1,1,2-TCA) were assessed for each species. Chlorinated solvent depletion and daughter product formation determined as a function of time following inoculation into anaerobic media revealed preferential dechlorination of 1,1,2-TCA over both 1,2-DCA and 1,2-DCP for both species. 1,2-DCA in particular was not dechlorinated until 1,1,2-TCA reached low concentrations. In contrast, both species concurrently dechlorinated 1,2-DCA and 1,2-DCP over a comparably large concentration range. This is the first report of substrate interactions during chlorinated alkane dehalogenation by pure cultures, and the results provide insights into the chlorinated alkane transformation processes that may be expected for contaminant mixtures in environments where Dehalogenimonas spp. are present.

Compendium of Technical Papers on the Reductive Dechlorination of Chlorinated Solvents.

Science.gov (United States)

1997-08-01

30), was added to cultures atarate of 20 pL (for in Thauer et al. (22) with temperature = 25 °C; pH = 7; HC0 3- = 70 supplement (E0),twas)added0to...34Biotransformation of chlorinated organic solvents in static niicrocosrrs." Environmental Toxicology and Chemistry 4: 739-742. Tandoi, V., T D. DiStefano, R A

Potential CO{sub 2} reduction by fuel substitution to generate electricity in Malaysia

Energy Technology Data Exchange (ETDEWEB)

Masjuki, H.H.; Mahlia, T.M.I.; Choudhury, I.A.; Saidur, R. [University of Malaysia, Kuala Lumpur (Malaysia). Dept. of Mechanical Engineers

2002-04-01

Because of changing fossil fuel prices, sources and environmental consciousness, Malaysian utilities have been forced to change the type of energy sources to generate electricity. This new policy of electricity generation companies will change fuel use gradually from 70% gas, 15% coal, 10% hydro and 5% petroleum in the year 2000 to 40% gas, 30% hydro, 29% coal and only 1% petroleum in the year of 2020. These changes tend to reduce CO{sub 2} emission. This study predicts the potential CO{sub 2} reduction due to these changes. The calculation is based on CO{sub 2} emission for unit electricity generated and the changing type of fuel percentages for electricity generation in Malaysia. The study found that the substitution will reduce CO{sub 2} emission from power plants in this country.

Microbial Community Response of an Organohalide Respiring Enrichment Culture to Permanganate Oxidation.

Science.gov (United States)

Sutton, Nora B; Atashgahi, Siavash; Saccenti, Edoardo; Grotenhuis, Tim; Smidt, Hauke; Rijnaarts, Huub H M

2015-01-01

While in situ chemical oxidation is often used to remediate tetrachloroethene (PCE) contaminated locations, very little is known about its influence on microbial composition and organohalide respiration (OHR) activity. Here, we investigate the impact of oxidation with permanganate on OHR rates, the abundance of organohalide respiring bacteria (OHRB) and reductive dehalogenase (rdh) genes using quantitative PCR, and microbial community composition through sequencing of 16S rRNA genes. A PCE degrading enrichment was repeatedly treated with low (25 μmol), medium (50 μmol), or high (100 μmol) permanganate doses, or no oxidant treatment (biotic control). Low and medium treatments led to higher OHR rates and enrichment of several OHRB and rdh genes, as compared to the biotic control. Improved degradation rates can be attributed to enrichment of (1) OHRB able to also utilize Mn oxides as a terminal electron acceptor and (2) non-dechlorinating community members of the Clostridiales and Deltaproteobacteria possibly supporting OHRB by providing essential co-factors. In contrast, high permanganate treatment disrupted dechlorination beyond cis-dichloroethene and caused at least a 2-4 orders of magnitude reduction in the abundance of all measured OHRB and rdh genes, as compared to the biotic control. High permanganate treatments resulted in a notably divergent microbial community, with increased abundances of organisms affiliated with Campylobacterales and Oceanospirillales capable of dissimilatory Mn reduction, and decreased abundance of presumed supporters of OHRB. Although OTUs classified within the OHR-supportive order Clostridiales and OHRB increased in abundance over the course of 213 days following the final 100 μmol permanganate treatment, only limited regeneration of PCE dechlorination was observed in one of three microcosms, suggesting strong chemical oxidation treatments can irreversibly disrupt OHR. Overall, this detailed investigation into dose

Chlorine isotope effects from isotope ratio mass spectrometry suggest intramolecular C-Cl bond competition in trichloroethene (TCE) reductive dehalogenation.

Science.gov (United States)

Cretnik, Stefan; Bernstein, Anat; Shouakar-Stash, Orfan; Löffler, Frank; Elsner, Martin

2014-05-20

Chlorinated ethenes are prevalent groundwater contaminants. To better constrain (bio)chemical reaction mechanisms of reductive dechlorination, the position-specificity of reductive trichloroethene (TCE) dehalogenation was investigated. Selective biotransformation reactions (i) of tetrachloroethene (PCE) to TCE in cultures of Desulfitobacterium sp. strain Viet1; and (ii) of TCE to cis-1,2-dichloroethene (cis-DCE) in cultures of Geobacter lovleyi strain SZ were investigated. Compound-average carbon isotope effects were -19.0‰ ± 0.9‰ (PCE) and -12.2‰ ± 1.0‰ (TCE) (95% confidence intervals). Using instrumental advances in chlorine isotope analysis by continuous flow isotope ratio mass spectrometry, compound-average chorine isotope effects were measured for PCE (-5.0‰ ± 0.1‰) and TCE (-3.6‰ ± 0.2‰). In addition, position-specific kinetic chlorine isotope effects were determined from fits of reactant and product isotope ratios. In PCE biodegradation, primary chlorine isotope effects were substantially larger (by -16.3‰ ± 1.4‰ (standard error)) than secondary. In TCE biodegradation, in contrast, the product cis-DCE reflected an average isotope effect of -2.4‰ ± 0.3‰ and the product chloride an isotope effect of -6.5‰ ± 2.5‰, in the original positions of TCE from which the products were formed (95% confidence intervals). A greater difference would be expected for a position-specific reaction (chloride would exclusively reflect a primary isotope effect). These results therefore suggest that both vicinal chlorine substituents of TCE were reactive (intramolecular competition). This finding puts new constraints on mechanistic scenarios and favours either nucleophilic addition by Co(I) or single electron transfer as reductive dehalogenation mechanisms.

Quantification of the Potential Gross Economic Impacts of Five Methane Reduction Scenarios

Energy Technology Data Exchange (ETDEWEB)

Keyser, David [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Warner, Ethan [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Curley, Christina [Colorado State Univ., Fort Collins, CO (United States)

2015-04-23

Methane (CH4) is a potent greenhouse gas that is released from the natural gas supply chain into the atmosphere as a result of fugitive emissions1 and venting2 . We assess five potential CH4 reduction scenarios from transmission, storage, and distribution (TS&D) using published literature on the costs and the estimated quantity of CH4 reduced. We utilize cost and methane inventory data from ICF (2014) and Warner et al. (forthcoming) as well as data from Barrett and McCulloch (2014) and the American Gas Association (AGA) (2013) to estimate that the implementation of these measures could support approximately 85,000 jobs annually from 2015 to 2019 and reduce CH4 emissions from natural gas TS&D by over 40%. Based on standard input/output analysis methodology, measures are estimated to support over $8 billion in GDP annually over the same time period and allow producers to recover approximately $912 million annually in captured gas.

Reduction of low potential electron acceptors requires the CbcL inner membrane cytochrome of Geobacter sulfurreducens.

Science.gov (United States)

Zacharoff, Lori; Chan, Chi Ho; Bond, Daniel R

2016-02-01

The respiration of metals by the bacterium Geobacter sulfurreducens requires electrons generated by metabolism to pass from the interior of the cell to electron acceptors beyond the cell membranes. The G. sulfurreducens inner membrane multiheme c-type cytochrome ImcH is required for respiration to extracellular electron acceptors with redox potentials greater than -0.1 V vs. SHE, but ImcH is not essential for electron transfer to lower potential acceptors. In contrast, deletion of cbcL, encoding an inner membrane protein consisting of b-type and multiheme c-type cytochrome domains, severely affected reduction of low potential electron acceptors such as Fe(III)-oxides and electrodes poised at -0.1 V vs. SHE. Catalytic cyclic voltammetry of a ΔcbcL strain growing on poised electrodes revealed a 50 mV positive shift in driving force required for electron transfer out of the cell. In non-catalytic conditions, low-potential peaks present in wild type biofilms were absent in ∆cbcL mutants. Expression of cbcL in trans increased growth at low redox potential and restored features to cyclic voltammetry. This evidence supports a model where CbcL is a component of a second electron transfer pathway out of the G. sulfurreducens inner membrane that dominates when redox potential is at or below -0.1 V vs. SHE. Copyright © 2015. Published by Elsevier B.V.

Change in corrosion potential of SUS304 in natural river water

International Nuclear Information System (INIS)

Yamamoto, Masahiro; Satoh, Tomonori; Tsukada, Takashi; Katayama, Hideki

2014-01-01

In the Fukushima Dai-ichi nuclear power plant, seawater and natural river water were poured into the spent nuclear fuel pools (SFP) for emergency cooling. At the early stage of the accident, corrosion of SFP's materials was worried because of high chloride ion concentration from seawater. The chloride ion concentration of the present time was decreased by dechlorination operation of feeding water of SFPs. However, the water was not treated in the viewpoint of microbial breeding and SFPs were in contact with open atmosphere, so that many microbes could be alive in the cooling water. Some researchers have reported microbially induced corrosion (MIC) occurred in the natural seawater or river water. So, we attempted to examine the ability of MIC occurrence by using of corrosion potential analysis. Corrosion potential measurements were performed in test solutions using SUS304 simple plate, creviced and welded samples. Natural river water in Ibaraki prefecture was used as standard test solution, and some amounts of NaCl and nutrient broth (NB) were added to the other solutions. Temperatures of these solutions were kept in 303 K. Growth of microbes in the test solution was confirmed using test kit. Corrosion potentials of all samples rose to about 300 mV nobler than the initial values in the NB added solution. The potentials of the welded samples more easily rose than the simple plate. These potential changes are attributed to the biofilms formed on the sample surface. (author)

Marginal abatement cost and carbon reduction potential outlook of key energy efficiency technologies in China's building sector to 2030

International Nuclear Information System (INIS)

Xiao, He; Wei, Qingpeng; Wang, Hailin

2014-01-01

China achieved an energy savings of 67.5 Mtce in the building sector at the end of the 11th Five-Year Plan and set a new target of 116 Mtce by the end of the 12th Five-Year Plan. In this paper, an improved bottom-up model is developed to assess the carbon abatement potential and marginal abatement cost (MAC) of 34 selected energy-saving technologies/measures for China's building sector. The total reduction potential is 499.8 million t-CO 2 by 2030. 4.8 Gt-CO 2 potential will be achieved cumulatively to 2030. By 2030, total primary energy consumption of Chinese building sector will rise continuously to 1343 Mtce in the reference scenario and 1114 Mtce in the carbon reduction scenario. Total carbon dioxide emission will rise to 2.39 Gt-CO 2 and 1.9 Gt-CO 2 in two scenarios separately. The average carbon abatement cost of the aforementioned technologies is 19.5 $/t-CO 2 . The analysis reveals that strengthening successfully energy-saving technologies is important, especially for the residential building sector. The central government's direct investments in such technologies should be reduced without imposing significant negative effects. - Highlights: • MAC of 34 energy-saving technologies of China's building sector is calculated. • Energy use and CO 2 emission of China's building sector by 2030 is forecasted. • The reference and the carbon reduction scenarios are compared

Reliability of sickness certificates in detecting potential sick leave reduction by modifying working conditions: a clinical epidemiology study

Directory of Open Access Journals (Sweden)

Johnsen Roar

2004-03-01

Full Text Available Abstract Background Medical sickness certificates are generally the main source for information when scrutinizing the need for aimed intervention strategies to avoid or reduce the individual and community side effects of sick leave. This study explored the value of medical sickness certificates related to daily work in Norwegian National Insurance Offices to identify sick-listed persons, where modified working conditions might reduce the ongoing sick leave. Methods The potential for reducing the ongoing sick leave by modifying working conditions was individually assessed on routine sickness certificates in 999 consecutive sick leave episodes by four Norwegian National Insurance collaborators, two with and two without formal medical competence. The study took place in Northern Norway in 1997 and 1998. Agreement analysed with differences against mean, kappa, and proportional-agreement analysis within and between groups of assessors was used in the judgement. Agreements between the assessors and the self-assessment of sick-listed subjects were additionally analysed in 159 sick-leave episodes. Results Both sick-listed subjects and National Insurance collaborators anticipated a potential reduction in sick leave in 20–30% of cases, and in another 20% the potential was assessed as possible. The chance corrected agreements, however, were poor (k Conclusion Information in medical sickness certificates proved ineffective in detecting cases where modified working conditions may reduce sick leave, and focusing on medical certificates may prevent identification of needed interventions. Strategies on how to communicate directly with sick-listed subjects would enable social authorities to exploit more of the sick leave reduction potential by modifying the working conditions than strategies on improving medical information.

Noise Reduction Potential of Cellular Metals

Directory of Open Access Journals (Sweden)

Björn Hinze

2012-06-01

Full Text Available Rising numbers of flights and aircrafts cause increasing aircraft noise, resulting in the development of various approaches to change this trend. One approach is the application of metallic liners in the hot gas path of aero-engines. At temperatures of up to 600 °C only metallic or ceramic structures can be used. Due to fatigue loading and the notch effect of the pores, mechanical properties of porous metals are superior to the ones of ceramic structures. Consequently, cellular metals like metallic foams, sintered metals, or sintered metal felts are most promising materials. However, acoustic absorption depends highly on pore morphology and porosity. Therefore, both parameters must be characterized precisely to analyze the correlation between morphology and noise reduction performance. The objective of this study is to analyze the relationship between pore morphology and acoustic absorption performance. The absorber materials are characterized using image processing based on two dimensional microscopy images. The sound absorption properties are measured using an impedance tube. Finally, the correlation of acoustic behavior, pore morphology, and porosity is outlined.

New potential of the reductive alkylation of amines

International Nuclear Information System (INIS)

Gusak, K N; Ignatovich, Zh V; Koroleva, E V

2015-01-01

Available data on the reductive alkylation of amines with carbonyl compounds — a key method for the preparation of secondary and tertiary amines — are described systematically. The review provides information on the relevant reducing agents and catalysts and on the use of chiral catalysts in stereo- and enantiocontrolled reactions of amine synthesis. The effect of the reactant and catalyst structures on the reaction rates and chemo- and stereo(enantio)selectivity is considered. The bibliography includes 156 references

Time-Frequency Data Reduction for Event Related Potentials: Combining Principal Component Analysis and Matching Pursuit

Directory of Open Access Journals (Sweden)

Selin Aviyente

2010-01-01

Full Text Available Joint time-frequency representations offer a rich representation of event related potentials (ERPs that cannot be obtained through individual time or frequency domain analysis. This representation, however, comes at the expense of increased data volume and the difficulty of interpreting the resulting representations. Therefore, methods that can reduce the large amount of time-frequency data to experimentally relevant components are essential. In this paper, we present a method that reduces the large volume of ERP time-frequency data into a few significant time-frequency parameters. The proposed method is based on applying the widely used matching pursuit (MP approach, with a Gabor dictionary, to principal components extracted from the time-frequency domain. The proposed PCA-Gabor decomposition is compared with other time-frequency data reduction methods such as the time-frequency PCA approach alone and standard matching pursuit methods using a Gabor dictionary for both simulated and biological data. The results show that the proposed PCA-Gabor approach performs better than either the PCA alone or the standard MP data reduction methods, by using the smallest amount of ERP data variance to produce the strongest statistical separation between experimental conditions.

Catalytic Destruction of a Surrogate Organic Hazardous Air Pollutant as a Potential Co-benefit for Coal-fired Selective Catalyst Reduction Systems

Science.gov (United States)

Catalytic destruction of benzene (C6H6), a surrogate for organic hazardous air pollutants (HAPs) produced from coal combustion, was investigated using a commercial selective catalytic reduction (SCR) catalyst for evaluating the potential co-benefit of the SCR technology for reduc...

Impacts of potential CO2-reduction policies on air quality in the United States.

Science.gov (United States)

Trail, Marcus A; Tsimpidi, Alexandra P; Liu, Peng; Tsigaridis, Kostas; Hu, Yongtao; Rudokas, Jason R; Miller, Paul J; Nenes, Athanasios; Russell, Armistead G

2015-04-21

Impacts of emissions changes from four potential U.S. CO2 emission reduction policies on 2050 air quality are analyzed using the community multiscale air quality model (CMAQ). Future meteorology was downscaled from the Goddard Institute for Space Studies (GISS) ModelE General Circulation Model (GCM) to the regional scale using the Weather Research Forecasting (WRF) model. We use emissions growth factors from the EPAUS9r MARKAL model to project emissions inventories for two climate tax scenarios, a combined transportation and energy scenario, a biomass energy scenario and a reference case. Implementation of a relatively aggressive carbon tax leads to improved PM2.5 air quality compared to the reference case as incentives increase for facilities to install flue-gas desulfurization (FGD) and carbon capture and sequestration (CCS) technologies. However, less capital is available to install NOX reduction technologies, resulting in an O3 increase. A policy aimed at reducing CO2 from the transportation sector and electricity production sectors leads to reduced emissions of mobile source NOX, thus reducing O3. Over most of the U.S., this scenario leads to reduced PM2.5 concentrations. However, increased primary PM2.5 emissions associated with fuel switching in the residential and industrial sectors leads to increased organic matter (OM) and PM2.5 in some cities.

Assessment of Alternative Scenarios for CO2 Reduction Potential in the Residential Building Sector

Directory of Open Access Journals (Sweden)

Young-Sun Jeong

2017-03-01

Full Text Available The South Korean government announced its goals of reducing the country’s CO2 emissions by up to 30% below the business as usual (BAU projections by 2020 in 2009 and 37% below BAU projections by 2030 in 2015. This paper explores the potential energy savings and reduction in CO2 emissions offered by residential building energy efficiency policies and plans in South Korea. The current and future energy consumption and CO2 emissions in the residential building were estimated using an energy–environment model from 2010 to 2030. The business as usual scenario is based on the energy consumption characteristic of residential buildings using the trends related to socio-economic prospects and the number of dwellings. The alternative scenarios took into account energy efficiency for new residential buildings (scenario I, refurbishment of existing residential buildings (scenario II, use of highly efficient boilers (scenario III, and use of a solar thermal energy system (scenario IV. The results show that energy consumption in the residential building sector will increase by 33% between 2007 and 2030 in the BAU scenario. Maximum reduction in CO2 emissions in the residential building sector of South Korea was observed by 2030 in scenario I. In each alternative scenario analysis, CO2 emissions were 12.9% lower than in the business as usual scenario by the year 2030.

Analysis of dechlorination kinetics of chlorinated aliphatic hydrocarbons by Fe(II) in cement slurries

Energy Technology Data Exchange (ETDEWEB)

Jung, Bahngmi [Department of Earth and Environmental Sciences, Wright State University, Dayton, OH 45435-0001 (United States)], E-mail: jung.bahngmi@gmail.com; Batchelor, Bill [Department of Civil Engineering, Texas A and M University, College Station, TX 77843-3136 (United States)

2008-03-21

Degradative solidification/stabilization with ferrous iron (DS/S-Fe(II)) has been found to be effective in degrading a number of chlorinated aliphatic hydrocarbons including 1,1,1-trichloroethane (1,1,1-TCA), 1,1,2,2-tetrachloroethane (1,1,2,2-TeCA), tetrachloroethylene (PCE), trichloroethylene (TCE), 1,1-dichloroethylene (1,1-DCE), vinyl chloride (VC), carbon tetrachloride (CT) and chloroform (CF). Previous studies have characterized degradation kinetics in DS/S-Fe(II) systems as affected by Fe(II) dose, pH and initial target organic concentration. The goal of this study is to investigate the importance of various chemical properties on degradation kinetics of DS/S-Fe(II). This was accomplished by first measuring rate constants for degradation of 1,1,1-TCA, 1,1,2,2-TeCA and 1,2-dichloroethane (1,2-DCA) in individual batch experiments. Rate constants developed in these experiments and those obtained from the literature were related to thermodynamic parameters including one-electron reduction potential, two-electron reduction potential, bond dissociation energy and lowest unoccupied molecular orbital energies. Degradation kinetics by Fe(II) in cement slurries were generally represented by a pseudo-first-order rate law. The results showed that the rate constants for chlorinated methanes (e.g. CT, CF) and chlorinated ethanes (e.g. 1,1,1-TCA) were higher than those for chlorinated ethylenes (e.g. PCE, TCE, 1,1-DCE and VC) under similar experimental conditions. The log of the pseudo-first-order rate constant (k) was found to correlate better with lowest unoccupied molecular orbital energies (E{sub LUMO}) (R{sup 2} = 0.874) than with other thermodynamic parameter descriptors.

Potential load reductions on megawatt turbines exposed to wakes using individual-pitch wake compensator and trailing-edge flaps

DEFF Research Database (Denmark)

Markou, Helen; Andersen, Peter Bjørn; Larsen, Gunner Chr.

2011-01-01

that typically focus on either load or power prediction. As a consequence, the wake affected inflow field generated by the DWM formulation opens for control strategies for the individual turbine. Two different control approaches for load reduction on the individual turbines are implemented in the multi-body aero-servo-elastic...... tool HAWC2, developed at Risø-DTU in Denmark, and their potential load reduction capabilities compared: (1) full-blade ‘individual-pitch controllers’ acting as wake compensators and (2) controllers using trailing-edge flaps. Information on the wake inflow conditions, induced by upstream turbines...... for the loading conditions of the individual turbines in the farm. The dynamic wake meandering model (DWM) is believed to capture the essential physics of the wake problem, and thus, both load and production aspects can be predicted, which is contrary to the traditional engineering wake prediction methods...

Utilization potentiality of coal as a reductant for the production of sponge iron. [5 refs

Energy Technology Data Exchange (ETDEWEB)

Mishra, H P

1976-10-01

With the ambitious plan of the Government of India to produce about 70 million tonnes of steel per annum towards the end of the century, the requirement of coal would be enormous. This calls for judicious planning and conservation of coal. Modern trend in steel plant practice is to use blast furnaces of capacity 10,000 to 12,000 t/day requiring superior quality coke of low ash content which will become scarce. Concerted efforts should be made to by-pass blast furnace technique by adopting direct reduction for the production of metallized iron ore, that is sponge iron, and using this as feed stock in electric furnaces. Experience has shown that the use of sponge iron as feed stock for electric arc furnaces instead of the scrap available from various fabrication and steel works results in better production of alloy steels. The use of non-coking coal as reductant for production of sponge iron will help conserve coking coal for bigger steel plants. In the solid state reduction process the technological design of the sponge iron plant has to be tailored to the type of feed stock to be used, particularly iron ore and coal. In India, non-coking coal is available at close proximity to the iron ore mines containing high grade iron ore. Planning for sponge iron, utilizing large reserves of non-coking coal as feed stock therefore has considerable potentiality. India has vast reserves of high grade iron ore and comparatively meager amount of coking coal. This calls for planning for sponge iron using non-coking coal as feed stock.

Chlorine Isotope Effects from Isotope Ratio Mass Spectrometry Suggest Intramolecular C-Cl Bond Competition in Trichloroethene (TCE Reductive Dehalogenation

Directory of Open Access Journals (Sweden)

Stefan Cretnik

2014-05-01

Full Text Available Chlorinated ethenes are prevalent groundwater contaminants. To better constrain (biochemical reaction mechanisms of reductive dechlorination, the position-specificity of reductive trichloroethene (TCE dehalogenation was investigated. Selective biotransformation reactions (i of tetrachloroethene (PCE to TCE in cultures of Desulfitobacterium sp. strain Viet1; and (ii of TCE to cis-1,2-dichloroethene (cis-DCE in cultures of Geobacter lovleyi strain SZ were investigated. Compound-average carbon isotope effects were −19.0‰ ± 0.9‰ (PCE and −12.2‰ ± 1.0‰ (TCE (95% confidence intervals. Using instrumental advances in chlorine isotope analysis by continuous flow isotope ratio mass spectrometry, compound-average chorine isotope effects were measured for PCE (−5.0‰ ± 0.1‰ and TCE (−3.6‰ ± 0.2‰. In addition, position-specific kinetic chlorine isotope effects were determined from fits of reactant and product isotope ratios. In PCE biodegradation, primary chlorine isotope effects were substantially larger (by −16.3‰ ± 1.4‰ (standard error than secondary. In TCE biodegradation, in contrast, the product cis-DCE reflected an average isotope effect of −2.4‰ ± 0.3‰ and the product chloride an isotope effect of −6.5‰ ± 2.5‰, in the original positions of TCE from which the products were formed (95% confidence intervals. A greater difference would be expected for a position-specific reaction (chloride would exclusively reflect a primary isotope effect. These results therefore suggest that both vicinal chlorine substituents of TCE were reactive (intramolecular competition. This finding puts new constraints on mechanistic scenarios and favours either nucleophilic addition by Co(I or single electron transfer as reductive dehalogenation mechanisms.

Efficiency potentials of heat pumps with combined heat and power. For maximum reduction of CO2 emissions and for electricity generation from fossil fuels with CO2 reduction in Switzerland

International Nuclear Information System (INIS)

Rognon, F.

2005-06-01

This comprehensive report for the Swiss Federal Office of Energy (SFOE) takes a look at how the efficiency potential of heat pumps together with combined heat and power systems can help provide a maximum reduction of CO 2 emissions and provide electricity generation from fossil fuel in Switzerland together with reductions in CO 2 emissions. In Switzerland, approximately 80% of the low-temperature heat required for space-heating and for the heating-up of hot water is produced by burning combustibles. Around a million gas and oil boilers were in use in Switzerland in 2000, and these accounted for approximately half the country's 41.1 million tonnes of CO 2 emissions. The authors state that there is a more efficient solution with lower CO 2 emissions: the heat pump. With the enormous potential of our environment it would be possible to replace half the total number of boilers in use today with heat pumps. This would be equivalent to 90 PJ p.a. of useful heat, or 500,000 systems. The power source for heat pumps should come from the substitution of electric heating systems (electric resistor-based systems) and from the replacement of boilers. This should be done by using combined heat and power systems with full heat utilisation. This means, according to the authors, that the entire required power source can be provided without the need to construct new electricity production plants. The paper examines and discusses the theoretical, technical, market and realisable potentials

Verification of Methods for Assessing the Sustainability of Monitored Natural Attenuation (MNA)

Science.gov (United States)

2013-01-01

halorespiring bacteria , 2) Groundwater at levels of dissolved oxygen (DO) below threshold levels necessary for efficient reductive dechlorination, and 3...substrates for heterotrophic bacteria in the subsurface, and the consumption of electron acceptors (EAs) associated with aerobic and anaerobic respiration...approximately 20-25 feet thick and is comprised of Pleistocene deposits that are characterized by well-sorted, coarse sand with dispersed lenses of

Combining Low-Energy Electrical Resistance Heating with Biotic and Abiotic Reactions for Treatment of Chlorinated Solvent DNAPL Source Areas

Science.gov (United States)

2015-01-01

particles. Environ. Sci. Technol. 2000, 34, 1794-1805. Atlas , R.M., and R. Bartha . 1987. Microbial Ecology : Fundamentals and Applications. The... microbial processes ( Atlas , 1987; Empadinhas, 2004; Suyama, 2002), and for reductive dechlorination reactions in particular (Kohring, 1989; Holliger...dissolution of DNAPLs, but biological reaction rates also increase with increasing temperature Microbial activity is a function of temperature, and for

Preventing preterm births: analysis of trends and potential reductions with interventions in 39 countries with very high human development index.

Science.gov (United States)

Chang, Hannah H; Larson, Jim; Blencowe, Hannah; Spong, Catherine Y; Howson, Christopher P; Cairns-Smith, Sarah; Lackritz, Eve M; Lee, Shoo K; Mason, Elizabeth; Serazin, Andrew C; Walani, Salimah; Simpson, Joe Leigh; Lawn, Joy E

2013-01-19

Every year, 1·1 million babies die from prematurity, and many survivors are disabled. Worldwide, 15 million babies are born preterm (rates in almost all countries with reliable data. The understanding of drivers and potential benefit of preventive interventions for preterm births is poor. We examined trends and estimate the potential reduction in preterm births for countries with very high human development index (VHHDI) if present evidence-based interventions were widely implemented. This analysis is to inform a rate reduction target for Born Too Soon. Countries were assessed for inclusion based on availability and quality of preterm prevalence data (2000-10), and trend analyses with projections undertaken. We analysed drivers of rate increases in the USA, 1989-2004. For 39 countries with VHHDI with more than 10,000 births, we did country-by-country analyses based on target population, incremental coverage increase, and intervention efficacy. We estimated cost savings on the basis of reported costs for preterm care in the USA adjusted using World Bank purchasing power parity. From 2010, even if all countries with VHHDI achieved annual preterm birth rate reductions of the best performers for 1990-2010 (Estonia and Croatia), 2000-10 (Sweden and Netherlands), or 2005-10 (Lithuania, Estonia), rates would experience a relative reduction of less than 5% by 2015 on average across the 39 countries. Our analysis of preterm birth rise 1989-2004 in USA suggests half the change is unexplained, but important drivers include non-medically indicated labour induction and caesarean delivery and assisted reproductive technologies. For all 39 countries with VHHDI, five interventions modelling at high coverage predicted a 5% relative reduction of preterm birth rate from 9·59% to 9·07% of livebirths: smoking cessation (0·01 rate reduction), decreasing multiple embryo transfers during assisted reproductive technologies (0·06), cervical cerclage (0·15), progesterone

Development of an integrated, in-situ remediation technology. Draft topical report for task No. 9. Part II. Entitled: TCE degradation using non-biological methods, September 26, 1994--May 25, 1996

Energy Technology Data Exchange (ETDEWEB)

Orth, R.G.; McKenzie, D.E.

1997-04-01

Contamination in low permeability soils poses a significant technical challenge to in-situ remediation efforts. Poor accessibility to the contaminants and difficulty in delivery of treatment reagents have rendered existing in-situ treatments such as bioremediation, vapor extraction, pump and treat rather ineffective when applied to low permeability soils present at many contaminated sites. The technology is an integrated in-situ treatment in which established geotechnical methods are used to install degradation zones directly in the contaminated soil and electro-osmosis is utilized to move the contaminants back and forth through those zones until the treatment is completed. The use of zero valence iron for reductive dechlorination of aliphatic chlorinated hydrocarbons is currently under investigation by a number of research groups as a potential method of in-situ treatment of contaminated ground water. The reaction appears to involve the transfer of electrons to chloro-aliphatic compounds by the oxidation of zero valence iron to ferrous iron (Fe{sup +2}). Our studies have indicated that this reaction is consistent with those of corrosion, and as such, can be influenced or increased by the presence of small amounts of metals (5% by weight) such as copper, tin, silver, gold and palladium coated on the iron surface. Incomplete coverage of the iron surface with a more electropositive metal results in an open galvanic cell, which increases the oxidation of iron and facilitates and increases the concurrent reduction of trichloroethylene and other chlorinated aliphatic compounds to the corresponding alkenes and alkanes. Our results show that plating more electropositive metals onto certain iron surfaces results in approximately a factor of ten increase in the dechlorination rate of small organochlorine compounds such as TCE.

Development of an integrated, in-situ remediation technology. Draft topical report for task No. 9. Part II. Entitled: TCE degradation using non-biological methods, September 26, 1994--May 25, 1996

International Nuclear Information System (INIS)

Orth, R.G.; McKenzie, D.E.

1997-01-01

Contamination in low permeability soils poses a significant technical challenge to in-situ remediation efforts. Poor accessibility to the contaminants and difficulty in delivery of treatment reagents have rendered existing in-situ treatments such as bioremediation, vapor extraction, pump and treat rather ineffective when applied to low permeability soils present at many contaminated sites. The technology is an integrated in-situ treatment in which established geotechnical methods are used to install degradation zones directly in the contaminated soil and electro-osmosis is utilized to move the contaminants back and forth through those zones until the treatment is completed. The use of zero valence iron for reductive dechlorination of aliphatic chlorinated hydrocarbons is currently under investigation by a number of research groups as a potential method of in-situ treatment of contaminated ground water. The reaction appears to involve the transfer of electrons to chloro-aliphatic compounds by the oxidation of zero valence iron to ferrous iron (Fe +2 ). Our studies have indicated that this reaction is consistent with those of corrosion, and as such, can be influenced or increased by the presence of small amounts of metals (5% by weight) such as copper, tin, silver, gold and palladium coated on the iron surface. Incomplete coverage of the iron surface with a more electropositive metal results in an open galvanic cell, which increases the oxidation of iron and facilitates and increases the concurrent reduction of trichloroethylene and other chlorinated aliphatic compounds to the corresponding alkenes and alkanes. Our results show that plating more electropositive metals onto certain iron surfaces results in approximately a factor of ten increase in the dechlorination rate of small organochlorine compounds such as TCE

Reduction potentials for 2,2'-bipyridine and 1,10-phenanthroline couples in aqueous solutions

International Nuclear Information System (INIS)

Krishnan, C.V.; Creutz, C.; Schwarz, H.A.; Sutin, N.

1983-01-01

From pulse-radiolysis studies of 2,2'-bipyridine (bpy), 1,10-phenanthroline (phen), and 4,4'-dimethyl-2,2'-bipyridine ((CH 3 ) 2 bpy) and an analysis of the pH and free-energy dependence of the rate constants for quenching of poly(pyridine)-ruthenium(II) excited states by the above aromatic amines (L) and their protonated counterparts (LH + , LH 2 2+ ), the following parameters concerning L and its one-electron reduction product L - have been deduced at 25 0 C: for L = bpy, pK/sub a/(LH 2 2+ ) = 0.05, pK/sub a/(LH + ) = 4.4, pK/sub a/(LH 2 + ) = 8.0, pK/sub a/(LH) approx. = 24, E 0 (LH 2 2+ -LH 2 + ) = -0.50 V, E 0 (LH + -LH) = -0.97 V; for L = phen, pK/sub a/(LH 2 2+ ) = -0.2, pK/sub a/(LH + ) = 4.9, pK/sub a/(LH) approx. = 24, E 0 (LH 2 2+ -LH 2 + ) = -0.47 V, E 0 (LH + -LH) = -0.85 V; and for L = (CH 3 ) 2 bpy, pK/sub a/(LH 2 2+ ) = 0.68, pK/sub a/(LH 2 + ) = 9.3, pK/sub a/(LH) approx. = 25, E 0 (LH 2 2+ -LH 2 + ) = -0.54 V, E 0 (LH + -LH) = -1.05 V. The reduction potentials and other electron-transfer parameters of these and related couples are discussed. 29 references, 7 figures, 4 tables

Major adverse cardiovascular event reduction with GLP-1 and SGLT2 agents: evidence and clinical potential

Science.gov (United States)

Røder, Michael E.

2017-01-01

Treatment of patients with type 2 diabetes is directed against treating symptoms of hyperglycemia, minimizing the risk of hypoglycemia, and the risk of microvascular and macrovascular complications. The majority of patients with type 2 diabetes die from cardiovascular or cerebrovascular disease. Future therapies should therefore focus on reducing cardiovascular morbidity in this high-risk population. Glucagon-like peptide-1 receptor agonists (GLP-1RA) and sodium-glucose co-transporter 2 inhibitors (SGLT2-i) are two drug classes with proven antihyperglycemic effect in type 2 diabetes. However, these drugs seem to have other effects such as weight reduction, low risk of hypoglycemia, and blood pressure reduction. Emerging evidence suggests pleiotropic effects, which potentially could be important in reducing cardiovascular risk. Prompted by regulatory authorities demanding cardiovascular outcome trials (CVOTs) assessing the cardiovascular safety of new antihyperglycemic drug candidates, many CVOTs are ongoing and a few of these are finalized. Somewhat surprising recent CVOTs in both drug classes have shown promising data on cardiovascular morbidity and mortality in patients with a very high risk of cardiovascular events. It is uncertain whether this is a class effect of the two drug classes, and it is yet unproven whether long-term cardiovascular benefits of these drugs can be extrapolated to populations at lower risk of cardiovascular disease. The aim of the present review is to give an overview of our current knowledge of the GLP-1RA and SGLT2-i classes, with specific focus on mechanisms of action, effects on cardiovascular risk factors and cardiovascular morbidity and mortality from the CVOTs presently available. The clinical potential of these data is discussed. PMID:29344329

Reducing air pollution from electricity-generating large combustion plants in the European Union. An assessment of potential emission reductions of NO{sub X}, SO{sub 2} and dust

Energy Technology Data Exchange (ETDEWEB)

Lodewijks, P.; Pieper, H.; Van Wortswinkel, L. [ETC partner Flemish Institute for Technological Research (VITO) (Belgium); Boyce, B.; Adams, M.; Goossens, E. [EEA, Copenhagen (Denmark)

2013-06-15

An assessment of potential emission reductions of NO{sub X}, SO{sub 2} and dust - This report presents an assessment of the hypothetical emission reduction potential of NO{sub x}, SO{sub 2} and dust from more than 1 500 of Europe's large combustion plants that operated in 2009. Emissions of these air pollutants could be significantly lower if all plants were to meet the emission limit values as set out in European Union legislation. (Author)

Research supporting potential modification of the NASA specification for dry heat microbial reduction of spacecraft hardware

Science.gov (United States)

Spry, James A.; Beaudet, Robert; Schubert, Wayne

Dry heat microbial reduction (DHMR) is the primary method currently used to reduce the microbial load of spacecraft and component parts to comply with planetary protection re-quirements. However, manufacturing processes often involve heating flight hardware to high temperatures for purposes other than planetary protection DHMR. At present, the specifica-tion in NASA document NPR8020.12, describing the process lethality on B. atrophaeus (ATCC 9372) bacterial spores, does not allow for additional planetary protection bioburden reduction credit for processing outside a narrow temperature, time and humidity window. Our results from a comprehensive multi-year laboratory research effort have generated en-hanced data sets on four aspects of the current specification: time and temperature effects in combination, the effect that humidity has on spore lethality, and the lethality for spores with exceptionally high thermal resistance (so called "hardies"). This paper describes potential modifications to the specification, based on the data set gener-ated in the referenced studies. The proposed modifications are intended to broaden the scope of the current specification while still maintaining confidence in a conservative interpretation of the lethality of the DHMR process on microorganisms.

Draft Technical Protocol: A Treatability Test for Evaluating the Potential Applicability of the Reductive Anaerobic Biological in Situ Treatment Technology (Rabitt) to Remediate Chloroethenes

National Research Council Canada - National Science Library

Morse, Jeff

1998-01-01

This draft, unvalidated protocol describes a comprehensive approach for conducting a phased treatability test to determine the potential for employing the Reductive Anaerobic Biological In Situ Treatment Technology (RABITT...

Complete Reductive Dehalogenation of Brominated Biphenyls by Anaerobic Microorganisms in Sediment

Science.gov (United States)

Bedard, Donna L.; Van Dort, Heidi M.

1998-01-01

We sought to determine whether microorganisms from the polychlorinated biphenyl (PCB)-contaminated sediment in Woods Pond (Lenox, Mass.) could dehalogenate brominated biphenyls. The PCB dechlorination specificities for the microorganisms in this sediment have been well characterized. This allowed us to compare the dehalogenation specificities for brominated biphenyls and chlorinated biphenyls within a single sediment. Anaerobic sediment microcosms were incubated separately at 25°C with 16 different mono- to tetrabrominated biphenyls (350 μM) and disodium malate (10 mM). Samples were extracted and analyzed by gas chromatography with an electron capture detector and a mass spectrometer detector at various times for up to 54 weeks. All of the tested brominated biphenyls were dehalogenated. For most congeners, including 2,6-dibromobiphenyl (26-BB) and 24-25-BB, the dehalogenation began within 1 to 2 weeks. However, for 246-BB and 2-2-BB, debromination was first observed at 7 and 14 weeks, respectively. Most intermediate products did not persist, but when 2-2-BB was produced as a dehalogenation product, it persisted for at least 15 weeks before it was dehalogenated to 2-BB and then to biphenyl. The dehalogenation specificities for brominated and chlorinated biphenyls were similar: meta and para substituents were generally removed first, and ortho substituents were more recalcitrant. However, the brominated biphenyls were better dehalogenation substrates than the chlorinated biphenyls. All of the tested bromobiphenyls, including those with ortho and unflanked meta and para substituents, were ultimately dehalogenated to biphenyl, whereas their chlorinated counterparts either were not dehalogenation substrates or were only partially dehalogenated. Our data suggest that PCB-dechlorinating microorganisms may be able to dehalogenate brominated biphenyls and may exhibit a relaxed specificity for these substrates. PMID:16349530

Evaluating the CO 2 emissions reduction potential and cost of power sector re-dispatch

Energy Technology Data Exchange (ETDEWEB)

Steinberg, Daniel C.; Bielen, David A.; Townsend, Aaron

2018-01-01

Prior studies of the U.S. electricity sector have recognized the potential to reduce carbon dioxide (CO2) emissions by substituting generation from coal-fired units with generation from under-utilized and lower-emitting natural gas-fired units; in fact, this type of 're-dispatch' was invoked as one of the three building blocks used to set the emissions targets under the Environmental Protection Agency's Clean Power Plan. Despite the existence of surplus natural gas capacity in the U.S., power system operational constraints not often considered in power sector policy analyses, such as transmission congestion, generator ramping constraints, minimum generation constraints, planned and unplanned generator outages, and ancillary service requirements, could limit the potential and increase the cost of coal-to-gas re-dispatch. Using a highly detailed power system unit commitment and dispatch model, we estimate the maximum potential for re-dispatch in the Eastern Interconnection, which accounts for the majority of coal capacity and generation in the U.S. Under our reference assumptions, we find that maximizing coal-to-gas re-dispatch yields emissions reductions of 230 million metric tons (Mt), or 13% of power sector emissions in the Eastern Interconnection, with a corresponding average abatement cost of $15-$44 per metric ton of CO2, depending on the assumed supply elasticity of natural gas.

Monitoring biodegradation of ethene and bioremediation of chlorinated ethenes at a contaminated site using compound-specific isotope analysis (CSIA).

Science.gov (United States)

Mundle, Scott O C; Johnson, Tiffany; Lacrampe-Couloume, Georges; Pérez-de-Mora, Alfredo; Duhamel, Melanie; Edwards, Elizabeth A; McMaster, Michaye L; Cox, Evan; Révész, Kinga; Sherwood Lollar, Barbara

2012-02-07

Chlorinated ethenes are commonly found in contaminated groundwater. Remediation strategies focus on transformation processes that will ultimately lead to nontoxic products. A major concern with these strategies is the possibility of incomplete dechlorination and accumulation of toxic daughter products (cis-1,2-dichloroethene (cDCE), vinyl chloride (VC)). Ethene mass balance can be used as a direct indicator to assess the effectiveness of dechlorination. However, the microbial processes that affect ethene are not well characterized and poor mass balance may reflect biotransformation of ethene rather than incomplete dechlorination. Microbial degradation of ethene is commonly observed in aerobic systems but fewer cases have been reported in anaerobic systems. Limited information is available on the isotope enrichment factors associated with these processes. Using compound-specific isotope analysis (CSIA) we determined the enrichment factors associated with microbial degradation of ethene in anaerobic microcosms (ε = -6.7‰ ± 0.4‰, and -4.0‰ ± 0.8‰) from cultures collected from the Twin Lakes wetland area at the Savannah River site in Georgia (United States), and in aerobic microcosms (ε = -3.0‰ ± 0.3‰) from Mycobacterium sp. strain JS60. Under anaerobic and aerobic conditions, CSIA can be used to determine whether biotransformation of ethene is occurring in addition to biodegradation of the chlorinated ethenes. Using δ(13)C values determined for ethene and for chlorinated ethenes at a contaminated field site undergoing bioremediation, this study demonstrates how CSIA of ethene can be used to reduce uncertainty and risk at a site by distinguishing between actual mass balance deficits during reductive dechlorination and apparent lack of mass balance that is related to biotransformation of ethene.

Accelerated remediation of pesticide-contaminated soil with zerovalent iron

Energy Technology Data Exchange (ETDEWEB)

Shea, P.J. [University of Nebraska-Lincoln, Lincoln, NE 68583-0915 (United States)]. E-mail: pshea@unl.edu; Machacek, T.A. [University of Nebraska-Lincoln, Lincoln, NE 68583-0915 (United States); Comfort, S.D. [University of Nebraska-Lincoln, Lincoln, NE 68583-0915 (United States)

2004-11-01

High pesticide concentrations in soil from spills or discharges can result in point-source contamination of ground and surface waters. Cost-effective technologies are needed for on-site treatment that meet clean-up goals and restore soil function. Remediation is particularly challenging when a mixture of pesticides is present. Zerovalent iron (Fe{sup 0}) has been shown to promote reductive dechlorination and nitro group reduction of a wide range of contaminants in soil and water. We employed Fe{sup 0} for on-site treatment of soil containing >1000 mg metolachlor, >55 mg alachlor, >64 mg atrazine, >35 mg pendimethalin, and >10 mg chlorpyrifos kg{sup -1}. While concentrations were highly variable within the windrowed soil, treatment with 5% (w/w) Fe{sup 0} resulted in >60% destruction of the five pesticides within 90 d and increased to >90% when 2% (w/w) Al{sub 2}(SO{sub 4}){sub 3} was added to the Fe{sup 0}. GC/MS analysis confirmed dechlorination of metolachlor and alachlor during treatment. Our observations support the use of Fe{sup 0} for ex situ treatment of pesticide-contaminated soil. - Capsule: Zerovalent iron promotes pesticide degradation in highly contaminated soil.

Biotransformation of monoaromatic and chlorinated hydrocarbons at an aviation-gasoline spill site

International Nuclear Information System (INIS)

Wilson, B.H.; Wilson, J.T.; Kampbell, D.H.; Bledsoe, B.E.; Armstrong, J.M.

1991-01-01

Loss of petroleum products from underground storage tanks, pipelines, and accidental spills are major sources of contamination of unsaturated soils, aquifer solids, and a shallow water table aquifer under the U.S. Coast Guard Air Station at Traverse City, MI, has acclimated to the aerobic and anaerobic transformation of monoaromatic hydrocarbons (BTX) released from an aviation gasoline spill. The aquifer also exhibits reductive dechlorination of a chlorinated solvent spill adjacent to the aviation gasoline spill. The groundwater is buffered near neutrality. The aviation gasoline plume is methanogenic and the aquifer contains enough iron minerals to support significant iron solubilization. Field evidence of both aerobic and anaerobic biotransformation of monoaromatics was confirmed by laboratory studies of aquifer material obtained from the site. In the laboratory studies, the removal of the monoaromatics in the anaerobic material was rapid and compared favorable with removal in the aerobic material. The kinetics of anaerobic removal of monoaromatics in the laboratory were similar to the kinetics at field scale in the aquifer. Biotransformation of the chlorinated solvents was not observed until late in the study, when daughter products from reductive dechlorination of the chlorinated solvents were identified by GC/MS

Fatty Acid Biosynthesis Inhibition Increases Reduction Potential in Neuronal Cells under Hypoxia

Directory of Open Access Journals (Sweden)

Stephen A Brose

2016-11-01

Full Text Available Recently, we have reported a novel neuronal specific pathway for adaptation to hypoxia through increased fatty acid (FA biosynthesis (FAS followed by esterification into lipids. However, the biological role of this pathway under hypoxia remains to be elucidated. In the presented study, we have tested our hypothesis that activation of FAS maintains reduction potential and reduces lactoacidosis in neuronal cells under hypoxia. To address this hypothesis, we measured the effect of FAS inhibition on NADH2+/NAD+ and NADPH2+/NADP+ ratios, and lactic acid levels in neuronal SH-SY5Y cells exposed to normoxic and hypoxic conditions. FAS inhibitors, TOFA (inhibits Acetyl-CoA carboxylase and cerulenin (inhibits FA synthase, increased NADH2+/NAD+ and NADPH2+/NADP+ ratios under hypoxia. Further, FAS inhibition increased lactic acid under both normoxic and hypoxic conditions, and caused cytotoxicity under hypoxia but not normoxia. These results indicate that FA may serve as hydrogen acceptors under hypoxia, thus supporting oxidation reactions including anaerobic glycolysis. These findings may help to identify a radically different approach to attenuate hypoxia related pathophysiology in the nervous system including stroke.

Fatty Acid Biosynthesis Inhibition Increases Reduction Potential in Neuronal Cells under Hypoxia.

Science.gov (United States)

Brose, Stephen A; Golovko, Svetlana A; Golovko, Mikhail Y

2016-01-01

Recently, we have reported a novel neuronal specific pathway for adaptation to hypoxia through increased fatty acid (FA) biosynthesis followed by esterification into lipids. However, the biological role of this pathway under hypoxia remains to be elucidated. In the presented study, we have tested our hypothesis that activation of FA synthesis maintains reduction potential and reduces lactoacidosis in neuronal cells under hypoxia. To address this hypothesis, we measured the effect of FA synthesis inhibition on [Formula: see text]/NAD + and [Formula: see text]/NADP + ratios, and lactic acid levels in neuronal SH-SY5Y cells exposed to normoxic and hypoxic conditions. FA synthesis inhibitors, TOFA (inhibits Acetyl-CoA carboxylase) and cerulenin (inhibits FA synthase), increased [Formula: see text]/NAD + and [Formula: see text]/NADP + ratios under hypoxia. Further, FA synthesis inhibition increased lactic acid under both normoxic and hypoxic conditions, and caused cytotoxicity under hypoxia but not normoxia. These results indicate that FA may serve as hydrogen acceptors under hypoxia, thus supporting oxidation reactions including anaerobic glycolysis. These findings may help to identify a radically different approach to attenuate hypoxia related pathophysiology in the nervous system including stroke.

Modified Feddes type stress reduction function for modeling root water uptake: Accounting for limited aeration and low water potential

Science.gov (United States)

Peters, Andre; Durner, Wolfgang; Iden, Sascha C.

2017-04-01

Modeling water flow in the soil-plant-atmosphere continuum with the Richards equation requires a model for the sink term describing water uptake by plant roots. Despite recent progress in developing process-based models of water uptake by plant roots and water flow in aboveground parts of vegetation, effective models of root water uptake are widely applied and necessary for large-scale applications. Modeling root water uptake consists of three steps, (i) specification of the spatial distribution of potential uptake, (ii) reduction of uptake due to various stress sources, and (iii) enhancement of uptake in part of the simulation domain to describe compensation. We discuss the conceptual shortcomings of the frequently used root water uptake model of Feddes and suggest a simple but effective improvement of the model. The improved model parametrizes water stress in wet soil by a reduction scheme which is formulated as function of air content where water stress due to low soil water potential is described by the original approach of Feddes. The improved model is physically more consistent than Feddes' model because water uptake in wet soil is limited by aeration which is a function of water content. The suggested modification is particularly relevant for simulations in heterogeneous soils, because stress parameters are uniquely defined for the entire simulation domain, irrespective of soil texture. Numerical simulations of water flow and root water uptake in homogeneous and stochastic heterogeneous soils illustrate the effect of the new model on root water uptake and actual transpiration. For homogeneous fine-textured soils, root water uptake never achieves its potential rate. In stochastic heterogeneous soil, water uptake is more pronounced at the interfaces between fine and coarse regions which has potential implications for plant growth, nutrient uptake and depletion.

Scenario analysis of energy saving and CO_2 emissions reduction potentials to ratchet up Japanese mitigation target in 2030 in the residential sector

International Nuclear Information System (INIS)

Wakiyama, Takako; Kuramochi, Takeshi

2017-01-01

This paper assesses to what extent CO_2 emissions from electricity in the residential sector can be further reduced in Japan beyond its post-2020 mitigation target (known as “Intended Nationally Determined Contribution (INDC)”). The paper examines the reduction potential of electricity demand and CO_2 emissions in the residential sector by conducting a scenario analysis. Electricity consumption scenarios are set up using a time-series regression model, and used to forecast the electricity consumption patterns to 2030. The scenario analysis also includes scenarios that reduce electricity consumption through enhanced energy efficiency and energy saving measures. The obtained results show that Japan can reduce electricity consumption and CO_2 emissions in the residential sector in 2030 more than the Japanese post-2020 mitigation target indicates. At the maximum, the electricity consumption could be reduced by 35 TWh, which contributes to 55.4 MtCO_2 of emissions reduction in 2030 compared to 2013 if the voluntarily targeted CO_2 intensity of electricity is achieved. The result implies that Japan has the potential to ratchet up post-2020 mitigation targets discussed under the Paris Agreement of the United Nations Framework Convention on Climate Change (UNFCCC). - Highlights: • Further reduction of electricity consumption is possible beyond Japan's post-2020 mitigation target. • Energy saving efforts by households and incentives to reduce electricity demands are required. • Improvement of CO_2 intensity from electricity is a key factor in the reduction of CO_2 emissions.

Estimate of the technological costs of CO{sub 2} emission reductions in passenger cars. Emission reduction potentials and their costs; Technikkostenschaetzung fuer die CO{sub 2}-Emissionsminderung bei Pkw. Emissionsminderungspotenziale und ihre Kosten

Energy Technology Data Exchange (ETDEWEB)

Herbener, Reinhard; Jahn, Helge; Wetzel, Frank [Umweltbundesamt, Dessau-Rosslau (Germany). Fachgebiet I 3.2 - Schadstoffminderung und Energieeinsparung im Verkehr

2008-08-06

The Federal Environmental Office intended to identify the current fuel consumption reduction potential and the cost of efficiency-enhancing measures on passenger cars. For this purpose, an extensive bibliographic search was carried out, and experts from research institutes and from the automobile supplier industry were asked for their opinion. The results are published in table form. (orig.)

Investigating the risk reduction potential of disaster insurance across Europe

NARCIS (Netherlands)