Abstract  In this paper we present the remediation possibilities of a trichloroethylene contaminated site of a former metalworking plant in Hungary, where high TCE concentration (150 mu g/L to 35.000 mu g/L) was detected in the groundwater Lab-scale experiments were performed to compare the potential bioremediation technology-alternatives eg.: enhanced biodegradation; pump & treat by UV irradiation (photodegradation); in situ chemical oxidation (ISCO) applying different oxidants (KMnO4, Na2S2O8 and H2O2). The lab-scale experiments showed in all cases reduction of the TCE-concentration of the water Comparing the removal efficacy and concerning the time requirement ISCO was the most effective in laboratory studies.

Abstract  Clay minerals were used as template-supporting matrices to synthesize nanoscaled zero-valent iron (ZVI). The size and distribution of the synthesized ZVI particles were related to clay structure, origin of negative charges, and surface charge density. The average particle size ranged from 0.5 nm (perpendicular to the clay layers) for the ZVI intercalated in smectite interlayers, to I to 2 fun for the ZVI residing on kaolinite and pyrophyllite surfaces, and 5 nm for the ZVI formed on illite and smectite external surfaces. The reactivity of the ZVI was evaluated based on the rate and extent of reduction of nitrobenzene to aniline. The results revealed that the reactivity of ZVI decreased with increasing particle size, and the ZVI intercalated in smectite clay manifested the highest reactivity. The reaction efficiency of the ZVI associated with smectite clay was estimated to be as high as 90% based on the equivalency of electron transfer from ZVI to nitrobenzene. The great reactivity and high efficiency of smectite-intercalated ZVI, along with many other advantageous properties of smectite (e.g., a layer structure that protects ZVI from aggregation and oxidation), warrants its potential utilization in the development of in situ remediation and treatment technologies for inorganic and organic contaminants.

Abstract  Inconsistent epidemiological findings, debate over interpretation, and extrapolation of findings from animal studies to humans have produced uncertainty surrounding the carcinogenicity of trichloroethylene (TCE) exposure in occupational settings. We updated meta-analyses of published case-control and cohort studies exploring occupational TCE exposure and kidney cancer risk, incorporating new analytical results from three recently published cohort studies and a case-control study. PubMed MEDLINE was searched for studies published from 1950 to 2011 assessing occupational exposure to chlorinated solvents, degreasers or TCE. All cohort (N=15) and case-control (N=13) studies included in analyses were stratified by assessment of occupational exposure to TCE specifically and to any chlorinated solvent. Significantly elevated summary estimates were observed for cohort studies (relative risk (RR) 1.26, 95% CI 1.02 to 1.56; p heterogeneity=0.65), case-control studies (OR 1.35, 95% CI 1.17 to 1.57; p heterogeneity=0.41), and cohort and case-control studies combined (RR 1.32, 95% CI 1.17 to 1.50, p heterogeneity=0.63) that specifically assessed TCE exposure after excluding outlier studies that contributed to heterogeneity. Non-significantly elevated summary estimates were generally observed for studies of workers exposed to chlorinated solvents but who were not assessed for TCE specifically. Regardless of study design, significant and stronger estimates were only observed in studies specifically assessing occupational exposure to TCE. Estimates were lower in studies assessing occupational exposure to chlorinated solvents. This updated meta-analysis supports an association between occupational TCE exposure and kidney cancer and provides evidence that exposure misclassification may weaken estimates assessing exposure to the broader class of chlorinated solvents.

Abstract  Humic acid (HA) comprises a significant fraction of natural organic matter (NOM), greatly influencing the performance of water and wastewater treatment processes. HA is expected to significantly affect the reactivity of nano-scale zero-valent iron (NZVI), which is receiving increasing attention due to its high reactivity. The effects of HA on nitrate reduction by NZVI were investigated to evaluate the potential of NZVI in practical applications. HA was characterized to identify the mechanism whereby HA affects. Nitrate reduction was enhanced at low HA concentration, but inhibited as HA concentration increased. HA decreased to reach a plateau and considerable amount of Fe3+ was detected when HA was present in dissolved phase. The increase in the degree of condensation of HA was verified by UV-vis spectroscopy, fluorescence spectroscopy, and size exclusion chromatography. Fourier transform infrared spectra confirmed that the Fe3+-HA complexes were formed in both the dissolved and solid fractions, without coexisting metal ions. The HA aggregation on NZVI and discrete HA macroaggregates were observed by transmission electron microscopy. The results suggest that HA induces complex effects on NZVI reactivity by improving iron dissolution, inhibiting readsorption of released iron, enhancing electron transfer, and inhibiting nitrate mass transfer via forming HA accumulation. It indicates that the clogging by aggregated NOM should be considered when NZVI is used for groundwater treatment or in combination with porous materials.

Abstract  Multicomponent nanoparticles containing two or more different types of functionalities show unique physical and chemical properties, leading to significantly enhanced performance. In this study, we have developed a new one-pot method to prepare Fe/FeS nanoparticles using dithionite at room temperature. The FeS precipitates on the Fe surface are formed by the interaction between dissolved iron species and hydrogen sulfide, one of the decomposition products of dithionite in solution. The resulting Fe/FeS nanoparticles have high surface area, good electrical conductivity, and strong magnetic responsivity. In addition, the Fe/FeS shows a much higher reactivity toward contaminants than the pure Fe nanoparticles. The above synthesized nanoparticles are successfully applied for the rapid removal of trichloroethylene (TCE) from water. The study reveals that Fe/FeS nanoparticles are a promising candidate for the efficient removal of pollutants.

Abstract  Using probe-type ultrasonic irradiation, the dissolution of ethylene vinyl acetate (EVA) in photovoltaic (PV) modules was investigated in various organic solvents, including O-dichlorobenzene (O-DCB), trichloroethylene (TCE), benzene, and toluene. The experiments were carried out at different solvent concentrations, temperatures, ultrasonic powers, and irradiation times. In the presence of 450 W of ultrasonic radiation, EVA in PV modules was completely dissolved in 3 M toluene at 70 degree C; however, the PV cell was damaged due to the swelling of EVA. At an irradiation power of 900 W, the dissolution ratio was greater than that obtained at a power of 450 W, and the effects of ultrasonic power were confirmed at 70 degree C. In TCE and benzene, a decrease in the dissolution of EVA was observed as the temperature increased from 55 to 70 degree C due to the occurrence of pyrolysis and pyrolytic reactions, which were attributed to the low boiling point and ultrasonic degradation of the solvent, respectively. Except when O-DCB was used, cracks were observed in the PV cell, and the complete dissolution of EVA was attained. Thus, O-DCB is the most effective solvent for recovering PV cells via ultrasonic irradiation.

Abstract  The compositions of bacterial groundwater communities of three sites contaminated with chlorinated ethenes were analyzed by pyrosequencing their 16S rRNA genes. For each location, the entire and the active bacterial populations were characterized by independent molecular analysis of the community DNA and RNA. The sites were selected to cover a broad range of different environmental conditions and contamination levels, with tetrachloroethene (PCE) and trichloroethene (TCE) being the primary contaminants. Before sampling the biomass, a long-term monitoring of the polluted locations revealed high concentrations of cis-1,2-dichloroethene (cDCE) and vinyl chloride (VC), which are toxic by-products of the incomplete bacterial degradation of PCE and TCE. The applied pyrosequencing technique enabled known dechlorinators to be identified at a very low detection level (<0.25%) without compromising the detailed analysis of the entire bacterial community of these sites. The study revealed that only a few species dominated the bacterial communities, with Albidiferax ferrireducens being the only highly prominent member found at all three sites. Only a limited number of OTUs with abundances of up to 1% and high sequence identities to known dechlorinating microorganisms were retrieved from the RNA pools of the two highly contaminated sites. The dechlorinating consortium was likely to be comprised of cDCE-assimilating bacteria (Polaromonas spp.), anaerobic organohalide respirers (mainly Geobacter spp.), and Burkholderia spp. involved in cometabolic dechlorination processes, together with methylotrophs (Methylobacter spp.). The deep sequencing results suggest that the indigenous dechlorinating consortia present at the investigated sites can be used as a starting point for future bioremediation activities by stimulating their anaerobic and aerobic chloroethene degradation capacities (i.e. reductive dechlorination, and metabolic and cometabolic oxidation).

Abstract  Amphiphilic polysiloxane graft copolymers (APGCs) were used as a delivery vehicle for nanoscale zerovalent iron (NZVI). The APGCs were designed to enable adsorption onto NZVI surfaces via carboxylic acid anchoring groups and polyethylene glycol (PEG) grafts were used to provide dispersibility in water. Degradation studies were conducted with trichloroethylene (TCE) as the model contaminant. TCE degradation rate with APGC-coated NZVI (CNZVI) was determined to be higher as compared to bare NZVI. The surface normalized degradation rate constants, k(SA) (Lm(2-) h(-1)), for TCE removal by CNZVI and bare NZVI ranged from 0.008 to 0.0760 to 007-0.016, respectively. Shelf life studies conducted over 12 months to access colloidal stability and 6 months to access TCE degradation indicated that colloidal stability and chemical reactivity of CNZVI remained more or less unchanged. The sedimentation characteristics of CNZVI under different ionic strength conditions (0-10 mM) did not change significantly. The steric nature of particle stabilization is expected to improve aquifer injection efficiency of the coated NZVI for groundwater remediation.

Abstract  The hydrogeologic framework of fractured sedimentary bedrock at the former Naval Air Warfare Center (NAWC),1 Trenton, New Jersey, a trichloroethylene (TCE)-contaminated site in the Newark Basin, is developed using an understanding of the geologic history of the strata, gamma-ray logs, and rock cores. NAWC is the newest field research site established as part of the U.S. Geological Survey Toxic Substances Hydrology Program, Department of Defense (DoD) Strategic Environmental Research and Development Program, and DoD Environmental Security Technology Certification Program to investigate contaminant remediation in fractured rock.

Abstract  Degradation of trichloroethylene (TCE) by a modified Fenton reaction was investigated in aqueous solution. Fenton reaction can be significantly enhanced in the presence of Fe(II) chelated by cross-linked chitosan (CS) with glutaraldehyde (GLA) at neutral pH. A remarkable oxidative degradation of TCE (1.838ha1) was observed in the modified Fenton system with Fe(II)-CS/GLA (10mM and 2gLa1, respectively) and H2O2 (318mM), while no significant degradation (0.005ha1) was observed in the classic Fenton reaction system with Fe(II) (10mM) and H2O2 (318mM) at pH 7 in 5h. The kinetic rate constants for the degradation of TCE in the modified Fenton system was dependent on the initial suspension pH, Fe(II) loading, CS/GLA dosage, and concentration of H2O2. We observed the formation of surface Fe(II)-CS/GLA complex using microscopic analyses and identified Fe oxidation (Fe(II) to Fe(III)) coupled with H2O2 reduction on the Fe(II)-CS/GLA surfaces during the modified Fenton reaction.

Abstract  Flower-like mesoporous Mn-doped CeO2 microspheres with three-dimensional (3D) hierarchical structures were successfully prepared by a hydrothermal method with the aid of glucose and acrylic acid and subsequent particular thermal treatment, and characterized by SEM, XRD, N-2 adsorption/desorption, H-2-TPR, XPS, Raman spectra and so on. The results show that the atomic ratios of Mn/(Ce + Mn) in the Ce-Mn-O samples as well as their morphologies affect obviously their catalytic performances for low-temperature catalytic combustion of trichloroethylene (TCE). These flower-like Ce-Mn-O microspheres have not only very excellent activity but also high stability, compared with pure flower-like CeO2 microspheres or bulk Ce-Mn-O samples. The flower-like sample with atomic ratio of Mn/(Ce + Mn) of 0.21 exhibits the best activity, for instance, T-50 (the temperature for 50% conversion of ICE) is as low as 87 degrees C, showing much higher catalytic activity than the sample prepared by a co-precipitation or sol-gel method. High surface area, high oxygen mobility and rich surface active oxygen species are responsible for the high catalytic performance of flower-like Mn-doped CeO2 microspheres, compared with general Ce-Mn-O mixed oxides. (C) 2010 Elsevier B.V. All rights reserved.

Abstract  1,4-Dioxane biodegradation was investigated in microcosms prepared with groundwater and soil from an impacted site in Alaska. In addition to natural attenuation conditions (i.e., no amendments), the following treatments were tested: (a) biostimulation by addition of 1-butanol (a readily available auxiliary substrate) and inorganic nutrients; and (b) bioaugmentation with Pseudonocardia dioxanivorans CB1190, a well-characterized dioxane-degrading bacterium, or with Pseudonocardia antarctica DVS 5a1, a bacterium isolated from Antarctica. Biostimulation enhanced the degradation of 50 mg L(-1) dioxane by indigenous microorganisms (about 0.01 mg dioxane d(-1) mg protein(-1)) at both 4 and 14 degrees C, with a simultaneous increase in biomass. A more pronounced enhancement was observed through bioaugmentation. Microcosms with 50 mg L(-1) initial dioxane (representing source-zone contamination) and augmented with CB1190 degraded dioxane fastest (0.16 +/- 0.04 mg dioxane d(-1) mg protein(-1)) at 14 degrees C, and the degradation rate decreased dramatically at 4 degrees C (0.021 +/- 0.007 mg dioxane d(-1) mg protein(-1)). In contrast, microcosms with DVS 5a1 degraded dioxane at similar rates at 4 degrees C and 14 degrees C (0.018 +/- 0.004 and 0.015 +/- 0.006 mg dioxane d(-1) mg protein(-1), respectively). DVS 5a1 outperformed CB1190 when the initial dioxane concentration was low (500 microg L(-1), which is representative of the leading edge of plumes). This indicates differences in competitive advantages of these two strains. Natural attenuation microcosms also showed significant degradation over 6 months when the initial dioxane concentration was 500 microg L(-1). This is the first study to report the potential for dioxane bioremediation and natural attenuation of contaminated groundwater in sensitive cold-weather ecosystems such as the Arctic.

Abstract  The reactivity of nanoscale zerovalent iron (NZVI) on removing chlorophenols (2-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol and pentachlorophenol) was remarkably enhanced by using a hydrophobic support of organobentonite (CTMA-Bent), namely the bentonite modified with organic cetyltrimethylammonium (CTMA) cations. The complete dechlorination of chlorophenols and total conversion into phenol using this novel NZVI/CTMA-Bent combination was observed in batch experiments. The kinetic studies suggested that the reduction of chlorophenols by NZVI was accelerated due to the enhanced adsorption onto CTMA-Bent, which facilitated the mass transfer of chlorophenols from aqueous to iron surface. The enhanced reduction rate by NZVI/CTMA-Bent was positively related to the hydrophobicity of chlorophenols, and an increasing linear relationship was obtained between the relative enhancement on reaction rate constants (k(2)/k(1)) and logK(ow) values of chlorophenols. XPS results suggested there were fewer precipitates of ferric (hydro)xides formed on the surface of NZVI/CTMA-Bent, which may also lead to the improved reactivity and repetitive usability of NZVI/CTMA-Bent on removing chlorophenols. (c) 2013 Elsevier Ltd. All rights reserved.

Abstract  Oxidation of p-chloroaniline (PCA) by persulfate (PS) performed with a novel supported copper oxidate catalyst in an aqueous solution at ambient temperature (i.e. 20 degrees C) was investigated in this study. This study focused mainly on determining the proportions of heterogeneous catalysis in the copper oxidate/PS combined system. There existed a more remarkable effect on the degradation of PCA in the copper oxidate/PS combined system than in the Cu2+/PS or only PS system. The effects of copper oxidate dosage, persulfate concentration, and initial solution pH on the oxidation of PCA were also evaluated. Higher copper oxidate dosage and persulfate concentration resulted in higher PCA degrading rates, the optimal initial pH was determined as 7.0. Moreover, the change in the degradation of PCA by pH was also investigated in terms of the contribution of dissolved copper ion in leaching solution. We inferred that homogeneous catalysis was of increasing importance and the copper ion dissolved from the copper oxidate was regarded as the key factor activating the persulfate under acidic conditions (pH 3.0), heterogeneous catalysis played the main role in the oxidation of PCA at pH 5-7. However, both heterogeneous catalysis and base-activated persulfate contributed to the degradation of PCA under alkaline conditions (pH 11). In addition, the radical mechanism was studied and three radical scavengers (phenol, methanol (MA) and Tert-butanol (TBA)) were used to determine the kind of major active areas taking part in the PCA degradation at pH 7. (C) 2012 Elsevier B.V. All rights reserved.

Abstract  Flash pyrolysis of p-PEG (pure PEG) and PEG/NiFe (mixture of PEG and nano Ni-Fe alloy) was carried out in argon atmosphere, aiming to study the effect of nano Ni-Fe alloy on the behavior and mechanism of PEG pyrolysis. A special combinational system was designed to perform pyrolysis experiment and collect pyrolysis products, while GC/MS was employed to identify the products. The experimental results showed that nano Ni-Fe alloy changed not only the relative contents but also the series of PEG pyrolysis products. It was interesting that all of 15 possible series of PEG pyrolysis products in theory were detected from p-PEG and/or PEG/NiFe pyrolysis in the present work. Six product series disappeared and two new product series were detected after adding nano Ni-Fe alloy. Based on quantitative analysis of the end groups of products, the effect of nano Ni-Fe alloy on PEG pyrolysis process as well as the mechanism was discussed. Ni and Fe played quite different roles in the process of PEG pyrolysis. Fe made end group -O-CH2-CH3, -O-CH=CH2, -OH and -O-CH3 transfer to -O-CH2-CHO by inducing hydrogen transfer and O-C bond cleavage; Ni made -O-CH=CH2 transfer to -O-CH2-CH3 by inducing hydrogenation. (C) 2012 Elsevier B.V. All rights reserved.

Abstract  Toluene dioxygenase (tod) is a multicomponent enzyme system in Pseudomonas putida F1. Tod can mediate the degradation of Trichloroethylene (TCE), a widespread pollutant. In this study, we try to explore the TCE-regulated tod expression by using real-time qRT-PCR. The minimal culture media were supplemented with glucose, toluene, or a mixture of glucose/toluene respectively as carbon and energy sources. The TCE was injected into each medium after a 12-hour incubation period. The TCE injection severely affected bacterial growth when cultured with toluene or toluene/glucose mixtures. The cell density dropped 61 % for bacteria growing in toluene and 36 % for bacteria in the glucose/toluene mixture after TCE injection, but the TCE treatment had little effect on bacteria supplied with glucose alone. The decrease in cell number was caused by the cytotoxicity of the TCE metabolized by tod. The results from the real-time qRT-PCR revealed that TCE was capable of inducing tod expression in a toluene-dependent manner and that the tod expression level increased 50 times in toluene and 3 times in the toluene/glucose mixture after 6 hours of TCE treatment. Furthermore, validation of the rpoD gene as a reference gene for P. putida F1 was performed in this study, providing a valuable foundation for future studies to use real-time qRT-PCR in the analysis of the P. putida F1 strain.

Abstract  In this study, aged (iron oxide coated) Fe(0) was applied to the degradation of trichloroethylene (TCE) in seawater. It was found that while the aged Fe(0) was inactive with regard to TCE degradation in Milli-Q water, more than 95% of the TCE present was degraded in real and synthetic seawater solutions after exposure to aged Fe(0) for 21 days. Results with individual salts from the synthetic seawater revealed that no significant TCE degradation was observed in the presence of Na2SO4, CaCl2, and NaHCO3. Partial TCE degradation (28.4%) was observed in 500 mM NaCl after 21 days, while a similar extent of degradation to that found in the seawater solutions was observed in 50 mM solutions of magnesium salts (MgCl2 and MgSO4). Results of open circuit potential analysis suggested that the Fe(0) corrosion potential was not a key determinant of extent of TCE reduction since the corrosion potential decreased to levels similar to that of Fe(0)/Fe(2+) in the presence of all salts examined. Lower final pH values and higher dissolved Fe(II) concentrations were observed in the presence of magnesium salts compared to other salts. Formation of the surface complex >FeOMg(+) was identified as being critical to protonation of surface sites, reductive dissolution of the passivating Fe(III) oxyhydroxide layer coating the underlying Fe(0) and enhancement in extent of TCE reduction. These findings provide insight into the molecular-scale mechanism of depassivation of aged Fe(0) by inorganic salts with particular implications for the Fe(0)-mediated degradation of contaminants in saline natural waters such as seawater and saline groundwaters.

Abstract  Density measurements are frequently associated to specific requirements to evaluate the quality of a process or to determine mass and/or volume of the material. Certified reference liquids can be used to assure metrological traceability of density measurements to the SI with uncertainty lower than 0.005%. This paper presents the new approach of INRIM to set density standards. The procedure involved accurate density determinations of some reference liquids which were supported by gas-chromatography coupled with mass spectrometry (GC-MS) in order to assess their homogeneity and short-term stability. GC-MS analyses on tetrachloroethylene and trichloroethylene were carried out before and after density measurements. Samples that had undergone to variations in density value showed also different gas-chromatographic profiles. In the same time, samples that had not undergone to density variations kept similar gas-chromatographic profiles. The results support the approach of combining independent methods in order to set physico-chemical properties of reference materials.

Abstract  The present study described the degradation behavior of tetrabromobisphenol A (TBBPA) in Fe-Ag suspension solutions under ultrasonic radiation (US). The Fe-Ag bimetallic nanoparticles with core-shell structure were successfully synthesized by reduction and deposition of Ag on nanoscale Fe surface, and were further characterized by BET, XRD, TEM, SEM, X-ray fluorescence and X-ray photo-electron spectroscopy. The results revealed that the displacement plating produced a non-uniform overlayer of Ag additive on iron; the as-synthesized bimetallic nanoparticles were spherical with diameters of 20100 nm aggregated in the form of chains. Batch studies demonstrated that the TBBPA (2 mg L(-1)) was completely degraded in 20 min over Fe-Ag nanoparticles, which has higher degradation efficiency than Fe nanoparticles under US. The effects of Fe-Ag bimetallic nanoparticles loading, initial TBBPA concentration, pH of the solution, Ag loading and temperature on the reduction efficiency of TBBPA under US were investigated. The complete reduction of TBBPA in 20 min was determined selectively under the conditions of pH (pH = 6.0 +/- 0.5), Ag loading (1 wt.%) at 30 degrees C over the fabricated Fe-Ag nanoparticles. Additionally, the major intermediates identified by LC-MS technique were tri-BBPA, di-BBPA, mono-BBPA and BPA and the degradation mechanism was also proposed. Crown Copyright (C) 2010 Published by Elsevier Ltd. All rights reserved.

Abstract  Chlorinated volatile organic compounds (CVOCs) are hazardous and potent environmental pollutants. Catalytic combustion has been regarded as one of the most promising technologies to eliminate CVOCs emissions. CH2Cl2 is difficult to be oxidized among CVOCs. A catalyst with high activity for CVOCs oxidation is desirable. In this paper, CrOx/Al2O3 catalysts with different Cr contents were prepared using a deposition-precipitation method and tested for CH2Cl2 oxidation. The highest activity was obtained over the catalyst with 18% Cr content, with a complete oxidation of CH2Cl2 at 350 degrees C. Characterization results indicated that both high oxidation state Cr species (Cr(VI) species) and crystalline Cr2O3 existed in the CrOx/Al2O3 catalysts, and the average valence of Cr species in the catalysts decreased with Cr content. It was found that the reaction rate for CH2Cl2 oxidation increased with increasing average valence of Cr, which indicated that high oxidation state Cr species were probably the active phase for the reaction. (C) 2011 Elsevier B.V. All rights reserved.

Abstract  Two things are needed for any technology to be suitable for use in the industry, viz. 1. Technical feasibility and 2. Economical feasibility. The use of ultrasound for waste water treatment has been shown to be technically feasible by numerous reports in the literature over the years. But there are hardly any exhaustive reports which address the issue of economical feasibility of the use of ultrasound for waste water treatment on industrial scale. Hence an attempt was made to estimate the cost for the waste water treatment using ultrasound. The costs have been calculated for 1000 L/min capacity treatment plant. The costs were calculated based upon the rate constants for pollutant degradation. The pollutants considered were phenol, trichloroethylene (TCE) and reactive azo dyes. Time required for ninety percent degradation of pollutant was taken as the residence time. The amount of energy required to achieve the target degradation was calculated from the energy density (watt/ml) used in the treatability study. The cost of treatment was calculated by considering capital cost and operating cost involved for the waste water treatment. Quotations were invited from vendors to ascertain the capital cost of equipments involved and operating costs were calculated based on annual energy usage. The cost was expressed in dollars per 1000 gallons of waste water treated. These treatment costs were compared with other established Advanced Oxidation Process (AOP) technologies. The cost of waste water treatment for phenol was in the range of $89 per 1000 gallons for UV/US/O(3) to $15,536 per 1000 gallons for US alone. These costs for TCE were in the range of $25 per 1000 gallons to $91 for US+UV treatment and US alone, respectively. The cost of waste water treatment for reactive azo dyes was in the range of $65 per 1000 gallon for US+UV+H(2)O(2) to $14,203 per 1000 gallon for US alone. This study should help in quantifying the economics of waste water treatment using ultrasound on industrial scale. We strongly believe that this study will immensely help the researchers working in the area of applications of ultrasound for waste water treatment in terms of where the technology stands today as compared to other available commercial AOP technologies. This will also help them think for different ways to improve the efficiency of using ultrasound or search for other ways of generating cavitation which may be more efficient and help reduce the cost of treatment in future.

Abstract  I test the level of information regarding possible groundwater contamination in the residential real estate market in Washington County, Minnesota. An approximately seven square-mile trichloroethylene plume has affected hundreds of households' water supplies since at least 1988 in the region. I find that homeowners were initially well-informed by market forces, but were later somewhat misinformed by government actions regarding the potential of water contamination from the plume. A disclosure law passed in 2003 may have added new, low-cost, and imperfect information to the market that could explain the change in informational awareness.

Abstract  Iron and iron oxide nanoparticles (NPs) are finding wide applications for the remediation of various toxic chloro-organic compounds (such as trichloroethylene, TCE), via reductive and oxidative processes. In this study, Fe NPs (30-50 nm) are synthesized by reduction from ferric ions immobilized (by ion exchange) on a platform (two types of sulfonated silica particles), in order to prevent the NP agglomeration. Next, the Fe NPs are oxidized and their effectiveness for the oxidative dechlorination of TCE via the heterogeneous decomposition of hydrogen peroxide to OH• on the surface of the iron oxide NPs was demonstrated. For the reductive approach, the use of ascorbic acid as a "green" reducing agent in conjunction with a secondary metal (Pd) inhibits NP oxidation and agglomeration through surface adsorbed species. The Fe/Pd NPs have been successfully applied for the dechlorination of TCE (k(SA), surface-area normalized reaction rate, = 8.1 ×10(-4) L/m(2)h).

Abstract  Hydrotalcite derived NiMgAl mixed oxide (NiHT) catalysts with different NiMgAl molar ratio were synthesized and tested in the selective gas-phase hydrodechlorination of trichloroethylene to ethylene. The mixed oxide was further promoted by Pd in order to obtain Pd/NiHT catalysts. The catalysts performances for hydrodechlorination of trichloroethylene depend on the Ni/Mg/Al molar ratio, reduction temperature, and method of noble metal incorporation. The main products obtained were ethylene, methane, ethane, chloroethylene and traces of dichloroethylene. The higher the Ni amount in the NiHT support was, the higher were the catalytic activity and ethylene selectivity. Introduction of Pd increases the catalytic activity. Application of higher reduction temperatures improved the selectivity towards ethylene formation due to an increase in the concentration of surface metallic Ni. A better Pd-Ni surface interaction was obtained by impregnation of Pd on a previously reduced (823 K) NiHT catalyst, resulting in higher ethylene selectivity (80%). The higher selectivity was associated to metallic Ni promoted by a Pd-Ni alloy, which was detected by HRTEM.

Abstract  Tritium-helium groundwater dating was carried out in a trichloroethylene (TCE)-contaminated valley-fill aquifer system in Quebec, Canada, where a numerical groundwater flow model was developed. Forty seven discrete groundwater and dissolved gas samples were obtained along two flow paths originating from known TCE source zones whose related plumes converge down gradient to form a single plume. Sampling points in monitoring wells were projected onto vertical sections showing particle tracks along the two flow paths. At these points, simulated advective ages obtained from particle tracking were matched to tritium-helium ages using different porosity values; the best match was 0.35. Ages were also obtained above and below a prodeltaic silty aquitard in a portion of the aquifer where some source zones are located, which provide groundwater and TCE transit times through the aquitard as well as a mean vertical hydraulic conductivity that agrees with previous estimates used in the model. In certain locations, anomalously old ages associated with high terrigenic (super 4) He indicate areas where groundwater from the underlying proglacial unit flows upward into the deltaic sand aquifer through aquitard windows. Upflow locations correspond with increased TCE concentrations, suggesting significant TCE provenance through the proglacial unit originating from a previously unrecognized TCE source zone. Copyright 2010 Springer-Verlag