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Contaminated Groundwater (contaminated + groundwater)
Selected AbstractsEvolution of a chlorobenzene degradative pathway among bacteria in a contaminated groundwater mediated by a genomic island in RalstoniaENVIRONMENTAL MICROBIOLOGY, Issue 3 2003Tina Andrea Müller Summary The genetic structure of two Ralstonia spp., strain JS705 and strain JS745, isolated from the same groundwater aquifer, was characterized with respect to the degradation capacities for toluene and chlorobenzene degradation. Cosmid library construction, cloning, DNA sequencing and mating experiments indicated that the genes for chlorobenzene degradation in strain JS705 were a mosaic of the clc genes, previously described for Pseudomonas sp. strain B13, and a 5 kb fragment identical to strain JS745. The 5 kb fragment identical to both JS705 and JS745 was flanked in JS705 by one complete and one incomplete insertion (IS) element. This suggested involvement of the IS element in mobilizing the genes from JS745 to JS705, although insertional activity of the IS element in its present configuration could not be demonstrated. The complete genetic structure for chlorobenzene degradation in strain JS705 resided on a genomic island very similar to the clc element (Ravatn, R., Studer, S., Springael, D., Zehnder, A.J., van der Meer, J.R. 1998. Chromosomal integration, tandem amplification, and deamplification in Pseudomonas putida F1 of a 105-kilobase genetic element containing the chlorocatechol degradative genes from Pseudomonas sp. strain B13. J Bacteriol 180: 4360,4369). The unique reconstruction of formation of a metabolic pathway through the activity of IS elements and a genomic island in the chlorobenzene-degrading strain JS705 demonstrated how pathway evolution can occur under natural conditions in a few ,steps'. [source] Molecular diversity and characterization of nitrite reductase gene fragments (nirK and nirS) from nitrate- and uranium-contaminated groundwaterENVIRONMENTAL MICROBIOLOGY, Issue 1 2003Tingfen Yan Summary Nitrate-contaminated groundwater samples were analysed for nirK and nirS gene diversity. The samples differed with respect to nitrate, uranium, heavy metals, organic carbon content, pH and dissolved oxygen levels. A total of 958 nirK and 1162 nirS clones were screened by restriction fragment length polymorphism (RFLP) analysis: 48 and 143 distinct nirK and nirS clones, respectively, were obtained. A single dominant nirK restriction pattern was observed for all six samples and was 83% identical to the Hyphomicrobium zavarzinii nirK gene. A dominant nirS pattern was observed for four of the samples, including the background sample, and was 95% identical to the nirS of Alcaligenes faecalis. Diversity indices for nirK and nirS sequences were not related to any single geochemical characteristic, but results suggested that the diversity of nirK genes was inversely proportional to the diversity of nirS. Principal component analysis (PCA) of the sites based on geochemistry grouped the samples by low, moderate and high nitrate but PCA of the unique operational taxonomic units (OTUs) distributions grouped the samples differently. Many of the sequences were not closely related to previously observed genes and some phylogenetically related sequences were obtained from similar samples. The results indicated that the contaminated groundwater contained novel nirK and nirS sequences, functional diversity of both genes changed in relation to the contaminant gradient, but the nirK and nirS functional diversity was affected differently. [source] In-Situ ozonation of contaminated groundwaterENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 3 2000Michael A. Nimmer This paper presents case studies in the application of insitu ozone sparging to remediate petroleum contaminated groundwater. This technology was developed and installed due to shortcomings with other conventional remedial technologies evaluated for groundwater remediation. The main objective of this study was to develop a system to supply ozone to the groundwater aquifer and to evaluate the system performance in the field. Three different applications were evaluated for this study, all containing petroleum-contaminated groundwater. The ozone sparging system consists of an air compressor, ozone generator, a programmable logic controller, and associated gauges and controls. The mixture of air and ozone is injected into the groundwater aquifer through microporous sparge points contained in various sparge well designs. The initial results from the three applications demonstrated that ozone sparging is a viable alternative to remediate petroleum -contaminated groundwater. Significant reductions in petroleum constituents we re observed shortly after system start-up at all sites. During the one to two years operation at the three sites, a number of maintenance items we re identified; these items we re addressed by modifications to the system design and operation. A long-term evaluation of the system operation has not yet been performed. [source] Geomorphologic control on pollutant retardation at the groundwater,surface water interfaceHYDROLOGICAL PROCESSES, Issue 24 2008J.W.N. Smith Abstract The results of research on the pollutant retardation potential of permeable riverbed sediments in catchments with significant groundwater,surface water (GW-SW) interaction are presented. The fraction of organic carbon and cation exchange capacity of fluvial sediments in various geomorphologic environments have been quantified. Sediments in selected reaches of the rivers Tern and Leith (UK), from the underlying Permian sandstone aquifers, and from along the length of the rivers Severn and Eden into which the Tern and Leith discharge have been investigated. Statistical analyses show significant variation in the geochemistry and pollutant retardation potential of sediments from different geomorphologic features, and between upland and lowland rivers. The sorption potential of fine-grained sediments deposited in pools was greater than sand in runs and coarser deposits in riffles. Similarly, sediments in lowland rivers were found to have a greater retardation potential than those in upland rivers. There was generally greater retardation potential in fluvial sediments of all types than in the underlying aquifers, and in lowland rivers the fluvial sediment retardation potential greatly dominated that of the aquifer. The findings demonstrate the potential for pollutant retardation processes in riverbed sediments of sandstone catchments, and suggest that consideration of retardation processes at the groundwater,surface water interface should be included into environmental risk-assessment studies, in order to better assess and manage the effects of contaminated groundwater discharges to rivers, particularly in lowland catchments. Copyright © 2008 John Wiley & Sons, Ltd. [source] Removal of arsenic from simulated groundwater by GAC-Fe: A modeling approachAICHE JOURNAL, Issue 7 2009P. Mondal Abstract A study on kinetics and equilibrium is presented on the adsorption of arsenic species from simulated groundwater containing arsenic (As(III):As(V)::1:1), Fe and Mn in concentrations of 0.188 mg/L, 2.8 mg/L and 0.6 mg/L, respectively, by iron impregnated granular activated charcoal (GAC-Fe). Also presented is the interaction effect of As, Fe and Mn on the removal of arsenic species from water, which simulates contaminated groundwater. Among conventional models, pseudo second-order kinetic model and Freundlich isotherm were adequate to explain the kinetics and equilibrium of adsorption process, respectively. However, in comparison to conventional isotherm empirical polynomial isotherm provided a more accurate prediction on equilibrium specific uptakes of arsenic species. Effects of initial concentrations of As, Fe and Mn on the removal of total arsenic (As(T)), As(V) & As(III) have been correlated within the error limit of ,0.2 to +5.64%. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Performance assessment of hanging funnel-and-gate structures designed by reverse particle tracking for capturing polluted groundwaterREMEDIATION, Issue 3 2007Paul F. Hudak The objective of this study was to evaluate the capability of partially penetrating (hanging) funnel-and-gate structures, designed using reverse flow trajectories, for capturing plumes of contaminated groundwater. Linear capture structures, comprised of two slurry cutoff walls on either side of a permeable gate, were positioned perpendicular to regional groundwater flow in a hypothetical unconfined aquifer. A four-step approach was used for each of two simulated settings: (1) a numerical mass transport model generated a contaminant plume originating from a source area; (2) a particle-tracking model projected groundwater flow paths upstream from a treatment gate; (3) the structure was widened and deepened until bounding path lines contained the plume; and (4) mass transport simulation tested the ability of the structure to capture the plume. Results of this study suggest that designing funnel-and-gate structures using reverse particle tracking may result in too small a structure to capture a contaminant plume. This practice generally ignores effects of hydrodynamic dispersion, which may enlarge plumes such that contaminants move beneath or around a capture structure. This bypassing effect may be considerable even for low values of dispersivity. Particle-tracking approaches may also underestimate the amount of time required to reduce contaminant concentrations to acceptable levels. © 2007 Wiley Periodicals, Inc. [source] Case study of ex situ remediation and conversion to a combined in situ/ex situ bioremediation approach at an oxygenated gasoline release siteREMEDIATION, Issue 2 2007Armand A. Juneau Jr. In response to an oxygenated gasoline release at a gas station site in New Hampshire, a temporary treatment system consisting of a single bedrock extraction well, a product recovery pump, an air stripper, and carbon polishing units was installed. However, this system was ineffective at removing tertiary butyl alcohol from groundwater. The subsequent remedial system design featured multiple bedrock extraction wells and an ex situ treatment system that included an air stripper, a fluidized bed bioreactor, and carbon polishing units. Treated effluent was initially discharged to surface water. Periodic evaluation of the remediation system performance led to system modifications, which included installing an additional extraction well to draw contaminated groundwater away from an on-site water supply well, adding an iron and manganese pretreatment system, and discharge of treated effluent to an on-site drywell. Later, the air stripper and carbon units were eliminated, and an infiltration gallery was installed to receive treated, oxygenated effluent in order to promote flushing of the smear zone and in situ bioremediation in the source area. This article discusses the design, operation, performance, and modifications to the remediation system over time, and provides recommendations for similar sites. © 2007 Wiley Periodicals, Inc. [source] Initial investigation on the use of waterjets to place amendments in the subsurfaceREMEDIATION, Issue 1 2005John W. Cable Quasi-passive in situ remediation technologies, such as the use of permeable reactive barriers to treat contaminated groundwater or applications of granular activated carbon to treat polychlorinated biphenyl (PCB)-contaminated, near-surface sediments, are proven or promising technologies that may be limited in application due to the traditional construction techniques normally used for placement in the environment. High-pressure waterjets have traditionally been used to excavate material during mining operations or to cut rock or other durable material. Waterjets have the potential to place amendments in the subsurface at depths greater than those that can be obtained using traditional construction techniques. Likewise, waterjets may have less negative impact on near-surface utilities and/or sensitive ecological systems. Laboratory experiments were performed to characterize the placement of two solid amendments in a simulated saturated aquifer. A second set of experiments was performed to characterize the effectiveness of waterjets for placing a third amendment in simulated intertidal sediments. The laboratory work focused on characterizing the nature of the waterjet penetration of the aquifer matrix and the saturated sediments, as well as the corresponding waterjet parameters of pressure, nozzle size, and injection time. The laboratory results suggest that field trials may be appropriate for future investigations. © 2005 Wiley Periodicals, Inc. [source] Treatment of Perchlorate-Contaminated Groundwater Using Highly Selective, Regenerable Ion-Exchange Technology: A Pilot-Scale DemonstrationREMEDIATION, Issue 2 2002Baohua Gu Treatment of perchlorate-contaminated groundwater using highly selective, regenerable ion-exchange technology has been recently demonstrated at Edwards Air Force Base, California. At an influent concentration of about 450 ,g/l ClO4,, the bifunctional anion-exchange resin bed treated approximately 40,000 empty bed volumes of groundwater before a significant breakthrough of ClO4, occurred. The presence of relatively high concentrations of chloride and sulfate in site groundwater did not appear to affect the ability of the bifunctional resin to remove ClO4,. The spent resin bed was successfully regenerated using the FeCl3,HCl regeneration technique recently developed at the Oak Ridge National Laboratory, and nearly 100 percent of sorbed ClO4, was displaced or recovered after elution with as little as about two bed volumes of the regenerant solution. In addition, a new methodology was developed to completely destroy ClO4, in the FeCl3,HCl solution so that the disposal of perchlorate-containing hazardous wastes could be eliminated. It is therefore anticipated that these treatment and regeneration technologies may offer an efficient and cost-effective means to remove ClO4, from contaminated groundwater with significantly reduced generation of waste requiring disposal. © 2002 Wiley Periodicals, Inc. [source] Treatment of Highly Contaminated Groundwater: A SITE Demonstration ProjectREMEDIATION, Issue 3 2001Daniel Sullivan From September through November 1994, the U.S. Environmental Protection Agency (EPA) conducted a field demonstration of the remediation of highly contaminated groundwater at the Nascolite Superfund site located in Millville, New Jersey. Besides high concentrations of the major contaminant, methyl methacrylate (MMA), the groundwater also contained small amounts of volatile and semivolatile organic compounds. ZenoGem® technology, an integrated bioreactor and ultrafiltration membrane system, was employed for this demonstration project. Approximately 30,000 gallons of groundwater containing MMA in concentrations of 567 to 9,500 milligrams per liter (mg/L) and chemical oxygen demand (COD) values ranging from 1,490 to 19,600 mg/L was treated. The demonstration focused on the system's ability to remove MMA and reduce COD from the groundwater. Results of the three-month demonstration showed that average MMA and COD removal efficiencies were greater than 99.9 and 86.9, respectively. The total cost of treatment, depending on the duration of the project, is estimated to vary from $0.22 to $0.55 (in 1994 dollars) per gallon of groundwater treated. © 2001 John Wiley & Sons. [source] Treatment of simulated arsenic contaminated groundwater using GAC-Cu in batch reactor: Optimization of process parametersTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2009P. Mondal Abstract This article deals with the experimental investigation related to the removal of arsenic from a simulated contaminated groundwater by the adsorption onto Cu2+ impregnated granular activated carbon (GAC-Cu) in presence of impurities like Fe and Mn. The effects of adsorbent concentration, pH, and temperature on the percentage removal of total arsenic (As(T)), As(III), and As(V) have been discussed. Under the experimental conditions, the optimum adsorbent concentration for GAC-Cu has been found to be 6,g/L with an agitation time of 24,h, which reduces the As(T) concentration from 188 to 8.5,µg/L. Maximum removal of As(V) and As(III) has been observed in the pH range of 7,9 and 9,11, respectively. Removal of all the above said arsenic species decreases slightly with increase in temperature. Presence of Fe and Mn increases the adsorption of arsenic species. Under the experimental conditions, at 30°C, maximum % removals of As(T), As(III), As(V), Fe, and Mn are found to be 95.5%, 93%, 98%, 100%, and 40%, respectively. It has also been observed that maximum regeneration (,94%) of spent GAC-Cu is exhibited by a 5NH2SO4 solution. Le présent document traite de la vérification expérimentale liée à l'élimination de l,arsenic, dans une eau souterraine à contamination simulée, par adsorption dans du charbon actif en grains (CAG-Cu) imprégné de Cu2+, en présence d'impuretés comme du fer et du manganèse. Les effets de la concentration adsorbante, du pH et de la température sur le pourcentage d'élimination de l,arsenic total (As [T]), As(III) et As(V) ont fait l,objet de discussions. Dans des conditions expérimentales, on a déterminé que la concentration adsorbante optimale dans le cas du CAG-Cu est de 6,g/L avec un temps d'agitation de 24,h, ce qui réduit la concentration d'As(T) de 188,µg/L à 8.5 µg/L. Selon les observations, l,élimination maximale d'As(V) et d'As(III) se situe dans les gammes de pH de 7 à 9 et 9 à 11 respectivement. L'élimination de toutes les espèces d'arsenic mentionnées ci-dessus décroît légèrement en fonction de l,augmentation de la température. La présence de fer et de manganèse augmente l,adsorption des espèces d'arsenic. Dans des conditions expérimentales, à 30 °C, on a déterminé que les pourcentages d'élimination maximums d'As(T), d'As(III), d'As(V), de Fe et de Mn sont de 95.5%, 93%, 98%, 100% et 40% respectivement. On a également observé que la régénération maximale (,94%) du CAG-Cu usé est représentée par une solution 5NH2SO4. [source] Toxicity of brominated volatile organics to freshwater biotaENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 9 2010Monique T. Binet Abstract As part of a larger study investigating the fate and effects of brominated volatile organic compounds (VOCs) in contaminated groundwaters discharging to surface waters, the toxicity of 1,2 dibromoethene (DBE) and 1,1,2-tribromoethene (TriBE) to freshwater aquatic biota was investigated. Their toxicity to bacteria (Microtox®), microalgae (Chlorella sp.), cladocerans (Ceriodaphnia dubia), duckweed (Lemna sp.) and midges (Chironomus tepperi) was determined after careful optimization of the test conditions to minimize chemical losses throughout the tests. In addition, concentrations of DBE and TriBE were carefully monitored throughout the bioassays to ensure accurate calculation of toxicity values. 1,2-Dibromoethene showed low toxicity to most species, with concentrations to cause 50% lethality or effect (LC/EC50 values) ranging from 28 to 420,mg/L, 10% lethality or effect (LC/EC10 values) ranging from 18 to 94,mg/L and no-observed-effect concentrations (NOECs) ranging from 22 to 82,mg/L. 1,1,2-Tribromoethene was more toxic than DBE, with LC/EC50 values of 2.4 to 18,mg/L, LC/EC10 values of 0.94 to 11,mg/L and NOECs of 0.29 to 13,mg/L. Using these limited data, together with data from the only other published study on TriBE, moderate-reliability water quality guidelines (WQGs) were estimated from species sensitivity distributions. The proposed guideline trigger values for 95% species protection with 50% confidence were 2,mg/L for DBE and 0.03,mg/L for TriBE. The maximum concentrations of DBE and TriBE in nearby surface waters (3 and 1,µg /L, respectively) were well below these WQGs, so the risk to the freshwater environment receiving contaminated groundwater inflows was considered to be low, with hazard quotients <1 for both VOCs. Environ. Toxicol. Chem. 2010;29:1984,1993. © 2010 SETAC [source] Heterogeneous aerobic benzene-degrading communities in oxygen-depleted groundwatersFEMS MICROBIOLOGY ECOLOGY, Issue 2 2006Anne Fahy Abstract A sandstone aquifer beneath a petrochemicals plant (SIReN site, UK) is heterogeneously contaminated with benzene and oxygen-depleted. Despite low redox potentials in three of the most contaminated groundwaters (benzene concentrations from 17.8 to 294 mg L,1), we observed aerobic benzene degradation in microcosms, indicating the presence in situ of a latent community of obligate aerobic microorganisms or an active community of facultative aerobes responding rapidly to oxygen ingress. Moreover, benzene degradation occurred at the ambient pH of 8.9 and 9.4, considerably more alkaline conditions than previously reported. 16S rRNA analyses showed that the groundwater microcosm communities were distinct from each other, despite sharing the function of aerobic benzene degradation. From DNA fingerprinting, one consortium was dominated by Acidovorax spp., another by Pseudomonas spp.; these benzene-degrading consortia were similar to the in situ communities, perhaps indicating that these organisms are active in situ and degrading benzene microaerophilically or by denitrification. Conversely, in the third sample, benzene degradation occurred only after the community changed from a Rhodoferax -dominated community to a mix of Rhodococcus and Hydrogenophaga spp. Four of the main benzene-degrading strains were brought into culture: Hydrogenophaga and Pseudomonas spp., and two strains of Rhodococcus erythropolis, a ubiquitous and metabolically versatile organism. [source] Mixed aerobic and anaerobic microbial communities in benzene-contaminated groundwaterJOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2009A. Aburto Abstract Aims:, To investigate the factors affecting benzene biodegradation and microbial community composition in a contaminated aquifer. Methods and Results:, We identified the microbial community in groundwater samples from a benzene-contaminated aquifer situated below a petrochemical plant. Eleven out of twelve groundwater samples with in situ dissolved oxygen concentrations between 0 and 2·57 mg l,1 showed benzene degradation in aerobic microcosm experiments, whereas no degradation in anaerobic microcosms was observed. The lack of aerobic degradation in the remaining microcosm could be attributed to a pH of 12·1. Three groundwaters, examined by 16S rRNA gene clone libraries, with low in situ oxygen concentrations and high benzene levels, each had a different dominant aerobic (or denitrifying) population, either Pseudomonas, Polaromonas or Acidovorax species. These groundwaters also had syntrophic organisms, and aceticlastic methanogens were detected in two samples. The alkaline groundwater was dominated by organisms closely related to Hydrogenophaga. Conclusions:, Results show that pH 12·1 is inimical to benzene biodegradation, and that oxygen concentrations below 0·03 mg l,1 can support aerobic benzene-degrading communities. Significance and Impact of the Study:, These findings will help to guide the treatment of contaminated groundwaters, and raise questions about the extent to which aerobes and anaerobes may interact to effect benzene degradation. [source] | ||||||||||||||||