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Higgins MR, Olson TM. Life-cycle case study comparison of permeable reactive barrier versus pump-and-treat remediation. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2009; 43:9432-9438. [PMID: 20000540 DOI: 10.1021/es9015537] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
A permeable reactive barrier (PRB) is a passive remediation technology, which over decades of use, may reduce lifetime environmental impacts when compared with a conventional pump-and-treat system (PTS). Greater material production requirements to install PRBs may offset the expected reductions in operational phase impacts and the trade-offs can be investigated in a life-cycle assessment (LCA). The life-cycle environmental impacts of a zerovalent iron (ZVI) containing PRB with a funnel and gate configuration and a PTS were compared in a case study. Potential impacts of the model PRB are driven by the ZVI reactive medium and the energy usage during construction, while for the PTS they are driven by the operational energy demand. Medium longevity governed the magnitude of the potential PRB impacts and the extent to which it was optimal relative to the PTS. Even at conservatively low estimates of longevity, the PRB offers significant environmental advantages in impact categories of human health and ozone depletion. The minimum ZVI longevity for PRB benefit over the PTS system in all impact categories was 10 years. Suggested PRB design innovations to reduce environmental impacts include the development of alternative reactive media and construction methods.
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Affiliation(s)
- Monica R Higgins
- Department of Civil and Environmental Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA
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52
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González A, Navia R, Moreno N. Fly ashes from coal and petroleum coke combustion: current and innovative potential applications. WASTE MANAGEMENT & RESEARCH : THE JOURNAL OF THE INTERNATIONAL SOLID WASTES AND PUBLIC CLEANSING ASSOCIATION, ISWA 2009; 27:976-987. [PMID: 19423583 DOI: 10.1177/0734242x09103190] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Coal fly ashes (CFA) are generated in large amounts worldwide. Current combustion technologies allow the burning of fuels with high sulfur content such as petroleum coke, generating non-CFA, such as petroleum coke fly ash (PCFA), mainly from fluidized bed combustion processes. The disposal of CFA and PCFA fly ashes can have severe impacts in the environment such as a potential groundwater contamination by the leaching of heavy metals and/or particulate matter emissions; making it necessary to treat or reuse them. At present CFA are utilized in several applications fields such as cement and concrete production, agriculture and soil stabilization. However, their reuse is restricted by the quality parameters of the end-product or requirements defined by the production process. Therefore, secondary material markets can use a limited amount of CFA, which implies the necessity of new markets for the unused CFA. Some potential future utilization options reviewed herein are zeolite synthesis and valuable metals extraction. In comparison to CFA, PCFA are characterized by a high Ca content, suggesting a possible use as neutralizers of acid wastewaters from mining operations, opening a new potential application area for PCFA that could solve contamination problems in emergent and mining countries such as Chile. However, this potential application may be limited by PCFA heavy metals leaching, mainly V and Ni, which are present in PCFA in high concentrations.
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Affiliation(s)
- Aixa González
- Department of Chemical Engineering, University of La Frontera, Temuco, Chile
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53
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Microbial communities and biodegradation in lab-scale BTEX-contaminated groundwater remediation using an oxygen-releasing reactive barrier. Bioprocess Biosyst Eng 2009; 33:383-91. [DOI: 10.1007/s00449-009-0336-7] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2009] [Accepted: 05/24/2009] [Indexed: 10/20/2022]
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54
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Hong JK, Jo HY, Yun ST. Coal fly ash and synthetic coal fly ash aggregates as reactive media to remove zinc from aqueous solutions. JOURNAL OF HAZARDOUS MATERIALS 2009; 164:235-246. [PMID: 18805638 DOI: 10.1016/j.jhazmat.2008.08.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2008] [Revised: 08/06/2008] [Accepted: 08/06/2008] [Indexed: 05/26/2023]
Abstract
Coal fly ash (CF) and synthetic coal fly ash aggregates (SCFAs) were evaluated as low-cost reactive media for the remediation of groundwater contaminated with Zn. The SCFAs were prepared by mixing CF, sodium silicate, and deionized (DI) water. Serial batch kinetic and static tests were conducted on both CF and SCFAs, under various conditions (i.e., pH, initial Zn concentration, reaction time, and solid dosage), using Zn(NO(3))(2).6H(2)O solutions. Serial column tests were also conducted on both CF and SCFAs. The final rather than the initial pH of the solution had a greater effect on the removal of Zn. At pH>7.0, the removal of Zn was due to precipitation, whereas at <7.0, the removal of Zn was due to adsorption onto the reactive media. The removal of Zn increased with increasing dosage of the reactive medium and decreasing initial Zn concentration. The results of the column and batch tests were comparable. Preferential flow paths were observed with CF, but not SCFA. The hydraulic conductivity of CF was more significantly decreased than that of SCFA with increasing dry density of the specimen.
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Affiliation(s)
- Jung-Ki Hong
- Department of Earth and Environmental Sciences, Korea University, Anam-dong, Seongbuk-gu, Seoul 136-713, Republic of Korea
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55
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Lee J, Graettinger AJ, Moylan J, Reeves HW. Directed site exploration for permeable reactive barrier design. JOURNAL OF HAZARDOUS MATERIALS 2009; 162:222-229. [PMID: 18573602 DOI: 10.1016/j.jhazmat.2008.05.026] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/26/2007] [Revised: 05/04/2008] [Accepted: 05/06/2008] [Indexed: 05/26/2023]
Abstract
Permeable reactive barriers (PRBs) are being employed for in situ site remediation of groundwater that is typically flowing under natural gradients. Site characterization is of critical importance to the success of a PRB. A design-specific site exploration approach called quantitatively directed exploration (QDE) is presented. The QDE approach employs three spatially related matrices: (1) covariance of input parameters, (2) sensitivity of model outputs, and (3) covariance of model outputs to identify the most important location to explore based on a specific design. Sampling at the location that most reduces overall site uncertainty produces a higher probability of success of a particular design. The QDE approach is demonstrated on the Kansas City Plant, Kansas City, MO, a case study where a PRB was installed and failed. It is shown that additional quantitatively directed site exploration during the design phase could have prevented the remedial failure that was caused by missing a geologic body having high hydraulic conductivity at the south end of the barrier. The most contributing input parameter approach using head uncertainty clearly indicated where the next sampling should be made toward the high hydraulic conductivity zone. This case study demonstrates the need to include the specific design as well as site characterization uncertainty when choosing the sampling locations.
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Affiliation(s)
- Jejung Lee
- Department of Geosciences, University of Missouri-Kansas City, Kansas City, MO 64110, USA.
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56
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Suzuki K, Anegawa A, Endo K, Yamada M, Ono Y, Ono Y. Performance evaluation of intermediate cover soil barrier for removal of heavy metals in landfill leachate. CHEMOSPHERE 2008; 73:1428-1435. [PMID: 18842283 DOI: 10.1016/j.chemosphere.2008.08.021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2008] [Revised: 08/06/2008] [Accepted: 08/06/2008] [Indexed: 05/26/2023]
Abstract
This pilot-scale study evaluated the use of intermediate cover soil barriers for removing heavy metals in leachate generated from test cells for co-disposed fly ash from municipal solid waste incinerators, ash melting plants, and shredder residue. Cover soil barriers were mixtures of Andisol (volcanic ash soil), waste iron powder, (grinder dust waste from iron foundries), and slag fragments. The cover soil barriers were installed in the test cells' bottom layer. Sorption/desorption is an important process in cover soil bottom barrier for removal of heavy metals in landfill leachate. Salt concentrations such as those of Na, K, and Ca in leachate were extremely high (often greater than 30 gL(-1)) because of high salt content in fly ash from ash melting plants. Concentrations of all heavy metals (nickel, manganese, copper, zinc, lead, and cadmium) in test cell leachates with a cover soil barrier were lower than those of the test cell without a cover soil barrier and were mostly below the discharge limit, probably because of dilution caused by the amount of leachate and heavy metal removal by the cover soil barrier. The cover soil barriers' heavy metal removal efficiency was calculated. About 50% of copper, nickel, and manganese were removed. About 20% of the zinc and boron were removed, but lead and cadmium were removed only slightly. Based on results of calculation of the Langelier saturation index and analyses of core samples, the reactivity of the cover soil barrier apparently decreases because of calcium carbonate precipitation on the cover soil barriers' surfaces.
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Affiliation(s)
- Kazuyuki Suzuki
- Faculty of Life Applied Sciences, Niigata University of Pharmacy and Applied Life Sciences, 265-1 Higashijima, Akiha-ku, Niigata 956-8603, Japan.
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57
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Gibert O, Pomierny S, Rowe I, Kalin RM. Selection of organic substrates as potential reactive materials for use in a denitrification permeable reactive barrier (PRB). BIORESOURCE TECHNOLOGY 2008; 99:7587-7596. [PMID: 18353637 DOI: 10.1016/j.biortech.2008.02.012] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2007] [Revised: 02/01/2008] [Accepted: 02/10/2008] [Indexed: 05/26/2023]
Abstract
The aim of the present study was to select a suitable natural organic substrate as a potential carbon source for use in a denitrification permeable reactive barrier (PRB). A number of seven organic substrates were first tested in batch tests. The materials attained varying degrees of success at promoting denitrification. Some of the organic substrates performed very well, achieving complete nitrate removal (>98%), while others were considered unsuitable for a variety of reasons, including: insufficient nitrate or nitrogen removal, excessive release of leachable nitrogen from the substrate or excessive reduction of nitrate to ammonium rather than removing it as gaseous N2. The top performing substrate in terms of denitrification extent (>98%) and rate (0.067 mgNO3(-)-N dm(-3)d(-1)g(sub)(-1)) was then selected for two bench-scale column experiments in an attempt to simulate the PRB. The inlet concentration was 50 mg dm(-3) NO3(-)-N and the columns operated at two different flow rates: 0.3 cm3 min(-1) (Column 1) and 1.1cm3 min(-1) (Column 2). The two columns showed different general patterns, making it clear that the flow rate was a key factor at the nitrate removal. Nitrate was completely removed (>96%) by the passage through Column 1, while only partially removed in Column 2 (66%). The results indicated that the selected organic substrate (Softwood) was applicable for further use as a filling material for a PRB.
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Affiliation(s)
- Oriol Gibert
- EERC, School of Planning Architecture and Civil Engineering, Queen's University Belfast, Stranmillis Road, Belfast, Northern Ireland BT9 5AG, United Kingdom.
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58
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Valderrama C, Cortina JL, Farran A, Marti V, Gamisans X, Heras FXDL. Characterization of Azo Dye (Acid Red 14) Removal with Granular Activated Carbon: Equilibrium and Kinetic Data. SOLVENT EXTRACTION AND ION EXCHANGE 2008. [DOI: 10.1080/07366290802053504] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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59
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Choy CC, Wazne M, Meng X. Application of an empirical transport model to simulate retention of nanocrystalline titanium dioxide in sand columns. CHEMOSPHERE 2008; 71:1794-801. [PMID: 18282593 DOI: 10.1016/j.chemosphere.2007.12.030] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2007] [Revised: 12/09/2007] [Accepted: 12/10/2007] [Indexed: 05/10/2023]
Abstract
Nanocrystalline titanium dioxide was injected into sand columns to simulate subsurface injection for creation of a permeable treatment barrier. Past usage of this material as an ex situ pilot scale treatment filter has shown that it has a high adsorption capacity for a number of heavy metals and therefore would be a good candidate for injection technology. Three suspension concentrations (50, 75 and 100 mg l(-1)) were pumped through packed sand columns at different flow velocities (3.0, 6.8 and 14.1 cm min(-1)). Little to no particles was detected in the effluent. Most of the nanoparticles remained in the sand columns, with an increasing then decreasing retained solids pattern. Application of a one-dimensional advection-dispersion flow model, that included two empirical kinetic terms to account for particle retention in the porous media, produced data fits that followed the general trend of the data, but did not truly capture the concentration maxima in the data sets. Discussion of these results highlights the limited ability of existing models to aid in predicting particle retention of non-ideal materials for engineering purposes.
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Affiliation(s)
- Christine Chin Choy
- Center for Environmental Systems, Stevens Institute of Technology, Castle Point on Hudson, NJ 07030, USA
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60
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61
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Valderrama C, Cortina J, Farran A, Gamisans X, de las Heras F. Evaluation of hyper-cross-linked polymeric sorbents (Macronet MN200 and MN300) on dye (Acid red 14) removal process. REACT FUNCT POLYM 2008. [DOI: 10.1016/j.reactfunctpolym.2007.11.005] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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62
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Labaky W, Devlin JF, Gillham RW. Probe for measuring groundwater velocity at the centimeter scale. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2007; 41:8453-8458. [PMID: 18200878 DOI: 10.1021/es0716047] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
A novel method of measuring small-scale groundwater velocities in unconsolidated noncohesive media uses the travel time of a tracer pulse between an injection port and two detectors located on the surface of a cylindrical probe, called a point-velocity probe (PVP), as the basis for velocity estimation. The direction and magnitude of the water velocity vector were determined to within +/- 9% of magnitude and +/- 8 in direction, on average, in ten laboratory tank tests conducted with the PVP, when the velocities were between 5 and 98 cm/ day. Numerical simulations supported the accuracy of the underlying theory for interpretation of the PVP data and indicated that the technology is capable of measuring velocity at a very fine scale (0.5 cm around the circumference). The benchtop and modeling investigations indicated that the probe is moderately sensitive to the condition of the porous medium immediately next to the cylinder surface, suggesting that challenges exist for the deployment of the instrument in the field.
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Affiliation(s)
- W Labaky
- Schlumberger Water Services, Waterloo, Ontario, Canada
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63
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Venditti F, Angelico R, Ceglie A, Ambrosone L. Novel surfactant-based adsorbent material for groundwater remediation. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2007; 41:6836-6840. [PMID: 17969703 DOI: 10.1021/es070643f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Many surfactants aggregate spontaneously in aqueous media to form small spherical structures called micelles. Among the numerous technical applications it is known that micelles have the ability to dissolve in their hydrophobic part significant amounts of water-insoluble organic compounds. In this study we investigated through UV-vis spectroscopy the micellar solubilization of 2,4,5-trichlorophenol (Tcp), an intermediate product of the microbial degradation of the broad-leaf herbicide 2,4,5-trichlorophenoxyacetic (2,4,5-T). Our results show that in the presence of the anionic surfactant sodium dodecylsulfate SDS the water solubility of Tcp increases six-fold whereas with cationic CTAB and nonionic Triton-X 100 the partition of chlorinated compound is not efficient. After the excess amount of the pollutant solubilized in SDS-micelles has been precipitated with CaCl2 the remaining fraction of Tcp has been successfully reduced within the toxicological limit for drinkable water through a cocurrent multistage operation. Finally, potential use in the decontamination of wastewater or soils of the new adsorbent material has been compared with the most commonly used activated carbon and silica gel.
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Affiliation(s)
- F Venditti
- Consorzio per lo sviluppo dei Sistemi a Grande Interfase, c/o Department of Food Technology DISTAAM, Università del Molise, via De Sanctis 86100 Campobasso, Italy
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64
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Valderrama C, Cortina JL, Farran A, Gamisans X, Lao C. Kinetics of sorption of polyaromatic hydrocarbons onto granular activated carbon and Macronet hyper-cross-linked polymers (MN200). J Colloid Interface Sci 2007; 310:35-46. [PMID: 17367802 DOI: 10.1016/j.jcis.2007.01.039] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2006] [Revised: 01/15/2007] [Accepted: 01/17/2007] [Indexed: 11/18/2022]
Abstract
Polymeric supports are presented as an alternative to granular activated carbon (GAC) for organic contaminant removal from groundwater using permeable reactive barriers (PRB). The search for suitable polymeric sorbents for hydrocarbon extraction from aqueous streams has prompted the synthesis of new resins incorporating new functionalities or modifying the polymer network properties that solve many of the existing problems. Between them, the new type of polymeric sorbents Macronet Hypersol containing a styrene-divinylbenzene macroporous hyperreticulated network has been evaluated. Because of their potential sorptive properties, tests were conducted to determine the feasibility of using them as a low-cost reactive material for groundwater applications. The present work describes the sorption of six polycyclic hydrocarbons (PAHs) from aqueous solution onto both Macronet polymeric sorbent MN200 and granular activated carbon. Batch experiments were performed to determine loading rates of a family of PAHs (naphthalene, fluorene, anthracene, acenaphthene, pyrene, and fluoranthene), from a simple two-rings PAH (naphthalene) up to a four-ring PAH (pyrene). The behavior of a non-functionalized Macronet support (MN200) was compared with the behavior of a recognized material, granular activated carbon (GAC). Analyses of the respective rate data with three theoretical models (pseudo-first- and pseudo-second-order reaction models and the Elovich model) were used to describe the PAH sorption kinetics. Sorption rate constants were determined by graphical analysis of the proposed models. The study showed that sorption systems followed a pseudo-first-order reaction model, although the pseudo-second-order reaction model provides an acceptable description of the sorption process. Graphical analysis showed that the sorption process with activated carbon is a more complex process than the one observed for hyper-cross-linked polymers (MN200). A simulation of the barrier thickness needed to treat a PAH-polluted plume showed that 0.1-1 m of sorption media is enough even for high water fluxes such as 0.1-2 m(3)/m(2)/day for both sorbents.
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Affiliation(s)
- C Valderrama
- Mining Engineering and Natural Resources Department, EPSEM, Universitat Politenica de Catalunya, 08240 Manresa, Spain
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65
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Hudak PF. Mass transport in groundwater near hanging-wall interceptors. JOURNAL OF ENVIRONMENTAL SCIENCE AND HEALTH. PART A, TOXIC/HAZARDOUS SUBSTANCES & ENVIRONMENTAL ENGINEERING 2007; 42:317-21. [PMID: 17365297 DOI: 10.1080/10934520601144550] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
This study investigated mass transport near trenches designed to capture contaminated groundwater. Numerical models simulated migration of contaminant plumes toward trenches oriented perpendicular to regional groundwater flow, partially penetrating a hypothetical unconfined aquifer. Plumes originated at the top of the simulated groundwater flow system. The smallest trench necessary to capture a contaminant plume was identified for various sets of mass transport parameters. Results suggest that, in predominantly horizontal flow systems such as those simulated here: (i) vertical hydraulic conductivity has relatively little effect on downward propagation of contaminant plumes and required trench size, (ii) transverse vertical dispersivity exerts significant control on plume and trench depth, and (iii) recharge dilutes and thus reduces plume and trench width, but may induce downward vertical hydraulic gradients that deepen plumes and trenches. For all cases considered, trenches oriented perpendicular to regional groundwater flow, placed close to the leading edge of a contaminant plume, and sized slightly larger than the plume (in transverse cross-section) facilitate plume capture.
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Affiliation(s)
- Paul F Hudak
- Department of Geography and Environmental Science Program, University of North Texas, Denton, TX 76203-5279, USA.
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66
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67
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Lapointe F, Fytas K, McConchie D. Using permeable reactive barriers for the treatment of acid rock drainage. ACTA ACUST UNITED AC 2005. [DOI: 10.1080/13895260500045241] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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68
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Bradl H, Xenidis A. Chapter 3 Remediation techniques. HEAVY METALS IN THE ENVIRONMENT: ORIGIN, INTERACTION AND REMEDIATION 2005. [DOI: 10.1016/s1573-4285(05)80022-5] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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69
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Construction methods of permeable reactive barriers. ACTA ACUST UNITED AC 2005. [DOI: 10.1016/s0927-5215(05)80006-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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70
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Lookman R, Bastiaens L, Borremans B, Maesen M, Gemoets J, Diels L. Batch-test study on the dechlorination of 1,1,1-trichloroethane in contaminated aquifer material by zero-valent iron. JOURNAL OF CONTAMINANT HYDROLOGY 2004; 74:133-44. [PMID: 15358490 DOI: 10.1016/j.jconhyd.2004.02.007] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2002] [Revised: 01/26/2004] [Accepted: 02/06/2004] [Indexed: 05/11/2023]
Abstract
Chlorinated aliphatic hydrocarbons are common groundwater contaminants. One possible remediation option is in-situ reductive dechlorination by zero-valent iron, either by direct injection or as reactive barriers. Chlorinated ethenes (tetrachloroethene: PCE; trichloroethene: TCE) have received extensive attention in this context. However, another common groundwater pollutant, 1,1,1-trichlorethane (TCA), has attracted much less attention. We studied TCA reduction by three types of granular zero-valent irons in a series of batch experiments using polluted groundwater, with and without added aquifer material. Two types of iron were able to reduce TCA completely with no daughter product concentration increases (1,1-dichloroethane: DCA; chloroethane: CA). One type of iron showed slower reduction, with intermediate rise of DCA and CA concentrations. When evaluating the formation of daughter products, the tests on the groundwater alone showed different results than the groundwater plus aquifer batches: DCA did not temporarily accumulate in the batches with added aquifer material, contrary to the batches without added aquifer material. 1,1-dichloroethene (DCE, also present in the groundwater as an abiotic degradation product of TCA) was also reduced slower in the batches without added aquifer material than in the batches with aquifer material. Redox potentials gradually decreased to low values in batches with aquifer material without iron, while the batches with groundwater alone maintained a constant higher redox potential. Either adsorption processes or microbiological activity in the samples could explain these phenomena. Polymerase Chain Reaction (PCR: a targeted gene probe technique) for chlorinated aliphatic compound (CAH)-degrading bacteria confirmed the presence of Dehalococcoides sp. (chloroethene-degraders) but was negative for Desulfobacterium autotrophicum (a known co-metabolic TCA degrader). DCA reduction was rate determining: first-order half-lives of 300-350 h were observed. TCA was fully removed within hours. CA is resistant to reduction by zero-valent iron but it is known to hydrolyze easily. Since CA did not accumulate in our batches, it may have disappeared by the latter mechanism or it may not have formed as a major daughter product.
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Affiliation(s)
- Richard Lookman
- Environmental Technology, Vito-Boeretang 200, Mol B-2400, Belgium.
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71
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Bryant DE, Stewart DI, Kee TP, Barton CS. Development of a functionalized polymer-coated silica for the removal of uranium from groundwater. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2003; 37:4011-4016. [PMID: 12967128 DOI: 10.1021/es020178g] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
A new active material for the treatment of uranium-contaminated groundwater using permeable reactive barriers has been developed. This material, called PANSIL, is an example of a tailored ligand system that selectively removes a contaminant from solution. The active medium in PANSIL is a polyacryloamidoxime resin derived from polyacrylonitrile, which is deposited from solution onto the surface of quartz sand to form a thin film coating. PANSIL is highly effective at sequestering UO2(2+) from solution when the pH is between about 5 and 8 and can preferentially sequester UO2(2+) from solutions that are typical of the groundwater from a mine tailings site, due to the stability of the polyacryloamidoxime uranyl complex formed. Uranium sequestration capacity will depend on the surface area of the sand that is resin coated, but in the batch of PANSIL tested (<2% resin by weight), it exceeds 4000 mg of UO2 per kg of PANSIL at pH 4.5 when the dissolved UO2(2+) concentration is greaterthan 300 mg/L. PANSIL largely retains the permeability and strength of the sand employed and therefore has suitable engineering properties for permeable reactive barrier applications.
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Affiliation(s)
- David E Bryant
- Department of Chemistry and School of Civil Engineering, University of Leeds, Leeds LS2 9JT, U.K
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