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Sookhak Lari K, Davis GB, Rayner JL, Bastow TP, Puzon GJ. Natural source zone depletion of LNAPL: A critical review supporting modelling approaches. WATER RESEARCH 2019; 157:630-646. [PMID: 31004979 DOI: 10.1016/j.watres.2019.04.001] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2018] [Revised: 03/23/2019] [Accepted: 04/01/2019] [Indexed: 06/09/2023]
Abstract
Natural source zone depletion (NSZD) of light non-aqueous phase liquids (LNAPLs) includes partitioning, transport and degradation of LNAPL components. NSZD is being considered as a site closure option during later stages of active remediation of LNAPL contaminated sites, and where LNAPL mass removal is limiting. To ensure NSZD meets compliance criteria and to design enhanced NSZD actions if required, residual risks posed by LNAPL and its long term behaviour require estimation. Prediction of long-term NSZD trends requires linking physicochemical partitioning and transport processes with bioprocesses at multiple scales within a modelling framework. Here we expand and build on the knowledge base of a recent review of NSZD, to establish the key processes and understanding required to model NSZD long term. We describe key challenges to our understanding, inclusive of the dominance of methanogenic or aerobic biodegradation processes, the potentially changeability of rates due to the weathering profile of LNAPL product types and ages, and linkages to underlying bioprocesses. We critically discuss different scales in subsurface simulation and modelling of NSZD. Focusing on processes at Darcy scale, 36 models addressing processes of importance to NSZD are investigated. We investigate the capabilities of models to accommodate more than 20 subsurface transport and transformation phenomena and present comparisons in several tables. We discuss the applicability of each group of models for specific site conditions.
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Affiliation(s)
- Kaveh Sookhak Lari
- CSIRO Land and Water, Private Bag No. 5, Wembley, WA, 6913, Australia; School of Engineering, Edith Cowan University, 270 Joondalup Drive, Joondalup, WA, 6027, Australia.
| | - Greg B Davis
- CSIRO Land and Water, Private Bag No. 5, Wembley, WA, 6913, Australia; School of Earth Sciences, The University of Western Australia, 35 Stirling Highway, Crawley, WA, 6009, Australia
| | - John L Rayner
- CSIRO Land and Water, Private Bag No. 5, Wembley, WA, 6913, Australia
| | - Trevor P Bastow
- CSIRO Land and Water, Private Bag No. 5, Wembley, WA, 6913, Australia
| | - Geoffrey J Puzon
- CSIRO Land and Water, Private Bag No. 5, Wembley, WA, 6913, Australia
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Rama F, Ramos DT, Müller JB, Corseuil HX, Miotliński K. Flow field dynamics and high ethanol content in gasohol blends enhance BTEX migration and biodegradation in groundwater. JOURNAL OF CONTAMINANT HYDROLOGY 2019; 222:17-30. [PMID: 30797547 DOI: 10.1016/j.jconhyd.2019.01.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2018] [Revised: 12/21/2018] [Accepted: 01/09/2019] [Indexed: 06/09/2023]
Abstract
Gasohol spills may easily descend through the soil column down and impact sensitive receptors as contaminants dissolve into the groundwater. Gasoline formulations are commonly blended with ethanol to alleviate environmental and economic issues associated with fossil fuels. However, the amount of ethanol added to gasoline and the groundwater hydraulic regime can significantly affect BTEX plume dynamics and lifespan. In this study, two long-term (5 and 10 years) field-scale gasohol releases with ethanol contents of 85% (E85) and 24% (E24), respectively, were assessed to discern the different dynamics undergone by gasohol blends. Statistical, geochemical, microbiological and trend approaches were employed to estimate the influence of groundwater flow variations on ethanol and dissolved BTEX transport, and the associated biodegradation rates of different gasohol blend spills. Ethanol and BTEX groundwater flow were quantified in terms of breakthrough curve characteristics, plume centroid positions and spreading, source depletion and mass degradation rates. In addition, bromide migration was evaluated to address the contribution of flow-driven dissolution. Results revealed that the high amount of ethanol along with a fast and dynamic flow exerted a flushing behavior that enhanced BTEX dissolution, migration (vertical and horizontal) and concentrations in groundwater. The higher amount of ethanol in E85 enhanced BTEX dissolution (and bioavailability) relative to E24 site and led to faster biodegradation rates, which can be explained by the cosolvency effect and metabolic flux dilution. Therefore, flow field dynamics and high ethanol content in gasohol blends enhance BTEX migration and biodegradation in gasohol-contaminated sites. The balance of these factors is crucial to determine fate and transport of contaminants in field sites. These findings suggest that hydraulic regime should be spatially and temporally characterized to support decisions on appropriate monitoring plan and remedial strategies for gasohol spills.
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Affiliation(s)
- Fabrizio Rama
- Núcleo Ressacada de Pesquisas Em Meio Ambiente (REMA) - Department of Sanitary and Environmental Engineering, Federal University of Santa Catarina (UFSC), Campus Universitário Sul da Ilha - Rua José Olímpio da Silva, 1326 - Bairro Tapera, 88049-500 Florianópolis, SC, Brazil.
| | - Débora Toledo Ramos
- Núcleo Ressacada de Pesquisas Em Meio Ambiente (REMA) - Department of Sanitary and Environmental Engineering, Federal University of Santa Catarina (UFSC), Campus Universitário Sul da Ilha - Rua José Olímpio da Silva, 1326 - Bairro Tapera, 88049-500 Florianópolis, SC, Brazil.
| | - Juliana Braun Müller
- Núcleo Ressacada de Pesquisas Em Meio Ambiente (REMA) - Department of Sanitary and Environmental Engineering, Federal University of Santa Catarina (UFSC), Campus Universitário Sul da Ilha - Rua José Olímpio da Silva, 1326 - Bairro Tapera, 88049-500 Florianópolis, SC, Brazil.
| | - Henry Xavier Corseuil
- Núcleo Ressacada de Pesquisas Em Meio Ambiente (REMA) - Department of Sanitary and Environmental Engineering, Federal University of Santa Catarina (UFSC), Campus Universitário Sul da Ilha - Rua José Olímpio da Silva, 1326 - Bairro Tapera, 88049-500 Florianópolis, SC, Brazil.
| | - Konrad Miotliński
- Núcleo Ressacada de Pesquisas Em Meio Ambiente (REMA) - Department of Sanitary and Environmental Engineering, Federal University of Santa Catarina (UFSC), Campus Universitário Sul da Ilha - Rua José Olímpio da Silva, 1326 - Bairro Tapera, 88049-500 Florianópolis, SC, Brazil.
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Sharma S, Slater L, Ntarlagiannis D, Werkema D, Szabo Z. Specific polarizability of sand-clay mixtures with varying ethanol concentration. NEAR SURFACE GEOPHYSICS 2017; 15:615-624. [PMID: 35299702 PMCID: PMC8925411 DOI: 10.3997/1873-0604.2017049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
We utilise a concept of specific polarizability (c s ), represented as the ratio of mineral-fluid interface polarization per pore-normalised surface area S p , to demonstrate the influence of clay-organic interaction on complex conductivity measurements. Complex conductivity measurements were performed on kaolinite- and illite-sand mixtures as a function of varying ethanol (EtOH) concentration (10% and 20% v/v). The specific surface area of each clay type and Ottawa sand was determined by nitrogen-gas-adsorption Brunauer-Emmett-Teller method. We also calculated the porosity and saturation of each mixture based on weight loss of dried samples. Debye decomposition, a phenomenological model, was applied to the complex conductivity data to determine normalised chargeability (m n ). Specific polarizability estimates from previous complex conductivity measurements for bentonite-sand mixtures were compared with our dataset. The c s for all sand-clay mixtures decreased as the EtOH concentration increased from 0% to 10% to 20% v/v. We observe similar c s responses to EtOH concentration for all sand-clay mixtures. Analysis of variance with a level of significance α = 0.05 suggests that the suppression in c s responses with increasing EtOH concentration was statistically significant for all sand-clay mixtures. On the other hand, real conductivity showed only 10% to 20% v/v changes with increasing EtOH concentration. The c s estimates reflect the sensitivity of complex conductivity measurements to alteration in surface chemistry at available surface adsorption sites for different clay types, likely resulting from ion exchange at the clay surface and associated with kinetic reactions in the electrical double layer of the clay-water-EtOH media. Our results indicate a much larger influence of specific surface area and ethanol concentration on clay-driven polarization relative to changes in clay mineralogy.
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Affiliation(s)
- Sundeep Sharma
- Department of Earth and Environmental Sciences, Rutgers University–Newark, Newark, NJ 07102, USA
| | - Lee Slater
- Department of Earth and Environmental Sciences, Rutgers University–Newark, Newark, NJ 07102, USA
| | - Dimitrios Ntarlagiannis
- Department of Earth and Environmental Sciences, Rutgers University–Newark, Newark, NJ 07102, USA
| | - Dale Werkema
- Environmental Chemistry Branch, Exposure Methods and Measurement Division, National Exposure Research Laboratory, Office of Research and Development, US Environmental Protection Agency, Las Vegas, NV 89119, USA
| | - Zoltan Szabo
- New Jersey Water Science Center, US Geological Survey, Lawrenceville, NJ 08648, USA
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Wilson JT, Adair C, White H, Howard RL. Effect of Biofuels on Biodegradation of Benzene and Toluene at Gasoline Spill Sites. GROUND WATER MONITORING & REMEDIATION 2016; 36:50-61. [PMID: 32699493 PMCID: PMC7375322 DOI: 10.1111/gwmr.12187] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The risk that benzene and toluene from spills of gasoline will impact drinking water wells is largely controlled by the natural anaerobic biodegradation of benzene and toluene. Benzene and toluene, as well as ethanol and other biofuels, are degraded under anaerobic conditions to the same pool of degradation products. Biodegradation of biofuels may produce concentrations of degradation products that make the thermodynamics for degradation of benzene and toluene infeasible under methanogenic conditions and produce larger plumes of benzene and toluene. This study evaluated the concentrations of fuel alcohols that are necessary to inhibit the anaerobic degradation of benzene and toluene under methanogenic conditions. At two ethanol spill sites, concentrations of ethanol greater ≥42 mg/L inhibited the anaerobic degradation of toluene. The pH and concentrations of acetate, dissolved inorganic carbon, and molecular hydrogen were used to calculate the Gibbs free energy for the biodegradation of toluene. In general, the anaerobic biodegradation of toluene was not thermodynamically feasible in water with ≥42 mg/L ethanol. In a microcosm study, when the concentrations of ethanol were ≥14 mg/L or the concentrations of n-butanol were ≥16 mg/L, the biodegradation of the alcohols consistently produced concentrations of hydrogen, dissolved inorganic carbon, and acetate that would preclude natural anaerobic biodegradation of benzene and toluene by syntrophic organisms. In contrast, iso-butanol and n-propanol only occasionally produced conditions that would preclude the biodegradation of benzene and toluene.
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Affiliation(s)
- John T. Wilson
- Scissortail Environmental Solutions, LLC, 2013 Foster Drive, Ada, OK 74820
| | - Cherri Adair
- U.S. EPA/ORD/NRMRL/GWERD, R.S. Kerr Center Drive, Ada, OK 74820; 580 436 8969
| | - Hal White
- U.S. EPA/OSWER/OUST, 1215 Jefferson Davis Highway, Arlington, VA 22202
| | - Robert L. Howard
- Virginia Certified Professional Geologist, MS, is at Virginia Department of Environmental Quality, Blue Ridge Regional Office, 3019 Peters Creek Road, Roanoke, VA 24019
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Ziegler BA, McGuire JT, Cozzarelli IM. Rates of As and Trace-Element Mobilization Caused by Fe Reduction in Mixed BTEX-Ethanol Experimental Plumes. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2015; 49:13179-89. [PMID: 26486694 DOI: 10.1021/acs.est.5b02341] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Biodegradation of organic matter, including petroleum-based fuels and biofuels, can create undesired secondary water-quality effects. Trace elements, especially arsenic (As), have strong adsorption affinities for Fe(III) (oxyhydr)-oxides and can be released to groundwater during Fe-reducing biodegradation. We investigated the mobilization of naturally occurring As, cobalt (Co), chromium (Cr), and nickel (Ni) from wetland sediments caused by the introduction of benzene, toluene, ethylbenzene, and xylenes (BTEX) and ethanol mixtures under iron- and nitrate-reducing conditions, using in situ push-pull tests. When BTEX alone was added, results showed simultaneous onset and similar rates of Fe reduction and As mobilization. In the presence of ethanol, the maximum rates of As release and Fe reduction were higher, the time to onset of reaction was decreased, and the rates occurred in multiple stages that reflected additional processes. The concentration of As increased from <1 μg/L to a maximum of 99 μg/L, exceeding the 10 μg/L limit for drinking water. Mobilization of Co, Cr, and Ni was observed in association with ethanol biodegradation but not with BTEX. These results demonstrate the potential for trace-element contamination of drinking water during biodegradation and highlight the importance of monitoring trace elements at natural and enhanced attenuation sites.
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Affiliation(s)
- Brady A Ziegler
- Department of Geosciences, Virginia Tech , Blacksburg, Virginia, 24061 United States
| | - Jennifer T McGuire
- Department of Biology, University of St. Thomas , St. Paul, Minnesota, 55105 United States
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Bioremediation Modeling of an Aquifer Contaminated by Benzene Using the Slow-Release Oxygen Source Technique. ARABIAN JOURNAL FOR SCIENCE AND ENGINEERING 2015. [DOI: 10.1007/s13369-015-1637-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Corseuil HX, Gomez DE, Schambeck CM, Ramos DT, Alvarez PJJ. Nitrate addition to groundwater impacted by ethanol-blended fuel accelerates ethanol removal and mitigates the associated metabolic flux dilution and inhibition of BTEX biodegradation. JOURNAL OF CONTAMINANT HYDROLOGY 2015; 174:1-9. [PMID: 25618389 DOI: 10.1016/j.jconhyd.2014.12.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2014] [Revised: 12/13/2014] [Accepted: 12/15/2014] [Indexed: 06/04/2023]
Abstract
A comparison of two controlled ethanol-blended fuel releases under monitored natural attenuation (MNA) versus nitrate biostimulation (NB) illustrates the potential benefits of augmenting the electron acceptor pool with nitrate to accelerate ethanol removal and thus mitigate its inhibitory effects on BTEX biodegradation. Groundwater concentrations of ethanol and BTEX were measured 2 m downgradient of the source zones. In both field experiments, initial source-zone BTEX concentrations represented less than 5% of the dissolved total organic carbon (TOC) associated with the release, and measurable BTEX degradation occurred only after the ethanol fraction in the multicomponent substrate mixture decreased sharply. However, ethanol removal was faster in the nitrate amended plot (1.4 years) than under natural attenuation conditions (3.0 years), which led to faster BTEX degradation. This reflects, in part, that an abundant substrate (ethanol) can dilute the metabolic flux of target pollutants (BTEX) whose biodegradation rate eventually increases with its relative abundance after ethanol is preferentially consumed. The fate and transport of ethanol and benzene were accurately simulated in both releases using RT3D with our general substrate interaction module (GSIM) that considers metabolic flux dilution. Since source zone benzene concentrations are relatively low compared to those of ethanol (or its degradation byproduct, acetate), our simulations imply that the initial focus of cleanup efforts (after free-product recovery) should be to stimulate the degradation of ethanol (e.g., by nitrate addition) to decrease its fraction in the mixture and speed up BTEX biodegradation.
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Affiliation(s)
- Henry Xavier Corseuil
- Federal University of Santa Catarina, Department of Sanitary and Environmental Engineering, Florianópolis, Santa Catarina, Brazil.
| | - Diego E Gomez
- University of Exeter, Centre for Water Systems, Exeter, Devon EX4 4QF, United Kingdom
| | - Cássio Moraes Schambeck
- Federal University of Santa Catarina, Department of Sanitary and Environmental Engineering, Florianópolis, Santa Catarina, Brazil
| | - Débora Toledo Ramos
- Federal University of Santa Catarina, Department of Sanitary and Environmental Engineering, Florianópolis, Santa Catarina, Brazil
| | - Pedro J J Alvarez
- Department of Civil and Environmental Engineering, Rice University, MS-317, 6100 Main St., Houston, TX 77005, USA
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Ugwoha E, Andresen JM. Sorption and phase distribution of ethanol and butanol blended gasoline vapours in the vadose zone after release. J Environ Sci (China) 2014; 26:608-616. [PMID: 25079274 DOI: 10.1016/s1001-0742(13)60436-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2013] [Revised: 04/18/2013] [Accepted: 05/17/2013] [Indexed: 06/03/2023]
Abstract
The sorption and phase distribution of 20% ethanol and butanol blended gasoline (E20 and B20) vapours have been examined in soils with varying soil organic matter (SOM) and water contents via laboratory microcosm experiments. The presence of 20% alcohol reduced the sorption of gasoline compounds by soil as well as the mass distribution of the compounds to soil solids. This effect was greater for ethanol than butanol. Compared with the sorption coefficient (Kd) of unblended gasoline compounds, the Kd of E20 gasoline compounds decreased by 54% for pentane, 54% for methylcyclopentane (MCP) and 63% for benzene, while the Kd of B20 gasoline compounds decreased by 39% for pentane, 38% for MCP and 49% for benzene. The retardation factor (R) of E20 gasoline compounds decreased by 53% for pentane, 53% for MCP and 48% for benzene, while the R of B20 gasoline compounds decreased by 39% for pentane, 37% for MCP and 38% for benzene. For all SOM and water contents tested, the Kd and R of all gasoline compounds were in the order of unblended gasoline > B20 > E20, indicating that the use of high ethanol volume in gasoline to combat climate change could put the groundwater at greater risk of contamination.
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Affiliation(s)
- Ejikeme Ugwoha
- Chemical and Environmental Engineering, University of Nottingham, Nottingham, NG7 2RD, United Kingdom.
| | - John M Andresen
- School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh, EH14 4AS, United Kingdom
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Personna YR, Slater L, Ntarlagiannis D, Werkema D, Szabo Z. Complex resistivity signatures of ethanol biodegradation in porous media. JOURNAL OF CONTAMINANT HYDROLOGY 2013; 153:37-50. [PMID: 23969406 DOI: 10.1016/j.jconhyd.2013.07.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2013] [Revised: 07/12/2013] [Accepted: 07/15/2013] [Indexed: 06/02/2023]
Abstract
Numerous adverse effects are associated with the accidental release of ethanol (EtOH) and its persistence in the subsurface. Geophysical techniques may permit non-invasive, real time monitoring of microbial degradation of hydrocarbon. We performed complex resistivity (CR) measurements in conjunction with geochemical data analysis on three microbial-stimulated and two control columns to investigate changes in electrical properties during EtOH biodegradation processes in porous media. A Debye Decomposition approach was applied to determine the chargeability (m), normalized chargeability (m(n)) and time constant (τ) of the polarization magnitude and relaxation length scale as a function of time. The CR responses showed a clear distinction between the bioaugmented and control columns in terms of real (σ') and imaginary (σ″) conductivity, phase (ϕ) and apparent formation factor (F(app)). Unlike the control columns, a substantial decrease in σ' and increase in F(app) occurred at an early time (within 4 days) of the experiment for all three bioaugmented columns. The observed decrease in σ' is opposite to previous studies on hydrocarbon biodegradation. These columns also exhibited increases in ϕ (up to ~9 mrad) and σ″ (up to two order of magnitude higher) 5 weeks after microbial inoculation. Variations in m and m(n) were consistent with temporal changes in ϕ and σ″ responses, respectively. Temporal geochemical changes and high resolution scanning electron microscopy imaging corroborated the CR findings, thus indicating the sensitivity of CR measurements to EtOH biodegradation processes. Our results offer insight into the potential application of CR measurements for long-term monitoring of biogeochemical and mineralogical changes during intrinsic and induced EtOH biodegradation in the subsurface.
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Affiliation(s)
- Yves Robert Personna
- Department of Earth and Environmental Sciences, Rutgers University, 101 Warren Street, Newark, NJ, 07102 USA.
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Microbial processes influencing the transport, fate and groundwater impacts of fuel ethanol releases. Curr Opin Biotechnol 2013; 24:457-66. [DOI: 10.1016/j.copbio.2012.09.005] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2012] [Revised: 08/30/2012] [Accepted: 09/04/2012] [Indexed: 11/20/2022]
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Personna YR, Slater L, Ntarlagiannis D, Werkema D, Szabo Z. Complex resistivity signatures of ethanol in sand-clay mixtures. JOURNAL OF CONTAMINANT HYDROLOGY 2013; 149:76-87. [PMID: 23603518 DOI: 10.1016/j.jconhyd.2013.03.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2012] [Revised: 03/17/2013] [Accepted: 03/22/2013] [Indexed: 06/02/2023]
Abstract
We performed complex resistivity (CR) measurements on laboratory columns to investigate changes in electrical properties as a result of varying ethanol (EtOH) concentration (0% to 30% v/v) in a sand-clay (bentonite) matrix. We applied Debye decomposition, a phenomenological model commonly used to fit CR data, to determine model parameters (time constant: τ, chargeability: m, and normalized chargeability: mn). The CR data showed a significant (P≤0.001) time-dependent variation in the clay driven polarization response (~12 mrad) for 0% EtOH concentration. This temporal variation probably results from the clay-water reaction kinetics trending towards equilibrium in the sand-clay-water system. The clay polarization is significantly suppressed (P≤0.001) for both measured phase (ϕ) and imaginary conductivity (σ″) with increasing EtOH concentration. Normalized chargeability consistently decreases (by up to a factor of ~2) as EtOH concentration increases from 0% to 10% and 10 to 20%, respectively. We propose that such suppression effects are associated with alterations in the electrical double layer (EDL) at the clay-fluid interface due to (a) strong EtOH adsorption on clay, and (b) complex intermolecular EtOH-water interactions and subsequent changes in ionic mobility on the surface in the EDL. Changes in the CR data following a change of the saturating fluid from EtOH 20% to plain water indicate strong hysteresis effects in the electrical response, which we attribute to persistent EtOH adsorption on clay. Our results demonstrate high sensitivity of CR measurements to clay-EtOH interactions in porous media, indicating the potential application of this technique for characterization and monitoring of ethanol contamination in sediments containing clays.
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Affiliation(s)
- Yves Robert Personna
- Department of Earth and Environmental Sciences, Rutgers University, 101 Warren Street, Newark, NJ 07102, USA.
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da Silva MLB, Gomez DE, Alvarez PJJ. Analytical model for BTEX natural attenuation in the presence of fuel ethanol and its anaerobic metabolite acetate. JOURNAL OF CONTAMINANT HYDROLOGY 2013; 146:1-7. [PMID: 23340452 DOI: 10.1016/j.jconhyd.2012.12.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2012] [Revised: 12/14/2012] [Accepted: 12/19/2012] [Indexed: 06/01/2023]
Abstract
Flow-through column studies were conducted to mimic the natural attenuation of ethanol and BTEX mixtures, and to consider potential inhibitory effects of ethanol and its anaerobic metabolite acetate on BTEX biodegradation. Results were analyzed using a one-dimensional analytical model that was developed using consecutive reaction differential equations based on first-order kinetics. Decrease in pH due to acetogenesis was also modeled, using charge balance equations under CaCO(3) dissolution conditions. Delay in BTEX removal was observed and simulated in the presence of ethanol and acetate. Acetate was the major volatile fatty acid intermediate produced during anaerobic ethanol biodegradation (accounting for about 58% of the volatile fatty acid mass) as suggested by the model data fit. Acetate accumulation (up to 1.1 g/L) near the source zone contributed to a pH decrease by almost one unit. The anaerobic degradation of ethanol (2 g/L influent concentration) at the source zone produced methane at concentrations exceeding its solubility (~/=26mg/L). Overall, this simple analytical model adequately described ethanol degradation, acetate accumulation and methane production patterns, suggesting that it could be used as a screening tool to simulate lag times in BTEX biodegradation, changes in groundwater pH and methane generation following ethanol-blended fuel releases.
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Personna YR, Slater L, Ntarlagiannis D, Werkema D, Szabo Z. Electrical signatures of ethanol-liquid mixtures: implications for monitoring biofuels migration in the subsurface. JOURNAL OF CONTAMINANT HYDROLOGY 2013; 144:99-107. [PMID: 23159764 DOI: 10.1016/j.jconhyd.2012.10.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2012] [Revised: 10/04/2012] [Accepted: 10/08/2012] [Indexed: 06/01/2023]
Abstract
Ethanol (EtOH), an emerging contaminant with potential direct and indirect environmental effects, poses threats to water supplies when spilled in large volumes. A series of experiments was directed at understanding the electrical geophysical signatures arising from groundwater contamination by ethanol. Conductivity measurements were performed at the laboratory scale on EtOH-water mixtures (0 to 0.97 v/v EtOH) and EtOH-salt solution mixtures (0 to 0.99 v/v EtOH) with and without a sand matrix using a conductivity probe and a four-electrode electrical measurement over the low frequency range (1-1000 Hz). A Lichtenecker-Rother (L-R) type mixing model was used to simulate electrical conductivity as a function of EtOH concentration in the mixture. For all three experimental treatments increasing EtOH concentration resulted in a decrease in measured conductivity magnitude (|σ|). The applied L-R model fitted the experimental data at concentration ≤0.4v/v EtOH, presumably due to predominant and symmetric intermolecular (EtOH-water) interaction in the mixture. The deviation of the experimental |σ| data from the model prediction at higher EtOH concentrations may be associated with hydrophobic effects of EtOH-EtOH interactions in the mixture. The |σ| data presumably reflected changes in relative strength of the three types of interactions (water-water, EtOH-water, and EtOH-EtOH) occurring simultaneously in EtOH-water mixtures as the ratio of EtOH to water changed. No evidence of measurable polarization effects at the EtOH-water and EtOH-water-mineral interfaces over the investigated frequency range was found. Our results indicate the potential for using electrical measurements to characterize and monitor EtOH spills in the subsurface.
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Affiliation(s)
- Yves Robert Personna
- Department of Earth and Environmental Sciences, Rutgers University, Newark, New Jersey 07102, USA.
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