Grantee Research Project Results
Final Report: Characterizing the Intrinsic Remediation of MTBE at Field Sites
EPA Grant Number: R828598C791Subproject: this is subproject number 791 , established and managed by the Center Director under grant R828598
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
Center: Texas - Indiana Virtual STAR Center
Center Director: Gustafsson , Jan-Ake
Title: Characterizing the Intrinsic Remediation of MTBE at Field Sites
Investigators: Rifai, Hanadi , Rixey, William G.
Institution: University of Houston - University Park
EPA Project Officer: Aja, Hayley
Project Period: September 1, 2000 through August 31, 2004
RFA: Gulf Coast Hazardous Substance Research Center (Lamar University) (1996) RFA Text | Recipients Lists
Research Category: Hazardous Waste/Remediation , Targeted Research
Objective:
MTBE, a common oxygenate, is used in 30% of the nation’s gasoline and usually composes 11 to 15% of the gasoline product. Although MTBE has beneficial properties for improving air quality, it also has several characteristics that make it a highly mobile groundwater contaminant. Recent studies in the literature documented the presence of MTBE in many of the nation’s groundwater aquifers. Initially thought recalcitrant, more current research points to the biodegradability of MTBE under aerobic and anaerobic conditions. In light of MTBE’s economic impact (in Texas alone, the MTBE industry accounts for approximately 25,000 jobs), and the lack of consensus on replacement additives, studies are needed to fully characterize MTBE’s behavior at the field scale and develop a better understanding of its attenuation potential on an individual site basis and on a more global scale as a gasoline additive.
This study develops a database of 127 MTBE sites and uses the historical data gathered at the selected sites to evaluate the MTBE plume spatially and temporally. Historical concentration data in individual wells were studied to determine trends over time. In order to assess overall plume status, the concentrations in source and tail wells at each site were analyzed using the Mann Kendall (MK) and linear regression statistical trend analysis methods. Overall plume stability was further evaluated by estimating the dimensions of the plume over time.
Attenuation rates were calculated for each site using concentration-time plots (point attenuation) and concentration distance plots (bulk attenuation). The bulk-attenuation analysis could only be completed for six sites out of the 127 in the database due to the lack of wells along the centerline. Geochemical indicator data were reported for only 22 of the 127 sites in the database, and were not used in the analysis due to the poor data quality.
Summary/Accomplishments (Outputs/Outcomes):
The project resulted in four peer reviewed publications and numerous presentations and conference proceedings papers. Two students received their master’s degrees as a result of the project funding and are currently employed in the private sector. The project also helped a post-doctoral researcher re-enter the workforce after a parenting leave.
A database of 127 sites was assembled for leaking petroleum storage tank (LPST) sites contaminated with MTBE using the Texas Commission of Environmental Quality (TCEQ) site records. A large percentage (61%) of the sites in the database were located along the Gulf Coast. The remaining sites cover most areas across Texas and therefore represent several geologies and lithologies. The 127 sites had mostly shallow groundwater (less than 30-ft (9.1-m) below ground surface) and the impacted water zone was not a drinking water source. The monitoring well networks at the 127 sites consisted of 12 monitoring wells on average but ranged from a minimum of 6 to a maximum of 64 wells.
The data in Figure 1 show the distribution of tank installation dates for the 127 sites. As can be seen, most sites began operation between 1969 and 1986 with more than half the PSTs installed prior to 1979 indicating the possibility of leaks that pre-date MTBE addition to gasoline. The data in Figure 2 indicate most PSTs were removed or repaired post 1988, just after Texas PST rules went into effect. The duration of operations prior to tank removal or repair ranged from 2 to 52-yrs with an average of 17 years.
The fraction of soil organic carbon (foc) was reported at 61 sites and ranged between 0.001% and 13.2%, with a median value of 0.7%. Retardation coefficients (R) ranged from 1-7 for MTBE and 1 to 21 for benzene. The median hydraulic conductivity in the database was 2,625-ft/yr. Hydraulic gradients at 85% of the sites were less than or equal to 0.03 ft/ft and the median value for all sites was 0.01 ft/ft. Calculated seepage velocities ranged from less than 0.001-ft/yr to over 15,000-ft/yr. This range, while not typical for groundwater, is the result of very low hydraulic conductivities and steep gradients reported at several sites in the database. The median seepage velocity was 44-ft/yr. These hydrogeologic characteristics of the 127 sites point to the possible specificity of results from this study to the Gulf Coast region but also maybe due to the relatively small number of sites studied.
MTBE concentrations were significantly correlated to benzene and toluene, although the correlation was weaker than that between benzene and toluene. The stronger correlation between benzene and toluene likely reflects their comparable solubilities and other physical properties, as well as similar source terms. Maximum soil and groundwater concentrations varied greatly among the 127 sites. MTBE soil data were rarely found in site reports and a clear relationship between benzene soil and groundwater concentrations could not be found. The MTBE and benzene plumes at the majority of sites had traveled off-site and the off-site plumes were often not fully delineated. This is a key concern for assessing MTBE plume behavior since most existing monitoring networks do not capture the full extent of the plume. In fact, only 36 sites had extensive monitoring networks that allowed an adequate definition of their plumes. A comparison of average plume lengths for each constituent at the 36 sites is shown in Figure 3 (top). The benzene and MTBE plume lengths were comparable with average and median plume lengths of benzene actually outstretching those of MTBE by approximately 36-ft (11.0-m). The MTBE and benzene plumes ranged in length from 88- to 1096-ft and 78- to 1013-ft, respectively. In contrast, both benzene and MTBE significantly outstretched toluene, which at some sites had been reduced to below its MCL concentration in all wells. Based on the data in Figure 3, it was clear that the measured plume lengths reflect the order of associated MCL magnitude and is the probable cause for benzene plumes measuring longer than those for MTBE and the significantly smaller length of toluene plumes. In fact, when MTBE plumes and toluene plumes are contoured using the 5 ppb levels as in the case of benzene, MTBE plumes outstretch benzene and toluene by approximately 35% (Figure 3-bottom).
Figure 1. Histogram of Installation Dates for 127 sites in the Database
Figure 2. Histogram of Tank Removal Date for Sites in Database
Concentration trends were evaluated for 1,074 MTBE wells, 1,206 benzene wells, and 1,185 toluene wells. The majority of well concentrations (over 70%) were stable or declining over time for both MTBE and benzene. Results from the Mann Kendall and linear regression analyses indicated that MTBE and benzene stability were comparable in source and tail areas. The analysis of change in plume length over time, completed for the 36 sites with fully delineated MTBE and benzene plumes indicated that MTBE and benzene plume lengths were most often defined as stable or as having “no trend”. Toluene plumes, however, appeared to be more likely stable or decreasing and their concentration reduced to below the toluene MCL (1000-ppb) in all wells across several sites as mentioned previously.
Figure 3. Plume Lengths for MTBE, Benzene and Toluene (Top – using cleanup standards in defining plume, Bottom – using drinking water standards)
Plume lengths based on the average measurements over time were also evaluated for influences from source removal actions. The results showed that the median length of MTBE plumes was 65-ft longer at sites where source removal occurred after the first year plume data were contoured than those sampled after source removal.
The MTBE, benzene, and toluene well data yielded estimates of point and bulk attenuation rates. Median point attenuation rate constants (half-life) of –7.8E-04/d (2.45-yr) for MTBE and -7.5E-04/d (2.53-yr) for benzene were calculated. The median point attenuation rate constant calculated using 79% of all toluene wells was slightly higher at –8.6E-04/d (2.22-yr). Additionally, the median MTBE half-lives for decreasing source and tail wells were very comparable (2.55-yr versus 2.43-yr). It should be noted, however, that when only the 36 sites with fully delineated MTBE plumes were considered, a longer half-life was found for MTBE (4.4-yr) and benzene (4.3-yr). This supports the importance of adequate monitoring networks when analyzing plume behavior with time and assessing the viability of natural attenuation. Bulk attenuation rate constants for MTBE and benzene were also very comparable (3.33/yr and 2.7/yr, respectively).
Journal Articles:
No journal articles submitted with this report: View all 6 publications for this subprojectSupplemental Keywords:
RFA, Scientific Discipline, INTERNATIONAL COOPERATION, Waste, Water, Remediation, Contaminated Sediments, Health Risk Assessment, Hazardous Waste, Ecology and Ecosystems, Hazardous, Groundwater remediation, sediment treatment, advanced treatment technologies, in situ remediation, contaminant dynamics, in situ treatment, biodegradation, MTBE, contaminated sediment, contaminated soil, emissions, BTEX, natural attenuation, chemical contaminants, in-situ treatment of chlorinated solvents, environmental engineering, treatment, hazadous waste streams, contaminated groundwater, chlorinated VOCs, air emissions, contaminated aquifers, VOC remediation, bioremediation, groundwater, aquifer remediationProgress and Final Reports:
Original AbstractMain Center Abstract and Reports:
R828598 Texas - Indiana Virtual STAR Center Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
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R822721C651 Adjustable Biopolymer Chelators for Cadmium, Lead and Mercury
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R822721C659 Subsurface Contamination Site Characterization via a Computer-Aided Visual Tool
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R822721C663 Soil Remediation with Ultra-High-Efficiency Hydrocyclones
R822721C669 Solid Acid Catalyzed Alkylation in Supercritical Fluids
R822721C679 Regeneration/Reactivation of Carbon Adsorbents by Radio Frequency (RF) Induction Heating
R822721C687 Improved Halogen Resistance of Catalytic Oxidation
R822721C696 Phytoremediation and Bioremediation of Land Contaminated By PAHs, PCBs, and TNT
R822721C697 Fundamental and Kinetic Investigation of Sorbent Technology for Optimum Mercury Emission Control
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R826694C620 Colloidal Fouling of Membranes: Implications in the Treatment of Textile Dye Wastes and Water Reuse
R826694C625 Enhanced Treatment of DNAPLs Contaminated Soils and Groundwater Using Biosurfactants: In-Situ Bioremediation
R826694C626 Catalytic Hydroprocessing of Chlorinated Wastes
R826694C627 The Interaction of Microbial Activity and Zero Valent Iron Permeable Barrier Technology
R826694C629 Biofiltration of BTEX in Petroleum-Contaminated Soil Remediation Off-Gas
R826694C630 Microbial Cometabolism of Recalcitrant Chemicals in Contaminated Air Streams
R826694C633 Catalyst Lifetime Studies for Chlorocarbon Steam Reforming
R826694C635 Electrokinetic/Surfactant-Enhanced Remediation of Hydrophobic Pollutants in Low Permeability Subsurface Environments
R826694C636 Transformation Reactions of Nitroaromatic and Nitrogen Heterocyclic Compounds on Granular Activated Carbon (GAC) Surfaces: Enhancement of GAC Adsorption in Natural and Engineered Environmental Systems
R826694C640 Environmentally Friendly Organic Synthesis in Supercritical Fluids
R826694C645 Development and Evaluation of an Integrated Model to Facilitate Risk-Based Corrective Action at Superfund Sites
R826694C651 Adjustable Biopolymer Chelators for Cadmium, Lead, and Mercury Remeidation
R826694C659 Subsurface Contamination Site characterization Via a Computer-Aided Visual Tool
R826694C661 New Insoluble supports for Protein Immobilization for Use in Metalloprotein Affinity Metal Chromatography
R826694C669 Solid Acid Catalyzed Alkylation in Supercritical Reaction Media
R826694C679 Regeneration and Reactivation of Carbon Adsorbents by Radio Frequency Induction Heating
R826694C696 Phytoremediation and Bioremediation of Land Contaminated By PAHs, PCBs, and TNT
R826694C697 Fundamental and Kinetic Investigation of Sorbent Technology for Optimum Mercury Emission Control
R826694C700 Effects of Natural Cyclic Variations on Contaminated Fate and Transport
R826694C703 Enhancement of DNAPL Dissolution Rates by Dechlorinating Anaerobes
R826694C705 A Pilot Plant for Producing Mixed Ketones from Waste Biomass
R826694C722 The Effects of an Oily-Phase on VOC Emissions from Industrial Wastewater
R826694C724 Mercury Removal from Stack Gas by Aqueous Scrubbing
R826694C725 Transport, Fate and Risk Implications of Environmentally Acceptable Endpoint Decisions
R826694C731 Development and Application of a Real-Time Optical Sensor for Atmospheric Formaldehyde
R826694C734 An Advanced System for Pollution Prevention in Chemical Complexes
R828598C001 Field Study Abstract: A Model of Ambient Air Pollution in Southeast Texas Using Artificial Neural Network Technology
R828598C002 Hollow Fiber Membrane Bioreactors for Treating Water and Air Streams Contaminated with Chlorinated Solvents
R828598C003 Fugitive Emissions of Hazardous Air Pollutants from On-Site Industrial Sewers
R828598C004 Biofiltration Technology Development
R828598C005 A Risk-Based Decision Analysis Approach for Aquifers Contaminated with DNAPLs
R828598C006 In-Situ Remediation for Contaminated Soils Using Prefabricated Vertical Drains
R828598C007 Membrane Technology Selection System for the Metal Finishing Industry
R828598C008 Sequential Environments for Enhanced Bioremediation of Chlorinated Aliphatic Hydrocarbons
R828598C009 Waste Minimization in the Magnetic Tape Industry: Waterborne Coating Formulations for Magnetic Tape Manufacture
R828598C010 Soil Remediation by Agglomeration with Petroleum Coke
R828598C011 Recovery of Dilute Phosphoric Acid in Waste Streams Using Waste Gas Ammonia: The Regenerative MAP/DAP Process
R828598C012 Stochastic Risk Assessment for Bioremediation
R828598C013 Selective Removal of Heavy Metals from Wastewater by Chelation in Supercritical Fluids
R828598C014 Optimization of Treatment Technologies for Detoxification of PCB Contaminated Soils
R828598C015 Wastewater Remediation by Catalytic Wet Oxidation
R828598C016 Permanence of Metals Containment in Solidified and Stabilized Wastes
R828598C017 Combustion Enhancement by Radial Jet Reattachment - Low Generation of Hazardous Gases and High Thermal Efficiency
R828598C018 A Process To Convert Industrial Biosludge and Paper Fines to Mixed Alcohol Fuels
R828598C019 Homogeneous Catalysis in Supercritical Carbon Dioxide
R828598C020 Ultrasonic Enhancement of the Removal of Heavy Metals
R828598C021 The Binding Chemistry and Leaching Mechanisms of Advanced Solidification/Stabilization Systems for Hazardous Waste Management
R828598C022 Development of an Air-Stripping and UV/H2O2 Oxidation Integrated Process To Treat a Chloro-Hydrocarbon-Contaminated Ground Water
R828598C023 A Comparative Study of Siting Opposition in Two Counties
R828598C024 Sonochemical Treatment of Hazardous Organic Compounds II: Process Optimization and Pathway Studies
R828598C025 Laser Diagnostics of the Combustion Process within a Rotary Kiln Incinerator
R828598C026 Use of Inorganic Ion Exchangers for Hazardous Waste Remediation
R828598C027 Kaolinite Sorbent for the Removal of Heavy Metals from Incinerated Lubricating Oils
R828598C028 Destruction of Chlorinated Hydrocarbons in Process Streams Using Catalytic Steam Reforming
R828598C029 Integrated Process Treatment Train (Bioremediation {Aerobic/Anaerobic} and Immobilization) for Texas Soils Contaminated with Combined Hazardous Wastes
R828598C030 Photo-Oxidation by H2O2/VisUV of Off-Gas Atmospheric Emissions from Industrial and Environmental Remediation Sources
R828598C031 Concentrated Halide Extraction and Recovery of Lead from Soil
R828598C032 Biodegradable Surfactant for Underground Chlorinated Solvent Remediation
R828598C033 A Software Guidance System for Choosing Analytical Subsurface Fate and Transport Models Including a Library of Computer Solutions for the Analytical Models
R828598C034 Hydrodynamic Modeling of Leachate Recirculating Landfill
R828598C035 Measurement of Oxygen Transfer Rate in Soil Matrices
R828598C036 Sorbent Technology for Multipollutant Control During Fluidized Bed Incineration
R828598C037 Pollution Prevention by Process Modification Using On-Line Optimization
R828598C038 Pollution Prevention by Process Modification
R828598C039 Water Solubility and Henry's Law Constant
R828598C040 Transferring Technical Information on Hazardous Substance Research by Publishing on the World Wide Web
R828598C041 Stress Protein Responses to Multiple Metal Exposure in Grass Shrimp
R828598C042 Life-Cycle Environmental Costing for Managing Pollution Prevention in the Chemical and Petroleum Refining Industries: A Cross-Border Approach
R828598C687 Improved Halogen Resistance of Catalytic Oxidation Through Efficient Catalyst Testing
R828598C696 Phytoremediation and Bioremediation of Land Contaminated By PAHs, PCBs, and TNT
R828598C697 Fundamental and Kinetic Investigation of Sorbent Technology for Optimum Mercury Emission Control
R828598C700 Effects of Natural Cyclic Variations on Contaminated Fate and Transport
R828598C703 Enhancement of DNAPL Dissolution Rates by Dechlorinating Anaerobes
R828598C705 A Pilot Plant for Producing Mixed Ketones from Waste Biomass
R828598C722 The Effects of an Oily-Phase on VOC Emissions from Industrial Wastewater
R828598C724 Mercury Removal from Stack Gas by Aqueous Scrubbing
R828598C725 Transport, Fate and Risk Implications of Environmentally Acceptable Endpoint Decisions
R828598C731 Development and Application of a Real Time Optical Sensor for Atmospheric Formaldehyde
R828598C734 An Advanced System for Pollution Prevention in Chemical Complexes
R828598C743 Field Demonstration of Ultrasound Enhancement of Permeable Treatment Walls
R828598C744 Optical Fibers Coated With Titania Membrane/UV-Generating Crystal in a Distributed-Light Photoreactor for VOC Oxidation
R828598C749 Characterization and Modeling of Indoor Particulate Contaminants In a Heavily Industrialized Community
R828598C753 Adsolubilization and Photocatalysis in a Semiconducting Monolithic Reactor for Wastewater Treatment
R828598C754 Remote Detection of Gas Emissions in Industrial Processes
R828598C759 Searching for Optimum Composition of Phosphogypsum: Fly ash: Cement Composites for Oyster Culch Materials
R828598C761 Development of a Phytologically-Based Biosorptive Water Treatment Process
R828598C766 Chlorinated Solvent Impact and Remediation Strategies for the Dry Cleaning Industry
R828598C769 Soil/Sediment Remediation by Hot Water Extraction Combined with In-Situ Wet Oxidation
R828598C771 Fluoracrylate Polymer Supported Ligands as Catalysts for Environmentally Benign Synthesis in Supercritical Fluids
R828598C774 The Feasibility of Electrophoretic Repair of Impoundment Leaks
R828598C777 Surfactant Enhanced Photo-oxidation of Wastewaters
R828598C778 Stationary Power Generation Via Solid Oxide Fuel Cells: A Response to Pollution and Global Warming
R828598C786 Photocatalytic Recovery of Sulfur and Hydrogen From Hydrogen Sulfide
R828598C787 Biosurfactant Produced from Used Vegetable Oil for removal of Metals From Wastewaters and Soils
R828598C789 Genetic Engineering of Enzymatic Cyanide Clearance
R828598C791 Characterizing the Intrinsic Remediation of MTBE at Field Sites
R828598C799 Simultaneous Water Conservation/Recycling/Reuse and Waste Reduction in Semiconductor Manufacturing
R828598C801 Building Defined Mixed Cultures To Biodegrade Diverse Mixtures Of Chlorinated Solvents
R828598C802 Engineering of Nanocrystal Based Catalytic Materials for Hydroprocessing of Halogenated Organics
R828598C807 Commercial Demonstration of Hydrogen Peroxide Injection to Control NOx Emissions from Combustion Sources
R828598C809 Evaluating Source Grouting and ORC for Remediating MTBE Sites
R828598C810 Application of Total Cost Assessment To Process Design In the Chemical Industry
R828598C846 Quantitative Demonstration of Source-Zone Bioremediation in A Field-Scale Experimental Controlled Release System
The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.
Project Research Results
Main Center: R828598
359 publications for this center
90 journal articles for this center