Grantee Research Project Results
1998 Progress Report: Reformulated Gasoline Transport and Clean-up of Spills to the Subsurface
EPA Grant Number: R821114Title: Reformulated Gasoline Transport and Clean-up of Spills to the Subsurface
Investigators: Powers, Susan E.
Institution: Clarkson University
EPA Project Officer: Packard, Benjamin H
Project Period: October 1, 1995 through September 30, 1998 (Extended to September 30, 1999)
Project Period Covered by this Report: October 1, 1997 through September 30, 1998
Project Amount: $240,479
RFA: Exploratory Research - Chemistry and Physics of Water (1995) RFA Text | Recipients Lists
Research Category: Water , Land and Waste Management , Safer Chemicals
Objective:
The overall goal of this project is to provide a better understanding of the effects of gasoline additives on the fate, transport, and remediation of reformulated gasolines in subsurface environments. Two specific types of gasoline additives in reformulated gasoline are of concern: oxygenates, such as ethers and alcohols, due to their impact on the solubility of carcinogenic and potentially carcinogenic species from the gasoline; and, deposit control additives and detergents due to their potential for adsorption to soil minerals, thereby affecting the soil wetability. Both of these types of additives lower gasoline-water interfacial tensions as well. Changes in the wetability and interfacial tension will impact the capillary nature of the multiphase fluid flow processes, and the increased solubility could cause greater exposure and human health risks associated with drinking water contaminated by reformulated gasoline.
Three separate tasks are currently being investigated to explore the overall impact of reformulated gasolines spilled to the subsurface
Progress Summary:
Task 1: Our study of the dissolution and long-term fate of ethanol bearing gasolines in the subsurface is on-going. The study is being carried out via a combination of computer modeling and laboratory studies.
Experimental studies quantifying the cosolvency effects associated with ethanol in groundwater has been completed. Current experimental efforts are focused on the diffusion and advection processes potentially limiting the transport of monoaromatics and the ethanol through the gasoline phase to the gasoline water interface. Preliminary results indicate that even with diffusion as the sole transport process, mass transfer of ethanol from the gasoline to the ground water is rapid. This is important because the rate of ethanol mass transfer critically determines the magnitude and duration of the cosolvency effect in the ground water body.
A numerical model describing the overall process of mass transport through the organic phase toward the gasoline/water interface and subsequent aqueous phase transport is being developed by coupling two separate codes, one for each phase. Preliminary modeling results indicate that when ethanol is present in gasoline at levels required for the reformulated and oxygenated fuels programs, generally benign increases in BTEX mass transfer occur. However it is anticipated that when sorption and biodegradation are incorporated into the model, increases in the overall mass transport will be predicted as a result of reduced sorption and biodegradation rates in the presence of ethanol.
Task 2: The impact of oxygenates and deposit control chemicals on surface and interfacial tensions (IFT) and capillary flow phenomena have been measured. Surrogate gasolines containing ethanol or dodecylamine (DDA) in isooctane were considered for most of the experiments. Additional experiments were conducted with the Philips Petroleum gasoline. The interfacial tension showed a marked decrease with increasing concentrations of both ethanol and DDA in the gasoline. IFTs for the surrogate gasolines were consistently higher, however, than the Philips gasoline. These experiments emphasize the importance of the complex mixtures that comprise gasolines on the overall capillary processes.
Capillary pressure-saturation relationships have been measured for both isooctane and the Philips gasoline as a function of ethanol content. As expected, these results indicate that the displacement pressure required to imbibe the gasoline into a water-saturated medium decreases with increasing ethanol content (decreasing IFT).
Task 3: The third task that has been completed has sought to identify sorbents that are more appropriate than activated carbon for the removal of methyl tert butyl ether (MTBE) from groundwater. These sorbents have been developed for other water treatment applications or for solid phase extraction (SPE) and have a high affinity for polar compounds. The synthetic carbonaceous resins tested were found to have capacities three to five times greater than activated carbon at an MTBE concentration of 1 mg/L. The application of the Dubinin-Astakov isotherm to data for the synthetic carbonaceous resins suggests that the mechanism of adsorption is micro-pore filling. Additional bisolute experiments with m-xylene as a representative gasoline contaminant indicate that the m-xylene is preferentially sorbed, depleting the micro-pore volume available for MTBE sorption.
Future Activities:
The bulk of the research work for this project has been completed. The final analysis and dissemination of results associated with Task 2 will be completed in the near future. Additional dissolution rate experiments will be conducted under Task 1 and the results incorporated into the numerical model to allow an assessment of the overall impact of ethanol containing gasolines on groundwater quality.
Journal Articles on this Report : 2 Displayed | Download in RIS Format
Other project views: | All 19 publications | 4 publications in selected types | All 3 journal articles |
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Davis SW, Powers SE. Alternative sorbents for removing MTBE from gasoline-contaminated ground water. Journal of Environmental Engineering 2000;126(4):354-360. |
R821114 (1998) R821114 (Final) |
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Heermann SE, Powers SE. Modeling the partitioning of BTEX in water-reformulated gasoline systems containing ethanol. Journal of Contaminant Hydrology 1998;34(4):315-341. |
R821114 (1998) R821114 (Final) |
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Supplemental Keywords:
gasoline, oxygenates, MTBE, gasohol, ethanol, groundwater contamination, synthetic adsorbents, carbonaceous resins, NAPL dissolution, cosolvency, free convection, interphase mass transfer, UNIFAC, UNIQUAC., RFA, Scientific Discipline, Industry Sectors, Toxics, Water, Waste, TREATMENT/CONTROL, Ecosystem Protection/Environmental Exposure & Risk, Remediation, Treatment Technologies, Physics, Chemistry, Contaminant Candidate List, Mining - NAIC 21, Fate & Transport, chemical mixtures, Hazardous Waste, Transportation and Warehousing - NAIC 48-49, Drinking Water, Hazardous, Engineering, Chemistry, & Physics, Groundwater remediation, EPCRA, Watersheds, fate and transport, gasoline, cosolvency, Methyl tert butyl ether, contaminant transport, gasoline additives, solubility, contaminated waters, cleanup, MTBE, oxygenates, BTEX, UNIQUAC, spills, treatment, oil spills, aquifer remediation design, analytical chemistry, chemical kinetics, sorbents, transport models, environmental transport and fate, environmental chemistry, groundwater contamination, NAPLs, UNIFAC, ground water, other - risk management, groundwaterRelevant Websites:
http://www-erd.llnl.gov/ethanol/Progress and Final Reports:
Original AbstractThe 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.