Grantee Research Project Results
Final Report: Development of Biodegradation System for Treatment of Groundwater Impacted by Methyl Tert-Butyl Ether (MTBE)
EPA Contract Number: 68D00237Title: Development of Biodegradation System for Treatment of Groundwater Impacted by Methyl Tert-Butyl Ether (MTBE)
Investigators: O'Connell, Joseph
Small Business: Environmental Resolutions Inc.
EPA Contact: Richards, April
Phase: I
Project Period: September 1, 2000 through March 1, 2001
Project Amount: $69,810
RFA: Small Business Innovation Research (SBIR) - Phase I (2000) RFA Text | Recipients Lists
Research Category: SBIR - Waste , Hazardous Waste/Remediation , Small Business Innovation Research (SBIR)
Description:
The objective of this project was to develop a biodegradation system for the treatment of methyl tert-butyl ether (MTBE) and other gasoline components. The work included: (1) evaluation of the effectiveness of growing MTBE-degrading cultures in ethanol as a method of quickly preparing feedstock for field units; (2) development of an appropriate process schematic for a system to treat groundwater contaminated by MTBE and other hydrocarbons; (3) development of startup processes for prototype systems; and (4) evaluation of the relative efficiency of pure and mixed cultures in biodegrading MTBE under field conditions where other hydrocarbons are present. Work was expanded to include parallel evaluation of fluidized bed reactors and evaluation of this biosystem for the biodegradation of tertiary butyl alcohol (TBA), a byproduct of MTBE often found in groundwater.The research has expanded from the original concepts laid out when the proposal was submitted in May 2000. Ethanol proved not to be a very effective growth enhancer, the initial site selected for the trickling bed reactors proved to have too little groundwater for an effective study, and the fluidized bed reactor has achieved performance far in excess of expectations.
Summary/Accomplishments (Outputs/Outcomes):
Ethanol was effective in promoting growth for the PM-1 pure culture isolated by Professor Kate Scow. However, a pure culture is very difficult to maintain outside a controlled laboratory. Pure cultures become mixed cultures when exposed to field conditions. Mixed cultures tend to lose their ability to metabolize MTBE when exposed to ethanol; therefore, ethanol is not an effective growth agent.A process schematic and startup procedures were developed for charging both trickling bed and fluidized bed reactors. It makes very little difference whether one starts with a pure or a mixed culture. Growth rates are nearly the same, and pure cultures do not stay "pure" very long when exposed to field conditions. The time from inoculation to full-fledged bioreaction in the trickling bed is about 2?4 weeks. Accurate determination of the bioreaction onset is complicated by the fact that the carbon used also absorbs MTBE. The recommended method for fluidized beds would be to inoculate with about one-half of the normal operating biomass from a growth reactor. In this case, full bioreaction would be reached in 14 days or less.
The trickling bed reactors were installed at an alternative site because the original site did not produce enough groundwater. This delay did not allow sufficient time to reach steady state, so meaningful data could not be collected from the new reactors. However, similar reactors have been in operation for more than 1 year at Healdsburg, and data collected from these steady-state reactors indicate that it is possible to operate trickling bed reactors in series or on parallel. At Healdsburg, MTBE was routinely reduced to about 15?20 percent of the incoming concentrations with an estimated residence time of 2?4 minutes.
The fluidized bed reactor affords complete mineralization (oxidation to carbon dioxide and water) of both MTBE and TBA from the high values often found at service stations (100,000 µg/L). Concentrations of MTBE and TBA exiting the fluidized bed reactor were below the limits of detectability. In a single pass through the pilot-scale fluidized bed reactor, MTBE concentrations were reduced from 1,300 µg/L to non-detectable at less than 1 µg/L with a residence time of about 15 minutes. TBA concentrations were reduced from 1,300 µg/L to non-detectable at less than 5 µg/L. The use of a recycle loop will allow treatment of incoming concentrations of 200,000 µg/L or more and produce effluent with concentrations less than 5 µg/L.
Conclusions:
Environmental Resolutions, Inc. has made a number of presentations to regulatory agencies in California and to major oil companies. The regulatory agencies have accepted the process as qualified to receive reimbursement from the cleanup fund. There are four major oil companies interested in prototype reactors at gasoline service stations in California. A major remaining challenge is to interest water purveyors in a wellhead treatment system for drinking water.Supplemental Keywords:
remediation, groundwater, treatment, leaking underground storage tanks, engineering, chemistry., Scientific Discipline, Air, Toxics, Waste, Water, Chemical Engineering, air toxics, Contaminated Sediments, Environmental Chemistry, Contaminant Candidate List, HAPS, Groundwater remediation, Engineering, Chemistry, & Physics, Environmental Engineering, biodegradability, Methyl tert butyl ether, hydrocarbon, MTBE, biodegradation, contaminated sediment, biodegradation system, treatmentThe 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.