Tables 24.13 and 24.14 summarize performance data for the 35 completed and 38 ongoing in situ bioremediation projects. The concentration of MTBE in groundwater prior to treatment was as high as 870,000 ^g/L and as low as 10 ^g/L. The data show that bioremediation (either alone or in combination with other technologies) has been employed to remediate MTBE in groundwater and soil to concentrations <50 |^g/L and has achieved MTBE concentration reductions >99%. The median project duration for the 20 completed sites ranged from 6 months to 1 year.
In addition to the performance data reported for MTBE, eight of the 12 projects in the dataset that reported treating TBA using bioremediation also provided performance data. All of these eight sites provided TBA concentration prior to bioremediation treatment (the highest initial concentration was 90,000 |ag/L) and two provided TBA concentrations following treatment (both achieved <5 ^g/L).
Completed In Situ Bioremediation Projects Performance for 35 Projects
Initial MTBE Final MTBE
Concentration (mg/L) Concentration (mg/L)
In situ bioremediation only
In situ bioremediation with air sparging and SVE
Projects Minimum Median Maximum Minimum Median Maximum
25 5 2800 100,000 1 35 33,000
Median Project Duration (months)
Source: Adapted from U.S. EPA, Technologies for Treating MTBE and Other Fuel Oxygenates, EPA 542-R-04-009, United
States Environmental Protection Agency, Washington, DC, May 2004. NR = Information not provided.
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