MTBE Concentration Range
Greater than 100,000^g/L Greater than or equal to 10,000 ng/L but less than 100,000^g/L Greater than or equal to 1000 ng/L but less than 10,000 ^g/L Greater than or equal to 100 ng/L but less than 1000 ^g/L Greater than or equal to 50 ng/L but less than 100 ^g/L Less than 50 ng/L
Number of Projects Reporting Number of Projects Reporting Initial MTBE Concentrations Posttreatment MTBE Concentrations
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.
Because of the heightened interest in bioremediation of TBA, additional information was obtained about several of these sites. These data, provided in the online database, show that several sites were able to reduce the concentration of TBA, sometimes to less than its site-specific cleanup level. For example, at several sites in Texas, including Turtle Bayou Easement Area and Rural Area Disposal Area, in situ bioremediation was used in conjunction with other technologies such as SVE, and in situ thermal desorption. At these sites, the concentrations of TBA were reduced to less than its cleanup goal, with concentrations after treatment ranging from 100 to 1000 |^g/L. At the Naval Base Ventura County, Port Hueneme, California, in situ bioremediation was used in a biobarrier configuration, and the concentration of TBA was reduced from >1000 to <5 |^g/L.
24.7.6 Costs of In Situ Bioremediation Treatment of Oxygenates
Project cost data were reported for 28 of the 73 bioremediation projects in the dataset; these include data for both ongoing and completed projects. In most cases, the components that make up the project costs were not reported. However, it is likely that the reported costs incorporate different components, such as treatment, monitoring, design, oversight, and health and safety. Most (21 projects) of the reported costs were for ongoing projects and represent either a partial actual cost or an estimated total project cost.
The median reported total cost for all bioremediation projects was approximately USD125,000, with most projects having a total cost between USD50,000 and USD350,000. The total cost for all
28 projects reporting this information ranged from USD4000 to USD5,200,000 per project, depending on scale, type of engineered application, and site conditions. For example, at the Port Hueneme site, a 152.5 m (500 ft) wide biobarrier was constructed in a shallow sand aquifer and had an installation cost of USD435,000, with first year operation and maintenance (O&M) costs of USD75,000. At a site in South Carolina, 11.36 m3 (3000 gallons) of a liquid microbial solution was injected through 40 monitoring and 15 injection points, for a total cost of USD63,500.
Because the area, volume, or mass treated was not consistently available for the 28 bioremediation projects, no unit costs were estimated. The cost per volume of subsurface treated was reported in one literature source33 as ranging from approximately USD222 to USD432/m3 (USD170-USD330/yd3) for in situ bioremediation in general. This source also reported unit costs for ex situ bioremediation ranging from USD15.7 (USD12) to more than USD1300/m3 (USD1000/yd3) treated. These results suggest that the cost for bioremediation is highly variable and depends on site-specific conditions and remedial goals.1,70 Overall, the cost of bioremediation is generally considered to be better than the average for applicable groundwater remediation technologies.34
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