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EFFECT OF BTEX AND ETHANOL ON ANAEROBIC BIOTRANSFORMATION OF MTBE
Citation:
Wilson*, J T., C J. Adair*, AND R. Kolhatlar. EFFECT OF BTEX AND ETHANOL ON ANAEROBIC BIOTRANSFORMATION OF MTBE. Presented at Battelle Conf.-7th Int'l. Symposium on In-Situ & On-Site Bioremediation, Orlando, FL, 06/2-5/2003.
Description:
We have recently demonstrated that natural anaerobic biotransformation of MTBE to TBA can account for the natural attenuation of MTBE in a plume from a gasoline spill at Parsippany, New Jersey. It is well established in the literature that the presence of the BTEX compounds naturally present in gasoline can inhibit biodegradation of MTBE under aerobic conditions. Ethanol is widely used as an oxygenate in gasoline as an alternative to MTBE. There is a reasonable prospect that gasoline with ethanol will be spilled on top of an older spill of gasoline with MTBE. This study examines the influence of BTEX compounds and ethanol on the natural anaerobic biodegradation of MTBE. Microcosms were constructed using aquifer sediment from the plume at Parsippany, New Jersey. The material as collected had background concentrations of MTBE and BTEX compounds; however, ethanol was not detected. Data were compared from three treatments: spiked with additional MTBE, spiked with additional MTBE and BTEX, and spiked with additional MTBE, BTEX, and ethanol.
The average initial concentration of MTBE in the four treatments varied from 2.0 to 2.6 mg/L, and the average initial concentration of total alkylbenzenes varied from 2.1 to 7.2 mg/L. The average initial concentration of ethanol in the treatments that were spiked with ethanol was 1,400 mg/L. There was no degradation of either MTBE or BTEX compounds in any of the treatments in the first 86 days of incubation.
In the treatment spiked with MTBE alone, the concentration was reduced to the detection limit (10 g/L) in three replicate microcosm after 177 days of incubation, and after 199 days of incubation.
In the treatment spiked with MTBE and BTEX compounds the removal of MTBE was mixed after 177 and 199 days of incubation. The concentration of MTBE was reduced by ten fold in three microcosms, while there was no change in the another three microcosms. After 268 days of incubation, the concentration was below the limit of detection in three replicate microcosms.
In the treatment spiked with MTBE, BTEX compounds, and ethanol, there was no removal of MTBE in one microcosm after 268 days of incubation, but there was at least a one-hundred fold removal in the other two microcosm. After 359 days of incubation, there was extensive removal in all the microcosms.
The removal of alkylbenzenes and MTBE were concurrent. The alkylbenzenes did not degrade before the MTBE. In a particular microcosm, either the concentrations of both MTBE and alkylbenenes were high , or both were low. The added BTEX compounds extended the time required to remove MTBE in all the replicate microcosms from 177 days to 268 days of incubation. The addition of ethanol and BTEX compounds together extended the time required from 177 days to 359 days.
Ethanol degraded very readily in the sediment from Parsippany, New Jersey. Within 28 days the concentration of ethanol was below the limit of quantitation (10 mg/liter) in all the microcosms. The presence of ethanol was not required for the addition of ethanol to have an effect on MTBE degradation.