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BIODEGRADATION OF METHYL TERT-BUTYL ETHER AND BTEX AT VARYING HYDRAULIC RETENTION TIMES
Citation:
Sedran, M. A., A. Pruden, G. J. Wilson, M. T. Suidan, AND A D. Venosa*. BIODEGRADATION OF METHYL TERT-BUTYL ETHER AND BTEX AT VARYING HYDRAULIC RETENTION TIMES. P. Tata (ed.), WATER ENVIRONMENT RESEARCH. Water Environment Federation, Alexandria, VA, 76(1):47-55, (2004).
Description:
The feasibility of biologically degrading methyl tert-butyl ether (MTBE) contaminated groundwater is dependent on the ability to degrade MTBE and its byproducts in the presence of other gasoline contaminants. This study investigates a mixed culture degrading both MTBE and benzene-toluene-ethylbenzene-xylene (BTEX) in a continuous flow reactor with a biomass retention system (porous pot) at varying hydraulic retention times (HRTs). The reactor was found to degrade both MTBE and BTEX simultaneously to less than the U.S. Environmental Protection Agency's (USEPA) drinking water regulations and recommendations at a hydraulic retention time of 3.76 days. MTBE was degraded from 75 mg/L to less than l µg/L and each BTEX compound was degraded from 17 mg/L to less than 1 µg/L. Effluent concentrations of MTBE and BTEX increased as the HRT was decreased from 3.76 days to 0.52 days, but remained below drinking water limits. The highest MTBE effluent concentration was at 0.52 days and continued to average below 10 µg/L. TBA (tert-butyl alcohol) is commonly cited as a degradation by-product of MTBE but remained below 1 µg/L throughout all reactor operation periods. MTBE and BTEX observed yield coefficients for the reactor ranged from 0.11 to 0.16 mg biomass/mg MTBE and BTEX. Degradation rates from the reactor were compared with results from batch studies with the same culture on MTBE and TBA alone and in the presence of BTEX. Results show that BTEX was not required for this culture to degrade MTBE. The presence of BTEX only had an effect on the rate of MTBE degradation at the highest concentration, while BTEX significantly delayed the degradation of TBA at all concentrations. Batch studies also showed that the rate of degradation of TBA was higher with and without BTEX than the rate of degradation of MTBE, explaining the lack of high levels of TBA in the reactor.