Effects of TCE and MTBE on Biodegradation of BTEX and BTEX Components

Debrah S. Bovard and Katherine H. Baker

Department of Environmental Engineering, Environmental Microbiology Reserach Laboratory (EMRL), Penn State Harrisburg.

Presented at the 1997 American Society for Microbiology 97^th General Meeting, Miami FL.

Abstract

Mixtures of petroleum hydrocarbons, fuel additives, and industrial solvents are found commonly in the same soil or aquifer. While there is extensive information on the biodegradation in indvidual compounds, little is known about the degradation of complex mixtures. We examined the effect of TCE and methyl-t-butyl-ether (MTBE) on the biodegradation of BTEX (total BTEX and individual aromatic compounds) by a strain (BB-1) isolated from gasoline contaminated soil. For degradation studies, serum bottles containing Bushnell-Haas broth and the appropriate compounds were inoculated with an overnight culture of BB-1. Degradation of BTEX, individual monoaromatic fractions of BTEX, TCE, and MTBE were monitored using headspace analysis. BB-1 was capable of degradation of each of the aromatic fractions of BTEX, either as a pure compound or within a BTEX mixture. Degradation of the individual compounds was significantly slower when they were present in a BTEX mixture. No degradation of either TCE or MTBE or TCE/MTBE mixture was found. Evaluation of degradation rates of total BTEX and individual BTEX components within the mixtures indicated that the response of the individual aromatic compounds was not always consistent with total BTEX degradation. While the degradation of individual aromatic compounds in a TCE/BTEX mixture followed the same pattern of response as seen with total BTEX degradation in such a mixture, the degradation of individual compond varied significantly from total BTEX degradation in either MTBE/BTEX or TCE/MTBE/BTEX mixtures. For example, MTBE in a mixture with BTEX resulted in decreased degradation of benzene, toluene and xylenes in BTEX while degradation of ethylbenzene was increased. Therefore, degradation of individual aromatic compounds of BTEX at a site contaminated with a mixture of compounds cannot be predicted on the basis of degradation rates of pure compounds.