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Effect of Biofuels on Biodegradation of Benzene and Toluene at Gasoline Spill Sites
Citation:
Wilson, J., C. Adair, H. White, AND R. Howard. Effect of Biofuels on Biodegradation of Benzene and Toluene at Gasoline Spill Sites. Ground Water Monitoring & Remediation. Wiley-Blackwell Publishing, Hoboken, NJ, 36(4):50-61, (2016). https://doi.org/10.1111/gwmr.12187
Impact/Purpose:
The risk that benzene and toluene from spills of gasoline will impact drinking water wells is largely controlled by the natural anaerobic biodegradation of benzene and toluene. Benzene and toluene as well as ethanol and other biofuels are degraded under anaerobic conditions to the same pool of degradation products. Biodegradation of biofuels may produce concentrations of degradation products that make the thermodynamics for degradation of benzene and toluene infeasible, and produce larger plumes of benzene and toluene. This study evaluated the concentrations of fuel alcohols that are necessary to inhibit anaerobic degradation of benzene and toluene. At two ethanol spill sites, concentrations of ethanol greater than 10 mg/L inhibited anaerobic degradation of toluene. The pH and concentrations of acetate, dissolved inorganic carbon and molecular hydrogen were used to calculate the Gibbs free energy for biodegradation of toluene. In general, the anaerobic biodegradation of toluene was not thermodynamically feasible in water with more than 10 mg/L ethanol. In a microcosm study, when the concentrations of ethanol or n-butanol were greater than 10 mg/L, biodegradation of the alcohols consistently produced concentrations of hydrogen, dissolved inorganic carbon, and acetate that would preclude natural anaerobic biodegradation of benzene and toluene by syntrophic organisms. In contrast, iso-butanol and n-propanol only occasionally produced conditions that would preclude the biodegradation of benzene and toluene.
Description:
The risk that benzene and toluene from spills of gasoline will impact drinking water wells is largely controlled by the natural anaerobic biodegradation of benzene and toluene. Benzene and toluene as well as ethanol and other biofuels are degraded under anaerobic conditions to the same pool of degradation products. Biodegradation of biofuels may produce concentrations of degradation products that make the thermodynamics for degradation of benzene and toluene infeasible, and produce larger plumes of benzene and toluene. This study evaluated the concentrations of fuel alcohols that are necessary to inhibit anaerobic degradation of benzene and toluene. At two ethanol spill sites, concentrations of ethanol greater than 10 mg/L inhibited anaerobic degradation of toluene. The pH and concentrations of acetate, dissolved inorganic carbon and molecular hydrogen were used to calculate the Gibbs free energy for biodegradation of toluene. In general, the anaerobic biodegradation of toluene was not thermodynamically feasible in water with more than 10 mg/L ethanol. In a microcosm study, when the concentrations of ethanol or n-butanol were greater than 10 mg/L, biodegradation of the alcohols consistently produced concentrations of hydrogen, dissolved inorganic carbon, and acetate that would preclude natural anaerobic biodegradation of benzene and toluene by syntrophic organisms. In contrast, iso-butanol and n-propanol only occasionally produced conditions that would preclude the biodegradation of benzene and toluene.
URLs/Downloads:
DOI: Effect of Biofuels on Biodegradation of Benzene and Toluene at Gasoline Spill Sites
https://onlinelibrary.wiley.com/doi/full/10.1111/gwmr.12187
Free access through PubMed Central