Accession Number:

ADA255696

Title:

Anaerobic Microbial Transformation of Aromatic Hydrocarbons and Mixtures of Aromatic Hydrocarbons and Halogenated Solvents

Descriptive Note:

Final rept. 30 Sep 1988-31 Mar 1992

Corporate Author:

STANFORD UNIV CA DEPT OF CIVIL ENGINEERING

Report Date:

1992-08-25

Pagination or Media Count:

151.0

Abstract:

Anaerobic microbial transformation of monoaromatic hydrocarbons MAH , chlorinated benzenes CB, and mixtures of MAH and CB, as well as MAH and chlorinated aliphatic solvents tetrachloroethylene -- PCE, and carbon tetrachloride -CT was studied in laboratory microcosms derived from hydrocarbon-contaminated groundwater aquifers. Some MAH, such as toluene and o- xylene, were completely degraded to CO2 and CH4 by mixed methanogenic cultures from a creosote-contaminated aquifer. This degradation was inhibited by the addition of accessory electron acceptors oxygen, nitrate, sulfate, indicating acclimation of the microbial community to methanogenic conditions. The addition of preferred substrates, such as acetate, propionate, methanol, fatty acids, glucose, casamino acids, pepton, yeast extract, or acetone also inhibited MAH degradation, indicating that the presence of natural organic substrates may preclude anaerobic biodegradation of MAH in situ. Cyclohexane, CT, and high concentrations of toluene and o-xylene had a toxic effect Under sulfate-reducing conditions, several MAH -toluene, all three xylene isomers, and benzene were mineralized to CO2, by microorganisms from a petroleum-contaminated, sulfidogenic aquifer. Whereas-toluene and xylenes were sequentially degraded in a mixture, benzene was degraded only if alone, or slowly transformed in a mixture with toluene. This explains previously reported recalcitrance of benzene under anaerobic conditions. Anaerobic Transformation, Monoaromatic Hydrocarbons, Chlorobenzenes, Carbon Tetrachloride, Tetrachloroethylene, Mixtures, Methanogenic, Sulfate-Reducing.

Subject Categories:

  • Biochemistry
  • Microbiology
  • Organic Chemistry

Distribution Statement:

APPROVED FOR PUBLIC RELEASE