Accession Number : ADA260498


Title :   Anaerobic Microbial Transformation of Aromatic Hydrocarbons and Mixtures of Aromatic Hydrocarbons and Halogenated Solvents.


Descriptive Note : Final rept. 30 Sep 88-31 Mar 92,


Corporate Author : STANFORD UNIV CA DEPT OF CIVIL ENGINEERING


Personal Author(s) : Edwards, Elizabeth A. ; Liang, Li-Nuo ; Dunia, Grbic-Galic


Full Text : http://www.dtic.mil/get-tr-doc/pdf?AD=ADA260498


Report Date : 25 AUG 1992


Pagination or Media Count : 151


Abstract : Anaerobic microbial transformation of monoaromatic hydrocarbons (NM), 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 CO 2 and CH 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 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 CO by microorganisms from a petroleum-contaminated, sulfidogenic aquifer. Whereas 2 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. The addition of preferred substrates (lactate, glucose, or yeast extract) to the cultures temporarily inhibited the degradation of MAH. Methanogenic microcosms from the creosote-contaminated aquifer reductively dechlorinated hexa-, penta-, tetra-, tri-, and di-chlorobenzene.


Descriptors :   *OXYGEN , *AROMATIC HYDROCARBONS , *SOLVENTS , *ANAEROBIC PROCESSES , *TRANSFORMATIONS , *HALOGENATED HYDROCARBONS , BENZENE , DEGRADATION , TOXICITY , SUBSTRATES , AQUIFERS , YEASTS , ACETONES , ELECTRON ACCEPTORS , CARBON DIOXIDE , CONTAMINATION , SULFATES , METHANE , CYCLOHEXANES , LABORATORIES , ELECTRON DONORS , GRANULES , LACTATES , FATTY ACIDS , CHLOROFORM , CRUDE OIL , NITRATES , TRICHLOROETHYLENE , MICROORGANISMS , ALIPHATIC HYDROCARBONS , PROPIONATES , PEPTONES , CREOSOTE , CHLOROBENZENE , CARBON TETRACHLORIDE , TOLUENES , BIODETERIORATION , GLUCOSE , MICROBIOLOGY , METABOLITES , ACETATES , ATMOSPHERES , CULTURE , SUBSURFACE , CHEMICAL ANALYSIS , XYLENES , METHANOLS , GROUND WATER , ISOMERS , SOLIDS , MIXTURES , MICROSCOPY


Subject Categories : BIOLOGY
      MICROBIOLOGY
      ORGANIC CHEMISTRY
      PHYSICAL CHEMISTRY


Distribution Statement : APPROVED FOR PUBLIC RELEASE