ANAEROBIC BIODEGRADATION OF ALKYLBENZENES AND TRICHLOROETHYLENE IN AQUIFER SEDIMENT DOWN GRADIENT OF A SANITARY-LANDFILL

The objective of this investigation was to evaluate the anaerobic biod egradability of benzene, toluene, ethylbenzene, ortho-, meta- and para -xylene (BTEX) and trichloroethylene (TCE) in aquifer sediment down gr adient of an unlined landfill. The major organic contaminants identifi ed in the shallow unconfined aquifer an cis-dichloroethylene (c-DCE) a nd toluene. The biodegradative potential of the contaminated aquifer w as measured in three sets: of microcosms constructed using anaerobic a quifer sediment from three boreholes down gradient of the landfill. Th e degradability of BTEX and TCE was examined under ambient and amended conditions, TCE was degraded in microcosms with aquifer material from all three boreholes. Toluene biodegradation was inconsistent, exhibit ing biodegradation with no lag in one set of microcosms but more limit ed biodegradation in two additional sets of microcosms, TCE exhibited an inhibitory effect on toluene degradation at one location. The addit ion of calcium carbonate stimulated TCE biodegradation which was not f urther stimulated by nutrient addition. TCE was converted to ethylene, a harmless byproduct, in all tests. Benzene, ethylbenzene and xylene isomers were recalcitrant in both ambient and amendment experiments. B iodegradation occurred under methanogenic conditions as methane was pr oduced in all experiments. Bromoethane sulfonic acid (BES), a methanog enic inhibitor, inhibited methane and ethylene production and TCE biod egradation. The results indicate the potential for intrinsic bioremedi ation of TCE and toluene down gradient of the Wilder's Grove, North Ca rolina, landfill. The low concentrations of TCE in monitoring wells wa s consistent with its biodegradation in laboratory microcosms.