TCE Remediation Using In Situ, Resting-State Bioaugmentation

Abstract

A field test has demonstrated that an in situ biofilter using resting-state cells effectively remediated groundwater with about 425 ppb of trichloroethene (TCE) as the sole contaminant species. About 5.4 kg (dry weight equivalent) of a strain of methanotrophic bacteria (Methylosinus trichosporium OB3b) was suspended in 1800 L of groundwater (5.4 × 10 9 cells/ mL) and injected into an aquifer through a single well at a depth of 27 m, several meters below the water table. The injected groundwater was devoid of TCE and growth substrates but was amended with a phosphate solution (10 mM) to buffer the pH and phenol red (20 µm) to act as a tracer. Approximately 50% of the injected bacteria attached to the sediments, forming an in situ, fixed-bed bioreactor of unknown geometry. Contaminated groundwater was subsequently withdrawn through the biofilter region by extracting at 3.8 L/min for 30 h and then at 2.0 L/min for the remaining 39 days of the field experiment. TCE concentrations in the extracted groundwater decreased from 425 to less than 10 ppb during the first 50 h of withdrawal, which is equivalent to a 98% reduction. TCE concentration extracted through the biofilter gradually increased to background values at 40 days when the experiment was terminated.

Processes in Microbial Transport in the Natural Subsurface

“…In particular, in situ bioremediation of contaminated groundwater may involve microbial transport promoted by intrinsic bioremediation (as part of natural attenuation; e.g., [21,173,178,188]), biostimulation (by the addition of substrates or electron donors; e.g., [113,184]), or bioaugmentation (by the introduction of microbial cells with specific function to the subsurface; e.g., [149,164]). Bioaugmentation in this context includes both injection of bacterial suspensions in the saturated zone near a contaminant plume and emplacement of solid media with attached bacteria as a ÔbiobarrierÕ through which mobile contaminant is expected to pass and be degraded [65,129].…”

Enhanced Anaerobic Biodegradation of Benzene-Toluene-Ethylbenzene-Xylene-Ethanol Mixtures in Bioaugmented Aquifer Columns

“…The benefits of bioaugmentation have been demonstrated in field tests for a wide variety of contaminants, including MTBE (52) and chlorinated solvents (23,24,26,40). Similarly, benzene degradation in a sulfate-reducing zone of a petroleumcontaminated aquifer was observed only after the inoculation of a benzene-oxidizing, sulfate-reducing enrichment from aquatic sediments (59).…”

Natural Genetic Transformation in Monoculture Acinetobacter sp. Strain BD413 Biofilms

“…If reactors lack the desired biocatalysts, they need to be bioaugmented to obtain efficient degradation. By addition of exogenous optimally constructed bacteria (11,43) or functionally adapted bacterial consortia (18) and communities (47), enrichment of the total gene pool can be obtained. Likewise, a reactor can be augmented by in situ gene transfer (42).…”