Motile Geobacter Dechlorinators Migrate into a Model Source Zone of Trichloroethene Dense Non-aqueous Phase Liquid: Experimental Evaluation and Modeling

摘要

Microbial migration towards a trichloroethene (TCE) dense non-aqueous phaseliquid (DNAPL) could facilitate the bioaugmentation of TCE DNAPL source zones.This study characterized the motility of the Geobacter dechlorinators in a TCEto cisdichloroethene dechlorinating KB-1TM subculture. No chemotaxis towards oraway from TCE was found using an agarose in-plug bridge method. A secondexperiment placed an inoculated aqueous layer on top of a sterile sand layerand showed that Geobacter migrated several centimeters in the sand layer injust $7$ days. A random motility coefficient for Geobacter in water of $0.24\pm 0.02$ cm$^2$ day$^{-1}$ was fitted. A third experiment used adiffusion-cell setup with a $5.5$ cm central sand layer separating a DNAPL froman aqueous top layer as a model source zone to examine the effect of randommotility on TCE DNAPL dissolution. With top layer inoculation, Geobacterquickly colonized the sand layer, thereby enhancing the initial TCE DNAPLdissolution flux. After $19$ days, the DNAPL dissolution enhancement was only$24\%$ lower than with an homogenous inoculation of the sand layer. Adiffusion-motility model was developed to describe dechlorination and migrationin the diffusion-cells. This model suggested that the fast colonization of thesand layer by Geobacter was due to the combination of random motility andgrowth on TCE.