The effect of particle mineralogy on the biodegradation of diesel No. 2 within particle slurries

This research investigated the impact of different particle mineralogies on the biodegradation of diesel fuel and its constituent compounds in particle slurry systems over 10 days. The effect of contaminant mixtures on the biodegradation rate of single compounds was also determined. This study utilized five different slurry systems: silica #430 (a large grain silica sand), silica #805 (a small grain silica sand), kaolinite, montmorillonite, and a system containing no particles. A mixed culture of soil microorganisms taken from a site contaminated with diesel fuel and Rhodococcus erythropolis (isolated from this mixed culture) were employed in these biodegradation studies. Results indicated that montmorillonite slurries demonstrated the greatest degree of diesel fuel biodegradation by the mixed culture and the fastest rate of alkane biodegradation in systems amended with just alkanes. Kaolinite slurries demonstrated the least degree of diesel fuel biodegradation by the mixed culture. Kaolinite slurries also demonstrated the slowest rate of alkane biodegradation within diesel fuel by both the mixed culture and Rhodococcus erythropolis. Naphthalene, phenanthrene, and chrysene were degraded by the mixed culture at the fastest rate in the systems containing no particles. The presence of alkanes in compound mixtures rather than as just alkanes had a distinct effect on the alkane biodegradation rate by the mixed culture. The mixed culture degraded alkanes at the fastest rate in systems amended with only alkanes, slower in the systems amended with diesel fuel, and slowest in systems amended with PAH and alkanes. In a comparison of the degradative abilities of the mixed culture and Rhodococcus erythropolis, it appears that Rhodococcus erythropolis was able to degrade diesel fuel and alkanes at a faster rate than the mixed culture; however, the mixed culture was able to degrade diesel fuel more completely by degrading more of the compounds within the diesel fuel mixture. The mixed culture was able to degrade naphthalene and phenanthrene, but Rhodococcus erythropolis demonstrated no degradation of these two aromatic compounds.