A laboratory column study on the biodegradation of toluene and methyl tert-butyl ether: The effect of substrate interactions

We investigated the effects of substrate interactions on the degradation of toluene and methyl tert-butyl ether (MTBE) by Pseudomonas putida during transport through quartz sand because of the coexistence of toluene and MTBE in aquifer systems. A laboratory test was conducted for a pulse injection of a toluene and/or MTBE solution with and without bacteria into a saturated sand column. We found that the effect of toluene on MTBE was negative because the mass recovery of MTBE increased by 30 % when toluene was added, whereas the effect of MTBE on toluene degradation was positive because the mass recovery of toluene decreased by 7 %. These results were comparable with those of a previous batch study on substrate interactions which reported that toluene can be more negative than MTBE at concentrations higher than 25 mg/L. This finding indicates that substrate interaction is also an important mechanism, controlling the fate of contaminants during transport through aquifer systems. In addition, bacteria-facilitated transport was also observed for both substrates. Therefore, for an efficient bioremediation scheme, care should be taken for substrate interaction as well as for bacteria-facilitated transport in porous media.