Bacteria associated transport of toluene in quartz sand: Model development and verification

In this study, we proposed a new model which is capable of describing bacteria associated transport of toluene which showed a significant tailing in the breakthrough curve (BTC) in the literature. In order to realize the tailing, a new model approach was attempted by inclusion of irreversible sorption for toluene onto solid matrix, kinetic reversible sorption for bacteria onto solid matrix, and kinetic reversible sorption for toluene onto bacterial surfaces in addition to biodegradation. Simulation of toluene transport with various sorption related model parameters revealed that the observed tailing part of the toluene BTC was best described by inclusion of kinetic reversible sorption of toluene onto bacterial surfaces. This indicates that (i) nonfacilitated or tailing enhanced transport of toluene can be described by using only the kinetic reversible process rather than irreversible or equilibrium sorption process, and (ii) the tailing enhanced transport is attributed to the biosorption as a result of sorption and desorption of toluene onto bacterial surfaces. This modeling approach to elucidate the evidence of bacteria associated transport of toluene in terms of enhanced tailing is the first attempt in the organic contaminant transport modeling and would be a benchmark in modeling the fate of toluene during transport.