Retention and Transport of PAH-Degrading Bacterium <Emphasis Type="Italic">Herbaspirillum chlorophenolicum</Emphasis> FA1 in Saturated Porous Media Under Various Physicochemical Conditions

Dispersal of functional microorganisms is a rate-limiting process during in situ bioremediation of contaminated soil and groundwater. In this work, series of column experiments were conducted to investigate the retention and transport behaviors of Herbaspirillum chlorophenolicum FA1, a promising bacterial agent for bioremediation, in saturated porous media under conditions of different combinations of grain size, solution pH, solution ionic strength (IS), and humic acid (HA) concentration. Experimental data showed that the mobility of FA1 in saturated porous media was strongly dependent on the physicochemical conditions. The breakthrough curves (BTCs) indicated that the amounts of FA1 in the effluent increased with increasing in sand size, solution pH, and HA concentration, but decreased with increase of solution IS. The shape of retention profiles (RPs) was hyper-exponential. The amounts of retained bacteria in the media also varied with the experimental conditions with opposite trends to that of effluent. Both experimental BTCs and RPs were simulated by a mathematical model that accounted for deposition kinetics to better interpret the effects of physicochemical conditions on FA1 deposition dynamics. Findings from this study showed that fate and transport of the functional bacterium FA1 in porous media strongly relied on the environmental conditions. Both experimental and modeling results can provide guidelines for field application of functional bacteria for soil and groundwater remediation.