This book includes transport studies with Batch and bench scale soil column to evaluate the effectiveness of Cr(VI) containment in confined aquifers using in-situ bio-transformation. Sorption studies were carried out to estimate the adsorption capacities of various soils for Cr(VI), Cr(III), Li and Molasses. Bio-kinetic parameters were evaluated for the enriched microbial system isolated from the contaminated site. Transport studies indicated that it would not be possible to contain Cr(VI) by adsorption alone. Transport and bio-transformation studies indicated that the pore velocity and the initial bio-mass concentration significantly affect the containment process. A mathematical model was also developed based on one-dimensional advection-dispersion reaction equations for Cr(VI) and molasses in saturated, homogeneous porous medium. It was found that this model was able to simulate the experimental results satisfactorily. The validated mathematical model was used to develop design charts, which can help in determining the minimum bio-barrier thickness for complete containment of the contaminant, given the initial microbial concentration and the input substrate concentration.